First study of vitellogenesis of the broad fish tapeworm Diphyllobothrium latum (Cestoda,Diphyllobothriidea), a human parasite with extreme fecundity

In the present study, the process of vitellogenesis of one of the most prolific organisms, the broad tapeworm, Diphyllobothrium latum, the causative agent of human diphyllobothriosis, was studied for the first time using transmission electron microscopy. Cytochemical staining with periodic acid-thiosemicarbazide-silver proteinate for detection of glycogen was applied. Starting from the periphery toward the center of the vitelline follicle four stages of vitellocytes are differentiated: immature vitellocytes, early maturing vitellocytes, advanced maturing and mature vitellocytes. Differentiation into mature vitellocytes involves the formation of shell globule clusters containing shell globules, large amount of saturated lipid droplets and glycogen. A peculiar ultrastructural feature of D. latum vitellogenesis is the presence of lamellar bodies in the cytoplasm of mature vitellocytes. This feature is similar to that present in the closely related caryophyllideans and spathebothriideans. Despite the great similarity observed in the embryonic development of diphylobothriideans, caryophyllideans and spathebothriideans, and the fact that their vitellocytes share a feature not reported from other cestode groups, there are substantial differences in the morphology of vitelline clusters, types, amount and localization of their nutritive reserves.     

Ultrastructure of vitellogenesis and vitellocytes in the trypanorhynch cestode Aporhynchus menezesi, a parasite of the velvet belly lanternshark Etmopterus spinax

This is the first TEM examination of vitellogenesis in the cestode Aporhynchus menezesi, a parasite of the velvet belly lanternshark Etmopterus spinax and a member of a little-studied trypanorhynch family, the Aporhynchidae. The synthetic activity of vitellocytes plays two important functions in the developmental biology of cestodes: (1) their shell-globules serve in eggshell formation; and (2) their accumulated reserves of glycogen and lipids represent a food source for the developing embryo. In A. menezesi, vitelline follicles consist of cells at various stages of development, from peripheral, immature cells of the gonial type to mature cells towards the centre of the follicle. These stages are: (I) immature; (II) early differentiation; (III) advanced maturation; and (IV) mature. Gradual changes involved in this process occur within each stage. Vitellogenesis involves: (1) an increase in cell volume; (2) the development of a smooth endoplasmic reticulum and an accelerated formation and accumulation of both unsaturated and saturated lipid droplets, along with their continuous enlargement and fusion; (3) the formation of individual β-glycogen particles and their accumulation in the form of glycogen islands scattered among lipid droplets in the cytoplasm of maturing and mature vitellocytes; (4) the rapid accumulation of large, moderately saturated lipid droplets accompanied by dense accumulations of β-glycogen along with proteinaceous shell-globules or shell-globule clusters in the peripheral layer during the advanced stage of maturation; (5) the development of cisternae of granular endoplasmic reticulum that produce dense, proteinaceous shell-globules; (6) the development of Golgi complexes engaged in the packaging of this material; and (7) the progressive and continuous enlargement of shell-globules into very large clusters in the peripheral layer during the advanced stage of maturation. Vitellogenesis in A. menezesi, only to some extent, resembles that previously described for four other trypanorhynchs. It differs in: (i) the reversed order of secretory activities in the differentiating vitellocytes, namely the accumulation of large lipid droplets accompanied by glycogenesis or β-glycogen formation during early differentiation (stage II), i.e. before the secretory activity, which is predominantly protein synthesis for shell-globule formation (stage III); (ii) the very heavy accumulation of large lipid droplets during the final stage of cytodifferentiation (stage IV); and (iii) the small number of β-glycogen particles present in mature vitellocytes. Ultracytochemical staining with PA-TCH-SP for glycogen proved positive for a small number of β-glycogen particles in differentiating and mature vitellocytes. Hypotheses, concerning the interrelationships of patterns of vitellogenesis, possible modes of egg formation, embryonic development and life-cycles, are commented upon.     

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     

Vitellogenesis of the digenean Plagiorchis elegans (Rudolphi, 1802) (Plagiorchioidea,Plagiorchiidae)

The ultrastructural organization of vitellogenesis of Plagiorchis elegans (Rudolphi, 1802), experimentally obtained from the golden hamster Mesocricetus auratus (Linnaeus, 1758), is described using transmission electron microscopy. This study is the first ultrastructural study of vitellogenesis in a member of the superfamily Plagiorchioidea. The four stages usually observed during vitellogenesis are described: stage I, cytoplasm of the vitellocytes mainly filled with ribosomes and few mitochondria; stage II, beginning of the synthetic activity; stage III, active synthesis of the shell globule clusters; stage IV, vitellocytes are filled with shell globule clusters and contain several lipid droplets, and glycogen granules are grouped around clusters and droplets. Vitellogenesis in P. elegans is compared with that of other Digenea. The differences among P. elegans and previously studied digeneans include, but are not limited to the occurrence of dense coiled endoplasmic reticulum saccules and the concentration of glycogen in the mesenchyme, which may be considered as a fifth stage of maturation of the vitelline glands. This peculiarity was not observed in all trematodes, which clearly indicates differences in the vitellogenesis in various digenean lineages at different stages of maturation of their vitelline cells.     

Ultrastructural aspects of the germovitellarium of two prorhynchids (Platyhelminthes,Lecithoepitheliata)

Summary

The female gonad of two fresh-water prorhynchids, Geocentrophora baltica and Prorhynchus stagnalis, has been investigated by means of conventional electron microscopy and cytochemical techniques. Both species have an unpaired germovitellarium located under the gut; accessory cells surround the germovitellarium of G. baltica. The germovitellarium consists of a restricted germinative area where early differentiating oocytes and vitellocytes are randomly associated, and an extensive growth area with follicular organization. Each follicle consists of a single alecithal oocyte surrounded by numerous vitellocytes. The main features of oocyte differentiation are the accumulation of lipid droplets and the appearance of Golgi complexes and small bodies possibly representing secondary lysosomes. Vitellocytes show features typical of secretory cells, including well-developed rough endoplasmic reticulum (RER) and Golgi complexes which are involved in the production of type A and type B inclusions, hi both species, type A inclusions appear first, have a glycoprotein content, do not contain polyphenols, and become localized in the peripheral cytoplasm of mature vitellocytes; they have been interpreted as eggshell forming granules. Type B inclusions are larger, have a proteinaceous content with a different structure in the two species examined, and remain scattered in the cytoplasm of mature vitellocytes; they are considered to be yolk. The finding of eggshell forming granules without polyphenols in prorhynchids contrasts with the condition in most platyhelminths that have a sclerotized eggshell formed through a tanning process of polyphenolic substances. The small bodies in the oocytes and the eggshell granules in the vitellocytes of Lecithoepitheliata differ from those observed in prolecithophorans, which have oocyte and vitellocyte inclusions similar to those of the Rhabdocoela.     

Ultrastructural study of vitellogenesis and oogenesis of Metadena depressa (Stossich, 1883) Linton, 1910 (Digenea,Cryptogonimidae), intestinal parasite of Dentex dentex (Pisces,Teleostei)

The ultrastructural organization of the female reproductive system of Metadena depressa, digenean intestinal parasite of Sparidae (Dentex dentex), was investigated by electron microscopy. The vitellogenesis is divided into four stages: stage I, vitellocytes have a cytoplasm mainly filled with ribosomes and few mitochondria; stage II, beginning of the synthetic activity; stage III, active shell globule clusters synthesis; stage IV, mature vitellocytes are filled with shell globule clusters and generally contain several large lipid droplets. Glycogen granules are grouped at the periphery of the cell. The three stages of the oogenesis process take place in the ovary: stage I, oogonia are undifferentiated small cells located at the periphery of the organ; stage II, primary oocytes possess a higher nucleo-cytoplasmic ratio and a nucleus with a nucleolus and synaptonemal complexes indicating the zygotene-pachytene stage of the first meiotic division; stage III, mature oocytes are located in the proximal region of the organ and possess a cytoplasmic chromatoid body and cortical granules in a monolayer close to the periphery of the cell.     

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.     

Ultrastructure of the vitelline follicles of Gorgoderina vitelliloba (Trematoda: Gorgoderidae)

An electron microscope study of the vitelline follicles of Gorgoderina vitelliloba indicates that they contain vitelline cells in various stages of development. Juvenile cells are small and characterised by a little cytoplasm. During differentiation a large amount of granular endoplasmic reticulum develops. In more mature cells, indistinct Golgi complexes give rise to globules of shell protein which migrate to form clusters at the periphery of the cell. Further maturation results in the appearance of large lipid bodies in the vitelline cell cytoplasm.Developing vitelline cells are ensheathed by nurse cell cytoplasm containing numerous small vacuoles which appear to be derived from smooth endoplasmic reticulum. It is suggested that nurse cells may have a role in selection and transport of nutrient material for vitelline cells and that they manufacture precursors of lipid which is subsequently stored as a food reserve in mature vitelline cells. Possible transport sites between parenchymal cells and nurse cells were identified.     

Ultrastructure of glial cells in the nervous system of <Emphasis Type="Italic">Grillotia erinaceus</Emphasis>

Until now, there has been no answer to the question of whether specialized glial cells exist in the nervous system of platyhelminths. The identification of these cells in parasitic flatworms is difficult due to their organization as parenchymal animals. The goal of this study was to reveal and describe structural elements corresponding to the term glia in the CNS of the parasitic flatworm Grillotia erinaceus (Cestoda: Trypanorhyncha). Three types of glial cells are revealed. The first type consists of fibroblast-like cells located in the cerebral ganglia that contain fibrils and excrete onto the surface fibrillar material and possess desmosomes; the presumable function of fibroblast-like glial cells is the isolation and support of ganglionar neurons. Glial cells of the second type form a myelin-like envelope of giant axons and bulbar nerves of the scolex and have laminar cytoplasm; they are numerous and exceed the number of neurons in the composition of nerves. Glial cells of the third type form multilayer envelopes in the main nerve cords and make contacts with the excretory epithelium; however, specialized junctions with neurons were not found. The existence of glia in other free living and parasitic flatworms is discussed.     

Changes of the cytoplasmic ultrastructure during development of sclerotia in Claviceps purpurea (Fr.) Tul.

The development of sclerotia of Claviceps purpurea was investigated by light and electron microscopy. During the first days after infection sterigma and conidiospores are formed. The spores show a moderately developed vacuolar system, they are thick walled and contain about 20% lipid (related to the cell volume) embedded in glycogen. The sterigma are cylindrical unicellular hyphae with electron dense cytoplasm and isolated strongly contrasted lipid droplets. In maturing sclerotia the hyphae become septated with increasingly thick cell walls and a large lipid content. The lipid forms small droplets in young cells, while in the mature sclerotium it occurs in the form of very large drops, occupying the major part of the cell. Simultaneously the composition of the lipid is changed. The mature cells have several nuclei. They are partially connected by osmiophilic substances, forming a network of intercellular spaces.Abbreviations HEPES N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid - DMSO Dimethylsulfoxide     

Ultrastructural and cytochemical aspects of the germarium and the vitellarium in Syndesmis patagonica (Platyhelminthes,Rhabdocoela, Umagillidae)

The cytoarchitecture of the female gonad of the endosymbiont umagillid Syndesmis patagonica has been investigated using electron microscopy and cytochemical techniques. The female gonad consists of paired germaria and vitellaria located behind the pharynx in the mid‐posterior region of the body. Both the germaria and the vitellaria are enveloped by an outer extracellular lamina and an inner sheath of accessory cells which contribute to the extracellular lamina. Oocyte maturation occurs completely during the prophase of the first meiotic division. Oocyte differentiation is characterized by the appearance of chromatoid bodies and the development of endoplasmic reticulum and Golgi complexes. These organelles appear to be involved in the production of round granules, about 2–2.5 μm in diameter, with a homogeneous electron‐dense core surrounded by a granular component and a translucent halo delimited by a membrane. These egg granules migrate to the periphery of mature oocytes, are positive to the cytochemical test for polyphenol detection, are unaffected by protease and have been interpreted as eggshell granules. The mature oocytes also contain a small number of yolk granules, lipid droplets, and glycogen particles scattered throughout the ooplasm. The vitellaria are branched organs composed of vitelline follicles with vitellocytes at different stages of maturation. Developing vitellocytes contain well‐developed rough endoplasmic reticulum and small Golgi complexes involved in the production of eggshell and yolk globules. Eggshell globules are round, measure 4–5 μm in diameter, and have a mosaic‐like patterned content which contains polyphenols. The yolk globules, 2–3 μm in diameter, show a homogeneous protein content of medium electron density, devoid of polyphenols, and completely digested by protease. The mature vitellocytes also contain glycogen as further reserve material. The presence of polyphenolic eggshell granules in the oocytes and of polyphenolic eggshell globules with a mosaic‐like pattern in the vitellocytes have been considered apomorphic features of the Rhabdocoela + Prolecithophora. J. Morphol. 275:703–719, 2014. © 2014 Wiley Periodicals, Inc.     

Histological changes during ovarian maturation in the tarnished plant bug,Lygus lineolaris (Palisot de beauvois) (Hemiptera : Miridae)

Histological changes during the first gonotropic cycle in the telotrophic ovarioles of Lygus lineolaris (Hemiptera : Miridae) were studied by light and transmission electron microscopy. Each oocyte goes through a gonotrophic cycle that lasts for ca 7 days during which time 3 distinct stages are observed: previtellogenic, vitellogenic and choriogenic. In the previtellogenic stage, oocytes descend into the vitellarium and increase in size, while maintaining contact with the trophic core by means of nutritive cords. During vitellogenesis, ovarioles are characterized by the development of intercellular spaces in the follicular epithelium and numerous microvilli on the oocyte surface. Yolk granules are incorporated by pinocytosis and the granules coalesce, resulting in large yolk droplets. The trophic core supplies ribosomes, mitochondria and lipid to the oocytes, and its morphology remains unchanged throughout the gonotropic cycle. Vitellogenesis ends with the formation of vitelline membrane on the oocyte surface. During choriogenesis, an egg shell consisting of an exo- and endochorion is formed on the surface of the vitelline membrane. With the completion of choriogenesis, the mature oocyte is ready to be ovulated. During the gonotropic cycle, the oocyte increases in size 10–12-fold, while the germarium remains unchanged in size.     

Schistosoma mansoni: development of the vitelline cell, its role in drug sequestration, and changes induced by Astiban.

The ultrastructure of four stages in the development of the vitelline cell of Schistosoma mansoni has been described, and the effect of different regimes of Astiban on the morphology of these cells was investigated. The drug had a highly selective action, rapidly destroying those cells at a stage of granular endoplasmic reticulum development, had a less immediate effect on the “mature” cells, and had no apparent effect on the first stages in development. These cells persisted and were able to continue development when the drug was withdrawn. Acid phosphatase tests at an ultrastructural level showed a considerable increase in activity in the cytosegresomes of affected “mature” cells. The ribosomal complexes present in the “mature” cells represent the early stages of cytosegresome formation, and these cytosegresomes increased in number in affected “mature” cells. X-ray analysis of both araldite and cryosections in the transmission electron microscope revealed a concentration of the element antimony in the cytosegresomes and vitelline droplets. On this basis, it is suggested that cytosegresomes play a role in drug sequestration by the vitelline cells.     

Schistosoma mansoni: Drug induced changes in the cell population of the vitelline gland

Using the electron microscope four stages in the development of the mature vitelline cell in normal Schistosoma mansoni have been defined precisely and the percentage of their contribution to the cell population of the vitelline lobule has been determined. The effects of Astiban, Lucanthone, and Hycanthone on this cell population were examined and compared with the composition of the normal vitelline lobule. Astiban damaged mature cells and those stages exhibiting protein synthesis. Undifferentiated, nonsynthetic cells did not exhibit morphological damage and rapidly developed and replenished the vitelline lobule so that a normal population was attained within a few days after cessation of drug treatment. In contrast, Lucanthone and Hycanthone appeared to inhibit the division of these undifferentiated cells so that they gradually disappeared from the lobule. The various developmental stages and mature cells which had arisen from these undifferentiated cells accumulated in the lobule, but were eventually damaged. With both these drugs, the lobule population eventually came to consist largely of mature cells. In the case of Hycanthone, it is suggested that the retention of these stages within the lobule was due to interference with the neuromuscular system so that the cells were not passed down the vitelline duct. Withdrawal of Lucanthone and Hycanthone did not result in the replenishment of the vitelline lobule. With all drugs used, cell death was associated with vacuolation, the appearance of myelin configuration, disruption of vitelline droplets, an increase in the lipid content of cells, and an increase in the density of the cytoplasm. The experiments indicate that these three drugs produced a differential cell death in the vitelline lobule, the precise changes in the cell population being dependant on the particular drug being used.     

Evolutionary Analysis of Mitogenomes from Parasitic and Free-Living Flatworms

Mitochondrial genomes (mitogenomes) are useful and relatively accessible sources of molecular data to explore and understand the evolutionary history and relationships of eukaryotic organisms across diverse taxonomic levels. The availability of complete mitogenomes from Platyhelminthes is limited; of the 40 or so published most are from parasitic flatworms (Neodermata). Here, we present the mitogenomes of two free-living flatworms (Tricladida): the complete genome of the freshwater species Crenobia alpina (Planariidae) and a nearly complete genome of the land planarian Obama sp. (Geoplanidae). Moreover, we have reanotated the published mitogenome of the species Dugesia japonica (Dugesiidae). This contribution almost doubles the total number of mtDNAs published for Tricladida, a species-rich group including model organisms and economically important invasive species. We took the opportunity to conduct comparative mitogenomic analyses between available free-living and selected parasitic flatworms in order to gain insights into the putative effect of life cycle on nucleotide composition through mutation and natural selection. Unexpectedly, we did not find any molecular hallmark of a selective relaxation in mitogenomes of parasitic flatworms; on the contrary, three out of the four studied free-living triclad mitogenomes exhibit higher A+T content and selective relaxation levels. Additionally, we provide new and valuable molecular data to develop markers for future phylogenetic studies on planariids and geoplanids.     

Ultrastructural and cytochemical aspects of the female gonad of Geoplana burmeisteri (Platyhelminthes, Tricladida, Terricola)

The ultrastructure of the female gonad of the land planarian Geoplana burmeisteri was investigated by means of electron microscopy and cytochemical techniques. It consists of two small germaria located ventral to the intestine and of two irregular, lateral rows of vitelline follicles, both enveloped by a tunica composed of an extracellular lamina and an inner sheath of accessory cells. Accessory cell projections completely surround developing oocytes and vitellocytes. The main feature of oocyte maturation is the appearance of chromatoid bodies and the development of the rough endoplasmic reticulum (RER) and Golgi complexes. These organelles appear to be correlated with the production of egg inclusions of medium electron density, about 1.5-1.8 microm in diameter, which remain scattered in the ooplasm of mature oocytes. On the basis of cytochemical tests demonstrating their glycoprotein composition, these inclusions were interpreted as residual yolk globules. Vitellocytes are typical secretory cells with well-developed RER and Golgi complexes that are mainly involved in the production of yolk globules and eggshell globules, respectively. Eggshell globules appear to arise from repeated coalescence of small Golgi-derived vesicles and, at an intermediate stage of maturation, show a multigranular pattern. Later, after vesicle fusion, they reach a diameter of 1.3-1.6 microm when completely mature and show a meandering/concentric pattern, as is typical of the situation seen in most Proseriata and Tricladida. The content of yolk globules is completely digested by pronase, while the content of eggshell globules is unaffected. Mature vitellocytes contain, in addition, a large quantity of glycogen and lipid droplets as further reserve material. On the basis of the ultrastructural characteristics of the female gonad described above and in relation to the current literature, we conclude that G. burmeisteri appears to be more closely related to the freshwater triclads, in particular to members of the Dugesiidae, than to the marine triclads.     

东方杯叶吸虫卵黄腺和卵巢的超微结构研究

本文应用透射电镜观察了东方杯叶吸虫卵黄腺和卵巢的超微结构,并与体外培养成虫进行比较。根据形态特征和内含物的存在情况,将卵黄细胞和卵母细胞的发育均分为不同时期,详细描述了各期的形态特征,探讨了卵黄球和皮质颗粒等内含物的生理功能。体外培养成虫成熟卵黄细胞中有散在的卵黄物质,成熟卵母细胞中线粒体囊泡化,这些可作为体外培养的评价指标。     

Ultrastructural and cytochemical studies of the female gonad of Prorhynchus sp. (Platyhelminthes,Lecithoepitheliata)

The female gonad of Prorhynchus is heterocellular (neoophoran organization) and consists of an unpaired, elongate germovitellarium enveloped by a finely granular extracellular lamina. It is composed of a posterior germinative area where early oocytes are randomly associated with differentiating vitellocytes and a growth area with follicular organization. In each follicle a single oocyte is surrounded by a layer of vitellocytes. By electron microscopy, the oocytes showed features typical of non-vitellogenic germ cells; they had chromatoid bodies, annulate lamellae, lipid droplets and R.E.R. and Golgi complexes producing small granules with a multilamellar pattern. Vitellocytes showed features typical of secretory cells with the R.E.R. and Golgi complex developed to a great extent and involved in the production of type A and type B globules, respectively. We speculate that type A globules are shell-globules and type B globules are yolk. The structure, composition and role of vitellocyte globules of Prorhynchus are compared with those of homologous inclusions from other Platyhelminthes.Abbreviations A type A globule - B type B globule - ECL extracellular lamina - GC Golgi complex - L lipid - RER rough endoplasmic reticulum - O oocyte - V vitellocyte     

Vitellogenesis in Echeneibothrium beauchampi Euzet, 1959 (Cestoda: Tetraphyllidea, Phyllobothriidae) (author's transl)]

The vitellogenesis in Echeneibothrium beauchampi is studied by means of electron microscopy. In the follicles, the vitelline cells undergo three progressive changes characterized by cellular size, membrane system development and nature of stored inclusions. 1. Immature cells have a gonial morphology. 2. Maturing cells display a very well developed membrane system. Their cytoplasm is gradually filled with abundant lipid droplets. At the same time, a small number of homogeneous vesicles occur which contain protein material moderately electron dense. Glycogen (alpha and beta) appears at the end of the vitellogenesis. 3. Mature cells show a conspicuous regression of the membrane system. Cellular organelles, nucleus and protein vesicles are found in the peripheral cytoplasmic layer which still contains numerous free ribosomes. The amorphous remaining cytoplasm is filled with large amounts of aggregated lipid droplets which often surround glycogen areas. 4. The presence of numerous lipid droplets and glycogen in the vitelline cells of E. beauchampi shows evidence that this Tetraphyllidea is close to Pseudophyllidea, but the aspect of protein vesicles (shell-protein material) brings it near the Cyclophyllidea.     

日本血吸虫卵黄培养细胞超微结构动态的研究

从超微结构水平研究日本血吸虫卵黄细胞培养的动态。在体外培养过程中,卵黄细胞对外界环境的改变比日本血吸虫的其它体细胞更加敏感。随着培养时间的延长,卵黄细胞发生不同程度的变性,成熟卵黄细胞比未成熟卵黄细胞发生变性。变性主要表现在核和胞质的电子密度降低;卵黄球相互融合,或卵黄球与膜之间的空隙逐步增大,最终卵黄球从中释放出来,变成裸露体;脂滴数目增多,体积增大;粗面内质网扩大和囊泡变,其上的核糖体脱颗粒等