1,720,960 research outputs found
Effect of auranofin on the mitochondrial generation of hydrogen peroxide. Role of thioredoxin reductase
No full textThe mitochondrial production of hydrogen peroxide, in the presence of different respiratory substrates ( succinate, glutamate, malate and isocitrate), is stimulated by submicromolar concentrations of auranofin, a highly specific inhibitor of thioredoxin reductase. This effect is particularly evident in the presence of antimycin. Auranofin was also able to unmask the production of hydrogen peroxide occurring in the presence of rotenone. However, at variance with whole mitochondria, auranofin does not stimulate hydrogen peroxide production in submitochondrial particles indicating that it does not alter the formation of hydrogen peroxide by the respiratory chain but prevents its removal. As the mitochondrial metabolism of hydrogen peroxide proceeds through the peroxidases linked to glutathione or thioredoxin, the relative efficiency of the two systems and the effects of auranofin were tested. In conclusion, the inhibition of thioredoxin reductase determines an increase of the basal flow of hydrogen peroxide leading to a more oxidized condition that alters the mitochondrial functions
Characterization of the 5 ' region of human CoQ2, a gene causing primary CoQ10 deficiency
No full textUbiquinone, coenzyme Q(10) or CoQ is a lipid-soluble component of the mitochondrial respiratory chain (RC) where it transfers reducing equivalents from complex I and complex II to complex III. CoQ10biosynthesis is still poor characterized in humans and consists of multiple enzymatic reactions. Primary CoQ10 deficiency causes a from of mitochondrial encephalomyopathy which is inherited as autosomal recessive trait, and in some patients it is associated to mutations in the COQ2 gene, encoding for Para-Hydroxybenzoate-Polyprenyl Transferase (Quinzii et al 2006).
Human COQ2 cDNA has been isolated from a human muscle and liver cDNA library (Forsgren et al, 2004) and encodes for a protein located in the mitochondrial inner membrane. The reported human sequence shows four different in frame ATG codons in the 5’ region of the gene. However by aligning the human protein with other mammalian COQ2 proteins, we found that the N-terminus of the reported sequence did not shown any homology with other mammalian COQ2 proteins, moreover there are no GENBANK ESTs corresponding to the reported 5’ region of the gene.
We therefore characterized the 5’ region of COQ2 by 5’-RACE and found different transcripts in human fibroblasts, but the most represented one (over 75% of total COQ2 mRNA) included only the fourth ATG. We then amplified cDNA using a fixed primer within exon 2 of the gene, distal to the predicted targeting sequence, and several primers located upstream of the fourth ATG. None of the detected PCR products included the first two reported ATG. To confirm the physiological relevance of these shorter mRNAs, we cloned the PCR fragments in frame with GFP, and we demonstrated that the resulting fluorescent fusion protein is targeted to mitochondria.
These data show that the functional human COQ2 mRNA is shorter than what previously was thought. We believe the reported COQ2 transcript represents a very rare mRNA, with little physiological significance. These findings are crucial to perform correct mutation screening in CoQ10 deficient patients
Argininosuccinate lyase deficiency: Mutational spectrum in Italian patients and identification of a novel ASL pseudogene.
No full textArgininosuccinic aciduria (ASAuria) is an inborn error of metabolism caused by mutations in the argininosuccinate lyase (ASL) gene, which leads to the accumulation of argininosuccinic acid (ASA) in body fluids and severe hyperammonemia. A severe neonatal form and a milder late-onset variant are described. We report a novel ASL pseudogene located in the centromeric region of chromosome 7, 14 novel mutations in the ASL gene, and a novel intronic polymorphism found in a cohort of Italian patients. Our approach relied exclusively on genomic DNA analysis. We found seven missense mutations, two nonsense, three small insertions/deletions, and two splicing mutations. Only two patients harbored previously described mutations, and among the novel variants only two were present in more than one kindred. The pathogenicity of the splicing mutations was demonstrated by a functional splicing assay that employed a hybrid minigene. We also performed molecular modeling using the reported three-dimensional structure of ASL to predict the functional consequences of the missense mutations. There was no genotype-phenotype correlation. Patients with neonatal onset display developmental delay and seizures despite adequate metabolic control. Moreover, hepatomegaly, fibrosis, and abnormal liver function tests are common complications in these patients, but not in patients with the late infancy form. We stress the importance of mutation analysis in patients with ASAuria, to confirm the clinical diagnosis, and to perform DNA-based prenatal diagnosis in future pregnancies of these families
Extracellular ATP signaling during differentiation of C2C12 skeletal muscle cells: role in proliferation
No full textEvidence shows that extracellular ATP signals influence myogenesis, regeneration and physiology of skeletal muscle. Present work was aimed at characterizing the extracellular ATP signaling system of skeletal muscle C2C12 cells during differentiation. We show that mechanical and electrical stimulation produces substantial release of ATP from differentiated myotubes, but not from proliferating myoblasts. Extracellular ATP-hydrolyzing activity is low in myoblasts and high in myotubes, consistent with the increased expression of extracellular enzymes during differentiation. Stimulation of cells with extracellular nucleotides produces substantial Ca(2+) transients, whose amplitude and shape changed during differentiation. Consistently, C2C12 cells express several P2X and P2Y receptors, whose level changes along with maturation stages. Supplementation with either ATP or UTP stimulates proliferation of C2C12 myoblasts, whereas excessive doses were cytotoxic. The data indicate that skeletal muscle development is accompanied by major functional changes in extracellular ATP signaling
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
hCOX18 and hCOX19: two human genes involved in cytochrome c oxidase assembly
Full text linkWe identified the human homologues of yCOX18 and yCOX19, two Saccharomyces cerevisiae genes involved in the biogenesis of mitochondrial respiratory chain complexes. In yeast, these two genes are required for the expression of cytochrome c oxidase: Cox18p catalyses the insertion of Cox2p COOH-tail into the mitochondrial inner membrane, and Cox19p is probably involved in metal transport to the intermembrane space. Both hCox18p and hCox19p present significant amino acid identity with the corresponding yeast polypeptides and reveal highly conserved functional domains. In addition, their subcellular localization is analogous to that of the yeast proteins. These data strongly suggest that the human gene products share similar functions with their yeast homologues. These two COX-assembly genes represent new candidates for mutational analysis in patients with isolated COX deficiency of unknown etiology
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