Muscle flex

'Muscleflex' is an installation comprising large scale fabric works, wall drawings, performance and digital video. The large-scale fabric works act as bodily extensions for two performers and constrain movement during the drawing process. These drawing performances are documented and re-presented as digital video works. This work examines the limits of language and subjectivity and offers a feminist engagement with the history of abstract painting. 'Muscle flex' was developed and presented for KINGS Artist Run Gallery, Melbourne in 2012 and revised for the exhibition 'I build my dwelling', at Metro Arts Galleries, Brisbane in 2012.

Localized agglutinin staining in muscle capillaries from normal and very old atrophic human muscle using winged bean ( Psophocarpus tetragonolobus ) lectin

The winged bean (Psophocarpus tetragonolobus) agglutinin (total lectin) and its basic (WBA I) and acidic isoform (WBA II) were used to analyze capillaries in sections from human muscle. The microvessels were clearly labeled after incubation with the lectins in both normal muscle and in old muscles with age-related type II atrophy or muscle fiber grouping. Muscle fibers, nerves, and connective tissue remained unstained. The total lectin detected muscle capillaries from all blood group AB0 individuals. The isoform WBA I reacted only with blood vessels in blood group A and B individuals, while the blood vessels in blood group 0 individuals were demonstrated with WBA II. WBA I staining was inhibited by p-nitrophenyl α-galactopyranoside and N-acetylgalactosamine, whereas 2′-fucosyllactose and preincubation with an antibody against type-1 chain H abolished capillary staining with WBA II. The study demonstrates the usefulness of WBA as a marker of capillaries in human muscle.

Expression of lactate transporters MCT1, MCT2, MCT4 and the ancillary protein CD147 in horse muscle and red blood cells

Monocarboxylate transporters (MCTs) transport lactate and protons across cell membranes. During intense exercise, lactate and protons accumulate in the exercising muscle and are transported to the plasma. In the horse, MCTs are responsible for the majority of lactate and proton removal from exercising muscle, and are therefore also the main mechanism to hinder the decline in pH in muscle cells. Two isoforms, MCT1 and MCT4, which need an ancillary protein CD147, are expressed in equine muscle. In the horse, as in other species, MCT1 is predominantly expressed in oxidative fibres, where its likely role is to transport lactate into the fibre to be used as a fuel at rest and during light work, and to remove lactate during intensive exercise when anaerobic energy production is needed. The expression of CD147 follows the fibre type distribution of MCT1. These proteins were detected in both the cytoplasm and sarcolemma of muscle cells in the horse breeds studied: Standardbred and Coldblood trotters. In humans, training increases the expression of both MCT1 and MCT4. In this study, the proportion of oxidative fibres in the muscle of Norwegian-Swedish Coldblood trotters increased with training. Simultaneously, the expression of MCT1 and CD147, measured immunohistochemically, seemed to increase more in the cytoplasm of oxidative fibres than in the fast fibre type IIB. Horse MCT4 antibody failed to work in immunohistochemistry. In the future, a quantitative method should be introduced to examine the effect of training on muscle MCT expression in the horse. Lactate can be taken up from plasma by red blood cells (RBCs). In horses, two isoforms, MCT1 and MCT2, and the ancillary protein CD147 are expressed in RBC membranes. The horse is the only species studied in which RBCs have been found to express MCT2, and the physiological role of this protein in RBCs is unknown. The majority of horses express all three proteins, but 10-20% of horses express little or no MCT1 or CD147. This leads to large interindividual variation in the capacity to transport lactate into RBCs. Here, the expression level of MCT1 and CD147 was bimodally distributed in three studied horse breeds: Finnhorse, Standardbred and Thoroughbred. The level of MCT2 expression was distributed unimodally. The expression level of lactate transporters could not be linked to performance markers in Thoroughbred racehorses. In the future, better performance indexes should be developed to better enable the assessment of whether the level of MCT expression affects athletic performance. In human subjects, several mutations in MCT1 have been shown to cause decreased lactate transport activity in muscle and signs of myopathy. In the horse, two amino acid sequence variations, one of which was novel, were detected in MCT1 (V432I and K457Q). The mutations found in horses were in different areas compared to mutations found in humans. One mutation (M125V) was detected in CD147. The mutations found could not be linked with exercise-induced myopathy. MCT4 cDNA was sequenced for the first time in the horse, but no mutations could be detected in this protein.

Drosophila indirect flight muscle specific Act88F actin mutants as a model system for studying congenital myopathies of the human ACTA1 skeletal muscle actin gene

Most human ACTA1 skeletal actin gene mutations cause dominant, congenital myopathies often with severely reduced muscle function and neonatal mortality. High sequence conservation of actin means many mutated ACTA1 residues are identical to those in the Drosophila Act88F, an indirect flight muscle specific sarcomeric actin. Four known Act88F mutations occur at the same actin residues mutated in ten ACTA1 nemaline mutations, A138D/P, R256H/L, G268C/D/R/S and R372C/S. These Act88F mutants were examined for similar muscle phenotypes. Mutant homozygotes show phenotypes ranging from a lack of myofibrils to almost normal sarcomeres at eclosion. Aberrant Z-disc-like structures and serial Z-disc arrays, ‘zebra bodies’, are observed in homozygotes and heterozygotes of all four Act88F mutants. These electron-dense structures show homologies to human nemaline bodies/rods, but are much smaller than those typically found in the human myopathy. We conclude that the Drosophila indirect flight muscles provide a good model system for studying ACTA1 mutations.

Two levels of MCT1 and CD147 expression in the equine red blood cells and muscle

Monocarboxylate transporters (MCTs), especially the isoforms MCT1 - MCT4, cotransport lactate and protons across the cell membranes. They are thus essential for pH regulation and homeostasis in glycolytic cells such as red blood cells (RBCs), and skeletal muscle cells during intense exercise. In 70% of the Standardbred horses the lactate transport activity (TA) in RBCs is high and transport is mediated mainly by MCTs. In the rest 30% of the Standardbreds MCT mediated transport route is not active and the TA is low. MCTs need an ancillary protein for their proper localization and functioning in the plasma membrane. The ancillary protein for MCT1 and MCT4 is a member of immunoglobulin superfamily, CD147. Here we determined the expression of MCT isoforms and CD147 in equine RBCs and gluteal muscle. We sequenced the cDNA of horse MCT1 and CD147 to achieve horse-specific antibodies and to reveal sequence variations that may affect the TA of RBCs. The amount of MCT1 and CD147 mRNA in muscle were also studied. ---- In all, 73 horses representing different breeds were used. Blood samples were drawn from the jugular vein and muscle samples were taken either from gluteal muscle using biopsy needle or during castration from expendable cremaster muscle. The TA of RBCs was studied using radiolabeled lactate and the amount of MCT isoforms and CD147 in the plasma membranes using Western blotting. The level of mRNA in muscle cells was determined using qPCR. Isoforms MCT1 and MCT2 were found in the RBCs and isoforms MCT1 and MCT4 in the muscle cells of horses. The TA of RBCs was dependent on the expression of CD147 and MCT1 in the plasma membrane. Sequence variations were found in the cDNA of both MCT1 and CD147, but they did not explain the inactivity of MCT1 mediated transport route. The single nucleotide polymorphism (SNP) Met125Val in CD147 that existed parallel with an SNP in 3´-untranslated region explained, however, attenuation in CD147 expression in Standardbreds. A single mutation Ile51Val also decreased the expression of CD147 in one Warmblood. The MCT1 and CD147 mRNA concentrations in the gluteal muscle were higher in horses with higher MCT1 and CD147 expression in RBCs and lower in horses with minor expression of CD147 and MCT1. This suggests that the bimodal distribution of TA is due to differences in transcriptional regulation that is functioning in parallel in MCT1 and CD147 gene.

Use of finite wordlength FIR digital filter structures with improved magnitude and phase characteristics for reduction of muscle noise in EEG signals

One of the main disturbances in EEG signals is EMG artefacts generated by muscle movements. In the paper, the use of a linear phase FIR digital low-pass filter with finite wordlength precision coefficients is proposed, designed using the compensation procedure, to minimise EMG artefacts in contaminated EEG signals. To make the filtering more effective, different structures are used, i.e. cascading, twicing and sharpening (apart from simple low-pass filtering) of the designed FIR filter Modifications are proposed to twicing and sharpening structures to regain the linear phase characteristics that are lost in conventional twicing and sharpening operations. The efficacy of all these transformed filters in minimising EMG artefacts is studied, using SNR improvements as a performance measure for simulated signals. Time plots of the signals are also compared. Studies show that the modified sharpening structure is superior in performance to all other proposed methods. These algorithms have also been applied to real or recorded EMG-contaminated EEG signal. Comparison of time plots, and also the output SNR, show that the proposed modified sharpened structure works better in minimising EMG artefacts compared with other methods considered.

Transcription factor erect wing (EWG) is involved in indirect flight muscle patterning, development and maintenance in Drosophila

Muscle development is a multistep process which includes myoblast diversification, proliferation, migration, fusion, differentiation and growth. A hierarchical exhibition of myogenic factors is important for dexterous execution of progressive events in muscle formation. EWG (erect wing) is a transcription factor known to have a role in indirect flight muscle development (IFM) in Drosophila. We marked out the precise spatio-temporal expression profile of EWG in the myoblasts, and in the developing muscles. Mutant adult flies null for EWG in myoblasts show variable number of IFM, suggesting that EWG is required for patterning of the IFM. The remnant muscle found in the EWG null flies show proper assembly of the structural proteins, which implies that some myoblasts manage to fuse, develop and differentiate normally indicating that EWG is not required for differentiation program per se. However, when EWG expression is extended beyond its expression window in a wild type background, muscle thinning is observed implying EWG function in protein synthesis inhibition. Mis-expression studies in wing disc myoblasts hinted at its role in myoblast proliferation. We thus conclude that EWG is important for regulating fusion events which in turn decides the IFM pattern. Also IFM in EWG null mutants show clumps containing broken fibres and an altered mitochondrial morphology. The vertebrate homolog of EWG is nuclear respiratory factor1 (NRF1) which is known to have a function in mitochondrial biogenesis and protection against oxidative stress. Gene expression for inner mitochondrial membrane protein, Opa1-like was found to be absent in these mutants. Also, these flies were more sensitive to oxidative stress, indicating a compromised mitochondrial functioning. Our results therefore demonstrate that EWG functions in maintaining muscles’ structural integrity by ensuing proper mitochondrial activity.

Effect of myonuclear number and mitochondrial fusion on Drosophila indirect flight muscle organization and size

Mechanisms involved in establishing the organization and numbers of fibres in a muscle are not completely understood. During Drosophila indirect flight muscle (IFM) formation, muscle growth is achieved by both incorporating hundreds of nuclei, and hypertrophy. As a result, IFMs provide a good model with which to understand the mechanisms that govern overall muscle organization and growth. We present a detailed analysis of the organization of dorsal longitudinal muscles (DLMs), a subset of the IFMs. We show that each DLM is similar to a vertebrate fascicle and consists of multiple muscle fibres. However, increased fascicle size does not necessarily change the number of constituent fibres, but does increase the number of myofibrils packed within the fibres. We also find that altering the number of myoblasts available for fusion changes DLM fascicle size and fibres are loosely packed with myofibrils. Additionally, we show that knock down of genes required for mitochondrial fusion causes a severe reduction in the size of DLM fascicles and fibres. Our results establish the organization levels of DLMs and highlight the importance of the appropriate number of nuclei and mitochondrial fusion in determining the overall organization, growth and size of DLMs. (C) 2013 Elsevier Inc. All rights reserved.