Date of Award:

5-1-1974

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Biology

Committee Chair(s)

Hugh P. Stanley

Committee

Hugh P. Stanley

Committee

James Bowman

Committee

John Simmons

Committee

Raymond Sanders

Committee

Paul Carter

Abstract

An experimental study was conducted to determine the role of cytoplasmic microtubules in normal spermiogenesis of Drosophila melanogaster. An earlier study of mutant ms(3)10R of Drosophila presented evidence that suggested a direct role of cytoplasmic microtubules in sperm development. This finding provided some direction toward the clarification of currently controversial and conflicting hypotheses; are cytoplasmic microtubules necessary subcellular organelles during sperm maturation? These conflicting hypotheses are particularly opposed on the role of microtubules in the normal modeling of the sperm nucleus. One hypothesis states that cytoplasmic microtubules around the nucleus ("manchette" microtubules or nuclear-sheath microtubules) apply a modeling force that is responsible for the shape changes. The alternate hypothesis proposes that the nuclear chromatin alterations (i.e., condensation and peripheralization) can better regulate nuclear morphogenesis and therefore these chromatin changes are the primary causal factors involved in nuclear modeling. The data obtained from mutant ms(3)10R, as stated above, supported the first hypothesis (i.e., direct microtubule involvement). Therefore, phenocopy spermiogenesis of mutant ms(3)10R was induced using chemical agents ("spindle poisons") known to disrupt assembled microtubules and prevent the formation of new microtubules from existing subunit pools. The description and interpretation of phenocopy spenniogenesis induced by chemical treatment are the subject of this paper. The data support the hypothesis that, at least in Drosophila, microtubules are necessary for normal spermiogenesis. Most significant in view of the above stated controversy, is the finding that microtubules are directly involved in nuclear morphopoiesis. A distinct difference in nuclear-sheath microtubules was noted, however, when comparison of the effects of the two spindle poisons was made. These differences are discussed with respect to the differing chemical affinities of the two agents for microtubular protein.

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