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Digitale Medien

Further Characterization of Phasic Calcium Influx in Rat Cerebrocortical Synaptosomes: Inferences Regarding Calcium Channel Type(s) in Nerve Endings (1989)

Suszkiw, J. B. ; Murawsky, M. M. ; Shi, M.

Oxford, UK : Blackwell Publishing Ltd

Journal of neurochemistry 52 (1989), S. 0

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ISSN: 1471-4159

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Medizin

Notizen: Abstract Under conditions minimizing the contribution of Na+/Ca2+ exchange to calcium entry in synaptosomes, the K+ depolarization-dependent calcium influx (JCa) is a single exponential function of time. JCa activates and slowly inactivates at membrane potentials positive to –50 mV, a result indicating the involvement of moderate voltage-activating, slowly inactivating calcium channels. Calcium channels in synaptosomes are characterized by stronger sensitivity to blockage by Cd2+ than Co2+, insensitivity to dihydropyridine calcium antagonists or the agonist Bay K 8644, and weak, partial sensitivity to the peptide toxin ω-conotoxin GVIA. These characteristics suggest that voltage-sensitive calcium channels in rat cerebrocortical synaptosomes are dissimilar from the somatic T, N, or L channel types. JCa is not affected by treatment of synaptosomes with the adenylate cyclase activator forskolin, the membrane permeant dibutyryl-cyclic AMP, or the kinase C activator phorbol 12-myristate 13-acetate diester, results suggesting that calcium channels in synaptosomes are not directly modulated by protein kinase A- or C-mediated phosphorylation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb01874.x

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Digitale Medien

Primary ion dependence of LiF direct recoil intensities and ion fractions (1987)

Chen, J. N. ; Shi, M. ; Rabalais, J. W.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 86 (1987), S. 2403-2410

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: Time-of-flight (TOF) spectra of the scattered and recoiled particles resulting from 1–10 keV He+, Ne+, Ar+, Kr+, and Xe+ ions impingent on surfaces of LiF thin films have been obtained. Measurements of directly recoiled (DR) neutrals plus ions and neutrals alone are used to calculate positive and negative ion fractions Y+,− from DR events. The oppositely charged ion fractions have a distinctly different behavior as a function of kinetic energy. The Y+ values exhibit a threshold at low energy followed by a plateau region at higher energy while the Y− values are maximum in the low energy region followed by a decreasing yield as energy increases. The energy dependence of Y+,− is interpreted in terms of the recently developed model [J. Chem. Phys. 85, 3615 (1986)] for electronic charge exchange in keV ion/surface collisions which considers electron promotions in the close atomic encounter and resonant and Auger transitions along the outgoing trajectory. The ionization potential of the primary ion relative to the energy levels of the target atom is shown to have a large influence on charge exchange in the close encounter. The ratio of direct recoil to scattering particle flux increases by a factor of 〉102 from He to Xe; scattering and recoil cross sections are used to model this process.