Cytoskeletal organization and zona sensitivity to digestion by chymotrypsin of frozen-thawed mouse oocytes.
Mouse oocyte-cumulus masses were added to 1.5 dimethyl sulphoxide (DMSO) + 20% fetal bovine serum (FBS) that had been precooled at +4 degrees C, were frozen by slow cooling to an intermediate temperature of -60 degrees C before being plunged into liquid nitrogen at -196 degrees C, subjected to a controlled thaw, expelled into 1.5 M DMSO + FBS at 4 degrees C, and then washed in medium + FBS at 37 degrees C. Of 7733 oocytes treated, 78.4% were viable (controls; no treatment: 94.2% of 2764 oocytes; cryoprotectant only: 92.2% of 2991 oocytes). The oocyte losses were not due to complete loss of all oocytes from some straws or mice, since analysis of individual straws containing oocytes from a single mouse revealed considerable inter-straw/mouse variation. Amongst surviving oocytes, no significant differences between frozen and control oocytes in spindle, chromosomal or microfilament organization were recorded. Two significant differences were observed: (i) fewer frozen-thawed oocytes had zonae resistant to chymotrypsin digestion, and (ii) spindle organization in control oocytes, but not frozen-thawed oocytes, was improved by 3 h incubation at 37 degrees C. More of the abnormal than the normal frozen-thawed and control oocytes were surrounded by zonae which were resistant to digestion by chymotrypsin.
Department of Anatomy, Cambridge, UK.
M A
MA
George
M H
MH
Johnson
D008841:Actin Cytoskeleton / Q000187:drug effects; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D002918:Chymotrypsin; D015925:Cryopreservation / Q000379:methods*; D003599:Cytoskeleton / Q000187:drug effects*; D005260:Female; D006358:Hot Temperature; D008677:Metaphase / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D008941:Spindle Apparatus / Q000187:drug effects; D015044:Zona Pellucida / Q000187:drug effects*
D002918:Chymotrypsin