The Cell Biology of Vitellogenic Follicles in Hyalophora and Rhodnius

Vitellogenesis and Post-Vitellogenic Maturation of the Insect Ovarian Follicle

“…The oocyte surface is not directly exposed to the hemolymph but is separated from it by the follicular epithelium. Wide channels form between the epithelial cells, a condition termed patency (Telfer et al, 1982;Raikhel and Lea, 1991;Davey, 1993;Zimowska et al, 1994), allowing passage of hemolymphderived proteins through the follicular epithelium toward the oocyte surface and into the oocyte.…”

“…Furthermore, the cellular organelles involved in oocyte RME are similar to those of somatic cells. However, unique features of RME in developing oocytes include an extraordinarily high level of endocytotic organelles in the oocyte cortex, as well as the final routing of internalized YPPs to specialized accumulation organelles, the mature yolk bodies (MYBs), in which YPPs are only minimally processed and are stored until the onset of embryonic development (Telfer et al, 1982;Raikhel, 1984;Raikhel and Dhadialla, 1992;Opresko and Wiley, 1987;Giorgi et al, 1993a;Raikhel and Snigirevskaya, 1998;Warrier and Subramoniam, 2002;Snigirevskaya and Raikhel, 2004). …”

“…Receptor-mediated endocytotic pathway of vitellogenin Most studies have been devoted to the internalization of the major YPP, Vg. Studies, at the electron microscopy (EM) level, particularly those that utilized electron dense tracers, have provided the foundation for our understanding of the ultrastructural morphology underlying the RME of YPPs in insect oocytes (see Telfer et al, 1982;Raikhel and Dhadialla, 1992). The purification of Vgs from different insects facilitated the introduction of immunocytochemical methods at the ultrastructural level.…”

Estudo de mecanismos envolvidos na incorporação de proteínas durante a ovogênese em Anopheles

“…Drosophila, e em Hyalophora e Rhodnius por Telfer et al (1982). Em Bombyx terrestris o processo é intraovariano, mas não endõgeno (isto é no interior do ovocito), pois a forma ção das proteínas ocorre nas células foliculares (Hopkins & King, 1966).…”

“…A primeira evidência de incorporação de proteínas, a partir da hemolinfa, pelo ovócito foi dada por Wigglesworth (19^3) em Rhodnius proltxus e em alguns aracnídeos. Trabalhos mais recentes sobre a formação e a deposição dos grânulos de proteínas no ovócito têm demons trado gue eles são sintetizados extra ovário e obtidos pelo ovócito a partir da hemol in_ fa, por pinocitose (Telfer, I960, 1965;Telfer et al, 1982;Bitsch, 1980). As vitelogeninas, proteínas da hemolinfa limitadas ao sexo feminino (Telfer, 195^> I960), que or_i_ ginam as vitelinas do vitelo, são produzidas em vários tecidos.…”