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  • 1
    Electronic Resource
    Electronic Resource
    Cytoskeletal features of the syncytial epidermis of the tapeworm Hymenolepis diminuta (1989)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 13 (1989), S. 41-56 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; ultrastructure ; tegument ; syncytium ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A hallmark feature of parasitic platyhelminths is a cytoarchitecturally unusual syncytial epidermis composed of a peripheral layer of continuous cytoplasm (the ectocytoplasm) connected to underlying nucleated cell bodies by small cytoplasmic bridges. The helminth epidermis, or tegument, plays important roles in protection and nutrient acquisition; cestodes, in fact, completely lack a gastrointestinal tract and absorb all nutritive material through the tegument. Perhaps not surprisingly, the cestode tegument bears certain resemblances to the mucosal epithelium of the vertebrate small intestine, including the possession of a microvillous brush border upon the surface of the ectocytoplasm. In contrast to the intestinal epithelial cell, however, very little is known concerning the nature and organization of the cytoskeleton within the helminth epidermis. Therefore, a number of different microscopical preparative techniques were used to examine the tegument of the tapeworm Hymenolepis diminuta for the presence and distribution of microfilaments, intermediate filaments, and microtubules. It was found that both actin-containing microfilaments and intermediate-sized filaments are present but are restricted to specific locations along the plasmalemmae of the ectocytoplasm. In contrast, microtubules are found throughout the tegument, and are concentrated in the supranuclear regions of the perikarya and in the cytoplasmic bridges interconnecting the perikarya and ectocytoplasm. Unlike brush borders of most other epithelia, the cestode epidermal brush border lacks a filamentous terminal web and is instead associated with microtubules. A network of fine filaments, 5-8 nm in diameter but distinct from actin-containing microfilaments, runs throughout the ectocytoplasm and appears to interlink tegumental vesicles. These fine filaments may represent the primary “skeletal” system responsible for maintaining the structure of the tegumental cytoplasm.
    Additional Material: 33 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970130106
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of dimethylsulfoxide on the tegumental brush border of the cestodeHymenolepis diminuta (1992)
    Springer
    Parasitology research 78 (1992), S. 66-73 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Dimethyl sulfoxide (DMSO), commonly used for cryoprotection or for the solvation of cytoskeleton-modifying drugs, causes changes in the topology of the plasma membrane of the tegumental brush border in the tapewormHymenolepis diminuta; however, relatively long exposures or high concentrations are required. In tapeworms treated with DMSO concentrations of ≥1% in the present study, the interaction of the tegumental surface membrane with the underlying cytoskeleton may have been disrupted at focal points in the brush border, resulting in a partial loss of the membrane anchoring required for the structural integrity of the brush border. Blebbing of the tegumental surface was prominent only after exposure to 1% DMSO for 20 h in vitro culture with RPMI 1640, and vesiculation of the membrane along the microvillar (microtriche) shafts, which may have been related to the in vitro conditions, was amplified by the presence of concentrations of ≥1% DMSO in the incubation medium. The tegumental response to DMSO was not uniform but regional, consistently appearing to be more prevalent on the distal aspects of each proglottid rather than on the edge proximal to the scolex. Blebbing and vesiculation were not seen on the basal aspect of the tegument, including the basal ectocytoplasmic plasma membrane, the perikarya, and the internuncial processes. Microvillar core bundles of actin microfilaments persisted following 8 h in vitro exposure to all three concentrations of DMSO tested (0.1%, 1%, 5%); however, only in tapeworms that were treated in vitro with 5% DMSO for ≥ 8 h did core microfilament bundles appear to lose the rigidly straight and parallel organization characteristic of control tapeworms that were incubated either in the absence of DMSO or with 0.1% DMSO. Other components of the brush border cytoskeleton (i.e., microvillar caps, junctional tubules, and tunics) appeared unaffected by DMSO except at foci where blebbing occurred. These data suggest that in vitro concentrations of 〈1% DMSO have little observable effect on the anchoring of the tegumental surface membrane to the underlying cytoskeleton or the organization of the microfilamentous cytoskeleton of the brush border microvilli. The present investigation thus provides baseline data on DMSO-induced artifact for future studies that require the use of DMSO but do not focus on its effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00936184
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  • 3
    Electronic Resource
    Electronic Resource
    Development and dynamics of regional specialization within the syncytial epidermis of the rat tapeworm,Hymenolepis diminuta (1991)
    Springer
    Parasitology research 77 (1991), S. 161-172 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The epidermis of the tapewormHymenolepis diminuta is a highly organized syncytium, composed of an outer layer of continuous cytoplasm, or ectocytoplasm, and an inner layer of nucleated cell bodies, or perikarya. The perikarya are in direct cytoplasmic continuity with the ectocytoplasm via narrow plasmalemma-bound bridges called internuncial process. Although distinct structural and functional differences are apparent between ectocytoplasm and perikarya, all of the perikarya along the body of the cestode are morphologically similar, as are all regions of ectocytoplasm. However, immunocytochemically distinct subpopulations of perikarya and regionally defined areas of ectocytoplasm were identified along the tapeworm strobila by the use of monoclonal antibodies raised against a preparation of isolated tegument. The different types of perikarya and the regionally specialized areas of ectocytoplasm were organized in a topographically precise manner along the body of the parasite. Examination of labeling patterns after colchicine treatment suggests that different types of perikarya are specialized for biosynthesis of specific tegumental molecules and for turnover or recycling of tegumental material. Furthermore, it appears that a 52 kDa polypeptide synthesized by one population of perikarya is transported through the syncytium and ultimately resorbed by a different population of tegumental perikarya. These data suggest that the syncytial epidermis of parasitic platyhelminthes exhibits a more complex organization of function than previously appreciated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00935431
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