Effects of Urethane on Mitosis and Meiosis in the Grasshopper, Poecilocera picta

抄録

The action of ethyl urethane on mitosis and meiosis in male grasshopper Poecilocera picta has been studied. A 0.2M solution in water injected into the body cavity induces very striking changes. Among the qualitative effects are supercontraction of mitotic chromosomes, stickiness and liquefaction, chromosome fragmentation and polyploidy. The cytoplasm too shows inability to divide and the spindle is also affected. Tripolar spindles are quite common. Perhaps the most interesting change is brought about in meiosis, where in a large percentage of first anaphase figures, the bivalents do not separate into their univalents but bodily move to the poles. This segregation of bivalents would seem to indicate a change or an upset of the centromere-spindle-centrosome mechanism. Dissolution of sperm heads is also seen.
An analysis of the division stages reveals that urethane has changed frequencies of stages in mitosis and meiosis. In the grasshopper, unlike other organisms, prophases are affected and a very large percentage of them are destroyed. Consequently metaphases are fewer. Similar observations are made in meiosis also where prophases undergo extensive damage. First anaphases, however, appear to increase in number, consequent on their blocking. Metaphases also increase for the same reason.