1,721,043 research outputs found
Loss and renewal of thick myofilaments in glucocorticoid-treated rat soleus after denervation and reinnervation
No full textDenervation of rat soleus muscle and simultaneous administration of high doses of corticosteroids for 7 days caused marked muscle fiber atrophy and selective loss of thick myofilaments from many muscle fibers by light and electron microscopy. Myosin heavy chain/actin ratios were greatly reduced on polyacrylamide gel electrophoresis. Nerve crush instead of cut permitted reinnervation after 2 weeks and demonstrated the reversibility of the muscle changes within a week after reinnervation. There was formation of new thick filaments and their reintegration into myofibrils without further breakdown, although large areas of Z-disc streaming appeared. The mechanism of A-band breakdown remains obscure, but it presumably starts with limited proteolysis and continues with disaggregation of myosin molecules. This is consistent with our observation that the muscle fibers retain a relatively good reactivity to antibodies against myosin heavy chain 1 week after denervation and corticosteroid administration. A syndrome recalling these experiments is seen in severely asthmatic patients receiving corticosteroids and pharmacologically paralyzed for mechanical respiration
Pattern of X-chromosome inactivation as a key determinant of the clinicopathologic phenotype of Duchenne muscular dystrophy carriers
No full textGlucocorticoids and immunosuppressants do not change the prevalence of necrosis and regeneration in mdx skeletal muscles
No full textTherapeutic doses of methylprednisolone, azathioprine, cyclosporin A, and cyclophosphamide administered to mdx mice between 15 and 45 days of age failed to significantly influence the time course and prevalence of necrosis and regeneration or serum creatine kinase activity. This finding contrasts with previously reported findings of beneficial effects of glucocorticoids in Duchenne muscular dystrophy (DMD). This may indicate that, mechanisms upon which beneficial effects of glucocorticoids depend in DMD, do not operate (sufficiently) in mdx mice
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Abnormal oxidative metabolism in exercise intolerance of undetermined origin
No full textTwenty-four patients with exercise intolerance of undetermined origin were examined by muscle phosphorus magnetic resonance spectroscopy (31P-MRS) to test for a possible underlying defect in oxidative metabolism. Results were compared to those of 37 normal controls and 22 patients with well-defined mitochondrial disorders. In 17 (71%) patients with exercise intolerance, ADP recovery after exercise, an index of mitochondrial function, was abnormally slow. The energy state of phosphate-containing metabolites at rest was abnormal in 33% of patients. In 17/22 patients with well-defined mitochondrial disorders, ADP recovery was similarly slow. Abnormalities at rest were slightly more prevalent (50%) in this group of patients. Other 31P-MRS measurements did not add to the overall sensitivity in detecting abnormalities in either of these groups. We suggest that many patients with exercise intolerance of undetermined cause may have impaired muscle oxidative metabolism, that is an important causative factor in the pathophysiology of their symptoms
Short-term dichloroacetate treatment improves indices of cerebral metabolism in patients with mitochondrial disorders
No full textWe performed a short-term, double-blind, placebo-controlled, crossover trial of sodium dichloroacetate (DCA) therapy in 11 patients affected by various primary mitochondrial disorders. Independent measures of oxidative metabolism (venous blood metabolites, exercise testing, phosphorus magnetic resonance [MR] spectroscopy of muscle, and proton MR spectroscopy of brain) were used in order to monitor metabolic responses to the drug. One week of DCA treatment produced significant decreases (p < 0.05) in blood lactate, pyruvate, and alanine at rest and after bicycle exercise. Proton MR spectra collected from a supraventricular volume of interest in brain of seven of 11 patients also showed significant changes. Brain lactate/creatine ratio decreased by 42% during DCA treatment (p < 0.05). Brain choline/creatine ratio (which is low in patients with myelinopathies) increased by 18% (p < 0.01) after therapy. N-Acetylaspartate/creatine ratio (an index of neuronal damage or loss) increased by 8% after treatment (p < 0.05). Proton MR spectra collected in two of 11 patients from a volume of interest including the basal ganglia showed similar results (decrease of 36.6% in lactate/creatine; increases of 16% in choline/creatine and 4.5% in N-acetylaspartate/creatine). Phosphorus MR spectroscopy of muscle and self-assessed clinical disability were unchanged. Our study indicates that short-term DCA treatment not only lowers blood lactate but also improves indices of both brain oxidative metabolism and neuronal and glial density or function
Short-term aerobic training response in chronic myopathies
No full textWe have previously demonstrated that patients with mitochondrial myopathies can benefit from short-term aerobic exercise training. In this study, we compared the responses to short-term aerobic training of patients with mitochondrial myopathies, patients with nonmetabolic myopathies, and sedentary normal subjects. Training consisted of 8 weeks of treadmill exercise at 70% to 85% of estimated maximum heart rate reserve. All groups showed significant improvements in estimated aerobic capacity as well as heart rate and blood lactate at submaximal exercise intensities. The increase in estimated aerobic capacity was greater in the mitochondrial myopathy patients than in the other two groups. Phosphorus magnetic resonance spectroscopy demonstrated increased oxidative capacity of muscle in patients with mitochondrial myopathies in response to this training but not in patients with other, nonmetabolic myopathies or sedentary control subjects. A self-assessed measurement of functional status (SF-36) suggested improved quality of life associated with the training. This study demonstrates that short-term aerobic training at low intensity can benefit patients with nonmetabolic myopathies but to a lesser extent than patients with mitochondrial myopathies
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