[Expression of human interferon beta in the mammary gland of transgenic rabbits].

A biotechnological system for the production of human beta interferon was developed on the basis of a hybrid gene constructed from the coding sequence of the beta interferon gene inserted into the first exon of the sheep beta lactoglobulin gene. It is intended for the expression of human beta interferon in mammary glands of transgenic animals. Two lines of transgenic rabbits were obtained using the hybrid gene.

[Production of cloned bovine embryos by somatic cell transfer into enucleated zona-free oocytes].

Cloned bovine embryos were produced at the blastocyst stage. Prior to enucleation, oocytes were freed from the zona pellucida. Fibroblasts isolated from the bovine fetus were used as nuclear donors.

Effect of donor cell age on the efficiency of nuclear transfer in rabbits.

The ability of rabbit fibroblasts of different ages to be reprogrammed following nuclear transfer (NT) to aged recipient oocytes was evaluated. The rate of NT blastocysts reconstructed with presumptive G1 stage morula cells or fetal fibroblasts was significantly higher (41.5% and 51.

[A study of factors affecting the efficiency of electrofusion of enucleated eggs and cell-donors of nuclei].

We studied the capacity of rabbit oocytes for electrofusion with morula blastomeres and fetal fibroblasts. The morula blastomeres fused with aging ooplasts more readily than the fetal fibroblasts: 92.9 versus 63.

[Effect of age of cell donors of nuclei on effectivness of developing cloned rabbit embryos].

We studied the capacity of nuclei of rabbit fibroblasts taken from various developmental stages for reprogramming in the cytoplasm of mature aging enucleated oocytes and development of the cloned embryos to the preimplantation stages. A negative correlation was found between the age of an animal--donor of fibroblasts and efficiency of the development of cloned embryos (rmorula-blastocyst = -0.826, rblastocyst = -0.