Increased Fiber Size Research Articles

A robust staggered localizing gradient enhanced isotropic damage model for failure prediction in heterogeneous materials

In the present work, a robust and efficient staggered localizing gradient damage model (LGDM) with a simple isotropic damage variable is adopted to predict crack growth phenomena in bi-material and fiber reinforced composites under mixed-mode loading. We first consider a series of three-point bend experiments conducted by Lee and Krishnaswamy (2000) on bi-material specimens of PMMA/Al6061, where the staggered LGDM is shown to capture correct crack profiles under different boundary conditions. It is observed that the numerical crack paths are well compared with the experimental crack paths. Next, a fiber reinforced composite with a central fiber is considered where the effect of change in fiber sizes on the overall structural responses is investigated. It is seen that the increasing fiber size results in reduced load carrying capacity of fiber reinforced composites. Finally, we consider a fiber reinforced composite with fibers located on opposite edges of the specimen. Here, a parametric study on the strength ratio of the matrix phase is conducted to investigate their effect on crack initiation, propagation, and orientation. These simulations highlight the predictive capability of the present model in terms of structural responses as well as sharp crack profiles.

A robust mix design method for steel fiber reinforced self-compacting concrete

The lack of robustness in the production of steel-fiber-reinforced self-compacting concrete (SFRSCC) can lead to unsatisfactory performance. The research aimed to develop an approach for assessing and designing the robustness of SFRSCC proportions. To achieve this, a semi-empirical workability framework was proposed, and slump flow tests were conducted for framework's parameter calibration and accuracy validation. Subsequently, the derived self-compacting zone (SCZ) from the framework was utilized as the robustness indicator, and further investigated its evolution law. The derivation indicated that the framework allowed for the quantification of component proportion based on film thickness and aggregate characteristics, as well as the workability configuration through film thickness and rheology, linking the workability and mix proportions of SFRSCC. Experiments results revealed negative correlations between interparticle and fiber-aggregate contacts with increasing film thickness, while the increasing fiber dosage enlarged inter-contact. The further contact calibration in the framework enabled precise delineation of the self-flow boundary, but the reliability of segregation boundaries decreased due to mortar instability. SCZ's evolution with film thickness and paste flowability demonstrated the inherent conflict between performance and mix proportion robustness, the increasing fiber size also significantly compressed SCZ ranges. The balance of performance and robustness, as well as the fiber size control, were crucial for achieving reliable SFRSCC production. This study provided valuable insights for the industrial prefabrication or on-site application of SFRSCC.

Agonist of growth hormone-releasing hormone improves the disease features of spinal muscular atrophy mice

Spinal muscular atrophy (SMA) is a severe autosomal recessive neuromuscular disease affecting children and young adults, caused by mutations of the survival motor neuron 1 gene (SMN1). SMA is characterized by the degeneration of spinal alpha motor neurons (αMNs), associated with muscle paralysis and atrophy, as well as other peripheral alterations. Both growth hormone-releasing hormone (GHRH) and its potent agonistic analog, MR-409, exert protective effects on muscle atrophy, cardiomyopathies, ischemic stroke, and inflammation. In this study, we aimed to assess the protective role of MR-409 in SMNΔ7 mice, a widely used model of SMA. Daily subcutaneous treatment with MR-409 (1 or 2 mg/kg), from postnatal day 2 (P2) to euthanization (P12), increased body weight and improved motor behavior in SMA mice, particularly at the highest dose tested. In addition, MR-409 reduced atrophy and ameliorated trophism in quadriceps and gastrocnemius muscles, as determined by an increase in fiber size, as well as upregulation of myogenic genes and inhibition of proteolytic pathways. MR-409 also promoted the maturation of neuromuscular junctions, by reducing multi-innervated endplates and increasing those mono-innervated. Finally, treatment with MR-409 delayed αMN death and blunted neuroinflammation in the spinal cord of SMA mice. In conclusion, the present study demonstrates that MR-409 has protective effects in SMNΔ7 mice, suggesting that GHRH agonists are promising agents for the treatment of SMA, possibly in combination with SMN-dependent strategies.

Tamoxifen improves muscle structure and function of Bin1- and Dnm2-related centronuclear myopathies.

Congenital myopathies define a genetically heterogeneous group of disorders associated with severe muscle weakness, for which no therapies are currently available. Here we investigated the repurposing of tamoxifen in mouse models of mild or severe forms of centronuclear myopathies due to mutations in BIN1 (encoding amphiphysin 2) or DNM2 (encoding dynamin 2), respectively. Exposure to a tamoxifen-enriched diet from 3 weeks of age resulted in significant improvement in muscle contractility without increase in fibre size in both models, underlying an increase in the capacity of the muscle fibres to produce more force. In addition, the histological alterations were fully rescued in the BIN1-centronuclear myopathies mouse model. To assess the mechanism of the rescue, transcriptome analyses and targeted protein studies were performed. Although tamoxifen is known to modulate the transcriptional activity of the oestrogen receptors, correction of the disease transcriptomic signature was marginal on tamoxifen treatment. Conversely, tamoxifen lowered the abnormal increase in dynamin 2 protein level in both centronuclear myopathies models. Of note, it was previously reported that dynamin 2 increase is a main pathological cause of centronuclear myopathies. The Akt/mTOR muscle hypertrophic pathway and protein markers of the ubiquitin-proteasome system (the E3 ubiquitin ligase cullin 3) and autophagy (p62) were increased in both models of centronuclear myopathies. Normalization of dynamin 2 level mainly correlated with the normalization of cullin 3 protein level on tamoxifen treatment, supporting the idea that the ubiquitin-proteasome system is a main target for the tamoxifen effect in the amelioration of these diseases. Overall, our data suggest that tamoxifen antagonizes disease development probably through dynamin 2 level regulation. In conclusion, the beneficial effect of tamoxifen on muscle function supports the suggestion that tamoxifen may serve as a common therapy for several autosomal forms of centronuclear myopathies.

MiR-29c Increases Protein Synthesis in Skeletal Muscle Independently of AKT/mTOR.

microRNAs negatively regulate gene expression by blocking translation or increasing mRNA degradation. In skeletal muscle, these molecules play important roles in adaptive responses, and ongoing investigations are necessary to understand the fine-tune regulation of skeletal muscle mass. Herein we showed that skeletal muscle overexpression of miR-29c increased fiber size and force at 7 and 30 days after electrotransfer. At both time points, AKT/mTOR pathway components were downregulated, and, surprisingly, overall protein synthesis was strongly elevated at day 7, which normalized by day 30 after pCMVmiR-29c electrotransfer. These results indicate that miR-29c expression induces skeletal muscle hypertrophy and gain of function, which involves increased overall protein synthesis in spite of the deactivation of the AKT/mTOR pathway.

Clinicopathological-genetic features of congenital myasthenic syndrome from a Chinese neuromuscular centre.

Congenital myasthenic syndrome (CMS) encompasses a heterogeneous group of inherited disorders affecting nerve transmission across the neuromuscular junction. The aim of this study was to characterize the clinical, physiological, pathohistological and genetic features of nine unrelated Chinese patients with CMS from a single neuromuscular centre. A total of nine patients aged from neonates to 34 years were enrolled who exhibited initial symptoms. Physical examinations revealed that all patients exhibited muscle weakness. Muscle biopsies demonstrated multiple myopathological changes, including increased fibre size variation, myofibrillar network disarray, necrosis, myofiber grouping, regeneration, fibre atrophy and angular fibres. Genetic testing revealed six different mutated genes, including AGRN (2/9), CHRNE (1/9), GFPT1 (1/9), GMPPB (1/9), PLEC (3/9) and SCN4A (1/9). In addition, patients exhibited differential responses to pharmacological treatment. Prompt utilization of genetic testing will identify novel variants and expand our understanding of the phenotype of this rare syndrome. Our findings contribute to the clinical, pathohistological and genetic spectrum of congenital myasthenic syndrome in China.

Findings of limb-girdle muscular dystrophy R7 telethonin-related patients from a Chinese neuromuscular center.

Limb-girdle muscular dystrophy (LGMD) is a group of clinically and genetically heterogeneous neuromuscular disorders. LGMD-R7, which is caused by telethonin gene (TCAP) mutations, is one of the rarest forms of LGMD, and only a small number of LGMD-R7 cases have been described and mostly include patients from Brazil. A total of two LGMD-R7 patients were enrolled at a Chinese neuromuscular center. Demographic and clinical data were collected. Laboratory investigations and electromyography were performed. Routine and immunohistochemistry staining of muscle specimens was performed, and a next-generation sequencing panel array for genes associated with hereditary neuromuscular disorders was used for analysis. The patients exhibited predominant muscle weakness. Electromyography revealed myopathic changes. The muscle biopsy showed myopathic features, such as increased fiber size variation, muscle fiber atrophy and regeneration, slight hyperplasia of the connective tissue, and disarray of the myofibrillar network. Two patients were confirmed to have mutations in the open reading frame of TCAP by next-generation sequencing. One patient had compound heterozygous mutations, and the other patient harbored a novel homozygous mutation. Western blotting analysis of the skeletal muscle lysate confirmed the absence of telethonin in the patients. We described two LGMD-R7 patients presenting a classical LGMD phenotype and a novel homozygous TCAP mutation. Our research expands the spectrum of LGMD-R7 due to TCAP mutations based on patients from a Chinese neuromuscular center.

Sinapic acid attenuates muscle atrophy in streptozotocin-induced diabetic mice.

Objective(s):Diabetes is fundamentally connected with the inability of skeletal muscle. Sinapic acid (SA) has multiple biologic functions and is diffusely utilized in diabetic complications. The purpose of this study was to explore the potential improvement effect and mechanisms of SA in streptozotocin (STZ)-induced diabetic muscle atrophy.Materials and Methods:The model of diabetic mice was established by intraperitoneal STZ (200 mg/kg) to evaluate the treatment effect of SA (40 mg/kg/d for 8 weeks) on muscle atrophy. Muscle fiber size was assessed by Hematoxylin and Eosin (HE) staining. Muscle force was measured by a dynamometer. Biochemical parameters were tested by using corresponding commercial kits. The expressions of Atrogin-1, MuRF-1, nuclear respiratory factor 1 (NRF-1), peroxisome proliferative activated receptor gamma coactivator 1 alpha (PGC-1α), CHOP, GRP-78, BAX, and BCL-2 were detected by Western blot.Results:Our data demonstrated that SA increased fiber size and weight of gastrocnemius, and enhanced grip strength to alleviate diabetes-induced muscle atrophy. In serum, SA restrained creatine kinase (CK), lactate dehydrogenase (LDH), malondialdehyde (MDA), tumor necrosis factor (TNF-a), and interleukin 6 (IL-6) levels, while enhancing total anti-oxidant capacity (T-AOC), superoxide dismutase (SOD) and catalase (CAT) levels to improve muscle injury. In gastrocnemius, SA promoted NRF-1, PGC-1α, and BCL-2 expressions, while inhibiting Atrogin-1, MuRF-1, CHOP, GRP-87, and BAX expressions.Conclusion:SA protected against diabetes-induced gastrocnemius injury via improvement of mitochondrial function, endoplasmic reticulum (ER) stress, and apoptosis, and could be developed to prevent and treat diabetic muscle atrophy.

Clinicopathological features of titinopathy from a Chinese neuromuscular center.

Titin, one of the largest proteins in humans, is a major component of muscle sarcomeres. Pathogenic variants in the titin gene (TTN) have been reported to cause a range of skeletal muscle diseases, collectively known as titinopathy. Titinopathy is a heterogeneous group of disabling diseases characterized by muscle weakness. In our study, we aimed to establish the clinicopathological-genetic spectrum of titinopathy from a single neuromuscular center. Three patients were diagnosed as having definite titinopathy, and additional three patients were diagnosed as having possible titinopathy according to the diagnostic criteria. All the patients showed initial symptoms from age one to 40 years. Physical examination revealed that five patients had muscle weakness, and that one patient experienced behavioral changes. Muscle biopsy specimens obtained from all six patients demonstrated multiple myopathological changes, including increased fiber size variation, muscle fiber hypertrophy or atrophy, formation of centralized cell nuclei, necklace cytoplasmic bodies, and formation of rimmed vacuoles and cores. Genetic testing revealed 11 different TTN alterations, including missense (6/11), nonsense (2/11), frameshift (2/11), and splicing (1/11) mutations. Our study provides further evidence that TTN mutations are more likely to be responsible for an increasing proportion of various myopathies, such as hereditary myopathy with early respiratory failure (HMERF), core myopathy, and distal myopathy with rimmed vacuoles, than currently recognized mutations. Our findings expand the clinical, pathohistological and genetic spectrum of titinopathy.

Quantitative analysis of clot density, fibrin fiber radius, and protofibril packing in acute phase myocardial infarction

IntroductionCoronary artery disease is associated with impaired clot structure. The aim of this study was to investigate acute phase myocardial infarction (AMI) and provide detailed quantitative analysis of clot ultrastructure. Materials and methodsClot formation and breakdown, pore size, fiber density, fiber radius and protofibril packing were investigated in plasma clots from AMI patients. These data were compared to those from healthy controls. ResultsAnalysis on clot formation using turbidity showed increased lag time, suggesting changes in protofibril packing and increased fiber size for AMI patients compared to healthy controls. Additionally, increased average rate of clotting and decreased time to maximum absorbance in AMI patients suggest that clots formed more quickly. Moreover, we observed increased time from max OD to max rate of lysis. Increased fibrinogen and decreased plasminogen in AMI patients were accounted for in represented significant differences. AMI samples showed increased time to 25% and 50% lysis, but no change in 75% lysis, representative of delayed lysis onset, but expediated lysis once initiated. These data suggest that AMI patients formed less porous clots made from more densely packed fibers with decreased numbers of protofibrils, which was confirmed using decreased permeation and increased fiber density, and decreased turbidimetry. ConclusionsAMI plasma formed clots that were denser, less permeable, and lysed more slowly than healthy controls. These findings were confirmed by detailed analysis of clot ultrastructure, fiber size, and protofibril packing. Dense clot structures that are resistant to lysis may contribute to a prothrombotic milieu in AMI.

Clot formation, lysis and ultrastructure in patients with acute phase myocardial infarction

Abstract Background/Introduction Patients with established coronary artery disease have impaired clot structure and lysis. Prior research has compared patients with myocardial infarction to those with stable coronary artery disease (without a healthy reference), or patients after myocardial ischemia. The role of clot structure in the acute phase of the disease is unknown. Purpose Investigate clot structure in the acute phase of myocardial infarction (AMI) compared to healthy controls. Methods Plasma clots from AMI patients (within 12 hours of symptoms onset) or healthy controls were analyzed by turbidity and lysis. Clot pore size was determined by permeation. Clot ultrastructure was determined by confocal and scanning electron microscopy. Average fiber radius and protofibril packing were investigated by turbidimetry. Results Analysis on clot formation, using turbidity, showed increased lag time (24%, p<0.05), suggesting changes in protofibril packing and increased fiber size for AMI patients compared to controls. Additionally, AMI clots formed more quickly as evidenced by average rate of clotting (2.9-fold increase, p<0.001) and time to maximum absorbance (38% decrease, p<0.0001). Decreased plasminogen in AMI patients (23%, p<0.05) had strong effects on clot lysis, including increased time to half lysis (1.72-fold, p<0.0001) and increased time to maximum lysis rate (7.96-fold, p<0.0001). Taken together, these results suggest that AMI patients form less porous clots made from densely packed fibers with decreased numbers of protofibrils, which was confirmed using permeation (1.05-fold decrease, p<0.0001), confocal (Figure 1) and scanning electron microscopy (46% increase, p<0.0001), and turbidimetry (16% decrease, p<0.05) respectively. Conclusions Plasma from patients with AMI form denser and less permeable clots that lyse more slowly than healthy controls. These data show marked abnormalities in clot ultrastructure that contribute to the high risk of thrombosis during the acute phase of myocardial infarction, which has not shown in previous investigations. Figure 1. Confocal microscopy of AMI vs. controls Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): Jagiellonian University Medical College to G.G. (N41/DBS/000096) and BHF Programme Grant to S.R.B. and R.A.S.A. (RG/18/11/34036).

Expression of Myosin Heavy Chain and Some Energy Metabolism-Related Genes in the Longissimus Dorsi Muscle of Krškopolje Pigs: Effect of the Production System.

The Slovenian Krškopolje pig is the only preserved local autochthonous breed, appreciated mainly for its good meat quality and considered more appropriate for processing into dry-cured products. However, the biological characteristics of the skeletal myofibers of the Krškopolje breed, specifically the heavy myosin chain-based contractile and metabolic phenotypes that could affect meat quality, have not been established under different husbandry systems. The breed is generally maintained in either conventional indoor or organic systems. In the present study, the morphological, contractile, and metabolic properties of myofibers of the longissimus dorsi muscle were compared between animals reared in either an organic or a conventional indoor system. The myofibers were studied using immunohistochemical and succinate dehydrogenase (SDH) activity-based classification, histomorphometric assessment, and qPCR. Results revealed that the organic production system influenced the composition of the longissimus dorsi myofiber type, characterized by a smaller myofiber cross-sectional area, a shift toward oxidative (SDH-positive) myofiber types, increased relative expression of myosin heavy chain (MyHC) isoforms I, IIa, and IIx, and downregulation of MyHC IIb. On the contrary, no apparent effect was observed on the metabolic phenotype of the myofiber as assessed through relative mRNA expression of energy metabolism-related genes [peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC-1α), peroxisome proliferator-activated receptor gamma (PPARγ), lipoprotein-lipase (LPL), carnitine palmitoyltransferase 1B (CPT1B), glycogen synthase 1 (GYS1), hexokinase 2 (HK2), and fatty acid synthase (FASN)]. Differences in MyHC expression were largely corroborated by the histochemical classification, indicating that the contractile protein content is directly regulated by the MyHC genes. A correlation between the muscle contractile and metabolic phenotypes was not established, except for that between the HK2 and MyHC I genes. In conclusion, the present study showed an evident effect of rearing on the longissimus dorsi myofiber contractile phenotype but not the metabolic phenotype. Moreover, obtained data suggest that rearing the Krškopolje pig breed in a conventional system would result in an increased fiber size and a greater proportion of type IIb myofibers, which are known to be negatively correlated with some meat quality traits.

Substrate Topography Regulates Differentiation of Annulus Fibrosus-Derived Stem Cells via CAV1-YAP-Mediated Mechanotransduction

Regeneration of annulus fibrosus (AF) through tissue engineering techniques shows promise as a treatment for patients with degenerative disc disease (DDD). Yet, it remains challenging because of the intrinsic heterogeneity of AF tissue and shortage of in-depth knowledge of its structure-function correlation. In the current study, we fabricated fibrous poly(ether carbonate urethane)urea (PECUU) scaffolds with various fiber sizes to mimic the microstructural feature of native AF and aimed to regulate the differentiation of AF-derived stem cells (AFSCs) by controlling the topographical cues of the scaffold. We found that the morphology of AFSCs varied significantly on scaffolds with various fiber sizes. Meanwhile, the expression of the phenotypic marker genes of outer AF was up-regulated on scaffolds with large fibers. Meanwhile, enhanced expression of the phenotypic marker genes of inner AF was seen on scaffolds with small fibers. Such topography-dependent gene expression in AFSCs approximated the biochemical profile of AF tissue in various zones. Moreover, cell spreading and nucleus translocation of Yes-associated protein (YAP) were facilitated with increased fiber size. Formation and maturation of focal adhesions of AFSCs were also promoted. We also found that Caveolin-1 (CAV1) positively modulated the mechano-responses of YAP in response to substrate topography. In conclusion, depending on the activation of the CAV1-YAP mechanotransduction axis, tuning the fiber size of scaffolds can effectively induce changes in cell shape, adhesions, and extracellular matrix expression. This work may therefore provide new insights in the design of novel materials toward AF tissue regeneration.

Effects of Tongue Exercise Frequency on Tongue Muscle Biology and Swallowing Physiology in a Rat Model.

Age-related changes in muscle composition and function are often treated using exercise, including muscles of the tongue to treat swallowing impairments (dysphagia). Although tongue exercise is commonly prescribed, optimal tongue exercise doses have not been determined. The purpose of this study was to evaluate effects of varying tongue exercise frequency on tongue force, genioglossus muscle fiber size, composition and metabolism, and swallowing in a rat model. We randomized 41 old and 40 young adult Fischer 344/Brown Norway rats into one of four tongue exercise groups: 5days/week; 3days/week; 1day/week; or sham. Tongue force was higher following all exercise conditions (vs sham); the 5day/week group had the greatest change in tongue force (p < 0.001). There were no exercise effects on genioglossus (GG) fiber size or MyHC composition (p > 0.05). Significant main effects for age showed a greater proportion of Type I fibers in (p < 0.0001) and increased fiber size of IIa fibers (p = 0.026) in old. There were no significant effects of citrate synthase activity or PGC-1α expression. Significant differences were found in bolus speed and area (size), but findings were potentially influenced by variability. Our findings suggest that tongue force is influenced by exercise frequency; however, these changes were not reflected in characteristics of the GG muscle assayed in this study. Informed by findings of this study, future work in tongue dose optimization will be required to provide better scientific premise for clinical treatments in humans.

Effects of Tree Species and Wood Fiber Size in the Core Layer on the Formaldehyde Emission of Three-Layers Fiberboard

Three-layered medium density fiberboards (MDFs) were produced using fine wood fibers in the face layers and coarse wood fibers in the core layer. The core layer were produced from pine wood fiber or beech wood fibers while the face fibers were produced pine fibers. The length of the beech fibers in the core layer increased from 4.3 mm to 28.2 mm while it increased from 4.9 to 29.1 mm for the pine fibers. The shelling ratio and panel thickness were 50/50 and 10 mm, respectively. Based on EN 120-method, the formaldehyde emission released from the MDFs were identified. The formaldehyde emission considerably declined with increasing fiber size at the same manufacturing parameters such as resin content, density, pressing parameters, and mat moisture content. Furthermore, MDF specimens having beech fibers in the core layer showed lower formaldehyde emission than that of the MDFs having pine fibers in the core layer.

Effect of alendronate or 8-prenylnaringenin applied as a single therapy or in combination with vibration on muscle structure and bone healing in ovariectomized rats

Bisphosphonate alendronate (ALN), phytoestrogen 8-prenylnaringenin (8-PN) and the whole body vibration exert a favorable effect on osteoporotic bone. However, the impact of these treatments and the combination of pharmacological therapies with biomechanical stimulation on muscle and bone has not yet been explored in detail. The effect of ALN and 8-PN and their combination with the vibration (Vib) on skeletal muscle and bone healing was investigated in ovariectomized (Ovx) rats.Three-month old rats were Ovx (n = 78), or left intact (Non-Ovx; n = 12). Five weeks after Ovx, all rats were treated according to the group assignment (n = 12/13): 1) Non-Ovx; 2) Ovx; 3) Ovx + Vib; 4) Ovx + ALN; 5) Ovx + ALN + Vib; 6): Ovx + 8-PN; 7) Ovx + 8-PN + Vib. Treatments with ALN (0.58 mg/kg BW, in food), 8-PN (1.77 mg/kg BW, daily s.c. injections) and/or with vertical vibration (0.5 mm, 35 Hz, 1 g, 15 min, 2×/day, 5×/week) were conducted for ten weeks. Nine weeks after Ovx, all rats underwent bilateral tibia osteotomy with plate osteosynthesis and were sacrificed six weeks later.Vibration increased fiber size and capillary density in muscle, enlarged callus area and width, and decreased callus density in tibia, and elevated alkaline phosphatase in serum. ALN and ALN + Vib enhanced capillarization and lactate dehydrogenase activity in muscle. In tibia, ALN slowed bone healing, ALN + Vib increased callus width and density, enhanced callus formation rate and expression of osteogenic genes. 8-PN and 8-PN + Vib decreased fiber size and increased capillary density in muscle; callus density and cortical width were reduced in tibia. Vibration worsened 8-PN effect on bone healing decreasing the callus width and area.Our data suggest that Vib, ALN, 8-PN, or 8-PN + Vib do not appear to aid bone healing. ALN + Vib improved bone healing; however application is questionable since single treatments impaired bone healing. Muscle responds to the anti-osteoporosis treatments and should be included in the evaluation of the drugs.

Pathological findings in a patient with non-dystrophic myotonia with a mutation of the SCN4A gene; a case report

BackgroundNon-dystrophic myotonias (NDMs) are skeletal muscle disorders involving myotonia distinct from myotonic dystrophy. It has been reported that the muscle pathology is usually normal or comprises mild myopathic changes in NDMs. We describe various pathological findings mimicking those of myotonic dystrophy (DM) in biopsied muscle specimens from a patient with NDMs with a long disease duration.Case presentationA 66-year-old Japanease man presented eye closure myotonia, percussion myotonia and grip myotonia together with the warm-up phenomenon and cold aggravation from early childhood. On genetic analysis, a heterozygous mutation of the SCN4A gene (c.2065 C > T, p.L689F), with no mutation of the CLCN1, DMPK, or ZNF9/CNBP gene, was detected. He was diagnosed as having NDMs. A biopsy of the biceps brachii muscle showed increasing fiber size variation, internal nuclei, chained nuclei, necrotic fibers, fiber splitting, endomysial fibrosis, pyknotic nuclear clumps and disorganized intermyofibrillar networks. Sarcoplasmic masses, tubular aggregates and ragged-red fibers were absent.ConclusionIt is noteworthy that the present study revealed various pathological findings resembling those seen in DM, although the pathology is usually normal or mild in NDMs. The pathological similarities may be due to muscular modification with long-standing myotonia or excessive muscle contraction based on abnormal channel activity.

The histopathological spectrum of malignant hyperthermia and rhabdomyolysis due to RYR1 mutations

ObjectiveThe histopathological features of malignant hyperthermia (MH) and non-anaesthetic (mostly exertional) rhabdomyolysis (RM) due to RYR1 mutations have only been reported in a few cases.MethodsWe performed a retrospective multi-centre cohort study focussing on the histopathological features of patients with MH or RM due to RYR1 mutations (1987–2017). All muscle biopsies were reviewed by a neuromuscular pathologist. Additional morphometric and electron microscopic analysis were performed where possible.ResultsThrough the six participating centres we identified 50 patients from 46 families, including patients with MH (n = 31) and RM (n = 19). Overall, the biopsy of 90% of patients showed one or more myopathic features including: increased fibre size variability (n = 44), increase in the number of fibres with internal nuclei (n = 30), and type I fibre predominance (n = 13). Abnormalities on oxidative staining, generally considered to be more specifically associated with RYR1-related congenital myopathies, were observed in 52%, and included unevenness (n = 24), central cores (n = 7) and multi-minicores (n = 3). Apart from oxidative staining abnormalities more frequently observed in MH patients, the histopathological spectrum was similar between the two groups. There was no correlation between the presence of cores and the occurrence of clinically detectable weakness or presence of (likely) pathogenic variants.ConclusionsPatients with RYR1-related MH and RM exhibit a similar histopathological spectrum, ranging from mild myopathic changes to cores and other features typical of RYR1-related congenital myopathies. Suggestive histopathological features may support RYR1 involvement, also in cases where the in vitro contracture test is not informative.

Congenital Titinopathy: Comprehensive characterization and pathogenic insights

ObjectiveComprehensive clinical characterization of congenital titinopathy to facilitate diagnosis and management of this important emerging disorder.MethodsUsing massively parallel sequencing we identified 30 patients from 27 families with 2 pathogenic nonsense, frameshift and/or splice site TTN mutations in trans. We then undertook a detailed analysis of the clinical, histopathological and imaging features of these patients.ResultsAll patients had prenatal or early onset hypotonia and/or congenital contractures. None had ophthalmoplegia. Scoliosis and respiratory insufficiency typically developed early and progressed rapidly, whereas limb weakness was often slowly progressive, and usually did not prevent independent walking. Cardiac involvement was present in 46% of patients. Relatives of 2 patients had dilated cardiomyopathy. Creatine kinase levels were normal to moderately elevated. Increased fiber size variation, internalized nuclei and cores were common histopathological abnormalities. Cap‐like regions, whorled or ring fibers, and mitochondrial accumulations were also observed. Muscle magnetic resonance imaging showed gluteal, hamstring and calf muscle involvement. Western blot analysis showed a near‐normal sized titin protein in all samples. The presence of 2 mutations predicted to impact both N2BA and N2B cardiac isoforms appeared to be associated with greatest risk of cardiac involvement. One‐third of patients had 1 mutation predicted to impact exons present in fetal skeletal muscle, but not included within the mature skeletal muscle isoform transcript. This strongly suggests developmental isoforms are involved in the pathogenesis of this congenital/early onset disorder.InterpretationThis detailed clinical reference dataset will greatly facilitate diagnostic confirmation and management of patients, and has provided important insights into disease pathogenesis. Ann Neurol 2018;83:1105–1124

Ethyl cellulose, cellulose acetate and carboxymethyl cellulose microstructures prepared using electrohydrodynamics and green solvents

Cellulose derivatives are an attractive sustainable material used frequently in biomaterials, however their solubility in safe, green solvents is not widely exploited. In this work three cellulose derivatives; ethyl cellulose, cellulose acetate and carboxymethyl cellulose were subjected to electrohydrodynamic processing. All were processed with safe, environmentally friendly solvents; ethanol, acetone and water. Ethyl cellulose was electrospun and an interesting transitional region was identified. The morphological changes from particles with tails to thick fibres were charted from 17 to 25 wt% solutions. The concentration and solvent composition of cellulose acetate (CA) solutions were then changed; increasing the concentration also increased fibre size. At 10 wt% CA, with acetone only, fibres with heavy beading were produced. In an attempt to incorporate water in the binary solvent system to reduce the acetone content, 80:20 acetone/water solvent system was used. It was noted that for the same concentration of CA (10 wt%), the beading was reduced. Finally, carboxymethyl cellulose was electrospun with poly(ethylene oxide), with the molecular weight and polymer compositions changed and the morphology observed.