Vital methylene blue (MB): (I) preservation of MB for electron microscopy; (II) selectivity for interstitial cells of Cajal (ICC); (III) selective accumulation of MB in the endoplasmic reticulum of ICC

Electric pacemaker activity drives peristaltic and segmental contractions in the gastrointestinal tract. Interstitial cells of Cajal (ICC) are responsible for spontaneous pacemaker activity. ICC remain rhythmic in culture and generate voltage-independent inward currents via a nonselective cation conductance. Ca2+ release from endoplasmic reticulum and uptake by mitochondria initiates pacemaker currents. This novel mechanism provides the basis for electric rhythmicity in gastrointestinal muscles.

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Selective accumulation of methylene blue by interstitial cells of Cajal in canine colon

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1993.264.1.g64 ◽

1993 ◽

Vol 264 (1) ◽

pp. G64-G73 ◽

Cited By ~ 3

Author(s):

L. W. Liu ◽

L. Thuneberg ◽

E. E. Daniel ◽

J. D. Huizinga

Keyword(s):

Methylene Blue ◽

Interstitial Cells Of Cajal ◽

Three Dimensional ◽

Circular Muscle ◽

Muscle Cells ◽

Muscle Layer ◽

Interstitial Cells ◽

Resting Membrane Potential ◽

Selective Staining ◽

Cells Of Cajal

The network of interstitial cells of Cajal (ICC) at the submucosal surface of the canine colon was selectively stained by incubation with 15-50 microM methylene blue for 30-45 min. The network was composed of regularly scattered ICC cell bodies interconnected by long processes. Circular muscle cells were unstained. Staining of neurons was limited to one or two axons within bundles. The ICC network had a thickness of a single cell, since no overlapping of ICC cell bodies was observed. The ICC network connected the circular muscle cells at the submucosal surface across the septa which circumferentially divided the circular muscle into lamellae. Methylene blue at 50 microM slightly decreased the resting membrane potential and increased the duration of slow waves, leading to an increase in the force of phasic contractions, with no significant influence on other slow-wave parameters. Methylene blue produced neither electrophysiological nor mechanical effects on circular muscle preparations from which the submuscular ICC network was removed, indicating that the excitatory effects of methylene blue on the full-thickness circular muscle layer were mediated by ICC. In summary, the three-dimensional aspects of the submuscular ICC network can be visualized after selective staining by methylene blue. This staining does not affect physiological characteristics of smooth muscle cells.

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Pacemaking in interstitial cells of Cajal depends upon calcium handling by endoplasmic reticulum and mitochondria

The Journal of Physiology ◽

10.1111/j.1469-7793.2000.t01-1-00355.x ◽

2000 ◽

Vol 525 (2) ◽

pp. 355-361 ◽

Cited By ~ 227

Author(s):

S. M. Ward ◽

T. Ördög ◽

S. D. Koh ◽

S. Abu Baker ◽

J. Y. Jun ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Interstitial Cells Of Cajal ◽

Interstitial Cells ◽

Calcium Handling ◽

Cells Of Cajal

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Pacemaker activity recorded in interstitial cells of Cajal of the gastrointestinal tract

AJP Cell Physiology ◽

10.1152/ajpcell.1989.257.4.c830 ◽

1989 ◽

Vol 257 (4) ◽

pp. C830-C835 ◽

Cited By ~ 84

Author(s):

C. Barajas-Lopez ◽

I. Berezin ◽

E. E. Daniel ◽

J. D. Huizinga

Keyword(s):

Methylene Blue ◽

Slow Wave ◽

Interstitial Cells Of Cajal ◽

Circular Muscle ◽

Interstitial Cells ◽

Wave Activity ◽

Slow Wave Activity ◽

Resting Membrane Potential ◽

Pacemaker Activity ◽

Cells Of Cajal

The hypothesis was tested that interstitial cells of Cajal can generate slow wave activity. Intracellular recordings were performed only in the most superficial cells at the submucosal surface of the canine colonic circular muscle layer. An omnipresent and characteristic slow wave activity was present in all cells with a mean amplitude of 37 +/- 3 mV, a frequency of 4.6 +/- 0.1 counts/min (cpm), and a duration of 5.6 +/- 0.5 s; the average resting membrane potential was -70 +/- 1 mV. To determine the type of cell from which these recordings were obtained, methylene blue was injected by microiontophoresis. The strips were immediately fixed while the microelectrode was kept in the cell. A small segment of the tissue containing this cell was then processed for electron microscopy and serially sectioned. Electron-microscopic evidence showed that the microelectrode tip was positioned in an interstitial cell of Cajal (ICC): 1) several sections were observed with round cytoplasmic lesions of decreasing diameter followed by sections from the same cell without the lesion and 2) electron-dense material was observed in these sections due to the injected methylene blue. These cells were identified as part of the ICC network present at the muscle-submucosa interface of the circular muscle and were positively identified as ICC by the presence of cell processes. This is the first report giving direct evidence for the occurrence of electrical slow waves in ICC. It is essential support for the hypothesis that ICC are the actual pacemaker cells of the gut musculature.

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