ISSN:
0886-1544
Keywords:
cell movement
;
microtubule-organizing center
;
nucleus
;
rapid-freeze substitution
;
immuno-fluorescence
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
The cytoplasmic microtubule system seems to influence the position and structure of nucleoli in Dictyostelium discoideum amoebae in several growing and migrating states. For example, nucleoli were usually excluded from the nuclear periphery near the microtubule-organizing center (MTOC) in all cases; and in migrating adherent cells, more than half the nucleoli were located opposite the MTOC. This localization was disrupted by nocodazole treatment, after which the nucleoli were largely dispersed except near the MTOC. More extensive effects of microtubules on nucleolar structure were seen in aggregating cells. In contrast to the normal oval structure in growing cells, nucleoli took on a different morphology: they protruded from the leading edge of nuclei and elongated to form nozzle-like structures. Analysis by rapid-freeze substitution and indirect immunofluorescence showed each nozzle surrounded by more than 10 microtubules; and in the presence of nocodazole, the microtubules shortened as expected and the nozzles disappeared. Between microtubules and the outer nuclear envelope, various-sized cross-bridges were seen. The implication that microtubules were associated with the nucleoli in aggregating cells was verified in vitro: nuclei isolated from growing cells contained the MTOC but few if any detectable microtubules; but nuclei from aggregating cells were surrounded by them. These data are consistent with the notion the microtubule system may help regulate the position and conformation of nucleoli during early development of Dictyostelium.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cm.970180406
