Induction Of Vitellogenin Synthesis Research Articles

Detection of vitellogenin in the haemolymph of larval female locusts (Locusta migratoria) treated with the neurohormone, Lom OMP

The ovary maturating parsin of Locusta migratoria (Lom OMP) is a gonadotropic neurohormone which is active during vitellogenesis over the same period as juvenile hormone (JH). For this reason, a possible vitellogenic effect of the Lom OMP was tested using fifth instar larvae. At this last larval stadium, locusts do not normally produce vitellogenin but the synthesis of vitellogenin can be induced at this time by high doses of JH analogues. Since vitellogenin is rapidly released into the haemolymph, the synthesis of vitellogenin was investigated by detecting the occurrence of vitellogenin in the haemolymph, using SDS-PAGE. The neurohormone Lom OMP was able to induce vitellogenin synthesis in females but not in males. The maximally efficient dose-range was narrow. The timing of vitellogenin occurrence was delayed as compared to that obtained with JH. The Lom OMP inducibility, evaluated by the number of responsive females, was lower than that obtained with JH provided by the implantation of a single corpus allatum. In allatectomized females, the Lom OMP inducibility was not suppressed but, on the contrary, increased. The gonadotropic activity of the Lom OMP thus acts through a vitellogenic effect similar to the gonadotropic activity of JH but the mode of action of Lom OMP is different to and independent of that of JH.

Vitellogenesis as a biomarker for estrogenic contamination of the aquatic environment.

A rapidly increasing number of chemicals, or their degradation products, are being recognized as possessing estrogenic activity, albeit usually weak. We have found that effluent from sewage treatment works contains a chemical, or mixture of chemicals, that induces vitellogenin synthesis in male fish maintained in the effluent, thus indicating that the effluent is estrogenic. The effect was extremely pronounced and occurred at all sewage treatment works tested. The nature of the chemical or chemicals causing the effect is presently not known. However, we have tested a number of chemicals known to be estrogenic to mammals and have shown that they are also estrogenic to fish; that is, no species specificity was apparent. Many of these weakly estrogenic chemicals are known to be present in effluents. Further, a mixture of different estrogenic chemicals was considerably more potent than each of the chemicals when tested individually, suggesting that enhanced effects could occur when fish are exposed simultaneously to various estrogenic chemicals (as is likely to occur in rivers receiving effluent). Subsequent work should determine whether exposure to these chemicals at the concentrations present in the environment leads to any deleterious physiological effects.

Completion of development in Athalia rosae (Hymenoptera) eggs matured with heterospecific Athalia infumata yolk protein

Previtellogenic immature ovaries of Athalia rosae (Hymenoptera) were transplanted into the abdomens of adult male Athalia infumata hosts, which were then treated with juvenile hormone III topically to induce vitellogenin synthesis. The A. rosae oocytes accumulated the A. infumata vitellogenins and matured. The donor ovaries themselves did not contribute vitellogenins, as no vitellogenin mRNA was detected. The A. rosae oocytes matured thus solely with the heterospecific vitellogenins. A fraction of mature eggs, upon artificial activation, completed embryonic development.

Distribution and significance of ecdysteroids in the female and male milkweed bug, Oncopeltus fasciatus

The ecdysteroid content of whole body extracts of newly hatched females is relatively high but drops sharply to low levels on day 2 and 3 after ecdysis. Then it rises again and stays more or less constant. The rise is correlated with the onset of egg maturation, and the majority of the ecdysteroids are located in the ovary. Ecdysteroid titres of the haemolymph do not reflect the fluctuations of whole body extracts and are always relatively low. Ovariectomized females exhibit a permanently low content in whole body extracts after day 4. There is experimental evidence that this low content is sustained by an ecdysteroid source outside the ovary (and the prothoracic glands which degenerate during the adult moult). The synthesis of vitellogenins is not impaired by ovariectomy and therefore not regulated by ovarian ecdysteroids. Virgin females retain mature eggs in the genital ducts; the ecdysteroid content of such females is correspondingly higher. The present and previous findings indicate that the ovarian ecdysteroids are mostly, if not exclusively, produced in the ovary and that little ecdysteroids, if any, leak from the ovary into the haemolymph. Whereas the ovarian ecdysteroids are incorporated into the egg where they might serve a function, the significance of the low levels of extraovarian ecdysteroids remains unknown. Repeated injection of makisterone A causes a decrease in female fertility, correlated with a dose-dependent suppression of the vitellogenins in the haemolymph. RP-HPLC/RIA analysis and metabolism of labelled exogenous ecdysone suggest that the ovarian ecdysteroids consist of a variety of metabolites especially of high polarity, including conjugates as well as makisterone A. Different female body compartments reveal different metabolite patterns. The ecdysteroid content of whole body extracts of males is comparable to that of females until day 3. Thereafter, it remains almost constantly low in males. The haemolymph titre is also low. Repeated treatment of males with makisterone A and the ecdysone agonist RH 5849 does not induce vitellogenin synthesis as previously reported. The role of ecdysteroids in male and female reproduction is discussed.

Involvement of Growth Hormone and Prolactin in the Induction of Vitellogenin Synthesis in Primary Hepatocyte Culture in the Eel, Anguilla japonica

Multihormonal effects of bovine growth hormone (GH) and ovine prolactin (PRL) on vitellogenin (Vg) synthesis in response to estradiol-17β (E 2) were electrophoretically examined in primary hepatocyte culture in the eel, Anguilla japonica. Newly synthesized protein after hormonal treatment was identified as Vg by immunoblot and immunoelectrophoresis. A single injection of E 2 into hypophysectomized eels failed in the induction of Vg synthesis. Similarly, E 2 alone was insufficient to induce Vg synthesis in the culture. On the other hand, the combination of E 2 with GH and/or PRL markedly stimulated Vg synthesis. Neither GH alone nor PRL alone had any effect on the induction of Vg synthesis by cultured hepatocytes. Hepatocytes isolated from E 2-primed eels also required GH or PRL for continuation of Vg synthesis. The highest Vg synthesis occurred at doses of 50 ng GH/ml and 1 μg PRL/ml in the presence of 2 × 10 -6 M E 2. These results indicate that the multihormonal stimulation of GH and/or PRL as well as E 2 is essential for the active synthesis of Vg in eels.

Polyamines in liver and their influence on chromatin condensation after 17-beta estradiol treatment of Atlantic salmon.

Atlantic salmon (Salmo salar) were treated with 17-beta estradiol to induce vitellogenin synthesis in liver. This led to an increase in liver wet weight and total DNA. After incubation with micrococcal nuclease (EC 3.1.31.1) less soluble chromatin was obtained from nuclei of the estradiol treated than the control fish, but active gene regions were solubilized by the nuclease. Thus, in the estradiol treated fish soluble mononucleosomes contained hybridizable vitellogenin gene sequences. As a result of estradiol treatment the content in total liver of putrescine rose 3-fold, that of spermidine 2-fold, while spermine was unchanged. In muscle no significant changes were observed. The regulatory functions of polyamines during gene expression were investigated by binding (14C)spermine to isolated liver nuclei depleted of endogenous polyamines. The number of binding sites was higher in nuclei of estradiol treated than control fish. (14C)spermine associated preferentially with micrococcal nuclease insensitive chromatin. Thus, the high content of putrescine and spermidine in liver supported the view of polyamine accumulation in proliferating tissues. The preferential binding to condensed chromatin indicated a stabilizing effect of polyamines on the organization of inactive chromatin structures.

Vitellogenin synthesis in andrectomized males of the terrestrial isopod, Armadillidium vulgare (Malacostracan Crustacea)

When adult females of Armadillidium vulgare were ovariectomized, the fat body continued to synthesize vitellogenin. On the other hand, females transplanted with androgenic glands decreased the synthetic activity for vitellogenin in their fat body. In order to elucidate effect of the androgenic hormone for vitellogenin synthesis, the occurrence of vitellogenin was studied with andrectomized males. Vitellogenin was estimated, using rocket immunoelectrophoresis. Vitellogenin synthesis in the fat body was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography. After andrectomy, males ceased elongation of the endopods (copulatory organs) and then vitellogenin was present in their hemolymph. Their vitellogenin titer continued to rise until it reached approximately three times higher than that of normal females. The accumulation level of vitellogenin was comparable with that of ovariectomized females. However, the activity of vitellogenin synthesis was at a low level in the fat body culture of andrectomized males, similar to ovariectomized females. These results indicate that andrectomized males are capable of vitellogenin synthesis, so one of the effects of the androgenic hormone is to inhibit vitellogenin synthesis. In A. vulgare, ovarian factors may not be involved in the induction of vitellogenin synthesis.

Induction of vitellogenin synthesis and maturation of transplanted previtellogenic eggs by juvenile hormone III in males of the sawfly, Athalia rosae

Both haploid and diploid adult males of the hymenoptera, Athalia rosae (Symphyta, Tenthredinidae), produced the two vitellogenins, L and S, in their haemolymph following topical application of juvenile hormone III. Previtellogenic ovaries transplanted into the abdoment of haploid adult males which were then given juvenile hormone III topically, maturated and the eggs upon in vitro activation successfully completed embryonic development.

Comparative developmental physiology and molecular cytology of the polytrophic ovarian follicles of the blowfly Sarcophaga bullata and the fruitfly Drosophila melanogaster

1. 1. The ovarian follicles of Sarcophaga and Drosophila consist of one oocyte and 15 nurse cells, the whole being surrounded by follicle cells. Although oocyte and nurse cells are genetically identical sibling cells, and although they are interconnected by cytoplasmic bridges, their physiology is very different. 2. 2. The DNA content of the oocyte nucleus (germinal vesicle) never exceeds 4C, while values of polyploidisation up to 1024C have been measured in the nurse cells, this being dependent on their position within a follicle. 3. 3. The nurse cell nuclei very actively synthesize RNA, while the germinal vesicle is almost completely inactive in this respect. 4. 4. It has been possible to visualise the major cytoskeletal elements in the different ovarian cell types. Cellular markers of polarity and dorsoventral asymmetry have been described. 5. 5. Electrophysiological measurements have been performed to find out whether or not the self-electrophoresis principle may be involved in polarised transport between nurse cells and oocyte. 6. 6. Most of the vitellogenin is synthesized by the fat body but some follicle cells also synthesize small amounts. 7. 7. The role of 20-OH ecdysone in the induction of vitellogenin synthesis in the fat body, as well as the presence of met-enkephalin like immunoreactivity in the gonads is well established in both species. Not so clear is the exact role of juvenile hormones and the nature of brain factors controlling ovarian development. 8. 8. Drosophila has the advantage of its well documented genetics while the larger species Sarcophaga is preferable for the study of (electro-) physiological and cell biological mechanisms.

Time‐course effects of repetitive oestradiol‐17β and thyroxine injections on the natural spring smolting of Atlantic salmon, Salmo salar L.

The impact of thyroxine and oestradiol injections on the smolting process of Salmo salar was investigated over 39 days. The increase in the degree of silvering was advanced by thyroxine but inhibited by oestradiol, as compared to controls. Oestradiol treatment increased the level of total calcium in the plasma, the hepatosomatic index and the concentration of RNA in the liver, indicating the induction of vitellogenin synthesis. The level of plasma chloride and protein in the liver remained unchanged in all experimental groups. Gill Na+/K+‐ATPase activity was low initially in the control fish, but increased steadily during the 39 days. The enzyme activity was advanced in the thyroxine‐treated fish, but inhibited by oestradiol. Gill chloride cell number increased in control fish and in the thyroxine‐treated fish until 25 days after the hormone treatment was initiated. Oestradiol‐treatment induced a lower chloride cell number on days 25 and 39. Altogether the present study demonstrates a reciprocal action of exogenous thyroxine and oestradiol during smolting in S. salar.

The influence of sex steroids in commercial fish meals and fish diets on plasma concentration of estrogens and vitellogenin in cultured Siberian sturgeonAcipenser baeri

Sex steroid levels were dctermined in various commercial fish meals and complcte dicts. The results obtained demonstrate that estrone (E,), 17P-estradiol (El) and androgens (A) (testosterone and 11ketotestosterone), are present in diets in high quantities (up to 935f 350ng/100g for E,, 615f 190ng/100g for El and 1 100&120ng/100g for A) and with considerable variation both between diffcrent dicts, and between differcnt batches of the same diet. These high levels of sex steroids are thought to influence the sex steroid plasmatic Icvels and plasma vitellogenin content in fish. Plasma sex steroid assays in the Siberian sturgeon Acipenser barri show that plasmatic 17 0-estradiol lcvels are ncvcr significantly different betwccn males and femalcs at various stages of oogenesis and spermatogencsis, exccpt in 6 year old fcmalcs in stage IV, which corresponds to the maximum incorporation of vitellogenin. In males the plasma 17P-cstradiol levels are exceptionally high and induce vitellogenin synthesis, as dcmonstrated by various chemical and immunological techniques.

Relationship between the absolute configuration and the biological activity of juvenile hormone III

The activity of the pure 10R (=natural) and 10S enantiomers of juvenile hormone III (JH III) was determined in 3 different bioassays, and the relative binding affinity of the 2 enantiomers to the haemolymph JH-binding protein of the cockroachNauphoeta cinerea was measured. In theGalleria wax test, a local morphogenetic assay, the 10R enantiomer was 5240 times more active than, the 10S enantiomer, 1Galleria unit corresponding to 0.42 pg of 10R-JH III as compared to 2.2 ng for 10S-JH III. In a systemic morphogenetic assay with the cockroachNauphoeta cinerea 380 times less 10R enantiomer was necessary in order to induce detectable juvenilisation (58 ng 10R and 22 μg 10S) and in a systemic gonadotropic assay withNauphoeta cinerea 255 times less 10R was needed to induce vitellogenin synthesis in 50% of the insects (6.7 ng 10R and 1710 ng 10S). In the JH-binding protein assay 10R-JH III had an affinity for the JH-binding protein (lipophorin) which was approximately 46 times higher than that of 10S-JH III.

Characterization of liver chromatin proteins after induction of vitellogenin synthesis in salmon ( Salmo salar)

1. 1. Vitellogenin synthesis was induced in liver of salmon ( Salmo salar) by injecting 17-β-estradiol. 2. 2. Liver nuclei were isolated and incubated with micrococcal nuclease. The chromatin was fractionated into a 3000 g pellet, a 100,000 g pellet and supernatant fraction. The chromatin fractions were extracted stepwise with 0.35 and 2 M NaCl. 3. 3. As analyzed by PAGE, histone HI together with a few non-histone proteins decreased after induction while the high mobility group proteins T and C increased. 4. 4. Anion-exchange HPLC revealed a high number of different proteins. Upon induction some of the proteins present in the 0.35 M NaCl extract of the controls shifted to the 2 M NaCl extract suggesting an increase in the binding of the proteins to DNA. 5. 5. The results obtained provide the basis for further studies on the isolation of proteins of relevance to the modulation of gene activity.

Vitellogenesis in a lady-beetle, Coccinella septempunctata in relation to the aestivation-diapause

Yolk-protein precursor, vitellogenin, synthesis and effects of juvenile hormone analogue on vitellogenesis were studied in a lady-beetle, Coccinella septempunctata, which enters aestivation-diapause in the adult stage. In the prediapause period, total protein synthesis in the fat body was relatively high but vitellogenin synthesis was negligible. During diapause, total protein synthesis declined to a low level (but detectable) and vitellogenin synthesis was not detected at all. In the course of diapause termination, total protein synthesis recovered gradually, but vitellogenin synthesis did not occur before feeding. Juvenile hormone analogue application to a diapausing female induces vitellogenin synthesis and consequent oviposition. Sensitivities to juvenile hormone analogue in the stimulation of vitellogenin synthesis depended on the stage of diapause: pre-diapause period, diapause period and post-diapause period. The time lags between juvenile hormone analogue application and vitellogenin induction in the haemolymph were shorter in the pre- and post-diapause period than that in diapausing females.

Effects of thyroxine on the ontogeny of the vitellogenic response in Pleurodeles waltli of both sexes.

In the newt, Pleurodeles waltli, vitellogenin synthesis can be induced by oestrogen prior to metamorphosis and well before vitellogenin synthesis is normally observed in females. Vitellogenin indicubility has been shown to occur during normal development at stage 53 in both sexes. Immersion of young larvae in thyroxine at concentrations that did not result in early morphological metamorphosis led to a precocious acquisition of liver responsiveness to oestrogen. Treatment of larvae with thiourea greatly diminished the ability of oestradiol to induce vitellogenin synthesis, although it did not abolish the hormonal response.

Vitellogenesis in the lizard Lacerta vivipara Jacquin : II. Vitellogenin synthesis during the reproductive cycle and its control by ovarian steroids

An analysis of the development of the vitellogenic process following artificial hibernation in the lizard Lacerta vivipara was undertaken. For that purpose, organ weights (ovaries, oviducts, liver, fat bodies) and plasma concentrations of total proteins, calcium, and estrogens were monitored. The induction of the vitellogenic growth of 2–5 oocytes per ovary was characterized by a rapid increase in calcemia (from 2.4–2.6 m M to 4–10 m M), and in oviduct and liver weights. During the active and continuous phase of vitellus incorporation (⋍3 weeks, follicle diameter 1.6–2.0 mm to >5 mm) the developments of ovaries and oviducts, were positively correlated, liver weight and calcemia remained elevated (respectively, 1.2–2.2 times and 2.5–3.5 times the previtellogenic values). Ovulation was preceded by a significant rise in calcemia and followed by a decrease in liver weight, but no modification of oviduct mass. Plasma concentration in total proteins (50–60 mg/ml) was not modified during the entire process. Plasma estrogens were difficult to measure in this small species. Levels of estradiol-17β were very often below the assay sensitivity (<0.3–0.6 ng/ml), never above 2 ng/ml, and very variable among individuals. No correlation with vitellogenin production could be established. Therefore, the abilities of different ovarian steroids to induce vitellogenin synthesis were tested in vivo. To reduce the rise of plasma estradiol titer (observed during a 4-week experiment), the steroids were implanted in ovariectomized lizards for a short time (5 days). The vitellogenic response was assessed by measuring the distribution of the 32P radioactivity between the acidoprecipitable plasma fraction and the plasma vitellogenin recognized by the lizard antivitellogenin serum. Plasma titers of estradiol-17β were monitored. The estrone potencies could not be determined as this treatment involved an important rise in estradiol level. Progesterone, Δ 4, testosterone, and 5α-androstanediol were unable to stimulate vitellogenin synthesis. Estradiol-17β was the only effective steroid. It was further demonstrated that the estradiol-induced hypercalcemia, hyperproteinemia, and liver growth in ovariectomized lizards were dependent upon the total amount of estrogen injected.

The role of the male accessory gland fluid in stimulating vitellogenesis in Aedes taeniorhynchus

AbstractInjection of 20‐hydroxyecdysone (20‐OH‐ecdysone) at high concentrations (5.0 μg) into intact or decapitated female Aedes taeniorhynchus induced vitellogenin synthesis, whereas low concentrations (5.0 ng) were ineffective. Injections of male accessory gland fluid (MAGF), however, at a concentration that was equivalent to 0.25 of the content of a pair of accessory glands, into intact or decapitated A. taeniorhynchus induced viteliogenin synthesis only in intact females. Ovariectomized mosquitoes did not synthesize vitellogenin after MAGF injection or blood feeding. Females that were first injected with MAGF and decapitated 12 h later synthesized viteliogenin at a rate that was 80% of intact controls.Egg development neurosecretory hormone (EDNH) activity in the heads of ovariectomized or intact females injected with MAGF was 9.0 pmol/min/head and 2.5 pmol/min/head, respectively, indicating that MAGF does not stimulate the corpus cardiacum (CC) to release EDNH.Incubation of MAGF and EDNH with fat bodies failed to induce vitellogenin synthesis. These results indicate that in A. taeniorhynchus the MAGF induces the ovary to release corpus cardiacum stimulating factor, which then signals CC to release stored EDNH.

Sexual differences in the in vitro induction of vitellogenesis in the turtle: Role of the pituitary and growth hormone

1. 1. Estradiol induces vitellogenin synthesis in liver cultures taken from normal and ovariectomized female turtles. 2. 2. By contrast, estradiol alone or with other hormonal or serum factors failed to induce vitellogenin synthesis in liver cultures established from normal and castrated males. 3. 3. In vitro induction of vitellogenesis was achieved only in cultures originated from hypophysectomized males and in the presence of both estradiol and mammalian growth hormone. 4. 4. These results demonstrated a clear sex difference in the hormonal stimuli required, in vitro, for the induction of vitellogenesis in the turtle. 5. 5. We suggest that pituitary growth hormone is an important synergist in the vitellogenic response to estrogen, possibly through an effect on estrogen receptors.

Vitellogenin synthesis in blood-fed Aedes aegypti in the absence of the head, thorax and ovaries

A blood meal initiates oöcyte maturation in Aedes aegypti, and we have used rocket immunoelectrophoresis to investigate the function of midgut, ovaries, and head in the onset of vitellogenin synthesis. Non-blood-fed females and those fed blood (by enema) containing soybean trypsin inhibitor never contained vitellogenin. This demonstrates that the pressure of an undigested blood meal on stretch receptors of the midgut plays no role in the induction of vitellogenin synthesis, rather the stimulus is a digestion product of blood. When females were ovariectomized or decapitated and then fed blood, the haemolymph contained newly synthesized vitellogenin 24 h later. This was also demonstrated in isolated ovariectomized abdomens. Apparently, induction of vitellogenin synthesis does not require factors from either the head, thorax, or ovaries. When ovariectomy or decapitation was postponed after a blood meal, the level of vitellogenin in the haemolymph rose. Therefore, interaction of factors from the head and ovaries maintain the synthesis needed for oöcyte maturation.

The estrogen-induced vitellogenin synthesis in chicken liver after estrogen withdrawal or antiestrogen treatment

1. (1) The induction of vitellogenin synthesis in chicken liver by an estrogen implant as well as the decline of vitellogenin synthesis and nuclear receptor concentration after withdrawal of the implant were studied. For the detection of vitellogenin the SAC immunoprecipitation technique was used. The nuclear receptor decreases very rapidly and somewhat earlier than the capacity of the liver to synthesize vitellogenin. 2. (2) The inhibition by antiestrogens of the estrogen-induced vitellogenin synthesis as well as of the accumulation of the estrogen-receptor complex in the nucleus was investigated. Tamoxifen as well as the recently described 1,1,2,2-tetramethyl-l,2-bis(4′-hydroxyphenyl)ethane were found to be true antiestrogens in the chicken liver, i.e. they inhibit estrogen-induced vitellogenin synthesis but themselves cause no induction.