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Effects of silver ions (Ag+) on contractile ring function and microtubule dynamics during first cleavage in Ilyanassa obsoletaThe terminal phase of cell division involves tight constriction of the cleavage furrow contractile ring, stabilization/elongation of the intercellular bridge, and final separation of the daughter cells. At first cleavage, the fertilized eggs of the mollusk, Ilyanassa obsoleta, form two contractile rings at right angles to each other in the same cytoplasm that constrict to tight necks and partition the egg into a trefoil shape. The cleavage furrow contractile ring (CF) normally constricts around many midbody microtubules (MTs) and results in cleavage; the polar lobe constriction contractile ring (PLC) normally constricts around very few MTs and subsequently relaxes without cleavage. In the presence of Ag+ ions, the PLC 1) begins MT-dependent rapid constriction sooner than controls, 2) encircles more MTs than control egg PLCs, 3) elongates much more than control PLCs, and 4) remains tightly constricted and effectively cleaves the polar lobe from the egg. If Ag(+)-incubated eggs are returned to normal seawater at trefoil, tubulin fluorescence disappears from the PLC neck and the neck relaxes. If nocodazole, a drug that depolymerizes MTs, is added to Ag(+)-incubated eggs during early PLC constriction, the PLC is not stabilized and eventually relaxes. However, if nocodazole is added to Ag(+)-incubated eggs at trefoil, tubulin fluorescence disappears from the PLC neck but the neck remains constricted. These results suggest that Ag+ accelerates and gradually stabilizes the PLC constriction by a mechanism that is initially MT-dependent, but that progressively becomes MT-independent.
Document ID
20050000388
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Conrad, A. H.
(Mount Desert Island Biological Laboratory Salsbury Cove, Maine)
Stephens, A. P.
Paulsen, A. Q.
Schwarting, S. S.
Conrad, G. W.
Spooner, B. S.
Date Acquired
August 22, 2013
Publication Date
January 1, 1994
Publication Information
Publication: Cell motility and the cytoskeleton
Volume: 27
Issue: 2
ISSN: 0886-1544
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Developmental Biology

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