The role of cellular polyploidy in the regeneration of the cirrhotic liver in rats and humans.

Polyploidy is a condition in which a cell has multiple diploid sets of chromosomes. Two forms of polyploidy are known. One of them, generative polyploidy, is characteristic of all cells of the organism, while the other form develops only in some somatic tissues at certain stages of postnatal ontogenesis. Whole genome duplication has played a particularly important role in the evolution of plants and animals, while the role of cellular (somatic) polyploidy in organisms remains largely unclear. In this work we investigated the contribution of cellular polyploidy to the normal and the reparative liver growth of Rattusnorvegicus (Berkenhout, 1769) and Homosapiens Linnaeus, 1758. It is shown that polyploidy makes a significant contribution to the increase of the liver mass both in the course of normal postnatal development and during pathological process.

Dynamics of the Glycogen ß-Particle Number in Rat Hepatocytes during Glucose Refeeding.

Glycogen is an easily accessible source of energy for various processes. In hepatocytes, it can be found in the form of individual molecules (ß-particles) and their agglomerates (α-particles). The glycogen content in hepatocytes depends on the physiological state and can vary due to the size and number of the particles. Using biochemical, cytofluorometric, interferometric and morphometric methods, the number of ß-particles in rat hepatocytes was determined after 48 h of fasting at different time intervals after glucose refeeding. It has been shown that after starvation, hepatocytes contain ~1.6 × 108 ß-particles. During refeeding, their number of hepatocytes gradually increases and reaches a maximum (~5.9 × 108) at 45 min after glucose administration, but then quickly decreases. The data obtained suggest that in cells there is a continuous synthesis and degradation of particles, and at different stages of life, one or another process predominates. It has been suggested that in the course of glycogenesis, pre-existing ß-particles are replaced by those formed de novo. The main contribution to the deposition of glycogen is made by an increase in the glucose residue number in its molecules. The average diameter of ß-particles of glycogen during glycogenesis increases from ~11 nm to 21 nm.

Postprandial Glycogen Content Is Increased in the Hepatocytes of Human and Rat Cirrhotic Liver.

Chronic hepatitises of various etiologies are widespread liver diseases in humans. Their final stage, liver cirrhosis (LC), is considered to be one of the main causes of hepatocellular carcinoma (HCC). About 80-90% of all HCC cases develop in LC patients, which suggests that cirrhotic conditions play a crucial role in the process of hepatocarcinogenesis. Carbohydrate metabolism in LC undergoes profound disturbances characterized by altered glycogen metabolism. Unfortunately, data on the glycogen content in LC are few and contradictory. In this study, the material was obtained from liver biopsies of patients with LC of viral and alcohol etiology and from the liver tissue of rats with CCl4-induced LC. The activity of glycogen phosphorylase (GP), glycogen synthase (GS), and glucose-6-phosphatase (G6Pase) was investigated in human and rat liver tissue by biochemical methods. Total glycogen and its labile and stable fractions were measured in isolated individual hepatocytes, using the cytofluorometry technique of PAS reaction in situ. The development of LC in human and rat liver was accompanied by an increase in fibrous tissue (20- and 8.8-fold), an increase in the dry mass of hepatocytes (by 25.6% and 23.7%), and a decrease in the number of hepatocytes (by 50% and 28%), respectively. The rearrangement of the liver parenchyma was combined with changes in glycogen metabolism. The present study showed a significant increase in the glycogen content in the hepatocytes of the human and the rat cirrhotic liver, by 255% and 210%, respectively. An increased glycogen content in cells of the cirrhotic liver can be explained by a decrease in glycogenolysis due to a decreased activity of G6Pase and GP.

Rat Left Ventricular Cardiomyocytes Characterization in the Process of Postinfarction Myocardial Remodeling.

Ischemic lesions of the heart, including myocardial infarction, are the most common pathologies of human cardiovascular system. Despite all the research and achievements of medicine in this field, the mortality from this disease remains heavy. Therefore, studying of processes occurring in the myocardium in the early and late postinfarction periods remains important. Rat left ventricular cardiomyocyte (CMC) ploidy, hypertrophy, hyperplasia, and ultrastructure were investigated in 2, 6, and 26 weeks after experimental myocardial infarction, caused by permanent ligation of left coronary artery. Cytofluorimetric study of CMC ploidy revealed no difference between normal, sham-operated, and infarcted animals for all the tested stages. However, interference microscopy indicated significant changes in cells size. CMC dry mass of infarcted rats in 2 weeks after surgery was 1.5 times lower than in control and sham operated groups. Electron microscopy analysis of CMC revealed disruption of sarcomere structure. However, in 6 weeks after surgery CMC dry mass was 1.6 times higher than in control. In 26 weeks after myocardial infarction CMC dry mass exceeded control only in peri-infarction zone. Cell counting showed that the number of left ventricular CMC, reduced as a result of myocardial infarction, was not restored during myocardial remodeling. © 2019 International Society for Advancement of Cytometry.

Glycogen content in hepatocytes is related with their size in normal rat liver but not in cirrhotic one.

BACKGROUND & AIMS: Hepatocytes differ from one another by the degree of the ploidy, size, position in the liver lobule, and level of the DNA-synthetic processes. It is believed, that the cell size exerts substantial influence on the metabolism of the hepatocytes and the glycogen content in them. The aim of the present study was to test this hypothesis. METHODS: Dry weight of hepatocytes, their ploidy and glycogen content were determined in the normal and the cirrhotic rat liver. Liver cirrhosis in rats was produced by chronic inhalation of CCl4 vapours in the course of 6 months. A combined cytophotometric method was used. Dry weight of the cell, its glycogen and DNA content were successively measured on a mapped preparation. RESULT: Hepatocytes of each ploidy class in the normal and the cirrhotic rat liver accumulated glycogen at the same rate. In the normal liver, there was a distinct correlation between the size of hepatocytes and glycogen content in them. This correlation was observed in each ploidy class, and was especially pronounced in the class of mononucleate tetraploid hepatocytes. In the cirrhotic liver, there was no correlation between the size of the cells and their glycogen content. CONCLUSIONS: The impairment of liver lobular structure probably explains the observed lack of correlation between hepatocyte size and their glycogen content in the cirrhotic liver. © 2016 International Society for Advancement of Cytometry.

Activity of glycogen synthase and glycogen phosphorylase in normal and cirrhotic rat liver during glycogen synthesis from glucose or fructose.

Cirrhotic patients often demonstrate glucose intolerance, one of the possible causes being a decreased glycogen-synthesizing capacity of the liver. At the same time, information about the rates of glycogen synthesis in the cirrhotic liver is scanty and contradictory. We studied the dynamics of glycogen accumulation and the activity of glycogen synthase (GS) and glycogen phosphorylase (GP) in the course of 120min after per os administration of glucose or fructose to fasted rats with CCl4-cirrhosis or fasted normal rats. Blood serum and liver pieces were sampled for examinations. In the normal rat liver administration of glucose/fructose initiated a fast accumulation of glycogen, while in the cirrhotic liver glycogen was accumulated with a 20min delay and at a lower rate. In the normal liver GS activity rose sharply and GPa activity dropped in the beginning of glycogen synthesis, but 60min later a high synthesis rate was sustained at the background of a high GS and GPa activity. Contrariwise, in the cirrhotic liver glycogen was accumulated at the background of a decreased GS activity and a low GPa activity. Refeeding with fructose resulted in a faster increase in the GS activity in both the normal and the cirrhotic liver than refeeding with glucose. To conclude, the rate of glycogen synthesis in the cirrhotic liver is lower than in the normal one, the difference being probably associated with a low GS activity.

Hepatocytes of cirrhotic rat liver accumulate glycogen more slowly than normal ones.

PURPOSE: To investigate the accumulation of glycogen in cirrhotic rat liver at several time intervals after per os administration of glucose to fasted animals. METHODS: Liver cirrhosis was produced by inhalation of the hepatotropic poison CCl4. Glycogen concentration in the liver was determined biochemically. Glycogen content in hepatocytes was measured cytofluorimetrically in the smears stained with a fluorescent PAS reaction. Glycogen content in the hepatocytes of the portal and the central zone of the liver lobule was determined by absorption cytophotometry. RESULTS: Rats poisoned with CCl4 for 6 months developed typical liver cirrhosis characterized by a fourfold (p < 0.001) increase in the proportion of the connective tissue. In the cirrhotic rats fasted for 48 h, glycogen concentration in the liver and glycogen content in hepatocytes were lower as compared with the control by 36 and 27 % (p < 0.01), respectively. According to data obtained by different methods, the control animals accumulated glycogen at a high rate. In particular, the glycogen content in hepatocytes increased by 34 % after 10 min (p < 0.01). In the cirrhotic rats, glycogen content remained at the same level for 20 min. In both groups of animals, hepatocytes of the portal zone accumulated more glycogen than those of the central zone. CONCLUSIONS: Glycogen accumulation in cirrhotic rats starts after a delay and proceeds at a lower rate than in the norm.

Chromosomal composition of the genome in the monomorphic diplokaryotic microsporidium Paranosema grylli: analysis by two-dimensional pulsed-field gel electrophoresis.

The molecular karyotype of Paranosema grylli Sokolova, Seleznev, Dolgikh et Issi, 1994, a monomorphic diplokaryotic microsporidium, comprises numerous bright and faint bands of nonstoichiometric staining intensity. Restriction analysis of chromosomal DNAs by "karyotype and restriction display" 2-D PFGE has demonstrated that the complexity of molecular karyotype of P. grylli is related to the pronounced length polymorphism of-homologous chromosomes. The background of this phenomenon is discussed in the context of ploidy state, reproductive strategy and population structure in this microsporidium. We propose that the remarkable size variation between homologous chromosomes in P. grylli may be a consequence of ectopic recombination at the chromosome extremities.