Date of Award:

5-1-1982

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

LeGrande C. Ellis

Committee

LeGrande C. Ellis

Committee

Raymond Sanders

Committee

Warren C. Foote

Committee

Gary Kelley

Committee

James Gessaman

Abstract

The purpose of this study was to examine the effects of light on the oscillations of the pineal enzyme, N-acetyltransferase through possible alterations in cyclic nucleotide metabolism. The levels of the cyclic nucleotides, cAMP and cGMP were measured in the chick pineal along with measurement of N-acetyltransferase activity in vivo and in vitro under cycling light (12 hours light: 12 hours dark) and under constant illumination. Activities of cAMP and cGMP phosphodiesterases and adenyl and guanyl cyclases were also measured under the same environmental conditions as those for the cyclic nucleotides, both in vivo and in vitro. Cyclic nucleotide levels showed daily changes in vivo and in vitro under cycling light and constant light, although levels under constant light were depressed. Cyclic nucleotide phosphodiesterases were found to show daily changes in activity both in vivo and in vitro, with peak activities occurring during the midday and midnight periods. Activities under constant light were found to be significantly higher. Cyclase activity was found to be greater during the noon times under cycling and constant light.

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