Effect of beta-endorphin on endocrine function

It has been disclosed that beta-endorphin exerts marked effect on the secretion of ACTH, prolactin, corticosterone, aldosterone and somatotrophin formation in the pituitary but does not produce any effect on blood thyrotropin. Maximal rise in the concentration of the hormones was seen at the 20th minute, despite the fact that an elevation in the content of some hormones was recorded at the 5th minute following intravenous injection of beta-endorphin. At the 60th minute after beta-endorphin injection the content of prolactin, corticosterone and aldosterone in the blood dropped to the control level, while ACTH content remained significantly higher than in intact animals. One of the possible mechanisms underlying the action of beta-endorphin on the secretion of the hormones indicated might be the changes in the ratio of brain monoamines (a decrease in dopamine).     

Effect of environmental factors on inactivation of B12-dependent glycerol dehydratase from Aerobacter aerogenes]

Effect of temperature, pH and univalent cation on kinetics of self-activation of B12-dependent glycerol dehydratase (GD) from Aerobacter aerogenes with Co alpha-[alpha-(5,6-dimethylbenzimidazolyl]-Co beta-adenosylcobamide (AdoCbl) was investigated. The activation energy of the process of GD inactivation is found to be 3.9 kkal/M, the effect of pH on GD inactivation being insignificant. Monovalent cation is not required for the formation of GD-AdoCbl complex, but it protects the complex from selfinactivation. The rate of GD inactivation greatly depends on concentration of monovalent cations. Effect of K+, Rb+, Cs+, Tl+ and NH4+ cations, which are enzyme cofactors, qualitatively differs from the effect of Na+ and Li+, which are inactive in a catalytic reaction. The presence of at least two cation-binding sites in GD molecule is suggested. Possible mechanism of the effect of environmental factors in self-inactivation of GD-AdoCbl complex is discussed.     

Curve of labeled mitoses in different kinetic states of cell proliferation. III. Experiments with a mathematical model]

By means of computer simulation, the dynamic structure of labeled mitoses curve (LMC) has been investigated. Experiments using computer demonstrated the dependence of LMC form not only on the values of temporal parameters of the mitotic cycle, but also on the state of cell proliferation kinetics before and after pulse labeling. Of particular interest was a case of a temporal block of cell entry into the S period which has been studied in a greater detail. The results of modelling experiments have shown that the universally accepted graphic procedures for the evaluation of mean durations of S- and G2-periods (using 50%-level of LMC) yield the satisfactory estimates only for systems with stationary age distribution for cells in the mitotic cycle (steady, in the strict sense, and exponential states of cell proliferation kinetics). The paper presents also the kinetic interpretation of certain abnormalities in LMC form arising from some peculiarities of cell population kinetics in the real biological experiment.