Biochemical and Electron Microscopic Studies of Rat Skin During Zinc Deficiency

The Ultrastructure of the Crop in the Zinc-deficient Chicken

“…Although the chicken crop epithelium is not normally keratinized, the reduction in tonofilaments and ribosomes may be associated with abnormal protein metabolism. Hsu et al (1974) found less rough endoplasmic reticulum in fibroblasts of zinc-deficient rats and they suggest that this indicates a derangement in ribosome formation.…”

“…The nucleolus normally contains some D N A and considerable amounts of R N A so that these morphological changes may reflect alterations of nucleic acid metabolism associated with zinc deficiency. Unequivocal evidence for the necessity for zinc in nucleic acid metabolism in birds is lacking (TURK, 1966;MACAPINLAC et al, 1968) but there is no doubt that D N A and R N A synthesis are impaired in zinc-deficient rats (CHESTERS, 1974; Hsu et al, 1974). Apart from species differences, difficulty in determining the significance of zinc deficiency in nucleic acid metabolism may result from different organs being unequally susceptible to its effects; HSU et al (1974) considered the skin of rats, which, like the crop, is a squamous epithelial tissue, to be a sensitive target for zinc deficiency.…”

“…The changes which occurred i n the cytoplasm of the epithelial cells of the crop also suggest reduced protein synthesis although it is uncertain whether this might be due to a direct effect of zinc on cytoplasmic metabolism or to the complex interrelationship of nucleolar, nuclear and cytoplasmic D N A and RNA. Diminished capacity to incorporate cystine-% and several other amino acids into the protein of rat skin has been demonstrated (HSU et al, 1974). Electron microscopic studies have shown that keratin is reduced in amount in the skin of the interdigital web of zinc-deficient ducks (WIGHT, 1977).…”

Some histochemical observations on zinc deficiency in chickens

“…Hsu et al, 1974). Chemical analysis has shown that RNA is decreased in the whole skin of rats (Hsu et al, 1974). Although the quantity of RNA in the nucleolus of the crop epithelium appears by histological methods to be increased, this does not necessarily mean that the total RNA content of the cell is also increased because from ultrastructural studies (Wight and Dewar, 1978) it appears that fewer ribosomes are present.…”

“…In the case of DNA, this may be through decreased thymidine kinase activity (Prasad and Oberleas, 1974) but the mechanism in RNA synthesis is less certain although involvement of RNA polymerase or ribonuclease have been suggested (cf. Hsu et al, 1974). Chemical analysis has shown that RNA is decreased in the whole skin of rats (Hsu et al, 1974).…”