Search Results (343)

Neuromuscular electrical stimulation (NMES) is integral to studying muscle function in healthy and dystrophic mice. Certain commercial electrodes and laboratory stimulators used for NMES in mice are no longer in production. We developed and/or tested low-cost, open-source alternatives to discontinued commercial standards. We performed two studies—a comparison of electrodes and a comparison of stimulators. In the electrode study, in vivo NMES was applied to the left hindlimb ankle dorsiflexors in healthy C57BL/6J and dysferlin-null BLAJ mice using three electrode types: a previously available commercial electrode, a custom 3D-Printed electrode, and a custom Pen electrode assembled from off-the-shelf components. Twitch and tetanic torque were measured and compared using two-way repeated-measures ANOVA. Twitch torque differed by electrode type (p = 0.031), with lower values observed for the Pen electrode compared with the 3D-Printed electrode (e.g., 573 ± 72 vs. 666 ± 70 mN.mm in C57BL/6J mice), whereas tetanic torque did not differ significantly between electrode types (p = 0.060). In the stimulator study, twitch and tetanic contractions were elicited using the open-source StimJim stimulator and compared with contractions elicited by the discontinued Grass S48 stimulator. Twitch torque was lower with the StimJim (588 ± 107 mN.mm) compared with the Grass S48 (698 ± 116 mN.mm; p < 0.001), whereas tetanic torque values were not statistically different (p = 0.055). These findings indicate that open-source electrodes and stimulators can produce similar maximal tetanic torque under the tested conditions, although differences in twitch torque and stimulation parameters should be considered. These results reflect a methodological validation of accessible tools rather than a formal equivalence analysis. Full article

Plant growth-promoting bacteria (PGPB)-based inoculants represent a promising alternative to mineral fertilizers. However, their application may be limited by constraints associated with the use of living microorganisms, particularly under field conditions. The objective of this study was to select a bacterial strain and a suitable carrier for the inoculation of rice cv. Selección 1. The effect of inoculation with 3 Rhizobium spp. strains on rice growth was evaluated under greenhouse conditions, enabling selection of the most promising strain. This strain was further characterized based on its motility, production of indolic compounds in the presence of tryptophan, and antagonistic activity against 3 rice phytopathogenic fungi. In addition, the effects of culture media based on aqueous extracts of soybean and rice seeds on bacterial growth and chemotactic response were evaluated, along with the shelf-life stability of the resulting inoculant formulations. Rhizobium sp. strain 5P1 significantly increased plant height (33%), root length (21%), shoot dry weight (30%), and root dry weight (17%) of rice cultivar Selección 1 under greenhouse conditions. The strain exhibited motility predominantly via swarming and twitching, produced indolic compounds (23.9 ± 0.8 µg mL⁻¹), and showed antagonistic activity against Magnaporthe oryzae (32.5% radial growth inhibition at 16 days), Curvularia oryzae (20.0%), and Bipolaris oryzae (6.6%) under in vitro conditions. Culture media based on molasses and soybean or rice seed extracts did not enhance bacterial growth relative to the conventional medium; however, they elicited a stronger chemotactic response. Formulations supplemented with sodium alginate and carboxymethylcellulose maintained cell viability above 10⁸ CFU mL⁻¹ after 105 days of storage at 4 °C. These findings propose Rhizobium sp. strain 5P1 and a molasses-based carrier formulation as strong candidates for the development of an effective bioinoculant for rice in Ferric Gleysol soils. Full article

Muscle fibers exhibit high plasticity: both the fast-twitch fiber type and slow-twitch fiber type can mutually transform under the regulation of phosphorylation. In this study, we characterized the muscle fiber profiles and phosphoproteomes of the m. extensor digitorum longus (EDL) and m. soleus (SOL) in slow-growing Xueshan chickens and fast-growing Ross 308 broilers. Fiber-type distribution was quantified by immunohistochemistry and RT-qPCR of MYH7B, MYH1A and MYH1B. TMT-based phosphoproteomics, combined with bioinformatic analysis, was used to identify differentially expressed phosphopeptides (DEPs) in two comparisons: Ross 308 SOL vs. Ross 308 EDL, and Xueshan EDL vs. Ross 308 EDL. The proportion of type I (slow-twitch) fibers in EDL was significantly higher in Xueshan chickens than in Ross 308 broilers (15.53% vs. 6.14%, p < 0.05), with no significant differences in fiber distribution or diameter between the SOL and EDL in Xueshan chickens (p > 0.05). A total of 3226 phosphopeptides corresponding to 1762 phosphoproteins were identified, with serine as the most abundant phosphorylated amino acid (73.92%). PDHA1, PHKB and PGAM1 were identified as the key DEPs common to both comparison groups. Bioinformatic analyses revealed that reversible site-specific phosphorylation regulates avian muscle fiber-type transformation mainly via the glycolysis/gluconeogenesis pathway. Full article

Objectives: Agonist–antagonist coordination is traditionally defined as simultaneous neural activation assessed by electromyography (EMG). The present study adopts a mechanical perspective, examining twitch-derived contractile ratio indexes between antagonistic muscle groups using tensiomyography (TMG). The aim was to determine whether sport expertise differentiates mechanical agonist–antagonist coordination in karate athletes. Methods: Fifty male participants were divided into four groups: elite karate athletes (EK; n = 7), national team members (NK; n = 14), basically trained karate practitioners (BK; n = 16), and physically active non-athlete controls (CG; n = 13). Bilateral TMG assessment of rectus femoris, vastus lateralis, vastus medialis, biceps femoris, and semitendinosus was performed. Contraction time (Tc), total contraction time (TcT), and rate of muscle tension development (RMTD) were extracted. Twelve twitch-derived contractile ratio indexes (CRI) were calculated separately for dominant (D) and non-dominant (ND) limbs. Results: Significant between-group differences were observed in the temporal coordination of the non-dominant leg. EK demonstrated the lowest index for average contraction time (CRI_Tc_AVG_ND = 17.13%; ANOVA p = 0.005; EK vs. NK p = 0.003) and total contraction time (CRI_TcT_AVG_ND = 9.72%; ANOVA p = 0.003; EK vs. NK p = 0.002). In contrast, velocity-related coordination in the dominant leg was highest in EK (CRI_RMTD_cV_D = 63.66%; ANOVA p = 0.002), differing from NK (p = 0.003), BK (p = 0.002), and CG (p = 0.009). Conclusions: Elite karate athletes exhibit distinct twitch-derived mechanical coordination profiles characterized by highly efficient temporal interplay in the non-dominant (supportive) limb and elevated velocity-related contractile ratio in the dominant (executive) limb. These findings suggest that sport expertise is associated with task-specific mechanical modulation between antagonistic muscle groups detectable through involuntary contractile responses. Full article

Skeletal muscle development and physiological homeostasis are profoundly influenced by environmental cues. Among these factors, ambient temperature represents a critical determinant of growth performance and metabolic adaptation in mammals. However, the effects of different ambient temperature ranges on skeletal muscle characteristics and on responses across multiple visceral tissues remain poorly understood. In this study, five ambient temperature conditions (16 °C, 20 °C, 24 °C, 28 °C, and 32 °C) were established to investigate their physiological impacts in a mouse model. Our results demonstrate that ambient temperature markedly influences growth performance and skeletal muscle phenotype. Notably, mice housed at 20 °C showed relatively preserved grip strength and a shift in myofiber cross-sectional area distribution, although these findings did not consistently indicate superior skeletal muscle development across all indices. Further analysis revealed that ambient temperature significantly modulated the expression profiles of myosin heavy chain (MyHC) isoforms in skeletal muscle. Specifically, cold exposure was associated with an upregulation of the slow-twitch-related MyHC I, whereas heat stress correlated with an elevation of the fast-twitch-related MyHC IIb. Functional assessments indicated that exposure to colder or hotter conditions was associated with impaired muscle performance, as reflected by reduced grip strength at 16 °C, 28 °C, and 32 °C, and decreased endurance capacity at 28 °C and 32 °C. Histological analyses of major visceral organs revealed no obvious structural alterations in the heart, liver, spleen, lung, or kidney across temperature conditions. However, exposure to thermal extremes (16 °C and 32 °C) significantly reduced intestinal villus height, suggesting compromised intestinal integrity under temperature stress. Collectively, these findings indicate that ambient temperature is associated with multi-tissue changes in skeletal muscle characteristics, functional performance, and intestinal morphology. This study provides new insights into how environmental temperature modulates tissue adaptation and physiological homeostasis in mammals. Full article

Different types of skeletal muscle fibers display marked heterogeneity in metabolic, mechanical, and regenerative properties. However, their role in chronic musculoskeletal pain remains insufficiently integrated into clinical models. Chronic pain is associated with altered neuromuscular control, prolonged low-level activation, and reduced recruitment of high-threshold motor units. These factors may promote fiber type-specific remodeling. This narrative review critically synthesizes current evidence on the relationship between musculoskeletal pain and muscle fiber types. The focus was on metabolic vulnerability, mechanical susceptibility, and regenerative capacity. A structured literature search was conducted in PubMed, Scopus, and Web of Science, focused on human studies and key translational models. Chronic musculoskeletal pain is characterized by acquired fiber type-specific adaptations rather than a fixed unfavorable profile. In chronic pain scenarios, Type I fibers present features of chronic overload, including hypertrophy with insufficient capillarization and increased satellite cell activity. Type II fibers exhibit relative disuse, atrophy, and reduced satellite cell content, resembling accelerated muscle aging. Symptom duration, neuromuscular control strategies, and task-specific loading patterns modulate these adaptations, with interindividual variation. Muscle dysfunction in chronic pain reflects maladaptive but potentially reversible neuromuscular and histological plasticity. These findings indicate that rehabilitation strategies should be individualized, involving context-specific exercise strategies to restore muscle structure, function, and regenerative potential in chronic musculoskeletal conditions. Full article

The global spread of high-risk clo1nes (HRCs) of multidrug-resistant (MDR) Pseudomonas aeruginosa has hindered infection control and treatment strategies worldwide. In Colombia, globally relevant HRCs such as ST235 and ST111 have been widely reported. In this study, we evaluated phenotypic and metabolic variations associated with intracellular survival and dissemination in P. aeruginosa. A total of 100 clinical isolates were collected from 22 hospitals in Colombia. The isolates had been previously characterized and classified as MDR or susceptible strains (SSs), and their sequence types (STs) had been earlier determined. Based on this prior characterization, isolates were grouped in this study as multidrug-resistant high-risk clones (HRC, n = 50; corresponding to sequence types ST235 and ST111), multidrug-resistant non-high-risk clones (NHRCs, n = 27; non-ST235/ST111), and susceptible strains (SS, n = 23; also, non-ST235/ST111). Phenotypic traits, including motility, spontaneous mutation frequency, biofilm formation, and pigment production, were evaluated. In addition, a subset of 30 isolates was assessed for intracellular survival in vitro and metabolomic profiling using liquid chromatography-mass spectrometry. HRC isolates exhibited significantly reduced motility compared with NHRC and SS isolates (swarming: HRC vs. NHRC, p = 0.0032; HRC vs. SS, p = 0.010; swimming: HRC vs. NHRC and SS, p < 0.0001; twitching: HRC vs. SS, p = 0.0004), as well as lower pigment production (pyocyanin: HRC vs. NHRC and SS, p < 0.0001; pyoverdine: HRC vs. NHRC, p < 0.0001). Metabolomic analysis revealed increased concentrations of metabolites associated with iron acquisition and siderophore-related pathways in HRC isolates. Overall, these findings suggest that P. aeruginosa HRCs display distinct phenotypic and metabolic patterns that may contribute to persistence and dissemination in clinical settings, contributing to their epidemiological success. Full article

Ferulic acid is a bioactive phenolic compound with potential benefits for skeletal muscle health. In this study, Mongolian horses were used as experimental subjects and were orally administered ferulic acid at doses of 5, 10, or 15 g per horse per day for 40 consecutive days. Muscle biopsy samples were analyzed using proteomics to assess fiber type composition and regulatory protein expression. Ferulic acid supplementation increased the proportion of fast-twitch fibers and upregulated key differentiation factors such as MUSTN1, while modulating glycolysis, ECM remodeling, and calcium signaling pathways. Although ferulic acid induced moderate oxidative stress, it did not trigger classical ferroptosis. Collectively, these findings demonstrate that ferulic acid promotes fast-twitch fiber transformation in horses through coordinated metabolic and signaling mechanisms, highlighting its potential as a nutritional strategy to enhance skeletal muscle adaptability and athletic performance in horses. Full article

Background: Voluntary activation testing quantifies the ability of the motor nervous system to produce maximal force. Laboratory assessment of ankle plantar flexor voluntary activation is common, but field testing in practical settings is limited by equipment portability. We aimed to compare plantar flexor voluntary activation and maximal voluntary contraction (MVC) using a portable device with a standardised laboratory method and evaluate the test–retest reliability of the portable protocol. Methods: We performed a pseudo-randomised, crossover design. Participants completed two protocols: (1) portable force plate testing and (2) a laboratory-based isokinetic dynamometer. Voluntary activation was assessed using twitch interpolation via tibial nerve stimulation. Differences between protocols were analysed using generalised estimating equations. Reliability was assessed with the intraclass correlation coefficient (ICC), standard error of measurement (SEM), and coefficient of variation (CV). Results: Twenty healthy participants (8 females, 12 males; median age 28.5 years) were included. No difference between protocols was detected for voluntary activation (β = 0.6, p = 0.68). The portable protocol demonstrated good reliability (ICC = 0.85) and low measurement error (SEM = 2.56%, CV = 2.79%). Conclusions: We demonstrated that the portable protocol is a valid and reliable method for assessing plantar flexor voluntary activation. It is suitable for assessing within-subject changes over time and can reduce participant attendance burden for neurophysiological muscle testing. Full article

Background: Developing an evidence base for physiotherapy programs for patients with Cerebral Palsy (CP) requires an understanding of the microscopic and metabolic processes in striated muscle. The gracilis muscle represents a logical object of study due to the significant morphological changes in individuals with cerebral palsy. This research aims to study morphological and biochemical alterations in the gracilis muscle depending on the severity of motor impairments in CP patients. Methods: The cross-sectional study included 24 patients stratified by the severity of motor impairment. Intraoperative gracilis muscle samples were obtained during tenomyotomies. Nutritional status of patients, morphometric, and biochemical parameters were evaluated. Results: Initial body mass and Quetelet index (p = 0.02) were lower in GMFCS V patients (p = 0.01) compared to GMFCS IV and GMFCS II-III. Muscle tissue predominated in histological samples of GMFCS II-III and GMFCS V patients (p = 0.79), while connective tissue content was higher in the GMFCS IV group (p = 0.03). Strong, fast-twitch, anaerobic fibers (p = 0.761) with reduced creatine phosphokinase activity (p = 0.012) were more frequently observed in the intraoperative samples of GMFCS V patients. Low creatine phosphokinase activity was revealed in children in the GMFCS V group (p = 0.012). Conclusions: The structural and metabolic abnormalities observed in gracilis muscle of patients with spastic cerebral palsy indicates profound functional muscular dysfunction, representing one of the factors limiting children’s motor ability. The morphological and biochemical alterations in the striated muscle of CP children correlate with severity of motor dysfunction conditioned by the primary upper motor neuron disorders. Less significant changes in muscles in ambulatory children reflect favorable basis for physical therapy. Full article

Background: Type 1 diabetes (T1D) is associated with metabolic and neuromuscular impairments that may influence fatigue mechanisms and limit exercise tolerance. Although previous investigations have characterized muscle performance in T1D, the peripheral fatigue threshold, defined as the maximal sustainable level of peripheral fatigue, remains poorly understood in this population. This study aimed to compare the amplitude of the maximal peripheral fatigue threshold between individuals with T1D and healthy controls to elucidate the effects of T1D on neuromuscular function. Methods: Twenty-two participants (11 with T1D and 11 healthy controls) completed two randomized experimental sessions. In each session, 60 quadriceps maximal voluntary contractions (MVCs) were completed, performed for 3 s with 2 s of rest between contractions. One session was conducted under a non-fatigued control condition (CTRL), and the other followed a fatiguing neuromuscular electrical stimulation (FNMES) protocol. Central and peripheral fatigue were evaluated from the pre- to post-exercise changes in potentiated twitch force (ΔPtw) and voluntary activation (ΔVA), respectively. Critical torque (CT) was calculated as the average torque produced during the last 12 contractions, whereas the curvature constant of the torque–duration relationship (W′) was quantified as the area above CT. Results: Although both groups exhibited a decline in pre-exercise Ptw following the FNMES condition, no significant within-group differences in ΔPtw were observed between sessions (T1D: p = 0.34; controls: p = 0.23). Nevertheless, the extent of peripheral fatigue was significantly lower in participants with T1D than in controls (ΔPtw = −38 ± 11% vs. −52 ± 17%; p < 0.05). Additionally, W′ values were reduced by 24% in the T1D group relative to controls during the CTRL condition (p = 0.02), and CT was significantly lower in T1D participants (262 ± 49 N) compared to controls (353 ± 71 N; p < 0.01). A significant positive correlation was observed between ΔPtw and W′ across groups (r² = 0.62, p < 0.001), suggesting a mechanistic link between peripheral fatigue tolerance and work capacity. Conclusions: The present results indicate that, although individuals with T1D retain the capacity to develop peripheral fatigue, their fatigue threshold and critical torque are markedly attenuated relative to those of healthy individuals. This reduction reflects impaired neuromuscular efficiency and diminished tolerance to sustained contractile activity. The strong relationship between peripheral fatigue and work capacity underscores the contribution of peripheral mechanisms to exercise intolerance in T1D. These results enhance current understanding of fatigue physiology in diabetes and emphasize the need for tailored exercise and rehabilitation strategies to improve fatigue resistance and functional performance in this population. Full article

Neuromuscular electrical stimulation (NMES) has been shown to provide health benefits similar to those of exercise. The aim of this study was to quantify the acute physiological effects of multiple muscle stimulation on the whole body and individual muscles. Nine healthy young adults were tested. NMES of eight muscle groups was performed with NMES stimulators. The vastus lateralis, biceps femoris, medial gastrocnemius, and tibialis anterior muscles of both legs were stimulated for ten minutes with twitch stimulations at the highest comfortable stimulation current. Whole-body metabolism was measured using a metabolic cart. A finger pulse oximeter and a tri-axial accelerometer were used to measure heart rate and muscle fatigue, respectively. Muscle metabolism (mVO₂) was measured using near-infrared spectroscopy (NIRS) during short periods of ischemia. Femoral artery blood flow was measured using Doppler ultrasound. Whole-body VO₂ and heart rate increased moderately by 36% and 22%, respectively, after 10 min of NMES. NMES increased mVO₂ by 12-fold higher than resting on average, with the gastrocnemius having the smallest increase and the vastus lateralis having the greatest increase. Peak diastolic blood flow velocity was significantly reduced by 50% after 10 min of NMES. Simultaneous lower-body NMES moderately improved whole-body metabolism, muscle metabolism, and blood flow, increasing our understanding of the beneficial effects of NMES. Full article

RNA methyltransferases are key regulators of bacterial physiology, yet their specific roles in virulence remain poorly defined. In this study, we characterize PA3840, a putative RNA methyltransferase in Pseudomonas aeruginosa (P. aeruginosa). Deletion of PA3840 specifically impaired twitching motility without affecting bacterial growth, swimming, or swarming. Notably, PA3840 was found to suppress the expression of Type III Secretion System (T3SS) genes, thereby reducing cytotoxicity and host cell rounding. Consistent with these observations, PA3840 expression attenuated pro-inflammatory cytokine production in epithelial cells by inhibiting NF-κB activation. Mechanistic analysis revealed that PA3840 is translocated into host cells in a Type VI Secretion System (T6SS)-dependent manner. This translocation was reduced by hcp1 deletion and nearly abolished by a double deletion of pscF and hcp3, suggesting the involvement of multiple T6SS components and potential interplay with T3SS machinery. However, direct transfection of PA3840 into host cells failed to suppress cytokine expression, indicating that its immunomodulatory function is mediated by a bacterium-intrinsic mechanism rather than direct intracellular action. Collectively, these findings identify PA3840 as a translocated effector that modulates twitching motility and dampens host inflammation by repressing T3SS and NF-κB signaling, revealing a novel layer of post-transcriptional virulence regulation in P. aeruginosa. Full article

Fast-twitch and slow-twitch muscle fibers not only differ in metabolic characteristics and physiological functions but also significantly influence the texture of livestock meat. RNA editing represents an important post-transcriptional regulatory process that can influence both gene expression and the resulting protein function. However, studies on RNA editing events in yak muscle remain limited. This study systematically identified RNA editing events in yak biceps femoris (BF, n = 3) and obliquus externus abdominis (OEA, n = 3) using transcriptomic data, discovering 17,713 unique editing sites, most located in non-coding regions. Within coding regions, 3350 sites were detected, with 1195 resulting in non-synonymous amino acid substitutions. Further analysis revealed that 785 sites potentially affected miRNA binding sites, suggesting RNA editing may participate in miRNA-mediated gene regulation. Tukey’s post hoc test (p < 0.05) identified 242 sites (involving 170 genes) with significantly different editing levels between BF and OEA. KEGG pathway analysis indicated that genes with differential RNA editing were predominantly associated with pathways involved in muscle fiber type transitions, including the MAPK and calcium signaling pathways. Collectively, this study maps the RNA editing landscape in yak muscle tissue and identifies distinct, fiber-type-specific RNA editing patterns between oxidative and glycolytic muscle fibers, including differences in editing levels and site distributions, supporting a potential association between RNA editing and muscle fiber type transformation. Full article

Volatile organic compounds produced by microbes are increasingly recognized as modulators of microbial interactions and mediators of both intra- and inter-kingdom communication. This study explored the possible ecophysiological roles of nine amides from Streptomyces sp. NP10 in quorum sensing (QS) and biofilm formation in Pseudomonas aeruginosa PAO1. GC-MS profiling, synthesis, spectral validation, and co-injection experiments confirmed compound identities. Notably, N-(3-methyl-2-butenyl)acetamide is reported as a new natural product and N-(2-methylbutyl)acetamide as a new Streptomyces-produced metabolite. At subinhibitory concentrations (250 μg/mL), most of the amides enhanced P. aeruginosa biofilm formation, with N-(2-methylbutyl)acetamide, N-(3-methyl-2-butenyl)acetamide, and 2-phenylacetamide showing the strongest effects. Simultaneously, these compounds suppressed QS by reducing the production of N-acyl homoserine lactones (AHLs) and 2-alkyl-4-quinolones (AHQs). Aliphatic acetamides preferentially inhibited short-chain AHLs, while N-acetyltyramine and 2-phenylacetamide mainly affected quinolone signaling. These opposing effects on QS and biofilm are consistent with the involvement of alternative regulatory circuits. Motility assays showed biofilm stimulation was not correlated with altered swarming or twitching. Cross-species assays revealed limited QS inhibition, with only N-acetyltryptamine reducing violacein production in Chromobacterium violaceum CV026. Most of the amides were non-cytotoxic at 100 μM (10.5–20.2 μg/mL), except for 2-phenylacetamide. Overall, these amides likely serve as microbial signals influencing QS and biofilm formation, offering leads for anti-virulence strategies. Full article