Effects of Vitrification with Self-made Carriers and Slow Programmed Freezing on Ovarian Tissue of Sheep / 中国医学科学院学报

Objective To investigate the effects of self-made carriers on the cryopreservation of ovarian tissue of sheep. Methods Thirty-two ovaries were randomly assigned to fresh group,programmed freezing group,self-made carrier I vitrification group,and self-made carrier Ⅱ vitrification group.The morphology,proliferation,apoptosis,and estrogen level of the ovarian tissue in each group were observed. Results After cryopreservation,the morphology normal rate of the primordial follicles in programmed freezing group,self-made carrier I vitrification group,and self-made carrier Ⅱ vitrification group were 74.2%,72.8%,and 72.3%,respectively,lower than that(83.7%)in the fresh group(χ

Prolonged exposure of human embryonic stem cells to heat shock induces necrotic cell death

We investigated the effects of prolonged heat shock treatment on human embryonic stem cell (hESC) viability. The hESC viability steadily declined with longer exposure to heat shock treatment (43ºC). After 4 h of exposure to heat shock at 43ºC, only 56.2 ± 1.5% of cells were viable. Viability subsequently declined to 37.0 ± 3.3% and 3.5 ± 0.7% after 8 h and 16 h, respectively of heat shock treatment at 43ºC. Transmission electron micrographs showed that the morphology of the dead/dying cells after heat shock treatment was characteristic of cellular necrosis with an uncondensed chromatin and a non-intact plasma membrane. This was further confirmed by flow cytometry analysis which showed that the DNA of the dead/ dying cells was still mostly intact, unlike the characteristic DNA fragmentation observed with apoptotic cells. In conclusion, prolonged exposure to heat shock treatment was detrimental to hESC viability. Hence, any future protocols developed for either the heat shock pre-conditioning of hESC prior to transplantation or for the temporary expression of specific genes with heat shock-responsive promoters should take these results into account; to achieve an optimal balance between the duration of heat shock exposure and the attainment of the desired effects.