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Integrated biomimetic carbon nanotube composites for in vivo systems
Singh, Manoj Kumar; Gracio, Jose; LeDuc, Philip; Gonçalves, Paula P.; Marques, Paula A. A. P.; Gonçalves, Gil; Marques, Filipa; Silva, Virgilia S.As interest in using carbon nanotubes for developing biologically compatible systems continues to grow, biological inspiration is stimulating new directions for in vivo approaches. The ability to integrate nanotechnology-based systems in the body will provide greater successes if the implanted material is made to mimic elements of the biological milieu especially through tuning physical and chemical characteris...
Acetylcholine release and choline uptake by cuttlefish (Sepia officinalis) opti...
Nunes, M. Alexandra; Santos, Sofia; Cordeiro, J. Miguel; Neves, Paulo; Silva, Virgilia S.; Sykes, Antonio; Morgado, Fernando; Dunant, YvesAcetylcholine (ACh), which is synthesized from choline (Ch), is believed to hold a central place in signaling mechanisms within the central nervous system (CNS) of cuttlefish (Sepia officinalis) and other coleoid cephalopods. Although the main elements required for cholinergic function have been identified in cephalopods, the transmembrane translocation events promoting the release of ACh and the uptake of Ch r...
Ca2+ Sensitivity of Synaptic Vesicle Dopamine, ?-Aminobutyric Acid, and Glutama...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.The effect of Ca2+ on the uptake of neurotransmitters by synaptic vesicles was investigated in a synaptic vesicle enriched fraction isolated from sheep brain cortex. We observed that dopamine uptake, which is driven at expenses of the proton concentration gradient generated across the membrane by the H+-ATPase activity, is strongly inhibited (70%) by 500 µM Ca2+. Conversely, glutamate uptake, which essentially ...
Distinction between Ca2+ pump and Ca2+/H+ antiport activities in synaptic vesic...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.Synaptic vesicles, isolated from a sheep brain cortex, accumulate Ca2+ in a manner that depends on the pH and pCa values. In the presence of 100 [mu]M CaCl2, most of the Ca2+ taken up by the vesicles was vanadate-inhibited (86%) at pH 7.4, whereas at pH 8.5, part of the Ca2+ accumulated (36%) was [Delta]pH-dependent (bafilomycin and CCCP inhibited) and part was insensitive to those drugs (31%). We also observed...
Methods for analysis of Ca2+/H+ antiport activity in synaptic vesicles isolated...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.The involvement of Ca2+-storage organelles in the modulation of synaptic transmission is well-established [M.K. Bennett, Ca2+ and the regulation of neurotransmitter secretion, Curr. Opin. Neurobiol. 7 (1997) 316-322 [1]; M.J. Berridge, Neuronal calcium signaling, Neuron 21 (1998) 13-26 [2]; Ph. Fossier, L. Tauc, G. Baux, Calcium transients and neurotransmitter release at an identified synapse, Trends Neurosci. ...
Synaptic vesicle Ca2+/H+ antiport: dependence on the proton electrochemical gra...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.Synaptic vesicles isolated from sheep brain cortex accumulate Ca2+ by a mechanism of secondary active transport associated to the H+-pump activity. The process can be visualized either by measuring Ca2+-induced H+ release or [Delta]pH-dependent Ca2+ accumulation. We observed that the amount of Ca2+ taken up by the vesicles increases with the magnitude of the [Delta]pH across the membrane, particularly at Ca2+ c...
Ionic selectivity of the Ca2+/H+ antiport in synaptic vesicles of sheep brain c...
Gonçalves, Paula P.; Meireles, Sandra M.; Neves, Paulo; Vale, M. Graça P.As we previously reported, synaptic vesicles isolated from sheep brain cortex contain a Ca2+/H+ antiport that permits Ca2+ accumulation inside the vesicles (~5 nmol/mg protein) at expenses of the pH gradient generated by the H+-pumping ATPase. We observed that the system associates Ca2+ influx to H+ release and operates with low affinity for Ca2+. In the present work, we found that Ca2+/H+ antiport mediates exc...
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