Levels of DNA and sex chromatin bodies in the myocyte nuclei of different sections of the human heart

Nuclei of ventricular, atrial and atrioventricular node myocytes of normal and hypertrophied human heart were studied on squash preparations and on 12 micron sections after the Feulgen staining. The cytophotometric DNA measurements have shown a distinction in the degree of polyploidization of nuclei in different heart compartments. In contrast to ventricular and atrial myocardia, in which polyploid nuclei predominate, the conduction system myocytes contain 77-88% of diploid nuclei. A correlation between DNA content and the number of sex chromatin bodies was observed for myocyte nuclei from all the compartments under investigation.     

Ultrastructure of the DNA-synthesizing cells of the sinoatrial node in mouse embryos according to electron microscopic autoradiographic data

By means of electron microscopic autoradiography with 3H-thymidine a study was made of the differentiation degree of DNA synthesizing muscle cells in the sinoatrial node (SAN) of the heart conductive system of the 18 day old mouse embryos. Clear myocytes (CM), predominating in the SAN at this stage, are irregular in shape, with interdigitating protrusions. Nuclei are clear, spherical or ellipsoidal. One hour following 3H-thymidine injection, about 6% of CM display labeled nuclei; this index is considerably lower than in working ventricular myocardium. Like unlabeled myocytes, CM being in phase S contain sparse, randomly located thin myofibrilles. In some areas of the sarcoplasm, only myofilament bundles and Z-disk material can be seen. The number of CM myofibrilles is always considerably less than in the working ventricular myocytes. Accumulations of intermediate (8--11 nm) filaments are present. Mitochondria with a few cristae are not numerous. The sarcoplasmic reticulum and Golgi apparatus being relatively well developed, multivesicular bodies, centrioles, and occasional cilia are often seen. Near the centrioles (basal bodies), striated filamentous bundles are found sometimes showing periodic dense lines separated by 50--70 nm. Specialized contacts between CM are rare, being presented only by desmosomes and primitive intercalated discs. Besides CM, sparse small dark cells occur filled with myofibrilles and mitochondria. In the peripheral regions of the node "transitional" cells are seen. The SAN of the 18 day old embryo mouse heart grown due to proliferation of CM with a poorly developed myofibrillar apparatus.     

Human fetal ventricular cardiomyocytes in vitro: proliferation and differentiation

In this study, in the primary cell culture of human fetal cardiomyocytes proliferation of myocytes combines with their differentiation. The cells were isolated enzymatically from 19-22 week-old human fetuses and cultured for 14 days. DNA synthesis, ultrastructure and presence of atrial natriuretic peptide (ANP) were examined. In 7 day-old culture, the myocytes make about 60%, in 14 day-old culture--about 50%. Myocytes synthesize DNA and divide mitotically. After a 24 h incubation with 3H-thymidine in 7 day-old culture 1.8 +/- 0.5% of muscle and 25.2 +/- 11.7% of non-muscle cells are labeled, in 14 day-old culture--2.5 +/- 0.5 and 8.1 +/- 1.7% of cells are labeled, respectively. In 7 and 14 day-old cultures the degree of redifferentiation of contractile apparatus in myocytes varies from scattered actin and myosin filaments surrounded by ribosomes to differentiating myofibrils with distinct sarcomeres and Z-discs. Single electron-dense granules, morphologically similar to secretory atrial granules, display ANP-immunoreactivity. Thus, human fetal ventricular cardiomyocytes in cell culture proliferate, differentiate and synthesize ANP for 14 days; this is indicative of vitality of these cells.     

At-4/1, an interactor of the Tomato spotted wilt virus movement protein, belongs to a new family of plant proteins capable of directed intra- and intercellular trafficking

The Tomato spotted wilt virus (TSWV) encoded NSm movement protein facilitates cell-to-cell spread of the viral genome through structurally modified plasmodesmata. NSm has been utilized as bait in yeast two-hybrid interaction trap screenings. As a result, a protein of unknown function, called At-4/1, was isolated from an Arabidopsis thaliana GAL4 activation domain-tagged cDNA library. Using polyclonal antibodies against bacterially expressed At-4/1, Western blot analysis of protein extracts isolated from different plant species as well as genome database screenings showed that homologues of At-4/1 seemed to be encoded by many vascular plants. For subcellular localization studies, At-4/1 was fused to green fluorescent protein, and corresponding expression vectors were used in particle bombardment and agroinfiltration assays. Confocal laser scannings revealed that At-4/1 assembled in punctate spots at the cell periphery. The protein accumulated intracellularly in a polarized fashion, appearing in only one-half of a bombarded epidermal cell, and, moreover, moved from cell to cell, forming twin-structured bodies seemingly located at both orifices of the plasmodesmatal pore. In coexpression studies, At-4/1 colocalized with a plant virus movement protein TGBp3 known to reside in endoplasmic reticulum-derived membrane structures located in close vicinity to plasmodesmata. Thus, At-4/1 belongs to a new family of plant proteins capable of directed intra- and intercellular trafficking.     

Immunolocalization of ANP in mast cells of rat and human pericardium

It is known that many heart diseases are accompanied by a significant increase in the level of atrial natriuretic peptide (ANP), a regulator of cardiovascular homeostasis, in the pericardial fluid. Cellular sources of ANP in pericardial cavity remain uncertain. By EM immunocytochemistry, we have examined the presence and localization of ANP in rat and human pericardium. ANP-immunoreactive material was revealed in granules of mast cells (MCs) situated in connective tissue of the pericardium. MCs have an oval form and measure about 6.5 x 12.5 and 9.1 x 13.6 microm in the rat and human pericardium, respectively. Density of MC population makes up about 50 and 10 cells/mm2 in the rat and human pericardium, respectively. Our data suggest possible participation of the pericardial MCs in endocrine function of pericardium and in control of the ANP level in pericardial cavity.     

The density of myocardial and pericardial rat mast cells in isoproterenol-induced heart failure

Myocardial mast cells (MC) respond to cardiovascular pathology. The behavior of MC population in myocardium and pericardium of rats has been studied 24 h, 14, 28 and 60 days after two isoproterenol injections (at 24 h intervals). The extent of heart failure has been estimated by supersonic inspection 28 and 60 days after isoproterenol injections. The density of MCs of different degrees of maturity was estimated on paraffin sections stained with Alcian blue--Safranin. The MC density in myocardium of intact and experimental rats was relatively low: from 4 to 6 cells/mm2. The MC density in pericardium of intact rats was several times higher than in myocardium: 48.6 +/- 13.0 cells/mm2. In 24 h and 14 days after isoproterenol injections the pericardial MC density was 1.5 times higher than in control rats (P < 0.05) at the expense of increase in the number of mature MCs with Safranine-positive granules without the increase in the number of immature cells with Alcian blue-positive granules. In 28 days the pericardial MC density was 2 times higher than in intact rats (P < 0.05) at the expense of increase in number of immature and mature cells. In 60 days after isoproterenol injections the pericardial MC density and the ratio of immature and mature cells compared with control did not reach statistical significance. The changes in pericardial MC population corresponded to severity of heart failure according to functional indices. The findings show active reaction of pericardial MCs on myocardium dysfunction that stimulates the maturation of resident immature MCs in pericardium and migration of immature cells to pericardium of damage heart.     

The Percentage of Cytoskeleton-Bound Polysomes as Affected by the Physiological Condition of Plant Cells

The effects of illumination, temperature, deficiency of water or oxygen, phytohormones, and seedling age on the proportion of cytoskeleton-bound polysomes (CBP) in plant tissues were studied. This proportion was shown to vary depending on factors affecting protein synthesis: it decreased under the influence of factors inhibiting protein synthesis and reducing the relative content of polysomes in tissues (oxygen and water deficiencies, seedling aging) and vice versaincreased under the influence of the factors promoting translation (cytokinin, light). The significance of reversible polysome attachment to the cytoskeleton as a mechanism controlling protein synthesis is discussed.     

Effects of mutations in Bacillus subtilis genome decreasing the protease activity on the formation of subtilisin molecular forms]

Multiple molecular forms of subtilisin--extracellular serine protease produced by the wild strain Bac. subtilis A-50 and its mutant strains with the protease activity decreased two-fold and more were studied. Six molecular forms of subtilisin were found on the whole when 33 mutant strains have been investigated under the experimental conditions. It is essential that both the wild and each of mutant strains under study produced not more than three out of these six forms. Three molecular forms of subtilisin from the mutant strains are similar to those found in the wild strain A-50, and have the molecular weight, of 27 000-30 000. Three other forms of subtilisin were revealed only in the mutant strains, and had the molecular weight of about 20 000. Apparently there is only one structural gene for subtilisin in Bac. subtilis genome. The appearence of multiple molecular forms of subtilisin may be due to the post-translational modifications (limited proteolysis) of the initial type of enzyme, i.e. pre-subtilisin. Probably, that certain mulations not affecting the structural gene can significantly change the expression of such gene by varying of the degree of product modifications.