Effect of low temperatures on the development of bovine oocytes and zygotes /
The objective of this research was to investigate fertilization, cleavage and development rate (percentage) of bovine oocytes and zygotes after exposure to three low temperatures for 3 different periods of time. Oocytes were cooled in an alcohol bath of a freezer unit at 20'C, IO'C or O�...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1994.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=741965141&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The objective of this research was to investigate fertilization, cleavage and development rate (percentage) of bovine oocytes and zygotes after exposure to three low temperatures for 3 different periods of time. Oocytes were cooled in an alcohol bath of a freezer unit at 20'C, IO'C or O'C for 5, 10 or 20 minutes. There were no differences (p>0.05) between times of exposure to the low temperatures when fertilization, penetration, or cleavage rates were compared. Fertilization rate was higher (p<0.05) for the oocytes maintained at 39'C (73.2%) when compared to oocytes cooled to 20'C (58.6%), IO'C (47.3%), or O'C (36.9%). Cleavage rates were 7.0%, 15.7%, 45.3%, and 58.3%, for O'C, IO'C, 20'C, and 390C, respectively (p<0.05). The lowest development rate to the monda/blastocyst stage was obtained with oocytes cooled to IO'C (0.8%) followed by OOC (1.8%), 20'C (9.5%), and 39'C (23.2%), respectively (p<0.05). In experiment 2, zona-free oocytes cooled at O'C or IO'C had higher penetration rates than zona-intact oocytes cooled at the same temperatures. However, there was no difference in penetration rate, when zona-free or zona-intact oocytes were cooled at 20'C or maintained at 39'C. Cleavage rates were higher for zygotes (p<0.05) cooled at 39'C (65.6%) and 20'C (62.4%) than for zygotes cooled at I O'C (3 7. 1) or O'C (I 5.4%). Development rates of zygotes treated at 39'C (24.4%) were higher than for zygotes treated to any other temperature. Time of exposure to the low temperatures had no effect on cleavage or development to the morula/blastocyst stage. In experiment 4, the percentage of embryos that cleaved was higher (p<0.05) for fresh pronuclei transferred to fresh cytoplasm (90.0%) than cooled pronuclei transferred to cooled cytoplasm (48.5%) and cooled pronuclei transferred to fresh cytoplasm (68.2%). The percentage of embryos developing to the morula/blastocyst stage was similar (p>0.05) for fresh pronuclei transferred to fresh cytoplasm (22.5%) and cooled pronuclei transferred to fresh cytoplasm (I 1.4%). Both were higher (P<0.05) than cooled pronuclei transferred to cooled cytoplasm (0.0%), and fresh pronuclei transferred to cooled cytoplasm (0.0%). These results show that pronuclei are more tolerant to cold temperatures than is cytoplasm. |
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| Item Description: | Vita. "Major subject: Physiology of Reproduction". Issued also on microfiche from University Microfilms Inc. |
| Physical Description: | xi, 100 leaves ; 28 cm. |
| Bibliography: | Includes bibliographical references. |