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Biology of Reproduction, Vol 25, 1009-1025, Copyright © 1981 by Society for the Study of Reproduction
1 Department of Obstetrics and Gynaecology,
Monash University,
Queen Victoria Medical Centre,
172 Lonsdale Street,
Melbourne, Australia 3000 The structural changes associated with freezing and thawing were examined in bovine embryos
at three developmental stages: Day 5, Day 7, and Day 13 (Day 0 = day of estrus). Embryos collected
at Day 5 had 8-16 cells, and contained numerous vesicles and primitive junctional regions between
some adjacent blastomeres. After cooling to 4°C, the distribution of organelles within blastomeres
as well as the spacial arrangement of blastomeres was disrupted. Day 7 embryos were at the early blastocyst stage and contained an intact ring of trophoblast
cells enclosing a disc of embryonic cells. Adjacent trophoblast cells were attached by a region of
junctional complexes which were structurally unaffected by freezing. Damage to blastocysts after
freezing included loss of the integrity of the trophoblast plasma membrane, leading to collapse of
the blastocoele. When some collapsed blastocysts were cultured for 24 h after thawing, a smaller
intact ring of trophoblast cells had reformed around the embryonic cells and debris from cryoinjured cells was excluded from the blastocoele. Day 13 embryos contained three morphologically distinct cell types: a layer of trophectoderm,
a disc of embryonic cells, and a continuous layer of endoderm cells surrounding the blastocoelic
cavity. After freezing and thawing, the embryonic cells were structurally intact while the trophectoderm had substantial damage to all cell components. In conclusion, cryoinjury in bovine embryos may be selective for one cell type within an
embryo, and its extent and nature are dependent on developmental stage.
Note:
ACKNOWLEDGMENTS
The authors wish to thank Ms. Anne Pugh for her
valuable technical assistance in collection, freezing,
and thawing of embryos. We also acknowledge the
assistance of Mr. Steve McPhee and staff at the Dept.
of Agriculture, Werribee, and Mr. Ken Old of Devondindi Transplant Co. for provision of embryos.
This article has been cited by other articles:
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S. Kaidi, S. Bernard, P. Lambert, A. Massip, F. Dessy, and I. Donnay Effect of Conventional Controlled-Rate Freezing and Vitrification on Morphology and Metabolism of Bovine Blastocysts Produced In Vitro Biol Reprod, October 1, 2001; 65(4): 1127 - 1134. [Abstract] [Full Text] [PDF]
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H. Ushijima, H. Yamakawa, and H. Nagashima Cryopreservation of Bovine Pre-Morula-Stage In Vitro Matured/In Vitro Fertilized Embryos after Delipidation and before Use in Nucleus Transfer Biol Reprod, February 1, 1999; 60(2): 534 - 539. [Abstract] [Full Text] [PDF]
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