| Summary: | 碩士 === 國立中興大學 === 畜產學系 === 90 === The objective of this study was to determine the effect of a short-term heat shock (HS) on the chromatin/chromosome and microtubular structures (MT) of the in vitro matured (IVM) pig and cattle oocytes. Cumulus-oocyte-complexes (COCs) were collected from local abattoirs and were IVM in NCSU#23 or M199 media for 42 h. Matured oocytes were selected and randomly allocated to different treatment groups. The COCs were cultured at 39 °C for 0 or 4 h in the control groups (without HS) and at 41.5°C for 1, 2, or 4 h in the HS groups. The IVM-derived oocytes were HS for 4 h and were fixed in MTSB-XF at 1, 2, 4, 8 and 16 h following HS for immunocytochemical staining or confocal microscopy. The average maturation rates of the oocytes were 60% (n=1570) and 42% (n=300) in pig and cattle oocytes, respectively. Some oocytes revealed chromatin abnormality in 1 h (34/113) or 2 h (53/104) of HS treatment. For the oocytes subjected to 4 h of HS, dispersed chromatin clusters with severe condensation occurred in both pig and cattle oocytes. Disassembly or complete disappearance of spindle MT (85%, n=111) and formation of cytoplasmic MT (87%, n=111) were also clearly observed 4 h after HS. Eight to sixteen hours after HS, resumption of MII chromosome and spindle morphology was only observed in 21% (7/34) and 24-32% (n=34) of oocytes, respectively. Around 91-97% of the HS oocytes showed cytoplasmic MT. In conclusion, a short-term or acute HS condenses the chromatins and disassembles spindle MT in the IVM-derived pig and cattle oocytes. Only a small proportion of HS oocytes were capable of recovering from the altered chromosomal and cytoskeletal configurations after prolonged culture at 39°C. These alterations may contribute to the reduced fertility in domestic species during the hot season.
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