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。     

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.     

Morphology of the epithelium of the extratesticular rete testis, ductuli efferentes and ductus epididymidis of the adult male rabbit

The fine structure of the epithelium lining the extratesticular rete testis, ductuli efferentes and ductus epididymidis of the rabbit has been investigated. In the ductuli efferentes the epithelium is composed of two cell types, principal cells and ciliated cells. The latter type is distinguished from principal cells by the presence of cilia projecting into the lumen and the position of the nucleus in the apical half of the cell. Principal cells in this segment are characterized by micropinocytotic vesicles on the surface plasma membrane and a variety of small dense bodies scattered throughout the cytoplasm. In the ductus epididymidis basal cells replace ciliated cells as the second cell type, but differences between various segments of the epididymis are related to the fine structure of the principal cells. In the proximal caput epididymidis (Nicander's region 1) the principal cells are tall with long microvilli. They typically contain a small Golgi apparatus and a cluster of dense bodies adjacent to the nucleus. In the distal caput epididymidis (Nicander's regions 2-5) the apical cytoplasm of principal cells is filled with numerous micropinocytotic vesicles and large multivesicular bodies; these features are interpreted as signs of absorptive activity. The multivesicular bodies are absent from the cytoplasm of principal cells in the corpus epididymidis (Nicander's region 6) and, instead, numerous elements of smooth endoplasmic reticulum, a large Golgi apparatus, lipid droplets and dense bodies characterize principal cells in this segment. Towards the proximal cauda epididymidis (Nicander's region 7), the number of dense bodies (lysosomes) in the cytoplasm increases considerably. In the globose cauda (Nicander's region 8), the principal cells are reduced in height, and in addition to the features described in region 7, are characterized by a concentric array of rough endoplasmic reticulum in the basal cytoplasm. These observations are discussed in relation to the role of the epididymis in promoting the maturation and survival of spermatozoa.     

Smooth muscle-like cells in ovaries of the hamster and gerbil

Summary Smooth muscle-like cells are present in thecae externae, corpora lutea, and interstitial tissue of hamsters and gerbils. The smooth muscle-like cells, as examined by electron microscopy, are fusiform with central nuclei; the cytoplasm contains numerous myofilaments, dense bodies, micropinocytotic vesicles, and dense accumulations of glycogen-like particles. In addition to the smooth muscle-like cells, fibroblasts and cells that have characteristics of both fibroblasts and smooth muscle are located in the thecae externae of both species. There is no ultrastructural evidence of innervation in the theca folliculi, corpora lutea, or interstitial tissue of either species.A possible function for the smooth muscle-like cells is discussed.     

Taenia crassiceps: effect of normal and immune serum on metacestodes in vitro.

The effect of normal and immune serum on Taenia crassiceps larvae in vitro was assessed by Evans blue dye uptake and electron microscopy. Normal guinea pig, rabbit, goat, and fetal calf serum did not have any significant detrimental effects upon the larvae after 7 days of culture in vitro. Culture for 7 days in normal mouse serum resulted in some loss of tegumental microtriches but the tegument itself remained intact. Culture in hyperimmune rabbit serum resulted in complete loss of the tegument and disruption of subtegumental structures within 48 hr. The effects of immune mouse serum in vitro closely paralleled those previously seen during early immune damage in vivo. Immune serum taken 2 to 4 weeks after secondary intraperitoneal infection with T. crassiceps metacestodes caused loss of the larval tegument and degeneration of the subtegumental tissues after 7 days in culture, whereas immune mouse serum taken 6 weeks after secondary infection caused only minor ultrastructural changes and appeared to be less toxic to larvae than normal mouse serum. Although complement appeared to increase the number and severity of the tegumental lesions, the presence of heat-labile components of complement was not essential for mediation of tegumental damage by immune mouse serum.     

Ultrastructural study of synovial membrane from the antebrachiocarpal joint of calves

The synovial intima from the antebrachiocarpal joint of 4-month-old calves was between 1 and 3 cells in thickness and did not have a basal lamina. Numerous areas of the intimal matrix were in direct contact with the joint lumen. The synovial membrane was comprised mainly of A-type synoviocytes usually located adjacent to the joint lumen. These cells were characterized by numerous filopodia (or lamellipodia), large, empty-appearing vacuoles, numerous lysosomes, large vacuoles containing granular material separated from the vacuolar membrane by a radiolucent band, and coated micropinocytotic vesicles. Smooth micropinocytotic vesicles were seen only rarely in these cells. In contrast, B-type cells had few filopodia, numerous smooth micropinocytotic vesicles, few coated micropinocytotic vesicles, a well-developed Golgi apparatus and rough endoplasmic reticulum, mitochondria that were longer and had a denser matrix than that of A cell mitochondria, and surprisingly, only few maturing or fully formed secretory granules. A distinct intermediate (C or AB) type synoviocyte could not be unequivocally identified. Desmosome-like structures were present between synoviocytes, although it was considered questionable if these were true intercellular junctions. No other junctions were present.     

Taenia crassiceps: Basic mechanisms of endocytosis in the cysticercus

The effects of glucose, yeast extract, fetal bovine serum albumin, and ruthenium red on endocytosis of smooth micropinocytotic vesicles (pinosomes) in the tegument of the cysticercus of Taenia crassiceps have been investigated stereologically. Glucose has been shown to stimulate pinocytosis, whether it was used alone or in combination with yeast extract or bovine serum albumin. Yeast extract was a stimulant of endocytosis. Bovine serum albumin was the most potent stimulant of all the substances investigated in this study. Although the time of incubation in ruthenium red was the same for all incubation experiments, varied numbers of ruthenium red-containing pinosomes were observed in different experiments. The role of ruthenium red as a stimulant and/or initiator of endocytosis and the possible explanations for differences in ruthenium red uptake are discussed.     

Immunohistochemical localization of 36 and 29 kDa proteins in sparganum.

Antigenic proteins of 36 and 29 kDa were localized in Spirometra mansoni plerocercoid (sparganum) immunohistochemically by avidin biotin complex (ABC) staining. When polyclonal antibodies such as BALB/c mouse serum immunized with crude saline extract of sparganum or confirmed sparganosis sera were reacted as primary antibodies, the positive chromogen (3-amino, 9-ethylcarbazole) reactions were recognized at syncytial tegument, tegumental cells, muscle and parenchymal cells and lining cells of excretory canals. A monoclonal antibody (MAb) which was reacting to 36 and 29 kDa proteins in the extract of the worm was localized at the syncytial tegument and tegumental cells. The present results suggested that the potent antigenic proteins of 36 and 29 kDa in sparganum were produced at the tegumental cells and transported to the syncytial tegument.     

Fine structure of spermatogonia and primary spermatocytes in rabbits

Summary The fine structure of rabbit Spermatogonia and primary spermatocytes in meiotic prophase has been studied with different methods of preparation, including a technique for acid phosphatase activity. The spermatogonial cytoplasm is rich in free ribosomes and containes moderate amounts of vesicular, smooth-surfaced endoplasmic reticulum and mitochondria, a simple Golgi-apparatus, some micropinocytotic vesicles, and occasional multivesicular bodies, vacuoles and dense bodies with acid phosphatase activity. The large type A Spermatogonia have a prominent nucleolus and their mitochondria sometimes form clusters with a dense intermitochondrial substance, similar to that in spermatocytes.The nucleus and cytoplasm of primary spermatocytes increase markedly in volume and density during meiotic prophase. The Golgi apparatus enlarges and becomes more differentiated and finally forms small proacrosome granules. The endoplasmic reticulum produces numerous small, mainly smooth vesicles and might also be the source of a new organelle: numerous piles of narrow cisternae with opaque contents. These piles disintegrate late in prophase. The mitochondria become aggregated in clusters with dense intermitochondrial substance and their internal structure is characterized by highly dilated cristae and small particles, interpreted as mitochondrial ribosomes, in the matrix. The role of these structures in the formation of new mitochondria is discussed. The clusters of mitochondria finally disperse and their cores of dense intermitochondrial substance, possibly containing ribonucleoprotein, coalesce into a large chromatoid body similar to that in spermatids. Micropinocytosis and a few lysosomes occur in most spermatocytes. The pachytene nuclei show prominent nucleoli and a distinct sex vesicle without any synaptinemal complex.The importance for spermatid differentiation of some events taking place in the cytoplasm of primary spermatocytes is emphasized.Financial support for this study was received from the Swedish Medical Research Council.     

TRANSFORMATION OF MONOCYTES IN TISSUE CULTURE INTO MACROPHAGES, EPITHELIOID CELLS, AND MULTINUCLEATED GIANT CELLS : An Electron Microscope Study

The sequential transformation of chicken monocytes into macrophages, epithelioid cells, and multinucleated giant cells in vitro was studied by electron microscopy after fixation and embedment in situ. The following changes occur. In the nucleus, margination of chromatin, evident in monocytes, decreases in later forms. Nucleoli become more complex and nuclear pores increase in number. In cytoplasm, a progressive increase in volume of the ectoplasm and endoplasm occurs in culture. Lysosomes increase in number and size prior to phagocytosis. During phagocytosis (most active from 1 to 3 days of culture) lysosome depletion occurs. Lysosomes are present in greatest number and show maximal structural variation in the epithelioid and young giant cells. Aging giant cells lose lysosomes. All stages possess variably large quantities of rough-surfaced endoplasmic reticulum and free ribosomes. The Golgi apparatus, small in monocytes, increases in size and complexity. Massive accumulations of lysosomes within the Golgi apparatus of macrophages and epithelioid cells suggest that lysosomes originate there. In giant cells, multiple Golgi regions occur, often ringing the nuclei. Monocytes and macrophages have few mitochondria. Mitochondria of epithelioid cells are larger, more numerous, and may have discontinuous outer membranes. Mitochondria are most numerous in giant cells where they increase with age and become polymorphous. Cytoplasmic filaments are approximately 50 to 60 A in diameter and of indeterminate length. They occur both singly and in bundles which touch cytoplasmic vesicles and mitochondria. Few filaments occur in monocytes and macrophages. A large increase in the number of filaments occurs in epithelioid cells, where filaments (90 to 100 A) surround the cytocentrum as a distinctive annular bundle often branching into the cytoplasm. The greatest concentration of filaments occurs in aged giant cells. Pseudopodia are always present. They are short and filiform in monocytes and giant cells, and broad, with abundant micropinocytotic vesicles, in macrophages and epithelioid cells. At every stage, the cell membrane contains dense cuplike structures. These may represent the membranous residue of lysosomes which have discharged to the outside, analogous to merocrine secretion. Contiguous epithelioid cells display elaborate cytoplasmic interdigitation. In places, the plasma membranes break down and epithelioid cells fuse to form giant cells.     

Schistosoma mansoni: changes in the outer membrane of the tegument during development from cercaria to adult worm

Hockley D. J. and McLaren D. J. 1973. Schistosoma mansoni: changes in the outer membrane of the tegument during development from cercaria to adult worm. International Journal for Parasitology3: 13–25. The tegumental outer membrane of the cercaria is trilaminate: the adult worm, however, has a seven-layered membrane. Formation of the heptalaminate membrane commences immediately after the cercaria has penetrated the vertebrate host: multilaminate membrane-bounded vacuoles are passed from subtegumental cells into the tegument where they enlarge, join to the outer membrane and open to the exterior. The heptalaminate limiting membrane of the vacuole thus becomes the outer membrane of the tegument. At the same time the original trilaminate tegumental membrane is formed into microvilli which are cast off and thus the cercarial outer membrane is lost. Schistosomula usually have a heptalaminate outer membrane within three hours of penetration. After this time the large vacuoles are replaced by smaller membraneous bodies which presumably contribute to the outer membrane during growth of the schistosomulum. The membraneous bodies are also present in the tegument of the adult worms and there is some evidence that the outer membrane is continually renewed.     

Localisation of proteins in coated micropinocytotic vesicles during transport across rabbit yolk sac endoderm

Summary Rabbit yolk sac splanchnopleur exposed in utero to IgG-HRP and IgG-ferritin conjugates, rabbit and bovine anti-HRP antibodies, free HRP, ferritin and human IgG, was examined ultrastructurally in an attempt to determine whether or not coated micropinocytotic vesicles are involved in selectively transporting immunoglobulins across yolk sac endodermal cells. Human, rabbit and bovine IgG-HRP conjugates, rabbit anti-HRP antibodies, free HRP and human IgG, all become localised in coated micropinocytotic vesicles. Differences were observed in that only human IgG and rabbit anti-HRP antibodies could be located in the intercellular space and bovine IgG-HRP conjugate could not be detected in coated micropinocytotic vesicles in confluence with the lateral and basal plasmalemma. Bovine anti-HRP antibodies, IgG-ferritin conjugates, and free ferritin, could not be observed in coated micropinocytotic vesicles. All proteins were detected in macropinocytotic vesicles, and dense bodies resembling phagolysosomes. Results are discussed in the light of a proposal that selection occurs at the cell surface during formation of coated micropinocytotic vesicles and is not linked to intracellular proteolysis.Supported by an award from the Medical Research Council, to whom grateful acknowledgement is made     

Ultrastructural aspects of early immune damage to Taenia crassiceps metacestodes

Siebert, A. E. Jr., Good A. H. and Simmons J. E. 1978. Ultrastructural aspects of early immune damage to Taenia crassiceps metacestodes. International Journal for Parasitology8: 45–53. Changes in the ultrastructure of the tegument and subtegumental cells of intraperitoneally implanted Taenia crassiceps metacestodes were studied by transmission electron microscopy over a 4-week period. Death of metacestodes without involvement of host inflammatory cells is indicated initially by vacuolization of the larval tegument followed by loss of the tegument and subsequent death of the larvae. Changes in the tegument involve loss of the glycocalyx, reduction in the numbers of mitochondria and microtriches present, and loss of secretory capacity. Subtegumental cells show an accumulation of secretory vacuoles and marked disruption of nuclear morphology. Tegument damage is attributed to a complement-mediated lysis of the outer tegument membrane and death of the larvae probably results from loss of tegument function.     

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.     

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.     

The reticular substance of the medulla oblongata of the albino rat

Summary The region of the reticular giganto-cellular nucleus, perfused with formalin and postfixed in osmium tetroxide, was studied with histochemical and electron microscopic techniques. The perikarya of the neurons have two zones. The peripheral cytoplasm contains Nissl bodies, mitochondria, and free RNP particles. The juxtanuclear cytoplasm contains the Golgi complex, mitochondria, RNP particles and dense bodies. The nucleus is indented and has a prominent nucleolus and a paranucleolar body. Dense bodies are found along the axon and dendrites as well. Three different types of synapses are described and two types of synaptic vesicles (spherical and ellipsoidal) are shown.The capillary endothelium shows microvilli and marginal flaps. The endothelial cytoplasm contains vacuoles, micropinocytotic vesicles, and a few dense bodies. Processes of pericapillary cells, surrounded by a basement membrane, also contain dense bodies. The dense bodies found in the neurons and endothelial cells show acid phosphatase activity. On the basis of their morphology and their enzymatic activity these bodies are identified as lysosomes.Partially supported by a school grant No RF 62051 from the Rockefeller Foundation, New York, USA, and Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.Fellows of the Consejo National de Investigaciones Científicas y Técnicas, Argentina. The authors wish to thank Dr. Mario H. Burgos for his constant interest and criticism, and to Dr. Eduardo Rodriguez Echandia and Dr. Fabio L. Sacerdote for their valuable assistance.     

Hymenolepis diminuta: ultrastructural observations on complement-mediated tegumental lysis and destrobilation of 4-day-old worms in vitro

Changes in the ultrastructure of the tegument and subtegumental cells of 4-day-old Hymenolepis diminuta were studied in vitro in 50% fresh normal rat serum over a 5-h period and compared with heat-inactivated serum and saline controls. First, membrane-bound vesicles accumulate above the microthrix-border. After 30–40 min large vacuoles, which may contain membranous elements, appear in the tegument at a time when the surface of the young strobila is virtually denuded of the microthrix-border. With prolonged incubations there are subtegumental secretory inclusions with dark, enveloping cytoplasm in the tegument and finally the apical plasma membrane, together with the majority of the matrix, is lost. The disrupted portion of the worm is abruptly demarcated from the comparatively intact scolex/anterior neck region by a constriction. Even after 5 h incubation there is no evidence of loss of tegumental matrix components from regions anterior to the constriction but the neck region shows a significant denudation of the microthrix layer and the tegument contains numerous inclusions. The scolex tegument only showed little evidence of loss of membrane from the surface. Possible mechanisms for the avoidance of complement-mediated lysis in the anterior region are discussed.     

Electron microscopy of the tumulus and origin of associated structures within the tegument of Eubothrium salvelini Schrank, 1790 (Cestoidea: Pseudophyllidea)

Tedesco J. L. and Coggins J. R. 1979. Electron microscopy of the tumulus and origin of associated structures within the tegument of Eubothrium salvelini Schrank, 1790 (Cestoidea: Pseudophyllidea). International Journal for Parasitology10: 275–280. Validity of the tumulus, a new organ recently described on the tegument of Eubothrium salvelini, is confirmed. Spherical, dense inclusions approximately 0.23–0.29 μm were associated with the tumulus and with subtegumental cell bodies. Origin of these inclusions within subtegumental cell bodies and their transport via ducts to the tumulus is described. Inclusions are synthesized within granular endoplasmic reticulum and packaged by Golgi apparatus prior to transport. Inclusions were observed only in association with the tumulus within the tegumental distal cytoplasm.     

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.     

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.