Stereoscopic analysis of microtubule pattern around the centrosome in interphase PK cells after treatment with taxol and nocodazole.
In the interphase PK cells, more than 85% of microtubules radiating from the centrosome were not longer than 1.5 microns. A half of microtubules had their proximal ends free. After nocodazole treatment (20 microM), the number of microtubules attached to the centrosome decreased by 20% after 10 min of treatment, remained the same after 20 min of treatment, and increased after 60 min of nocodazole treatment slightly above the control level. After 5 and 60 min of treatment, the number of attached microtubules with the length over 0.7 micron increased twice as compared to the control level. During the first 20 min of nocodazole treatment, the immunofluorescent staining of cells with antibodies to gamma-tubulin was the same as in the control cells. The number of free microtubules decreased fourfold during the first 5 min, then it decreased slowly (for 20 min) and remained at the same level after 60 min. After 10 min of taxol (12 microM) treatment, the number of attached and free microtubules increased more than two times, whereas the number of attached microtubules with the length over 0.7 micron increased more than tenfold. After 15 min of treatment, the number of attached microtubules was slightly higher, and the number of free microtubules was half of the control level. After 20-60 min of treatment, the number of microtubules of all types decreased. Thus, upon the nocodazole treatment, the microtubules attached to the centrosome were more resistant to depolymerization: however, these microtubules were the most reactive to taxol treatment. The data obtained suggest that (a) in PK cells, the centrosome-attached microtubules occupy not all of the existing templates; (b) during prolonged treatment with inhibitors, the centrosome performed the compensatory reaction-the inhibition of microtubule assembly results in the decrease in the number of active templates on the centrosome; the inhibition of microtubule depolymerization results in the inactivation of hitherto active reserve templates. The microtubules formed on the centrosome within the first minutes disengage from it and then leave the chromosomal region.
Alieva
I B
IB
Belosersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Russia.
Vorobjev
I A
IA
D000818:Animals; D002478:Cells, Cultured; D018385:Centrosome / Q000187:drug effects; D004847:Epithelial Cells; D007399:Interphase; D007668:Kidney / Q000166:cytology / Q000196:embryology; D008854:Microscopy, Electron / Q000379:methods; D008870:Microtubules / Q000187:drug effects*; D015739:Nocodazole / Q000494:pharmacology*; D017239:Paclitaxel / Q000494:pharmacology*; D013552:Swine; D014404:Tubulin / Q000032:analysis
D014404:Tubulin; D017239:Paclitaxel; D015739:Nocodazole