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  • 1
    Electronic Resource
    Electronic Resource
    Agmatine recognizes α2-adrenoceptor binding sites but neither activates nor inhibits α2-adrenoceptors (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 351 (1994), S. 10-16 
    Details
    ISSN: 1432-1912
    Keywords: Key words Agmatine ; α2-Adrenoceptor binding sites ; α2-Adrenoceptors ; Clonidine-displacing substance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It has been suggested that agmatine (decarboxylated arginine) is an endogenous clonidine-displacing substance (CDS) which recognizes α2-adrenoceptor and non-adrenoceptor, imidazoline binding sites. We have examined the effect of agmatine at α2-adrenoceptor binding sites and pre- and postjunctional α2-adrenoceptors. Agmatine produced a concentration-dependent inhibition of 1 nmol/l 3H-clonidine binding to both rat (pKi–5.10±0.05) and bovine (pKi–4.77±0.38) cerebral cortex membranes. However, agmatine (0.1–100 μM) failed to activate pre-junctional α2-adrenoceptors regulating transmitter release in the guinea-pig isolated ileum and rat isolated vas deferens, nor did it activate postjunctional α2-adrenoceptors of the porcine isolated palmar lateral vein which mediate contraction or inhibition of forskolin-stimulated cyclic AMP formation. High concentrations of agmatine (10–30-fold the pKi at α2-adrenoceptor binding sites) failed to influence α2-adrenoceptor activation by either clonidine or UK-14304 (5-bromo-6-[2-imidazolin-2-ylamino]-quinoxaline bitartrate) in any of the peripheral preparations examined. Moreover, even in a preparation where an interaction with α2-adrenoceptor binding sites on cell membranes can be demonstrated, the rat cerebral cortex, agmatine failed to inhibit forskolin-stimulated cyclic AMP in the intact tissue or affect the inhibition produced by the selective α2-adrenoceptor agonist UK-14304. Agmatine was also devoid of agonist activity in two preparations, the rat isolated thoracic aorta and the rat isolated gastric fundus, in which CDS has been reported to produce non-adrenoceptor effects. Thus, we have confirmed that agmatine recognizes α2-adrenoceptor binding sites and, therefore, is a CDS. However, since agmatine is devoid of pharmacological activity at either peripheral or central α2-adrenoceptors it can not account for earlier reports suggesting that brain-derived CDS can activate α2-adrenoceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169058
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Responsiveness of cells in the cat's superior colliculus to textured visual stimuli (1979)
    Springer
    Experimental brain research 37 (1979), S. 231-240 
    Details
    ISSN: 1432-1106
    Keywords: Cat superior colliculus ; Visual texture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Responses to texture motion (visual noise) were investigated in the superior colliculus of paralysed cats, lightly anaesthetized with N2O/O2 supplemented with pentobarbitone or Althesin. Within the superficial layers two classes of texture-sensitive neurones were found: Type I units with weak responses to noise, often related to specific elements in the texture and Type II units which were driven independently of the texture structure, and tended to be recorded deep to the Type I units. Type III units recorded from the deep collicular layers were insensitive to texture. Anatomical bases for this differential sensitivity and the notion of two collicular subsystems are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237710
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Differential responsiveness of cells in the visual zones of the cat's LP-pulvinar complex to visual stimuli (1981)
    Springer
    Experimental brain research 43 (1981), S. 25-33 
    Details
    ISSN: 1432-1106
    Keywords: Cat ; LP-pulvinar complex ; MIN ; Visual texture ; Receptive field properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Multiple visual field representations are contained within the feline LP-pulvinar complex; regions differentiated by their afferent and efferent connectivity patterns as the striate-, tecto- and retino-recipient zones. Cell responses from these visuotopic zones were investigated in immobilized cats under N2O/O2 supplemented with pentobarbitone or Althesin, using spot, bar and textured stimuli. Response fields recorded within the LP-pulvinar complex were classified as diffuse, concentric, movement-, direction- or orientation-sensitive. Concentric receptive fields were further classified as sustained (X), transient (Y) or tonic/phasic W-cells. Direction-and movement-sensitive cells predominated in the striate- and tecto-recipient zones, respectively. Motion of noise fields, or noise bars against an identical stationary noise background elicited vigorous responses from cells in the striate zone, many showing a preference for noise stimuli. In contrast, cells from the tectal zone and other divisions of the LP-pulvinar complex were insensitive to noise. The retino-recipient zone at the lateral margin of the pulvinar nucleus was characterized by cells with concentric receptive fields, the majority exhibiting properties similar to W-cells in the LGNd. The evidence supports the notion of functional subdivision within the LP-pulvinar complex corresponding to the visuotopically organized regions defined by their connectivity patterns. Consideration of the retino-recipient zone as an extension of the LGNd-MIN complex is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238806
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Agmatine recognizes α2-adrenoceptor binding sites but neither activates nor inhibits α2-adrenoceptors (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 351 (1995), S. 10-16 
    Details
    ISSN: 1432-1912
    Keywords: Agmatine ; α2-Adrenoceptor binding sites ; α2-Adrenoceptors ; Clonidine-displacing substance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It has been suggested that agmatine (decarboxylated arginine) is an endogenous clonidine-displacing substance (CDS) which recognizes α2-adrenoceptor and non-adrenoceptor, imidazoline binding sites. We have examined the effect of agmatine at α2-adrenoceptor binding sites and pre- and postjunctional α2-adrenoceptors. Agmatine produced a concentration-dependent inhibition of 1 nmol/l 3H-clonidine binding to both rat (pKi–5.10+-0.05) and bovine (pKi–4.77+-0.38) cerebral cortex membranes. However, agmatine (0.1–100 μM) failed to activate pre-junctional α2-adrenoceptors regulating transmitter release in the guinea-pig isolated ileum and rat isolated vas deferens, nor did it activate post-junctional α2-adrenoceptors of the porcine isolated palmar lateral vein which mediate contraction or inhibition of forskolin-stimulated cyclic AMP formation. High concentrations of agmatine (10–30-fold the pKi at α2-adrenoceptor binding sites) failed to influence α2-adrenoceptor activation by either clonidine or UK-14304 (5-bromo-6-[2-imidazolin-2-ylamino]-quinoxaline bitartrate) in any of the peripheral preparations examined. Moreover, even in a preparation where an interaction with α2-adrenoceptor binding sites on cell membranes can be demonstrated, the rat cerebral cortex, agmatine failed to inhibit forskolin-stimulated cyclic AMP in the intact tissue or affect the inhibition produced by the selective α2-adrenoceptor agonist UK-14304. Agmatine was also devoid of agonist activity in two preparations, the rat isolated thoracic aorta and the rat isolated gastric fundus, in which CDS has been reported to produce non-adrenoceptor effects. Thus, we have confirmed that agmatine recognizes α2-adrenoceptor binding sites and, therefore, is a CDS. However, since agmatine is devoid of pharmacological activity at either peripheral or central α2-adrenoceptors it can not account for earlier reports suggesting that brain-derived CDS can activate α2-adrenoceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169058
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Interaction of human α-thrombin with artificial surfaces and reactivity of adsorbed α-thrombin (1980)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 14 (1980), S. 467-476 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Thrombin adsorbed onto Cuprophane or poly(vinyl chloride) (PVC) was shown to be inactive with respect to amidase activity. Desorbed thrombin from these two artificial surfaces showed only low amidase activity. However, in the presence of albumin, the surface-bound thrombin appeared to exhibit increased amidase activity. This apparent activity may be due to the action of thrombin displaced from the surfaces by albumin. Thrombin bound to Cuprophane or PVC was shown to be capable of reacting with antithrombin III (AT III) only in the presence of heparin. On the other hand, AT III bound to Cuprophane or PVC was unable to react with thrombin in either the absence or presence of heparin. Fibrin formation on or at surfaces was demonstrated by phase contrast microscopy when Cuprophane or PVC pretreated with thrombin and carefully rinsed was incubated in a fibrinogen solution. This fibrin formation is time dependent and likely is the result of direct interaction of adsorbed thrombin with fibrinogen in solution. Glass, Cuprophane, and PVC pretreated with thrombin were shown to attract more platelets than respective untreated surfaces. The enhancing effect of adsorbed thrombin on platelet adhesion was similar to the enhancing effect of adsorbed fibrinogen. Thrombin adsorbed onto PVC and crosslinked by glutaraldehyde treatment was shown to be antigenically active with a 125I-labeled monospecific antithrombin IgG produced in rabbits. No other plasma proteins adsorbed singly or from plasma or serum onto PVC reacted significantly with the antithrombin IgG preparation. The possible significance of these observations is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820140413
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    An in vitro test system for estimation of blood compatibility of biomaterials (1974)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 8 (1974), S. 341-356 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An in vitro test cell is described which permits exposure of artificial surfaces in sheet or film form to native human blood in the absence of a blood-air interface. Evaluation of Cuprophane, polyethylene, Silastic, and silicone-coated glass in the in vitro cell showed Cuprophane and silicone-coated glass to produce the least activation of the intrinsic coagulation system, while Silastic produced the greatest degree of activation. Polyethylene gave results intermediate between those obtained with the other materials. Each of these four different materials was evaluated in the elliptical cell test system multiple times with blood from 13 different donors.Our data suggest that with the present test system and the proper experimental design, one might expect that, “on the average,” performance of 36 tests on each of two materials will be sufficient for a 10% difference in their compatibility with blood to be statistically significant at the 5% level. The number of tests is 26 for significance at the 10% level.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820080602
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Some species differences in fibrinolysis and blood coagulation (1971)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 121-128 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The plasminogen levels and the reactivities of plasmas in two commonly used blood coagulation tests have been compared for man and seven mammals. The plasmas of three nonhuman primates in general reacted as did human plasma in tests for plasminogen activation and in reactivity in the partial thromboplastin time test. The dog had the highest level of plasminogen, and the goat the lowest, of the eight species tested. Overall, the pig appeared to have the most reactive blood coagulation mechanism, clotting the fastest and lysing the slowest, while man's was among the least reactive in clotting and intermediate in lytic activity of those tested. Aside from the nonhuman primates, the calf's clotting and lytic mechanisms resembled those of man more nearly than did those of the other mammals tested. The influence of these species differences on selection of animals for in vivo evaluation of blood vascular prosthetic materials and devices is discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820050109
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