Jan D. Huizinga

Assessment of gastric emptying using a low fat meal: establishment of international control values.

OBJECTIVE:The diagnosis of gastroparesis implies delayed gastric emptying. The diagnostic gold standard is scintigraphy, but techniques and measured endpoints vary widely among institutions. In this study, a simplified scintigraphic measurement of gastric emptying was compared to conventional gastric scintigraphic techniques and normal gastric emptying values defined in healthy subjects.METHODS:In 123 volunteers (aged 19–73 yr, 60 women and 63 men) from 11 centers, scintigraphy was used to assess gastric emptying of a 99Tc-labeled low fat meal (egg substitute) and percent intragastric residual contents 60, 120, and 240 min after completion of the meal. In 42 subjects, additional measurements were taken every 10 min for 1 h. In 20 subjects, gastric emptying of a 99Tc-labeled liver meal was compared with that of the 99Tc-labeled low fat meal.RESULTS:Median values (95th percentile) for percent gastric retention at 60, 120, and 240 min were 69% (90%), 24% (60%) and 1.2% (10%) respectively. A power exponential model yielded similar emptying curves and estimated T50 when using images only taken at 1, 2 and 4 h, or with imaging taken every 10 min. Gastric emptying was initially more rapid in men but was comparable in men and women at 4 h; it was faster in older subjects (p < 0.05) but was independent of body mass index.CONCLUSIONS:This multicenter study provides gastric emptying values in healthy subjects based on data obtained using a large sample size and consistent meal and methodology. Gastric retention of >10% at 4 h is indicative of delayed emptying, a value comparable to those provided by more intensive scanning approaches. Gastric emptying of a low fat meal is initially faster in men but is comparable in women at 4 h; it is also faster in older individuals but is independent of body mass.

The anxiolytic effect of Bifidobacterium longum NCC3001 involves vagal pathways for gut–brain communication

Background  The probiotic Bifidobacterium longum NCC3001 normalizes anxiety‐like behavior and hippocampal brain derived neurotrophic factor (BDNF) in mice with infectious colitis. Using a model of chemical colitis we test whether the anxiolytic effect of B. longum involves vagal integrity, and changes in neural cell function.

Interstitial cells of Cajal direct normal propulsive contractile activity in the mouse small intestine

BACKGROUND & AIMS Interstitial cells of Cajal (ICC) have been linked to the generation of intestinal pacemaker activity, but their role in in vivo motor dysfunction is unclear. In this study, we investigated the hypothesis that ICC play a role in the generation of distention-induced peristalsis using W/Wv mice that lack ICC associated with Auerbachs plexus. METHODS Radiological observations were made of the movement of contrast fluid through the proximal small intestine. Electrical activities were recorded in the external muscle layers. In addition, intraluminal pressure changes were recorded in isolated intestinal segments. RESULTS In control mice, after gavage of 0.5 mL of barium sulfate in the stomach, the contrast fluid moved through the proximal small intestine in peristaltic waves at approximately 47 times a minute, propagating aborally at approximately 2 cm/s. Electrical slow waves and intraluminal pressure waves were synchronized at similar frequencies and propagation velocities. In W/Wv mice, such regular peristaltic waves were not observed. Action potentials and contractions appeared random, and contents moved back and forth in an irregular manner. The net propulsive effect of contractile activity in W/Wv mutant mice was much weaker than that in controls. CONCLUSIONS Slow wave controlled peristalsis occurs in the normal proximal small intestine upon gastric emptying of a semiliquid. This motor pattern is absent in W/Wv mice that lack ICC.

Developmental origin and Kit-dependent development of the interstitial cells of Cajal in the mammalian small intestine

Interstitial cells of Cajal (ICCs) form a network of cells between the external longitudinal and circular muscle layers at the level of the Auerbachs plexus in the mammalian small intestine. These cells express the Kit receptor tyrosine kinase and are essential for intestinal pacemaker activity. W mutant mice carrying structural mutations in the Kit gene lack both the network of ICCs and intestinal pacemaker activity. We were interested in the developmental origin of the cells that make up the network of ICCs. In addition, the specific stages of ICC development that require a functional Kit receptor have not been characterized. We show that ICCs originate from mesenchymal progenitor cells that coexpress both Kit and smooth muscle myosin heavy chain, a marker specific for smooth muscle, during embryogenesis. ICC and longitudinal smooth muscle lineages begin to diverge late in gestation. Embryos homozygous for the regulatory Wbanded (Wbd) mutation do not express Kit in these mesenchymal progenitor cells. Nevertheless, Wbd/Wbd mice display a normal network of ICCs and normal smooth muscle layers at postnatal day 5 (p5). Adult Wbd/Wbd mice lack a functional ICC network and intestinal pacemaker activity due to a failure of the ICCs to increase in numbers after p5.  These data suggest a common developmental origin of the ICCs and the longitudinal smooth muscle layers in the mammalian small intestine and show that Kit expression is necessary for the postnatal development and proliferation of ICCs but not for the initial cell lineage decision toward an ICC fate during embryogenesis or for smooth muscle development. Dev. Dyn. 1998;211:60‐71.

Lactobacillus reuteri enhances excitability of colonic AH neurons by inhibiting calcium-dependent potassium channel opening

Probiotics are live non‐pathogenic commensal organisms that exert therapeutic effects in travellers’ diarrhea, irritable bowel syndrome and inflammatory bowel disease. Little is known about mechanisms of action of commensal bacteria on intestinal motility and motility‐induced pain. It has been proposed that probiotics affect intestinal nerve function, but direct evidence for this has thus far been lacking. We hypothesized that probiotic effects might be mediated by actions on colonic intrinsic sensory neurons. We first determined whether sensory neurons were present in rat colon by their responses to chemical mucosal stimulation and identified them in terms of physiological phenotype and soma morphotype. Enteric neuron excitability and ion channel activity were measured using patch clamp recordings. We fed 109Lactobacillus reuteri (LR) or vehicle control to rats for 9 days. LR ingestion increased excitability (threshold for evoking action potentials) and number of action potentials per depolarizing pulse, decreased calcium‐dependent potassium channel (IKCa) opening and decreased the slow afterhyperpolarization (sAHP) in sensory AH neurons, similar to the IKCa antagonists Tram‐34 and clotrimazole. LR did not affect threshold for action potential generation in S neurons. Our results demonstrate that LR targets an ion channel in enteric sensory nerves through which LR may affect gut motility and pain perception.

Gut peristalsis is governed by a multitude of cooperating mechanisms.

Peristaltic motor activity of the gut is an essential activity to sustain life. In each gut organ, a multitude of overlapping mechanisms has developed to acquire the ability of coordinated contractile activity under a variety of circumstances and in response to a variety of stimuli. The presence of several simultaneously operating control systems is a challenge for investigators who focus on the role of one particular control activity since it is often not possible to decipher which control systems are operating or dominant in a particular situation. A crucial advantage of multiple control systems is that gut motility control can withstand injury to one or more of its components. Our efforts to increase understanding of control mechanism are not helped by recent attempts to eliminate proven control systems such as interstitial cells of Cajal (ICC) as pacemaker cells, or intrinsic sensory neurons, nor does it help to view peristalsis as a simple reflex. This review focuses on the role of ICC as slow-wave pacemaker cells and places ICC into the context of other control mechanisms, including control systems intrinsic to smooth muscle cells. It also addresses some areas of controversy related to the origin and propagation of pacemaker activity. The urge to simplify may have its roots in the wish to see the gut as a consequence of a single perfect design experiment whereas in reality the control mechanisms of the gut are the messy result of adaptive changes over millions of years that have created complementary and overlapping control systems. All these systems together reliably perform the task of moving and mixing gut content to provide us with essential nutrients.

Non-invasive multimodal functional imaging of the intestine with frozen micellar naphthalocyanines

Overview There is a need for safer and improved methods for non-invasive imaging of the gastrointestinal tract. Modalities based on X-ray radiation, magnetic resonance and ultrasound suffer from limitations with respect to safety, accessibility or lack of adequate contrast. Functional intestinal imaging of dynamic gut processes has not been practical using existing approaches. Here, we report the development of a family of nanoparticles that can withstand the harsh conditions of the stomach and intestine, avoid systemic absorption, and give rise to good optical contrast for photoacoustic imaging. The hydrophobicity of naphthalocyanine dyes was exploited to generate purified ~20 nm frozen micelles, which we call nanonaps, with tunable and large near-infrared absorption values (>1000). Unlike conventional chromophores, nanonaps exhibited non-shifting spectra at ultrahigh optical densities and, following oral administration in mice, passed safely through the gastrointestinal tract. Non-invasive, non-ionizing photoacoustic techniques were used to visualize nanonap intestinal distribution with low background and remarkable resolution with 0.5 cm depth, and enabled real-time intestinal functional imaging with ultrasound co-registration. Positron emission tomography following seamless nanonap radiolabelling allowed complementary whole body imaging.

Inflammation modulates in vitro colonic myoelectric and contractile activity and interstitial cells of Cajal

Inflammation suppresses phasic contractile activity in vivo. We investigated whether inflammation also suppresses in vitro phasic contractile activity and, if so, whether this could in part be due to the alteration of specific slow wave characteristics and morphology of the interstitial cells of Cajal (ICC). Circular muscle strips were obtained from normal and inflamed distal canine colon. Inflammation was induced by mucosal exposure to ethanol and acetic acid. The amplitudes of spontaneous, methacholine-induced, substance P-induced, and electrical field stimulation-induced contractions were smaller in inflamed muscle strips than in normal muscle strips. Inflammation reduced the resting membrane potential and the amplitude and duration of slow waves in circular muscle cells. Inflammation did not affect the amplitude of inhibitory junction potentials but did decrease their duration. Ultrastructural studies showed expansion of the extracellular space between circular muscle cells, reduction in the density of ICC and associated neural structures, damage to ICC processes, vacuolization of their cytoplasm, and blebbings of the plasma membrane. We conclude that inflammation-induced alterations of slow wave characteristics contribute to the suppression of phasic contractions. These alterations may, in part, be due to the damage to ICC. Inflammation impairs both the myogenic and neural regulation of phasic contractions.

Physiology, Injury, and Recovery of Interstitial Cells of Cajal: Basic and Clinical Science

In the last 15 years, our understanding of the cellular basis of gastrointestinal function has been altered irreversibly by the discovery that normal gastrointestinal (GI) motility requires interstitial cells of Cajal (ICC). Research in this relatively short time period has modified our original concept that the core unit that controls motility is made up of nerves and smooth muscle, to one that now includes ICC. This concept has now expanded to beyond the GI tract, suggesting that it may be a fundamental property of the regulation of smooth muscle function that requires rhythmic contraction. ICC are distributed throughout the GI tract, have important functions in the control of GI motility, and are often abnormal in diseased states. Recently, significant steps forward have been made in our understanding of the physiology of ICC as well as mechanisms of injury and recovery. These advances are the focus of this review. The Physiology of ICC Unique motor patterns are intrinsic to every organ of the GI tract, which suit their functions related to mixing, absorption, and anally directed movement. The ICC are an integral part of the control of these motor activities. The distribution of ICC throughout the musculature is associated with nerve structures. Myenteric pacemaker ICC surround the myenteric or Auerbach’s plexus and intramuscular ICC are associated with nerve varicosities throughout the muscle layers (Figures 1 and 2). Other subpopulations of ICC are associated with nonganglionated plexuses of nerve varicosities at the inner borders of the circular muscle layers in the intestine and colon (Figures 1 and 2). The best understood function is that of pacemaker activity in the stomach and small intestine where the ICC generate a periodic depolarization at a characteristic frequency in each of these organs that is called the slow wave or pacemaker activity.

Severe idiopathic gastroparesis due to neuronal and interstitial cells of Cajal degeneration: pathological findings and management

Delayed gastric emptying can be due to muscular, neural, or humoral abnormalities. In the absence of an identified cause, gastroparesis is labelled as idiopathic. We present the case of a patient with severe idiopathic gastroparesis. Pharmacological approaches failed, as well as reduction in gastric emptying resistance with pyloric injection of botulinum toxin and pyloroplasty. Therefore, subtotal gastrectomy was performed. Histological and immunohistochemical study of the resected specimen showed hypoganglionosis, neuronal dysplasia, and a marked reduction in both myenteric and intramuscular interstitial cells of Cajal. To our knowledge, this is the first time these rare histological findings have been described in a patient with idiopathic gastroparesis.