Maturity and fertility of rhesus monkey oocytes collected at different intervals after an ovulatory stimulus (human chorionic gonadotropin) in in vitro fertilization cycles

Abstract

In rhesus monkeys undergoing ovarian stimulation for in vitro fertilization (IVF), a midcycle injection of human chorionic gonadotropin (hCG) substitutes for the LH surge and induces preovulatory oocyte maturation. The time interval between injection and oocyte collection, ideally, allows for the completion of oocyte maturation without ovulation, which would reduce the number of oocytes available for harvest. To evaluate the influence of this time interval on oocyte parameters following hCG administration, we conducted a series of gonadotropin treatment protocols in 51 animals in which the interval from hCG administration to follicular aspiration was systematically varied from 27 to 36 hr. Follicle number and size, evaluated prior to hCG administration by sonography, did not vary significantly or consistently with preovulatory maturation time. Oocytes were harvested by laparotomy or laparoscopy, and scored for maturity before insemination. The percentage of mature, metaphase II (MII) oocytes at recovery increased significantly with increasing preovulatory time and was inversely proportional to that of metaphase I (MI) oocytes. However, oocyte yield tended toward a progressive decrease with increasing preovulatory maturation times from a high of 27 oocytes at 27 hr to a low of 17 oocytes/animal at the 36 hr time interval. Fertilization levels declined significantly from a high of 50% at 27 hr to a low of 30% at 36 hr. Thus, although higher percentages of mature oocytes were recovered at the longer time intervals, optimal oocyte/embryo harvests were realized after the shorter time intervals (27 and 32 hr) and are most compatible with the goal of achieving high yields of fertile oocytes and embryos following gonadotropin stimulation in rhesus monkeys. © 1996 Wiley‐Liss, Inc.

Somatic cell nuclear transfer using transported in vitro-matured oocytes in cynomolgus monkey

“…Maturation rate (70.6%) was almost same as reported, 64.7% (Ng et al ., 2002) and 61–91% (VandeVoort et al ., 2003). Although there was a report that the optimal time from hCG injection to oocyte collection was a 27 h interval (Wolf et al ., 1996), a subsequent report by same group showed that lengthening this interval to 30–34 h during nuclear transfer studies produced a higher yield of mature MII oocytes (Wolf et al ., 1999). Regarding the number of oocytes collected in different times after hCG, the results in this study (15.4 oocytes/retrieval at 24 h after hCG) was no different to our previous report of 16.5 oocytes retrieved at 34–36 h after hCG (Ng et al ., 2004).…”

Rhesus macaque embryos derived from MI oocytes maturing after retrieval display high rates of chromosomal anomalies

“…When a number of follicles have reached an optimal size after hormonal ovarian stimulation, the resumption of meiosis in human and rhesus macaque oocytes is induced by the administration of hCG. In both humans and rhesus macaques, meiosis resumes within 18 h and attains metaphase II between 28 and 38 h after hCG exposure (Seibel et al, 1982;Wolf et al, 1996). Given that all follicles do not develop synchronously during hormonal ovarian stimulation, follicles of various sizes are present at the time of retrieval.…”

Maturation and fertilization of nonhuman primate oocytes are compromised by oral administration of a cyclooxygenase-2 inhibitor

“…A GnRH antagonist (Ganirelix (30 µg/kg body weight; Schering-Plough) or Antide (0.5 mg/kg body weight; Serono)) was also administered daily to prevent an endogenous ovulatory LH surge. Adequate follicular development was monitored by serum estradiol levels and ultrasonography (16). In some animals, follicular aspiration was performed 36 hours after administration of 1000 IU r-hCG (Serono).…”

“…Aspirates were subjected to centrifugation, and the pelleted cells were resuspended in TALP media containing HEPES (16). Cells were maintained at 37C while oocytes were mechanically removed.…”