Esophageal motility

Electrokinesiographic Study of Oropharyngeal Swallowing in Neurogenic Dysphagia

Electrokinesiographic study of swallowing (EKSS) can be useful for the assessment of patients with suspected or overt neurogenic dysphagia. EKSS consists of multichannel recording of the electromyographic (EMG) activity of the suprahyoid/submental muscle complex (SHEMG), the EMG activity of the cricopharyngeal muscle (CPEMG), and the laryngopharyngeal mechanogram (LPM). The LPM is an expression of the mechanical changes that the laryngopharyngeal structures undergo during the pharyngeal phase of swallowing. This method allows detailed evaluation of the magnitude, duration and temporal relations of the different events that characterize oropharyngeal swallowing, and thus in-depth exploration both of physiological deglutition mechanisms and of pathophysiological features of swallowing in neurogenic dysphagia. Furthermore, EKSS can guide dysphagia treatment strategies, allowing identification of optimal solutions for single patients. For instance, CPEMG recording can identify incomplete or absent relaxation of the upper esophageal sphincter during the pharyngeal phase of swallowing, thus suggesting a therapeutic approach based on botulinum toxin injection into the cricopharyngeal muscle. More recently, the 'shape' of SHEMG and the reproducibility of both SHEMG and LPM over repeated swallowing acts have been implemented as novel electrokinesiographic parameters. These measures could be valuable for straightforward non-invasive investigation of dysphagia severity and response to dysphagia treatment in clinical practice.

Esophageal Bolus Domain Pressure and Peristalsis Associated With Experimental Induction of Esophagogastric Junction Outflow Obstruction

Background/Aims

Intrabolus pressures are important for esophageal bolus transport and may detect obstructed bolus flow. This study measured the effect esophageal outflow obstruction experimentally induce by a leg-lift protocol.

Methods

Twenty-five gastroesophageal reflux disease patients referred for esophageal manometry and a normal motility diagnosis were included. Supine liquid swallows were tested. Leg-lift protocol generated esophageal outflow obstruction by increasing abdominal pressure. Esophageal pressure topography and intrabolus pressure metrics were calculated. These included, (1) mid-domain bolus distension pressure during esophageal emptying (DPE, mmHg) and (2) ramp pressure (mmHg/sec), generated by compression of the bolus between the peristaltic contraction and esophagogastric junction (EGJ).

Results

EGJ relaxation pressure was increased by leg-lift from 13 (11-17) to 19 (14-30) mmHg (P < 0.005) and distal contractile integral also increased from 1077 (883-1349) to 1620 (1268-2072) mmHg∙cm∙sec (P < 0.001) as a physiological response to obstruction. All bolus pressures were increased by leg lift; DPE increased from 17 (15-20) to 27 (19-32) mmHg (P < 0.001), and ramp pressure increased from 3 (1-4) to 5 (2-9) mmHg/sec (P < 0.05).

Conclusion

Measuring pressures within the intrabolus domain can quantify changes related to obstruction to outflow and may serve as adjunct measures for confirming a diagnosis EGJ outflow obstruction.

Interstitial cells of Cajal and human colon motility in health and disease

Our understanding of human colonic motility, and autonomic reflexes that generate motor patterns, has increased markedly through high-resolution manometry. Details of the motor patterns are emerging related to frequency and propagation characteristics that allow linkage to interstitial cells of Cajal (ICC) networks. In studies on colonic motor dysfunction requiring surgery, ICC are almost always abnormal or significantly reduced. However, there are still gaps in our knowledge about the role of ICC in the control of colonic motility and there is little understanding of a mechanistic link between ICC abnormalities and colonic motor dysfunction. This review will outline the various ICC networks in the human colon and their proven and likely associations with the enteric and extrinsic autonomic nervous systems. Based on our extensive knowledge of the role of ICC in the control of gastrointestinal motility of animal models and the human stomach and small intestine, we propose how ICC networks are underlying the motor patterns of the human colon. The role of ICC will be reviewed in the autonomic neural reflexes that evoke essential motor patterns for transit and defecation. Mechanisms underlying ICC injury, maintenance, and repair will be discussed. Hypotheses are formulated as to how ICC dysfunction can lead to motor abnormalities in slow transit constipation, chronic idiopathic pseudo-obstruction, Hirschsprung's disease, fecal incontinence, diverticular disease, and inflammatory conditions. Recent studies on ICC repair after injury hold promise for future therapies.

Origin and role of the cerebrospinal fluid bidirectional flow in the central canal

Circulation of the cerebrospinal fluid (CSF) contributes to body axis formation and brain development. Here, we investigated the unexplained origins of the CSF flow bidirectionality in the central canal of the spinal cord of 30 hpf zebrafish embryos and its impact on development. Experiments combined with modeling and simulations demonstrate that the CSF flow is generated locally by caudally-polarized motile cilia along the ventral wall of the central canal. The closed geometry of the canal imposes the average flow rate to be null, explaining the reported bidirectionality. We also demonstrate that at this early stage, motile cilia ensure the proper formation of the central canal. Furthermore, we demonstrate that the bidirectional flow accelerates the transport of particles in the CSF via a coupled convective-diffusive transport process. Our study demonstrates that cilia activity combined with muscle contractions sustain the long-range transport of extracellular lipidic particles, enabling embryonic growth.

In vitro constitution of esophageal muscle tissue with endocyclic and exolongitudinal patterns

Smooth muscle tissue is the main functional structure of the esophagus and comprises of the endocircular and exolongitudinal muscle layers. To construct a tissue engineered smooth muscle by mimicking the esophageal muscle tissue, we have designed a silicon wafer where a daughter mold was prepared using soft PDMS. The daughter mold was, in turn, casted with poly(ester urethane) (PU) solution to fabricate the tissue scaffolds. The casted PU scaffolds were available in two configurations. Prototype 1 (P1) have microchannels of 100 μm width and discontinuous channel wall with gaps of 30 μm at regular intervals. Prototype 2 (P2) have microchannels of 200 μm width and continuous channel walls. The wall thickness and depth of the microchannels are 30 μm. A tubular scaffold with micropattern P1 in the lumen and micropattern P2 on the exterior was fabricated with the aim of regenerating muscle tissue with endocircular and exolongitudinal muscle architecture. After grafting with natural silk fibroin (SF), the PU micropatterned scaffold demonstrated the ability to promote smooth muscle cell (SMC) growth and differentiation; differentiation is believed to contribute to maintain the contractile function of SMCs. Results from the preliminary in vivo test revealed that the tubular scaffold patterned with microchannels is capable of supporting esophageal muscle regeneration.

Brain stem control of the phases of swallowing

The phases of swallowing are controlled by central pattern-generating circuitry of the brain stem and peripheral reflexes. The oral, pharyngeal, and esophageal phases of swallowing are independent of each other. Although central pattern generators of the brain stem control the timing of these phases, the peripheral manifestation of these phases depends on sensory feedback through reflexes of the pharynx and esophagus. The dependence of the esophageal phase of swallowing on peripheral feedback explains its absence during failed swallows. Reflexes that initiate the pharyngeal phase of swallowing also inhibit the esophageal phase which ensures the appropriate timing of its occurrence to provide efficient bolus transport and which prevents the occurrence of multiple esophageal peristaltic events. These inhibitory reflexes are probably partly responsible for deglutitive inhibition. Three separate sets of brain stem nuclei mediate the oral, pharyngeal, and esophageal phases of swallowing. The trigeminal nucleus and reticular formation probably contain the oral phase pattern-generating neural circuitry. The nucleus tractus solitarius (NTS) probably contains the second-order sensory neurons as well as the pattern-generating circuitry of both the pharyngeal and esophageal phases of swallowing, whereas the nucleus ambiguus and dorsal motor nucleus contain the motor neurons of the pharyngeal and esophageal phases of swallowing. The ventromedial nucleus of the NTS may govern the coupling of the pharyngeal phase to the esophageal phase of swallowing.

Properties of inhibitory junctional transmission in smooth muscle of the guinea pig lower esophageal sphincter

Inhibitory neurotransmission in guinea pig lower esophageal sphincter (LES) muscles was investigated by using electrophysiological methods. Transmural nerve stimulation (TNS) initiated an inhibitory junction potential (i.j.p.); the amplitude increased 35% by atropine (10(-6) M) and converted to a muscarinic excitatory junction potential (e.j.p.) by apamin (10(-7) M) plus Nomega-nitro-L-arginine (L-NNA, 10(-5) M). In atropinized tissue, the i.j.p. amplitude was reduced 58% by guanethidine (5 x 10(-6) M), 41% by L-NNA (10(-5) M), 57% by suramin (10(-4) M), and it was abolished by apamin (10(-7) M), suggesting that this potential was produced by ATP and nitric oxide (NO) released from adrenergic and nitrergic nerves, respectively, through the activation of Ca2+-sensitive K+ channels. Hyperpolarizations produced by ATP and NO were inhibited by apamin. The i.j.p. amplitude was reduced after desensitizing the membrane with ATP. In atropinized tissue, TNS produced a relaxation that was reduced 15% by guanethidine (5 x 10(-6) M), 50% by L-NNA (10(-5) M), and 30% by apamin (10(-7) M). Thus the LES receives cholinergic excitatory and adrenergic and nitrergic inhibitory innervations; the latter two components contribute evenly to the i.j.p. generation. The relaxation is mainly produced by NO in a membrane potential-independent way.

A new technique for measuring lower oesophageal sphincter competence in patients

Oesophageal sphincter measurements were carried out on 80 patients using the stationary pull through technique; Normals (n = 21), Nutcracker (n = 12), Refluxers (n = 21), and Barrett's (n = 26). Sphincter pressure (LOSP), abdominal length of sphincter, and overall sphincter length were measured. The Sphincter Function Index (SFI) was calculated as the product of sphincter pressure and percentage sphincter length (AL) exposed to abdominal pressure. Patients also had routine endoscopy and 24 hour pHmetry. SFI values discriminated between all four groups. LOSP was significantly different for Barrett's (p < 0.01) and Nutcracker (p < 0.01) compared to normals. AL was significant for Refluxers (p < 0.001) and Barrett's (p < 0.001) compared to normals. SFI gives better discrimination than LOSP or AL alone and may be useful in evaluating the response to treatment.