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Biomedical subjects

G W Evans

Publications and source records attributed to G W Evans.

9 recordsLinked to original sources
PubMed1979

Zinc absorption in the rat determined by radioisotope dilution.

Zinc absorption in rats was examined by use of an isotope dilution technique. Young rats and mature rats fed varying levels of dietary zinc were injected intramuscularly with 65Zn. Nine days later, a zinc balance study was begun and continued for 5 days. The rats were then decapitated and the intestines and kidneys were removed and analyzed for zinc and 65Zn content. The feces were analyzed for zinc and 65Zn content and the specific activities of the intestines and kidneys were used to compute the contribution of endogenous zinc to total daily zinc excretion and thus calculate the true daily absorption of zinc. The zinc concentration of the intestines and kidneys did not differ significantly among groups but the specific radioactivity in these organs decreased as dietary zinc intake increased. Endogenous zinc excretion was greatest in mature rats and young rats fed the highest level of dietary zinc. Mature rats actually absorbed as much or more zinc than young rats fed the same dietary level of zinc. The results demonstrate that zinc homeostasis in rats is maintained by zinc secretion from the intestine rather than by regulation of zinc absorption.

Aging↗
PubMed1979

Visual and verbal memory for objects and their spatial locations.

Four experiments assessed the role of verbal and visual processing in memory for aspects of a simulated, real-world spatial display. Subjects viewed a three-dimensional model of a city with 16 bulidings that were placed on the display. The buildings were represented on the model with or without an accompanying name label on each buliding. After studying the display, subjects were tested on recall and recognition of the building names, picture recognition of the buildings, and spatial memory for where the bulidings had been located. Overall picture recognition accuracy was low, and the presence of a name label on each building significantly reduced picture recognition accuracy but improved relocation accuracy. Spatial location information was not encoded independently of verbal and visual identity information. However, location information was more accurately retained with memory for verbal than visual aspects of the stimuli. The results are discussed in terms of the theoretical importance of differentiating memory for the identity of visual stimuli from descriptive memory for their physical characteristics in "visual memory" research.

Discrimination, Psychological↗
PubMed1978

Relative zinc availability in human breast milk, infant formulas, and cow's milk.

The concentration and bioavailability of zinc was analyzed in 10 varieties of milk. The concentration of zinc averaged 4.1 microgram/ml in unprocessed (raw) cow's milk; fortified infant formulas contained about 3 to 5 microgram Zn/ml; human breast milk and processed cow's milk contained approximately 2 microgram Zn/ml; sweetened condensed milk contained 1.3 microgram Zn/ml, and reconstituted nonfat dry milk contained 0.4 microgram Zn/ml. The mean values for zinc bioavailability to rats were as follows: sweetened condensed milk = 66%; human breast milk 59.2%, processed cow's milk = 43.7 to 50.9%; unprocessed (raw) cow's milk = 42%; nonfat dry milk = 41.2%, and infant formulas = 26.8 to 39.5%. Assuming similar absorption of zinc in rats and humans, our experimental results provide some guidelines for estimating the quantity of zinc that would actually be absorbed from various types of milk.

Animals↗