1387 - Absorption Of Non-haem Iron In Normal Women Measured By The Incorporation Of Two Stable Isotopes Into Erythrocytes.
Iron absorption was quantitatively measured as the incorporation of physiological doses of stable Fe isotopes into erythrocytes. On 2 consecutive days 57Fe 5 mg orally and 58Fe 250 µg intravenously were given to 5 healthy women 24 to 31 years old. After 14 days the changes in the 57Fe:56Fe and 58Fe:56Fe ratios in the erythrocytes of each subject were measured using an inductively coupled plasma mass spectrometer. Isotope ratios were also measured in 2 subjects who were not given any enriched isotope. Concomitant measurements of plasma volume using a dye-dilution technique enabled the estimation of body Fe mass and the calculation of Fe absorption. The mean coefficients of variation for the 57Fe:56Fe ratio and the 58Fe:56Fe ratio were 0.22% and 0.47%, respectively. This precision allowed enrichments of basal ratios to be reliably detected in all cases. The mean change in the 57Fe:56Fe ratio was 0.00116 and in the 58Fe:56Fe ratio was 0.00035. Control subjects showed no enrichment. The calculated Fe absorption ranged from 10 to 34%, and the amount of absorption was related to the Fe stores of the subjects. Percentage Fe absorption was identical when estimates of the plasma volume (derived from a body mass equation) were used instead of the plasma volume estimated by dye-dilution measurements. Incorporation of intravenous Fe into erythrocytes was on average 81, range 68 to 93%. The method is especially applicable to the study of Fe absorption during pregnancy when incorporation into erythrocytes cannot be predicted.
Cet article décrit une méthode de mesure de la biodisponibilité du fer utilisant deux isotopes stables du fer (57Fe et 58Fe) donnés par voie orale et intra-veineuse chez l'Homme. L'utilisation des isotopes stables permet d'envisager le développement d'études de mesure de l'absorption du fer chez les femmes enceintes. Reférence utile pour les scientifiques.1388 - Efficacy Of Weekly Compared With Daily Iron Supplementation.
A reduction in the frequency of iron supplement administration to once or twice weekly is being widely examined in developing countries on the assumption that the side effects of oral iron will decrease and that the reduction in administered iron will be offset by a lesser inhibition in absorption from iron taken on the previous day. We examined this premise by measuring iron absorption from 50 mg radiolabeled ferrous sulfate in 23 female volunteer subjects divided into two groups. In the first group, a labeled ferrous sulfate supplement was given with water, and in the second group it was given with a rice-based meal. In both groups, absorption was measured in a randomized fashion twice in each subject, once with daily and once with weekly supplementation. Those tested for daily supplementation were given an iron supplement daily for 6 d before testing whereas those tested for weekly supplementation were given no iron for 6 d before testing. When the labeled iron supplement was given with water only, absorption averaged 8.5% with daily and 9.8% with weekly administration compared with 2.3% and 2.6%, respectively, when given with food. The 13% lower absorption observed with daily administration in both groups was not statistically significant (p >/ 0.20). These results indicate that there is no significant absorptive advantage in giving iron less often than once daily.
Cette étude de mesure de la biodisponibilité du fer à l'aide d'isotopes radioactifs chez des femmes en âge de procréer, suggère que la supplémentation intermittente par le fer (une fois par semaine) n'a pas d'avantages sur le plan de l'absorption par rapport à la supplémentation martiale quotidienne.1389 - Effects Of Low-dose Iron Supplementation In Women With Low Serum Ferritin Concentration.
The effects of dose and treatment duration during low-dose iron supplementation were examined in premenopausal, non-pregnant women, with initial serum ferritin and haemoglobin concentrations </20 µg/liter and &ge/120 g/liter, respectively. The study was randomized, double-blind and placebo-controlled. 3 groups completed a 6-month study: placebo (n= 27), FE-9 (Fe 9 mg daily, n = 18) and FE-27 group (Fe 27 mg daily, n = 19). The supplement consisted of 11% heme and 89% inorganic iron. In FE-27, serum ferritin increased from (mean, 95% confidence interval) 11.8 to 25.3 µg/liter in 1 month, and remained stable after that (ANOVA: group effect, p =0.0003). In both FE-9 and FE-27, blood haemoglobin levels increased from 136 to 142 g/liter in 1 month, remaining constant after that (group effect, p =0.001). Hence, the 27 mg daily dose of organic/inorganic Fe corrected both mild anaemia and storage Fe depletion, whereas the 9 mg dose did not affect Fe stores
TREATMENT:
duration above 1 month brought about only minor changes.
Cet essai randomisé versus placebo, réalisé chez des femmes en âge de procréer, déplétées en fer et anémiques, met en évidence qu'une supplémentation par 27 mg de fer par jour (11 % de fer héminique et 89 % de fer inorganique) pendant 6 mois permet une correction de l'anémie et de la déplétion des réserves en fer. Un apport de seulement 9 mg/j, sur la même durée, permet une amélioration de l'hémoglobine sans effet sur les réserves en fer.1390 - Environmental And Physical Stress And Nutrient Requirements.
When faced with hot, cold, or high-altitude environments, humans can either modify the microenvironment to fit human physiology, adapt their physiology to fit the environment, or use a combination of these two tactics. Metabolic adaptations to heat, cold, and high-altitude exposure may, in some instances, be accompanied by changes in nutrient requirements. Energy expenditure is increased in all three environments. B-vitamin cofactor requirements increase in proportion to energy expenditure (oxidation of fat and carbohydrate). Increased B-vitamin nutrient requirements are usually adequately met by an increased consumption of the diet to meet energy requirements. Other nutrients such as iron may be required in greater amounts to meet the altitude-induced hematopoietic response in females. Additional quantities of vitamins and minerals with antioxidant properties may be beneficial to reduce the increased oxidative stress associated with work in heat, cold, or high-altitude outdoor environments.
Revue sur les modifications des besoins nutritionnels dans les situations de stress (chaleur, froid, altitude,...). Dans ces circonstances, les besoins en énergie, en vitamine B, en fer et en vitamines et minéraux antioxydants sont augmentés.1391 - Spinal Bone Loss In Postmenopausal Women Supplemented With Calcium And Trace Minerals.
The effects of calcium supplementation (as calcium citrate malate, 1000 mg elemental Ca/d) with and without the addition of zinc (13.0 mg/d), manganese (5.0 mg/d) and copper (2.5 mg/d) on spinal bone loss (L2=L4 vertebrae) was evaluated in healthy older postmenopausal women (n = 59, mean age 66 y) in a 2-y, double-blind, placebo-controlled trial. Changes (means ±/ SEM) in bone density were -3.53 ±/ 1.24% (placebo), -1.89 ±/ 1.40% (trace minerals only), -1.25 ±/ 1.46% (calcium only) and 1.48 ±/ 1.40% (calcium plus trace minerals). Bone loss relative to base-line value was significant (p = 0.0061) in the placebo group but not in the groups receiving trace minerals alone, calcium alone, or calcium plus trace minerals. The only significant group difference occurred between the placebo group and the group receiving calcium plus trace minerals (p = 0.0099). These data suggest that bone loss in calcium- supplemented, older postmenopausal women can be further arrested by concomitant increases in trace mineral intake.
Un essai randomisé en double aveugle (sur 2 ans chez des femmes ménopausées en bonne santé) a permis de mettre en évidence un intérêt de la supplémentation par le calcium associé aux oligoéléments pour réduire la perte osseuse. Reférence utile pour les scientifiques et les praticiens.1392 - Iron Absorption From The Whole Diet: Comparison Of The Effect Of Two Different Distributions Of Daily Calcium Intake.
The possibility of reducing calcium inhibition of iron absorption by decreasing calcium intake in lunch and dinner meals, which provided the most dietary iron, was ex-amined in 21 healthy female volunteers. During a 10-d period, nonheme iron in all meals was extrinsically labeled with radioisotopic iron to a uniform specific activity. Iron absorption from two identical 10-d periods was compared when meals were labeled with two different iron radioisotopes and when the same amount of calcium (937 mg) was distributed in two ways, in either mainly breakfast and late evening meals or more evenly in all meals. About 30-50% more iron was absorbed when no milk or cheese was served with lunch or dinner. The difference was statistically significant. Median iron requirements (1.61 mg/d) calculated from body weight and menstrual iron losses agreed with the mean value of median iron absorption in the two 10-d periods (1.54 mg/d), which supports the validity of the present method. A reasonable separation of calcium and iron intakes would improve iron nutrition.
La biodisponibilité du fer mesurée chez des femmes à l'aide d'isotopes radioactifs, met en évidence que le calcium a un effet inhibiteur sur l'absorption du fer lorsque la consommation de fer et de lait est concomitante au cours du même repas. Une séparation raisonnable des consommations de fer et de calcium devrait permettre d'améliorer le statut en fer.1393 - The Effects Of Iron Deficiency And Iron Overload On Cell-mediated Immunity In The Mouse.
The influence of Fe status on cell-mediated immunity was studied in weanling mice fed on Fe-deficient (7 mg Fe/kg), Fe-sufficient (120 mg Fe/kg) and high-Fe (3000 or 5000 mg Fe/kg) diets for 7 weeks. The contact sensitivity (CS) response to dinitrofluorobenzene (DNFB), the in vivo delayed-type hypersensitivity (DTH) response to sheep erythrocytes (SRBC) and the ability of primed spleen cells to transfer DTH response to naive normal mice were suppressed in mice consuming the Fe-deficient diet. High-Fe diets (3000 or 5000 mg Fe/kg) selectively suppressed the CS response to DNFB, but the DTH response to SRBC or the transfer of DTH response by primed spleen cells to naive normal mice remained normal. Spleen cell functions associated with the expression of class II major histocompatibility (MHC) surface antigens, concanavalin A-induced interleukin-2 (IL-2) secretion or the antigen-presenting cell (APC) ability to stimulate antigen-dependent proliferation of an SRBC-specific helper T-lymphocyte clone were not altered by Fe status. However, consistent with the suppressed DTH response in the Fe-deficient mice was the suppressed concanavalin A-induced T-lymphocyte blastogenesis and the interferon-y (INF-y) production by spleen cells from mice fed on the Fe-deficient diet. Spleen cells from mice fed on excess levels of Fe in the diet secreted less INF-y than the control mice, although T- lymphocyte proliferation remained unaffected. Suppression of the cellular immune response associated with Fe deficiency may be related in part to impaired T-lymphocyte proliferation and INF-y secretion rather than to deficits in IL-2 secretion or APC function.
Article plutôt destiné aux chercheurs. Chez la souris, les apports insuffisants ou excessifs de fer par l'alimentation entraînent des perturbations de l'immunité à médiation cellulaire.1394 - Influence Of Lactoferrin On Iron Absorption From Human Milk In Infants.
Lactoferrin (Lf) is a major iron-binding protein in human milk and has been suggested to facilitate Fe absorption. The potential effect of Lf on Fe absorption was investigated by measuring Fe absorption in infants given breast-milk (with its native content of Lf) and the same milk from which Lf had been removed (>/97%) by treatment with heparin-Sepharose. Eight breast-fed infants (2-10 months) were given 700-1000 g of each milk in a randomized, cross-over design, with each child acting as his/her own control. The milk was labeled with 8.6 µmol (0.5 mg) 58Fe and Fe absorption was measured by quantifying the incorporation of the isotope into red blood cells 14 days after intake using thermal ionization MS. Fractional Fe absorption was significantly lower (P</0.05) from breast-milk than from Lf-free breast-milk. The geometric mean (range) was 11.8% (3.4-37.4%) for breast-milk and 19.8% (8.4-72.8%) for Lf-free breast-milk. These results do not support a direct role for Lf in the enhancement of Fe absorption from human milk at this age. In addition, Fe absorption (11.8%) from human milk given over several feeds was lower than that previously reported for single-feed studies.
Une étude évaluant la biodisponibilité du fer dans le lait maternel, mesuré chez le nourrisson, à l'aide d'isotopes stables, met en évidence que la destruction de la lactoferrine du lait ne modifie pas l'absorption du fer. Ces résultats suggèrent que la lactoferrine n'a pas un effet direct sur l'absorption du fer du lait maternel.1395 - Iron-deficiency Anaemia And Physical Performances In Adolescent Girls From Different Ethnic Backgrounds.
One hundred and fourteen 11-14-year-old schoolgirls from Wembley, Middlesex, were assessed for Fe status (haemoglobin (Hb), packed cell volume and mean corpuscular Hb concentration, height, weight, eating habits, and ethnic origin, and undertook a step test to assess physical performance. Overall, 20 % of girls had Hb less than 120 g/l, ranging from 11 % in White girls to 22-25% in girls of Asian origin. Prevalence of low Hb was 20% in vegetarians, higher in White vegetarians compared with non-vegetarians (23 v. 4%), but lower in the Indian vegetarians compared with non-vegetarians (17 v. 32 %). Low Hb was present in 25 % of girls who had tried to lose weight in the previous year, and was more common in girls from manual social class backgrounds than non-manual (24 v. 10 %). At the start of the step test the twenty-three girls with low Hb had heart rates similar to those with normal Hb, but heart rates in the low Hb group were significantly elevated immediately after the step test, and still significantly elevated 1 min later. The present results confirm the findings of a previous study in White girls, and suggest that physical performance may be compromised at mild levels of anaemia.
Cette étude réalisée chez 114 écolières anglaises de 11 à 14 ans, met en évidence la fréquence élevée des anémies dans cette tranche d'âge, notamment chez les jeunes filles d'origine indienne, chez les végétariennes et chez celles ayant suivi un régime amaigrissant au cours de l'année précédente. Le point majeur est que ces anémies modérées peuvent avoir des conséquences négatives sur la capacité physique mesurée par un test objectif (rythme cardiaque à l'effort).1396 - Sodium iron EDTA [NaFe(III)EDTA] as a food fortificant: the effect on the absorption and retention of zinc and calcium in women.
The iron fortificant NaFeEDTA could have a potential negative effect on the metabolism of other minerals. We have used stable isotopes to monitor zinc and calcium metabolism in 10 women consuming a single meal of high-extraction wheat rolls (100 g flour) fortified with 5 mg Fe as either FeSO4 or NaFeEDTA. Six-day chemical balances were made simultaneously to study apparent zinc and calcium retention from the complete diet containing the differently iron-fortified breads (200 g flour/ 10 mg added Fe/d). Mean 70Zn absorption from the bread meal increased from 20.9% with FeSO4 to 33.5% with NaFeEDTA (p </ 0.05) whereas mean 44Ca absorption was 53.3% from both breads. When NaFeEDTA-fortified bread was consumed, there was a small but significant increase in urinary excretion of 70Zn and 44Ca. There was a similar small increase in urinary zinc excretion during the 6-d balance, although the apparent retention of zinc and calcium was not different. Thus, we found no negative overall effect of NaFeEDTA consumption on the metabolism of zinc and calcium. In contrast, the results suggest that NaFeEDTA added to low-bioavailability diets might increase zinc absorption as well as provide iron with high bioavailability.
Le fer NaFeEDTA utilisé pour l'enrichissement de certains aliments n'a pas d'effet négatif sur le métabolisme du zinc et du calcium. Au contraire, l'adjonction de NaFeEDTA à un repas de faible biodisponibilité pourrait augmenter l'absorption du zinc tout en apportant un fer de biodisponibilité correcte. Article destiné aux scientifiques.1397 - Functional Consequences Of Iron Supplementation In Iron-deficient Female Cotton Mill Workers In Beijing, China.
Eighty iron-deficient, nonpregnant female workers were randomly assigned to ferrous sulphate (60 or 120 mg Fe/d) or placebo treatment for 12 wk. Energy expenditure was estimated during 3 d by heart rate (HR) recording. Production efficiency (PE) was calculated as the ratio of productivity to energy expenditure. In the iron-treated group mean hemoglobin (Hb) increased from 114 to 127 g/L (p </ 0.001), mean serum ferritin increased from 9.7 to 30.0 µg/L (p </ 0.001), and mean free erythrocyte protoporphyrin decreased from 1.01 to 0.49 µmol/L (p </ 0.001). Mean HR at work decreased from 95.5 to 91.1 beats/min (p </ 0.001), which was inversely correlated with the change in Hb (r = -0.60, p </ 0.001). PE increased significantly in the iron-treated group (p </ 0.001) and its change paralleled the change in Hb (r = 0.58, p </ 0.001). The results show that iron supplementation enabled these women to do the same work at a lower energy cost.
Un essai randomisé en double aveugle versus placebo met en évidence que la supplémentation par le fer de femmes carencées en fer permet, après correction du statut en fer, la réalisation d'un travail physique à un moindre coût énergétique.1398 - Iron Deficiency And Infant Development.
It has been shown that iron-deficient anemic infants are not as successful in tests of mental and motor development as their iron-sufficient age-matched counterparts. A recent study has confirmed that iron intervention can reverse developmental delays, while placebo-treated anemic infants showed no such improvement. The etiology of the developmental delay and its effect on later performance remain to be elucidated.
Cet article décrit les relations entre le statut en fer, les performances intellectuelles et le développement psychomoteur chez l'enfant. Un essai d'intervention démontre l'efficacité d'un apport supplémentaire en fer sur les performances intellectuelles chez des enfants anémiques ferriprives (bien que les mécanismes exacts ne soient pas connus).1399 - Adverse Effect Of Iron Supplementation On Weight Gain Of Iron-replete Young Children.
The efficacy of iron supplementation for iron-deficient subjects is in no doubt. However, the assumption that iron supplementation of iron-replete subjects is harmless may not be valid. We have studied the effect of iron supplementation on growth rate in 47 iron-sufficient young children (12-18 months) in Indonesia. The children were randomly assigned either ferrous sulphate (3 mg/kg daily) or placebo every day for 4 months. Before treatment the length, weight, and arm circumference of the two groups were similar. During the 4 months of supplementation the rate of weight gain was significantly greater in the placebo group than in the iron-supplemented group (0-106 [SE 0.010&rsqb/ vs 0.070 &lsqb/0.011&rsqb/ kg every 2 weeks, p=0.02). The rates of gain in length and arm circumference did not differ significantly by treatment. There were no differences between the groups in rates of respiratory and gastrointestinal infections. These results suggest that iron supplementation of iron-replete children may retard their growth.
La supplémentation par le fer s'avère chez des enfants déficients en fer, par contre elle semble pouvoir retarder la croissance chez des enfants ayant un bon statut en fer en Indonésie.1400 - Body Iron Stores And The Riskof Coronary Heart Disease.
Background Recent studies have suggested an association between higher body iron stores and the risk of coronary heart disease. To assess these findings, we examined the association between transferrin saturation and the risk of coronary heart disease, myocardial infarction, overall mortality, and mortality from cardiovascular causes in a large population.
METHOD:
We studied a total of 4518 men and women from the first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study, using a multivariate Cox proportional-hazards model. Base-line data were collected from 1971 to 1974, with follow-up through 1987. Transferrin saturation (serum iron concentration divided by total iron-binding capacity) was used as a measure of the amount of circulating iron available to tissues.
RESULTS:
The risk of coronary heart disease was not related to transferrin-saturation levels in white men or women. Estimates of the relative risk of coronary heart disease for the fifth quintile of transferrin saturation as compared with the first quintile were 0.72 (95 percent confidence interval, 0.51 to 1.00) for men and 0.85 (95 percent confidence interval, 0.60 to 1.21) for women. The results were similar for myocardial infarction. A significant inverse association with transferrin saturation was found for overall mortality and for mortality from cardiovascular causes in white men and women. Transferrin saturation was not associated with any of the clinical outcomes in blacks, possibly owing to the small sample.
CONCLUSION:
Higher transferrin-saturation levels were not associated with an increased risk of coronary heart disease or myocardial infarction. On the contrary, the results indicate that there may be an inverse association of iron stores with overall mortality and with mortality from cardiovascular causes.
Le suivi de près de 17 ans d'une cohorte de plus de 45 000 hommes et femmes aux USA a mis en évidence que les niveaux initiaux de saturation de la transferrine les plus élevés ne sont pas associés à une augmentation du risque de maladies coronariennes et d'infarctus du myocarde. A l'inverse, il est retrouvé une corrélation inverse entre les réserves en fer et la mortalité globale et la mortalité par maladies cardio-vasculaires.1401 - A Double Stable Isotope Technique For Measuring Iron Absorption In Infants.
A stable isotope technique has been developed which uses 57Fe and 58Fe as labels and which enables the simultaneous measurement of Fe absorption from two test meals in infants. The method was evaluated by measuring Fe absorption from a commercial whey-adjusted infant formula in nine healthy infants aged 13-25 weeks. Each infant was fed 210 ml formula, labeled with either 57Fe or 58Fe, on four consecutive mornings, in random order. The total Fe content in each feed was 2.5 mg Fe/ either as 2.5 mg 57Fe, or 0.6 mg 58Fe plus 1.9 mg Fe with normal isotopic composition. Isotopic enrichment of Fe in erythrocytes was measured by thermal ionization mass spectrometry 14 d after the last administration, and Fe absorption was calculated based on isotope ratio shifts, total circulating Fe and intake of each isotope. Geometric mean absorption for the 57Fe and 58Fe labels was 6.72 and 6.58 % respectively, and the absorption of the two isotopes was not significantly different (Student''s paired t test). By this technique, paired comparisons of Fe absorption can be obtained and systematic studies of the influence of dietary factors on Fe absorption during infancy can be conducted.
Cet article présente une méthode de mesure de l'absorption du fer alimentaire utilisant des isotopes stables (double marquage) et donc applicable à l'enfant. L'utilisation de cette nouvelle technique peut permettre de connaître, dans le futur, la biodisponibilité du fer dans différents aliments ou repas, chez l'enfant et de mieux préciser le rôle de facteurs activateurs ou inhibiteurs de l'absorption du fer dans cette population.1402 - Consideration On The Bioavailability Of Iron In Foods.
The bioavailability of iron in foods is reviewed. There is a section on the terminology used in the study of intrinsic or physiological and extrinsic or dietetic factors which affect the availability of Fe. The bioavailability of Fe in foods of animal and plant origin and in fortified foods is discussed as is the position of Fe as a contaminant.
Revue générale sur la biodisponibilité du fer alimentaire natif (aliments végétaux ou animaux), ou utilisé pour l'enrichissement en fer des aliments ou du fer de contamination. Rôle des facteurs activateurs ou inhibiteurs de l'absorption du fer alimentaire.1403 - Effects Of Calcium Supplementation, Calcium Source And Lactose On Iron Absorption In The Rat.
Ca-supplemented diets (containing 1.0% Ca) were prepared by substituting milk, cheese, yogurt, CaCO3, or Ca citrate-malate (CaCM) into 2 control diets (containing 0.5% Ca and either no lactose or 20% lactose). The diets were labeled with 59Fe and offered to fasted rats aged 21 d, 40 d, and 100 d. Fe absorption was determined by whole-body counting. The effect of Ca supplementation was most pronounced in the 21 d rats supplementation with yogurt, CaCM, and CaCO3, but not milk or cheese, depressed 59Fe absorption (p</ 0.05). In 40 d rats, supplementation with CaCM but none of the other sources depressed 59Fe absorption. There was no effect with any of the sources in the 100 d rats. Lactose dramatically increased 59Fe absorption from the milk and control diets in 21 d rats, decreased 59Fe absorption from CaCM in 40 d rats but had no effect in other treatments. These data suggest that Ca in the form of CaCO3 and CaCM, has a more pronounced effect on iron bioavailability than Ca in dairy products (except for yogurt) and that Fe-Ca interactions are influenced by the physiological state of the animal.
Cette étude réalisée sur des rats, suggère que le calcium sous forme de carbonate de calcium ou de citrate-malate calcique a un effet inhibiteur de l'absorption du fer plus fort que le calcium présent dans les produits laitiers (excepté les yaourts).1404 - Haemoglobin, Ferritin, And Iron Intakes In British Children Aged 12-14 Years: A Preliminary Investigation.
The purpose of the study was to assess the prevalence of Fe deficiency and Fe-deficiency anaemia in a group of apparently healthy adolescents, and to assess the value of a food frequency and amount questionnaire as a screening tool to identify children at risk of Fe deficiency. White school children (399) aged 12-14 years living in a Southwest London suburb completed a food frequency and amount questionnaire to assess usual Fe and vitamin C intake, and provided a thumb-prick blood sample for analysis of haemoglobin (Hb), packed cell volume (PCV), and serum ferritin (SF). Children were classified as ''anaemic'' if Hb was below the Dallman 3rd percentile (girls: </ 120 g/l / boys: </ 122, </ 124 and </ 126 g/l at ages 12, 13 and 14 years respectively)/ and ''low'' or ''borderline'' in Fe stores if SF was </ 12 µg/l, or between 12 and 20 µg/l respectively. Of the boys and girls 3-5 and 10.5% respectively were anaemic/ 1 % of boys and 4% of girls had low ferritin values, and 14% of boys and 16% of girls were borderline. Fe intakes were significantly higher in boys than in girls (12.3 v. 9.6 mg/d, p </ 0.001). Prevalence of anaemia was 14.5 % in the group with both low Fe intakes (</ lower reference nutrient intake) and low vitamin C intakes (</ median), compared with 2.3 % in the group with both high Fe intakes (>/ reference nutrient intake) and high vitamin C intakes (>/ median). Anaemia was three times more common in vegetarians than omnivores (25 v. 9%), and in girls who had tried to lose weight in the last year compared with those who had not (23 v. 7%). The questionnaire did not prove satisfactory as a screening tool for risk of Fe deficiency. The higher-than-expected prevalence of Fe deficiency in apparently healthy white girls suggests that other groups should also be investigated.
Cet article a l'intérêt de mettre en évidence la fréquence élevée des carences en fer chez les adolescents britanniques du sud de Londres (n=399), âgés de 12 à 14 ans et considérés en bonne santé. La prévalence des anémies est plus élevée chez les sujets dont les apports alimentaires en fer et en vitamine C s'éloignent des recommandations. L'anémie est 3 fois plus fréquente chez les végétariens et les adolescentes ayant suivi un régime alimentaire.1405 - Iron Overload: Prevalance And Impact On Health.
Clinical manifestations attributable to the damaging effects of iron occur when the total body iron is 5-10 times higher than normal. In adults this degree of iron overload occurs in hereditary hemochromatosis, a human leukocyte antigen (HLA)-linked autosomal recessive disorder, as well as in secondary iron-overload conditions.
Revue générale sur la surcharge en fer avec des données de prévalence, l'étiologie et les aspects génétiques, ainsi qu'une évaluation de l'impact sur la santé.1406 - Weekly Versus Daily Oral Iron Administration: Are We Asking The Right Questions?
The separation of oral iron doses to conform to the cycle of intestinal mucosa turnover has been suggested by some as a method to improve the efficiency of uptake for therapeutic doses of iron. A short-term study in healthy American women failed to confirm a superiorabsorption of radioiron with a 7-day interval versus everyday administration of a 50-mg iron dose, but the iron status of the experimental subjects may have produced an inappropriate population on which to test a question relevant to Third World populations.
Dans cette étude réalisée sur des jeunes femmes américaines, l'absorption du fer mesurée par des isotopes radioactifs n'a pas été retrouvée meilleure dans le cas d'une seule dose semanale, par rapport à une prise quotidienne de 50 mg de fer élément par jour. Cette étude ne préjuge pas d'une éventuelle meilleure efficacité de la dose semanale dans des populations déficientes en fer, comme ceci est le cas dans les pays en développement.1407 - Results Of Surveys To Assess Iron Status In Europe.
Many studies have been undertaken to assess the iron status of Europeans. However, differences in dietary patterns, methodology, contraceptive choice, and epidemiologic factors lead to confounding factors that need consideration as the data from available studies are reviewed.
Revue générale sur les études de prévalence de la déficience en fer et de la surcharge en fer en Europe, avec passage en revue des facteurs de confusion à prendre en considération pour l'interprétation des différentes études.1408 - Efficiency Of The Iron Supplementation Programme For Pregnant Women In Jeneponto, Sulawesi, Indonesia.
An official iron supplementation programme for pregnant women in Jeneponto, South Sulawesi, Indonesia was assessed for efficiency. Data were collected in a cross-sectional study of 107 women in the second or third trimester of pregnancy from 18 villages. 47.7% of the women were anaemic, although 63.6% stated they had received prenatal care. Of the 68 women who had received prenatal care, 49 had obtained iron tablets. However, 32.7% of the 49 women who received iron admitted that they had not taken all of the tablets. Mean Hb levels of women in the second trimester who had received tablets was 9 g/l higher (p =0.049) than that of women who had not received tables. To improve the efficiency of the iron supplementation programme there must be an improvement in the coverage of pre-natal care, in the completeness of iron tablet distribution, and in efforts to assure that the pregnant women actually take the tablets given to them.
Article plutôt destiné aux chercheurs. Un programme de supplémentation par le fer des femmes enceintes indonésiennes s'avère efficace, sur le plan de leur niveau d'hémoglobine, chez celles qui ont reçu des tablettes de fer dans le cadre des soins anté-nataux. La compliance semble être un facteur majeur qui doit être pris en compte.1409 - Mechanism Underlying The Inhibitory Effect Of High Calcium Carbonate Intake On Iron Bioavailability From Ferrous Sulphate In Anaemic Rats.
The influence of high CaCO3 intake on the bioavailability of Fe from FeSO4 was assessed during Fe repletion of rats with Fe-deficiency-induced anaemia. Fe-deficient rats with a mean blood haemoglobin concentration of 4.1 mmol/l were fed on purified Fe-adequate diets containing either 6.2 or 25.0 g CaCO3/kg (ten rats per group). Haemoglobin repletion after 14 d was significantly depressed by high CaCO3 intake (9.5 v. 9.8 mmol/l for high and low CaCO3 intake respectively/ p = 0.03), as was apparent Fe retention (367 v. 552 µg/d during days 5-7, p </ 0.001/ 146 v. 196 µg/d during days 19-21, p </ 0.001). The concentration of Fe in the liquid phase of the proximal half of the small intestine was significantly lower in the high-CaCO3 group (3.71 v. 5.20 µg/g digesta/ p = 0.02). Mucosal uptake and mucosal transfer of Fe were determined with orally administered 59Fe and Cr as a non-absorbable marker. Mucosal transfer was significantly diminished by CaCO3 loading (90 v. 100% of mucosal uptake/ p = 0.04), whereas mucosal uptake was not. 59Fe retention values at 14 d after administration were not significantly different (57.6 v. 51.9 % / p = 0.14). Fe contents of liver and spleen were significantly decreased by high compared with low CaCO3 intake (879 v. 590 µg Fe in liver, p </ 0.001/ 92 v. 63 µg Fe in spleen, p </ 0.001). It is concluded that high intake of CaC03 depresses Fe bioavailability in rats. The CaCO3-induced decrease in Fe solubility in the digesta probably was associated with an increased efficiency of mucosal Fe uptake so that the amount of mucosal uptake remained unaltered. The CaCO3-induced decrease in Fe transfer through the mucosal cytoplasm and/or basolateral membrane may have been responsible for the concurrent decrease in Fe bioavailability.
Article plutot destiné à des chercheurs. Cette étude réalisée chez le rat anémié par carence en fer, et nourri avec des niveaux d'apports calciques différents, permet de mettre en évidence un effet négatif des régimes riches en calcium sur l'absorption du fer et le statut en fer des animaux. Les mécanismes en cause seraient une diminution de la solubilité du fer et une diminution du transfert du fer à travers le cytoplasme muqueux et/ou la membrane basolatérale.1410 - Plasma Transferrin Receptor Helps To Predict Iron Deficiency In The Anemia Of Chronic Disease.
A recent study by Ahluwalia and colleagues used a discriminant statistical analysis approach to determine that a combination of serum ferritin, plasma transferrin receptor concentration, and erythrocyte sedimentation rate was the optimal set of variables for differentiating iron deficiency and the anemia associated with chronic disease in a group of elderly women. Iron deficiency was defined as a significant response in hemoglobin concentration after iron supplementation. The findings of this study suggest that iron deficiency can be relatively common among elderly anemic women with rheumatoid arthritis. Use of these three biochemical measures should be clinically useful to differentiate iron deficiency in the anemia of chronic disease.
La carence en fer est relativement commune chez les femmes âgées atteintes d'arthrite rhumatoïde. Chez ces patients, l'utilisation d'une combinaison de 3 indicateurs (récepteurs circulants à la transferrine, ferritine sérique et vitesse de sédimentation) permet de diagnostiquer la carence en fer au cours de l'anémie des maladies chroniques.1411 - Exercise And Mineral Status Of Athletes: Calcium, Magnesium, Phosphorus, And Iron.
Calcium, magnesiurn, phosphorus, and iron are important to a wide variety of body functions, such as mineralization of bones, serving as cofactors to many enzyme systems, sustaining muscle and nerve excitation, and, in the case of iron, maintaining the oxygen carrying capacity of the blood. Many female athletes consume less calcium than the recommended dietary allowance (RDA). This is of concern because of the need to achieve peak bone mass during adolescence and the possible relationship of poor calcium intake to stress fractures. Athletes appear to have adequate magnesium and phosphorus status. However, those athletes who are on calorie-restricted diets may not be ingesting sufficient quantities of magnesium and possibly phosphorus. Limited data have suggested that magnesium status is indirectly related to strength improvement as well as the incidence of muscle cramps. Acute ingestion of phosphorus (phosphate loading) has been shown to improve aerobic capacity. Iron depletion is common in female athletes but similar to the general population. Iron supplements are of health benefit, but of questionable performance benefit, to those who are iron depleted and nonanemic. To maintain optimal status of these minerals, it is recommended that nutrient rich foods be ingested including dairy products and foods high in heme iron.
De nombreuses femmes athlètes ont des apports de calcium en dessous des apports nutritionnels recommandés, ce qui peut poser des problèmes en termes de minéralisation osseuse notamment chez les adolescentes. Celles ayant une restriction énergétique ont des apports en magnésium également insuffisants. La déficience en fer est largement répandue dans cette population. La consommation de produits laitiers et d'aliments à teneur en fer héminique élevée est recommandée pour assurer un statut minéral optimal dans ces minéraux pour cette population.1412 - Effects of environment upon fluoride content in nails of children"
Gas chromatography (GC) was evaluated as a method to estimate fluoride in nails of 5 groups of a total of 284 Polish school children 10 to 12 years old. Group I resided in the environs of an industrial plant for processing phosphorites and apatites/ their drinking water was not fluoridated. The drinking water of group II was artificially fluoridated at 0.64 mg/litre. Groups III, IV and V resided in localities with 400 000, 800 000 and 10 000 inhabitants with no factories and with non-fluoridated drinking water. A preliminary study using nails of single subjects estimated the reliability and repeatability of the GC method
RESULTS:
of the environmental study showed that F in nails of group I was significantly higher than in other groups.
Effet de facteurs environnementaux sur le contenu en fluor des ongles chez l'enfant. Par chromatographie gazeuse, on peut évaluer la quantité de fluor contenu dans les ongles. Cette étude a été faite en Pologne chez des enfants de 10 à 12 ans. Ceux-ci résidaient dans les environs d'une zone industrielle rejetant de grandes quantités de phosphore . Leur eau de boisson n'était pas fluorée. Un autre groupe recevait de l'eau artificiellement fluorée à 0,64 mg/l. Ce travail préliminaire a simplement montré que l'estimation du taux de fluor dans les ongles est valable et qu'il a un taux de répétabilité correct. Le fluor dans les ongles dans le groupe 1 proche de l'usine était significativement plus élevé que dans les autres d'où l'influence de l'environnement probable.1413 - Effects On Demineralization Of Enamel By Fluoridated Sucrose: A Pilot Study In An In Situ Caries Mode.
Blocks of human enamel, placed in removable partial dentures, were allowed to acquire natural plaque for seven days and were exposed extra-orally to a cariogenic challenge by repeated periods in a fluoride-sucrose solution. As a control, enamel blocks were exposed extra-orally to a sucrose solution. After two weeks of cariogenic challenge, the blocks were examined for mineral loss by quantitative microradiography on thin sections of the enamel. The results from six subjects showed that no significant effect on demineralization could be detected by the addition of fluoride corresponding to fluoride/sugar content of 1 mg/kg, 5 mg/kg, or 10 mg/kg (dry weight). One subject did not develop lesions at all, either with fluoride-sucrose or with sucrose exposure alone.
On a étudié par comparaison l'action du fluor dans une solution de sucrose par rapport à une solution de sucrose l'une pure, l'autre avec du fluorure ajouté à 1 mg, 5 mg ou 10 mg/Kg sur des préparations d'émail en culture et en dehors de l'organisme. Après deux semaines d'essai d'activité cario-génique, les blocs d'émail sont contrôlés l'un et l'autre, en fait, il n'y a pas d'effet significatif sur la déminéralisation lorsque du fluor est ajouté à la solution sucrée.1414 - Effects of fluoride-supplemented sucrose on experimental dental caries and dental plaque pH.
Sucrose, 5% and 10% (w/v), supplemented with between 0 and 5 ppm fluoride (F), was tested for its influence in vitro on plaque-induced experimental in vitro enamel caries and plaque pH. Plaque growth on bovine enamel was initiated from saliva inocula and sustained in a multiple plaque growth system for up to 31 days by means of a basal medium with periodic applications of sucrose or sucrose supplemented with F. Change in enamel mineralization was assessed, before and after plaque growth, by microhardness testing and microradiography/ pH was monitored with microelectrodes. It was found that enamel demineralization was inversely related to the F concentration in the range 2 to 5 ppm, for both 5% and 10% sucrose. Plaque pH responses were unaffected by the F supplements.
Etude expérimentale sur la croissance de la plaque de l'émail bovine sous l'influence d'apports de sucrose à 10 ou 20 % supplémenté avec du fluorure ( de 0 jusqu à 5 ppm). Les modifications de la minéralisation de l'émail sont étudiées avant et après la croissance de la plaque. le résultat la déminéralisation de l'émail est proportionnellement et inversement lié à la concentration de fluor entre les taux de 2 à 5 PPM pour l' apport de sucrose à 5 et 10 %. Par contre, la réponse du pH de la plaque n'est pas modifiée par ses suppléments.1415 - Fluoride and sugar intake among adults and youth in Mauritius: preliminary results.
The potential use of different vehicles for delivering fluoride to prevent dental caries has been discussed recently in Mauritius. Water fluoridation was found not to be feasible, and extending the fluoride tablet program would not be easy. Thus, sugar fluoridation as one possibility was considered. For these purposes, the average fluoride and sugar intake was estimated in Mauritius. The results are based on two studies--a Survey on Diet, Health and Lifestyle of Youth in Mauritius (1990) and the Mauritius Diet and Health Survey. Information was collected by trained interviewers using food-frequency and 24-hour-recall questionnaires. The daily total sugar intake, manufactured and natural, was found to be 62 g per day in young people and 50 g per day in adults. In the younger groups, daily frequencies of raw sugar, sweets, and biscuit (cookie) consumption were 1.5, 0.2, and 0.2 times a day, respectively. For adults, the mean daily frequency of consuming sugar-containing foods was 2.6 (SD = 1.3). The daily sucrose intake was rather high, representing about 10% of the daily energy intake. The fluoride levels of foods were calculated by use of Finnish and other available fluoride tables. The mean fluoride intakes per day were 0.64, 0.72, and 0.62 mg per day for 8-17-year-, 18-24-year-, and 30-64-year-old groups, respectively. The median fluoride intake for the oldest group was 0.62 mg/day. The estimated fluoride intake from food did not correspond with the proposed level for the prevention of caries (Murray, 1986) except for the 18-24-year-olds, where it might have been just above the lower recommended limit. However, further data based on analysis of the fluoride contents of Mauritian food samples, especially of whole daily diet, are needed.
A l'Ile Maurice, on entame des discussions sur les meilleurs moyens de lutter contre la carie dentaire. La fluorisation de l'eau n'est pas possible dans ce pays, pour des raisons stratégiques et culturelles. Les programmes de supplément par tablettes, laissées à l'appréciation des familles, a peu de chance d'être efficace. On a donc imaginé de fluorer le sucre. Le taux de sucre absorbé par les enfants et même les adultes est plutôt élevé. Il représente plus de 10 % de l'énergie ingérée quotidienne. Malgré tout, l'expérimentation montre que l'effet préventif n'est pas atteint, car l'apport de fluor est encore trop bas. Il y a donc lieu de poursuivre ces études.1416 - A Quater Century Of Changes In Oral Health In The United State.
This paper provides an overview of the oral health status of Americans since the 1960s. Data from seven national surveys, conducted between 1960 and 1987, have been presented. Estimates of coronal and root caries, periodontal diseases, and tooth loss were reviewed. In addition, data on edentulism and oral cavity and pharyngeal cancer were included. Although the purpose of this paper is descriptive rather than analytical, some important trends have been noted: The number of children who were free from dental caries increased dramatically between 1963 and 1987. By 1987, almost one-half of school children between the ages of 5 and 17 were caries-free.
Bonne mise au point.1417 - Osmoregulation, The Secretion Of Arginine Vasopressin And Its Metabolism During Pregnancy.
This review stresses changes in osmoregulation as well as the secretion and metabolism of arginine vasopressin during pregnancy, focusing on human gestation. Pregnant women experience a decrease in body tonicity, plasma osmolality decreasing immediately after conception to a nadir &tilde/10 mosmol/kg below non-pregnant levels early in pregnancy, after which a new steady state is maintained until term. Data from both human and rodent gestation have led to a formation of how these changes occur. The osmotic thresholds for thirst and antidiuretic hormone release decrease in parallel. Lowering the threshold to drink stimulates increased water intake and dilution of body fluids. Because arginine vasopressin (AVP) release is not suppressed at the usual level of body tonicity, the hormone continues to circulate and the ingested water is retained. Plasma osmolality declines until it is below the osmotic thirst threshold, and a new steady state with little change in water turnover is established. Pregnancy is characterized by increments in intravascular volume, but volume-sensing AVP release mechanisms appear to adjust as gestation progresses so that each new volume status is "sensed" as normal. The metabolic clearance of AVP increases fourfold, the rise paralleling that of circulating cystine aminopeptidase (vasopressinase), and enzyme produced by the placenta. Furthermore, the disposal rate of 1-deamino-8-D-AVP, and AVP analogue resistant to inactivation by vasopressinase, is unaltered in pregnancy. Thus, the increase in AVP''s metabolism and the high circulating aminopeptidase levels have been implicated in certain forms of transient diabetes insipidus that occur in late pregnancy. Finally, methanisms responsible for the altered osmoregulation in pregnancy are obscure, but chorionic gonadotropin and relaxin may be implicated in the changes.
Intéressant, mais données déjà acquises dans d'autres références de la base.1418 - Diabetes Insipidus In Pregnancy.
Diabetes insipidus (Dl) and pregnancy may coexist and, when they do, present challenging diagnostic and therapeutic problems. Women with preexisting central DI usually experience increased thirst and require additional hormone replacement. Women with nephrogenic Dl have an increased water turnover. Of interest is a group of women with transient Dl of gestation. In some of these patients, central DI is brought to the fore by increases in water turnover during pregnancy as well as increments in the metabolic clearance of arginine vasopressin (AVP), especially near term. Others have a "vasopressin-resistant" form of the disease, which in one case followed by us appeared to be due to marked increments in circulating cystine-aminopeptidase (vasopressinase). This patient''s DI was resistant to pitressin, but she concentrated her urine when given dDAVP. Her vasopressinase levels 2 weeks postpartum were still several-fold those of normal term gravidas. Her DI remitted, and she concentrated her urine appropriately 2 months postpartum. This article reviews the different forms of DI peculiar to pregnancy.
Intéressant, mais revue de la littérature à propos d'un seul cas clinique.1419 - Changes In The Metabolic Clearance Of Vasopressin And In Plasma Vasopressinase Throughout Human Pregnancy.
Metabolic clearance rates (MCR) of arginine vasopressin (AVP) were measured serially in five women starting before conception, during gestational weeks 7-8 (early), 22-24 (middle), and 36-38 (late pregnancy), and again 10-12 wk postpartum. Hormonal disposal rates were determined after water loading to suppress endogenous AVP release using a constant infusion method designed to achieve three different steady-state concentrations of plasma AVP (PAVP) on each test occasion. Dose schedules were altered in mid- and late pregnancy to obtain comparable AVP levels at each stage of the protocol. Prehydration decreased plasma osmolality sufficiently to suppress AVP release, as circulating AVP-neurophysin measured serially in three of the women was undetectable. The MCR of AVP was similar before conception (0.75±/0.31, 0.79±/0.34, and 0.76±/0.28 liters/min at PAVP of 2.6±/1.9, 4.7±/2.4, and 8.3±/3.9 pg/ml), in early pregnancy (0.89±/0.34, 0.97±/0.04, and 0.95±/0.40 liters/min at PAVP of 2.2±/2.1, 3.9±/3.2, and 7.9±/3.4 pg/ml), and postpartum (0.70±/0.21, 0.69±/0.24, and 0.75±/0.20 liters/min at PAVP 3.5±/1.8, 5.1±/3.7, and 9.1±/4.2 pg/ml). Values at mid-pregnancy (2.8±/1.3, 3.0±/1.2, and 2.7±/1.2 liters/min at PAVP 2.3±/2.2, 4.0±/3.6, and 7.7±/3.9 pg/ml) and late pregnancy (3.2±/1.4, 3.3±/1.4, and 2.9±/1.2 liters/min at PAVP 1.9±/2.0, 3.8±/2.6, and 7.4±/4.1 pg/ml) increased 3-4-fold (all p </ 0.01). Plasma vasopressinase, undetectable at 7-8 gestational wk, increased markedly by mid- and slightly more by late gestation. Finally, relationships between PAVP and urine osmolality were similar before, during, and after pregnancy. We conclude that marked increments in the MCR of AVP occur between gestational weeks 7 and 8 and mid-pregnancy, which parallel the period of greatest rise in both trophoblastic mass and plasma vasopressinase. There was no evidence of a renal resistance to AVP during gestation.
Intéressant article corrélant les modifications de la régulation du métabolisme de l'eau chez la mère et l'activité de la vasopressinase.1420 - Intake Of Tapwater And Total Water By Pregnant And Lactating Women.
BACKGROUND:
Despite theoretically higher requirements for water due to physiologic demands of pregnancy and lactation, little is of actual ranges of intake in pregnant and lactating women.
METHOD:
Population-based estimates of total water and tapwater intake in women of reproductive age were derived using data from the 1977-78 USDA Nationwide Food Consumption Survey. Three-day average intakes were calculated for 188 pregnant women, 77 lactating women, and 6,201 non-pregnant, non-lactating control women.
RESULTS:
Total water intake (mean ±/ SD) was, 1,940 ±/ 686 g/day (median 1,835) for control women, 2,076 ±/ 743 g/day (median 1,928) for pregnant women and 2,242 ±/ 658 g/day (median 2,164) for lactating women. Tapwater intake was 1,157 ±/ 635 g/day (median 1,065) for control women, 1,189 ±/ 699 g/day (median 1,063) for pregnant women, and 1,310 ±/ 591 g/day (median 1,330) for lactating women. Total water intake was equal to or greater than 3,000 g/day among 7 percent of control women, 11 percent of pregnant women, and 13 percent of lactating women. Tapwater intake was equal to or greater than 2,000 g/day among 10 percent of control women, 15 percent of pregnant women, and 8 percent of lactating women.
CONCLUSION:
These results should be useful in estimating amounts of nutrients and toxic substances that women of reproductive age obtain through the water supply.
A conserver absolument même s'il peut régner quelques doutes sur les qualités méthodologiques de l'étude.1421 - Volume Homeostasis And Osmoregulation In Human Pregnancy.
This chapter reviews alterations in volume and sodium homeostasis and osmoregulation during human pregnancy. Pregnant women undergo extracellular and plasma volume increases of 50-70%, and these changes accompany market cumulative sodium retention shared by both mother and fetus. Pregnancy alters several factors with opposing effects on renal salt handling/ however, mechanisms by which gestational sodium accumulation and volume expansion are achieved remain obscure. Furthermore, despite substantial increases in absolute blood volume, considerable uncertainty exists as to how this volume is sensed, particularly in late pregnancy when a rapid increase in volume is associated with decreases in peripheral resistance and blood pressure. Attempts to assess ''effective'' intravascular volume suggest that pregnant women sense their volume as normal. -- Osmoregulation is also changed,. Body tonicity and the osmotic thresholds for AVP release and thirst decrease by about 10 mosm/kg. The mechanisms responsible for the osmoregulatory changes are obscure. Haemodynamic stimuli such as decrements in blood pressure and of ''effective circulating volume'' do not seem to account for them. Of the many increments in hormone levels known to accompany gestation, only hCG has so far been implicated in these changes. -- Pregnant women experience three-to fourfold increments in AVP disposal, rates between early and mid pregnancy/ this may be caused by the striking rise in circulating cystine-aminopeptidase (vasopressinase) which also occurs during this period. The increments in MCR may be one reason why the hormonal response to a given osmotic stimulus appears to decrease in late pregnancy. -- All these alterations permit speculation on the manner in which the decrease in Posm occurs and is maintained within narrow limits. Lowering the osmotic threshold to drink stimulates a rise in water intake and dilution of body fluids. Since AVP release is not suppressed at the usual level of hypotonicity, AVP continues to circulate at levels sufficient to permit water retention. Posm continues to decline until it decreases below the new osmotic thirst threshold, when a new steady state is established. At this point water turnover, too, resembles that in the non-pregnant state. -- The change in MCR and the marked increment in plasma vasopressinase may explain certain observations regarding disordered water metabolism during late pregnancy. These are the transient DI syndromes due either to subclinical hypothalamic disease or to a disorder peculiar to pregnancy which is AVP-resistant but dDAVP-responsive/ the latter analogue resists degradation by vasopressinase.
Revue générale sur l'osmorégulation pendant la grossesse humaine.1422 - Osmoregulation Of Thirst And Vasopressin During Normal Menstrual Cycle.
Changes in osmoregulation during normal menstrual cycle were examined in 15 healthy women. In 10 women, studied repetitively during two consecutive menstrual cycles, basal plasma osmolality, sodium, and urea decreased by 4 mosmol/kg, 2 meq/1, and 0.5 mM, respectively (all p </ 0.02) from the follicular to luteal phase. Plasma vasopressin, protein, hematocrit, mean arterial pressure, and body weight did not change. In five other women, diluting capacity and osmotic control of thirst and vasopressin release were assessed in follicular, ovulatory, and luteal phases. Responses of thirst and/or plasma vasopressin, urine osmolality, osmolal and free water clearance to water loading, and infusion of hypertonic saline were normal and similar in the three phases. However, the plasma osmolality at which plasma vasopressin and urine osmolality were maximally suppressed as well as calculated osmotic thresholds for thirst and vasopressin release were lower by 5 mosmol/kg in the luteal than in the follicular phase. This lowering of osmotic thresholds for thirst and vasopressin release, which occurs in the luteal phase, is qualitatively similar to that observed in pregnancy and should be taken into account when studying water balance and regulation of vasopressin secretion in healthy cycling women.
Intéressant papier qui suggère, dans l'espèce humaine, une possible régulation par les hormones stéroïdes de l'équilibre hydroélectrolytique.1423 - Water Metabolism And Vasopressin Secretion During Pregnancy.
Alterations in water handling and osmoregulation are among the earliest and most striking physiologic changes that occur during pregnancy. This chapter reniews these alterations, emphasizing changes in the control of secretion of the antidiuretic hormone arginine vasopressin (AVP). In addition, polyuria complicating pregnancy is discussed, focusing on possible aetiologies of this interesting clinical problem.
Bonne référence mais redite de publications faites par les mêmes auteurs.1424 - Osmoregulatory Adaptation In Pregnancy And Its Disorders.
The physiological osmoregulatory adaptations of pregnancy include decreased thresholds for both thirst and AVP secretion and increased MCR for AVP. The combined effects of these changes may unmask sub-clinical DI. In view of the altered relationship between serum osmolality and thirst, caution is required in investigating thirst and polyuria in pregnancy lest an erroneous diagnosis of psychogenic polydipsia be made.
Intéressant pour la pratique des investigations paracliniques en cas de suspicion de diabète insipide au cours de la grossesse.1425 - The Effects Of Antidiuretic Hormone On Urine Flow And Composition In The Chronically-cannulated Ovine Fetus.
The fetuses of nine pregnant ewes were chronically cannulated between 86 and 130 days with cannulae in one carotid artery, one jugular vein, the fetal bladder and the amniotic cavity. The effects of infused AVP on fetal urine flow rate and composition were studied. A dose of 35 pmol./h always caused an increase in urine osmolality and a decrease in flow rate and free water clearance without change in blood pressure. Higher doses (140 pmol./h) were significantly pressor and caused increased excretion of sodium, chloride, urea and creatinine. Although this dose always caused an increase in urine osmolality, in five experiments the flow rate also rose. It is concluded that the ovine fetus has the ability to control its own urine flow and composition, and possibly also amniotic fluid volume and composition.
Expérimentation animale sur un nombre limité d'observations mais qui démontre l'action de la vasopressine sur le rein fœtal.1426 - Xiii. The Effect Of The Administration Of Fluids Intravenously To Mothers Upon The Concentrations Of Water And Electrolytes In Plasma Of Human Fetuses.
The normal relationship between fetal and maternal plasma of total osmotic pressures and concentrations of sodium and potassium were determined in women with uncomplicated pregnancies at full term. The total osmotic pressure of fetal plasma was found to be 3.6 mOsm/kg of water higher than the maternal, probably not representing a physiologically significant difference. No significant difference in sodium concentrations of plasma was found. The potassium concentration in the fetal plasma was 0.7 meq/l higher than in the maternal plasma. The administration of 5% glucose or 20% mannitol intravenously to pregnant women prior to delivery was shown to have a prompt effect upon the total osmotic pressure and concentration of sodium and total protein of fetal plasma.
Article ancien, mais d'intérêt, montrant les relations de osmolalités plasmatiques maternelles et fœtales.1427 - Transient Oligohydramnios In A Severely Hypovolemic Gravid Woman At 35 Weeks'' Gestation, With Fluid Reaccumulating Immediately After Intravenous Maternal Hydration.
Oligohydramnios is known to accompany chronically hypovolemic maternal conditions, usually preeclampsia, pregnancy-induced hypertension, and intrauterine growth retardation. A case is presented in which an acute maternal hypovolemic situation with oligohydramnios was treated vigorously with intravenous fluid hydration/ ultrasonography documented immediate reaccumulation of normal amniotic fluid volume.
Intéressant pour la relation volume maternel - volume du liquide amniotique, mais une seule observation clinique.1428 - Concentration Thresholds For Fetal Swallowing And Vasopressin Secretion.
In adults, plasma osmolality thresholds for hypernatremia-induced arginine vasopressin (AVP) secretion are similar or less than thresholds for stimulation of thirst. In the fetus, the thresholds for swallowing stimulation and AVP secretion have not been defined. Fetal swallowing and AVP secretory response to hypertonic NaCl and urea were determined in six fetuses (130 ±/ 1 days) chronically prepared with thyrohyoid, nuchal and thoracic esophagus, and diaphragm electromyograms (EMG), an esophageal flow probe, and vascular catheters. Fetuses received intracarotid injections (0.15 ml/kg) of increasing concentrations of NaCl (0.15, 0.30, 0.45, 0.60, 0.75, and 0.90 M), administered at 2-min intervals. A swallow was defined as a coordinated time-sequence of fetal thyrohyoid, nuchal esophagus, and thoracic esophagus EMG activity. The threshold saline concentration for swallowing was defined as the minimum NaCl dose eliciting swallow responses (within 20 s) after four of five injections at each dose. During a 2-h control period swallowing averaged 25.0 ±/ 10.1 ml/h and 39.4 ±/ 14.6 swallows/h. The mean NaCl threshold concentration for swallowing stimulation was 0.56 ±/ 0.06 M. Fetal plasma AVP (2.6 ±/ 0.9 pg/ml) increased significantly at the maximum subthreshold (7.6 ±/ 4.0 pg/ml) and the threshold NaCl concentration (8.2 ±/ 4.0 pg/ml) that stimulated swallowing. On a subsequent day, equiosmolar urea injections increased plasma AVP (from 2.2 ±/ 0.7 to 7.6 ±/ 2.6 pg/ml) but had no effect on swallowing activity. Fetal mean arterial blood pressure increased after injections of threshold saline and urea concentrations. Fetal arterial blood osmolality and sodium concentration did not change during any study. These studies demonstrate fetal swallowing stimulation by intracarotid saline injections. The stimulation of AVP secretion before fetal swallowing indicates a greater osmotic sensitivity for AVP secretion than thirst during fetal development. Hypertonic urea stimulation of secretion though not swallowing is consistent with discrete osmoreceptors for AVP secretion and thirst.
L'espèce n'est pas mentionnée : brebis ? Les auteurs voulaient vérifier que chez le fœtus (comme chez l'adulte) le seuil d'hyperosmolarite induite par injections intracarotidiennes de NaCl ou d'urée hypertonique est plus bas pour la sécrétion d'AVP que pour la réponse dipsique (déglutition vérifiée par canules et EMG diaphragmatique.) Ce fut le cas. En plus l'urée hypertonique n'a entraîné que des réponses d'AVP, ce qui leur fait dire que les osmorécepteurs pour l'AVP sont différents de ceux de la soif.1429 - Maternal Dehydration-rehydration: Fetal Plasma And Urinary Responses.
Pregnant women may be exposed to exercise, thermal, or gastrointestinal (hyperemesis) water loss, all of which commonly induce a >/10 mosmol increase in plasma osmolality. Although fetal osmolality is dependent on maternal osmolality, the impact of maternal dehydration and subsequent maternal rehydration on the fetus has not been explored. Five pregnant ewes with singleton fetuses (136 ±/ 1 day) were water deprived for 36 h resulting in a significant increase in plasma osmolality (298 ±/ 3.4 to 313 ±/ 5.0 mosmol). In response to maternal dehydration, fetal plasma osmolality (297.0 ±/ 4.1 to 309.3 ±/ 4.1 mosmol), arginine vasopressin (AVP) levels (1.5 ±/ 0.2 to 7.9 ±/ 1.0 pg/ml), hematocrit (35.1 to 38.6%), and urine osmolality (161.3 ±/ 10.7 to 348.9 ±/ 21.9 mosmol) significantly increased. Subsequently, ewes were rehydrated over 4 h with intravenously infused 0.45% saline (20 ml./kg./h). In response to maternal rehydration, maternal and fetal plasma osmolality decreased to basal values (298.9 ±/ 3.2 and 300.1 ±/ 3.8 mosmol, respectively) and fetal glomerular filtration rate (1.72 ±/ 0.30 to 3.08 ±/ 0.66 ml/min) and urine volume significantly increased (0.33 ±/ 0.02 to 0.71 ±/ 0.13 ml/ min). However, fetal hematocrit (37.4%), plasma AVP (3.1 ±/ 0.9 pg/ml), and urine osmolality (255.4 + 28.8 mosmol) did not return to basal levels during the observation period. These results demonstrate fetal hyperosmolality, blood volume contraction, AVP secretion, and altered urine production in response to maternal dehydration. Despite maternal rehydration and normalization of maternal and fetal plasma osmolality, fetal endocrine and fluid responses are prolonged. These results suggest that episodic dehydration during pregnancy may significantly alter fetal and amniotic fluid dynamics.
Très intéressant pour la connaissance de la physiologie du liquide amniotique mais article ancien et expérimentation animale.1430 - Maternal/fetal Dehydration: Prolonged Effects And Responses To Oral Rehydration.
Dehydration induces marked alterations in maternal-fetal fluid homeostasis and accompanying fetal endocrine responses. We sought to determine if the increase in fetal plasma arginine vasopressin (AVP) levels during maternal dehydration is mediated by fetal plasma hypolemia in addition to hyperosmolality and to examine maternal and fetal plasma atrial natriuretic factor (ANF) responses to maternal dehydration and oral rehydration. Seven pregnant ewes (127 ±/ 1 day) were water deprived for 72-96 h, and five of these were orally rehydrated. Dehydration induced significant increases in maternal plasma osmolality (pOSM) (300 ±/ 2 to 325 ±/ 8 mosmol/kg) and AVP (3.0 ±/ 0.4 to 18.9 ±/ 4.0 pg/ml), and decreases in plasma ANF levels (28.1 ±/ 3.1 to 19.7 ±/ 3.1 pg/ml). Fetal pOSM (293 ±/ 3 to 314 ±/ 4 mosmol/kg), AVP (2.5 ±/ 0.6 to 8.1 ±/ 4.8 pg/ml), and urinary fractional sodium excretion increased significantly, whereas plasma ANF and fetal blood volume did not change. After maternal water access maternal plasma AVP decreased rapidly in comparison to the gradual decrease in maternal pOSM. Fetal plasma AVP levels did not change significantly and fetal pOSM decreased more slowly than maternal pOSM. Fetal plasma ANF increased in association with increased urine flow and glomerular filtration rate after maternal rehydration. These data indicate marked differences in fetal and maternal plasma ANF and AVP responses with dehydration-induced increases in fetal plasma AVP being secondary to plasma hyperosmolality, rather than hypovolemia. Rapid suppression of maternal plasma AVP may contribute to the slower equilibration of fetal pOSM during oral, as compared with intravenous, maternal rehydration.
Intéressant mais expérimentation animale.1431 - Amniotic Fluid Volume And Its Relationship To Fetal Fluid Balance: Review Of Experimental Data.
The studies described above collectively suggest that, whenever there is a decrease in fluid balance in the fetus, both fetal urine flow and tracheal secretion into the amniotic space are decreased. Conversely, when fetal hydration is increased, both urine and tracheal flows into the amniotic fluid may be increased. These observations suggest the hypothesis that, except under pathological conditions, aberrations in amniotic fluid volume may be the consequence of the existing state of hydration of the fetus. In addition, it appears that under many circumstances, these deviations from normal in fetal fluid balance may be due to maternal influences. Of course, the concept that fetal fluid balance is the primary factor determining amniotic fluid volume needs to be modified to incorporate transmembrane fluxes. However, these fluxes have yet to be documented as they relate to amniotic fluid volume and its regulation.
Synthèse intéressante des relations entre l'hydratation fœtale et le volume du liquide amniotique.1432 - Increase In Fetal Hydration During Long-term Intraamniotic Isoltonic Saline Infusion.
The purpose of this study was to determine whether a long-term infusion of saline into the amniotic space alters amniotic fluid volume or fetal fluid balance. Isotonic saline solution was infused continuously at a rate of 1 L/day for 3 days into the amniotic cavity of eight fetal sheep, resulting in an increase in amniotic fluid volume that averaged 50% of the infused volume. This amniotic volume expansion persisted during a 36-hour recovery period. During the infusion, fetal urine flow increased by 600 ml/day and was accompanied by a significant rise in renal electrolyte excretion. Fetal swallowing of amniotic fluid rose in parallel by 600 ml/day and fetal blood volume significantly increased by 5%. Maternal parameters were not changed during the experimental or recovery periods. Thus the present data suggest that direct intraamniotic infusion on a long-term basis in pregnant sheep appears to be an effective method for increasing fetal hydration and amniotic fluid volume.
Très intéressant car réponse partielle sur la dynamique du liquide amniotique. Mais expérimentation animale.1433 - Fetal-maternal Fluid And Electrolyte Relations During Chronic Fetal Urine Loss In Sheep.
Our aim was to determine the effects of prolonged removal of fetal urine during late gestation on fetal-maternal fluid and electrolyte relationships. We measured the volume and composition of fetal urine and amniotic and allantoic fluids and the composition of fetal and maternal plasma in sheep before and during continuous urine drainage, which began at 130 days of gestation and continued until the onset of labor/ a control group was also studied. The response to fetal urine drainage occurred in two phases. In the "acute" phase (1-3 days), amniotic and allantoic fluid volumes decreased significantly, presumably due to their reabsorption into the fetal chorionic circulation or swallowing of amniotic fluid by the fetus. During the "chronic" phase, starting 3-5 days after urine drainage, a significant reversal in the transplacental osmotic gradient occurred due to a decrease in maternal plasma osmolality. During the entire drainage period (14.1 ±/ 1.1 days, mean ±/ SE, n = 5) at least 542 ml/day of water and 24 mmol/day of electrolytes passed from the mother into the fetal circulation and fetal plasma osmolality was unchanged. We conclude that, despite the loss of substantial water and electrolytes, the fetus is able to maintain its growth and fluid and electrolyte homeostasis by obtaining water and electrolytes initially from the amniotic and allantoic fluids and subsequently from its mother. The movement of water and electrolytes to the fetus would have been facilitated by the reversed transplacental osmotic gradient.
Intéressant pour les conséquences physiopathologiques de l'interruption de la diurèse fœtale, mais expérimentation animale.1434 - Acute Maternal Hydration In Third-trimester Oligohydramnios: Effects On Amniotic Fluid Volume, Uteroplacental Perfusion, And Fetal Blood Flow And Urine Output.
OBJECTIVE:
Our purpose was to determine whether acute maternal hydration in pregnancies with third-trimester oligohydramnios (1) Increases amniotic fluid index and hourly tetal urine production rate and (2) alters uteroplacental perfusion and fetal blood flow. --
STUDY DESIGN:
Ten women with third-trimester oligohydramnios (amniotic fluid index &le/5 cm) and 10 controls with normal amniotic fluid volume (amniotic fluid index >/7 cm) were prospectively recruited for this study. Maternal plasma and urine osmoblity amniotic fluid index hourly tetal urine production rate, and Doppler flow velocimetry of maternal uterine artery and fetal umbilical descending aorta, middle cerebral, and renal arteries were determined before and after oral hydration by having the patient drink 2 L of water over 2 hours. --
RESULTS:
There was a significant reduction in maternal plasma (p hydration. Hydration increased amniotic fluid volume in women with oligohydramnios (mean change in amniotic fluid index 3.2 cm, 95% confidence intervals 1.1 to 5.3/ p fluid volume (mean change in amniotic fluid index -2.0, 95% confidence intervals -4.1 to +0.2). The hourly fetal urine production rate however did not increase in either group (mean change in hourly fetal urine production rate 3.5 ml/hr, 95% confidence intervals -11.7 to +18.7 and -6.8 ml/hr, 95% confidence intervals -2.9 to -10.7, respectively). Hydration was associated with an increase in uterine artery mean velocity in the oligohydramnios group (mean change in mean velocity 16.7 cm/sec, 95% confidence intervals 8.0 to 25.3/ p confidence intervals -19.7 to +22.1). There was no change in pulsatility index or in velocity in any of the tetal vessels studied in either group. --
CONCLUSION:
Short-term maternal oral hydration increases the amniotic fluid index in women with third-trimester oligohydramnios. Although the mechanism for this effect remains unclear, it could not be accounted for by fetal urination in this study but instead was associated with improved uteroplacental perfusion.
Voici une des toutes premières études sur l'hyperhydratation maternelle et l'augmentation de la quantité de liquide amniotique au 3ème trimestre de la grossesse en cas d'oligoamnios. Cet article a ouvert la voie sur les travaux touchant à la pathologie materno-foetale. Il reste à montrer, et c'est un long travail, que la morbidité foetale et néonatale pourrait en être améliorée.1435 - Serial Evaluation Of Vasopressin Release And Thirst In Human Pregnancy - Role Of Human Chorionic Gonadotrophin In The Osmoregulatory Changes Of Gestation.
Serial studies were designed to characterize changes in osmoregulation throughout gestation. Eight women underwent a 2-h infusion of hypertonic saline before conception, during gestational weeks 5-8,10-12, and 28-33, and then 10-12 wk post-partum. Basal plasma osmolality (Posmol) was already significantly decreased by 5-8 wk (p </ 0.001) and remained 10 mosmol.kg -1 below nonpregnant values throughout pregnancy. The apparent threshold for AVP release (defined as the abscissal intercept of the regression line relating plasma AVP [PAVP] to Posmol) was also decreased significantly throughout gestation, as was the osmotic threshold for thirst (derived from analogue scales relating desire to drink to Posmol). The decrement in osmotic thirst threshold appeared to precede that for AVP release, and consistent with this 24-h urine volumes were significantly greater at 5-8 wk gestation (P</0.05). The slopes of each regression equation defining PAVP vs. Posmol (whose r values ranged from 0.79 to 0.99), very reproducible before and after pregnancy, were similar at 5-8 and 10-12 wk, but were markedly reduced in the third trimester (p </ 0.001). These volunteers had randomly undergone an additional infusion before conception (both tests in the luteal phase of the menstrual cycle) when 10,000 IU of human chorionic gonadotrophin (hCG) had been given intramuscularly over a 5-d period. Serum hCG values between 0.2 and 3.3 U./ml were lower than usually seen in pregnancy, but the osmotic thresholds for AVP release and thirst decreased by 3 and 4 mosmol./kg, respecti</ (P</ 0.05). Finally we studied a patient with a molar pregnancy in whom thresholds for hormone release and thirst were both decreased to values resembling normal gestation and remained so for &tilde/6 wk postevacuation, only normalizing when hCG had virtually disappeared from her serum. In contrast, thresholds increased within the first two puerperal weeks in two women with normal pregnancies. These data demonstrate (a) osmotic thresholds for both AVP release and thirst decrease within the very first gestational weeks/ (b) increment in PAVP per unit increase in Posmol is reduced late in gestation/ and (c) hCG may be involved in the osmoregulatory changes of pregnancy.
Etude essentielle car met en évidence le rôle d'HCG dans les modifications de la régulation de l'osmolarité plasmatique au cours de la grossesse.1436 - Relationship Between Amniotic Fluid Volume And Maternal Plasma Volume Expansion.
Amniotic fluid and maternal plasma volumes were estimated in high-risk obstetric patients suspected of being hypovolemic. Excluding cases of intrinsic maternal or fetal disease, there were good (p </ 0.001) correlations between maternal plasma volume expansion and amniotic fluid volume. In the presence of oligohydramnios, there is usually maternal hypovolemia, and vice versa. Oligohydramnios may often be corrected by vigorous maternal plasma volume expansion, which is sometimes indicated in the treatment of cases of fetal distress. It is presumed that only when maternal plasma volume expansion is normal, is uterine perfusion sufficient to provide amniotic fluid formation in normal amounts. The varying amounts of amniotic fluid seen in normal pregnancies at term probably reflect the varying fetal activities of swallowing and voiding.
Bon article de base montrant les relations entre le volume plasmatique maternel et le volume du liquide amniotique.1437 - The Missing Link In Amniotic Fluid Volume Regulation: Intramembranous Absorption.
Although fetal urine output and swallowing are major contributors to amniotic fluid regulation, other pathways for fluid movement must be involved in the regulation of amniotic fluid volume because many studies report fetal urine output to be greater than swallowing. This study was designed to examine the possibility of fluid transfer between the amniotic cavity and the fetal blood that perfuses the fetal membranes and surface of the placenta in the ovine fetus. We injected warmed distilled water into the amniotic fluid in three groups of chronically catheterized fetal sheep. In normal fetuses, there was rapid absorption of the water into the fetal circulation, resulting in highly significant decreases in fetal osmolality, plasma electrolytes, and heart rate as well as increases in arterial pressure and fetal hemolysis. Concomitantly, there was a small, delayed fall in maternal osmolality. In a second group of fetuses with ligated esophagi, these same responses occurred except that the fetal osmolality and electrolyte changes occurred earlier and were significantly greater. In a third group of fetuses killed just before the water injection, maternal osmolality was unchanged. These data suggest the intramembranous pathway as a major route of amniotic fluid absorption in the ovine fetus. In addition, esophageal ligation appears to augment the conductance of this pathway, as evidenced by a significantly greater estimated filtration coefficient and rate of water absorption in the ligated animals than in controls. Finally, the transmembranous pathway directly to the mother does not appear to be a major route.
Expérimentation animale. Permet de discuter du rôle des membranes amniochoriales dans la résorption du liquide amniotique.1438 - Maternal Dehydration: Impact On Ovine Amniotic Fluid Volume And Composition.
Maternal dehydration consistent with mild water deprivation or moderate exercise results in maternal and fetal plasma hyperosmolality and increased plasma arginine vasopressin (AVP). Previous studies have demonstrated a reduction in fetal urine and lung fluid production in response to maternal dehydration or exogenous fetal AVP. As fetal urine and perhaps lung liquid combine to produce amniotic fluid, maternal dehydration may affect the amniotic fluid volume and/or composition. In the present study, six chronically-prepared pregnant ewes with singleton fetuses (128 ±/ 1 day) were water deprived for 54 h to determine the effect on amniotic fluid. Maternal plasma osmolality (306.5 ±/ 0.9 to 315.6 ±/ 1.9 mOsm/kg) and AVP (1.9 ±/ 0.2 to 22.2 ±/ 3.2 pg/ml) significantly increased during dehydration. Similarly, fetal plasma osmolality (300.0 ±/ 0.9 to 312.7 ±/ 1.7 mOsm/kg) and AVP (1.4 ±/ 0.1 to 10.4 ±/ 2.4 pg/ml) increased in parallel to maternal values. Amniotic fluid osmolality (276.8 ±/ 5.7 to 311.6 ±/ 6.5 mOsm/kg) and sodium (139.8 ±/ 4.8 to 154.0 ±/ 5.4 mEq/l) and potassium (9.1 ±/ 1.3 to 13.9 ±/ 2.4 mEq/l) concentrations increased while a significant (35%) reduction in amniotic fluid volume occurred (871 ±/ 106 to 520 ±/ 107 ml). These results indicate that maternal dehydration may have marked effects on maternal-fetal-amniotic fluid dynamics, possibly contributing to the development of oligohydramnios.
Expérimentation animale bien conduite qui démontre la relation entre déshydratation maternelle et oligoaminos.1439 - The Effect Of Maternal Fluid Intake On The Volume And Composition Of Fetal Urine.
The effects on fetal renal function of restricting maternal water intake to 1 l/day for 6 days was investigated in 7 chronically-catheterized fetuses (gestation age 118-131 days). Restriction of water intake caused a significant decrease in maternal urine flow rate and significant increases in maternal plasma and urinary osmolality. -- Fetal renal function was investigated on the third and sixth days of the period of restricted maternal intake of water. Urine flow rate from the fetus was depressed significantly, and urinary osmolality increased significantly. The glomerular filtration rate remained unchanged, and free water clearance was decreased. These changes indicate increased water reabsorption in the distal parts of the nephron, probably consequent upon increased circulating levels of antidiuretic hormone. In 3 fetuses whose mothers subsequently had free access to water, these changes in urine flow rate and free water clearance that occurred during water restriction were reversed. There was an inverse correlation between maternal plasma osmolality and fetal free water clearance corrected for glomerular filtration rate. It is concluded that when water intake by a pregnant animal is restricted, the availability of water to the fetus is reduced and fetal sheep respond by producing a concentrated urine.
Expérimentation animale sur les effets d'une restriction hydrique sur les fonctions rénales maternelles et fœtales.1440 - Maternal Hydration Increases Amniotic Fluid Index.
Although adequate amniotic fluid (AF) volume is considered an important aspect of fetal well-being, the etiology of decreased AF volume is not well understood. A randomized blinded trial was designed to examine our hypothesis that maternal hydration would increase the AF index in women with low AF indexes. Women seen in our testing centers were randomized into control or hydration groups. The control group was instructed to drink their normal amount of fluid/ the hydration group was instructed to drink 2 L of water, in addition to their usual amount of fluid, 2-4 hours before the post-treatment AF index. The women returned for the post-treatment AF index the same or following day. The mean post-treatment AF index was significantly greater in the hydration group (6.3 versus 5.1/ p </ .01), as was the mean change in AF index (post-treatment AF index - pre-treatment AF index: 1.5 versus 0.31/ p </ .01). These findings suggest that maternal oral hydration increases AF volume in women with decreased fluid levels.
Etude contrôlée qui montre qu'une hyperhydratation maternelle augmente le volume du liquide amniotique.1441 - Maternal Hydration Increases Amniotic Fluid Index In Women With Normal Amniotic Fluid.
OBJECTIVE:
To test the hypothesis that maternal oral hydration would increase the amniotic fluid (AF) index in pregnancies with normal AF. --
METHOD:
Forty women with a normal AF index (7.0-24.0 cm) were randomized to either the control or hydration group. Women in the hydration group drank 2 L of water and returned for the post-treatment AF index in 4-6 hours, whereas women in the control group drank only 100 mL of water during the same time period. The investigator performing the AF index was blinded to the subject''s group. The pre- and post-treatment AF indexes and maternal urine specific gravities were compared between the groups. --
RESULTS:
The mean AF index in the hydration group increased significantly by 3.0 ±/ 2.4 cm (P &le/ .0001) whereas it declined significantly by 1.5 ±/ 2.7 cm in the control group (P &le/ .02). The maternal urine specific gravities also changed significantly in the expected direction, with those in the hydration group decreasing and those in the control group increasing (P &le/ .0001). There was a regression coefficient of -0.6 (P &le/ .0001) between the change in urine specific gravity and the change in AF index. The mean time between the pre- and post-treatment AF indexes was not different between the groups. --
CONCLUSION:
Maternal oral hydration increased the AF index by approximately 16%, whereas fluid restriction decreased the AF index by 8% in women with normal AF. These findings support previous data that maternal hydration increased the AF index by 31% in women with decreased AF and suggest that maternal fluid volume or osmolality may have a role in maintaining the AF volume.
Voici la première étude qui montre l'effet positif de l'hydratation maternelle surla quantité de liquide amniotique quand celui-ci est normal. Elle montre aussi l'effet néfaste de la restriction hydrique sur celui-ci. Cette étude a ouvert une voie qui aura de nombreuses applications.1442 - The Relation Betwen Pulmonary Hypoplasia And Amniotic Fluid Volume : Lessons Learned From Discordant Urinary Tract Anomalies In Monoamniotic Twins.
BACKGROUND:
Adequate amniotic fluid (AF) volume is one of several factors felt to be essential for normal lung development. Renal agenesis and urinary tract obstruction usually result in oligohydramnios and pulmonary hypoplasia. -- Case: Two sets of monoamniotic twins with discordant urinary tract anomalies were seen. One twin in each set had anomalies that in a singleton or diamniotic pregnancy would likely have resulted in fetal pulmonary hypoplasia and subsequent death. However, neither of these infants had pulmonary hypoplasia. One infant is unique in being the first case reported of normal pulmonary function and survival despite the anomaly. --
CONCLUSIONS:
Adequate AF provided by a monoamniotic twin environment may prevent pulmonary hypoplasia, which usually results from oligohydramnios due to certain fetal urinary tract anomalies.
Très intéressant comme indication des relations entre volume du liquide amniotique et développement pulmonaire mais il ne s'agit que de la relation de 2 cas cliniques.1443 - Amniotic Fluid Assessment - Methods And Role In Fetal Assessment.
AFV assessment by one method or another has become an adjunct to nonstress testing in most pregnancies requiring surveillance. Evaluation by nonstress test and amniotic fluid assessment for fetuses with maternal risk factors in a protocol such as that outlined by Devoe is common practice. Adaptation of that algorithm (Fig. 4) to the needs of the clinical setting are simple. Quantitative and nonquantitative methods show an increase in perinatal morbidity and mortality with abnormal values. Those trends are most evident in studies involving postdate gestations, such as those by Marks and Lagrew. -- The literature and its applied lessons for clinical practice are confused by the many variables considered by those investigating AFV assessment. Superiority of one method over another has not been demonstrated consistently from one study to the next. The good correlation in AFV estimated by ultrasonography and determined by dye-dilution techniques is still based on limited studies that are unlikely to be replicated soon because of the invasive nature of the test. Even in the best circumstances, errors at extremes of AFV are common with the use of ultrasonography. -- At present, the best recommendations from the literature seem to take two main directions. Antenatal testing of the fetus at risk should include some evaluation of AFV. The fetus with apparently abnormal AFV should be studied anatomically and considered for delivery if decreased AFV is associated with other test abnormalities -- i.e., a nonreactive nonstress test.
Article général sur la relation entre volume de liquide amniotique et l'état néonatal.1444 - Peripheral Arterial Vasodilation Hypothesis Of Sodium And Water Retention In Pregnancy: Implications For Pathogenesis Of Preeclampsia-eclampsia.
Primary peripheral arterial vasodilation with relative underfilling of the arterial circulation occurs in early pregnancy and leads to several consequences, including decreased systolic and diastolic blood pressures, enhanced cardiac output secondary to afterload reduction, stimulation of the renin-angiotensin-aldosterone axis, nonosmotic stimulation of thirst and vasopressin release, and renal sodium and water retention with expansion of the extracellular fluid and plasma volume compartments. These are events known to occur in all states of arterial vasodilation. Pregnancy has, however, several unique features. Primary arterial vasodilation generally is associated with no change or a decrease in renal blood flow and glomerular filtration rate and failure to escape from the sodium-retaining effects of aldosterone. In early pregnancy, renal blood flow and glomerular filtration rate increase by 3-50% in parallel with the peripheral arterial vasodilation but before plasma volume expansion. No known vasodilator exhibits such a profound effect on renal hemodynamics. Vasodilating prostaglandins may contribute to, but cannot explain, this remarkable enhancement of renal hemodynamics in early pregnancy. Therefore, a highly potent, as yet undefined, systemic and renal vasodilator must be unique to pregnancy. The increased glomerular filtration rate and filtered sodium load with enhanced distal tubular sodium delivery allows escape from aldosterone, an effect not observed in other states of arterial underfilling. This vasodilator may also account, at least in part, for the vascular resistance to angiotensin known to occur in normal pregnancy. This hypothesis for the normal physiology of pregnancy sets the stage for understanding the pathogenesis of preeclampsia-eclampsia. With endothelial damage and attenuation of the normal vasodilation of pregnancy, a decrease in glomerular filtration rate and renal blood flow, impaired escape from aldosterone, and enhanced sensitivity to angiotensin are observed. Therefore, these events may lead to hypertension, edema, and proteinuria, the hallmarks of preeclampsia-eclampsia, particularly because angiotensin and hypertension may combine to cause proteinuria.
Intéressant, à conserver même s'il n'est pas très directement lié à l'objectif "eau et santé".1445 - Aluminium Accumulation During Treatment With Aluminium Hydroxide And Dialysis In Children And Young Adults With Chronic Renal Disease.
Abstract
BACKGROUND:
The control of hyperphosphatemia is a major clinical problem in patients with chronic renal failure receiving regular dialysis treatment. Despite continuing concern about aluminum toxicity, aluminum containing antacids are still used in many of these patients as phosphate-binding agents. Although maximal acceptable doses of aluminum hydroxide have been recommended, the safety and efficacy of these guidelines have not been evaluated.
METHOD:
Seventeen children and young adults (mean [+/- SD] age, 14.1 +/- 3.7 years) undergoing regular peritoneal dialysis were randomly assigned to treatment with either aluminum hydroxide (n = 7/ maximal dose, 30 mg per kilogram of body weight per day) or calcium carbonate (n = 10/ dose range, 2.5 to 12 g per day, according to serum phosphorus levels). Aluminum retention was assessed by serial measurements of plasma aluminum, deferoxamine-infusion tests, and measurements of bone aluminum content during a mean (+/- SD) follow-up of 13 +/- 2 months. The evolution of bone disease was also evaluated.
RESULTS:
Plasma aluminum levels and the increment in plasma aluminum after infusion of deferoxamine increased from base-line values in the patients treated with aluminum hydroxide, and aluminum-related bone disease developed in one patient. Serum phosphorus levels remained higher and serum calcium levels lower in the patients receiving aluminum hydroxide than in those receiving calcium carbonate. The skeletal lesions of secondary hyperparathyroidism improved in 7 of 10 patients receiving calcium carbonate but persisted or progressed in 6 of 7 patients given aluminum hydroxide (P less than 0.025).
CONCLUSION:
Aluminum hydroxide is less effective than calcium carbonate as a phosphate-binding agent for the control of hyperphosphatemia and is associated with aluminum retention in children and young adults with chronic renal failure who are receiving dialysis therapy.
Taux d'aluminium dans le plasma plus élevée chez les patients traités par hydroxide d'aluminium par rapport à ceux traités par carbonate de calcium.1446 - Influence Of The Magnesium Content Of Drinking Water And Of Magnesium Therapy On The Occurrence Of Preeclampsia.
SUMMARY:
A reverse relationship was found between the magnesium content of drinking water, ie. an adequate supply of highly available dietary magnesium, and the occurrence of preeclampsia. Where various parts of a settlement receive their drinking water from different sources (for example, surface water or well water) there may be an important difference in the level of magnesium supply to different population groups. In the population studied here, the occurrence of preeclampsia varied pari passu with the magnesium content of the drinking water in different parts of the city. -- The results show that during pregnancy the magnesium content of serum and erythrocytes decreases. This decrease may be prevented by magnesium therapy, which lowers the incidence of preeclampsia.
Cette étude montre une relation inverse entre le magnésium contenu dans l'eau de boisson et l'incidence de pré-éclampsie. Les différences d'occurrence de pré-éclampsie apparaissent dans la même ville et en liaison avec la source d'eau de boisson, eau "de surface" vs. eau de puits.1447 - Effects of intravenous magnesium in suspected acute myocardial infarction: overview of randomised trials.
OBJECTIVE:
To investigate the effect of intravenous magnesium on mortality in suspected acute myocardial infarction.
DESIGN:
Systematic overview of all available randomised trials in which patients were allocated to receive either intravenous magnesium or otherwise similar treatment without magnesium.
SETTINGS:
Coronary care units of several hospitals.
PATIENTS:
1301 patients in seven randomised trials.
MAIN OUTCOME MEASURES:
Short term mortality.
RESULTS:
Considering the seven trials collectively there were 25 (3.8%) deaths among 657 patients allocated to receive magnesium and 53 (8.2%) deaths among 644 patients allocated control, generally during hospital follow up. This represents a 55% reduction in the odds of death (p less than 0.001) with 95% confidence intervals ranging from about one third to about two thirds. 70 of 648 patients allocated magnesium compared with 109 of 641 controls had serious ventricular arrhythmias, suggesting that magnesium reduces the incidence, though the definition varied among trials. Other adverse effects were rare in the limited number of patients for whom this data were available.
CONCLUSIONS:
Despite the limited number of patients randomised this overview suggests that intravenous magnesium therapy may reduce mortality in patients with acute myocardial infarction. Further large scale trials to confirm (or refute) these findings are desirable.
Cette étude a repris les études randomisées concernant l'administration intraveineuse de magnésium dans l'infarctus du myocarde (au total 1 301 sujets). Résultats : considéré de manière collectivement, il y a eu 3.8 % de décès chez les 657 patients recevant du magnésium contre 8.2 % parmi les 644 patients contrôles. Ceci représente une réduction de 50 % du risque de décès (P < 0.001). En conclusion, ces résultats suggèrent que l'administration intraveineuse de magnésium pourrait réduire la mortalité chez les patients en infarctus du myocarde aigu.1448 - Arrghythmia Prophylaxis After Coronary Artery Surgery.
ABSTRACT:
One hundred and thirty patients undergoing elective myocardial revascularisation were randomised to receive an intravenous infusion containing either 50 mmol magnesium chloride or placebo during the first 48 h following surgery. Magnesium was given to 66 patients and a placebo infusion to 64 patients. Postoperative serum magnesium concentrations fell in the placebo group (from 0.83 ±/ 0.06 to 0.79 ±/ 0.11 mmol/l) but were elevated in the magnesium group (from 0.82 ±/ 0.05 to 1.2 ±/ 0.25 mmol/l). In total, 35 patients (26.9%) had a supraventricular arrhythmia, of which 11 were in the magnesium group (16.7%) and 24 (37.5%) in the placebo group (p = 0.013). Three patients in the magnesium group had an episode of ventricular fibrillation and three patients in the placebo group had frequent ventricular ectopics. There was one death in the magnesium group associated with a perioperative myocardial infarction. This study shows that intravenous magnesium supplements reduce the incidence of supraventricular arrhythmias following coronary artery surgery.
130 patients devant bénéficier d'une revascularisation myocardique ont été randomisés pour recevoir par voie intraveineuse soit du magnésium soit du placebo dans les 48 heures suivant la chirurgie. 16.7 % des sujets ayant reçu du magnésium ont fait une tachycardie supraventriculaire contre 37.5 % dans le groupe placebo (P = 0.01). Cette étude montre qu'une perfusion intraveineuse de magnésium réduit l'incidence des arythmies supraventriculaires suivant une intervention chirurgicale coronaire.1449 - Effects Of Magnesium Infusion On Thrombolytic And Non-thrombolytic Treated Patients With Acute Myocardial Infarction.
A total of 109 consecutive patients were included in a double blind, randomized trial of the effect of intravenous magnesium sulfate in acute myocardial infarction. Of these 63% received intravenous fibrinolytic therapy. Twenty four-how Holter monitoring of heart rhythm was performed during the initial hospital stay. A significant reduction in total cardiac mortality in hospital and during the 9 months follow-up was found in the magnesium treated non-thrombolytic group (p </ 0.05). Within this subgroup development of heart failure was decreased (p </ 0.01). No effect of magnesium infusion on ventricular arrhythmias was demonstrated, instead we found a greater proportion of patients with short runs of ventricular tachycardias in the magnesium treated non-thrombolytic group (p </ 0.05), which may represent an increase in spontaneous reperfusion.
CONCLUSIONS:
these results indicates that magnesium infusion may have a beneficial effect on mortality in patients with acute myocardial infarction not receiving thrombolytic therapy, but opposes the view that the benefit is related to an antiarrhythmic effect. No additional effect of magnesium to ongoing fibrinolytic therapy could be demonstrated regarding mortality, reinfarction and heart failure.
Dans cette étude en double-aveugle et randomisée avec 109 patients ayant un IDM, le Mg sulfate en IV réduit la mortalité cardiaque totale et la fréquence de choc cardiaque dans le groupe sous thrombolytiques. De courtes salves de TV étaient plus fréquentes dans le même groupe Mg. Aucun autre bénéfice lié au Mg n'a été trouvé dans le groupe sous thrombolytiques.1450 - Intracellular Magnesium Deficiency In Acute Myocardial Infarction.
It has been hypothesized that intracellular magnesium deficiency is a pathogenetic factor in acute myocardial infarction. This study examined the time course of changes in the erythrocyte magnesium concentration and the correlation between the erythrocyte magnesium concentration and the severity of acute myocardial infarction in 49 consecutive patients with transmural acute myocardial infarction. The data were compared with results from 20 control patients without ischemic heart disease. The erythrocyte magnesium concentration (mg/dl) decreased significantly during the acute phase of the infarction (4.86±/0.09 on day 1, 4.89±/0.10 on day 2 and 4.86±/0.10 on day 3 versus 5.26iO±/0.19 for controls, all P</0.05) and then normalized gra dually to 5.25±/0.10 on day 28. The serum magnesium concentration (mg/dl) also decreased significantly during the acute phase of the infarction (1.93±/0.04 on day 1 and 2.11±/0.03 on day 2 versus 2.26±/0.08 for controls, all P</0.05), before recovering to 2.28±/0.06 on day 28. There were significant correlations between the erythrocyte magnesium concentration on day 1 and maximal values of serum cardiac enzymes (r = - 0.30 for creatine kinase, r = - 0.34 for glutamic oxaloacetic transaminase and r = - 0.57 for lactate dehydrogenase, all P</0.05). Moreover, the erythrocyte magnesium concentration was significantly lower in patients with (4.32±/0.08 mg/dl, n=13) than in those without (5.06±/0.09 mg/dl, n=36, P</0 .0001) serious arrhythmias. These data indicate that intracellular magnesium deficiency is involved in the acute phase of myocardial infarction.
Une série de 49 patients avec IDM transmural a été comparée à 20 contrôles. La concentration érythrocytaire et sérique décroît durant la phase aiguë de l'IDML Mg érythrocytaire était significativement plus bas chez les patients développant des salves de TV.1451 - Effect Of Magnesium In Heart Attack Survivors.
No abstract available.
La supplémentation orale en Mg (15 mmoles/j pendant 1 an chez 468 patients ayant présenté un infarctus aigu du myocarde) ne diminue pas l'incidence d'accidents cardiovasculaires et a tendance, au contraire, à l'augmenter. Cette étude n'amène pas à recommander ce traitement chez ce type de patients.1452 - Drug Therapy For Torsade De Pointes.
Torsade de Pointes. Torsade de pointes is an uncommon and unique type of ventricular tachycardia. It differs from other forms of ventricular tachycardia by its morphological features, underlying mechanism, and modes of therapy. Recognizing torsade de pointes is of major clinical importance, as standard antiarrhythmic regimens might not only be ineffective in abolishing this life-threatening arrhythmia but may aggravate it. Torsade de pointes is most commonly precipitated by QT prolonging drugs, mainly type IA antiarrhythmic therapy such as quinidine and disopyramide, and other antiarrhythmic agents are reported to cause torsade de pointes as well. Predisposing factors known to increase the likelihood of developing torsade de pointes are: electrolyte imbalance (hypokalemia, hypomagnesemia, or both) and slow heart rate induced either by sinus bradycardia or heart block
TREATMENT:
of torsade de pointes is aimed at shortening the QT interval. By acceleration of the heart rate, the QT interval is shortened, thus preventing the recurrence of the arrhythmia Treatment of torsade de pointes includes: isoproterenol infusion, cardiac pacing, and intravenous atropine. Intravenous magnesium sulfate, a relatively new mode of therapy for torsade de pointes, was proven to be extremely effective and is now regarded as the treatment of choice for this arrhythmia.
Revue générale sur la physiopathologie et le traitement des torsades de pointe. Il est suggéré que le sulfate de Mg par IV est le traitement de choix des arythmies.1453 - Magnesium And The Heart: Antiarrhythmic Therapy With Magnesium.
SUMMARY:
Magnesium is an essential transmembrane and intracellular modulator of the electrical activity of cardiac cells. This review provides an up-to-date consideration of the cellular and clinical electrophysiological role of magnesium. This ubiquitous element seems to be important from both the theoretical and clinical point of view, because magnesium salts (MgSO4, MgCI2) administered intravenously are particularly effective in those arrhythmias in which the mechanism involves early or delayed after depolarization-induced triggered activity. The authors share the view that I.V. magnesium is the drug of choice in "torsade de pointes" ventricular tachycardia accompanying acquired long QT/QTU syndrome. It is a complementary therapeutic agent in digitalis-induced tachycardias. Further studies are needed to elucidate magnesium''s mode of action and efficacy in other types of clinical tachyarrhythmias.
Le rôle électrophysiologique cellulaire et clinique du Mg est ici revu. Les sels de Mg semblent efficaces dans les arythmies pour lesquels il existe un déclenchement provoqué par un mécanisme de dépolarisation précoce ou retardée. Il est recommandé pour le traitement des TV par torsades de pointe et comme traitement d'appoint dans les tachycardies induites par les digitaliques.1454 - Mesure Des Compartiments Rapidement Echangeables, Des Taux D''echange Et De Transfert Du Magnésium À L''aide Du 28mg Chez L''adulte Normal Et Pathologique.
Studies on the kinetics of metabolism of rapidly exchangeable magnesium were carried out in man by determining the change of specific plasma activity in time and by measuring the activity in urine and faeces after injection of 28MgCl2. 30 subjects were examined, eight of which were normal and 22 pathologic/ of the latter,17 showed a syndrome of normocalcaemic tetany. The kinetics of the rapidly exchangeable magnesium can be schematized by an open three-compartment system showing the passage of magnesium into urine and faeces, and at the same time a remarkable exchange taking place with a slowly renewing magnesium pool. In some pathological cases significant differences were found concerning the normal values of parameters of this system (pool-size of each compartment, rate of exchange, passage into urine and faeces). No connection with the respective clinical picture was observed.
L'utilisation de traceurs isotopiques qui permet d'étudier la décroissance et l'enrichissement plasmatique urinaire et fécal en isotopes, donne accès à des paramètres intéressants pour évaluer le statut et le métabolisme du Mg (taille et nombre des pools, vitesse d'échange). Cependant l'isotope radioactif Mg28 présente de nombreux inconvénients et tend, à l'heure actuelle, à être remplacé par des isotopes stables (Mg25, Mg26) pour des études chez l'Homme.1455 - La Consommation Maternelle Du Magnésium Et Le Nouveau-né.
Resumé: La consommation quotidienne du magnésium par 513 femmes vers la fin du premier trimestre de la grossesse est calculée en utilisant un semainier des aliments consommés. La consommation du magnesium est corrélée avec les poids à la naissance, la taille à la naissance, la circonférence de la tête du nouveau-né et la durée de la gestation. L''analyse statistique montre que la correlation entre la consommation du magnésium d''une part et la durée de la grossesse et les mesures du nouveau-né d''autre part n''est seulement significative que pour les demi-groups des nouveau-nés les plus petits. Parmi les 7 élements significativement associés avec les mesures étudiées au cours de la grossesse et celles cle nouveau-né le magnésium présent l''une des 3 correlations les plus significatives après celles du sodium et du chlore. Une supplementation quotidienne de 10 mg/jour à un sous-groupe de mères pendant les deuxième et troisième trimestres n''a montré aucun resultat significatif sur les mesures du nouveau-né, suggerant que toute action du magnésium pendant la grossesse limitée au cours du premier trimestre ou auparavant. Une consommation maternelle quotidienne de 300 mg de magnésium correspond à l''optimum observé des dimensions du nouveau-né: poids de naissance, taille et périmètre céphalique optimal.
La revue des habitudes alimentaires de 513 femmes au cours du 3ème trimestre de grossesse témoigne qu'un apport quotidien de 300 mg de Mg répond aux critères "idéaux" de naissance.1456 - Effect Of Hypomagnesemia And Exercise On Slowly Exchanging Pools Of Magnesium.
The effects of hypomagnesemia and exercise on the slowly exchanging pools of magnesium. Skeletal muscle, bone, erythrocytes, and plasma, were examined in four groups of male Sprague-Dawley rats: sedentary-normal diet (SN), exercise-normal diet (EN), sedentary-hypomagnesemic diet (SH), and exercise-hypomagnesemic diet (EH). The exercise groups swam 5 d/wk-1 for 6 weeks. The hypomagnesemic diet contained 80 ppm and the normal diet about 640 ppm of magnesium. Compared with normal-diet rats (SN and EN), dietary -deficient rats (SH and EH) gained less weight and had lower concentrations of magnesium in all tissue samples and plasma (P</.01). Exercise groups (EN and EH) demonstrated significantly higher magnesium levels in skeletal muscle (P</.01) and a tendency for lower levels of magnesium in plasma, erythrocytes, and bone compared with sedentary groups (SN &/ SH). EH rats normalized skeletal muscle magnesium, mEq . /kg wet tissue, (19.9 ±/ 5.1) compared with the SN group (20.6 ±/2.1). Assuming that magnesium stores that are rapidly exchanged are maintained at the expense of those that are slowly exchanged, magnesium stores in skeletal muscle appear to be most protected, with the effect accentuated by exercise.
Chez des rats Sprague-Dawley, une alimentation pauvre en Mg est associée avec un gain de poids moindre et des taux plasmatiques et tissulaires abaissés. L'exercice accroît notablement la concentration musculaire en Mg, alors que les concentrations plasmatique, érythrocytaire et osseuse tendent à baisser.1457 - Urine Composition In Patients With Urolithiasis During Treatment With Magnesium Oxide.
SUMMARY:
Fifteen patients with recurrent renal stone formation were treated with 400 mg magnesium oxide daily. Urine composition was analyzed before the start of treatment and after 6 - 12 months. The urinary excretion of magnesium before and during treatment was 321 ±/ 120 (mean ±/ SD) and 409 ±/ 140 mmol per mol creatinine respectively, a difference that was not statistically significant. Urinary calcium increased from 473 ±/ 186 to 662 ±/213 mmol per mol creatinine (p </0.05). All patients who increased their excretion of magnesium also increased the urinary output of calcium and, as a result of this, the calcium/magnesium-quotients were unaffected by the treatment. No significant effect was observed on urine oxalate excretion. Serum concentrations of calciurn, magnesium and urate all remained at the pre-treatment level. From the results obtained in this study, magnesium oxide in this dosage cannot be recommended for use in treatment of patients with urolithiasis.
Cette étude, conduite chez 15 patients atteints de lithiase calcique récidivante, montre qu'un traitement par 400 mg/jour d'oxyde de magnésium pendant un an, n'a entraîné qu'une augmentation minime et non significative de la magnésurie de 321 à 409 mg/jour, associée à une augmentation indésirable et mal expliquée de la calciurie de 473 à 662 mg/jour.1458 - Magnesium Reduces Calcium Oxalate Crystal Formation In Human Whole Urine.
1. A low urinary magnesium was induced in normal volunteer subjects by giving cellulose phosphate/ magnesium was added in vitro to yield urine samples of normal and high magnesium concentrations. -- 2. After rapid evaporation of these urine samples at pH 5.3 to standard osmolality the calcium oxalate crystals were measured by microscopy and isotopic methods. -- 3. There was a clear inverse correlation between magnesium concentration and calcium oxalate crystal formation. -- 4. The case for treating calcium oxalate urolithiasis with magnesium is strengthened.
Une des études princeps sur le rôle inhibiteur des ions magnésium sur la formation des cristaux d'oxalate de calcium.1459 - The Effect Of Magnesium On The Crystal Growth Rate Of Calcium Oxalate In Human Urine.
The effect of Mg2+ on the relative crystal growth rate of calcium oxalate (= CaOx) in artificial urine (pH = 6) has been measured by the gel crystallization method (= GCM) and compared with calculated thermodynamic data. The GCM is a highly efficient microprocedure which allows the determination of crystal growth kinetics by computer controlled scanning microphotometry. -- CaOx crystal growth rate is significantly decreased by increasing Mg2+ concentration which may be accounted for by the alteration of the CaOx activity product and, possibly, a minor kinetic contribution. However, the effect is relatively small compared with those of other urinary constituents (i.e. calcium, oxalate, citrate). -- The results are discussed with respect to the potential role of Mg2+ in CaOx urolithiasis.
Les auteurs ont étudié l'influence de la concentration en ions magnésium sur la cristallisation oxalocalcique à l'aide d'une méthode de cristallisation en gel, sur des urines a