Biomedical subjects
Publications and source records attributed to T M Tretyak.
Apurinic and/or apyrimidinic (AP) sites were excised from PM2 phage DNA by two enzymes: an AP endodeoxyribonuclease isolated from rat neocortex chromatin and a rat brain exodeoxyribonuclease, DNase B III. The resulting gap was filled with DNA polymerase beta prepared from rat liver and finally ligated by Escherichia coli DNA ligase.
Exploratory activity in the open field and noradrenaline concentration in the neocortex and brain stem were investigated in intact rats (n = 10) and in the following groups of rats with early postnatal neurotoxic (6-hydroxydopamine) lesion of the catecholaminergic system: (i) rats with embryonal locus coeruleus grafts in the frontal neocortex (n = 5); (ii) rats with the same grafts in lateral ventricles (n = 4); (iii) a control group with intracortical hippocampal tissue grafts (n = 3); (iv) sham-operated rats (n = 3). Experiments were performed by four independent groups of investigators using a double-blind method. In sham-operated rats as well as in rats with hippocampal grafts, and with locus coeruleus grafts in the ventricles, both exploratory activity and noradrenaline content of the forebrain were significantly lowered. In the rats with intracortical locus coeruleus grafts the level of exploratory activity was much higher (almost as in intact controls). This improvement of exploratory behaviour correlated highly with increased noradrenaline concentration in the forebrain. In all animals with locus coeruleus in lateral ventricles a significant increase in noradrenaline level of the brain stem was present, but no change of exploratory behaviour was observed. The grafts with the 3-mm-thick slabs of the adjacent tissue were dissected from the brain and used for histological analysis. The presence of typical locus coeruleus cells was shown in neocortex of all animals which received the grafts of corresponding tissue. The data show the possibility of stable compensation of the forebrain noradrenaline level and exploratory behaviour by embryonic noradrenergic neurons grafted into the neocortex, but not into lateral ventricles.
The development of alloxan-induced diabetes in rats is shown to be accompanied by a decrease in the norepinephrine (NE) and serotonin (5-OT) content in the neocortex and caudal segment of the brain stem. Simultaneously the intensity of 3H-leucine labelling of the brain tissue was decreased. The attempt to compensate the diabetic syndrome in rats by transplanting the embryonic pancreas (EP) into the anterior chamber of the eye (ACE) was successful. All the animals with the adapted transplant showed a return of the monoamine level to the normal, a decrease in urine glucose, as well as normalization of protein synthesis by the 14th-20th days.
An exodeoxynuclease with single-stranded DNA specificity has been isolated from rat brain and purified to electrophoretic homogeneity. Approximately 1100-fold purification with a yield of 16% has been achieved by chromatography on DNA-agarose, hydroxyapatite and Sephadex G-200. The enzyme has a pH optimum at 8.4, requires Mg2+ or Mn2+ as a cofactor and has a molecular weight of about 60000. It hydrolyzes homologous, heterologous, synthetic and depurinated substrates at the same rate liberating nucleoside 5'-monophosphates but does not attack ultraviolet-irradiated polydeoxyribonucleotides. This DNase is localized predominantly in neuronal cell nuclei and appears to be lacking in rat liver tissue.