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Recent studies using atomic force microscopy demonstrate for the first time the …


Biology Articles » Biophysics » Fusion Pore in Live Cells » Figures

Figures
- Fusion Pore in Live Cells

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FIGURE 1. Topology of the apical cell surface of an isolated live pancreatic acinar cell, observed by using atomic force microscopy. Scattered pits (one shown with dotted outline) and depressions (arrowheads) are identified. See Schneider et al. (19).

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FIGURE 2. Nanometer resolution of a single depression or fusion pore in a live pancreatic acinar cell. Note the cone-shaped fusion pore, with a 100- to 150-nm opening. See Cho et al. (8).


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FIGURE 3. Dynamics of depressions following stimulation of secretion. Top: a number of depressions within a pit in a live pancreatic acinar cell. The scan line across 3 depressions is represented graphically at middle and defines the diameter and relative depth of the depressions; the middle depression is represented by red arrowheads. Bottom: percentage of total cellular amylase release in the presence and absence of the secretagogue Mas7. Notice an increase in the diameter and depth of depressions, correlating with an increase in total cellular amylase release at 5 min after stimulation of secretion. At 30 min after stimulation of secretion, there is a decrease in diameter and depth of depressions, with no further increase in amylase release over the 5-min time point. No significant increase in amylase secretion or depression diameter were observed in resting acini or those exposed to the nonstimulatory mastoparan analog Mas17. See Schneider et al. (19).

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FIGURE 4. Fusion pores (depressions) dilate to allow expulsion of vesicular contents. A–C: atomic force microscopy (AFM) micrographs of pits (dashed circle) and depressions (red circles) showing enlargement of depressions following stimulation of secretion (from A to B). Exposure of live cells to gold-conjugated to amylase antibody results in specific localization of gold to secretory sites (C). Note the localization of amylase-specific immunogold at the edge of depressions. D: AFM micrograph of pits and depressions with immunogold localization is also demonstrated in cells immunolabeled and then fixed. See Cho et al. (8).

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FIGURE 5. Schematic diagram of the plasma membrane (PM) showing a pit with smaller depressions within. Depressions are the fusion pores where membrane-bound secretory vesicles (SV) dock and fuse to release vesicular contents.


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