1. Volume 18, Issue 6, Pages 857-863 (June 1997)
Ca2+-Triggered Peptide Secretion in Single Cells Imaged with Green Fluorescent Protein and Evanescent-Wave Microscopy 
Thorsten Lang, Irene Wacker, Jürgen Steyer, Christoph Kaether, Ilse Wunderlich, Thierry Soldati, Hans-Herman Gerdes, Wolfhard Almers 
Neuron 
Volume 18, Issue 6, Pages (June 1997)
DOI: /S (00)

2. Figure 1
Fluorescence from hCgB–GFP and hpNPY–GFP Is Concentrated in Neurites of NGF-Differentiated PC12 Cells
GFP fluorescence (A) and immunofluorescence (B) with anti-DβH antibody. Aldehyde-fixed cells (see Experimental Procedures). GFP fluorescence (C and D) in two live cells. Transfection with hCgB–GFP (A–C) and hpNPY–GFP (D).
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3. Figure 2 Colocalization of GFP and a Dense-Core Granule Marker
Localization of hCgB–GFP (A) and DβH (B) in an aldehyde-fixed neurite of a hCgB–GFP-transfected cell. Confocal high magnification scan; some areas of extensive colocalization are outlined. In (B) (lower left), note fluorescence from a neighboring and apparently untransfected cell.
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4. Figure 3 Extent of hCgB–GFP/DβH Colocalization
(A) and (B), same as in (2A) and (2B), but on a different cell. In (C) and (D), 500 nm diameter circles were superimposed on selected spots of GFP fluorescence in (A), and
red to identical pixel locations in (B). In (C), circles are numbered clockwise. Arrows, granules positive for DβH are negative for GFP fluorescence.
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5. Figure 4 Calcium Stimulates Release of GFP
Digitized images of a neurite of a cell grown in the presence of NGF. Brightfield (A and B) and epifluorescence (C and D). The cell body lay outside the pictures towards the upper left. Note accumulation of fluorescence in the neurite. (A) and (C) before, and (B) and (D) after 3 min depolarization in K,Ca2+-HBS (see Experimental Procedures). Note diminished fluorescence in (D). (E), analysis of (C) and (D) and other, similar experiments. The fluorescent portion of the neurite was outlined in (C) and the light collected within the outline, F1, was measured. The outline was slightly larger than the fluorescent area in order to capture all the light emitted, and in order to minimize errors due to any movement of the neurite later in the experiment. To measure background fluorescence, B1, the outline was duplicated and moved to an area towards the upper right of the frame. Both areas were then
red to identical locations in (D), yielding fluorescence, F2, and background, B2, values after stimulation. The fractional fluorescence remaining after stimulation, Rf, was calculated as Rf (%) = 100(B1/B2)(F2 − B2)/(F1 − B1), where the factor B1/B2 corrects for any changes in lamp intensity during the experiment. Data are shown for K,Ca2+-HBS (Ca, 9 neurites) and an identical
solution where all Ca2+ was replaced with Mg2+ and no Ca2+influx could take place (Mg, 5 neurites). Fluorescence was lost in the Ca2+-containing but not the Mg2+-containing solution. The difference is significant at p < 0.07 (one-tailed t test).
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6. Figure 5 Fluorescence Excitation with an Evanescent Wave
The method takes advantage of the refractive index, n, being lower in the cell than in the glass substrate to which it adheres tightly. A laser beam enters the coverslip through the microscope objective at an angle causing it to be totally reflected at the glass–buffer interface, or at the interface between the coverslip and the cell. Although dense-core granules in a cell are uniformly labeled, only those within the evanescent wave fluoresce and are detected by the microscope.
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7. Figure 6 Imaging Single Granules
(A) Fluorescence originating in a 300 nm thick layer of cytosol, where an hCgB–GFP-transfected cell adheres to a glass coverslip. Most or all of the fluorescent spots probably represent single dense-core granules. Live cell in a buffer containing 118 mM NaCl, 2 mM glutamine, 3.3 mM KCl, 2 mM CaCl2, 1 mM MgSO4, 1 mM Na-hydrogenphosphate, 10 mM glucose, and 25 mM HEPES (pH 7.0). (C–F) Successive images of a small region of another cell, permeabilized for 2 min with 7.5 mM digitonin added to a buffer containing 139 mM K glutamate, 5 mM EGTA, 4.5 mM CaCl2, 1 mM MgATP, 5 mM glucose, and 20 mM K-PIPES (pH 6.6), as in McInnes and Dolly This buffer remained after digitonin was withdrawn; [Ca2+] = 18 μM was measured with a Ca2+electrode. Images are samples from a 64 s sequence taken at 0.5 Hz; acquisition times are indicated relative to the disappearance of the granule (presumably due to exocytosis) after the 31st image. Positions of the granule (B) marked by the arrows in (C–F).
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