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Find video protocols related to scientific articles indexed in Pubmed.
Whole-thorax irradiation induces hypoxic respiratory failure, pleural effusions and cardiac remodeling.
J. Radiat. Res.
PUBLISHED: 11-05-2014
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To study the mechanisms of death following a single lethal dose of thoracic radiation, WAG/RijCmcr (Wistar) rats were treated with 15 Gy to the whole thorax and followed until they were morbid or sacrificed for invasive assays at 6 weeks. Lung function was assessed by breathing rate and arterial oxygen saturation. Lung structure was evaluated histologically. Cardiac structure and function were examined by echocardiography. The frequency and characteristics of pleural effusions were determined. Morbidity from 15 Gy radiation occurred in all rats 5 to 8 weeks after exposure, coincident with histological pneumonitis. Increases in breathing frequencies peaked at 6 weeks, when profound arterial hypoxia was also recorded. Echocardiography analysis at 6 weeks showed pulmonary hypertension and severe right ventricular enlargement with impaired left ventricular function and cardiac output. Histologic sections of the heart revealed only rare foci of lymphocytic infiltration. Total lung weight more than doubled. Pleural effusions were present in the majority of the irradiated rats and contained elevated protein, but low lactate dehydrogenase, when compared with serum from the same animal. Pleural effusions had a higher percentage of macrophages and large monocytes than neutrophils and contained mast cells that are rarely present in other pathological states. Lethal irradiation to rat lungs leads to hypoxia with infiltration of immune cells, edema and pleural effusion. These changes may contribute to pulmonary vascular and parenchymal injury that result in secondary changes in heart structure and function. We report that conditions resembling congestive heart failure contribute to death during radiation pneumonitis, which indicates new targets for therapy.
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Triadopathies: an emerging class of skeletal muscle diseases.
Neurotherapeutics
PUBLISHED: 08-30-2014
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The triad is a skeletal muscle substructure responsible for the regulation of excitation-contraction coupling. It is formed by the close apposition of the T-tubule and the terminal sarcoplasmic reticulum. A rapidly growing list of skeletal myopathies, here referred to as triadopathies, are caused by gene mutations in components of the triad. These disorders, at their root, are caused by defects in excitation contraction coupling and intracellular calcium homeostasis. Secondary abnormalities in triad structure and/or function are also reported in several muscle diseases, most notably certain muscular dystrophies. This review highlights the current understanding of both primary and secondary triadopathies, and identifies important concepts yet to be fully addressed in the field. The emphasis of the review is both on the pathogenesis of triadopathies and their potential treatment.
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Tissue triage and freezing for models of skeletal muscle disease.
J Vis Exp
PUBLISHED: 08-01-2014
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Skeletal muscle is a unique tissue because of its structure and function, which requires specific protocols for tissue collection to obtain optimal results from functional, cellular, molecular, and pathological evaluations. Due to the subtlety of some pathological abnormalities seen in congenital muscle disorders and the potential for fixation to interfere with the recognition of these features, pathological evaluation of frozen muscle is preferable to fixed muscle when evaluating skeletal muscle for congenital muscle disease. Additionally, the potential to produce severe freezing artifacts in muscle requires specific precautions when freezing skeletal muscle for histological examination that are not commonly used when freezing other tissues. This manuscript describes a protocol for rapid freezing of skeletal muscle using isopentane (2-methylbutane) cooled with liquid nitrogen to preserve optimal skeletal muscle morphology. This procedure is also effective for freezing tissue intended for genetic or protein expression studies. Furthermore, we have integrated our freezing protocol into a broader procedure that also describes preferred methods for the short term triage of tissue for (1) single fiber functional studies and (2) myoblast cell culture, with a focus on the minimum effort necessary to collect tissue and transport it to specialized research or reference labs to complete these studies. Overall, this manuscript provides an outline of how fresh tissue can be effectively distributed for a variety of phenotypic studies and thereby provides standard operating procedures (SOPs) for pathological studies related to congenital muscle disease.
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Differential muscle hypertrophy is associated with satellite cell numbers and Akt pathway activation following activin type IIB receptor inhibition in Mtm1 p.R69C mice.
Am. J. Pathol.
PUBLISHED: 02-21-2014
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X-linked myotubular myopathy is a congenital myopathy caused by deficiency of myotubularin. Patients often present with severe perinatal weakness, requiring mechanical ventilation to prevent death from respiratory failure. We recently reported that an activin receptor type IIB inhibitor produced hypertrophy of type 2b myofibers and modest increases of strength and life span in the severely myopathic Mtm1?4 mouse model of X-linked myotubular myopathy. We have now performed a similar study in the less severely symptomatic Mtm1 p.R69C mouse in hopes of finding greater treatment efficacy. Activin receptor type IIB inhibitor treatment of Mtm1 p.R69C animals produced behavioral and histological evidence of hypertrophy in gastrocnemius muscles but not in quadriceps or triceps. The ability of the muscles to respond to activin receptor type IIB inhibitor treatment correlated with treatment-induced increases in satellite cell number and several muscle-specific abnormalities of hypertrophic signaling. Treatment-responsive Mtm1 p.R69C gastrocnemius muscles displayed lower levels of phosphorylated ribosomal protein S6 and higher levels of phosphorylated eukaryotic elongation factor 2 kinase than were observed in Mtm1 p.R69C quadriceps muscle or in muscles from wild-type littermates. Hypertrophy in the Mtm1 p.R69C gastrocnemius muscle was associated with increased levels of phosphorylated ribosomal protein S6. Our findings indicate that muscle-, fiber type-, and mutation-specific factors affect the response to hypertrophic therapies that will be important to assess in future therapeutic trials.
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Gene therapy prolongs survival and restores function in murine and canine models of myotubular myopathy.
Sci Transl Med
PUBLISHED: 01-24-2014
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Loss-of-function mutations in the myotubularin gene (MTM1) cause X-linked myotubular myopathy (XLMTM), a fatal, congenital pediatric disease that affects the entire skeletal musculature. Systemic administration of a single dose of a recombinant serotype 8 adeno-associated virus (AAV8) vector expressing murine myotubularin to Mtm1-deficient knockout mice at the onset or at late stages of the disease resulted in robust improvement in motor activity and contractile force, corrected muscle pathology, and prolonged survival throughout a 6-month study. Similarly, single-dose intravascular delivery of a canine AAV8-MTM1 vector in XLMTM dogs markedly improved severe muscle weakness and respiratory impairment, and prolonged life span to more than 1 year in the absence of toxicity or a humoral or cell-mediated immune response. These results demonstrate the therapeutic efficacy of AAV-mediated gene therapy for myotubular myopathy in small- and large-animal models, and provide proof of concept for future clinical trials in XLMTM patients.
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Dystrophin-deficient cardiomyocytes derived from human urine: new biologic reagents for drug discovery.
Stem Cell Res
PUBLISHED: 01-18-2014
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The ability to extract somatic cells from a patient and reprogram them to pluripotency opens up new possibilities for personalized medicine. Induced pluripotent stem cells (iPSCs) have been employed to generate beating cardiomyocytes from a patient's skin or blood cells. Here, iPSC methods were used to generate cardiomyocytes starting from the urine of a patient with Duchenne muscular dystrophy (DMD). Urine was chosen as a starting material because it contains adult stem cells called urine-derived stem cells (USCs). USCs express the canonical reprogramming factors c-myc and klf4, and possess high telomerase activity. Pluripotency of urine-derived iPSC clones was confirmed by immunocytochemistry, RT-PCR and teratoma formation. Urine-derived iPSC clones generated from healthy volunteers and a DMD patient were differentiated into beating cardiomyocytes using a series of small molecules in monolayer culture. Results indicate that cardiomyocytes retain the DMD patient's dystrophin mutation. Physiological assays suggest that dystrophin-deficient cardiomyocytes possess phenotypic differences from normal cardiomyocytes. These results demonstrate the feasibility of generating cardiomyocytes from a urine sample and that urine-derived cardiomyocytes retain characteristic features that might be further exploited for mechanistic studies and drug discovery.
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Pulmonary hemorrhage with capillaritis secondary to mycophenolate mofetil in a heart-transplant patient.
Arch. Pathol. Lab. Med.
PUBLISHED: 10-31-2013
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Immunosuppressive drugs are an integral part of therapy in organ transplantation. However, they are not without side effects, and although rare, these agents should be considered in the differential diagnosis of pulmonary complications in patients receiving transplants. We present a case of a patient who developed acute respiratory failure 7 days after orthotopic heart transplantation and who had been on both mycophenolate mofetil (MMF) and tacrolimus agents. Lung biopsy revealed features of pulmonary hemorrhage with capillaritis. Considered as a possible etiology, MMF was withdrawn. There was immediate improvement of the patients symptoms. The temporal relationship between MMF exposure and onset of pulmonary symptoms in the absence of other possible etiologies strongly suggests a causal relationship. Previously published reports of pulmonary toxicity from MMF included interstitial fibrosis. To the best of our knowledge, this is the first reported case of pulmonary hemorrhage with capillaritis because of administration of MMF.
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Recessive truncating titin gene, TTN, mutations presenting as centronuclear myopathy.
Neurology
PUBLISHED: 08-23-2013
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To identify causative genes for centronuclear myopathies (CNM), a heterogeneous group of rare inherited muscle disorders that often present in infancy or early life with weakness and hypotonia, using next-generation sequencing of whole exomes and genomes.
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G-protein coupled receptor 56 promotes myoblast fusion through serum response factor- and nuclear factor of activated T-cell-mediated signalling but is not essential for muscle development in vivo.
FEBS J.
PUBLISHED: 07-01-2013
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Mammalian muscle cell differentiation is a complex process of multiple steps for which many of the factors involved have not yet been defined. In a screen to identify the regulators of myogenic cell fusion, we found that the gene for G-protein coupled receptor 56 (GPR56) was transiently up-regulated during the early fusion of human myoblasts. Human mutations in the gene for GPR56 cause the disease bilateral frontoparietal polymicrogyria; however, the consequences of receptor dysfunction on muscle development have not been explored. Using knockout mice, we defined the role of GPR56 in skeletal muscle. GPR56(-/-) myoblasts have decreased fusion and smaller myotube sizes in culture. In addition, a loss of GPR56 expression in muscle cells results in decreases or delays in the expression of myogenic differentiation 1, myogenin and nuclear factor of activated T-cell (NFAT)c2. Our data suggest that these abnormalities result from decreased GPR56-mediated serum response element and NFAT signalling. Despite these changes, no overt differences in phenotype were identified in the muscle of GPR56 knockout mice, which presented only a mild but statistically significant elevation of serum creatine kinase compared to wild-type. In agreement with these findings, clinical data from 13 bilateral frontoparietal polymicrogyria patients revealed mild serum creatine kinase increase in only two patients. In summary, targeted disruption of GPR56 in mice results in myoblast abnormalities. The absence of a severe muscle phenotype in GPR56 knockout mice and human patients suggests that other factors may compensate for the lack of this G-protein coupled receptor during muscle development and that the motor delay observed in these patients is likely not a result of primary muscle abnormalities.
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Deleting exon 55 from the nebulin gene induces severe muscle weakness in a mouse model for nemaline myopathy.
Brain
PUBLISHED: 05-28-2013
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Nebulin--a giant sarcomeric protein--plays a pivotal role in skeletal muscle contractility by specifying thin filament length and function. Although mutations in the gene encoding nebulin (NEB) are a frequent cause of nemaline myopathy, the most common non-dystrophic congenital myopathy, the mechanisms by which mutations in NEB cause muscle weakness remain largely unknown. To better understand these mechanisms, we have generated a mouse model in which Neb exon 55 is deleted (Neb(?Exon55)) to replicate a founder mutation seen frequently in patients with nemaline myopathy with Ashkenazi Jewish heritage. Neb(?Exon55) mice are born close to Mendelian ratios, but show growth retardation after birth. Electron microscopy studies show nemaline bodies--a hallmark feature of nemaline myopathy--in muscle fibres from Neb(?Exon55) mice. Western blotting studies with nebulin-specific antibodies reveal reduced nebulin levels in muscle from Neb(?Exon55) mice, and immunofluorescence confocal microscopy studies with tropomodulin antibodies and phalloidin reveal that thin filament length is significantly reduced. In line with reduced thin filament length, the maximal force generating capacity of permeabilized muscle fibres and single myofibrils is reduced in Neb(?Exon55) mice with a more pronounced reduction at longer sarcomere lengths. Finally, in Neb(?Exon55) mice the regulation of contraction is impaired, as evidenced by marked changes in crossbridge cycling kinetics and by a reduction of the calcium sensitivity of force generation. A novel drug that facilitates calcium binding to the thin filament significantly augmented the calcium sensitivity of submaximal force to levels that exceed those observed in untreated control muscle. In conclusion, we have characterized the first nebulin-based nemaline myopathy model, which recapitulates important features of the phenotype observed in patients harbouring this particular mutation, and which has severe muscle weakness caused by thin filament dysfunction.
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Troponin activator augments muscle force in nemaline myopathy patients with nebulin mutations.
J. Med. Genet.
PUBLISHED: 04-09-2013
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Nemaline myopathy-the most common non-dystrophic congenital myopathy-is caused by mutations in thin filament genes, of which the nebulin gene is the most frequently affected one. The nebulin gene codes for the giant sarcomeric protein nebulin, which plays a crucial role in skeletal muscle contractile performance. Muscle weakness is a hallmark feature of nemaline myopathy patients with nebulin mutations, and is caused by changes in contractile protein function, including a lower calcium-sensitivity of force generation. To date no therapy exists to treat muscle weakness in nemaline myopathy. Here, we studied the ability of the novel fast skeletal muscle troponin activator, CK-2066260, to augment force generation at submaximal calcium levels in muscle cells from nemaline myopathy patients with nebulin mutations.
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Cost of a group translation of the Diabetes Prevention Program: Healthy Living Partnerships to Prevent Diabetes.
Am J Prev Med
PUBLISHED: 03-19-2013
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Although numerous studies have translated the Diabetes Prevention Program lifestyle intervention into various settings, no study to date has reported a formal cost analysis.
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The Healthy Living Partnerships to Prevent Diabetes study: 2-year outcomes of a randomized controlled trial.
Am J Prev Med
PUBLISHED: 03-19-2013
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Since the Diabetes Prevention Project (DPP) demonstrated that lifestyle weight-loss interventions can reduce the incidence of diabetes by 58%, several studies have translated the DPP methods to public health-friendly contexts. Although these studies have demonstrated short-term effects, no study to date has examined the impact of a translated DPP intervention on blood glucose and adiposity beyond 12 months of follow-up.
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Selenoprotein N deficiency in mice is associated with abnormal lung development.
FASEB J.
PUBLISHED: 01-16-2013
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Mutations in the human SEPN1 gene, encoding selenoprotein N (SepN), cause SEPN1-related myopathy (SEPN1-RM) characterized by muscle weakness, spinal rigidity, and respiratory insufficiency. As with other members of the selenoprotein family, selenoprotein N incorporates selenium in the form of selenocysteine (Sec). Most selenoproteins that have been functionally characterized are involved in oxidation-reduction (redox) reactions, with the Sec residue located at their catalytic site. To model SEPN1-RM, we generated a Sepn1-knockout (Sepn1(-/-)) mouse line. Homozygous Sepn1(-/-) mice are fertile, and their weight and lifespan are comparable to wild-type (WT) animals. Under baseline conditions, the muscle histology of Sepn1(-/-) mice remains normal, but subtle core lesions could be detected in skeletal muscle after inducing oxidative stress. Ryanodine receptor (RyR) calcium release channels showed lower sensitivity to caffeine in SepN deficient myofibers, suggesting a possible role of SepN in RyR regulation. SepN deficiency also leads to abnormal lung development characterized by enlarged alveoli, which is associated with decreased tissue elastance and increased quasi-static compliance of Sepn1(-/-) lungs. This finding raises the possibility that the respiratory syndrome observed in patients with SEPN1 mutations may have a primary pulmonary component in addition to the weakness of respiratory muscles.
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Enzyme replacement therapy rescues weakness and improves muscle pathology in mice with X-linked myotubular myopathy.
Hum. Mol. Genet.
PUBLISHED: 01-09-2013
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No effective treatment exists for patients with X-linked myotubular myopathy (XLMTM), a fatal congenital muscle disease caused by deficiency of the lipid phosphatase, myotubularin. The Mtm1?4 and Mtm1 p.R69C mice model severely and moderately symptomatic XLMTM, respectively, due to differences in the degree of myotubularin deficiency. Contractile function of intact extensor digitorum longus (EDL) and soleus muscles from Mtm1?4 mice, which produce no myotubularin, is markedly impaired. Contractile forces generated by chemically skinned single fiber preparations from Mtm1?4 muscle were largely preserved, indicating that weakness was largely due to impaired excitation contraction coupling. Mtm1 p.R69C mice, which produce small amounts of myotubularin, showed impaired contractile function only in EDL muscles. Short-term replacement of myotubularin with a prototypical targeted protein replacement agent (3E10Fv-MTM1) in Mtm1?4 mice improved contractile function and muscle pathology. These promising findings suggest that even low levels of myotubularin protein replacement can improve the muscle weakness and reverse the pathology that characterizes XLMTM.
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Modeling the human MTM1 p.R69C mutation in murine Mtm1 results in exon 4 skipping and a less severe myotubular myopathy phenotype.
Hum. Mol. Genet.
PUBLISHED: 11-07-2011
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X-linked myotubular myopathy (MTM) is a severe neuromuscular disease of infancy caused by mutations of MTM1, which encodes the phosphoinositide lipid phosphatase, myotubularin. The Mtm1 knockout (KO) mouse has a severe phenotype and its short lifespan (8 weeks) makes it a challenge to use as a model in the testing of certain preclinical therapeutics. Many MTM patients succumb early in life, but some have a more favorable prognosis. We used human genotype-phenotype correlation data to develop a myotubularin-deficient mouse model with a less severe phenotype than is seen in Mtm1 KO mice. We modeled the human c.205C>T point mutation in Mtm1 exon 4, which is predicted to introduce the p.R69C missense change in myotubularin. Hemizygous male Mtm1 p.R69C mice develop early muscle atrophy prior to the onset of weakness at 2 months. The median survival period is 66 weeks. Histopathology shows small myofibers with centrally placed nuclei. Myotubularin protein is undetectably low because the introduced c.205C>T base change induced exon 4 skipping in most mRNAs, leading to premature termination of myotubularin translation. Some full-length Mtm1 mRNA bearing the mutation is present, which provides enough myotubularin activity to account for the relatively mild phenotype, as Mtm1 KO and Mtm1 p.R69C mice have similar muscle phosphatidylinositol 3-phosphate levels. These data explain the basis for phenotypic variability among human patients with MTM1 p.R69C mutations and establish the Mtm1 p.R69C mouse as a valuable model for the disease, as its less severe phenotype will expand the scope of testable preclinical therapies.
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Nanogel scavengers for drugs: local anesthetic uptake by thermoresponsive nanogels.
Acta Biomater
PUBLISHED: 10-16-2011
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The use of functional nanogels based on poly(N-isopropylacrylamide) for effectively scavenging compounds (here, the model drug bupivacaine) is demonstrated using an in vitro cell-based assay. Nanogels containing higher loadings of acidic functional groups or more core-localized functional group distributions bound more bupivacaine, while nanogel size had no significant effect on drug binding. Increasing the dose of nanogel applied also facilitated more bupivacaine binding for all nanogel compositions tested. Binding was driven predominantly by acid-base interactions between the nanogels (anionic) and bupivacaine (cationic) at physiological pH, although both non-specific absorption and hydrophobic partitioning also contributed to drug scavenging. Nanogels exhibited minimal cytotoxicity to multiple cell types and were well tolerated in vivo via peritoneal injections, although larger nanogels caused limited splenic toxicity at higher concentrations. The cell-based assay described herein is found to facilitate more robust drug uptake measurements for nanogels than conventional centrifugation-based assays, in which nanogels can be compressed (and thus drug released) during the measurement.
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An in vivo rodent model of contraction-induced injury in the quadriceps muscle.
Injury
PUBLISHED: 06-24-2011
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Most animal studies of muscle contractile function utilise the anterior or posterior crural muscle (dorsiflexors and plantarflexors, respectively). An advantage to using these muscles is that the common fibular and tibial nerves are readily accessible, while the small size of the crural muscles is a disadvantage. Working with small muscles not only makes some in vivo imaging and the muscle testing techniques more challenging, but also provides limited amounts of tissue to study. The purpose of this study was to describe a new animal muscle injury model in the quadriceps that results in a significant and reproducible loss of force. The thigh of Sprague Dawley rats (N=5) and C57BL/10 mice (N=5) was immobilised and the ankle was attached to a custom-made lever arm. The femoral nerve was stimulated using subcutaneous electrodes and injury was induced using 50 lengthening ("eccentric") contractions through a 70° arc of knee motion. This protocol produces a significant and reproducible injury, with comparable susceptibility to injury in the rats and mice. This novel model shows that the quadriceps muscle provides a means to study whole muscle contractility, injury, and recovery in vivo. In addition to the usual benefits of an in vivo model, the larger size of the quadriceps facilitates in vivo imaging and provides a significant increase in the amount of tissue available for histology and biochemistry studies. A controlled muscle injury in the quadriceps also allows one to study a muscle, with mixed fibre types, which is extremely relevant to gait in humans and quadruped models.
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One-year results of a community-based translation of the Diabetes Prevention Program: Healthy-Living Partnerships to Prevent Diabetes (HELP PD) Project.
Diabetes Care
PUBLISHED: 05-18-2011
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Although the Diabetes Prevention Program (DPP) and the Finnish Diabetes Prevention Study (FDPS) demonstrated that weight loss from lifestyle change reduces type 2 diabetes incidence in patients with prediabetes, the translation into community settings has been difficult. The objective of this study is to report the first-year results of a community-based translation of the DPP lifestyle weight loss (LWL) intervention on fasting glucose, insulin resistance, and adiposity.
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Novel mutations in NEB cause abnormal nebulin expression and markedly impaired muscle force generation in severe nemaline myopathy.
Skelet Muscle
PUBLISHED: 04-15-2011
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Nemaline myopathy (NM) is a congenital muscle disease associated with weakness and the presence of nemaline bodies (rods) in muscle fibers. Mutations in seven genes have been associated with NM, but the most commonly mutated gene is nebulin (NEB), which is thought to account for roughly 50% of cases.
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Experimental determination of circumferential properties of fresh carotid artery plaques.
J Biomech
PUBLISHED: 03-07-2011
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Carotid endarterectomy (CEA) is currently accepted as the gold standard for interventional revascularisation of diseased arteries belonging to the carotid bifurcation. Despite the proven efficacy of CEA, great interest has been generated in carotid angioplasty and stenting (CAS) as an alternative to open surgical therapy. CAS is less invasive compared with CEA, and has the potential to successfully treat lesions close to the aortic arch or distal internal carotid artery (ICA). Following promising results from two recent trials (CREST; Carotid revascularisation endarterectomy versus stenting trial, and ICSS; International carotid stenting study) it is envisaged that there will be a greater uptake in carotid stenting, especially amongst the group who do not qualify for open surgical repair, thus creating pressure to develop computational models that describe a multitude of plaque models in the carotid arteries and their reaction to the deployment of such interventional devices. Pertinent analyses will require fresh human atherosclerotic plaque material characteristics for different disease types. This study analysed atherosclerotic plaque characteristics from 18 patients tested on site, post-surgical revascularisation through endarterectomy, with 4 tissue samples being excluded from tensile testing based on large width-length ratios. According to their mechanical behaviour, atherosclerotic plaques were separated into 3 grades of stiffness. Individual and group material coefficients were then generated analytically using the Yeoh strain energy function. The ultimate tensile strength (UTS) of each sample was also recorded, showing large variation across the 14 atherosclerotic samples tested. Experimental Green strains at rupture varied from 0.299 to 0.588 and the Cauchy stress observed in the experiments was between 0.131 and 0.779 MPa. It is expected that this data may be used in future design optimisation of next generation interventional medical devices for the treatment and revascularisation of diseased arteries of the carotid bifurcation.
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Changes in cross-bridge cycling underlie muscle weakness in patients with tropomyosin 3-based myopathy.
Hum. Mol. Genet.
PUBLISHED: 02-28-2011
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Nemaline myopathy, the most common non-dystrophic congenital myopathy, is caused by mutations in six genes, all of which encode thin-filament proteins, including NEB (nebulin) and TPM3 (? tropomyosin). In contrast to the mechanisms underlying weakness in NEB-based myopathy, which are related to loss of thin-filament functions normally exerted by nebulin, the pathogenesis of muscle weakness in patients with TPM3 mutations remains largely unknown. Here, we tested the hypothesis that the contractile phenotype of TPM3-based myopathy is different from that of NEB-based myopathy and that this phenotype is a direct consequence of the loss of the specific functions normally exerted by tropomyosin. To test this hypothesis, we used a multidisciplinary approach, including muscle fiber mechanics and confocal and electron microscopy to characterize the structural and functional phenotype of muscle fibers from five patients with TPM3-based myopathy and compared this with that of unaffected control subjects. Our findings demonstrate that patients with TPM3-based myopathy display a contractile phenotype that is very distinct from that of patients with NEB-based myopathy. Whereas both show severe myofilament-based muscle weakness, the contractile dysfunction in TPM3-based myopathy is largely explained by changes in cross-bridge cycling kinetics, but not by the dysregulation of sarcomeric thin-filament length that plays a prominent role in NEB-based myopathy. Interestingly, the loss of force-generating capacity in TPM3-based myopathy appears to be compensated by enhanced thin-filament activation. These findings provide a scientific basis for differential therapeutics aimed at restoring contractile performance in patients with TPM3-based versus NEB-based myopathy.
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Inhibition of activin receptor type IIB increases strength and lifespan in myotubularin-deficient mice.
Am. J. Pathol.
PUBLISHED: 02-02-2011
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X-linked myotubular myopathy (XLMTM) is a congenital disorder caused by deficiency of the lipid phosphatase, myotubularin. Patients with XLMTM often have severe perinatal weakness that requires mechanical ventilation to prevent death from respiratory failure. Muscle biopsy specimens from patients with XLMTM exhibit small myofibers with central nuclei and central aggregations of organelles in many cells. It was postulated that therapeutically increasing muscle fiber size would cause symptomatic improvement in myotubularin deficiency. Recent studies have elucidated an important role for the activin-receptor type IIB (ActRIIB) in regulation of muscle growth and have demonstrated that ActRIIB inhibition results in significant muscle hypertrophy. To evaluate whether promoting muscle hypertrophy can attenuate symptoms resulting from myotubularin deficiency, the effect of ActRIIB-mFC treatment was determined in myotubularin-deficient (Mtm1?4) mice. Compared with wild-type mice, untreated Mtm1?4 mice have decreased body weight, skeletal muscle hypotrophy, and reduced survival. Treatment of Mtm1?4 mice with ActRIIB-mFC produced a 17% extension of lifespan, with transient increases in weight, forelimb grip strength, and myofiber size. Pathologic analysis of Mtm1?4 mice during treatment revealed that ActRIIB-mFC produced marked hypertrophy restricted to type 2b myofibers, which suggests that oxidative fibers in Mtm1?4 animals are incapable of a hypertrophic response in this setting. These results support ActRIIB-mFC as an effective treatment for the weakness observed in myotubularin deficiency.
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Elasticity and safety of alkoxyethyl cyanoacrylate tissue adhesives.
Acta Biomater
PUBLISHED: 01-28-2011
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Cyanoacrylate glues are easily applied to wounds with good cosmetic results. However, they tend to be brittle and can induce local tissue toxicity. A series of cyanoacrylate monomers with a flexible ether linkage and varying side-chain lengths was synthesized and characterized for potential use as tissue adhesives. The effect of side-chain length on synthesis yield, physical and mechanical properties, formaldehyde generation, cytotoxicity in vitro and biocompatibility in vivo were examined. The incorporation of etheric oxygen allowed the production of flexible monomers with good adhesive strength. Monomers with longer side-chains were found to have less toxicity both in vitro and in vivo. Polymerized hexoxyethyl cyanoacrylate was more elastic than its commercially available and widely used alkyl analog 2-octyl cyanoacrylate, without compromising biocompatibility.
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Activation of paternally expressed genes and perinatal death caused by deletion of the Gtl2 gene.
Development
PUBLISHED: 07-07-2010
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The Dlk1-Gtl2 imprinting locus is located on mouse distal chromosome 12 and consists of multiple maternally expressed non-coding RNAs and several paternally expressed protein-coding genes. The imprinting of this locus plays a crucial role in embryonic development and postnatal growth. At least one cis-element, the intergenic differentially methylated region (IG-DMR) is required for expression of maternally expressed genes and repression of silenced paternally expressed genes. The mechanism by which the IG-DMR functions is largely unknown. However, it has been suggested that the unmethylated IG-DMR acts as a positive regulator activating expression of non-coding RNAs. Gtl2 is the first non-coding RNA gene downstream of the IG-DMR. Although its in vivo function in the mouse is largely unknown, its human ortholog MEG3 has been linked to tumor suppression in human tumor-derived cell lines. We generated a knockout mouse model, in which the first five exons and adjacent promoter region of the Gtl2 gene were deleted. Maternal deletion of Gtl2 resulted in perinatal death and skeletal muscle defects, indicating that Gtl2 plays an important role in embryonic development. The maternal deletion also completely abolished expression of downstream maternally expressed genes, activated expression of silenced paternally expressed genes and resulted in methylation of the IG-DMR. By contrast, the paternal inherited deletion did not have this effect. These data strongly indicate that activation of Gtl2 and its downstream maternal genes play an essential role in regulating Dlk1-Gtl2 imprinting, possibly by maintaining active status of the IG-DMR.
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Effect of the look AHEAD study intervention on medication use and related cost to treat cardiovascular disease risk factors in individuals with type 2 diabetes.
Diabetes Care
PUBLISHED: 03-23-2010
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To examine the effect of a lifestyle intervention to produce weight loss and increased physical fitness on use and cost of medications to treat cardiovascular disease (CVD) risk factors in people with type 2 diabetes.
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Neuropathology of a fatal case of posterior reversible encephalopathy syndrome.
Pediatr. Dev. Pathol.
PUBLISHED: 02-16-2010
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The pathology of posterior reversible encephalopathy syndrome (PRES) is undefined, since it is rarely fatal and is biopsied in only exceptional circumstances. We describe rapidly progressive PRES following stem cell transplant for acute lymphoblastic leukemia. After development of altered mental status, this 8-year-old girl had T2 prolongation of the white matter in a posterior-dominant distribution, eventually developing cerebellar edema, hemorrhage, hydrocephalus, and herniation. Despite surgical and medical management, she died 36 hours later. At autopsy, the occipital and cerebellar white matter and focal occipital cortical gray matter showed a spectrum of microvascular changes, including dilated perivascular spaces containing proteinaceous exudates and macrophages, as well as fibrinoid necrosis and acute hemorrhage, in a distribution corresponding to the neuroimaging abnormalities and reminiscent of those seen in patients with acute hypertensive encephalopathy. Of note, similar microvascular changes were not seen in the kidney or other systemic sites. Thus, the findings indicate a brain-specific microvascular compromise as the substrate of PRES, at least in the rare instance of cases progressing to fatal outcome.
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Three-dimensional conductive constructs for nerve regeneration.
J Biomed Mater Res A
PUBLISHED: 07-03-2009
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The unique electrochemical properties of conductive polymers can be utilized to form stand-alone polymeric tubes and arrays of tubes that are suitable for guides to promote peripheral nerve regeneration. Noncomposite, polypyrrole (PPy) tubes ranging in inner diameter from 25 microm to 1.6 mm as well as multichannel tubes were fabricated by electrodeposition. While oxidation of the pyrrole monomer causes growth of the film, brief subsequent reduction allowed mechanical dissociation from the electrode mold, creating a stand-alone, conductive PPy tube. Conductive polymer nerve guides made in this manner were placed in transected rat sciatic nerves and shown to support nerve regeneration over an 8-week time period.
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Healthy Living Partnerships to Prevent Diabetes (HELP PD): design and methods.
Contemp Clin Trials
PUBLISHED: 05-07-2009
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Although the Diabetes Prevention Program (DPP) developed a lifestyle weight loss intervention that has been demonstrated to prevent type 2 diabetes in high-risk individuals, it has yet to be widely adopted at the community level. The Healthy Living Partnership to Prevent Diabetes study (HELP PD) was designed to translate the DPP approach for use in community settings as a cost-effective intervention led by Community Health Workers (CHWs) and administered through a Diabetes Care Center (DCC). Approximately 300 overweight and obese (BMI 25-40 kg/m(2)) individuals with prediabetes (fasting blood glucose 95-124 mg/dl) were randomly assigned to either a lifestyle weight loss intervention (LW) or an enhanced usual care comparison condition (UC). The goal of LW is >or=7% weight loss achieved through increases in physical activity (180 min/wk) and decreases in caloric intake (approximately 1500 kcal/day). The intervention consists of CHW-led group-mediated cognitive behavioral meetings that occur weekly for 6 months and monthly thereafter for 18 months. UC consists of 2 individual meetings with a registered dietitian and a monthly newsletter. The primary outcome is change in fasting blood glucose. Secondary outcomes include cardiovascular risk factors, health-related quality of life, and social cognitive variables. Outcomes are masked and are collected every 6 months. The cost-effectiveness of the program will also be assessed. A community-based program that is administered through local DCCs and that harnesses the experience of community members (CHWs) may be a promising strategy for the widespread dissemination of interventions effective at preventing type 2 diabetes in high risk individuals.
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Prolonged duration local anesthesia with minimal toxicity.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 04-13-2009
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Injectable local anesthetics that would last for many days could have a marked impact on periprocedural care and pain management. Formulations have often been limited in duration of action, or by systemic toxicity, local tissue toxicity from local anesthetics, and inflammation. To address those issues, we developed liposomal formulations of saxitoxin (STX), a compound with ultrapotent local anesthetic properties but little or no cytotoxicity. In vitro, the release of bupivacaine and STX from liposomes depended on the lipid composition and on whether dexamethasone was incorporated. In cell culture, bupivacaine, but not STX, was myotoxic (to C2C12 cells) and neurotoxic (to PC12 cells) in a concentration- and time-dependent manner. Liposomal formulations containing combinations of the above compounds produced sciatic nerve blockade lasting up to 7.5 days (with STX + dexamethasone liposomes) in male Sprague-Dawley rats. Systemic toxicity only occurred where high loadings of dexamethasone increased the release of liposomal STX. Mild myotoxicity was only seen in formulations containing bupivacaine. There was no nerve injury on Epon-embedded sections, and these liposomes did not up-regulate the expression of 4 genes associated with nerve injury in the dorsal root ganglia. These results suggest that controlled release of STX and similar compounds can provide very prolonged nerve blocks with minimal systemic and local toxicity.
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Effect of chemical permeation enhancers on nerve blockade.
Mol. Pharm.
PUBLISHED: 03-24-2009
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Chemical permeation enhancers (CPEs) have the potential to improve access of local anesthetics to the nerve, thereby improving nerve block performance. We assessed the effects of six CPEs on nerve blockade from tetrodotoxin (TTX) and from bupivacaine. Each of the six surfactants, representing three CPE subgroups (anionic, cationic, and nonionic surfactants) was coinjected with TTX or bupivacaine at the sciatic nerve of Sprague-Dawley rats. Myotoxicity of CPEs, alone and with TTX, was assessed in vitro in C2C12 myotubes and in vivo via histological analysis. All enhancers produced marked concentration-dependent improvements in the frequency and duration of block with TTX but not bupivacaine. An in vitro toxicity assay showed a wide range of CPE myotoxicity, but in vivo histological assessment showed no signs of muscle or nerve damage at concentrations of CPEs that produced a half-maximal increase in the duration of block of TTX (except in the case of the cationic surfactant DDAB). This study demonstrates that CPEs can provide marked prolongation of nerve blockade from TTX but not bupivacaine, without apparent local tissue toxicity. These results may enhance the clinical applicability of TTX for prolonged-duration local anesthesia.
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Myotubularin-deficient myoblasts display increased apoptosis, delayed proliferation, and poor cell engraftment.
Am. J. Pathol.
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X-linked myotubular myopathy is a severe congenital myopathy caused by deficiency of the lipid phosphatase, myotubularin. Recent studies of human tissue and animal models have discovered structural and physiological abnormalities in myotubularin-deficient muscle, but the impact of myotubularin deficiency on myogenic stem cells within muscles is unclear. In the present study, we evaluated the viability, proliferative capacity, and in vivo engraftment of myogenic cells obtained from severely symptomatic (Mtm1?4) myotubularin-deficient mice. Mtm1?4 muscle contains fewer myogenic cells than wild-type (WT) littermates, and the number of myogenic cells decreases with age. The behavior of Mtm1?4 myoblasts is also abnormal, because they engraft poorly into C57BL/6/Rag1null/mdx5cv mice and display decreased proliferation and increased apoptosis compared with WT myoblasts. Evaluation of Mtm1?4 animals at 21 and 42 days of life detected fewer satellite cells in Mtm1?4 muscle compared with WT littermates, and the decrease in satellite cells correlated with progression of disease. In addition, analysis of WT and Mtm1?4 regeneration after injury detected similar abnormalities of satellite cell function, with fewer satellite cells, fewer dividing cells, and increased apoptotic cells in Mtm1?4 muscle. These studies demonstrate specific abnormalities in myogenic cell number and behavior that may relate to the progression of disease in myotubularin deficiency, and may also be used to develop in vitro assays by which novel treatment strategies can be assessed.
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Oxygen gas-filled microparticles provide intravenous oxygen delivery.
Sci Transl Med
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We have developed an injectable foam suspension containing self-assembling, lipid-based microparticles encapsulating a core of pure oxygen gas for intravenous injection. Prototype suspensions were manufactured to contain between 50 and 90 ml of oxygen gas per deciliter of suspension. Particle size was polydisperse, with a mean particle diameter between 2 and 4 ?m. When mixed with human blood ex vivo, oxygen transfer from 70 volume % microparticles was complete within 4 s. When the microparticles were infused by intravenous injection into hypoxemic rabbits, arterial saturations increased within seconds to near-normal levels; this was followed by a decrease in oxygen tensions after stopping the infusions. The particles were also infused into rabbits undergoing 15 min of complete tracheal occlusion. Oxygen microparticles significantly decreased the degree of hypoxemia in these rabbits, and the incidence of cardiac arrest and organ injury was reduced compared to controls. The ability to administer oxygen and other gases directly to the bloodstream may represent a technique for short-term rescue of profoundly hypoxemic patients, to selectively augment oxygen delivery to at-risk organs, or for novel diagnostic techniques. Furthermore, the ability to titrate gas infusions rapidly may minimize oxygen-related toxicity.
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Thermoresponsive nanogels for prolonged duration local anesthesia.
Acta Biomater
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Nanogels based on poly(N-isopropylacrylamide) are attractive vehicles for prolonged duration local anesthesia because of their tunable size, number of functional groups, thermoresponsiveness and anionic charge. Nerve block durations of up to 9h were achieved using acrylic acid-loaded nanogels loaded with bupivacaine. Increasing the anionic charge density of the nanogels or (for more highly acid-functionalized nanogels) decreasing the nanogel size facilitated longer duration of anesthetic release. Small (<300 nm diameter) nanogels formed dense aggregates upon injection in vivo and induced only mild inflammatory responses, while large (>500 nm diameter) nanogels typically remained as liquid-like residues in vivo and induced more severe inflammatory reactions.
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Toxicogenomic analysis of a sustained release local anesthetic delivery system.
Biomaterials
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Concerns over neurotoxicity have impeded the development of sustained release formulations providing prolonged duration local anesthesia (PDLA) from a single injection, for which there is an urgent clinical need. Here, we have used toxicogenomics to investigate whether nerve injury occurred during week-long continuous sciatic nerve blockade by microspheres containing bupivacaine, tetrodotoxin, and dexamethasone (TBD). Animals treated with amitriptyline solution (our positive control for local anesthetic-associated nerve injury) developed irreversible nerve blockade, had severely abnormal nerve histology, and the expression of hundreds of genes was altered in the dorsal root ganglia at 4 and 7 days after injection. In marked contrast, TBD-treated nerves reverted to normal function, were normal histologically and there were changes in the expression of a small number of genes. Toxicogenomic studies have great potential in delineating patterns of gene expression associated with specific patterns of tissue injury (e.g. amitriptyline neurotoxicity), and in identifying related changes in gene expression upon exposure to a drug, biomaterial, or drug delivery system.
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JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.