Date of Award

1983

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Section I: The daily rhythm of plasma levels of adrenal corticol hormones (ACH) differed in phase and amplitude in Japanese quail of different ages and reproductive condition. Treatment with thiouracil accelerated and thyroxine delayed maturation of the ACH rhythm and development of the reproductive system. In contrast to the ACH rhythm, the rhythm of plasma thyroxine concentrations was similar at all ages tested. Section II: The roles of circadian rhythms in photoperiodism as they relate to adrenal cortical hormone (ACH) were examined in male Japanese quail, Coturnix coturnix japonica. Plasma ACH concentration was found to undergo circadian variations, which varied in phase with respect to the daily photoperiod depending on the length of photoperiod and condition of the reproductive system. The ACH peak occurred at light onset in sexually regressed quail maintained on LD 8:16 and at 12 and 16 hours after light onset in sexually developed quail kept on LD 8:16 or LD 16:8 respectively. In blind, sexually developed quail maintained on LD 16:8, daily injections of corticosterone for 15 days given early during the photoperiod (4 hours after light onset) induced a 40% reduction in the left testis volume (LTV) whereas injections 16 hours after light onset were ineffective. Thus, it appears that the daily rhythm of plasma concentrations of ACH and the photosensitivity rhythm are expressions of the same neural oscillation, and that injections of corticosterone at different times with respect to the photoperiod can entrain the oscillation so as to shift the photoinducible phase into or out of the light. Section III:The roles of the eyes and the daily rhythm of adrenal cortical hormone (ACH) and thyroxine in photoperiodism were examined in male Japanese quail. The reproductive system of quail developed in continuous darkness (DD) after pretreatment with LD 8:16 for 3 weeks. The reproductive system of Japanese quail raised and enucleated after 6 weeks exposure to LD 16:8 regressed initially in response to LD 8:16, but recrudesced during the next 8 months exposure to LD 8:16. Reproductively undeveloped quail raised and enucleated on LD 8:16, developed reproductively when exposed to LD 16:8 and did not regress on subsequent exposure to LD 8:16 unless treated with 0.2% 2-thiouracil in the food. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI.

Pages

116

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