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  • 1
    ISSN: 1432-1424
    Keywords: Cerebellar granule neuron ; Heloderma horridum ; Helothermine ; Potassium current ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Helothermine, a recently isolated toxin from the venom of the Mexican beaded lizard Heloderma horridum horridum was tested on K+ currents of newborn rat cerebellar granule cells. In whole-cell voltageclamp experiments, cerebellar granule neurons exhibited at least two different K+ current components: a first transient component which is similar to an I A-type current, is characterized by fast activating and inactivating kinetics and blocked by 4-aminopyridine; a second component which is characterized by noninactivating kinetics, is blocked by tetraetylammonium ions and resembles the classical delayed-rectifier current. When added to the standard external solution at concentrations ranging between 0.1 and 2 μm helothermine reduced the pharmacologically isolated I A-type current component in a voltage- and dose-dependent way, with a half-maximal inhibitory concentration (IC50) of 0.52 μm. A comparison between control and nelothermine-modified peak transient currents shows a slowdown of activation and inactivation kinetics. The delayed-rectifier component inhibition was concentration dependent (IC50 = 0.86 μm) but not voltage dependent. No frequency-or use-dependent block was observed on both K+ current types. Perfusing the cells with control solution resulted in quite a complete current recovery. We conclude that helothermine acts with different affinities on two types of K+ current present in central nervous system neurons.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2017-04-04
    Description: Coda-Q estimates for the Granada Basin (Southern Spain) are obtained by analyzing earthquakes occurring within or close to the borders of this area. The data set is composed of 54 earthquakes with local magnitudes ranging between 2.2 and 4.0 and with epicentral distances to the nearest station smaller than 10 km. A single-scattering process is assumed. Coda-Q values obtained show a clear dependence on frequency according to the relationship Q = Qof", where n ranges from 0.81 to 0.89. After removing the main site effects and discussing the possible multiple-scattering influence, the lapse-time dependence is interpreted as due to attenuation variations with depth. This result agrees with the variation of coda Q obtained by using different sets of events with increasing hypocentral depth ranges.
    Description: Published
    Description: 1232-1244
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Seismic attenuation ; Coda-Q ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2017-04-04
    Description: Intrinsic and scattering attenuation parameters, Q~ and Qs, have been measured in three different tectonic areas for local and shallow earthquakes located close to the receiver. The approach developed by Wennerberg (1993), which takes into account the numerical correction of the coda-Q parameter for the multiple scat- tering formulation of Zeng, was used to infer from the estimates of coda Q and direct S-wave Q the intrinsic (Qi) and scattering (Qs) Q values. Results for 1 to 12 Hz range show that Q~ is comparable to Qs for the Etna volcano and for the Campi Flegrei area, while Qi for the tectonically active area of Granada is lower than Qs. Coda Q is close to intrinsic Q, suggesting that, at least in the crust, coda Q is a good estimate of the intrinsic Q. Volcanic areas show a reasonable higher degree of heterogeneity, if compared with the nonvolcanic area of Granada.
    Description: Published
    Description: 1373-1380
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Seismic scattering ; Seismic attenuation ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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