Gametogenesis and Fertilization in Plasmodium yoelii nigeriensis: A Transmission Electron Microscope Study

摘要: The ultrastructure of the micro- and macro-gametocytes Plasmodium yoelii nigeriensis nuclear cytoplasmic changes during gametogenesis fertilization were examined with electron microscope. Osmiophilic bodies, dispersed in cytoplasm, served to distinguish gametocytes from other erythrocytic stages thought play a part gametocytes' escape host cells by attachment parasite's plasmalemma causing dissolution overlying erythrocyte cytoplasm. Macrogametocytes distinguished microgametocytes their greater density ribosomes, more elaborate endoplasmic reticulum, which contained dense material, numerous mitochondria smaller nucleus. In microgametogenesis division was endomitotic genome segregated on three successive spindle formations. Microtubule organizing centres developed adjacent envelope gave rise orthogonal tetrads kinetosomes found at opposite poles first spindle. Axoneme assembly kinetosome followed usual pattern addition sub-units terminally A subfibres, and, slight lag, B subfibres. closely linked centriolar plaques pores envelope, poles. axonemes provided mechanism each haploid set chromosomes eventually endowed single axoneme. At time final segregation newly formed juxta-kinetosomal sphere granule became surrounded basket work irregular tubules lay close bud nucleus containing pole now highly condensed chromatin. During exflagellation granule, together axoneme forced through perikinetosomal perpendicularly towards surface distended plasmalemma. gamete formation, slid off tangentially also passed basket, separated main body nucleoplasm incorporated as gamete. free microgamete its distal granule. intertwined After emergence there contrastingly few macrogamete. absence intranuclear spindles maturation bodies evidence that meiosis did not occur this stage. one applied macrogamete, amorphous material outer surfaces confluent. This allowed contact fusion plasmalemmas. naked into cytoplasm Decondensation chromatin may have occurred before two nuclei. chromosome number about ten estimated for microgametes numbers kinetochores microtubules spindles. accords estimate sporogonic stages. been described previously malaria parasites. former skeletal function directing surface. latter, position end assist penetration macrogamete mediating plasmalemmas gametes, though we able determine kinetosomal is contacts