Variability in the muscle composition of rat esophagus and neural pathway of lower esophageal sphincter relaxation

Several studies from our laboratory show that axial stretch of the lower esophageal sphincter (LES) in an oral direction causes neurally mediated LES relaxation. Under physiological conditions, axial stretch of the LES is caused by longitudinal muscle contraction (LMC) of the esophagus. Because longitudinal muscle is composed of skeletal muscle in mice, vagal-induced LMC and LES relaxation are both blocked by pancuronium. We conducted studies in rats (thought to have skeletal muscle esophagus) to determine if vagus nerve-mediated LES relaxation is also blocked by pancuronium. LMC-mediated axial stretch on the LES was monitored using piezoelectric crystals. LES and esophageal pressures were monitored with a 2.5-Fr solid-state pressure transducer catheter. Following bilateral cervical vagotomy, the vagus nerve was stimulated electrically. LES, along with the esophagus, was harvested after in vivo experiments and immunostained for smooth muscle (smooth muscle α-actin) and skeletal muscle (fast myosin heavy chain). Vagus nerve-stimulated LES relaxation and esophageal LMC were reduced in a dose-dependent fashion and completely abolished by pancuronium (96 μg/kg) in six rats ( group 1). On the other hand, in seven rats, LES relaxation and LMC were only blocked completely by a combination of pancuronium ( group 2) and hexamethonium. Immunostaining revealed that the longitudinal muscle layer was composed of predominantly skeletal muscle in the group 1 rats. On the other hand, the longitudinal muscle layer of group 2 rats contained a significant amount of smooth muscle ( P < 0.05). Our study shows tight coupling between axial stretch on the LES and relaxation of the LES, which suggests a cause and effect relationship between the two. We propose that the vagus nerve fibers that cause LMC induce LES relaxation through the stretch-sensitive activation of inhibitory motor neurons.

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Membrane currents recorded from a fragment of rabbit intestinal smooth muscle cell

AJP Cell Physiology ◽

10.1152/ajpcell.1986.251.3.c335 ◽

1986 ◽

Vol 251 (3) ◽

pp. C335-C346 ◽

Cited By ~ 63

Author(s):

Y. Ohya ◽

K. Terada ◽

K. Kitamura ◽

H. Kuriyama

Keyword(s):

Smooth Muscle ◽

Longitudinal Muscle ◽

Outward Current ◽

Ionic Currents ◽

Muscle Layer ◽

Dependent Manner ◽

Rabbit Ileum ◽

Longitudinal Muscle Layer ◽

Inward Current ◽

K Currents

Properties of ionic currents in smooth muscle membranes of the longitudinal muscle layer of the rabbit ileum were investigated using the single electrode voltage clamp method. In the present experiments, this method was applicable only to the smooth muscle ball (fragment) and not for the dispersed whole cell, because of incompleteness of the voltage clamping. A voltage step elicited a transient inward current followed by an outward current. This outward current was partly inhibited by Mn2+ or nisoldipine or by a reduction in the extracellular [Ca2+] ([Ca2+]o). Tetraethylammonium (TEA) reduced the delayed outward current in a dose-dependent manner, but 50 mM TEA did not produce a complete block of a residual current. When the pipette contained K+-free (Cs+ with TEA+) solution, the residual outward current was abolished. The inward current was elicited at -30 mV (holding potential of -60 mV) and reached the maximal value at +10 mV; the polarity was reversed at +60 mV. This inward current depended on the [Ca2+]o and was blocked by Mn2+ or nisoldipine. Ba2+ also permeated the membrane, and the inward current evoked by Ba2+ was also blocked by Mn2+ or nisoldipine. Reduction of [Na+]o in a solution containing 2.4 mM Ca2+ neither modified the current-voltage relation nor the decay of the inward current, but when [Ca2+]o was reduced to below 1 microM, Na+ permeated the membrane and was blocked by nisoldipine. In conclusion, ionic currents were recordable from the fragmented ball of the longitudinal muscle of rabbit ileum. There were at least two K+ currents as the outward current (Ca2+-dependent K+ and delayed K+ currents) and a Ca2+ current as the inward current. The property of the Ca2+ channel was similar to that observed with other preparations.

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In vitro microelectrode study of the electrical properties of smooth muscle in equine ileum

Veterinary Record ◽

10.1136/vr.149.23.707 ◽

2001 ◽

Vol 149 (23) ◽

pp. 707-711 ◽

Cited By ~ 10

Author(s):

N. P. H. Hudson ◽

I. G. Mayhew ◽

G. T. Pearson

Keyword(s):

Smooth Muscle ◽

Membrane Potential ◽

Smooth Muscle Cells ◽

Longitudinal Muscle ◽

Muscle Cells ◽

Muscle Layer ◽

Potential Oscillations ◽

Longitudinal Muscle Layer ◽

Membrane Potential Oscillations

Intracellular microelectrode recordings were made from smooth muscle cells in cross-sectional preparations of equine ileum, superfused in vitro. Membrane potential oscillations and spike potentials were recorded in all preparations, but recordings were made more readily from cells in the longitudinal muscle layer than from cells in the circular layer. The mean (se) resting membrane potential (RMP) of smooth muscle cells in the longitudinal muscle layer was -51.9 (1.2) mV, and the membrane potential oscillations in this layer had a mean amplitude of 4.8 (0.4) mV, a frequency of 9.0 (0.1) cycles per minute and a duration of 5.8 (0.2) seconds. The membrane potential oscillations were preserved in the presence of tetrodotoxin. A waxing and waning pattern of membrane potential oscillation activity was observed. Nifedipine abolished the spiking contractile activity of the smooth muscle, did not abolish the membrane potential oscillations but did alter their temporal characteristics.

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Rhythmic Electrical Activity in Stomach and Intestine of Toad

Journal of Experimental Biology ◽

10.1242/jeb.86.1.237 ◽

1980 ◽

Vol 86 (1) ◽

pp. 237-248

Author(s):

ALLEN MANGEL ◽

C. LADD PROSSER

Keyword(s):

Smooth Muscle ◽

Longitudinal Muscle ◽

Circular Muscle ◽

Sodium Concentration ◽

Muscle Layer ◽

Free Solution ◽

Longitudinal Muscle Layer ◽

Longitudinal Smooth Muscle ◽

Mammalian Intestine ◽

Periodic Changes

The intact stomach of the toad initiates rhythmic slow-spikes of 5–15 s duration and frequency of 3-5 min−1. The spontaneous electrical waves originate in the longitudinal muscle layer; isolated circular muscle is quiescent. Aboral conduction velocity is 0.12–0.9 mm s−1. Reduction of external sodium concentration from 89.5 to 15 mM produced no effect on slow spikes, although further reduction to 1.5 mM increased frequency and decreased amplitude. Slow-spikes were unaffected by ouabain or by incubation in potassium-free solution. When calcium in the medium was reduced, slow-spike amplitude and frequency decreased. Slow-spikes exhibited a change in amplitude of 16 mV per decade change in CaO2+; slow-spikes were eliminated at 10−8 M CaO2+ and by blockers of calcium conductance channels. Intact intestine of toad demonstrated slow-waves which resembled those of mammalian intestine. These were sensitive to changes in external sodium and were eliminated by 1 × 10−4M ouabain. It is suggested that rhythmic slow-spikes of longitudinal smooth muscle of amphibian stomach may result from periodic changes in Ca conductance whereas endogenous electrical waves of intestine may result from rhythmic extrusion of sodium.

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Inhibitory actions of eugenol on rat isolated ileum

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y02-117 ◽

2002 ◽

Vol 80 (9) ◽

pp. 901-906 ◽

Cited By ~ 21

Author(s):

José H Leal-Cardoso ◽

Saad Lahlou ◽

Andrelina N Coelho-de-Souza ◽

David N Criddle ◽

Glória I.B Pinto Duarte ◽

...

Keyword(s):

Smooth Muscle ◽

Methyl Ester ◽

Essential Oil ◽

Transmembrane Potential ◽

Longitudinal Muscle ◽

Direct Action ◽

Muscle Layer ◽

Free Solution ◽

Longitudinal Muscle Layer ◽

Rat Ileum

The effects of eugenol (12000 μM) on rat isolated ileum were studied. Eugenol relaxed the basal tonus (IC50 83 μM) and the ileum precontracted with 60 mM KCl (IC50 162 μM), an action unaltered by 0.5 μM tetrodotoxin, 0.2 mM NG-nitro-L-arginine methyl ester, 0.5 mM hexamethonium, and 1 μM indomethacin. Eugenol did not alter the resting transmembrane potential (Em) of the longitudinal muscle layer under normal conditions (5.0 mM K+) or in depolarised tissues. Eugenol reversibly inhibited contractions induced by submaximal concentrations of acetylcholine (ACh) and K+ (40 mM) with IC50 values of approximately 228 and 237 μM, respectively. Eugenol blocked the component of ACh-induced contraction obtained in Ca2+-free solution (0.2 mM EGTA) or in the presence of nifedipine (1 μM). Our results suggest that eugenol induces relaxation of rat ileum by a direct action on smooth muscle via a mechanism largely independent of alterations of Em and extracellular Ca2+ influx.Key words: essential oil, eugenol, ileum, smooth muscle, antispasmodic.

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Localization and steroid regulation of prostaglandin E2 receptor protein expression in ovine cervix

Reproduction ◽

10.1530/rep.1.00767 ◽

2006 ◽

Vol 131 (4) ◽

pp. 743-750 ◽

Cited By ~ 20

Author(s):

Thomas Schmitz ◽

Brian A Levine ◽

Peter W Nathanielsz

Keyword(s):

Smooth Muscle ◽

Protein Expression ◽

Longitudinal Muscle ◽

Muscle Layer ◽

Cervical Dilatation ◽

Cervical Ripening ◽

Receptor Protein ◽

Longitudinal Muscle Layer ◽

Ripening Process ◽

Ep Receptor

Although prostaglandin E2(PGE2) has been identified as a central mediator of the cervical ripening process, the mechanisms responsible for PGE2ripening are still poorly understood, partly because of the lack of information concerning the precise cellular localization and regulation of PGE2(EP) receptors in the cervix. To provide new insights into the mechanisms of cervical ripening, we used indirect immunofluorescence to localize cervical EP receptor protein expression in ovariectomized ewes and examined the effect of administration of progesterone or estradiol. EP receptors were widely distributed in cervical blood vessels, epithelium of the cervical canal, circular and longitudinal muscles, and stroma. Estradiol replacement decreased EP1and EP3receptor protein in blood vessel media (by 23 and 31% respectively,P< 0.05) and decreased EP1receptor protein expression in the longitudinal muscle layer (by 27%,P< 0.05). Stromal EP1and EP3receptor protein expression was also reduced by estradiol (by 29 and 20% respectively,P< 0.05). Progesterone replacement had no significant effect on EP receptor protein expression. The arterial changes would favor PGE2-induced vasodilatation, subsequent edema and leukocyte infiltration during the cervical ripening process whereas the muscular alterations would facilitate smooth muscle relaxation and cervical dilatation. Furthermore, estradiol provoked perinuclear localization of EP3receptor protein in the longitudinal muscle layer. This latter result suggests that cellular EP receptor localization is regulated by estradiol and that PGE2may also control smooth muscle contraction and regulate ovine cervical dilatation in an intracrine manner via EP3receptors.

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Pro- and macroglycogenolysis: relationship with exercise intensity and duration

Journal of Applied Physiology ◽

10.1152/jappl.2001.90.3.873 ◽

2001 ◽

Vol 90 (3) ◽

pp. 873-879 ◽

Cited By ~ 33

Author(s):

T. E. Graham ◽

K. B. Adamo ◽

J. Shearer ◽

I. Marchand ◽

B. Saltin

Keyword(s):

Skeletal Muscle ◽

Metabolic Regulation ◽

Human Skeletal Muscle ◽

Exercise Period ◽

Group 3 ◽

Group 2 ◽

Male Subjects ◽

Muscle Biopsies ◽

Over Time ◽

Group 1

We examined the net catabolism of two pools of glycogen, proglycogen (PG) and macroglycogen (MG), in human skeletal muscle during exercise. Male subjects ( n = 21) were assigned to one of three groups. Group 1 exercised 45 min at 70% maximal O2 uptake (V˙o 2 max) and had muscle biopsies at rest, 15 min, and 45 min. Group 2 exercised at 85%V˙o 2 max to exhaustion (45.4 ± 3.4 min) and had biopsies at rest, 10 min, and exhaustion. Group 3 performed three 3-min bouts of exercise at 100%V˙o 2 max separated by 6 min of rest. Biopsies were taken at rest and after each bout. Group 1 had small MG and PG net glycogenolysis rates (ranging from 3.8 ± 1.0 to 2.4 ± 0.6 mmol glucosyl units · kg−1 · min−1) that did not change over time. In group 2, the MG glycogenolysis rate remained low and unchanged over time, whereas the PG rate was initially elevated (11.3 ± 2.3 mmol glucosyl units · kg−1 · min−1) and declined ( P ≤ 0.05) with time. During the first 10 min, PG concentration ([PG]) declined ( P ≤ 0.05), whereas MG concentration ([MG]) did not. Similarly, in group 3, in both the first and the second bouts of exercise [PG] declined ( P ≤ 0.05) and [MG] did not, although by the end of the second exercise period the [MG] was lower ( P ≤ 0.05) than the rest level. The net catabolic rates for PG in the first two exercises were 22.6 ± 6.8 and 21.8 ± 8.2 mmol glucosyl units · kg−1 · min−1, whereas the corresponding values for MG were 17.6 ± 6.0 and 10.8 ± 5.6. The MG pool appeared to be more resistant to mobilization, and, when activated, its catabolism was inhibited more rapidly than that of PG. This suggests that the metabolic regulation of the two pools must be different.

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First reported case of per anal endoscopic myectomy (PAEM): A novel endoscopic technique for resection of lesions with severe fibrosis in the rectum

Endoscopy International Open ◽

10.1055/s-0042-122965 ◽

2017 ◽

Vol 05 (03) ◽

pp. E146-E150 ◽

Cited By ~ 1

Author(s):

David Rahni ◽

Takashi Toyonaga ◽

Yoshiko Ohara ◽

Francesco Lombardo ◽

Shinichi Baba ◽

...

Keyword(s):

Longitudinal Muscle ◽

Circular Muscle ◽

Muscle Layer ◽

Rectal Tumor ◽

Resection Margins ◽

Submucosal Layer ◽

Longitudinal Muscle Layer ◽

Circular Muscle Layer ◽

Tunneling Method ◽

Severe Fibrosis

Background and study aims A 54-year-old man was diagnosed with a rectal tumor extending through the submucosal layer. The patient refused surgery and therefore endoscopic submucosal dissection (ESD) was pursued. The lesion exhibited the muscle retraction sign. After dissecting circumferentially around the fibrotic area by double tunneling method, a myotomy was performed through the internal circular muscle layer, creating a plane of dissection between the internal circular muscle layer and the external longitudinal muscle layer, and a myectomy was completed.The pathologic specimen verified T1b grade 1 sprouting adenocarcinoma with 4350 µm invasion into the submucosa with negative resection margins.

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Sodium nitrite, a potent relaxant of rat stomach fundus: in vitro evidence

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y98-107 ◽

1998 ◽

Vol 76 (10-11) ◽

pp. 989-999 ◽

Cited By ~ 2

Author(s):

Michal Ceregrzyn ◽

Tsuyoshi Ozaki ◽

Atsukazu Kuwahara ◽

Maria Wiechetek

Keyword(s):

Methylene Blue ◽

Potassium Channels ◽

Guanylate Cyclase ◽

Sodium Nitrite ◽

Longitudinal Muscle ◽

Circular Muscle ◽

Muscle Layer ◽

Rat Stomach ◽

Longitudinal Muscle Layer ◽

Stomach Fundus

The effects of sodium nitrite (0.1, 1, 10 mM) on mechanical activity of isolated rat stomach fundus muscle and the influence of guanylate cyclase activity inhibitor (methylene blue) and channel inhibitors (tetrodotoxin, charybdotoxin, apamin) were studied. Nitrite evoked dose-dependent relaxation in the longitudinal and circular muscle layers. The lowest effective concentration of sodium nitrite was 0.1 mM, which is comparable with the NOAEL (no observed adverse effect level). Tetrodotoxin (1 µM) markedly inhibited electrically induced contraction and rebound relaxation, but did not influence the nitrite-induced relaxation. Charybdotoxin (100 nM) decreased the relaxation evoked by 10 mM nitrite to 52.3 and 65.7% of control reaction in the circular and longitudinal muscle layer, respectively. Apamin (100 nM) did not influence the nitrite-induced relaxation. Methylene blue (10 µM) decreased relaxation induced by nitrite in the longitudinal and circular muscle layer, respectively, to 66.7 and 54.3% of the response to 1 mM nitrite alone. Relaxation induced by nitrite was decreased in the presence of L-cysteine (5 mM), and in the circular and longitudinal muscle layer reached 29.6 and 23.1%, respectively, of the response to 1 mM nitrite alone. We conclude that the relaxing effect of nitrite on gastric fundus results from its direct action on smooth muscle cells and probably the enteric nervous system is not involved in this action. The nitrite-elicited relaxation depends on activation of guanylate cyclase and high conductance Ca2+-activated potassium channels; however, activation of potassium channels might be a part of or might act in parallel with the mechanism involving the cyclic GMP system. Effects of nitrite observed in the presence of L-cysteine suggest that nitrosothiols are not responsible for nitrite-evoked activation of guanylate cyclase.Key words: nitrite, gastric motility, tetrodotoxin, methylene blue, charybdotoxin, L-cysteine.

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In Vivo Analysis of Trypanosoma cruzi Persistence Foci at Single-Cell Resolution

mBio ◽

10.1128/mbio.01242-20 ◽

2020 ◽

Vol 11 (4) ◽

Cited By ~ 2

Author(s):

Alexander I. Ward ◽

Michael D. Lewis ◽

Archie A. Khan ◽

Conor J. McCann ◽

Amanda F. Francisco ◽

...

Keyword(s):

Skeletal Muscle ◽

Immune Response ◽

Smooth Muscle ◽

Trypanosoma Cruzi ◽

Parasite Burden ◽

Circular Muscle ◽

Muscle Layer ◽

Chronic Infections ◽

Content Type ◽

Chronic Stage

ABSTRACT Infections with Trypanosoma cruzi are usually lifelong despite generating a strong adaptive immune response. Identifying the sites of parasite persistence is therefore crucial to understanding how T. cruzi avoids immune-mediated destruction. However, this is a major technical challenge, because the parasite burden during chronic infections is extremely low. Here, we describe an integrated approach involving comprehensive tissue processing, ex vivo imaging, and confocal microscopy, which allowed us to visualize infected host cells in murine tissue with exquisite sensitivity. Using bioluminescence-guided tissue sampling, with a detection level of <20 parasites, we showed that in the colon, smooth muscle myocytes in the circular muscle layer are the most common infected host cell type. Typically, during chronic infections, the entire colon of a mouse contains only a few hundred parasites, often concentrated in a small number of cells each containing >200 parasites, which we term mega-nests. In contrast, during the acute stage, when the total parasite burden is considerably higher and many cells are infected, nests containing >50 parasites are rarely found. In C3H/HeN mice, but not BALB/c mice, we identified skeletal muscle as a major site of persistence during the chronic stage, with most parasites being found in large mega-nests within the muscle fibers. Finally, we report that parasites are also frequently found in the skin during chronic murine infections, often in multiple infection foci. In addition to being a site of parasite persistence, this anatomical reservoir could play an important role in insect-mediated transmission and have implications for drug development. IMPORTANCE Trypanosoma cruzi causes Chagas disease, the most important parasitic infection in Latin America. Major pathologies include severe damage to the heart and digestive tract, although symptoms do not usually appear until decades after infection. Research has been hampered by the complex nature of the disease and technical difficulties in locating the extremely low number of parasites. Here, using highly sensitive imaging technology, we reveal the sites of parasite persistence during chronic-stage infections of experimental mice at single-cell resolution. We show that parasites are frequently located in smooth muscle cells in the circular muscle layer of the colon and that skeletal muscle cells and the skin can also be important reservoirs. This information provides a framework for investigating how the parasite is able to survive as a lifelong infection, despite a vigorous immune response. It also informs drug development strategies by identifying tissue sites that must be accessed to achieve a curative outcome.

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