Effect of adrenoreceptor blockaders on the mitotic activity of regenerating liver]

One hour before resection of the liver and repeatedly 24 hours after the operation male rats were given phentholamine--a blocker of alpha-adrenoceptors; this preparation inhibited the mitotic activity of the regenerating liver. A double administration at the same periods of propanol--a blocker of beta-adrenoceptors--caused an elevation of the mitotic activity. A conclusion was drawn that by stimulation of beta-adrenoceptors it was possible to inhibit the regenerative process. Adrenaline stimulated this process by acting through beta-adrenoceptors.     

Effect of preliminary stress on mitotic activity of the regenerating liver]

Male rats were exposed to 14- or 24-hour immobilization before partial hepatectomy. Some of these animals were given subcutaneous theophylline injections immediately after and the next day after the immobilization. A tendency to increase of the mitotic activity of the regenerating liver was seen in the stress-subjected animals. This effect was particularly pronounced in rats given theophylline.     

Effect of the functional state of adrenoreceptors on the mitotic activity of regenerating rat liver

Phentolamine, a blocker of alpha-adrenoceptors, given in a single dose (one hour before or 30 minutes, 8 and 24 hours after liver resection) decreased the mitotic index and the coefficient of mitotic phases, and elevated the glycogen content. The number of two-nucleated cells in rats exposed to phentolamine rose 8 hours after resection (p < 0.05). Obsidan, a blocker of beta-adrenoceptors, administered at the same periods, increased the mitotic index and the coefficient of mitotic phases. It is suggested that phentolamine prolonged the late mitotic phases, inhibiting the entry of the cells into mitosis. Obsidan elicited an opposite effect.     

Topographic distribution of dividing hepatocytes in the regenerating liver lobule in the period of maximum mitotic activity

Topographic distribution of dividing hepatocytes was studied in the liver lobule after hepatectomy performed at 10-11.30 a. m. The studies were conducted 20-32 h after surgery during the first increase in mitotic activity. It has been established that dividing hepatocytes appear simultaneously in all lobule areas, i. e. that all the hepatocytes are capable of responding to regenerating stimuli. However, further behaviour of dividing hepatocytes becomes different. It is concluded that hepatocytes from outer and intermediate lobule areas possess a more pronounced proliferative potential during peak mitotic activity after partial hepatectomy.     

Bacterial dry matter content and biomass estimations

Approximately 20% dry-matter content appears to be an accepted standard value for bacterial cells. We have found that the dry-matter content of bacteria may be more than twice as high as generally assumed. The main reason for the low estimates seems to be that proper corrections for intercellular water have not been made when estimating the wet weight of the cells. Using three different bacterial strains, we determined a dry-matter content of cells ranging from 31 to 57%, suggesting not only that the accepted standard value is much too low but also that it is far from standard. To convert bacterial biovolume into biomass (carbon content), we suggest that 0.22 g of C cm-3 should be used as a conversion factor.     

Nonspecific esterase and alpha-glycerolphosphate dehydrogenase activity and the fat content in the regenerating chicken liver]

The data on histochemical study of changes in the activity of esterases, alpha-glycerophosphate dehydrogenase and the fat content in the chick regenerating liver are presented. The accumulation of the fat in hepatocytes during the early periods of regeneration (1--5th day of the experiment) is partially conditioned by the reduction of the activity of nonspecific esterases. The maximal liver steatosis is accompanied also by an increase in the activity of alpha-glycerophosphate dehydrogenase which indicates intensification of glycolysis and synthesis of triacylglycerines (liver spare lipids) during regeneration.     

Bacterial dry matter content and biomass estimations.

Approximately 20% dry-matter content appears to be an accepted standard value for bacterial cells. We have found that the dry-matter content of bacteria may be more than twice as high as generally assumed. The main reason for the low estimates seems to be that proper corrections for intercellular water have not been made when estimating the wet weight of the cells. Using three different bacterial strains, we determined a dry-matter content of cells ranging from 31 to 57%, suggesting not only that the accepted standard value is much too low but also that it is far from standard. To convert bacterial biovolume into biomass (carbon content), we suggest that 0.22 g of C cm-3 should be used as a conversion factor.     

Xanthine oxidase activity in regenerating liver

The xanthine oxidase activity of mouse regenerating liver has been shown to be elevated during the period of rapid liver growth and proliferation. This increase is evident when the enzyme activity is expressed per unit wet tissue weight, per unit nitrogen, or per cell. The adrenal cortex probably plays only a minor role in implementing this phenomenon. Further augmentation of the xanthine oxidase level of regenerating liver is not induced by the administration of large quantities of the substrate, xanthine, to the animal.     

Sialyltransferase activity in regenerating rat liver

Liver microsomal fractions catalyse the transfer of sialic acid from CMP-N-acetyl-neuraminic acid to various exogenous acceptors such as desialylated fetuin, desialylated human Tamm–Horsfall glycoprotein and desialylated bovine submaxillary-gland mucin. An increase in the rate of incorporation of sialic acid into desialylated glycoproteins was found after a lag period (7h) in regenerating liver. The increase was maximum 24h after partial hepatectomy for all acceptors tested. At later times after operation the sialyltransferase activity remained high only for desialylated fetuin. No soluble factors from liver or serum of partially hepatectomized animals influenced the activity of the sialyltransferases bound to the microsomal fraction. The sensitivity of sialyltransferases to activation by Triton X-100, added to the incubation medium, was unchanged in the microsomal preparation from animals 24h after sham operation or partial hepatectomy. The full activity of sialyltransferases towards the various desialylated acceptors showed some differences. Human Tamm–Horsfall glycoprotein was a good acceptor of sialic acid only when desialylated by mild acid hydrolysis. After this treatment, but not after enzymic hydrolysis, a decrease in molecular weight of human Tamm–Horsfall glycoprotein was observed. Further, the sialyltransferase activity as a function of incubation temperature gave different curves according to the acceptor used. The relationship between the biosynthesis of glycoproteins by regenerating liver and the sialyltransferase activity of microsomal fraction after partial hepatectomy is discussed.     

Nicotinamide coenzyme content in the normal and regenerating liver of rats

The content of NADH and NADPH was measured in the intact and regenerating rat liver. In the intact rat liver, the content of NAD+, NADH, NADP+ and NADPH was 235 +/- 6.4, 66.6 +/- 4.3, 73.3 +/- 2.5 and 148.0 +/- 4.6 micrograms/g crude liver weight, respectively. Seasonal alterations in the rat liver content of coenzymes were established. No changes were found in the content of nicotinamide coenzymes in the regenerating liver 4 and 18 h after operation. Twenty-four hours after operation, a 25.6% increase in the content of NAD+ and a 57.8% reduction in the NADH content were recorded in the liver of hepatectomized animals. At the same time the total content of NAD+ plus NADH changed but insignificantly (14.7%). The total content of NADP+ plus NADPH dropped by 29.8% (within the above period). Thirty-two hours after operation the content of all the nicotinamide coenzymes returned to the initial level.