Correlation between electrical and morphological properties of canine pyloric circular muscle

1991 ◽  
Vol 260 (3) ◽  
pp. G390-G398 ◽  
Author(s):  
F. Vogalis ◽  
S. M. Ward ◽  
K. M. Sanders
Keyword(s):  
Single Cells ◽  
Electrical Coupling ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Morphological Properties ◽  
Morphological Examination ◽  
Isolated Cells ◽  
Time Constants ◽  
Morphological Studies ◽  
Cable Properties

Electrical slow waves decay in amplitude as they conduct from the myenteric to the submucosal regions of the circular muscle layer in the canine pyloric sphincter. We used the partitioned chamber method to study the passive and active properties of pyloric muscles, and we found that length constants of circular muscles of myenteric region were significantly longer than muscles near the submucosal surface. These data suggested differences in either membrane resistance, junctional resistance, or cytoplasmic resistance. The first parameter was evaluated by measuring time constants in intact tissues and single cells isolated from the submucosal and myenteric regions. Membrane time constants were not different in the two regions, nor were differences found in the input resistances of isolated cells. Morphological studies failed to demonstrate differences in cell diameters in the two regions suggesting that cytoplasmic resistances are similar. These findings suggest that the different cable properties in the two regions may be due to differences in electrical coupling. Morphological examination revealed similar numbers of gap junctions between cells in the two regions, but large differences were noted in the size of muscular bundles. Muscles of the myenteric region were arranged into large, tightly packed bundles, whereas muscles of the submucosal region consisted of small bundles with an extensive extracellular space filled with connective tissue. We suggest that the difference in cable properties may be due to differences in electrical coupling between bundles. These data suggest that submucosal muscles function more like a multiunit smooth muscle, whereas myenteric muscles behave as a single unit.

Electrical coupling in the circular muscles of dog jejunum

1979 ◽  
Vol 57 (6) ◽  
pp. 578-580 ◽  
Author(s):  
Elane Zelcer ◽  
E. E. Daniel
Keyword(s):  
Gap Junctions ◽  
Electrical Coupling ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Dense Layer ◽  
Isolated Cells ◽  
Alternate Pathway ◽  
Significant Difference ◽  
Circular Layer ◽  
Passive Current

Two distinct layers of circular muscle have previously been demonstrated in dog jejunum, the main circular layer containing many gap junction contacts, and an inner dense muscle layer where no gap junctions have been found. Length constants were determined for these muscle layers and no significant difference was found between these values. The main circular muscle cells had lower membrane potentials and may have had abnormally low space constants owing to injury. It was concluded that the absence of gap junctions in the inner dense layer does not reduce the spread of passive current as might be expected of electrically isolated cells, and it is suggested that an alternate pathway for passive current exists in this layer.

Pacemaker activity in septal structures of canine colonic circular muscle

1990 ◽  
Vol 259 (2) ◽  
pp. G264-G273 ◽  
Author(s):  
S. M. Ward ◽  
K. M. Sanders
Keyword(s):  
Slow Wave ◽  
Electrical Coupling ◽  
Circular Muscle ◽  
Proximal Colon ◽  
Slow Waves ◽  
Pacemaker Activity ◽  
Electrical Measurements ◽  
Morphological Studies ◽  
Circular Layer ◽  
And Function

Morphological and electrophysiological experiments were performed to characterize the pacemaker areas of the circular muscle in the canine proximal colon. Morphological studies showed interstitial cells of Cajal lining the submucosal surface of the circular layer and the septal structures that separate the circular layer into bundles. Electrical measurements suggested that slow waves may propagate into the thickness of the circular muscle in a regenerative manner along the surface of these septa. Removal of the submucosal pacemaker region blocked generation of slow waves in nonseptal regions of the circular muscle, but slow-wave activity continued in the circular muscle near septa. These data suggest that slow-wave pacemaker activity is not limited to a two-dimensional surface at the submucosal surface but extends into the interior of the circular layer along septal invaginations. Experiments were also performed to determine the dominance of pacemaker activity (i.e., septal vs. submucosal), and examples were found in which both areas appeared to initiate slow waves in intact muscles. Other studies showed that slow waves could propagate across septa, suggesting some form of electrical coupling between circular muscle bundles. This study provides a more complete view of the structure and function of pacemaker areas in the canine proximal colon.

Passive and active membrane properties of canine gastric antral circular muscles

1986 ◽  
Vol 251 (2) ◽  
pp. C268-C273 ◽  
Author(s):  
A. J. Bauer ◽  
K. M. Sanders
Keyword(s):  
Electrical Activity ◽  
Time Constant ◽  
Myenteric Plexus ◽  
Circular Muscle ◽  
Membrane Properties ◽  
Time Constants ◽  
Active Membrane ◽  
Cable Properties ◽  
Length Constant ◽  
Chamber Technique

Experiments were performed to determine the mechanisms responsible for the gradient of electrical activity within circular muscle of the canine gastric antrum. Cable properties of canine gastric antral circular muscles were determined using the partitioned chamber technique of Abe and Tomita (J. Physiol. Lond. 196: 87-100, 1968). The length constant of the circular muscle near the myenteric plexus was 2.4 mm. This was significantly greater than the length constant of the circular muscle near the submucosa (1.7 mm). Membrane time constants were determined by two techniques. Although the time constant of the circular muscle near the myenteric plexus tended to be greater than that of the circular muscle near the submucosa, this difference was not statistically significant. The two regions of circular muscle also differed in their relative levels of excitability. Submucosal circular muscles demonstrated considerably more outward rectification on depolarization and were difficult to bring to threshold for slow waves. This study demonstrates that significant differences exist in the passive and active membrane properties of myenteric and submucosal circular muscle cells. The data help explain the gradient of electrical activity through the thickness of antral circular muscle.

Improved propagation in myometrium associated with gap junctions during parturition

1989 ◽  
Vol 256 (1) ◽  
pp. C130-C141 ◽  
Author(s):  
S. M. Miller ◽  
R. E. Garfield ◽  
E. E. Daniel
Keyword(s):  
Gap Junction ◽  
Electrical Coupling ◽  
Circular Muscle ◽  
Axial Direction ◽  
Muscle Layer ◽  
Circumferential Direction ◽  
Electrical Excitation ◽  
Myometrial Cells ◽  
Relaxation Oscillators ◽  
Junction Formation

The hypothesis that gap junction (GJ) formation between myometrial cells at term improves electrical coupling was tested. We measured the spread of electrical excitation from six extracellular electrodes aligned on uterine strips in either the longitudinal (axial) or transverse (circumferential) direction. Spontaneous bursts propagated over the entire 15-mm recording distance in the axial direction at both preterm and parturition and showed some characteristics of a system of coupled relaxation oscillators. However, individual spikes within the bursts propagated further and with higher velocity at parturition than at preterm. In the circumferential direction, both bursts and individual spikes propagated further at parturition than before. Propagation in this axis at parturition appeared to require an intact circular muscle layer. Spikes evoked by electrical stimulation also propagated further and with higher velocity in both axes at parturition. Electron microscopy showed many GJs between uterine smooth muscle cells during parturition, but few and sometimes no GJs at preterm. Thus improved propagation was associated with increased GJ contact between myometrial cells, consistent with the hypothesis that gap junction formation at term improves electrical coupling.

Electrical coupling and pacemaker activity in colonic smooth muscle

1988 ◽  
Vol 255 (5) ◽  
pp. C653-C660 ◽  
Author(s):  
J. D. Huizinga ◽  
A. Shin ◽  
E. Chow
Keyword(s):  
Slow Wave ◽  
Electrical Coupling ◽  
Circular Muscle ◽  
Input Resistance ◽  
Wave Activity ◽  
Slow Wave Activity ◽  
Pacemaker Activity ◽  
Isolated Cells ◽  
Current Spread ◽  
Length Constant

The effect of heptanol on electrical coupling between submucosal circular muscle cells of the dog colon and consequences for slow-wave activity were investigated. Electrotonic potentials showed exponential decay giving a length constant of 2.6 +/- 0.5 mm and a time constant of 157 +/- 48 ms. Heptanol reversibly abolished electrotonic current spread, and subsequently no slow-wave activity was recorded. The length constant decreased to less than 0.2 mm. The input resistance increased from 3 to 36 M omega, suggesting a change from tissue syncytium to electrically isolated cells. D600 (5 X 10(-6) M) also abolished slow wave activity but had opposite effects on electrotonic current spread. The data are consistent with the hypothesis that heptanol reversibly inhibits intercellular coupling, resulting in loss of spread of extracellularly applied current, uncoupling of cells, and loss of pacemaker activity. Regulation of intercellular communication may be important in the control of intestinal motility.

Contraction mediated by Ca2+ influx in esophageal muscle and by Ca2+ release in the LES

1987 ◽  
Vol 253 (6) ◽  
pp. G760-G766 ◽  
Author(s):  
P. Biancani ◽  
C. Hillemeier ◽  
K. N. Bitar ◽  
G. M. Makhlouf
Keyword(s):  
Single Cells ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Enzymatic Digestion ◽  
The Body ◽  
Tissue Specimens ◽  
Resting Tone ◽  
Esophageal Contraction ◽  
Esophageal Muscle

Single cells and whole tissue specimens were used in this study to determine sources of Ca2+ utilized for contraction of the circular muscle layer of esophagus and lower esophageal sphincter (LES) of the cat. In vitro circular muscle specimens from the cat esophagus respond to electrical stimulation with phasic contractions at the end of the stimulus, whereas the LES spontaneously maintains tonic contraction and relaxes during stimulation. In Ca2+-free buffer, esophageal contractions rapidly decline and disappear within 10 min after the removal of Ca2+, while LES tone is only partially reduced. Similarly, incubation in a solution containing the Ca2+ influx blocker, La3+, abolishes esophageal contraction but only partially decreases LES tone. Conversely, strontium and caffeine substantially reduce LES tone without affecting the amplitude of esophageal contractions. In single muscle cells isolated by enzymatic digestion from the LES and the body of the esophagus, blockade of extracellular Ca2+ influx by methoxyverapamil (D 600) or ethyleneglycol-bis-(beta-aminoethylether) N,N'-tetraacetic acid abolished esophageal contraction in response to acetylcholine without affecting LES cells, and conversely, strontium abolished LES contraction without affecting esophageal cells. These data are consistent with the view that extracellular Ca2+ is required to initiate esophageal phasic contraction, while the LES has the ability to utilize intracellular Ca2+ to maintain resting tone and to contract in response to acetylcholine.

Galanin induces contraction of isolated cells from circular muscle layer of pig ileum

1991 ◽  
Vol 32 (3) ◽  
pp. 369-374 ◽  
Author(s):  
Michel Delvaux ◽  
Alain Botella ◽  
Jean Fioramonti ◽  
Jacques Frexinos ◽  
Lionel Bueno
Keyword(s):  
Circular Muscle ◽  
Muscle Layer ◽  
Isolated Cells ◽  
Circular Muscle Layer

COMPARATIVE EVALUATION OF MULTIPARAMETRIC ENDORECTAL ULTRASOUND AND ENHANCED IMAGING COLONOSCOPY IN THE DIAGNOSIS OF EARLY COLORECTAL CANCER

2020 ◽  
Vol 19 (3) ◽  
pp. 49-64
Author(s):  
E. M. Bogdanova ◽  
Yu. L. Trubacheva ◽  
O. M. Yugai ◽  
S. V. Chernyshov ◽  
E. G. Rybakov ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Statistical Significance ◽  
Muscle Layer ◽  
Endorectal Ultrasound ◽  
Diagnostic Methods ◽  
Early Colorectal Cancer ◽  
Morphological Examination ◽  
Optical Magnification ◽  
The Difference ◽  
Enhanced Imaging

AIM: to compare multiparametric endorectal ultrasound (ERUS) and enhanced imaging colonoscopy in the diagnosis of early colorectal cancer.PATIENTS AND METHODS: the study included 78 patients with epithelial rectal tumor. All the patients underwent multiparametric ERUS and colonoscopy with examination by narrow beam imaging (NBI) at optical magnification. All the patients were operated.RESULTS: a morphological examination removed specimens revealed adenomas in 48 cases, in 19 specimens – adenocarcinomas in situ and T1, and in 11 specimens – adenocarcinomas with invasion of the muscle layer or deeper. When calculating the accuracy indicators of diagnostic methods for groups of patients with adenoma, Tis-T1 adenocarcinoma, and T2-T3 adenocarcinoma, the difference in the sensitivity and specificity of the methods in none of the presented groups did not reach the level of statistical significance (p>0.05).ROC analysis showed that ultrasound has a prognostic value comparable to colonoscopy. The area difference was 0.013 (p=0.85).CONCLUSION: endoscopy and ultrasound have similar value in the diagnosis of malignant transformation of rectal adenomas.

Effects of ouabain on background and voltage-dependent currents in canine colonic myocytes

1990 ◽  
Vol 259 (3) ◽  
pp. C402-C408 ◽  
Author(s):  
E. P. Burke ◽  
K. M. Sanders
Keyword(s):  
Membrane Potential ◽  
Potential Gradient ◽  
Circular Muscle ◽  
Input Resistance ◽  
Pump Current ◽  
Muscle Layer ◽  
Membrane Properties ◽  
Resting Potential ◽  
Voltage Dependent ◽  
In Cells

Previous studies have suggested that the membrane potential gradient across the circular muscle layer of the canine proximal colon is due to a gradient in the contribution of the Na(+)-K(+)-ATPase. Cells at the submucosal border generate approximately 35 mV of pump potential, whereas at the myenteric border the pump contributes very little to resting potential. Results from experiments in intact muscles in which the pump is blocked are somewhat difficult to interpret because of possible effects of pump inhibitors on membrane conductances. Therefore, we studied isolated colonic myocytes to test the effects of ouabain on passive membrane properties and voltage-dependent currents. Ouabain (10(-5) M) depolarized cells and decreased input resistance from 0.487 +/- 0.060 to 0.292 +/- 0.040 G omega. The decrease in resistance was attributed to an increase in K+ conductance. Studies were also performed to measure the ouabain-dependent current. At 37 degrees C, in cells dialyzed with 19 mM intracellular Na+ concentration [( Na+]i), ouabain caused an inward current averaging 71.06 +/- 7.49 pA, which was attributed to blockade of pump current. At 24 degrees C or in cells dialyzed with low [Na+]i (11 mM), ouabain caused little change in holding current. With the input resistance of colonic cells, pump current appears capable of generating at least 35 mV. Thus an electrogenic Na+ pump could contribute significantly to membrane potential.

scholarly journals The use of a slide spinner in the analysis of cell dispersion.

1976 ◽  
Vol 24 (1) ◽  
pp. 11-15 ◽  
Author(s):  
R C Wolley ◽  
H M Dembitzer ◽  
F Herz ◽  
K Schreiber ◽  
L G Koss
Keyword(s):  
Cell Suspension ◽  
Single Cells ◽  
Cell Loss ◽  
Optimum Conditions ◽  
Isolated Cells ◽  
Cell Dispersion ◽  
Cervical Cancer Cells ◽  
A Cell ◽  
Human Cervical Cancer Cells ◽  
Human Cervical Cancer

A simple and reliable method of determining the degree of dispersion of a cell suspension has been developed using the Perkin-Elmer Uni-Smear Spinner. Optimum conditions regarding rate and duration of spin, etc., were first ascertained using dispersed cell cultures including human cervical cancer cells as well as gynecologic samples. After spinning, single cells in suspension appeared as isolated cells on the slides. Cell aggregates, on the other hand, remained together. Therefore, the distribution of cells in various sized aggregates could be easily quantitated and the slides retained for future review. This method was used to evaluate the dispersing effects of trypsin, ethylenediaminetetraacetate and and syringing human on human gynecology samples obtained by routine cervical scrapes. None of the dispersion methods has, so far, produced an adequate monodispersed cell suspension without unacceptable cell loss.

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