Variation In Fiber Size Research Articles

An intronic LINE-1 element insertion in the dystrophin gene aborts dystrophin expression and results in Duchenne-like muscular dystrophy in the corgi breed

Duchenne muscular dystrophy (DMD) is a dystrophin-deficient lethal muscle disease. To date, the catastrophic muscle wasting phenotype has only been seen in dystrophin-deficient humans and dogs. Although Duchenne-like symptoms have been observed in more than a dozen dog breeds, the mutation is often not known and research colonies are rarely established. Here, we report an independent canine DMD model originally derived from the Pembroke Welsh corgi breed. The affected dogs presented clinical signs of muscular dystrophy. Immunostaining revealed the absence of dystrophin and upregulation of utrophin. Histopathologic examination showed variable fiber size, central nucleation, calcification, fibrosis, neutrophil and macrophage infiltration and cardiac focal vacuolar degeneration. Carrier dogs also displayed mild myopathy. The mutation was identified as a long interspersed repetitive element-1 (LINE-1) insertion in intron 13, which introduced a new exon containing an in-frame stop codon. Similar mutations have been seen in human patients. A colony was generated by crossing carrier females with normal males. Affected puppies had a normal birth weight but they experienced a striking growth delay in the first 5 days. In summary, the new corgi DMD model offers an excellent opportunity to study DMD pathogenesis and to develop novel therapies.

ABC in muscle pathology

Muscle pathology plays a central role in the diagnosis of muscle diseases. Proper handling, fixation and transportation of muscle biopsy specimens are necessary to avoid artifacts. Hematoxylin and eosin provides information on basic morphological abnormalities, including general structural changes, fiber size variation, necrosis and regeneration, endomysial fibrosis and lymphocyte infiltration. Modified Gomori trichrome is useful to detect abnormal structures including protein aggregates. NADH-tetrazolium reductase highlights intermyofibrillar network, thus serving to detect myofibrillar disorganization. Myosin ATPase is used for evaluating fiber types. Selective type 1 fiber atrophy reflects myopathic process while fiber type grouping reinnervating process. The final interpretation whether the biopsy demonstrates myopathic or neuropathic changes is based upon all these findings.

Effect of Fiber Property Variation on Hollow Fiber Membrane Module Performance in the Production of a Permeate Product

The literature demonstrates the detrimental effects of variability in the inner diameter, permeance, and selectivity of hollow fiber membranes for the production of a retentate product, for example, nitrogen purification from air. This past work is extended to the production of a permeate product. Additionally, simultaneous variation of multiple fiber properties is considered. Fiber variability is detrimental to permeate production; the ratio of product to feed flow rate decreases with an increase in variability. However, the permeate product flow rate remains unchanged in contrast to the large changes observed for a retentate product. Simultaneous, independent variation of multiple fiber properties makes performance worse. However, correlations between the variations in fiber properties can improve performance. Theoretical performance predictions compare favorably with experimental measurements for the production of oxygen from air if either simultaneous variation of fiber size with permeance occurs or significant deviations from countercurrent flow exist. The results may be used to develop manufacturing guidelines for the production of hollow fiber membranes.

Muscle biopsies from the supraspinatus in retracted rotator cuff tears respond normally to passive mechanical testing: a pilot study

The aim of the present study was to assess the function of the isolated muscle component in retracted rotator cuff tears. Muscle biopsies were harvested from the supraspinatus and the ipsilateral deltoid in seven patients undergoing surgery for a large, retracted rotator cuff tear. Single fibres and fibre bundles were subjected to passive stretching in vitro with subsequent recordings of tension and sarcomere lengths using the laser diffraction technique. Stress-strain curves were plotted, and the elastic modulus was calculated for all preparations. Morphology was evaluated with regard to collagen fraction, ratio between fast and slow fibres, fibre size and fibre size variability using standard staining techniques. Intra-individual comparisons of the stress-strain curves showed a high degree of conformity in terms of both shape and tangent values, and there were no statistically significant differences in the elastic modulus for single fibres and bundles in the deltoid and supraspinatus muscles, respectively, supported by the analysis of the observed confidence interval of the differences between the paired values of the elastic modulus. There were no differences in collagen content, fibre size and ratio between fast and slow fibres in the deltoid and supraspinatus muscles, respectively. We conclude that muscle biopsies from the supraspinatus in retracted rotator cuff tears respond normally to mechanical testing in vitro.

PONM04 Myofibrillar myopathy caused by a mutation in the desmin gene: expanding the phenotype

BackgroundMyofibrillar myopathy (MFM) is a group of morphologically distinct muscle disorders, with genetic and phenotypic variability. When a mutation in the desmin gene is found, it is termed a desminopathy....

MTM1 mutation associated with X-linked myotubular myopathy in Labrador Retrievers

Mutations in the MTM1 gene encoding myotubularin cause X-linked myotubular myopathy (XLMTM), a well-defined subtype of human centronuclear myopathy. Seven male Labrador Retrievers, age 14-26 wk, were clinically evaluated for generalized weakness and muscle atrophy. Muscle biopsies showed variability in fiber size, centrally placed nuclei resembling fetal myotubes, and subsarcolemmal ringed and central dense areas highlighted with mitochondrial specific reactions. Ultrastructural studies confirmed the centrally located nuclei, abnormal perinuclear structure, and mitochondrial accumulations. Wild-type triads were infrequent, with most exhibiting an abnormal orientation of T tubules. MTM1 gene sequencing revealed a unique exon 7 variant in all seven affected males, causing a nonconservative missense change, p.N155K, which haplotype data suggest derives from a recent founder in the local population. Analysis of a worldwide panel of 237 unaffected Labrador Retrievers and 59 additional control dogs from 25 other breeds failed to identify this variant, supporting it as the pathogenic mutation. Myotubularin protein levels and localization were abnormal in muscles from affected dogs, and expression of GFP-MTM1 p.N155K in COS-1 cells showed that the mutant protein was sequestered in proteasomes, where it was presumably misfolded and prematurely degraded. These data demonstrate that XLMTM in Labrador Retrievers is a faithful genetic model of the human condition.

CK elevation and progressive toe walking in a 14-year old girl

We present the case of a 14-year old girl with progressive toe walking and great difficulties in climbing stairs. The neurological exam was remarkable for weakness of the shoulder girdle musculature with bilateral scapula alata, positive Gower's sign, hyperlordosis upon climbing stairs, inability to walk on heels and positive Trendelenburg's sign when walking. Repeated CK levels were in the range of 3500 U/L. A muscle MRI showed fatty degeneration of calf muscles and to a lesser degree of the dorsal thigh musculature on T1 weighted images. Atrophy of dorsal thigh musculature was present. Muscle biopsy of the deltoid muscle was performed. Conventional histology showed modest myopathic alterations with significant variation in fiber size, increase in endo- and perimysial connective tissue and necrosis of type 1 and 2 muscle fibers. Immunostaining of the material was unremarkable. Eventually a form of limb-girdle muscular dystrophy was suspected Sequencing of the calpain-3 gene was performed and confirmed this diagnosis. The genetic analysis found a compound heterozygosity with a deletion in Exon 4 (c.550delA) which is a known founder mutation in Eastern Europe. The other allele carries a novel deletion of exons 11–13 causing the reading frame to shift. As a result of both mutations there is a complete absence of functional calpain-3 protein.

Skeletal Muscle Abnormalities and Genetic Factors Related to Vertical Talus

Congenital vertical talus is a fixed dorsal dislocation of the talonavicular joint and fixed equinus contracture of the hindfoot, causing a rigid deformity recognizable at birth. The etiology and epidemiology of this condition are largely unknown, but some evidence suggests it relates to aberrations of skeletal muscle. Identifying the tissue abnormalities and genetic causes responsible for vertical talus has the potential to lead to improved treatment and preventive strategies. We therefore (1) determined whether skeletal muscle abnormalities are present in patients with vertical talus and (2) identified associated congenital anomalies and genetic abnormalities in these patients. We identified associated congenital anomalies and genetic abnormalities present in 61 patients affected with vertical talus. We obtained abductor hallucis muscle biopsy specimens from the affected limbs of 11 of the 61 patients and compared the histopathologic characteristics with those of age-matched control subjects. All muscle biopsy specimens (n = 11) had abnormalities compared with those from control subjects including combinations of abnormal variation in muscle fiber size (n = 7), type I muscle fiber smallness (n = 6), and abnormal fiber type predominance (n = 5). Isolated vertical talus occurred in 23 of the 61 patients (38%), whereas the remaining 38 patients had associated nervous system, musculoskeletal system, and/or genetic and genomic abnormalities. Ten of the 61 patients (16%) had vertical talus in one foot and clubfoot in the other. Chromosomal abnormalities, all complete or partial trisomies, were identified in three patients with vertical talus who had additional congenital abnormalities. Vertical talus is a heterogeneous birth defect resulting from many diverse etiologies. Abnormal skeletal muscle biopsies are common in patients with vertical talus although it is unclear whether this is primary or secondary to the joint deformity. Associated anomalies are present in 62% of all cases.

Amyloid myopathy: a therapeutic trial for the rare and underdiagnosed myopathy with bortezomib

A 69-year-old woman was referred to our clinic because of a 6-month history of progressive muscle weakness. Five years previously, when she was diagnosed as having nephrotic syndrome, the renal biopsy showed deposition of AL-amyloid. Subsequent investigations revealed multiple myeloma with k-type Bence-Jones protein at stage 3 according to the international staging system. A course of vincristine, doxorubicin and dexamethasone (VAD) and an additional course of cyclophosphamide were administered, followed by another course of melphalan (L-PAM) at age 67. The proteinuria slightly improved but persisted for 5 years, when proximal weakness developed. Neurological examination revealed proximally dominant weakness with MRC scale 4 in the deltoid and 3 in the iliopsoas muscles and she was unable to stand up from a full squat. Serum creatine kinase (CK) elevated to 3,399 U/L. Electromyography showed a myogenic pattern with small motor unit potentials, fibrillation potentials and early recruitment pattern. Muscle biopsy revealed a variation of fiber size, little infiltration of inflammatory cells, and homogeneous accumulations beneath the muscle membrane (Fig. 1a). Congo red-positive materials were noted both in vessel walls and in muscle fibers (Fig. 1b, c, d) with fluorescence for rhodamine, consistent with amyloid deposition, the hallmark of amyloid myopathy. We were not able to identify whether the deposits were located beneath the basal lamina or the plasmalemma due to lack of electron microscopic preparation. Five years ago, the serum CK value was 110 U/L (Fig. 2). Two years later, when her nephrotic syndrome deteriorated, the CK elevated to 2,336 IU/L without overt weakness. Interestingly, after she received L-PAM, the CK decreased to 120 U/L just 1 month after the treatment. When girdle weakness developed 6 months ago, the CK again soared to 3,378 U/L. The fluctuation of CK and the amyloid deposition in the muscle led us to the diagnosis of amyloid myopathy due to multiple myeloma. We then administered two consecutive courses of bortezomib (1.3 mg/m on days 1, 4, 8, and 11 for the first course and 1.0 mg/m on days 1, 4, 8, and 11 for the second course). The treatment reduced the proportion of myeloma cells from 16.8 to 1.2%. The CK started to fall a few weeks after the first course and eventually fell to 187 U/L 1 month after the second course, when she was able to rise from a sitting position more easily. However, multiple myeloma deteriorated in the following months and the CK again elevated to 694 U/L. She was not able to receive additional treatment because of her poor general status. Amyloid myopathy, a progressive myopathy in a proximally dominant fashion, is caused by a variety of primary amyloidoses, such as familial amyloidosis, AL-amyloidosis and multiple myeloma [1–3]. Postulated mechanisms include impaired muscle metabolism or failed electrical conduction by amyloid deposition beneath the muscle membrane [4, 5]. Therapeutic trials have included plasmapheresis, administration of corticosteroid, and high-dose K. Shiga (&) R. Mizutani R. Isayama T. Tokuda M. Nakagawa Department of Neurology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Hirokoji-agaru, Kawaramachi-dori, Kamigyo-ku, Kyoto 602-0841, Japan e-mail: kenshiga@koto.kpu-m.ac.jp

Human disease caused by loss of fast IIa myosin heavy chain due to recessive MYH2 mutations

Striated muscle myosin heavy chain is a molecular motor protein that converts chemical energy into mechanical force. It is a major determinant of the physiological properties of each of the three muscle fibre types that make up the skeletal muscles. Heterozygous dominant missense mutations in myosin heavy chain genes cause various types of cardiomyopathy and skeletal myopathy, but the effects of myosin heavy chain null mutations in humans have not previously been reported. We have identified the first patients lacking fast type 2A muscle fibres, caused by total absence of fast myosin heavy chain IIa protein due to truncating mutations of the corresponding gene MYH2. Five adult patients, two males and three females, from three unrelated families in UK and Finland were clinically assessed and muscle biopsy was performed in one patient from each family. MYH2 was sequenced and the expression of the corresponding transcripts and protein was analysed in muscle tissue. The patients had early-onset symptoms characterized by mild generalized muscle weakness, extraocular muscle involvement and relatively favourable prognosis. Muscle biopsy revealed myopathic changes including variability of fibre size, internalized nuclei, and increased interstitial connective and adipose tissue. No muscle fibres expressing type IIa myosin heavy chain were identified and the MYH2 transcripts were markedly reduced. All patients were compound heterozygous for truncating mutations in MYH2. The parents were unaffected, consistent with recessive mutations. Our findings show that null mutations in the fast myosin heavy chain IIa gene cause early onset myopathy and demonstrate that this isoform is necessary for normal muscle development and function. The relatively mild phenotype is interesting in relation to the more severe phenotypes generally seen in relation to recessive null mutations in sarcomeric proteins.

Myopathy causing camptocormia in idiopathic Parkinson's disease: A multidisciplinary approach

Extreme forward flexion of the spine, named camptocormia (CC), and head drop syndrome (HD) may be among the most disabling symptoms in Parkinson's disease (PD). This study aims to eludicate the etiology of PD-associated CC and HD via a multidisciplinary approach (clinical examination, electromyography, MRI, genetic analysis, muscle morphology) centering on the histology of the paraspinal muscles. We studied 17 patients with the clinical diagnosis of PD and CC or head drop syndrome and six controls. We performed muscle biopsies of paraspinal muscles and deep neck extensor muscles. Mean age at onset of postural abnormality was 66 years and mean latency between onset of parkinsonian symptoms to first signs of CC or head drop was 7 years. The electromyogram of paraspinal muscles was abnormal in 13-14 patients. Histopathology revealed chronic myopathic changes in 14 of 17 biopsies, consisting of abnormal variation in fiber size, increase in internal nuclei, and increase in connective tissue, myofibrillar disarray and similarities to protein surplus myopathies. Interestingly, heterozygous variants in the Parkin gene were found in 2 of 9 investigated patients. We conclude that CC and HD in PD are predominantly myopathic. Aberrant protein aggregation may link PD and CC.

Therapeutic Potential of Proteasome Inhibition in Duchenne and Becker Muscular Dystrophies

Duchenne muscular dystrophy (DMD) and its milder allelic variant, Becker muscular dystrophy (BMD), result from mutations of the dystrophin gene and lead to progressive muscle deterioration. Enhanced activation of proteasomal degradation underlies critical steps in the pathogenesis of the DMD/BMD dystrophic process. Previously, we demonstrated that treatment with the proteasome inhibitor MG-132 rescues the cell membrane localization of dystrophin and the dystrophin glycoprotein complex in mdx mice, a natural genetic mouse model of DMD. The current work aims to thoroughly define the therapeutic potential in dystrophinopathies of Velcade, a drug that selectively blocks the ubiquitin-proteasome pathway. Velcade is particularly intriguing since it has been approved for the treatment of multiple myeloma. Therefore, its side effects in humans have been explored. Velcade effects were analyzed through two independent methodological approaches. First, we administered the drug systemically in mdx mice over a 2-week period. In this system, Velcade restores the membrane expression of dystrophin and dystrophin glycoprotein complex members and improves the dystrophic phenotype. In a second approach, we treated with the compound explants from muscle biopsies of DMD or BMD patients. We show that the inhibition of the proteasome pathway up-regulates dystrophin, alpha-sarcoglycan, and beta-dystroglycan protein levels in explants from BMD patients, whereas it increases the proteins of the dystrophin glycoprotein complex in DMD cases.

Muscular Dystrophies: Histology, Immunohistochemistry, Molecular Genetics and Management

Muscle degeneration and regeneration are two of the most evident pathological events characterizing muscular diseases and in particular muscular dystrophies. Muscular dystrophies are an heterogeneous group of hereditary diseases affecting both children and adults, and are characterized by muscle wasting and weakness. Until now at least 30 different genes have been associated with muscular dystrophies. They have been divided into several subgroups depending on the distribution of the muscle weakness. Thus, the histopathological markers of all these forms are dystrophic changes at the muscle biopsy characterized by fiber size variability, fibres necrosis, regeneration, inflammation and connective tissues deposition. As for now, no effective therapy is available for these diseases but new inside has now been expanded in regenerative therapy such as cell therapy and gene therapy. This review is focused on muscular dystrophies and new acknowledgments in regenerative therapy.

Brody Disease: Insights Into Biochemical Features of SERCA1 and Identification of a Novel Mutation

Brody disease is an inherited disorder of skeletal muscle function characterized by increasing impairment of relaxation during exercise. The autosomal recessive form can be caused by mutations in the ATP2A1 gene, which encodes for the sarcoplasmic/endoplasmic reticulum Ca-ATPase 1 (SERCA1) protein. We studied 2 siblings affected by Brody disease. The patients complained of exercise-induced delay of muscle relaxation and stiffness since childhood and had gene analysis of ATP2A1. Morphologic and biochemical studies were performed on a muscle biopsy from 1 patient. The biopsy showed fiber size variation and increased numbers of fibers with internal nuclei. Ultrastructural examination revealed dilatation of lateral cisternae and proliferation of tubular elements of the sarcoplasmic reticulum. By immunohistochemistry, SERCA1 was expressed in a normal pattern, but sarcoplasmic reticulum Ca-ATPase activity was significantly reduced. Immunoblotting after high-resolution 2-dimensional gel electrophoresis showed a significant difference in the amount of SERCA1 protein between the patient and controls. Both patients were found to have 2 previously unreported in-frame deletions in ATP2A1. Because SERCA1 protein has specific biochemical characteristics in our patient, these results underline the importance of a pathologic and biochemical analyses for the diagnosis. In addition, we describe 2 novel mutations in the ATP2A1 gene.

Vici syndrome associated with sensorineural hearing loss and evidence of neuromuscular involvement on muscle biopsy

Vici syndrome is a rare, genetically unresolved congenital multisystem disorder comprising agenesis of the corpus callosum, cataracts, immunodeficiency, cardiomyopathy, and hypopigmentation. An associated neuromuscular phenotype has not previously been described in detail. We report on an infant with clinical features suggestive of Vici syndrome and additional sensorineural hearing loss. Muscle biopsy revealed several changes including markedly increased variability in fiber size, increased internal nuclei, and abnormalities on Gomori trichrome and oxidative stains, raising a wide differential diagnosis including neurogenic atrophy, centronuclear myopathy (CNM) or a metabolic (mitochondrial) cytopathy. Respiratory chain enzyme studies, however, were normal and sequencing of common CNM-associated genes did not reveal any mutations. This case expands the clinical spectrum of Vici syndrome and indicates that muscle biopsy ought to be considered in infants presenting with suggestive clinical features. In addition, we suggest that Vici syndrome is considered in the differential diagnosis of infants presenting with congenital callosal agenesis and that additional investigation has to address the possibility of associated ocular, auditory, cardiac, and immunologic involvement when this radiologic finding is present.

Terminal reflections in fiber-optic image guides

Fibered image guides for confocal reflectance endomicroscopy suffer from Fresnel reflections at the fiber terminals, which can limit signal-to-noise ratio in these systems. A model that describes these terminal reflections is presented to better understand how they can be managed most effectively. An expression for the refractive index of termination that minimizes the reflection as a function of the fiber's normalized frequency is derived for step-index fibers, while a graphical solution is presented for graded-index fibers. The model predicts that terminal reflections from graded-index fibers are more sensitive to variations in fiber size and changes in wavelength than step-index fibers. A method is also presented to measure the refractive index that allows one to minimize the terminal reflections in an image guide. The technique uses the inherent mode coupling of the fibers in the image guide, allowing the isolation and measurement of reflections from only one end of the fiber. An achievable minimum backreflection of -36 dB was measured at 635 nm in a commercial image guide with 30,000 fibers.

Isolated inflammatory myopathy with rimmed vacuoles presenting with dropped head

We describe an unusual case of inflammatory myopathy with rimmed vacuoles associated with dropped head syndrome. Muscle biopsy in our patient revealed variations in fiber size with fiber necrosis and regeneration, accompanied by many rimmed vacuoles and areas of endomysial cell infiltration. Electron microscopy demonstrated autophagic vacuoles and tubulofilamentous inclusions. This myopathy can cause dropped head syndrome in a subgroup of patients.

Congenital monomelic muscular hypertrophy of the upper extremity

Pathological muscular hypertrophy results from either muscular or neurogenic damage. Rarely, it is caused by a congenital malformation consisting of a unilateral muscular hyperplasia of the upper extremity. We report on a young woman with an enlargement of the right upper extremity. Electromyography showed polyphasic, large motor unit potentials in the affected muscles. MRI and ultrasound assessment demonstrated diffuse enlargement of muscle mass without signs of edema. Muscle biopsy revealed sections with marked variations in fiber size with no signs of inflammation or marked loss of muscle fibers. Factors assumed to be important in the pathophysiology of this phenomenon are discussed.

The distribution and characterization of skeletal muscle lesions in dysferlin-deficient SJL and A/J mice

The pathogenesis of limb-girdle muscular dystrophy type 2B (LGMD2B) dysferlinopathy remains to be investigated. The distribution and characterization of skeletal muscle lesions were examined in two different LGMD2B mouse models, SJL and A/J mice (at 10 and 35 weeks old), in association with the endoplasmic reticulum (ER) stress. SJL mice showed an earlier age of onset and a faster progression of skeletal muscle lesions as compared with those of A/J mice; the sensitivity difference to muscular dystrophic lesions between SJL and A/J mice was observed in the lumbar muscles (particularly, lumbar longissimus and sublumbar muscles); the lesions seen mainly in SJL mice at 35 weeks old consisted of degeneration, necrosis, fatty infiltration, variation in muscle fiber size and atrophy in muscle fibers. Enzyme-histochemically, the fast-twitch muscle fiber was predominant for the degenerative changes seen in the rectus femoris and lateral longissimus muscles of SJL mice. Immunohistochemically, the main reactive cell type observed in and around degenerative and/or necrotic muscle fibers was macrophages, demonstrable with an anti-F4/80 antibody. Because the analyses of spliced XBP1 mRNA, a marker of ER stress, did not show the increased expression, it was considered that ER stress did not affect the progression of skeletal muscle lesions in SJL mice with the advanced stage of dysferlinopathy.

Novel Mutation of Early, Perinatal-Onset, Myopathic-Type Very-Long-Chain Acyl-CoA Dehydrogenase Deficiency

A male neonate demonstrated fetal distress, neonatal asphyxia, and transient hyper-creatine kinase-emia (8400IU/L), followed by repeated episodes of rhabdomyolysis 1-2 times/year during infancy and early childhood. At age 6 years, decreased levels of total and free carnitine in serum, and mild fiber size variation and increased fatty droplets in muscle, were confirmed. Both blood and serum fatty-acid analysis demonstrated elevated 5-tetradecenoate levels, and the acyl-CoA dehydrogenase activity of the palmitoyl-CoA/octanoyl-CoA ratio decreased in skin fibroblasts. The sequenced clone analysis of a complimentary DNA fragment revealed a compound heterozygote mutation of exon 9 (A790G) and exon 10 (997 ins T), which is a novel mutation of a myopathic-type very-long-chain acyl-CoA dehydrogenase deficiency. The patient has reached age 13 years. By treatment with an avoidance of fasting, feeding with a high-carbohydrate and low-fat diet, and intravenous drip infusion soon after every onset of rhabdomyolysis, his physical and mental development has stayed within the normal range. Patients with a perinatal onset of myopathic-type very-long-chain acyl-CoA dehydrogenase deficiency have not yet been reported. His novel mutation might be related to his clinical characterization.