Variation In Fiber Size Research Articles

Predicting extent of anisotropy in anisotropic hollow fiber membrane formation

The relationships between processing conditions and ultimate membrane properties that exist in the spinning of hollow fiber membranes are not fully understood. To address the need for a widely applicable fiber spinning model, the present work builds on the thin filament analysis (TFA) model of the fiber spinning process and predicts the variation of fiber size, velocity, and temperature in the draw zone, including the effects of surface tension. By modeling concentration gradients in the draw zone, this model also predicts both the extent of anisotropy (portion of membrane thickness containing a pore size gradient) and degree of anisotropy (indicative of the pore size range across the membrane thickness). For typical hollow fiber membrane spinning, predicted membrane extent of anisotropy is most sensitive to the diffusion coefficient. The predicted degree of anisotropy is most sensitive to the viscosity activation energy, affected significantly by the diffusion coefficient and spinning temperature, and affected slightly by the air gap length. Trends in the model-predicted and experimental measurements of final fiber outer diameter, ratio of outer to inner diameter (OD/ID), and extent of anisotropy agree. While model sensitivity studies show that surface tension can reduce the rate of fiber elongation, it has little effect on the predicted degree and extent of anisotropy. Furthermore, this analysis allows prediction of counter-intuitive concentration changes associated with temperature dependence of the diluent vapor pressure: for some cases, the degree of anisotropy can increase and then decrease along the draw zone during spinning. Reducing the dependence of vapor pressure on temperature eliminates this phenomenon.

Muscle involvement in association with filarial chyluria

Twenty unselected consecutive patients of filarial chyluria were evaluated clinically, electromyographically, and histopathologically for neuromuscular dysfunction. None of the patients showed clinical evidence of muscle wasting or weakness suggesting myopathy, although generalized muscle weakness was complained by all of them particularly while climbing the stairs or on getting up or during lifting heavy weights. Electromyographic abnormalities were found in nine patients and slight histopathological abnormalities in two. The average duration of motor unit potentials and the mean amplitude were reduced, compatible with myopathy. There were no fibrillation potentials. Histological abnormalities consisted of a marked variation in muscle fibre size, sarcolemmal nuclear proliferation, and mild interstitial fatty infiltration. None of the patients showed evidence of clinical neuropathy, abnormalities in conduction velocity along the nerves or signs of segmental demyelination in the biopsy of the nerve. Our data suggest that muscle weakness in these patients is myopathic in nature without peripheral nerve involvement, and is possible due to hypoproteinaemia and hypolipidaemia, as these patients lose excessive amounts of protein and fat in their urine.

VARIATION IN TEXTURE OF FARMED ATLANTIC SALMON (SALMO SALAR L). RELEVANCE OF MUSCLE FIBER CROSS‐SECTIONAL AREA

ABSTRACT Mechanical properties were studied between and within fillets of 80 conventionally farmed Atlantic salmon (3.5 kg) using a Warner–Bratzler blade (WB) and a 12.5‐mm flat‐ended cylinder. The relationship between the muscle fiber cross‐sectional area versus mechanical response variables was examined. The average muscle fiber area differed significantly between salmon of similar size. Mechanical properties also varied substantially among individuals and between locations within fillets, showing firmer texture in the posterior fillet part on average. Shear force (WB) was 2–2.4 times higher with a wider range for analyses performed perpendicular than parallel to the muscle fibers. Raw fillets with low fiber cross‐sectional area (<12.500 µm2 on average) had significantly firmer texture compared with fillets with larger fibers. However, correlation analyses of individual data showed relatively low overall influence of muscle fiber size on the texture properties (r ≤ 0.35). Thus, the texture of salmon fillets is clearly multifactorial where muscle fiber size is not a major determinant.PRACTICAL APPLICATIONSSoft salmon flesh reduces consumer acceptability and causes quality downgrading in the salmon processing industry. Therefore, it is important to elucidate antemortem and postmortem factors influencing fillet firmness, including knowledge about intrapopulation variations of conventionally farmed salmon. The present study showed pronounced variation between individuals and between sections of the same fillet. It is suggested that sectioning of salmon fillets for different products or markets may improve utilization of intrinsic texture qualities. Furthermore, development of invasive online methods for sorting fillets according to firmness would be beneficial for the industry. Variations in muscle fiber size explained less than 12% of the overall texture variations. However, the indicated relationship between small muscle fibers and texture firmness implies that better understanding of the underlying basis for muscle growth pattern (rate of fiber recruitment versus volume growth of existing fiber) is needed.

Histopathological findings in horses with and without clinical signs of rhabdomyolysis with special reference to polysaccharide storage myopathy

Objective of the study was to assess histopathological changes in horses with a clinical history of exertional rhabdomyolysis (ER) with special reference to polysaccharide storage myopathy and to compare histopathological findings in horses with and without a clinical history of ER. In total 39 muscle samples were collected, from horses with a history of repeated episodes of exertional rhabdomyolysis (test group, 10 horses) and from horses without clinical signs of muscular disorders in their history (control group, 29 horses). Frozen muscle samples were stained with haematoxylin and eosin and periodic acid-Schiff with and without amylase digestion. Histopathologic changes (amylase resistant polysaccharide, subsarcolemmal glycogen, intracytoplasmic masses, subsarcolemmal vacuoles, fibre size variation and internal nuclei) were evaluated. There was a statistically significant difference between groups in the presence of subsarcolemmal amylase sensitive glycogen deposits (P ≤ 0.0001), the risk ratio was 5.22. Statistically significant differences between groups were not found regarding the presence of intracytoplasmic masses, subsarcolemmal vacuoles, amylase resistant polysaccharide, fibre size variation and internal nuclei. Presence of amylase resistant polysaccharide within muscle fibres of apparently healthy horses could be a manifestation of different phenotype expression of PSSM but also the insufficient specificity of this diagnostic criterion.

An autopsy case of chronic progressive external ophthalmoplegia with renal insufficiency

An autopsy of a 44-year-old Japanese woman with mitochondrial cytopathy confirmed the presence of chronic progressive external ophthalmoplegia (CPEO). Immunohistochemistry using antimitochondrial antibody was performed to observe the ultrastructure of the skeletal muscle and renal tissues. The patient was born of consanguineous parents, developed normally, and was of average intelligence. At 22 years of age, the patient noticed hearing loss, and subsequently, over time, developed a progressive generalized muscle weakness, which included limitation of eye movement and ptosis. At age 41, a muscle biopsy was performed using the modified Gomori trichrome method and demonstrated the presence of ragged red fibers. After the evaluation of her results in conjunction with her clinical course, she was diagnosed with CPEO. Renal insufficiency was discovered at age 30, and the patient died at the age of 44 of respiratory failure caused by respiratory muscle weakness and pneumonia. The autopsy revealed fiber size variation within the skeletal muscle, and an antimitochondrial antibody analysis demonstrated the accumulation of mitochondria between the bundles of myofibrils, as well as in subsarcolemmal locations. Ultrastructurally, abnormal mitochondria with disoriented cristae and paracrystalline inclusions were seen. Although no remarkable histological changes were noted in the kidneys, tubular epithelial cells exhibited accumulated abnormal mitochondria, similar to those seen in the skeletal muscle. Because mitochondrial diseases can affect other energy-dependent organs in addition to the skeletal muscle, immunohistochemical examinations employing an antimitochondrial antibody are useful for obtaining further ultrastructural observations that can assist in making a distinct diagnosis of this systemic disorder.

Dystrophic-Like Alterations Characterize Orbicularis Oris and Palatopharyngeal Muscles in Patients Affected by Cleft Lip and Palate

This study analyzed histological and histochemical features of specimens of the orbicularis oris muscle, and palatal and pharyngeal muscles biopsied during surgery from 33 patients affected by cleft lip and palate. Three groups were studied: 20 patients affected by cleft palate with or without cleft lip (at the time of primary palatoplasty), seven by cleft lip with or without cleft palate (primary lip closure), and six by cleft lip with or without cleft palate (secondary cheiloplasty). Muscle sections were stained with hematoxylin-eosin, modified Gomori trichrome, ATPase reaction at pH 9.4, and NADH-TR. Analyzed parameters included organization, muscle fiber size and type, nuclear changes, presence of ragged-red fibers, degree of fibrosis, and presence of inflammatory infiltrate. In all patients who underwent primary palatoplasty and lip closure we noted dystrophic-like alterations of orbicularis oris and palatopharyngeal muscles, such as variability of fiber size, fiber disorganization, and increased fibrosis. The same alterations were found in adult patients submitted to secondary cheiloplasty, notwithstanding surgical repair. Furthermore, in all groups neither neurogenic atrophy nor ragged-red fibers or inflammatory infiltrate were detected. Muscle damage is a constant event in this deformity, and it could play an important role in its etiopathogenesis. Muscular biopsy during cheiloplasty and palatoplasty could offer useful information about muscle condition and possible functional recovery in cleft lip and palate patients.

Muscle Biopsy and In Vitro Contracture Test in Subjects with Idiopathic HyperCKemia

Persistent high creatine kinase (CK) levels may reflect underlying subclinical myopathies. In most cases, pathogenesis is unknown and clinical management is unclear. Though clinically asymptomatic, these subjects are potentially susceptible to malignant hyperthermia. The authors analyzed 37 subjects with persistent elevation of CK without significant weakness or other neurologic symptoms. Neurologic examination was performed according to manual muscle testing. Muscle biopsy and the in vitro contracture test were performed in all subjects. Twenty-three subjects (51.1%) were completely asymptomatic. The others had minor symptoms such as occasional cramps (11 subjects, 24.4%), fatigue (5 subjects, 11.1%), a combination of cramps and fatigue (5 subjects, 11.1%), and muscle pain (1 case, 2.2%). Muscle biopsy enabled precise diagnosis in 3 cases and was normal in 3 cases. The more frequent changes were variation in fiber size (31.1%), a combination of nuclear internalization and variation in fiber size (26.6%), nuclear internalization (6.6%), minor mitochondrial changes (4.4%), and neurogenic atrophy (4.4%). Immunocytochemical analysis was normal in all patients. In vitro contracture testing detected one malignant hyperthermia-susceptible and one malignant hyperthermia-equivocal subject. The evidence of malignant hyperthermia susceptibility by in vitro contracture test seems to be relatively infrequent among subjects with idiopathic hyperCKemia, but the incidence of true malignant hyperthermia in idiopathic hyperCKemia is unknown. Muscle biopsy should be considered a useful, though not very sensitive, diagnostic tool in idiopathic hyperCKemia, because it enables potentially treatable disorders, such as inflammatory myopathies, to be discovered. No uniform morphologic finding typical of idiopathic hyperCKemia or malignant hyperthermia susceptibility was identified by muscle biopsy.

Histomorphometric analysis of the response of rat skeletal muscle to swimming, immobilization and rehabilitation

The objective of the present study was to determine to what extent, if any, swimming training applied before immobilization in a cast interferes with the rehabilitation process in rat muscles. Female Wistar rats, mean weight 260.52 +/- 16.26 g, were divided into 4 groups of 6 rats each: control, 6 weeks under baseline conditions; trained, swimming training for 6 weeks; trained-immobilized, swimming training for 6 weeks and then immobilized for 1 week; trained-immobilized-rehabilitated, swimming training for 6 weeks, immobilized for 1 week and then remobilized with swimming for 2 weeks. The animals were then sacrificed and the soleus and tibialis anterior muscles were dissected, frozen in liquid nitrogen and processed histochemically (H&E and mATPase). Data were analyzed statistically by the mixed effects linear model (P < 0.05). Cytoarchitectural changes such as degenerative characteristics in the immobilized group and regenerative characteristics such as centralized nucleus, fiber size variation and cell fragmentation in the groups submitted to swimming were more significant in the soleus muscle. The diameters of the lesser soleus type 1 and type 2A fibers were significantly reduced in the trained-immobilized group compared to the trained group (P < 0.001). In the tibialis anterior, there was an increase in the number of type 2B fibers and a reduction in type 2A fibers when trained-immobilized rats were compared to trained rats (P < 0.001). In trained-immobilized-rehabilitated rats, there was a reduction in type 2B fibers and an increase in type 2A fibers compared to trained-immobilized rats (P < 0.009). We concluded that swimming training did not minimize the deleterious effects of immobilization on the muscles studied and that remobilization did not favor tissue re-adaptation.

Pathologic Findings in Equine Muscle (Excluding Polysaccharide Storage): A Necropsy Study

Gross and histopathologic evaluation of skeletal muscle was performed in 229 equids (217 horses, 8 ponies, 3 donkeys, and 1 mule) 1 year of age or older undergoing postmortem examination at Oregon State University in a 2.5-year period. Animals were evaluated for grossly evident muscle lesions, and muscle samples were fixed in formalin, processed routinely, and stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) for glycogen. Muscle lesions were detected in 149 animals (65%). Chronic myopathic change (excessive fiber size variation and internal nuclei) was evaluated in horses without polysaccharide storage myopathy and was the most common finding (36 animals; 15.7%). Chronic myopathic change was more common in older animals. Generalized muscle atrophy was present in 30 animals (13.1%). Myonecrosis was attributed to endotoxic injury (11 animals; 4.8%), bone fracture (8 animals; 3.5%), bacterial infection (5 animals; 2.2%), muscle rupture (3 animals; 1.3%), selenium deficiency (2 animals; 0.9%), and exertional rhabdomyolysis (1 horse; 0.4%); cause was not determined in 9 animals (3.9%). Intramyofiber protozoa were detected in 19 horses and ponies (8.3%). Denervation atrophy was detected in 14 animals (6.1%). Neoplasia involving muscle occurred in 3 animals (1.3%), injection site reactions were detected in 4 animals (1.7%), and focal lymphocytic infiltrates were found in 6 animals (2.6%). Other findings were ring fibers (2 horses; 0.9%), fiber splitting (2 horses; 0.9%), and fat infiltration (1 horse; 0.4%). Skeletal muscle lesions are common in equids examined at postmortem. Transverse sections stained with HE and PAS are invaluable when evaluating equine muscle.

Congenital Myasthenic Syndromes in childhood: Diagnostic and management challenges

The Congenital Myasthenic Syndromes (CMS), a group of heterogeneous genetic disorders of neuromuscular transmission, are often misdiagnosed as congenital muscular dystrophy (CMD) or myopathies and present particular management problems. We present our experience of 46 children with CMS, referred to us between 1992–2007 with provisional diagnoses of congenital myopathy (22/46), CMS or limb-girdle myasthenia (9/46), central hypotonia or neurometabolic disease (5/46), myasthenia gravis (4/46), limb–girdle or congenital muscular dystrophy (4/46) and SMA (2/46). Diagnosis was often considerably delayed (up to 18y4 m), despite the early symptoms in most cases. Diagnostic clues in the neonates were feeding difficulties (29/46), hypotonia with or without limb weakness (21/46), ptosis (19/46), respiratory insufficiency (12/46), contractures (4/46) and stridor (6/46). Twenty–five children had delayed motor milestones. Fatigability developed in 43 and a variable degree of ptosis was eventually present in 40. Over the period of the study, the mainstay of EMG diagnosis evolved from repetitive nerve stimulation to stimulation single fibre EMG. The patients were studied by several different operators. 66 EMGs were performed in 40 children, 29 showed a neuromuscular junction abnormality, 7 were myopathic, 2 had possible neurogenic changes and 28 were normal or inconclusive. A repetitive CMAP was detected in only one of seven children with a COLQ mutation and neither of the two children with Slow Channel Syndrome mutations. Mutations have been identified so far in 32/46 children: 10 RAPSN, 7 COLQ, 6 CHRNE, 7 DOK7, 1 CHRNA1 and 1 CHAT. 24 of 25 muscle biopsies showed myopathic changes with fibre size variation; 14 had type-1 fibre predominance. Three cases showed small type-1 fibres resembling fibre type disproportion, and four showed core-like lesions. No specific myopathic features were associated with any of the genes. Twenty children responded to Pyridostigmine treatment alone, 11 to Pyridostigmine with either 3, 4 DAP or Ephedrine and five to Ephedrine alone. Twenty one children required acute or chronic respiratory support, with tracheostomy in 4 and nocturnal or emergency non-invasive ventilation in 9. Eight children had gastrostomy. Another 11 were underweight for height indicative of failure to thrive and required dietetic input. A high index of clinical suspicion, repeat EMG by an experienced electromyographer and, if necessary, a therapeutic trial of Pyridostigmine facilitates the diagnosis of CMS with subsequent molecular genetic confirmation. This guides rational therapy and multidisciplinary management, which may be crucial for survival, particularly in pedigrees where previous deaths have occurred in infancy.

Effects of Growing Location and Irrigation on Attributes and Ethanol Yields of Selected Grain Sorghums

ABSTRACTNine sorghum cultivars (five inbred lines and four hybrids) were grown in 2006 in three locations (Mount Hope, KS, Halstead, KS, and Plainview, TX) under different irrigation conditions and were evaluated for composition and ethanol fermentation efficiency. The objective was to study, in one growing season, the effects of genotype, growing location, and irrigation on the physical and chemical properties and fermentation efficiencies of grain sorghum. Genotype had a significant effect on chemical composition, physical properties, and ethanol yield. The cultivars showed a large variation in starch (61.0–74.8%), protein (7.56–16.35%), crude fat (2.79–4.77%), crude fiber (0.58–2.57%), ash (1.25–2.26%), kernel weight (20.0–35.9 mg), kernel hardness (49.6–97.5), and kernel size (1.9–2.7 mm) and were the most important factors affecting ethanol fermentation efficiency (87.5–93.9%). Starch and protein contents were significantly affected by growing location but not by irrigation. Environment had a significant effect on ethanol yields. Unexpectedly, irrigation somewhat reduced fermentation efficiency.

Neuronal Fiber Composition of the Corpus Callosum Within Some Odontocetes

Odontocetes (toothed whales) evolved from terrestrial mammals approximately 55 million years ago and have since remained on a unique evolutionary trajectory. This study used formalin-fixed tissue and light microscopy to quantify the size and number of fibers along the corpus callosum of the bottlenose dolphin (n = 8). Two other species, the Amazon River dolphin (n = 1) and the killer whale (n = 1), were included for comparison. A large amount of variation in the shape and area of the corpus callosum was observed. The odontocete corpus callosum is a heterogeneous structure with variation in fiber size and density along the length of the corpus callosum in all specimens examined. Using the species with the largest sample size, the bottlenose dolphin, comparisons by sex and age (sexually mature verses immature) were made for the area of the corpus callosum, five subregions, and fiber densities. Although no sex differences were detected, age appeared to affect the size, shape, and fiber composition of the bottlenose dolphin corpus callosum.

Type 2 Myotonic Dystrophy Can Be Predicted by the Combination of Type 2 Muscle Fiber Central Nucleation and Scattered Atrophy

The diagnosis of Type 2 myotonic dystrophy (DM2/proximal myotonic myopathy) is often overlooked because of a nonspecific clinical presentation and muscle biopsy findings of a "denervation-like" pattern of unknown specificity that combines increased fiber size variation, central nucleation, small angulated fibers, Type 2 fiber atrophy, and nuclear clumps. We determined the presence of these features in 104 patients designated as having an unidentified myopathy from a series of 2,100 muscle biopsies. Because CCUG expansions form pathogenic ribonuclear accumulations that can be detected by in situ hybridization, we validated and then used automated (CCUG)8 in situ hybridization as a reference standard to evaluate the value of each histologic feature for DM2 detection, identifying 8 DM2-positive and 96 DM2-negative cases. Multivariate analyses identified the combination of Type 2 fiber atrophy and central nucleation as the most predictive of DM2 (sensitivity, 1.0; specificity, 0.92). These features were mutually exclusive in non-DM2 patients (p < 0.0001). The relevance of this combination of features was confirmed in an additional independent series (15 DM2-positive vs 17 DM2-negative). Further investigation revealed that central nucleation selectively affects Type 2 fibers in DM2 and, conversely, that it affects Type 1 fibers in DM1 (p < 0.0001). These results will facilitate the routine detection of DM2 and further support the concept that DM2 has a distinct pathophysiology involving type 2 myofibers.

臨床的に三好型ミオパチーを呈した肢帯型筋ジストロフィー２Ａ型の１例

We reported a 23-year-old woman with distal myopathy and highly elevated serum creatine kinase (CK) caused by calpainopathy. Although muscle weakness was not evident, a muscle CT scan revealed replacement by adipose tissue in the medial head of the gastrocnemius. The gluteus maximus and biceps femoris were also affected to a lesser degree, but the lateral head of the gastrocnemius was preserved. A histological study of a biopsied specimen of the biceps brachii revealed obvious variation in fiber size and a few necrotic or regenerating fibers. Rimmed vacuoles or lobulated fibers were absent in vacuoles. Although the clinical features suggested Miyoshi's distal myopathy, gene analysis of calpain 3 revealed a c.802-9G > A mutation in intron 5 and a c.1319G > A (p.Arg440Gln) in exon 10. Mini-multiplex Western Blotting (MMW) of the patient's muscle showed no band in calpain 3 (p94) and calpain 3 30 kDa fragments and immunoblotting did not reveal any dysferlin abnormalities. Calpainopathy should be also considered in patients with clinical manifestations of Miyoshi distal myopathy.

Novel VCP mutations in inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia

Inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD, OMIM 167320) has recently been attributed to eight missense mutations in valosin-containing protein (VCP). We report novel VCP mutations N387H and L198W in six individuals from two families who presented with proximal muscle weakness at a mean age of diagnosis of 40 years, most losing the ability to walk within a few years of onset. Electromyographic studies in four individuals were suggestive of 'myopathic' changes, and neuropathic pattern was identified in one individual in family 1. Muscle biopsy in four individuals showed myopathic changes characterized by variable fiber size, two individuals showing rimmed vacuoles and IBM-type cytoplasmic inclusions in muscle fibers, and electron microscopy in one individual revealing abundant intranuclear inclusions. Frontotemporal dementia associated with characteristic behavioral changes including short-term memory loss, language difficulty, and antisocial behavior was observed in three individuals at a mean age of 47 years. Detailed brain pathology in one individual showed cortical degenerative changes, most severe in the temporal lobe and hippocampus. Abundant ubiquitin-positive tau-, alpha-synuclein-, polyglutamine repeat-negative neuronal intranuclear inclusions and only rare intracytoplasmic VCP positive inclusions were seen. These new mutations may cause structural changes in VCP and provide some insight into the functional effects of pathogenic mutations.

Light and electron microscopy characteristics of the muscle of patients with SURF1 gene mutations associated with Leigh disease

Aims:Leigh syndrome (LS) is characterised by almost identical brain changes despite considerable causal heterogeneity. SURF1 gene mutations are among the most frequent causes of LS. Although deficiency of cytochrome c...

Mitochondrial complex III deficiency in a case of HCV related noninflammatory myopathy

Sirs: Muscle involvement in the course of Hepatitis C Virus (HCV) infection has mainly been reported as a myositis secondary to an immunologically mediated reaction or to a direct effect of viral infection. Myositis was confirmed in these cases by the presence of perivascular infiltration of inflammatory cells in the muscle biopsy [1, 2]. However, lack of evidence for viral multiplication in muscle [3, 4] suggested a virus-triggered immune-mediated mechanism, rather than direct infection and in situ replication. On the other hand, several cases of HCV associated myopathy lacked signs of inflammation in the muscle biopsy [2, 5] suggesting other pathogenic mechanisms. A 60-year-old woman was admitted in April 2002 with a 3 year history of slowly progressive bilateral eyelid ptosis, diplopia, generalized weakness, severe distal upper limb weakness and respiratory distress after minimal exercise. Neurological examination disclosed mild neck and proximal upper limb weakness, bilateral ptosis and diplopia both in horizontal and upward gaze. Ptosis increased after sustained upward gaze. A mild impairment in the upward gaze was present mainly on the left side. Her family history was unremarkable. The patient had a post-transfusion HCV infection detected by chance ten years before the appearance of ptosis, and not treated with immunotherapy because of the benign course. Neoplastic, autoimmune, thyroidal, and rheumatologic diseases were excluded by appropriate tests. Repetitive stimulation (right ulnar nerveabductor digiti minimi muscle and facial nerve-nasalis muscle) did not show a decremental response. Acetylcholine receptor antibodies were absent. Ptosis did not improve after edrophonium chloride intravenous injection. Chest computed tomography (CT), spirometry, electrocardiography and echocardiography, brain and orbit, CT and magnetic resonance imaging were normal. Immunoglobulin G and immunoglobulin M cryoglobulins were detected (cryocrit value: 2 %). Electroneurography was completely normal. Automatic interference pattern analysis was consistent with a myopathic dysfunction. The patient had an abnormal turns/amplitude ratio demonstrated by scores below the sexand age-specific reference range in frontal muscle, left biceps brachii and quadriceps. The same muscles showed rapid recruitment of short duration and low amplitude motor unit potentials. Fibrillations and fasciculations were absent. A biopsy taken from the left deltoid muscle revealed moderate fiber atrophy, marked variation of fiber size with round or angular shape, type 2 myofiber predominance with increased nuclear centralization. Perivascular inflammation, necrosis, and ragged red fibers were absent. Mitochondrial enzyme activities showed decreased decylbenzoquinol cytochrome c reductase activity (complex III deficiency) (51.1 nmol/min mg, normal values: 70–150) while citrate synthase activity was normal (153 nmol/min mg, normal value: 80–210). Mitochondrial complex I, II IV and V activities were normal. The ultrastructural study showed increased subsarcolemmal accumulation of glycogen, and mitochondria with altered shape and concentric cristae. To verify these findings a LETTER TO THE EDITORS

Spider capture silk: performance implications of variation in an exceptional biomaterial

Spiders and their silk are an excellent system for connecting the properties of biological materials to organismal ecology. Orb-weaving spiders spin sticky capture threads that are moderately strong but exceptionally extensible, resulting in fibers that can absorb remarkable amounts of energy. These tough fibers are thought to be adapted for arresting flying insects. Using tensile testing, we ask whether patterns can be discerned in the evolution of silk material properties and the ecological uses of spider capture fibers. Here, we present a large comparative data set that allows examination of capture silk properties across orb-weaving spider species. We find that material properties vary greatly across species. Notably, extensibility, strength, and toughness all vary approximately sixfold across species. These material differences, along with variation in fiber size, dictate that the mechanical performance of capture threads, the energy and force required to break fibers, varies by more than an order of magnitude across species. Furthermore, some material and mechanical properties are evolutionarily correlated. For example, species that spin small diameter fibers tend to have tougher silk, suggesting compensation to maintain breaking energy. There is also a negative correlation between strength and extensibility across species, indicating a potential evolutionary trade-off. The different properties of these capture silks should lead to differences in the performance of orb webs during prey capture and help to define feeding niches in spiders.

Electromyography (EMG) Accuracy Compared to Muscle Biopsy in Childhood

Reports show wide variability of electromyography (EMG) in detecting pediatric neuromuscular disorders. The study's aim was to determine EMG/nerve conduction study accuracy compared to muscle biopsy and final clinical diagnosis, and sensitivity for myopathic motor unit potential detection in childhood. Of 550 EMG/nerve conduction studies performed by the same examiner from a pediatric neuromuscular service, 27 children (ages 6 days to 16 years [10 boys; M:F, 1:1.7]) with muscle biopsies and final clinical diagnoses were compared retrospectively. Final clinical diagnoses were congenital myopathies (5 of 27,18%), nonspecific myopathies (biopsy myopathic, final diagnosis uncertain; 6 of 27, 22%), congenital myasthenic syndrome (3 of 27, 11%), juvenile myasthenia gravis (1 of 27, 4%), arthrogryposis multiplex congenita (2 of 27, 7%), hereditary motor and sensory neuropathy (1 of 27, 4%), bilateral peroneal neuropathies (1 of 27, 4%), and normal (8 of 27, 30%). There were no muscular dystrophy or spinal muscular atrophy patients. EMG/nerve conduction studies had a 74% agreement with final clinical diagnoses and 100% agreement in neurogenic, neuromuscular junction, and normal categories. Muscle biopsies concurred with final diagnoses in 87%, and 100% in myopathic and normal categories. In congenital myasthenic syndrome, muscle biopsies showed mild variation in fiber size in 2 of 3 children and were normal in 1 of 3. EMG sensitivity for detecting myopathic motor unit potentials in myopathies was 4 of 11 (36%), greater over 2 years of age (3 of 4, 75%), compared to infants less than 2 years (1 of 7, 14%), not statistically significant (P = .0879). EMGs false-negative for myopathy in infants < 2 years of age were frequently neurogenic (3 of 6, 50%). In congenital myopathies EMG detected myopathic motor unit potentials in 40%, with false-negative results neurogenic (20%) or normal (40%). Because our study has no additional tests for active myopathies, for example Duchenne muscular dystrophy genetic testing, our sensitivity for myopathies is lower than if we used a more global view. In conclusion, EMG detection rate of myopathic motor unit potentials at a young age was low, improving in children over 2 years of age. In neurogenic and neuromuscular junction disorders, the EMG has a very high detection rate. In children with mild to moderate neurogenic EMG findings and normal nerve conduction, a myopathy should always be considered.

Contractile Properties of Single Permeabilized Muscle Fibers from Congenital Cleft Palates and Normal Palates of Spanish Goats

Analysis of the composition of muscle fibers constituent to a cleft palate could provide significant insight into the cause of velopharyngeal inadequacy. The authors hypothesized that levator veli palatini muscle dysfunction inherent to cleft palates could affect the timing and outcome of cleft palate repair. Single, permeabilized muscle fibers from levator veli palatini muscles of three normal (n = 19 fibers) and three chemically induced congenital cleft palates (n = 21 fibers) of 14-month-old goats were isolated, and contractile properties were evaluated. The maximum isometric force and rate constants of tension redevelopment (ktr) were measured, and the specific force and normalized power were calculated for each fiber. The ktr measures indicate that cleft fibers are predominantly fast-fatigable; normal fibers are slow fatigue-resistant: after a 10-minute isometric contraction, fibers from cleft palates had a loss of force 16 percent greater than that from normal palates (p = 0.0001). The cross-sectional areas of the fibers from cleft palates (2750 +/- 209 microm2) were greater (p = 0.05) than those from normal palates (2226 +/- 143 microm2). Specific forces did not differ between the two groups. Maximum normalized power of fibers from cleft palates (11.05 +/- 1.82 W/l) was greater (p = 0.0001) than fibers from normal palates (1.60 +/- 0.12 W/l). There are clear physiologic differences in single muscle fibers from cleft palates and normal palates: cleft palate fibers are physiologically fast, have greater fatigability, and have greater power production. Detection of functional and/or fiber type differences in muscles of cleft palates may provide preoperative identification of a patient's susceptibility to velopharyngeal inadequacy and permit early surgical intervention to correct this clinical condition.