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Query: UMLS:C0276640 (TEM)
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Ultrastructural investigations (SEM, TEM) combined with lectin-binding analysis, have revealed concurrent modifications in tegumentary structure and surface glycoconjugates during the establishment and differentiation of Echinococcus multilocularis metacestodes in jirds. The laminated layer, which is amorphous and rich in polysaccharides when initially secreted by the young cyst, takes on a different appearance and has a different glycoconjugate composition according to whether the cyst becomes fertile or sterile. The laminated layer of fertile cysts transforms into a microfibrillar matrix, the protein content of which may increase while sugar content decreases during protoscolex differentiation. Independently of this structure, brood capsules, from which arise protoscoleces, are formed by invagination of the cyst tegument. The intense secretion of glycoconjugates from the brood capsule wall during invagination may serve to interact with host factors passing through the laminated layer. The combined use of ultrastructural study and lectin labelling has allowed the demonstration of an ultrastructural and biochemical gradient of differentiation of the protoscolex. Seven stages of differentiation have been described. The possibility that the excreted-secreted tegumentary glycoconjugates, revealed by lectin labelling during protoscolex differentiation, might be the gradual biochemical expression of one or several stimuli implicated in the phenomenon of protoscolex maturation, is discussed.
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PMID:Developmental changes of Echinococcus multilocularis metacestodes revealed by tegumental ultrastructure and lectin-binding sites. 161 30

The presence of glycoconjugates in the otolithic organ of developing chick embryos was investigated histochemically using lectins. On the 6-day-old chick embryo, intense labelling with lectins was observed in the sensory epithelium, on the surface of the epithelium and on the immature otoconia. The otoconia were intensely labelled with lectins at every stage of the chick embryos, while the labelling with lectins in the sensory epithelium became weaker with the maturing of the otoconia. In TEM observation, the secretory granules of the supporting cells of the sensory epithelium were labelled with lectin. The reaction of lectin was more intense in the electronic dense zone of the otoconium than in the electronic lucent zone at every stage of the chick embryos. These findings indicate that the precursors of the otoconia are secreted by the supporting cells of the sensory epithelium and that glycoconjugates play an important role in otoconial formation.
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PMID:Glycoconjugates in the otolithic organ of the developing chick embryo. 192 61

From a very early phase we studied 15 patients suffering from a dry-eye condition ant associated to systemic diseases. Conjunctival biopsies were studied in Transmission (TEM) and Scanning (SEM) electron microscopy. Moreover, the lectin-gold cytochemistry at ultrastructural level was applied to investigate the distribution of some glycosidic receptors produced by both the goblet cells and the vesicles belonging to the Second Mucus System (SMS). No evidence of epithelial stratification and only a decrease in the goblet cell population was observed. The SMS vesicles and the superficial cell microvilli did not appear greatly reduced in number. A difference in the mucus composition in terms of content of glycosidic residues was detected in dry-eye patients compared to the normal subjects. The role of the mucus produced by both the goblet cells and the SMS vesicles in debated. A possible correlation between the alteration of the mucus content and the failure of the tear film stability is proposed. On the basis of these data, a new therapeutic approach for eye dryness is suggested.
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PMID:Mucus alteration and eye dryness. A possible relationship. 280 Oct 51

Colloidal gold may be conjugated to a wide variety of macromolecules, provides a versatile system for immunocytochemical studies by various types of microscopy (light and fluorescent microscopy, scanning (SEM) and transmission (TEM) electron microscopy), and is significantly contributing to the development of SEM immunocytochemistry as a routine analytical procedure. A comprehensive overview has been compiled of the literature on SEM bioapplications of colloidal gold. This is illustrated through a selected series of studies focussing on a) cell surface receptor-ligand interactions; b) expression of cell surface lectin-binding sites; c) surface distribution of extracellular matrix components; and d) visualization of gold-labelled cytoskeletal elements with emphasis on the use of backscattered electron imaging as a powerful analytical adjunct in the development of SEM immunocytochemistry.
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PMID:Colloidal gold--a powerful tool in scanning electron microscope immunocytochemistry: an overview of bioapplications. 329 62

A method using low concentrations of formaldehyde and dithiothreitol was applied to obtain 'right-side out' luminal plasmalemma-derived vesicles from bovine aortic endothelial cells (EC) in culture, and from human umbilical vein and bovine or porcine aortas perfused ex vivo with the vesiculation solution. Vesicle formation and shedding were examined by phase-contrast microscopy and by transmission (TEM) and scanning electron microscopy (SEM). Vesicles showed the characteristic trilaminar pattern of the unit membrane and did not contain cellular organelles. As detected in freeze-fracture preparations, vesicle membrane displayed intramembrane particles and filipin-detectable cholesterol. Like EC plasmalemma, vesicle surface was heavily stained by Ruthenium Red and bound under a normal pattern cationized ferritin and ferritin hydrazide. As indicated by lectin agglutination assays and by ultrastructural cytochemistry, vesicles maintained on their ectodomains glycoconjugates bearing monosaccharides such as N-acetyl-neuraminic acid, beta-N-acetylglucosamine and beta-D-galactose, and expressed 5'-nucleotidase activity. The electrophoretic profiles of externally disposed 125I-labelled polypeptides of vesicles were found to be similar to those of intact EC. Chemically-induced vesiculation appears as a suitable method to obtain EC plasmalemma for studying its composition and functions in various vascular beds.
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PMID:Endothelial cell plasma membrane obtained by chemically induced vesiculation. 359 39

The role of tight junctions (zonula occludens) in the formation of apical plasma membrane (PM) domains was investigated in the embryonic rat pancreas. In the present study, lectin-rhodamine (WGA-TRITC and RCAII-TRITC) and lectin-gold (WGA-Au and RCAII-Au) conjugates were used to monitor apical PM domain formation and freeze-fracture analysis was used to monitor tight junction formation in the pancreatic epithelium of embryonic, neonatal, and adult rats. Fluorescent and TEM analysis of WGA and RCAII binding indicated that an apical PM domain is formed as early as Day 13 of gestation in the pancreatic epithelium. While apical WGA binding remained into adult life, RCAII binding was lost by 1 day after birth. In contrast, tight junctions were not observed until Day 14 of gestation. At this time, tight junctions were found to be incomplete in formation and typically consisted of linear arrays of IMPs or discontinuous arrays of sealing strands (focal adherens). Continuous tight junctions were not completely formed until Day 15 of gestation. Continued development of tight junctions during gestation was characterized by (1) an increase in the number of sealing strands and (2) a more parallel arrangement of sealing strands within each junctional complex. By 8 weeks after birth, tight junctions were more loosely organized and contained fewer sealing strands as compared to that observed in the fetus. These results suggest that lateral diffusion of apical PM glycoconjugates may be restricted even in the absence of complete tight junctional complexes during development of the rat pancreas.
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PMID:Development of an apical plasma membrane domain and tight junctions during histogenesis of the mammalian pancreas. 384 Oct 81

A fucose binding protein was detected in boar spermatozoa by means of a specifically developed modified enzyme-linked-lectin-assay using glycosylated peroxidase derivatives. The distribution of the fucose binding protein was assessed by means of fluorescence microscopy with fluoresceinyl-glycosylated peroxidase. Fucose binding was particularly prominent at the apical region of the sperm head. In order to gain more insight into the precise localization of the carbohydrate binding protein electron microscopical studies were performed using fucosyl peroxidase coupled to colloidal gold. In ultrathin sections as well as in specimens prepared in toto for TEM an intensive binding of fucosylperoxidase-colloidal gold was predominantly found at the apical part of the acrosome appearing as a crescent-like area. In some cases this binding pattern was replaced by a triangle-like intensive labelling at the equatorial segment as revealed clearly by specimens prepared in toto. By SDS-PAGE of the SDS-extractable sperm-proteins, followed by transblotting to nitrocellulose and visualization with the fucosylperoxidase by enzymatic amplification with 4-chloro-1-naphthol mainly one protein with the reduced molecular weight of approximately 53 kdal and some small proteins with apparent molecular weights less than 20 kdal was found to be responsible for the fucose-binding ability of porcine spermatozoa.
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PMID:Evidence for a fucose-binding protein in boar spermatozoa. 390 13

Endothelia lining the 2 surfaces (arterial and ventricular) of the posterior cusp of aortic valves from normocholesterolemic, New Zealand white rabbits were found to display pleomorphic surface features characterized by differences in cellular shape and orientation to the direction of blood flow, microappendage populations (microvilli and blebs), nuclear contours and the surface reactions of cationic dyes (RR, AB) and peroxidase-conjugated lectins (Con A, Limulin, WGA). With the aid of SEM and TEM, the cells lining the arterial surfaces appeared relatively smooth and flattened with a moderate to heavy reaction of the carbohydrate cell coat at the blood interface. By contrast, the contours of the endothelia lining the ventricular surfaces were noticeably raised with numerous plasmalemmal microappendages and only a moderate dye/lectin reaction. Observations of similar endothelial populations from diet-induced, hypercholesterolemic rabbits (500 mg/dl) revealed a variety of dramatic changes in the cells lining the arterial surfaces of the valvular cusps. No severe changes were observed in the endothelia of the ventricular surfaces. Such findings are suggestive further of the importance of the interaction between the environment and the endothelial cell coat as influencing factors in the onset of intramural lipid infiltration.
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PMID:Surface responses of aortic valve endothelia from diet-induced, hypercholesterolemic rabbits. 399 84

Echis coloratus venom (ECV) treated human and mouse lymphocytes were examined for synthesizing activities and morphologic alterations. RNA, DNA and protein synthesis were markedly inhibited. Human cells were less affected than mouse lymphocytes. No mitogenic activity was observed. Transmission (TEM) and scanning electron microscopy (SEM) revealed membranal damage in all types of lymphocytes and a considerable degree of agglutination. Human lymphocytes showed concentration of the microvilli at one pole of the cell. This phenomenon was considered as a capping effect. The action of ECV may be compared with the effect of the nonmitogenic lectin RCAII, known to penetrate the cells by endocytosis and to inhibit their protein synthesis.
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PMID:Lectin-like effect of Echis coloratus Venom on human and mouse lymphocytes. 616 59

Binding sites for Con A and WGA were detected on bovine spermatozoa during epididymal maturation. We used colloidal gold as an EM-marker. The spermatozoa were treated according to a two-step method for lectin and colloidal gold, then adsorbed to lysine-coated nickel grids and subsequently examined by TEM in toto. Using this method we rapidly got information about the topographic distribution of lectin-binding sites. Major differences exist for WGA between caput and cauda spermatozoa. Conceding that cell-thickness poses some limitation, we consider this method to be practical and especially useful in studies concerning topographic distribution of cell surface components in single cell systems.
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PMID:Con A- and WGA-binding sites on bovine epididymal spermatozoa: TEM of specimens in toto. 623 81


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