| 1. |
- Dunevall, Johan, 1984, et al.
(author)
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Vesicle impact electrochemical cytometry compared to amperometric exocytosis measurements
- 2017
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In: Current Opinion in Electrochemistry. - : Elsevier BV. - 2451-9103 .- 2451-9111. ; 5:1, s. 85-91
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Journal article (peer-reviewed)abstract
- Three new tools are discussed for understanding chemical communication between cells and primarily to delve into the content and structure of nanometer transmitter vesicles. These are amperometric measurements of exocytosis, vesicle impact electrochemical cytometry, and intracellular vesicle impact electrochemical cytometry. These are combining in the end nanoscale mass spectrometry imaging to begin determination of vesicle structure. These methods have provided solid evidence for the concept of open and closed exocytosis leading to partial release of the vesicle content during normal exocytosis. They have also been used to discover cases where the fraction of transmitter released is not changed, and other cases where the vesicle transmitter fraction released is altered, as with zinc, thought to alter cognition. Overall, the combination of these methods is showing us details of vesicular processes that would not be measureable without these micro and nano electrochemical methods.
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| 2. |
- Li, Xianchan, 1982, et al.
(author)
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Mechanistic Aspects of Vesicle Opening during Analysis with Vesicle Impact Electrochemical Cytometry
- 2017
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 89:17, s. 9416-9423
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Journal article (peer-reviewed)abstract
- Vesicle impact electrochemical cytometry (VIEC) has been used to quantify the vesicular transmitter content in mammalian vesicles. In the present study, we studied the mechanism of VIEC by quantifying the catecholamine content in single vesicles isolated from pheochromocytoma (PC12) cells. These vesicles contain about one tenth of the catecholamine compared with adrenal chromaffin vesicles. The existence of a prespike foot for many events suggests the formation of an initial transiently stable pore at the beginning of vesicle rupture. Increasing the detection temperature from 6 to 30 degrees C increases the possibility of vesicle rupture on the electrode, implying that there is a temperature-dependent process that facilitates electroporation. Natively larger vesicles are shown to rupture earlier and more frequently than smaller ones in VIEC. Likewise, manipulating vesicle content and size with drugs leads to similar trends. These data support the hypothesis that electroporation is the primary force for pore opening in VIEC. We further hypothesize that a critical step for initiating vesicle opening by electroporation is diffusion of membrane proteins away from the membrane region of contact with the electrode to allow closer contact, increasing the lateral potential field and thus facilitating electroporation.
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| 3. |
- Lovric, Jelena, 1980, et al.
(author)
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Nano Secondary Ion Mass Spectrometry Imaging of Dopamine Distribution Across Nanometer Vesicles
- 2017
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In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 11:4, s. 3446-3455
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Journal article (peer-reviewed)abstract
- We report an approach to spatially resolve the content across nanometer neuroendocrine vesicles in nerve-like cells by correlating super high-resolution mass spectrometry imaging, NanoSIMS, with transmission electron microscopy (TEM). Furthermore, intracellular electrochemical cytometry at nanotip electrodes is used to count the number of molecules in individual vesicles to compare to imaged amounts in vesicles. Correlation between the NanoSIMS and TEM provides nanometer resolution of the inner structure of these organelles. Moreover, correlation with electrochemical methods provides a means to quantify and relate vesicle neurotransmitter content and release, which is used to explain the slow transfer of dopamine between vesicular compartments. These nanoanalytical tools reveal that dopamine loading/unloading between vesicular compartments, dense core and halo solution, is a kinetically limited process. The combination of NanoSIMS and TEM has been used to show the distribution profile of newly synthesized dopamine across individual vesicles. Our findings suggest that the vesicle inner morphology might regulate the neurotransmitter release event during open and closed exocytosis from dense core vesicles with hours of equilibrium needed to move significant amounts of catecholamine from the protein dense core despite its nanometer size.
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| 4. |
- Majdi, Soodabeh, 1980, et al.
(author)
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DMSO Chemically Alters Cell Membranes to Slow Exocytosis and Increase the Fraction of Partial Transmitter Released
- 2017
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In: Chembiochem. - : Wiley. - 1439-4227 .- 1439-7633. ; 18:19, s. 1898-1902
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Journal article (peer-reviewed)abstract
- Dimethyl sulfoxide (DMSO) is frequently used as a solvent in biological studies and as a vehicle for drug therapy; but the side effects of DMSO, especially on the cell environment, are not well understood, and controls with DMSO are not neutral at higher concentrations. Herein, electrochemical measurement techniques are applied to show that DMSO increases exocytotic neurotransmitter release, while leaving vesicular contents unchanged. In addition, the kinetics of release from DMSO-treated cells are faster than that of untreated ones. The results suggest that DMSO has a significant influence on the chemistry of the cell membrane, leading to alteration of exocytosis. A speculative chemical mechanism of the effect on the fusion pore during exocytosis is presented.
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| 5. |
- Mashadi Fathali, Hoda, 1983, et al.
(author)
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Extracellular Osmotic Stress Reduces the Vesicle Size while Keeping a Constant Neurotransmitter Concentration
- 2017
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In: Acs Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 8:2, s. 368-375
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Journal article (peer-reviewed)abstract
- Secretory cells respond to hypertonic stress by cell shrinking, which causes a reduction in exocytosis activity and the amount of signaling molecules released from single exocytosis events. These changes in exocytosis have been suggested to result from alterations in biophysical properties of cell cytoplasm and plasma membrane, based on the assumption that osmotic stress does not affect the secretory vesicle content and size prior to exocytosis. To further investigate whether vesicles in secretory cells are affected by the osmolality of the extracellular environment, we used intracellular electrochemical cytometry together with transmission electron microscopy imaging to quantify and determine the catecholamine concentration of dense core vesicles in situ before and after cell exposure to osmotic stress. In addition, single cell amperometry recordings of exocytosis at chromaffin cells were used to monitor the effect on exocytosis activity and quantal release when cells were exposed to osmotic stress. Here we show that hypertonic stress hampers exocytosis secretion after the first pool of readily releasable vesicles have been fused and that extracellular osmotic stress causes catecholamine filled vesicles to shrink, mainly by reducing the volume of the halo solution surrounding the protein matrix in dense core vesicles. In addition, the vesicles demonstrate the ability to perform adjustments in neurotransmitter content during shrinking, and intracellular amperometry measurements in situ suggest that vesicles reduce the catecholamine content to maintain a constant concentration within the vesicle compartment. Hence, the secretory vesicles in the cell cytoplasm are highly affected and respond to extracellular osmotic stress, which gives a new perspective to the cause of reduction in quantal size by these vesicles when undergoing exocytosis.
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