Histochemical observation of the cortical zone of oocyte of Indian wall lizard, Hemidactylus flaviviridis (Rüppel).

The cortical zone of oocytes, which lies just below the follicular epithelium appears in the early stages of development, but reaches its fullest growth in vitellogenic oocytes. In the present studies it was found that the cortical zone of Hemidactylus flaviviridis consists of proteins, lipoproteins, carbohydrates, fatty yolk, RNA and little amount of DNA in mature oocytes along with mitochondria and Golgi bodies. In the early oocyte, this zone is fine granular in nature, but during the yolky stages of oocyte, it becomes filled by the vacuolar structure, which shows in it's the presence of fatty and compound yolk. The L1 and L2 types of lipid globules are also observed in the cortical zone during vitellogenic oocyte.     

Ultrastructural characteristics of the follicle cell-oocyte interface in the oogenesis of Ceratophrys cranwelli

In this work we carried out an ultrastructural analysis of the cell interface between oocyte and follicle cells during the oogenesis of the amphibian Ceratophrys cranwelli, which revealed a complex cell-cell interaction. In the early previtellogenic follicles, the plasma membrane of the follicle cells lies in close contact with the plasma membrane of the oocyte, with no interface between them. In the mid-previtellogenic follicles the follicle cells became more active and their cytoplasm has vesicles containing granular material. Their apical surface projects cytoplasmic processes (macrovilli) that contact the oocyte, forming gap junctions. The oocyte surface begins to develop microvilli. At the interface both processes delimit lacunae containing granular material. The oocyte surface has endocytic vesicles that incorporate this material, forming cortical vesicles that are peripherally arranged. In the late previtellogenic follicle the interface contains fibrillar material from which the vitelline envelope will originate. During the vitellogenic period, there is an increase in the number and length of the micro- and macrovilli, which become regularly arranged inside fibrillar tunnels. At this time the oocyte surface exhibits deep crypts where the macrovilli enter, thus increasing the follicle cell-oocyte junctions. In addition, the oocyte displays coated pits and vesicles evidencing an intense endocytic activity. At the interface of the fully grown oocyte the fibrillar network of the vitelline envelope can be seen. The compact zone contains a fibrillar electron-dense material that fills the spaces previously occupied by the now-retracted microvilli. The macrovilli are still in contact with the surface of the oocyte, forming gap junctions.     

The origin and nature of cortical vacuoles in the Amphioxus egg

Summary The origin and nature of cortical vacuoles have been studied in the Amphioxus egg. They originate adjacent to the plasma membrane of the growing oocyte and are finally arranged in the cortical ooplasm of the egg. The cortical vacuoles do not contain any material demonstrable with cytochemical techniques for lipids, carbohydrates, proteins, or nucleic acids. The cortical vacuoles of the Amphioxus egg are comparable to those of the fish egg.     

Studies on biosynthesis of sterol/steroid from dopamine

The in vitro incubation of the anterior kidney, posterior kidney, liver, brain, spleen and ovarian tissue homogenates of the fish Nandus nandus with DOPA has been studied with regards to cholesterol production. All tissues except liver give highly positive results. There is also an increase in the neutral 17-ketosteroids. Injections of Dopamine also produce similar results. It is then concluded that DOPA and Dopamine are important precursors of cholesterol in the fish tissues.     

Comparative histomorphology of the Mauthner cells in some freshwater teleosts.

The histomorphological observations are made on the Mauthner cells in eight species of teleosts belonging to six different families. The cells are better developed in Channa punctatus, Heteropneustes fossilis, Labeo rohita, Danio, malabaricus and Puntius ticto. They are symmetrically situated in Nandus nandus and are found to be absent in Mastocembalus armatus. Their position, shape and size vary in different species. The axon cap is well developed in Channa punctatus, Heteropneustes fossilis and carps. The cell body sends lateral and ventral dendrites besides several small dendrites. The lateral dendrite emerges through the axon cap, turns dorsolateral and becomes myelinated to form Mauthner axon. The Mauthner axon extends in the spinal region upto the caudal peduncle and forms synapses with the spinal motoneurons of the front column. There are numerous synapses and end bulbs from the vestibular fibres and VIIIth nerve distributed on the perikaryan of the Mauthner cell body. It is suggested that the Mauthner cells are comparatively well developed in those species in which the tail fin is better utilized for swimming.     

Electron microscopic study of the cortical reaction of an ophiuroid echinoderm.

The egg coats of an ophiuroid echinoderm (Ophiopholis aculeata) are described by electron microscopy before and after fertilization. The unfertilized egg is closely invested by a vitelline coat about 40 A thick, and the peripheral cytoplasm is crowded with cortical granules five or six deep. During the cortical reaction, which rapidly follows insemination, exocytosis of cortical granules takes place. Some of the cortical granule material is evidently added to the vitelline coat to form a composite structure, the fertilization envelope, which is made up of a 400 A thick middle layer separating inner and outer dense layers, each about 50 A thick. The elevation of the fertilization envelope from the egg surface creates a perivitelline space in which the hyaline layer soon forms. The hyaline layer is about 2 micron thick, finely granular, and apparently derived from cortical granule material. The extracellular layers of the early developmental stages of ophiuroids and echinoids are quite similar in comparison to those of asteroids; this finding helps support Hyman's argument that the ophiuroids are more closely related to the echinoids than to the asteroids.     

The role of an epithelial occlusion zone in the termination of vitellogenesis in Hyalophora cecropia ovarian follicles.

At the end of vitellogenesis, the follicular epithelium of Hyalophora cecropia follicles forms an occlusion zone that can halt the access of horseradish peroxidase to the oocyte surface in living follicles, and of lanthanum nitrate in fixed preparations. It is proposed that this barrier is responsible for terminating the uptake of blood proteins by the oocyte. Although three types of interfollicle cell junctions were observed, only tight junctions appeared to be responsible for the observed impermeability. Sodium dodecyl sulfate-acrylamide gel electrophoresis of [³H]leucinelabeled proteins revealed no change in the protein synthetic pattern during the transformation of follicles from vitellogenesis to the subsequent terminal growth period; in addition, pinocytotic figures continued to be formed in the postvitellogenic oocyte. These findings suggest that the epithelial secretion which the oocyte is known to deposit in yolk during vitellogenesis continues to be sequestered in the absence of blood proteins after occlusion zone formation. The proposal explains the origin of a layer of membrane-limited bodies which occupy the cortex of the oocyte in mature silkworm eggs, and which differ markedly in appearance from the protein yolk spheres assembled earlier.     

Histochemical mapping of certain enzymes in few fresh water teleosts. I. Acid phosphatase.

A detailed investigation of the distribution pattern of acid phosphatase in the different parts of alimentary canal and associated glands of Colisa fasciatus, Macrognathus aculeatus, Notopterus notopterus and Nandus nandus has been made. Though this enzyme shows its hydrolytic activity in all the parts of the digestive system yet its intense activity has been noted in the intestine, pyloric caeca, liver and pancreas of all the 4 fishes. Mucosal and submucosal layers of all the parts of the alimentary canal are the main seat of localization of this enzyme.     

不同发育时期哲罗鱼卵黄的超微结构

应用透射电镜观察了不同发育时期哲罗鱼(Hucho taimen)卵黄的超微结构.根据哲罗鱼卵黄物质在卵母细胞中的加工合成、积累以及卵母细胞中参与卵黄颗粒形成的细胞器的变化,可将该鱼卵黄发生分为4个特征时期,即卵黄发生前期、卵黄泡期、卵黄积累期和卵黄积累完成期.卵黄发生前期是指卵母细胞发育过程中的卵黄物质开始积累前的时期,此时期核仁不断分裂,出现线粒体云和早期的滤泡细胞层、基层和鞘细胞层;卵黄泡期特点主要是细胞器不断变化产生卵黄泡和皮层泡;卵黄积累期的滤泡膜由内向外依次为放射带、颗粒细胞层、基层和鞘细胞层,此时外源性卵黄前体物质不断经过血液汇集于鞘细胞层,后经微胞饮作用穿过胶原纤维组成的基层,经过多泡体作用转运至颗粒细胞内,在细胞内经过加工和修饰形成小的卵黄蛋白颗粒,卵黄蛋白颗粒经微胞饮穿过放射带进入卵母细胞边缘形成的空泡中,不断积累形成卵黄球;进入卵黄积累完成期,卵黄球体积变大,向细胞中心聚集,填满大部分卵母细胞,卵黄积累完毕.     

Ultrastructure of Spermiogenesis and the Spermatozoon of Mathevotaenia herpestis(Cestoda), Intestinal Parasite of Atelerix albiventrisin Senegal

Spermiogenesis in M. herpestisbegins with the formation of a differentiation zone which contains two centrioles associated with an electron–dense, finely granular material. This granular material very quickly becomes striated, a median cytoplasmic extension forms, one of the centrioles becomes laterally oriented in a cytoplasmic bud and the other gives rise to a flagellum. After the migration of the nucleus, a helicoidal crested–like body forms, then the old spermatid separates from the residual cytoplasm. The mature M. herpestisspermatozoon exhibits an apical cone of electron–dense material, a crested–like body and cortical microtubules which are electron–dense centred and spiralized except at their posterior extremity where they are parallel to the spermatozoon axis. The axoneme is of the 9 + ‘1’ pattern. It reaches the posterior extremity of the gamete where the cytoplasm is very electron–dense. The presence of centrioles flanked by ‘striated roots’ has never, to our knowledge, been reported in a platyhelminth. Likewise, a nucleus with an annular cross–section and unevenly distributed electron–dense peri–axonemal material has never been described in a cestod.     

Elektronenmikroskopische und histotopochemische Untersuchungen über Struktur und Bildung der Zona pellucida menschlicher Eizellen

Summary Examined with the electron microscope the zona pellucida of human oocytes represents an extracellular, amorphous substance with slight differences in density. There is a greater consolidation in the inner parts and a drecrease of density towards the periphery. The plasmalemma of the oocyte forms a large number of slender projections (microvilli) penetrating the homogeneous groundsubstance of the zona pellucida. Plasmatic elongations of the follicle cells extending towards the oocyte traverse the zona in oblique or tangential directions and end at the oocytes surface forming a contact relationship (partially characteristic desmosomes). No syncytial communication between ooplasma and follicle cell cytoplasm can be demonstrated. The follicle cell processes contain finely granular material. The cytoplasm of numerous follicle cells facing the oocyte containes branched deposits of compact and dense substances with a granular ground-structure. Histochemically these substances react like anionic polysaccharides. Alternating zones of the follicle cell membranes show vaguely outlined lesser density. Intra- and extraplasmatic granular concentrations in these areas probably represent secretion processes. Acid mucopolysaccharides are the primary substrat of the zona pellucida whose deposition begins almost in the state of a bilaminar secondary follicle. Possibly this material is incorporated in the definite complex of glycoproteins by means of loss or binding of the acid groups (uronic acids, ester sulphates). PAS-positive inclusions about 1,0 to 1,5 in diameter lying in the cytoplasm of the follicle cells immediately adjacent to the plasmalemma or in open communication with the perivitelline space, represent probably paraplasmatic components for the building of the zona. Studied with the electron microscope these inclusions resemble strikingly the amorphous and cloudy ground substance of the zona pellucida. Stratified structures which would embody an appositional growth of the zona have not been demonstrated.     

The testicular cycle of a percoid teleost--Nandus nandus (Ham.).

Small paired testes of Nandus nandus are situated posteriorly in the body cavity. They open posteriorly in a common sperm duct. A urinogenital sinus is present. Each testis consists of a large number of seminiferous tubules extending from the periphery towards the centre. The seminiferous tubules are separated from each other by a layer of interstitial tissue. 6 different stages of spermatogenesis are recognised. On the basis of morphological and histological changes in the testes during different months of the year, the reproduvtice cycle has been divided into post-spawning (October to December), pre-spawning (January to March) and spawning (April to August) periods. The monthly volume of testes is in direct correlation with the monthly changes in water temperature. Statistical observations indicate that the process of spermatogenesis is very active during pre-spawning period. The relative number of spermatozoa is maximum in July (69.89%), suddenly decreases in August (54.28%) and continues to decrease upto October (49.66%) indicating the maximum spawning in July and August.     

Vitellogenesis in decapod cephalopods: evolution of oocytes and follicular cells during genital maturation]

The investigation was carried out on two Cephalopods: Sepia officinalis and Loligo vulgaris. During previtellogenesis, the follicle cells (F.C.), originally arranged at the periphery of the oocyte, form strands, through the axis of which runs a blood vessel. The follicle strands then make their way down into the ooplasm. They end up by occuping the greater part of the volume of the oocyte. At this stage, despite their increase in size, the F.C. do not undergo conspicuous cytological transformations. In the ooplasm, excepting a few specialized structures (annulate lamellae), the organites display no notable differentiation. The onset of vitellogenesis is characterized by the appearance in the ooplasm of elements paracrystalline in structure. A zona pellucida appears between the oocyte and the F.C., and it is at the point that yolk of a permanent type begins to accumulate. Concurrently the F.C. undergo characteristic reorganization: hypertrophy of the nucleolar mass, multiplication of granular reticulum cisternae, increase both in the number and the size of the Golgi complexes. The saccules of the Golgi complex process a material rich in carbohydrate protein bearing the same cytochemical characteristics as the yolk. In the basal zone of the F.C., deep invaginations of the wall of blood vessels scallop the cytoplasm. F.C. look like "podocyte cells". Immunofluorescence study suggest there is no immunological identity between blood and yolk proteins. The formation of chorion is accompanied by a fresh transformation of the F.C.: the granular endoplasmic reticulum breaks up into rounded cisternae containing a dense material. Concurrently the morphology of the Golgi complex is modified. The earliest chorion elements accumulate, firstly in the forme of isolated lobules within the zona pellucida. They then fuse to make a continous layer bounding the microvilli of the F.C. These cells eventually enter into a phase of degeneration and disappear, whilst the oocyte is set free by dehiscence into coelomic cavity.     

Oogenesis in the leech Glossiphonia heteroclita (Annelida, Hirudinea, Glossiphoniidae) II. Vitellogenesis, follicle cell structure and egg shell formation

By the end of previtellogenesis, the oocytes of Glossiphonia heteroclita gradually protrude into the ovary cavity. As a result they lose contact with the ovary cord (which begins to degenerate) and float freely within the hemocoelomic fluid. The oocyte's ooplasm is rich in numerous well-developed Golgi complexes showing high secretory activity, normal and transforming mitochondria, cisternae of rER and vast amounts of ribosomes. The transforming mitochondria become small lipid droplets as vitellogenesis progresses. The oolemma forms microvilli, numerous coated pits and vesicles occur at the base of the microvilli, and the first yolk spheres appear in the peripheral ooplasm. A mixed mechanism of vitellogenesis is suggested. The eggs are covered by a thin vitelline envelope with microvilli projecting through it. The envelope is formed by the oocyte. The vitelline envelope is produced by exocytosis of vesicles containing two kinds of material, one of which is electron-dense and seems not to participate in envelope formation. The cortical ooplasm of fully grown oocytes contains many cytoskeletal elements (F-actin) and numerous membrane-bound vesicles filled with stratified content. Those vesicles probably are cortical granules. The follicle cells surrounding growing oocytes have the following features: (1) they do not lie on a basal lamina; (2) their plasma membrane folds deeply, forming invaginations which eventually seem to form channels throughout their cytoplasm; (3) the plasma membrane facing the ovary lumen is lined with a layer of dense material; and (4) the plasma membrane facing the oocyte forms thin projections which intermingle with the oocyte microvilli. In late oogenesis, the follicle cells detach from the oocytes and degenerate in the ovary lumen.     

Asymmetry in the cytoplasm of oocytes of largescale yellowfish Labeobarbus marequensis Smith 1841 (Teleostei: Cypriniformes: Cyprinidae)

The ovaries of the largescale yellowfish, Labeobarbus marequensis (Teleostei: Cypriniformes: Cyprinidae), are made up of the germinal epithelium, nests of late chromatin nucleolus stage oocytes, and ovarian follicles. Each follicle is composed of a single oocyte, which is surrounded by somatic follicular cells and a basal lamina covered by thecal cells. We describe polarization and ultrastructure of oocytes during the primary growth stage. The oocyte nucleus contains lampbrush chromosomes, nuclear bodies and fibrillar material in which multiple nucleoli arise. Nuage aggregations composed of material of a nuclear origin are present in the perinuclear cytoplasm. The Balbiani body (Bb) contains aggregations of nuage, rough endoplasmic reticulum, individual mitochondria and complexes of mitochondria with nuage (cement). Some mitochondria in the Bb come into close contact with endoplasmic reticulum cisternae and vesicles that contain granular material. At the start of primary growth, the Bb is present in the cytoplasm close to the nucleus. Next, it expands towards the oocyte plasma membrane. In these oocytes, a spherical structure, the so-called yolk nucleus, arises in the Bb. It consists of granular nuage in which mitochondria and vesicles containing granular material are immersed. Later, the Bb becomes fragmented and a fully grown yolk nucleus is present in the vegetal region. It contains numerous threads composed of granular nuage, mitochondria, lysosome-like organelles and autophagosomes. We discuss the formation of autophagosomes in the cytoplasm of primary growth oocytes. During the final step of primary growth, the cortical alveoli arise in the cytoplasm and are distributed evenly. The eggshell is deposited on the external surface of the oocyte plasma membrane and is made up of two egg envelopes that are pierced by numerous pore canals. The external egg envelope is covered in protuberances. During primary growth no lipid droplets are synthesized or stored in the oocytes.     

Studies on the ovotestis of the slug Agriolimax reticulatus (Müller)

Summary The follicle cells, nurse cells and germinal epithelia, which are closely associated with the oocyte of Agriolimax reticulatus (Müller) during its development in the ovotestis, have been studied using light and electron microscopy. The various secretory, digestive and phagocytic activities of these cells have also been investigated using electron cytochemical tests for oxidisable polysaccharide, acid phosphatase and electron-opaque tracer molecules. The oocyte lies initially between the germinal epithelia and a layer of nurse cells but, as oocyte vitellogenesis proceeds, it becomes encapsulated by a layer of follicle cells. Both the follicle and the nurse cells are active in secretion and digestion and contain Golgi apparatus, granular endoplasmic reticulum and acid phosphatase-rich digestive vacuoles. The significance of these activities is discussed in relation to oocyte vitellogenesis, secondary envelope formation and the digestion and recycling of cellular material.     

Ultrastructural studies of differentiation in the oocyte of the polyclad turbellarian,Prostheceraeus floridanus

Oocyte differentiation in the polyclad turbellarian Prostheceraeus floridanus has been examined to determine the nature of oogenesis in a primitive spiralian. The process has been divided into five stages. (1) The early oocyte: This stage is characterized by a large germinal vesicle surrounded by dense granular material associated with the nuclear pores and with mitochondria. (2) The vesicle stage: The endoplasmic reticulum is organized into sheets which often contain dense particles. Vesicles are found in clusters in the cytoplasm, some of which are revealed to be lysosomes by treatment with the Gomori acid phosphatase medium. (3) Cortical granule formation: Cortical granules are formed by the fusion of filled Golgi vasuoles which have been released from the Golgi saccules. The association between the endoplasmic reticulum and Golgi suggests that protein is synthesized in the ER and transferred to the Golgi where polysaccharides are added to form nascent cortical granules. (4) Yolk synthesis: After a large number of cortical granules are synthesized, yolk bodies appear. They originate as small membrane-bound vesicles containing flocculent material which subsequently increase in size and become more compact. Connections between the forming yolk bodies and the endoplasmic reticulum indicate that yolk synthesis occurs in the ER. (5) Mature egg: In the final stage, the cortical granules move to the periphery and yolk platelets and glycogen fill the egg. At no time is there any evidence of uptake of macromolecules at the oocyte surface. Except for occasional desmosomes between early oocytes, no membrane specialization or cell associations are seen throughout oogenesis. Each oocyte develops as an independent entity, a conclusion supported by the lack of an organized ovary.     

Distribution of prosome proteins and their relationship with the cytoskeleton in oogenesis of Xenopus laevis

The presence of prosome proteins (p25K and p27K) was shown and their distribution was studied in oogenesis of Xenopus laevis using immunoblotting and immunofluorescence. These proteins form numerous granular clusters of variable size all over the cell. At previteilogenic stages, the prosome antibodies homogeneously stain the oocyte nucleus and the evenly distributed relatively large clusters in the cytoplasm. As the oocyte grows, the pattern of distribution of the prosome proteins undergoes changes: animal-vegetal and cortical gradients appear in the cytoplasm. In the course of oocyte maturation the size of clusters diminishes. Artificial activation of the egg leads to a dorso-ventral gradient in distribution of the prosome proteins. In this way, specific localization of prosome proteins is first visualized during formation of the dorso-ventral polarity. Co-localization of prosome proteins and actin and myosin was found in the oocyte by double staining. Small clusters of prosomes dispersed in the cytoplasm acquire capability of movement (after artificial activation) due, in all likelihood, to persisting connection with the acto-myosin complex of the egg. © 1994 Wiley-Liss, Inc.