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Changes in follicle cell morphology were correlated with changes in rates of protein synthesis and DNA synthesis by the ovary during ovarian maturation in Leucophaea maderae. During the vitellogenic period of oocyte development, which lasts approx, 15 days, morphological changes in the follicle cells are accompanied by moderate rates of ovarian protein synthesis and rapid rates of ovarian DNA synthesis. At approx. 15 days after mating, the shape of the follicle cells changes from cuboidal to squamous, ovarian DNA synthesis is arrested, and ovarian protein synthesis increases slightly. During the final period of oocyte development, which lasts approx, two days, the interfollicular channels between the follicle cells have disappeared and the squamous follicle cells, which contain an extensive rough endoplasmic reticulum, deposit a chorion around the mature oocyte. These morphological changes are accompanied by a radical increase in ovarian protein synthesis, while ovarian DNA synthesis remains arrested. Immediately before ovulation, ovarian protein synthesis starts to decline, reaching a minimal level 24 hr post-ovulation. Ovarian maturation is dependent on the presence of juvenile hormone (JH) only during the vitellogenic stage of oocyte development. Decapitation of insects at any point during the first 10 days after mating arrests the synthesis of DNA and retards the synthesis of protein by the ovary, resulting in degeneration of the oocyte. Subsequent injection of JH restores both events to normal levels within 72 hr. Decapitation on or after the tenth day following mating does not alter normal oocyte development, chorion deposition, ovulation or egg case formation. Primary induction of protein synthesis in ovaries from virgin females can be achieved by either an in vivo or in vitro exposure of the tissue to JH, thus confirming a site of action for JH to be ovarian tissue. Electrophoretic analysis of the soluble proteins from JH-exposed ovaries in vivo reveals that JH stimulates general protein synthesis, rather than the synthesis of a specific major protein such as vitellogenin. |
