Abstract
Summary
Mitotically active rat blastocysts on Day 5 of castration-induced delayed pregnancy are initially more sensitive to the lethal effects of X-irradiation in vivo than are mitotically dormant blastocysts on Day 9. However, embryonic survival in animals irradiated on Day 5 increases significantly if implantation is postponed for 24 or 48 hr, indicating that recovery from potentially lethal X-ray damage can occur during early delayed implantation. Although the quiescent blastocyst on Day 9 of delayed pregnancy is initially more resistant to radiation insult than is the embryo on Day 5, the former exhibits no capacity to repair lethal X-ray damage.
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