UV IRRADIATION OF CHROMOSOMAL DNA AND ITS EFFECT UPON MPF AND MEIOSISIN MAMMALIAN OOCYTES

Bovine oocytes were irradiated at germinal vesicle (GV) or metaphase I I (MII) stage, after Hoechst staining, with chromosomally focused UV-C (254 nm) or UV-A (>330 nm). UV-C irradiation at GV stage did not inhi bit germinal vesicle breakdown (GVBD) or chromosomal condensation; spi ndle formation was abolished and maturation promoting factor (MPF) lev els failed to increase. UV-A irradiation at GV stage caused meiotic ar rest at anaphase I; MPF levels were lower than control. UV-C irradiati on at MII stage led to subsequent abnormal parthenogenetic activation when MPF levels failed to decrease. A normal male but no female pronuc leus was formed at fertilization. UV-A irradiation at MII stage also c aused abnormal activation; MPF levels declined normally. A normal male and abnormal female pronucleus formed at fertilization. UV-A irradiat ion results have implications for oocyte evaluation during development using Hoechst staining. UV-C irradiation is a potential means for ooc yte enucleation in nuclear transfer. (C) 1995 Wiley-Liss, Inc.