Postendocytic vitellin processing in ovarian follicles of the stick insect Carausius morosus (Br.)

Newly laid eggs of the stick insect Carausius morosus contain two native vitellins (Vit A and Vit B). Under denaturing conditions, these vitellins resolved into 3 (A₁, A₂, and A₃) and 2 (B₁ and B₂) polypeptides. All of these polypeptides had counterparts in the female hemolymph from which they were shown to be derived by in vivo labelling. During ovarian development, the 2 vitellins changed both in charge and polypeptide composition. In EV and LV follicles, Vit A resolved into 4 distinct vitellin polypeptides (A₀, A₁, A₂ and A₃). Using a panel of monoclonal antibodies, polypeptide A₀ proved to be immunologically related to polypeptide A₂. In follicles about to begin choriongenesis, polypeptide A₃ was gradually replaced by a lower M_r polypeptide. Over the same time period, polypeptide B₁ changed in charge, but not in M_r. To confirm the existence of a polypeptide processing in C. morosus, ovarian follicles of different developmental stages were exposed in vivo to [³⁵S]-methionine from 6 to 72 h. Data showed that A₀ and B₁ were the polypeptides most heavily labelled after short time exposures to the radioisotope. Polypeptides B₂ and A₃ were also labelled to some extent. With progressively longer exposures, polypeptides A₁ and A₂ also became labelled. In vivo exposure to [³H]-GlcNAc caused all vitellin polypeptides to become heavily labelled. Autoradiographic analysis of ovarian follicles labelled this way showed that, during development, radioactivity was gradually transferred from newly formed yolk spheres in the cortical ooplasm to the central ooplasm. Data were interpreted as suggesting a causal relationship between polypeptide processing and progressive yolk sphere fusion to yield the central ooplasm. © 1993 Wiley-Liss, Inc.     

Oögenesis defects in the ecd-1 mutant of Drosophila melanogaster, deficient in ecdysteroid at high temperature

Oögenesis defects observed in ecd-1 females depend on the stage at which the shift from the permissive temperature (20°C) to the non-permissive temperature (28.5°C) is performed. Pupae shifting earlier than 48 hours after puparium formation have underdeveloped ovaries and die at emergence. In ecd-1 females shifted 2 days or more after puparium formation, egg chambers develop normally up to the early vitellogenic stage, and then degenerate—no mature oöcytes are formed. When the shift is performed after maturation of the females at 20°C, their egg-laying rate decreases slowly after the shift; the eggs display abnormal chorions and fail to develop into larvae. By shifting the ecd-1 females back to 20°C, a complete reversal of abnormalities of eggshell formation and egg development may be observed. The temperature-sensitive periods related to these different defects were determined. For egg development, the period extends from 2 days to 1 day before laying. For eggshell formation, the beginning and end of the temperature-sensitive period were not separated—both were located around 24 hours before laying. For the block of vitellogenesis, we concluded that this is probably due to an inhibition of yolk uptake. This inhibition would be effective only in follicles younger than the previtellogenic stage 7 when submitted to the non-permissive temperature.     

Juvenile hormone and ovarian growth in Manduca sexta

In Manduca sexta the major size increase of ovarian follicles is accomplished by two processes: (1) vitellogenesis in which follicular volume and dry weight increase simultaneously, and (2) hydration in which absorption of water by the oocyte accounts for an 80% increase in volume prior to chorion formation. Vitellogenic growth occurs in both a slow and rapid phase. Rapid vitellogenic growth is initiated only by follicles of a threshold size (1 mm) and is a juvenile hormone (JH)-dependent event. In the absence of JH follicles grow to 1 mm and then degenerate.     

Regulation of vitellogenin synthesis and uptake in the boll weevil, Anthonomus grandis

Abstract. Hormonal factors influencing reproductive development were examined in adult boll weevils, Anthonomus grandis (Boheman) (Coleoptera: Curculionidae). Long-day, high-temperature rearing conditions promote reproduction whereas short-day, low-temperature conditions do not. Implants of corpora allata (CA), brains, or brains plus retrocerebral complexes taken from long-day donors, or hormone analogue treatments were used to examine onset of vitellogenin synthesis and uptake in decapitated bodies of adult weevils reared in short-day, low-temperature conditions. Weevils decapitated within 2 days after eclosion and reared in short-day, low-temperature conditions never initiated vitellogenin production or ovarian development. Females and males decapitated on day 2 showed haemolymph vitellogenin within 5 days following treatment with Juvenile Hormone (JH) analogue or implantation of CA, but not after implantation of brain alone or implantation of muscle (sham). Uptake of vitellogenin into the oocytes did not occur unless both JH analogue and brain were given as replacement therapy. These experiments indicated that JH is necessary and sufficient to stimulate vitellogenin synthesis in this species but that a brain factor must be present for vitellogenin uptake.     

Immunolocalization of a proton V-ATPase in ovarian follicles of the tobacco hornworm Manduca sexta

A monoclonal antibody, directed against an H⁺ translocating V-ATPase of the midgut of Manduca sexta, has been used for immunolocalization studies in ovarian follicles and testes of Manduca sexta. In testes, no distinct staining above background levels was observed. In vitellogenic follicles, V-ATPase immunoreactivity first appears in the cytoplasm of the trophocytes and then in the oocyte, but by far the strongest reaction is present in the region of the oolemma during endocytosis. All types of follicle cells surrounding both the oocyte and the trophocyte compartments show a distinct positive reaction. In the cylindrical follicle cells surrounding the oocyte, the immunoreactivity is clearly restricted to the basal part. Our results suggest an important role for V-ATPase in vitellogenin uptake in Manduca, similar to that suggested on electro-physiological grounds in Hyalophora cecropia. © 1995 Wiley-Liss, Inc.     

Inhibition of the onset of vitellogenesis by abnormal retention of mature eggs in the stick insect,Carausius morosus

Mature eggs stored in the lateral oviducts are unusual in Carausius morosus. When egg laying is experimentally prevented, ovarian production is inhibited by the accumulation of mature eggs within the lateral oviducts. Such storage affects only the very small terminal oocytes and not the vitellogenic follicles, which attain to term and are ovulated. The fact that unilateral retention of eggs affects only the corresponding ovary strongly suggests that the mature eggs themselves inhibit ovarian production in the stick insect without the involvement of an endocrine organ. It is likely that this mode of action, different from that suggested for the housefly or Rhodnius prolixus, is correlated with the independence of ovarian development from the corpus allatum hormone in the stick insect.     

The effect of growth rate,size, and season on oocyte development and maturity of Atlantic cod (Gadus morhua L.)

The effect of growth rate, body weight, age, and season on ovarian development and maturation was investigated for Atlantic cod (Gadus morhua L.) reared in the laboratory over 10 months, for each of two consecutive years, 1978–1980. Cod were also collected from the Gulf of St. Lawrence, the Scotian Shelf, Georges Bank, the Flemish Cap, and the N.E. Newfoundland Shelf.The state of maturity was recognized by oocyte size. Stage I oocytes did not vary in size with growth rate, season, age, or maturity, while the size of stage II oocytes was positively correlated with maturity and negatively correlated with maximum stage of development achieved. Ovarian wall thickness was positively correlated with age and maturity.The frequency distribution of stage I and II oocytes distinguished the state of maturation, with cod that would mature by the next spawning season having a minimum of 20% ($\text{x}\text{?}\text{= 42\%}$) of their oocytes at stage II or greater level of development.Maturing 3-yr-old cod had greater life specific growth rates than immature 3-yr-olds, but growth rates during the third year itself were not significantly different. A hypothesis of a three-part density-dependent mechanism controlling fecundity is postulated. Future reductions in partial recruitment and total fecundity are predicted for the Gulf of St. Lawrence cod stock based on calculated growth rates for Gulf cod in 1979.     

Vitellogenesis in Acanthoscelides obtectus (Coleoptera: Bruchidae). I—Oocyte development and vitellogenin in a European strain

Oocyte development was studied in a European strain of the bean weevil, Acanthoscelides obtectus. In the experimental system used, oocyte growth begins after several hours of imaginal life. The lengths of the terminal and penultimate oocytes were measured and correlations between these measurements showed that the latter stopped growing when the former was in the phase of accelerated growth.

Vitellogenin could be immunologically detected in the hemolymph of sexually mature females and was undetectable in males, larvae and in females immediately after imaginal exuviation. The moment of vitellogenin appearance in young females varies from one insect to another.

It appears that no specific external stimulus is required to initiate the synthesis and incorporation of the vitellin protein in this European strain.