Cytogenetic technique for mouse metaphase II oocytes

Abstract

The acquisition of cytogenetic data from mammalian oocytes has required considerable time and expense, since only a relatively small number of oocytes could be processed from three to four animals daily. The availability of a procedure that would facilitate fixation and preparation of air-dried slides from 25–30 superovulated mice within a 3-h period would enhance development of germ cell cytogenetic data by reducing technician time and animal maintenance expense. We present such a procedure for mouse metaphase II oocytes. Mice were superovulated and the oocytes collected were fixed en masse prior to making air-dried slides. Chromosomes were subsequently C-banded to enhance objective cytogenetic analysis. The reliability of the procedure was determined by harvesting 44,814 oocytes from 1,875 mice over a 9-month period and calculating the proportion of cells cytogenetically analyzed to those not analyzed. Cytogenetic analysis of oocytes is an assay for chemicals (and other agents) capable of inducing numerical and structural chromosomal aberrations.