Use of spectral characteristics of ryodipine in the study of dihydropyridine receptor complex of neuronal membranes]

A fluorescent dihydropyridine (DHP) derivative, ryodipine, was used to study structural characteristics of the DHP-sensitive Ca-channels in nerve terminals (synaptosomes) isolated from the rat cerebral cortex. It was found that an inductive resonance energy transfer from membrane proteins to ryodipine occurred in synaptosomal membranes. Two groups of membrane proteins differentially accessible to ryodipine were found by quenching of their own fluorescence. The percentage of group I proteins (20%) whose fluorescence was quenched by up to 1 microM ryodipine, was increased by 50% upon K(+)-depolarization and remained unchanged upon the addition of 100 microM Ni2+, whereas the addition of 100 microM Cd2+ prevented the increase induced by K(+)-depolarization. Nifedipine and nicardipine competed with ryodipine for the DHP receptor as evidenced by the change in percentage of group I proteins. The percentage of group II proteins (50% at 10 microM ryodipine) remained unchanged during various functional alterations of the synaptosomal membranes. Model experiments on proteoliposomes demonstrated that binding of ryodipine to synaptosomal membranes was due mainly to the hydrophobicity of DHP but not the ligand-receptor interaction. Nonetheless we that the membrane proteins-ryodipine system could be a qualitative test for the functional state of DHP-sensitive Ca-channels.     

Response to light-shade difference in anucleate and polynucleate specimens of Amoeba proteus

The enucleated specimens of Amoeba proteus, the anucleate fragments, and the polynucleate individuals which all are capable of cortical contraction but not of locomotion, may be reactivated by the light-shade difference established across their body. Individual cells or fragments migrate toward the shade. The motory polarity and coordinated movement disappear immediately after cessation of the stimulus. The results are interpreted according to the earlier hypothesis that the necessary to maintain the motory polarity of amoebae. It is suggested that the anucleate and polynucleate specimens are incapable of coordinated movements when non-stimulated, because of a deficiency or an excess, respectively, of the regulatory relaxing factor secreted by the nucleus of Amoeba proteus.     

The catecholamine system in rat fetal brain with a disrupted corticosteroid balance]

The disturbance of corticosteroids balance of female rats on the 16 and 18 days of pregnancy by injections of exogenous corticosterone or methopyrone--blocker of endogenous hormone formation--decreased both body weight and activity of the rate-limiting catecholamine synthesising enzyme--tyrosine hydroxylase (TH) in the stem half of the 21 day fetal brain. Concomitantly with inhibitory action, which may be caused by general retardation of the organism development, corticosteroids stimulated TH activity during prenatal ontogenesis. Fetuses developed under elevated corticosteroid level had lower body weight but higher TH activity in comparison with fetuses endured the deficit of these hormones. Besides, corticosterone injection to the females on the 20th day of gestation increased in 6 hours TH activity in stem half of their fetus brain. The data obtained suggested the prominent role of corticosteroids in the prenatal development of brain catecholaminergic system.     

Changes in enzymes during aging of human diploid cells. Glucose-6-phosphate dehydrogenase]

The thermal inactivation kinetics of glucose-6-phosphate dehydrogenase during ageing of human diploid cells were studied. It was shown that semi-logarithmic anamorphisms of the thermal inactivation kinetic curves may be presented as a total of two rectilinear sites corresponding to the thermolabile and thermostable fractions of the enzyme. In ageing cells the enzyme stability is decreased as compared to the young ones due to the increase in the amount of the thermolabile fraction. It was also found that despite a certain variability in the process of the cell growth at the 22nd passage the thermal stability of glucose-6-phosphate dehydrogenase is decreased, while the enzyme thermal stability in the cells at the 52nd passage is monotonously increased. Purification of the enzyme from ageing and young human diploid cells results in an increase of the enzyme stability. However, when the enzyme was isolated from young cells, it possessed a higher thermal stability.