Vegetalization of Sea Urchin Larvae Induced with Cycloheximide |
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Authors: | TAKAHITO YOSHIMI IKUO YASUMASU |
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Institution: | Department of Biology, School of Education, Waseda University, Nishiwaseda, Shinjuku-ku, Tokyo 160, Japan |
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Abstract: | The embryos, kept at 20°C for 3 hr–6 hr from the time of fertilization (at the morula stage), were cultured in sea water containing cycloheximide (10–16 mM) for successive 3 hr and then transferred to normal sea water. The embryos, thus treated, became vegetalized larvae. With the same treatment performed at a developmental stage prior to 3 hr of fertilization, most of embryos developed to small blastulae filled with mesenchyme-like cells. The treatment at a stage after 6 hr of fertilization yielded normal plutei. From the embryos exposed to both 14C-leucine and 3H-thymidine during the treatment, labelled chromatin was isolated. Only in the presumptive vegetalized embryos obtained by the cycloheximide treatment of morulae, ratio of 14C-radioactivity found in proteins of chromatin to 3H-radioactivity in DNA was markedly lower than that observed in chromatin from control embryos. The rate of 3H-radioactivity-decrease by DNase I treatment was higher in chromatin isolated from the presumptive regetalized embryos than that observed in chromatin isolated from control ones. Probable failure of chromatin structure formation, due to cycloheximide-inhibition of chromatin protein synthesis, seems to disturb the determination in the embryos at the morula stage, resulting in an induction of vegetalized embryos. |
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