Deep-freezing of monozygotic twin cattle blastocysts produced by use of microsurgery of non-surgically collected day 5-6 morula stages
1981
Lehn-Jensen, H. | Willadsen, S.M.
Monozygotic twin cattle blastocysts were produced using microsurgery on non-surgically recovered Day 5-6 morulae and cultured in ligated sheep oviducts in an agar cylinder. The blastocysts produced containing approx. half the ideal cell number were allocated to two experiments. In Experiment 1 the 'half' blastocysts while sitting in the agar cylinder were frozen in 1.4 M glycerol in PBS medium (0.3 deg C/min to -35 deg C) and stored in liquid nitrogen. They were thawed in water at 37 deg C and after culture for 6-8 h in PBS + 20 per cent sheep serum stained with acetoorcein. Nine out of fifteen (60 per cent) were judged to have survived the freeze/thaw/culture procedure. In Experiment 2 identical 'half' blastocycts were separated from each other and frozen separately in order to allow independent thawing later on. Four 'half' blastocysts transferred to two recipients resulted in two live calves whose identical twins are still kept in a frozen state. The briefly described techniques open up possibilities for the production of monozygotic twins of preselected parentage either of the same or of different age.
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