Clinical Practice Guidelines for the Assessment of Uninvestigated Esophageal Dysphagia.

BACKGROUND AND AIMS: Our aim is to review the literature and provide guidelines for the assessment of uninvestigated dysphagia. METHODS: A systematic literature search identified studies on dysphagia. The quality of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development, and Evaluation (GRADE) approach. Statements were discussed and revised via small group meetings, teleconferences, and a web-based platform until consensus was reached by the full group. RESULTS: The consensus includes 13 statements focused on the role of strategies for the assessment of esophageal dysphagia. In patients presenting with dysphagia, oropharyngeal dysphagia should be identified promptly because of the risk of aspiration. For patients with esophageal dysphagia, history can be used to help differentiate structural from motility disorders and to elicit alarm features. An empiric trial of proton pump inhibitor therapy should be limited to four weeks in patients with esophageal dysphagia who have reflux symptoms and no additional alarm features. For patients with persistent dysphagia, endoscopy, including esophageal biopsy, was recommended over barium esophagram for the assessment of structural and mucosal esophageal disease. Barium esophagram may be useful when the availability of endoscopy is limited. Esophageal manometry was recommended for diagnosis of esophageal motility disorders, and high-resolution was recommended over conventional manometry. CONCLUSIONS: Once oropharyngeal dysphagia is ruled out, patients with symptoms of esophageal dysphagia should be assessed by history and physical examination, followed by endoscopy to identify structural and inflammatory lesions. If these are ruled out, then manometry is recommended for the diagnosis of esophageal dysmotility.

Achalasia-Specific Quality of Life After Pneumatic Dilation or Laparoscopic Heller Myotomy With Partial Fundoplication: A Multicenter, Randomized Clinical Trial.

OBJECTIVES: Achalasia is a chronic, progressive, and incurable esophageal motility disease. There is clinical uncertainty about which treatment should be recommended as first-line therapy. Our objective was to evaluate the effectiveness of pneumatic dilation compared with laparoscopic Heller myotomy with partial fundoplication in improving achalasia-specific quality of life. METHODS: This was a prospective, multicenter, randomized trial at five academic hospitals in Canada. Fifty previously untreated adults with a clinical diagnosis of primary achalasia, confirmed by manometric testing, were enrolled between November 2005 and March 2010, and followed for 5 years after treatment. Randomization was stratified by site, in random blocks of size four and with balanced allocation. Patients were treated with pneumatic dilation or laparoscopic Heller myotomy with partial fundoplication. The primary outcome was the difference between the treatments in the mean improvement of the achalasia severity questionnaire (ASQ) score at 1 year from baseline. Prespecified secondary outcomes included general and gastrointestinal quality of life, symptoms, esophageal physiology measures (lower esophageal sphincter relaxation and pressure, esophageal emptying, abnormal esophageal acid exposure), complications, and incidence of retreatment. Functional and imaging studies were performed blinded and all outcome assessors were blinded. RESULTS: There were no significant differences between treatments in the improvement of ASQ score at 1 year from baseline (27.5 points in the Heller myotomy arm vs. 20.2 points in the pneumatic dilation arm; difference 7.3 points, 95% confidence interval -4.7 to 19.3; P=0.23). There were no differences between treatments in improvement of symptoms, general and gastrointestinal quality of life, or measures of esophageal physiology. Improvements in ASQ score diminished over time for both interventions. At 5 years, there were no differences between treatments in improvement of ASQ score, symptoms, and general or gastrointestinal quality of life. There were no serious adverse events. No patient who received Heller myotomy required retreatment, whereas five patients treated initially with pneumatic dilation required retreatment. CONCLUSIONS: Treatment with pneumatic dilation or laparoscopic Heller myotomy similarly improves achalasia-specific disease severity at 1 year. Either of the therapeutic approaches can be used as first-line therapy for previously untreated adults with achalasia.

Identification of dysphagia using the Toronto Bedside Swallowing Screening Test (TOR-BSST©): are 10 teaspoons of water necessary?

Dysphagia screening often includes administration of water. This study assessed the accuracy in identifying dysphagia with each additional teaspoon of water. The original research of the TOR-BSST(©) permitted this assessment. Trained nurses from acute and rehabilitation facilities prospectively administered the TOR-BSST(©) to 311 eligible stroke inpatients. A sensitivity analysis was conducted for the water item using 10 teaspoons plus a sip as the standard. The proportion of positive screenings was 59.2% in acute and 38.5% in rehabilitation. Of all four items that form the TOR-BSST(©), the water swallow item contributed to the identification of dysphagia in 42.7% in acute and 29.0% in rehabilitation patients. Across all patients, dysphagia accuracy was that five teaspoons resulted in a sensitivity of 79% (95% confidence interval [CI] = 70-86), eight a sensitivity of 92% (95% CI = 85-96) and 10 a sensitivity of 96% (95% CI = 90-99). Although a primary contributor, the water swallow item alone does not identify all patients with dysphagia. For a water swallow to accurately identify dysphagia, it is critical to administer 10 teaspoons. The TOR-BSST(©) water swallow item contributes largely to the total TOR-BSST(©)'s screening score and in making the test highly accurate and reliable.

White matter abnormalities in irritable bowel syndrome and relation to individual factors.

Patients with irritable bowel syndrome (IBS) have abnormal cortical responses to rectal distension and grey matter thinning in brain areas associated with nociception. These abnormalities may be driven by white matter changes and individual factors. Therefore, we tested the hypothesis that WM subserving the pain system is compromised in IBS, and that disease characteristics and personality contribute to these abnormalities. MRI diffusion tensor imaging (DTI) images were obtained from 10 female IBS patients (20-54 years old, mean±SD 32.8±10.4), and 16 female healthy controls (20-44 years old, mean±SD 29.1±7.9). Mean fractional anisotropy (FA) was extracted from WM regions associated with nociception. The IBS group had higher FA in the fornix and external capsule adjacent to the right posterior insula. IBS chronic pain severity correlated with FA of the bilateral anterior insula and lateral thalamus and left anterior insula FA correlated with pain unpleasantness. IBS duration correlated with FA in the external capsule adjacent to the left posterior insula. Neuroticism correlated with FA in the left medial thalamus in IBS patients only. Pain catastrophizing correlated negatively to cingulum FA in IBS, whereas controls showed correlation between pain catastrophizing and FA of the external capsule adjacent to the left anterior and posterior insula. Thus, fornix and insular white matter is related to IBS symptoms. These data suggest that dysregulation of brain-gut communication via the neuroendocrine pathway or via abnormal visceral sensory and homeostatic input has a role in the pathology of IBS chronic pain.

Interstitial cells of Cajal: pacemaker cells of the pancreatic duct?

OBJECTIVES: Ramon y Cajal discovered interstitial cells in the pancreas associated with intrinsic nerves. It was our aim to provide evidence for or against the hypothesis that the pancreatic duct harbors interstitial cells of Cajal (ICCs) that may function as pacemakers for duct motility. METHODS: We used immunohistochemistry using c-Kit as the ICC marker and protein gene product 9.5 for nerves. Electron microscopy further characterized the cells and their interrelationships. RESULTS: c-Kit-positive cells were associated with smooth muscle cells and nerve fibers of the duct wall and were rich in mitochondria, rough endoplasmic reticulum, and intermediate filaments; they possessed occasional caveolae and had a discontinuous basal lamina. They were connected by small gap junctions to each other and to smooth muscle cells. c-Kit-positive cells around large blood vessels were similar. c-Kit-positive cells within acini were similar in structure but were not associated with smooth muscle cells. CONCLUSIONS: The c-Kit-positive cells around the main duct were identified as ICCs and have the morphological criteria to likely function as pacemaker cells for the previously observed spontaneous rhythmic pancreatic duct contractions. Interstitial cells of Cajal around the large blood vessels likely affect vessel wall rhythmicity.

Nitric oxide activation of a potassium channel (BK(Ca)) in feline lower esophageal sphincter.

AIM: To assess the effect of nitric oxide (NO) on the large conductance potassium channel (BK(Ca)) in isolated circular (CM) and sling (SM) muscle cells and muscle strips from the cat lower esophageal sphincter (LES) to determine its regulation of resting tone and relaxation. METHODS: Freshly enzymatically-digested and isolated circular smooth muscle cells were prepared from each LES region. To study outward K+ currents, the perforated patch clamp technique was employed. To assess LES resting tone and relaxation, muscle strips were mounted in perfused organ baths. RESULTS: (1) Electrophysiological recordings from isolated cells: (a) CM was more depolarized than SM (-39.7 ± 0.8 mV vs -48.1 ± 1.6 mV, P < 0.001), and maximal outward current was similar (27.1 ± 1.5 pA/pF vs 25.7 ± 2.0 pA/pF, P > 0.05); (b) The NO donor sodium nitroprusside (SNP) increased outward currents only in CM (25.9 ± 1.9 to 46.7 ± 4.2 pA/pF, P < 0.001) but not SM (23.2 ± 3.1 to 27.0 ± 3.4 pA/pF, P > 0.05); (c) SNP added in the presence of the BK(Ca) antagonist iberiotoxin (IbTX) produced no increase in the outward current in CM (17.0 ± 2.8 vs 13.7 ± 2.2, P > 0.05); and (d) L-NNA caused a small insignificant inhibition of outward K+ currents in both muscles; and (2) Muscle strip studies: (a) Blockade of the nerves with tetrodotoxin (TTX), or BK(Ca) with IbTX had no significant effect on resting tone of either muscle; and (b) SNP reduced tone in both muscles, and was unaffected by the presence of TTX or IbTX. CONCLUSION: Exogenous NO activates BK(Ca) only in CM of the cat. However, as opposed to other species, exogenous NO-induced relaxation is predominantly by a non-BK(Ca) mechanism, and endogenous NO has minimal effect on resting tone.

Cognitive factors affect treatment response to medical and psychological treatments in functional bowel disorders.

OBJECTIVES: For clinical trials in functional bowel disorders (FBD), the definition of a responder, one who meets the predefined criteria for a clinical response, is needed. Factors that determine clinical response aside from treatment itself are unknown. The aim of this study was to determine what baseline and post-treatment factors affect treatment response. METHODS: Females (n=397) with FBD entering a 12-week, four-arm, randomized NIH treatment trial (desipramine (DES), CBT, pill placebo, and education) were studied at baseline and after treatment. Demographic, clinical, psychosocial, and physiological variables were considered in the analysis. A responder was defined as a patient obtaining a score>3.5 on an averaged eight-item, five-point satisfaction-with-treatment questionnaire. Baseline and post-treatment logistic regressions were performed for each treatment condition to predict the responder outcome variable. RESULTS: Similar cognitive features predisposed participants to treatment response across the treatment conditions: sense of control over the condition, positive relationship with therapist or study coordinator, confidence in treatment, improvement in maladaptive cognitions, and quality of life during treatment. Demographic and clinical variables studied were not predictive. Some treatment-specific effects predicting responder status were noted, including a reduction in stool frequency with DES treatment and lack of abuse history in the placebo group. CONCLUSIONS: For medication, psychological, and placebo treatment in FBD, satisfaction with treatment depends on cognitive factors of confidence in treatments, perceived control over illness and symptoms, and reduction in negative cognitions related to symptom experience. Addressing these issues among patients with FBD may enhance treatment response to a variety of treatments.

Altered brain structure in irritable bowel syndrome: potential contributions of pre-existing and disease-driven factors.

BACKGROUND & AIMS: Brain imaging studies have identified abnormal rectal-evoked responses and cortical thinning in patients with irritable bowel syndrome (IBS). However, it is not known whether these abnormalities are pre-existing or develop as result of long-term IBS. Therefore, we tested whether abnormal structural gray matter integrity in IBS correlates with individual disease symptoms, duration of the IBS, or the personality characteristic of pain catastrophizing. METHODS: Eleven IBS patients and 16 age-matched healthy subjects underwent structural magnetic resonance imaging. Voxel-based morphometry and cortical thickness analysis were used to identify abnormalities in subcortical and cortical regions, respectively, and their correlation to individual characteristics. RESULTS: The IBS group showed increased hypothalamic gray matter and cortical thinning in the anterior midcingulate cortex compared with controls, a strong negative correlation between dorsolateral prefrontal cortex thickness and pain catastrophizing, and a positive correlation between anterior insula thickness and pain duration. In the insula, there was cortical thinning in patients with short-term IBS, but long-term IBS pain was associated with a more normal insula thickness. CONCLUSIONS: Our findings provide new insight into IBS and chronic pain through evidence for structural changes that could fit with functional abnormalities. We report that patients with IBS have increased hypothalamic gray matter, which may be related to the association among IBS, stress, and the hypothalamic-pituitary-adrenal axis. Furthermore, we have identified some supraspinal abnormalities that may be pre-existing and contribute to vulnerability, and others that may develop over time, possibly because of chronic abnormal inputs.

Perceptions of psychological issues related to dysphagia differ in acute and chronic patients.

The objectives of this study were (1) to compare and contrast the psychological issues perceived by patients with oropharyngeal dysphagia and explore if the differences relate to recovery trajectory, and (2) to determine whether patients, caregivers, and clinicians had different perceptions of how psychological issues interacted with the lung and nutrition issues as consequences of dysphagia. Two focus groups (one each of acute and chronic patients) were conducted with a total of 8 participants. Four focus groups (3 with clinicians and 1 with caregivers) were also conducted. Through the constant comparison method of grounded theory, the differences in perceptions between acute and chronic patients with dysphagia as well as clinicians and caregivers were explored using theoretical sampling. Two themes evolved: (1) acute and chronic patients differed on how they perceived and prioritized major psychological dimensions; (2) acute patients, chronic patients, caregivers, and clinicians varied in their perceptions of how psychological issues interacted with lung and nutrition issues. The qualitative methodology was successful in identifying contrasting opinions on psychological issues of dysphagia between acute and chronic patients, which differ from the perspectives of clinicians and caregivers. It is important for treating clinicians to be aware of psychological issues, to address them according to the patients' clinical recovery, and to consider the interplay between psychological and biomedical consequences.

Irritable bowel syndrome subtypes defined by Rome II and Rome III criteria are similar.

BACKGROUND: The implications of the Rome III recommendations to change the irritable bowel syndrome (IBS) subtype criteria for stool pattern are unknown. AIM: (1) Determine the level of agreement between Rome II and Rome III subtypes and (2) compare the behaviors of Rome II and Rome III subtypes over time. METHODS: Female patients (n=148) with Rome II defined IBS were prospectively tracked over 5 consecutive 3-month periods. At baseline, bowel habit reports on questionnaires were used to subclassify patients into Rome II and Rome III subtypes. Over the subsequent 15 months, bowel habit reports on diary cards were used to subclassify patients based on previously derived surrogate criteria into Rome II and Rome III IBS subtypes. RESULTS: The level of agreement between Rome II and Rome III subtype assignments was quite high (86.5%; kappa 0.79). The behavior of Rome II and Rome III subtypes over time was also similar in terms of subtype prevalence, subtype stability, and the proportion of subjects who met criteria for alternating irritable bowel syndrome. CONCLUSIONS: Rome II and Rome III IBS subtypes are in high agreement and behave similarly over time. Therefore, studies that used Rome II subtype criteria and studies that will use Rome III criteria will define comparable populations.

Not all side effects associated with tricyclic antidepressant therapy are true side effects.

BACKGROUND & AIMS: Patients with functional gastrointestinal disorders treated with tricyclic antidepressants sometimes report nongastrointestinal symptoms; it is unclear whether these are drug side effects or reflect a behavioral tendency to report symptoms. We evaluated whether symptoms reported before treatment with a tricyclic antidepressant (desipramine) increased in number or worsened in severity after 2 weeks of treatment and assessed the baseline factors that predispose patients to report symptoms. METHODS: Female patients in a multicenter National Institutes of Health trial for functional bowel disorders completed a 15-item symptom questionnaire at baseline (before randomization), 2 weeks after they were given desipramine (n = 81) or placebo (n = 40), and at study completion (12 weeks). Patients were asked about the severity and frequency of 15 symptoms. Results were analyzed from 57 patients given desipramine who completed the questionnaires. RESULTS: Symptoms reported as side effects to have occurred more frequently and also worsened at week 2 in the group given desipramine included dizziness, dry mouth/thirstiness, lightheadedness, jittery feelings/tremors, and flushing. Symptoms that did not change in severity or showed improvement at week 2 in the group given desipramine included morning tiredness, nausea, blurred vision, headaches, appetite reduction, and trouble sleeping. Psychologic distress but not desipramine blood level correlated with symptom reporting. CONCLUSIONS: Most symptoms often attributed to side effects of desipramine were present before treatment; only a few, related to anticholinergic effects, worsened 2 weeks after treatment, suggesting that most so-called side effects were not associated specifically with desipramine use. Such symptoms might instead be associated with psychologic distress.

Using different perspectives to generate items for a new scale measuring medical outcomes of dysphagia (MOD).

OBJECTIVE: To compare and contrast clinician, patient, and caregiver perspectives to generate all important and salient items for a new scale to measure medical consequences relevant to adult patients with dysphagia. STUDY DESIGN AND SETTING: Six focus groups (three with clinicians, two with patients, and one with caregivers) were conducted with a total of 33 participants. Through the constant comparison method of Grounded Theory, analysis began with open coding and progressed with higher-order categorization to derive perceptions from differing vantage points. RESULTS: Three themes evolved: (1) clinicians, caregivers, and patients each limited the medical consequences of dysphagia to the same impairment domains: pulmonary, nutritional, and psychological; (2) these consequences were given the same priority by clinicians and caregivers, but patients ranked them differently; (3) within each impairment domain, few dimensions were derived by clinicians and many by patients. Patients were more elaborate in their descriptions of psychological consequences. CONCLUSIONS: The use of qualitative methodology to generate different perspectives derived different content. Clinicians, caregivers, and patients all agreed on the importance of three domains but differed in their prioritization and specific issues. These findings provide the necessary foundation for development of a comprehensive tool to measure medical consequences among patients with dysphagia.

The Toronto Bedside Swallowing Screening Test (TOR-BSST): development and validation of a dysphagia screening tool for patients with stroke.

BACKGROUND AND PURPOSE: Dysphagia occurs in 55% of all acute stroke patients. Early identification of dysphagia from screening can lead to earlier treatments and thereby reduce complications. We designed and validated a new bedside dysphagia screening tool-the Toronto Bedside Swallowing Screening Test (TOR-BSST) for stroke survivors in acute and rehabilitative settings. METHODS: The TOR-BSST initially contained 5 items with proven high predictive ability for dysphagia. Trained screeners administer and score the TOR-BSST in less than 10 minutes. Trained nurses from 2 acute and 2 rehabilitation facilities administered the TOR-BSST to consecutively admitted stroke inpatients. A positive screen identified patients at risk for dysphagia. Blinded repeat screenings were conducted within 24 hours. Test-retest reliability was established with the first 50 administrations at an ICC=0.92 (CI, 0.85 to 0.96). Items were eliminated if they contributed or=90% and negative predictive value >or=90%. RESULTS: 311 stroke inpatients were enrolled; 103 acute and 208 rehabilitation. Screening was positive in 59.2% acute and 38.5% rehabilitation patients. The pharyngeal sensation item did not meet inclusion criteria and was eliminated. The TOR-BSST demonstrated excellent validity with sensitivity at 91.3% (CI, 71.9 to 98.7), and negative predictive values at 93.3% in acute and 89.5% in rehabilitation settings. CONCLUSIONS: The TOR-BSST is a simple accurate tool to identify stroke patients with dysphagia regardless of severity and setting.

Patient-centered measures for achalasia.

BACKGROUND: Various instruments may be used to measure health-related quality of life in patients with achalasia. METHODS: We administered four patient-centered measures used for evaluation of achalasia severity [an achalasia severity questionnaire we developed previously, an achalasia symptom checklist, the Gastrointestinal Quality-of-Life Index (GIQLI), and the Medical Outcomes Study 36-item Short-Form survey (SF-36)] to 25 subjects enrolled in a randomized controlled trial comparing pneumatic dilatation and laparoscopic Heller myotomy. We estimated correlations between the different measures. RESULTS: Twenty-five patients (13 male, 12 female) were studied; 12 were treated by pneumatic dilatation and 13 by laparoscopic myotomy. The average age of patients was 48.5 [range 25-69, standard deviation (SD) 13.7] years. Baseline scores demonstrated a substantial burden of impairment. The mean (SD) score on the achalasia severity measure [ranges from 0 (best) to 100 (worst)] was 62.3 (13.4). The mean (SD) symptom checklist score [ranges from 0 (best) to 36 (worst)] was 23.2 (6.6). The mean (SD) GIQLI [ranges from 0 (worst) to 144 (best)] was 77.04 (19.4). The SF-36 mean (SD) for the physical component score (PCS) was 45.29 (9.21) and the mean for the mental component score (MCS) was 37.61 (14.97). The achalasia severity measure correlated highly with the GIQLI (r = -0.57, p = 0.01), and the symptom checklist (r = 0.65, p = 0.004). The achalasia severity measure correlated well with the SF-36 PCS (r = -0.42, p = 0.039), but not with the MCS (r = -0.14, p = 0.501). CONCLUSION: Subjects recruited to a randomized controlled trial of achalasia treatment demonstrated impairment in both generic quality-of-life and disease-specific measures. Scores on achalasia-specific measures correlated well with each other, but less well with measures of generic quality-of-life and mental health scales. Because of the multidimensional nature of achalasia, disease-specific measures should be combined with generic health measures for the best assessment of patient outcome.

Survival dependency of intramuscular ICC on vagal afferent nerves in the cat esophagus.

Interstitial cells of Cajal (ICC) have been proposed as stretch receptors for vagal afferent nerves in the stomach based on immunohistochemical studies. The aim of the present study was to use electron microscopy and the anterograde degeneration technique to investigate ultrastructural features and survival dependency of ICC associated with vagal afferent innervation of the cat esophagus. This is the first report on the ultrastructural characteristics of ICC in the cat esophagus. Intramuscular ICC (ICC-IM) were identified throughout the musculature, whereas ICC in the myenteric plexus were rare. ICC-IM were particularly numerous in septa aligned with smooth muscle bundles. They were in synapse-like contact with nerve varicosities and in gap junction contact with smooth muscle cells. Smooth muscle cells also made contact with ICC through peg and socket junctions. Precision damage through small-volume injection of saline in the center of the nodose ganglion from the lateral side, known to selectively affect sensory nerves, was followed within 24 h by degeneration of a subset of nerve varicosities associated with ICC-IM, as well as degeneration of the associated ICC-IM. Smooth muscle cells were not affected. Nerves of Auerbachs plexus and associated ICC were not affected. In summary, ICC-IM aligning the esophageal muscle bundles form specialized synapse-like contacts with vagal afferent nerves as well as gap junction and peg-and-socket contacts with smooth muscle cells. This is consistent with a role of ICC-IM as stretch receptors associated with vagal afferent nerves; the ICC-vagal nerve interaction appears essential for the survival of the ICC.

Characterization of health related quality of life (HRQOL) for patients with functional bowel disorder (FBD) and its response to treatment.

BACKGROUND AND AIMS: Assessing health related quality of life (HRQOL) is becoming more important in research and clinical care. However, little information is available on the performance of HRQOL questionnaires for the functional bowel disorders (FBD). The aims of this study were to (a) understand the performance of the Sickness Impact Profile (SIP) and IBS-QOL for the functional bowel disorders at baseline and after treatment, (b) determine which HRQOL subscales best improve with treatment, (c) determine clinically meaningful improvement, and (d) determine the predictors of HRQOL at baseline and in response to treatment. METHODS: Women with moderate to severe FBD were evaluated using both medical (desipramine vs placebo) and psychological (cognitive-behavioral therapy vs education) treatments. Clinical and psychosocial questionnaires along with the SIP and IBS-QOL were given at baseline and after 12-wk treatment. RESULTS: (a) Patients with FBD experience functional limitations in social interactions, home management, and recreational activities, respond emotionally to the pain, feel helpless, out of control, depressed, and irritable, and perceive restrictions in lifestyle relating to toilet accessibility, and eating; (b) HRQOL is not different among the FBD diagnoses or IBS subgroups; (c) the IBS-QOL is more responsive to treatment than the SIP; (d) meaningful clinical improvement is 2.8 points for SIP and 14 for IBS-QOL; and (e) improvement is demonstrated primarily in psychosocial rather than physical domains. In addition, we found that expectation of benefit is greater for taking a pill over a psychological intervention, and the predictive effects of abuse history and pain on outcome is mediated by psychosocial factors. CONCLUSIONS: The data support the value of the IBS-QOL over the SIP, and provide new information on the profile of impairment in FBD, and the ways in which medical and psychological treatments produce improvement in HRQOL.

Modulation of the K(v)4.3 channel by syntaxin 1A.

The SNARE protein syntaxin 1A (Syn1A) is known to inhibit delayed rectifier K(+) channels of the K(v)1 and K(v)2 families with heterogeneous effects on their gating properties. In this study, we explored whether Syn1A could directly modulate K(v)4.3, a rapidly inactivating K(v) channel with important roles in neuroendocrine cells and cardiac myocytes. Immunoprecipitation studies in HEK293 cells coexpressing Syn1A and K(v)4.3 revealed a direct interaction with increased trafficking to the plasma membrane without a change in channel synthesis. Paradoxically, Syn1A inhibited K(v)4.3 current density. In particular, Syn1A produced a left-shift in steady-state inactivation of K(v)4.3 without affecting either voltage dependence of activation or gating kinetics, a pattern distinct from other K(v) channels. Combined with our previous reports, our results further verify the notion that the mechanisms involved in Syn1A-K(v) interactions vary significantly between K(v) channels, thus providing a wide scope for Syn1A modulation of exocytosis and membrane excitability.

Unique distribution of interstitial cells of Cajal in the feline pylorus.

The feline gastrointestinal (GI) tract is an important model for GI physiology but no immunohistochemical assessment of interstitial cells of Cajal (ICC) has been performed because of the lack of suitable antibodies. The aim of the present study was to investigate the various types of ICC and associated nerve structures in the pyloric sphincter region, by using immunohistochemistry and electron microscopy to complement functional studies. In the sphincter, ICC associated with Auerbach's plexus (ICC-AP) were markedly decreased within a region of 6-8 mm in length, thereby forming an interruption in this network of ICC-AP, which is otherwise continuous from corpus to distal ileum. In contrast, intramuscular ICC (ICC-IM) were abundant within the pylorus, especially at the inner edge of the circular muscle adjacent to the submucosa. Similar distribution patterns of nerves positive for vesicular acetylcholine transporter (VAChT), nitric oxide synthase (NOS) and substance P (SP) were encountered. Quantification showed a significantly higher number of ICC-IM and the various types of nerves in the pylorus compared with the circular muscle layers in the adjacent antrum and duodenum. Electron-microscopic studies demonstrated that ICC-IM were closely associated with enteric nerves through synapse-like junctions and with smooth muscle cells through gap junctions. Thus, for the first time, immunohistochemical studies have been successful in documenting the unique distribution of ICC in the feline pylorus. A lack of ICC-AP guarantees the distinct properties of antral and duodenal pacemaker activities. ICC-IM are associated with enteric nerves, which are concentrated in the inner portion of the circular muscle layer, being part of a unique innervation pattern of the sphincter.

Distinct modulation of Kv1.2 channel gating by wild type, but not open form, of syntaxin-1A.

SNARE proteins, syntaxin-1A (Syn-1A) and SNAP-25, inhibit delayed rectifier K(+) channels, K(v)1.1 and K(v)2.1, in secretory cells. We showed previously that the mutant open conformation of Syn-1A (Syn-1A L165A/E166A) inhibits K(v)2.1 channels more optimally than wild-type Syn-1A. In this report we examined whether Syn-1A in its wild-type and open conformations would exhibit similar differential actions on the gating of K(v)1.2, a major delayed rectifier K(+) channel in nonsecretory smooth muscle cells and some neuronal tissues. In coexpression and acute dialysis studies, wild-type Syn-1A inhibited K(v)1.2 current magnitude. Of interest, wild-type Syn-1A caused a right shift in the activation curves of K(v)1.2 without affecting its steady-state availability, an inhibition profile opposite to its effects on K(v)2.1 (steady-state availability reduction without changes in voltage dependence of activation). Also, although both wild-type and open-form Syn-1A bound equally well to K(v)1.2 in an expression system, open-form Syn-1A failed to reduce K(v)1.2 current magnitude or affect its gating. This is in contrast to the reported more potent effect of open-form Syn-1A on K(v)2.1 channels in secretory cells. This finding together with the absence of Munc18 and/or 13-1 in smooth muscles suggested that a change to an open conformation Syn-1A, normally facilitated by Munc18/13-1, is not required in nonsecretory smooth muscle cells. Taken together with previous reports, our results demonstrate the multiplicity of gating inhibition of different K(v) channels by Syn-1A and is compatible with versatility of Syn-1A modulation of repolarization in various secretory and nonsecretory (smooth muscle) cell types.

Two populations of pancreatic islet alpha-cells displaying distinct Ca2+ channel properties.

In low or absence of glucose, alpha-cells generate rhythmic action potentials and secrete glucagon. alpha-Cell T-type Ca(2+) channels are believed to be pacemaker channels, which are expected to open near the resting membrane potential (around -60 mV) to initiate a small depolarization. A previous publication, however, showed that alpha-cell T-type Ca(2+) channels have an activation threshold of -40 mV, which does not appear to fulfill their role as pacemakers. In this work, we investigated the Ca(2+) channel characteristics in alpha-cells of mouse-insulin-promoter green-fluorescent-protein (MIP-GFP) mouse. The beta-cells of MIP-GFP were conveniently distinguished as green cells, while immunostaining indicated that the majority of non-green cells were alpha-cells. We found that majority of alpha-cells possessed T-type Ca(2+) channels having an activation threshold of -40 mV; these cells also had high-voltage-activated (HVA) Ca(2+) channels (activation threshold of -20 mV). A novel finding here is that a minority of alpha-cells had T-type Ca(2+) channels with an activation threshold of -60 mV. This minor population of alpha-cells was, surprisingly, devoid of HVA Ca(2+) channels. We suggest that this alpha-cell subpopulation may act as pacemaker cells in low or absence of glucose.