Multipolar mitosis in procaine-treated polyspermic sea urchin eggs and in eggs fertilized with UV-irradiated spermatozoa with a computer model to simulate the positioning of centrosomes.
Procaine-treated eggs can be penetrated by more than one spermatozoon. Supernumerary male pronuclei can fuse with the female one giving raise to multipolar spindles or remain isolated within the egg's cytoplasm forming their own spindle. In all types of multiple mitotic figures (asters and spindles) the distribution of asters is equidistant either uniplanar or at maximum distance like at the apices of a polyhedron. Astral rays are not different from spindle fibers: they can attach to and attract chromosomes of "foreign" mitotic figures. When several mitotic figures are present in one egg, the partner asters are always of the same size, and microtubules of one aster never interdigitate with those of others. The hypothesis that positioning of centrosomes is brought about by spreading of a centrosome organizer in the form of an expanding calotte on the surface of the nucleus (Mazia, D., Int. Rev. Cytol. 100, 49-92 (1987)) is supported by a computer model.
Czihak
G
G
Department of Genetics and Developmental Biology, University of Salzburg, Austria.
Kojima
M
M
Linhart
J
J
Vogel
H
H
D000818:Animals; D002467:Cell Nucleus / Q000648:ultrastructure; D003198:Computer Simulation; D005306:Fertilization; D008297:Male; D008938:Mitosis; D010063:Ovum / Q000166:cytology / Q000187:drug effects*; D011343:Procaine / Q000494:pharmacology*; D012617:Sea Urchins; D013094:Spermatozoa / Q000166:cytology* / Q000528:radiation effects
D011343:Procaine