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Biomedical subjects

N W Solomons

Publications and source records attributed to N W Solomons.

At least 145 records · Page 8Linked to original sources
PubMed1982

The effect of temporary venous occlusion on trace mineral concentrations in plasma.

The effects of short-term venous occlusion on plasma concentration of trace minerals--zinc, iron, and copper--were studied in normal volunteers. In one experiment, antecubital vein blood samples were drawn simultaneously from both arms of 14 subjects while their left arms remained free and their right arms had been occluded from 60 s at 40 mm Hg pressure. Statistical comparison of paired samples showed a significant increase in zinc (p less than 0.05) and iron (p less than 0.001), but not copper concentrations in plasma from the occluded extremity. The mean increase in concentration in the right (ligated) arms with respect to the left (unligated) arms was 3.7 and 24.6%, for zinc and iron, respectively. In a second experiment, simultaneous blood samples were drawn from five subjects with neither arm occluded. No significant difference between right and left was observed. Thus, application of tourniquets during the sampling of venous blood for trace mineral analysis introduces a nonrandom factor. Standardization of sampling techniques is essential to overall reliability of trace mineral determinations.

Adult↗
PubMed1982

Bioavailability of nickel in man: effects of foods and chemically-defined dietary constituents on the absorption of inorganic nickel.

By serial determination of the change in plasma nickel concentration following a standard dose of 22.4 mg of nickel sulfate hexahydrate containing 5 mg of elemental nickel, the bioavailability of nickel was estimated in human subjects. Plasma nickel concentration was stable in the fasting state and after an unlabeled test meal, but after the standard dose of nickel in water was elevated 48.8, 73.0, 80.0, and 53.3 microgram/1, respectively, at hours 1, 2, 3, and 4. Plasma nickel did not rise above fasting levels when 5 mg of nickel was added to two standard meals: a typical Guatemalan meal and a North American breakfast. When 5 mg of nickel was added to five beverages-whole cow milk, coffee, tea, orange juice, and Coca Cola-the rise in plasma nickel was significantly suppressed with all but Coca Cola. Response to nickel also was suppressed in the presence of 1 g of ascorbic acid. Phytic acid in a 2:1 molar ratio with nickel, however, did not affect the rise in plasma nickel. The chelate of iron and ethylenediaminetetraacetate, NaFeEDTA, an iron-fortifying agent suggested for application in Central America, slightly but not significantly depressed plasma nickel rise at 2 hours, whereas disodium EDTA depressed plasma nickel levels significantly below the fasting nickel curve at 3 and 4 hours postdose. These studies suggest that the differential responses of inorganic nickel to distinct foods, beverages, and chemically-defined dietary constituents could be important to human nutrition.

Absorption↗
PubMed1982

Bioavailability of zinc from a diet based on isolated soy protein: application in young men of the stable isotope tracer, 70Zn.

With the aid of the stable isotope, 70Zn, as a tracer and neutron activation analysis, a combination of extrinsic labeling of meals and fecal monitoring of isotope excretion was used as a safe and noninvasive approach for assessing the effects of the vegetable (soy) and animal (milk, beef) proteins on the absorption of zinc in healthy, adult human volunteers. A known amount of 70Zn was added as ZnCl2, to six consecutive meals over a 2-day period during which either one of three isonitrogenous liquid formulas (skim milk; soy isolate; or a 50:50 mixture) or one of two bologna sausages (soy isolate of beef) were given. The mean absorption of 70Zn from milk, soy and soy/milk was 41 +/- 4, 34 +/- 4, and 41 +/- 7% (mean +/- SEM), respectively, the presence of soy protein having no effect on absorption of the extrinsic label. For beef bologna and soy bologna, fractional absorption of the 70Zn tracer was 41 +/- 4 and 30 +/- 3%, respectively. Beef might favor absorption of extrinsic zinc. The kinetics of isotope excretion, pooling procedures, for stool samples and the utility of fecal markers were also evaluated.

Adult↗
PubMed1982

Application of a rapid dark adaptation test in children.

The rapid dark adaptation test (after Thornton) has been shown to correlate with classical dark adaptation test results and vitamin A nutriture in adults. Using this test, 27 children in Guatemala (aged 5-12 years) and 18 children in Baltimore (aged 4 and 5 years) were studied. Plasma for vitamin A and zinc analysis was obtained from the Guatemalan children and dietary histories were obtained from the parents of the Baltimore children. All but two children (ages 4 and 5) were able to complete the study. For the Guatemalan group, the mean time to complete the test was 144 s, and for the Baltimore group, 171 s. Rapid dark adaptation test performance was significantly correlated to the dietary intake of vitamin A by a logarithmic model, p less than 0.05. The rapid dark adaptation test appears to be acceptable for use in childhood populations and could complement biochemical determination of vitamin A and/or zinc in clinical settings, field surveys, and research.

Adolescent↗
PubMed1982

Factors affecting the bioavailability of zinc.

Host factors and dietary factors determine the absorption of zinc by an individual. There is evidence that the entrance of zinc into the body is regulated at the level of the intestinal mucosa by the adequacy of the host's zinc nutriture. Moreover, a variety of gastrointestinal diseases that interfere with the digestion of food, the secretion of zinc-binding ligand, or transmucosal absorption, per se, reduce the efficiency of zinc absorption. Zinc appears to be more available from breast milk than from cow's milk, and, in general, from foods of animal origin than from foods of plant origin. The task of nutrition researchers is to unravel further the mechanisms involved in normal absorption of dietary zinc in human beings and to pursue the identification of foods and to pursue the identification of foods andars to be more available from breast milk than from cow's milk, and, in general, from foods of animal origin than from foods of plant origin. The task of nutrition researchers is to unravel further the mechanisms involved in normal absorption of dietary zinc in human beings and to pursue the identification of foods and chemicals that enhance or inhibit zinc absorption.

Absorption↗
PubMed1981

Some biochemical indices of nutrition in treated cystic fibrosis patients.

Postprandial levels of copper, ceruloplasmin, iron, total iron binding capacity, cholesterol, vitamin A, carotene, folic acid, vitamin C, albumin, and total globulins in plasma, of 25-OH-vitamin D in serum, and of glutathione reductase activity, an index of riboflavin status, in erythrocytes were determined in a group of 18 juvenile cystic fibrosis patients receiving specialized outpatient care with attention to diet, vitamin supplementation, and pancreatic enzyme replacement. Bone mineralization was assessed by radiographic and photon beam technique. In the plasma of cystic fibrosis patients, levels were elevated for copper, ceruloplasmin, total globins, and total proteins and were depressed for iron, vitamin D, vitamin A, carotene, and albumin. Cortical thickness was diminished in the patients, but bone density was not. For patients with cystic fibrosis, a relation was established between forced vital capacity and certain biochemical indices in plasma. As forced vital capacity decreased, plasma levels increased for copper, total globulins and total proteins and decreased for albumin.

Adolescent↗
PubMed1981

Studies on the bioavailability of zinc in humans: effects of heme and nonheme iron on the absorption of zinc.

The change in the concentration of plasma zinc after oral administration of zinc was used as the index of zinc absorption in the study of the interaction of zinc and iron in the human intestine. With zinc sulfate as the source of inorganic zinc, and ferrous sulfate as the source of nonheme iron, a ratio of Fe/Zn of 1:1 slightly inhibited zinc absorption while Fe/Zn ratio of 2:1 and 3:1 substantially inhibited zinc uptake. No effect on zinc absorption was observed, however, when heme iron, as heme chloride, was ingested in a 3:1 Fe/Zn ratio with inorganic zinc. Atlantic oysters providing about 54 mg of zinc were consumed with or without 100 mg of ferrous iron; Fe/Zn ratio was 2:1. With this "organic" form of zinc, iron did not significantly affect zinc absorption. The evidence for competitive interaction of zinc and iron was strongest with nonheme iron and inorganic zinc. Thus, the possibility that intrinsic iron in formulas for feeding infants and in vitamin-mineral supplement might inhibit the absorption of zinc justifies concern about the Fe/Zn ratio in the formulation of these products.

Adult↗