Inhibition of second meiotic division and a switching over to flagellar formation in secondary spermatocytes of newt by cycloheximide.

10.0 micro M cycloheximide (CH) was found to completely inhibit the second meiotic division of newt spermatocytes. Under continuous incubation with CH from the beginning of interphase II, secondary spermatocytes fail to initiate chromosomal condensation and thus remain in interphase II. After 12-15 h of incubation, a single motile flagellum, about 5 micrometers in length, was observed on each of the secondary spermatocytes. These flagella grew to a length of 60-80 micrometers, but thereafter ceased to grow, whereas ordinarily spermatids grew flagella up to 500 micrometers in length in the absence of CH [1]. When CH was applied within 2 h following telophase I, the percentage of meiosis II inhibition was almost 100% and when applied even later, it became less, which showed that the early half period during interphase II was sensitive to CH. Regardless of the length of incubation time with CH, flagella were found to grow within a period of 12-15 h following telophase I. Upon removal of CH, even after 60 h of incubation, the flagella of the secondary spermatocytes shortened and disappeared completely. These spermatocytes underwent the second meiotic divisions. Also, flagella grew on the resulting spermatids. The possibility that a particular centriole which participated in the first meiotic division changes into a basal body for flagellar formation under the influence of CH and vice versa upon removal of it, is discussed in the following.