Cyclic AMP reversal of hypoxanthine-arrested preimplantation mouse embryos is EDTA-dependent

Hypoxanthine phosphoribosyltransferase (HPRT)-deficiency is associated with impaired fertility in the female rat

The purine hypoxanthine plays important role in regulating oocyte maturation and early embryonic development. The enzyme hypoxanthine phosphoribosyltransferase (HPRT) recycles hypoxanthine to generate substrates for nucleotide synthesis and key metabolites, and here we show that HPRT deficiency in the rat disrupts early embryonic development and causes infertility in females.

Serial Culture Is Critical for In Vitro Development of Parthenogenetic Embryos in the Golden Syrian Hamster

Unlike oocytes of many other mammalian species, parthenogenetically activated hamster oocytes have not been reported to develop beyond the two-cell stage. This study investigated the in vitro development into blastocysts of parthenogenetic embryos of Golden Syrian hamsters. We observed that hamster oocytes could easily be artificially activated (AA) by treatment with ionomycin plus 6-dimethylaminopurine + cycloheximide + cytochalasin B as assessed by embryo cleavage in HECM-9 (63.15%) or HECM-10 (63.82%). None of the cleaved embryos developed beyond the two-cell stage when cultured in either of the two media. However, some of the embryos overcame the two-cell block and developed to the blastocyst stage (26.45%) when they were first cultured in HECM-10 for 24 hours and then in HECM-9 (serial culture media HECM-10-9) for 72 hours. Blastocyst development was further significantly (66.2%) improved when embryos were cultured in HECM-10 supplemented with ethylenediaminetetraacetic acid for 24 hours, then in HECM-9 supplemented with glucose for 72 hours (serial culture media HECM-11a-b). Hamster oocytes activated with ionomycin, ethanol, or a combination of the two treatments would develop to the blastocyst stage in serial culture media HECM-11a-b, whereas none of the spontaneously activated oocytes cleaved (0% vs. 86.93%, p < 0.05). DNA and microtubule configurations of spontaneously activated and AA oocytes were assessed by immunocytochemical staining and fluorescence microscopy. The results indicate that serial culture and the method of activation are critical for overcoming the in vitro developmental block of hamster parthenogenetic embryos. This study is the first to report blastocyst development from parthenogenetically activated hamster oocytes.

Reduced levels of dopamine and altered metabolism in brains of HPRT knock-out rats: a new rodent model of Lesch-Nyhan Disease

Lesch-Nyhan disease (LND) is a severe neurological disorder caused by loss-of-function mutations in the gene encoding hypoxanthine phosphoribosyltransferase (HPRT), an enzyme required for efficient recycling of purine nucleotides. Although this biochemical defect reconfigures purine metabolism and leads to elevated levels of the breakdown product urea, it remains unclear exactly how loss of HPRT activity disrupts brain function. As the rat is the preferred rodent experimental model for studying neurobiology and diseases of the brain, we used genetically-modified embryonic stem cells to generate an HPRT knock-out rat. Male HPRT-deficient rats were viable, fertile and displayed normal caged behaviour. However, metabolomic analysis revealed changes in brain biochemistry consistent with disruption of purine recycling and nucleotide metabolism. Broader changes in brain biochemistry were also indicated by increased levels of the core metabolite citrate and reduced levels of lipids and fatty acids. Targeted MS/MS analysis identified reduced levels of dopamine in the brains of HPRT-deficient animals, consistent with deficits noted previously in human LND patients and HPRT knock-out mice. The HPRT-deficient rat therefore provides a new experimental platform for future investigation of how HPRT activity and disruption of purine metabolism affects neural function and behaviour.

Effects of serum-free culture media on in vitro development of domestic cat embryos following in vitro maturation and fertilization

This study was conducted to determine the adequate medium for a serum-free culture system of domestic cat embryos produced by in vitro maturation (IVM) and fertilization (IVF). Cumulusoocyte complexes recovered from cat ovaries were matured in vitro for 24 h, and then inseminated in vitro for 12 h. After insemination, the oocytes were cultured in five media [Ham's F10, Waymouth 752/1 (Waymouth), TCM199, modified Earle's balanced salt solution (MK-1) and CR1aa], each of which contained 0.4% bovine serum albumin. There were no significant differences among the rates of fertilization of oocytes cultured in five media following IVF. The rate of oocytes/embryos developed to at least the morula stage was significantly lower (p < 0.05) in Waymouth than in MK-1, TCM199 and CR1aa. Moreover, none of the embryos cultured in Ham's F10 and Waymouth developed to the blastocyst stage. There were no differences among the rates of development to the blastocyst stage of oocytes/embryos cultured in MK-1, TCM199 and CR1aa. These results indicate that the type of serum-free medium has a major impact on in vitro development of domestic cat embryos derived from IVM/IVF, and MK-1, TCM199 and CR1aa media are suitable for in vitro culture of cat embryos in a serum-free culture system.