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J K Chesters

Publications and source records attributed to J K Chesters.

34 records · Page 2Linked to original sources
PubMed1978

The assessment of zinc status of an animal from the uptake of 65Zn by the cells of whole blood in vitro.

1. 65Zn uptake by blood cells in vitro has been compared with plasma Zn concentration and plasma alkaline phosphatase (EC 3.1.3.1) activity as indicators of an animal's Zn status. 2. Dietary Zn deficiency, low food intake, reduced dietary protein content and endotoxin administration all reduced plasma Zn concentration in the rat. In each case there was a parallel reduction in plasma alkaline phosphatase activity and an increase in 65Zn uptake in vitro by cells of whole blood. 3. A similar relationship between the three measurements existed in sheep with lowered plasma Zn concentrations whether these were caused by dietary deficiency or by post-surgical stress. 4. 65Zn uptake by cells of whole blood did not differentiate dietary Zn deficiency from the other factors which reduce plasma Zn under 'field' conditions. 5. 65Zn uptake by the cells in whole blood in vitro was three to five times less rapid in blood of ruminant origin than in that from non-ruminants. This difference related to the erythrocytes rather than to the leukocytes or the plasma.

Alkaline Phosphatase↗
PubMed1978

Effect of age, weight and adequacy of zinc intake on the balance between alkaline ribonuclease and ribonuclease inhibitor in various tissues of the rat.

1. Deficiency of zinc inhibits growth and also increases the activity of alkaline ribonuclease in certain tissues of the rat (Prasad & Oberleas, 1973). Zn could influence ribonuclease activity by direct effects on the enzyme or its natural inhibitor, or non-specifically as occurs when growth rate is affected by various other factors. These possibilities were studied. 2. Alkaline ribonuclease was shown to be inhibited by Zn in vitro, but the concentrations of Zn required were so high that the enzyme was probably not directly affected by changes in tissue Zn concentration caused by dietary deficiency. 3. At lower concentrations, Zn added in vitro increased the activity of alkaline ribonuclease in tissue homogenates probably by inactivating the inhibitor of the enzyme. 4. Age, weight and particularly food restriction caused tissue-specific alterations of ribonuclease and ribonuclease inhibitor concentrations in liver, kidney, oesophagus, testis and thymus. 5. The ribonuclease activities in liver, kidney and testis of Zn-deficient rats were unaltered in comparison with those of pair-fed rats. In thymus, which decreased in weight in the Zn-deficient animals, there was a concomitant increase in ribonuclease activity, but in oesophagus, the deficiency reduced the activity of ribonuclease. 6. The effects of Zn deficiency upon alkaline ribonuclease and its inhibitor are probably secondary consequences of reductions in food intake or growth.

Age Factors↗
PubMed1975

Comparison of the effects of zinc deprivation and actinomycin D on ribonucleic acid synthesis by stimulated lymphocytes.

1. EDTA inhibited incorporation of [3H]uridine into RNA of lymphocytes, but did not decrease uptake into the cold-acid-soluble fraction of the cells. The inhibition by EDTA was largely reversible by simultaneous addition of Zn2+. 2. Low concentrations pf actinomycin D (3 ng/ml) added at the time of stimulation of the cells inhibited [3H]uridine incorporation into RNA, but concentrations of 50-100 ng/ml were required to produce the same degree of inhibition if addition of actinomycin D was delayed until just before the incorporation was measured. This difference in sensitivity did not reg within the cells. 3. When added immediately before phytohaemagglutinin, actinomycin D (3 ng/ml) and EDTA produced similar time-courses of inhibition of uridine incorporation. 4. Uridine incorporation at 32h was inhibited when actinomycin D (3 ng/ml) or EDTA was added just before stimulation of the cells, but was only slightly affected when they were added at 32h. At intermediate times the incorporation of uridine remained sensitive to addition of EDTA for longer than it was sensitive to actinomycin D. 5. Polyacrylamide-gel separation of RNA synthesized in EDTA-treated cultures in the presence or absence of added Zn2+ showed that lower availability of Zn2+ resulted in a decreased rate of transfer of radioactivity from 32S to 28S rRNA and decreased survival of 28S rRNA relative to 18S rRNA. 6. Close similarities have been shown to exist between the effects of EDTA and low concentrations of actinomycin D. Not all the effects of EDTA could be explained by postulating that Zn2+ was a constituent of RNA polymerase I, nor were the effects of actinomycin D readily explained by previously suggested mechanisms of action of this antibiotic.

Animals↗
PubMed1972

The role of zinc ions in the transformation of lymphocytes by phytohaemagglutinin.

1. Incorporation of [(3)H]thymidine into DNA was inhibited by EDTA and diethylenetriamine-NNN'N''N''-penta-acetate but not by nitrilotriacetate even when Ca(2+) was present at more than twice the concentration of the chelators. 2. The inhibition caused by EDTA was most effectively reversed by Zn(2+) but also to a lesser extent by Cd(2+). Very little if any activation of the EDTA-inhibited system was obtained with Co(2+), Cu(2+), Fe(3+), Mn(2+) or Ni(2+) added alone. 3. Fe(3+) added to the Zn(2+)-activated lymphocytes in the presence of EDTA markedly increased thymidine incorporation. Addition of Cd(2+) prevented the inhibition of incorporation which occurred at high Zn(2+) concentrations. 4. If EDTA was added more than 15h after phytohaemagglutinin, the inhibition of incorporation was less than that obtained by its addition at zero time. If Zn(2+) was added later than 12h after EDTA and phytohaemagglutinin, the inhibition of incorporation by EDTA was not fully reversed. A study of the time-course of the effects of delayed additions of EDTA and Zn(2+) suggested that, on average, the cells required Zn(2+) between 20 and 30h after phytohaemagglutinin addition to allow the full rate of thymidine incorporation at 37h. 5. The increase in the rate of protein synthesis caused by phytohaemagglutinin was not inhibited by EDTA until about 8h. The further increase after this was totally inhibited by EDTA but this inhibition was fully reversible with Zn(2+). The rate of protein synthesis in EDTA-inhibited cultures at 40h was the same as that at 10h. 6. There was a close similarity between the effects of EDTA on lymphocyte stimulation and those reported by Kay et al. (1969) with low doses of actinomycin D.

Animals↗
PubMedDate not supplied

Thymidine incorporation is less sensitive to lack of zinc in human than in rodent cells.

The inhibition of thymidine incorporation by inadequate availability of zinc induced by adding a chelator to the culture medium was significantly less in human cell lines than in rodent cell lines. In contrast, zinc uptake into the human cells was inhibited by the chelator to a greater extent than with rodent cells. The possible implications of these observations for the dietary zinc requirements of humans and rodents are discussed.

Animals↗