Chemical Nature and Mode of Stabilization of Egg-shell in Helicometra pulchella (Rudolphi, 1819) (Digenea: Opecoelidae)

The chemical nature and mode of stabilization of egg-shell protein in digenetic trematode Helicometra pulchella (Rudolphi, 1819) have been investigated using histochemical techniques. It was found that the egg-shell is stabilized by quinone-tanning together with dityrosine. Other structural proteins (elastin, collagen and keratin-like proteins), glycogen and acid mucopolysaccharides were absent in egg-shell. Tyrosine was present in vitelline cells and immature egg-shell indicating that the proteins involved in quinone-tanning were tyrosine rich and tyrosyl residues are modified to form dityrosine in mature egg-shell.     

Vitellocytes and vitellogenesis in cestodes in relation to embryonic development, egg production and life cycle

Vitellocytes have two important functions in cestode embryogenesis: (1) formation of hard egg-shell (e.g. Pseudophyllidea) or a delicate capsule (e.g. Cyclophyllidea), and (2) supplying nutritive reserves for the developing embryos. During evolution any of these two functions can be reduced or intensified in different taxa depending on the type of their embryonic development, degree of ovoviviparity and life cycles. Within the Cestoda, there are three monozoic taxa with only one set of genital organs: Amphilinidea, Gyrocotylidea and Caryophyllidea. In these monozoic taxa and some polyzoic groups with well developed vitellaria (e.g. Pseudophyllidea, Trypanorhyncha) a single oocyte [=germocyte] and a large number of vitellocytes (up to 30) are enclosed within a thick, hardened egg-shell, forming a type of eggs typical for the basic pattern of Neodermata. Only one type of egg-shell enclosures, the so-called 'heterogeneous shell-globule vesicle' is common for the above mentioned cestode taxa. Each membrane-bounded vesicle of mature vitellocytes contains numerous electron-dense shell globules embedded in a translucent matrix. In free-living Neoophora and Monogenea there are two types of vesicles with dense granules; the second is considered to be proteinaceous reserve material. Within the Cestoda, the numbers of vitellocytes per germocyte are reduced in those taxa forming eggs of the 'Cyclophyllidean-type' (e.g. Cyclophyllidea, Tetraphyllidea, Pseudophyllidea). This is particularly evident in Cyclophyllidea; for example, in vitellocytes of Hymenolepis diminuta (Hymenolepididae) there are numerous vitelline granules of homogeneously electron-dense material; in Catenotaenia pusilla (Catenotaeniidae) there are three large, homogenous vitelline vesicles, while in Inermicapsifer madagascariensis (Anoplocephalidae) there is only one large vitelline vesicle, containing homogeneously electron-dense material, which occupies most of the vitelline cell volume. In this respect the Tetraphyllidea and Proteocephalidea, in forming eggs that lack a hard egg-shell, hold an intermediate position. A comparison of interrelationships which exist among types of vitellocytes, vitellogenesis, types of embryonic development, ovoviviparity and life cycles indicates parallelisms and analogies in adaptation to the parasitic way of life in different groups of cestodes. Knowledge on cestode vitellogenesis may also have an important applied aspect. Vitellocytes, due to their high metabolic rate, represent a very sensitive target for analysing effect of anthelminthic drugs upon the egg formation (ovicidal effects); rapid degeneration of vitellocytes is usually accompanied by a cessation of egg production.     

The egg-shell of Drosophila melanogaster III. Covalent crosslinking of the chorion proteins involves endogenous hydrogen peroxide

Utilizing two cytochemical methods, namely, diaminobenzidine for the assay of peroxidases and cerium(III) chloride for the localization of hydrogen peroxide it was found that the enzyme exists in two out of the five egg-shell layers: the innermost choronic layer and the endochorion. In addition, hydrogen peroxide which acts as a substrate for the enzyme in vitro enabling the formation of covalent bonding between the egg-shell proteins, was found to be produced at the follicle cell plasma membrane during the last stage of oogenesis. It is concluded that hydrogen peroxide is an endogenous, programmed product of the follicle cells, responsible for the action of peroxidase in order to oxidize the tyrosyl residues producing di-tyrosine and tri-tyrosine bonds between the chorion polypeptides.     

The structure of the egg-shell of gLobodera rostochiensis (Nematoda: Tylenchida)

Perry R. N., Wharton D. A. and Clarke A. J. 1982. The structure of the egg-shell of Globodera rostochiensis (Nematoda: Tyienchida). International Journal for Parasitology12: 481–485. The ultrastructure and histochemistry of the egg-shell of Globodera rostochiensis are described. The eggshell consists of an outer vitelline layer, a chitinous layer and an inner lipid layer. The vitelline layer is not unit membrane-like and has strands of particulate material attached to its outer surface. The chitinous layer is made up of fibres consisting of a chitin microfibril core, surrounded by a protein coat. The lipid layer contains lipoprotein membranes. These vary in number, the most commonly observed pattern being two or three membranes loosely associated with the inner surface of the egg-shell.     

The chemical nature of the egg-shell of helminths. I. Absence of quinone tanning in the egg-shell of the liver fluke, Fasciola hepatica

Ramalingam K. 1973. The chemical nature of the egg-shell of helminths—I. Absence of quinone tanning in the egg-shell of the liver fluke, Fasciola hepatica. International Journal for Parasitology, 3: 67–75. The mode of stabilization of the egg-shell protein of Fasciola hepatica has been studied. It was observed that quinone tanning is absent in the egg-shell. Unlike quinone-tanned proteins, egg-shell proteins show auto-fluorescence. Investigation on the fluorescent compounds present in the egg-shell protein shows the presence of di-tyrosine. In addition to the presence of di-tyrosine, the egg-shell protein is stabilized by —S—S—bonding. The resistant properties of the egg-shell of F. hepatica are attributed to the presence of the above types of cross-links.     

The structure of the egg-shell of Porrocaecum ensicaudatum (Nematoda: Ascaridida)

Wharton D. A. 1979. The structure of the egg-shell of Porrocaecum enslcaudatum (Nematoda: Ascaridida). International Journal for Parasltology9: 127–131. The egg-shell of Porrocaecum ensicaudatum is oval with an opercular plug at either end. The shell consists of three layers: an inner lipid layer, a middle chitinous layer and an outer vitelline layer. The vitelline layer has strands of particulate material attached to its outer surface. The chitinous layer consists of 8.5 nrn fibrils which are made up of a chitin microfibril core surrounded by a protein coat. The fibrils are oriented randomly or in parallel, there being no indication of helicoidal architecture.The chitinous layer varies in thickness to form a pattern of interconnecting ridges on the surface of the egg. This pattern presumably increases the shell's structural strength.     

Selective adsorption and recovery of precious metal ions using protein-rich biomass as efficient adsorbents

Various types of protein-rich biomass were examined as selective and environment-friendly adsorbents for precious metal ions. In the presence of base metal ions, Au³⁺, Pd²⁺ and Pt⁴⁺ ions were selectively adsorbed to samples of protein-rich biomass. Among the biomass samples tested, egg-shell membrane exhibited the highest adsorption ability and had high selectivity for Au, Pd and Pt ions. The maximum adsorption amount of Au, Pd and Pt ions to egg-shell membrane was approximately 250, 110 and 50 mg/g, respectively, in the presence of 0.1 M HCl. Microscopic observations and metal-ion desorption studies suggested that the precious metal ions were adsorbed and a portion of them was reduced to form metal nanoparticles on the egg-shell membrane, leading to high adsorption ratios. Investigations using glycoproteins indicated the importance of sugar chains in the adsorption of Au ions to the egg-shell membrane. Successful recovery of Au, Pd and Pt ions from industrial waste solutions was also demonstrated using egg-shell membrane. Biomass sheets (1 mm thick) made from egg-shell membrane also exhibited adsorption abilities for precious metal ions.     

浙江天台晚白垩世伤齿龙(troodontids)蛋化石的新发现

浙江天台上白垩统赤城山组中发掘出属伤齿龙类的棱柱形蛋化石。研究认为,棱柱形蛋从伤齿龙类恐龙中产出就具有较高刚度的蛋壳,可直接插入松软的泥沙里,明显区别于其他大多数恐龙及现代爬行类所产的韧性蛋壳蛋,韧性蛋壳的恐龙蛋往往因重力作用产生变形而呈扁球形和扁椭球形。伤齿龙类的棱柱形蛋的刚性蛋壳很接近现代鸟蛋的蛋壳,暗示伤齿龙类恐龙生殖系统在蛋壳形成方面与现代鸟类有一定相似性。同时,伤齿龙类的棱柱形蛋或多或少地以向外倾斜的形式排布,反映出伤齿龙类恐龙产卵时可能面向巢穴外,是一种对生存环境的适应行为。     

The structure and formation of the egg-shell of Syphacia obvelata Rudolphi (Nematoda: Oxyurida)

The egg of Syphacia obvelata is a flattened elipsoid. The egg-shell consists of 5 layers: external uterine layer, internal uterine layer, vitelline layer, chitinous layer and lipid layer. An operculum is present at one pole of the egg. The opercular groove consists of a break in the uterine layers and the modification of the chitinous layer by the deposition of lipoprotein material. On the curved side of the egg the uterine layers are modified to form alternate ridges and depressions. Discrete spaces are present in the internal uterine layer between the ridges. These are open to the exterior via pores in the external uterine layer. The structure of the uterine layers is quite different on the flattened side of the egg. The morphology of the reproductive system and the formation of the egg-shell is described. It is suggested that the complex structure of the uterine layers of oxyurids forms by a self-assembly process.     

Ultrastructural studies on the reproductive system of Gyrocotylidea and Amphilinidea (Cestoda)

Summary The vitellaria, vitellocyte development and vitelloduct of Gyrocotyle urna are described at the ultrastructural level. Vitellar follicles are surrounded by an extracellular lamina; vitellocytes and the periphery of the follicles are enclosed by a cytoplasmic sheath. Immature vitellocytes are spherical and show a high nucleus-to-plasma ratio. During maturation of vitellocytes their cytoplasmic content increases and numerous dictyosomes, endoplasmic reticulum, egg-shell granules and lipid droplets are formed. Lipid droplets and egg-shell granules fill most of the volume of mature vitellocytes. The vitelloduct is ciliated and shows intraepithelial nuclei and intraluminal folds. No cell borders have been found within the vitelloduct. Vitellogenesis and the vitelloduct morphology of Gyrocotyle are compared with those of other parasitic Plathelminthes.Abbreviations I immature vitellocyte - II maturing vitellocyte - III mature vitellocyte - Az cytoplasmic sheath surrounding the vitellocytes and the follicle - bb basal body - ci cilia of the vitelloduct - ld lipid droplet - mi mitochondrium - nu nucleus - rer rough endoplasmic reticulum - sg egg-shell granulum - ve vesicles     

Polyphenol oxidase and scleroprotein/melanin pigments of Isoparorchis hypselobagri.

The polyphenol oxidase activity of Isoparorchis hypselobagri was estimated biochemically and was believed to be associated with egg-shell formation in the parasite. The eggs gave positive tests to color reaction of scleroprotein/melanin.     

The egg-shell of Drosophila melanogaster. VI, Structural analysis of the wax layer in laid eggs

Utilizing freeze-fracturing conventional electron microscopy and scanning electron microscopy methods, a wax layer was identified, sealing the oocyte of Drosophila melanogaster. In mature egg-shells wax forms a hydrophobic layer surrounding the oocyte and lying between, and in very close contact with the vitelline membrane (interiorly) and the crystalline intermediate chorionic layer (exteriorly). In cross-fractured views it is less than 50 A thick whereas in longitudinal fracturing it reveals smooth fracture faces of a multilayered material in the form of hydrophobic areas or plaques (0.5-1 microns in diameter) which are partially overlapping and highly compressed between the vitelline membrane and the innermost chorionic layer. The evidence for this layer being a wax are the facts that a) it is not preserved in conventional fat-extracting electron microscopy methods, b) it directs laterally the fracture planes during freeze-fracturing and reveals smooth fracture faces. Analysis of the structural features of wax in mature egg-shell in various species of Drosophilidae have shown that the wax layer exhibits indistinguishable (among the species) hydrophobic plaques, which have the same size and thickness with Drosophila melanogaster. These data provide structural evidence explaining the physiological resistance of the insect eggs studied, against water loss or water uptake, whenever they are laid on substrates with extreme environmental conditions. In addition, the data demonstrate how an extracellular substance can be organized to perform that function.     

The egg bundles of the monogenean Dionchus remorae and their attachment to the gills of the remora, Echeneis naucrates

Gills of three remoras, Echeneis naucrates L., from Heron Island, Queensland, Australia had few adults but many attached egg bundles of the monogenean, Dionchus remorae. Studies of fresh, and preserved and cleared, primary gill lamellae bearing egg bundles and investigations with scanning electron microscopy and serial wax sections reveal proliferated host epithelium surrounding and embedding part of a loop of egg-shell material to which eggs are tethered, but eggs in each bundle hang free of gill tissue. This hyperplasia appears to anchor egg bundles to the host's gills. However, hyperplasia will take time to develop and cannot play a part in tethering newly laid egg bundles. Possible advantages to the parasite by attaching eggs to the gills of its host include improved oxygenation of the eggs, and a reduced risk of egg predation. Egg attachment by D. remorae to their remora hosts seems well adapted to successful larval invasion of fish which exhibit phoresy.     

Structural proteins in the egg-shell of the oriental garden cricket, Gryllus mitratus

1. The egg-shell of the oriental garden cricket, Gryllus mitratus, contained at least two different types of structural protein in an approximate ratio of 5:1. The major fraction was extracted in a solvent containing dithiothreitol, EDTA and 8m-urea, and was purified to apparent homogeneity as judged by free-boundary electrophoresis and ultracentrifugation. This was designated SH-fraction and its S-carboxymethyl derivative (CM-fraction) was also prepared. The minor fraction, insoluble in the solvent, was designated insoluble residue. 2. The major fraction was a phosphoprotein, rich in serine (29.8mol% of the total amino acids) and phosphate (nearly equimolar to serine), and O-phosphoserine was identified in its partial acid hydrolysate. The content of cystine was rather low (0.9mol%) in spite of the importance of this amino acid residue in the native form of the protein. The insoluble residue contained only a small amount of phosphorus, and its amino acid composition was clearly different from the major fraction. 3. CM-fraction, a fibrous protein with an average molecular weight of 57500, behaved as a typical polyanion owing to the high content of phosphate. SH-fraction and CM-fraction were precipitable from their aqueous solutions by the addition of bivalent metal cations, and the precipitation of CM-fraction by Ca(2+) and Mg(2+) was studied in detail. 4. When SH-fraction was exposed to air, intermolecular disulphide linkages were formed, yielding a net-like gel that changed its volume with changes in Ca(2+), Mg(2+) and Na(+). 5. The possible role of this protein fraction in maintaining the integrity of the egg-shell, and a comparison of its composition and properties with other egg-shell proteins and other phosphoproteins, are discussed.     

日本鳗鲡精卵的超微结构以及受精过程观察

通过扫描电镜和透射电镜对经人工催产获得的日本鳗鲡(Anguilla japonica)精子、卵膜的超微结构以及受精过程进行了观察。实验观察到,除一般硬骨鱼类的精子特性外,日本鳗鲡精子有其独特的结构。精子头部为不规则的梨形,有背腹面之分。一个巨大的球形线粒体位于头部顶端。精子中段向后伸出一支根,支根位于袖套腔外精子的背侧,前端向精子头部线粒体方向延伸,支根的微管结构为"8+2"结构,并在精子入卵过程中起到切断鞭毛的作用。精子的尾部由鞭毛和鞭毛末端的结组成。鞭毛横切面呈圆形,无侧鳍,鞭毛微管结构为"9+0"结构。受精卵的整个表面密布着无规律延伸的脊、脊包围形成的窝和窝中的孔所组成的脊孔复合体,但无典型特征的受精孔。受精卵超薄切片观察发现,日本鳗鲡卵膜分为外层壳膜和内层卵黄膜。壳膜与卵黄膜间为卵周隙。壳膜只观察到放射带,未见透明带。放射带可分为三个亚层:最外层为脊孔复合体的脊,中间层为皱纹层,最内层为致密的平滑层。脊孔复合体的孔横穿整个放射带,在放射带内层形成一个乳突状结构。日本鳗鲡的卵膜不仅具有保护卵子的作用,而且还参与了受精。实验还通过扫描电镜观察了日本鳗鲡精子的入卵过程。观察结果认为:日本鳗鲡精子入卵过程可分为卵膜对精子的吸引、精子对卵膜的锚定、精核的进入和孔封闭等4个阶段。但由于研究只观察到受精过程中日本鳗鲡精子和卵膜的形态变化,因此对精子穿过卵膜的方式和特征等尚需做进一步的研究。整个受精过程为1min30s左右。此外,研究还探讨了日本鳗鲡精子结构的特殊性和受精过程的特殊性,为进一步突破日本鳗鲡人工育苗技术提供了理论依据。       

Morphology of dry-resistant eggs in parthenogenetic Heterocypris incongruens (Ramdohr, 1808) (Ostracoda, Crustacea)

It has been known that many organisms evolved to survive in temporary or ephemeral inland waters. Many of them have dry-resistant eggs against desiccation. The structural feature of egg shell is important because only this will ensure to survive the dry period. Structural features of egg shell in the parthenogenetic Heterocypris incongruens (Ramdohr, 1808) was investigated by scanning electron microscope. Results showed that egg shell structure consists of two distinct layers; an outer layer with holes or alveoli and an inner layer consisting of two dense sublayers. Also, structural similarities in egg-shell of H. incongruens and some other crustaceans which combat desiccation problem will be discussed.     

The egg-shell of Labiostrongylus eugenii (nematoda,strongyloidea): Structure and function

The egg-shell of Labio-strongylus eugenii consists of three layers; an outer vitelline layer, a middle chitinous layer and an inner lipid layer. The presence of chitin and protein in the middle layer was demonstrated by the use of chitinase and differential staining. The lipid layer was found to be made up of two layers, the innermost having large globules on its outer face. The shell was found to be permeable to liquid water, as demonstrated by the penetration of vital dyes. Eggs were able to develop normally with little or no loss of volume during periods of moisture stress when either osmotic or suction pressures were applied. The survival of eggs, as measured by hatching success, over periods of time at a range of saturation deficits and osmotic pressures was measured, and compared with known survival rates for other nematode species. The problems of working with nematode species whose life cycles have not been established are discussed. Possible survival strategies for Australian strongylids during periods of moisture stress are outlined.     

Non-invasive method of sex identification of crane chicks by the DNA from capillary vessels of allantois

The non-invasive method of determining the sex of chicks after hatching based on the DNA isolated from capillary vessels of allantois of the egg-shell membranes was demonstrated on four crane species (Gruinae, Aves), which were bred in the Crane Breeding Centre of the Oka Nature Reserve in 2009–2012. Using the EE0.6 molecular marker of sex, the gender of 26 Siberian (Grus leucogeranus), 15 Red-crowned (G. japonensis), 4 Common (G. grus) and 1 Demoiselle (Anthropoides virgo) crane chicks was identified. This method can be recommended for determining the sex of chicks and the ratio of sexes in cranes that reproduce both in captivity and natural populations.     

人工授精平角涡虫早期胚胎和幼虫的扫描电镜观察

为探明平角涡虫(Planocera reticulata)胚胎发育规律,采用人工授精方法,获得不同发育阶段的无卵外胶膜胚胎,并运用扫描电镜技术,观察了受精卵早期胚胎发育和幼虫发育.结果表明,从第3次卵裂开始表现出螺旋式卵裂的特征.在囊胚时期和原肠时期在动物极顶端有几个卵裂球向内下陷形成一凹陷.浮游幼虫期的幼虫利用体表纤...