title: Role of the centrosome in mitosis: UV micro-irradiation study.
abstract: Ultraviolet micro-irradiation (UV-MI) of the PK (pig kidney embryo) cell centrosome (lambda max = 280 nm, spot diameter 1.6 mm, exposure time 5-15 s) at metaphase and anaphase resulted in functional damage of the centrosome. After UV-MI of the centrosome at early metaphase, chromosomes quickly (in 1-3 min) moved away from the irradiated pole and then encircled the non-irradiated pole. Within 10 min after UV-MI the spindle disassembled and chromosomes remained unseparated. The minimal dose inducing this effect in 90% of cells was accumulated in 5 s. After the same UV-MI at late metaphase, chromosomes shifted towards the non-irradiated pole; however, anaphase started and chromosome motion towards the non-irradiated pole continued normally. UV-MI of the centrosome at early anaphase for 5-15 s slowed down and then stopped chromosome motion towards the irradiated pole. This was a result of rapid (within 2-3 min) disorganization of the half-spindle. Chromosomes continued to move towards the opposite pole normally, while cytokinesis was significantly retarded. No visible lesion was revealed by electron microscopy after 5 s UV-MI, while 15 s irradiation resulted in the truncation of the microtubule bundles 1.5-2 microns from the centrosome. We concluded that UV-MI inactivates the centrosome and induces disaggregation of microtubule initiation sites. The critical point (checkpoint) in mitosis up to which this damage induces mitotic arrest is mid-metaphase.
mesh_terms: D000705:Anaphase; D000818:Animals; D018385:Centrosome / Q000528:radiation effects / Q000648:ultrastructure*; D002875:Chromosomes / Q000528:radiation effects / Q000648:ultrastructure; D004622:Embryo, Mammalian; D005455:Fluorescent Antibody Technique; D007668:Kidney / Q000473:pathology / Q000528:radiation effects; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence / Q000295:instrumentation / Q000379:methods; D018715:Microscopy, Video / Q000295:instrumentation / Q000379:methods; D008938:Mitosis / Q000502:physiology / Q000528:radiation effects; D013552:Swine; D014466:Ultraviolet Rays