Physiology and pathophysiology of the interstitial cell of Cajal: from bench to bedside. II. Gastric motility: lessons from mutant mice on slow waves and innervation

Motor dysfunction of the gut in Duchenne muscular dystrophy: A review

BACKGROUND

Duchenne's muscular dystrophy (DMD) is a severe type of hereditary, neuromuscular disorder caused by a mutation in the dystrophin gene resulting in the absence or production of truncated dystrophin protein. Conventionally, clinical descriptions of the disorder focus principally on striated muscle defects; however, DMD manifestations involving gastrointestinal (GI) smooth muscle have been reported, even if not rigorously studied.

PURPOSE

The objective of the present review is to offer a comprehensive perspective on the existing knowledge concerning GI manifestations in DMD, focusing the attention on evidence in DMD patients and mdx mice. This includes an assessment of symptomatology, etiological pathways, and potential corrective approaches. This paper could provide helpful information about DMD gastrointestinal implications that could serve as a valuable orientation for prospective research endeavors in this field. This manuscript emphasizes the effectiveness of mdx mice, a DMD animal model, in unraveling mechanistic insights and exploring the pathological alterations in the GI tract. The gastrointestinal consequences evident in patients with DMD and the mdx mice models are a significant area of focus for researchers. The exploration of this area in depth could facilitate the development of more efficient therapeutic approaches and improve the well-being of individuals impacted by the condition.

Erratum: Spontaneous transverse colon volvulus in a patient with Duchenne muscular dystrophy: An unreported complication

[This corrects the article DOI: 10.1016/j.radcr.2022.12.062.][This corrects the article DOI: 10.1016/j.radcr.2023.03.026.].

Spontaneous transverse colon volvulus in a patient with Duchenne muscular dystrophy: An unreported complication

A 22-year-old male patient with Duchenne muscular dystrophy (DMD) and chronic constipation presents to the emergency room with severe abdominal pain and hive closed to feces and gas. Contrast-enhanced computed tomography of the abdomen demonstrates mechanical ileus due to volvulus of the transverse colon: torsion of the transverse mesocolon is confirmed and subtotaly colectomy is performed, revealing multiple ischemic areas with focal perforations. DMD is frequently associated with gastrointestinal motility disorders, including chronic constipation and life-threatening conditions like intestinal pseudo-obstruction and sigmoid volvulus. To date, transverse colic localization of volvolus represents an unreported condition among patients with DMD.

High-resolution in vivo monophasic gastric slow waves to quantify activation and recovery profiles

BACKGROUND

Gastric bio-electrical slow waves are, in part, responsible for coordinating motility. Spatial dynamics about the recovery phase of slow wave recordings have not been thoroughly investigated due to the lack of suitable experimental techniques.

METHODS

A high-resolution multi-channel suction electrode array was developed and applied in pigs to acquire monophasic gastric slow waves. Signal characteristics were verified against biphasic slow waves recorded by conventional surface contact electrode arrays. Monophasic slow wave events were categorized into two groups based on their morphological characteristics, after which their amplitudes, activation to recovery intervals, and gradients were quantified and compared. Coverage of activation and recovery maps for both electrode types were calculated and compared.

KEY RESULTS

Monophasic slow waves had a more pronounced recovery phase with a higher gradient than biphasic slow waves (0.5 ± 0.1 vs. 0.3 ± 0.1 mV·s^-1 ). Between the 2 groups of monophasic slow waves, there was a significant difference in amplitude (1.8 ± 0.5 vs. 1.1 ± 0.2 mV), activation time gradient (0.8 ± 0.2 vs. 0.3 ± 0.1 mV·s^-1 ), and recovery time gradient (0.5 ± 0.1 vs. 0.3 ± 0.1 mV·s^-1 ). For the suction and conventional contact electrode arrays, the recovery maps had reduced coverage compared to the activation maps (4 ± 6% and 43 ± 11%, respectively).

CONCLUSIONS AND INFERENCES

A novel high-resolution multi-channel suction electrode array was developed and applied in vivo to record monophasic gastric slow waves. Slow wave recovery phase analysis could be performed more efficiently on monophasic signals compared with biphasic signals, due to the more identifiable recovery phases.

Quantification of Gastric Slow Wave Velocity using Bipolar High-Resolution Recordings

OBJECTIVE

Gastric bio-electrical slow waves are, in part, responsible for coordinating motility. High-resolution (HR) in vivo recordings can be used to capture the wavefront velocity of the propagating slow waves. A standard marking-and-grouping approach is typically employed along with manual review. Here, a bipolar velocity estimation (BVE) method was developed, which utilized local directional information to estimate the wavefront velocity in an efficient manner.

METHODS

With this approach, unipolar in vivo HR recordings were used to construct bipolar recordings in different directions. Then, the local directionality of the slow wave was extracted by calculating time delay information. The accuracy of the method was verified using synthetic data and then validated with in vivo HR pig experimental recordings.

RESULTS

Against ventilator noise amplitude of 0% - 70% of the average slow wave amplitude, the direction and speed error increased from 4.4 and 0.9 mm/s to 8.6 and 1.4 mm/s. For signals added with high-frequency noise with signal-to-noise ratios of 60 dB - 12 dB, the error increased from 8.0 and 1.0 mm/s to 9.8 and 1.2 mm/s. For experimental signals, the BVE algorithm resulted in 19.2 1.7 of direction error and 2.0 0.2 mm/s of speed error, when compared to the standard marking-and-grouping method.

CONCLUSION

Gastric slow wave wavefront velocities were estimated rapidly using the BVE algorithm with minimal errors.

SIGNIFICANCE

The BVE algorithm enables the ability to estimate wavefront velocities in HR recordings in an efficient manner.

Transmural recordings of gastrointestinal electrical activity using a spatially-dense microelectrode array

Objective. High-resolution serosal recordings provide detailed information about the bioelectrical conduction patterns in the gastrointestinal (GI) tract. However, equivalent knowledge about the electrical activity through the GI tract wall remains largely unknown. This study aims to capture and quantify the bioelectrical activity across the wall of the GI tract.Approach. A needle-based microelectrode array was used to measure the bioelectrical activity across the GI wallin vivo. Quantitative and qualitative evaluations of transmural slow wave characteristics were carried out in comparison to the serosal slow wave features, through which the period, amplitude, and SNR metrics were quantified and statistically compared.Main results. Identical periods of 4.7 ± 0.3 s with amplitudes of 0.17 ± 0.04 mV versus 0.31 ± 0.1 mV and signal to noise ratios of 5.5 ± 1.3 dB versus 14.4 ± 1.1 dB were observed for transmural and serosal layers, respectively. Four different slow wave morphologies were observed across the transmural layers of the GI wall. Similar amplitudes were observed for all morphology types, and Type 1 and Type 2 were of the highest prevalence, dominating the outer and inner layers. Type 2 was exclusive to the middle layer while Type 4 was primarily observed in the middle layer as well.Significance. This study demonstrates the validity of new methodologies for measuring transmural slow wave activation in the GI wall and can now be applied to investigate the source and origin of GI dysrhythmias leading to dysmotility, and to validate novel therapeutics for GI health and disease.

Gut-organ axis: a microbial outreach and networking

Human gut microbiota (GM) includes a complex and dynamic population of microorganisms that are crucial for well-being and survival of the organism. It has been reported as diverse and relatively stable with shared core microbiota, including Bacteroidetes and Firmicutes as the major dominants. They are the key regulators of body homeostasis, involving both intestinal and extra-intestinal effects by influencing many physiological functions such as metabolism, maintenance of barrier homeostasis, inflammation and hematopoiesis. Any alteration in GM community structures not only trigger gut disorders but also influence other organs and cause associated diseases. In recent past, the GM has been defined as a 'vital organ' with its involvement with other organs; thus, establishing a link or a bi- or multidirectional communication axis between the organs via neural, endocrine, immune, humoral and metabolic pathways. Alterations in GM have been linked to several diseases known to humans; although the exact interaction mechanism between the gut and the organs is yet to be defined. In this review, the bidirectional relationship between the gut and the vital human organs was envisaged and discussed under several headings. Furthermore, several disease symptoms were also revisited to redefine the communication network between the gut microbes and the associated organs.

A Spatially-dense Microfabricated Photolithographic Electrode Array for Gastrointestinal Slow Wave Recordings. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020;2020:3957-3960. [PMID: 33018866 DOI: 10.1109/embc44109.2020.9175780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Gastrointestinal slow wave activity is, in part, responsible for governing gut motility. Dysrhythmic slow wave activity has been associated with a number of functional motility disorders, but the mechanisms involved are poorly understood. There exist a number of transgenic small animal models with functional motility disorders. However, current slow wave mapping methods are targeted towards humans and large animals and are not readily translatable. To overcome these shortcomings, a novel electrode array was developed using photolithography. The developed photolithographic electrode array (PEA) was experimentally validated in vivo against a standard flexible printed circuit (FPC) array for comparison. Mean amplitudes of 0.13 ± 0.06 mV and 0.88 ± 0.05 mV were reported by the PEA and the FPC array, respectively. Mean signal to noise ratios (SNR) of 13.4 ± 6.4 dB and 8.3 ± 5.1 dB were achieved for the PEA and the FPC array, respectively. Our findings showed that the PEA acquired slow wave signals with higher amplitude and SNR. In this study, we showed that microfabrication techniques could be successfully implemented with optimized resolution for the investigation of normal and abnormal slow wave activity in smaller animals, which will enable a better understanding of the pathophysiological mechanisms and aid in the diagnosis and treatment of gastrointestinal motility disorders.Clinical Relevance - The ability to characterize the slow wave activity in transgenic animals with functional motility disorders would be a critical advance for the diagnosis and treatment of these disorders. Microfabrication techniques enable miniaturization of high-resolution electrode arrays suitable for mapping electrical activity in normal and transgenic small laboratory animals such as rats and mice.

Changes in colonic contractility in response to inflammatory bowel disease: Long-term assessment in a model of TNBS-induced inflammation in rats

AIMS

Inflammatory bowel disease is a chronic relapsing inflammation that affects the gastrointestinal tract, causing changes in colonic motility. The evolution of these changes is not completely understood and possibly related to symptoms that appear in different degrees of the intestinal inflammation. Therefore, our aim is evaluate during 14 days of assessment aspects of colonic contractility using 2,4,6-trinitrobenzenesulfonic acid (TNBS) model of inflammation in rats and associate the inflammatory process with colonic motility.

METHODS

Contractility and inflammatory parameters were assessed in the same animal in six different moments: before intestinal inflammation induction, 2, 5, 8, 11, and 14 days after induction. The mechanical activity was determined by alternating current biosusceptometry (ACB) and subdivided into rhythmic propagating ripples (RPR) and rhythmic propulsive motor complexes (RPMC). We assessed inflammation by determining myeloperoxidase activity in feces.

RESULTS

Transient and permanent changes were observed in colonic motility as a function of the inflammatory process evaluated through myeloperoxidase activity. We identified two contraction profiles: RPR and RPMC. The microscopic analysis demonstrated a depth of damage caused by an injury that was associated with changes in motility.

CONCLUSIONS

We implemented a robust and adequate (specific) signal processing to quantify two measured colonic frequency patterns. Thus, we performed a detailed temporal analysis of the consequences of TNBS-induced inflammation on colonic motility in rats. Our approach enables further long-term assessments in the same animal with different mechanisms and duration of injury, remission, treatments and their motor consequences.

Telocytes express ANO-1-encoded chloride channels in canine ventricular myocardium

INTRODUCTION

It is unknown if ANO-1 is expressed in the heart, though the presence of a calcium-activated chloride current has been proposed to mediate some cardiac dysrhythmias. Furthermore, a specific cell type termed telocytes, morphologically mimicking Cajal cells which use ANO-1 to modulate their pacemaker activity in the gut, have been described in the heart. We therefore sought to determine whether this channel is expressed in the canine heart.

METHODS

Myocardium was sampled from the ventricles of five canines. Sections were labeled with anti-Kit and anti-ANO-1 antibodies. Slides were reviewed by four investigators looking at cell morphology, distribution, and co-localization. Identification of telocytes was based on criteria including morphology, Kit positivity (+), and ANO-1 positivity (+).

RESULTS

Clusters of cells meeting criteria for telocytes were seen in the epicardium, sub-epicardium, and mid-myocardium. A small subset of cells that were morphologically similar to myocytes was ANO-1 (+) but Kit (-). In total, three different cell classes were found: (i) Kit (+), ANO-1 (+) cells with the appearance of telocytes; (ii) Kit (+), ANO-1 (-) cells; and (iii) Kit (-), ANO-1 (+) cells with the morphologic appearance of cardiac myocytes.

CONCLUSIONS

Telocytes are present in the canine ventricle and express ANO-1. These data merit further study to elucidate the functional expression of these channels in the heart and whether they may be targets for cardiac arrhythmias.

A comparison of various intragastric balloons for the assessment of gastric motility

BACKGROUND

There is a clear need for a novel method to readily assess gastric motility in daily clinical practice.

METHODS

In a crossover design, 10 noncompliant balloons of different shape and volume (25-350 mL), attached to a classic feeding tube, were introduced in the stomach of eight healthy volunteers. In the same experiment, a High-Resolution Manometry (HRM) catheter was positioned throughout the stomach. Gastric motility was recorded during fasting (2 hours) and liquid nutrient administration (30 minutes). Motility was quantified using a peak detection algorithm. Symptoms were recorded throughout the experiment using visual analog scales (100 mm). Results are presented as mean ± SD.

KEY RESULTS

The % time during which motility-induced pressure increments could be detected with HRM but not by the balloon varied from 42 ± 24% in the smallest (25 mL) balloon to 1 ± 1% in the 330 mL balloon. On the other hand, bloating, discomfort and nausea scores were 0 ± 0, 0 ± 0 and 2 ± 5 mm, respectively, for the smallest balloon (25 mL) while these scores were 28 ± 38, 13 ± 30, and 38 ± 30 mm, respectively, for the largest balloon (350 mL). A phase III contraction pattern was consistently evoked in balloons with a volume >200 mL.

CONCLUSION

Gastric motility could be assessed more accurately with larger volume balloons, while epigastric symptoms were evoked with increasing balloon volume. The optimal balloon to measure gastric motility has a 5 cm diameter and is 11 cm long (210 mL). A nasogastric balloon catheter can now be developed that enables relatively easy monitoring of gastric motility in patients with epigastric symptoms.

Intestinal Transit Time and Cortisol-Mediated Stress in Zebrafish

Intestinal motility, the spontaneous and rhythmic smooth muscle contraction, is a complex process that is regulated by overlapping and redundant regulatory mechanisms. Primary regulators intrinsic to the gastrointestinal tract include interstitial cells of Cajal, enteric neurons, and smooth muscle cells. Extrinsic primary regulators include the autonomic nervous system, immune system, and the endocrine system. Due to this complexity, a reductionist approach may be inappropriate if the ultimate goal is to understand motility regulation in vivo. Motility can be directly visualized in intact zebrafish, with intact regulatory systems, because larvae are transparent. Intestinal motility can therefore be measured in a complete system. However, the intestinal tract may respond to external influences, such as handling, which may invoke a stress response and influence intestinal transit. We used SR4G transgenic zebrafish, which express green fluorescent protein following activation of glucocorticoid receptors, and showed that handling required for the intestinal motility assay induces stress. Separate experiments showed that exogenous application of hydrocortisone did not influence intestinal transit, suggesting that handling may not interfere with transit measurements in intact zebrafish larvae. These experiments contribute to further development of the zebrafish model for intestinal motility research.

Modification of Calcium-Activated Chloride Currents in Cerebellar Purkinje Neurons

The whole-cell voltage clamp technique was employed to record the total ionic currents in rat cerebellar Purkinje neurons. When intrapipette solution contained 120 mM KCl, replacement of the standard external physiological saline with Na-free solution resulted in appearance of inward tail current after the end of the depolarizing pulse. When intrapipette potassium ions were replaced for cesium ones, the tail currents were observed even in the presence of normal Na⁺ concentration (140 mM) in the external solution. Tail currents were not observed when external solution contained no Cl^- and/or Ca²⁺ ions. Niflumic acid (25-100 μM) blocked these currents by 80-100%. Complete replacement of external Na⁺ for Tris ions pronouncedly augmented the amplitude and duration of the tail currents. These findings suggest that the tail transients in rat cerebellar Purkinje neurons are calcium-activated chloride currents whose amplitude and kinetics depend on ionic composition of the extracellular and intracellular solutions.

Interstitial cells of Cajal and telocytes in the gut: twins, related or simply neighbor cells?

In the interstitium of the connective tissue several types of cells occur. The fibroblasts, responsible for matrix formation, the mast cells, involved in local response to inflammatory stimuli, resident macrophages, plasma cells, lymphocytes, granulocytes and monocytes, all engaged in immunity responses. Recently, another type of interstitial cell, found in all organs so far examined, has been added to the previous ones, the telocytes (TC). In the gut, in addition to the cells listed above, there are also the interstitial cells of Cajal (ICC), a peculiar type of cell exclusively detected in the alimentary tract with multiple functions including pace-maker activity. The possibility that TC and ICC could correspond to a unique cell type, where the former would represent an ICC variant outside the gut, was initially considered, however, further studies have clearly shown that ICC and TC are two distinct types of cells. In the gut, while the features and the roles of the ICC are established, part of the scientific community is still disputing these 'new' interstitial cells to which several names such as fibroblast-like cells (FLCs), interstitial Cajal-like cells or, most recently, PDGFRα+ cells have been attributed. This review will detail the main features and roles of the TC and ICC with the aim to establish their relationships and hopefully define the identity of the TC in the gut.

Gastrointestinal Dysfunction in Patients with Duchenne Muscular Dystrophy

Background

In adult patients with Duchenne muscular dystrophy (DMD) life-threatening constipation has been reported. Since gastrointestinal function in DMD has not been rigorously studied we investigated objective and subjective manifestations of gastrointestinal disturbances in DMD patients.

Methods

In 33 patients with DMD, age 12–41 years, eating behavior and gastrointestinal symptoms were evaluated by questionnaires. Gastric emptying half time (T_1/2) and oro-cecal transit time (OCTT) were evaluated by analyzing ¹³CO₂ exhalation curves after ingestion of ¹³C labeled test meals. Colonic transit time (CTT) was measured by abdominal radiography following ingestion of radiopaque markers.

Results

The median (quartiles) T_1/2 was 187 (168, 220) minutes, the OCTT was 6.3 (5.0, 7.9) hours, both substantially longer than normal data (Goetze 2005, T_1/2: 107±10; Geypens 1999, OCTT 4.3±0.1 hours). The median CTT was 60 (48, 82) hours despite extensive use of laxative measures (Meier 1995, upper limit of normal: 60 hours). T_1/2 and OCTT did not correlate with symptoms evaluated by the Gastroparesis Cardinal Symptom Index (GCSI) (Spearman r = -0.3, p = 0.1; and r = -0.15, p = 0.4, respectively). CTT was not correlated with symptoms of constipation assessed by ROME III criteria (r = 0.12, p = 0.5).

Conclusions

DMD patients have a markedly disturbed gastrointestinal motor function. Since objective measures of impaired gastrointestinal transport are not correlated with symptoms of gastroparesis or constipation our findings suggest that measures assuring adequate intestinal transport should be taken independent of the patient’s perception in order to prevent potentially life threatening constipation, particularly in older DMD patients.

Structure and function of TMEM16 proteins (anoctamins)

TMEM16 proteins, also known as anoctamins, are involved in a variety of functions that include ion transport, phospholipid scrambling, and regulation of other membrane proteins. The first two members of the family, TMEM16A (anoctamin-1, ANO1) and TMEM16B (anoctamin-2, ANO2), function as Ca2+-activated Cl- channels (CaCCs), a type of ion channel that plays important functions such as transepithelial ion transport, smooth muscle contraction, olfaction, phototransduction, nociception, and control of neuronal excitability. Genetic ablation of TMEM16A in mice causes impairment of epithelial Cl- secretion, tracheal abnormalities, and block of gastrointestinal peristalsis. TMEM16A is directly regulated by cytosolic Ca2+ as well as indirectly by its interaction with calmodulin. Other members of the anoctamin family, such as TMEM16C, TMEM16D, TMEM16F, TMEM16G, and TMEM16J, may work as phospholipid scramblases and/or ion channels. In particular, TMEM16F (ANO6) is a major contributor to the process of phosphatidylserine translocation from the inner to the outer leaflet of the plasma membrane. Intriguingly, TMEM16F is also associated with the appearance of anion/cation channels activated by very high Ca2+ concentrations. Furthermore, a TMEM16 protein expressed in Aspergillus fumigatus displays both ion channel and lipid scramblase activity. This finding suggests that dual function is an ancestral characteristic of TMEM16 proteins and that some members, such as TMEM16A and TMEM16B, have evolved to a pure channel function. Mutations in anoctamin genes (ANO3, ANO5, ANO6, and ANO10) cause various genetic diseases. These diseases suggest the involvement of anoctamins in a variety of cell functions whose link with ion transport and/or lipid scrambling needs to be clarified.

Disturbed development of the enteric nervous system after in utero exposure of selective serotonin re-uptake inhibitors and tricyclic antidepressants. Part 1: Literature review

The increase in selective serotonin re-uptake inhibitor (SSRI) use during pregnancy, questions concerning abnormal development of the enteric nervous system (ENS), increase in laxative use in children and the association of fluoxetine with infantile hypertrophic pyloric stenosis (IHPS) gave rise to this pharmacological literature review. The role of 5-HT and the NE uptake in ontogeny of the ENS and the effects SSRIs and TCAs might have on the development of the ENS were investigated. The literature study showed that SSRIs may influence the development of the ENS in two ways. Blockage of the serotonin re-uptake transporter (SERT) during foetal development could influence migration, differentiation and survival of cells. This could lead to abnormal development in the first trimester of pregnancy. The other way is that 5-HT seems to be a growth factor in the primitive ENS. This growth factor like action is mediated through the 5-HT(2B) receptor and stimulation of this receptor by SSRIs influences the fate of late-developing enteric neurons. This could lead to abnormal development in the second and third trimester. TCAs could influence the development of the ENS, besides through inhibition of the SERT, through inhibition of the norepinephrine transporter (NET). Expression of the NET seems to be essential for a full development of enteric neurons and especially for serotonergic neurons. In addition the NET was detected early in ontogeny and precedes neuronal differentiation, which suggests that TCAs might influence development of the ENS when exposed early in pregnancy. The insights of this study gave rise to hypotheses which will be tested in an epidemiological cohort study.

Basally activated nonselective cation currents regulate the resting membrane potential in human and monkey colonic smooth muscle

Resting membrane potential (RMP) plays an important role in determining the basal excitability of gastrointestinal smooth muscle. The RMP in colonic muscles is significantly less negative than the equilibrium potential of K(+), suggesting that it is regulated not only by K(+) conductances but by inward conductances such as Na(+) and/or Ca(2+). We investigated the contribution of nonselective cation channels (NSCC) to the RMP in human and monkey colonic smooth muscle cells (SMC) using voltage- and current-clamp techniques. Qualitative reverse transcriptase-polymerase chain reaction was performed to examine potential molecular candidates for these channels among the transient receptor potential (TRP) channel superfamily. Spontaneous transient inward currents and holding currents were recorded in human and monkey SMC. Replacement of extracellular Na(+) with equimolar tetraethylammonium or Ca(2+) with Mn(2+) inhibited basally activated nonselective cation currents. Trivalent cations inhibited these channels. Under current clamp, replacement of extracellular Na(+) with N-methyl-D-glucamine or addition of trivalent cations caused hyperpolarization. Three unitary conductances of NSCC were observed in human and monkey colonic SMC. Molecular candidates for basally active NSCC were TRPC1, C3, C4, C7, M2, M4, M6, M7, V1, and V2 in human and monkey SMC. Comparison of the biophysical properties of these TRP channels with basally active NSCC (bI(NSCC)) suggests that TRPM4 and specific TRPC heteromultimer combinations may underlie the three single-channel conductances of bI(NSCC). In conclusion, these findings suggest that basally activated NSCC contribute to the RMP in human and monkey colonic SMC and therefore may play an important role in determining basal excitability of colonic smooth muscle.

Ultrastructural features and possible functional role of kit-positive interstitial cells in the guinea pig corpus cavernosum

The objective of the present study was to identify kit-positive interstitial cells (ICs) in guinea pig corpus cavernosum and examine their relationships with adjacent smooth muscle cells (SMCs) and intramural nerves. In addition, we investigated the possible involvement of ICs in nitric oxide (NO)-mediated relaxation of corpus cavernosum smooth muscle (CCSM). ICs were identified by their immunoreactivity to the kit receptor, a cell surface marker encoded by c-kit proto-oncogene and specific for interstitial cells of Cajal. ICs were abundantly distributed in guinea pig corporal tissues. Ultrastructural investigation by conventional transmission electron microscopy revealed the ultrastructural features of ICs and gap junctions located between ICs and adjacent SMCs, furthermore, a close contact between ICs and intramural nerves for the first time. Western blot analysis of purified ICs by fluorescence-activated cell sorting revealed coexpression of soluble guanylate cyclase (sGC)α1, sGCβ1 and kit receptor tyrosine kinase protein in them. These observations imply that ICs express the NO-sensitive sGC molecule and may be involved in the NO-mediated relaxation of CCSM in the guinea pig corpus cavernosum.

Gastric dysmotility in healthy first-degree relatives of patients with schizophrenia

Gastric dysmotility has been reported in patients suffering from major depression or schizophrenia. An increased sympathetic activity modulating the gastric pacemaker located in the antrum of the stomach has been suggested as the underlying pathology. Similar to patients suffering from schizophrenia, their first-degree relatives showed alterations in cardiac autonomic modulation. Here we aimed to investigate gastric myoelectrical activity in healthy relatives of patients suffering from paranoid schizophrenia. Electrogastrography (EGG) was performed before and after test meal ingestion in 20 patients with paranoid schizophrenia, 20 of their first-degree relatives and 20 healthy matched controls. Autonomic and abdominal symptoms were assessed by the autonomic symptom score as previously reported. Autonomic parameters were correlated with the positive and negative syndrome scale (PANSS). Only minimal differences were observed before test meal ingestion between relatives and controls. In contrast, after test meal ingestion we observed a significantly increased tachygastria within the signal of the gastric pacemaker in relatives compared to controls, whereas normogastria was reduced. Significant difference between relatives and controls were also found for postprandial ICDF (instability coefficient of dominant frequency) and slow wave, which represents the dominant frequency of gastric pacemaker activity, indicating gastric dysmotility in relatives. Between relatives and patients just a difference for ICDP (instability coefficient of dominant power) was observed. After stimulation of the enteric nervous system we have observed an increased sympathetic modulation in first-degree relatives of patients suffering from schizophrenia. This result adds evidence to an ongoing debate on the genetic influence of autonomic dysfunction in the disease.

Gastric dysmotility in major depression

BACKGROUND

Somatic symptoms of the gastrointestinal tract occur frequently in major depressive disorder (MDD) and might be associated with the known autonomic imbalance in the disease. Hence, we have investigated gastric electrical activity in patients suffering from major depression before and after treatment by means of electrogastrography (EGG) to investigate a putative association with either the disease state and its symptoms or its relation to the treatment.

METHODS

EGG readings before and after ingestion of a test meal of 27 patients suffering from major depression were recorded before and after treatment with antidepressants and compared with age-matched controls. Abdominal symptoms were rated by a specific Autonomic Nervous Symptom-score.

RESULTS

We found a significantly increased amount of tachygastria before and after medication, indicating increased sympathetic modulation. A significant difference was observed for the instability coefficients before and after medication, indicating gastric dysmotility in our patients prior to treatment. The elevated approximate entropy measure points to increased complexity and dysregulation. Furthermore, we have observed a correlation between subjective sensation of sweating and dry mouth with the sympathetic parameter tachygastria.

DISCUSSION

Our results suggest that major depression is associated with gastric dysrhythmia possibly caused by increased sympathetic modulation. Linear and non-linear EGG measures emphasize a possible role of the autonomic nervous system in the development of gastric symptoms. The treatment with antidepressants seems to increase the activity of the sympathetic nervous system, without aggravating gastric symptoms. The association of increased sympathetic modulation with somatic symptoms was indicated by correlation analysis with these symptoms.

New insights into the pathogenesis of infantile pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is the most common surgical cause of vomiting in infants. Despite numerous hypotheses, the aetiopathogenesis of IHPS is not fully understood. Genetic, extrinsic and hormonal factors have been implicated in the pathogenesis of the disease. Furthermore, abnormalities of various components of the pyloric muscle such as smooth muscle cells, growth factors, extracellular matrix elements, nerve and ganglion cells, synapses, nerve supporting cells, neurotransmitters and interstitial cells of Cajal have been reported. Recently, genetic studies have identified susceptibility loci for IHPS and molecular studies have concluded that smooth muscle cells are not properly innervated in IHPS.

Linear and non-linear measures indicate gastric dysmotility in patients suffering from acute schizophrenia

Cardiac autonomic dysfunction has been reported in patients suffering from schizophrenia. The aim of the present study was to evaluate gastric electrical activity in unmedicated patients suffering from acute schizophrenia in relation to their symptoms. Electrogastrography was performed before and after test meal ingestion in 26 patients suffering from schizophrenia and 26 matched controls. The non-linear measure approximate entropy (ApEn) was calculated for the first time from the obtained signal in addition to standardized measures. Results were correlated with the scales for the assessment of positive symptoms and negative symptoms. In addition, autonomic and abdominal symptoms were assessed by the autonomic symptom score. We found a significantly increased amount of tachygastria and arrhythmia within the signal of the activity of the gastric pacemaker before and after test meal digestion in patients compared to controls, indicating increased sympathetic modulation within the enteric nervous system. A significant difference was observed for slow wave, which represents the dominant frequency of gastric pacemaker activity, indicating gastric dysmotility in our patients. The elevated ApEn measure points to increased complexity and dysregulation. In addition, we have observed a correlation between delusions and tachygastria. Sympathetic function seems to be altered in the enteric nervous system of patients suffering from schizophrenia. Future studies need to explore the influence of the disease on different branches of the autonomic nervous system and clinical consequences of enteric dysfunction. Our findings point to a possible systemic autonomic imbalance that needs to be studied in respect to the neurobiology of schizophrenia.

Updating old ideas and recent advances regarding the Interstitial Cells of Cajal

Since their discovery by Cajal in 1889, the Interstitial Cells of Cajal (ICC) have generated much controversy in the scientific community. Indeed, the nervous, muscle or fibroblastic nature of the ICC has remained under debate for more than a century, as has their possible physiological function. Cajal and his colleagues considered them to be neurons, while contemporary histologists like Kölliker and Dogiel categorized these cells as fibroblasts. More recently, the role of ICC in the origin of slow-wave peristaltism has been elucidated, and several studies have shown that they participate in neurotransmission (intercalation theory). The fact that ICC assemble in the circular muscular layer and that they originate from cells which emerge from the ventral neural tube (VENT cells), a source of neurons, glia and ICC precursors other than the neural crest, suggests a neural origin for this particular subset of ICC. The discovery that ICC express the Kit protein, a type III tyrosine kinase receptor encoded by the proto-oncogene c-kit, has helped better understand their physiological role and implication in pathological conditions. Gleevec, a novel molecule designed to inhibit the mutant activated version of c-Kit receptors, is the drug of choice to treat the so-called gastrointestinal stromal tumours (GIST), the most common non-epithelial neoplasm of the gastrointestinal tract. Here we review Cajal's original contributions with the aid of unique images taken from Cajal's histological slides (preserved at the Cajal Museum, Cajal Institute, CSIC). In addition, we present a historical review of the concepts associated with this particular cell type, emphasizing current data that has advanced our understanding of the role these intriguing cells fulfil.

Interstitial cells of Cajal reduce in number in recto-sigmoid Hirschsprung's disease and total colonic aganglionosis

Interstitial cells of Cajal (ICCs) play a key role in regulating gastrointestinal tract motility. The pathophysiological basis of colonic aperistalsis in Hirschsprung's disease (HD) is still not fully understood. Many studies reported that decreased numbers or disrupted networks of ICCs were associated with HD. Little information is available on the distribution of different subtypes of ICCs in HD. The aim of this study was to determine the alterations in density of different subtypes of ICC in colonic specimens of patients with total colonic and recto-sigmoid HD. Full thickness colonic specimens were obtained from five children with total colonic aganglionosis (TCA), sixteen with recto-sigmoid HD and seven controls. ICCs were visualized in frozen sections by c-Kit (CD117) fluorescent staining. In the control colon, c-Kit positive ICCs formed a dense network surrounding the myenteric plexus (IC-MY), along the submucosal surface of the circular muscle layer (IC-SM) and in the circular and longitudinal muscle layer (IC-IM). In the aganglionic region of the colon of the patients affected by HD, the number of ICCs (especially IC-IM and IC-SM) was markedly reduced and IC-MY networks were disrupted. Nearly total lack of three subtypes of ICCs was observed in the TCA specimens. This study demonstrated the altered distribution of different subtypes of ICCs in the resected colon of patients with recto-sigmoid HD and TCA. These findings suggest that the reduction of each subtype of ICCs may play an important role in the etiology of HD.

Pyloric sphincter dysfunction in nNOS-/- and W/Wv mutant mice: animal models of gastroparesis and duodenogastric reflux

BACKGROUND & AIMS

Nitrergic nerves and interstitial cells of Cajal (ICC) have been implicated in the regulation of pyloric motility. The purpose of these studies was to define their roles in pyloric function in vivo.

METHODS

Pyloric sphincter manometry was performed in wild-type controls, neuronal nitric oxide synthase-deficient (nNOS(-/-)) mice, and ICC-deficient W/W(v) mice, and the effect of deafferented cervical vagal stimulation was examined.

RESULTS

Mice showed a distinct approximately 0.6-mm-wide zone of high pressure at the antroduodenal junction, representing the pyloric sphincter. In wild-type controls, the pylorus exhibited tonic active pressure of 12.4 +/- 1.6 mm Hg with superimposed phasic contractions. The motility indices, minute motility index, and total myogenic activity were reduced by vagal stimulation, and the reduction was antagonized by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). In nNOS(-/-) mice, pyloric basal tone, minute motility index, and total myogenic activity were not significantly different from those in controls, but vagal stimulation paradoxically increased pyloric motility. In contrast, the W/W(v) mice had significantly reduced resting pyloric pressure that was suppressed by vagal stimulation in an L-NAME-sensitive manner. The stomachs of fasted nNOS(-/-) mice showed solid food residue and bezoar formation, while W/W(v) mice showed bile reflux.

CONCLUSIONS

In nNOS(-/-) mice, loss of nitrergic pyloric inhibition leads to gastric stasis and bezoars. In contrast, basal pyloric hypotension with normal nitrergic inhibition predisposes W/W(v) mice to duodenogastric bile reflux.

Does vivid emotional imagery depend on body signals?

The recall and re-experiencing of a personal emotional event (emotional imagery) are thought to evoke neural activity in the central nervous system that can affect the physiology of bodily states. It has been proposed that the more active the neural systems previously engaged in the emotional experience, and the more active the bodily state associated with that experience, the more vivid the emotional imagery is. The sympathetic nervous system (SNS) and the gastrointestinal system (GI) are engaged in emotional reactions. On this basis, we hypothesized that vivid emotional imagery would be accompanied by strong increases in gastrointestinal and sympathetic nervous system activity. To test this hypothesis, 17 healthy participants performed emotional imagery of strong autobiographical memories involving various emotional states (happy, fear, disgust, sadness, anger). SNS and GI changes, measured by skin conductance and electrogastrogram, respectively, correlated positively with subjective ratings of arousal during the imagery. However, the SNS changes did not correlate with ratings of emotional imagery vividness, and even more intriguingly, the GI changes correlated strongly and negatively with vividness ratings. To account for these findings, we propose that in highly vivid imagery experience, the central nervous system is simulating the whole emotional experience strongly, and bodily information plays a lesser role. In low vivid imagery experience, the central nervous system is not simulating very strongly the emotional experience, and information coming from the body (including the GI system) plays a greater role. This interpretation is set forth in the context of Damasio's [Damasio, A., (1999) The feeling of what happens: body and emotion in the making of consciousness, Orlando, Fl, Harcourt.] theoretical framework, which predicts such a dissociation between a "body loop" and an "as if body loop" for the experiencing and re-experiencing of emotions and feelings.

Deficiency of intramuscular ICC increases fundic muscle excitability but does not impede nitrergic innervation

The motility of the gastrointestinal tract is generated by smooth muscle cells and is controlled to a large extent by an intrinsic neural network. A gap of approximately 200 nm usually separates nerve varicosities from smooth muscle cells, which suggests that direct innervation of the smooth muscle by synapses does not occur. Enteric nerves do make synapse-like contact with proposed regulatory cells, the interstitial cells of Cajal (ICC), which in turn may be in gap junction contact with smooth muscle cells. The role played by ICC in enteric innervation is controversial. Experimental evidence has been presented in vitro for the hypothesis that nitrergic inhibitory innervation is strongly reduced in the absence of ICC. However, in vivo data appear to dispute that. The present report provides evidence that explains the discrepancy between in vivo and in vitro data and provides evidence that inhibitory neurotransmitters can reach smooth muscle cells without hindrance when ICC are absent. The fundic musculature shows increased responses to substance P-mediated innervation and shows marked spontaneous activity, which is consistent with increased muscle excitability.

Symptomatology, pathophysiology, diagnostic work-up, and treatment of Hirschsprung disease in infancy and childhood

In the majority of infants and children with constipation, no obvious cause can be identified. A rare cause of constipation is Hirschsprung disease (HD). HD is characterized by the absence of ganglion cells from the anorectum for a variable length up to the duodenum. The extent of the aganglionic segment varies, but in most patients the lesion does not extend beyond the rectum and sigmoid colon. This review focuses on the passage of meconium, the recognition of HD, and new insights in its pathophysiology and genetics. The authors also provide a summary of the diagnostic evaluation and treatment of HD in infancy and childhood.

A quantitative model of gastric smooth muscle cellular activation

A physiologically realistic quantitative description of the electrical behavior of a gastric smooth muscle (SM) cell is presented. The model describes the response of a SM cell when activated by an electrical stimulus coming from the network of interstitial cells of Cajal (ICC) and is mediated by the activation of different ion channels species in the plasma membrane. The conductances (predominantly Ca2+ and K+) that are believed to substantially contribute to the membrane potential fluctuations during slow wave activity have been included in the model. A phenomenological description of intracellular Ca2+ dynamics has also been included because of its primary importance in regulating a number of cellular processes. In terms of shape, duration, and amplitude, the resulting simulated smooth muscle depolarizations (SMDs) are in good agreement with experimentally recordings from mammalian gastric SM in control and altered conditions. This model has also been designed to be suitable for incorporation into large scale multicellular simulations.

Neuropathophysiology of functional gastrointestinal disorders

The investigative evidence and emerging concepts in neurogastroenterology implicate dysfunctions at the levels of the enteric and central nervous systems as underlying causes of the prominent symptoms of many of the functional gastrointestinal disorders. Neurogastroenterological research aims for improved understanding of the physiology and pathophysiology of the digestive subsystems from which the arrays of functional symptoms emerge. The key subsystems for defecation-related symptoms and visceral hyper-sensitivity are the intestinal secretory glands, the musculature and the nervous system that controls and integrates their activity. Abdominal pain and discomfort arising from these systems adds the dimension of sensory neurophysiology. This review details current concepts for the underlying pathophysiology in terms of the physiology of intestinal secretion, motility, nervous control, sensing function, immuno-neural communication and the brain-gut axis.

Ultrastructural observations of the tunica muscularis in the small intestine of Xenopus laevis, with special reference to the interstitial cells of Cajal

The distribution and ultrastructure of the interstitial cells of Cajal (ICC) has been examined in the small intestine of the frog Xenopus laevis, as the physiological significance of these cells remains obscure in amphibians and other lower vertebrates. The present study has revealed the existence of a special type of interstitial cell in the tunica muscularis of the small intestine of Xenopus; this cell is characterized by the presence of numerous caveolae, many small mitochondria, and the formation of intercellular connections with the same type of cell. Since these ultrastructural features are shared with mammalian ICC, the cells in the small intestine of Xenopus probably correspond to ICC. These cells also form close contacts with neighboring smooth muscle cells and with nerve varicosities containing accumulations of synaptic vesicles. These cellular networks are likely to be involved in the transmission of nerve impulses to muscle cells, as has been suggested for mammalian tissues. However, true gap junctions have not been detected; they occur neither between the same type of cells nor between the putative ICC and smooth muscle cells. The widespread distribution of ICC or equivalent cells in different groups of vertebrates, together with the conservation of their ultrastructural features, suggests that they differentiated early in vertebrate evolution to play key regulatory roles in gastrointestinal movement.

IL-9 enhances growth of ICC, maintains network structure and strengthens rhythmicity of contraction in culture

Interstitial cells of Cajal (ICC) play a critical role in the control of gastrointestinal motility as pacemaker cells and as regulators of enteric innervation. ICC are one of the first cell types that are injured during an inflammatory process and maintenance of ICC health or promotion of growth and development maybe crucial in recovery after injury. The aim of this study was to evaluate the role of IL-9 in the growth, development and maintenance of ICC in culture. IL-9 in concentrations from 0.02 to 1 microg/ml promoted individual ICC growth and maintenance of the ICC network structure inside tissue explants under culture conditions. The number of ICC grown out of the explants increased significantly at day 4 of culture in the presence of 0.02, 0.5 and 1 microg/ml IL-9. In the presence of 0.5 microg/ml IL-9, explants in culture maintained a higher frequency and stabilized the frequency of spontaneous contractile activity. The ultrastructure of the ICC after 4 days in culture was similar to that in situ. Our data indicate that IL-9 promotes ICC growth in culture and it can be hypothesized that IL-9 is a critical factor in the maintenance of ICC health and ICC repair after injury.

A biomagnetic assessment of colonic electrical activity in pigs

The electrical control activity of the large intestine was recorded in six pigs using a SQUID magnetometer. The study was performed in pre- and post-colectomy/sham-colectomy conditions. The biomagnetic field associated with colonic ECA changed drastically in subjects that underwent the colectomy procedure, whereas the signal for the control animals was nearly unchanged. Power spectral analysis was used to determine the average changes of dominant frequency and amplitude between baseline versus colectomy and sham-colectomy conditions. The dominant frequency was increased by 68 +/- 24% (versus 2 +/- 3% in control). The amplitude was decreased by 69 +/- 24% (versus 13 +/- 17% in control). This is the first study of transabdominal magnetic fields associated with colonic ECA, suggests some of the side effects generated in colectomy surgery and shows the utility of the biomagnetic technique in studies of the large intestine.

Distribution of muscarinic receptor subtypes and interstitial cells of Cajal in the gastrointestinal tract of healthy dairy cows

OBJECTIVE

To describe the distribution of muscarinic receptor subtypes M(1) to M(5) and interstitial cells of Cajal (ICCs) in the gastrointestinal tract of healthy dairy cows.

SAMPLE POPULATION

Full-thickness samples were collected from the fundus, corpus, and pyloric part of the abomasum and from the duodenum, ileum, cecum, proximal loop of the ascending colon, and both external loops of the spiral colon of 5 healthy dairy cows after slaughter.

PROCEDURES

Samples were fixed in paraformaldehyde and embedded in paraffin. Muscarinic receptor subtypes and ICCs were identified by immunohistochemical analysis.

RESULTS

Staining for M(1) receptors was found in the submucosal plexus and myenteric plexus. Antibodies against M(2) receptors stained nuclei of smooth muscle cells only. Evidence of M(3) receptors was found in the lamina propria, in intramuscular neuronal terminals, on intermuscular nerve fibers, and on myocytes of microvessels. There was no staining for M(4) receptors. Staining for M(5) receptors was evident in the myocytes of microvessels and in smooth muscle cells. The ICCs were detected in the myenteric plexus and within smooth muscle layers. Distribution among locations of the bovine gastrointestinal tract did not differ for muscarinic receptor subtypes or ICCs.

CONCLUSIONS AND CLINICAL RELEVANCE

The broad distribution of M(1), M(3), M(5), and ICCs in the bovine gastrointestinal tract indicated that these components are likely to play an important role in the regulation of gastrointestinal tract motility in healthy dairy cows. Muscarinic receptors and ICCs may be implicated in the pathogenesis of motility disorders, such as abomasal displacement and cecal dilatation-dislocation.

Interstitial cells of Cajal in the urethra

The smooth muscle layer of the urethra generates spontaneous myogenic tone that is thought to make a major contribution to urinary continence. The mechanisms underlying generation of tone remain unclear, however recent studies from our laboratory highlighted a role for a specialised population of pacemaker cells which we originally referred to as interstitial cells (IC) and now term ICC. Urethra ICC possess an electrical pacemaker mechanism characterised by rhythmic activation of Ca(2+)-activated Cl(-) channels leading to spontaneous transient inward currents (STICs) under voltage clamp and spontaneous transient depolarisations (STDs) under current clamp conditions. Both STICS and STDs are now known to be associated with spontaneous Ca(2+) oscillations that result from a complex interplay between release of Ca(2+) from intracellular stores and Ca(2+) influx across the plasma membrane. In this review we will consider some of the precise mechanisms involved in the generation of pacemaker activity and discuss how these are modulated by excitatory and inhibitory neurotransmitters.

Involvement of M(2) muscarinic receptors in relaxant response of circular muscle of mouse gastric antrum

Our previous study showed that atropine significantly inhibited the sustained relaxation induced by electrical field stimulation (EFS) in the circular muscle strips prepared from the mouse antrum, and that pituitary adenylate cyclase activating peptide (PACAP) partially mediated the sustained relaxation. The muscarinic receptor subtype associated with the sustained relaxation was examined in the present study by using each muscarinic receptor subtype of knockout (KO) mice. EFS-induced sustained relaxation in the antrum prepared from M(2) receptor KO mice was significantly less than that of wild-type mice. Atropine failed to inhibit this relaxation. On the other hand, similar sustained relaxation and inhibitory effects of atropine to those of wild-type mice were observed in M(1), M(3) and M(4) receptor KO mice. Exogenously added PACAP-27 relaxed the antral strips of wild-type and M(2) receptor KO mice to a similar extent. Immunohistochemical study revealed that M(2) receptor immunoreactivity was localized with PACAP-immunoreactivity in enteric neurons within the antrum of wild-type mice. In contrast, atropine did not affect the EFS-induced sustained relaxation in the gastric fundus. These results suggest that M(2) receptors modulate the sustained relaxation, probably through the regulation of PACAP release, in the mouse antrum.

Relationships between neurokinin receptor-expressing interstitial cells of Cajal and tachykininergic nerves in the gut

The so-called interstitial cells of Cajal (ICC) are distributed throughout the muscle coat of the alimentary tract with characteristic intramural location and species-variations in structure and staining. Several ICC sub-types have been identified: ICC-DMP, ICC-MP, ICC-IM, ICC-SM. Gut motility is regulated by ICC and each sub-type is responsible for the electrical activities typical of each gut region and/or muscle layer. The interstitial position of the ICC between nerve endings and smooth muscle cells has been extensively considered. Some of these nerve endings contain tachykinins. Three distinct tachykinin receptors (NK1r, NK2r and NK3r) have been demonstrated by molecular biology. Each of them binds with different affinities to a series of tachykinins (SP, NKA and NKB). In the ileum, SP-immunoreactive (SP-IR) nerve fibers form a rich plexus at the deep muscular plexus (DMP), distributed around SP-negative cells, and ICC-DMP intensely express the SP-preferred receptor NK1r; conversely a faint NK1r-IR is detected on the ICC-MP and mainly after receptor internalization was induced by agonists. ICC-IM are never stained in laboratory mammals, while those of the human antrum are NK1r- IR. RT-PCR conducted on isolated ileal ICC-MP and gastric ICC-IM showed that these cells express NK1r and NK3r. Colonic ICC, except those in humans, do not express NK1r-IR, at least in resting conditions. Outside the gut, NK1r-IR cells were seen in the arterial wall and exocrine pancreas. In the mouse gut only, NK1r-IR is present in non-neuronal cells located within the intestinal villi, so-called myoid cells, which are c-kit-negative and alpha-smooth muscle actin-positive. Immunohistochemistry and functional studies confirmed that ICC receive input from SP-IR terminals, with differences between ICC sub-types. In the rat, very early after birth, NK1r is expressed by the ICC-DMP and SP by the related nerve varicosities. Studies on pathological conditions are few and those on mutant strains practically absent. It has only been reported that in the inflamed ileum of rats the NK1r-IR ICC-DMP disappear and that at the peak of inflammatory conditions ICC-MP are NK1r-IR. In the ileum of mice with a mutation in the W locus, ICC-DMP were seen to express c-kit-IR but not NK1-IR, and SP-IR innervation seems unchanged. In summary, there are distinct ICC populations, each of them under a different tachykininergic control and, likely, having different functions. Further studies are recommended at the aim of understanding ICC involvement in modulating/transmitting tachykininergic inputs.

Roles of PACAP and PHI as inhibitory neurotransmitters in the circular muscle of mouse antrum

Mediators of neurogenic responses of the gastric antrum were studied in wild-type and pituitary adenylate cyclase-activating polypeptide (PACAP) -knockout (KO) mice. Electrical field stimulation (EFS) to the circular muscle strips of the wild-type mouse antrum induced a triphasic response; rapid transient relaxation and contraction, and sustained relaxation that was prolonged for an extended period after the end of EFS. The transient relaxation and contraction were completely inhibited by L-nitroarginine and atropine, respectively. The sustained relaxation was significantly inhibited by a PACAP receptor antagonist, PACAP(6-38). The antral strips prepared from PACAP-KO mice unexpectedly exhibited a tri-phasic response. However, the sustained relaxation was decreased to about one-half of that observed in wild-type mice. PACAP(6-38) inhibited EFS-induced sustained relaxation (33.5% of control) in PACAP-KO mice. Anti-peptide histidine isoleucine (PHI) serum partially (the 30% inhibition) or significantly (the 60% inhibition) inhibited the sustained relaxations in the wild-type and PACAP-KO mice, respectively. The immunoreactivities to the anti-PACAP and anti-PHI serums were found in myenteric ganglia of the mouse antrum. These results suggest that nitric oxide and acetylcholine mediate the transient relaxation and contraction, respectively, and that PACAP and PHI separately mediate the sustained relaxation in the antrum of the mouse stomach.

Electrogastrography in patients with Chagas' disease

Electrogastrograghy (EGG) was performed in 33 patients with Chagas' disease and in 15 healthy volunteers-control group. The EGG was performed in two different periods: in fasting and postprandial. The EGG was submitted to a continuous spectral analysis. The following parameters were evaluated: % dominant frequency in spectral bands: normogastria (2-4 cpm), bradygastria (1-2 cpm), tachygastria (4-10 cpm) and duod/resp (10-15 cpm). EGG was considered normal if normogastria > 65% in both EGG periods. The chagasic group showed % normogastria significantly lower (basal, P < 0.01), % bradygastria (basal, P = 0.01) and % tachygastria (basal and postprandial, P =.001) significantly higher than the control group. EGG was normal in 14/15 (93%) in control group x 16/33 (53%) in chagasic group (P < 0.05). It was concluded that: 1) the prevalence of gastric dysrhythmias was higher in chagasic patients than in comparison to a control group 2) gastric dysrhythmias may be considered one of the abnormalities presented in the chagasic gastropathy.

About the presence of interstitial cells of Cajal outside the musculature of the gastrointestinal tract

Santiago Ramon y Cajal observed a special cell type that appeared to function as endstructures of the intrinsic nervous system in several organs. These cells were structurally and functionally further characterized in the gut musculature and named interstitial cells of Cajal (ICC). In recent years, interstitial cells have been identified in the vasculature, urinary tract, glands and other organs. Their morphologies and functions are just beginning to be clarified. It is likely that amongst them, subtypes will be discovered that warrant the classification of interstitial cells of Cajal. This "point of view" continues the discussion on the criteria that should be used to identify ICC outside the musculature of the gut.

Robotic Transperitoneal Detrusor Myotomy: Description of a Novel Technique

The da Vinci Surgical Robotic System has recently been added to the armamentarium of minimally invasive surgeon and has been shown to be useful to urologists in performing complex operations. We report the first case of detrusor myotomy performed using the da Vinci, describe the novel technique, and review the indications and published outcomes of detrusor myotomy to identify potential applications of this novel technique in patients with neurogenic bladder.

Motility patterns and distribution of interstitial cells of Cajal and nitrergic neurons in the proximal, mid- and distal-colon of the rat

The aim of this work was to study the patterns of spontaneous motility in the circular and longitudinal muscle strips and to characterize the distribution of c-kit positive interstitial cells of Cajal (ICCs) and nitrergic neurons (nNOS) in the proximal, mid- and distal-colon of Sprague-Dawley rats. We described two types of spontaneous contractions: high frequency (HF) and low frequency (LF) contractions, which were recorded in the presence of tetrodotoxin, suggesting a non-neurogenic origin. Regional differences were found in the motility patterns depending on the muscle layer and on the part of the colon studied. Muscle strips without submuscular plexus (SMP) showed only LF contractions. The density of ICCs was of the same magnitude along the extent of the colon: about 90-120 cells mm(-2) at Auerbach's plexus (AP) and 50-60 cells mm(-2) at the SMP. nNOS positive cells were found at the level of the AP and the major density was found in the mid-colon. Electrical field stimulation abolished LF but did not affect HF contractions. Our results indicate that HF contractions are due to the ICC network found associated with the submuscular plexus (ICC-SMP). The origin of LF contractions is still unknown.

Modelling gastrointestinal bioelectric activity

The development of an anatomically realistic biophysically based model of the human gastrointestinal (GI) tract is presented. A major objective of this work is to develop a modelling framework that can be used to integrate the physiological, anatomical and medical knowledge of the GI system. The anatomical model was developed by fitting derivative continuous meshes to digitised data taken from images of the visible man. Structural information, including fibre distributions of the smooth muscle layers and the arrangement of the networks of interstitial cells of Cajal, were incorporated using published information. A continuum modelling framework was used to simulate electrical activity from the single cell to the whole organ and body. Also computed was the external magnetic field generated from the GI electrical activity. The set of governing equations were solved using a combination of numerical techniques. Activity at the (continuum) cell level was solved using a high-resolution trilinear finite element procedure that had been defined from the previously fitted C1 continuous anatomical mesh. Multiple dipolar sources were created from the excitation waves which were embedded within a coupled C1 continuous torso model to produce both the cutaneous electrical field and the external magnetic field. Initial simulations were performed using a simplified geometry to test the implementation of the numerical solution procedure. The numerical procedures were shown to rapidly converge with mesh refinement. In the process of this testing, errors in a long standing analytic solution were identified and are corrected in Appendix B. Results of single cell activity were compared to published results illustrating that the key features of the slow wave activity were successfully replicated. Simulations using a two-dimensional slice through the gastric wall produced slow wave activity that agreed with the known frequency and propagation characteristics. Three-dimensional simulations were also performed using the full stomach mesh and results illustrated the slow wave propagation throughout the stomach musculature.

Ultrastructural changes in the interstitial cells of Cajal and gastric dysrhythmias in mice lacking full-length dystrophin (mdx mice)

At least two populations of c-kit positive interstitial cells of Cajal (ICC) lie in the gastric wall, one located at the myenteric plexus level has a pace-making function and the other located intramuscularly is intermediary in the neurotransmission and regenerates the slow waves. Both of these ICC sub-types express full-length dystrophin. Mdx mice, an animal model lacking in full-length dystrophin and used to study Duchenne muscular dystrophy (DMD), show gastric dismotilities. The aim of the present study was to verify in mdx mice whether: (i) gastric ICC undergo morphological changes, through immunohistochemical and ultrastructural analyses; and (ii) there are alterations in the electrical activity, using intracellular recording technique. In control mice, ICC sub-types showed heterogeneous ultrastructural features, either intramuscularly or at the myenteric plexus level. In mdx mice, all of the ICC sub-types underwent important changes: coated vesicles were significantly more numerous and caveolae significantly fewer than in control; moreover, cytoskeleton and smooth endoplasmic reticulum were reduced and mitochondria enlarged. c-Kit-positivity and integrity of the ICC networks were maintained. In the circular muscle of normal mice slow waves, which consisted of initial and secondary components, occurred with a regular frequency. In mdx mice, slow waves occurred in a highly dysrhythmic fashion and they lacked a secondary component. We conclude that the lack of the full-length dystrophin is associated with ultrastructural modifications of gastric ICC, most of which can be interpreted as signs of new membrane formation and altered Ca(2+) handling, and with defective generation and regeneration of slow wave activity.

[Networks of pacemaker cells for gastrointestinal motility]

In the wall of the digestive tract, there are pacemaker and conduction systems which can be compared with those in the heart. The introduction of c-Kit as a specific marker of the cells, ICCs, have dramatically clarified morphological and functional understanding of the cells. Mutant animals that lack c-Kit lose or decrease intestinal motility. Four classes of ICCs have been identified and these are distributed along the digestive tract in an organ- and tissue-specific manner: 1) IC-MY locate along the myenteric plexus; 2) IC-DMP, along the deep muscular plexus of small intestine; 3) IC-SMP, along the interface between the submucosa and circular muscle layer of large intestine; and 4) IC-IM, within the muscular layer of the stomach and large intestine. Basically, IC-MY and IC-SMP have pacemaker functions, whereas IC-DMP and IC-IM link signals between the enteric nervous system and smooth muscle cells (SMC). All classes of the cells are connected by gap junctions. Immunocytochemical observations using specific antibodies against various gap junction proteins, connexins (Cx), revealed that Cx43 was localized in the gap junctions between SMC and ICCs, whereas Cx45 was specifically expressed in IC-DMP as it is in the cardiac conduction systems. Mutant animals that we produced enabled us to show cells expressing Cx45 mRNA by replacing the Cx45 locus with a LacZ reporter gene and revealed that most of SMC express Cx45, where so far gap junctions were not demonstrated by electron microscopy or immunocytochemistry, probably due to their small size.

Protein kinases expressed by interstitial cells of Cajal

Interstitial cells of Cajal (ICC) are involved in the generation of electrical rhythmicity of intestinal muscle and in the transduction of neural inputs in the gut. Although the expression of receptors for neurotransmitters and hormones and some second messengers have been investigated in ICC, the protein kinases present in these cells have not been well documented. This study has demonstrated the immunohistochemical localisation of PKA, PKC gamma and PKC theta in ICC that were identified by the known ICC marker, c-Kit, in the guinea-pig gut. Other PKCs, PKC alpha, beta, delta, epsilon, eta, iota and lambda, and Ca(2+)-calmodulin-dependent protein kinase II were not localised in ICC. Double labelling studies were conducted on longitudinal muscle-myenteric plexus and external muscle-myenteric plexus preparations of the oesophagus, stomach (fundus, corpus and antrum), duodenum, distal ileum, caecum, proximal and distal colon, and rectum. The three protein kinases were detected in c-Kit-immunoreactive ICC at the level of the myenteric plexus (IC-MY), in the muscle (IC-IM) and at the level of the deep muscular plexus (IC-DMP) in the small intestine. PKA was found in over 90% of IC-IM in all regions examined, and in over 90% of IC-MY in the gastric body and antrum and throughout the small and large intestines. PKC gamma was in the majority of ICC in the gastric body and antrum and in the small intestine, but was largely absent from ICC in the oesophagus, proximal stomach and large intestine. PKC theta occurred in the majority of ICC in all regions except the rectum. The intensity of staining was greatest for PKA, with PKC gamma giving comparatively weak labelling of ICC. PKA was also detected in myenteric neurons, smooth muscle, macrophages and fibroblast-like cells. PKC gamma labelling occurred in large, multipolar neurons throughout the small and large intestine, as well as in lymph vessels and in capillaries. It is concluded that PKA, PKC gamma and PKC theta are all present in ICC, with the differences in their localisations suggesting specific roles for each in ICC function.

Distribution of heme oxygenase-2 in nerves and interstitial cells of Cajal in the normal pylorus and in infantile hypertrophic pyloric stenosis

CONTEXT

Interstitial cells of Cajal (ICCs) are pacemaker cells, which are of fundamental importance in regulating gastrointestinal motility. Recent evidence suggests that carbon monoxide is a neurotransmitter involved in neurotransmission between ICC and smooth muscle cells. Heme oxygenase-2 (HO-2) is the major physiological mechanism for the generation of carbon monoxide in the enteric nervous system.

OBJECTIVE

To investigate the immunocolocalization of HO-2 and ICCs in the normal pylorus and in infantile hypertrophic pyloric stenosis (IHPS).

DESIGN

Specimens from 18 infants with IHPS and 8 control specimens were examined using double-immunostaining with c-Kit and HO-2 antibodies. The immunolocalization was detected with the help of confocal laser scanning microscopy.

RESULTS

Abundant HO-2 immunoreactivity was found in ICCs in the smooth muscle layer of normal pylorus. There was a decrease in the number of ICCs and lack of HO-2 immunoreactivity in ICCs in IHPS.

CONCLUSIONS

The results of the present study provide the first evidence for the presence of HO-2 in ICCs in the normal human pylorus. The lack of ICCs and HO-2 in IHPS suggests impaired intracellular communication between ICCs and smooth muscle cells, contributing to motility dysfunction in IHPS.