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Biomedical subjects

D R Fraser

Publications and source records attributed to D R Fraser.

At least 19 recordsLinked to original sources
PubMed1991

Bone mineral content of British and rural Gambian women aged 18-80+ years.

The bone mineral content (BMC) of the mid-shaft radius was measured in 446 rural Gambian and 349 British women aged 18-80+ years using single-photon absorptiometry. The two groups of women differed substantially in habitual calcium intake, calcium requirements for reproduction, physical activity and incidence of minimal-trauma fractures. The relationships of BMC with bone width (BW) and with body weight and height were explored using stepwise multiple regression analysis. The pattern of BMC with age was similar in The Gambia and Britain; BMC increased slightly to a peak at the end of the fourth decade followed by a decrease of about 30% between 40 and 70+ years. Gambian women had significantly lower BMC than British women of the same age (-5.6%, P less than 0.001) but after adjusting for weight, height and BW, the BMC of Gambian women was shown to be slightly higher than that of British women (+2.1%, P less than 0.05).

Absorptiometry, Photon↗
PubMed1990

Bone mineral content of Gambian and British children aged 0-36 months.

The influence of age, sex and body size on the bone mineral content of the radius (BMC) measured by single-photon absorptiometry has been studied in 134 British and 243 rural Gambian children aged 0-36 months. Growth rates and childhood nutrition, including calcium intakes, were markedly different in the two communities. In both groups BMC increased with age and was higher in boys (8%, P less than 0.001). Adjustment for body size (height, weight, bone width), using multiple regression analysis, removed the age effect and reduced the sex difference to 4% (P less than 0.01). Gambian children had significantly lower BMCs than British children of the same age (P less than 0.001), averaging 11% close to birth and diverging to a calculated difference of 31% at 36 months. The differential was reduced after adjustment for body size but remained significant (P less than 0.01) with BMC values diverging from birth to a predicted difference of 12% at 15 kg body weight. The extent to which these results reflect the low calcium intakes of Gambian children requires further study.

Aging↗
PubMed1990

Breast-milk calcium concentrations during prolonged lactation in British and rural Gambian mothers.

Detailed investigation of breast-milk calcium concentrations during 2 years of lactation have been conducted in Cambridge, UK, and rural Gambia. Mature milk concentrations remained steady for 3 months but declined during months 4-12 by over 25% (p less than 0.001). The pattern was identical in both communities despite differences in breast-feeding practices. Calcium concentrations were not related to feed frequency or breast-milk sodium concentrations, suggesting that breast involution is not responsible for the decrease after 3 months. Breast-milk calcium concentrations were characteristic of the individual, varied twofold between mothers and were independent of maternal age, parity and milk output. Gambian breast-milk contained 19% less calcium than Cambridge milk, throughout lactation (p less than 0.001). The extent to which this reflected the lower calcium intakes of Gambian mothers is unknown. Further studies are required to determine factors regulating breast-milk calcium secretion.

Breast Feeding↗
PubMed1988

Vitamin D supply to the rat fetus and neonate.

The prevention of neonatal rickets by oral supplementation with vitamin D2 (ergocalciferol) has tended to obscure our ignorance of the natural mechanism by which young mammals receive an adequate supply of vitamin D. To investigate the possibility of specific intrauterine transfer and storage of vitamin D in fetal tissues, vitamin D-deficient female rats were given depot injections of 3H- or 14C-labeled vitamin D3 (cholecalciferol) before mating and the 3H-labeled animals were killed at stages during the last third of gestation. Analysis of lipid extracts from whole fetuses revealed a linear increase in the concentration of 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3, and D3 itself between days 14 and 19 of gestation. During this period the elimination half-time of 3H-labeled molecules in maternal plasma fell from 27.1 to 4.4 d, suggesting that a specific mechanism was transferring vitamin D molecules into the fetuses. The vitamin was stored predominantly as 25-hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3, with the highest concentrations in fetal muscle. Immediately after birth, pups from 3H- and 14C-labeled mothers were exchanged and later killed after 1-3 wk of suckling. Analysis of total lipid extracts for 3H and 14C content determined the relative contributions of vitamin D supplied before birth via the placenta and after birth in the maternal milk. The vitamin D content of the rat milk was relatively high, between 1.0 and 3.5 micrograms/liter. Nevertheless, the supply of vitamin D in utero, rather than from milk, was the main determinant of vitamin D status in early neonatal life. This is the first indication in a mammal of a specific transfer mechanism that allows the fetus to accumulate vitamin D from the mother during the last third of gestation.

24,25-Dihydroxyvitamin D 3↗
PubMed1987

Metabolic inactivation of vitamin D is enhanced in primary hyperparathyroidism.

1. The elimination half-time of 25-hydroxyvitamin D in plasma was estimated after intravenous injection of the radioactively labelled metabolite in seven patients with primary hyperparathyroidism before and after excision of a parathyroid adenoma. 2. The elimination half-time of 25-hydroxyvitamin D was significantly shortened in primary hyperparathyroidism and reverted towards normal after parathyroidectomy. 3. The increased metabolic clearance of 25-hydroxyvitamin D in primary hyperparathyroidism was accounted for by an increased excretion of vitamin D-derived inactivation products in the faeces. 4. Enhanced hepatic inactivation of 25-hydroxyvitamin D may be important in the development of vitamin D deficiency in primary hyperparathyroidism.

Aged↗
PubMed1976

Vitamin D in the avian egg. Its molecular identity and mechanism of incorporation into yolk.

The chemical identity of vitamin D in the egg of the domestic fowl was studied by analysing radioactivity in eggs from hens injected with [3H]cholecalciferol. Labelled molecules were found throughout the egg, but the concentration of total radioactivity in albumin was only 5-7% of that in yolk. In lipid extracts of yolk, more than 90% of the radioactivity was as unchanged cholecalciferol and 5% as 25-hydroxycholecalciferol. Only about 3% of the radioactivity in albumin was chloroform-soluble, and of this 40% was 25-hydroxycholecalciferol and 15% was cholecalciferol. Evidence is presented to support the idea that the specific transport of cholecalciferol into yolk is mediated by a cholecalciferol-binding protein in blood. This protein forms a complex with yolk proteins in transit from liver to ovary via the blood. A cholecalciferol-binding protein, chromatographically similar to that from blood, was found in egg yolk. It is postulated that cholecalciferol forms part of a complex with its specific binding protein, Ca2+ and the yolk phosphoprotein, phosvitin. This complex is then incorporated into yolk by the thecal cells of the ovarian follicle.

Animals↗