Studies on deoxyribonucleoproteins. IX. Subfractions of deoxyribonucleoproteins from rat and mouse liver.

By carrier-free continuous electrophoresis, deoxyribonucleoprotein from rat and mouse liver could be separated into two subfractions. The more anodic fraction (DNP I), comprising 5 - 8 per cent of the total, contains fewer proteins (two types of histones only). [3H]Cyclophosphamide caused in vivo a 2.5 times higher alkylation of the DNA in in DNP I than of the DNA in DNP II. These and additional results led to the suggestion of a structural model with DNP I as a spacer in the deoxyribonucleoprotein fiber.     

Novel copper amine oxidase activity from rat liver mitochondria matrix

Copper containing amine oxidases (Cu-AO) represent a heterogeneous class of enzymes classified as EC 1.4.3.6. The present study reports preliminary results on the presence of a novel amine oxidase activity in rat liver mitochondria lysates. Such enzymatic activity was found in the soluble mitochondrial fraction, obtained by simple osmotic shock. The mitochondrial amine oxidase was isolated by affinity chromatography on a newly synthesised spermine-Sepharose. SDS-PAGE showed a single band at about 60 kDa. Upon chromatographic purification, the enzymatic activity was very labile. The crude enzyme activity was tested by spectrophotometric measurements, determining hydrogen peroxide production following oxidative deamination of different substrates, such as polyamines (spermine, spermidine, putrescine and cadaverine) and monoamines (dopamine and benzylamine). The activity, observed on polyamines and not on monoamines, was inhibited by semicarbazide and azide, but not by pargyline, clorgyline and l-deprenil. Enzyme specificity was tested on several diamines characterized by different carbon atom chain length in the range 2-6 carbon atoms. The highest activity was found with 1,2-diamino-ethane and the highest affinity with 1,5-diamino-pentane. The above reported results suggest the presence of a novel copper-dependent amine oxidase in liver mitochondria matrix.     

Effect of cobalt on heme biosynthesis in rat liver and spleen.

1. Succinate-cytochrome c reductase activity in rat liver decreased to about 60% of the control value after a single injection of cobalt or in a steady state of intoxication, but the activity in the spleen was unaltered. 2. Incorporation of radioactive glycine and 5-aminolevulinate into heme of the liver was markedly inhibited by cobalt treatment. 3. 5-Aminolevulinate synthase [EC 2.3.1.37] activity in the liver decreased to 40% of the control value 4 hr after cobalt injection, and completely recovered 20 hr later. Phenylhydrazine-induced 5-aminolevulinate synthase activity in the spleen was not decreased by cobalt injection. 4. Porphobilinogen synthase [EC 4.2.1.24] activity in the liver decreased and reached its minimum value (42% of the control) 12 hr after cobalt injection. On the other hand, the activity in the spleen showed a marked increase 24 hr after coblat injection. 5. Ferrochelatase [EC 4.99.1.1] activity in the liver was essentially unaltered by cobalt treatment, while the activity in the spleen was elevated dramatically after 24 hr. 6. Concentrations of cobalt after a single injection were about 0.3 mM and 0.03 mM in the liver and spleen, respectively. 7. Inhibitions of 5-aminolevulinate synthase and porphobilinogen synthase activities by cobalt in vitro were not as marked as expected from in vivo experiments.     

Effect of ionizing radiation on methylation of lysyl tRNA synthetase from rat liver

X-irradiation of animals with an absolutely lethal dose of 0.21 C/kg increases the incorporation of a methyl group into aminoacyl-tRNA-synthetases the radioactive label being traced in lysine, arginine, and histidine. The isolated protein methyltransferase methylated total preparations of aminoacyl-tRNA-synthetases and lysyl-tRNA-synthetase of rat liver in the in vitro experiments with the use of S-adenosylmethionine-14CH3 as a donor of methyl groups: the radioactive label was traced in arginine, lysine, histidine, aspartic and glutamic acids.     

Measurement and activity of cytosolic deoxyribonucleoside-activated nucleotidase in various cell types from rat liver and spleen

The enzyme activity was measured in hepatocytes, Kupffer cells, endothelial cells and spleen cells. Hepatocytes showed proportionality between enzyme activity and cytosol concentration, but with Kupffer cells, endothelial cells and spleen cells the specific activity decreased with decreasing cytosol concentration when the amount of cytosol protein in 250 microliters incubation mixture was below 80, 60 and 20 micrograms, respectively. The specific activities in hepatocytes, Kupffer cells, endothelial cells and spleen cells were 2, 16, 18 and 115 nmol/min per mg of cytosol protein, respectively.     

Effect of transcortin on the corticosterone-transforming activity of cytosol from the rat liver

The study of transcortin role in 3H-corticosterone metabolism has shown that transcortin of blood plasma from rats bearing Walker carcinosarcoma preserves the hormone conversion to dihydrocompounds 4 time less intensively than transcortin taken from healthy rats. Inactivated transcortin exerts no effect on the rate of formation of 5 beta-metabolites. Under the influence of homogeneous transcortin samples, a decrease in the content of 5 beta-reduced corticosterone metabolites is revealed to occur depending on transcortin concentration in the system. It is shown that in incubation systems where hormone is in the bound state the metabolism preserving capacity of transcortin depends on the temperature degree. The transcortin activity on corticosterone metabolism is supposed to be closely related to the intensity of its complexing with transcortin.     

Effect of retinoids on rat spleen

It has been shown in experiments on Wistar male rats with the use of light and electron microscopy and morphometry that a single intraperitoneal injection of high doses of all-trans-methylretinoate and methyl-7,8- dihydroretinoate leads to an increase in the spleen weight, the appearance in the spleen of red cells changed in the shape, activation of phagocytic intensity of macrophages, intercellular interaction, lymphocyte proliferation and formation of new lymph follicles.