To optimize fertilization, mating should occur within 3 h of ovulation and should be planned from 11 to 17 h after hCG for C.B-17/Icr-scid/scid mice and 9 to 15 h after hCG in B6SJLF 1 mice. Therefore the best time to harvest pronuclear embryos should be 14 to 16 h after hCG administration in C.B-17/Icr-scid/scid mice and 12 h after hCG in B6SJLF 1 mice. Superovulated C.B-17/Icr-scid/scid mice finish ovulation 2 to 4 h later than do B6SJLF 1 mice. These results suggest that the timing of ovulation may be more tightly controlled in superovulated B6SJLF 1 than in C.B-17/Icr-scid/scid mice. The number of ovulated oocytes also increased in C.B-17/Icr- scid/scid mice, although more gradually. The mean number of ovulated oocytes increased markedly between 10 to 12 h after hCG in B6SJLF 1 mice. There was no difference in the mean number of oocytes collected at 14 and 16 h. For both time points, differences were at the 1% level of significance. A statistically significant strain difference between mean oocytes collected was detected at 10 and 12 h. Ovum counts peaked at 12 h in B6SJLF 1 mice and at 16 h in C.B-17/Icr-scid/scid mice. Both mouse strains began ovulating at 8 h after hCG administration. The oviducts were flushed with M-2 medium, and the number of oocytes from each mouse was counted under a binocular Nikon dissecting microscope. Ovaries and oviducts from each mouse were removed and placed in M-2 collection medium in one well of a 9-well Pyrex culture plate. Nine mice of each strain were sacrificed (3 mice x 3 replicates) at 8, 10, 12, 14, and 16 h after hCG injection. Mice were kept on a 14-h light cycle, with lights off at 1900. Mice received intraperitoneal injections of 5 IU of equine chorionic gonadotropin (CG) followed by 5 IU of human (h) CG 48 h apart. In this chapter, we discuss the current state of development of these strains of mice, the remaining deficiencies, and how approaches used to increase the engraftment and function of human hematolymphoid cells in CB 17-scid mice and in previous models based on NOD-scid mice may enhance human hematolymphoid engraftment and function in NOD-scid IL2rgamma(null) mice.The time of induced ovulation after superovulation was evaluated in 3- to 8-week-old C.B-17/Icr-scid/scid and B6SJLF 1 mice. These new strains of immunodeficient IL2rgamma(null) mice are now being used for studies in human hematopoiesis, innate and adaptive immunity, autoimmunity, infectious diseases, cancer biology, and regenerative medicine. Third, immunodeficient mice bearing a targeted mutation in the IL-2 receptor common gamma chain (IL2rgamma(null)) were developed independently by four groups between 20, and a major increase in the engraftment and function of human hematolymphoid cells as compared with NOD-scid mice has been reported. NOD-scid mice have been the 'gold standard' for studies of human hematolymphoid engraftment in small animal models over the last 10 years. Second, NOD-scid mice were developed and their enhanced ability to engraft with human hematolymphoid tissues as compared with CB17-scid mice was reported in 1995. First, CB 17-Prkdc(scid) (abbreviated CB 17-scid) mice were discovered in 1983, and engraftment of these mice with human fetal tissues (SCID-Hu model) and peripheral blood mononuclear cells (Hu-PBL-SCID model) was reported in 1988. Progress in development of small animal models for the in vivo investigation of human hematopoiesis and immunity has seen three major breakthroughs over the last three decades. There is a growing need for effective animal models to carry out experimental studies on human hematopoietic and immune systems without putting individuals at risk.

Cb 17 scid