We thank the NINDS Intramural Research Programs (ZIA NS003009-13 and ZIA NS003105-08) for supporting this work.

<ol>
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The authors have no conflicts of interest to disclose.

A confocal microscopic imaging method is described to detect the dynamics of fusion pore and transmitter release, as well as three fusion modes, close-fusion, stay-fusion, and shrink-fusion in bovine adrenal chromaffin cells4,24. An electrophysiological method to depolarize the cell and thereby evoke exo- and endocytosis is described. Systematic confocal image processing provides information about different modes of pore behaviors for fusion and fission events.</...

Membrane fusion mediates many biological functions, including synaptic transmission, blood glucose homeostasis, immune response, and viral entry1,2,3. Exocytosis, involving vesicle fusion at the plasma membrane, releases neurotransmitters and hormones to achieve many important functions, such as neuronal network activities. Fusion opens a pore to release vesicular contents, after which the pore may close to retrieve the fusing vesicle, which is termed kiss-and-run1,4. Both irreversible and reversible fusion pore opening can be measured with cell-attached capacitance recordings combined with fusion pore conductance recordings of single vesicle fusion.
This is often interpreted as reflecting full-collapse fusion, involving dilation of the fusion until flattening of the fusing vesicle, and kiss-and-run, involving fusion pore opening and closure, respectively5,6,7,8,9,10,11,12,13. Recent confocal and stimulated emission depletion (STED) imaging studies in chromaffin cells directly observed fusion pore opening and closure (kiss-and-run, also called close-fusion), fusion pore opening that maintains an &#937;-shape with an open pore for a long time, termed stay-fusion, and shrinking of the fusing vesicle until it complete merges with the plasma membrane, which replaces full-collapse fusion for merging fusing vesicles with the plasma membrane4,8,14,15,16,17.
In neurons, fusion pore opening and closure have been detected with imaging showing the release of quantum dots preloaded in vesicles that are larger than the fusion pore and with fusion pore conductance measurements at the release face of nerve terminals5,18,19. Adrenal chromaffin cells are widely used as a model for the study of exo- and endocytosis20,21. Although chromaffin cells contain large dense-core vesicles, whereas synapses contain small synaptic vesicles, the exocytosis and endocytosis proteins in chromaffin cells and synapses are quite analogous10,11,12,20,21,22,23.
Here, a method is described to measure these three fusion modes using a confocal imaging method combined with electrophysiology in bovine adrenal chromaffin cells (Figure 1). This method involves loading of fluorescent false neurotransmitters (FFN511) into vesicles to detect exocytosis; addition of Atto 655 (A655) in the bath solution to fill the fusion-generated &#937;-shape profile, and labeling of the plasma membrane with the PH domain of phospholipase C &#948; (PH), which binds to PtdIns(4,5)P2 at the plasma membrane8,15,24. Fusion pore dynamics can be detected through changes in different fluorescent intensities. Although described for chromaffin cells, the principle of this method described here can be applied widely to many secretory cells well beyond chromaffin cells.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Adenosine 5&#39;-triphosphate magnesium salt</td>
			<td>Sigma</td>
			<td>A9187-500MG</td>
			<td>ATP for preparing internal solution</td>
		</tr>
		<tr>
			<td>Atto 655</td>
			<td>ATTO-TEC GmbH</td>
			<td>AD 655-21</td>
			<td>Atto dye to label bath solution</td>
		</tr>
		<tr>
			<td>Basic Nucleofector for Primary Neurons</td>
			<td>Lonza</td>
			<td>VSPI-1003</td>
			<td>Electroporation transfection buffer along with kit</td>
		</tr>
		<tr>
			<td>Boroscilicate capillary glass pipette</td>
			<td>Warner Instruments</td>
			<td>64-0795</td>
			<td>Standard wall with filament OD=2.0 mm ID=1.16 mm Length=7.5 cm</td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>Sigma</td>
			<td>A2153-50G</td>
			<td>Reagent for gland digestion</td>
		</tr>
		<tr>
			<td>Calcium Chloride 2 M</td>
			<td>Quality Biological</td>
			<td>351-130-721</td>
			<td>Reagent for preparing bath solution</td>
		</tr>
		<tr>
			<td>Cell Strainers, 100 &#181;m</td>
			<td>Falcon</td>
			<td>352360</td>
			<td>Material for filtering chromaffin cell suspension</td>
		</tr>
		<tr>
			<td>Cesium hydroxide solution</td>
			<td>Sigma</td>
			<td>232041</td>
			<td>Reagent for preparing internal solution and Cs-glutamate/Cs-EGTA stock buffer</td>
		</tr>
		<tr>
			<td>Collagenase P</td>
			<td>Sigma</td>
			<td>1.1214E+10</td>
			<td>Enzyme for gland digestion</td>
		</tr>
		<tr>
			<td>Coverslip</td>
			<td>Neuvitro</td>
			<td>GG-14-Laminin</td>
			<td>GG-14-Laminin, 14 mm dia.#1 thick 60 pieces Laminin coated German coverslips</td>
		</tr>
		<tr>
			<td>D-(+)-Glucose</td>
			<td>Sigma</td>
			<td>G8270-1KG</td>
			<td>Reagent for preparing Locke&#8217;s solution and bath solution</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>ThermoFisher Scientific</td>
			<td>11885092</td>
			<td>Reagent for preparing culture medium</td>
		</tr>
		<tr>
			<td>EGTA</td>
			<td>Sigma</td>
			<td>324626-25GM</td>
			<td>Reagent for preparing Cs-EGTA stock buffer for bath solution</td>
		</tr>
		<tr>
			<td>Electroporation and Nucleofector</td>
			<td>Amaxa Biosystems</td>
			<td>Nucleofector II</td>
			<td>Transfect plasmids into cells</td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>ThermoFisher Scientific</td>
			<td>10082147</td>
			<td>Reagent for preparing culture medium</td>
		</tr>
		<tr>
			<td>FFN511</td>
			<td>Abcam</td>
			<td>ab120331</td>
			<td>Fluorescent false neurotransmitter to label vesicles</td>
		</tr>
		<tr>
			<td>Guanosine 5&#39;-triphosphate sodium salt hydrate</td>
			<td>Sigma</td>
			<td>G8877-250MG</td>
			<td>GTP for preparing internal solution</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>H3375-500G</td>
			<td>Reagent for preparing Locke&#8217;s solution</td>
		</tr>
		<tr>
			<td>Igor Pro</td>
			<td>WaveMetrics</td>
			<td>Igor pro</td>
			<td>Software for patch-clamp analysis and imaging data presentation</td>
		</tr>
		<tr>
			<td>Leica Application Suite X software</td>
			<td>Leica</td>
			<td>LAS X software</td>
			<td>Confocal software for imaging data collection and analysis</td>
		</tr>
		<tr>
			<td>Leica TCS SP5 Confocal Laser Scanning Microscope</td>
			<td>Leica</td>
			<td>Leica TCS SP5</td>
			<td>Confocal microscope for imaging data collection</td>
		</tr>
		<tr>
			<td>L-Glutamic acid</td>
			<td>Sigma</td>
			<td>49449-100G</td>
			<td>Reagent for preparing Cs-glutamate stock buffer for bath solution</td>
		</tr>
		<tr>
			<td>Lock-in amplifier</td>
			<td>Heka</td>
			<td>Lock-in</td>
			<td>Software for capacitance recording</td>
		</tr>
		<tr>
			<td>Magnesium Chloride 1 M</td>
			<td>Quality Biological</td>
			<td>351-033-721EA</td>
			<td>Reagent for preparing internal solution and bath solution</td>
		</tr>
		<tr>
			<td>Metallized Hemacytometer Hausser Bright-Line</td>
			<td>Hausser Scientific</td>
			<td>3120</td>
			<td>Counting chamber</td>
		</tr>
		<tr>
			<td>Microforge</td>
			<td>Narishige</td>
			<td>MF-830</td>
			<td>Polish pipettes to enhance the formation and stability of giga-ohm seals</td>
		</tr>
		<tr>
			<td>Millex-GP Syringe Filter Unit, 0.22 &#181;m</td>
			<td>Millipore</td>
			<td>SLGPR33RB</td>
			<td>Material for glands wash and digestion</td>
		</tr>
		<tr>
			<td>mNG(mNeonGreen)</td>
			<td>Allele Biotechnology</td>
			<td>ABP-FP-MNEONSB</td>
			<td>Template for PH-mNeonGreen construction</td>
		</tr>
		<tr>
			<td>Nylon mesh filtering screen 100 micron</td>
			<td>EIKO filtering co</td>
			<td>03-100/32</td>
			<td>Material for filtering medulla suspension</td>
		</tr>
		<tr>
			<td>Patch clamp EPC-10</td>
			<td>Heka</td>
			<td>EPC-10</td>
			<td>Amplifier for patch-clamp data collection</td>
		</tr>
		<tr>
			<td>PH-EGFP</td>
			<td>Addgene</td>
			<td>Plasmid #51407</td>
			<td>Backbone for PH-mNeonGreen construction</td>
		</tr>
		<tr>
			<td>Pipette puller</td>
			<td>Sutter Instrument</td>
			<td>P-97</td>
			<td>Make pipettes for patch-clamp recording</td>
		</tr>
		<tr>
			<td>Potassium Chloride</td>
			<td>Sigma</td>
			<td>P5404-500G</td>
			<td>Reagent for preparing Locke&#8217;s solution and bath solution</td>
		</tr>
		<tr>
			<td>Pulse software</td>
			<td>Heka</td>
			<td>Pulse</td>
			<td>Software for patch-clamp data collection</td>
		</tr>
		<tr>
			<td>Recording chamber</td>
			<td>Warner Instruments</td>
			<td>64-1943/QR-40LP</td>
			<td>coverslip chamber, apply patch-clamp pipette on live cells</td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Sigma</td>
			<td>S7653-1KG</td>
			<td>Reagent for preparing Locke&#8217;s solution, bath solution and internal solution</td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Sigma</td>
			<td>S5881-500G</td>
			<td>Reagent for preparing Locke&#8217;s solution</td>
		</tr>
		<tr>
			<td>Sodium phosphate dibasic</td>
			<td>Sigma</td>
			<td>S0876-500G</td>
			<td>Reagent for preparing Locke&#8217;s solution</td>
		</tr>
		<tr>
			<td>Sodium phosphate monobasic</td>
			<td>Sigma</td>
			<td>S8282-500G</td>
			<td>Reagent for preparing Locke&#8217;s solution</td>
		</tr>
		<tr>
			<td>Stirring hot plate</td>
			<td>Barnsted/Thermolyne</td>
			<td>type 10100</td>
			<td>Heater for pipette coating with wax</td>
		</tr>
		<tr>
			<td>Syringe, 30 mL</td>
			<td>Becton Dickinson</td>
			<td>302832</td>
			<td>Material for glands wash and digestion</td>
		</tr>
		<tr>
			<td>Tetraethylammonium chloride</td>
			<td>Sigma</td>
			<td>T2265-100G</td>
			<td>TEA for preparing bath solution</td>
		</tr>
		<tr>
			<td>Trypsin inhibitor</td>
			<td>Sigma</td>
			<td>T9253-5G</td>
			<td>Reagent for gland digestion</td>
		</tr>
		<tr>
			<td>Type F Immersion liquid</td>
			<td>Leica</td>
			<td>195371-10-9</td>
			<td>Leica confocal mounting oil</td>
		</tr>
	</tbody>
</table>

confocal microscopy to measure three modes of fusion pore dynamics in adrenal chromaffin cells

Dynamic fusion pore opening and closure mediate exocytosis and endocytosis and determine their kinetics. Here, it is demonstrated in detail how confocal microscopy was used in combination with patch-clamp recording to detect three fusion modes in primary culture bovine adrenal chromaffin cells. The three fusion modes include 1) close-fusion (also called kiss-and-run), involving fusion pore opening and closure, 2) stay-fusion, involving fusion pore opening and maintaining the opened pore, and 3) shrink-fusion, involving shrinkage of the fusion-generated &#937;-shape profile until it merges completely at the plasma membrane.
To detect these fusion modes, the plasma membrane was labeled by overexpressing mNeonGreen attached with the PH domain of phospholipase C &#948; (PH-mNG), which binds to phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) at the cytosol-facing leaflet of the plasma membrane; vesicles were loaded with the fluorescent false neurotransmitter FFN511 to detect vesicular content release; and Atto 655 was included in the bath solution to detect fusion pore closure. These three fluorescent probes were imaged simultaneously at ~20-90 ms per frame in live chromaffin cells to detect fusion pore opening, content release, fusion pore closure, and fusing vesicle size changes. The analysis method is described to distinguish three fusion modes from these fluorescence measurements. The method described here can, in principle, apply to many secretory cells beyond chromaffin cells.

Following the experimental procedures shown in Figure 1 and Figure 2, chromaffin cells from bovine adrenal glands were transfected with PH-mNG to label the plasma membrane; A655 was added to the bath solution to detect fusion pore closure; and fluorescent false neurotransmitter FFN511 was loaded in vesicles for detection of release. Next, XY-plane confocal timelapse imaging of FFN511, PH-mNG, and A655 was performed every 20-90 ms at the cell bottom (Z-focal plan...

Watch this Scientific Journal Video about Confocal Microscopy to Measure Three Modes of Fusion Pore Dynamics in Adrenal Chromaffin Cells at JoVE.com

Confocal Microscopy to Measure Three Modes of Fusion Pore Dynamics in Adrenal Chromaffin Cells

This protocol describes a confocal imaging technique to detect three fusion modes in bovine adrenal chromaffin cells. These fusion modes include 1) close-fusion (also called kiss-and-run), involving fusion pore opening and closure, 2) stay-fusion, involving fusion pore opening and maintaining the opened pore, and 3) shrink-fusion, involving fused vesicle shrinkage.

Dynamic fusion pore opening and closure mediate exocytosis and endocytosis and determine their kinetics. Here, it is demonstrated in detail how confocal ...

confocal-microscopy-to-measure-three-modes-fusion-pore-dynamics

Research

JoVE Journal

Neuroscience

2.1K Views.  National Institute of Neurological Disorders and Stroke. This protocol describes a confocal imaging technique to detect three fusion modes in bovine adrenal chromaffin cells. These fusion modes include 1) close-fusion (also called kiss-and-run), involving fusion pore opening and closure, 2) stay-fusion, involving fusion pore opening and maintaining the opened pore, and 3) shrink-fusion, involving fused vesicle shrinkage. 

Video: Confocal Microscopy to Measure Three Modes of Fusion Pore Dynamics in Adrenal Chromaffin Cells

A Simple Way to Measure Ethanol Sensitivity in Flies

Low doses of ethanol cause flies to become hyperactive, while high doses are sedating. The sensitivity to ethanol-induced sedation of a given fly strain is correlated with that strain s ethanol preference, and therefore sedation is a highly relevant measure to study the genetics of alcohol responses and drinking. We demonstrate a simple way to expose flies to ethanol and measure its intoxicating effects. The assay we describe can determine acute sensitivity, as well as ethanol tolerance induced by repeat exposure. It does not require a technically involved setup, and can therefore be applied in any laboratory with basic fly culture tools.

A simple assay to measure the sedating effects of ethanol on Drosophila flies, based on the loss of righting reflex, is described.

Low doses of ethanol cause flies to become hyperactive, while high doses are sedating. The sensitivity to ethanol-induced sedation of a given fly strain ...

Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding fundamental biological mechanisms. Striking progress has been particularly evident in Drosophila, whose extensive toolkit of mutants and transgenic lines provides a convenient model to study evolutionarily-conserved developmental and cell biological mechanisms. We are interested in understanding the mechanisms that control cell fate specification in the adult peripheral nervous system (PNS) in Drosophila. Bristles that cover the head, thorax, abdomen, legs and wings of the adult fly are individual mechanosensory organs, and have been studied as a model system for understanding mechanisms of Notch-dependent cell fate decisions. Sensory organ precursor (SOP) cells of the microchaetes (or small bristles), are distributed throughout the epithelium of the pupal thorax, and are specified during the first 12 hours after the onset of pupariation. After specification, the SOP cells begin to divide, segregating the cell fate determinant Numb to one daughter cell during mitosis. Numb functions as a cell-autonomous inhibitor of the Notch signaling pathway.
Here, we show a method to follow protein dynamics in SOP cell and its progeny within the intact pupal thorax using a combination of tissue-specific Gal4 drivers and GFP-tagged fusion proteins 1,2.This technique has the advantage over fixed tissue or cultured explants because it allows us to follow the entire development of an organ from specification of the neural precursor to growth and terminal differentiation of the organ. We can therefore directly correlate changes in cell behavior to changes in terminal differentiation. Moreover, we can combine the live imaging technique with mosaic analysis with a repressible cell marker (MARCM) system to assess the dynamics of tagged proteins in mitotic SOPs under mutant or wildtype conditions. Using this technique, we and others have revealed novel insights into regulation of asymmetric cell division and the control of Notch signaling activation in SOP cells (examples include references 1-6,7 ,8).

Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae

In this video, we describe a method for live cell imaging of asymmetrically dividing sensory organ progenitor cells and epidermal cells in intact Drosophila pupae

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding ...

Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury

After brain stroke microglia/macrophages (M/M) undergo rapid activation with dramatic morphological and phenotypic changes that include expression of novel surface antigens and production of mediators that build up and maintain the inflammatory response. Emerging evidence indicates that M/M are highly plastic cells that can assume classic pro-inflammatory (M1) or alternative anti-inflammatory (M2) activation after acute brain injury. However a complete characterization of M/M phenotype marker expression, their colocalization and temporal evolution in the injured brain is still missing.	
	Immunofluorescence protocols specifically staining relevant markers of M/M activation can be performed in the ischemic brain. Here we present immunofluorescence-based protocols followed by three-dimensional confocal analysis as a powerful approach to investigate the pattern of localization and co-expression of M/M phenotype markers such as CD11b, CD68, Ym1, in mouse model of focal ischemia induced by permanent occlusion of the middle cerebral artery (pMCAO). Two-dimensional analysis of the stained area reveals that each marker is associated to a defined M/M morphology and has a given localization in the ischemic lesion. Patterns of M/M phenotype marker co-expression can be assessed by three-dimensional confocal imaging in the ischemic area. Images can be acquired over a defined volume (10 &mu;m z-axis and a 0.23 &mu;m step size, corresponding to a 180 x 135 x 10 &mu;m volume) with a sequential scanning mode to minimize bleed-through effects and avoid wavelength overlapping. Images are then processed to obtain three-dimensional renderings by means of Imaris software. Solid view of three dimensional renderings allows the definition of marker expression in clusters of cells. We show that M/M have the ability to differentiate towards a multitude of phenotypes, depending on the location in the lesion site and time after injury.

A way to gain new insights into the complexity of the brain inflammatory response is presented. We describe immunofluorescence-based protocols followed by three-dimensional confocal analysis to investigate the pattern of co-expression of microglia/macrophage phenotype markers in a mouse model of focal ischemia.

After brain stroke microglia/macrophages (M/M) undergo  rapid activation with dramatic morphological and phenotypic changes that  include expression of ...

Methods for Cell-attached Capacitance Measurements in Mouse Adrenal Chromaffin Cell

Neuronal transmission is an integral part of cellular communication within the brain. Depolarization of the presynaptic membrane leads to vesicle fusion known as exocytosis that mediates synaptic transmission. Subsequent retrieval of synaptic vesicles is necessary to generate new neurotransmitter-filled vesicles in a process identified as endocytosis. During exocytosis, fusing vesicle membranes will result in an increase in surface area and subsequent endocytosis results in a decrease in the surface area. Here, our lab demonstrates a basic introduction to cell-attached capacitance recordings of single endocytic events in the mouse adrenal chromaffin cell. This type of electrical recording is useful for high-resolution recordings of exocytosis and endocytosis at the single vesicle level. While this technique can detect both vesicle exocytosis and endocytosis, the focus of our lab is vesicle endocytosis. Moreover, this technique allows us to analyze the kinetics of single endocytic events. Here the methods for mouse adrenal gland tissue dissection, chromaffin cell culture, basic cell-attached techniques, and subsequent examples of individual traces measuring singular endocytic event are described.

After exocytosis, fused plasma membrane is retrieved through a process known as endocytosis. This mechanism reforms new synaptic vesicles for the next round of release. Individual endocytic events are captured and analyzed through the use of the cell-attached capacitance recordings in mouse adrenal chromaffin cells.

Neuronal transmission is an integral part of cellular communication within the brain. Depolarization of the presynaptic membrane leads to vesicle fusion ...

The Neuromuscular Junction: Measuring Synapse Size, Fragmentation and Changes in Synaptic Protein Density Using Confocal Fluorescence Microscopy

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. Structural changes at the NMJ can result in neurotransmission failure, resulting in weakness, atrophy and even death of the muscle fiber. Many studies have investigated how genetic modifications or disease can alter the structure of the mouse NMJ. Unfortunately, it can be difficult to directly compare findings from these studies because they often employed different parameters and analytical methods. Three protocols are described here. The first uses maximum intensity projection confocal images to measure the area of acetylcholine receptor (AChR)-rich postsynaptic membrane domains at the endplate and the area of synaptic vesicle staining in the overlying presynaptic nerve terminal. The second protocol compares the relative intensities of immunostaining for synaptic proteins in the postsynaptic membrane. The third protocol uses Fluorescence Resonance Energy Transfer (FRET) to detect changes in the packing of postsynaptic AChRs at the endplate. The protocols have been developed and refined over a series of studies. Factors that influence the quality and consistency of results are discussed and normative data are provided for NMJs in healthy young adult mice.

The neuromuscular junction (NMJ) is altered in a variety of conditions that can sometimes culminate in synaptic failure. This report describes fluorescence microscope-based methods to quantify such structural changes.

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. ...

TIRFM and pH-sensitive GFP-probes to Evaluate Neurotransmitter Vesicle Dynamics in SH-SY5Y Neuroblastoma Cells: Cell Imaging and Data Analysis

Synaptic vesicles release neurotransmitters at chemical synapses through a dynamic cycle of fusion and retrieval. Monitoring synaptic activity in real time and dissecting the different steps of exo-endocytosis at the single-vesicle level are crucial for understanding synaptic functions in health and disease.
Genetically-encoded pH-sensitive probes directly targeted to synaptic vesicles and Total Internal Reflection Fluorescence Microscopy (TIRFM) provide the spatio-temporal resolution necessary to follow vesicle dynamics. The evanescent field generated by total internal reflection can only excite fluorophores placed in a thin layer (&#60;150 nm) above the glass cover on which cells adhere, exactly where the processes of exo-endocytosis take place. The resulting high-contrast images are ideally suited for vesicles tracking and quantitative analysis of fusion events.
In this protocol, SH-SY5Y human neuroblastoma cells are proposed as a valuable model for studying neurotransmitter release at the single-vesicle level by TIRFM, because of their flat surface and the presence of dispersed vesicles. The methods for growing SH-SY5Y as adherent cells and for transfecting them with synapto-pHluorin are provided, as well as the technique&#160;to perform TIRFM and imaging. Finally, a strategy aiming to select, count, and analyze fusion events at whole-cell and single-vesicle levels is presented.
To validate the imaging procedure and data analysis approach, the dynamics of pHluorin-tagged vesicles are&#160;analyzed under resting and stimulated (depolarizing potassium concentrations) conditions. Membrane depolarization increases the frequency of fusion events and causes a parallel raise of the net fluorescence signal recorded in whole cell. Single-vesicle analysis reveals modifications of fusion-event behavior (increased peak height and width). These data suggest that potassium depolarization not only induces a massive neurotransmitter release but also modifies the mechanism of vesicle fusion and recycling.
With the appropriate fluorescent probe, this technique can be employed in different cellular systems to dissect the mechanisms of constitutive and stimulated secretion.

This paper provides a method for investigating neurotransmitter vesicle dynamics in neuroblastoma cells, using a synaptobrevin2-pHluorin construct and Total Internal Reflection Fluorescence Microscopy. The strategy developed for image processing and data analysis is also reported.

Synaptic vesicles release neurotransmitters at chemical synapses through a dynamic cycle of fusion and retrieval. Monitoring synaptic activity in real ...

Protocol for Three-dimensional Confocal Morphometric Analysis of Astrocytes

As glial cells in the brain, astrocytes have diverse functional roles in the central nervous system. In the presence of harmful stimuli, astrocytes modify their functional and structural properties, a condition called reactive astrogliosis. Here, a protocol for assessment of the morphological properties of astrocytes is presented. This protocol includes quantification of 12 different parameters i.e. the surface area and volume of the tissue covered by an astrocyte (astrocyte territory), the entire astrocyte including branches, cell body, and nucleus, as well as total length and number of branches, the intensity of fluorescence immunoreactivity of antibodies used for astrocyte detection, and astrocyte density (number/1,000 &#181;m2). For this purpose three-dimensional (3D) confocal microscopic images were created, and 3D image analysis software such as Volocity 6.3 was used for measurements. Rat brain tissue exposed to amyloid beta1-40 (A&#946;1-40) with or without a therapeutic&#160;intervention was used to present the method. This protocol can also be used for 3D morphometric analysis of other cells from either in vivo or in vitro conditions.

Astrocytes in the CNS change their functional and structural properties in response to harmful stimuli. This report presents a protocol for assessment of three-dimensional astrocyte morphology in diseased conditions or after therapeutic interventions.

As glial cells in the brain, astrocytes have diverse functional roles in the central nervous system. In the presence of harmful stimuli, astrocytes modify ...

SNARE-mediated Fusion of Single Proteoliposomes with Tethered Supported Bilayers in a Microfluidic Flow Cell Monitored by Polarized TIRF Microscopy

In the ubiquitous process of membrane fusion the opening of a fusion pore establishes the first connection between two formerly separate compartments. During neurotransmitter or hormone release via exocytosis, the fusion pore can transiently open and close repeatedly, regulating cargo release kinetics. Pore dynamics also determine the mode of vesicle recycling; irreversible resealing results in transient, &#34;kiss-and-run&#34; fusion, whereas dilation leads to full fusion. To better understand what factors govern pore dynamics, we developed an assay to monitor membrane fusion using polarized total internal reflection fluorescence (TIRF) microscopy with single molecule sensitivity and ~15 msec time resolution in a biochemically well-defined in vitro system. Fusion of fluorescently labeled small unilamellar vesicles containing v-SNARE proteins (v-SUVs) with a planar bilayer bearing t-SNAREs, supported on a soft polymer cushion (t-SBL, t-supported bilayer), is monitored. The assay uses microfluidic flow channels that ensure minimal sample consumption while supplying a constant density of SUVs. Exploiting the rapid signal enhancement upon transfer of lipid labels from the SUV to the SBL during fusion, kinetics of lipid dye transfer is monitored. The sensitivity of TIRF microscopy allows tracking single fluorescent lipid labels, from which lipid diffusivity and SUV size can be deduced for every fusion event. Lipid dye release times can be much longer than expected for unimpeded passage through permanently open pores. Using a model that assumes retardation of lipid release is due to pore flickering, a pore &#34;openness&#34;, the fraction of time the pore remains open during fusion, can be estimated. A soluble marker can be encapsulated in the SUVs for simultaneous monitoring of lipid and soluble cargo release. Such measurements indicate some pores may reseal after losing a fraction of the soluble cargo.

Here, we present a protocol to detect single, SNARE-mediated fusion events between liposomes and supported bilayers in microfluidic channels using polarized TIRFM, with single molecule sensitivity and ~15 msec time resolution. Lipid and soluble cargo release can be detected simultaneously. Liposome size, lipid diffusivity, and fusion pore properties are measured.

In the ubiquitous process of membrane fusion the opening of a fusion pore establishes the first connection between two formerly separate compartments. ...

Assay to Measure Nucleocytoplasmic Transport in Real Time within Motor Neuron-like NSC-34 Cells

Nucleocytoplasmic transport refers to the import and export of large molecules from the cell nucleus. Recently, a number of studies have shown a connection between amyotrophic lateral sclerosis (ALS) and impairments in the nucleocytoplasmic pathway. ALS is a neurodegenerative disease affecting the motor neurons and resulting in paralysis and ultimately in death, within 2-5 years on average. Most cases of ALS are sporadic, lacking any apparent genetic linkage, but 10% are inherited in a dominant manner. Recently, hexanucleotide repeat expansions (HREs) in the chromosome 9 open reading frame 72 (C9orf72) gene were identified as a genetic cause of ALS and frontotemporal dementia (FTD). Importantly, different groups have recently proposed that these mutants affect nucleocytoplasmic transport. These studies have mostly shown the final outcome and manifestations caused by HREs on nucleocytoplasmic transport, but they do not demonstrate nuclear transport dysfunction in real time. As a result, only severe nucleocytoplasmic transport deficiency can be determined, mostly due to high overexpression or exogenous protein insertion. 
This protocol describes a new and very sensitive assay to evaluate and quantify nucleocytoplasmic transport dysfunction in real time. The rate of import of a NLS-NES-GFP protein (shuttle-GFP) can be quantified in real time using fluorescent microscopy. This is performed by using an exportin inhibitor, thus allowing the shuttle GFP only to enter the nucleus. To validate the assay, the C9orf72 HRE translated dipeptide repeats, poly(GR) and poly(PR), which have been previously shown to disrupt nucleocytoplasmic transport, were used. Using the described assay, a 50% decrease in the nuclear import rate was observed compared to the control. Using this system, minute changes in nucleocytoplasmic transport can be examined and the ability of different factors to rescue (even partially) a nucleocytoplasmic transport defect can be determined.

This protocol describes a method to sensitively measure the nucleocytoplasmic transport rate within motor neuron-like NSC-34 cells by quantifying the real-time change in the nuclear import of a NLS-NES-GFP protein.

Nucleocytoplasmic transport refers to the import and export of large molecules from the cell nucleus. Recently, a number of studies have shown a ...

Three-dimensional Navigation-guided, Prone, Single-position, Lateral Lumbar Interbody Fusion Technique

Lateral interbody fusion provides a significant biomechanical advantage over the traditional transforaminal lumbar interbody fusion due to the large implant size and optimal implant position. However, current methods for lateral interbody cage placement require either a two-staged procedure or a single lateral decubitus position that precludes surgeons from having either full access to the posterior spine for direct decompression or comfortable pedicle screw placement.
Herein is one institution's experience with 10 cases of a prone single-position approach for simultaneous access to the anterior and posterior lumbar spine. This allows both lateral lumbar interbody cage placement, direct posterior decompression, and pedicle screw placement, all in one position. Three-dimensional (3D) navigation is utilized for increased precision in both approaching the lateral spine and interbody cage placement. The traditional blind psoas muscle tubular dilation was also modified. Tubular retractors and lateral vertebral body retractor pins were used to minimize the risks to the lumbar plexus.

The single-position, prone, lateral approach allows for both lateral lumbar interbody placement and direct posterior decompression with pedicle screw placement in one position.

Lateral interbody fusion provides a significant biomechanical advantage over the traditional transforaminal lumbar interbody fusion due to the large ...