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Biomedical subjects

J M Hsu

Publications and source records attributed to J M Hsu.

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

Zinc deficiency and alterations of free amino acid levels in plasma, urine and skin extract.

The effects of zinc deficiency, in rats, on the levels of free amino acid in urine, plasma and skin extract were studied. In urine, significantly higher concentrations of taurine, urea, threonine, glutamic acid, valine, isoleucine, leucine and lysine were observed in zinc-deficient rats. In plasma, however, the levels of most individual amino acids in zinc-deficient rats were about the same as those in zinc-supplemented pair-fed controls with the exception of threonine, leucine and isoleucine. These three were significantly higher in rats receiving zinc-deficient diet. On the other hand, the zinc-supplemented ad libitum-fed rats had a significantly increased concentration of taurine, aspartic acid, threonine, serine, glutamic acid, alanine, lysine and arginine than either the pair-fed zinc-supplemented rats or zinc-deficient rats. In skin extracts, threonine, valine, leucine tyrosine, lysine, methionine, cystine, aspartic acid and alanine levels were significantly lower in zinc-deficient rats as compared to zinc-supplemented ad libitum-fed controls. However, the zinc-deficient rats had the same amount of methionine, cystine and glycine as the zinc-supplemented pair-fed rats. This observation suggests that the impairment of skin protein synthesis from injected labeled amino acids in zinc-deficient rats as opposed to zinc-supplemented pair-fed controls is not related to the availability or pool size of the precursors.

Amino Acids↗
PubMed1976

Hypomyelination in copper-deficient rats. Prenatal and postnatal copper replacement.

Copper deficiency induced by a low copper diet in three generations of rats was associated with substantial reductions in the yield of myelin (56%), brain weight (11%), and body weight (43%) in F2 generation rat pups nursed by their own copper-deficient mothers. The composition of the purified myelin was not different from that of controls in the content of individual proteins, lipids, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) activity, or GM1 ganglioside. The major myelin-associated glycoprotein (mGP) was consistently shifted slightly toward higher apparent molecular weight in the copper-deficient animals. Postnatal copper replacement by a foster mother produced a normal yield of myelin per gram of brain tissue, but failed to reverse the deficiency of brain and body growth. After copper replacement in a copper-deficient mother's diet prior to conception, a subsequent litter showed correction of all abnormalities found in her previous litters. The results suggest that copper is essential for myelin formation and general growth during critical periods in development.

Age Factors↗
PubMed1975

Enzyme activities in the epidermis of zinc-deficient rats.

Fifteen enzymes participating in epidermal energy metabolism in zinc-deficient and -supplemented rats were assayed utilizing fluorometric microchemical techniques. In the zinc-deficient group, the activities of six enzymes catalyzing glycolysis decreased by 30 to 50% of the control; the most dramatic decreases were found in phosphofructokinase and glyceraldehyde-3-phosphate dehydrogenase. Zinc deficiency caused a 31% decrease in the activity of glucose-6-phosphate dehydrogenase, a 63% decrease in fumarate hydratase, a 46% decrease in glutamate dehydrogenase, and a 30 to 40% decrease in aminotransferases.

Alcohol Oxidoreductases↗
PubMed1975

Free amino acids in plasma and tissue of rats born to underfed dams.

Amino acids were determined in plasma, muscle, and liver tissues of adult male rats born of mothers on restricted or nonrestricted diets during pregnancy and lactation. The concentrations of plasma alanine, glutamic acid, glycine, proline, arginine, and valine were significantly lower in the progeny of restricted mothers as compared to non-restricted mothers. Similar changes were observed in liver tissues. The concentrations of free amino acids in muscle of the perinatally malnourished progeny, however, did not differ significantly from those of the controls. The differences determined in this study are of special significance in view of the fact that the animals studied had been maintained on an adequate diet since weaning. The demonstrated effect of the maternal diet on the plasma aminogram of the off-spring some months later must be considered when interpreting plasma aminograms in studies of malnourished children.

Alanine↗
PubMed1975

Effect of zinc deficiency and repletion on thymidine metabolism.

We studied the effect of zinc deficiency on thymidine metabolism in intact and wounded rats. Zinc deficiency was associated with significantly decreased incorporation of [methyl-3H] thymidine into skin DNA of both intact and wounded rats, as shown by liquid scintillation counting and autoradiography. With wounding, proliferation--as gauged by the labeling index--increased to about twice normal for zinc-supplemented rats, but 3.5-fold for zinc-deficient rats. However, despite the increased proliferation rate, wound-healing in deficient rats was always slower than in zinc-supplemented animals. Incorporation of 3H-labeled thymidine into spleen DNA at 2 and 4 h, and liver DNA at 4 h was also significantly less in zinc-deficient rats than in zinc-supplemented rats. Conversely, DNA synthesis was enhanced in the thymus gland of zinc-deficient rats. Further studies showed that significantly higher percentages of [methyl-14C] thymidine were oxidized by zinc-deficient rats. The specific involvement of the methyl group of thymidine was indicated by the observation of normal oxidattions of [2-14C] thymidine. These findings support the view that zinc directly regulates DNA synthesis.

Animals↗
PubMed1973

Pure culture studies of Erwinia carotovora with 3,5-diiodo-4-hydroxybenzonitrile.

Interactions of ioxynil (3,5-diiodo-4-hydroxybenzonitrile) with a pure culture of Erwinia carotovora grown in a glucose-simple salts medium were studied. Growth of E. carotovora was inhibited by ioxynil and, to a lesser extent, by its acid form at 25 and 50 mug/ml. Growth was not inhibited by the amide or ester forms of ioxynil or p-hydroxybenzonitrile at the same concentrations. E. carotovora could be trained to grow in 50 mug or higher concentrations of ioxynil per ml by serial transfers of the organism through increasing ioxynil concentrations. No degradation or detoxification of ioxynil was detected. Toxicity tests indicated that, in the adapted culture, cell-free supernatant fluid remained toxic to a nonadapted culture. Adaptation of E. carotovora resulted in a lengthened lag phase, a decreased growth rate, and very few adverse effects on the total population. The adapted resistant culture retained this characteristic only when ioxynil was present. Adaptation was demonstrated to be a physiological variation, not a selection of a mutant or of preexisting resistant cells. Ioxynil slightly stimulated the respiration rate of E. carotovora and moderately inhibited that of an adapted culture. Because the respiration rate of an adapted culture in the absence of ioxynil surpassed that of a parent culture still in the presence of ioxynil, a competition of two alternate routes of electron transport is implied. These data support the conclusion that an alternate growth mechanism is involved in the adaptation mechanism.

Carbon Dioxide↗