Gonadotropin triggers the generation of proteinaceous factor in vitellogenic perch (Anabas testudineus) oocyte which stimulates ovarian aromatase activity.

Oocytes of vitellogenic stage were collected from A. testudineus and incubated in vitro for 4 hr in the absence (control) or presence of 500 ng of piscine gonadotropic hormone (GtH). After the termination of incubation, oocytes were repeatedly washed and then homogenized and ultracentrifuged at 100,000 g to obtain the supernatant fraction (100K sup). Addition of 100K sup from GtH treated oocytes to the oocyte incubation caused a 3-fold increase in ovarian aromatase activity as compared to the control, whereas 100K sup from control oocytes had no such stimulatory activity. Addition of cycloheximide (50 micrograms/ml) along with GtH blocked the stimulatory effect of 100K sup. Treatment of 100K sup from GtH incubate with pepsin or heat also destroyed its stimulatory effect. All these indicate proteinaceous nature of the factor. This factor was purified to 161-fold by utilizing Sephadex G-75 and DEAE Sephacel chromatography. Addition of increasing concentrations of partially purified GtH induced protein (GIP) to oocyte incubation caused a dose dependent increase in ovarian aromatase activity. Both dbcAMP and forskolin mimicked GIP activity. Results indicate that GtH induces the synthesis of a protein factor in perch oocytes which stimulates aromatase activity via the mediation of cAMP.

Effect of juvenile hormone and ecdysone on initiating blood meal-dependent vitellogenic ovarian cycles in autogenous and anautogenous culex pipiens [Diptera: culicidae]

The effect of juvenile hormone [JH] and ecdysone on initiating blood meal - stimulated ovarian cycles was studied in autogenous [2[nd] ovarian cycle] and anautogenous [1[st] ovarian cycle] Cx. pipiens. Although vitellogenesis was initiated in both mosquitoes in response to ecdysone, JHI and sequential JHI-ecdysone treatments induced vitellogenesis in anautogenous females only. JHI treatment initiated vitellogenesis in Ca. 30% of anautogenous females and only half of those were able to form mature eggs. Sequential JHI- ecdysone treatment triggered vitellogenesis in 10 out of 25 anautogenous females and mature eggs were formed in three females only. In response to ecdysone, vitellogenesis in 10 out of 18 autogenous females and mature eggs were formed in two individuals. In Ca. 70% of anautogenous siblings vitellogenesis was initiated and in most of those females mature eggs were developed. Our data suggests that differences in hormone - dependent events of vitellogenesis in autogenous and anautogenous Cx. pipiens seem to be related to the regulation of ecdysteroide release