Effects of chilling to 0 degrees C on the morphology of meiotic spindles in human metaphase II oocytes.
OBJECTIVE
To determine the effects of chilling to 0 degrees C on the meiotic spindle of human metaphase II oocytes, as observed by optical sectioning microscopy.


METHODS
Laboratory study.


METHODS
Academic research laboratory in a medical school.


METHODS
Seventy-two women undergoing infertility treatment donated a total of 108 oocytes.


METHODS
Metaphase II oocytes were stripped of their cumulus cells, cooled directly to 0 degrees C, and held for periods of 1 to 10 minutes. They were then fixed at 37 degrees C, stained for immunofluorescence, and examined microscopically.


METHODS
Morphology of the meiotic spindle in chilled and control oocytes.


RESULTS
Microscopic evaluations of 46 chilled oocytes revealed various time-dependent changes in microtubules compared to 9 control oocytes. After 1 minute at 0 degrees C, spindle damage was negligible, but in oocytes cooled for 2 or 3 minutes, there was obvious shortening of the spindle and loss of polarity. Cooling to 0 degrees C for 4 to 9 minutes resulted in increasingly more drastic changes; by 10 minutes the spindles had totally disappeared. Despite depolymerization of microtubular tubulin at 0 degrees C, the chromosomes did not become dispersed, but remained anchored even in the absence of spindles.


CONCLUSIONS
Even brief exposure of human oocytes to temperatures near 0 degrees C causes profound alterations of the meiotic spindle.
Zenzes
M T
MT
Division of Reproductive Sciences, Department of Obstetrics/Gynaecology, University of Toronto, Toronto, Ontario, Canada.
Bielecki
R
R
Casper
R F
RF
Leibo
S P
SP
D002877:Chromosomes, Human / Q000648:ultrastructure; D003080:Cold Temperature; D005260:Female; D006801:Humans; D007700:Kinetics; D008540:Meiosis; D008677:Metaphase; D008870:Microtubules / Q000648:ultrastructure; D009865:Oocytes / Q000166:cytology* / Q000502:physiology; D008941:Spindle Apparatus / Q000648:ultrastructure*; D013997:Time Factors; D020858:Tissue and Organ Harvesting / Q000379:methods