Muscle Morphology Research Articles

Evaluation of the paraspinal muscles mophology using magnetic resonance imaging in adult patients with nonspecific chronic low back pain in Port Harcourt Rivers State Nigeria

Background: Nonspecific chronic low back pain (CLBP) is a major public health concern globally and the leading cause of musculoskeletal disability, affecting mainly adults in their productive years with a high economic impact in the society. Objective: This study was designed to evaluate the changes in the paraspinal muscles (lumbar multifidus) morphology using data obtained from MRI of the lumbosacral spine in adult participants with non-specific chronic low back pain. Materials and methods: This was a cross-sectional study, involving 200 adult participants with non-specific chronic low back pain undergoing MRI of the lumbosacral spine at the Department of Radiology, Rivers State University Teaching Hospital (RSUTH), Port Harcourt, Nigeria, during a six months period. Data recorded include lumbar multifidus muscle (LMM) morphology and lumbar spine pathologies Results: The LMM CSA for L1, L2, L3, L4 and L5 were 2.24±0.84, 3.59±1.15, 5.18±1.60, 6.66±1.75 and 7.27±2.62 respectively. The frequency distribution of LMM fatty infiltration in percentage showed Grade 0 was highest at L1 (86.5%, n= 173) and lowest at L5 (6.5%, n=13); Grade 1 was highest at L4 (73%, n=146) and lowest at L1 (13.5%, n=2) and Grade 2 was highest at L5 (22.5%, n=45) and lowest at L1 (0.0%, n=0). The lumbar pathologies noted were 200(100%) disc abnormalities, while 178(89.0%) had neural foraminal narrowing, nerve root compression and spinal canal stenosis each. Facet joint arthrosis and spondylosis were 177(88.5%) and 176(88.0%) respectively. Conclusion: Dysfunctional LMM was observed to increase with advancing age, severe in females and individuals with elevated BMI and cuts across various occupations. Measures aimed at improving and maintaining the quality of the LMM should be encouraged, as this will help in reducing the prevalence of nonspecific CLBP

Quantitative assessment of masticatory muscles based on skull muscle attachment areas in Carnivora.

Masticatory muscles are composed of the temporalis, masseter, and pterygoid muscles in mammals. Each muscle has a different origin on the skull and insertion on the mandible; thus, all masticatory muscles contract in different directions. Collecting in vivo data and directly measuring the masticatory muscles anatomically in various Carnivora species is practically problematic. This is because some carnivorans can be ferocious, rare, or even extinct. Consequently, the most practical method to collect data on the force generated by the masticatory muscle is to estimate the force based on skulls. The physiological cross-sectional area (PCSA) of each masticatory muscle, which correlates to the maximum force that can be produced by a muscle, was quantified. Using computed tomography, we defined the three-dimensional measurement area for 32 carnivoran species based on the origin and insertion of masticatory muscles specified by observable crests, ridges, and scars. Subsequent allometric analysis relating the measurement area on skull surface to the PCSA for each masticatory muscle measured in fresh specimens revealed a strong correlation between the two variables. This finding indicates that within Carnivora, an estimation of absolute masticatory muscle PCSA can be derived from measurements area on skull surface. This method allows for the use of cranial specimens, housed in museums and research institutions, that lack preserved masticatory muscles in quantitative studies involving masticatory muscle PCSA. This approach facilitates comprehensive discussions on the masticatory muscle morphology of Carnivora, including rare and extinct species.

GSK3 inhibition improves skeletal muscle function and whole-body metabolism in male mouse models of Duchenne muscular dystrophy

Inhibiting glycogen synthase kinase 3 (GSK3) improves muscle function, metabolism, and bone health in many diseases and conditions; however, whether GSK3 should be targeted for Duchenne muscular dystrophy (DMD), a severe muscle wasting disorder with no cure, remains unknown. Here, we show the effects of GSK3 inhibition in male DBA/2J (D2) and C57BL/10 (C57) mdx mice. Treating D2 mdx mice with GSK3 inhibitors alone or in combination with aerobic exercise improves muscle strength, endurance, and morphology, attenuates the hypermetabolic phenotype, and enhances insulin sensitivity. GSK3 inhibition in C57 mdx mice also improves muscle fatigue resistance and increases cage ambulation. Moreover, muscle-specific GSK3 knockdown in mdx mice augments muscle force production and endurance. In both mdx strains, GSK3 inhibition increases bone mineral content and density. Overall, these improvements to muscle, metabolic, and bone health with GSK3 inhibition in mdx mice may have clinical implications for patients with DMD, where the current standard of care, glucocorticoids, delay the loss of ambulation but increase the risk for insulin resistance and osteoporosis. Along with our observation of lowered β-catenin content in DMD myoblasts, a known cellular target for GSK3, this study provides ample evidence in support of inhibiting GSK3 for this disease.

Optimizing Rehabilitation Outcomes Through Rehabilitative Ultrasonography: Applications in Musculoskeletal Care

Rehabilitative ultrasonography (RUS) has significantly enhanced musculoskeletal care by providing real-time, detailed visualizations of muscle, tendon, and soft tissue structures. This symposium explores the diverse applications of RUS, highlighting its advantages over traditional imaging methods. In muscle rehabilitation, RUS is pivotal for assessing muscle morphology, activation patterns, and providing biofeedback, thereby optimizing personalized rehabilitation programs. For tendon injuries, RUS facilitates precise evaluation of tendon integrity, enabling accurate diagnosis, monitoring, and guiding therapeutic interventions. Beyond muscles and tendons, RUS is invaluable in diagnosing and managing soft tissue pathologies, such as ligament and fascia injuries, allowing for targeted treatment strategies. By offering superior precision, safety, and cost-effectiveness, RUS sets a new benchmark in rehabilitation practices, leading to improved patient outcomes and a deeper understanding of musculoskeletal conditions. The integration of RUS into rehabilitation medicine represents a transformative advancement in patient care and treatment efficacy.

Muscle type-specific effects of bilateral abobotulinumtoxinA injection on muscle growth and contractile function in spastic mice.

Intramuscular injection of botulinum neurotoxin type A (BoNT-A) is commonly used to improve or maintain the joint range of motion in young children with spasticity. However, the effectiveness of BoNT-A treatment is variable and movement limitations are recurrent. Here we show long-term effects of a single, bilateral abobotulinumtoxinA (aboBoNT-A) injection in the gastrocnemius medialis and soleus muscles of wild-type and spastic (B6.Cg-Glrbspa/J with a mutation in the glycine receptor) mice at a young age (6-7 days). Specifically, we evaluated the impact of aboBoNT-A-A on gait, physical performance, and spontaneous physical behavior, as well as on contractile force characteristics, morphology, and histological phenotype of soleus and gastrocnemius muscles by comparing their results to those of saline-injected controls up to 9 weeks after the injection. The detailed time course of the study specifies the timing of the aboBoNT-A injection at 1 week, the period of behavioral studies from 4-9 weeks, and the age of the mice (10 weeks) at the time of contractile force characteristics and histology assessments. In spastic mice, aboBoNT-A injection had a minor and very specific effect on physical performance, by only modestly increasing stride length as a function of age. aboBoNT-A injection caused a reduction in the force-generating capacity and a slightly smaller physiological cross-sectional area in gastrocnemius medialis, but not in soleus. Reduced physiological cross-sectional area in aboBoNT-A-injected muscles was due to a lower number of muscle fibers, rather than reduced muscle fiber cross-sectional area. The percentage of slow-type muscle fibers and mitochondrial succinate dehydrogenase activity were increased, which was associated with an improved muscle endurance capacity. In conclusion, aboBoNT-A injection reduced the number of muscle fibers, causing muscle hypertrophy in remaining fibers and a shift towards more oxidative fibers, resulting in an improved endurance capacity and gait. This study proposed potential cellular mechanisms for the therapeutic efficacy of aboBoNT-A in spasticity.

Effect of selective dorsal rhizotomy on neuromuscular symptoms, muscle morphology, and motor function in children with spastic cerebral palsy.

To investigate the effect of selective dorsal rhizotomy (SDR) on an integrated outcome set 1-year post-SDR, in a cohort of children with spastic cerebral palsy (CP). Fifteen children with bilateral spastic CP (median age 8 years 8 months [interquartile range 3 years 3 months], 11 males, four females, eight in Gross Motor Function Classification System (GMFCS) level II, seven in GMFCS level III) were measured pre- and 1-year post-SDR. Clinical scales and goniometry assessed plantar flexor spasticity, range of motion, strength, and selectivity. Spasticity was also quantified via an instrumented assessment. Medial gastrocnemius macroscopic muscle morphology (absolute and normalized muscle belly, tendon and muscle-tendon unit length, cross-sectional area, muscle volume) was assessed using ultrasound. Gait profile score, ankle and knee gait variable scores, walking speed, cadence, and step length were extracted from gait analysis. Gross motor function was assessed using the Gross Motor Function Measure-66 item set. Wilcoxon signed-rank test was used to analyse pre- and post-SDR changes. A reference database was used to qualitatively judge muscle growth post-SDR with respect to muscle growth of children with spastic CP without SDR intervention. Significant changes (p < 0.05) were seen for spasticity, selectivity, all absolute morphology parameters, normalized tendon and muscle-tendon unit length, and all gait parameters, except walking speed and cadence. Muscle growth of children with and without SDR was comparable. SDR is an effective spasticity reducing treatment and does not adversely affect natural muscle growth in spastic CP.

Molecular basis of photoinduced seasonal energy rheostasis in Japanese quail (Coturnix japonica)

Seasonal rhythms in photoperiod are a predictive cue used by many temperate-zone animals to time cycles of lipid accumulation. The neuroendocrine regulation of seasonal energy homeostasis and rheostasis are widely studied. However, the molecular pathways underlying tissue-specific adaptations remain poorly described. We conducted two experiments to examine long-term rheostatic changes in energy stability using the well-characterized photoperiodic response of the Japanese quail. In experiment 1, we exposed quails to photoperiodic transitions simulating the annual photic cycle and examined the morphology and fat deposition in liver, muscle, and adipose tissue. To identify changes in gene expression and molecular pathways during the vernal transition in lipid accumulation, we conducted transcriptomic analyses of adipose and liver tissues. Experiment 2 assessed whether the changes observed in Experiment 1 reflected constitutive levels or were due to time-of-day sampling. We identified increased expression of transcripts involved in adipocyte growth, such as Cysteine Rich Angiogenic Inducer 61 and Very Low-Density Lipoprotein Receptor, and in obesity-linked disease resistance, such as Insulin-Like Growth Factor Binding Protein 2 and Apolipoprotein D, in anticipation of body mass gain. Under long photoperiods, hepatic transcripts involved in fatty acid (FA) synthesis (FA Synthase, FA Desaturase 2) were down-regulated. Parallel upregulation of hepatic FA Translocase and Pyruvate Dehydrogenase Kinase 4 expression suggests increased FA uptake and inhibition of the pyruvate dehydrogenase complex. Our findings demonstrate tissue-specific biochemical and molecular changes that drive photoperiod-induced adipogenesis. These findings can be used to determine conserved pathways that enable animals to accumulate fat without developing metabolic diseases.

Sex-differences in neuromuscular control of hip abductors during isometric submaximal tasks

BackgroundOne key focus in the literature is the need to better understand how males and females perform neuromuscular control, which requires consideration of muscle morphology, as it may change neural drive during force production. Although previous studies focused on muscles around the knee and ankle, it is crucial to explore the behavior of other muscles, such as the hip abductors, since many lower limb conditions more common in females have been associated with alterations in hip muscles. Research questionsAre electromyography (EMG) variables (amplitude and low- and high frequency bands) of hip abductors during submaximal isometric tasks different between males and females? How is muscle size associated with EMG responses during these tasks? MethodsThirty-six participants (males, n = 18; females, n = 18) had muscle and subcutaneous thickness of gluteus medius (GMed) and tensor fascia latae (TFL) measured. They then performed an estimated one-repetition maximum (1RM) test in a side-lying hip abduction exercise, followed by two 10-s submaximal tasks: (i) side-lying hip abduction with 50 % 1RM and (ii) with 20 % 1RM. GMed and TFL EMG amplitude and frequency bands (low and high frequency components) were analyzed. ResultsFemales had higher GMed EMG amplitude, lower low-frequency, and higher high-frequency components than males in both tasks (p = 0.001–0.040). No differences were observed in TFL EMG variables. Greater GMed thickness was associated with lower amplitudes in the 50 % 1RM task (r = − 0.35; p = 0.03), while greater TFL thickness was associated with lower low-frequency [20 % 1RM: r = − 0.70; p = 0.002; 50 %-1RM: r = − 0.65; p = 0.005] and higher high-frequency components [20 % 1RM: r = 0.74; p = 0.001; 50 %-1RM: r = 0.76; p < 0.001] only in females. SignificanceMales and females employ different neuromuscular control strategies, which vary among the synergists for hip abduction.

Reliability of Ultrasonographically Acquired Muscle Morphology Based on a Cohort of Men and Women

Objective: The objective was to evaluate intrarater and inter-rater reliability of ultrasonography muscle morphology measurements in men and women, considering morphological differences between the genders. Materials and Methods: Thirty-two healthy subjects (16 male; 16 female; 26.6 ± 4.9 years) participated in two evaluation days. On day 1, subjects were evaluated by a single experienced rater, who repeated the evaluation on the next testing day along with two other raters. Muscle morphology of quadriceps femoris (QMT), rectus femoris (RFMT), vastus intermedius (VIMT), vastus medialis (VMMT), and vastus lateralis (VLMT) muscle thickness, rectus femoris muscle cross-sectional area (RFCSA), vastus lateralis muscle fascicle length (VLFL), and pennation angle (VLPA) were obtained. Reliability was evaluated by intraclass correlation coefficients (ICCs). Results: All intrarater comparisons demonstrated good reliability (ICC &gt;0.90), even after participants’ gender stratification (ICC &gt;0.81). Inter-rater comparisons for RFCSA, and muscle thickness showed good reliability (ICC &gt;0.76). Male’s VLFL and VLPA reliability was considered insufficient (ICC = 0.58 and 0.60, respectively), while female’s was slightly higher (ICC = 0.79 and 0.75, respectively). Conclusion: Ultrasonography has potential to be used to observe changes in muscle size, but pennation angle and fascicle length should be evaluated by the same rater.

The strength of associations between ultrasound measures of upper limb muscle morphology and isometric muscle strength: An exploratory study.

Assessing upper limb muscle strength is important for understanding health outcomes, such as daily function and mortality. Ultrasound (US) is increasingly used to evaluate muscle health, but the relationship between its measures of morphology and isometric strength has not been thoroughly explored in upper limb muscles. The aim of this study was to evaluate the associations between US morphological measures and isometric strength in functionally relevant upper limb muscles in healthy adults. Twenty-four healthy volunteers (30.0 ± 10.8 years) underwent B-mode, axial US scans of the first dorsal interosseus (FDI), flexor pollicis longus (FPL), biceps brachii (BB), brachialis (BR), and triceps brachii lateral head (TB). Participants performed corresponding maximal voluntary contractions (MVC), including first digit distal phalanx flexion, second digit abduction, and elbow flexion and extension. US images were segmented to obtain maximal muscle thickness (MT) and cross-sectional area (CSA). Strong positive correlations were found between muscle strength and BB MT (r = .83; p < .001), BR CSA (r = .84; p < .001), and TB MT (r = .70; p < .001). Moderate positive correlations were found for strength and FDI CSA (r = .67; p < .001), FDI MT (r = .47; p < .05), FPL CSA (r = .54; p < .01), and FPL MT (r = .42; p < .05). No significant correlation was found between strength and BR MT (r = .16; p > .05). Our data showed moderate-to-strong associations between US muscle morphology and strength, suggesting that US is likely a good biomarker for strength. However, its use is not "one size fits all." Future investigations should continue to assess this relationship in different muscles and expand the generalizability to clinical populations.

The Activation of Endogenous Proteases in Shrimp Muscle Under Water-Free Live Transport.

Water-free transportation (WFT) causes shrimp (Penaeus vannamei) flesh quality deterioration. However, the roles of endogenous protease-induced protein hydrolysis have been neglected in the research. In the present study, calpain zymography, gelatinase zymography, the hematoxylin-eosin staining method, and other methods were applied to investigate the response of various endogenous proteases (cathepsin, calpain, and gelatinase), the myofibril fragmentation index (MFI), and the microscopic morphology of shrimp muscle during WFT in comparison with the shrimp under the conventional water transportation strategy (WT). The results showed that the total activity of proteases in shrimp muscle increased significantly (p ≤ 0.05) after simulated transportation. Cathepsins and gelatinases were activated during WFT. No significant (p > 0.05) changes of the activity of caspase-3 and the muscle cell apoptosis rate were detected in shrimp muscle cells after WFT. In addition, the MFI increased and the gap among muscle fiber bundles enlarged after WFT. Compared with WFT, no significant (p > 0.05) effect on the activities of calpain, gelatinase, and caspase-3 in the muscle of shrimp was found after WT, and only the activity of cathepsin L significantly increased (p ≤ 0.05). Based on the findings, we concluded that the activation of various endogenous proteases was induced during WFT.

Intra-Rater Reliability of Panoramic Ultrasound Imaging for Determining Quadriceps Muscle Cross-Sectional Area inMiddle-Aged and Elderly Adults.

Panoramic ultrasound (US) is an extended field-of-view (EFOV) imaging technique that enables visualization of large-scale skeletal muscles. This technique has previously been found to produce valid and reliable quantifications of muscle morphology in primarily young male subjects. The purpose was to investigate the intra-rater between-session test-retest reliability of panoramic US imaging for determining vastus lateralis (VL) and rectus femoris (RF) cross-sectional area (mCSA) in healthy middle-aged to elderly adults. In this cross-sectional study, axial panoramic US images of the RF and VL muscles were captured in 23 healthy females and males aged 47 to 78. Assessed across two sessions 3-7 days apart, intra-rater reliability was evaluated by intraclass correlation coefficients (ICC3,2), within-subject coefficient of variation , standard error of measurement (SEM), and minimal detectable change (MDC). Mean mCSA for RF was mean ± SD, 7.5 ± 2.7 cm2 on both test days, with a numeric difference of 0.8%. Mean VL mCSA was 20.6 ± 6.6 cm2 and 20.5 ± 6.5 cm2 on test days 1 and 2, respectively. Test-retest ICC were: 0.997 (95% CI: 0.994-0.999) for RF and 0.995 (95% CI: 0.989-0.998) for VL. was 2.6% for RF and 2.4% for VL. SEM was 0.2 cm2 for RF and 0.5 cm2 for VL. MDC was 0.4 cm2 for RF and 1.3 cm2 for VL. In conclusion, panoramic EFOV US is a highly reliable imaging technique for assessing RF and VL mCSA in middle-aged and elderly adults. These findings endorse the clinical and research utility of EFOV US and its sensitivity for detecting even minor changes in skeletal muscle size.

A comparative analysis of lumbar paraspinal muscle morphology between two movement system impairment subgroups of chronic nonspecific low back pain

BackgroundBased on the kinesiopathologic model, the Movement System Impairment (MSI) classification of LBP has shown that repetitive movements could contribute to pathoanatomic tissue changes. However, these changes have not been evaluated in different MSI classification subgroups of patients with LBP. ObjectiveThis study compared the grades of fatty infiltration as one of the muscle's pathologic changes in the lower lumbar paraspinal and psoas muscles between the two subgroups of patients diagnosed with MSI syndromes having opposite movement direction impairments. DesignObservational cross-sectional study. MethodForty-five participants with chronic LBP were enrolled in the study, with 23 patients in the lumbar flexion-rotation (FlexRot) subgroup and 22 in the lumbar extension-rotation (ExtRot) subgroup of MSI. Magnetic resonance imaging (MRI) and the Goutallier Classification System (GCS) were used for fatty grading of lumbar paraspinal and psoas muscles. After the reliability of this grading scale was evaluated, the results were compared between the two subgroups. ResultsThe Mann–Whitney U Test showed significantly higher fat infiltration of lower lumbar multifidus and erector spinae muscles in the lumbar ExtRot subgroup, with no significant difference between the two subgroups in terms of psoas muscles (P ≤ 0.05). Inter-rater reliability of GCS was acceptable to excellent, and intra-rater reliability was good to excellent. ConclusionThe fatty infiltration grade of lumbar paraspinal muscles in L4-L5 and L5-S1 levels are significantly different between the two LBP subgroups of MSI that have two opposite movement direction impairments. The lumbar paraspinal muscles, which contribute to extension, have a higher grade of fat in the ExtRot subgroup, whose symptoms are aggravated by lumbar extension.

Classifications Based on Dynamic Navicular Drop during Gait and Characteristics of Flat Foot Muscle Morphology

Classifications Based on Dynamic Navicular Drop during Gait and Characteristics of Flat Foot Muscle Morphology

Preventive and therapeutic effects of molecular iodine in a model of diabetes mellitus induced by streptozotocin

Diabetes mellitus (DM) is a multifactorial condition that involves oxidative alterations and dysbiosis of the gut microbiota associated with an imbalance in glucose metabolism. Therefore, the need to develop integrative therapies that are both effective and have fewer side effects has become evident in recent years. Molecular iodine (I2) has antioxidant effects in preclinical hyperglycemic models. The present work analyzes the preventive and therapeutic effects of oral I2 supplementation in a DM model induced by low doses of streptozotocin (STZ). Male CD1 mice (12 weeks old) were divided into the following groups: control, STZ (20 mg/kg/day, i.p., for 5 days), I2 (0.2 mg/Kg in drinking water), preventive (STZ + I2), and therapeutic (I2 supplementation from day 35 to day 90; STZ + I2(Ther)). The supplementation with I2 prevented and normalized hyperglycemia, hypercholesterolemia, and hypertriglyceridemia associated with STZ, preserving pancreatic, liver, muscle, and adipose tissue morphology and normalizing inflammatory gene induction (TLR2, TLR4, NFkβ, TNFα) in several tissues. Furthermore, compared to the STZ group, the presence of I2 favored a more significant abundance of beneficial bacteria that support the integrity of the intestinal epithelial barrier and higher α-diversity. In conclusion, the I2 supplement has preventive and therapeutic effects, reducing oxidative damage and reestablishing microbiota diversity following STZ exposure.

Oxidative state is associated with migration distance, but not traits linked to flight energetics

Flight can be highly energy demanding, but its efficiency depends largely on flight style, wing shape and wing loading, and a range of morphological and lifestyle adaptations that can modify the cost of sustained flight. Such behavioural and morphological adaptations can also influence the physiological costs associated with migration. For instance, during intense flight and catabolism of reserves, lipid damage induced by pro‐oxidants increases, and to keep oxidative physiological homeostasis under control, the antioxidant machinery can be upregulated. Studies on the oxidative physiology of endurance flight have produced contradictory results, making generalization difficult, especially because multispecies studies are missing. Therefore, to explore the oxidative cost of flight and migration, we used samples collected during the breeding season from 113 European bird species and explored the associations of measures of antioxidant capacity (total antioxidant status, uric acid and glutathione concentration) and oxidative damage of lipids (malondialdehyde) with variables reflecting flight energetics (year‐round or specifically during migration) using a phylogenetic framework. We found that none of the traits predicting year‐round flight energy expenditure (flight style, wing morphology and flight muscle morphology) explained any measures of oxidative state. Our results suggest that birds endure their everyday flight exercise without or with low oxidative cost. However, oxidative damage to lipids and one component of the endogenous antioxidant system (uric acid), measured after the end of spring migration on breeding adult birds, increased with migration distance. Our results suggest that migration could have oxidative consequences that might be carried over to subsequent life‐history stages (breeding).

Decoding Ultramarathon: Muscle Damage as the Main Impediment to Performance.

The biological determinants of performance have been well described for running races up to and including the marathon (42.2km). Ultramarathon is more complex. Events range from 50 to 5000km in single or multiple stages, are contested in various environments and terrains, and force athletes to contend with diverse performance-limiting issues such as fueling, hydrating, gastrointestinal distress, muscle damage, and sleep deprivation. Ultramarathons are not simply "long marathons." Nevertheless, scientific developments over the past decade have inched us toward a more complete picture of the psychophysiological factors underpinning performance. In this Current Opinion, we argue that muscle damage and associated fatigue is the main impediment to performance in long ultramarathons; more performance-limiting than aerobic capacity, running economy, or gastrointestinal distress. To assess an athlete's tolerance to ultramarathon-specific muscle damage and fatigue, we propose a lab-based protocol comprising downhill running with pre- to post-exercise measures of muscle contractile function following electrical or magnetic stimulation of the quadriceps muscles or their central nerves, muscle damage biomarkers (e.g., creatine kinase, lactate dehydrogenase, and myoglobin), and muscle morphology via imaging techniques. We close by offering training and racing advice on mitigating the deleterious effects of muscle damage. The twofold aims of this paper are (i) to enable athletes and their teams to better prepare for races and (ii) to help medical personnel identify the physiological milieu most likely to afflict the ultrarunner.

EMC1 Is Required for the Sarcoplasmic Reticulum and Mitochondrial Functions in the Drosophila Muscle

EMC1 is part of the endoplasmic reticulum (ER) membrane protein complex, whose functions include the insertion of transmembrane proteins into the ER membrane, ER–mitochondria contact, and lipid exchange. Here, we show that the Drosophila melanogaster EMC1 gene is expressed in the somatic musculature and the protein localizes to the sarcoplasmic reticulum (SR) network. Muscle-specific EMC1 RNAi led to severe motility defects and partial late pupae/early adulthood lethality, phenotypes that are rescued by co-expression with an EMC1 transgene. Motility impairment in EMC1-depleted flies was associated with aberrations in muscle morphology in embryos, larvae, and adults, including tortuous and misaligned fibers with reduced size and weakness. They were also associated with an altered SR network, cytosolic calcium overload, and mitochondrial dysfunction and dysmorphology that impaired membrane potential and oxidative phosphorylation capacity. Genes coding for ER stress sensors, mitochondrial biogenesis/dynamics, and other EMC components showed altered expression and were mostly rescued by the EMC1 transgene expression. In conclusion, EMC1 is required for the SR network’s mitochondrial integrity and influences underlying programs involved in the regulation of muscle mass and shape. We believe our data can contribute to the biology of human diseases caused by EMC1 mutations.

Evolutionary divergence of facial muscle physiology between domestic dogs and wolves.

Domestic dogs (Canis familiaris) are descended from gray wolf (Canis lupus) populations that inhabited Western Europe and Siberia. The specific timing of dog domestication is debated, but archeological and genetic evidence suggest that it was a multi-phase process that began at least 15,000 years ago. There are many morphological differences between dogs and wolves, including marked divergence in facial muscle morphology, but we know little about the comparative physiology of these muscles. A better understanding of comparative facial muscle physiology between domestic dogs and gray wolves would improve our conceptual framework for the processual mechanisms in dog domestication. To address these issues, we assessed the myosin profiles (type I and type II) from the zygomaticus and orbicularis oris muscles of 6 domestic dogs and 4 gray wolves. Due to small sample sizes, statistical analyses were not done. Results reveal that sampled domestic dogs have almost 100% fast-twitch (type II) muscle fibers while gray wolves have less than 50%, meaning that dog faces can contract fast while wolf faces are able to sustain facial muscle contraction. Sample sizes are limited but the present study indicates that dog domestication is associated with not only a change in facial muscle morphology but a concomitant change in how these muscles function physiologically. Selective pressures in the development of communication between dogs and humans using facial expression may have influenced this evolutionary divergence, but the paedomorphic retention of barking in adult dogs may have also played a role.

Long-Term Effects of Different Number of Botulinum Toxin Injections Into the Gastrocnemius Muscle on Function and Muscle Morphology in Children With Cerebral Palsy

BackgroundBotulinum toxin (BoNT) injections are used to reduce spasticity, and sometimes repeated injections are required. The aim of this study is to investigate the effects of the number of BoNT injections into the gastrocnemius muscle on function, muscle morphology, muscle stiffness, and muscle vascularization in children with cerebral palsy (CP). MethodsThe study included 22 children with spastic-type CP aged five to 13 years who had previously received one, two, or three BoNT injections into the gastrocnemius muscle. A total of 29 gastrocnemius muscles were evaluated. Gastrocnemius muscle morphology was examined by ultrasonography, muscle stiffness by shear wave ultrasound elastography, and muscle vascularization by superb microvascular imaging. The functional status of the children was evaluated by the Gross Motor Function Measurement, the Timed-Up-and-Go Test, the Squat Test, the Vertical Jumping Test, and the Sit-and-Reach Test. ResultsIn the motor functions and muscle morphology values were similar in all three groups (P > 0.05). Muscle stiffness values were higher (P = 0.035) and vascularization values were lower (P = 0.03) in the group that received three injections compared with the groups that received one injection. There was a moderate positive correlation of the number of BoNTs with muscle stiffness (P < 0.05, r = 0.454) and a moderate negative correlation with muscle vascularization (P < 0.05, r = −0.497). ConclusionsRepeated BoNT applications have no effect on motor functions and muscle morphology in children with CP, whereas BoNT injections administered three times increase muscle stiffness and decrease vascularization.