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  • 1985-1989  (4)
  • Biomechanical impedance  (2)
  • Angiotensin II  (1)
  • Astrocyte  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 77 (1989), S. 357-368 
    ISSN: 1432-0533
    Keywords: Hepatic encephalopathy ; Glutamine synthetase ; Methionine sulfoximine ; Oligodendrocyte ; Astrocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To investigate the roles imposed on astrocytes for glutamate metabolism, a specific inhibitor of glutamine synthetase (GS), methionine sulfoximine (MSO), was repeatedly administered to rats and histopathological changes were correlated with glycogen accumulation and the immunocytochemistry of GS and glial fibrillary acidic protein (GFAP). Prolonged MSO-loading (every 12 h up to three times, 100–150 mg/kg body weight) brought about the appearance of astrocytes with swollen, watery nuclei reminiscent of Alzheimer II glia chiefly in the neocortex, hippocampus and lateral thalamus after 24 h. Concomitantly, profound accumulation of glycogen ensued in the superficial three layers of the neocortex, hippocampus and pyriform cortex. GS immunoreactivity appeared enhanced in the cortex, hippocampus and lateral thalamus with parallel increase in GFAP immunoreactivity after prolonged treatment. Oligodendrocytes in the diencephalon and brain stem also normally contained GS immunoreactivity. Some animals developed necrotic lesions in the dorsolateral neocortex. The area of glycogen accumulation coincided with the known distribution ofN-methyld-aspartate (NMDA) glutamate receptors and, thus, GS may play important roles in NMDA receptor-mediated glutamate metabolism. The Alzheimer II type changes, however, did not correlate with NMDA-receptor distribution. These results indicate certain regionalizations in the roles of astrocytes and oligodendrocytes in glutamate and ammonia metabolisms.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 80 (1989), S. 59-72 
    ISSN: 1573-4919
    Keywords: heart cells ; aortic cells ; Ca2- current ; K+ current ; slow Na+ current ; Angiotensin II ; calcium blockers ; potassium blockers ; patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary The whole-cell voltage clamp technique was used to study the slow inward currents and K+ outward currents in single heart cells of embryonic chick and in rabbit aortic cells. In single heart cells of 3-day-old chick embryo three types of slow inward Na+ currents were found. The kinetics and the pharmacology of the slow INa, were different from those of the slow Ica in older embryos. Two types of slow inward currents were found in aortic single cells of rabbit; angiotensin 11 increased the sustained type and d-cAMP and d-cGMP decreased the slow transient component. Two types of outward K+ currents were found in both aortic and heart cells. Single channel analysis demonstrated the presence of a high single K+ channel conductance in aortic cells. In cardiac and vascular smooth muscles, slow inward currents do share some pharmacological properties, although the regulation of these channels by cyclic nucleotides and several drugs seems to be different.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 25 (1987), S. 631-637 
    ISSN: 1741-0444
    Keywords: Biomechanical impedance ; Biomechanical properties ; Impedance ; Living body structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A physical model for biomechanical impedance has already been proposed. This model is characterised by three impedance spectra: soft, intermediate and hard pattern. An impedance spectrum of the body surface represents mostly the soft pattern, The formative mechanisms of all three patterns have been unsolved until now. Because the physical model is expressed by experimental equations, its theoretical background is not apparent. In the paper a simulating material (simulator) is used, whose tactility is not unlike human skin, and the formative mechanism of biomechanical impedance is revealed through experiments on the simulator under various measuring conditions. The influences of the measuring circumstances, living body structure and physical constants of the body tissues on the experimental equations of the physical model are fully discussed. The formative mechanism of biomechanical impedance which represents the physical model is explained in terms of an equivalent mass, a dynamic equivalent stiffness, a dynamic viscosity and a composite characteristic. The dependence between body parts from which the measurements are taken and soft, intermediate and hard patterns are demonstrated.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 24 (1986), S. 493-498 
    ISSN: 1741-0444
    Keywords: Biomechanical impedance ; Biomechanical properties ; Impedance ; Modelling of human body
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract New experimental modelling of biomechanical impedance is proposed. The parameters which express the impedance characteristics are simply determined by impedance measurement. Audiofrequencies below about 1000 Hz and comparatively lower preloads (below about 6370 kg m−2) are chosen as the research domain. This model, however, can express wide range of body surface impedance not only in soft but also in stiff and intermediate tissues. It will never introduce the impracticably ideal conditions found in the mathematcial models proposed to date. Furthermore the parameters which express the model cannot be determined by impedance measurement alone. The impedance Z(jw) is expressed in two parts: the impedance Z1 (jw) at a higher frequency including a complex mass and the impedance Z2(jw) at a lower frequency including a complex compliance of Cole-Cole’s type. Z1(jw) is the property of body fluid and Z2(jw) is that of a viscoelastic body.
    Type of Medium: Electronic Resource
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