Strain preservation of rats: vitrification of two-cell stage embryos for multiple inbred strains.

OBJECTIVE: We examined whether the vitrification method using P10 and PEPeS is suitable for the cryopreservation of two-cell stage embryos collected from multiple rat strains with the objective of strain preservation of inbred rat strains. RESULTS: The average numbers of two-cell stage embryos collected per female for F344/Jcl, ACI/N, BUF/N, and WKY/N strains were 7.0 to 12.0, and survival rates of the embryos after vitrification were 94.2 to 96.3 % The in vitro development rates of vitrified embryos transferred were 47.1 to 60.8 %. CONCLUSION: At least two offspring produced from the embryos collected from one female are required for strain preservation of inbred strain. Taken together, the results of the experiment indicated expected numbers of surviving fetuses for embryos collected from one female were 3.2 to 6.7, and all were usable for strain preservation. The results suggest that this vitrification method is suitable for strain preservation of multiple inbred rat strains.

The origin and role of confronting cisternae in selected fetal mouse and rat tissues.

Confronting cisternae (CC) are described for the first time in normal fetal rat and mouse liver and intestinal epithelial cells. In these cells, CC characteristically consist of 2 parallel cisternae which are devoid of ribosomes on their juxtaposed surfaces. The intracisternal spacing is consistently 20 nm. While CC occur in rapidly proliferating tissues such as fetal liver and intestinal epithelium, they do not occur in hepatocytes following partial hepatectomy. Although it has been postulated that the intact CC profiles represent a mechanism of assuring the presence of pre-formed nuclear envelope (NE) or rough endoplasmic reticulum (RER) in cells, it is more likely that the subunits which result from CC degradation serve as a pool of membrane precursors for new NE or RER.