[Intrapopulation autosomal polymorphism in the common vole Microtus arvalis from the Transcaucasian region].

The broad autosomal polymorphism in form obscurus of common voles Microtus arvalis from the Transcaucasian region that is associated with the variation of subtelocentric chromosome pair 5, as well as the mechanism and evolutionary significance of this polymorphism, are discussed. Based on the morphological analysis of heterozygotes for chromosome pair 5 after differential G-, C-, and Ag-NOR-banding and on the measurements of homologues, the following conclusion has been made. The occurrence of the acrocentric chromosome 5 is the result of a double chromosomal rearrangement: a pericentric inversion and a duplication of the chromosomal material.

[A rare case of chromosome mutation in the ground vole Terricola majori (Arvicolinae, Rodentia)].

A rare case of chromosome variability is described for the ground vole, Terricola majori, from the Lagodekhi Nature Reserve (Georgia). This species is characterized by a stable karyotype (2n = 54, NF = 60), but we found an animal in which 2n = 53, NF = 60. The change in the diploid number resulted from a Robertsonian translocation accompanied by a local amplification of satellite sequences in centrometric heterochromatin.

[Sex chromosome behavior in meiosis in the gray hamster (Cricetulus migratorius Pallas, 1770)].

The sequence of X and Y chromosomes pairing at meiotic prophase in the Armenian hamster Cricetulus migratorius Pall., 1770 gas been studied. The results of differential staining (C-, Ag-NOR) of mitotic chromosomes are presented.

[The physiological mechanisms of the neurohumoral regulation of vascular tonus].

Neuronal organisation of hypothalamo-bulbar mechanisms of regulation of vascular tonus was studied in anesthetised and immobilised cats. The descending influence of posterior, tuberal and anterior structures of the hypothalamus on the activity of antidromically identified sympatho-activating reticulospinal neurons of the ventrolateral region of medulla oblongata is realised by mono-, oligo- and polysynaptic mechanisms. Chronic neurogenic hypertension was induced in rats by overloading the higher nervous activity.