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Biomedical subjects

L V Belousov

Publications and source records attributed to L V Belousov.

At least 19 recordsLinked to original sources
PubMed2000

[Cytomechanical control of morphogenesis].

The role of mechanically strained state of cells and multicellular structures in morphogenesis regulating in vertebrate embryos is discussed. Regular changes in patterns of mechanical strain during embryonic development are described. Artificial relaxation of mechanical strain performed on definite developmental stages and retension of embryonic tissues in arbitrary directions considerably affects morphogenesis and cell differentiation patterns. Cytomechanical models of morphogenesis are reviewed and a concept of hyperrestoration of mechanical strain as a possible driving force of morphogeneiss is suggested.

Animals↗
PubMed1983

[Intercellular relay interactions in explants of amphibian embryonic tissues. I. Intercellular relay interactions in normal explant morphogenesis].

In the explants of lateral mesoderm, together or without the overlaying ectoderm, taken from the neurula-early tail bud of amphibian embryos (Xenopus laevis, Rana temporaria) within 5-30 min, several types of cytological transformations have been observed, some of these being: formation of a microfilamentous layer under the naked explant surface, morphological polarization, and unilateral spreading of cells. These processes are described at the light and electron microscopy levels. It is suggested that these may be of relay character, that is, each transformed cell induces the same transformation in the adjacent one. The cytological transformations are correlated with metabolic ones described elsewhere.

Animals↗
PubMed1982

[Method of recording the linear growth and cell mass displacement of multicellular animals and plants].

A photoelectrical method has been developed of registration of the linear growth and cell mass movements in the actively zones (growing tips, edges, etc). The device proposed transforms to electrical signals the changes in lighting of microscopic visual field caused by shifting the growing structures in the area restricted by the aperture of the ocular field diaphragm of the "cat-eye" type. By means of this technique, oscillograms of growth of the number of multicellular organisms have been obtained for the first time. In many cases (blastodisc edge and tail bud of the salmon Oncorhynchus gorbusha, mantle edge of Mytilus edulis, osculum edge of the sponge Tethya, apical area of brown alga Fucus and of red algae Polyides and Ahnfeltsia), a pulsatory character of growth (with periods of some minutes) were registered. A similar growth character was also confirmed for several species of Thecaphora hydroids. No pulsations was registered during the linear growth of a brown alga Laminaria (which contrary to Fucus is growing intercalarly), of Nitella (Charophyta) and of several high plants.

Animals↗
PubMed1980

Relation of the intensity of metabolism with the process of determination in embryonic cell. Comparison of the experimental data with theory.

Relation between the level of the power metabolism and the degree of the determination of the embryos was investigated by comparison of the experimental material with theory. It was shown that the high level of metabolism promotes the change of the system to a differentiated state (i.e. leads to the limitation of tissue potency). The lowering of metabolism intensity is connected with a dedifferentiation of the tissue (or with expansion of it potency).

Amphibians↗
PubMed1979

[Regional differences in the sensitivity of the metabolism of coelenterate larvae to external influences].

The regional differences in the sensitivity of protein synthesis and free radical processes to temperature, trypsin, urea and LiCl were studied in Obelia flexuosa by means of autoradiography. The regional differences were also determined with respect to the rate of incorporation and excretion of a labelled aminoacid under the normal conditions. The metabolic reactions of larvae can be divided in primary (the first 30 min following the effect) and subsequent adaptive ones. The primary reactions are characterized by the greater sensitivity of the anterior larval regions to all factors under study. The subsequent reactions are characterized by synchronous and unidirectional metabolic starts in both the anterior and posterior larval regions, the starts being bigger in the anterior regions. The restoration of the normal ratios of metabolic activities of the opposite larval regions does not always correlate with the restoration of the normal absolute level of metabolism. The adaptive reactions are better expressed for protein synthesis, rather than for free radical processes. The anterior larval region has the greatest metabolic non-stability by a series of indices.

Adaptation, Physiological↗
PubMed1978

[Formation and cellular structure of the lines of tension in the axial rudimenta of amphibian embryos].

The lines of mechanical tension (cross-lines) in axial rudiments of the amphibian embryo represent bands of polarized cells. They form in the inner layers of the rudiments as separate bundles of polarized cell which, then, merge, attain the external surface and gather in lengthy planes (cross-planes) and, later, degrade. The primary inductor induces the formation of cross-lines in the ventral ectoderm of the early gastrula. The growth of cross-lines in considered as one of the types of contact cells polarization. The morphogenetic role of contact polarization is discussed. The connection between the subsequent tension patterns is based on the fact that the lines of exit of the cross-planes on the surface of the embryo coincide with the direction of the previously established tensions.

Amphibians↗
PubMed1978

[Effect of neuropharmacologic preparations and colchicine on morphogenetic processes in embryonal amphibian cells].

The effect of antagonists of biogenous amines (antitransmitters--AT) and colchicine on rapid morphogenetic processes in the explants of embryonic ectoderm with underlying mesoderm cut from the lateral region of Rana temporaria embryos at the late neurula-early taibud stages was studied. The normal morphogenesis of the explants consists of two successive phases: phase of contact polarization and phase of cell movement into the fragment. The high concentrations of AT inhibited completely the morphogenesis of explants but somewhat lower concentrations inhibited the second phase of morphogenesis and not only did not prevent the cell polarization but even assisted its propagation over all the fragment. The inhibiting effect of AT was relieved by 5-hydroxytryptamine which per se stimulated the morphogenesis of explants. Thus, AT exert a specific inhibition of the motility of embryonic cells but do not prevent the contact interactions responsible for cell polarization within every layer.

Amphetamines↗
PubMed1977

[Electron microscopic study of rapid morphogenetic processes in embryonic tissue explants of amphibia].

Submicroscopic rearrangements are described. They serve as the bases of rapid (up to 20 min) changes in the form of the common frog neurula explants: formation of filamentous layer under "naked" surface, appearance of lobopodia on "naked" surface, their "flow", cell polarization and submersion. In all these processes an active part appears to be played by microtubules and microfilaments the bundles of which are always oriented along the long axes of active cells or the directions of passive mechanical tensions. In the cells which are not yet polarized the microtubules form under the surface adjacent to the already polarized cell. This may be considered as one of the chains of cooperative cell polarization.

Amphibians↗
PubMed1977

[Dynamics of the regional metabolic differences in the early development of the sea urchin].

The regional differences in Strongylocentrotus intermedius from the stage of 32 blastomeres till the middlelate gastrula stage were studied by the vital and supravital staining (intensity of oxidative-reductive processes), the incorporation of 3H-leucine (intensity of protein synthesis) and 14C-acrilamide (intensity of free radical processes). Two periods of rapid switches of metabolic intensity correlated within the same embryo were established. The beginning of the first period coincides with the onset of blastula epithelization and that of the second one with the onset of gastrulation. The metabolic "patterns" are multivariant up to the second switch although, in the most cases, the metabolic activity of the equatorial area is the lowest. From the onset of gastrulation the metabolic patterns become uniform: the vegetative area dominates by the intensity of precursors' incorporation and by the sensitivity of its respiratory systems to the oxygen deficiency. The relationships between the metabolic and morphological rearrangements are discussed.

Acrylamides↗
PubMed1977

[Instability and stability in biological morphogenesis].

The concept of morphogenesis is determined and the mathematical image of the developing system is considered. A certain amount of stable and unstable states and slow changes of the potential relief (parameters) are inherent in the latter. The developing systems are intermediate between the deterministic and statistic ones. They are distinctly multiple-levelled. The microprocesses of morphogenesis and the laws of macromorphogenesis are described, the instabilities and stable periods of morphogenesis are considered. All of them in the multiple-leveled system tend to the formation of through hierarchies, or cascades, where the upper levels parametrize the lower ones. This tendency increases as the evolutionary progress proceeds. The genetic regulation is considered also as a parametric regulation in the domains of instabilities. The approach contemplated may be considered both as the generalization of the available data and as the programme of investigation, more adequate to the biological reality than the causal-analytical methodology.

Animals↗
PubMed1977

[Contractility and epithelization in the chick embryo axial mesoderm].

The still unsegemented axial mesoderm was cross cut at different distances form the last somite under the normal physiological conditions, at the low temperature and under the effect of cytochalasin B. Under the normal conditions the inner cells of the axial mesoderm formed a lens-shaped cleft immediately after the operation; this movement was suppressed at the low temperature and absent under the effect of cytochalasin B. This suggests the active contractility of the mesodermal syncytium. The wound margin near the last somite acquired the epithelial structure already within several minutes after the cut, whereas in the more caudal regions it preserved the connective tissue character for a long time. The importance of the axial mesoderm contractility and its ability of epithelization for the somitogenesis is discussed.

Animals↗
PubMed1976

[Patterns of mechanical stress at the successive stages of early development of frog].

The immediate relaxation deformations have been studied in the embryonic frog tissues from the late blastula stage till the early tail bud stage. As a result, the maps of mechanical stresses were constructed which were characterized by the existence of distinct tension-lines dissecting the embryonic tissues (cross-lines). A few discrete moments of development were established when new cross-lines formed or the previous ones disappeared; they are separated by the topologically invariant periods of development. The cross-lines play an important role in morphogenesis in that they determine the ways of active cell migration and trace the boundaries between different anlages. The orientation of the cross-lines coincides, as a rule, with the direction of predominant tension of tissues during the preceding topologically invariant period of development.

Animals↗
PubMed1975

Rapid changes in shape and cell architecture of isolated fragments of amphibian embryonic tissues as an experimental model of morphogenesis.

Changes in the shape and cell architecture of pieces of epithelial and neural ectoderm, mesoderm, neural tube, and combined ectomesodermal fragments from embryos of Rana temporaria 0-60 min after isolation were studied. The fragments were capable of changing their shape quickly (actually during separation) or after a latent period of several minutes. Rapid deformations were not prevented by cooling or by moderate doses of cyanide; as a rule they were connected with contraction of the surface area of the cells of the fragment and they can be regarded as relaxation to forms with lower mechanical energy. The direction of the deformation usually coincides with the subsequent normal morphogenesis of the particular anlage. Deformations with a latent period are suppressed by cooling and by the addition of cyanide, which lead to an increase in the surface area of individual cells, but they reduce the total surface area of the fragment. The shape of the fragments becomes more complex: they become irregularly twisted, they form folds, and they separate into spherical regions with stretched surfaces ("drops"). These processes are connected with the performance of positive mechanical work by the intracellular contractile systems. The reasons why the fragments become more complex in shape are discussed.

Animals↗
PubMed1974

[Mechanisms of growth and morphogenesis of hydroid polyps as revealed by time lapse microcinematography].

By means of time lapse microcinematography, parameters of growth fluctuations in hydroid polyps Obelia and Dynamena were improved, the pulse pattern of morphogenetic processes was shown, the "antiphase" phenomenon was established in the growth fluctuations of adjacent rudiments of Dynamena. In the phase of rudiment stretching, the length of ectodermal epithelial-muscular cells reduces and their orientation changes, thus leading to the displacement of the whole cellular "column" in the distal direction. In the phase of rudiment partial shortening, endodermal cells loose and lengthen, their internal ends displace in the proximal direction and their external ends slide rapidly in the distal direction with respect to hydrotheca. Changes in the form of rudments arise as a direct mechanical result of periodical contractions of cells densely packed in the epithelial layer. On the basis of these data, morphogenetic processes in hydroid polyps related to the appearance and development of folds and to the rudiment flexures are analyzed.

Animals↗