Phase angle and bioelectrical impedance vectors in adolescent and adult male athletes.

The aim of the current study was to assess phase angle (PA) and bioelectrical impedance vectors (BIVA) in adolescent (n = 105, 12-19 y) and adult (n = 90, 20-50 y) male athletes practicing varied sports modalities. Bioelectrical impedance analysis (BIA) was performed with a single-frequency tetrapolar impedance analyzer after the athletes had fasted overnight for 8 h. PA and BIVA were determined from BIA data. PA presented correlations (P < .01) with body-mass index (r = .58) in all athletes and also with age in adolescent (r = .63) and adult (r = -.27) athletes. Compared with adults, adolescent athletes presented lower PA and higher frequency of PA below the 5th percentile of a reference population (P < .001). The adolescents with low PA were mostly football and basketball players. The BIVA confidence ellipses of adult and adolescent athletes were different (P < .001) between them and from their respective reference populations and were closer than those of adult and adolescent nonathletes. About 80% of the athletes were in the 95th percentile of BIVA tolerance ellipses and in quadrants consistent with adequate body cell mass and total body water. The adolescent athletes outside the 95th percentile ellipse were all football and basketball players who showed indications of decreased water retention and body cell mass and of increased water retention, respectively. PA and BIVA ellipses showed that the intense training routine of the athletes changed functional and hydration parameters and that the magnitude of these changes in adolescents may depend on the sport modality practiced.

n-6 and n-3 Long-chain polyunsaturated fatty acids in the erythrocyte membrane of Brazilian preterm and term neonates and their mothers at delivery.

Placental transfer of the long-chain polyunsaturated fatty acids (LCPUFA) arachidonic (AA) and docosahexaenoic (DHA) acids is selectively high to maintain accretion to fetal tissues, especially the brain. The objectives of the present study were to investigate the essential fatty acid (EFA) and LCPUFA status at birth of preterm and term Brazilian infants and their mothers, from a population of characteristically low intake of n-3 LCPUFA, and to evaluate the association between fetal and maternal status, by the determination of the fatty acid composition of the erythrocyte membrane. Blood samples from umbilical cord of preterm (26-36 weeks of gestation; n = 30) and term (37-42 weeks of gestation; n = 30) infants and the corresponding maternal venous blood were collected at delivery. The LCPUFA composition of the erythrocyte membrane and DHA status were similar for mothers of preterm and term infants. Neonatal AA was higher (P < 0.01) whereas its precursor 18:2n-6 was lower (P < 0.01) than maternal levels, as expected. There was no difference in LCPUFA erythrocyte composition between preterm and term infants, except for DHA. Term infants presented a worse DHA status than preterm infants (P < 0.01) and than their mothers (P < 0.01) at delivery. There was a negative correlation of neonatal DHA with maternal AA and a positive correlation between neonatal AA and maternal AA and 18:2n-6 only at term. These results suggest that the persistent low DHA maternal status, together with the comparatively better AA and 18:2n-6 status, might have affected maternal-fetal transfer of DHA when gestation was completed up to term, and possibly contributed to the worse DHA status of term neonates compared with the preterm neonates.

Longitudinal change in plasma total homocysteine during pregnancy and postpartum in Brazilian women and its relation with folate status and other factors.

Fasting plasma total homocysteine (tHcy) concentration was determined in a cohort of pregnant Brazilian women (n = 46) supplemented with folic acid from the second trimester of pregnancy. Blood samples were obtained in the first and third trimesters from all women, and 30-40 days postpartum from seventeen women. Plasma tHcy decreased during pregnancy from 10.3 to 8.7 micromol/L, and was 11.6 micromol/L in the postpartum. Plasma and erythrocyte folate increased, consistent with use of the folate supplement, but decreased slightly in the postpartum, whereas the opposite occurred for plasma vitamin B12. tHcy was inversely correlated with plasma and erythrocyte folate in the third trimester (r = -0.585 and -0.460, respectively). This relationship occurred despite the fact that all women had attained what could be considered adequate levels of folate indices. Furthermore, the change (third trimester minus first trimester levels) of tHcy was inversely correlated (p < 0.01) with the changes in plasma (r = -0.573) and erythrocyte folate (r = -0.525). tHcy had no correlation in any of the periods tested with plasma vitamin B12, plasma albumin, hematocrit, hemoglobin, iron indices, dietary intakes of folate, vitamins B12 and B6, and levels of folate supplement.

Partial characterization of folate uptake in microvillous membrane vesicles isolated from human placenta

The purpose of the present study was to determine biochemical parameters of folate uptake, and the putative contribution of the membrane-anchored folate receptor in microvillous membrane vesicles obtained from the syncytiotrophoblast of human term placenta. Uptake of [3H]-pteroylglutamic acid (PGA) by microvillous membrane vesicles was pH dependent with a maximum at pH 6.0, and attained equilibrium at 60 min of incubation. Uptake was higher in the presence of an inward pH gradient (pHout = 6.0; pHin = 7.5) than in the absence of the gradient (pHout = pHin = 6.0). The effect of changes in medium osmolality showed that both binding to the vesicular membrane and internalization contributed to the measured [3H]-PGA uptake. Equilibrium uptake experiments using [3H]-PGA concentrations within the physiological range of folate in blood serum showed that saturation was achieved at 30 nM and revealed a single class of binding sites with a Kd of 1.8 nM for [3H]-PGA. Cleavage of the glycosyl-phosphatidylinositol moiety of the folate receptor, which anchors the receptor to the membrane, with phosphatidylinositolspecific phospholipase C resulted in a reduction of about 80 per cent in [3H]-PGA uptake. In conclusion, our results showed that the folate uptake in the maternally facing membrane of the human placenta presents a saturable component and is mediated by the folate receptor to ensure an adequate maternal-fetal folate transfer.

Iron uptake from lactoferrin by intestinal brush-border membrane vesicles of human neonates

It is uncertain to what extent the binding of human lactoferrin (LF) to its receptor in the intestinal brush-border membrane affects iron uptake in infants. The purpose of this study was to investigate iron uptake from human LF by brush-border membrane vesicles (BBMV) obtained from the small intestine of human neonates. LF was purified from pooled human colostrum. Uptake experiments were performed by incubation of 55Fe-citrate or 55Fe-LF with BBMV, followed by rapid filtration through microporous filters. 55Fe uptake from LF by BBMV was dependent on pH, with a maximum at 7.5, and increased with incubation time, reaching a maximum at 1 min. When 55Fe was bound to citrate, uptake was slower (maximum at 5 min) and not dependent on pH. In both experiments, the maximum uptake of iron bound to LF was about twice that of iron bound to citrate (230 pmol and 105 pmol/mg microvillus protein, respectively). Partial degradation of LF in two fragments resulted in the loss of its capacity to increase iron uptake by BBMV. From these preliminary results we conclude that LF may increase iron absorption during the neonatal period, contributing to the high bioavailability of this mineral in human milk.

Lactoferrin levels and unsaturated iron-binding capacity in colostrum of Brazilian women of two socioecomic levels

The objetive of this study was to compare lactoferrin (LF) levels and unsaturated iron-binding capacity (UIBC) of colostrum from Brazilian women aged 20-38 years of low (N = 28) and high (N = 15) socioeconomic level. Both groups received a similar amount of supplental iron (25-65 mg/day) during pregnancy. We also determined the relationship between LF levels and UIBC, and between these components and maternal iron status. Both groups (low and high socieconomic level) showed adequate and similar mean hematocrit (35.0 ñ 13% and 35.9 ñ 1.3%, respectively) and serum ferritin (64 ñ 12 µg/1 and 57 ñ 12 µg/1, respectively) levels. Furthermore, LF levels (5.7 ñ 0.9 mg/ml and 5.5 ñ 0.6 mg/ml) and UIBC (3.8 ñ 0.3 µg/ml and 3/1 ñ 0.3 µg/ml) were not significantly different in the two groups of women, nor were they related to maternal hematocrit or serum ferritin. UIBC was significantly (P = 0.009), although weakly positively correlated (r= 0.45) with LF levels, suggesting that other colostrum ligands may contribute substantially to the capacity of colostrum to bind exogenous iron

Estado Nutricional y composición de la leche materna en Hierro, Zinc, Folato y Vitamina B12 de madres de bajo nivel socioeconómico de Río de Janeiro / Nutritional status and iron, zinc, folate and vitamin B12 milk composition in mothers of low socioeconomic level in Río de Janeiro

El objetivo del estudio fue verificar si el uso durante el embarazo de suplemento de hierro, folato y vitamina B12 por mujeres brasileñas de bajo nivel socioeconómico es suficiente para lograr un estado nutricional satisfactorio en estos nutrientes durante la amamantación y una composición adecuada de la leche. Como complemento del estudio fue analizado el estado nutricional de las madres y la composición de la leche en relación al zinc. Considerando los valores promedio, el estado nutricional de las madres en relación a los nutrientes estudiados fue adecuado. Sin embargo algunas madres tuvieron índices menores que los normales para mujeres no embarazadas. Estos bajos índices especialmente 30 días después del parto, sugieren que estas madres presentan un estado nutricional inadecuado. La composición de la leche en relación a los nutrientes estudiados fue comparable a la de mujeres bien nutridas de países desarrollados. Las madres que recibieron suplemento de folato durante el embarazo tuvieron niveles más altos en el suero inmediatamente después del parto, que las que no recibieron suplemento. Sin embargo, la composición de la leche no fue afectada. Se concluye que el suplemento recibido fue insuficiente para cubrir las demandas de este período y mantener reservas adecuadas

Characterization of the vitamin B12 - binding protein isolated from sow's milk and its affinity for cyanocobalamin and other corrinoids

1. Unsaturated vitamin B12-binding protein was isolated from sow's milk whey by affinity chromatography on a vitamin B12-Sepharose colmn with a yield of 54% (3920-fold purification). The purified binding protein was homogeneous was homogeneous by the criteria of polyacrylamide gel electrophoresis and high speed sedimentation equilibrium. 2. The isolated vitamin B12-biding protein was a glycoprotein was a glycoprotein with 24% carbohydrates (fucose, galactose, mannose, galactosamine, glucosamine and sialic acid_ and high levels of aspartic and glutamic acids. The protein which has a molecular weight of 61800 determined by ultracentrifugation, consisted of a single polypepide chain, bound vitamin B12 on an equimolar vasis and had a partial specific volume of 0.697 ml/g (mechanical oscillaltor technique). 3. Its dissociation constant, Kd'for cyanocoballamin was 8.8 x 10-10M. The binding protein showed similar affinities for hidroxo-, and adenosylcobalamin when compared to cyanocobalamin relative affinity ratios, but lower affinities (31-49%) for cobinamide, Co-alfa [adenyl] cobamide and Co-alfa-[2-methyl-adenyl]cobamide. Therefore, the substitution of axial ligand to the cobalt atom in the corin ring of vitamin B12 had no effect on affinity, whereas the differences in the nucleotide part of the molecule caused a small decrease in energy of the interation. 4. The present results indicate close similarity of the vitamin B12-binding protein from sow's milk to vitamin B12-biding proteins from other