Izant J G
Chromosoma. 1983;88(1):1-10. doi: 10.1007/BF00329497.
Calcium-containing solutions were microinjected into dividing PtK1 cells to assess the effect of calcium ion concentration on the morphology and physiology of the mitotic spindle. Solutions containing 50 microM or more CaCl2 are immediately and irreversibly toxic to PtK1 cells. Those containing 5-10 microM CaCl2 cause reversible reduction in spindle birefringence followed by normal anaphase and cytokinesis. Microinjection of 5 microM or less CaCl2 into anaphase PtK1 cells has no detectable effect on the rate or extent of chromosome movement. Metaphase cells tend to enter anaphase 4-5 min after injection with 1-10 microM CaCl2, compared with an average of 16 min after injection with calcium-free buffer. Reducing the intracellular calcium concentration by injection of EGTA-CaCl2 buffers increases the lag between injection and anaphase to 20 min or more. Microinjection of calcium solutions does not promote precocious chromatid separation in nocodazole-arrested metaphase cells, indicating that the increase in calcium concentration does not induce centromere separation directly. An increase in the concentration of free calcium ions during metaphase appears to stimulate the onset of anaphase. Such an increase, regulated by the cell itself, may contribute to the initiation of chromosome separation in mammalian cells.
将含钙溶液微量注射到分裂的PtK1细胞中，以评估钙离子浓度对有丝分裂纺锤体形态和生理的影响。含有50微摩尔或更高浓度氯化钙的溶液对PtK1细胞具有即时且不可逆的毒性。含有5 - 10微摩尔氯化钙的溶液会导致纺锤体双折射可逆性降低，随后出现正常的后期和胞质分裂。向后期PtK1细胞微量注射5微摩尔或更低浓度的氯化钙，对染色体移动的速率或程度没有可检测到的影响。中期细胞在注射1 - 10微摩尔氯化钙后往往在4 - 5分钟进入后期，而注射无钙缓冲液后平均为16分钟。通过注射EGTA -氯化钙缓冲液降低细胞内钙浓度会使注射与后期之间的延迟增加到20分钟或更长时间。在诺考达唑阻滞的中期细胞中微量注射钙溶液不会促进早熟染色单体分离，这表明钙浓度的增加不会直接诱导着丝粒分离。中期游离钙离子浓度的增加似乎会刺激后期的开始。这种由细胞自身调节的增加可能有助于哺乳动物细胞中染色体分离的启动。
