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Biomedical subjects

Silvia Alvarez

Publications and source records attributed to Silvia Alvarez.

14 recordsLinked to original sources
PubMed2007

Isolated type 5 antimitochondrial autoantibodies are associated with a history of thrombocytopenia and fetal loss.

OBJECTIVE: To report an unusual case of clinical antiphospholipid syndrome seen with recurrent fetal loss, chronic thrombocytopenia, and recurrent idiopathic thrombocytopenic purpura, in which the only laboratory marker was M5-type antimitochondrial autoantibodies (AMA). DESIGN: Case report. SETTING: University general hospital, tertiary level of clinical care. Institutional practice. PATIENT(S): A 65-year-old woman with antiphospholipid syndrome associated with autoimmune polyglandular syndrome of IIIC type. INTERVENTION(S): Clinical history and biochemical and immunologic markers. MAIN OUTCOME MEASURE(S): The presence of M5-type AMA in clinical antiphospholipid syndrome isolated by indirect immunofluorescence. RESULT(S): During the 10-year follow-up, immunologic studies detected a persistent positive M5-type AMA at high titer (1/640), antithyroid antibodies, anti-gastric parietal cells, and anti-intrinsic factor. Antinuclear, anti-DNA, and antiphospholipid (anticardiolipin, anti-beta(2)-glycoprotein I) autoantibody tests were all repeatedly negative. Results of coagulation studies and negative lupus anticoagulant were normal on several occasions. CONCLUSION(S): Our findings suggest the necessity of determining M5-type AMA in the study panel of antiphospholipid syndrome diagnosis, particularly in the absence of other typical autoantibodies.

Abortion, Habitual↗
PubMed2007

Nitric oxide and oxygen metabolism in inflammatory conditions: sepsis and exposition to polluted ambients.

Nitric oxide and cytokines constitute the molecular markers and the intracellular messengers of inflammatory conditions which are derived from the activation of the NF-kappaB pathway and the transcription of proinflammatory genes. Sepsis occurs with an exacerbated inflammatory response that damages tissue mitochondria and impairs bioenergetic processes. One of the current hypotheses for the molecular mechanisms underlying the complex condition of sepsis is that enhanced NO production by mtNOS leads to excessive peroxynitrite production and protein nitration in the mitochondrial matrix, causing mitochondrial dysfunction and organ failure. The mechanism of particulate matter-health effects are believed to involve inflammation and oxidative stress. Components in particles that elicit inflammation are poorly investigated, although recent research points out to the contribution of compositional elements and particle size. Nitric oxide and reactive oxygen species appears to be involved in the inflammatory conditions associated to particulate matter inhalation.

Air Pollutants↗
PubMed2006

Sodium butyrate activates genes of early pancreatic development in embryonic stem cells.

Embryonic stem (ES) cells can differentiate into any tissue, including pancreatic islet cell types. Protocols for the efficient generation of these cells in vitro could have therapeutic applications for type I diabetes. Here we describe a simple method for the differentiation of mouse ES cells into epithelial cells with a gene expression profile consistent with that expected of early pancreatic progenitors (PP). It is based on the addition of sodium butyrate, an agent known to induce chromatin rearrangements. Variations on the length of exposure to butyrate result in the generation of hepatocytes or PP-like cells. qRT-PCR indicates that butyrate induces mesendoderm/definitive endoderm, but not neuroectoderm differentiation. PPlike cells show a strong upregulation of Ipf1/Pdx1, p48, Isl-1 and Nkx6.1, but not Ngn3, NeuroD/ Beta2 or Pax4. PP-like cells also express the epithelial marker E-cadherin. Taken together, our observations suggest that butyrate stimulates early events of pancreatic specification, prior to the onset of endocrine differentiation. These findings are discussed in the context of the development of protocols for the in vitro differentiation of islets.

Animals↗
PubMed2004

Mitochondrial nitric oxide metabolism in rat muscle during endotoxemia.

In this study, heart and diaphragm mitochondria produced 0.69 and 0.77 nmol nitric oxide (NO)/min mg protein, rates that account for 67 and 24% of maximal cellular NO production, respectively. Endotoxemia and septic shock occur with an exacerbated inflammatory response that damages tissue mitochondria. Skeletal muscle seems to be one of the main target organs in septic shock, showing an increased NO production and early oxidative stress. The kinetic properties of mitochondrial nitric oxide synthase (mtNOS) of heart and diaphragm were determined. For diaphragm, the KM values for O2 and L-Arg were 4.6 and 37 microM and for heart were 3.3 and 36 microM. The optimal pH for mtNOS activity was 6.5 for diaphragm and 7.0 for heart. A marked increase in mtNOS activity was observed in endotoxemic rats, 90% in diaphragm and 30% in heart. Diaphragm and heart mitochondrial O2*- and H2O2 production were 2- to 3-fold increased during endotoxemia and Mn-SOD activity showed a 2-fold increase in treated animals, whereas catalase activity was unchanged. One of the current hypotheses for the molecular mechanisms underlying the complex condition of septic shock is that the enhanced NO production by mtNOS leads to excessive peroxynitrite production and protein nitration in the mitochondrial matrix, causing mitochondrial dysfunction and contractile failure.

Animals↗
PubMed2004

Polyphenols and red wine as antioxidants against peroxynitrite and other oxidants.

The antioxidant capacity of polyphenols (+)-catechin, (-)-epicatechin and myricetin, and of different types of red wines (Cabernet Sauvignon, Malbec and blended wine) was evaluated by three assays. (a) NADH oxidation by peroxynitrite (ONOO-): the ONOO- scavenging activity was higher for myricetin (IC50=35 microM) than for (+)-catechin (IC50=275 microM) and (-)-epicatechin (IC50=313 microM). (b) Peroxynitrite initiated chemiluminescence in rat liver homogenate: (-)-epicatechin (IC50=7.0 microM) and (+)-catechin (IC50=13 microM) were more potent than myricetin (IC50=20 microM) in inhibiting the chemiluminescence signal. (c) Lucigenin chemiluminescence in aortic rings: (-)-epicatechin (IC50=15 microM) and (+)-catechin (IC50=18 microM) showed higher antioxidant capacity than myricetin (IC50=32 microM). All the assayed red wines were able to scavenge the oxidants and free radical species that generate the signal in each assay. Cabernet Sauvignon was the red wine with the highest antioxidant capacity in comparison with Malbec and blended wine. It is concluded that the use of sensitive biological systems (as the aortic ring chemiluminescence) provides important information in addition to the results from chemical (NADH oxidation by peroxynitrite) and biochemical (homogenate chemiluminescence) assays and offers advances in the physiological role of polyphenols.

Animals↗
PubMed2003

Oxygen dependence of mitochondrial nitric oxide synthase activity.

The effect of O(2) concentration on mitochondrial nitric oxide synthase (mtNOS) activity and on O(2)(-) production was determined in rat liver, brain, and kidney submitochondrial membranes. The K(mO(2)) for mtNOS were 40, 73, and 37 microM O(2) and the V(max) were 0.51, 0.49, and 0.42 nmol NO/minmg protein for liver, brain, and kidney mitochondria, respectively. The rates of O(2)(-) production, 0.5-12.8 nmol O(2)(-)/minmg protein, depended on O(2) concentration up to 1.1mM O(2). Intramitochondrial NO, O(2)(-), and ONOO(-) steady-state concentrations were calculated for the physiological level of 20 microM O(2); they were 20-39 nM NO, 0.17-0.33 pM O(2)(-), and 0.6-2.2 nM ONOO(-) for the three organs. These levels establish O(2)/NO ratios of 513-1000 that correspond to physiological inhibitions of cytochrome oxidase by intramitochondrial NO of 16-25%. The production of NO by mtNOS appears as a regulatory process that modulates mitochondrial oxygen uptake and cellular energy production.

Animals↗
PubMed2003

Kidney mitochondrial nitric oxide synthase.

Nitric oxide synthase activity was recognized in rat renal cortex mitochondria (mtNOS) with nitric oxide (NO) production rates of 0.14-0.78 nmol/min/mg of protein. Rat pretreatment with enalapril (30 mg/kg/day i.p., up to 15 days) increased NO production in kidney, liver, and heart mitochondria. In kidney, mtNOS activity and mtNOS protein, measured by western blot densitometry, were 5 and 2.3 times increased, respectively. Electron paramagnetic resonance analysis with the probe N-methyl-D-glucamine dithiocarbamate/FeSO(4) detected NO production in mitochondria isolated from enalapril-treated rats, but not in control untreated animals. Polyclonal antibodies anti-iNOS and anti-nNOS detected kidney mtNOS in western blots and inhibited mtNOS biochemical activity. The enzymatic activity of kidney mtNOS generates intramitochondrial NO concentrations that regulate mitochondrial functions: state 3 respiration was decreased by 12-28%, and state 4 hydrogen peroxide production was increased 12-35%.

Animals↗
PubMed2002

The role of mitochondrial nitric oxide synthase in inflammation and septic shock.

Nitric oxide and cytokines constitute the molecular markers and the intercellular messengers of inflammation and septic shock. Septic shock occurs with an exacerbated inflammatory response that damages tissue mitochondria. Skeletal muscle appears as one of the main target organs in septic shock, showing an increased nitric oxide (NO) production, an early oxidative stress, and contractile failure. Mitochondria isolated from rat and human skeletal muscle in septic shock show a markedly increased NO generation and a decreased state 3 respiration, more marked with nicotinamide adenine dinucleotide (NAD)-linked substrates than with succinate, without uncoupling or impairment of phosphorylation. One of the current hypothesis for the molecular mechanisms of septic shock is that the enhanced NO production by mitochondrial nitric oxide synthase (mtNOS) leads to excessive peroxynitrite (ONOO(-)) production and protein nitration in the mitochondrial matrix, to mitochondrial dysfunction and to contractile failure. Surface chemiluminescence is a useful assay to assess inflammation and oxidative stress in in situ liver and skeletal muscle. Liver chemiluminescence in inflammatory processes and phagocyte chemiluminescence have been found spectrally different from spontaneous liver chemiluminescence with increased 440-600 nm emission, likely due to NO and ONOO(-) participation in the reactions leading to the formation of excited species.

Animals↗
PubMed2002

Enzymatic cleaning of inorganic ultrafiltration membranes fouled by whey proteins.

The aim of this work was to study the cleaning of inorganic membranes fouled with whey protein solutions using the enzymatic formulation Alcalase (Novo Nordisk A/S). Hydraulic and chemical methods were considered to characterize the cleanliness of the membranes. Cleaning efficiency was observed to be a function of the operating conditions. The operating conditions tested were the following: recycling versus non-recycling of permeate, pH of the cleaning solution, addition of alkali to regulate the pH, enzymatic agent concentration, and cleaning time. The best conditions to perform the cleaning were related to the best conditions to hydrolyze whey proteins in a discontinuous reactor using the same enzyme preparations. Very high cleaning efficiencies (>90%) were achieved in short operating times (20 min). However, residual matter was observed on the membrane surface.

Equipment Contamination↗
PubMed2002

Inhibition by wine polyphenols of peroxynitrite-initiated chemiluminescence and NADH oxidation.

Peroxynitrite (ONOO(-)) is a powerful oxidant produced by neutrophils, macrophages, and lymphocytes as a signaling and cytotoxic molecule from their primary production of nitric oxide (NO) and superoxide anion (O(2)(-)). In the vascular space, ONOO(-) will likely oxidize lipoproteins and promote atherogenesis. Pure wine flavonoids (catechin, epicatechin, myricetin), hydroxycinnamates (caffeic acid, ferulic acid, chlorogenic acid), and plain Argentine red wines were assayed as ONOO(-) scavengers in two assays: (a) ONOO(-)-initiated chemiluminescence and (b) ONOO(-)-dependent oxidation. The assayed polyphenols as well as the red wines were effective inhibitors of the ONOO(-)-driven oxidation reactions. Fifty percent of the pure substances were observed in the range of 30-300 microM and in the case of red wines with the equivalent of 80-120 microM of flavonoids. The amphipatic nature of wine polyphenols will lead to their accumulation at the lipoprotein surface, according to the Gibbs adsorption equation, where they are likely to prevent ONOO(-)-induced tyrosine nitration and LDL modification.

Flavonoids↗
PubMed2002

Polyphenols and red wine as peroxynitrite scavengers: a chemiluminescent assay.

A novel chemiluminescent assay for evaluating peroxynitrite (ONOO(-))-scavenging capacity was developed. The experimental protocol ensures sensitivity and reproducibility of measurements. The addition of 0-500 microM ONOO(-) to rat liver homogenate generated a luminous signal that was analyzed by chemiluminescence in a LKB Wallac liquid scintillation counter. The obtained optimal conditions were: 1-2 mg/mL of homogenate protein in 120 mM KCl, 30 mM phosphate buffer (pH 7.4), and 220 microM ONOO(-) at 30 degrees C. As polyphenols we used (+)-catechin, (-)-epicatechin, and myricetin. The most efficient of the compounds tested was myricetin with an IC(50) of 20 microM. The effectiveness of this method was verified by evaluating the antioxidant ability of three red wine samples to decrease peroxynitrite-initiated chemiluminescence. The ONOO(-)-scavenging activity of wines measured by this assay was related to the phenolic level of the samples. The quickness and reliability of this assay makes it particularly suitable for a large-scale screening of watery food extracts.

Animals↗
PubMedDate not supplied

Heart mitochondrial nitric oxide synthase. Effects of hypoxia and aging.

The production of NO by heart mitochondria was 0.7-1.1 nmol NO/min.mg protein, an activity similar to the ones observed in mitochondrial membranes from other organs. Heart mtNOS seems to contribute with about 56% of the total cellular NO production. The immunological nature of the mtNOS isoform of cardiac tissue remains unclear; in our laboratory, heart mtNOS reacted with an anti-iNOS anti-body. Heart mtNOS expression and activity are regulated by physiological and pharmacological effectors. The state 4/state 3 transition regulates heart mtNOS activity and NO release in intact respiring mitochondria: NO production rates in state 3 were 40% lower than in state 4. Heart mtNOS expression was selectively regulated by O(2) availability in hypobaric conditions and the activity was 20-60% higher in hypoxic rats than in control animals, depending on age. In contrast, NADH-cytochrome c reductase and cytochrome oxidase activities were not affected by hypoxia. The activity of rat heart mtNOS decreased 20% on aging from 12 to 72 weeks of age. On the pharmacological side, mitochondrial NO production was increased after enalapril treatment (the inhibitor of the angiotensin converting enzyme) with modification of heart mtNOS functional activity in the regulation of mitochondrial O(2) uptake and H(2)O(2) production. Thus, heart mtNOS is a highly regulated mitochondrial enzyme, which in turn, plays a regulatory role through mitochondrial NO steady state levels that modulate O(2) uptake and O(2)(-) and H(2)O(2) production rates. Nitric oxide and H(2)O(2) constitute signals for metabolic control that are involved in the regulation of cellular processes, such as proliferation and apoptosis.

Aging↗