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At least 199 records · Page 11Linked to original sources
PubMed1984

Involvement of lysine residues in the binding of ovine chorionic somatomammotropin to lactogenic and somatotropic receptors.

The biological activities of several ovine chorionic somatomammotropin (oCS) derivatives obtained by chemical modification of the lysine residues were studied by radioreceptor assays using rabbit mammary homogenates (lactogenic activity, L.A.) and liver homogenates (somatotropic activity, S.A.). Even if the control treatment with BH-4 markedly decreased the L.A., it was clear that methylation mainly affected the S.A. and that ethylation reduced both activities. Guanidination inactivated almost completely both activities and acetimidination at a very low degree (3 of 14 lysines) led to less than 50% of both activities. These results show the involvement of lysine residues in the interaction of oCS with lactogenic and somatotropic receptors.

Animals↗
PubMed1976

Inhibition of mouse testicular DNA synthesis by mutagens and carcinogens as a potential sample mammalian assay for mutagenesis.

Since mutagenic substances induce structural changes in DNA, studies were undertaken to determine whether substances would modify DNA replicative activity. DNA synthesis was quantitated 3.5 h after drug administration as uptake into DNA of a 30-min pulse of 10 muCi of [3H] thymidine. Combinations of methylurea (20000 mg/kg) and sodium nitrite (150 mg/kg) administered p.o. resulted in gastric synthesis of nitrosomethylurea and inhibited testicular DNA synthesis by 83%. Combinations of methylurea and sodium nitrite of 1000 and 100 mg/kg respectively inhibited DNA synthesis by 75%. With dimethylamine and sodium nitrite, a combination which results in gastric synthesis of dimethylnitrosamine, inhibitions of 65 and 57% were observed at 2000 mg/kg together with 150 mg/kg and 1000 mg/kg in combination with 100 mg/kg, respectively. In separate experiments, dimethylnitrosamine (50 mg/kg, p.o.) and diethylnitrosamine (100 mg/kg, i.p.) inhibited thymidine uptake by 30 and 89%, respectively. The mutagenic polynucelar hydrocarbon 3-methylcholanthrene (15 mg/kg) inhibited DNA synthesis by 95% and safrole (640 mg/kg), a mutagenic methylenedioxybenzene derivative, inhibited by 60%. Cadmium chloride (10 mg/kg), acetylaminofluorene (160 mg/kg) and dibutylnitrosamine (500 mg/kg) also induced statistically significant effects. Noncarcinogenic analogues of these substances (anthracene, 125 mg/kg; diphenyl-nitrosamine, 500 mg/kg; piperonyl butoxide, 640 mg/kg, and methylurea, 2000 mg/kg in combination with sodium nitrate) were inactive. Highly toxic substances (potassium cyanide, 2.5 mg/kg; 2,4-dinitrophenol, 20 mg/kg; and lead acetate, 150 mg/kg) were also inactive. This index of mutagenicity appears to have considerable sensitivity and therefore may have potential in drug evaluation.

Animals↗
PubMed1982

Inhibition of mutagenicity of a model nitrosation reaction by naturally occurring phenolics, coffee and tea.

Several plant phenolics, one instant coffee, one instant decaffeinated coffee, one roasted coffee, one Japanese tea, one black Indian tea, and one Chinese tea were examined for their inhibitory properties on mutagenicity resulting from the nitrosation of methylurea. Mutagenicity was estimated as the number of his+ revertants per survivor of Salmonella typhimurium TA1535 which was exposed in suspension to the nitrosation mixtures and the modulating agents for 20 min. Tannic acid, gallic acid and chlorogenic acid suppressed the mutagenicity of the model nitrosation system at concentrations similar to or even lower than ascorbic acid. The three tested coffees and three tested teas exerted an inhibitory effect on the mutagenicity of the test system at doses at which they are consumed.

Chlorogenic Acid↗