Doctoral Dissertations

Date of Award

8-1982

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Zoology

Major Professor

Joseph C. Daniel, Jr.

Abstract

Holes punched in the ears of rabbits are repaired by regeneration of new tissues from blastemas and the unwounded tissues found at the periphery of the wounds. The biochemical, physiological, morphological and kinetic parameters of this regeneration have been investigated both to characterize the system and to show how the process is similar to embryonic development. The proportion of animals which successfully regenerated was greater in males than females, and in ovariectomized does given testosterone than in those given only corn oil carrier; yet the speed of closure did not differ in these groups. Holes in juveniles closed faster than holes in older animals. Second holes punched on the same site where earlier tissues had been regenerated closed earlier, had a thicker cartilage layer, and a higher success rate than primary punches indicating a 'primary' effect from the primary punch. Holes punched closer to the head were more successful than those punched distally and holes punched on the edge of the pinna did not regenerate. Regenerated hair reestablished the original color pattern, and the hair regenerating after punching through transplants of back skin to the ear had characteristics of back skin hair in color, length, and orientation. Other mammals were found capable of partial ear tissue regeneration when punches were made on the proximal pinna. Similar morphological characteristics were shared among the successful animals. Biochemical changes in collagen were monitored throughout the regeneration process and these changes were similar to those seen in the embryonic development of cartilage containing tissues. Type I collagen was found in skin and connective tissue and Type II in cartilage at day 0. Type II was not iv V found during early regeneration but Type I and two unusual types, Type I-Trimer, and Type Ill were found. Type II was found again once chondrogenesis began and the two unusual types were no longer found. Amounts of soluble collagen varied during the process and collagenase was inversely correlated with the changes in collagen. Similarities between regenerating tissues and embryonic supporting tissues were observed: Gallium-67 was found to localize in regenerating ear tissues, and a protein was found which cross-reacted with antibodies to both the high molecular weight and uteroglobin fractions of rabbit uterine flushings taken on day 5 post coitum. It is suggested that regenerating tissues exhibit a greater similarity to embryonic tissues than to tissues comprising a wound.

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