[The embryonic brain-derived neuralizing factor (EBDNF): its partial purification by ion-exchange and affinity chromatography].

The data are presented about isolation from the brain of 7.5-day chick embryos of a factor capable of neuralizing effect on the early gastrula ectoderm of the grass frog Rana temporaria L. Earlier this factor was defined as embryonic brain-derived neuralizing factor (EBDNF) (Mikhailov, Gorgoliuk, 1989).

[Forskolin and cyclic adenosine monophosphate inhibit the neurulation action of concanavalin A on explants of the gastrula ectoderm of amphibians].

We studied effects of forskolin, an activator of adenylate cyclase activity, and dioctanoyl-cyclic adenosine monophosphate (do-cAMP) on neutralizing (N) activity of concanavalin A (Con A). Biological testing was performed using explanted animal pole ectoderm of the Rana temporaria early gastrula. Con A treatment (200 micrograms/ml, 2 h) resulted in neutralization of 70-90% explants.

[Plant lectins and embryonic tissue factors as probes for studying the mechanisms of neural induction in amphibians].

Using various experimental techniques, we have demonstrated that animal pole ectoderm (APE) of Rana temporaria embryos at the stage of early gastrula is a good target tissue for testing the neuralizing (N) factors. In this respect R. temporaria APE is comparable with APE of some other amphibian species.

[Concanavalin-binding proteins and cytokeratins in different tissues of the early amphibian gastrula (Rana temporaria, Xenopus laevis)].

Concanavalin A (con A), a lectin which specifically interacts with aD-mannose and aD-glucose, has a neutralizing effect on the explants of the early gastrula ectoderm of several amphibian species. Consequently, it was interesting to study con A-binding protein spectrum of the ectoderm and compare it to those of other early gastrula tissues. Animal pole ectoderm (APE), dorsal blastopore lip (DBL) and vegetal pole endoderm (VPE) were dissected from early gastrulae of Rana temporaria and Xenopus laevis.

[Neural differentiation of ectodermal explants of the early gastrula from Rana temporaria under the action of various mitogens and kainic acid].

The following mitogens: concanavalin A (con A), phytohemagglutinin (PHA), hydra growth factor (HGF) as well as neurotoxic agent kainic acid, caused neural differentiation (N) effects differed in value and also in character of dependence on concentration of the agent. The lowest effective concentration of con A was 75 micrograms/ml (15% neural differentiation, treatment during 3 h), and the effect reached maximum of 50-60% at 100-200 micrograms/ml. Con A concentration 50 micrograms/ml showed no effect but after 1% rabbit gamma-globulin was added, 17% neural differentiation was detected.