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  • 1
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The surface topography of three cestode parasites from the gut ofSqualus acanthias is described with the aid of scanning electron microscopy (SEM). The cestodes areTrilocularia acanthiaevulgaris, which occurs in both stomach and spiral valve, andPhyllobothrium squali andGilquinia squali, which only appear in the latter. Differences between the stomach and spiral valve forms ofT. acanthiaevulgaris are recorded. The anterior third of the free proglottis of this species is covered by numerous large, backwardly-projecting spines. Bands of similar, though smaller, spines encircle the anterior margins of proglottides still attached to the strobila and grow larger as the proglottides mature. The adherent surface of the bothridia ofP. squali is covered by large numbers of minute “ear-of-corn” projections, in addition to more normal microtriches, whilst that ofG. squali bears numerous flat, plamate structures. The mature and free proglottides ofG. squali possess large numbers of short, rod-like structures around the genital pore and they are surrounded by a ring of hummock-like papillae. The possibilities of these microtopographical features being used in a sensory and/or attachment role are considered. The value of SEM as a taxonomic aid in cestode systematics is briefly discussed.
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  • 2
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Differences in the internal anatomy and ultrastructure ofTrilocularia acanthiaevulgaris from the stomach and spiral valve of the spiny dogfish are described with the aid of electron microscopy and light microscope histochemistry. Worms from the stomach rarely exceed 7 mm in length and do not exhibit signs of segmentation. In contrast, spiral valve worms are segmented, reach a length of some 30 mm and release free proglottides which mature whilst detached from the strobila. Numerous calcareous corpuscles and large glycogen-filled vacuolations occur throughout the body of stomach worms, but are almost totally absent from spiral valve worms. The neck region of spiral valve worms is packed with many germinative cells. The distal tegumental cytoplasm of the stomach worm contains many electron-lucid vesicles, mitochondria and forming microtriches. Microtriches on the tegumental surface are scant, and those present are directed posteriorly. The distal tegumental cytoplasm of the spiral valve worm contains few electron-lucid vesicles and mitochondria but has many dumb-bell-shaped vesicles. Microtriches are longer and more numerous than those of stomach worms. The differences suggest thatT. acanthiaevulgaris worms from the stomach are juveniles which migrate to the spiral valve where they develop into the adult.
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  • 3
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mature calcareous corpuscles in the juvenile (stomach) worms of Trilocularia acanthiaevulgaris comprise a number of concentric lamellae interspersed with areas of flocculent material. Each lamella is composed of a pair of membranous rings to which amorphous, non-crystalline material is attached. The process of corpuscle formation is intracellular, beginning with the autophagic breakdown of the cytoplasm to produce a central vacuole within a parenchymal cell. The vacuole enlarges until only a thin layer of cytoplasm remains at the periphery and the nucleus is displaced to one end of the cell. Paired, concentrically arranged membranes are laid down beneath the peripheral cytoplasmic layer and eventually occlude the central vacuole. X-ray analysis of the corpuscles indicates the presence of calcium, phosphorus, sulphur, zinc and molybdenum, with the major peaks representing calcium, phosphorus and sulphur. Calcium appears to be bound to the lamellae rather than associated with the material between lamellae. The possible functions of the corpuscles are discussed in relation to the biology of T. acanthiaevulgaris and its developmental sequence in the dogfish gut.
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  • 4
    ISSN: 1432-1432
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 5
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The ultrastructure of the scolex glands ofTrilocularia acanthiaevulgaris is described with the aid of transmission electron microscopy. The syncytial scolex gland cells exhibit an ultrastructure which is typical of secretory cells, in that they contain extensive and distended cisternae of granular endoplasmic reticulum (GER), numerous Golgi complexes and secretory vesicles. The vesicles are transported via microtubule-lined ducts to the apex of the scolex where they are released from the tegumental surface by an eccrine process. The secretion is often accumulated in reservoirs created by a lateral swelling of the ducts. Cytochemical studies show that the secretion has a glycoprotein nature. It is suggested that the secretion probably acts as an adhesive, aiding attachment of the worm to the host mucosa. This may be more important in juvenile worms which have less well-developed scoleces.
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  • 6
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The localisation and distribution of the cholinergic and serotoninergic components of the nervous system in the plerocercoid, adult and free proglottis stages of the tetraphyllidean tapewormTrilocularia acanthiaevulgaris were determined by enzyme histochemical and immunocytochemical techniques. The central nerve ring (CNR) in the scolex contains two lateral ganglia and gives rise to five pairs of longitudinal nerve cords (LNC's; three lateral, two median). The nerve cords run posteriorly throughout the bodies of the plerocercoid and adult worms and the free proglottis. Nerves from the CNR and accessory lateral LNC's pass to the bothridia, where they give rise to extensive nerve plexuses. As the individual proglottides develop along the strobila, a small nerve ring forms at the anterior end of each proglottis; within the nerve ring, distinct bilateral ganglia develop prior to the release of the proglottis. All ten LNC's are present in the free proglottis. The genital atrium and cirrus sac are innervated by cholinergic and serotoninergic elements. The cholinergic nervous system predominates in the CNS within the scolex, whereas there is a larger population of 5-HT-immunoreactive nerve cells associated with the LNC's and segmental ganglia along the strobila and within the free proglottis.
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  • 7
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The fine structure of the excretory system in the juvenile (plerocercoid-like) form ofTrilocularia acanthiaevulgaris is described. The flame cell bears a bunch of 50–70 cilia, which are anchored in the cytoplasm by means of basal bodies possessing striated rootlets. All the cilia in the “flame” are aligned in the same direction. The flame and duct cells are connected by interdigitating ribs of cytoplasm separated by a fibrous sheet. Both internal and external leptotriches are also present. The lumen of the excretory ducts is intracellular in origin. The apical surface of the cytoplasm lining the duct is convoluted and its surface area is further amplified by means of microvilli. The fine structure of the excretory system in this primitive tapeworm is compared with that described for other parasitic and free-living flatworms.
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  • 8
    ISSN: 1573-2568
    Keywords: inflammatory bowel disease ; lymphoma ; colitis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We describe the first reported case of mantle zone lymphoma of the colon presenting as diffuse ileocolitis simulating severe inflammatory bowel disease. This case serves to illustrate the importance of immunohistochemistry in establishing the diagnosis of lymphoma in extranodal sites.
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  • 9
    ISSN: 1435-1803
    Keywords: Potassium channel openers ; monophasic action potentials ; refractory period ; dofetilide ; calcium currents ; guinea pig ventricular myocytes ; whole cell patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of the potassium channel openers (KCO), cromakalim or pinacidil, were evaluated in an anesthetized porcine model of pacing- and ischemia-induced ventricular fibrillation (VF). Hearts were paced at 180 bpm and the left anterior descending coronary artery was occluded until VF was induced. Reproducible times to VF (in seconds) were obtained allowing at least 20 min recovery following defibrillation. Cromakalim (0.3 mg/kg) or pinacidil (3 mg/kg) produced equivalent drops in mean arterial blood pressure. At these doses, cromakalim reduced monophasic action potential duration measured at 90% repolarization (APD90). Although time to VF in the cromakalim group was significantly greater than the vehicle treated group, it was not significantly different from its predrug value. In contrast, pinacidil reduced APD90, and significantly increased time to VF from 134±5 to 322±62 s (p〈0.05). Neither cromakalim nor pinacidil affected whole-cell calcium currents recorded in guinea pig myocytes. During ischemia, cromakalim or pinacidil further reduced APD90; however, pinacidil had a two-fold greater effect than did cromakalim. The Class III antiarrhythmic agent, dofetilide, prolonged APD90, but did not increase time to VF. In conclusion, the increased time to VF observed with pinacidil coincides with its ability to shorten APD, and is consistent with activation of ATP-sensitive K+ channels (K+ ATP). It is suggested that indirect reduction of calcium influx through K+ ATP activation and APD shortening is sufficient to increase time to VF in this model. However, the inability of dofetilide to be effective suggests that this model would not be useful to test for Class III antiarrhythmic agents.
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