Search Results (52)

To enable the practical application of passive back-support exoskeletons employing pneumatic artificial muscles (PAMs) in tasks such as agricultural work, we evaluated their assistive effectiveness in a half-squatting posture with a staggered stance. In this context, assistive force profiles were adjusted according to body posture to achieve more effective support. The targeted assistive force profile was designed to be continuously active from the standing to the half-squatting position, with minimal variation across this range. The assistive force profile was developed based on a PAM contractile force model and implemented using a cam mechanism. The effectiveness of assistance was assessed by measuring body flexion angles and erector spinae muscle activity during lifting and carrying tasks. The results showed that the assistive effect was greater on the side with the forward leg. Compared to the condition without exoskeleton assistance, the conventional pulley-based system reduced muscle activity by approximately 20% whereas the cam-based system achieved a reduction of approximately 30%. Full article

It was unknown whether hyperthermia increased the efficacy of histamine to raise the force of cardiac contractions via human H1-histamine receptors. To that end, we measured the force in isolated human atrial preparations (HAPs) excised from the right atrium of patients who underwent cardiac surgery due to severe two- or three-vessel coronary heart disease. For comparison, we also measured the force in paced (1 Hz) left and spontaneously beating right atrial preparations of transgenic mice overexpressing cardiac human H1-histamine receptors (H1-TG). Histamine (100 µM) was less efficient in raising the force in left atrial preparations from H1 TG mouse atria under hyperthermia than under hypothermia. Oppositely, histamine was more efficient in augmenting force during hyperthermia than during hypothermia in isolated electrically stimulated (1 Hz) HAPs. In sum, the contractile response to activation of H1-histamine receptor in H1-TG mice and in HAPs are opposite with regard to hyperthermia dependence. In patients with fever, histamine might thus be important, to preserve cardiac contractile function as a compensatory mechanism. Full article

Living myocardial slices (LMSs) have shown great promise in cardiac research, allowing multicellular and complex interplay analyses with disease and patient specificity, yet their wider clinical use is limited by the large tissue sizes usually required. We therefore produced mini-LMSs (<10 mm²) from routine human cardiac surgery specimens and compared them with medium (10–30 mm²) and large (>30 mm²) slices. Size effects on biomechanical properties were examined with mathematical modeling, and viability, contraction profiles, and histological integrity were followed for 14 days. In total, 34 mini-, 25 medium, and 30 large LMS were maintained viable, the smallest measuring only 2 mm². Peak twitch force proved to be size-independent, whereas time-to-peak shortened as slice area decreased. Downsized LMSs displayed excellent contractile behavior for five to six days, after which a gradual functional decline and micro-architectural changes emerged. These findings confirm, for the first time, that mini-LMSs are feasible and viable, enabling short-term, patient-specific functional studies and pharmacological testing when tissue is scarce. Full article

Background: Gallbladder hypomotility is a key pathogenic factor in cholelithiasis. Non-invasive interventions to enhance gallbladder contractility remain limited. Ultrasound therapy has shown promise in various muscular disorders, but its effects on gallbladder function are unexplored. Methods: This study employed low-intensity pulsed ultrasound (LIPUS) at a 3 MHz frequency and 0.8 W/cm² intensity with a 20% duty cycle to irradiate the gallbladder region of fasting guinea pigs. Gallbladder contractile function was evaluated through multiple complementary approaches: in vivo assessment via two-dimensional/three-dimensional ultrasound imaging to monitor volumetric changes; quantitative functional evaluation using nuclear medicine scintigraphy (^99mTc-HIDA); and ex vivo experiments including isolated gallbladder muscle strip tension measurements, histopathological analysis, α-smooth muscle actin (α-SMA) immunohistochemistry, and intracellular calcium fluorescence imaging. Results: Ultrasound significantly enhanced gallbladder emptying, evidenced by the volume reduction and increased ejection fraction. Scintigraphy confirmed accelerated bile transport in treated animals. Ex vivo analyses demonstrated augmented contractile force, amplitude, and frequency in ultrasound-treated smooth muscle. Histological examination revealed smooth muscle hypertrophy, α-SMA upregulation, and elevated intracellular calcium levels. Extended ultrasound exposure produced sustained functional improvements without tissue damage. Conclusions: Ultrasound effectively enhances gallbladder contractile function through mechanisms involving smooth muscle structural modification and calcium signaling modulation. These findings establish the experimental foundation for ultrasound as a promising non-invasive therapeutic approach to improve gallbladder motility and potentially prevent gallstone formation. Full article

Heart failure with preserved ejection fraction (HFpEF) shows diverse disease patterns, with various combinations of comorbidities and symptoms. A common hallmark is exercise intolerance, caused by alterations in the peripheral skeletal muscle (SKM) including a recently indicated titin hyperphosphorylation. Our aim is to compare a metabolic syndrome- (ZSF-1 rats) and a hypertension-driven (Dahl salt-sensitive (DSS) rats) HFpEF rat-model in relation to SKM function and titin phosphorylation. Obese ZSF-1 and high-salt fed DSS rats (HFpEF) were compared to lean ZSF-1 and low-salt fed rats (con). HFpEF was confirmed by echocardiography and invasive haemodynamic measurements. SKM atrophy, in vitro force measurements, titin- and contractile protein expression were evaluated. Obese ZSF-1 HFpEF rats showed muscle atrophy, reduced muscle force and increased titin phosphorylation compared to controls, which was not detected in hypertensive DSS rats. Fiber type specific troponins, myostatin and four and a half LIM domain 1 were differently regulated between the two models. Altogether, our results show that both animal models of HFpEF exhibit different SKM phenotypes, probably based on the divergent disease etiologies, which may help to define the most suitable animal model for HFpEF to test potential treatment regimens. Full article

Background: Quasipaa spinosa crude extract (QSce), a natural source rich in proteins such as parvalbumin (PV), has been traditionally used to promote physical recovery. However, its mechanisms in mitigating exercise-induced fatigue remain unclear. Methods: Using a murine treadmill exhaustion model, we evaluated the effects of QS-derived Parvalbumin (QsPV) (30 and 150 mg/kg/day) on endurance capacity, oxidative stress, tissue injury, and muscle function. Indicators measured included time to exhaustion, intracellular calcium levels, antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GSH-Px)], lipid peroxidation (malondialdehyde, MDA), injury markers [creatine kinase (CK), lactate dehydrogenase (LDH), cardiac troponin I (cTnI)], renal function (blood urea), and muscle force. Results: QsPV-150 significantly increased time to exhaustion by 34.6% compared to the exercise-only group (p < 0.01). It reduced MDA by 41.2% in skeletal muscle and increased SOD and GSH-Px levels by 35.4% and 28.1%, respectively. Serum CK, LDH, and cTnI were reduced by 39.5%, 31.7%, and 26.8%, respectively, indicating protection against muscle and cardiac injury. QsPV also decreased blood urea by 22.3% and improved renal histology, with reduced glomerular damage and tubular lesions. At the molecular level, QsPV restored calcium balance and downregulated calpain-1/2 and atrophy-related genes (MuRF-1, MAFbx-32). Muscle contractile force (GAS and SOL) improved by 12.2–20.3%. Conclusions: QsPV attenuates exercise-induced fatigue through multi-organ protection involving calcium buffering, oxidative stress reduction, and anti-atrophy effects. These findings support its potential as a natural recovery-enhancing supplement, pending further clinical and pharmacokinetic studies. Full article

Recent studies on myogenic satellite cells (SCs) in Duchenne muscular dystrophy (DMD) documented altered division capacities and impaired regeneration potential of SCs in DMD patients and animal models. It remains unknown, however, if SC-intrinsic effects trigger these deficiencies at pre-contractile stages of myogenesis rather than resulting from the pathologic environment. In this study, we isolated SCs from a porcine DMD model and age-matched wild-type (WT) piglets for comprehensive analysis. Using immunofluorescence, differentiation assays, traction force microscopy (TFM), RNA-seq, and label-free proteomic measurements, SCs behavior was characterized, and molecular changes were investigated. TFM revealed significantly higher average traction forces in DMD than WT SCs (90.4 ± 10.5 Pa vs. 66.9 ± 8.9 Pa; p = 0.0018). We identified 1390 differentially expressed genes and 1261 proteins with altered abundance in DMD vs. WT SCs. Dysregulated pathways uncovered by gene ontology (GO) enrichment analysis included sarcomere organization, focal adhesion, and response to hypoxia. Multi-omics factor analysis (MOFA) integrating transcriptomic and proteomic data, identified five factors accounting for the observed variance with an overall higher contribution of the transcriptomic data. Our findings suggest that SC impairments result from their inherent genetic abnormality rather than from environmental influences. The observed biological changes are intrinsic and not reactive to the pathological surrounding of DMD muscle. Full article

Spasticity, characterized by elevated muscle tone, is commonly managed with botulinum toxin type A (BTX-A). However, BTX-A can paradoxically increase passive muscle forces, narrow muscles’ length range of force exertion (l_range), and elevate extracellular matrix (ECM) stiffness. C3 transferase, known to inhibit myofibroblast and fascial tissue contractility, may counteract ECM stiffening. This study investigated whether combining BTX-A with C3 transferase reduces active forces without altering passive forces or l_range. Additionally, we examined the isolated effects of C3 transferase on muscle levels. Male Wistar rats received injections into the tibialis anterior (TA): Control (n = 7, saline) and C3 + BTX-A (n = 7, 2.5 µg C3 + 0.1U BTX-A). TA forces were measured one month post-injection, and isolated C3 transferase effects were assessed in separate groups (Control and C3, n = 6 each). Active forces were 43.5% lower in the C3 + BTX-A group compared to the Control group. No differences between groups in passive forces (p = 0.33) or l_range (p = 0.19) were observed. C3 transferase alone had no significant effect on relative muscle mass (p = 0.298) or collagen content (p = 0.093). Supplementing BTX-A with C3 transferase eliminates BTX-A’s adverse effects at the muscle level. C3 transferase alone causes no atrophy or collagen increase, which are key factors in BTX-A-induced ECM stiffening. This novel neurodenervant formula shows promise for advancing spasticity management. Full article

Background: Three-dimensional skeletal muscle organoids (3D SkMO) are becoming of increasing interest for preclinical studies in Duchenne muscular dystrophy (DMD), provided that the used platform demonstrates the possibility to form functional and reproducible 3D SkMOs, to investigate on potential patient-related phenotypic differences. Methods: In this study, we employed fibrin-based 3D skeletal muscle organoids derived from immortalized myogenic precursors of DMD patients carrying either a stop codon mutation in exon 59 or a 48–50 deletion. We compared dystrophic lines with a healthy wild-type control (HWT) by assessing microtissue formation ability, contractile function at multiple timepoints along with intracellular calcium dynamics via calcium imaging, as well as expression of myogenic markers. Results: We found patient-specific structural and functional differences in the early stages of 3D SkMO development. Contractile force, measured as both single twitch and tetanic responses, was significantly lower in dystrophic 3D SkMOs compared to HWT, with the most pronounced differences observed at day 7 of differentiation. However, these disparities diminished over time under similar culturing conditions and in the absence of continuous nerve-like stimulation, suggesting that the primary deficit lies in delayed myogenic maturation, as also supported by gene expression analysis. Conclusions: Our results underline that, despite the initial maturation delay, DMD muscle precursors retain the capacity to form functional 3D SkMOs once this intrinsic lag is overcome. This suggests a critical role of dystrophin in early myogenic development, while contraction-induced stress and/or an inflammatory microenvironment are essential to fully recapitulate dystrophic phenotypes in 3D SkMOs. Full article

Type 2 diabetes (T2D) is a chronic disease that damages blood vessels and increases the risk of cardiovascular disease (CVD). Heat-shock protein 70 (HSP70), a family of chaperone proteins, has been recently reported as a key player in vascular reactivity that affects large blood vessels like the aorta. Hyperglycemia, a hallmark of diabetes, correlates with the severity of vascular damage and circulating HSP70 levels. In diabetes, blood vessels often show impaired contractility, contributing to vascular dysfunction. However, HSP70’s specific role in T2D-related vascular contraction remains unclear. We hypothesized that blocking HSP70 would improve vascular function in a widely used diabetic mouse model (db/db). To test this, we measured both vascular intracellular and serum circulating HSP70 levels in control and diabetic male mice using immunofluorescence and Western blotting. We also examined the aorta’s contractile response using a wire myograph system, which measured the force produced in response to phenylephrine (PE), both with and without VER155008, a pharmacological inhibitor that targets the ATPase domain of HSP70, and after removing extracellular calcium. Our findings show that intracellular HSP70 (iHSP70) levels were similar in control and diabetic groups, while circulating HSP70 (eHSP70) levels were higher in the serum of diabetic mice, altering the iHSP70/eHSP70 ratio. Even though VER155008 attenuated both phases of the contractile curve in the diabetic and control groups, enhanced vasoconstriction to PE was only observed in the tonic phase of the curve in the db/db group, which was prevented by iHSP70 inhibition. This effect involved calcium mobilization, as both the maximal and total contraction forces to PE were restored in groups treated with VER155008. Additionally, internal calcium levels in aortic rings treated with VER155008 decreased, as observed in force generation upon calcium reintroduction, which was further corroborated using a biochemical calcium assay. In conclusion, our study demonstrates that blocking HSP70 improves vascular reactivity in the hyperglycemic state of T2D by restoring proper vascular contraction. Full article

Background/Objectives: Thick-filament-based regulation in muscle is generally conceived as processes that modulate the number of myosin heads capable of force generation. It has been generally assumed that biochemical and structural assays of myosin active and inactive states provide equivalent measures of myosin recruitment, but recent studies indicate that this may not always be the case. Here, we studied the steady-state and dynamic mechanical changes in skinned porcine myocardium before and after treatment with omecamtiv mecarbil (OM) or piperine to help decipher how the biochemical and structural states of myosin separately affect contractile force. Methods: Force–Ca²⁺ relationships were obtained from skinned cardiomyocytes isolated from porcine myocardium before and after exposure to 1 μM OM and 7 μM piperine. Crossbridge kinetics were acquired using a step response stretch activation protocol allowing myosin attachment and detachment rates to be calculated. Results: OM augmented calcium-activated force at submaximal calcium levels that can be attributed to increased thick filament recruitment, increases in calcium sensitivity, an increased duty ratio, and from decelerated crossbridge detachment resulting in slowed crossbridge cycling kinetics. Piperine, in contrast, was able to increase activated force at submaximal calcium levels without appreciably affecting crossbridge cycling kinetics. Conclusions: Our study supports the notion that thick filament activation is primarily a process of myosin recruitment that is not necessarily coupled with the chemo-cycling of crossbridges. These new insights into thick filament activation mechanisms will need to be considered in the design of sarcomere-based therapies for treatment of myopathies. Full article

Background/Objectives: The correlation of handgrip strength (HGS) and morphological characteristics with Big Five personality traits is well documented. However, it is unclear whether these relationships also exist in highly trained and specialized populations, such as tactical athletes, and whether there are specific differences compared to the general population. This study aimed to explore the interplay of handgrip neuromuscular, morphological, and psychological characteristics in tactical athletes and the general population of both genders. Methods: The research was conducted on a sample of 205 participants. A standardized method, procedure, and equipment (Sports Medical solutions) were used to measure the isometric neuromuscular characteristics of the handgrip. Basic morphological characteristics of body height, body mass, and body mass index were measured with a portable stadiometer and the InBody 720 device. Psychological characteristics were assessed with the Mental Toughness Index and Dark Triad Dirty Dozen questionnaires. Results: Numerous significant correlations were obtained, as well as differences between tactical athletes and the general population of both genders. The most prominent correlations were between the excitation index with Psychopathy and the Dark Triad (ρ = −0.41, −0.39) in female tactical athletes, as well as Neuroticism with body height, maximal force, and the maximum rate of force development in the male general population (ρ = 0.49, 0.43, 0.41). The obtained results also revealed gender and occupational specific patterns of researched relationships. Conclusions: Although the results of this study indicated the possibility of the existence of correlations between handgrip neuromuscular, morphological, and psychological characteristics in tactical athletes of both genders, nevertheless, at the moment, there is not enough solid evidence for that. That is why new research is needed. An analysis of muscle contractile and time parameters as neuromuscular indicators in the HGS task proved to be a possible promising method, which brought numerous new insights about the researched relationships. For practical application in the field, we propose including Mental Toughness and the Dark Triad traits in the selection process for future police officers and national security personnel based on the obtained results. Full article

The present study examined three hallucinogenic amphetamine derivatives, namely, 2,5-dimethoxy-4-iodoamphetamine (DOI) as well as 2,5-dimethoxy-4-methylamphetamine (DOM) and 4-methylmethcathinone (mephedrone). The objective of this study was to test the hypothesis that DOI, DOM, and mephedrone would increase the contractile force in isolated human atrial preparations in a manner similar to amphetamine. To this end, we measured contractile force under isometric conditions in electrically stimulated (1 Hz) human atrial preparations obtained during open surgery. DOI and DOM alone or in the presence of isoprenaline reduced the contractile force concentration-dependently in human atrial preparations. These negative inotropic effects of DOM and DOI were not attenuated by 10 µM atropine. However, mephedrone increased the contractile force in human atrial preparations in a concentration- and time-dependent manner. Furthermore, these effects were attenuated by the subsequent addition of 10 µM propranolol or pretreatment with 10 µM cocaine in the organ bath. Therefore, it can be concluded that amphetamine derivatives may exert opposing effects on cardiac contractile force. The precise mechanism by which DOI and DOM exert their negative inotropic effects remains unknown at present. The cardiac effects of mephedrone are probably due to the release of cardiac noradrenaline. Full article

The diaphragm muscle is essential for breathing, and its dysfunctions can be fatal. Many disorders affect the diaphragm, including muscular dystrophies. Despite the clinical relevance of targeting the diaphragm, there have been few studies evaluating diaphragm function following a given experimental treatment, with most of these involving anti-inflammatory drugs or gene therapy. Cell-based therapeutic approaches have shown success promoting muscle regeneration in several mouse models of muscular dystrophy, but these have focused mainly on limb muscles. Here we show that transplantation of as few as 5000 satellite cells directly into the diaphragm results in consistent and robust myofiber engraftment in dystrophin- and fukutin-related protein-mutant dystrophic mice. Transplanted cells also seed the stem cell reservoir, as shown by the presence of donor-derived satellite cells. Force measurements showed enhanced diaphragm strength in engrafted muscles. These findings demonstrate the feasibility of cell transplantation to target the diseased diaphragm and improve its contractility. Full article

There are only a few studies devoted to the comparative and simultaneous study of the mechanisms of the length-dependent regulation of atrial and ventricular contractility. Therefore, an isometric force-length protocol was applied to isolated guinea pig right atrial (RA) strips and ventricular (RV) trabeculae, with a simultaneous measurement of force (Frank–Starling mechanism) and Ca²⁺ transients (CaT) or transmembrane action potentials (AP). Over the entire length-range studied, the duration of isometric contraction, CaT and AP, were shorter in the RA myocardium than in the RV myocardium. The RA myocardium was stiffer than the RV myocardium. With the increasing length of the RA and RV myocardium, the amplitude and duration of isometric contraction and CaT increased, as well as the amplitude and area of the “CaT difference curves” (shown for the first time). However, the rates of the tension development and relaxation decreased. No contribution of AP duration to the heterometric regulation of isometric tension was found in either the RA or RV myocardium of the guinea pig. Changes in the degree of overlap of the contractile proteins of the guinea pig RA and RV myocardium mainly affect CaT kinetics but not AP duration. Full article