Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Schuler, G; Plattner, H; Aberer, W; Winkler, H.
Particle segregation in chromaffin granule membranes by forced physical contact.
Biochim Biophys Acta. 1978; 513(2):244-254
Doi: 10.1016/0005-2736(78)90177-3
Web of Science
PubMed
FullText
FullText_MUG
Google Scholar
- Co-Autor*innen der Med Uni Graz
- Aberer Werner
- Altmetrics:
- Dimensions Citations:
- Plum Analytics:
- Scite (citation analytics):
- Abstract:
- Bovine chromaffin granules were exposed to different isotonic non-ionic and ionic solutions (sucrose; Ca2+- and Mg2+-free phosphate-buffered saline; Tris-HCl + NaCl; Ca2+- and Mg2+-free phosphate-buffered saline + sucrose; Tris-HCl + sucrose) at pH 7 and then frozen either in suspension or as firm pellets. Freezing was performed without prefixation or antifreeze treatments either by 'standard' techniques (approx. 1 mm3 suspended or pelleted material on gold specimen supports dipped into liquid Freon) or with increased cooling rates by spraying suspensions into liquid propane ('spray-freezing'). Regardless of the freezing method, membrane-intercalated particles were always randomly distributed when chromaffin granules were frozen in suspension. In contrast, forced physical contact between granules produced by centrifugation (12000 X g, 25 min) provoked dispersal of membrane-intercalated particles, but only in the presence of ions. Sucrose or EDTA in an ionic environment had no inhibitory effect. The following conclusions are derived: (1) Even below the reported phase transition region particle clustering is possible. (2) Chromaffin granule membranes are not liable to thermotropic segregation of membrane-intercalated particles. (3) Although the low freezing rates of 'standard' freezing techniques produce large-scale segregation artefacts (by which suspended chromaffin granules are pushed together within the segregated solute) this does not result in intramembraneous particle segregation. (4) Forced physical contact produces a Ca2+-independent particle segregation, but only when repulsive electrostatic forces of membrane components are partially screened in an ionic environment. (5) This does not invalidate results obtained by others, showing Ca2+-mediated chromaffin granules agglomeration and segregation of membrane-intercalated particles, but it might indicate the occurrence of another, not directly Ca2+-dependent particle segregation mechanism in a prefusional stage of close membrane-to-membrane contact during exocytosis.
- Find related publications in this database (using NLM MeSH Indexing)
- Animals -
- Calcium -
- Cattle -
- Centrifugation -
- Chemistry, Physical -
- Chromaffin Granules - physiology
- Chromaffin System - physiology
- Exocytosis - physiology
- Freeze Fracturing - physiology
- Membrane Fluidity - physiology
- Methods - physiology