Effect of chilling on the organization of tubulin and chromosomes in rhesus monkey oocytes

Objective: To determine the effects of chilling on the organization and distribution of tubulin and chromosomes in rhesus monkey oocytes. Design: Comparative laboratory study. Setting: Academic research laboratory. Animal(s): Eight adult female rhesus monkeys (Macaca mulatta) aged 6-16 years. Intervention(s): A total of 171 oocytes retrieved from eight rhesus monkeys were separated into nine groups. One group of control oocytes was held at 37°C during the experiment. Four groups of oocytes were rapidly cooled to 0°C and held for 1, 5, 10, or 30 minutes and then fixed and stained. Four other groups of oocytes were cooled to 0°C, held for 1, 5, 10, or 30 minutes, warmed and incubated at 37°C for 60 minutes, and then fixed and stained. Main Outcome Measure(s): Organization of cytoskeleton and chromosomes. Result(s): Exposure of rhesus oocytes to 0°C for only 1 minute resulted in complete depolymerization of tubulin. Incubation of chilled oocytes at 37°C for 60 minutes caused partial restoration of tubulin, although most oocytes exhibited abnormal alignment of chromosomes and disorganized meiotic spindles. Conclusion(s): We conclude that rhesus monkey oocytes are extremely sensitive to chilling injury. Their successful cryopreservation may require rapid cooling to outpace this injury.