Induction of DNA synthesis by 20-hydroxyecdysone in the prothoracic gland cells of the silkworm Bombyx mori during the last larval instar.
DNA synthesis in the prothoracic gland cells of the silkworm Bombyx mori was studied immunocytochemically after in vivo labeling with 5-bromo-2'-deoxyuridine (BrdU), and its developmental changes during the last larval instar were examined. During the first 3 days of the last larval instar, no DNA-synthesizing cells were detected. On day 4, the number of DNA-synthesizing cells increased and peaked on day 7. When larvae were fed 20-hydroxyecdysone-supplemented mulberry leaves throughout the last larval instar, the number of DNA-synthesizing cells dramatically increased 2 days after 20-hydroxyecdysone treatment and reached a high level on day 5. The mechanism by which 20-hydroxyecdysone treatment induces DNA synthesis of prothoracic gland cells was further examined by using continuous in vitro BrdU labeling for a 2-day incubation. We conclude that 20-hydroxyecdysone may exert its growth-promoting action indirectly.
Gu
S H
SH
Department of Zoology, National Museum of Natural Science, 1 Kuan Chien Road, Taichung, Taiwan 40419, Republic of China. gu330@mail.nmns.edu.tw
Chow
Y S
YS
D000818:Animals; D012831:Bombyx / Q000254:growth & development* / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis*; D004441:Ecdysterone / Q000235:genetics* / Q000494:pharmacology; D004702:Endocrine Glands / Q000187:drug effects / Q000378:metabolism*; D006458:Hemolymph / Q000502:physiology; D007700:Kinetics; D007814:Larva / Q000378:metabolism*
D004441:Ecdysterone; D004247:DNA