The equilibrium between assembled and disassembled microtubules was studied in human platelets exposed to aggregating agents. Soluble and insoluble tubulin were “frozen” by addition of a glycerol-dimethyl sulfoxide-containing medium. The two pools were estimated by measuring the colchicine binding activities of total and polymerized tubulin. Resting platelets were found to contain an average of 56.2 μg tubulin/1 × 109 cells of which 56.7% was in polymerized form. Platelet aggregation induced by thrombin, ADP, epinephrine, or collagen produced a transient decrease in the pool of polymerized tubulin which was evident within 15 s after addition of the aggregating agent. A return to base-line values occurred within 1-4 min depending upon the specific aggregating agent used. Neither secretory release nor aggregation of platelets were found to be prerequisites for the temporary disturbance of the equilibrium between soluble and polymerized tubulin. With thrombin as the aggregating agent a clear threshold concentration could be demonstrated above with a dose-dependent dissociation response of microtubules was evident. We conclude that microtubules exist in a dynamic equilibrium between polymerized and depolymerized forms in human platelets, which is transiently disturbed by their interaction with aggregating agents.
M. Steiner, Y. Ikeda
Usage data is cumulative from November 2023 through November 2024.
Usage | JCI | PMC |
---|---|---|
Text version | 125 | 0 |
84 | 23 | |
Scanned page | 212 | 1 |
Citation downloads | 42 | 0 |
Totals | 463 | 24 |
Total Views | 487 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.