The possible role of close contacts (nexuses) in the propagation of control electrical activity in the stomach and small intestine

Daniel, E. E.; Robinson, Kathleen; Duchon, G.; Henderson, Ruth M.

doi:10.1007/bf02239220

Cited by 10 publications

(8 citation statements)

References 33 publications

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“…1 and 2). In preparations fixed with glutaraldehyde by intra-arterial perfusion, we have never failed to find in the main circular muscle layer numerous nexuses in approximately the same range of frequency (6 to [7,14,30,17]. When stained en b l o c [47,39], these junctions have a clear 2 nm gap between the plasma membranes; thus they are gap junctions (Fig.…”

Section: Intestinal Musclementioning

confidence: 94%

“…This will be examined in detail elsewhere. There are, however, two candidate structures which occur in these and other smooth muscles [30,14,31]: (1) of the subadjacent cytoplasm; (2) close appositions with a gap of 10-30 n m between apposed, structurally undifferentiated membranes. Intermediate contacts are often f o u n d between an appendage of one cell and the surrounding m e m b r a n e of another cell into which it is inserted.…”

Section: Freeze Fracture Of Longitudinal Musclementioning

confidence: 98%

“…3 b). After hypertonic perfusion to the point of electrical uncoupling of intestinal control potentials or slow waves as previously described [14], there were, in one experiment, 97 nexal structures in 699 cells from circular muscle cut in cross section (0.132 nexus/cell), while in control muscles perfused with isotonic solutions there were 39 nexuses in 250 cells (0.156 nexus/cell). Similarly, treatment of the muscle with KC1, acetylcholine, or other contraction stimulants or with relaxants such as adrenaline or EDTA prior to fixation did not alter the number or distribution of nexal structures.…”

Section: Intestinal Musclementioning

confidence: 99%

“…If required, as in experiments on the effects of hypertonic solutions or metabolic inhibitors, intestinal segments were first perfused with various Ringer solutions before fixation. The procedures used for perfusion of hypertonic solutions have been described [14]. In some cases, intestinal muscle was isolated, separated from the mucosa, and incubated for varying times at 37 ~ in K.R.…”

Section: Tissues and Fixationmentioning

confidence: 99%

“…solution containing glutaraldehyde as previously described [14,29]. If required, as in experiments on the effects of hypertonic solutions or metabolic inhibitors, intestinal segments were first perfused with various Ringer solutions before fixation.…”

Section: Tissues and Fixationmentioning

confidence: 99%

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Is the nexus necessary for cell-to-cell coupling of smooth muscle?

Daniel

Duchon

et al. 1976

J. Membrain Biol.

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Electronmicroscopic study of electrically coupled smooth muscles was undertaken to determine the distribution of nexuses in various types of smooth muscle. The study revealed that while nexal structures were commonplace in some types of smooth muscle, they were very rare or absent in others, even though in some cases these cells were only a few nanometers distant from one another. The persistence in thin section of these structures in the main circular muscle of dog intestine after poor fixation, fixation under strain, cell shrinkage, and metabolic damage of various sorts seems to rule out the thesis that they are labile. The absence of nexuses in longitudinal muscle of dog intestine examined both by thin section and by freeze fracture suggests that in this tissue they are absent or very rare in vivo and cannot account for electrical coupling. Nexuses were discernible in thin sections of main circular muscle after a variety of experimental conditions of fixation. Metabolic inhibition or in vitro permanganate fixation partially destroyed nexal contacts. These procedures induced tissue, membrane apposition and an accompanying increase in the number of structures which resemble nexuses at low magnification (nexus-like structures). "Nexus-like" structures occurred in all smooth muscle fixed by in vitro permanganate associated with apposition of membranes and poor preservation of basement membrane. A technique of in vitro permanganate fixation was developed which prevented tissue swelling; consequently "nexus-like" structures were absent in tissues so treated. The suggestion is made that some structures described in the literature as nexuses, following permanganate fixation, may represent "nexus-like" structures. The balance of evidence suggests that nexuses need not be present for electrical coupling of some smooth muscle cells, in which other types of cell-to-cell contacts must be invoked.

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Section: Intestinal Musclementioning

confidence: 94%

Section: Freeze Fracture Of Longitudinal Musclementioning

confidence: 98%

Section: Intestinal Musclementioning

confidence: 99%

Section: Tissues and Fixationmentioning

confidence: 99%

Section: Tissues and Fixationmentioning

confidence: 99%

See 3 more Smart Citations

Is the nexus necessary for cell-to-cell coupling of smooth muscle?

Daniel

Duchon

et al. 1976

J. Membrain Biol.

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Gap Junctions in Smooth Muscle

Daniel

1987

Cell-to-Cell Communication

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Spontaneous Electrical Activity and Rhythmicity in Gastrointestinal Smooth Muscles

Sanders

2019

Advances in Experimental Medicine and Biology

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The gastrointestinal (GI) tract has multifold tasks of ingesting, processing, and assimilating nutrients and disposing of wastes at appropriate times. These tasks are facilitated by several stereotypical motor patterns that build upon the intrinsic rhythmicity of the smooth muscles that generate phasic contractions in many regions of the gut. Phasic contractions result from a cyclical depolarization/repolarization cycle, known as electrical slow waves, which result from intrinsic pacemaker activity. Interstitial cells of Cajal (ICC) are electrically coupled to smooth muscle cells (SMCs) and generate and propagate pacemaker activity and slow waves. The mechanism of slow waves is dependent upon specialized conductances expressed by pacemaker ICC. The primary conductances responsible for slow waves in mice are Ano1, Ca 2+ -activated Cl − channels (CaCCs), and Ca V 3.2, T-type, voltage-dependent Ca 2+ channels. Release of Ca 2+ from intracellular stores in ICC appears to be the initiator of pacemaker depolarizations, activation of T-type current provides voltage-dependent Ca 2+ entry into ICC, as slow waves propagate through ICC networks, and Ca 2+ -induced Ca 2+ release and activation of Ano1 in ICC amplifies slow wave depolarizations. Slow waves conduct to coupled SMCs, and depolarization elicited by these events enhances the open-probability of L-type voltage-dependent Ca 2+ channels, promotes Ca 2+ entry, and initiates contraction. Phasic contractions timed by the occurrence of slow waves provide the basis for motility patterns such as gastric peristalsis and segmentation. This chapter discusses the properties of ICC and proposed mechanism of electrical rhythmicity in GI muscles.

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The possible role of close contacts (nexuses) in the propagation of control electrical activity in the stomach and small intestine

Cited by 10 publications

References 33 publications

Is the nexus necessary for cell-to-cell coupling of smooth muscle?

Is the nexus necessary for cell-to-cell coupling of smooth muscle?

Gap Junctions in Smooth Muscle

Spontaneous Electrical Activity and Rhythmicity in Gastrointestinal Smooth Muscles

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