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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 175 (1994), S. 415-423 
    ISSN: 1432-1351
    Keywords: Aplysia ; Calcium ; Circadian ; Light ; Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The eye of the marine mollusk Aplysia californica contains an oscillator that drives a circadian rhythm of spontaneous compound action potentials in the optic nerve. Both light and serotonin are known to influence the phase of this ocular rhythm. The aim of the present study was to evaluate the role of extracellular calcium in both light and serotonin-mediated phase shifts. Low calcium treatments were found to cause phase shifts which resembled those produced by the transmitter serotonin. However, unlike serotonin, low calcium neither increased ocular cAMP levels nor could these phase shifts be prevented by increasing extracellular potassium concentration. Low calcium-induced phase shifts were prevented by the simultaneous application of the translational inhibitor anisomycin and low calcium treatment resulted in changes in [35S]methionine incorporation into several proteins as measured by a two-dimensional electrophoresis gel analysis. Finally, light treatments failed to produce phase shifts in the presence of low calcium or the calcium channel antagonist nickel chloride. These results are consistent with a model in which serotonin phase shifts the ocular pacemaker by decreasing a transmembrane calcium flux through membrane hyperpolarization while light-induced phase shifts are mediated by an increase in calcium flux.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1619-7089
    Keywords: Key words: Familial amyloid polyneuropathy ; Metaiodobenzylguanidine ; Heart rate variability ; Autonomic nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Familial amyloid polyneuropathy (FAP) is a rare and severe hereditary form of amyloidosis, due to nervous deposits of a genetic variant transthyretin produced by the liver and characterized by both sensorimotor and autonomic neuropathy. Left ventricular systolic dysfunction is rare, but conduction disturbances and sudden deaths can occur. The neurological status of the heart has not been elucidated, and an alteration of the sympathetic nerves may be involved. We studied 17 patients (42±12 years) before liver transplantation by iodine-123 metaiodobenzylguanidine (MIBG) scintigraphy, heart rate variability analysis, coronary angiography, radionuclide ventriculography, rest thallium single-photon emission tomography (SPET) and echocardiography. Coronary arteries, left ventricular systolic function and rest thallium SPET were normal in all patients. Only mild evidence of amyloid infiltration was found at echocardiographic examination. Cardiac MIBG uptake was dramatically decreased in patients compared with age-matched control subjects (heart-to-mediastinum activity ratio at 4 h: 1.36±0.26 versus 1.98±0.35, P〈0.001), while there was no difference in MIBG washout rate. Heart rate variability analysis showed a considerable scatter of values, with high values in four patients despite cardiac sympathetic denervation as assessed by MIBG imaging. The clinical severity of the polyneuropathy correlated with MIBG uptake at 4 h but not with the heart rate variability indices. Cardiac MIBG uptake and the heart rate variability indices did not differ according to the presence or absence of conduction disturbances. Patients with FAP have sympathetic cardiac denervation as assessed by MIBG imaging despite a preserved left ventricular systolic function and cardiac perfusion, without correlation with conduction disturbances. Results of the heart rate variability analysis were more variable and this technique does not seem to be the best way to evaluate the extent of cardiac sympathetic denervation in FAP patients.
    Type of Medium: Electronic Resource
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