The induction of de novo centrioles in sea urchin eggs: a possible common mechanism for centriolar activation among parthenogenetic procedures.
Eggs from two species of sea urchins were subjected to a variety of novel two-step parthenogenetic activation procedures. These treatments readily resulted in the formation of cytasters and centrioles. Centrioles are restricted to the cytasters, as well as to the broad perinuclear zone, and it appears that all cytasters contain one or more centrioles. The mode of centriolar origin and maturation, as revealed by these new procedures, is identical to that of centrioles induced by other procedures. Both centriolar and cytastral development are retarded by the parthenogenetic treatments; also, mitosis is generally delayed. These results, along with those of others, reveal that parthenogenetic agents have opposing effects on eggs. The agents are stimulatory in that they activate latent centrioles and the cell cycle, in general. They are inhibitory in that they suppress a variety of physiochemical events. Of these events, only one appears to be common to all parthenogenetic agents: the inhibition of protein synthesis. Egg centrioles may be kept in a latent state by repressor proteins. If these proteins normally cycle rapidly, then an inhibition of their continuous synthesis will disrupt their normal replacement rate. As such, a delay in replacement will allow functioning repressor proteins, associated with latent centrioles, to become nonfunctional, which in turn allows latent centrioles to become derepressed. This deblocking reaction would then activate the appearance of de novo centrioles in eggs.
Kallenbach
R J
RJ
Department of Zoology, University of California, Berkeley, CA 94720/USA.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D002502:Centrioles / Q000378:metabolism*; D017666:Deuterium Oxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008854:Microscopy, Electron; D010063:Ovum / Q000187:drug effects / Q000502:physiology; D010312:Parthenogenesis / Q000187:drug effects; D012617:Sea Urchins / Q000196:embryology*; D013696:Temperature; D013997:Time Factors; D014508:Urea / Q000494:pharmacology
D014508:Urea; D017666:Deuterium Oxide; D002118:Calcium