The effects on hemopoiesis of 2-amino-5,6-dihydro-4H-1,3-thiazine administered to mice prior to x irradiation was investigated. The radioprotective effectiveness of this substance was discussed.

A study was made of radiosensitivity and sulfhydryl group content of haploid and diploid Saccharomyces cerevisiae yeast of the ''wild type'' with the rad 54 mutation. It was established that, in ''wild type'' yeast, cells in the logarithmic phase of growth are not only more radioresistant than cells in the stationary phase of growth, but they contain more SH groups. In yeast carrying the rad 54 mutation, cells in the logarithmic phase of growth differ little from those in the stationary phase, with regard to both radioresistance and SH group content. No substantial differences were demonstrated in SH group content of haploid and diploid cells of different genotypes at the stationary phase of growth. The hypothesis is expounded that the influence of the rad 54 mutation on differences in radiosensitivity of yeast in different growth phases may be related to the disturbances in regulation of SH compound synthesis induced by this mutation.