Proteins of interstitial cells of Cajal and intestinal smooth muscle, colocalized with caveolin-1.
The murine jejunum and lower esophageal sphincter (LES) were examined to determine the locations of various signaling molecules and their colocalization with caveolin-1 and one another. Caveolin-1 was present in punctate sites of the plasma membranes (PM) of all smooth muscles and diffusely in all classes of interstitial cells of Cajal (ICC; identified by c-kit immunoreactivity), ICC-myenteric plexus (MP), ICC-deep muscular plexus (DMP), ICC-serosa (ICC-S), and ICC-intramuscularis (IM). In general, all ICC also contained the L-type Ca(2+) (L-Ca(2+)) channel, the PM Ca(2+) pump, and the Na(+)/Ca(2+) exchanger-1 localized with caveolin-1. ICC in various sites also contained Ca(2+)-sequestering molecules such as calreticulin and calsequestrin. Calreticulin was present also in smooth muscle, frequently in the cytosol, whereas calsequestrin was present in skeletal muscle of the esophagus. Gap junction proteins connexin-43 and -40 were present in circular muscle of jejunum but not in longitudinal muscle or in LES. In some cases, these proteins were associated with ICC-DMP. The large-conductance Ca(2+)-activated K(+) channel was present in smooth muscle and skeletal muscle of esophagus and some ICC but was not colocalized with caveolin-1. These findings suggest that all ICC have several Ca(2+)-handling and -sequestering molecules, although the functions of only the L-Ca(2+) channel are currently known. They also suggest that gap junction proteins are located at sites where ultrastructural gap junctions are know to exist in circular muscle of intestine but not in other smooth muscles. These findings also point to the need to evaluate the function of Ca(2+) sequestration in ICC. (+info)
Crural diaphragm inhibition during esophageal distension correlates with contraction of the esophageal longitudinal muscle in cats.
Esophageal distension causes simultaneous relaxation of the lower esophageal sphincter (LES) and crural diaphragm. The mechanism of crural diaphragm relaxation during esophageal distension is not well understood. We studied the motion of crural and costal diaphragm along with the motion of the distal esophagus during esophageal distension-induced relaxation of the LES and crural diaphragm. Wire electrodes were surgically implanted into the crural and costal diaphragm in five cats. In two additional cats, radiopaque markers were also sutured into the outer wall of the distal esophagus to monitor esophageal shortening. Under light anesthesia, animals were placed on an X-ray fluoroscope to monitor the motion of the diaphragm and the distal esophagus by tracking the radiopaque markers. Crural and costal diaphragm electromyograms (EMGs) were recorded along with the esophageal, LES, and gastric pressures. A 2-cm balloon placed 5 cm above the LES was used for esophageal distension. Effects of baclofen, a GABA(B) agonist, were also studied. Esophageal distension induced LES relaxation and selective inhibition of the crural diaphragm EMG. The crural diaphragm moved in a craniocaudal direction with expiration and inspiration, respectively. Esophageal distension-induced inhibition of the crural EMG was associated with sustained cranial motion of the crural diaphragm and esophagus. Baclofen blocked distension-induced LES relaxation and crural diaphragm EMG inhibition along with the cranial motion of the crural diaphragm and the distal esophagus. There is a close temporal correlation between esophageal distension-mediated LES relaxation and crural diaphragm inhibition with the sustained cranial motion of the crural diaphragm. Stretch caused by the longitudinal muscle contraction of the esophagus during distension of the esophagus may be important in causing LES relaxation and crural diaphragm inhibition. (+info)
Signal-transduction pathways that regulate smooth muscle function I. Signal transduction in phasic (esophageal) and tonic (gastroesophageal sphincter) smooth muscles.
Contraction of esophageal (Eso) and lower esophageal sphincter (LES) circular muscle depends on distinct signal-transduction pathways. ACh-induced contraction of Eso muscle is linked to phosphatidylcholine metabolism, production of diacylglycerol and arachidonic acid (AA), and activation of the Ca(2+)-insensitive PKCepsilon. Although PKCepsilon does not require Ca(2+) for activation, either influx of extracellular Ca(2+) or release of Ca(2+) from stores is needed to activate the phospholipases responsible for hydrolysis of membrane phospholipids and production of second messengers, which activate PKCepsilon. In contrast, the LES uses two distinct intracellular pathways: 1) a PKC-dependent pathway activated by low doses of agonists or during maintenance of spontaneous tone, and 2) a Ca(2+)-calmodulin-myosin light chain kinase (MLCK)-dependent pathway activated in response to maximally effective doses of agonists during the initial phase of contraction. The Ca(2+) levels, released by agonist-induced activity of phospholipase C, determine which contractile pathway is activated in the LES. The Ca(2+)-calmodulin-MLCK-dependent contractile pathway has been well characterized in a variety of smooth muscles. The steps linking activation of PKC to myosin light chain (MLC20) phosphorylation and contraction, however, have not been clearly defined for LES, Eso, or other smooth muscles. In addition, in LES circular muscle, a low-molecular weight pancreatic-like phospholipase A2 (group I PLA2) causes production of AA, which is metabolized to prostaglandins and thromboxanes. These AA metabolites act on receptors linked to heterotrimeric G proteins to induce activation of phospholipases and production of second messengers to maintain contraction of LES circular muscle. We have examined the signal-transduction pathways activated by PGF(2alpha) and by thromboxane analogs during the initial contractile phase and found that these pathways are the same as those activated by other agonists. In response to low doses of agonists or during maintenance of tone, presumably due to low levels of calcium release, a PKC-dependent pathway is activated, whereas at high doses of PGF(2alpha) and thromboxane analogs, in the initial phase of contraction, calmodulin is activated, PKC activity is reduced, and contraction is mediated, in part, through a Ca(2+)-calmodulin-MLCK-dependent pathway. The PKC-dependent signaling pathways activated by PGF(2alpha) and by thromboxanes during sustained LES contraction, however, remain to be examined, but preliminary data indicate that a distinct PKC-dependent pathway may be activated during maintenance of tonic contraction, which is different from the one activated during the initial contractile response. The initial contractile response to low levels of agonists depends on activation of G(q). Sustained contraction in response to PGF(2alpha) may involve activation of the monomeric G protein RhoA, because the contraction is inhibited by the RhoA-kinase antagonist Y27632. This shift in signal-transduction pathways between initial and sustained contraction has been recently reported in intestinal smooth muscle. (+info)
Manometric evaluation of achalasia in the elderly.
BACKGROUND: The effect of ageing on oesophageal motility in patients with achalasia is not well described. Oesophageal contraction amplitude is decreased in otherwise healthy elderly subjects. AIM: To evaluate whether ageing influences the motor function of the oesophagus in achalasia. METHODS: Initial manometry studies of patients with achalasia were reviewed and findings (lower oesophageal sphincter basal and residual pressures and oesophageal body contraction amplitudes) were compared between two groups of patients, those 65 years of age or older (49 patients) and those younger than 65 years (68 patients). The older group was further divided into those > or =70 years and those <70 years. RESULTS: Patients 65 years and older had significantly higher lower oesophageal sphincter basal pressures compared with younger patients (65.6 +/- 4.9 vs. 52.3 +/- 2.7, P = 0.02). At an age cut-off of 70 years, older patients had significantly higher basal (70.7 +/- 1.6 vs. 53.0 +/- 2.4, P = 0.02) and residual (19.7 +/- 1.6 vs. 15.9 +/- 0.7, P = 0.03) lower oesophageal sphincter pressures compared with younger patients. Amplitude of oesophageal contractions was not different between the groups. Across all age groups, there was no linear correlation between age and basal or residual lower oesophageal sphincter pressures (r = 0.28 and 0.12, respectively). CONCLUSIONS: Older patients with achalasia have higher lower oesophageal sphincter pressures, however there is no linear correlation between age and lower oesophageal sphincter pressures. Unlike healthy subjects, advanced age is not associated with a decrease in oesophageal contraction amplitude in patients with achalasia. (+info)
Adenocarcinoma of oesophagus: what exactly is the size of the problem and who is at risk?
The incidence of oesophageal adenocarcinoma is increasing and the prognosis is poor. There is a strong predominance of white males, and heredity plays a minor role. The established risk factors are Barrett's oesophagus, gastro-oesophageal reflux, and obesity. Infection with Helicobacter pylori and use of non-steroidal anti-inflammatory drugs might reduce the risk. Medications that relax the lower oesophageal sphincter might contribute to increasing the risk. Among dietary factors, low intake of fruit, vegetables, and cereal fibres seem to increase the risk of oesophageal adenocarcinoma. The role of tobacco smoking is probably limited and alcohol consumption is not a risk factor. It is uncertain which factors cause the increasing incidence. Increasing prevalences of reflux and obesity, and decreasing prevalence of H pylori infection may contribute to this development; however, the sex distributions of these factors do not match the incidence trends well. Endoscopic surveillance for oesophageal adenocarcinoma among persons with reflux and obesity is discussed, but presently there is no evidence that strongly supports such a strategy. (+info)
Metabolic changes in the lower esophageal sphincter influencing the result of anti-reflux surgical interventions in chronic gastroesophageal reflux disease.
AIM: With the availability of a minimally invasive approach, anti-reflux surgery has recently experienced a renaissance as a cost-effective alternative to life-long medical treatment in patients with gastroesophageal reflux disease (GERD). We are not aware of the fact whether reflux episodes causing complaints for a long time i.e., at least for one year are associated with metabolic changes in the lower esophageal sphincter, and if so, whether these may influence functional results achieved after anti-reflux surgery. METHODS: Between 1 January 2001 and 31 December 2002 we performed anti-reflux surgery on 79 patients. Muscle samples were taken from the lower esophageal sphincter (LES) in 33 patients during anti-reflux surgery. Inclusion criteria were: LES resting pressure below 10 mmHg and a marked, pH proven acid exposure to the esophagus of at least one year's duration, causing subjective complaints and requiring continuous proton pump inhibitor treatment. Control samples were obtained from muscle tissue in the gastroesophageal junction that had been removed from 17 patients undergoing gastric or esophageal resection. Metabolic and lysosomal enzyme activities and special protein concentrations 16 parameters in total were evaluated in tissue taken from control specimens and tissue taken from patients with GERD. The biochemical parameters of these intra-operative biopsies were used to correlate the results of anti-reflux operations (Visick I and II-III). RESULTS: In the reflux-type muscle, we found a significant increase of the energy-enzyme activities e.g., creatine kinase, lactate dehydrogenase, beta-hydroxybutyrate dehydrogenase, and aspartate aminotransaminase-. The concentration of the structural protein S-100 and the myofibrillar protein troponin I were also significantly increased. Among lysosomal enzymes, we found that the activities of cathepsin B, tripeptidyl-peptidase I, dipeptidyl-peptidase II, beta-hexosaminidase B, beta-mannosidase and beta-galactosidase were significantly decreased as compared to the control LES muscles. By analyzing the activity values of the 9 patients in Visick groups II and III at two months post-surgery, we found a significant increase in the activity of the so-called energy-enzyme values and in the concentration of structural and myofibrillar proteins as compared to the rest of the reflux patients. CONCLUSION: Our results call attention to the metabolic changes that occurred in the LES muscles of reflux patients. The developing hypertrophy-like changes of LES muscles may be a reason for complaints after anti-reflux surgery, which consisted mainly of reports of persisting dysphagia. (+info)
Inhibition of transient lower esophageal sphincter relaxations by electrical acupoint stimulation.
Acupuncture has been shown to modulate visceral sensation and function. Traditionally, stimulation at the Neiguan (pericardial meridian) has been used to treat upper gastrointestinal symptoms. Some of the effects of acupuncture may be mediated through release of endogenous opioids and are reversed by naloxone. Gastric distension is the major trigger for transient lower esophageal sphincter (LES) relaxations (TLESRs). The aim of this study was to investigate the effect of electric stimulation at the Neiguan and naloxone on the TLESRs. In 14 healthy volunteers, electrical acupoint stimulation was applied at the Neiguan and a sham point on the hip in randomized order on the same day. In 12 healthy volunteers, the effects of naloxone (80 microg/kg iv bolus injection) and saline on electrical acupoint stimulation were compared on separate days at least 1 wk apart. Esophageal motility was measured during distension of the proximal stomach with 500 ml of air using a barostat balloon. Electric acupoint stimulation at the Neiguan decreased the rate of TLESRs by approximately 40% from a median of 6/h to 3.5/h (P < 0.02). Acupoint stimulation had no effect on basal LES pressure, the residual LES pressure during TLESRs, the duration of TLESRs, or gastrointestinal symptoms of fullness, bloating, discomfort, or nausea. The effect of acupoint stimulation was not inhibited by naloxone. Electric acupoint stimulation at the Neiguan significantly inhibits the frequency of TLESRs in response to gastric distention in healthy subjects. This effect does not appear to be mediated through mu-opioid receptors. (+info)
Body mass index and chronic unexplained gastrointestinal symptoms: an adult endoscopic population based study.
BACKGROUND: We aimed to determine whether obese subjects experience more gastro-oesophageal reflux (GORS) symptoms than normal subjects, and further to determine if this association was explained by oesophagitis or medications that lower oesophageal sphincter pressure. METHODS: In a representative Swedish population, a random sample (n = 1001, mean age 53.5 years, 51% women) had upper endoscopy. GORS was defined as any bothersome heartburn or acid regurgitation. RESULTS: The prevalence of obesity (body mass index > or =30) was 16%; oesophagitis was significantly more prevalent in obesity (26.5%) than in normal subjects (9.3%). There were associations between obesity and GORS (odds ratio (OR) 2.05 (95% confidence interval (CI) 1.39, 3.01)), epigastric pain (OR 1.63 (95% CI 1.05, 2.55)), irritable bowel symptoms (OR 1.58 (95% CI 1.05, 2.38)), any abdominal pain (OR 1.59 (95% CI 1.08, 2.35)), vomiting (OR 3.11 (95% CI 1.18, 8.20)), retching (OR 1.74 (95% CI 1.1.3, 2.67)), diarrhoea (OR 2.2 (95% CI 1.38, 3.46)), any stool urgency (OR 1.60 (95% CI 1.04, 2.47)), nocturnal urgency (OR 2.57 (95% CI 1.33, 4.98)), and incomplete rectal evacuation (OR 1.64 (95% CI 1.09, 2.47)), adjusting for age, sex, and education. When subjects with oesophagitis and peptic ulcer were excluded, only diarrhoea, incomplete evacuation, and vomiting were significantly associated with obesity. The association between GORS and obesity remained significant adjusting for medication use (OR 1.9 (95% CI 1.3, 3.0)). CONCLUSIONS: GORS is associated with obesity; this appears to be explained by increased upper endoscopy findings in obesity. (+info)