The distribution of membrane-associated calcium has been determined at various stages of mitosis in Haemanthus endosperm cells with the fluorescent chelate probe chlorotetracycline (CTC). CTC fluorescence in Haemanthus has two components: punctate, because of mitochondrial and plastid membrane-Ca++; and diffuse, primarily because of Ca++ associated with endoplasmic reticulum membranes. Punctate fluorescence assumes a polar distribution throughout mitosis. Cones of diffuse fluorescence in the chromosomse-to-pole regions of the metaphase spindle appear to coincide with the kinetochore fibers; during anaphase, the cones of fluorescence coalesce and this region of the spindle exhibits uniform diffuse fluorescence. Perturbation of the cellular Ca++ distribution by treatment with lanthanum, procaine, or EGTA results in a loss of diffuse fluorescence with no accompanying change in the intensity of punctate fluorescence. Detergent extraction of cellular membranes causes a total elimination of CTC fluorescence. CTC fluorescence of freshly teased crayfish claw muscle sarcoplasmic reticulum coincides with the A bands and is reduced by perfusion with lanthanum, procaine, and EGTA in a manner similar to that for diffuse fluorescence in the endosperm cells. These results are consistent with the hypothesis that a membrane system in the chromosome-to-pole region of the mitotic apparatus functions in the localized release of sequestered Ca++, thereby regulating the mechanochemical events of mitosis.
Detection of the membrane-calcium distribution during mitosis in Haemanthus endosperm with chlorotetracycline.
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S M Wolniak, P K Hepler, W T Jackson; Detection of the membrane-calcium distribution during mitosis in Haemanthus endosperm with chlorotetracycline.. J Cell Biol 1 October 1980; 87 (1): 23–32. doi: https://doi.org/10.1083/jcb.87.1.23
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