Selection of follicles, preculture oocyte evaluation, and duration of culture for in vitro maturation of equine oocytes.
Abstract: Equine oocytes (n = 537) were collected from slaughterhouse ovaries (n = 118 mares) by scraping the internal follicular wall. Preculture record was made of the appearance of oocyte investments (no cumulus, corona radiata only, compact cumulus, expanded cumulus), appearance of cytoplasm (homogeneous, condensed heterogeneous/fragmented), and nuclear maturation stages (germinal vesicle, germinal-vesicle breakdown, metaphase I, metaphase II, degenerated). There was no difference between follicles > 30 mm and follicles < or = 30 mm in the preculture frequency distribution among the 5 nuclear stages; 96% were at either the germinal vesicle or germinal-vesicle breakdown stages. Oocytes from follicles 5 to 30 mm were cultured in modified TCM-199 for 18, 24, 36 and 48 h. Postculture nuclear maturation classifications were immature (germinal vesicle, germinal-vesicle breakdown, and metaphase I), mature (metaphase II or secondary oocyte), and degenerated. The frequency distribution of oocytes among the 3 postculture maturation classifications changed (P < 0.05) at 18 h (15% mature oocytes), changed (P < 0.05) further at 24 h (55% mature oocytes), with no additional change for 36 or 48 h. The only preculture cytoplasm group that affected the postculture results was the heterogeneous/fragmentation group which had a high proportion of postculture degenerated oocytes (67%); however, only 4% of oocytes were in this group. Luteal status of the mare had an effect (P < 0.05) on the frequencies of the maturation classifications, but not enough to be useful in selecting oocytes. Consistency of the follicle and the type of oocyte investment did not alter significantly the maturation frequencies. The frequency of degenerated oocytes after culture was high under the following conditions: 1) diameter of the follicle from which the oocyte was selected was 5 to 10 mm (44% degenerated oocytes), 2) the largest follicle per pair of ovaries was < or = 10 mm (63%), and 3) the mare was pregnant (66%). These results were probably related to the reported high frequency of atretic follicles in the 5- to 10-mm population. In summary, oocytes from individual follicles < or = 10 mm or from follicles in which the largest follicle per mare was < or = 10 mm were the poorest candidates for in vitro maturation.
Publication Date: 1995-05-01 PubMed ID: 16727700DOI: 10.1016/0093-691x(95)00086-nGoogle Scholar: Lookup
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- Journal Article
Summary
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This research primarily focused on investigating the optimal conditions and factors affecting the in vitro maturation of equine oocytes. The results showed that oocytes from individual follicles with a diameter of less than or equal to 10mm had a poor success rate in in vitro maturation.
Research Methodology
- The researchers collected 537 equine oocytes from the ovaries of 118 mares obtained from a slaughterhouse.
- The oocytes were carefully harvested by scraping the internal follicular wall.
- Before the culturing process, the appearances of oocyte investments and cytoplasm, as well as the stages of nuclear maturation, were examined and recorded.
- The oocytes were then placed in a modified TCM-199 culture medium to mature in vitro and checked again after different time periods – 18 hours, 24 hours, 36 hours, and 48 hours.
Key Findings
- No significant differences were noted in the pre-culture condition of oocytes from follicles larger than 30mm and those equal to or smaller than 30mm.
- The culture time had a significant influence on the maturity of the oocytes, with a significant increase in the number of mature oocytes noted in the 18 to 24-hour window, and no further changes were observed after 24 hours.
- Oocytes determined as having a heterogeneous or fragmented appearance pre-culture were most likely to be degenerated after culturing.
- The researchers found a high frequency of degenerated oocytes in the following conditions: the diameter of the follicle from which the oocyte was selected was between 5 to 10 mm, the largest follicle per pair of ovaries was less than or equal to 10 mm, and the mare was pregnant.
Conclusions
- Overall, the research highlights that oocytes from smaller follicles (with a diameter of less than or equal to 10mm) or when the largest follicle per mare was of this dimension, had a lower success rate of in vitro maturation.
- It suggests that the size of the follicle, the appearance of the oocyte pre-culture, and the mare’s pregnancy status can all influence the maturation of oocytes in vitro.
- These results have significant implications for the selection of oocytes for in vitro maturation in horses and could assist in optimizing the process to increase success rates.
Cite This Article
APA
Del Campo MR, Donoso X, Parrish JJ, Ginther OJ.
(1995).
Selection of follicles, preculture oocyte evaluation, and duration of culture for in vitro maturation of equine oocytes.
Theriogenology, 43(7), 1141-1153.
https://doi.org/10.1016/0093-691x(95)00086-n Publication
Researcher Affiliations
- Department of Meat and Animal Science, University of Wisconsin, Madison, WI 53706, USA.
Citations
This article has been cited 1 times.- Abdel-Khalek EA, El-Harairy MA, Shamiah ShM, Khalil WA. Effect of ovary preservation period on recovery rate and categories of dromedary camel oocytes. Saudi J Biol Sci 2010 Jul;17(3):231-5.
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