Effect of menstrual cycle and menopause on human gastric electrophysiology.

Chronic gastroduodenal symptoms disproportionately affect females of childbearing age; however, the effect of menstrual cycling on gastric electrophysiology is poorly defined. To establish the effect of the menstrual cycle on gastric electrophysiology, healthy subjects underwent noninvasive Body Surface Gastric Mapping (BSGM; 8x8 array) with the validated symptom logging App (Gastric Alimetry, New Zealand). Participants included were premenopausal females in follicular ( = 26) and luteal phases ( = 18) and postmenopausal females ( = 30) and males ( = 51) were controls.

Effects of peristaltic amplitude and frequency on gastric emptying and mixing: a simulation study.

The amplitude and frequency of peristaltic contractions are two major parameters for assessing gastric motility. However, it is not fully understood how these parameters affect the important functions of the stomach, such as gastric mixing and emptying. This study aimed to quantify the effects of peristaltic amplitude and frequency on gastric mixing and emptying using computational fluid dynamics simulation of gastric flow with an anatomically realistic model of the stomach.

Effect of cilia-induced surface velocity on cerebrospinal fluid exchange in the lateral ventricles.

Ciliary motility disorders are known to cause hydrocephalus. The instantaneous velocity of cerebrospinal fluid (CSF) flow is dominated by artery pulsation, and it remains unclear why ciliary dysfunction results in hydrocephalus. In this study, we investigated the effects of cilia-induced surface velocity on CSF flow using computational fluid dynamics.

The influence of interstitial cells of Cajal loss and aging on slow wave conduction velocity in the human stomach.

Loss of interstitial cells of Cajal (ICC) has been associated with gastric dysfunction and is also observed during normal aging at ~13% reduction per decade. The impact of ICC loss on gastric slow wave conduction velocity is currently undefined. This study correlated human gastric slow wave velocity with ICC loss and aging.

Multiscale modeling of human cerebrovasculature: A hybrid approach using image-based geometry and a mathematical algorithm.

The cerebral vasculature has a complex and hierarchical network, ranging from vessels of a few millimeters to superficial cortical vessels with diameters of a few hundred micrometers, and to the microvasculature (arteriole/venule) and capillary beds in the cortex. In standard imaging techniques, it is difficult to segment all vessels in the network, especially in the case of the human brain. This study proposes a hybrid modeling approach that determines these networks by explicitly segmenting the large vessels from medical images and employing a novel vascular generation algorithm.

A computational fluid dynamics simulation of liquid swallowing by impaired pharyngeal motion: bolus pathway and pharyngeal residue.

Common practices to improve the ability to swallow include modifying physical properties of foods and changing the posture of patients. Here, we quantified the effects of the viscosity of a liquid bolus and patient posture on the bolus pathway and pharyngeal residue using a computational fluid dynamics simulation. We developed a computational model of an impaired pharyngeal motion with a low pharyngeal pressure and no pharyngeal adaptation.

Quantification of gastric emptying caused by impaired coordination of pyloric closure with antral contraction: a simulation study.

Proper coordination of gastric motor functions is required for healthy gastric emptying. However, pyloric function may be impaired by functional disorders or surgical procedures. Here, we show how coordination between pyloric closure and antral contraction affects the emptying of liquid contents.

Perioperative Hemodynamic Changes in the Thoracic Aorta in Patients With Aortic Valve Stenosis: A Prospective Serial 4D-Flow MRI Study.

This study investigated hemodynamic changes in the thoracic aorta and aortic arch branches before and after aortic valve replacement (AVR) by 4D-flow MRI in patients with aortic valve stenosis (AS). Thoracic 4D-flow MRI was performed in 10 AS patients before and after AVR (mean 27 ± 1.9 days).

Factors Diminishing Cytoadhesion of Red Blood Cells Infected by Plasmodium falciparum in Arterioles.

Cytoadhesion of red blood cells infected by Plasmodium falciparum (Pf-IRBCs) is predominantly found in postcapillary venules, rather than in arterioles. However, factors influencing this phenomenon remain unclear. Here, we conduct a systematic study using a numerical model coupling the fluid and solid mechanics of the cells and cellular environment with the biochemical ligand-receptor interaction.

Effects of combination of mitiglinide with various oral antidiabetic drugs in streptozotocin-nicotinamide-induced type 2 diabetic rats and Zucker fatty rats.

We examined the effects of combining the rapid insulin secretagogue, mitiglinide, with various oral hypoglycaemic drugs including biguanides, pioglitazone, α-glucosidase inhibitors, and sodium-glucose co-transporter 2 inhibitors in a rat model of type 2 diabetes. The oral glucose tolerance test (OGTT) using glucose, sucrose, or a liquid meal was used to compare the effects of mitiglinide with those of the four oral hypoglycaemic drugs and examine their combined effects on blood glucose levels and insulin secretion in the rat model. The combination of mitiglinide with other oral hypoglycaemic drugs suppressed the plasma glucose levels more than either agent did alone.

Capture of microparticles by bolus flow of red blood cells in capillaries.

Previous studies have concluded that microparticles (MPs) can more effectively approach the microvessel wall than nanoparticles because of margination. In this study, however, we show that MPs are not marginated in capillaries where the vessel diameter is comparable to that of red blood cells (RBCs). We numerically investigated the behavior of MPs with a diameter of 1 μm in various microvessel sizes, including capillaries.

Shear-induced platelet aggregation and distribution of thrombogenesis at stenotic vessels.

Objective: SIPA, which is mediated by vWF, is a key mechanism in arterial thrombosis under an abnormally high shear rate of blood flow. We investigated the influence of SIPA on thrombogenesis, focusing on alterations in blood flow at stenotic vessels.

Methods: We carried out a computer simulation of thrombogenesis in stenotic vessels at three different injury positions (ie, upstream, apex, and downstream of the stenosis) to evaluate the effect of SIPA.

Functional physiology of the human terminal antrum defined by high-resolution electrical mapping and computational modeling.

High-resolution (HR) mapping has been used to study gastric slow-wave activation; however, the specific characteristics of antral electrophysiology remain poorly defined. This study applied HR mapping and computational modeling to define functional human antral physiology. HR mapping was performed in 10 subjects using flexible electrode arrays (128-192 electrodes; 16-24 cm) arranged from the pylorus to mid-corpus.

Relationship between gastric motility and liquid mixing in the stomach.

The relationship between gastric motility and the mixing of liquid food in the stomach was investigated with a numerical analysis. Three parameters of gastric motility were considered: the propagation velocity, frequency, and terminal acceleration of peristaltic contractions. We simulated gastric flow with an anatomically realistic geometric model of the stomach, considering free surface flow and moving boundaries.

Cell adhesion during bullet motion in capillaries.

A numerical analysis is presented of cell adhesion in capillaries whose diameter is comparable to or smaller than that of the cell. In contrast to a large number of previous efforts on leukocyte and tumor cell rolling, much is still unknown about cell motion in capillaries. The solid and fluid mechanics of a cell in flow was coupled with a slip bond model of ligand-receptor interactions.

Deformation of a micro-torque swimmer.

The membrane tension of some kinds of ciliates has been suggested to regulate upward and downward swimming velocities under gravity. Despite its biological importance, deformation and membrane tension of a ciliate have not been clarified fully. In this study, we numerically investigated the deformation of a ciliate swimming freely in a fluid otherwise at rest.

Flow of a circulating tumor cell and red blood cells in microvessels.

Quantifying the behavior of circulating tumor cells (CTCs) in the blood stream is of fundamental importance for understanding metastasis. Here, we investigate the flow mode and velocity of CTCs interacting with red blood cells (RBCs) in various sized microvessels. The flow of leukocytes in microvessels has been described previously; a leukocyte forms a train with RBCs in small microvessels and exhibits margination in large microvessels.

Numerical methods for simulating blood flow at macro, micro, and multi scales.

In the past decade, numerical methods for the computational biomechanics of blood flow have progressed to overcome difficulties in diverse applications from cellular to organ scales. Such numerical methods may be classified by the type of computational mesh used for the fluid domain, into fixed mesh methods, moving mesh (boundary-fitted mesh) methods, and mesh-free methods. The type of computational mesh used is closely related to the characteristics of each method.

Hemodynamics in the microcirculation and in microfluidics.

Hemodynamics in microcirculation is important for hemorheology and several types of circulatory disease. Although hemodynamics research has a long history, the field continues to expand due to recent advancements in numerical and experimental techniques at the micro-and nano-scales. In this paper, we review recent computational and experimental studies of blood flow in microcirculation and microfluidics.

Structure of dimeric axonemal dynein in cilia suggests an alternative mechanism of force generation.

The mechanism by which the two different heads of the ciliary outer dynein arm produce force to translocate the microtubule during beating is still unknown. In this report we use cryo-electron tomography and image processing to analyze the conformational changes and the relative abundance of each conformation of the two dynein heads from mouse respiratory cilia. In the absence of nucleotides the majority of dynein dimers are in the apo form and both heads are tightly packed, whereas they are dissociated and move independently in the presence of nucleotides.

Numerical analysis of a red blood cell flowing through a thin micropore.

Red blood cell (RBC) deformability plays a key role in microcirculation, especially in vessels that have diameters even smaller than the nominal cell size. In this study, we numerically investigate the dynamics of an RBC in a thin micropore. The RBC is modeled as a capsule with a thin hyperelastic membrane.

Separation of motile bacteria using drift velocity in a microchannel.

Separation of certain bacteria from liquids is important in the food, water quality management, bioengineering, and pharmaceutical industries. In this study, we developed a microfluidic device for the hydrodynamic separation of motile bacteria (Escherichia coli) using drift velocity. We first investigated drift tendencies of bacteria and found that cells tended to move in a spanwise direction with similar velocities regardless of the flow rate.

Fluctuation of cilia-generated flow on the surface of the tracheal lumen.

Although we inhale air that contains many harmful substances, including, for example, dust and viruses, these small particles are trapped on the surface of the tracheal lumen and transported towards the larynx by cilia-generated flow. The transport phenomena are affected not only by the time- and space-average flow field but also by the fluctuation of the flow. Because flow fluctuation has received little attention, we investigated it experimentally in mice.