tailieunhanh - Atomic Force Microscopy in Cell Biology Episode 1 Part 4

Tham khảo tài liệu 'atomic force microscopy in cell biology episode 1 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 46 Jena and Cho EXOCYTOSIS A. Total Fusion B. Transient Fusion 1 FUSION PORE ZYMOGEN GRANULES -fl gWiaWPlBW u Fig. 10 Schematic representation of total fusion A where secretory vesicle membranes are completely incorporated with the plasma membrane and transient fusion B of secretory vesicles at specific sites depressions of the cell plasma membrane to release vesicular contents to the cell exterior during exocytosis. Reproduced with permission from Jena B. P. 1997 . Exocytic fusion Total or transient Cell. Biol. Int. 21 5 257-259. fusion would require the cell to expend much more energy than transient fusion Fig. 10B . In fact there is little evidence to support total fusion. Studies using transmission electron microscopy TEM rarely show the total incorporation of secretory vesicle membrane at the cell plasma membrane. On the contrary the majority of the TEM studies demonstrate that following stimulation of secretion there is an enriched presence of several intact but empty or partially empty secretory vesicles within cells Lawson et al. 1975 . Similar changes are also identifiable in the pancreas and parotid exocrine cell of rats Jamieson 1972 . Fast freeze-fracture EM studies on mast cells Chandler and Heuser 1980 show that even after fusion of the vesicle membrane at the cell plasma membrane much of the 2. AFM Cellular Structure-Function Studies 47 granule membrane is present and well separated from the plasma membrane Chandler and Heuser 1980 . Electrophysiological studies in mast cells Alvarez de Toledo et al. 1993 Monck et al. 1995 as well as in adrenal chromaffin cells Chow et al. 1992 suggest that the fusion pores either irreversibly expand total fusion or close following stimulation of secretion transient fusion . Quantitative electron microscopy on stimulated and resting bovine chromaffin cells demonstrates no significant change following stimulation of secretion in the number of peripheral densecore vesicles Plattner et al. 1997 . An increase followed by

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