[Heart arrhythmias and conduction disorders in patients with acromegaly: the role of cardiac magnetic resonance imaging].

Unlabelled: Cardiovascular complications including arrhythmias and cardiac conduction disorders are one of the main reasons of high mortality rate in acromegaly, while they have not been well explored.

Aim: To estimate arrhythmias frequency in acromegaly, identify risk factors leading to the development of arrhythmia and cardiac conduction disorder, to determine the role of cardiac MRI in detecting structural and functional changes.

Materials And Methods: A single-center prospective cohort study, which included 461 patients (151 men and 310 women) with acromegaly, was conducted.

[Surface Microdeformations and Regulation of Cell Movements in Xenopus Development].

The velocities and directions of movements of individual outer ectodermal cells of Xenopus embryos in the course of normal development from the blastula to the early tail-bud stage, as well as after mechanical relaxation in the early gastrula, were measured. An alternation of the periods of directed movements of large cell masses and local cell wanderings was detected. In both cases, the trajectories of individual cells consisted primarily of orthogonal segments.

[Mechano-geometric generative rules of morphogenesis].

The ideographical approach aimed at detecting specific causative relationships within the process of development prevails in modern embryology. The present work considers the possibilities of using the nomothetic approach aimed at putting forward nonspecific general laws based on the general scientific theory of self-organization and can be formulated in morphomechanical terms based on feedback links between passive and active mechanical stress. The perspectives of this approach and the involvement of genetic factors in the regulation of feedback links are discussed.

[Statistical study of rapid mechanodependent cell movements in deformed explants of African clawed frog Xenopus laevis embryonic tissues].

Computer analysis of artificially deformed (stretched or compressed) double explants (sandwiches) of the blastocoel roof (BRs) and suprablastoporal region (SBRs) of African clawed frog Xenopus laevis early gastrula has been performed using frames of time-lapse microfilming. During the first 14 min after cutting off, the velocities and displacement angles of several hundreds of cells relative to one another, as well as to fixed points and the extension axis, were measured in the control and deformed samples. It has been found that the deformation of samples leads to a rapid reorientation of large cell masses and increase in the velocities of movements along the extension axes or perpendicularly to the compression axes.

[Passive and active reactions of embryonic tissues to the action of dosed mechanical forces].

With the help of a suction manometric device, the relation between the deformation of Xenonus laevis embryo at the gastrula and neurula stages and the value of the applied force has been studied. Stiffness modules of embryonic tissues were in the order of several dozens of Pascal and they were inversely proportional during deformation from 40 to 20%. At the gastrula stage, a uniform or an increasing rate of expansion of the embryo body in the suction capillary with the diameter of approximately half that of the embryo was observed for 30 min after the action of the suction forces.

[Parametric models of ontogenetic diversities].

Modeling of morphogenesis demonstrates that they form rather wide regions of structural stability and narrow zones of instability in parametric space. Within instability zones, small parameter shifts lead to drastic changes in the morphology of buds. These particular zones are the sources of ontogenetic diversities and represent the reserve for evolutionary variation.

[Changes in topology and geometry of the embryonic epithelium of Xenopus during relaxation of mechanical tension].

The paper presents the results of statistical evaluation of the changes of cellular apex connections, apical angles, and apical indices of ventral cells of the epiectodermal gastrula of Xenopus during the first HC-four hours after the relaxation of mechanical tension. In the unrelaxed epithelium, an overwhelming majority of cells have three apical connections, apical angles close to 120 degrees, and apical indices around one (isodiametric cells); after relaxation, the number of cells with more than three connections, the number of apical angles deviating substantially from 120 degrees, and the percentage of columnar cells with high apical index increase. Apices with more than three connections tend to gather in enclosed groups, forming a smooth line of cell walls.

[Mechanodependent cell movements in the axial rudiments of Xenopus gastrulae].

Sandwich explants of the suprablastoporal area of Xenopus early-mid gastrula and same stages of entire embryos were stretched with two needles perpendicular to the direction of natural elongation of the axial rudiments. The changes in the embryonic shape and histological structure were monitored as well as the arrangement of descendants of one of dorsal blastomers labeled with fluorescein-dextran at the 16-cell stage. A substantial fraction of stretched explants reoriented along the applied stretch direction.

[Mechanical feedback in morphogenesis and cell differentiation].

The review is concerned with studies of mechanical stresses and mechanical feedbacks on the cellular level. The dependence of responses of cells and embryonic tissues on mechanical stresses and their ability to generate these stresses by themselves have been shown. Regular feedbacks between external (passive) and internal (active) mechanical stresses have been established that are required for the viability of cells, determine the direction of their differentiation, and provide the self-organization of morphogenetic processes.

["Our standpoint different from common ..." (scientific heritage of Alexander Gurwitsch)].

The work of prominent Russian biologist Alexander Gavrilovich Gurwitsch (1874-1954) on the theory of organism development are reviewed. Alexander Gurwitsch introduced the concept of embryonic (morphogenetic, biological, and cellular) field and proposed several revisions of it from 1912 to 1944. Although neither of them can be considered as a final theory of development, his the persistent search for the invariant law that allows the shape (spatial structure) to be proposed for each next developmental stage from the previous shape is of imperishable methodological interest.

[Ultraweak emissions of the developing Xenopus laevis eggs and embryos].

We measured ultraweak emissions of the Xenopus laevis eggs and embryos during normal development and under the influence of stress factors in a spectral range of 250 to 800 nm using a photomultiplier. The registered emissions were analyzed by several basic characteristics: mean intensity, histograms, kurtosis, linear trends, and Fourier spectra. We followed relationships between these parameters and developmental stage, as well as the number of individuals in optic contact with each other.

[Role of cooperative cell movements and mechano-geometric constrains in patterning of axial rudiments in Xenopus laevis embryos].

The role of cooperative cell movements has been explored in establishment of regular segregation of the marginal zone of Xenopus laevis embryos into the main axial rudiments: notochord, somites and neural tissue. For this purpose, the following operations were performed at the late blastula-early gastrula stages: (1) isolation of marginal zones, (2) addition of the ventral zone fragments to the marginal zones, (3) dissection of isolated marginal zones along either ventral (a) or dorsal (b) midlines, (4) immediate retransplantation of excised fragments of the suprablastoporal area to the same places without rotation or after 90 degrees rotation, (5) pi-shaped separation of the suprablastoporal area either anteriorly or posteriorly. In experiments 1, 4, and 5, lateromedial convergent cell movements and differentiation of the axial rudiments were suppressed.

[A morphomechanical aspect of epigenesis].

Epigenesis in classical embryology is regarded as self-complication of spatial organization of the embryo during its development. The reality of the phenomenon of self-complication at the cellular and supracellular levels has been demonstrated by classical experimental embryology. Today, in light of studies of cell differentiation mechanisms, this problem acquired a molecular aspect.

[Kinetics of the reaction of yolk cell surface in the loach to puncture and mechanic deformation].

Circumferential and radial components of the yolk cell surface movements were measured in the loach embryos at the late blastula stage within 40-50 min after puncture or indentation by an obliquely directed glass rod. The yolk cell surface was preliminarily marked by coal particles. It was shown that even closely located regions of the surface differed markedly in the rate and direction of their movements.

[Structurization of cortical layer of loach yolk cell after wounding as a "minimal" model of morphogenesis].

Structural rearrangements of the yolk cell surface were studied in loach embryos using SEM and TEM, which take place within 30 min after a point-like puncture at the late blastula stage. The effects of sucking off or addition of a part of yolk, lowered temperature, and absence of Ca2+ on structurization were studied. Around the area of puncture, the yolk granules were submerged, the number of vesicles increased, and numerous membrane folds were formed.

[Statistical and frequency-amplitude characteristics of ultra-weak emissions of loach eggs and embryos under normal conditions and on their optic interactions. II. Changes in characteristics of ultra-weak emissions upon optic interaction of groups of embryos of different ages. ].

We compared the characteristics of ultraweak emissions from groups of loach embryos of different ages in the presence or absence of optic interaction. The percentage of zero values of emission gradually increased during the first hour of optic interaction. The number and height of rare big pulses estimated by the value of kurtosis increased in parallel.

[A quantitative study of regional and stage specific reaction of African clawed frog embryonic tissues on mechanical stress].

Residual deformation of fragments of the embryonic tissues preserved after relaxation of the stretching force serve as a criterion of active redistribution of their cells caused by this stretching. We measured residual deformations of the Xenopus laevis ventral and dorsal ectoderm at the early gastrula and lateral ectoderm at the late gastrula-early neurula after stretching of varying time and force. While the samples responded to moderate (up to 40%) short-term stretching as elastic bodies (residual deformations were absent), residual deformation appeared in the early gastrula tissues after 30-60-min stretching, which were more pronounced in the ventral tissues than in the dorsal ones.

[Statistical and frequency-amplitude characteristics of ultra weak emissions of the loach eggs and embryos under the normal conditions and during their optic interactions. I. Characteristics of ultra weak emission in normal development and the optic role of egg envelope].

Ultraweak emissions of groups comprising several dozens of unfertilized and fertilized loach eggs, embryos, larvae, and their egg envelopes were measured on a photomultiplier tube. The envelopes absorbed the light from external sources but readily gave it back in the absence of embryos. We carried out statistical and frequency-amplitude analyses of ultraweak emissions and studied the autocorrelation structure of their frequency spectra.

[Correlation of fine structures of distributions of amplitudes of a photomultiplier dark current fluctuations with the Earth rotations about its axis].

The fine structures of distributions of photomultiplier dark current fluctuations measured in two laboratories 2000 km distant from other: in the international Institute of Biophysics (Neuss, Germany) and in the Moscow State University (Moscow, Russia) were compared. It is shown that similar forms of appropriate histograms are apparently more often realized at both locations at the same local time. This confirms the previous conclusion that the fine structure of distributions correlates with rotation of the Earth about its axis.

[Artificially applied tensions normalize development of relaxed Xenopus Laevis embryos].

Relaxation of tensions of the surface of Xenopus laevis embryos at the late blastula stage leads to deep and diverse developmental defects and increased variability in mutual position and volume ratios of the axial rudiments. Here, we demonstrate that the development of such embryos was markedly normalized if the relaxed tensions were restored in one of two ways: (1) isotropic stretching of the blastocoel roof induced by incubation of relaxed embryos in a hypotonic medium or (2) anisotropic stretching of embryos on two needles. In the latter case, we succeeded in restoring the morphological axis not only after longitudinal stretching, but also after transverse stretching, and the new axis had signs of anteroposterior polarity.

[Work of morphogenesis in the Department of Embryology of Moscow State University: toward understanding the dynamic architecture of development].

This is a review of studies on morphogenesis carried out at the Department of Embryology, Moscow State University, over the past 30 years. The main direction of studies has been to reveal and describe the properties of self-organizing fields of mechanical stresses in developing embryos.

[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.

[Tensotaxis--a collective movement of embryonic cells up along the gradients of mechanical tensions].

We have examined the active collective movement of ectodermal cells from early gastrula of Xenopus laevis towards the point source of stretching, using techniques of videomicroscopy and scanning electron microscopy. We define this mode of cell movement as tensotaxis. This movement begins near the source of tension 5-10 min after the beginning of stretching and is spread in a relay fashion to more distant cells.

[Morphogenetic and differentiation sequelae to relaxation of mechanical tensions in Xenopus laevis blastula].

Using microsurgical technique, we have conducted relaxation of circular tensions on the surface of X. laevis embryo at the stage of late blastula. Results of these operations were examined by optical and scanning electron microscopy, heteroplastic marking, and morphometry.

[Ultraweak emissions from chicken eggs and embryos: the nonadditive interaction of 2 emitters and stable nonequilibrium].

Ultraweak emission of the optic range from developing, unfertilized, and dead chicken eggs and their components (isolated blastoderm and embryo, entire yolk, white, and shell) was measured at the normal and abnormal temperatures of incubation using a photomultiplier tube. Two sources of ultraweak emission were found: blastoderm and yolk from the fertilized eggs until day 4 of incubation and shell from all eggs, including the unfertilized and dead ones. Emission from the former source was weaker and almost light independent, was recorded only at the temperature of incubation, and had a wavelength of no more than 3000 nm.