Biomedical subjects
Publications and source records attributed to G E Bunce.
Subcutaneous injection of sodium selenite into young rats produces a nuclear cataract within 72 hours. A three-fold elevation in lens calcium and a two-fold increase in lens inorganic phosphate have been found to precede opacification. Scanning electron micrographs suggested weakened cell-to-cell adhesion in the cataractous nuclear zone.
Female rats were fed defined diets limiting in one or more of certain amino acids and with or without vitamin E throughout gestation and lactation. Deficits of tryptophan, phenylalanine/tyrosine, or methionine/cystine reduced the body weight of progeny to about 50% or less of normal but only low tryptophan was cataractogenic. When total dietary amino acids were 12.4%, a low (65 mg%) level of tryptophan resulted in 34% incidence of cataract if vitamin E was simultaneously withheld. Elevation of total amino acids to 24.8% while maintaining tryptophan at 65 mg% caused 70 or 90% incidence of nuclear lens opacities in the presence or absence, respectively, of vitamin E. Maternal dietary amino acid imbalance was also associated with a 50% decrease in lens insoluble (membrane) proteins in the progeny independent of dietary vitamin E or the occurrence of opacities.
1. Pregnant rats were fed either low (less than 1 p.p.m.) Zn or control (40 p.p.m. Zn) diets from day 10 of gestation. They were killed at intervals during the last 96 h preceding the normal time for onset of parturition, and differences in plasma progesterone, oestradiol-17 beta and ovarian 20 alpha-hydroxysteroid dehydrogenase were assessed. 2. Gestation was prolonged in Zn-deficient rats. 3. Although the preparturient decline in plasma progesterone began at the same time in all groups, at term, plasma progesterone concentration in Zn-deficient rats remained significantly higher than in normal females. 4. Induction of ovarian 20 alpha-hydroxysteroid dehydrogenase activity was delayed by about 8 h by Zn deficiency. This delay was not observed if prostaglandin F2 alpha was injected previously. 5. The results suggest a Zn-dependent step(s) in uterine synthesis and/or release of prostanoids.
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Fractions rich in either primary or secondary lysosomes were prepared from rat renal cortex by differential centrifugation and evaluated for their capacity for net calcium uptake. No uptake was observed in the absence of ATP. A vigorous uptake did take place in the presence of ATP but it was largely prevented by azide and other inhibitors of mitochondrial calcium uptake, suggesting that it was attributable to contamination by mitochondria. Evidence was obtained for an inhibitory influence of the secondary lysosomal fraction on mitochondrial calcium uptake.
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The relative effect upon lens transparency of a diet low in both tryptophan and vitamin E was compared to diets low in either nutrient alone during development. Thirty-three percent of 126 progeny from 19 litters at weaning were found to have either unilateral or bilateral lenticular opacities when the maternal diet during gestation and lactation provided only 75 mg L-tryptophan and 0.1 mg dl-alpha-tocopheryl acetate per 100 g diet. No opacities were seen in 179 progency from 20 litters when tryptophan alone was restricted, and only 6% incidence was detected when vitamin E was the sole limiting nutrient. The data reveal a previously unrecognized association between tryptophan and vitamin E relative to fetal lens development.
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