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Biomedical subjects

A M Prentice

Publications and source records attributed to A M Prentice.

178 records · Page 10Linked to original sources
PubMed1982

Physiological tests during an improvement in riboflavin status in lactating Gambian women.

During several weeks riboflavin supplementation of lactating African women, which reduced their mean activation coefficient of erythrocyte glutathione reductase (EGRAC) from 1.65 to 1.21 and initiated an improvement in clinical deficiency signs, measurements were made of physiological functions which may be connected with riboflavin status. No specific response to the supplement could be detected in body weight, grip strength, haematological parameters, osmotic fragility and resistance to oxidative stress of erythrocytes, plasma iron levels and related indices, or plasma hormone levels. There was a cross-sectional relationship between erythrocyte distribution on Percoll density gradients and EGRAC before supplementation, and between the Percoll pattern and total haemoglobin concentration. It is not yet known, however, whether a direct causal relationship exists between these variables.

Adult↗
PubMed1981

A biochemical evaluation of the erythrocyte glutathione reductase (EC 1.6.4.2) test for riboflavin status. 2. Dose-response relationships in chronic marginal deficiency.

1. Chronic marginal riboflavin deficiency was induced in groups of weanling rats by feeding a deficient diet supplemented with 0, 0.5, 1.0 and 1.5 mg riboflavin/kg diet. Ad lib.- and pair-fed controls received 3.0 and 15 mg riboflavin/kg diet respectively. 2. Serial measurement of erythrocyte NAD(P)H2 glutathione oxidoreductase (glutathione reductase; EC 1.6.4.2) and its activation coefficient revealed that after 12 weeks a steady-state of deficiency had been reached following initial fluctuations in status; the animals were then killed, and their tissues analysed. 3. Food intake, growth rate and the appearance of pathological signs were directly proportional to riboflavin content; however relative liver weight was increased above control levels only in the most-severely-deficient group, and anaemia was not detected in any group. 4. The activation coefficient of glutathione reductase in erythrocytes and liver was closely related to dietary riboflavin content; that of skin responded maximally even in the least-severely-depleted animals. 5. Hepatic and renal flavin contents were directly proportional to dietary riboflavin, FAD being conserved at the expense of riboflavin and FMN. ATP:riboflavin 5-phosphotransferase (flavokinase; EC 2.7.1.26) activity was reduced, even in the least-severely-deficient animals; ATP:FMN adenylyltransferase(FAD pyrophosphorylase; EC 2.7.7.2) was increased in liver, but only in the most-severely-deficient animals. 6. Hepatic succinate:(acceptor) oxidoreductase (succinate dehydrogenase; EC 1.3.99.1) activity fell sharply between 1.5 and 0.5 mg riboflavin/kg diet, producing an S-shaped dose-response curve; it showed smaller or less specific changes in other tissues such as brain, skin and intestine. NADH:(acceptor) oxidoreductase (NADH dehydrogenase; EC 1.6.99.3) activity declined in liver and intestine, but not in skin or brain. 7. The activation coefficient of glutathione reductase was correlated strongly with nearly all the riboflavin-sensitive variables measured, once equilibrium had been reached in this chronic deficiency model, and it was particularly strongly correlated with hepatic and renal FAD levels. Under equilibrium conditions, therefore, it appears to represent a good index of the extent of riboflavin deficiency, and significant changes in flavin levels and enzymes in the internal organs were detected even under conditions of marginal deficiency, associated with relatively small increases in the activation coefficient.

Animals↗
PubMed1981

Breast-milk fat concentrations of rural African women. 1. Short-term variations within individuals.

1. Detailed studies of variations in breast-milk fat concentrations were performed over 12 or 24 h periods on sixty rural Gambian women feeding on demand. The creamatocrit method (Lucas et al. 1978) was used. 2. The complex pattern of within-feed and between-feed changes in fat concentration was largely explained by differences in volume per feed and time interval between feeds. 3. No consistent difference in fat production between the breasts of each individual was found despite the local custom of starting all feeds on the right breast. 4. A marked diurnal variation in the mean fat concentration per feed was noted. On average the highest values occurred in the early morning, the lowest values in the late afternoon. 5. There was significantly greater between-individual than within-individual variation in the mean fat concentration per feed over 12 h (P less than 0.001). 6. A simple, rational and non-intrusive sampling procedure was devised for the estimation of whole-day mean fat levels based on the finding that the mean fat concentration of small samples of milk (0.25 ml) taken from both breasts before and after one specific feed of the day was closely correlated with 12 h and 24 h mean fat concentrations.

Breast Feeding↗
PubMed1981

Breast-milk fat concentrations of rural African women. 2. Long-term variations within a community.

1. Long-term variations in breast-milk fat concentration of mothers feeding on demand were studied in 120 rural West African women over a 12-month period. 2. The over-all mean 12 h breast-milk fat concentration was 39.3 g/l. 3. Mean breast-milk fat concentrations were affected by season in a manner which was correlated with seasonal changes in maternal subcutaneous fat stores (P less than 0.05) but which was unrelated to seasonal variations in maternal energy intake and breast-milk output. 4. Breast-milk fat concentrations were highest in early lactation, decreasing to a constant level during the first year. 5. There was significantly greater between-mother than within-mother variation in breast-milk fat concentrations measured in successive months, after correcting for season and stage of lactation (P less than 0.001). 6. Breast-milk fat concentrations were highest for primiparous mothers, decreasing to a constant level at parity 4 and higher. 7. A mother's relative breast-milk fat concentration was not correlated with her levels of dietary energy intake and breast-milk output but was positively correlated with her relative subcutaneous fat deposits (P less than 0.01).

Energy Intake↗
PubMed1981

Long-term energy balance in child-bearing Gambian women.

The energy intake of 143 pregnant and lactating Gambian women was measured prospectively each week for a year. Anthropometric, birth weight, and breast milk output measurements were also obtained. The average energy intakes (+/- SE) during the dry and wet seasons respectively were: pregnancy, 1483 +/- 22 and 1417 +/- 41 kcal/day; lactation (1st trimester), 1773 +/- 31 and 1474 +/- 42 kcal/day; lactation (subsequent trimesters), 1662 +/- 16 and 1413 +/- 37 kcal/day. Pregnant women gained 1.4 kg body weight per month in the dry season, but only 0.4 kg in the wet season. Lactating women gained weight in the dry season and lost weight in the wet season. Maternal nutritional status did not deteriorate with increasing parity. Mean birth weights (+/- SE) were: 2.94 +/- 0.07 and 2.78 +/- 0.11 kg in dry and wet seasons, respectively. Breast milk output and quality and early infant growth were close to values from well-nourished communities during the dry season, but deteriorated markedly during the wet season. Wet season energy intakes were clearly inadequate, but these results indicate that, despite being low by international standards, the dry season intake was compatible with a good lactational performance. Except for a somewhat low birth weight, which is partly explained by small maternal stature, progress during pregnancy was also remarkably normal during the dry season.

Birth Weight↗
PubMed1981

Riboflavin status in Gambian pregnant and lactating women and its implications for Recommended Dietary Allowances.

Riboflavin status by the erythrocyte glutathione reductase (NAD(P)H2:glutathione oxidoreductase EC1.6.4.2) test, and dietary riboflavin intake, were measured in 156 pregnant and lactating women in Keneba, a rural Gambian village, and in 59 pregnant and lactating women in Cambridge, England. The Keneba women were studied longitudinally, for up to 19 months. In Keneba, where the mean daily riboflavin intake was 0.5 mg, the mean erythrocyte glutathione reductase activation coefficient was 1.78 and there was a marked deterioration of biochemical status near parturition. In Cambridge, where the mean intake was 2.3 mg/day, the mean activation coefficient was 1.19. A vitamin fortified diet supplement, given to lactating women in Keneba for 8 months, raised their mean riboflavin intake for 0.5 to 1.5 mg/day and reduced the mean activation coefficient to 1.42. It is therefore likely that an intake even greater than the current United Kingdom or United States recommended daily amounts would be needed to achieve biochemical 'normality' in these women.

Adolescent↗
PubMed1981

The influence of G-6-PD activity on the response of erythrocyte glutathione reductase to riboflavin deficiency.

Erythrocyte NAD(P)H2 glutathione oxidoreductase (EC 1.6.4.2.) activation coefficients (EGR AC) and D-glucose-6-phosphate: NADP 1-oxidoreductase, EC 1.1.1.49 (G-6-PD) activities were measured in 155 West African women to determine whether heterozygous G-6-PD deficiency produces false negative results in the EGR test for riboflavin deficiency. A positive correlation was found between EGR AC and G-6-PD activity demonstrating that heterozygous G-6-PD deficiency does result in abnormally depressed EGR AC values when G-6-PD activity is significantly reduced. However, heterozygous deficient genotypes with normal G-6-PD activity showed undepressed EGR AC values. These results indicate that, in its present form, the EGR test is not a suitable index of riboflavin status in subjects whose G-6-PD activity is less than 9 IU/g Hb when measured by the WHO-37 degrees assay.

Adult↗
PubMed1980

Dietary supplementation of Gambian nursing mothers and lactational performance.

A dietary supplement, resulting in a mean net increase in energy intake of over 700 kcal/day, was supplied to all nursing mothers in a West African village for 12 months. The supplement produced a slight initial improvement in maternal body weight and subcutaneous fat stores but did not increase breast-milk output or fat content.

Body Weight↗
PubMed1980

Influence of maternal diet on plasma-prolactin levels during lactation.

An improvement in maternal diet produced significant reductions in plasma-prolactin concentration at all stages of lactation. The prolonged high prolactin concentrations found in undernourished mothers may ensure milk synthesis when food intake is limited, by preferentially channelling nutrients towards the breast. The lower hormonal levels associated with improved maternal nutrition may shorten the period of post-partum infertility despite prolonged breast-feeding.

Amenorrhea↗
PubMed1980

Refection in rats fed on a sucrose-based, riboflavin-deficient diet.

1. Refection, resulting in an increased supply of riboflavin to riboflavin-deficient rats through coprophagy, was demonstrated on a sucrose-based diet when sensitive biochemical tests of riboflavin status were employed: these included measurements of NAD(P)H2:glutathione oxidoreductase (EC 1.6.4.2); succinate:(acceptor) oxidoreductase (EC 1.3.99.1) and NADH:(acceptor) oxidoreductase (EC 1.6.99.3). 2. The use of tail-cups to eliminate coprophagy, and hence refection, resulted in a more rapid and reproducible progress into severe deficiency. 3. The occurrence of refection on a sucrose-based diet may account for hitherto unexplained differences between previous publications on the biochemical effects of riboflavin deficiency.

Animals↗
PubMed1979

New method for measuring milk intakes in breast-fed babies.

A method for the measurement of milk intake in young breast-fed babies is described in which heavy water (2H2O) enrichment in saliva is measured on only two occasions after a single oral dose of 2H2O. Values obtained by this method are compared with those obtained by test-weighing. This new method is ideal for routine surveys since it does not interfere with feeding habits and maternal life style, and no technical expertise is required of the mother.

Breast Feeding↗
PubMed1978

Factors influencing lactation performance in rural Gambian mothers.

Breast-milk consumption has been measured in a rural African community in which breast-feeding on demand is universally practised until the baby is 18 mos old. The mother's long-term capacity for breast-milk production is determined by the end of the second month of lactation, yield being closely correlated with the infant's birth-weight. Other factors significantly influencing output were parity, month of lactation, baby's weight-for-age, season, and maternal diet. Daily milk consumption was limited primarily by the amount delivered per feed, not the frequency of feeding.

Body Weight↗