title: Kinetochore function can be altered by ultraviolet microbeam irradiation without loss of the associated birefringent spindle fibre.
abstract: We have irradiated kinetochores of chromosomes in spermatocytes of crane flies (Nephrotoma abbreviata (Loew)) and Nephrotoma suturalis (Loew), while observing the cells using polarization microscopy. Irradiation of a kinetochore of one sex chromosome with 0.106 ergs microns-2, the minimum dose needed to stop movement, had no effect on the birefringence of the irradiated kinetochore's spindle fibre. Irradiation of the kinetochore of an autosomal half-bivalent in anaphase, with the same dose, had no effect on the birefringence of the irradiated kinetochore's spindle fibre, but nonetheless the anaphase movements of all six autosomal half-bivalents were stopped, temporarily, for up to 20 min. Irradiations of the kinetochores of an autosomal half-bivalent with higher doses (0.301 ergs microns-2) caused loss of birefringence of the irradiated kinetochore's spindle fibre, and the movements of all six autosomal half-bivalents were stopped permanently. We argue that the ultraviolet microbeam differentially affects two functions of the kinetochore: (1) a 'signalling' function, and (2) microtubule attachment, with the signalling function being altered at doses lower than that of microtubule attachment.
authors.affiliation: Biology Department, York University, North York, Ontario, Canada.
authors.forename: J A
authors.initials: JA
authors.lastname: Swedak
authors.forename: A
authors.initials: A
authors.lastname: Forer
mesh_terms: D000818:Animals; D001718:Birefringence; D002503:Centromere / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure; D007313:Insecta / Q000648:ultrastructure; D007814:Larva / Q000648:ultrastructure; D008297:Male; D008870:Microtubules / Q000528:radiation effects* / Q000648:ultrastructure; D013090:Spermatocytes / Q000648:ultrastructure; D008941:Spindle Apparatus / Q000528:radiation effects / Q000648:ultrastructure; D014466:Ultraviolet Rays