[Hepatic leiomyosarcoma: a case report].

The authors present a review of pathogenesis, diagnosis and various approaches to treatment for an extremely rare tumor - primary hepatic leiomyosarcoma. This tumor is dif- ficult to be diagnosed by imaging examinations. The prevalent method of treatment is a radical resection (RO surgery).

[The Petergof genetic collection of microorganisms].

The Petergof Genetic Collection (PGC) of microalgae was created in the 1960s during study of the regularities of mutational processes. A collection of yeasts has been maintained at the Department of Genetics and Selection of St. Petersburg State University since 1977.

Rapid genetic test for discrimination between haploid and polyploid transformants in Saccharomyces.

Spheroplast fusion induced by polyethylene glycol often occurs during transformation of yeast spheroplasts. It leads to the appearance of polyploid transformants. We have developed a method of discriminating between haploid and polyploid transformants, based on qualitative comparison of the frequency of mitotic homozygotization for a recessive marker, lys2, in diploid and polyploid hybrids of transformants crossed with a tester haploid bearing lys2.

[Genetic express-test for distinguishing between haploids and autodiploids in the yeast Saccharomyces].

Some originally haploid strains of yeast Peterhof breeding stocks obtained in tetrad analysis of diploids turned out to be spontaneous autodiploids after storage. They produced polyploid hybrids, as shown by tetrad analysis. An express-test for discrimination between haploids and autodiploids, based on the frequency of mitotic homozygotisation for a recessive marker has been developed.

[Regulation of purine nucleotide biosynthesis in mutant Saccharomyces cerevisiae yeasts with increased sensitivity of the pathway for de novo synthesis to inhibition by exogenous guanine].

Aza 165 and aza 238 Saccharomyces cerevisiae mutants characterized by a 2.5 times higher sensitivity of the de novo purine synthesis to the inhibitory effect of exogenous guanine, as compared with the wild type strain, have been selected by their sensitivity to 8-azaguanine. The exogenous guanine somewhat inhibits the growth and synthesis of nucleis acids in mutants, this being due in vivo neither to permeability changes of the cell membrane, nor to concentration changes of guanilic derivatives in the acid-soluble pool of yeast cells.