ISSN:
0886-1544
Keywords:
unequal cell division
;
spindle positioning
;
spindle anchorage
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
We investigated the nature of the asymmetric positioning and attachment of Chaetopterus oocyte meiotic spindles to the animal pole cortex by micromanipulation. The manipulated spindle's behavior was analyzed in clarified oocyte fragments using video-enhanced polarized light microscopy. As the spindle was drawn towards the cell interior with a microneedle, the cell surface dimpled inwards adjacent to the outer spindle pole. As the spindle was pulled further inwards, the dimple suddenly receded indicating a rupture of a mechanical link between the cell cortex and outer spindle pole. The spindle paused briefly when released from the microneedle; then it spontaneously migrated back to the original attachment site and reassociated with the cell cortex. Positive birefringent astral fibers were seen running between the outer spindle pole and the cortex during the migration. The velocity of the spindle during its migration tended to increase as it came closer to the cortex. Velocities as high as 1.25 μm/sec. were measured. If removed too far from the attachment site cortex ( 〉 35 μm), the spindle remained stationary until pushed closer to the original attachment site. Spindles, inverted by micromanipulation, migrated and reattached to the cortical site by their former inner pole; thus either spindle pole can seek out and migrate to the original attachment site. However, spindle poles pushed against other cortical regions did not attach demonstrating that there is only one unique, localized attachment site for spindle attachment.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cm.970110202
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