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Biomedical subjects

N J Fuller

Publications and source records attributed to N J Fuller.

42 records · Page 3Linked to original sources
PubMed1986

The effect of riboflavin deficiency on methylenetetrahydrofolate reductase (NADPH) (EC 1.5.1.20) and folate metabolism in the rat.

1. Riboflavin deficiency at two levels of severity was produced in weanling rats by feeding deficient diets for 6 weeks and using neck collars to prevent coprophagy. The severity of deficiency was monitored by growth, liver flavin levels and the activation coefficient of erythrocyte glutathione oxidoreductase (NAD(P)H) (EC 1.6.4.2). Control groups, receiving the same diet with ample added riboflavin, were fed either ad lib., or were pair-fed with the deficient animals. 2. The hepatic flavoenzyme, methylenetetrahydrofolate reductase (NADPH) (EC 1.5.1.20), was very markedly affected by severe riboflavin deficiency and was significantly, but less markedly, affected by the intermediate level of deficiency. This reduction in activity was due primarily to the direct effect of the diminished supply of riboflavin, and occurred to only a small extent as a result of inanition, demonstrated by a moderate reduction in activity in the more severely food-restricted of the two pair-fed groups. Since the enzyme is assayed in the presence of its flavin cofactor, FAD, it clearly cannot be reactivated in vitro, as some other depleted flavoenzymes can. The discriminatory ability in distinguishing between severe and moderate riboflavin deficiency in vivo confers some potential advantages on this oxidoreductase as a possible index of riboflavin status. 3. The hepatic activity of another key folate-metabolizing enzyme, dihydrofolate reductase (EC 1.5.1.3), was not diminished by riboflavin deficiency in the present study. 4. The ratio, labelled 5-methyltetrahydrofolic acid:other labelled compounds derived from intraperitoneally injected pteroylglutamic acid in extracts of hepatic tissue was significantly reduced in the riboflavin-deficient groups, indicating the possibility of an effect of riboflavin deficiency on folate metabolism in vivo.

Animals↗
PubMed1986

Folate status during pregnancy and lactation in a West African rural community.

Red cell folate concentration was used to measure folate status in 89 rural Gambian women, 81 of whom were pregnant or lactating for the duration of the study. During pregnancy, the women received a haematinic supplement of 500 micrograms pteroyl glutamic acid and 47 mg iron a day, and a food supplement was also given to some of the women during either pregnancy, or lactation, or both. During pregnancy, the red cell folate levels reached a peak around the fifth month, attributable to the haematinic supplement. By the third month of lactation they had fallen back to a low plateau, which was below the accepted lower limit of normality in 56 per cent of those who did not receive a food supplement during lactation. In addition to these changes, there was a significant cyclical variation with season, peak values occurring in the rainy season. Plasma iron values followed the red cell folate patterns quite closely. Changes in blood haemoglobin levels during pregnancy were similar to those reported from other communities; there was also an increase in mean red cell volume during the first half of pregnancy, reaching a peak at the same stage as the peaks of red cell folate and plasma iron. There was no indication of the presence of raised cell volumes in association with low folate indices which might suggest megaloblastosis. It is concluded that the 500 micrograms daily folate supplement is both necessary and adequate to maintain red cell folate levels during pregnancy in this community, but that in the absence of further supplements during lactation, red cell folate levels will fall to undesirably low levels in many subjects by the third-to-sixth month of lactation.

Adolescent↗
PubMed1985

Susceptibility of riboflavin and vitamin A in breast milk to photodegradation and its implications for the use of banked breast milk in infant feeding.

Up to 50% of the riboflavin and up to 70% of the vitamin A in human drip breast milk samples were destroyed during controlled exposure to daylight, either in translucent polythene bottles, or where the milk was pumped through naso-gastric tubing from a syringe to mimic the conditions of enteral feeding. Losses were also observed in milk which was exposed to standard phototherapy illumination under conditions similar to those encountered in the ward, and in this case riboflavin was destroyed to a greater extent than vitamin A. Photodegradation of riboflavin may contribute to the high incidence of biochemical riboflavin deficiency reported in preterm infants receiving breast milk without vitamin supplements. The implications of these findings for feeding high risk term and preterm infants on donor milk are discussed, and the use of low actinic vessels and tubing to minimise photodegradation is recommended.

Female↗
PubMedDate not supplied

Prediction of body composition in elderly men over 75 years of age.

A comprehensive number of body composition predictions (involving weight, height, skinfold thicknesses, bioelectrical impedance and near-infrared interactance-NIRI) were evaluated against total body water (TBW from isotope dilution), in 23 randomly selected men over 75 years old, and dual-energy X-ray absorptiometry (DXA), in 15 volunteers from this group. Comparisons were made between anthropometric and impedance methods for estimating limb muscle mass (obtained using DXA). Bias and 95% limits of agreement between measured TBW and DXA estimates were -2.1 kg and 3.1 kg, respectively (for fat, 5.4% and 6.1% body weight). Agreement between TBW predictions and reference measurements was remarkably variable, irrespective of whether TBW was predicted from TBW-specific equations or indirectly from estimates of fat or fat-free mass: for predictions using anthropometry, bias ranged from -4.7 kg to 1.6 kg and 95% limits of agreement from bias +/- 3.8 kg to +/- 5.0 kg; using impedance, bias was -8.8 kg to 3.2 kg and 95% limits of agreement were bias +/- 3.6 kg to +/- 7.8 kg; corresponding values for NIRI were -5.3 kg and +/- 5.4 kg. Although some non-age-specific equations appeared valid, age-specific equations generally predicted TBW better. Limb muscle mass (DXA) was predicted better using the segmental impedance method, from indices of limb muscle area (r = 0.76; SEE = 1.9 kg) and volume (r = 0.86; SEE = 1.6 kg), than by anthropometry alone (r = 0.61 and 0.71; SEE = 2.3 kg and 2.1 kg, respectively). In conclusion, some body composition predictions are unacceptable (at least for TBW) in older men, and care is recommended when selecting from these methods or equations. Also, the segmental impedance method is as good as, if not better than, anthropometry alone in predicting limb muscle mass (DXA) in older men.

Absorptiometry, Photon↗