title: Induction of DNA synthesis by 20-hydroxyecdysone in the prothoracic gland cells of the silkworm Bombyx mori during the last larval instar.
abstract: 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.
authors.affiliation: Department of Zoology, National Museum of Natural Science, 1 Kuan Chien Road, Taichung, Taiwan 40419, Republic of China. gu330@mail.nmns.edu.tw
authors.forename: S H
authors.initials: SH
authors.lastname: Gu
authors.forename: Y S
authors.initials: YS
authors.lastname: Chow
mesh_terms: 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*
chemical_list: D004441:Ecdysterone; D004247:DNA