Linked Life Data

172481

Source:http://linkedlifedata.com/resource/pubmed/id/172481

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1976-2-9
pubmed:abstractText
In paramecia the membranes of alveoli and trichocysts are permanently connected to the cell membrane by membrane-junctions, which consist of membrane-intercalated particles in a regular geometrical arrangement. Trichocysts contain secretory material discharged by exocytosis. In unfixed or fixed cells these two compartments were impermeable to the following tracers: To "microperoxidases", i.e. a cytochrome c-derived heme-nonapeptide and a heme-undecapeptide (WM approximately 1650, 1900) applied in vivo, as well as to lanthanum and cytochrome c used during (La) or after (cytochrome c) fixation. The heme-nonapeptide was prepared by TPCK trypsin digestion of cytochrome c and subsequent purification by Sephadex gel chromatography--a simple and inexpensive new procedure resulting in preparations of high yield and purity. Tracers entered alveoli only when the plasmalemma and the alveolar membranes ruptured upon glutardialdehyde fixation. In no case were transmembraneous channels detectable in regions containing membrane-intercalated particles; this holds true for all tracers used and for freeze-fracture replicas obtained by tantalum-tungsten evaporation. With regard to attachment sites over trichocysts our results do not support the assumptions by others according to which exocytosis would be driven by an osmotic shift via transmembraneous channels (which would be analogous to inter-cellular coupling phenomena mediated by gap-junctions), unless such channels would be assumed to operate as carriers rather than via diffusion. Tracers did not penetrate trichocysts before exocytosis occurred. The functional role of membrane-intercalated particles on trichocyst attachments remains unclear. Despite some resemblance with gap-junctions all types of intra-cellular membrane-junctions investigated are functionally "tight" at the level of "resolution" obtained with tantalumtungsten-shadowing and with the tracers used.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0301-5564
pubmed:author
pubmed:issnType
Print
pubmed:day
7
pubmed:volume
45
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1-21
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1975
pubmed:articleTitle
Tracer and freeze-etching analysis of intra-cellular membrane-junctions in Paramecium with a note on a new heme-nonapeptide tracer.
pubmed:publicationType
Journal Article