High harmonic emission from a superposition of multiple unrelated frequency fields.

We report observations and analysis of high harmonic generation driven by a superposition of fields at 1290 nm and 780 nm. These fields are not commensurate in frequency and the superposition leads to an increase in the yield of the mid-plateau harmonics of more than two orders of magnitude compared to using the 1290 nm field alone. Significant extension of the cut-off photon energy is seen even by adding only a small amount of the 780 nm field. These observations are explained by calculations performed in the strong field approximation. Most importantly we find that enhancement is found to arise as a consequence of both increased ionization in the sum-field and modification of the electron trajectories leading to an earlier return time. The enhanced yield even when using modest intensity fields of 5 x 10(13) Wcm(-2) is extended to the 80 eV range and is a promising route to provide a greater photon number for applications in XUV imaging and time-resolved experiments at a high repetition rate.

Preactivation of neutrophils and systemic oxidative stress in dogs with hyperleptinemia.

High occurrence of obesity currently constitutes the main nutritional disease of the canine species. There is evidence that leptin increases during obesity in dogs. Hyperleptinemia is associated with increased neutrophil oxidative metabolism in obese humans and contributes to oxidative stress. However, in obese dogs, the probable relationship between this condition and the activation of the oxidative metabolism of neutrophils has yet to be established. Thus, we investigated the hypothesis that neutrophil activation and systemic oxidative stress occur in dogs with hyperleptinemia. A control group of 24 healthy dogs with a body condition score (BCS) of 4-5, an overweight group of 25 dogs with a BCS of 6-7, and 27 obese dogs with a BCS of 8-9, were composed. Two subgroups were formed composed of dogs with and without hyperleptinemia, grouped according to the 95% confidence interval obtained for plasma leptin values of the control group. Changes in obesity markers (body condition score, adiponectin and plasma leptin) and plasma oxidative stress (lipid peroxidation, total antioxidant and oxidant capacities and oxidative stress index) were measured in all the dogs selected. Neutrophil oxidative metabolism was evaluated in flow cytometry by superoxide production with the probe hydroethidine and by hydrogen peroxide production with the probe 2',7'-dichlorofluorescein diacetate, with or without phorbol myristate acetate (PMA) stimulation. Apoptosis and neutrophil viability were quantified in a capillary flow cytometer using Annexin VPE, with or without camptothecin apoptosis inducing effect. Obese dogs presented higher systemic oxidative stress, hyperleptinemia and preactivated neutrophils with accelerated apoptosis. Dogs with hyperleptinemia and obese dogs presented higher neutrophil superoxide production under PMA stimulation and the presence of systemic oxidative stress compared with control. To our knowledge, this is probably the first evidence that preactivation of the oxidative metabolism of circulating neutrophils occurs in dogs with hyperleptinemia, a condition that can induce systemic oxidative stress in the canine species.

Hemólise interfere na mensuração dos biomarcadores plasmáticos de estresse oxidativo em cães / Hemolysis interferes in the measurement of plasma biomakers of oxidative stress in dogs

Considerando que, entre todas as fontes de erro analítico, a hemólise é a mais importante na rotina laboratorial, o presente estudo teve como objetivo investigar o efeito da hemólise in vitro sobre os principais biomarcadores plasmáticos de estresse oxidativo mensurados (BPEO) de cães. Para tal, amostras de sangue total de 19 cães clinicamente saudáveis foram hemolisadas em diferentes graus por ação mecânica. Amostras controle contendo baixa concentração de hemoglobina (Hb) no plasma foram comparadas com quatro graus de hemólise (<0,36; 0,36-0,60; 0,61-1,0; 1,1-4g/L Hb). Imediatamente após a hemólise, foram mensuradas as concentrações plasmáticas de ácido úrico (AU), albumina, bilirrubina, gamaglutamiltransferase (GGT), capacidade antioxidante total (TAC) e concentração de oxidante total (TOC). Os erros relativos causados pelos diferentes graus de hemólises foram calculados e confrontados com o erro total aceitável (ETA) e com o limite de erro permitido (LEP) empregados nos programas de controle de qualidade de exames laboratoriais. Foi observado que mesmo pequeno grau de hemólise gera algum erro analítico não aceitável (ETA e/ou LEP) nos BPEO mensurados, exceto na bilirrubina. Foi possível concluir que a hemólise é um fator limitante para avaliação do estresse oxidativo sistêmico mensurado no plasma, podendo causar erros que potencialmente comprometem o diagnóstico clínico.(AU)

Among all the various sources of analytical error, hemolysis is the most important in the laboratory routine. The present study aimed to investigate the effect of hemolysis "in vitro" on the main plasma biomarkers of oxidative stress (BPEO) dogs. For this purpose, whole blood samples from 19 healthy dogs were hemolyzed in different degrees by mechanical action. Control samples containing low concentration of hemoglobin (Hb) levels in plasma were compared with four degrees of hemolysis (<0.36, from 0.36 to 0.60, 0.61 to 1.0, 1.1 to 4g/L Hb). Immediately after causing hemolysis, plasma concentrations of uric acid (UA), albumin, bilirubin, gamma glutamyl transferase (GGT), total antioxidant capacity (TAC), and total oxidant concentration (TOC) were measured. The relative errors caused by several levels of hemolysis were calculated and compared with the total acceptable error (TAE) and allowed error limit (LEP) by employees in quality control programs for laboratory tests. Even small levels of hemolysis generate unacceptable analytical error (TAE and / or LEP) in BPEO measured, except for bilirubin. Hemolysis is a limiting factor for the assessment of systemic oxidative stress measured in plasma and may cause errors that potentially compromise clinical diagnosis.(AU)