170,432 research outputs found
Encephalomyopathies caused by abnormal nuclear-mitochondrial intergenomic cross-talk
No full textAutosomal dominant Progressive External Ophthalmoplegias are Mendelian disorders characterized by the accumulation of multiple deletions of mitochondrial DNA in critical tissues. Most of the Autosomal dominant Progressive External Ophthalmoplegias families carry heterozygous mutations in one of three genes: ANT1, encoding the muscle-heart specific mitochondrial adenine nucleotide translocator, Twinkle, encoding the mitochondrial DNA helicase, and POLG1, encoding the catalytic subunit of the mitochondrial DNA-specific polymerase. Mutations in both POLG1 alleles are also found in autosomal recessive Progressive External Ophthalmoplegias sibships with multiple affected members and in apparently sporadic cases. In addition, recessive POLG1 mutations are responsible for three additional diseases: Alpers-Huttenlocher hepatopathic poliodystrophy, Sensory-Ataxic Neuropathy Dysarthria and Ophthalmoplegia and juvenile SpinoCerebellar Ataxia-Epilepsy syndrome. Mitochondrial neuro-gastro-intestinal encephalomyopathy is an autosomal recessive disorder of juvenile onset, caused by mutations in the gene encoding Thymidine Phosphorylase. Thymidine Phosphorylase is involved in the control and maintenance of the pyrimidine nucleoside pool of the cell. Finally, mitochondrial DNA depletion syndrome is a heterogeneous group of disorders characterized by a reduction in mitochondrial DNA copy number. Clinically, they include a myopathic form, a more generalized encephalomyopathic form and a fatal infantile hepato-cerebral syndrome leading to rapidly progressive liver and brain failure. To date, eight genes have been associated with mitochondrial DNA depletion syndrome. Novel disease genes have recently been added to this list, including OPA1 and GFER, and new clinical variants add further complexity to this expanding area of mitochondrial medicine
Myoclonus epilepsy in mitochondrial disorders
No full textMitochondrial disorders is a group of clinical entities associated with abnormalities of the mitochondrial respiratory chain (MRC), which carries out the oxidative phosphorylation (OXPHOS) of ADP into ATP. As the MRC is the result of genetic complementation between two separate genomes, nuclear and mitochondrial, OXPHOS failure can derive from mutations in either nuclear-encoded, or mitochondrial-encoded, genes. Epilepsy is a relatively common feature of mitochondrial disease, especially in early-onset encephalopathies of infants and children. However, the two most common entities associated with epilepsy include MERRF, for Myoclonic Epilepsy with Ragged Red Fibers, and AHS, or Alpers-Huttenlocher syndrome, also known as hepatopathic poliodystrophy. Whilst MERRF is a maternally inherited condition caused by mtDNA mutations, particularly the 8344A>G substitution in the gene encoding mt-tRNALys, AHS is typically caused by recessive mutations in POLG, encoding the catalytic subunit of polymerase gamma, the only mtDNA polymerase in humans. AHS is the most severe, early-onset, invariably fatal syndrome within a disease spectrum, which also include other epileptogenic entities, all due to POLG mutations and including Spino-cerebellar Ataxia and Epilepsy (SCAE). This review reports the main clinical, neuroimaging, biochemical, and molecular features of epilepsy-related mitochondrial syndrome, particularly MERRF and AHS
Vocalizzi preparatorii per la scuola del canto, composti dal ... G. B. Lamperti ... Per contralto.
No full text1 p.l., 40 p. 35 cm.55688 G. Ricordi & C
The Lamperti correspondence extended to Lévy processes and semi-stable Markov processes in locally compact groups
No full textAbstractWe establish Lamperti representations for semi-stable Markov processes in locally compact groups. We also study the particular cases of processes with values in R and C under the hypothesis that they do not visit 0. These Lamperti representations yield some properties of these semi-stable Markov processes
A redundancy resolution method for an anthropomorphic dual-arm manipulator based on a musculoskeletal criterion
No full textIn order to make humans feeling comfortable when working with robots, it is necessary for robots to be as much as possible “human-like” in both their appearance and movements. In redundant manipulators, it is possible to use the additional degrees of freedom in order to make the robot motion more human-like, thus increasing the quality of the human-robot interaction. In this work, a redundancy resolution method to address this issue is presented. Such a method considers the human musculoskeletal system and a biomechanical model of the human upper limbs in order to define a strategy to solve the redundancy for a dual-arm anthropomorphic manipulator as a human would do, then making the robot able to both perform the prescribed task and to assume human-like postures
Digital Servitization and Business Model Innovation in SMEs: A Model to Escape From Market Disruption
No full textThe progress and the adoption of digital technologies can rapidly make products, processes, and business models obsolete, until disrupting entire markets. In this context, small–medium enterprises (SMEs) operating in manufacturing are especially challenged due to their limited resources and smallness liabilities. Firms can implement, design, and deliver new smart and connected products that change the way they compete and trigger the provision of services—until redesigning the entire business model. However, little knowledge is available on how SMEs may effectively trigger and catalyze such transition. Using an interpretative research approach inspired by the design research methodology, in this article, we explore how SMEs may leverage digital servitization to escape from a disrupted market. Based on our findings, an original digital servitization model tailored for SMEs is proposed. Finally, the study provides a set of research and managerial implications on how SMEs can overcome market disruption in the manufacturing context through digital servitization and business model innovation
MELAS-like encephalomyopathy caused by a new pathogenic mutation in the mitochondrial DNA encoded cytochrome c oxidase subunit I
No full textWe report a 35-year-old woman presenting a stroke-like episode with transitory aphasia followed by generalized tonic-clonic seizures. She had severe hearing loss and suffered from frequent episodes of migraine. Although a brain MRI disclosed a T2-hyperintense lesion in the left parietal lobe, she had hardly any long-term sequela. Exercise intolerance, myalgias and limb-girdle muscle weakness indicated a slowly progressive myopathy. Extra-neurological features included short stature, and secondary amenorrhea with low gonadotropin levels, indicating secondary hypogonadism. However, she had three mutation-free, healthy children by ovarian stimulation. A muscle biopsy showed ragged-red, cytochrome c oxidase-negative fibers, and an isolated defect of cytochrome c oxidase activity in muscle mitochondria. Sequence analysis of muscle mtDNA revealed a previously unreported heteroplasmic m.6597C>A transversion in the MTCOI gene, encoding subunit I of cytochrome c oxidase, corresponding to p.Q232K aminoacid change. Analysis on transmitochondrial cybrids demonstrated that the mutation is indeed associated with COX deficiency, i.e. pathogenic. © 2012 Elsevier B.V
A Hu-Washizu variational approach to self-stabilized quadrilateral Virtual Elements: 2D linear elastodynamics
No full textA recent mixed formulation of the Virtual Element Method in 2D elastostatics, based on the Hu-Washizu variational principle, is here extended to 2D elastodynamics. The independent modeling of the strain field, allowed by the mixed formulation, is exploited to derive first order quadrilateral Virtual Elements (VEs) not requiring a stabilization (namely, self-stabilized VEs), in contrast to the standard VEs, where an artificial stabilization is always required for first order quads. Lumped mass matrices are derived using a novel approach, based on an integration scheme that makes use of nodal values only, preserving the correct mass in the case of rigid-body modes. In the case of implicit time integration, it is shown how the combination of a self-stabilized stiffness matrix with a self-stabilized lumped mass matrix can produce excellent performances both in the compressible and quasi-incompressible regimes with almost negligible sensitivity to element distortion. Finally, in the case of explicit dynamics, the performances of the different types of derived VEs are analyzed in terms of their critical time-step size
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