Peristaltic Waves Research Articles

Optogenetic control of gut movements reveals peristaltic wave-mediated induction of cloacal contractions and reactivation of impaired gut motility.

Gut peristalsis, recognized as a wave-like progression along the anterior-posterior gut axis, plays a pivotal role in the transportation, digestion, and absorption of ingested materials. The embryonic gut, which has not experienced ingested materials, undergoes peristalsis offering a powerful model for studying the intrinsic mechanisms underlying the gut motility. It has previously been shown in chicken embryos that acute contractions of the cloaca (an anus-like structure) located at the posterior end of the hindgut are tightly coupled with the arrival of hindgut-derived waves. To further scrutinize the interactions between hindgut and cloaca, we here developed an optogenetic method that produced artificial waves in the hindgut. A variant form of channelrhodopsin-2 (ChR2(D156C)), permitting extremely large photocurrents, was expressed in the muscle component of the hindgut of chicken embryos using Tol2-mediated gene transfer and in ovo electroporation techniques. The D156C-expressing hindgut responded efficiently to local pulses of blue light: local contractions emerge at an ectopic site in the hindgut, which were followed by peristaltic waves that reached to the endpoint of the hindgut. Markedly, the arrival of the optogenetically induced waves caused concomitant contractions of the cloaca, revealing that the hindgut-cloaca coordination is mediated by signals triggered by peristaltic waves. Moreover, a cloaca undergoing pharmacologically provoked aberrant contractions could respond to pulsed blue light irradiation. Together, the optogenetic technology developed in this study for inducing gut peristalsis paves the way to study the gut movement and also to explore therapeutic methodology for peristaltic disorders.

Novel Diagnostic Techniques in the Evaluation of Gastroesophageal Reflux Disease (GERD).

In our present clinical paradigm, patient symptoms and presentation in the setting of traditional findings from endoscopy (erosive esophagitis, Barrett's esophagus, reflux-mediated stenosis), esophageal high-resolution manometry, and/or ambulatory reflux monitoring (distal esophageal acid exposure time, numbers of reflux events, reflux-symptom association) guide the care of patients with suspected GERD. However, novel metrics and techniques acquired from or performed at endoscopy, manometry, or pH-impedance monitoring, beyond conventional evaluation, are of great interest to the gastroenterology community given the frequent (and sometimes challenging) presentation of suspected GERD. These novel and evolving diagnostic approaches have the potential to enhance the evaluation of these patients and optimize their management. In this invited review, we discuss the present evidence and potential clinical utility of selected GERD metrics and techniques of interest at endoscopy (dilated intercellular spaces, mucosal impedance), manometry (contractile integral, impedance analysis, straight leg raise, multiple rapid swallow maneuvers), and reflux monitoring (mean nocturnal baseline impedance, post-reflux swallow-induced peristaltic wave indices), and how these tools may be most optimally adopted and utilized for clinical care (Fig.1).

The Effect of Uterine Contractions on Fertility Outcomes in Frozen Embryo Transfer Cycles: A Cohort Study.

The relationship between uterine peristalsis before embryo transfer and the success of assisted reproductive techniques (ARTs) has not been properly investigated. In this study, the effect of uterine contractions on embryo implantation in frozen embryo transfer (FET) cycles was investigated to determine whether the frequency of uterine contractions can be used as a quantitative marker to assess endometrial receptivity. In this cohort study of 68 eligible FET candidates, one hour before embryo transfer (ET), frequency of uterine contractions was assessed with transvaginal ultrasonography. Patients were followed up for 20 weeks. The association between FET outcomes including clinical pregnancy, abortion, and ectopic pregnancy with uterine contractions was evaluated. Binary logistic regression was conducted to test the association between clinical pregnancy outcomes in different groups. The p<0.05 were considered statistically significant. Of 68 patients, 25 (36.8%) experienced clinical pregnancy. Multiple logistic regression for omitted confounders (age, BMI, duration, type and cause of infertility) revealed that patients with uterine peristaltic wave frequency less than 2≤ wave/min had higher chance of successful pregnancy compared to those with ≥4 wave/min (odds ratio: 10.8; 95% confidence interval: 1.5-79.4, p=0.019). The Pearson's correlation showed a statistically significant relationship between the frequency of uterine contraction and endometrial thickness (r= 0.42, p=0.002). Patients with uterine peristalsis of <4.0 wave/min before embryo transfer had a higher chance of successful implantation and pregnancy compared with those with higher contraction frequencies. It seems that measuring uterine contraction frequency before embryo transfer might help to predict pregnancy outcomes.

Numerical simulation of peristalsis to study co-localization and intestinal distribution of a macromolecular drug and permeation enhancer

In this work, simulations of intestinal peristalsis are performed to investigate the intraluminal transport of macromolecules (MMs) and permeation enhancers (PEs). Properties of insulin and sodium caprate (C10) are used to represent the general class of MM and PE molecules. Nuclear magnetic resonance spectroscopy was used to obtain the diffusivity of C10, and coarse-grain molecular dynamics simulations were carried out to estimate the concentration-dependent diffusivity of C10. A segment of the small intestine with the length of 29.75 cm was modeled. Peristaltic speed, pocket size, release location, and occlusion ratio of the peristaltic wave were varied to study the effect on drug transport. It was observed that the maximum concentration at the epithelial surface for the PE and the MM increased by 397 % and 380 %, respectively, when the peristaltic wave speed was decreased from 1.5 to 0.5 cm s−1. At this wave speed, physiologically relevant concentrations of PE were found at the epithelial surface. However, when the occlusion ratio is increased from 0.3 to 0.7, the concentration approaches zero. These results suggest that a slower-moving and more contracted peristaltic wave leads to higher efficiency in transporting mass to the epithelial wall during the peristalsis phases of the migrating motor complex.

Analysis of Joule heating and Hall effects on the electro-osmotic flow of third-grade nanofluid regulated by peristaltic waves through a porous medium with double diffusion

The current analysis is based on the third-grade nanofluid flow triggered by the combined effects of peristaltic pumping and an external electric field. The effects of double diffusion convection and viscous dissipation in nanofluids across a porous symmetric channel were explored. Thermal radiation, the Hall effect and Joule heating are the key phenomena discussed in the flow problem. The governing model is modified by using the Lubrication theory and Debye-Hückel linearization. A highly non-linear system of equations was solved by Mathematica software to scrutinize the effects of Joule heating, Hall effect, electro-osmotic velocity, Grashof numbers, thermophoresis, and Brownian motion on the flow characteristics. Brinkman number and the thermal radiation show opposite characteristics on the temperature profile.

Connective and magnetic effects in a curved wavy channel with nanoparticles under different waveforms

Abstract The present study describes the peristaltic flow of Jeffrey fluid with nanomaterial bounded under peristaltic waves in a curved channel. Silver (Ag) is the nanomaterial used for this purpose, and base fluid is water. The diversity of peristaltic waves is captured under four different wave profiles traveling along the curved channel. The consequences of heat generation and mass concentration are also taken. The problem is modeled under physical laws and then simplified using the lubrication technique. The obtained system is sketched in graphs directly using a numerical scheme. The physical outcomes of involved parameters on axial velocity, temperature variation, concentration profile, and streamline patterns are discussed in the last section.

Outcomes of Partial Slip on Double-Diffusive Convection on Peristaltic Waves of Johnson–Segalman Nanofluids Under the Impact of Inclined Magnetic Field

Outcomes of Partial Slip on Double-Diffusive Convection on Peristaltic Waves of Johnson–Segalman Nanofluids Under the Impact of Inclined Magnetic Field

Application of Artificial Intelligence in Measuring Novel pH-Impedance Metrics for Optimal Diagnosis of GERD

Novel metrics extracted from pH-impedance monitoring can augment the diagnosis of gastroesophageal reflux disease (GERD). Artificial intelligence (AI) is being widely used to improve the diagnostic capabilities of various diseases. In this review, we update the current literature regarding applications of artificial intelligence in measuring novel pH-impedance metrics. AI demonstrates high performance in the measurement of impedance metrics, including numbers of reflux episodes and post-reflux swallow-induced peristaltic wave index and, furthermore, extracts baseline impedance from the entire pH-impedance study. AI is expected to play a reliable role in facilitating measuring novel impedance metrics in patients with GERD in the near future.

BF2-Azadipyrromethene Fluorophores for Intraoperative Vital Structure Identification.

A series of mono- and bis-polyethylene glycol (PEG)-substituted BF2-azadipyrromethene fluorophores have been synthesized with emissions in the near-infrared region (700-800 nm) for the purpose of fluorescence guided intraoperative imaging; chiefly ureter imaging. The Bis-PEGylation of fluorophores resulted in higher aqueous fluorescence quantum yields, with PEG chain lengths of 2.9 to 4.6 kDa being optimal. Fluorescence ureter identification was possible in a rodent model with the preference for renal excretion notable through comparative fluorescence intensities from the ureters, kidneys and liver. Ureteral identification was also successfully performed in a larger animal porcine model under abdominal surgical conditions. Three tested doses of 0.5, 0.25 and 0.1 mg/kg all successfully identified fluorescent ureters within 20 min of administration which was sustained up to 120 min. 3-D emission heat map imaging allowed the spatial and temporal changes in intensity due to the distinctive peristaltic waves of urine being transferred from the kidneys to the bladder to be identified. As the emission of these fluorophores could be spectrally distinguished from the clinically-used perfusion dye indocyanine green, it is envisaged that their combined use could be a step towards intraoperative colour coding of different tissues.

The Modular Gait Design of a Soft, Earthworm-like Locomotion Robot Driven by Ultra-Low Frequency Excitation

In complex and extreme environments, such as pipelines and polluted waters, gait programming has great significance for multibody segment locomotion robots. The earthworm-like locomotion robot is a representative multibody bionic robot, which has the characteristics of low weight, multibody segments, and excellent movement performance under the designed gait. The body segment cell can realize large deformation under ultra-low frequency excitation. The multibody segment robot can locomote under ultra-low frequency excitation with appropriate shifts. In this paper, a modular gait design principle for a soft, earthworm-like locomotion robot is proposed. The driven modules defined by modular gait generation correspond to the peristaltic wave transmissions of the excitation in the robot for different modular gait modes. A locomotion algorithm is presented to simulate the locomotion of the earthworm-like robot under different locomotion gaits. Moreover, the locomotion speeds are obtained for different modular gait modes. The results show that locomotion speed is related to the original state of the body segments and modular gaits. As the initial actuated segments and driven modules (which correspond to the excitation frequency and shift) increase, faster movement speeds can be realized, which resolves the speed saturation of the earthworm-like robot. The proposed modular gait design method gives a new gait generation principle for the improvement of the locomotion performance of soft, earthworm-like robots.

Passive tracer transport in peristaltic pumping of non-Newtonian blood flow: A mathematical model

The large time behavior of passive contaminant in non-Newtonian peristaltic blood flow in a two-dimensional (2D) channel (capillary) has been examined in this paper. The power-law model is employed in order to highlight the non-Newtonian blood characteristic. The study was conducted using the Reynolds decomposition technique, which converts a 2D transport problem into a 1D transport model in which species concentration can be decomposed into sectional average concentration and variation from its mean value. For flow velocity, the same decomposition method is used. This allows the derivation of the dispersion coefficient and convection coefficient. Using Fick’s law, the advection–diffusion equation is modified by replacing these coefficients by their corresponding average values and analytical solutions for the mean concentration are derived. In the absence of peristalsis effects ([Formula: see text]), i.e., for the straight rigid channel, the dispersion coefficient is invariant along the channel length. With increasing modulation (peristaltic wave) parameter, [Formula: see text], there is a strong elevation in advection coefficient in the initial half of the channel with a subsequent suppression in the second half of the channel, indicating that the location in the channel strongly influences advection characteristics. Advection coefficient is significantly elevated with increment in power-law rheological index (for shear-thinning fluids, [Formula: see text]) across the channel length and exhibits an oscillatory nature due to the peristaltic waves. In the shear-thickening range ([Formula: see text]), with progressive increase in n, an increment in peristaltic modulation parameter, [Formula: see text], induces a marked reduction in the axially average relative advection coefficient. Dispersion coefficient is initially boosted along the early section of the channel with increment in modulation parameter whereas further long the channel this trend is reversed. Increasing aspect ratio and Péclet number consistently boost dispersion coefficient along the entire channel length. The study provides a solid benchmark for further generalized simulations with computational fluid dynamics.

Peristaltic pumping of Boron Nitride-Ethylene Glycol nanofluid through a complex wavy micro-channel under the effect of induced magnetic field and double diffusive

The main objective of this work is to present a comprehensive study that scrutinize the influence of DD convection and induced magnetic field on peristaltic pumping of Boron Nitride—Ethylene Glycol nanofluid flow through a vertical complex irregular microchannel. Experimental study showed that the nanofluid created by suspending Boron Nitride particles in a combination of Ethylene Glycol exhibited non-Newtonian characteristics. Further, the Carreau's fluid model provides accurate predictions about the rheological properties of BN-EG nanofluid. In order to imitate complicated peristaltic wave propagation conditions, sophisticated waveforms are forced at the walls. The essential properties of Brownian motion and thermophoresis phenomena are also included in simulating of heat equation as well as viscous dissipation. Mathematical simulation is performed by utilizing the lubrication approach. The resulting nonlinear coupled differential equation system is solved numerically using the built-in command (ND Solve function) in the Mathematica program. Numerical and pictorial evidence is used to illustrate the importance of various physiological features of flow quantities. The major findings demonstrated that the thermal resistance is observed to rise as the Soret and Dufour numbers increase, while the dissolvent concentration and nanoparticles volume fraction have the opposite effect.

On-therapy impedance-pH monitoring can efficiently characterize PPI-refractory GERD and support treatment escalation.

On-therapy impedance-pH monitoring is recommended in patients with documented GERD and PPI-refractory heartburn in order to establish whether the unremitting symptom is reflux-related or not. To define on-PPI cut-offs of impedance-pH metrics allowing proper interpretation of on-therapy impedance-pH monitoring. Blinded expert review of impedance-pH tracings performed during double-dosage PPI, prospectively collected from 150 GERD patients with PPI-refractory heartburn and 45 GERD patients with PPI-responsive heartburn but persisting extra-esophageal symptoms. Acid exposure time (AET), number of total refluxes (TRs), post-reflux swallow-induced peristaltic wave (PSPW) index, and mean nocturnal baseline impedance (MNBI) were assessed. On-PPI cut-offs were defined and evaluated with ROC analysis and the area under curve (AUC). All the four impedance-pH metrics significantly differed between PPI-refractory and PPI-responsive heartburn cases. At ROC analysis, AUC was 0.73 for AET, 0.75 for TRs, 0.81 for PSPW index, and 0.71 for MNBI; best cut-offs were ≥1.7% for AET, ≥45 for TRs, ≤36% for PSPW index, and ≤ 1847 Ω for MNBI; AUC of such cut-offs was 0.66, 0.71, 0.73, and 0.68, respectively. Analysis of PSPW index and MNBI added to assessment of AET and TRs significantly increased the yield of on-therapy impedance-pH monitoring in the PPI-refractory cohort (97% vs. 83%, p < 0.0001). Notably, suboptimal acid suppression as shown by AET ≥1.7% was detected in 43% of 150 PPI-refractory cases. We have defined on-PPI cut-offs of impedance-pH metrics by which comprehensive assessment of impedance-pH tracings, including analysis of PSPW index and MNBI can efficiently characterize PPI-refractory GERD and support treatment escalation.

Valveless Pumping at Low Reynolds Numbers

Pumping at low Reynolds number is a ubiquitously encountered feature, both in biological organisms and engineered devices. Generating net flow requires the presence of an asymmetry in the system, which traditionally comes from geometric flow rectifiers. Here, we study a valveless system of $N$ oscillating pumps in series, where the asymmetry comes not from the geometry but from time, that is the phase shifts between the pumps. Experimental and theoretical results are in very good agreement. We provide the optimal phase shifts leading to the maximal net flow in the continuous $N\rightarrow \infty$ limit, larger by 25\% than that of a traditional peristaltic sinusoidal wave. Our results pave the way for the design of more efficient microfluidic pumps.

Non–Linear Peristaltic Flow of Power-Law Fluid in the Tapered Asymmetric Channel

Abstract: The effect of non-uniform wall properties on the peristaltic flow of a power law fluid in an asymmetric channel is investigated under Long wavelength and low Reynolds number assumptions. The tapered channel asymmetry is produced by choosing the peristaltic wave train on non-uniform walls to have different amplitudes and phase. Exact solutions are established for the longitudinal velocity, stream function, and pressure gradient. The expression for an average rise in pressure is computed numerically by evaluating the numerical integration. The effect of the power-law nature of the fluid on trapping is studied in detail. Prominent features of the key parameters entering the present flow are also displayed, and important conclusions are pointed out.

An analysis to capture magnetic effects in esophagus walls under different waveforms

The presented work describes the flow of Jeffrey fluid in esophagus walls under different periodic waveforms. The gravitational effects in terms of mixed convection are retained. The diversity of peristaltic waves is captured by four different wave profiles traveling along the curved channel. Such considerations in the alimentary canal result in heat generation and fluid propagation. Hence, the consequences of heat generation and slip conditions are also taken. The flow stream is further set up with an externally applied magnetic field to regulate the fluid flow. The problem is modeled under physical laws and then simplified using lubrication techniques. The obtained system is then sketched in graphs directly using the numerical scheme. The result reveals that the rise in the Hartmann number leads to a decline in the velocity profile. The temperature profile can be enhanced by increasing the values of both the Hartmann number and the viscoelastic parameter.

Novel Impedance-pH Parameters in Pre-Bariatric Assessment of Patients: A Pilot Study.

Novel impedance-pH parameters, Mean Nocturnal Baseline Impedance (MNBI) and Post-Reflux Swallow-Induced Peristaltic Wave (PSPW) index, have been proposed to improve the gastro-esophageal reflux disease (GERD) diagnostic yield. This study aims to determine the integrity of the esophageal epithelial barrier and chemical clearance using these novel parameters and to correlate them with acid exposure time (AET) and acid clearance time (ACT) in obese patients who are candidates for bariatric surgery (BS). Twenty impedance-pHmetry tracings of patients prior to BS were reviewed. Nine (45%) patients with a conclusive diagnosis of GERD had significantly higher ACT, lower MNBI in the distal esophagus and lower PSPW indexes compared to obese patients without GERD. Moreover, 100% of obese patients with GERD had a pathological ACT compared to obese patients without GERD (p = 0.003). However, the percentage of pathological MNBI and PSPW index did not differ between obese patients with and without GERD. The PSPW index and MNBI of the distal channel significantly correlated with ACT and AET. Further studies are needed to assess the role of time-consuming novel parameters in the routine evaluation of morbidly obese patients candidates for BS. The value of acid clearance time is confirmed as a relevant impedance-pH parameter in these patients.

Ambulatory pH-Impedance Findings Confirm That Grade B Esophagitis Provides Objective Diagnosis of Gastroesophageal Reflux Disease.

The Lyon Consensus designates Los Angeles (LA) grade C/D esophagitis or acid exposure time (AET) >6% on impedance-pH monitoring (MII-pH) as conclusive for gastroesophageal reflux disease (GERD). We aimed to evaluate proportions with objective GERD among symptomatic patients with LA grade A, B, and C esophagitis on endoscopy. Demographics, clinical data, endoscopy findings, and objective proton-pump inhibitor response were collected from symptomatic prospectively enrolled patients from 2 referral centers. Off-therapy MII-pH parameters included AET, number of reflux episodes, mean nocturnal baseline impedance, and postreflux swallow-induced peristaltic wave index. Objective GERD evidence was compared between LA grades. Of 155 patients (LA grade A: 74 patients, B: 61 patients, and C: 20 patients), demographics and presentation were similar across LA grades. AET >6% was seen in 1.4%, 52.5%, and 75%, respectively, in LA grades A, B, and C. Using additional MII-pH metrics, an additional 16.2% with LA grade A and 47.5% with LA grade B esophagitis had AET 4%-6% with low mean nocturnal baseline impedance and postreflux swallow-induced peristaltic wave index; there were no additional gains using the number of reflux episodes or symptom-reflux association metrics. Compared with LA grade C (100% conclusive GERD based on endoscopic findings), 100% of LA grade B esophagitis also had objective GERD but only 17.6% with LA grade A esophagitis ( P < 0.001 compared with each). Proton-pump inhibitor response was comparable between LA grades B and C (74% and 70%, respectively) but low in LA grade A (39%, P < 0.001). Grade B esophagitis indicates an objective diagnosis of GERD.

A protein restricted diet induces a stable increased fat storage phenotype in flies.

Scientific evidence has revealed possible confounders in diet induced obesity models of Drosophila melanogaster. High Sugar Diet (HSD) induction of obesity in flies has been associated with fly hyperosmolarity and glucotoxicity, while High Fat Diet (HFD) induction has been associated with lipotoxicity. The objective of this study was to assess for a healthy obesity phenotype by comparison of fly survival, physio-chemical and biochemical changes associated with HSD, HFD and Protein Restricted Diet (PRD) obesity induction models of male Drosophila melanogaster. Here, we provide information on a PRD as the plausible option in obesity research not involving cancer, diabetes, glucotoxicity and lipotoxicity studies. Obesity was induced by exposing Drosophila melanogaster white mutant w1118 to four experimental diets for four weeks. Group 1 was fed regular food (control), group 2 was fed a 0.5% less yeast than in regular feed (PRD), group 3 was fed a 30% w/v sucrose to regular cornmeal food (HSD) and group 4 was fed a 10% w/v food-grade coconut oil to regular cornmeal food (HFD). Peristaltic waves were measured on 3rd instar larvae of all experimental groups. Negative geotaxis, fly survival, body mass, catalase activity, triglycerides (TG/TP), sterol, and total protein were measured in adult Drosophila melanogaster after four weeks. Triglycerides (TG/TP) and total protein levels were significantly higher in HSD phenotype. Sterols were higher in HFD phenotype. Though catalase enzyme activity was highest in PRD phenotype, this activity was not statistically significant when compared to that of HSD and HFD phenotypes. However, PRD phenotype had the lowest mass, highest survival rate and the highest negative geotaxis, thus demonstrating a balanced, stable and more viable metabolic status in the experimental model. A protein restricted diet induces a stable increased fat storage phenotype in Drosophila melanogaster.

Esophageal secondary peristalsis following acid infusion and chemical clearance correlate with mucosal integrity and acid sensitivity in GERD patients.

Acid sensitivity can be altered in patients with gastroesophageal reflux disease (GERD). Secondary peristalsis helps clear gastro-esophageal refluxate and residual ingested food bolus. The aim of this study was to investigate the associations among acid sensitivity, esophageal mucosal integrity, chemical clearance, and secondary peristalsis before and after esophageal acid infusion. This was an investigator-initiated, prospective, cross-sectional study. Adult reflux patients underwent high resolution manometry and 24 h impedance-pH monitoring off acid suppression to identify GERD phenotypes, including non-erosive reflux disease (NERD), reflux hypersensitivity (RH), and functional heartburn (FH). Secondary peristalsis was assessed using five rapid 20 mL air injections into the esophagus before and after infusion of hydrochloric acid (0.1 N) into the mid-esophagus. Conventional acid infusion parameters recorded included lag time, intensity rating, and sensitivity score. Chemical clearance was evaluated using the post-reflux swallow-induced peristaltic wave (PSPW), and mucosal integrity was assessed by the mean nocturnal baseline impedance (MNBI) derived from impedance-pH monitoring. A total of 88 patients (age 21-64 years, 62.5% women) completed the study including 12 patients with NERD, 45 with RH, and 31 with FH. There was no significant difference in acid infusion parameters between patients with NERD, RH, and FH. Upon acid infusion, patients who exhibited successful secondary peristalsis had longer lag time, higher MNBI, and shorter bolus contact time than those without secondary peristalsis. Meanwhile, patients with intact PSPW demonstrated significantly higher intensity ratings in response to acid perfusion and higher MNBI than those with impaired PSPW. The lag time correlated positively with MNBI (r = 0.285; p = 0.007). In conclusion, the protective effect of esophageal secondary peristalsis and chemical clearance on esophageal mucosal integrity was demonstrated. Concerning acid sensitivity, longer lag time in patients with intact secondary peristalsis may be attributed to better esophageal mucosal integrity, while stronger intensity ratings may have a greater tendency to induce PSPW and protect esophageal mucosal integrity.