[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.

[The loach--the object of experimental embryologic research in the Department of Embryology].

This paper provides a history of research at the Department of Embryology on the teleostean loach fish Misgurnus fossilis L. as a model. The use of the loach in education is briefly described.

[Transcription, in frog oocytes and transgenic mice, of recombinant plasmids with long terminal repeats of retrovirus proviruses].

RNA-DNA hybridization was used to study the transcription efficiency of the genes controlled by the long terminal repeats (LTR) from two different retroviral proviruses (exogenous provirus of the chicken Rous sarcoma virus and endogenous xenotropic provirus of the mouse). The oocyte nuclei of Xenopus laevis and the liver of transgenic mice were used as the transcription systems. The transcription efficiency of genes with the above mentioned promoters was shown to be roughly the same for both systems.

[Differentiation of the retina and pigment epithelium in the ontogeny of the common frog. 2. Pigment epithelium].

Changes in the differentiating pigment epithelium cells have been studied in Rana temporaria by transmission electron microscopy. Ultrastructural features of the pigment epithelium functions at successive developmental stages have been established: the phagocytic function appears the first (judging by utilization of embryonic pigment from the primary eye cavity), it is followed by the transport and barrier functions (as the secondary eye cavity and vascular envelope develop), while phagocytosis related to the process of renovation of the external segments of photoreceptors and the function of screening appear later.

[Differentiation of the retina and pigment epithelium in the ontogeny of the common frog. 1. The retina].

Changes in the ultrastructure of the differentiating retinal cells were studied by means of electron microscopy in Rana temporaria at successive developmental stages. Common features of the onset of differentiation of the retinal cells have been shown: appearance of the granular endoplasmic reticulum elements, of the polysomes, beginning of utilization of the yolk and lipids, elimination of ovarial melanosomes. Later during the differentiation of retinal neurons the protein synthesizing machinery and Golgi complex of these cells develop markedly, the number of mitochondria increases.

[Translation of the genomic and subgenomic RNAs of cucumber virus 3 in a cell free system from wheat embryos and in Xenopus laevis oocytes].

The purified preparation of cucumber virus 3 (CV3) (one of the member of tobamovirus group) contains, besides full-length (2.0 X 10(6)) genomic RNA, a short (0.24 X 10(6)) subgenomic RNA coding for coat protein in Xenopus laevis oocytes as well as in the cell-free protein synthesizing system from wheat embryos.