Journal ArticleDOI
An Estimate of the Amount of Microtubule Protein in the Isolated Mitotic Apparatus
W. D. Cohen,L. I. Rebhun +1 more
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The microtubule content of the isolated mitotic apparatus of sea-urchin eggs has been investigated by electron microscopy and the total number of microtubules in an aster is calculated, close to those reported for the 4-5s protein, but are considerably lower than the amount of 22s protein.Abstract:
The microtubule content of the isolated mitotic apparatus of sea-urchin eggs ( Arbacia punctulata has been investigated by electron microscopy. Cross-sections were made through asters or spindles of flat-embedded mitotic apparatuses of known mitotic stage and specific orientation in the block. Cross-sections between chromosomes and poles of five metaphase half-spindles revealed approximately 2000-2300 sectioned microtubules. The number was somewhat higher in three anaphase half-spindles examined, approximately 2400-2600. A method was devised for calculating the total number of microtubules in an aster, based upon the number of microtubules appearing in cross-sections. Application of this method to selected mitotic apparatuses enabled calculation of the total number of microtubules in metaphase mitotic apparatuses of average dimensions. Using a 13-protofilament model of the microtubule and existing data on possible monomer sizes and molecular weights, the total amount of microtubule protein in the isolated mitotic apparatus was calculated. The values obtained are in the range of about 1-2 x 10 -8 mg microtubule protein per isolated mitotic apparatus. These values are close to those reported for the 4-5s protein of the isolated mitotic apparatus, but are considerably lower than the amount of 22s protein. The results are discussed with respect to cellular factors which determine microtubule number, and the possible sources and origin of mitotic microtubule protein.read more
Citations
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Journal ArticleDOI
Antimitotic activity of the potent tumor inhibitor maytansine.
TL;DR: Maytansine and vincristine inhibit in vitro polymerization of tubulin at about the same concentrations, but vINCristine is about 100 times less effective as an inhibitor of cleavage in marine eggs.
Book ChapterDOI
Polarized intracellular particle transport: saltatory movements and cytoplasmic streaming.
TL;DR: It is demonstrated that except for the possibility that channels of low viscosity exist in cells, it is not likely that the motive force giving rise to the movements originates from molecular kinetic processes.
Journal ArticleDOI
The role of membranes in the organization of the mitotic apparatus
TL;DR: It is proposed that the vesicle system functions to control the polymerization and depolymerization of microtubules by calcium ion regulation.
Journal ArticleDOI
Rapid rate of tubulin dissociation from microtubules in the mitotic spindle in vivo measured by blocking polymerization with colchicine.
TL;DR: Much slower rates of tubulin association are predicted from the characteristics of end-dependent microtubule assembly measured previously in vitro when the association rate constant is corrected for the lower rate of tub insulin diffusion in the embryo cytoplasm.
Journal ArticleDOI
Synthesis and storage of microtubule proteins by sea urchin embryos
TL;DR: Study employing colchicine binding, precipitation with vinblastine sulfate, and acrylamide gel electrophoresis confirm earlier proposals that Arbacia punctulata and Lytechinus pictus eggs and embryos contain a store of microtubule proteins, and provides the first protein encoded by stored or "masked" mRNA in sea urchin embryos to be identified.
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Cell motility by labile association of molecules. The nature of mitotic spindle fibers and their role in chromosome movement.
Shinya Inoué,Hidemi Sato +1 more
TL;DR: This article summarizes the current views on the dynamic structure of the mitotic spindle and its relation to mitotic chromosome movements based on measurements of birefringence of spindle fibers in living cells, normally developing or experimentally modified by various physical and chemical agents.
Journal ArticleDOI
The mitotic apparatus. physical-chemical factors controlling stability.
TL;DR: The results indicate that the action of long chain glycols in stabilizing the mitotic apparatus is non-specific and is similar to their effects on the solubility of proteins, opening a variety of new experimental approaches to this problem.
Journal ArticleDOI
The mitotic apparatus. Identification of the major soluble component of the glycol-isolated mitotic apparatus.
TL;DR: Mitotic apparatuses isolated from metaphase sea urchin eggs in 12% hexylene glycol at pH 6.4 can be dissolved rapidly in 0.6 M KCl, and more than one-half of the total protein of the MA is soluble under these conditions.
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