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Biomedical subjects

L Leeper

Publications and source records attributed to L Leeper.

4 recordsLinked to original sources
PubMed1987

Effects of soy formulas on mineral metabolism in term infants.

We studied 40 healthy term infants who received a soy-based formula containing either a single carbohydrate (glucose polymers) or dual carbohydrates (glucose polymers and sucrose). Ten exclusively breast-fed infants served as controls for the first four months of the study. All infants were studied at 2 weeks, 2 months, and 4 months of age for anthropometric development, biochemical values, and bone mineral content. There were no differences among the three groups in weight, length, or head circumference gains. Serum levels of calcium, phosphorus, magnesium, copper, 25-hydroxycholecalciferol, and alkaline phosphatase were also similar. However, at 4 months of age, the breast-fed group had a higher plasma zinc level than both formula-fed groups, and at 2 and 4 months of age, it had higher bone mineral content and bone density.

Calcium↗
PubMed1982

Intestinal maturation: in vivo magnesium transport.

We investigated with an in vivo single pass perfusion technique net transport of magnesium in the jejunum, ileum and colon segments of suckling, weanling and adolescent rats. The concentration of magnesium in the isotonic sodium chloride solution perfused through the intestinal segments was either below (0 and 0.5 mmoles/liter) or above (1, 2.5 and 5 mmoles/liter) serum ionized magnesium. The relationship between net transport rates (mumoles/h per g dry weight) and luminal magnesium concentration was liner in all three intestinal segments of the suckling rats. In the weanling and adolescent rats, the relationship between net transport and luminal magnesium concentration was linear in the small intestinal segments; however, a change to a saturable, curvilinear relationship was noted in the colon segments. Rates of transport were significantly greater in all segments of suckling rats compared to corresponding segments of the adolescent rats, when luminal magnesium concentration was 2.5 and 5 mmoles/liter. Net transport rates in the colonic segments at all ages were either equal to or greater than rates in the small intestinal segment at the same age period. The change in the relationship between transport rates and luminal magnesium in the colonic segments suggested that the mode of magnesium transport change at the time of weaning from mainly a passive mechanism in the suckling period to mainly a carrier mediated mechanism in the adolescent rats. This is the first demonstration of developmental characteristics of magnesium transport in animals.

Aging↗