<Emphasis Type="Italic">Ex situ</Emphasis> conservation of some endemic and protected plant species in Georgia

Ecological and biological characteristics of eight, endemic, economically important, Georgian Red Data species (Convallaria transcaucasica Utkin ex Grossh., Cyclamen colchicum (Albov) Albov, Dioscorea caucasica Lipsky, Erythronium caucasicum Woronow, Gymnospermium smirnowii (Trautv.) Takht., Iris iberica Hoffm, Paeonia mlokosewitschii Lomak and Tulipa eichleri Regel) were studied. The current status of wild populations was assessed throughout their distributional area; exact locations of target populations were recorded using GPS, and fertility and vitality of individual populations were evaluated. Structural aspects of seed formation were studied, reproduction capacity was calculated, and the ratio of seed production (actual seed-forming capacity) to the number of ovules (potential seed-forming capacity) was determined. Optimum periods for the collection of mature seeds were identified for each target species. Seed germinability, sprouting capacity and potential for seedling development were tested experimentally in the laboratory on Petri dishes, in pots and outdoors. Ex situ conservation activities have been carried out: a seed bank was established and a stock of seedlings was produced for the purpose of in situ restoration of species with high conservation value.     

The involvement of topoisomerases and DNA polymerase I in the mechanism of induced thermal and radiation resistance in yeast

Either an ionizing radiation exposure or a heat shock is capable of inducing both thermal tolerance and radiation resistance in yeast. Yeast mutants, deficient in topoisomerase I, in topoisomerase II, or in DNA polymerase I, were used to investigate the mechanism of these inducible resistances. The absence of either or both topoisomerase activities did not prevent induction of either heat or radiation resistance. However, if both topoisomerase I and II activities were absent, the sensitivity of yeast to become thermally tolerant (in response to a heat stress) was markedly increased. The absence of only topoisomerase I activity (top1) resulted in the constitutive expression of increased radiation resistance equivalent to that induced by a heat shock in wild-type cells, and the topoisomerase I-deficient cells were not further inducible by heat. This heat-inducible component of radiation resistance (or its equivalent constitutive expression in top1 cells) was, in turn, only a portion of the full response inducible by radiation. The absence of polymerase I activity had no detectable effect on either response. Our results indicate that the actual systems that confer resistance to heat or radiation are independent of either topoisomerase activity or DNA polymerase function, but suggest that topoisomerases may have a regulatory role during the signaling of these mechanisms. The results of our experiments imply that maintenance of correct DNA topology prevents induction of the heat-shock response, and that heat-shock induction of a component of the full radiation resistance in yeast may be the consequence of topoisomerase I inactivation.     

Cytogenetic surveillance of tobacco-areca nut (mava) chewers, including patients with oral cancers and premalignant conditions

Three cytogenetic endpoints were studied in non-chewing healthy controls and 3 groups of tobacco-areca nut chewers, viz. normal chewers, chewers with oral submucous fibrosis and chewers with oral cancer. Frequencies of sister-chromatid exchanges and chromosome aberrations in peripheral blood lymphocytes and of micronucleated cells in exfoliated buccal mucosa were evaluated. All the parameters showed statistically significant elevations in all 3 groups of chewers compared to the controls. The data indicate possible application of the parameters as sensitive endpoints for monitoring tobacco-areca nut chewers, the group of individuals at higher risk of developing oral cancer, the commonest cancer among Indian males.