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  • 1
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The relative effects on tegumental Na+/ K+ -ATPase activity in Fasciola hepatica of the deacetylated (amine) metabolite of diamphenethide (DAMD) (10 Μg/ml, 18 h) and the Na+/K+-ATPase inhibitor ouabain (0.1 mM, 0.5 h) have been assessed cytochemically. In the normal tegument, Na+/K+-ATPase activity is particularly concentrated along the invaginations of the apical plasma membrane and the infoldings of the basal plasma membrane. Ouabain pretreatment significantly reduces the overall level of Na+/K+-ATPase activity, but does not induce swelling of the basal infolds. In contrast, DAMD does not significantly reduce either the level or distribution of Na+/K+-ATPase activity, but does cause a pronounced swelling of the basal infolds. The results are discussed in relation to the postulated action of diamphenethide as an inhibitor of Na+/K+-ATPase activity.
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  • 2
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effect on the tegument of adultFasciola hepatica of incubation in the sodium ionophore monensin, the Na+/K+-ATPase inhibitor ouabain and ouabain pretreatment followed by monensin has been determined in vitro by scanning and transmission electron microscopy (SEM, TEM). With monensin incubation alone (1×10−6 M), a flattening of the tegument with some loss of spines on the ventral surface is evident from 0.5 h onwards. Internally, the subtegumental musculature becomes grossly swollen, although there is no swelling of the infoldings of the basal plasma membrane of the tegument, even after 24 h incubation. Ouabain incubation (1×10−3 M) induces folding of the apical surface of the tegument from 0.5 h onwards, and this is accompanied by the formation of bleds and microvilli. Brief (0.5 h) exposure to ouabain (1×10−3 M) followed by monensin treatment (1×10−4 M, 3 h) leads to gross “vacuolation” of the tegument, but this is not due to swelling of the basal infoldings. The other main feature of ouabain-pretreated flukes is the projection of basal lamina-like material into the tegumental syncytium. Monensin treatment alone (1×10−6 M) results in the Golgi complexes of the tegumental cells becoming very diffuse from 1.5 h onwards, and relatively few secretory bodies are present in the cytoplasm. After 0.5 h incubation in ouabain (1×10−3 M), the Golgi complexes of the tegumental cells are indistinct, although numerous secretory bodies are still present. The classical monensin-induced swelling of the Golgi cisternae is observed in the tegumental cells only when monensin treatment (1×10−4 M, 3 h) was preceded by brief (0.5 h) exposure to ouabain (1×10−3 M). The results are discussed in relation to the postulated osmoregulatory role of the tegument and the role of sodium pumps in membrane function in the fluke.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 305 (1995), S. 309-316 
    ISSN: 1573-5117
    Keywords: platyhelminths ; neuropeptides ; localisation ; isolation ; molecular studies ; physiological roles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-8412
    Keywords: conceptual analysis ; knowledge representation ; knowledge engineering ; semantic networks ; text analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Media Resources and Communication Sciences, Journalism
    Notes: Abstract This article addresses the methodological problem of the non-linear representation of philosophical systems in a computerized knowledge base. It is a problem of knowledge representation as defined in the field of artificial intelligence. Instead of a purely theoretical discussion of the issue, we present selected results of a practical experiment which has in itself some theoretical significance. We show how one can represent different philosophies using CODE, a knowledge engineering system developed by artificial intelligence researchers. The hypothesis is that such a computer based representation of philosophical systems can give insight into their conceptual structure. We argue that computer aided text analysis can apply knowledge representation tools and techniques developed in artificial intelligence and we estimate how philosophers as well as knowledge engineers could gain from this cross-fertilization. This paper should be considered as an experiment report on the use of knowledge representation techniques in computer aided text analysis. It is part of a much broader project on the representation of conceptual structures in an expert system. However, we intentionally avoided technical issues related to either Computer Science or History of Philosophy to focus on the benefit to enhance traditional humanistic studies with tools and methods developed in AI on the one hand and the need to develop more appropriate tools on the other.
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  • 5
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract At a concentration of 1×10−4 M (28.84 Μg/ml), with a solvent concentration of 1.0% (v/v) ethanol, the deacetylated (amine) metabolite of diamphenethide (DAMD) causes an initial stimulation of activity, followed by suppression, leading to a paralysis within 3 h. These changes are accompanied by an increase in muscle tone of more than 200 mg. However, ethanol alone at a concentration of 1.0% (v/v) causes an initial stimulation of activity and increase in muscle tone (approximately 550 mg). If the concentration of DAMD is kept at 1×10−4 M (28.84 Μg/ml) but the solvent concentration reduced [e.g., 0.05% (v/ v) dimethyl sulphoxide], then only a suppression of motility and flaccid paralysis are observed. This response is also seen at the lower concentration of 10 Μg/ml, which corresponds to the maximum blood levels of DAMD in vivo. The sodium ionophore monensin induces a suppression of motility, leading to a rapid flaccid paralysis (in approximately 1.5 h at 1×10−7 M, and within a few minutes at higher concentrations). Ouabain, an inhibitor of Na+/K+-ATPase activity, also causes a suppression of motility, but this is accompanied by an increase in muscle tone, leading to a spastic paralysis (in approximately 2.5 h at 1×10−3 M, and 3.5 h at 1×10−4 M). Pretreatment with ouabain (1×10−3 M for 15 min) followed by monensin (1×10−5 M) reverses the original effect of monensin by inducing a rapid spastic paralysis (in approximately 50 min). A similar effect is observed with DAMD (10 Μg/ml) following ouabain pretreatment; a spastic paralysis is reached after approximately 80 min. The results are discussed in relation to the postulated activity of DAMD as a sodium ionophore, Na+/K+-ATPase inhibitor, or neuromuscular depressant.
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  • 6
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The present study describes the effects of the H+ ionophore and anthelmintic closantel upon the in vitro motility and in vivo ultrastructure of the liver fluke,Fasciola hepatica. At a concentration of 50 μg/ml, closantel caused an initial stimulation, then suppression of activity, which was accompanied by an increase in muscle tone and led to a spastic paralysis within 2 h. The pattern of response was similar at lower concentrations, although the initial stimulation was not always evident, but the onset of paralysis could be reached more quickly. Scanning electron microscopy revealed gross surface damage from 24 h onwards in vivo, in the form of erosion of the anterior and posterior extremities of the fluke and large-scale sloughing of the tegument on both dorsal and ventral surfaces. Tegumental changes prior to sloughing included some swelling of the basal infolds and an apical accumulation of T1 secretory bodies. In the underlying tegumental cells there was reduced secretory activity and the mitochondria were consistently swollen and deformed. Reduced secretory activity was a feature of the gastrodermal cells as well; these cells were characterized by swollen, electron-lucent mitochondria, vesiculated GER cisternae and apical blebbing of packets of cytoplasm. The vitelline follicles became severely disrupted as a result of the breakdown of the nurse cell cytoplasm. The stem and intermediate type 1 (It1) cells rounded up and showed nuclear abnormalities. There did not appear to be a severe disruption of shell protein production in the intermediate vitelline cells, but there was a noticeable absence of glycogen in the mature vitelline cells. The effects of closantel are discussed in relation to its proposed mode of action as an uncoupler of oxidative phosphorylation.
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  • 7
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0878
    Keywords: Neuropeptides (pancreatic polypeptide, peptide YY, neuropeptide Y) ; Immunocytochemistry ; Confocal scanning laser microscopy ; Schistosoma mansoni (Scolecida, Trematoda)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The presence and distribution of neuropeptides belonging to the pancreatic polypeptide family have been demonstrated by an indirect immunofluorescence technique in the nervous systems of adult male and female Schistosoma mansoni. Seven antisera of differing regional specificity to pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY) were employed on both whole-mount and cryostat-sectioned material. Positive immunoreactivity (IR) was obtained with all antisera except an N-terminally-directed antiserum to NPY. In the CNS, immunoreactivity was restricted to cell bodies and nerve fibres in the anterior ganglia, central commissure and dorsal and ventral nerve cords of both sexes, whereas, in the PNS, positive-IR was present in the plexuses innervating the subtegumental musculature and the oral and ventral suckers. Intense immunoreactivity was observed in a plexus of nerve fibres and cell bodies in the lining of the gynaecophoric canal and in fine nerve fibres innervating the dorsal tubercles of the male. In contrast, in the female, strong immunoreactivity was evident in nerve plexuses innervating the lining of the ovovitelline duct and in the wall of the ootype, but most notably in a cluster of cells in the region of Mehlis' gland. Results suggest that molecules with C-terminal homology to the PP-family are present in S. mansoni. These peptides would appear to be important regulatory molecules in the parasite's nervous system and may play a role in the control of egg production.
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Knowledge Acquisition 5 (1993), S. 305-346 
    ISSN: 1042-8143
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Computer Science
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 287 (1980), S. 467-467 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] CHRISTIE AND SCLATER'S refraction results1 corroborate our inference from regional gravity2 that the crust under the Buchan and Witchground Graben area of the North Sea is anomalously thin (see Fig. 1). However, their mechanism3 for the development of the grabens, invoking crustal stretching by a ...
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