Том 48, № 1 (2017)

The human oocyte is surrounded by the zona pellucida—an elastic, transparent extracellular matrix consisting of specific glycoproteins. The zona pellucida is preserved after fertilization and surrounds the developing human embryo for a few days. The embryo needs to get out of the zona pellucida before implantation to establish cell contacts between the trophectoderm and endometrial epithelium. The release of the embryo from the zona pellucida is carried out at the stage of the blastocyst and called zona hatching. During zona hatching the blastocyst breaks the zona pellucida and performs active movements to escape through a gap formed in the zona. While microscopic description of zone hatching is well known, biochemical and cytological basis of zone hatching remains poorly understood. The break of the zona pellucida occurs under the influence of two forces: mechanical pressure of the growing blastocyst on the zone and chemical dissolution of the zone material with secreted lytic enzymes. There is only one paper (Sathananthan et al., 2003), which describes the specialized cells in the trophectoderm that locally dissolve the zona pellucida, promoting the emergence of the hole for blastocyst release. Taking into account the singleness of the paper and the absence of further development of this subject by the authors in the following decade, the existence of specialized cells for zone hatching should be assumed with great care. Lytic enzymes, secreted by cells of the trophectoderm for dissolving the zona pellucida, are different. Depending on the species of the mammal, different classes of proteases participate in the zone hatching process: serine proteases, cysteine proteases, metal-loproteinases. Proteases, secreted by human trophectoderm, are not described. The mechanisms of the active movement during blastocyst hatching are investigated to a lesser degree. Only the involvement of the cytoskeleton of trophectoderm cells in the mechanism of blastocyst compression was shown, and the participation of desmosomes in the coordinated change in the form of trophectoderm cells during compression is suggested. This review summarizes literature data on the possible mechanisms of zone hatching in the development of human embryos, obtained in experiments in vitro, as well as in animal models.

The analysis of kinetic curve of redox potential changes (ORP) of aqueous medium in the process of loach embryo population development at 17°C was conducted. The system of critical points defining periodization of the major stages of embryo development was identified on the ORP curve in the time interval up to τ₀ using novel methods for processing of nonlinear signals. It was shown that τ₀ was a natural periodization parameter of main morphological changes in an embryo known in the developmental biology.

A variety of early ontogenetic events of anuran species (growth, structural and biochemical diversification, metamorphosis) offers a unique opportunity to evaluate the effectiveness and application limits of mass spectrometry method for the analysis of metabolic and transformation events in developing organisms. The dynamics of relative carbon and nitrogen contents and stable isotopes of these elements during larval development in the period of metamorphosis climax and after its conclusion in moor frog specimens developing in their natural habitat and in vitro on a referent diet are traced. A decrease in C/N ratio and enrichment of the tissues with heavy stable isotopes of carbon and nitrogen during embryonal and larval development (prior to the beginning of independent feeding) indicates the increase in the portion and variety of proteins, accompanied by consumption of yolk lipids. The relative nitrogen content increase and C/N ratio decreases with the growth and development of independently feeding tadpoles, which indicates surpassing increase of the portion of proteins in tissues. In growing tadpoles, the rates of tissue renewal in general and rates of protein metabolism in particular affect the kinetics of changes of tissue isotope composition, which approaches isotope composition of the consumed food. A decrease in С/N ratio in the bodies of metamorphs during mass tissue decomposition is indicative of continuing reconstruction of larval organs and growth of anlage of definitive organs. Significant increase of C/N ratio and depletion of liver samples by heavy carbon isotopes are associated with intensive synthesis and reservation of lipids within the organ. Strong enrichment of metamorphs’ tissues with heavy nitrogen isotope indicates the substitution of ammoniotelic type of nitrogen metabolism by urotelic type. Decrease in C/N ratio and enrichment of tissues by heavy carbon isotope may be connected to intensive oxidation of lipids, which supports the growing energy costs of terrestrial underyearlings. Relative contents of heavy nitrogen isotope in the tissues of underyearlings does not change compared to the tissues of metamorphs.

In this study, modern techniques of laser microsurgery of cell spheroids have been used to develop a new simple, reproducible model for studying the mechanisms of repair and regeneration in vitro. Nanosecond laser pulses were applied to perform a microdissection of the outer and the inner zones of the spheroids from dermal fibroblasts. To achieve effective dissection and preservation of spheroid viability, the optimal parameters were chosen: 355 nm wavelength, 100 Hz frequency, 2 ns pulse duration, laser pulses in the range of 7–9 μJ. After microdissection, we observed injury of the spheroids: the edges of the wound surface opened and the angular opening reached a value of more than 180°. As early as during the first hour after spheroid microdissection with laser radiation, the surviving cells changed their shape: cells on the spheroid surface and directly in the damaged area became rounded. One day after microdissection, the structure of the spheroids began to partially recover, the cells in the surface layers began to take the original flattened shape; debris of dead damaged cells and their fragments was gradually cleared from the spheroid composition. In the proposed model, the first data on stimulation of structure recovery of injured spheroids from dermal fibroblasts with a P199 synthetic polypeptide, which is used in cosmetology for the initiation of antiaging and regenerative effects in the skin, were received. After microdissection, recovery of the spheroids structure with a few surface layers of flattened imbricated arranged cells and polygonal cells of the inner zone in the presence of P199 peptide was faster than in the control group, and was completed within 7 days, presumably due to the remodeling of the survived cells.

We demonstrate regeneration capability of the skin pigment system of clawed frog larvae after local damage to melanophores without skin rupture. The contribution to recovery of pigmentation of the injured area of de novo differentiation of melanophores is compared to contribution of mitotic division of undamaged melanophores localized on the boundaries of the injured area. The regeneration process is observed during various stages of pigment system development of larvae. We establish that, compared to ontogenetic dynamics, pigmentation development in animals is more intense during the regeneration.