Pulse oximetry and transcutaneous oxygen tension for detection of hypoxemia in critically ill infants and children.

We tested the performance of transcutaneous oxygen monitoring (TcPO2) and pulse oximetry (tcSaO2) in detecting hypoxia in critically ill neonatal and pediatric patients. In 54 patients (178 data sets) with a mean age of 2.4 years (range 1 to 19 years), arterial saturation (SaO2) ranged from 9.5 to 100%, and arterial oxygen tension (PaO2) from 16.4 to 128 mmHg. Linear correlation analysis of pulse oximetry vs measured SaO2 revealed an r value of 0.95 (p less than 0.001) with an equation of y = 21.1 + 0.749x, while PaO2 vs tcPO2 showed a correlation coefficient of r = 0.95 (p less than 0.001) with an equation of y = -1.04 + 0.876x. The mean difference between measured SaO2 and tcSaO2 was -2.74 +/- 7.69% (range +14 to - 29%) and the mean difference between PaO2 and tcPO2 was +7.43 +/- 8.57 mmHg (range -14 to +49 mmHg). Pulse oximetry was reliable at values above 65%, but was inaccurate and overestimated the arterial SaO2 at lower values. TcPO2 tended to underestimate the arterial value with increasing PaO2. Pulse oximetry had the best sensitivity to specificity ratio for hypoxia between 65 and 90% SaO2; for tcPO2 the best results were obtained between 35 and 55 mmHg PaO2.

Indicadores fisiológicos da interação entre deficit hídrico e acidez do solo em cana-de-açúcar

O objetivo deste trabalho foi avaliar os indicadores fisiológicos da interação entre deficit hídrico e acidez do solo em plantas jovens de cana-de-açúcar. As plantas foram submetidas a três tratamentos de disponibilidade hídrica, medidos em percentagem de capacidade de campo (CC) - sem estresse (70% CC), estresse moderado (55% CC) e estresse severo (40% CC); e três tratamentos de acidez no solo, medidos em termos de saturação por bases (V) - baixa acidez (V = 55%), média acidez (V = 33%) e alta acidez (V = 23%). O experimento foi realizado em casa de vegetação a 29,7±4,3ºC e 75±10% UR. O delineamento experimental utilizado foi o de blocos ao acaso, em esquema fatorial 3x3, com quatro repetições. Após 60 dias, foram determinados os teores de solutos compatíveis - trealose, glicina betaína e prolina - na folha diagnóstico e o crescimento inicial da parte aérea. Os solutos compatíveis trealose, glicina betaína e prolina são indicadores do efeito da interação dos estresses hídrico e ácido no solo. O acúmulo dos solutos compatíveis nos tecidos foliares das plantas não é capaz de impedir a redução na produção de matéria seca da cana-de-açúcar, resultante do agravamento nas condições de disponibilidade hídrica e de acidez no solo.

Metabolic alterations in the cortex of a mouse model with glutathione deficit - relevance to schizophrenia

Background: Glutathione (GSH) is a major redox regulator and antioxidant and is decreased in cerebrospinal fluid and prefrontal cortex of schizophrenia patients [Do et al. (2000) Eur J Neurosci 12:3721]. The genes of the key GSH-synthesizing enzyme, glutamate- cysteine ligase catalytic (GCLC) and modifier (GCLM) subunits, are associated with schizophrenia, suggesting that the deficit in GSH synthesis is of genetic origin [Gysin et al. (2007) PNAS 104:16621]. GCLM knock-out (KO) mice, which display an 80% decrease in brain GSH levels, have abnormal brain morphology and function [Do et al. (2009) Curr Opin Neurobiol 19:220]. Developmental redox deregulation by impaired GSH synthesis and environmental risk factors generating oxidative stress may have a central role in schizophrenia. Here, we used GCLM KO mice to investigate the impact of a genetically dysregulated redox system on the neurochemical profile of the developing brain. Methods: The neurochemical profile of the anterior and posterior cortical areas of male and female GCLM KO and wild-type mice was determined by in vivo 1H NMR spectroscopy on postnatal days 10, 20, 30, 60 and 90, under 1 to 1.5% isoflurane anaesthesia. Localised 1H NMR spectroscopy was performed on a 14.1 T, 26 cm VNMRS spectrometer (Varian, Magnex) using a home-built 8 mm diameter quadrature surface coil (used both for RF excitation and signal reception). Spectra were acquired using SPECIAL with TE of 2.8 ms and TR of 4 s from VOIs placed in anterior or posterior regions of the cortex [Mlynárik et al. (2006) MRM 56:965]. LCModel analysis allowed in vivo quantification of a neurochemical profile composed of 18 metabolites. Results: GCLM KO mice displayed nearly undetectable GSH levels as compared to WT mice, demonstrating their drastic redox deregulation. Depletion of GSH triggered alteration of metabolites related to its synthesis, namely increase of glycine and glutamate levels during development (P20 and P30). Concentrations of glutamine and aspartate that are produced from glutamate were also increased in GCLM KO animals relative to WT. In addition, GCLM KO mice also showed higher levels of N-acetylaspartate that originates from the acetylation of aspartate. These metabolites are particularly implicated in neurotransmission processes and in mitochondrial oxidative metabolism. Their increase may indicate impaired mitochondrial metabolism with concomitant accumulation of lactate in the adult mice (P60 and P90). In addition, the GSH depletion triggers reduction of GABA concentration in anterior cortex of the P60 mice, which is in accordance with known impairment of GABAergic interneurons in that area. Changes were generally more pronounced in males than in females at P60, which is consistent with earlier disease onset in male patients. Discussion: In conclusion, the observed metabolic alterations in the cortex of a mouse model of redox deregulation suggest impaired mitochondrial metabolism and altered neurotransmission. The results also highlight the age between P20 and P30 as a sensitive period during the development for these alterations.

Respostas biométricas e fisiológicas ao deficit hídrico em cana-de-açúcar em diferentes fases fenológicas

O objetivo deste trabalho foi avaliar as respostas biométricas e fisiológicas de cana-de-açúcar (Saccharum spp.) ao deficit hídrico (DH), em diferentes fases fenológicas. Os genótipos IACSP 94-2094 e IACSP 96-2042 foram submetidos a DH nas fases de crescimento inicial, crescimento máximo e de acúmulo de sacarose no colmo. O delineamento experimental foi inteiramente casualizado. A suscetibilidade ao DH foi determinada pela redução de matéria seca do colmo e do conteúdo de sólidos solúveis no caldo. O deficit hídrico causou redução nas trocas gasosas, nas três fases fenológicas, em ambos os genótipos. Foi observada menor altura das plantas, menor acúmulo de matéria seca do colmo e de sólidos solúveis, e redução no número e comprimento de entrenós, apenas na fase de crescimento inicial, no clone IACSP 96-2042. Na fase de crescimento inicial, observou-se tolerância ao DH no genótipo IACSP 94-2094, com evidências de aclimatação fisiológica, e redução na produção de fitomassa e de sólidos solúveis no genótipo IACSP 96-2042, como resposta à menor condutância estomática e à menor eficiência aparente de carboxilação da fotossíntese. Independentemente da fase fenológica, o genótipo IACSP 94-2094 foi tolerante ao deficit hídrico, pois manteve a produção de fitomassa mesmo com redução das trocas gasosas.

Acute post-exercise oxygen uptake, hormone and plasma metabolite response in obese men.

This study aimed to compare oxygen uptake (  V˙O2), hormone and plasma metabolite responses during the 30 min after submaximal incremental exercise (Incr) performed at the same relative/absolute exercise intensity and duration in lean (L) and obese (O) men. Eight L and 8 O men (BMI: 22.9±0.4; 37.2±1.8 kg · m(-2)) completed Incr and were then seated for 30 min.   V˙O2 was monitored during the first 10 min and from the 25-30(th) minutes of recovery. Blood samples were drawn for the determination of hormone (catecholamines, insulin) and plasma metabolite (NEFA, glycerol) concentrations. Excess post-exercise oxygen consumption (EPOC) magnitude during the first 10 min was similar in O and in L (3.5±0.4; 3.4±0.3 liters, respectively, p=0.86). When normalized to percent change (  V˙O2END=100%), %   V˙O2END during recovery was significantly higher from 90-120 s in O than in L (p≤0.04). There were no significant differences in catecholamines (p≥0.24), whereas insulin was significantly higher in O than in L during recovery (p=0.01). The time-course of glycerol was similar from 10-30 min of recovery (-42% for L; -41% for O, p=0.85), whereas significantly different patterns of NEFA were found from 10-30 min of recovery between groups (-18% for L; +8% for O, p=0.03). Despite similar EPOC, a difference in   V˙O2 modulation between groups was observed, likely due to faster initial rates of   V˙O2 decline in L than in O. The different patterns of NEFA between groups may suggest a lower NEFA reesterification during recovery in O, which was not involved in the rapid EPOC component.

Cultured 3T3L1 adipocytes dispose of excess medium glucose as lactate under abundant oxygen availability

White adipose tissue (WAT) produces lactate in significant amount from circulating glucose, especially in obesity;Under normoxia, 3T3L1 cells secrete large quantities of lactate to the medium, again at the expense of glucose and proportionally to its levels. Most of the glucose was converted to lactate with only part of it being used to synthesize fat. Cultured adipocytes were largely anaerobic, but this was not a Warburg-like process. It is speculated that the massive production of lactate, is a process of defense of the adipocyte, used to dispose of excess glucose. This way, the adipocyte exports glucose carbon (and reduces the problem of excess substrate availability) to the liver, but the process may be also a mechanism of short-term control of hyperglycemia. The in vivo data obtained from adipose tissue of male rats agree with this interpretation.

Deficit hídrico e secamento parcial do sistema radicular em pomar de lima ácida

O objetivo deste trabalho foi avaliar o efeito do deficit hídrico associado ao secamento parcial do sistema radicular ("partial rootzone drying", PRD) na produção e eficiência de uso de água, em pomar de lima ácida 'Tahiti', na Região do Semiárido baiano. Utilizou-se o delineamento de blocos ao acaso, com seis tratamentos e seis repetições. Os tratamentos com PRD foram realizados pela alternância periódica (7, 14 ou 21 dias) dos lados em que o microaspersor localizava-se em relação às plantas. Esses tratamentos foram conduzidos com lâmina d'água equivalente a 50% da evapotranspiração da cultura (ETc) e comparados ao tratamento com deficit hídrico de 50% da ETc com microaspersor fixo em um dos lados das plantas, e ao tratamento 100% da ETc, com aspersores de ambos os lados das plantas. Avaliou-se também o PRD (21 dias) com diminuição da irrigação em 25% da ETc. O PRD com 50% da ETc não difere do tratamento com esse mesmo deficit e sem alternância de lados da irrigação, em termos de produtividade, eficiência do uso da água, e diâmetro e peso dos frutos, independentemente do período de alternância dos lados de irrigação. O PRD com diminuição da irrigação em 25% da ETc não causa perdas em relação à condição sem deficit e sem localização da irrigação.

Septal lesions impair the acquisition of a cued place navigation task: attentional or memory deficit?

These experiments were designed to analyze how medial septal lesions reducing the cholinergic innervation in the hippocampus might affect place learning. Rats with quisqualic lesions of the medial septal area (MS) were trained in a water maze and on a homing table where the escape position was located at a spatially fixed position and further indicated by a salient cue suspended above it. The lesioned rats were significantly impaired in reaching the cued escape platform during training. In addition rats, did not show any discrimination of the training sector during a probe trial in which no platform or cue was present. This impairment remained significant during further training in the absence of the cue. When the cued escape platform was located at an unpredictable spatial location, the MS-lesioned rats showed no deficit and spent more time under the cue than control rats during the probe trial. On the homing board, with a salient object in close proximity to the escape hole, the MS rats showed no deficit in escape latencies, although a significant reduction in spatial memory was observed. However, this was overcome by additional training in the absence of the cue. Under these conditions, rats with septal lesions were prone to develop a pure guidance strategy, whereas normal rats combined a guidance strategy with a memory of the escape position relative to more distant landmarks. The presence of a salient cue appeared to decrease attention to environmental landmarks, thus reducing spatial memory. These data confirm the general hypothesis that MS lesions reduce the capacity to rely on a representation of the relation between several landmarks with different salience.

On optimal dividend strategies with deficit or incomplete information

Rapport de synthèse Cette thèse consiste en trois essais sur les stratégies optimales de dividendes. Chaque essai correspond à un chapitre. Les deux premiers essais ont été écrits en collaboration avec les Professeurs Hans Ulrich Gerber et Elias S. W. Shiu et ils ont été publiés; voir Gerber et al. (2006b) ainsi que Gerber et al. (2008). Le troisième essai a été écrit en collaboration avec le Professeur Hans Ulrich Gerber. Le problème des stratégies optimales de dividendes remonte à de Finetti (1957). Il se pose comme suit: considérant le surplus d'une société, déterminer la stratégie optimale de distribution des dividendes. Le critère utilisé consiste à maximiser la somme des dividendes escomptés versés aux actionnaires jusqu'à la ruine2 de la société. Depuis de Finetti (1957), le problème a pris plusieurs formes et a été résolu pour différents modèles. Dans le modèle classique de théorie de la ruine, le problème a été résolu par Gerber (1969) et plus récemment, en utilisant une autre approche, par Azcue and Muler (2005) ou Schmidli (2008). Dans le modèle classique, il y a un flux continu et constant d'entrées d'argent. Quant aux sorties d'argent, elles sont aléatoires. Elles suivent un processus à sauts, à savoir un processus de Poisson composé. Un exemple qui correspond bien à un tel modèle est la valeur du surplus d'une compagnie d'assurance pour lequel les entrées et les sorties sont respectivement les primes et les sinistres. Le premier graphique de la Figure 1 en illustre un exemple. Dans cette thèse, seules les stratégies de barrière sont considérées, c'est-à-dire quand le surplus dépasse le niveau b de la barrière, l'excédent est distribué aux actionnaires comme dividendes. Le deuxième graphique de la Figure 1 montre le même exemple du surplus quand une barrière de niveau b est introduite, et le troisième graphique de cette figure montre, quand à lui, les dividendes cumulés. Chapitre l: "Maximizing dividends without bankruptcy" Dans ce premier essai, les barrières optimales sont calculées pour différentes distributions du montant des sinistres selon deux critères: I) La barrière optimale est calculée en utilisant le critère usuel qui consiste à maximiser l'espérance des dividendes escomptés jusqu'à la ruine. II) La barrière optimale est calculée en utilisant le second critère qui consiste, quant à lui, à maximiser l'espérance de la différence entre les dividendes escomptés jusqu'à la ruine et le déficit au moment de la ruine. Cet essai est inspiré par Dickson and Waters (2004), dont l'idée est de faire supporter aux actionnaires le déficit au moment de la ruine. Ceci est d'autant plus vrai dans le cas d'une compagnie d'assurance dont la ruine doit être évitée. Dans l'exemple de la Figure 1, le déficit au moment de la ruine est noté R. Des exemples numériques nous permettent de comparer le niveau des barrières optimales dans les situations I et II. Cette idée, d'ajouter une pénalité au moment de la ruine, a été généralisée dans Gerber et al. (2006a). Chapitre 2: "Methods for estimating the optimal dividend barrier and the probability of ruin" Dans ce second essai, du fait qu'en pratique on n'a jamais toute l'information nécessaire sur la distribution du montant des sinistres, on suppose que seuls les premiers moments de cette fonction sont connus. Cet essai développe et examine des méthodes qui permettent d'approximer, dans cette situation, le niveau de la barrière optimale, selon le critère usuel (cas I ci-dessus). Les approximations "de Vylder" et "diffusion" sont expliquées et examinées: Certaines de ces approximations utilisent deux, trois ou quatre des premiers moments. Des exemples numériques nous permettent de comparer les approximations du niveau de la barrière optimale, non seulement avec les valeurs exactes mais également entre elles. Chapitre 3: "Optimal dividends with incomplete information" Dans ce troisième et dernier essai, on s'intéresse à nouveau aux méthodes d'approximation du niveau de la barrière optimale quand seuls les premiers moments de la distribution du montant des sauts sont connus. Cette fois, on considère le modèle dual. Comme pour le modèle classique, dans un sens il y a un flux continu et dans l'autre un processus à sauts. A l'inverse du modèle classique, les gains suivent un processus de Poisson composé et les pertes sont constantes et continues; voir la Figure 2. Un tel modèle conviendrait pour une caisse de pension ou une société qui se spécialise dans les découvertes ou inventions. Ainsi, tant les approximations "de Vylder" et "diffusion" que les nouvelles approximations "gamma" et "gamma process" sont expliquées et analysées. Ces nouvelles approximations semblent donner de meilleurs résultats dans certains cas.

Transpiração e crescimento foliar de plantas de mandioca em resposta ao deficit hídrico no solo

O objetivo deste trabalho foi determinar a transpiração e o crescimento foliar de duas cultivares de mandioca, em resposta ao conteúdo de água disponível no solo representado pela fração de água transpirável no solo (FATS). Foram realizados dois experimentos, em vasos de 8 L, com as cultivares Fécula Branca e Fepagro RS 13. O plantio foi feito em 11/9/2009 e 8/9/2010, em delineamento experimental inteiramente casualizado. A água disponível, a transpiração e o crescimento foliar foram medidos diariamente, em cada experimento,durante o período de imposição da deficiência hídrica. A FATS crítica, em que a transpiração começa a serreduzida, foi de 0,45 para 'Fécula Branca' e 0,50 para 'Fepagro RS 13'. A redução do crescimento foliar começou quando a FATS atingiu 0,51 para 'Fécula Branca' e 0,49 para 'Fepagro RS 13'. A FATS crítica para transpiração e crescimento foliar difere em condições de atmosfera com baixa e com alta demanda evaporativa do ar, conforme a cultivar de mandioca utilizada.