Spurck T, Forer A, Pickett-Heaps J
School of Botany, University of Melbourne, Parkville, Vic., Australia.
Cell Motil Cytoskeleton. 1997;36(2):136-48. doi: 10.1002/(SICI)1097-0169(1997)36:2<136::AID-CM4>3.0.CO;2-7.
Ultraviolet (UV) microbeam irradiations of crane-fly spermatocyte and newt epithelial spindles severed kinetochore fibres (KT-fibres), creating areas of reduced birefringence (ARBs): the remnant KT-fibre consists of two "stubs," a pole-stub attached to the pole and a KT-stub attached to the kinetochore. KT-stubs remained visible but pole-stubs soon became undetectable [Forer et al., 1996]. At metaphase, in both cell types the KT-stub often changed orientation immediately after irradiation and its tip steadily moved poleward. In spermatocytes, the chromosome attached to the KT-stub remained at the equator as the KT-stub elongated. In epithelial cells, the KT-stub sometimes elongated as the associated chromosome remained at the equator; other times the associated chromosome moved poleward together with the KT-stub, albeit only a short distance toward the pole. When an ARB was generated at anaphase, chromosome(s) with a KT-stub often continued to move poleward. In spermatocytes, this movement was accompanied by steady elongation of the KT-stub. In epithelial cells, chromosomes accelerated polewards after irradiation until the KT-stubs reached the pole, after which chromosome movement returned to normal speeds. In some epithelial cells fine birefringent fibres by chance were present along one edge of ARBs; these remnant fibres buckled and broke as the KT-stub and chromosome moved polewards. Similarly, KT-stubs that moved into pole stubs (or astral fibres) caused the pole stubs (or astral fibres) to bend sharply from the point of impact. Our results contradict models of chromosome movement that postulate that force is generated by the kinetochore disassembling the KT-fibre. Instead, these results suggest that poleward directed forces act on the KT-fibre and the KT-stub and suggest that continuity of microtubules between kinetochore and pole is not obligatory for achieving anaphase motion to the pole.
用紫外线（UV）微束照射大蚊精母细胞和蝾螈上皮纺锤体，切断动粒纤维（KT纤维），形成双折射降低区域（ARBs）：残余的KT纤维由两个“短柄”组成，一个附着于极的极短柄和一个附着于动粒的KT短柄。KT短柄仍可见，但极短柄很快就检测不到了[福勒等人，1996年]。在中期，在这两种细胞类型中，KT短柄在照射后常常立即改变方向，其顶端稳定地向极移动。在精母细胞中，随着KT短柄伸长，附着于KT短柄的染色体仍留在赤道面。在上皮细胞中，有时KT短柄伸长，而相关染色体仍留在赤道面；其他时候，相关染色体与KT短柄一起向极移动，尽管只向极移动了很短的距离。当在后期产生一个ARB时，带有KT短柄的染色体常常继续向极移动。在精母细胞中，这种移动伴随着KT短柄的稳定伸长。在上皮细胞中，染色体在照射后加速向极移动，直到KT短柄到达极，之后染色体移动恢复到正常速度。在一些上皮细胞中，偶然在ARBs的一条边缘存在细双折射纤维；随着KT短柄和染色体向极移动，这些残余纤维弯曲并断裂。同样，移入极短柄（或星体纤维）的KT短柄会使极短柄（或星体纤维）从撞击点急剧弯曲。我们的结果与假设动粒通过拆卸KT纤维产生力的染色体运动模型相矛盾。相反，这些结果表明，向极的力作用于KT纤维和KT短柄，并表明动粒与极之间微管的连续性对于实现向极的后期运动不是必需的。
