Potential emigration of Siberian cattle germplasm on Chirikof Island, Alaska.

Feral cattle residing in Chirikof Island, Alaska, are relatively distinct from breeds used in commercial production in North America. However, preliminary evidence suggested that they exhibit substantial genetic relationship with cattle from Yakutian region of Siberia. Thus, our objective was to further elucidate quantify the origins, admixture and divergence of the Chirikof Island cattle relative to cattle from Siberia and USA. Subject animals were genotyped at 15 microsatellite loci. Compared with Turano-Mongolian and North American cattle, Chirikof Island cattle had similar variation, with slightly less observed heterozygosity, fewer alleles per locus and a positive fixation index. Analysis of the genetic distances revealed two primary clusters; one that contained the North American breeds and the Kazakh White head, and a second that contained the Yakutian and Kalmyk breeds, and the Chirikof population. Thus, it is suggested that Chirikof Island cattle may be a composite of British breeds emanating from North America and Turano-Mongolian cattle. A potential founder effect, consistent with historical records of the Russian-American period, may contribute to the adaptation of the Chirikof Island cattle to their harsh high-latitude environment. Further study of adaptive mechanisms manifest by these cattle is warranted.

[Effect of tamponade on the nucleotide composition and cytosine methylation level of DNA in the heart muscle of dogs]. / Vliianie tamponady na nukleotidnyi sostav i uroven' metilirovaniia tsitozina DNK v myshtse serdtsa sobak.

Base composition and quantitative changes in the 5-methylcytosine (m5c) content in DNA isolated from male dogs' heart muscle under the acute tamponade have been studied. Due to the effect of tamponade statistically reliable decrease (15%) in m5c content in DNA has been found to take place in experiment in comparison with control. Possible mechanisms of DNA methylation decrease by cytosine are under discussion.

[Autoradiographic analysis of molecular mechanisms of differential staining of sister chromatids]. / Avtoradiograficheskii analiz molekuliarnykh mekhanizmov differentsial'nogo okrashivaniia sestrinskikh khromatid.

The significance of procedures involved in the technique of differential staining of sister chromatids is estimated by quantitative autoradiography. Photolysis of bromodeoxyuridine-substituted DNA is shown to be the main process determining the quality of differential staining under certain experimental conditions. On the basis of modes provoking DNA degradation and washing DNA fragments off the chromosomes, a simplified method including only irradiation of chromosomes under a mercury lamp and treatment with a sodium citrate solution is proposed.