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The time course of extrusion of the vesicular contents during exocytosis has been examined at adrenal medullary cells with carbon-fiber microelectrodes. Two electrochemical techniques were used: cyclic voltammetry and amperometry. Spikes obtained by amperometry had a faster time course than those measured by cyclic voltammetry, consistent with the different(More)
Amperometric detection of exocytosis at single chromaffin cells has shown that the distribution of spike areas, or quantal size, is dependent on the volume and catecholamine concentration of individual secretory vesicles. The present work offers an alternate, simplified model to analyze the current spikes due to single exocytotic events. When the cube root(More)
The temporal resolution of carbon-fiber microelectrodes has been exploited to examine the plasticity of quantal secretory events at individual adrenal medullary cells. The size of individual quantal events, monitored by amperometric oxidation of released catecholamines, was found to be dependent on the extracellular ionic composition, the secretagogue, and(More)
Many of the molecules involved in biological signaling processes are easily oxidized and have been monitored by electrochemical methods. Temporal response, spatial considerations, and sensitivity of the electrodes must be optimized for the specific biological application. To monitor exocytosis from single cells in culture, constant potential amperometry(More)
The stages of the complex events involved in exocytotic secretion after vesicle-cell membrane fusion have been examined at the level of individual vesicles. Catecholamine flux from single bovine adrenal medullary cells was measured with carbon-fiber microelectrodes firmly touching the cell surface. The data reveal that secretion during exocytotic events has(More)
"Snapshot" images of localized Ca2+ influx into patch-clamped chromaffin cells were captured by using a recently developed pulsed-laser imaging system. Transient opening of voltage-sensitive Ca2+ channels gave rise to localized elevations of Ca2+ that had the appearance of either "hotspots" or partial rings found immediately beneath the plasma membrane.(More)
The relationship between cytosolic Ca2+ and catecholamine secretion during stimulus-secretion coupling has been examined at individual chromaffin cells isolated from the cow and rat. Vesicular catecholamine exocytosis was determined via amperometric measurements with carbon fibre microelectrodes and fura-2 was used for simultaneous fluorescent monitoring of(More)
Disclaimer: Working Papers contain preliminary research, analysis, findings, and recommendations. They are circulated to stimulate timely discussion and critical feedback and to influence ongoing debate on emerging issues. Most working papers are eventually published in another form and their content may be revised. Parties to the United Nations Framework(More)
Previous investigations of the role of Ca2+ in stimulus-secretion coupling have been undertaken in populations of adrenal chromaffin cells. In the present study, the simultaneous detection of intracellular Ca2+, with the fluorescent probe fura-2, and catecholamine release, using a carbon-fiber microelectrode, are examined at single chromaffin cells in(More)
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