Studies on development of the sexual stages in Plasmodium

研究了啮齿动物伯氏疟原虫配子体发生和卵母细胞向卵囊发育的诱导机制。1)配子发生的诱导受两种不同的机制调控，一种是低温依赖的DNA合成，另一种是ph依赖的发育事件控制，导致小配子的组装和脱落。在这些事件中，Ca^<2+>和cGMP被发现作为第二信使。2)小配子细胞的DNA合成和轴素形成受Ca^<2+>/钙调素依赖性代谢途径的调控，而进一步的脱毛事件由cGMP控制。3)两种独立的离子交换剂，即依赖Na^+的HCO_3^-（内流）/H ^+（外排）交换剂和非依赖阳离子的Cl^-（内流）/HCO_3-（外排）交换剂，参与了配子发生诱导过程中的离子调节。(4)电镜观察发现，卵母细胞通过胞内途径进入奥莫按蚊的中肠壁，但也观察到卵母细胞在胞内发生。5)与蚊子细胞共培养或不共培养的离体培养均可实现卵母细胞向幼卵囊发育。然而，所有转化的幼卵囊都没有进一步发育，即既没有卵囊囊的沉积，也没有观察到核分裂。

Induction mechanisms of gametogenesis and in vitro development of ookinetes to oocysts in a rodent malaria parasite, Plasmodium berghei, were investigated.1)Induction of gametogenesis was regulated by two distinct mechanisms, one is a low-temperature-dependent DNA synthesis and the other is a pH-dependent control of developmental events leading to microgamete assembly and exflagellation. In these events, Ca^<2+> and cGMP were found to act as second messengers.2)DNA synthesis and axoneme formation in microgametocytes were regulated by Ca^<2+>/calmodulin-dependent metabolic pathways, whereas further events to exflagellation was controlled by cGMP.3)Two separate ion exchangers, i. e., Na^+-dependent HCO_3^-(influx)/ H^+(efflux)and nonspecific-cation-dependent Cl^-(influx)/HCO_3-(efflux)exchangers, were involved in the ionic regulation in the induction of gametogenesis.4)Electron microscopy revealed that ookinetes penetrate the midgut wall of a mosquito, Anopheles omorii, by the intracellular route, although the intracellular occurrence of the parasite was also observed.5)Development of ookinetes to young oocysts was achieved in in vitro culture with or without co-cultivation of mosquito's cells. However, all of transformed young oocysts failed to develop further, i. e., neither deposition of the oocysts capsule nor nuclear division was observed.