[Spatial-temporal dynamics of morphogenetic blastoderm potencies in early embryogenesis of the loach].

The degree of differentiation of axial structures (notochord, neuroectoderm, and somites) in 24-hour explants (a total of 380) of the loach embryonic blastoderm was determined on histological sections according to a developed scale of estimates. Before the beginning of epiboly, axial structures were formed only from fragments of the dorsal sector of the blastoderm marginal zone. Its other sectors acquired the capacity of forming axial structure only with the beginning of epiboly, as the germ ring was formed in the marginal zone, unlike the cells outside the germ ring.

[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.

[Dorsoventral differences of morphogenetic potencies of the loach blastoderm in experiments with alteration of the mass of explanted fragments].

We studied the influence of doubling the mass of explanted fragments of the dorsal and ventral loach blastoderm at the early gastrula stage on their capacity for differentiation of axial structures. The dorsoventral differences are as follows: the differentiation of somites correlates, according to the results of factor analysis, with the shape complication only in double dorsal explants, while the notochord is more differentiated in the ventral fragments, if it is present, than in the dorsal ones. Doubling of the mass of dorsal fragments of the blastoderm enhances their morphogenetic potencies and shifts differentiation towards the formation of trunk axial structures.

[Appearance of dendritic cells in the basal layer of the corneal epithelium during metamorphosis of the grass frog Rana temporaria L].

A population of dendritic cells was found at the light optic level in the basal layer of the corneal epithelium in Rana temporaria L. The cells had wide short processes which penetrated between neighboring epithelial cells. The bases lied on the basal membrane while the bodies are slightly elongated perpendicularly to the epithelium surface.