摘要:

The kinetic profiles of vitellin degradation, protease activity and free amino acids in the embryo and larvae of the Pacific oyster,Crassostrea gigas, have been investigated during the period from the unfertilized egg through the 48 h straight-hinge larva. Immunoblotting using anti-vitellin showed that two major bands (179 and 110 kD) and several faint bands detected in the unfertilized egg become weak at the trochophore stage and disappear 48 h postfertilization. In gel filtration the main peak of the intact molecule of vitellin, estimated to be 530 kD, tended to become low from the blastula stage onwards. The relative vitellin content determined by enzyme-linked immunosorbent assay showed the same decreasing pattern as in gel filtration. The increase in the protease activity during larval development agreed well with the timing of the vitellin degradation and this protease directly degraded larval vitellin protein. The total free amino acids drastically increased at the same time as the increase in protease activity and were reduced at the 24 h straight-hinge larva stage. The results obtained here suggest that oyster vitellin is degraded during larval development and free amino acids, generated by hydrolysis of vitellin protein, may play a role in embryonic and larval development.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652337

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Botrylloides violaceus, a viviparous colonial ascidian, produces small alecithal eggs which develop into large tadpole larvae after a long period of gestation (about 1 month) in the colonial tunic. Unlike other botryllids, embryo development occurs in a brood pouch which soon becomes detached from the atrial epithelium to reach the colonial tunic and is independent of parent life. This study analyzes the ultrastructural differentiation of the brood pouch—from ovulation to larva release—in order to verify its role in the production, secretion and transport of nutrients for the embryo. Results show that brood pouch cells undergo modifications during embryogenesis, including: (a) increase in baso-lateral foldings of membranes and formation of long basal membranal channels; (b) shifting of tight junctions towards the base of the cells and increase in apical cell region by means of polymorphic, cytoplasmic protrusions; (c) synthesis, storage and secretion towards the embryo of proteinaceous materials and glycogen. All these features indicate that the brood pouch epithelium is involved in nutritional exchanges between the blood flowing into the tunic and the embryo. Aspects of viviparity in ascidians and comparison between the brood pouches ofB. violaceusand of the ovoviviparousBotrylloides leachiare discussed.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652338

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Rising and subsequent falling rates of juvenile hormone (JH) synthesis occurred concurrently with synchronous growth and atrophy of CA cells during the ovarian cycle in mated adult females ofDiploptera punctata.Ultrastructural observations revealed that growth of CA cells resulted from synchronous proliferation of cellular machinery required for JH synthesis. Cell growth was suppressed in CA of virgin females, in which rates of JH synthesis remained low, but was stimulated by mating or by severance of nerves leading from the brain to the CA. Atrophy of CA cells during declining rates of JH synthesis was due to synchronous autophagy of cellular organelles. While the mechanism initiating autophagy is unclear, it is independent of nervous connections between the CA and brain. We propose that under normal physiological conditions the quantity of JH synthesized by a corpus allatum is determined largely by the total amount of cellular machinery available for JH production. Therefore, the cycle of JH synthesis in mated adult females ofD. punctatais regulated mainly through synchronous proliferation of cell components (under neural inhibition) followed by synchronous autophagy (nerve independent). In the course of this study, we have found that individual CA cells fromD. punctata, like those fromBlattella germanica, retain their ability to synthesize JH III following enzymatic dissociation of the CA.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652339

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Oocyte maturation in the lugwormArenicola marinatakes place in the coelomic fluid and is induced by a coelomic maturation factor (CMF) (Watson and Bentley, 1997). CMF production itself results from the action of a prostomial maturation hormone. A recently describedin vitroassay for oocyte maturation inA. marinahas been adopted, distinguishing immature (full sized, prophase I) from mature (full sized, metaphase I) oocytes and enabling the action and nature of CMF to be investigated (Watson and Bentley, 1997). In this study, immunocytochemical techniques were used to characterize microtubule structures during oocyte maturation and post-fertilization development. Prior to the discovery of CMF, mature oocytes could be obtained only by collecting eggs from females that had spawned spontaneously in the laboratory or following the injection of homogenized prostomia thereby inducing maturation and spawning of the oocytes. Mature oocytes can now be obtained by thein vitroincubation of oocytes in coelomic fluid containing CMF. These three methods of maturation were employed and compared with respect to meiotic spindle morphology and post-fertilization development. Oocytes maturedin vitrohave a meiotic spindle identical to those maturedin vivo.Post-fertilization development inin vitromatured oocytes is, however, retarded by approximately one mitotic cycle after 5h incubation at 10°C. These results suggest that oocytes maturedin vivodiffer in some way from those maturedin vitro.The modification of development time in spawned vs.in vitromatured oocytes is discussed.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652340

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Sperm development, structure of the gametes and some aspects of fertilization in the far-eastern chitonsLeptochiton assimilis, Deschayesiella curvata(fam. Leptochitonidae),Tonicella undocaerulea(fam. Tonicellidae),Mopalia retifera(fam. Mopaliidae) andIschnochiton hakodadensis(fam. Ischnochitonidae) are described by transmission electron microscopy. In the testis spermatogenetic cells are closely associated with auxiliary cells, which are structurally identical to those of other mollusks and probably have a nutritive function. Spermatogenesis in all species did not differ from that of chiton species already studied and it was confirmed that an acrosome is formed from the Golgi apparatus during spermiogenesis. The spermatozoa of all studied species have a structure that is typical for chitons. The sperm ofDeschayesiella curvata(Order Lepidopleurida) have a head consisting of a large acrosome and nucleus with an (3.5–4.2μm) asymmetrically positioned anterior extension. The centrioles are surrounded by five spherical mitochondria. The spermatozoa inTonicella undocaerulea, Mopalia retiferaandIschnochiton hakodadensis(Order Chitonida) have a small acrosome and a nucleus with long thin anterior extension; mitochondria are lateral to the nucleus. There are considerable interspecific differences in the structure of egg envelopes. Our results, along with those of other workers, show that gamete structure of chitons is specific to each family. A cortical reaction which results in formation of a fertilization envelope takes place in the egg of chitons after fertilization.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652341

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Light and transmission electron microscopic examination of the X-organ-sinus gland complex in adultNephrops norvegicusreveals a high density of active neurosecretory axon endings (53%) abutting onto an undulatory-release surface. At least six different categories of neurosecretory granules and related vesicles have been identified on the basis of their texture, electron density, and diameter. Computer-aided three-dimensional reconstruction ofN. norvegicussinus gland defined by its fuchsinophilia on 2.5 μm serial sections shows a multilobed organ 1.25×10−2mm3in volume. Immunocytochemical studies were carried out using polyclonal antibodies raised against purifiedAstacus leptodactylusCHH (Gorgels-Kallen and Van Herp, 1981) andHomarus americanusGIH (Meusy and Soyez, 1991). Immunocytochemical localization of CHH and GIH (VIH) at the LM and EM level specifically locate the massive presence of CHH and a more superficial and scattered distribution of GIH in the axon endings. Under TEM, specificity in type and content of granules appears to be confined to single axons. Heterologous antibodies reacting with even phylogenetically distant taxa stress a conservative homology at least of some common reactive epitopes.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652342

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Few studies have addressed endocrinology of the corpora allata (CA) in insect embryos. We now report on development and biosynthetic activity of CA in embryos of a viviparous cockroach,Diploptera punctata.When newly-eclosed adult females ofD. punctatawere mated, they oviposited and gave birth, respectively, about 8 and 73 days later; thus, gestation and corresponding embryogenesis lasted approximately 65 days. Dorsal closure, which coincides with differentiation of the CA, was concluded when embryos were about 13 days old and had completed 20% of embryogenesis. Reverse phase-high performance liquid chromatography revealed that embryonic CA released predominantly juvenile hormone III (JH)in vitro.Furthermore, anin vitroradiochemical assay showed that between day 28 of embryogenesis (43% of embryonic development completed) and hatch rates of JH synthesis rose, plateaued and then fell. When CA activity was increasing or was high, from day 28 to 54 (83% development), mitosis occurred at low and constant rates within embryonic CA, and corpus allatum cell number increased gradually. Between days 56 (86% development) and 60 (92% development), CA activity fell to a low level, rates of mitosis peaked, and corpus allatum cell number rose rapidly. Throughout embryogenesis, CA volume increased in parallel with CA cell number, suggesting that glandular growth was due largely to cell proliferation. Although CA activity and volume changed considerably in embryos, the diameter of corpus allatum cells, as measured from enzymatically dissociated CA, remained surprisingly constant at 11–12 μm on days 32, 46 and 60 (49, 71 and 92% development). Ultrastructural observations confirmed the large size of cells in low-activity CA of 60-day-old embryos and also showed that these cells, like those in highly active CA of 46-day-old embryos, contained abundant cytoplasm, ribosomes, microtubules and mitochondria.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652343

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Eggs of the king crabLithodes santollawere exposed to cadmium (0.2 and 2 mg/1) and lead (0.16 and 1.6 mg/1) for 30 days. Concentrations used represented 1/10 and 1 of the respective LC50 values for zoea I of the studied species. Proportion of larvae hatching, meantime of eclosion and proportion of abnormal larvae were recorded. Abnormalities detected were hydropsy; small size; and atrophy of dorsal, rostral and telson spines, as well as atrophy of pereiopods and telson setae. The mean time of eclosion was inversely correlated to the incidence of structural abnormalities such as atrophy of spines and setae. These results suggest that both cadmium and lead caused an early eclosion of underdeveloped larvae, but while cadmium caused also a significant increase in hatching rate, lead produced a significant decrease in the proportion of larvae hatching.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652344

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The kinetic profiles of vitellin accumulation in the oyster ovary during oocyte growth and the effectsin vivoandin vitroof estradiol-17β (E2) on vitellin formation were examined in this study. The relative vitellin content measured by an enzyme-linked immunosorbent assay (ELISA) shows an apparent increase as the oocyte develops. Immunoblotting of the vitellin using anti-vitellin indicated that two main bands (179 and 110 kD), which begin to accumulate at an early stage of maturation, become pronounced during oocyte growth. Meanwhile, the major peak of the intact form of vitellin (530 kD) in gel filtration also enlarges with oocyte growth, supporting the results of immunoblot analysis and vitellin determination. E2treatmentin vivocauses significant increases in oocyte diameter and vitellin content in the female oyster. A similar trend was observed in ovarian tissues cultured in the presence of E2. It is concluded that E2is one of the major factors which control the vitellogenesis in the oyster and that the ovary is undoubtedly the site of synthesis of vitellin.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652345

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652346

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor