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Plexus muscularis profundus and associated interstitial cells. II. Ultrastructural studies of mouse small intestine.

Authors
  • Rumessen, J J
  • Thuneberg, L
  • Mikkelsen, H B
Type
Published Article
Journal
The Anatomical record
Publication Date
May 01, 1982
Volume
203
Issue
1
Pages
129–146
Identifiers
PMID: 7103120
Source
Medline
License
Unknown

Abstract

The ultrastructure of plexus muscularis profundus (PMP) of the mouse small intestine was investigated subsequent to vascular perfusion with ruthenium red-containing and routine aldehyde fixatives. Four types of nerve terminals were revealed. Type I: numerous 500-A agranular vesicles and few 1,000-A granular vesicles. Type II: predominantly large (1,000-1,500 A), granular vesicles and fewer 500-A agranular vesicles. Type III: an abundance of mitochondria and many flattened vesicles (300 A X 700-1,300 A). Type IV was identified by abundant smooth cisternae 200 A in width. Types I-III formed close (200 A), synapse-like contacts to interstitial cells of Cajal (ICC-III). Presynaptic densities were frequent in type I endings. A direct innervation of muscle cells via PMP was only very occasionally suggested. ICC-III possessed a basal lamina and numerous caveolae associated with subsurface SER-cisternae. Mitochondria were very abundant in ICC-III-processes. ICC-III formed multiple, large gap junctions with outer circular-muscle cells and with other ICC-III. Also reflexive gap junctions were observed. Fibroblastlike cells (FLC) were distinguished by their prominent GER, the frequent presence of lipid droplets, and the lack of caveolae and a basal lamina. FLC never participated in synaptic arrangements or gap junctions. Macrophage-like cells were occasionally encountered. It is concluded that possible efferent and afferent nerve terminals in PMP may chiefly, if not exclusively, innervate ICC-III, the ultrastructure of which is compatible with efferent and/or afferent modulatory actions.

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