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.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 147-163).

名古屋大学博士学位論文 学位の種類 : 博士(医学)(論文) 学位授与年月日:平成5年2月19日 竹中晃氏の博士論文として提出された

Duchenne and Becker muscular dystrophies (DMD, BMD) are allelic X-linked diseases which affect approximately one in 3500 male newborns. They are caused by mutations in a gene positioned on the short arm of the X chromosome at Xp21. The first indication of the location of this gene was the description of rare females expressing DMD and who were found to have constitutional X;autosome translocations with an X chromosome breakpoint at this site. There are now 24 such females known worldwide. They express DMD as a consequence of preferential inactivation of the normal X chromosome. In order to contribute to the understanding of the aetiology of mutations causing DMD and the aetiology of constitutional translocations, two types of study have been performed here. Firstly, the detailed mapping of the X chromosome breakpoints of DMD-associated X;autosome translocations has been investigated. The results of this study have been compared with data on the physical distribution of mutations causing DMD in male patients. Secondly, one translocation, an X;l translocation with an autosomal breakpoint at Ip34, has been selected for more detailed investigation and the DNA sequence has been determined at the site of the rearrangement. Translocation breakpoint mapping studies were performed by somatic cell hybrid analysis. Hybrids were karyotyped and this information was used to construct a hybrid panel for the purpose of determining the autosomal localisations of anonymous DNA probes. The mapping of seven probes using this panel is described. The work described in this thesis revealed that the distribution of translocation breakpoints within the DMD gene appears to be random and may differ from the distribution of mutations in male patients. The X;l translocation whose breakpoints are cloned and sequenced was found to involve two expressed loci, one coding for dystrophin on the X chromosome and one for the leukocyte antigen related protein on chromosome 1. Sequence data revealed that a deletion of four to seven nucleotides from the X chromosome and a duplication of two to five nucleotides are associated with the translocation. The possible involvement of trinucleotides adjacent to the breakpoints, and of a LINE, a SINE and a stretch of potential Z-DNA within 1 kb of the X chromosome or the chromosome 1 breakpoint, is discussed.

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.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. "December 2007" Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 121-147).

A Distrofia Muscular de Duchenne (DMD) é um tipo de miopatia grave, degenerativa e progressiva, geneticamente determinada e ligada ao cromossomo X. Além dos graves distúrbios cardiorrespiratórios e da motricidade, o paciente apresenta disfunções do sistema digestório, caracterizadas pelas desordens da motilidade. Entretanto, sabe-se que tais disfunções não ocorrem no camundongo MDX. O objetivo deste estudo foi estimar a densidade numérica por área da população total de neurônios (QA[T]) e dos neurônios nitrérgicos (QA[N]); assim como a área de secção transversal média do corpo celular destes neurônios (A[T] e A[N]) do plexo mioentérico esofágico e a largura média das fibras estriadas (L) das camadas musculares. Foram utilizados 40 camundongos machos da linhagem C57BL/10 nas idades de 4 e 10 semanas, distribuídos entre grupos experimentais (MDX4 e MDX10), e controles (C4 e C10). As estimativas foram analisadas em preparados de membrana dos esôfagos, e técnicas histoquímicas de NADH-diaforase (NADH-d) e NADPH-diaforase (NADPH-d) foram utilizadas para evidenciar toda a população de neurônios e os neurônios nitrérgicos, respectivamente. Os resultados mostraram que a QA[T] foi significativamente maior no grupo MDX10 em relação ao C10 (p<0.05); enquanto a QA[N] foi menor no grupo MDX4 em relação ao C4 (p<0.05). A A[T] foi menor no grupo MDX10 em relação ao MDX4 e ao C10 (p<0.05); enquanto que para a A[N] não houve diferença significativa entre os grupos controle e experimental, e tampouco entre os grupos de 4 e de 10 semanas. A variável L foi maior nos grupos MDX4 e MDX10 em relação aos seus respectivos controles de mesma idade (p<0.05). Concluímos que no plexo mioentérico esofágico de camundongos MDX existe uma redução dos neurônios mediadores do relaxamento, especialmente em animais jovens (MDX4), provavelmente porque o organismo tenta manter íntegra a função peristáltica do órgão. Esse fato pode explicar a adaptação e ausência de disfunções esofágicas durante quase toda a vida desses animais. / Duchenne Muscular Dystrophy (DMD) is the most common and the most severe muscular dystrophy of childhood. DMD is degenerative, progressive and a genetic X-linked disease. Besides the cardiomyopathy and the movement disorders, the patients have serious disfunctions in the alimentary system, characterized by motility disorders. However, it is known that such changes do not exist in MDX mice. The aim of this study was to estimate the neuronal numerical density/area of total (QA[T]) and nitregic neurons (QA[N]), the average cross-sectional area of total (A[T]) and nitregic (A[N]) neurons in myenteric plexus of the oesophagus and the average width of striped muscle of muscular layer (L). Forty C57BL/10 male mice were studied from four to ten weeks of age, divided into four groups: MDX mice formed the experimental groups (MDX4 and MDX10) and C57BL/10 male mice without the mutation formed the control groups (C4 and MDX10). Whole mounts preparations were obtained from the samples and histochemistry for NADH-diaphorase (NADH-d) and NADPH-diaphorase (NADPH-d) were used for morphometric evaluation. The results showed a significant increase of the QA[T] in the MDX10 than C10 (p<0.05), and a decrease of the QA[N] in MDX4 comparing to C4 (p<0.05). The A[T] decreased significantly in MDX10 comparing to both MDX4 and C10 (p<0.05), while no significant differences were observed among all the groups regarding the A[N]. The groups MDX4 and MDX10 showed a significant increase in L when compared to its controls at the same age (p<0.05). We conclude that in the myenteric plexus of the oesophagus in MDX mice there is a reduction of the inhibitory neurons, manly in the young animals (MDX4), probably to keep normal the peristaltic functions. Thus, it may explain the adaptation and the absence of oesophageal disfunction during almost the whole life in this animal model.

A Distrofia Muscular dos cães Golden Retriever (GRMD), é uma miopatia degenerativa causada pela ausência de uma proteína, a distrofina, geneticamente homóloga à distrofia muscular de Duchenne que acomete humanos, portanto, estes cães são considerados modelos experimentais para estudos que buscam tratamentos para esta doença progressiva e sem cura. Neste trabalho, foram selecionadas sete diferentes medicamentos, entre eles: Sildenafil; Ácido ursodesoxicólico; Acetilcisteína; Losartana Potássica; Micofenolato de Mofetila; Talidomida e Diltiazen, formando um coquetel de medicamentos com a finalidade de tratar os efeitos deletérios causados pela distrofia muscular, proporcionando dessa forma, uma melhor qualidade e sobrevida para os pacientes distróficos. Cada medicamento foi escolhido pela sua ação: sildenafil, aumento do óxido nítrico; ácido ursodesoxicólico, antiinflamatório; Acetilcisteína, antioxidante; Losartana Potássica, antifibrótico e cardioprotetor; Micofenolato de Mofetila, imunossupressor; Talidomida, antiTNF; diltiazen, bloqueador dos canais de cálcio. Para o experimento, foram utilizados 6 cães machos GRMD, sendo 2 controle e 4 experimentais, com o tratamento iniciado aos 80 dias até 10 meses de idade. Os animais foram avaliados em diferentes momentos, com exames séricos, histologia básica, imuno-histoquímica e PCR.Após avaliações, podemos concluir que o coquetel de medicamentos, não causou melhora clínica nos cães do grupo experimental. A dosagem de leucócitos, TGP, CK e a expressão de NFk&beta; e TGF&beta;1 foi menor no grupo experimental comparado com o grupo controle, sugerindo uma melhora do processo inflamatório e tardia progressão da distrofia muscular no grupo experimental. / The Golden Retriever Muscular Dystrophy (GRMD), is a degenerative myopathy caused by the absence of a protein, dystrophin, genetically homologous to the Duchenne Muscular Dystrophy that affects humans, so these dogs are considered experimental models for studies that seek treatments for this progressive disease with no cure. In this work, we selected seven different medications, including: Sildenafil, Ursodeoxycholic Acid, Acetylcysteine, Losartan Potassium, Mycophenolate mofetil, Thalidomide and Diltiazem concomitantly forming a cocktail of drugs in order to treat the deleterious effects of muscular dystrophy, thereby providing a better quality and survival for patients dystrophic. Each drug was chosen for its action: sildenafil, increasing nitric oxide; ursodeoxycholic acid, anti-inflammatory; acetylcysteine, an antioxidant; losartan, antifibrotic and cardioprotective; mycophenolate mofetil, an immunosuppressant; thalidomide, antiTNF; Diltiazem, calcium channel blocker. For the experiment, 6 male dogs were utilized GRMD, and two control and four experimental. Treatment started with 80 days to 10 months of age. The animals were evaluated at different times with serum levels, basic histology, immunohistochemistry and PCR. After the evaluations, we conclude that the cocktail of drugs, no clinical improvement in the experimental group. The dosage of leukocytes, ALT, CK and NFk&beta; and TGF&beta;1 expression was lower in the experimental group compared with the control group, suggesting an improvement in the inflammatory process and delayed progression of muscular dystrophy in the experimental group.