No description available.

No description available.

Myotonic dystrophy type 1 (DM1) is the most common adult muscular dystrophy affecting ~1/8000 people worldwide. DM1 is characterized by accelerated skeletal muscle weakness and wasting, myotonia and insulin resistance, ultimately causing impaired function and diminished quality of life. A trinucleotide (CTG) repeat expansion in the 3’ region upstream of the DMPK gene results in dysregulation of several RNA binding proteins (RNABPs) important for muscle health such as MBNL and CUGBP1. Exercise was shown to ameliorate DM1 pathology in mice and to be safe for DM1 patients. This thesis aimed to investigate the muscular adaptations of 12-weeks of aerobic exercise in DM1 patients. Eleven DM1 patients (DM1, 42.6 ± 3 y) were recruited from the Neuromuscular and Neurometabolic clinic at McMaster University and age matched to healthy controls (CON, 42.5 ± 2 y). DM1 and CON performed incremental VO2peak testing, muscle and spirometry functional tests and a skeletal muscle biopsy from the Vastus lateralis. After 12-weeks of training on a cycle ergometer (3x/wk @ ~65 %VO2peak), DM1 patients completed post-testing. Exercise training significantly increased total lean mass (TLM) by ~ 1.6 kg (p<0.05) and fibre cross-sectional area by ~30 % in DM1 patients. Aerobic fitness was enhanced following training from 19.7 ± 1.5 mL/kg/min to 26.0 ± 2.1 mL/kg/min (p<0.05). Furthermore, training improved 6-min walk test, timed up & go, and 5X sit-to-stand scores (p<0.05). Mechanistically, exercise modestly altered expression of RNABPs, and augmented mitochondrial function and protein content. This is the first study to comprehensively investigate the effects of aerobic training on muscle health and function in DM1. Our data provides evidence that exercise training can augment fitness, functional capacity and muscle mass in DM1. Further understanding the influence of exercise on DM1 pathology could outline the efficacy of a simple life intervention and provide insight for future pharmacological discoveries for DM1. / Thesis / Master of Science (MSc)

Background: Duchenne and Becker muscular dystrophies, collectively referred to as dystrophinopathies, are recessive X-linked disorders characterized by progressive muscle weakness and ultimately cardiac and respiratory failure. Immediate family members are often primary caregivers of individuals with a dystrophinopathy. Methods: We explored the impact of this role by inviting primary caregivers (n = 209) of males diagnosed with childhood-onset dystrophinopathy who were identified by the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) to complete a mailed questionnaire measuring perceived social support and stress, spirituality, and family quality of life (FQoL). Bivariate and multivariate analyses examined associations between study variables using the Double ABCX model as an analytic framework. Results: Higher stressor pile-up was associated with lower perceived social support (r = -0.29, p <.001), availability of supportive family (r = -0.30, p <.001) or non-family (r = -0.19, p <.01) relationships, and higher perceived stress (r = 0.33, p <.001); but not with spirituality (r = -0.14, p > 0.05). FQoL was positively associated with all support measures (correlations ranged from: 0.25 to 0.58, p-values 0.01-0.001) and negatively associated with perceived stress and control (r = -0.49, p <.001). The association between stressor pile-up and FQoL was completely mediated through global perceived social support, supportive family relationships, and perceived stress and control; supportive non-family relationships did not remain statistically significant after controlling for other mediators. Conclusions: Findings suggest caregiver adaptation to a dystrophinopathy diagnosis can be optimized by increased perceived control, supporting family resources, and creation of a healthy family identity. Our findings will help identify areas for family intervention and guide clinicians in identifying resources that minimize stress and maximize family adaptation.

As doenças neuromusculares são um grupo heterogêneo de doenças genéticas, causadas por mutações nos genes codificando proteínas musculares sarcolemicas, sarcoméricas, e citosolicas. A Distrofia Muscular de Duchenne (DMD) é uma miopatia degenerativa progressiva, caracterizada pela ausência da proteína distrofina na superfície da membrana da célula muscular. O modelo de cão Golden Retriever Muscular Dystrophy (GRMD) apresenta semelhanças clínicas de DMD devido ao seu tamanho maior e significativa fraqueza muscular, é geneticamente homólogo a DMD humana, sendo considerado modelo experimental para estudos de novas propostas terapêuticas e melhor entendimento da fisiopatogenia da doença. Não existe até o momento uma terapia efetiva em bloquear ou reverter o processo da distrofia muscular. Embora a terapia gênica e o transplante de células tronco possam fornecer a cura para a DMD, resultados positivos podem demorar algum tempo até serem clinicamente viáveis. Neste sentido, a busca de informações fisiopatológicas que podem estar correlacionadas com a distrofia, e, com o avanço da pesquisa há possibilidade de melhora na condição vital do paciente, por retardo da progressão dos sinais clínicos ou cura. Existem poucos estudos endócrinos em animais portadores de distrofia como aves, GRMD e o mdx, assim como no homem. Mediante a falta de dados, houve a necessidade de quantificar e comparar hormônios, ainda não analisados, assim como avaliar a morfologia de glândulas endócrinas no modelo experimental GRMD. Para que fosse possível a correlação na interferência hormonal na evolução da Distrofia Muscular do cão, os exames sanguíneos foram comparados com cães normais e com as portadoras, todos da raça Golden Retriever. A mensuração hormonal de triiodotironina total (T3T), tiroxina total (T4T), a tireotropina (TSH) e o cortisol foram processados através de \"kits\" comerciais para radioimunoensaio, e o tiroxina livre (T4L) com \"kit\" comercial por diálise. As análises morfológicas das adrenais e da tireóide foram feitas através da macroscopia, microscopia de luz e microscopia eletrônica de transmissão de materiais de GRMD e de cães sadios. Anatomica e morfológicamente as glândulas não apresentaram alterações. Os níveis de cortisol não variaram significantemente entre os grupos estudados. Os níveis de T3 total foi semelhante para os animais sadios, portadoras e afetados. T4 total apresentou-se em diferentes níveis em alguns grupos. O T4 livre não variou significantemente entre os grupos estudados. Os níveis séricos de TSH da maioria dos Golden Retriever, afetados, portadores e sadios, apresentaram-se abaixo do limite apresentado pelos valores de referência. / Neuromuscular diseases are a heterogeneous group of genetic diseases caused by mutations in genes encoding proteins muscle sarcolemma, sarcomeric, and cytosol. Duchenne Muscular Dystrophy (DMD) is a progressive degenerative myopathy characterized by absence of dystrophin on the surface membrane of muscle cells. The Golden Retriever Muscular Dystrophy (GRMD) shows clinical similarities of DMD due to its size and significant muscle weakness, is genetically homologous to human DMD, and is considered an experimental model for studies of new therapeutic approaches and better understanding of the pathogenesis of the disease.There is not an effective therapy to block or reverse the process of muscular dystrophy yet. Although gene therapy and stem cell transplantation may provide a cure for DMD, positive results may take some time to be clinically viable.In this sense, the search for pathologic and physiologic information can be correlated with muscular dystrophy, and with the advancement of research there is room for improvement in the vital condition of the patient by delaying the progression of clinical signs or cure.There are a few studies in animals with endocrine dystrophy such as birds, and GRMD mdx as well as in man. By lack of data, there was a need to quantify and compare hormones, not yet analyzed, as well as evaluating the morphology of endocrine glands in experimental model GRMD. To make possible the hormonal correlation in the evolution of muscular dystrophy in dogs, blood tests were compared with normal dogs and carriers, all Golden Retrievers. Measurement of total triiodothyronine hormone (T3T), total thyroxine (T4T), the thyrotropin (TSH) and cortisol were processed using commercial kits for radioimmunoassay, and free thyroxine (FT4) with commercial kit by dialysis.The morphological analysis of adrenal and thyroid were made by macroscopic, light microscopy and transmission electron microscopy of materials GRMD and healthy dogs. Anatomical and morphological glands were unaffected. Cortisol levels did not differ significantly between groups. The levels of total T3 was similar to the healthy animals, carriers and affected. The T4 presented at different levels in some groups. The free T4 did not differ significantly between groups. Serum TSH of most Golden Retriever, affected patients and healthy individuals, were below the limit presented by the reference values.

No description available.

The mdx mouse is widely used as a model for Duchenne Muscular Dystrophy, a fatal X-linked disease caused by a deficiency of the sub-sarcolemmal protein, dystrophin. This dissertation reports characterisation of the features of dystrophy in the mdx mouse, including parameters such as electrophysiological and contractile properties of dystrophic cardiac tissue, quantitative evaluation of kyphosis throughout the mdx lifespan, and contractile properties of respiratory and paraspinal muscles. Following these characterisation studies, the efficacy of antisense oligonucleotides (AOs) to induce alternative mRNA splicing in mdx skeletal muscles (diaphragm and paraspinal muscles) was evaluated. The left atria of younger (<6 weeks) and older (>15 months) mdx mice showed consistently lower basal forces and responsiveness to increased calcium, while action potential duration was significantly shorter in young mice (3 weeks) and older mice (9 and 12 months) (P<0.05). Cardiac fibrosis increased with age in mdx atria and ventricles and was elevated in young (6-8 weeks) and old (15 months) mdx compared to control mice (P<0.01). This study provided insights into DMD cardiomyopathy, and suggested that very young or old mdx mice provide the most useful models. Mdx mice show thoracolumbar kyphosis like boys with Duchenne Muscular Dystrophy. A novel radiographic index, the Kyphotic Index (KI), was developed and showed that mdx mice are significantly more kyphotic from 9 months of age, an effect maintained until 17 months (P<0.05). At 17 months, the paraspinal and respiratory muscles (latissimus dorsi, diaphragm and intercostal muscles) are significantly weaker and more fibrotic (P<0.05). Administration of AOs at four sites within the diaphragm at 4 and 5 months of age significantly increased twitch and tetanic forces compared to sham treated mdx (P<0.05). However, no difference in collagen was evident and dystrophin was not detected, possibly due to the low concentration of AO utilised. This study suggested that AOs can provide functional improvement in treated skeletal muscles. Monthly injections with AOs into the paraspinal muscles from 2 months to 18 months of age alleviated kyphosis, without significantly altering twitch and tetanic forces of latissimus dorsi, diaphragm and intercostal muscles. There was evidence of less fibrosis in diaphragm and latissimus dorsi muscles (P<0.05) and reduced central nucleation of the latissimus dorsi and intercostal muscles (P<0.05). Again, dystrophin was not detected by immunoblot. These studies indicate that very young and old mdx mice display previously uncharacterised dystrophic features, and are useful models for testing new therapies such as AOs. Low doses of AOs were shown to be safe and efficacious for long-term use, however there remains a need for testing higher concentrations and improved delivery strategies.

Oculopharyngeal muscular dystrophy (OPMD) is an adult-onset disorder characterized by progressive eyelid drooping, swallowing difficulties, and proximal limb weakness. The autosomal dominant form of this disease is caused by the expansion of a polyalanine stretch from 10 to 12--17 alanines in the N-terminus of PABPN1. Mutated PABPN1 (mPABPN1) is able to induce the formation of filamentous intranuclear inclusions that are the pathological hallmark of OPMD. PABPN1 is predominantly localized to the nucleus, binds RNA poly(A) tail, forms oliogmers, and is involved in polyadenylation. In this study we first demonstrated that oligomerization of PABPN1 is mediated by two potential oligomerization domains (OD), while inactivating oligomerization of mPABPN1 by deletions of 6--8 residues in either of the ODs prevents intranuclear protein aggregation. Expression of mPABPN1 in COS-7 cells is associated with cell death, whereas preventing nuclear protein aggregation by inactivating oligomerization of mPABPN1 significantly reduces cell death. We then identified two PABPN1 interacting proteins, hnRNP A1 and A/B, using a yeast two-hybrid library screen. The interaction between PABPN1 and hnRNP A1 or A/B was confirmed by GST pull-down and co-immunoprecipitation assays. When coexpressed with mPABPN1 in COS-7 cells, predominantly nuclear localized hnRNP A1 and A/B co-localize with mPABPN1 to the insoluble intranuclear aggregates. Patient studies showed that hnRNP A1 is sequestered in OPMD nuclear inclusions. We finally found a nuclear localization signal (NLS) in PABPN1 that is not homologous to any known NLSs. The 18 amino acids 289RGRVYRGRARATSWYSPY 306 in PABPN1 are necessary and sufficient for nuclear translocation. Attaching this sequence to cytoplasmic protein PKM2 completely re-localizes it to the nucleus. Alanine-scanning mutagenesis analysis showed that the last 9 residues 298RATSWYSPY306 are crucial to the function as an NLS. Our studies showed that mPABPN1 induced intran

The dystrophinopathies are a group of disorders characterised by cellular absence of the membrane stabilising protein, dystrophin. Duchenne muscular dystrophy is the most severe disorder clinically. The deficiency of dystrophin, in the muscular dystrophy X-linked (mdx) mouse causes an elevation in intracellular calcium in cardiac myocytes. Potential mechanisms contributing to increased calcium include enhanced influx, sarcoplasmic reticular calcium release and\or reduced sequestration or sarcolemmal efflux. This dissertation examined the potential mechanisms that may contribute to an intracellular calcium overload in a murine model of muscular dystrophy. The general cardiomyopathy of the mdx myocardium was evident, with the left atria from mdx consistently producing less force than control atria. This was associated with delayed relaxation. The role of the L-type calcium channels mediating influx was initially investigated. Dihydropyridines had a lower potency in contracting left atria corresponding to a redued dihydropyridine receptor affinity in radioligand binding studies of mdx ventricular homogenates (P<0.05). This was associated with increased ventricular dihydropyridine receptor protein and mRNA levels (P<0.05). The function of the sarcoplasmic reticulum in terms of release and also sequestration of calcium via the sarco-endoplasmic reticulum ATPase were investigated. A lower force of contraction was evident in mdx left atria in response to a range of stimulation frequencies (P<0.05) and concentrations of extracellular calcium (P<0.05). However, in the presence of 1 nM Ryanodine to block sarcoplasmic reticular calcium release, increased stimulation frequency caused similar forces to those obtained in control mice suggesting enhanced calcium influx via L-type calcium channels in mdx. Rapid cooling contractures showed a reduced contracture in mdx compared to control in response to cooling. This suggests some dysfunction in SR storage, which may be associated with the delayed relaxation time. Concentration-response curves to inhibitors of the sarco-endoplasmic reticulum showed no difference in function of the enzyme responsible for calcium uptake into the sarcoplasmic reticulum. Although sarco-endoplasmic reticulum ATPase mRNA was upregulated, no functional benefit was evident. This study indicates that a deficiency of dystrophin leads to upregulation of L-type calcium channels that contribute to increased calcium influx, with no functional change in sarcoplasmic reticular sequestration. Upregulation of the influx pathway is a potential mechanism for the calcium overload observed in mdx cardiac muscle.

Thesis (Ph.D.)--Victoria University (Melbourne, Vic.), 2007.