The behaviour of the nuclei of the X. laevis vitellogenic oocytes was studied by their transplantation into the cytoplasm of the axolotl maturing oocytes. After the germinal vesicle breakdown, in the case the transplanted nuclei were located close to each other a common giant spindle united the chromosomes of all transplanted nuclei. A mosaic spindle united sometimes the chromosomes of the two amphibian species. The embryonic nuclei transplanted in the cytoplasm of the maturing oocytes formed, after the nuclear envelope breakdown, individual spindles, sometimes united in multipolar figures. Thus, the nuclei of different cell types, embryonic cells and germ cells, behave in a different way in the same environment, the cytoplasm of the maturing oocytes.

Ambystoma↗

PubMedDate not supplied

[Effect of the method of preparing dental cements on their physicochemical properties].

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Chemical Phenomena↗

PubMedDate not supplied

[The action of neurotransmitters and their antagonists on oocyte maturation. The action of serotonin antagonists on the in-vitro maturation of amphibian oocytes].

Serotonin antagonists (inmecarb hydrochloride and inmecarb methiodide) stimulate in vitro maturation of Bufo viridis and Xenopus laevis oocytes or potentiate the action of progesterone. In contrast to that, serotonin inhibits or blocks oocyte maturation stimulated by progesterone or serotonin antagonists. Sensitivity of B. viridis oocytes to serotonin, its agonists and antagonists is subject to seasonal changes. A maximum sensitivity of intact oocytes is observed in February-March, and that of denuded ones in May-June. We suggest that endogenous serotonin is involved in maintenance of the block of meiosis and in the oocyte maturation control in amphibians.

Animals↗

PubMedDate not supplied

[The action of tiazofurin on the development of sea urchin embryos and larvae].

The effects of the antitumor drug tiazofurin on development of sea urchins Sphaerechinus granularis, Paracentrotus lividus, Strongylocentrotus intermedius, and Arbacia lixula were studied. When 0.01-200 microM tiazofurin (TAF) was introduced in the incubation medium (artificial sea water) just after fertilization or at the midblastula stage, the development proceeded quite normally until the beginning of gastrulation. But later TAF blocked gastrulation and induced formation of mobile ball-shaped larvae with normal pigment cells but devoid of the nervous system, skeletal spicules and digestive tract. The threshold TAF concentrations varied from 0.05 microM (S. granularis) to 2-5 microM (all other species). When TAF was introduced during gastrulation and just after gastrulation, the larvae had defective nervous system and skeleton and suppressed expression of gangliosides. The nonhydrolyzable analog of GTP, GTP-gamma-S (5-20 microM), introduced in artificial sea water no later than at the midblastula stage prevented all above mentioned developmental defects.

Adenosine Triphosphate↗

PubMedDate not supplied

[Cold sterilization of medical wares made of plastic].

To many objects and articles made of polymeric materials the traditional methods of sterilization are inapplicable. This has given rise to the need for devising new methods and means, for sterilization with chemical solutions. Pertinent investigations have ascertained that with the use of the preparation "Desoxon-1" the physico-mechanical properties of polymeric materials remain practically unchanged. With an exposure of 15 min there could be achieved complete sterilization of the study objects made of the cast acrylate material "Dacryl-4", copolymer of ethylene with vinylacetate, of a high-pressure polyethylene, copolymer of styrene, and of other materials.

Plastics↗

PubMedDate not supplied

[Serotonin inhibits phorbol ester-induced oocyte maturation in the green toad (Bufo viridis)].

The activator of protein kinase C phorbol-12-myristat-13-acetate (PMA) induces maturation of the definitive intact (coated with the follicular envelopes) and defolliculated oocytes of the green toad. This effect is more pronounced in case of defolliculated oocytes. The amount of matured oocytes depends on the PMA concentration in solution. Serotonin (5-HT) inhibits or blocks maturation of the oocytes induced either by progesterone or by PMA. A possible mechanism of this effect is discussed with special reference to its role in regulation of oocyte maturation.

Animals↗