Lubrication of Stone-Wales transformations in graphene by hydrogen and hydroxyl functional groups.

First-principles calculations were performed to address the role of functional groups (hydrogen atoms and hydroxyl molecules) in lubricating the fundamental transformation by which a Stone-Wales defect is formed in graphene. Energy barriers in the presence of a single H atom, as well as in the case of two, four, and six H atoms chemisorbed in graphene in several distinct site configurations are found to be smaller than in pristine graphene. Our study examines in detail the electronic mechanism behind the stabilization, by the functional groups, of the transition state of the defect-forming reaction relative to the reactants (functionalized graphene and Stone-Wales defect), due to partial strain relaxation and electronic saturation of the transition-state dangling bonds. We frame these findings in terms of the reactivity, to the functional groups, of the reactants and transition states. Our calculations point to a very favorable kinetic pathway with a strongly reduced activation barrier, in which two H atoms bind to next-nearest-neighbor C atoms, and saturate the two transition-state dangling bonds, resulting in a strong barrier reduction of 5.6 eV (from 9.3 eV without functional groups to 3.7 eV). In the case of two chemisorbed OH molecules, we find a further reduction of the Stone-Wales transformation barrier for one configuration considered, when compared to the similar one with two H atoms, providing additional confirmation of the reactivity-based mechanism.

Non-hexagonal-ring defects and structures induced by healing and strain in graphene and functionalized graphene.

We perform ab initio calculations for the strain-induced formation of non-hexagonal-ring defects in graphene, graphane (hydrogen-functionalized graphene) and graphenol (hydroxyl-functionalized graphene). We find that the simplest of such topological defects, the Stone-Wales defect, acts as a seed for strain-induced dissociation and multiplication of topological defects. Through the application of inhomogeneous deformations to graphene, graphane and graphenol with varying initial concentrations of pentagonal and heptagonal rings and small-sized voids, we obtain several novel stable structures that possess, at the same time, large concentrations of non-hexagonal rings (from fourfold to elevenfold) and small formation energies.

Reproductive adverse effects of fipronil in Wistar rats.

The purpose of the present study was to investigate possible reproductive adverse effects of fipronil (Frontline TopSpot) in female Wistar rats. The pesticide was topically applied to rats (single dose) at different concentrations (70, 140 and 280 mg/kg) and hormonal analysis, estrous cycle, and pregnancy and outcome data were determined. Treatment with fipronil altered cyclicity of female rats lengthening the estrous cycle (days) after a single topic administration of 70 mg/kg (9.7+/-1.18) or 280 mg/kg (14.5+/-1.45) when compared to control (4.8+/-0.17). In the mating study fipronil reduced the pregnancy index (67%) in the highest dose group (280 mg/kg). Plasma progesterone and estradiol levels, obtained in different periods after treatment with fipronil (70 mg/kg), were significantly different 96 h after treatment, when compared to controls. In summary, the results of the present study indicate that fipronil may alter the normal functioning of the endocrine system and cause adverse reproductive effects in female rats.

Effect of vitamin E on red blood cell preservation.

The effect of exogenous vitamin E (2.1 mg/100 ml) was determined on the preservation of red blood cell integrity (PCV and RBC counts) during long-term storage. Cells from healthy human blood donors, normal rats and rats raised on a vitamin E-deficient diet were stored in CE medium at 4 degrees C for 40-60 days. The addition of vitamin E to the CE medium protected normal rat RBC and those from vitamin E-deficient animals to even a larger extent. Neither the PVC nor RBC count in human blood changed during storage for up to 60 days and no effect of exogenous vitamin E was demonstrable.

Correlation of discocyte frequency and ATP concentration in preserved blood. A morphological indicator of red blood cell viability.

Red blood cells (RBC) are viable if kept in an adequate preservative solution, although gradual changes in morphology and metabolism may occur. There is a gradual decrease in adenosine-5'-triphosphate (ATP) concentration, pH, glucose consumption, and enzyme activity during preservation. The normal discocyte shapes are initially replaced by echinocytes and stomatocytes and, at final stages, by spherocytes, the last step before splenic sequestration. Post-transfusional survival has been correlated with the ATP concentration. RBC preserved in ADSOL, a solution containing adenine, dextrose, sodium chloride, and mannitol, are viable for transfusion for up to 6 weeks. Erythrocytes from 10 blood units taken from healthy adult donors were preserved for 12 weeks in ADSOL at 4 degrees C. We now report a significant correlation (r2 = 0.98) between the percentage of discocytes (89 to 7%) and ATP (100 to 10%) concentration in ADSOL-preserved RBC. The results suggest that the percent of discocyte shapes used as an indicator of ATP concentration may be a useful indicator for quality control of RBC viability in centers which have limited assay facilities.

The X-X-/E+E+ genotype of the XbaI/EcoRI polymorphisms of the apolipoprotein B gene as a marker of coronary artery disease in a Brazilian sample.

Studies that consider polymorphisms within the apolipoprotein B (apo B) gene as risk factors for coronary artery disease (CAD) have reported conflicting results. The aim of the present study was to search for associations between two DNA RFLPs (XbaI and EcoRI) of the apo B gene and CAD diagnosed by angiography. In the present study we compared 116 Brazilian patients (92 men) with CAD (CAD+) to 78 control patients (26 men) without ischemia or arterial damage (CAD-). The allele frequencies at the XbaI (X) and EcoRI (E) sites did not differ between groups. The genotype distributions of CAD+ and CAD- patients were different (chi (1) = 6.27, P = 0.012) when assigned to two classes (X-X-/E+E+ and the remaining XbaI/EcoRI genotypes). Multivariate logistic regression analysis showed that individuals with the X-X-/E+E+ genotype presented a 6.1 higher chance of developing CAD than individuals with the other XbaI/EcoRI genotypes, independently of the other risk factors considered (sex, tobacco consumption, total cholesterol, hypertension, and triglycerides). We conclude that the X-X-/E+E genotype may be in linkage disequilibrium with an unknown variation in the apo B gene or with a variation in another gene that affects the risk of CAD.

Induction of ovulation with epimestrol and luteinizing hormone-releasing hormone (LH-RH).

Luteinizing hormone-releasing hormone (LH-RH) was used to induce LH surge and ovulation in 20 patients in whom follicular maturation was provoked by epimestrol, used in a dose of 5 mg/day from the fifth to 14th day of the cycle. Patients with elevated prolactin levels and galactorrhea were not included in the study. Complete follicular maturation, as inferred by estradiol levels above 200 pg/ml, were observed in 13 of 20 patients following epimestrol treatment. LH-RH induced ovulation in 90% of these patients following a three-day course of treatment. Normal corpus luteum function with progesterone levels above 8 ng/ml was observed in most cases. Five pregnancies occurred in the first two cycles of treatment. In patients with low estradiol levels, following epimestrol priming, the administration of LH-RH did not result in ovulation.

Enzymes and membrane proteins of ADSOL-preserved red blood cells.

CONTEXT: The preservative solution ADSOL (adenine, dextrose, sorbitol, sodium chloride and mannitol) maintains red cell viability for blood trans-fusion for 6 weeks. It would be useful to know about its preservation qualities over longer periods. OBJECTIVE: To determine some red cell biochemical parameters for peri-ods of up to 14 weeks in order to determine whether the red cell metabo-lism integrity would justify further studies aiming at increasing red cell preservation and viability. DESIGN: Biochemical evaluation designed to study red cell preservation. SETTING: São Paulo University erythrocyte metabolism referral center. SAMPLE: Six normal blood donors from the University Hospital of the Universidade Federal do Paraná, Curitiba, Brazil. MAIN MEASUREMENTS: Weekly assay of erythrocyte adenosine-5;-triphosphate (ATP), 2, 3-diphosphoglycerate (2,3DPG), hexokinase (HX), phosphofructokinase (PFK), pyruvate kinase (PK), glucose-6-phosphate dehydrogenase (G-6-PD), 6-phosphogluconic dehydrogenase (6-PGD), glyceraldehyde-3-phosphate dehydrogenase (GAPD), glutathione reduc-tase (GR), glutathione peroxidase (GSHPx), plasma sodium and potas-sium, blood pH, and membrane proteins of red cells preserved in ADSOL were studied during storage for 14 weeks storage. RESULTS: During ADSOL preservation, erythrocyte ATP concentration decreased 60% after 5 weeks, and 90% after 10 weeks; the pH fell from 6.8 to 6. 4 by the 14th week. 2,3-DPG concentration was stable during the first week, but fell 90% after 3 weeks and was exhausted after 5 weeks. By the end of the 5th week, an activity decrease of 16-30% for Hx, GAPD, GR, G-6-PD and 6-PGD, 35% for PFK and GSHPx, and 45% for PK were observed. Thereafter, a uniform 10% decay was observed for all enzymes up to the 14th week. The red blood cell membrane pro-teins did not show significant alterations in polyacrylamide gel electro-phoresis (SDS-PAGE) during the 14 weeks. CONCLUSION: Although the blood viability was shown to be poor from the 6th week up to the 14th week of storage due to ATP and 2,3-DPG depletion, the other biochemical parameters remained in fairly good condition for longer storage. As there is a gradual and uniform decay in activity throughout these 14 weeks, it seems that ADSOL-preserved red cells may be used as red cell enzyme standards and membrane proteins as well.

[Nitrotyrosyl]cytochrome c. Studies of the effect of iron binding, protein denaturants and oxidation-reduction potentials.

Static measurements of the reaction of ligand binding were done by conventional spectrophotometry. The ligand-binding reactions with nitrated cytochrome c were performed with imidazole, iminazole, CO and NO. The stoicheiometry was found to be 1:1, and the stability constants for the complexes formed between the nitrated cytochrome c and the ligands are: 2.58 X 10(4) M-1 (imidazole); 1.01 X 10(2) M-1 (iminazole); 3.6 X 10(4) M-1 (CO); 2.74 X 10(4) M-1 (NO). It was found that the electrometric potentials at pH 7.0 and 25degreesC of [aminotyrosyl]cytochrome c are E'o form II = 0.115 V and E'o form I = 0.260 V, where forms I and II are two species of protein co-existing in the protein solution. The isoelectric point for the oxidized form of [nitrotyrosyl]cytochrome c was 10.05, at 4degreesC.

Studies on the ATPase of Bacillus cereus.

The membrane ATPase (EC 3.6.1.3) of Bacillus cereus was solubilized by a 'shock-wash' process and purified. The non-specific phosphatase contaminant was separated by glycerol density gradient centrifugation. The optimum temperature was 39.5 degrees C and the pH optimum at 7.5. On SDS-polyacrylamide gel electrophoresis two classes of subunits were observed in equal proportions with molecular weights of 70 K and 83 K. The effect of various compounds on the enzymatic activity was studied. The enzyme was insensitive to NaN3, oligomycin and to divalent cations, but was inhibited by citrate and oxalate.

Effect of amiodarone (AMD) on the antioxidant enzymes, lipid peroxidation and mitochondrial metabolism.

The effects of amiodarone (AMD) on lipid peroxidation of rat liver mitochondria, the formation of superoxide anions at the respiratory chain level, and the cytosolic and mitochondrial enzymatic protective mechanisms of oxidative stress were studied. An attempt of classify AMD according to its toxic ability to interfere with the integrated function of electron transport enzymes was also investigated. The results confirm the effects of AMD on complex I and permit the placing of this drug in class A of the classification of Knobeloch, together with rotenone, amytal and chaotropic agents. AMD has no effect on the activity of the enzymes superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase, nor on glucose 6-phosphate dehydrogenase. AMD did not promote an increase in the formation of anion superoxide at the respiratory chain level. Pre-incubation with AMD (16.6 microM) inhibited about 70 per cent of lipid peroxidation. The results suggest a protective effect of AMD against lipid peroxidation in mitochondrial membranes by iron-dependent systems.

Effect of sodium oleate on oxidative metabolism of isolated mitochondria and submitochondrial particles.

Using conventional polarographic and spectrophotometric methods, the effect of sodium oleate on isolated mitochondria dn submitochondrial particles was analysed. A loose coupling was developed in isolated mitochondria in the presence of about 10 nmoles oleate per mg protein. Oleate stimulates and activity of bovine heart mitochondrial Mg-ATPase, and it was found to be dependent on substrate concentration. Investigation of the membrane potential showed that the delta psi is abolished at high concentration of oleate. The deterioration of the morphological appearance of mitochondria, occurring on addition of oleate, is also described.

Sugar derivatives and liver mitochondria. V - Effect of 6-O-benzoyl-3-deoxy-3-fluoro-1,2-O-isopropylidene-alpha-D-glucofuranose.

Using conventional polarographic and mannometric techniques for assaying oxidative phosphorylation and oxygen uptake in isolated rat liver mitochondria, it was observed a decrease in ADP:O ratio and RC coefficient as a function of treatment with 6-O-benzoyl-3-deoxy-3-fluoro-1,2-O-isopropylidene-alpha-D-glucofuranose, using succinate and alpha-ketoglutarate as substrates. The enzymes activities of different segments of the respiratory chain, indicated an inhibition of NADH-oxidase activity as a result of treatment with 6-O-benzoyl-3-deoxy-fluoro-1,2-O-isopropylidene-alpha-D-glucofuranose. The oxidation of NADH-linked substrates by rat liver mitochondria was depressed by the compound used, while the succinate oxidation was increased.

Studies on rat liver mitochondria. II. Formation of lipid peroxides in mitochondria preserved at 0-4 degrees C.

Levels of lipid peroxides were monitored in freshly isolated rat liver mitochondria, aged mitochondria, and preserved mitochondria by reaction with TBA (2-thiobarbituric acid) and spectrophotometric absorption at 233 nm. In aged mitochondria, the levels of lipid peroxides increased gradually during 120 hr, while in preserved mitochondria they increased rapidly up to 24-48 hr. Under such conditions, the respiratory control coefficients and the levels of total Pi were about 40% those of fresh mitochondria, and the decrease of the levels of lipid peroxides followed the decrease of the respiratory control coefficients and levels of total Pi. These results suggest that stimulation of the formation of lipid peroxides occurs when the vital activity of mitochondria is preserved.

Studies on rat liver mitochondria. 6. The effect of contaminating particles in mitochondria stored at 0-4 degrees C.

Rat liver mitochondria were stored at 0-4 degrees C for several days using an appropriate medium and energy source. The elimination of the majority of microsomes and lysosomes, that normally contaminate isolated mitochondria, had a positive effect in preservation of respiratory control, P:O ratio, and monoamine oxidase activity during long term storage.

Studies on rat liver mitochondria in vitamin E-deficiency and during storage at 0-4 degrees C.

Isolated rat liver mitochondria, freed from microsomes and lysosomes contaminants, were maintained at 0-4 degrees C for several days using an appropriate medium and energy source. It was observed that the phospholipase A2 activity of mitochondria deficient in vitamin E is higher than in normal mitochondria, and that the presence of vitamin E in the preservation medium diminishes the phospholipase A2 activity in deficient mitochondria. In vitamin E deficient mitochondria up to 45% of phospholipids was digested by the endogenous phospholipase with little loss in the energy linked function or without considerable activation of the latent enzymes monoamine oxidase and ATPase. These results are consistent with the occurrence of phospholipids in the mitochondrial membrane which would render it more accessible to the action of phospholipase A2.

Studies on rat liver mitochondria: 4. Enzyme activities in mitochondria preserved at 0-4 degrees C.

Rat liver mitochondria, stored with the energy-linked functions preserved or in aging conditions, were used to assay the activity of various enzymes during five days. The preservation of energy-linked functions was monitored by the respiratory control coefficient. ATPase, cytochrome oxidase and NADH dehydrogenase showed increased activity when the energy-linked functions were preserved. In aging conditions, cytochrome oxidase, NADH dehydrogenase and ATPase showed decreased activity. The ATPase activity increased only when mitochondria were stored in the presence of inhibitors of the electron transport chain. The activity of NADH oxidase did not change, and succinate oxidase and succinate dehydrogenase showed a small decrease in their activity. The enzymes of the matrix, alpha-ketoglutarate dehydrogenase, malate dehydrogenase and aspartate aminotransferase showed little decrease in activity under either of the conditions of storage. The total protein content decreased slightly under both conditions of storage. These results show that the activity of the enzymes analysed was maintained at reasonable levels, when the energy-linked functions of isolated mitochondria were preserved.

Correlation of discocyte frequency and ATP concentration in preserved blood: a morphological indicator of red cell viability

Red blood cells (RBC) are viable if kept in an adequate preservative solution, although gradual changes in morphology and metabolism may occur. There is a gradual decrease in adenosine-5'-triphosphate (ATP) cocentration, pH, glucose consumption, and enzyme activity during preservation. The normal discocyte shapes are initially replaced by echimocytes and stomatocytes and, at final stages, by spherocytes, the last before eplenic sequestration. Post-transfusional survival has been correlated with the ATP concentration. RBC preserved in ADSOL, a solution containing adenine, dextrose, sodium chloride, and mannitol, are viable for transfusion for up to 6 weeks. Erythrocytes from 10 blood units taken from healthy adult donors were preserved for 12 weeks in ADSOL at 4 graus Celsius. We now report a significant correlation (r2 = 0.98) between the percentage of discocytes (89 to 7 percent) and ATP (100 to 10 percent) concentration in ADSOL-preserved RBC. The results suggest that the percent of discocyte shapes used as an indicator OF ATP concentration may be a useful indicator for quality control of RBC viability in centers which have limited assay facilites.

The X-X-/E+E+ genotype of the XbaI/EcoRI polymorphisms of the apolipoprotein B gene as a marker of coronary artery disease in a Brazilian sample

Studies that consider polymorphisms within the apolipoprotein B (apo B) gene as risk factors for coronary artery disease (CAD) have reported conflicting results. The aim of the present study was to search for associations between two DNA RFLPs (XbaI and EcoRI) of the apo B gene and CAD diagnosed by angiography. In the present study we compared 116 Brazilian patients (92 men) with CAD (CAD+) to 78 control patients (26 men) without ischemia or arterial damage (CAD-). The allele frequencies at the XbaI (X) and EcoRI (E) sites did not differ between groups. The genotype distributions of CAD+ and CAD- patients were different (chi²(1) = 6.27, P = 0.012) when assigned to two classes (X-X-/E+E+ and the remaining XbaI/EcoRI genotypes). Multivariate logistic regression analysis showed that individuals with the X-X-/E+E+ genotype presented a 6.1 higher chance of developing CAD than individuals with the other XbaI/EcoRI genotypes, independently of the other risk factors considered (sex, tobacco consumption, total cholesterol, hypertension, and triglycerides). We conclude that the X-X-/E+E genotype may be in linkage disequilibrium with an unknown variation in the apo B gene or with a variation in another gene that affects the risk of CAD

Padronizaçao para a dosagem de hemoglobina extracelular pelo metodo da cianometemoglobina / Cianomethemoglobin method padronization for supernatant hemoglobin determination

A concentraçao de hemoglobina (Hb) extracelular e um indice adequado para a avaliaçao da hemolise intravascular em estados hemoliticos diversos,bem como para a monitoraçao da integridade celular durante a preservaçao de eritrocitos in vitro. O metodo da cianometemoglobina e reconhecido como excelente quanto a exatidao e reprodutibilidade, e esta perfeitamente padronizado para determinar as concentraçoes de hemoglobina presentes no sague total. Entretanto, a dosagem de microquantidades de hemoglobina no meio extracelular, por este metodo, depende de uma padronizaçao no que diz respeito a diluiçoes a serem empregadas e a faixa de sensibilidade. Neste trabalho, demonstrou-se a linearidade do metodo na faixa de sensibilidade de 1 a 60 mg/dl de hemoglobina, nas condiçoes de ensaio, e indicou-se diluiçoes adequadas para a medida de hemoglobina extracelular em funçao (i) do grau dehemolise observado visualmente, (ii) da obtençaode observancias na faixa de sensibilidade do metodo. Na aplicaçao do metodo, determinou-se a hemoglobina extracelular em amostras de eritrocitos preservados a 4C em ADSOL, uma soluçao aditiva empregada rotineiramente em Banco de Sangue. De acordo com o esperado, a hemolise aumentou gradativamente durante 12 semanas de preservaçao e os valores obtidos variavam entre 0,008g/dl e 1,625g/dl de hemoglobina extracelular,neste periodo.