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Results for “Vitellogenesis”

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At least 19 recordsLinked to original sources

PubMed1977

Endocrine control of vitellogenesis in Drosophila melanogaster: effects of the brain and corpus allatum.

The endocrine control of yolk deposition in Drosophila melanogaster was studied by ligation and transplantation techniques. Endocrine events associated with the initiation of vitellogenesis were found to be synchronized with eclosion rather than the completion fo adult development. Decapitation experiments showed that a cephalic event occurring at about the time of eclosion is necessary for each animal to initiate vitellogenesis. The morphogenetic effect of the head could be replaced by a juvenile hormone analog (JHA). In addition to the cephalic event, a thoracic factor is required for each follicle to initiate vitellogenesis, since preparation of isolated abdomens before 16 hours after eclosion prevented vitellogenesis. In abdomens isolated after this time, no early vitellogenic stages were formed. The suppression of vitellogenesis in isolated abdomens was reversed by implanting corpora allata or by treating these preparations with JHA, but not by implanting corpora cardiaca. Ovaries that were artificially induced to mature by treating isolated abdomens with JHA still displayed the normal complement of ovarian proteins after electrophoresis in polyacrylamide gels. These results show that a circadian clock triggers vitellogenesis via a cephalic signal at eclosion, which in turn triggers events in the thorax or abdomen. The cephalic signal can be superseded by juvenile hormone, whose presence is necessary for each follicle to become vitellogenic.

Animals↗

PubMed1977

Changes in serum glucose and lipids, and liver glycogen and phosphorylase during vitellogenesis in nature in the flounder (Platichtys flesus, L.).

1. During vitellogenesis in nature the concentration of phospholipid in serum of female flounders is correlated to the concentration of vitellogenin. 2. High levels of glucose and total lipid in blood occur before the onset of vitellogenesis. During early vitellogenesis the values decrease. At spawning they reach maximum levels. After spawning they decrease to low levels. 3. The concentration of glycogen in the liver oscillates during the period August to May. The phosphorylase activity shows peak activities with high concentrations of glycogen in the liver. There is no simple correlation between glycogen concentration in the liver and glucose concentration in the blood.

Animals↗

PubMed2026

Lipid metabolism in hepatopancreas and ovaries of the mud crab Scylla paramamosain during vitellogenesis.

Ovarian lipids are essential nutrients that fundamentally determine oocyte and offspring quality, and ultimately affect the reproductive performance of decapod crustaceans. Lipids accumulated in the ovaries during vitellogenesis are mainly derived from the hepatopancreas. However, the molecular mechanisms underlying lipid metabolism in the hepatopancreas and ovaries during vitellogenesis remain largely unclear. In this study, comparative transcriptomic and lipidomic analyses were conducted on the hepatopancreas and ovaries of the mud crab Scylla paramamosain. From early to late vitellogenic stages, 454 lipid species were significantly increased and 17 decreased in abundance in the hepatopancreas, and 609 increased and 23 decreased in abundance in the ovaries. Meanwhile, there were 1481 upregulated and 963 downregulated transcripts in the hepatopancreas, and 3402 upregulated and 1478 downregulated transcripts in the ovaries. Subsequently, KEGG pathway co-enrichment analysis showed that the de novo biosynthesis of glycerophospholipids and glycerolipids was enhanced in the hepatopancreas, with upregulated ALDH, GPAT, plsC, PLPP, FASN, and HSD17B8 transcripts and elevated abundances of PC, PE, PS, PA, PG, DG, and TG species from the early to late vitellogenic stages in mud crabs. In contrast, glycerophospholipid catabolism and conversion were activated in the ovaries, with upregulated PLA2G, LYPLA1, NTE, GPCPD1, PLD_1, PGS1, and CRLS transcripts and elevated abundances of LPC, LPE, LPS species. These findings provide novel insights into the molecular mechanisms of lipid metabolism during vitellogenesis in decapod crustaceans.

Animals↗

PubMed1979

Vitellogenin, lipid and carbohydrate metabolism during vitellogenesis and pregnancy, and after hormonal induction in the blenny Zoarces viviparus (L.).

1. Ovarian vitellogenic growth in Zoarces viviparus lasts about 2 months. Vitellogenesis is immediately followed by ovulation, fertilization and a pregnancy period of 4 months. Vitellogenin is observed in the blood during vitellogenesis, but declines during the first month of pregnancy. 2. The largest amount of liver lipid is found before vitellogenesis is initiated. During pregnancy the liver is depleted of lipid and glycogen, and total lipid and phospholipid is accumulating in the blood. 3. Estradiol treatment during pregnancy results in a dose-dependent increase in vitellogenin and lipids of the blood. 4. In late pregnancy, birth can be provoked with progesterone alone, or with combined progesterone and estradiol treatment.

Animals↗

PubMed1978

The effects of four arthropod diets on the body and organ weights of the leopard frog, Rana pipiens, during vitellogenesis.

Wild-caught adult Rana pipiens females were captured in midsummer and fed diets of crickets, flies sowbugs or wax moth larvae during a three-month period of active vitellogenesis. The cricket diet supported the most extensive body weight gain during this time and promoted a prolonged period of weight increase in an additional long-term study. Synchronous growth of the oocytes occurred in all four groups, but the ovaries and oviducts of cricket-fed animals were significantly larger than those of frogs on the other three diets. The significantly higher liver weights of frogs fed wax moth larvae may have reflected an augmentation of hepatic energy stores. Fat body weights were also highest in this group of animals. Frogs fed crickets and wax moth larvae possessed larger fat bodies than did the midsummer control animals killed immediately after their arrival in the laboratory. In contrast, frogs fed flies and sowbugs had smaller fat bodies than did the initial controls, suggesting that animals on these diets had utilized fat body lipid during vitellogenesis. Gastrocnemius and final body weights were lowest in frogs fed wax moth larvae. These findings may have reflected the nutritional content of the diet or the reduction in appetite frequently noted in these animals during observations of feeding behavior.

Animals↗

PubMed1975

The histological and histochemical studies on the ovary in relation to vitellogenesis in the dragonfly, Orthetrum chrysis Selys (Libellulidae: Odonata).

The ovaries consist of large number of panoistic ovarioles in the last instar nymph and the adult dragonfly Orthetrum chrysis (Selys). In the nymph the vitellaria are compactly filled with the primary oocytes and the vitellogenesis takes place only in the adult stage. During vitellogenesis oocytes change widely in their shape, size and cytological organisation and their developmental stages can be divided into pre-vitellogenic, early-vitellogenic, vitellogenic, late-vitellogenic and maturation age. PAS-positive material appears first around the germinal vesicle in the early-vitellogenic stage and lateron it migrates towards the periphery. Glycogen appears in the late-vitellogenic stage. DNA is abundantly present in the nuclei of the oocytes during the pre-vitellogenic and completely absent in early-vitellogenic, vitellogenic, late-vitellogenic and maturation stages. It is observed in the nuclei of follicular epithelial cells of all the stages. RNA is abundantly present in cytoplasm of the pre-vitellogenic oocytes but lateron is gradually decreases. During the early-vitellogenic and vitellogenic stages high concentration of RNA in the follicular epithelial cells has been observed. The protein bodies appear first in the interfollicular spaces and towards the periphery of the oocytes just near the enveloping follicular epithelial cells, during the early-vitellogenic stage suggesting the formation of yolk proteins from the haemolymph. In Orthetrum chrysis the sudanophilic bodies appear first in the follicular cells and then lie in the peripheral region of the oocytes suggesting the incorporation of yolk lipid either from the follicular epithelium or from the haemolymph through the follicular epithelium. The phospholipids are synthesised in pre-vitellogenic to the late-vitellogenic stages. In the late-vitellogenic stages the phospholipid granules are present abundantly in the follicular epithelium while in the maturation stage they disappear suggesting their utilisation in the formation of membranes like vitelline and chorion. The neutral fats are present in the form of large number of droplets in the oocytes during the maturation stage.

Alkaline Phosphatase↗

PubMed1977

The role of diacylglycerol-carrying lipoprotein I in lipid transport during insect vitellogenesis.

A diacylglycerol-carrying lipoprotein was isolated from mature eggs of the silkworm, Philosamia cynthia and compared, for physiochemical properties, with the major diacylglycerol-carrying lipoprotein I (LP-I) of hemolymph. The two molecules are identical an electrophoretic mobility, structural configuration as revealed by electron microscopy, and amino acid composition. In addition mannose was detected in the lipid-free protein moiety, thus enabling classification of the molecules as glycoproteins. The molecules differ in lipid content with egg-LP-I containing only 3.6% of the diacylglycerol content of hemolymph LP-I and the phospholipid and cholesterol components also showing a marked reduction. Analysis of the LP-I and vitellogenin (another diacylglycerol-carrying lipoprotein; LP-II) concentrations of mature eggs indicates that the amounts of the two glycolipoproteins in eggs are insufficient to account for the total acylglycerol content of the eggs. The results suggest that LP-I functions as a true carrier-protein serving to transport diacylglycerol from the fat body to the ovary. This proposal is supported by the observation that LP-I isolated from the egg retains the physiological capacity of hemolymph-LPi to take up diacylglycerol from fat body. Thus it is suggested that LP-I is the major source of lipid for vitellogenesis, whereas vitellogenin is the primary source of protein.

Amino Acids↗

PubMed1979

Vitellogenesis stimulated by thoracic ganglion implants into destalked immature spider crabs, Libinia emarginata.

Since destalked immature female Libinia emarginata fail to molt to maturity (Hinsch, 1972) and implants of thoracic ganglion of adult females into young females of Potamon dehaani caused a doubling of ovarian weight and differentiation of yolk granules (Otsu, 1963), the effects of the thoracic ganglion implantation on sexual maturation in Libinia was investigated. Destalked immature Libinia with a maximum carapace length of 4-5 cm received two implants of adult female thoracic ganglion at 10-day intervals. All of the surviving experimental animals and destalked controls molted to immaturity. Most of the experimental animals failed to complete a successful molt and few survived longer than 3-4 days. The experimental animals that survived for over a week showed signs of yolk deposition not observed in the destalked controls. Eggs in several stages of vitellogenesis were scattered throughout the gonad in the animal showing the most pronounced effect. This was not observed in any of the destalked controls.

Animals↗

PubMed1976

RNA synthesis in the ovarian follicle cells of Periplaneta americana during vitellogenesis.

The RNA and DNA pattern in the follicle cells of cockroach ovary during vitellogenesis has been studied. Evidences indicate that there is an active synthesis of these two nucleic acids in the nucleus. It has been suggested from the observations presented that RNA is synthesized in the chromosomes and are then transported to nucleolus before being sent to the cytoplasm. It is also shown that the follicle cells do not contribute any RNA material to the vitellogenic oocyte.

Animals↗

PubMed1977

Developmental studies of vitellogenesis in a dipteran insect, Chironomus thummi.

Vitellogenesis of developing oocytes of a Dipteran insect Chironomus thummi has been investigated. The onset of yolk deposition is marked by the differentiation of the oolemma including the formation of microvilli and endocytosis. These changes are accompanied by the appearance of small electron dense granules, similar in density to the yolk platelets, arising through the sequential accumulation of material into the matrices of the multivesicular bodies (MVBs). These latter structures are produced in the previtellogenic oocytes of the pharate pupae and early pharate adults. Often the limiting membrane of the MVBs bears bristle coats resembling those of the coated vesicles of pinocytotic origin, suggesting that it is through the fusion with the pinocytotic vesicles that the accumulation of dense material in the MVBs results. That the Mvbs transform into structures resembling yolk granules is supported by statistical analysis which indicates that the decrease in the number of electron-dense MVBs coincides with the increase in the occurrence of small dense yolk granules. In the late pharate adult stage the yolk granules are considerably larger than those of earlier stages. It is during this period that at least one type of electron-dense granule occurs at the oocyte follicle cell border, and that these apparently contribute to the formation of the vitelline envelope. The results of the present study indicate that preformed oocytic elements, the MVBs, play a strategic role in the formation and arrangement of the yolk granules in Chironomus. Since these structures account for the bulk of the ooplasm, it appears that the MVBs are at least partly responsible for the correct ordering of the cytoplasmic constituents of the oocytes, which is critical for the proper development and differentiation of the embryo.

Animals↗

PubMed1978

[Modifications in the liver and elaboration of vitelline proteins during vitellogenesis following hormone treatments in Spondyliosoma cantharus L].

A fish (Sparidae) Spondyliosoma cantharus L. has been chosen because of his protogynous hermaphroditism. Histology and immuno-precipitation show that during the period of vitellogenesis or after hormone treatments (androgens and estrogens), the liver of female takes a caracteristic apperance. This aspect has been observed before in the gonochoric species and it concerns the elaboration of the vitellin proteins and their blood transportation from liver to ovary. The immatures and males are sensitive to the estrogens, but react only exceptionally to androgens.

Animals↗

PubMed1977

[Induction of oocyte maturation at stages of incomplete vitellogenesis in toads and the starred sturgeon].

The intracellular injection of cytoplasm from the maturing oocytes of X. laevis and A. stellatus in oocytes of the same species which did not complete the vitellogenesis and are not able to mature under the effect of progesterone resulted in the disintegration of the germinal vesicle membrane in the oocytes of all sizes under study. In X. laevis the ability to mature under the effect of progesterone appears in the oocytes with the diameter over 1.1 mm. Cycloheximide inhibits the germinal vesicle membrane disintegration in the X. laevis oocytes, but not in those of A. stellatus. Cycloheximide inhibits the pseudogastrulation which was observed in the X. laevis oocytes with the diameter from 0.8 to 1.4 mm.

Animals↗

PubMed1979

Oogenesis in Campodea sp. (Diplura): the ultrastructure of the egg chamber during vitellogenesis.

The egg chamber of Campodea consists of a group of nurse cells and an oocyte, and is surrounded by a simple, markedly flattened follicular epithelium. Three types of yolk occur in the oocytes: type I appears within elements of the rough endoplasmic reticulum; type II is produced by specific complexes of endoplasmic reticulum and dictyosomes; type III is incorporated by micropinocytosis. Histochemical tests show that mature yolk spheres contain proteins and polysaccharides. The main function of the nurse cells is to synthesize RNA, but they also produce small amounts of type I yolk. Phylogenetic conclusions are drawn from this and other studies of oogenesis in apterygote insects.

Animals↗

PubMed1978