Developmental competence of nuclear transfer cow oocytes after direct injection of fetal fibroblast nuclei.

We have examined the in vitro and in vivo development of cloned embryos produced by incorporation of fetal fibroblast into in vitro matured and enucleated cow oocytes by direct injection and by fusion. For injection, nuclei were either mechanically isolated using the microinjection needle or chemically isolated by treatment with NP-40 lysis buffer. Fetal fibroblasts were serum starved and treated with calcium ionophore before injection to induce chromatin condensation.

Reprogramming cattle somatic cells by isolated nuclear injection.

The development of a somatic cell nuclear transfer procedure for the production of blastocyst stage cattle embryos is described. Bovine fetal fibroblasts were used for fusion experiments with surgically enucleated oocytes (cytoplasts) following the establishment of optimal parameters for electrofusion from isofusion contours. Fusion rates were increased by decreasing size of the cytoplasts used but cleavage was decreased by decreasing size of the cytoplast used (quarter, half and whole cytoplasts).