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Biomedical subjects

D Barltrop

Publications and source records attributed to D Barltrop.

At least 37 records · Page 2Linked to original sources
PubMed1977

Absorption and endogenous faecal excretion of calcium by low birthweight infants on feeds with varying contents of calcium and phosphate.

Low birthweight infants aged 4-41 days were given from birth one of three experimental milk formulae varying widely in content of calcium and phosphate. Ca and P in feed, urine, and faeces were measured between carmine markers corresponding to a metabolic period of 48 hours. Calcium enriched in 46Ca to provide a marker for the dietary Ca was added to one feed and 46Ca measured in urine and faeces. True absorption of Ca and endogenous excretion into the bowel could then be inferred. True absorption of Ca was proportional to Ca intake and independent of P intake. Endogenous faecal excretion seemed to be independent of both Ca P intakes, and varied widely between different infants in the range 4-150 mg/day. Urine Ca was low and retention was essentially the difference between true absorption and endogenous faecal excretion. Retention of Ca tended to be much greater on a high Ca intake, but the variability in retention between infants on a given intake was large, paralleling the variability in endogenous faecal excretion. The variability in plasma Ca concentrations in newborn infants may in part be a consequence of wide individual variability in endogenous faecal excretion. The 46Ca marker technique provides a means of investigating the factors determining this variability.

Calcium↗
PubMed1977

Urinary and faecal excretion of marker calcium (46Ca) by low birthweight infants.

Low birthweight infants were given calcium enriched in 46Ca in a single feed. The specific activity of successive urine samples showed that the absorption of the marker was largely complete in about 4 hours. The rate of decrease of urinary specific activity after 3 1/2 hours was exponential and very similar in 8 sets of observations in 6 infants. Its extrapolation backwards to 1 hour may indicate the size of the exchangeable calcium pool, usually about 200 mg/kg body weight. Completeness of faecal collection for estimation of 46Ca is essential for accurate determination of true absorption and endogenous faecal excretion of natural Ca. In 5 infants examined, nor marker was detectable in faeces excreted later than 48 hours after the first stool containing marker. Nevertheless, reasons are given why a collection period limited to 48 hours may sometimes involve error.

Calcium↗
PubMed1977

Significance of Ca-soap formation for calcium absorption in the rat.

The significance of calcium soap formation in the inhibition of calcium absorption has been studied in rats. 47Ca labelled soaps of fatty acids were introduced into the duodenum and the absorption of calcium measured after four hours in a whole body counter. The absorption of calcium was inversely correlated with the chain length of the fatty acid varying from 1% for Ca-stearate to 60% for Ca-hexanoate. Increasing the degree of unsaturation of the fatty acid was accompanied by increased calcium absorption. The availability of calcium for absorption from the soaps was correlated with their solubility in 1% aqueous Na-tauroglycocholate. The percentages of calcium as soap in the small intestine and the faeces after intragastric administration of calcium and fats were similar, which suggests that the faecal content of calcium soaps is an index of intestinal soap formation. Soap formation was negligible when CaCl2 was given with tristearate, triolaeate, or tridecanoate and no depression of calcium absorption was observed. Calcium absorption was markedly impaired by the addition of phosphates at a Ca/P ratio of 1:1 irrespective of the presence of neutral fats. Stearic acid resulted in significant soap formation and reduced calcium absorption. The degree of Ca-soap formation and the inhibition of calcium absorption were well correlated. The results suggest that, although calcium soap formation may markedly depress calcium absorption in the rat, no significant soap formation takes place when fats are given in the form of triglycerides.

Animals↗
PubMed1976

The influence of dietary minerals and fat on the absorption of lead.

The nutritional factors influencing the absorption of lead from the gut have been studied using both intact animals and ligated gut loop preparation. Short-term feeding studies have been made in groups of six animals using diets of constant lead content (0.075%) but in which the nutritional components were varied sequentially. Dietary lead was labelled with 203Pb. Absorption was determined in the carcass and individual organs by means of a small-animal wholebody counter. The results showed that absorption was enhanced to twenty-times control value by diets deficient in minerals and seven-fold by diets of high fat content. Conversely, high mineral diets have been shown to result in a two-fold reduction in lead absorption. The interaction of lead with individual dietary components has been further studied under controlled conditions using ligated gut loop preparations. Using this technique the relative roles of luminal interaction and tissue response for lead absorption have been explored and the kinetics of lead absorption determined.

Animals↗
PubMed1974

Children and lead.

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Air Pollution↗
PubMed1974

Significance of high soil lead concentrations for childhood lead burdens.

The lead exposure of children and their mothers has been studied in two towns with mean soil lead contents of 900 and 400 ppm. No significant difference in blood or fecal lead contents was demonstrated between the two populations, but a small difference in hair lead content was shown. The blood lead content of children was greater than that of their mothers and was higher in the summer than in the spring samples. Children with pica for soil in the control area had increased lead content of blood and hair. Preliminary data for children and mothers from villages with mean soil lead contents of 500 ppm and 10,000 ppm are reported which show significant differences in blood and hair lead content within the normal range. The data suggest that soil lead content of 10,000 ppm may result in increased absorption of lead in children, but to a degree which is unlikely to be of biological significance.

Adult↗