FGF4 Independent Derivation of Trophoblast Stem Cells from the Common Vole

The derivation of stable multipotent trophoblast stem (TS) cell lines from preimplantation, and early postimplantation mouse embryos has been reported previously. FGF4, and its receptor FGFR2, have been identified as embryonic signaling factors responsible for the maintenance of the undifferentiated state of multipotent TS cells. Here we report the derivation of stable TS-like cell lines from the vole M. rossiaemeridionalis, in the absence of FGF4 and heparin. Vole TS-like cells are similar to murine TS cells with respect to their morphology, transcription factor gene expression and differentiation in vitro into derivatives of the trophectoderm lineage, and with respect to their ability to invade and erode host tissues, forming haemorrhagic tumours after subcutaneous injection into nude mice. Moreover, vole TS-like cells carry an inactive paternal X chromosome, indicating that they have undergone imprinted X inactivation, which is characteristic of the trophoblast lineage. Our results indicate that an alternative signaling pathway may be responsible for the establishment and stable proliferation of vole TS-like cells

Regimes of combustion of a premixed mixture of gases in a heated microchannel with the wall temperature smoothly increasing in the downstream direction

Specific features of the unsteady flame in a microchannel with a controlled wall temperature are theoretically studied within the framework of a one-dimensional diffusion-thermal model. The case with the channel wall temperature increasing in the gas flow direction and the channel size being smaller than the critical value determined on the basis of the ambient temperature is considered. Depending on the flow rate of the combustible mixture of gases through the channel, either flame stabilization or alternation of flame repetitive extinction/ignition is possible. The influence of the characteristic length of channel wall heating on the domains of existence of various combustion modes is studied for the first time. The theoretical study shows that there exists a critical value of the temperature gradient in the channel walls, below which the regime of flame repetitive extinction/ignition is no longer observed. At small values of the temperature gradient, a hysteresis phenomenon is found, which is associated with different changes in the flame position in the cases with increasing and decreasing flow rates of the gas

Difference between random and imprinted X inactivation in common voles.

During early development in female mammals, most genes on one of the two X-chromosomes undergo transcriptional silencing. In the extraembryonic lineages of some eutherian species, imprinted X-inactivation of the paternal X-chromosome occurs. In the cells of the embryo proper, the choice of the future inactive X-chromosome is random. We mapped several genes on the X-chromosomes of five common vole species and compared their expression and methylation patterns in somatic and extraembryonic tissues, where random and imprinted X-inactivation occurs, respectively. In extraembryonic tissues, more genes were expressed on the inactive X-chromosome than in somatic tissues. We also found that the methylation status of the X-linked genes was always in accordance with their expression pattern in somatic, but not in extraembryonic tissues. The data provide new evidence that imprinted X-inactivation is less complete and/or stable than the random form and DNA methylation contributes less to its maintenance