| Summary: | Rederivation allows laboratory animal populations to be purged from specified pathogens and thus turns these animals to the SPF (specified pathogens free) status. Results of the rederivation of two unique rat strains selected at the Institute of Cytology and Genetics and one mouse strain are presented. The two rat strains are: tame Norway rats and rats with Inherited Stress Induced Arterial Hypertension (ISIAH strain). The ICR mouse strain has been named as abbreviation of the Institute of Cancer Research wherefrom these mice were distributed to laboratories all over the world. The SPF status of the rats after rederivation was confirmed by the method of indicator animals (sentinel animals). The optimized model of rederivation offered here involves a combination of such embryotechnological methods as freezing/cryopreservation of embryos, their washing through the number of fresh volumes of sterile media, growing in vitro for 48 hours, and subsequent transfer into either one or both uterine horns of recipient females. Application of this model to rederivation of ICR mice yielded 39 pups born in an SPF vivarium. It should be noticed that the effectiveness of the procedure met international standards, and characteristic features of phenotype were retained in all the three strains after rederivation.
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