ISSN:
0886-1544
Keywords:
Dictyostelium discoideum
;
video and fluorescence microscopy
;
random ameboid movement
;
stationary mitotic amebae
;
cytoskeleton
;
microtubule center
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
We investigated, by video-light microscopy and fluorescence microscopy with probes specific for microtribules (MTs) and F-actin, the relationship between cytoskeletal elements, cell shape and behavior of vegetative, undifferentiated amebae of Dictyostelium discoideum, strain NC-4. In an unconstrained situation, as on the underside of a coverglass in a thin layer of liquid medium, interphase cells moved around randomly in a polypodial or monopodial fashion. Locomotion was characterized by the formation of pseudodigits, rounded or pointed pseudopodia, and retraction fibers. F-actin occurred in all these structures, as well as in a thin cortical layer. Microtubules extended into some of the cellular extensions rich in F-actin. Pseudopodial activity, but not locomotion, also took place at the interface between medium and air, demonstrating that ameboid movement requires contact with a solid substrate. Stationary mitotic amebae on glass were studded with continuously changing, peripheral spike-shaped filopodia that also contained F-actin. During telophase and cytokinesis the spikes were gradually replaced by pseudopodia in transition to the fully motile phase.In live cells, the nucleus-associated body (NAB), which is at the center of the complex of cytoplasmic MTs [CMTC; term from Brinkley, Fuller, and Highfield, 1975] was in a rather fixed position; it did not orient in a concerted fashion to follow changes in the direction of cell movement. In amebae fixed and processed for fluorescence microscopy after a period of recorded movement, the NAB was not preferentially positioned with respect to the nucleus and the direction of movement. It is unlikely that the NAB exerts a directional control during randon ameboid movement. The complex of cytoskeletal MTs must be very dynamic or flexible to adjust to the rapid changes of cell shape.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cm.970060216
