Ultrastructural and histochemical observations on the tegument of Gastrodiscoides hominis (Paramphistoma: Digenea).

The tegument of the paramphistome, Gastrodiscoides hominis, is basically similar to that of other digeneans. It is folded into concentrically arranged furrows and ridges bearing numerous tightly packed tubercules, and extends into the oral cavity. An area of specialized tegument is present on the ventral surface, anterior to the disc region. Mitochondria are absent from the tegumental syncytium and underlying tegumental cells, suggesting that the tegument may serve principally as a protective layer rather than in active uptake phenomena. However, extensions of the lymph and parenchyma systems are closely associated with the base of the tegumental syncytium and may provide ATP for active processes. Ciliated and non-ciliated sensory papillae are present, particularly around the oral opening. Numerous lymph channels are present in the sub-tegument and may be involved in osmoregulation.     

Ultrastructural observations on the redial tegument of Paramphistomum epiclitum from the planorbid snail, Indoplanorbis exustus.

The morphology of the tegument in the redia of Paramphistomum epiclitum (Digenea: Paramphistomidae) resembles that shown by most larval and adult digeneans; an outer surface syncytium is in continuity with the cytoplasm of in-sunken, nucleated cytons. Although tegumental cytons usually contain a single nucleus, some display up to six nuclei. The tegumental syncytium lining the pharynx of P. epiclitum rediae lack underlying cytons. The apical membrane of the tegument is elaborated by folds and microvilli, which presumably facilitate uptake of nutrients and/or exchange of ions involved in osmoregulation. A single type of secretory body, resulting from the fusion of smaller vesicles produced at Golgi complexes in the cytons, occurs throughout the tegument. Uniciliate sensory receptors occur in the surface syncytium particularly around the oral opening.     

东方杯叶吸虫体被的超微结构

扫描电镜显示东方杯叶吸虫体被有许多族生棘,具纤毛乳突和无纤毛窝状乳突,附着器皮层特化为微毛。透射电镜观察表明,皮层是由合胞体、基膜和肌肉层组成,合胞体通过细胞通道与皮层细胞相连。文中详细描述了这些结构,揭示无纤毛窝状乳突为腺乳突,皮层细胞间存在线粒体细胞和附着器皮层形成微毛,探讨了这些结构的生理功能。体外培养成虫皮层结构的某些不正常变化,如皮层细胞的空虚松散,可作为评价吸虫体外培养的一种指标。     

Ultrastructure and cytochemistry of the tegument of Orthocoelium scoliocoelium and Paramphistomum cervi (Trematoda: Digenea)

The tegument of Orthocoelium scoliocoelium and Paramphistomum cervi was examined using histochemical techniques and electron microscopy. On the basis of the distribution of acid and alkaline phosphatase (E.C. 3.1.3.2, E.C. 3.1.3.1), non-specific esterase (E.C. 3.1.1.1), cholinesterase (E.C. 3.1.1.7) and succinate dehydrogenase (E.C. 1.3.99.1) at light microscope level two distinct regions were recognized, an outer and an inner zone. Electron microscopy revealed that the tegument comprises an outer surface syncytium underlain by a thick subsyncytial zone and musculature. Deeper still occur the nucleated "tegumental cells". The latter are in cytoplasmic continuity with the surface syncytium via vacuolated cytoplasmic trabeculae which traverse the muscle layers and the subsyncytial zone. Three types of tegumental cells each lacking mitochondria were observed. The T1 cells synthesize discoid and electron dense T1 bodies while T2 cells produce oval and electron lucent T2 bodies. The third type of tegumental cells apparently produce no secretory bodies and may represent an embryonic cell type. The surface syncytium contains T1 and T2 secretory bodies and is bounded apically by a plasma membrane invested externally by a fuzzy and filamentous glycocalyx. The surface syncytium lacks mitochondria and is traversed by infoldings of the basal plasma membrane. Beneath the surface syncytium the subsyncytial zone is largely comprised of fibrous interstitial material. This zone, which is particularly thick in the amphistomes, is traversed by trabeculae and extensions of underlying parenchymal cells which usually contain mitochondria and lysosomes. The subsyncytial zone overlies numerous circular and longitudinal muscle fibres. The absence of mitochondria and enzymes associated with active transport suggests that the amphistome tegument may be mainly specialized for protection of the worm against mechanical and chemical conditions prevailing in the rumen. Active uptake of nutrients is probably not a primary function.     

Fasciola hepatica: A light and electron microscope autoradiographic study of incorporation of monosaccharides into glycogen and glycoprotein

Incorporation of [³H]galactose and [³H]glucose into the parenchyma, tegument, testis, and muscle of Fasciola hepatica slices was studied by lightand electron-microscope autoradiography. “Accumulation” labeling periods of up to 60 min were used.Both monosaccharides were found to be readily incorporated into glycogen in the parenchymal cells and muscle and [³H]glucose entered the glycogen stores of spermatozoa.No evidence was found for the involvement of any particular cell organelle in glycogenesis, but the demonstration of high synthetic activity in parenchymal evaginations to the base of the surface syncytial tegument supports physiological evidence that glucose enters the fluke mainly across the tegument.Ethylene glycol-dehydrated preparations showed that [³H]galactose was incorporated into glycoprotein by Type I tegumental cells, and perhaps also by sperm morulae. The carbohydrate component seems to be added to the tegumental secretions in the vesicular-lamellar region of the Golgi complex.Following the longest periods of incubation, labeling was observed in the tubules connecting the tegumental cells and syncytium, but not in the surface syncytium itself.     

Ultrastructure of the tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955 (Monogenea, Microcotylidae).

The ultrastructure of the body tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955, parasite of Mugil liza from Brazil, was studied by transmission electron microscopy. The body tegument is composed of an external syncytial layer, musculature, and an inner layer containing tegumental cells. The syncytium consists of a matrix containing three types of body inclusions and mitochondria. The musculature is constituted of several layers of longitudinal and circular muscle fibers. The tegumental cells present a well-developed nucleus, cytoplasm filled with ribosomes, rough endoplasmatic reticulum and mitochondria, and characteristic organelles of tegumental cells.     

Fasciola gigantica: Histology of the digestive tract and the expression of cathepsin L

The digestive tract of Fasciola gigantica is composed of the oral sucker, buccal tube, pharynx, esophagus, and caecum. The tegumental-type epithelium lines the first four parts of the digestive tract while the caecal-type epithelium lines the remaining parts from the caecal bifurcation. The caecal-epithelial cells are classified into 3 types according to their staining properties and ultrastructural characteristics, as related to the amount of food contents in the caecal lumen. All caecal-type epithelial cells synthesize and secrete cathepsin L, a major group of enzymes in the digestive tract, as detected by in situ hybridization and immunolocalization. Moreover, the secreted cathepsin L is also adsorbed on the outer surface of the tegument and the glycocalyx coating of the surface of the tegument, whereas the tegumental cells and tegumental syncytium covering the parasite’s body and lining the proximal part of the digestive tract exhibit no in situ hybridization signal and immunostaining for cathepsin L.     

河鲈锚首吸虫体壁的超微结构观察

寄生鳜鳃部的河鲈锚首吸虫的体壁由表皮合胞体、基板、环肌、纵肌和表皮细胞核周体所组成。合胞体顶部质膜起伏形成表皮的嵴纹,基部质膜折叠形成指状突起伸入到合胞体中。合胞体表面覆盖着一层糖萼。河鲈锚首吸虫的表皮中含有四类分泌体,即电子致密的分泌颗粒、中等电子致密的分泌颗粒、有膜包围的电子稀疏的分泌体和多囊体．可见分泌体和合胞体基质通过胞吐作用排到体外,未见吞饮小泡,推测表皮的主要功能在于分泌和渗透压调节而非营养吸收。在外侧头瓣的乳突状结构所在处,合胞层较薄,基板平滑,在实质组织中的一腔体样结构中可见囊状体、电子致密度各异的颗粒体、泡状体和电子致密的基质团,神经突起分布于腔体周围,这类乳突可能代表一类新的非纤毛感受器类型。     

Scanning and transmission electron microscopical observations on the tegument of excysted metacercariae and adults of Zygocotyle lunata.

Scanning and transmission electron microscopical observations were made on the tegument of excysted metacercariae and adults of the paramphistome, Zygocotyle lunata (Digenea: Trematoda). In accord with other paramphistomes studied, this species lacks spines and mitochondria in the tegumentary syncytium and associated cytons. The newly excysted metacercarie, which possessed relatively few tegumental papillae, were cylindrical in comparison to adults which were distinctly flat. The adults had large numbers of tegumental papillae in the region of the oral sucker and acetabulum.     

Scanning and transmission electron microscopy of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000 (Microcotylidae, Monogenea), parasite of a Brazilian catfish, Hypostomus regani

The surface topography and ultrastructure of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000, a microcotylid monogenean parasite from the gills of Hypostomus regani (Ihering, 1905) (Loricariidae) was studied by scanning (SEM) and transmission electron microscopy (TEM). By SEM, it was observed that the tegument presents transversal ridges, forming folds in the ventral and dorsal surfaces and microvillous-like tegumental projections in the anterior and median regions of body. These projections were also observed by TEM. The tegument is made up of a syncytium delimited by apical and basal plasma membranes, containing inclusion bodies and mitochondria, connected to the nucleated region by means of cytoplasmatic processes. The tegumental cells present a well developed nucleus and cytoplasm containing inclusion bodies, similar to those found on the external layer, mitochondria, rough endoplasmatic reticulum and free ribossomes.     

The ultrastructural characterization of the tegument of Clonorchis sinensis (Cobbold, 1875) cercaria.

The tegumental ultrastructure of the cercaria of the liver fluke, Clonorchis sinensis (Cobbold, 1875), was studied by scanning and transmission electron microscopy. The body surface is almost encircled by many rows of regularly arranged spines. The tegumental syncytium of the body contains many rod-shaped dense granules and central electron-lucent bodies, neither of which are present in the tail tegument. There are four rows of hooked teeth and modified spines on the oral cone. These teeth are differentiated morphologically and probably functionally from the other body spines. Disc-shaped papillae with long or short cilia are distributed on the body in a bilaterally symmetrical pattern dorsally and ventrally. There are 30 to 37 papillae with much longer cilia laterally. Four pairs of papillae were found on the tail. From their structure and location these papillae appear to have a mainly tango- or rheoreceptive function. Another type of sheathed papillae is situated around the oral sucker. The cuticular tegument is expanded laterally at the base of the tail, forming a characteristic sac-like structure.     

Antigenic localities in the tissues of Metagonimus yokogawai observed by immunogoldlabeling method]

In order to determine the antigenic localization in the tissues of the adult Metagonimus yokogawai, immunogoldlabeling method was applied using serum immunoglobulins(IgG) of cats which were infected with isolated metacercariae from Plecoglossus altivelis. The sectioned worm tissue was embedded in Lowicryl HM 20 medium and stained with infected serum IgG and protein A gold complex(particle size: 12 nm). It was observed by electron microscopy at each tissue of the worm. The gold particles were observed on the tegumental syncytium as well as cytoplasm of tegumental cells and epithelial lamella of the caecum. The gold particles were not observed on the basal lamina of the tegument, interstitial matrix of the parenchyma, the muscle tissue and mitochondria of the tegument. The gold particles were specifically labeled in the secretory granules in the vitelline cells. They were also labeled on the lumen of bladder and egg shell. The above findings showed that antigenic materials in the tissue of adult worms were specifically concentrated on the tegumental syncytium as well as cytoplasm of tegumental cells and epithelial lamella of the caecum.     

Fasciola hepatica: Autoradiography of protein synthesis,transport, and secretion by the tegument

Transverse slices of Fasciola hepatica adults were incubated for up to 3 hr in the presence of [³H]leucine. The incorporation of this tracer molecule into macromolecules and its subsequent movement through the tegument was visualized by electron microscope autoradiography. It appeared that protein synthesis in the Type 1 tegumental cells occurred by a GER/Golgi-mediated mechanism similar to that in vertebrate tissues. Mature T1 secretory bodies entered the surface syncytium via the connecting tubules and accumulated in the basal cytoplasm prior to rapid transit to the surface and discharge at the apical plasma membrane. In adult flukes, which are partly protected from immune attack by virtue of their location, glycocalyx replacement and T1 synthesis may be retarded. The Type 1 cells also appear to manufacture proteins which are not membrane bound. These move with the T1 secretory bodies into the surface syncytium and may have structural or enzymic functions within the cytoplasm.     

Fasciola hepatica: stereological analysis of effects of certain metabolic inhibitors on synthesis of secretory bodies by the tegument of tissue slices.

The influence of several well-known inhibitors on the production and distribution of Type 1 secretory bodies in the tegument of Fasciola hepatica slices has been analyzed stereologically.Cycloheximide was found to inhibit the production of these bodies by the Golgi complex of the tegumental cells, but apparently had little effect on intracellular transport and discharge. The metabolic inhibitors, DNP and iodoacetate, seemed to block all three processes.The results provide physiological evidence that the GER-Golgi system in the tegumental cells of this fluke carry out protein or glycoprotein synthesis, that a functional relationship exists between the tegumental cells and the surface syncytium in the transport and discharge of the secretory bodies, and that synthesis, transport, and discharge of the bodies are all energy-dependent processes.     

Tegumental ultrastructures of Echinoparyphium recurvatum according to developmental stages

The present study was performed to observe tegumental ultrastructure of Echinoparyphium recurvatum according to developmental stages. Worms (1, 3, 5 and 15-day old) were recovered from chicks experimentally infected with metacercariae from Radix auricularia coreana. One-day old worms were elongated and ventrally concave, and covered with peg-like tegumental spines except the adjacent areas of the head crown and excretory pore. Type I sensory papillae were distributed on the lip of the oral sucker, and grouped ciliated papillae were around the oral sucker. Peg-like tegumental spines were densely distributed on the anterior surface of the ventral sucker level. The ventral sucker had an aspinous tegument and no sensory papillae. Tegumental spines on the posterior surface of the ventral sucker level were sparsely distributed and disappeared posteriorly. In 3 and 5-day old worms, the tegument around the oral sucker was aspinose and wrinkled concentrically. The ventral sucker had a wrinkled tegument and many bulbous papillae. Type I sensory papillae were distributed between the bulbous papillae. Tegumental spines were spade-shaped with a terminal tip. A total of 45 collar spines including 4 end group ones on both ventral corners was alternately arranged in 2 rows. The 15-day old worms were very stout and their tegumental spines were tongue-shaped without a terminal tip. From the above results, it is confirmed that the surface ultrastructure of E. recurvatum was generally similar to that of other echinostomatid flukes. However, some features, i.e., morphological change of tegumental spines and appearance of sensory papillae on the ventral sucker according to development, and number, shape and arrangement of collar spines, were characteristic, which may be of taxonomic and bioecological significance.     

Functions of the tegument of schistosomes: clues from the proteome and lipidome

The tegumental outer-surface of schistosomes is a unique double membrane structure that is of crucial importance for modulation of the host response and parasite survival. Although several tegumental proteins had been identified by classical biochemical approaches, knowledge on the entire molecular composition of the tegument was limited. The Schistosoma mansoni genome project, together with recently developed proteomic and lipidomic techniques, allowed studies on detailed characterisation of the proteins and lipids of the tegumental membranes. These studies identified tegumental proteins and lipids that confirm the function of the tegument in nutrient uptake and immune evasion. However, these studies also demonstrated that compared to the complete worm, the tegument is enriched in lipids that are absent in the host. The tegument is also enriched in proteins that share no sequence similarity to any sequence present in databases of species other than schistosomes. These results suggest that the unique tegumental structures comprise multiple unique components that are likely to fulfil yet unknown functions. The tegumental proteome and lipidome, therefore, imply that many unknown molecular mechanisms are employed by schistosomes to survive within their host.     

Antigenic localities in the tissues of the young adult worm of Paragonimus westermani using immunogold labeling method

In order to observe the antigenic localization in the tissues of the young adult Paragonimus westermani, immunogold labeling method was applied using serum immunoglobulins(IgG) of the dog which infected with isolated metacercariae from Cambaroides similis. The sectioned worm tissue was embedded in Lowicryl HM 20 medium and stained with infected serum IgG and protein A gold complex (particle size; 12 nm). It was observed by electron microscopy at each tissues of the worm. The gold particles were not observed on the basal lamina of the tegument, interstitial matrix of the parenchyma, the muscle tissue and mitochondria of the tegument. The gold particles were specifically labeled in the secretory granules in the vitelline cells. They were predominantly labeling on the epithelial lamela and lumen of caecum. The above finding showed that antigenic materials in young adult worm tissue were specifically concentrated on the tegumental syncytium as well as cytoplasm of tegumental cells.     

Schistosoma spp.: Isolation of microtubule associated proteins in the tegument and the definition of dynein light chains components

Schistosomes are parasitic blood flukes that reside in human mesenteric veins or urinary bladder veins, depending on species of the parasite. The syncytial tegument of these parasites represents a dynamic interface that regulates nutritional and immunological interactions between the parasite and the host. It is known that the components for biogenesis and maintenance of the tegument are supplied via vesicles from the nucleated cell bodies beneath the syncytium and muscle layer. To investigate the common motor components of vesicular transport in the tegument of schistomes, we extracted Schistosoma mansoni tegumental microtubule associated proteins utilizing detergent/high-salt procedure and raised antiserum against these proteins. The antiserum was applied to screen Schistosoma haematobium λgt11 expression library and some of the isolated clones were sequenced. Blast search for the sequences against NCBI database identified clones that are dynein light chains and myosin genes. Further analysis of schistosome dynein genes in the databases identified three families of dynein light chains (Dlcs). The Tctex family protein sequences are significantly different from the mammalian homologs and, therefore, offer a potential vaccine/drug target against schistosomes.     

Surface ultrastructure of the plagiorchid trematode Glossidium pedatum Looss, 1899 from bagrid fish in Egypt

The present study concerned the morphology and surface ultrastructure of a plagiorchid, Glossidium pedatum, from bagrid fish of the river Nile in Egypt. Adult G. pedatum have an elongate body, tapered towards the anterior and posterior ends. Their oral sucker is small, sub‐terminal and rounded, measuring 0.200 mm in diameter. Sensory papillae around the oral sucker usually occur in small clusters of three to eight each. The ventral sucker is large, situated at the anterior end of the second third of the body, 0.299 mm in diameter, and is surrounded by three pairs of sensory papillae. Both suckers have rounded rims covered by tegumental spines. On the anterior part of the ventral surface of the body tegumental spines are small, pointed and closely spaced. A small triangular area of tegument anterior to the ventral sucker is devoid of spines. Tegumental spines on the mid‐region of the body slightly increase in size and number, especially towards the lateral aspects and posterior to the ventral sucker. Towards the posterior end of the body the spines progressively decrease in both size and number. The dorsal side exhibits similar surface features but the spines are less numerous and slightly smaller.     

Fasciola hepatica: Glycocalyx replacement in the juvenile as a possible mechanism for protection against host immunity

The response of newly excysted juvenile Fasciola hepatica to immune sheep serum under in vitro conditions was examined using indirect fluorescent antibody labeling and electron microscopy. Flukes acquired a continuous layer of host IgG over the surface during incubation in the presence of antiserum, but when transferred to a medium lacking antiserum they actively sloughed this layer and replaced the former glycocalyx, by a new antigenically similar surface coat. Electron microscope examination of juvenile flukes verified than an immune complex formed at and sloughed from the tegumental surface of those which were incubated in immune serum. T0 secretory bodies produced by the GER/Golgi system of the tegumental cells and stored in the metacercariae were discharged at the apical surface of the tegument, possibly in response to antibody binding. When cycloheximide was included with immune serum in the incubation medium the tegumental cells were unable to synthesize new T0 bodies to replace losses and the number of T0 bodies decreased so that the cytoplasm of the tegumental cells and surface syncytium became virtually devoid of T0 bodies within 48 hr.