[Changes in alpha-actinin localization and myofibrillogenesis in rat cardiomyocytes under cultivation]. / Izmeneniia lokalizatsii al'fa-aktinina i miofibrillogenez v kardiomiotsitakh krys pri kul'tivirovanii.

By indirect immunofluorescence with monoclonal anti-alpha-actinin antibodies the localization of this contractile protein was studied in ventricular cardiac myocytes from newborn 2-4-day old rats in the course of their cultivation. In freshly isolated heart muscle cells a predominant longitudinal orientation of myofibrils was observed; in some cells on the periphery of cytoplasm the contours of Z-lines are indistinct. During cell spreading, in the areas of intercalated discs, growing processes were observed mostly containing no contractile structures at earlier stages of cultivation. On days 3 to 14, the cytoplasmic processes and ruffles are filled with developing myofibrils. The cultures are heterogeneous in the morphology of contractile apparatus of individual cells. In most cardiomyocytes mature myofibrils are well-developed in the central part of the cytoplasm, whereas in its peripheral areas non-myofibrillar stress-fiber-like structures and bundles with continuous distribution of alpha-actinin frequently connected to myofibrils are more typical. In the areas of active myofibrillogenesis, located mainly on the cell periphery, numerous alpha-actinin dots are observed; most of them are arranged linearly and periodically at a distance of 0.3-1.5 microns and seem to be structural precursors of Z-lines. The data obtained show that the cultures of mammalian cardiac cells may be a convenient object for studying myofibrillogenesis in the course of cardiomyogenic differentiation.

[A morphometric study of myocytes of normal and hypertrophic human atria]. / Morfometricheskoe issledovanie miotsitov normal'nykh i gipertrofirovannykh predserdii cheloveka.

Morphometric study of myocytes of normal and hypertrophic human atria was performed in semithin and paraffin sections. The hypertrophy is followed by the increase of size of both the myocytes and their nuclei: the average nuclei diameter increases from 5.9 to 7.5 microns, the average length from 13.7 to 20.2 microns. The same parameters of the cell change from 13.5 to 18.5 microns and from 121.6 to 143.9 microns. The increase of the nuclei length correlates with the increase of its ploidy. The ratio nucleus cytoplasm remains unchanged as well as the ratio between muscles and connective tissue. The number of binucleated cells in the hypertrophied atrium increases by factor of 3 or 4. The number of myocytes in the atrium was calculated and was equal to 1790.10(6) +/- 241.10(6) under normal conditions and 1890.10(6) +/- 336.10(6) in case of hypertrophy. The mechanisms of the heart weight increase is discussed.

[Comparative cytophotometric analysis of the nucleic acid content in the cardiomyocytes of normal rats and following experimental infarct]. / Sravnitel'naia tsitofotometricheskii analiz soderzhaniia nukleinovykh kislot v kardiomiotsitakh krysy v norme i posle éksperimental'nogo infarkta.

The cytophotometrical investigation of gallocyanine-chrome alum stained cardiac muscle cells allows to ascertain that a mean content of the nucleic acids calculated for a single nucleus is essentially higher in the left ventricle myocytes in comparison with the left auricle cells of healthy adult rats. These values in 1-, 2- and 3-nuclear cells of the ventricle are, respectively, 21.3, 19.3, and 18.0, and 14.1, 13.7, 13.5 of arbitrary units (a. u.) in the auricle cells. A difference in cytoplasmic RNA contents of the same cells is more significant, these values are 65.7, 116.4, and 158.9 a. u. in ventricle myocytes, and 33.4, 60.8 and 95.2 a. u. in auricle cells. The nucleic acids content in the nuclei and RNA content in the cytoplasm increase with the development of proliferation in myocytes after experimental myocardial infarction. A relative increase in the nucleic acids content in the nuclei of the same cell types reaches 50, 24, and 10% 11 days after infarction and 56, 38, and 45% 31 days after infarction. A relative increase in cytoplasmic RNA of the same cells reaches, respectively, 52, 17, and 25%, and 70, 57, and 53% 11 and 31 days after infarction. These findings evidence on the greatest synthetic activity of the single-nuclear auricle muscle cells in the process of heart restoration after infarction.

[Levels of DNA and sex chromatin bodies in the myocyte nuclei of different sections of the human heart]. / Soderzhanie DNK i telets polovogo khromatina v iadrakh miotsitov raznykh otdelov serdtsa cheloveka.

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.

[Initial stages of the myocardial differentiation of the lymph hearts of frog tadpoles. A study by the methods of electron microscopy and electron microscopic autoradiography]. / Nachal'nye étapii differentsirovki "miokarda" limfaticheskikh serdets u golovastikov travianoi liagushki. Issledovanie metodami élektronnoi mikroskopii i élektronno-mikroskopicheskoi avtoradiografii.

Using electron microscope autoradiography, a study was made of the ultrastructure of early stages of muscle differentiation and 3H-thymidine (3H-T) labelled cells in the wall of the developing lymph heart of larvae of Rana temporaria L. The mononucleated postmitotic myoblasts with small bundles of thin and thick myofilaments deprived of Z-bodies were found in the lymph heart wall. No thin or intermediate-sized subsarcolemmal filaments were detected in the cytoplasm of these myoblasts. Myosatellites occurred under the basal lamina of muscle cells at stages 41-42. The primitive muscle-nerve junction was found at stages 44-45. Four hours after a single 3H-T administration only mononuclear cells without myofilaments were labelled. If the fixation was made 72 hours after a single 3H-T administration, the label was found, in addition, on the muscle cell nuclei. These data evidence that at the early stages of muscle differentiation in the developing lymph heart wall DNA synthesis and muscle specific protein synthesis are incompatible.

[Proliferative processes in the myocardium in different parts of the heart during the creation of experimental myocardial infarct of the left ventricle in 2- and 3-week-old rats]. / Proliferativnye protsessy v miokarde raznykh otdelov serdtsa pri sozdanii éksperimental'nogo infarkta miokarda levogo zheludochka u dvukh- i trekhnedel'nykh krysiat.

As a result of 30 times repeated injections of 3H-thymidine (3HTdr) to neonate rats, beginning from days 13 or 21 post partum, ca. 20 and 10% of myonuclei in the left and right atria were labeled, respectively, while in both ventricles cumulative labeling of myocytes was nearly ten times lower. In rats of the same age with experimental infarction of the left ventricular myocardium the number of myonuclei labeled after 30-fold 3HTdr injections increased in atria up to 40-50%, in perinecrotic myofibers of the left ventricles up to 8-11%, and in myofibers of the left and right ventricle located far from the necrotic foci up to 3-4 and 2-3%, respectively. In some of rats subendocardial and/or subepicardial layers of the surviving left ventricular myocardium contained up to 15-35% of labeled myonuclei. Thus, in neonatal rats the extent of DNA synthesis reactivation in the nuclei of cardiomyocytes, the majority of which have recently completed normal ontogenetic proliferation, is, on the whole, of the same order as found in similar experiments on adult rats (Rumiantsev, Kassem, 1976; Oberpriller et al., 1984). However, still immature ventricular myocytes of neonatal rats resume mitotic cycle easier than those of adult animals which is evidenced not only by higher numbers of 3HTdr labeled myonuclei in subepicardial and subendocardial ventricular myocardia of some rats, but even more by reactivation of DNA synthesis in a limited fraction (2-3%) of the whole population of non-perinecrotic myocytes in both ventricles. Besides, reactive proliferation of cardiomyocytes in the atria of neonate rats, unlike in adults, starts on day 3 rather than on day 5 after infarction is induced. In the atria of neonatal rats polyploidization of myonuclei at later postinfarction stages is less pronounced than in adult rats which may be accounted for by formation of individual daughter nuclei during acytokinetic mitoses or, more seldom, by completion of cytotomy.

[Processes of the differentiation and reproduction of different types of muscle cells]. / Protsessy differentsirovki i reproduktsii raznykh tipov myshechnykh kletok.

The present review is regarding a vast evidence on reproduction, differentiation, and regenerative capacity of various muscle cells on the basis of A. A. Zavarzin's (Senior) parallelism conception. It is specially emphasized that parallelism in the subcellular organization of contractile structures of somatic and of heart muscle goes well together with a totally different principle of organization of these cellular elements (symplasts, or cells, respectively), and with different mechanisms of their histogenesis and regeneration (proliferation of, respectively, myoblasts, or immature myocytes). According to their ultrastructure and pattern of interrelation between proliferation and differentiation process, muscles of lymphatic hearts are closer to somatic muscles rather than to ordinary myocardium. Special attention is called to paradoxical situations, such as the presence of satellite-like cells in the myocardium of Decapoda, DNA-synthesizing capacity observed in the nuclei of growing somatic muscles of the silkworm, or DNA-synthesizing and chromosome-reproducing capacity of adult primate and human cardiomyocytes.

[DNA synthesis in cultures of atrial and ventricular cardiomyocytes in the rat]. / Sintez DNK v kul'turakh predserdnykh i zheludochkovykh kardiomiotsitov krysy.

By means of 3H-thymidine autoradiography DNA replicative activity has been studied in cultured atrial and ventricular myocytes, and non-muscle cells from hearts of 2-week-old rats (age when cell proliferation in the myocardium is already significantly depressed). PAS-reaction was used as a cytochemical marker of cardiomyocytes: atrial myocytes are richer in glycogen than ventricular cells. Labeling indices of atrial myocytes after a 24 hour exposure to 3H-thymidine were higher than ventricular ones: on day 6 of culturing--47 and 5%, and on day 11-34 and 8%, respectively. After 10 days of culturing the number of binucleated atrial myocytes, non-typical for atrial myocardium in vivo, increased by 25-40% as compared with 8-13% on days 2-3 in culture. In 10-day cultures, 3- and 4-nucleated atrial myocytes were observed. Both mononucleated and binucleated atrial and ventricular myocytes incorporated 3H-thymidine. To find out whether the deeper inhibition of replicative activity in ventricular myocytes influences fibroblasts and endothelial cells from ventricles, the proliferative activity of non-muscle cells was studied. Non-muscle cells, both in atrial and ventricular cultures, behaved as a totally proliferating population (labeling indices on the 6th day are about 75-90%) and their growth rate decreased during the formation of the contact-inhibited monolayer. These cells, contrary to myocytes, are predominantly mononucleated in all the periods studied. The deeper depression of replication in ventricular myocytes appears to be related with their higher level of differentiation as compared to myocytes of the atrial myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

[Muscle tissue histogenesis of the lymph hearts of chick embryos]. / Gistogenez myshechnoi tkani limfaticheskikh serdets kurinykh émbrionov.

By means of electron microscope autoradiography, the ultrastructure of muscle fibers, and the capacity if muscle of cell nuclei of 3H-thymidine (3H-T) incorporating of were studed in developing lymph hearts of 0-13 day old chick embryos, rather active sarcomerogenesis developing lymph hearts of 9-13 day old chick embryos, a rather active sarcomerogenesis being observed. Filament of intermediate size microtubules, Golgi complexes, centrioles, and numbers free ribosomes and polysomes were observed in the sarcoplasm. The sarcoplasmic reticulum channels were not numerous, their terminal cisterns often formed "subsarcolemmal cisternae". Between muscle fibers, cell junctions of fasciae adherentes type were observed. Two hours after 3H-T administrations, only mononuclear cells without myofilaments were labeled. If fixation was made 70 hours after 3H-T administration, then the label was found in addition on muscle fiber nuclei. These data evidence that the lymph heart muscle tissue histogenesis undergoes the same patterns of development as does the somatic muscle tissue.

[Quantity of DNA, sex chromatin bodies and nucleoli in the nuclei of the muscle cells of normal and hypertrophied human atria]. / Issledovanie kolichestva DNK, telets polovogo khromatina i iadryshek v iadrakh myshechnykh kletok normal'nykh i gipertrofirovannykh predserdii cheloveka.

Nuclei of myocytes of normal and hypertrophied human heart atrium were studied on squash preparations. Judging by the sex chromatin body pattern, it is the polyploidization that is responsible for the increased DNA contents in these nuclei. The cytophotometric DNA measurements demonstrated the up to 93% occurrence of polyploid nuclei even in myocytes of normal atrium. Myocytes of hypertrophied atrium contained nuclei of higher ploidy degrees. The total area of nucleoli per nucleus was shown to be proportional to a degree of ploidy.

[Ultrastructure of the myocytes of the sinoatrial node of the mouse embryonic heart in mitosis]. / Ul'trastruktura miotsitov sinoatrial'nogo uzla serdtsa émbrionov myshi v mitoze.

The sinoatrial node (SAN) of 16-18-day old mouse embryos contains only 0.4% of myocytes in mitosis; this index is by ten times lower than that of the working ventricular myocardium. The SAN myocyte contractile apparatus is also less differentiated than that of the working ventricular and atrial myocardium. In interphase and early prophase thin and sparse myofibrils with poorly developed Z-disks occur. In prometaphase (perhaps in midprophase) myofibril disintegration takes place as a result of Z-band material resorption. In metaphase, anaphase, and telophase, Z-disks are absent; there are only dispersed thin myofilament bundles. In late telophase or in G1 phase, patches of Z-band material appear among myofilament bundles, thus indicating myofibrillar gradual restoration. Unlike Z-bands, desmosomes and fasciae adherentes of intercalated disks remain through all the stages of mitosis. In telophase, after nuclear envelope reconstruction, chromosomal spindle microtubules can enter the nucleus to retain the connection with chromatin. A cleavage furrow can be seen in early telophase, but cytokinesis occurs not in all the cells, which results in the appearance of single binucleate cells. Myofibrils of SAN and ventricular embryonal myocytes undergo the same reversible disintegration during mitosis. The cyclic changes of other organelles are also similar to those occurring in the ventricular embryonal myocytes.

[Lysosome changes in exponentially growing, synchronized and differentiating L-cell cultures]. / Izmeneniia lizosom v éksponentsial'no rastushchei, sinkhronizi-rovannoi i differentsiruiushcheisia kul'turakh L-kletok.

Using supravital fluorescent staining of lysosomes with Euchrysine 3R, the morphology of these organelles was studied in L cells examined from cultures being at different growth phases in the course of cell cycle and after adipocyte conversion of L cells due to the 60% bovine serum administration. As cells were passing from the lag-phase to the stationary phase of culture growth, the number of lysosomes was seen to increase. The appearance of large lysosomes is characteristic of cells in confluent and senescent cultures. During G1-period, lysosomes are often confined to the perinuclear area of L-cells, to be extended later during S and G2-periods. In dividing cells, these are commonly seen scattered throughout the cell periphery, around the mitotic spindle. In cells undergoing differentiation, within 4-7 days the seeding in the medium supplemented with 60% bovine serum, the number of lysosomes became augmented to be gradually reduced during the next 10-15 days, concomittantly with the accumulation of lipid drops in the cell cytoplasm. The activity of the Golgi complex and the intensity of autophagy are discussed as possible regulation points of lysosome formation during the cell growth.

[Formation of a complex system of cytoplasmic membranes and microfilament bundles in the period of nuclear fragmentation completion of giant trophoblast polykaryocytes]. / Obrazovanie slozhnoi sistemy tsitoplazmaticheskikh membran i puchkov mikrofilamentov v period zaversheniia fragmentatsii iader gigantskikh polkariotsitov trofoblasta.

A study of the ultrastructure of the rat trophoblast giant multinuclear cells (polykaryocytes) has shown that each separating nuclear fragment is enveloped with a thick cytoplasmic area. Simultaneously, membraneous complexes are involved in the separation of small cellular territories near the nuclear fragments within the polykaryocyte. Long outgrowings of the outer nuclear membrane go inside the cytoplasm and, on branching, produce a system of flat cisternae of the smooth endoplasmic reticulum, which, in turn, participates in the formation of plasmatic membranes that are separated within small karyocytes. Flat cisternae of the smooth endoplasmic reticulum display desmosome-like structures, both in the areas separating neighbouring cells and in those directly associated with the perinuclear space of the nuclear envelope. Formation of microvilli was seen after smooth endoplasmic reticulum membranes were separated and broad lacunae were produced. Microfilament bundles, 9 nm in diameter, have been seen in the cytoplasm of separating cells. These filaments are, as a rule, connected by one end with the outer nuclear membrane, touching membranous structures of the cytoplasm with the other end. The nature and possible functional importance of these bundles are discussed.

[Ultrastructure of the DNA-synthesizing cells of the sinoatrial node in mouse embryos according to electron microscopic autoradiographic data]. / Ul'trastruktura sinteziruiushchikh DNK kletok sinoatrial'nogo uzla serdtsa émbrionov myshi po dannym élektronno-mikroskopicheskoi avtoradiografii.

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.

[DNA synthesis and mitotic division of myocytes of the ventricles, atria and conduction system of the heart during the myocardial development in mammals]. / Sintez DNK i mitoticheskoe delenie miotsitov zheludochkov, predserdii i provodiashchei sistemy serdtsa pri razvitii miokarda mlekopitaiushchikh.

The degree of differentiation of various types of muscle and non-muscle cells that synthesize DNA in myocardia of mouse embryos and suckling rats was estimated by means of electron microscopic autoradiography with 3H-thymidine. No morphologically undifferentiated myoblasts were observed. DNA synthesizing capacity and mitotic activity are typical of numerous moderately differentiated myocytes in all myocardial compartments studied. As judged from proliferation kinetics studies, ventricular myocytes proliferate at embryonal stages and during the 1st postnatal week more actively than do atrial ones, specialized muscle cells from the conductive system replicating much less intensely as compared with both these kinds of myocytes. However, at the 2nd postnatal week, the withdrawal of myocytes from the mitotic cycle proceeds more rapidly in ventricles than in other heart compartments which results in a relatively more active proliferation of myocytes in atria and conductive system beginning from the end of the 2nd postnatal week. By the 17--18th days of the postnatal life, practically all the myocytes, irrespective of their topology, cease to proliferate. Nevertheless, even after this term, up to 0.1--0.5% of atrial and/or conductive system myocytes still go on entering periodically the mitotic cycle. The duration of S and G2 + 1/2 M periods is similar in both the ventricular and atrial myocytes of suckling rats. Probable causes and significance of the observed asynchrony of the myocyte proliferation rates in different heart compartments is discussed.

[Ultrastructure of the cells and DNA synthesis in skeletal muscle regeneration. A study of the regeneration of the frog sartorius muscle by an electron microscopic autoradiographic method]. / Ul'trastruktura kletok i sintez DNK pri regeneratsii skeletnykh myshts. Issledovanie regeneratsii portniazhkoi myshtsy liagushki metodom.

The ultrastructure of cells of the regenerating frog's sartorius muscle and their capacity to synthesize DNA was studied by means of 3H-thymidine (3HT) electron microscope autoradiography. On the 8-17th post injury (p.i.) days, 2 hours following 3HT administration, only mononuclear cells were seen labeled, the myotube nuclei incorporating no 3HT. Along with the endothelial cells, fibroblasts, phagocytes and cells identified conventionally as myoblasts, satellite cells examined from both necrotic and viable parts of injured myofibers were labeled. No myoblast sequestration from the injured myofibers occurred. By the 13-15th p.i. days, numerous myoblast-like cells are accumulated beneath the glycocalix layer covering the free ends of myotubes which are rich in ribosomes and display an active sarcomerogenesis. Some of these myoblast-like cells become labeled after 3HT pulse. The 13 day p.i. regenerates examined 72 hours following 3HT injection display labeling in numerous myotube nuclei. This is indicative of the myoblast fusion, which is believed to play a principal role in the regenerative somatic myogenesis. Within the myonuclei adjacent to the areas of the regeneration, membranous and/or fibrillar structures of an unknown origin were frequently observed.