[Yersinia pseudotuberculosis in a model marine ecosystem (experimental research)]. / Yersinia pseudotuberculosis v model'noi morskoi ékosisteme (éksperimental'noe issledovanie).

Materials on the behavior of Y. pseudotuberculosis in the model of marine ecosystem are presented. Y. pseudotuberculosis, both carrying and having lost the virulence plasmid of 45 MD, die in nonsterile sea water, but are capable of prolonged survival in sterile sea water and in the bodies of echinoderms. The death of these bacteria is accelerated in the presence of larvae of echinoderms. In sea water at low temperature Y. pseudotuberculosis maintained their high pathogenicity potential which they use on contact with eukaryotes. Under these conditions Y. pseudotuberculosis preserve their virulence plasmid, thus causing the disease and death of animals.

[Embryonic development of the sea urchin after low-temperature preservation]. / Razvitie zarodyshei morskogo ezha posle nizkotemperaturnoi konservatsii.

The sea urchin embryos were cooled to -196 degrees by two-step freezing with the use of 1-1.5 M dimethyl sulfoxide as a cryoprotectant. The embryos were equilibrated with the cryoprotectant for 20-30 min at 0 +/- 2 degrees. At -7 degrees ice crystallization was induced and the embryos were cooled to -38-42 degrees at a rate of 6-8 degrees /min. The embryos were then transferred into liquid nitrogen. The embryos were thawed in a water bath at 19 degrees. No less than 90% of the embryos frozen at the stages of blastula, gastrula, or pluteus were capable of recovery and normal development. The length of cryopreservation did not affect the survival of the embryos.