The Mechanism and Control of Yolk Formation

Telfer, William H.

doi:10.1146/annurev.en.10.010165.001113

Cited by 311 publications

(65 citation statements)

References 41 publications

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“…This process, which has been found to be quite complex (1), involves the elaboration of yolk for later use by the developing embryo. The major proteins which become yolk are synthesized by the fat body, secreted into the hemolymph, and selectively taken up by the developing oocyte (2,3). These proteins have been termed vitellogenins (4).…”

mentioning

confidence: 99%

The ovary as a source of alpha-ecdysone in an adult mosquito.

Hagedorn¹,

O’Connor²,

Fuchs³

et al. 1975

Proc. Natl. Acad. Sci. U.S.A.

319

154

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The ovaries of the mosquito Aedes aegypti cultured in vitro secrete material that behaves like ecdysone in a radioimmunoassay. The material was identified as aecdysone by high-resolution liquid and gas-liquid chromatography. Secretion reached a maximum 16 hr after a blood meal as shown by bioassay and direct determination. Ovariectomy reduced the concentration of ecdysone in the adult after a blood meal. Qualitative analysis of whole-body extracts indicated fi-ecdysone to be the principal species present. Thus the ovaries appear to secrete a prohormone, a-ecdysone, which is converted to,-ecdysone. ,-ecdysone plays a significant role in stimulating egg development in the adult mosquito and may have reproductive roles in other insects.In mosquitoes the blood meal triggers egg development. This process, which has been found to be quite complex (1), involves the elaboration of yolk for later use by the developing embryo. The major proteins which become yolk are synthesized by the fat body, secreted into the hemolymph, and selectively taken up by the developing oocyte (2, 3). These proteins have been termed vitellogenins (4). Recent investigations into the control of this process showed that, in contrast with most insects, the mosquito ovary was the source of a hormonal factor which activated and maintained vitellogenin synthesis by the fat body (5). Thus synthesis by the fat body was abolished by ovariectomy and restored by reimplantation. Further, when ovaries from blood-fed females were incubated in vitro with the inactive fat body from unfed females, synthesis of vitellogenin was activated. This ovarian hormone was designated the vitellogenin stimulating hormone, VSH (1).The discovery that injected f3-ecdysone stimulates egg development (6) and dopa decarboxylase activity (7) in the absence of a blood meal led us to investigate the possibility that VSH might be f3-ecdysone. Our results indicated that f3-ecdysone mimicked VSH in vivo and in vitro (8) and that material with ecdysone-like activity could be detected in mosquitoes after a blood meal (9). These lines of evidence strongly suggested that VSH was fl-ecdysone or a closely related steroid. We here describe experiments designed to identify the secretory product of the ovary. METHODSMosquitoes (Aedes aegypti) were reared at 27 + 0.50 using standard techniques (8, 9). The assay for vitellogenin synthesis has been described in detail (1, 8). The radioimmunoassay (RIA) was performed as previously described (10, 11).Ovaries were removed from females 15 hr after a rabbit blood meal and incubated at 250 with gentle shaking in groups of 100 in 100,ul of a defined medium (8). After 24 hr the medium was removed and the ovaries were rinsed with saline. An equal volume of methanol was added to the combined medium and rinse. Particulates were removed by filtration. The extract was evaporated to dryness under reduced pressure, redissolved in chloroform:methanol (2:1) and partitioned against water according to Folch et al. (12). The epiphase was dried under vacuum ...

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mentioning

confidence: 99%

The ovary as a source of alpha-ecdysone in an adult mosquito.

Hagedorn¹,

O’Connor²,

Fuchs³

et al. 1975

Proc. Natl. Acad. Sci. U.S.A.

319

154

View full text Add to dashboard Cite

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“…The large subunit observed in lane 4 of Fig. 6 is present because it is coimmunoprecipitated with the small subunit by antibodies specific to the latter.…”

Section: Qsns N S S S S S S S Rmentioning

confidence: 91%

“…Vgs are secreted into the blood or hemolymph, specifically accumulated by developing oocytes, and later utilized by embryos as a source of nutrients (4)(5)(6)(7). Vgs are large phospholipoglycoproteins that share a limited structural homology and, presumably, a common origin (8,9).…”

mentioning

confidence: 99%

Subunit cleavage of mosquito pro-vitellogenin by a subtilisin-like convertase.

Chen

Raikhel

1996

Proc. Natl. Acad. Sci. U.S.A.

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“…Con relación al escaso retículo endoplásmico rugoso, así como la ausencia total de retículo endoplásmico liso y de complejos de Golgi en dichas células de D. coccus, es conocido que en general el citoplasma de las células nutricias en Hemiptera presentan una muy alta concentración de ribonucleoproteínas y mitocondrias, mientras que los organelos membranosos tales como el retículo endoplásmico rugoso y los complejos de Golgi son raros (Telfer 1965;King & Büning 1985). La presencia de escaso retículo endoplásmico rugoso en las células nutricias de D. coccus, indicó cierta actividad sintética de proteínas realizada por estas células, proteínas que podrían ser enviadas hacia el ovocito en el vitelario, tal como sucede en el caso de Dysdercus intermedius Distant (Pyrrhocoridae) (Biczkowski & Dittmann 1995).…”

Section: Aunque Por Microscopía De Luzunclassified

Ultraestructura del germario de Dactylopius coccus Costa, 1829 (Hemiptera: Coccoidea: Dactylopiidae)

Ramírez-Cruz

2012

AZM

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Ramírez-Cruz, A. 2012. Ultraestructura del germario de Dactylopius coccus Costa, 1829 (Hemiptera: Coccoidea: Dactylopiidae). Acta Zoológica Mexicana (n. s.), 28(3): 586-593. RESUMEN. Se realizó la descripción ultraestructural del germario de hembras adultas de Dactylopius coccus Costa, 1829, mediante microscopía electrónica de transmisión. El germario está rodeado por una cubierta epitelial interna y por una túnica propia. Contiene además grandes células nutricias con núcleos de forma irregular, cuya membrana estaba perforada con gran cantidad de poros nucleares, observándose además uno o más nucléolos. Por otra parte, su citoplasma contenía una gran cantidad de ribosomas y mitocondrias, pero escaso retículo endoplásmico rugoso. No se observaron retículo endoplásmico liso ni complejos de Golgi. En las células nutricias de las hembras de dos días se observaron bacterias, aparentemente simbiontes, quedando por determinar su posible función en la fisiología de los ovarios. En algunas células nutricias de las hembras de diez días se observaron pequeños grupos de laminillas anulares, las cuales podrían estar relacionadas con un proceso degenerativo de dichas células. Los cordones tróficos se conformaron por una gran cantidad de microtúbulos y entre ellos se observaron numerosos ribosomas y numerosas mitocondrias, muchas de ellas de forma alargada. Palabras clave: Dactylopius coccus, germario, ultraestructura. Ramírez-Cruz, A. 2012. Ultrastructure of the tropharium of Dactylopius coccus Costa, 1829 (Hemiptera:Coccoidea: Dactylopiidae). Acta Zoológica Mexicana (n. s.), 28(3): 586-593. ABSTRACT. An ultrastructural description of adult females tropharium of Dactylopius coccus Costa, 1829, by electron microscopy transmission was realized. The tropharium is surrounded by an inner epithelial sheath and by a tunica propria. Furthermore, it contains large nurse cells with irregular-shaped nuclei and their nuclear membrane is abundantly perforated with nuclear pores; further one or more nucleoli were seen. Moreover their cytoplasm contained large numbers of ribosomes and mitochondria, but scarce rough endoplasmic reticulum. Neither smooth endoplasmic reticulum nor Golgi complex were observed. In the nurse cells of the females of two days-old, bacteria apparently symbionts were found, but their possible role in the ovarian physiology is unknown. Some nurse cells of females at ten days-old, had small groups of annular lamellae, which could be related with a degenerative process in these cells. The trophic cords were made of great number of microtubules and between them numerous ribosomes and mitochondria, many of them of elongated form.

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The Mechanism and Control of Yolk Formation

Cited by 311 publications

References 41 publications

The ovary as a source of alpha-ecdysone in an adult mosquito.

The ovary as a source of alpha-ecdysone in an adult mosquito.

Subunit cleavage of mosquito pro-vitellogenin by a subtilisin-like convertase.

Ultraestructura del germario de Dactylopius coccus Costa, 1829 (Hemiptera: Coccoidea: Dactylopiidae)

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