[Artificial Inversion of the Left-Right Visceral Asymmetry in Vertebrates: Conceptual Approaches and Experimental Solutions].

Externally, vertebrates are bilaterally symmetrical; however, left-right asymmetry is observed in the structure of their internal organs and systems of organs (circulatory, digestive, and respiratory). In addition to the asymmetry of internal organs (visceral), there is also functional (i.e., asymmetrical functioning of organs on the left and right sides of the body) and behavioral asymmetry. The question of a possible association between different types of asymmetry is still open. The study of the mechanisms of such association, in addition to the fundamental interest, has important applications for biomedicine, primarily for the understanding of the brain functioning in health and disease and for the development of methods of treatment of certain mental diseases, such as schizophrenia and autism, for which the disturbance of left-right asymmetry of the brain was shown. To study the deep association between different types of asymmetry, it is necessary to obtain adequate animal models (primarily animals with inverted visceral organs, situs inversus totalis). There are two main possible approaches to obtaining such model organisms: mutagenesis followed by selection of mutant strains with mutations in the genes that affect the formation of the left-right visceral asymmetry and experimental obtaining of animals with inverted internal organs. This review focuses on the second approach. We describe the theoretical models for establishing left-right asymmetry and possible experimental approaches to obtaining animals with inverted internal organs.

[Establishment of visceral left-right asymmetry in mammals: the role of ciliary action and leftward fluid flow in the region of Hensen's node].

During individual development of vertebrates, the anteroposterior, dorsoventral, and left-right axes of the body are established. Although the vertebrates are bilaterally symmetric outside, their internal structure is asymmetric. Of special interest is the insight into establishment of visceral left-right asymmetry in mammals, since it has not only basic but also an applied medical significance. As early as 1976, it was hypothesized that the ciliary action could be associated with the establishment of left-right asymmetry in mammals. Currently, the majority of researchers agree that the ciliary action in the region of Hensen's node and the resulting leftward laminar fluid flow play a key role in the loss of bilateral symmetry and triggering of expression of the genes constituting the Nodal-Ptx2 signaling cascade, specific of the left side of the embryo. The particular mechanism underlying this phenomenon is still insufficiently clear. There are three competing standpoints on how leftward fluid flow induces expression of several genes in the left side of the embryo. The morphogen gradient hypothesis postulates that the leftward flow creates a high concentration of a signaling biomolecule in the left side of Hensen's node, which, in turn, stimulates triggering of.gene expression of the Nodal-Ptx2 cascade. The biomechanical hypothesis (or two-cilia model) states that the immotile cilia located in the periphery of Hensen's node act as mechanosensors, activate mechanosensory ion channels, and trigger calcium signaling in the left side of the embryo. Finally, the "shuttle-bus model" holds that leftward fluid flow carries the lipid vesicles, which are crashed when colliding immotile cilia in the periphery of Hensen's node to release the contained signaling biomolecules. It is also noteworthy that the association between the ciliary action and establishment of asymmetry has been recently discovered in representatives of the lower invertebrates. In this paper, the author considers evolution of concepts on the mechanisms underlying establishment of visceral left-right asymmetry since 1976 until the present and critically reexamines the current concepts in this field of science. According to the author, serious arguments favoring the biomechanical hypothesis for determination of left-right asymmetry in mammals have been obtained.

[Artificially applied tensions normalize development of relaxed Xenopus Laevis embryos]. / Iskusstvenno nalozhennye natiazheniia normalizuiut razvitie relaksirovannykh zarodyshei shportsevoi liagyshki.

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. The role of isotropic and anisotropic tensions in organization of the early amphibian development is discussed.

Action of nonviral gene delivery vectors on human complement system: low anticomplementary activity of lipoplexes based on lacZ plasmid and phospholipid/oligocation liposomes.

A simple test-system has been developed for the first time in order to detect the ability of effectors (lipoplexes) to activate the complement system in an antibody-independent manner to serve as acceptors of nascent C4b and to inhibit formation of the key enzyme of complement, C3-convertase. The effect of plasmid DNA (pCMV-SPORT-LacZ), negatively charged cardiolipin (CL), neutral phosphatidylcholine (PC) vesicles and their lipoplexes, on the complement system was studied using the method developed. It was revealed that PC vesicles did not affect the complement system, while CL vesicles manifested low activation. The influence of plasmid DNA and its lipoplex based on PC liposomes as well on the complement system was very low. PC/LacZ lipoplex (143 microg/ml) acted on the complement system like 5.36 microg/ml heat aggregated IgG (agg) (the level of no pathological ruptures), whereas CL/LacZ lipoplex (143 microg/ml) acted similar to 10.7 microg/ml IgG (agg). Thus, weak activation of the complement system with CL lipoplex, and even weaker for the PC lipoplex testified to the use of neutral and positively charged lipoplexes preferably in gene therapy protocols. The technique can also be used for testing the influence of injectable gene therapy vectors on the complement system.

[Gene and gene cellular therapy and neurodegenerative diseases]. / Gennaia i genno-kletochnaia terapiia i neirodegenerativnye zabolevaniia.

The modern methods of the treatment of the neurodegenerative diseases are considered. Neurodegenerative diseases originate due to the degeneration of the neuronal cells of central nervous system that leads to imbalance of the neurotransmitter synthesis and, as a consequence, movement disorders and mental disabilities. Traditional methods of pharmacotherapy and neurosurgery give short-term effect. Since 1980 neurotransplantation was developed as a new technology for the treatment of the neurodegenerative diseases. This approach represents a case of cell therapy being used for transplantation of the human fetal material. Cell transplantation compensates the local deficiency of the neurotransmitter level by substitution of degenerated neurons of patient's brain (e.g. dopaminergic neurons). Gene-cell conjunction of cell therapy with modification of genome of transplanted cells is the most perspective approach to increase an efficiency of neurotransplantation. Short description of gene therapy approaches and a search for optimal gene-cell protocols for therapy of neurodegenerative diseases are presented in this paper.

[Cytomechanical control of morphogenesis]. / Tsitomekhanicheskii kontrol' morfogeneza.

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.

[Variation and asymmetry of axial rudiments of Xenopus laevis embryos in response to a disturbance of cell movements and tension fields in the marginal gastrula]. / Izmenchivost' i asimmetriia osevykh zachatkov zarodyshei shpotsevoi liagushki pri narushiiakh kletochnykh dvizhenii i polei natiazhenii v marginal'noi zone rannei gatruly.

We studied changes of volume, disturbances of mutual volumetric proportions, and asymmetry of axial rudiments in the embryo of Xenopus laevis after partial separation of the dorsal blastopore lip with P-shaped incisions from the remaining part of the marginal zone. This was conducted at the stage of early gastrula. The incision was directed either towards the lip (series 1) or away from the lip (series 2). Gastrulation movements were inhibited in both series of experiments. In series 1, the dorsal zone acquired isotropic structure, and in series 2, it quickly restored the initial longitudinal tensions. Sometimes and pairwise (but strongly asymmetric) notochord rudiments were formed in the lateral lips of the unclosed blastopore. In both experimental series, we have noted a high (exceeding the control by an order of magnitude) variation in the volume and mutual proportions of axial rudiments, their high asymmetry, and low volume correlations. Asymmetry of chordal rudiments in the lateral lips was higher in series 1, and the occurrence of the notochord in the dorsal region was higher in series 2. The results are discussed from the point of view of a possible role of gastrulation movements and the associated tension fields in the marking of axial rudiments.

[Morphogenetic and differentiation sequelae to relaxation of mechanical tensions in Xenopus laevis blastula]. / Morfogeneticheskie i differentsirovochnye posledstviia relaksatsii mekhanicheskikh natiazhenii v blastule shportsevoi liagushki.

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. The most important outcomes of tension relaxation included disappearance of blastocoel, intermixing of cells of the animal part of the embryo and their local migration from the embryo surface. This was followed by the appearance of slit-like depressions and protuberances, some of the protuberances showed branching. Morphological abnormalities of several types were observed 1.5-2 days later. Some of the abnormal embryos resembled the embryos of lower chordates. We have noted sharp increase in the variation of absolute volumes and mutual volume ratios of axial rudiments. Incubation of the operated animals in a hypotonic solution restored the blastocoel and led to significant normalization of development. The results obtained demonstrate that at the stage of late blastula mechanical tensions play an important role in the maintenance of normal morphological and differentiational structure of amphibian embryos.