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The arterial intima is continuously under pulsatile wall shear stresses (WSS) imposed by the circulating blood. The knowledge of the contribution of smooth muscle cells (SMC) to the response of endothelial cell (EC) to WSS is still incomplete. We developed a co-culture model of EC on top of SMC that mimics the inner in vivo structure of the arterial intima of large arteries. The co-cultured model, as well as a monolayer model of EC, were developed in custom-designed wells that allowed for mechanobiology experiments. Both the monolayer and co-culture models were exposed to steady flow induced WSS of up to 24 dyne/cm 2 and for lengths of 60 min. Quantification of WSS induced alterations in the cytoskeletal actin filaments (F-actin) and vascular endothelial cadherin (VE-cadherin) junctions were utilized from confocal images and flow cytometry. High confluency of both models was observed even after exposure to the high WSS. The quantitive analysis revealed larger post WSS amounts of EC F-actin polymerization in the monolayer, which may be explained by the relative help of the SMC to resist the external load of WSS. The VE-cadherin demonstrated morphological alterations in the monolayer model, but without significant changes in their content. The SMC in the co-culture maintained their contractile phenotype post high WSS which is more physiological, but not post low WSS. Generally, the results of this work demonstrate the active role of SMC in the intima performance to resist flow induced WSS., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The physical mechanism that drives blood flow in the valveless tubular embryonic heart is still debatable whether it is peristaltic flow or valveless dynamic suction. Previous studies of valveless pumping were concerned with either the role of the excitation parameters or the mechanisms that generate the unidirectional outflow. In this study, a dimensionless one-dimensional (1D) analysis of the valveless pumping due to local excitation at an asymmetric longitudinal location was performed for non-uniform thick-wall elastic tubes, including tubes with local bulging and tapering. A general tube law that accounts for wall thicknesses was implemented for describing the physically realistic dynamics of the tube and the two-step MacCormack algorithm was utilized for the numerical analysis. A comprehensive analysis was conducted to explore the affecting roles of the system (e.g., tube geometry) and the working (e.g., Strouhal number and flow friction parameter) parameters on the net outflow of the pump. The maximal positive net outflow in all the tested cases always occurred when the natural Strouhal number was about π. Flow reversals were observed only for relatively low friction parameters. A local bulging at the site of excitation and thick walls contributed to larger outflows, while tube tapering reduced the net outflow., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.jbiomech.2015.03.019. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy., (Copyright © 2015.)

Modeling the complex deformations of cylindrical tubes under external pressure is of interest in engineering and physiological applications. The highly non-linear post-buckling behavior of cross-section of the tube during collapse attracted researchers for years. Major efforts were concentrated on studying the behavior of thin-wall tubes. Unfortunately, the knowledge on post-buckling of thick-wall tubes is still incomplete, although many experimental and several theoretical studies have been performed. In this study we systematically studied the effect of the wall thickness on post-buckling behavior of the tube. For this purpose, we utilized a computational model for evaluation of the real geometry of the deformed cross-sectional area due to negative transmural (internal minus external) pressure. We also developed an experimental method to validate the computational results. Based on the computed cross-sections of tubes with different wall thicknesses, we developed a general tube law that accounts for thin or thick wall tubes and fits the numerical data of computed cross-sectional areas versus transmural pressures., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The distribution of intrauterine embryo implantation site(s) in most mammalian species shows remarkably constant patterns: in monotocous species such as humans, an embryo tends to implant in the uterine fundus; in polytocous species such as rodents, embryos implant evenly along the uterine horns. These long-time evolved patterns bear great biological significance because disruption of these patterns can have adverse effects on pregnancies. However, lack of suitable models and in vivo monitoring techniques has impeded the progress in understanding the mechanisms of intrauterine embryo distribution. These obstacles are being overcome by genetically engineered mouse models and newly developed high-resolution ultrasound. It has been revealed that intrauterine embryo distribution involves multiple events including uterine sensing of an embryo, fine-tuned uterine peristaltic movements, time-controlled uterine fluid reabsorption and uterine luminal closure, as well as embryo orientation. Diverse molecular factors, such as steroid hormone signaling, lipid signaling, adrenergic signaling, developmental genes, ion/water channels, and potentially embryonic signaling are actively involved in intrauterine embryo distribution. This review covers the biomechanical and molecular aspects of intrauterine embryo distribution (embryo spacing at the longitudinal axis and embryo orientation at the vertical axis), as well as its pathophysiological roles in human reproductive medicine. Future progress requires multi-disciplinary research efforts that will integrate in vivo animal models, clinical cases, physiologically relevant in vitro models, and biomechanical/computational modeling. Understanding the mechanisms for intrauterine embryo distribution could potentially lead to development of therapeutics for treating related conditions in reproductive medicine., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The ultimate goal of a vaccine is to protect vaccinated animals against re-exposure to the same pathogen and provide sterile immunity. However, a cutaneous clinical manifestation appeared, following re-exposure of cattle that had been vaccinated with the RM65 strain, to LSDV infection during an epidemic in 2006-2007. Four thousand six hundred and seven vaccinated cows entered the study after being re-exposed to LSDV infection. Of them, 513 (11%) presented lumps, and there was a marked difference between the proportions of dairy and feedlot animals that were affected: 146 out of 3517 and 367 out of 1090 (6.6 and 33.7%, respectively). This data suggests that the potency of the vaccine need to be re-assessed for beef cattle.

Healthy humans normally breathe through their nose even though its complex geometry imposes a significantly higher resistance in comparison with mouth breathing. The major functional roles of nasal breathing are defense against infiltrating particles and conditioning of the inspired air to nearly alveolar conditions in order to maintain the internal milieu of the lung. The state-of-the-art of the existing knowledge on nasal air-conditioning will be discussed in this review, including in vivo measurements in humans and computational studies on nasal air-conditioning capacity. Areas where further studies will improve our understanding and may help medical diagnosis and intervention in pathological states will be introduced.

Lung ventilation is a mechanical process in which the respiratory muscles are acting in concert to remove air in and out of the lungs. Any alteration in the performance of the respiratory muscle may reduce the effectiveness of ventilation. Thus, early diagnosis of their weakness is vital for treatment and rehabilitation. Different techniques, which are based on different measurement protocols, can be utilized for evaluation of respiratory muscle strength. Respiratory muscle strength can be assessed using pressure measurement either from the mouth or from the nostril during quasi-static breathing. However, it estimates only global performance of respiratory muscles. Techniques that are based on electromyography measurements during muscle contraction (EMG) enable the differentiation between the different respiratory muscles. Along with the above clinical and physiological techniques for assessment of respiratory muscle strength and endurance, mechanical and mathematical models of the chest wall were developed in the last few decades for analysis of chest wall movements and the contribution of its components to respiration. In this review, the different methods and the models utilized for evaluation of respiratory muscles function will be discussed.

The possibility that respiratory muscles may fatigue during extreme physical activity and thereby become a limiting factor leading to exhaustion is debated in the literature. The aim of this study was to determine whether treadmill marching exercise induces respiratory muscle fatigue, and to compare the extent and rate of respiratory muscle fatigue to those of the calf musculature. To identify muscle fatigue, surface electromyographic (EMG) signals of the inspiratory (sternomastoid, external intercostals), expiratory (rectus abdominis and external oblique) and calf (gastrocnemius lateralis) muscles were measured during a treadmill march of 2 km at a constant velocity of 8 km/h. The extent of fatigue was assessed by determining the increase in root-mean-square (RMS) of EMG over time, and the rate of fatigue was assessed from the slope of the EMG RMS versus time curve. Results indicated that (i) the inspiratory and calf muscles are the ones experiencing the most dominant fatigue during treadmill marching, (ii) the rate of fatigue of each muscle group was monotonic between the initial and terminal phases of exercise, and (iii) the inspiratory muscles fatigue significantly faster than the calf at the terminal phase of exercise, and are likely to fatigue faster during the initial exercise as well. Accordingly, this study supports the hypothesis that fatigue of the inspiratory muscles may be a limiting factor during exercise.

Embryo transfer (ET) is the final manual intervention during which the newly formed embryo is placed within the uterus by a transcervical catheter. The loading of the syringe-catheter complex with the transferred volume consists of the transfer media (which contains the embryos) separated by air spaces on both sides. The dynamics involved in injecting the syringe-catheter complex is not well understood nor has it been investigated to date. We developed an in vitro experimental setup for simulations of ET into a rigid transparent uterine model. The catheter was loaded in sequences of liquid and air as it is in the clinical setting. The transferred liquid was colored with a dye and its dispersion within the uterine cavity was recorded by a video camera. The results demonstrated, for the first time, the importance of having a gas phase in the catheter load. The resulting air bubbles within the uterus were carried upward towards the fundus by buoyant forces, thereby dragging behind them the transferred liquid which contained the embryos. This could be expected to substantially increase the probability for the embryos to be present near the fundal wall at the time window for implantation. There was also evidence of a dependency of the rate of injection upon the catheter load into the uterus: a low speed generated several air bubbles which led to more of the transferred liquid being carried towards the fundal end, thus possibly enhancing the potential for implantation.

Single-lung transplantation may induce asynchronous performance between the respiratory muscles of the chest. The objective of this study was to investigate the influence of a single transplanted lung on respiratory muscle mechanics. The force and power of the sternomastoid, external intercostal and external oblique muscles were evaluated throughout a range of respiratory maneuvers in emphysematic patients with a single transplanted lung and compared with that of healthy subjects. A significant differences was observed between the force, work and power of the muscles on the two sides of the chest in emphysematic patients (P<0.05). The control group demonstrated higher averaged maximal force, work and power. The total work done during either inspiration or expiration by the external intercostal and external oblique muscles on the side of the transplanted lung were higher compared with that of the native lung side and compared with the control group. The asynchrony between the lungs after single-lung transplant leads to asynchronous muscle force and work and lesser muscle strength compared to healthy subjects.

A realistic two-dimensional (2D) model of the human trunk was developed for quantitative analysis of the relative contribution to breathing mechanics of seven groups of respiratory muscles. Along with noninvasive measurements of electromyography (EMG) signals from respiratory muscles near the skin surface, it provides predictions for the forces generated by inner respiratory muscles as well as the instantaneous work of each muscle. The results revealed that inspiratory muscles reach their maximal force towards the end of inspiration, while expiratory muscles reach their maximal force at mid-expiration. Inspiratory muscles contributed to the work of breathing even at low efforts, while that of the expiratory muscles was observed only at relatively high efforts. The study clearly showed that the diaphragm muscle generates forces, which are of the same order as those generated by other inspiratory muscles, but performed 60-80% of the inspiratory work. The contribution of the external intercostal muscle to inspiration was not negligible, especially at high breathing efforts.

The respiratory muscles constitute the respiratory pump, which determines the efficacy of ventilation. Any functional disorder in their performance may cause insufficient ventilation. This study was designed to quantitatively explore the relative contribution of major groups of respiratory muscles to global lung ventilation throughout a range of maneuvers in healthy subjects. A computerized experimental system was developed for simultaneous noninvasive measurement of inspired/expired airflow, mouth pressure and up to 8 channels of EMG surface signals from major respiratory muscles which are located near the skin (e.g., sternomastoid, external intercostal, rectus abdominis and external oblique) during various respiratory maneuvers. Lung volumes values were calculated by integration of airflow data. Hill's muscle model was utilized to calculate the forces generated by the muscles from the acquired EMG data. Analysis of EMG measurements and respiratory muscles forces revealed the following characteristics: (a) muscle activity increased with increased breathing effort, (b) inspiratory muscles contributed to inspiration even at relatively low flow rates, while expiratory muscles are recruited at higher flow rates, (c) the forces generated by the muscle depended on the muscle properties as well as on their EMG performance and (d) the pattern of the muscle's force curves varied between subjects, but were generally consistent for the same subject regardless of breathing effort.

Peyronie's disease is a pathological condition of the penis which is characterized by localized ossification of the tunica albuginea. A common symptom of the chronic stage is penile deformity during erection, which is frequently associated with pain and erectile dysfunction. A two-dimensional biomechanical model of the penis was applied to study the development of Peyronie's disease by simulating the mechanical stress distribution which would result from the interaction of the ossified tunical tissue with other penile soft tissues. The model was solved by using commercial finite element software for a characteristic erectile pressure. The results demonstrate that Peyronie's plaques may induce intensified stresses around the penile nerves and blood vessels, up to double those in the normal penis. These elevated stresses may cause a painful sensation of neural origin or ischemia in regions of compressed vascular tissue. Severe penile deformities have been shown to develop if Peyronie's plaques develop only around one of the corpora cavernosa due to the non-homogeneous resistance of the tunica to expansion during erection. The present model can be clinically applied as an aid in the planning process of reconstructive surgery or insertion of a prosthesis.

The alveolar septum consists of a skeleton of fine collagen and elastin fibers, which are interlaced with a capillary network. Its mechanical characteristics play an important role in the overall performance of the lung. An alveolar sac model was developed for numerical analysis of the internal stress distribution and septal displacements within the alveoli of both normal and emphysematic saline-filled lungs. A scanning electron micrograph of the parenchyma was digitized to yield a geometric replica of a typical two-dimensional alveolar sac. The stress-strain relationship of the alveolar tissue was adopted from experimental data. The model was solved by using commercial finite-element software for quasi-static loading of alveolar pressure. Investigation of the state of stresses and displacements in a healthy lung simulation yielded values that compared well with experimentally reported data. Alteration of the mechanical characteristics of the alveolar septa to simulate elastin destruction in the emphysematic model induced significant stress concentrations (e.g., at a lung volume of 60% total capacity, tensions at certain parts in an emphysematic lung were up to 6 times higher than those in a normal lung). The combination of highly elevated stress sites together with the cyclic loading of breathing may explain the observed progressive damage to elastin fibers in emphysematic patients.

This paper describes a field trial involving 13 calves raised on a farm known to be endemic for Trichophyton verrucosum infection. Seven calves were immunized by subcutaneous inoculations with a crude ribosomal fraction (CRF) of T. verrucosum suspended in aluminium hydroxide as adjuvant. Six animals were sham-immunized with buffer suspended in the adjuvant and served as controls. Two injections were given: one at the age of 2 weeks and a second 2 weeks later. CRF was prepared from T. verrucosum cultures grown in a vitamin-enriched liquid medium. The fungal mat was disrupted mechanically and CRF was separated from the cell-free extract by differential ultracentrifugation. The CRF was characterized biochemically (RNA and protein content) and physically (electron microscopy). The protection induced by vaccination was assessed through a clinical follow-up of the animals to determine the presence and duration of dermatophyte infection following their exposure to a T. verrucosum-contaminated environment. Vaccination with the CRF resulted in a statistically significant decrease in the period during which clinical signs of dermatophytosis were observed (from a mean of 9.5 weeks to 3.7 weeks). To assess the humoral response, serum samples were taken before each vaccination and 2 weeks after the second inoculation. For the cell-mediated immune (CMI) response assessment, whole-blood samples were taken 2 weeks after the second vaccination. The presence of anti-T. verrucosum antibodies in the sera was determined by ELISA and the CMI response was assessed in vitro by the lymphocyte stimulation test.(ABSTRACT TRUNCATED AT 250 WORDS)

The immunogenicity of a crude ribosomal fraction (CRF) extracted from Microsporum canis was tested by assessing protection of vaccinated guinea-pigs (GP) against a challenge with the dermatophyte. Stimulation of the humoral as well as the cellular immune systems of these animals was evaluated by ELISA and the lymphocyte stimulation tests, respectively. In addition, the immune response elicited by the M. canis CRF was examined for cross-reactivity towards Trichophyton verrucosum antigen. The duration of the infection induced by M. canis in GP was reduced to 8 days in vaccinated animals versus 37 days in the control GP. Both humoral and cellular immune systems were stimulated by the CRF. Sera of GP vaccinated with M. canis CRF revealed presence of anti-T. verrucosum antibodies, albeit at titres significantly lower than against M. canis.