Active Contraction Research Articles

Atrial strain assessment in elite athletes: unveiling physiologic adaptation

Abstract Background Left atrial (LA) strain, measured by speckle-tracking echocardiography, provides insights into cardiac function beyond traditional volumetric assessments. In athletes, the effects of chronic exercise on LA strain are unclear, with conflicting findings on whether it reflects physiological adaptation or potential dysfunction. Aims This study aimed to comprehensively assess LA remodeling and function in professional soccer players compared to controls. We hypothesized that while athletes would exhibit LA enlargement, their atrial function would remain preserved due to the physiological nature of cardiac remodeling in this population. Methods A retrospective analysis of echocardiographic parameters, namely left atrial strain, was carried out in a group of professional male athletes compared to a control group of healthy male individuals. A GE Vivid E95 echocardiographic ultrasound system and EchoPAC V.206 software (GE Vingmed Ultrasound AS, Horten, Norway) were used. Shapiro-Wilk test was used to test data distribution, ANOVA and t-test were used as a parametric tests, and Man-Whitney as a non-parametric Test (SPSS v.27). Results The study analyzed 111 athletes with a median age of 24 (21-31) years and 70 healthy male individuals from the control group with a median age of 27 (23-32) years. Athletes had a significantly higher indexed left atrial end-systolic volume compared to the control group (41 ± 9 ml/m² vs. 31 ± 7 ml/m², p<0.001). Despite the difference in volume, the early and late diastolic tissue velocities were similar in both groups and E/E’ was lower (4.4 ± 0.9 vs. 5.0 (4.5-5.8), p<0.001). There were no significant differences between athletes and the control group in Left Atrial Reservoir Strain (LASr) and Left Atrial Conduit Strain (LAScd). The active contraction of the left atrium during atrial systole is reduced in athletes, which had a significantly lower left atrial contraction strain compared to the control group (-9 (-11 – -8)% vs. -12 ± 4%, p<0.001). Conclusion The data suggests that athletes' hearts have undergone specific adaptations, particularly in terms of increased left atrial size and altered contraction patterns. Maintaining atrial reservoir strain (the most validated parameter for normality) and atrial conduit strain within normal ranges may indicate that morphological changes are merely normal adaptations to the high cardiac output demands during exercise. Descriptive analysis LA strain example

Fascia and Muscle Stiffness in Soccer Athletes with and Without Previous Hamstring Injury

Background/Objectives: Despite extensive efforts to reduce injuries to the hamstrings, the injury rate among athletes is increasing. The purpose of this study was to examine fascia and muscle stiffness differences between ten soccer players with a previous biceps femoris long head (BF) injury and thirteen controls. Methods: The shear-wave elastic (SWE) modulus and surface electromyography signal from the semitendinosus (ST) and BF were measured during passive and active knee flexion efforts from 0°, 45°, and 90° knee flexion angles. Anatomical cross-sectional area (CSA) and maximum isometric strength were also obtained. Results: Analysis of variance showed that the injured group showed significantly greater active (p < 0.05) but similar passive SWE modulus of BF and ST fascia and muscle than the uninjured group. Compared to the non-injured group, injured athletes had lower isometric strength and BF anatomical CSA (p < 0.05) but similar electromyographic activation amplitude (p > 0.05). Conclusions: The greater fascia stiffness during active submaximal contractions, in comparison to controls, might have an impact on hamstring function in soccer players with BF injuries who returned to play. Injured players may benefit from therapeutic interventions that aim to restore fascia and muscle tissue stiffness.

Moving with the trouble: How vulnerability and critical hope enable reckoning with complicity in entrepreneurial initiatives

Entrepreneurial initiatives aiming to transform organizations from the bottom up are often complicit with the power structures they seek to change, reproducing the old while trying to cultivate the new. To unleash the transformative potential of these initiatives, it is crucial to better understand how workers can productively reckon with complicity and how this reckoning drives the entrepreneurial process. We address these questions through a longitudinal, qualitative, single-case study in a private contemporary art museum in Russia, where museum workers strive to create a more inclusive and politicized organization. Drawing on research by social justice education scholars, we unfold how vulnerability and critical hope—here as affective orientations—enable workers to sense and address complicity in their entrepreneurial activities. We develop a process model that theorizes the interplay between these affective orientations and links them to the expansion or contraction of entrepreneurial activities and their reckoning with complicity. The study contributes to the surging interest in vulnerability and hope within entrepreneurship studies while providing new insights into how entrepreneurs remain affected by the contrary effects of their own efforts, channeling these experiences into imaginative actions toward different futures.

Deciphering the interplay between biology and physics with a finite element method-implemented vertex organoid model: A tool for the mechanical analysis of cell behavior on a spherical organoid shell.

Understanding the interplay between biology and mechanics in tissue architecture is challenging, particularly in terms of 3D tissue organization. Addressing this challenge requires a biological model enabling observations at multiple levels from cell to tissue, as well as theoretical and computational approaches enabling the generation of a synthetic model that is relevant to the biological model and allowing for investigation of the mechanical stresses experienced by the tissue. Using a monolayer human colon epithelium organoid as a biological model, freely available tools (Fiji, Cellpose, Napari, Morphonet, or Tyssue library), and the commercially available Abaqus FEM solver, we combined vertex and FEM approaches to generate a comprehensive viscoelastic finite element model of the human colon organoid and demonstrated its flexibility. We imaged human colon organoid development for 120 hours, following the evolution of the organoids from an immature to a mature morphology. According to the extracted architectural/geometric parameters of human colon organoids at various stages of tissue architecture establishment, we generated organoid active vertex models. However, this approach did not consider the mechanical aspects involved in the organoids' morphological evolution. Therefore, we applied a finite element method considering mechanical loads mimicking osmotic pressure, external solicitation, or active contraction in the vertex model by using the Abaqus FEM solver. Integration of finite element analysis (FEA) into the vertex model achieved a better fit with the biological model. Therefore, the FEM model provides a basis for depicting cell shape, tissue deformation, and cellular-level strain due to imposed stresses. In conclusion, we demonstrated that a combination of vertex and FEM approaches, combining geometrical and mechanical parameters, improves modeling of alterations in organoid morphology over time and enables better assessment of the mechanical cues involved in establishing the architecture of the human colon epithelium.

Ventricular Depolarization Abnormalities and Their Role in Cardiac Risk Stratification - A Narrative Review.

Ventricular depolarization refers to the electrical activation and subsequent contraction of the ventricles, visible as the QRS complex on a 12-lead electrocardiogram (ECG). A well-organized and efficient depolarization is critical for cardiac function. Abnormalities in ventricular depolarization may indicate various pathologies and can be present in all leads if the condition is general, or in a subgroup of anatomically contiguous leads if the condition is limited to the corresponding anatomic location of the heart. Furthermore, the assessment of depolarization abnormalities on the ECG may either be identified visually or this may depend on further processing. In recent decades, assessment of depolarization abnormalities has received a lot of attention for cardiac risk stratification. This risk stratification aims to identify patients at high risk of adverse cardiac events, to tailor preventive or therapeutic interventions. In this review, we provide an oversight of different techniques for assessing abnormal ventricular depolarization and their value in diagnosing certain conditions, in risk stratification of adverse events, and in guiding therapeutic decisions. This includes QRS alterations directly corresponding to cardiac conditions, such as bundle branch blocks, or the presence of a delta wave, and also metrics aiming to qualitatively or quantitatively assess myocardial scarring, such as QRS (micro)fragmentation and QRS-scoring, and techniques assessing abnormal late depolarizations, such as signal-averaged ECG. While most established assessments of abnormal depolarization rely on human interpretation and are limited by visual detection, recently introduced analyses, such as QRS micro-fragmentation, aim to tackle these limitations. Besides eliminating bias, these automated analyses bypass the need for human interpretation, thereby paving the way for large population studies.

The Role of Preoperative Inflammatory Markers in Cervical Cerclage Success.

To compare the inflammatory markers between therapeutic and emergency cerclage and assess the predictive role of inflammatory markers for the latency period. Descriptive study. Place and Duration of the Study: Department of Obstetrics and Gynaecology, Bursa Yuksek Ihtisas Training and Research Hospital, Turkiye, from January 2016 to September 2022. The therapeutic cerclage group (n = 64) included patients with a history of cervical insufficiency, normal prenatal screening test results, and who underwent cerclage based on history indications. The emergency cerclage group (n = 14) included patients with painless cervical dilation in the second trimester or a history of preterm and a short cervix on ultrasonography. Exclusion criteria composed of multiple pregnancies, active uterine contractions, vaginal bleeding, chorioamnionitis, membrane rupture, foetal anomalies, history of conization or abdominal cerclage, and having inflammatory diseases. Sociodemographic features, perinatal outcomes, and inflammatory markers such as neutrophil-to-lymphocyte ratio, C-reactive protein, and systemic immune-inflammation index were compared. Systemic immune-inflammation index was calculated by formulating the multiplication value of the neutrophil and platelet count divided by the lymphocyte count. The latency period was shorter (5.5 (0-29) vs. 20 (1-31) weeks, p <0.001) in the emergency cerclage group. Neutrophil-to- lymphocyte ratio and systemic immune-inflammation index, which are representatives of increased inflammatory state, were significantly higher in the emergency cerclage group (p = 0.007 for both). Systemic immune-inflammation index was correlated with cerclage to delivery interval for all patients (r = -0.307, p = 0.006). Also, it predicted neonatal mortality with a cut-off value of 1078.08, 90% sensitivity and 70.59% specificity (AUC = 0.776, p <0.001) and low Apgar scores with 57.1% sensitivity and 74% specificity (AUC = 0.641, p = 0.038). Systemic immune-inflammation index, correlated with cerclage to delivery interval, could be a marker for predicting neonatal mortality and morbidity in cerclage patients. Cervical cerclage, Inflammatory markers, Perinatal outcomes, Systemic immune-inflammation index.

Forces Acting on the Foot of the American Alligator (Alligator mississippiensis) During Pedal Anchoring.

This study was undertaken to explore the forces acting on the pes during pedal anchoring and to discern if pedal anchoring required the activation of the intrinsic pedal musculature. Replica feet equipped with strain gauges were moved over mud substrate, mimicking locomotion and pedal anchoring. Quantification of the substrate tracks demonstrated that they were similar to those made by freely moving Alligator, that the locomotor and pedal anchoring tracks were significantly different, and that the composition of the artificial feet significantly altered the tracks. Strain gauges revealed significantly different forces at different locations (e.g., digit vs. heel) on the pes and between locomotor and pedal anchoring motions. Collectively, the results of the present study demonstrate that the forces acting on the pes during pedal anchoring are different from those during locomotion. Furthermore, varying the composition of the feet used in this study demonstrated the importance of flexion at the metatarsal/phalangeal joints. Resistance to this flexion in living crocodylians requires active muscle contraction, meaning that pedal anchoring is an active, not passive, behavior. These results offer the first insights into the mechanics of pedal anchoring and demonstrate how technologies like 3D printing can be applied to established problems like fossil trackways.

Fluid mechanics of luminal transport in actively contracting endoplasmic reticulum.

The endoplasmic reticulum (ER), the largest cellular compartment, harbours the machinery for the biogenesis of secretory proteins and lipids, calcium storage/mobilisation, and detoxification. It is shaped as layered membranous sheets interconnected with a network of tubules extending throughout the cell. Understanding the influence of the ER morphology dynamics on molecular transport may offer clues to rationalising neuro-pathologies caused by ER morphogen mutations. It remains unclear, however, how the ER facilitates its intra-luminal mobility and homogenises its content. It has been recently proposed that intra-luminal transport may be enabled by active contractions of ER tubules. To surmount the barriers to empirical studies of the minuscule spatial and temporal scales relevant to ER nanofluidics, here we exploit the principles of viscous fluid dynamics to generate a theoretical physical model emulating in silico the content motion in actively contracting nanoscopic tubular networks. The computational model reveals the luminal particle speeds, and their impact in facilitating active transport, of the active contractile behaviour of the different ER components along various time-space parameters. The results of the model indicate that reproducing transport with velocities similar to those reported experimentally in single-particle tracking would require unrealistically high values of tubule contraction site length and rate. Considering further nanofluidic scenarios, we show that width contractions of the ER's flat domains (perinuclear sheets) generate local flows with only a short-range effect on luminal transport. Only contractions of peripheral sheets can reproduce experimental measurements, provided they are able to contract fast enough.

Urban Environmental Management Practices and Green Roof Technologies in Malaysia: A Path to Sustainable Development

Malaysia is the developing country, which develop in contraction, agriculture, and many more kinds of activities. The construction activities for Malaysia is less implemented the green materials technology and the Environmental Management. The Environmental Management Practices is not usually applied by the construction workers. The government also show no enforcement and awareness on the Environmental Management Practices in Malaysia. There are some importance of the Environmental Management Practices is described and also the plan to improve the implementation of Environmental Management Practices under construction of Malaysia. The green roof is one of the technologies of green materials. There three kinds of green roof system as intensive green roof system, semi-intensive green roof system, and extensive green roof system. These three different systems have its own advantages and this advantages. The green materials that can be used for the green roof construction are bamboo, stones, and recycled bricks. The green materials or green roof system help to reduce the environment impact, social impact, and economic impact of Malaysia. The better environment, social life and economic can lead to sustainable development in Malaysia.

Poisson’s ratio transition in strain crystallizing elastomer: from rubbery amorphous to semicrystalline

AbstractThe Poisson’s ratio (μ) of natural rubber (NR) undergoing strain-induced crystallization (SIC) during uniaxial stretching was investigated as a function of the applied stretch ($${\lambda }_{{||}}$$ λ ∣ ∣ ) over a broad $${\lambda }_{{||}}$$ λ ∣ ∣ range, encompassing the SIC onset stretch ($${{\lambda }_{{||}}}^{* }$$ λ ∣ ∣ * ≈ 4.1). Below $${{\lambda }_{{||}}}^{* }$$ λ ∣ ∣ * , μ remains near 1/2, indicating the incompressible behavior of NR in its fully rubbery amorphous state. However, once $${\lambda }_{{||}}$$ λ ∣ ∣ exceeds $${{\lambda }_{{||}}}^{* }$$ λ ∣ ∣ * , μ decreases as the degree of crystallinity (χc) increases. As $${\lambda }_{{||}}$$ λ ∣ ∣ increases from $${{\lambda }_{{||}}}^{* }$$ λ ∣ ∣ * to fracture stretch ($${\lambda }_{{||}}$$ λ ∣ ∣ ≈ 7.1), χc increases to 18%, and μ gradually decreases to 0.33. This reduction in μ reflects the transformation of the NR matrix from a rubbery amorphous state to a semicrystalline state. In fact, the true stress (force per cross-sectional area in the deformed state) at the fracture point, obtained via actual lateral contraction, is approximately 85% of that estimated under the assumption μ = 1/2. These findings provide a critical foundation for accurately modeling the mechanical behavior of strain-crystallizing elastomers.

A kinematically reasonable mechanism of tongue forward protrusion considering hyoid bone movements

The tongue has a wide variety of motor functions, which are driven by tongue muscle contractions and associated with movements of the hyoid bone (HB) connected to the tongue root. HB movement has been observed in many situations, including swallowing, breathing, and speech. However, the relationships between HB movement and tongue kinematic function have received little attention, and have not been considered in most previous biomechanical tongue modeling research, except studies of swallowing. The current study aimed to clarify the effects of HB movement on tongue kinematics during tongue forward protrusion, which is an essential tongue motor function associated with speech disorder. HB displacement during tongue forward protrusion was quantified using ultrasound imaging in four healthy controls. Furthermore, computational mechanical simulations of tongue forward protrusion were conducted with observed HB movements and active contraction of the genioglossus (GG) muscle, which is conventionally considered to be the driving muscle in tongue forward protrusion. Ultrasound imaging revealed anterosuperior HB displacement in tongue forward protrusion, with a similar magnitude in each direction (anterior: 6.3 ± 2.8 mm, superior: 5.8 ± 1.6 mm). Computational simulation demonstrated that the HB movement described above caused not only anterosuperior displacement, but also forward rotation of the tongue body, which was caused by kinematic constraints of GG. The resulting anterior displacement of the tongue tip was 1.5 times greater compared with that without HB movement. These findings indicate that the HB and associated tongue body movements play non-negligible roles in the tongue kinematics of forward protrusion.

Whole-body-electro-myostimulation for the care of inclusion body myositis-A case report.

External muscle stimulation, possibly combined with active muscle contraction, could improve physical functioning and performance in inclusion body myositis. Inclusion body myositis (IBM) is a chronic, progressive inflammatory muscle disease with largely unknown causes. It typically affects men more than women, usually beginning in the latter half of life. IBM leads to muscle weakness and wasting, especially in the arms and legs, which significantly impairs daily functioning and complicates participation in exercise training. Few studies have examined the impact of physical training on fitness, inflammation markers, and quality of life in IBM patients. The patient, a Caucasian male (78.3 kg, 174.0 cm, born October 1948), was diagnosed with IBM in October 2011. From October 2017 to September 2019, he underwent exercise training focused on external muscle stimulation combined with active muscle contractions. Regular assessments included cardiopulmonary exercise testing, functional tests (6-min walking test, modified timed up and go test, modified chair rise test), lung function exams, blood parameters, body composition, and quality of life questionnaires. The decline in physical fitness may have been slowed during the intervention period, as indicated by some improvements like peak oxygen uptake and the functional test results while other parameters remained unchanged or declined like peak power output, fat-free mass or lung functioning. However, a recurrence of his prostate cancer after treatment with androgen deprivation therapy may have led to further declines and thus increased muscle wasting. The data may suggest that supportive exercise programs focusing on external muscle stimulation, possibly combined with active muscle contraction, might improve physical functioning, exercise performance, and quality of life in IBM management.

Effectiveness of palatal anchorage device (PAD) for maxillary anterior retraction with clear aligners using finite element study.

The palatal anchorage device (PAD) is commonly used in fixed appliance for anchorage, but the biomechanics of PAD in patients treated with clear aligners(CAs)remains poorly understood, especially in its elastic mode and force magnitude. This study aimed to assess the biomechanical effects of using PAD for retraction during clear aligner treatment (CAT) with the extraction of two maxillary first premolars. Four finite element models were created: (1) Incisors retraction (IR) with active contraction of the clear aligner only; (2) IR with PAD using different forces (50,75,100g) or not; (3) PAD without IR (forces of 50,75,100g), and (4) Different elastic directions (D1, D2, D3) from aligner to PAD without IR. IR caused lingual tipping and extrusion of the central incisors, as well as mesial and buccal tipping of the first molar. PAD during IR provided strong anchorage for the first molar, with elastics slightly increasing the lingual tipping and extrusion of the central incisors. Elastics applied to the U-shaped arch led to central incisor intrusion and reduced lingual retraction. The highest stress was observed on the mesial attachment of the canine. PAD effectively reinforced posterior anchorage in CAT, while anterior positioning facilitated anterior teeth intrusion. The biomechanical importance of the canine's mesial attachments in maxillary teeth treatment planning was highlighted.

Engineering hiPSC-derived tissue models for advanced amyloidosis research and therapy development

Abstract Introduction Transthyretin (TTR) amyloid cardiomyopathy (ATTR-CM) is a life-threatening disease currently lacking an optimal therapy, stemming from the absence of representative models. Our work aims to stablish for the first time an all-human 3D model of ATTR-CM where the main cellular and extracellular players of the pathology are present. Methodology A human induced pluripotent stem cell (hiPSC) line was derived from a patient carrying a p.Ser43Asn TTR mutation and differentiated into hepatocytes (hiPSC-HEPs), cardiomyocytes (hiPSC-CMs) and cardiac fibroblasts (hiPSC-CFs). Cells were embedded in a hydrogel (tailored for each cell type) and combined with a designed 3D printed scaffold using Melt Electro Writing (MEW) technology. Tissues were maintained in culture for up to 4 weeks and characterized by staining, albumin production, electrophysiological, plus genomic analysis. Exposure to TTR fibrils (TTR-FIB) was evaluated. Results Human hepatic and cardiac functional tissues can be generated using MEW-designs. These constructs exhibited albumin production and an active spontaneous contraction, respectively. Moreover, tissues displayed well distributed cells throughout the 3D-structure, positive for specific hepatic and cardiac mature markers. Interestingly, electrophysiological analysis showed that cardiac tissues displayed shortened calcium transients after TTR-FIB exposure compared to unexposed tissues. However, no differences were found in terms of beat rate, metabolic activity and gene expression for the concentrations used. Conclusion We have developed an advanced model of ATTR-CM capable of recapitulating the multisystem complexity of the disease, which will contribute to advancing our understanding of the mechanisms of the disease, and help discovering and formulating new treatments.

Atrial function after cardioversion in patients with persistent atrial fibrillation

Abstract Background After cardioversion for persistent atrial fibrillation (AF), restitution of normal left atrial (LA) function is said to need several days to recover. However, in previous studies, the evaluation of LA function was only used transesophageal or transthoracic echocardiography. During catheter ablation (CA) for AF, pulmonary venous (PV) blood flow can be measured accurately using an intracardiac echocardiogram (ICE). The atrial systolic PV regurgitation (PVa) wave measured by ICE is a good indicator of LA contractility because it reflects the active contraction of the LA. Purpose This study aims to investigate the LA function in the hyperacute phase and the factors which affect after cardioversion. Methods 40 AF patients (18 paroxysmal AF, 22 persistent AF) who underwent CA were enrolled. PVa wave was measured twice before RFCA and after the procedure using intracardiac ultrasound. Voltage map of the LV was obtained using the CARTO system at the end of the session, and the percentage of low voltage area which was determined area as less than 0.1mV in the mapped LA surface area (LVA%) was calculated. Results Preoperative PVa was 1.61 ± 0.09 m/sec in the paroxysmal AF group (PaAF), and no PVa was observed in the persistent AF group (PeAF). Postoperative PVa were comparable between PaAF (0.18±0.06 m/sec) and PeAF (0.18±0.07 m/sec). Then, the PeAF were divided into 2 groups based on LVA% in the anterior area, posterior area, and total LA area (cutoff 1,5 and 10%, respectively). In the anterior lower LVA% group, PVa were significantly increased (0.20 ± 0.07 m/sec) after defibrillation compared with the anterior higher LVA% group (0.14 ± 0.06 m/sec; P=0.02), whilst no difference was observed when it was divided in the posterior wall or overall. Conclusion Even in PeAF, LA function improves to the same degree as in the PaAF immediately after cardioversion, and the posterior wall LVA, including posterior wall isolation, may not affect LA function.

Sacubitril/valsartan improves diastolic left ventricular stiffness with increased titin phosphorylation via cGMP-PKG activation in diabetic mice

Titin, a giant sarcomeric protein, regulates diastolic left ventricular (LV) passive stiffness as a molecular spring and could be a therapeutic target for diastolic dysfunction. Sacubitril/valsartan (Sac/Val), an angiotensin receptor neprilysin inhibitor, has been shown to benefit patients with heart failure with preserved ejection fraction. The effect of Sac/Val is thought to be due to the enhancement of the cGMP/PKG pathway via natriuretic peptide. In this study, the effects of Sac/Val on LV diastolic dysfunction are demonstrated in a mouse diabetic cardiomyopathy model focusing on titin phosphorylation. Sac/Val-treated diabetic mice showed a greater increase in myocardial levels of cGMP-PKG than Val-treated and control mice. Conductance catheter analysis showed a significant reduction in LV stiffness in diabetic mice, but not in non-diabetic mice. Notably, diastolic LV stiffness was significantly reduced in Sac/Val-treated diabetic hearts compared with Val-treated or vehicle-treated diabetic mice. The phosphorylation level of titin (N2B), which determines passive stiffness and modulates active contraction, was higher in Sac/Val-treated hearts compared with Val-treated hearts in diabetic mice. Given that alteration of titin phosphorylation through PKG contributes to myocardial stiffness, the beneficial effects of Sac/Val in heart failure might be partly attributed to the induction of titin phosphorylation.

Impact of anisotropic conduction and premature atrial contraction on the fractionated atrial potentials.

Fractionated atrial potential (FAP) during sinus rhythm (SR) may be a new target for ablation of atrial fibrillation (AF). However, the effects of the direction of activation and premature atrial contraction (PAC) on FAP is unknown. Therefore, we examined the impact of anisotropic conduction and PAC on the distribution and areas of FAP. FAP map in the left atrium was created in 40 patients with AF before ablation. The distribution and areas of FAP were compared during SR, distal coronary sinus (CS) pacing (S1) and extrastimulus (S2), and paced PAC after SR. FAP was defined as a potential with four or more fragmented deflections. FAPs during SR were found in the right and mid-anterior walls and septum in most patients. During S1 compared to SR, FAPs significantly decreased in the right and mid-anterior walls, appendage, septum, and right inferior wall, while significantly increased in the lateral wall. During S2 compared to S1, FAPs significantly increased in the mid anterior and right and mid posterior walls. During PAC compared to SR, FAPs significantly decreased in the right and mid anterior walls and roof, while significantly increased in the left anterior, left inferior and lateral walls. A rotational activation pattern at the FAP area during CS pacing was observed in 12 patients (30%), mostly in the left inferior wall. The distribution and areas of FAP vary with anisotropic conduction and extrastimulus. Therefore, FAP should be evaluated not only during SR but also during extrastimulus from the distal CS.

Role of High Frequency Ultrasound in Assessment of Acute and Chronic Muscle Injuries in Comparison to MRI

Abstract Background The most common mechanism of injury of muscles is related to muscle strain (indirect muscle injury), mainly in the lower limbs. Muscles are at risk for disruption during eccentric contraction, as the force of active contraction is added to the passive stretching force applied to the myotendinous junction (MTJ). Although clinical examinations remain very important, it has been shown that radiological findings can aid clinicians in the initial assessment. Objective To evaluate the accuracy and specificity of high frequency ultrasound in identification and characterization of acute and chronic muscle injuries in comparison with MRI. Methods This ultrasonography &amp; cross sectional study was done in private radiological centers with a period of 24 months on a random sample of 30 patients. Our study included 30 patients complaining of traumatic acute and chronic muscle injuries, 26 males (86.7%) and 4 females (13.3%), ranging in age from 18 to 55 years with a mean age of 37.5 years. Results The accuracy, sensitivity &amp; specificity of ultrasound in detecting all muscle injuries in comparison to MRI: 86.7%, 87.5% &amp; 83.3% respectively. The accuracy, sensitivity &amp; specificity of ultrasound in detecting acute muscle injuries in comparison to MRI: 66.7%, 66.7 % &amp; 66.7% respectively. The accuracy, sensitivity &amp; specificity of ultrasound in detecting chronic muscle injuries in comparison to MRI: 95.2%, 94.4% &amp; 100% respectively. Conclusion Ultrasound is highly operator dependent, useful for diagnosis of chronic muscle injury in comparison to the MRI, yet with pitfalls in acute muscle injuries, yet the ultrasound classification criteria for muscle injury can be used to predict the severity of injury and guide decision on the type of treatment and MRI is still considered the main diagnostic tool for muscle injuries and classification.

Native mechano-regulative matrix properties stabilize alternans dynamics and reduce spiral wave stabilization in cardiac tissue.

The stability of wave conduction in the heart is strongly related to the proper interplay between the electrophysiological activation and mechanical contraction of myocytes and extracellular matrix (ECM) properties. In this study, we statistically compare bioengineered cardiac tissues cultured on soft hydrogels ( kPa) and rigid glass substrates by focusing on the critical threshold of alternans, network-physiological tissue properties, and the formation of stable spiral waves that manifest after wave breakups. For the classification of wave dynamics, we use an improved signal oversampling technique and introduce simple probability maps to identify and visualize spatially concordant and discordant alternans as V- and X-shaped probability distributions. We found that cardiac tissues cultured on ECM-mimicking soft hydrogels show a lower variability of the calcium transient durations among cells in the tissue. This lowers the likelihood of forming stable spiral waves because of the larger dynamical range that tissues can be stably entrained with to form alternans and larger spatial spiral tip movement that increases the chance of self-termination on the tissue boundary. Conclusively, we show that a dysfunction in the excitation-contraction coupling dynamics facilitates life-threatening arrhythmic states such as spiral waves and, thus, highlights the importance of the network-physiological interplay between contractile myocytes and the ECM.

A chemo-mechanical model for growth and mechanosensing of focal adhesion

Focal adhesion (FA), the complex molecular assembly across the lipid membrane, serves as a hub for physical and chemical information exchange between cells and their microenvironment. Interestingly, studies have shown that FAs can grow along the direction of contractile forces generated by actomyosin stress fibers and achieve larger sizes on stiffer substrates. In addition, the cellular traction transmitted to the substrate was observed to reach the maximum near the FA center. However, the biomechanical mechanisms behind these intriguing findings remain unclear. To answer this important question, here we first developed a one-dimensional (1D) chemo-mechanical model of FA where key features like adhesion plaque deformation, active contraction by stress fibers, force-dependent association/dissociation of integrin bonds connecting two surfaces, and substrate compliance have all been considered. Within this formulation, we showed that the rigidity-sensing capability of FAs originates from the deformability of stress fibers while the force-dependent breakage of integrin bonds leads to the appearance of the traction peak at the FA center. Furthermore, by extending the model into three-dimensional as well as incorporating assembly/dis-assembly kinetics of adhesion proteins, we also demonstrated how anisotropic stress/strain field within the adhesion plaque will be induced by the presence of contractile forces which leads to the directional growth of the FA.