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  • 1
    ISSN: 1573-675X
    Keywords: Apoptosis ; beta cells ; cytokines ; Islets of Langerhans ; nitric oxide ; peroxynitrite ; superoxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have shown that nitric oxide treatment for 30–90 min causes inhibition of insulin secretion, DNA damage and disturbs sub-cellular organization in rat and human islets of Langerhans and HIT-T15 cells. Here rat islets and beta-cell lines were treated with various free radical generating systems S-nitrosoglutathione (nitric oxide), xanthine oxidase plus hypoxanthine (reactive oxygen species), 3-morpholinosydnonimine (nitric oxide, super-oxide, peroxynitrite, hydrogen peroxide) and peroxynitrite and their effects over 4 h to 3 days compared with those of the cytokine combination interleukin-1β, tumour necrosis factor-α and interferon-γ. End points examined were de novo protein synthesis, cellular reducing capacity, morphological changes and apoptosis by acridine orange cytochemistry, DNA gel electrophoresis and electron microscopy. Treatment (24–72 h) with nitric oxide, superoxide, peroxynitrite or combined cytokines differentially decreased redox function and inhibited protein synthesis in rat islets of Langerhans and in insulin-containing cell lines; cytokine effects were arginine and nitric oxide dependent. Peroxynitrite gave rare apoptosis in HIT-T15 cells and superoxide gave none in any cell type, but caused the most beta cell-specific damage in islets. S-nitroso-glutathione was the most effective agent at causing DNA laddering or chromatin margination characteristic of apoptotic cell death in insulin-containing cells. Cytokine-induced apoptosis was observed specifically in islet beta cells, combined cytokine effects on islet function and death most resembled those of the mixed radical donor SIN-1.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Microsomal fractions from wheat coleoptiles and pea stems contain a microsomal ATPase activity that requires divalent cations (Ca2+ is more effective than Mg2+) and shows further stimulation by KCl. The effects of added indoleacetic acid were inconclusive. Cytochemical studies on both species showed most pronounced staining for ATPase in the plasmalemma at pH 7.0. However, at pH 5.5, the coleoptile cells showed heaviest staining for ATPase in the endoplasmic reticulum and dictyosomes. The results are discussed with regard to the postulated role of ATPase activity in relation to proton pumping and plant cell elongation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4927
    Keywords: heterozygosity ; neutralism ; selectionism ; Porifera ; Coelenterata ; enzyme structure ; enzyme function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In this paper extensive data on enzyme variation in 23 species of coelenterates and sponges were used to investigate the possible correlation of levels of genetic variation with various parameters of enzyme molecular structure and function. The data provide an opportunity not only to look for such correlations for the first time in lower invertebrates, but also to study organisms with far higher average levels of genetic variability than those used in any previous work. A clear inverse relationship was found between enzyme subunit number and levels of polymorphism, with monomers being more variable than dimers or tetramers. No significant difference in polymorphism could be found in enzymes of the functional groups I and II of Gillespie and Langley (1974). Regulatory enzymes appeared to be significantly more polymorphic than nonregulatory enzymes, but a significant relationship was observed between regulatory power and subunit structure which could bias this result. The results suggest that both neutralist and selectionist ideas may have a useful role to play in the understanding of the factors which can influence or limit levels of genetic variation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    AI & society 9 (1995), S. 258-272 
    ISSN: 1435-5655
    Keywords: Action ; Design ; Discourse ; Innovation ; Language ; Methodology ; Tacit knowledge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This contribution to design methodology reflects upon the barriers to effectiveness imposed by our tendency to gravitate towards the over-formal in human affairs. We see a correspondingly cleaned-up description of the process of design, a failure to consider its jagged elements and to take proper account of the non-formal in knowledge (e.g. tacit knowledge) and communication. Discipline in methodology is accordingly wrongly equated with formality. The failure of design to be effective is more likely for innovative design rather than routine design. It is suggested by way of explanation that design methodology especially in the field of information technology is infused with the ghost of positivism, manifest in an unconditional belief in the value of rationality and an implied naive realist conviction about the fixed, singular and transparent nature of the environment for which design is undertaken. We need to be able to work with uncertainty rather than try for its entire elimination. A breadth of approach in carrying out the activity of design is threatened by lack of attention to the variety of forms which knowledge and corresponding forms of discourse can take. We undertake the disciplined reduction from the messy real work to metaphors tidy enough to work with, or models as they are usually misnamed. The notion of “language of struggle” is invoked as a suitable metaphor for the non-formal discourse particularly relevant to innovative design. A complementary exploration is offered of socio-linguistic space which is the common context for design. In view of the concern with social space necessary to effective design, it may be enlightening to consider the designer as applied anthropologist.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 420 (2000), S. 165-184 
    ISSN: 1573-5117
    Keywords: genetic variation ; invertebrates ; fisheries ; stocks ; larvae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The application of genetic techniques to invertebrate fisheries is in many ways essentially similar to that in vertebrate (i.e. finfish) fisheries, for which there is already an extensive body of published data. However, there are also relative differences which lead to particular problems in the use of genetic data to study commercially important invertebrate species. The main role for genetics of both vertebrates and invertebrates has been, and is likely to continue to be, the identification of groups of interbreeding individuals as the basis for a fishery. It is in the identification of the breeding unit that the genetic differences between vertebrates and invertebrates can be of practical significance. The genetic breeding unit, usually called a 'stock' in fisheries biology, generally shows a certain uniformity of size in most marine fish which have been studied. Smaller or less mobile fish (e.g. flatfish) may only range a few tens of kilometres to their breeding grounds, whilst in more mobile, particularly migratory pelagic species (e.g. Scombridae), the area occupied by a stock is likely to be far greater and for a few (e.g. large pelagic elasmobranchs), a single unit of stock may be almost circumglobal. However, marine fish generally, particularly those large or plentiful enough to be of commercial interest, are likely to be fairly mobile and in many cases the order of mobility is likely to be in the region we might predict from our knowledge of the biology and habits of the species. In the genetic assessment of `stocks' for invertebrate fisheries, we face a number of additional problems, mostly related to the large evolutionary range of invertebrates exploited and their widely different biology. Although in Europe and North America marine invertebrate fisheries may be thought of as being mainly for decapod crustaceans and bivalve molluscs, globally commercially important marine invertebrate fisheries range from sponges to squid and include such diverse groups as sea cucumbers, barnacles, krill, octopuses, cuttlefish, sea anemones, ascidians, polychaetes, sea urchins, gastropods and jellyfish. An obvious feature of many of these invertebrates is that the adult (i.e. commercial) stage of the life cycle is sessile (e.g. barnacles, sponges, ascidians) or of very limited mobility (e.g. sea anemones, sea urchins, bivalves, gastropods), with the result that the dispersive phase of the life cycle is the larva. Other groups (e.g. krill, jellyfish) are planktonic or nektonic and may cover very large distances, but, unlike fish, have little control over the distance or direction of travel, whilst some of the open ocean pelagic squid are more mobile than most fish and may migrate thousands or kilometres to spawning grounds. The very low mobility of both larva and adult in some invertebrates indicates that dispersal, and hence stock size, is likely to be low and that, therefore, stocks are far more vulnerable to overfishing than in most fish species. An additional difficulty is that genetic studies to date indicate a remarkably high incidence of cryptic speciation in marine invertebrates, sometimes even in comparatively well studied commercially important species. Thus, although to date marine invertebrate fisheries have not received the same level of attention from geneticist as finfish fisheries, it is clear that for invertebrate fisheries genetic data are relatively far more important if a fishery is to be exploited without being endangered.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5117
    Keywords: Crustacea ; Majidae ; allozymes ; gene flow ; larval dispersal ; Inachus ; Hyas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spider crabs Inachus dorsettensis (Pennant) and Hyas coarctatus Leach are widespread in subtidal areas of muddy sand or gravel around western Europe. Both species have a life cycle with an obligatory planktonic larval phase of several weeks, which might be expected to cause widespread larval dispersal and consequent genetic homogeneity over considerable distances. However, earlier work on both taxa has indicated differences in growth pattern between populations separated by tens of kilometres. This study was undertaken to determine whether these differences were purely environmental or whether, despite the short distances involved, differences may have a genetic basis. A study of gene frequencies, as indicated by allozymes in samples of adults collected off the Isle of Man (northern Irish Sea), indicates significant genetic differentiation between populations over a geographical distance of only about 40 km in both Inachus dorsettensis (θ = 0.086 ± 0.048) and Hyas coarctatus (θ = 0.023 ± 0.017). Variability measures differed between species, showing I. dorsettensis to have a mean number of alleles per locus of 2.5–2.6 and a range of gene diversity of 0.216–0.241, while H. coarctatus showed lower values of mean number of alleles (1.9–2.0) and a range of gene diversity from 0.122 to 0.124. Given the high expected larval mobility of the two species the results are most surprising. Possible explanations are discussed in relation to population discontinuities and patterns of larval drift.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5117
    Keywords: aquatic resources ; management ; top down effects ; life history strategies ; population genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5168
    Keywords: Na+ exchange ; salmon migration ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Whole-body (but predominantly gill) Na+ exchange, gill Na+/K+/ATPase activity and seawater tolerance were examined in juvenile Atlantic salmon during the smolting period. Transepithelial net Na+ gain decreased steadily from late February showing a net loss in April and early May, returning to approximate equilibrium in mid-May. This seasonal net loss of Na+ to the environment occurred slightly after maximal gill epithelial Na+/K+/ATPase activity and preceded maximal seawater tolerance. The results are discussed in relation to changes in gill permeability and salt intake via the diet.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 261 (1998), S. 241-244 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron ionization (EI) spectra and both positive and negative chemical ionization (CI) spectra have been obtained for four isoquinolinium ylides and two pyridinium ylides. Electron transfer reactions dominate the CI mass specra. The base peak in negative chemical ionization is the [M]-· ion, formed by electron capture. In the positive methane CI spectra the molecular ion, [M]+·, is relatively more intense than [MH]+ showing electron transfer to be the main positive ionization process. In the positive ammonia CI spectra, proton transfer to give [MH]+ is the main ionization process, but electron transfer is also observed. The EI spectra show fragmentations in which the aromatic nitrogen moiety retains the charge and fragmentation is by loss of radicals or small neutral molecules from the side-chains. Radical driven reactions are proposed to explain these spectra.
    Additional Material: 9 Tab.
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