Delay in vesicle fusion revealed by electrochemical monitoring of single secretory events in adrenal chromaffin cells
TL;DR: In this article, the authors show that under voltage-clamp conditions, stochastically occurring signals can be recorded from adrenal chromaffin cells using a carbon-fibre electrode as an electrochemical detector.
Abstract: In synapses, a rise in presynaptic intracellular calcium leads to secretory vesicle fusion in less than a millisecond, as indicated by the short delay from excitation to postsynaptic signal. In nonsynaptic secretory cells, studies at high time resolution have been limited by the lack of a detector as fast and sensitive as the postsynaptic membrane. Electrochemical methods may be sensitive enough to detect catecholamines released from single vesicles. Here, we show that under voltage-clamp conditions, stochastically occurring signals can be recorded from adrenal chromaffin cells using a carbon-fibre electrode as an electrochemical detector. These signals obey statistics characteristic for quantal release; however, in contrast to neuronal transmitter release, secretion occurs with a significant delay after short step depolarizations. Furthermore, we identify a pedestal or 'foot' at the onset of unitary events which may represent the slow leak of catecholamine molecules out of a narrow 'fusion pore' before the pore dilates for complete exocytosis.
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TL;DR: The results obtained allowed us to assess the importance of knowing the carrier and removal status of canine coronavirus, as a source of infection for other animals, not necessarily belonging to the same breeds.
1,018 citations
TL;DR: The wide range of cell types in which regulated secretory granule exocytosis occurs is described and the evidence for the expression of the conserved fusion machinery in these cells is assessed.
Abstract: Regulated exocytosis of secretory granules or dense-core granules has been examined in many well-characterized cell types including neurons, neuroendocrine, endocrine, exocrine, and hemopoietic cells and also in other less well-studied cell types. Secretory granule exocytosis occurs through mechanisms with many aspects in common with synaptic vesicle exocytosis and most likely uses the same basic protein components. Despite the widespread expression and conservation of a core exocytotic machinery, many variations occur in the control of secretory granule exocytosis that are related to the specialized physiological role of particular cell types. In this review we describe the wide range of cell types in which regulated secretory granule exocytosis occurs and assess the evidence for the expression of the conserved fusion machinery in these cells. The signals that trigger and regulate exocytosis are reviewed. Aspects of the control of exocytosis that are specific for secretory granules compared with synaptic vesicles or for particular cell types are described and compared to define the range of accessory control mechanisms that exert their effects on the core exocytotic machinery.
900 citations
TL;DR: A given synaptic vesicle can exocytose with high probability within a few hundred microseconds, if [Ca2+]i rises above lOOµM, and these properties provide for the extremely rapid signalling required for neuronal communication.
Abstract: Rapid calcium-dependent exocytosis underlies neurotransmitter release from nerve terminals. Despite the fundamental importance of this process, neither the relationship between presynaptic intracellular calcium ion concentration ([Ca2+]i) and rate of exocytosis, nor the maximal rate of secretion is known quantitatively. To provide this information, we have used flash photolysis of caged Ca2+ to elevate [Ca2+]i rapidly and uniformly in synaptic terminals, while measuring membrane capacitance as an index of exocytosis and monitoring [Ca2+]i with a Ca(2+)-indicator dye. When [Ca2+]i was abruptly increased to > 10 microM, capacitance rose at a rate that increased steeply with [Ca2+]i. The steepness suggested that at least four calcium ions must bind to activate synaptic vesicle fusion. Half-saturation was at 194 microM, and the maximal rate constant was 2,000-3,000 s-1. A given synaptic vesicle can exocytose with high probability within a few hundred microseconds, if [Ca2+]i rises above 100 microM. These properties provide for the extremely rapid signalling required for neuronal communication.
729 citations
TL;DR: Since BDNF has been proposed to play a critical role as an intercellular synaptic messenger in long-term potentiation (LTP) in the hippocampus, this article tries to reconcile this possible role of BDNF in LTP with the recently described features of synaptic BDNF secretion.
665 citations
TL;DR: The molecular and genetic results demonstrate that, although synaptotagmin is required for the proper function of the presynaptic nerve terminal in C. elegans, some neurotransmitter release persists in synaptogamin mutants, indicating that the mutants do not have a complete block of neurotransmitterRelease.
550 citations
References
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Book•
01 Jan 1956
TL;DR: Though it incorporates much new material, this new edition preserves the general character of the book in providing a collection of solutions of the equations of diffusion and describing how these solutions may be obtained.
Abstract: Though it incorporates much new material, this new edition preserves the general character of the book in providing a collection of solutions of the equations of diffusion and describing how these solutions may be obtained
20,495 citations
TL;DR: The extracellular patch clamp method, which first allowed the detection of single channel currents in biological membranes, has been further refined to enable higher current resolution, direct membrane patch potential control, and physical isolation of membrane patches.
Abstract: 1. The extracellular patch clamp method, which first allowed the detection of single channel currents in biological membranes, has been further refined to enable higher current resolution, direct membrane patch potential control, and physical isolation of membrane patches. 2. A description of a convenient method for the fabrication of patch recording pipettes is given together with procedures followed to achieve giga-seals i.e. pipette-membrane seals with resistances of 10(9) - 10(11) omega. 3. The basic patch clamp recording circuit, and designs for improved frequency response are described along with the present limitations in recording the currents from single channels. 4. Procedures for preparation and recording from three representative cell types are given. Some properties of single acetylcholine-activated channels in muscle membrane are described to illustrate the improved current and time resolution achieved with giga-seals. 5. A description is given of the various ways that patches of membrane can be physically isolated from cells. This isolation enables the recording of single channel currents with well-defined solutions on both sides of the membrane. Two types of isolated cell-free patch configurations can be formed: an inside-out patch with its cytoplasmic membrane face exposed to the bath solution, and an outside-out patch with its extracellular membrane face exposed to the bath solution. 6. The application of the method for the recording of ionic currents and internal dialysis of small cells is considered. Single channel resolution can be achieved when recording from whole cells, if the cell diameter is small (less than 20 micrometer). 7. The wide range of cell types amenable to giga-seal formation is discussed.
17,136 citations
TL;DR: The present edition of this now classic text offers substantial refinements and improvements over the first edition and includes some new material as mentioned in this paper, including an improved derivation of the macroscopic equations, monopoles, causality and dispersion relations, signal propagation in a dispersive media.
Abstract: J D Jackson Chichester: J Wiley 1975 pp xxii + 848 price £10.75 The present edition of this now classic text offers substantial refinements and improvements over the first edition and includes some new material. New topics on electromagnetism include an improved derivation of the macroscopic equations, monopoles, causality and dispersion relations, signal propagation in a dispersive media.
2,786 citations
TL;DR: It was found that the size of the end-plate response approached that of the spontaneous potential and at the same time exhibited large random fluctuations, apparently involving steps of unit size.
Abstract: In this paper a further study is made of the spontaneous synaptic potentials in frog muscle (Fatt & Katz, 1952a), and their relation to the end-plate response. It has been suggested that the end-plate potential (e.p.p.) at a single nerve-muscle junction is built up statistically of small all-or-none units which are identical in size with the spontaneous 'miniature e.p.p.'s'. The latter, therefore, could be regarded as the least unit, or the 'quantum', of end-plate response. A convenient picture of how hundreds of such quanta, each capable of producing a miniature potential of 0 5-1 0 mV, can build up an e.p.p. of, say, 70-80 mV is provided by the hypothesis that separate parcels of acetylcholine (ACh), released from discrete spots of the nerve endings, short-circuit the muscle membrane. The unit changes of membrane conductance produced at many parallel spots summate and lead to an intense depolarization of the muscle fibre. Although this is a plausible view, there is no direct proof that the normal e.p.p. is made up in this quantal fashion. The evidence comes from experiments in which the 'quantum content' of the e.p.p. had been reduced to a small number by lowering the external calcium concentration (Fatt & Katz, 1952 a). It was then found that the size of the end-plate response approached that of the spontaneous potential and at the same time exhibited large random fluctuations, apparently involving steps of unit size. Similar observations were made by Castillo & Engbaek (1954) on muscles treated with Mg-rich solutions. The statistical behaviour of the end-plate response under these conditions has been investigated in more detail and subjected to a quantitative analysis.
2,013 citations