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Effects of low temperatures on in vitro produced bovine zygotes
Author(s) -
Azambuja R.M.,
Kraemer D.C.,
Westhusin M.E.
Publication year - 1997
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(199708)47:4<435::aid-mrd10>3.0.co;2-v
Subject(s) - pronucleus , zygote , blastocyst , biology , embryo , cytoplasm , andrology , cytoplast , microinjection , embryogenesis , microbiology and biotechnology , medicine
The objective of this research was to investigate the effects of cooling on the development of bovine zygotes. One‐cell bovine embryos were maintained at 39°C (control), 20°C, 10°C, or 0°C for 5, 10, or 20 minutes, then cultured in vitro for 7 days and the proportion of embryos developing to the compact morula or blastocyst stage compared between different treatments. Duration of exposure time had no effect on development. Development rates to the compact morula or blastocyst stage were 3.9%, 11.4%, 17.4%, and 24.4% for zygotes maintained at 0°C, 10°C, 20°C, and 39°C, respectively, with differences in embryo yield between every treatment ( P < 0.05). In a second experiment, bovine pronuclei (karyoplasts) and cytoplasts were cooled at 0°C or maintained at 39°C for 5 minutes. Pronuclear transplantation was then utilized to create 4 types of reconstructed embryos, those with: 1) non‐cooled pronuclei and non‐cooled cytoplasm, 2) non‐cooled pronuclei and cooled cytoplasm, 3) cooled pronuclei and non‐cooled cytoplasm, and 4) cooled pronuclei and cooled cytoplasm. The proportion of embryos developing to the blastocyst stage was highest when non‐cooled pronuclei were transferred into non‐cooled cytoplasm (18.9%), and similar to that of non‐cooled, non‐manipulated control zygotes (13.2%, P > 0.05). No embryos developed to the blastocyst stage when pronuclei (cooled or non‐cooled) were transferred into cooled cytoplasm. However, zygotes with cooled pronuclei transferred into non‐cooled cytoplasm yielded 4.5% blastocysts ( P < 0.05). More embryos developed to the compact morula or blastocyst stage when non‐cooled vs. cooled cytoplasm was utilized, regardless of whether the pronuclei were cooled ( P < 0.05). These data demonstrate that pronuclei are more tolerant to low temperature exposure than is ovum cytoplasm. Mol. Reprod. Dev. 47:435–439, 1997. © 1997 Wiley‐Liss, Inc.