Date of Award

1991

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

Kenneth L. White

Abstract

The first objective of this investigation was to determine if either X-irradiation or thermal stress exerted differential effects on the two major cell types of the blastocyst stage murine embryo. Results of this study indicate that X-irradiation dosages of 0 rads, 500 rads, 600 rads, 700 rads, 800 rads, 900 rads or 1000 rads had no effect on the ability of treated embryos to either hatch or develop into trophoblastic outgrowths (P $<$.05). In contrast, X-irradiation treatment over the levels tested did have a detrimental effect on the ability of embryos to develop into trophblastic outgrowths possessing an ICM region (P $>$.05). X-irradiation over the levels tested had no effect on the mean two-dimensional outgrowth surface areas ($\mu$m$\sp2$) (P $>$.05). However, X-irradiation was found to have a detrimental effect on both the mean ICM surface area ($\mu$m$\sp2$) (P $<$.01) and the mean ICM area/outgrowth area ratio (P $<$.01). It was also found that subjecting blastocysts to a thermal insult of 43$\sp\circ$C for an interval of 0 min, 30 min, 45 min, 60 min or 75 min had detrimental effects on hatching rates (P $<$.001). However, thermal stress had no effect on either percentage of embryos forming outgrowths or percent of outgrowths with ICMs (P $>$.05). Additionally, it was found thermal stress over the levels tested had no adverse influence on the mean two-dimensional outgrowth surface areas ($\mu$m$\sp2$) (P $>$.05). In contrast, thermal stress was found to have detrimental effects on both the mean ICM surface area ($\mu$m$\sp2$) and the mean ICM area/outgrowth area ratio (P $<$.05). The second objective of this investigation was to determine the feasibility of producing nonchimeric offspring as a result of microsurgical injection of murine ICMs into the blastocoele of mouse embryos which had been previously subjected to either thermal stress or X-irradiation. Pretreatment of ICM recipient blastocyts with an X-irradiation dose resulted in the birth of only chimeric offspring. However, of these offspring, all exhibited 80-100% overt chimerism towards the donor ICM strain. Pretreatment of recipient embryos with a thermal insult resulted in no births.

Pages

123

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