Intravoxel incoherent motion perfusion imaging in acute stroke: initial clinical experience.

INTRODUCTION: Intravoxel incoherent motion (IVIM) imaging is an MRI perfusion technique that uses a diffusion-weighted sequence with multiple b values and a bi-compartmental signal model to measure the so-called pseudo-diffusion of blood caused by its passage through the microvascular network. The goal of the current study was to assess the feasibility of IVIM perfusion fraction imaging in patients with acute stroke. METHODS: Images were collected in 17 patients with acute stroke. Exclusion criteria were onset of symptoms to imaging >5 days, hemorrhagic transformation, infratentorial lesions, small lesions <0.5 cm in minimal diameter and hemodynamic instability. IVIM imaging was performed at 3 T, using a standard spin-echo Stejskal-Tanner pulsed gradients diffusion-weighted sequence, using 16 b values from 0 to 900 s/mm(2). Image quality was assessed by two radiologists, and quantitative analysis was performed in regions of interest placed in the stroke area, defined by thresholding the apparent diffusion coefficient maps, as well as in the contralateral region. RESULTS: IVIM perfusion fraction maps showed an area of decreased perfusion fraction f in the region of decreased apparent diffusion coefficient. Quantitative analysis showed a statistically significant decrease in both IVIM perfusion fraction f (0.026 ± 0.019 vs. 0.056 ± 0.025, p = 2.2 · 10(-6)) and diffusion coefficient D compared with the contralateral side (3.9 ± 0.79 · 10(-4) vs. 7.5 ± 0.86 · 10(-4) mm(2)/s, p = 1.3 · 10(-20)). CONCLUSION: IVIM perfusion fraction imaging is feasible in acute stroke. IVIM perfusion fraction is significantly reduced in the visible infarct. Further studies should evaluate the potential for IVIM to predict clinical outcome and treatment response.

Motion compensation strategies in magnetic resonance imaging.

Image quality in magnetic resonance imaging (MRI) is considerably affected by motion. Therefore, motion is one of the most common sources of artifacts in contemporary cardiovascular MRI. Such artifacts in turn may easily lead to misinterpretations in the images and a subsequent loss in diagnostic quality. Hence, there is considerable research interest in strategies that help to overcome these limitations at minimal cost in time, spatial resolution, temporal resolution, and signal-to-noise ratio. This review summarizes and discusses the three principal sources of motion: the beating heart, the breathing lungs, and bulk patient movement. This is followed by a comprehensive overview of commonly used compensation strategies for these different types of motion. Finally, a summary and an outlook are provided.

Systemic effects of epidural Methylprednisolone injection on glucose tolerance in diabetic patients.

ABSTRACT: BACKGROUND: Several studies have shown that in diabetic patients, the glycemic profile was disturbed after intra-articular injection of corticosteroids. Little is known about the impact of epidural injection in such patients. The goal of this study was double, at first comparing the glycaemic profile in diabetic patients after a unique injection of 80 mg of acetate methylprednisolone either intra-articular or epidural and secondly to compare the amount of systemic diffusion of the drug after both procedures. METHODS: Seventeen patients were included. Glycemic changes were compared in 9 diabetic patients following intra-articular (4 patients) and epidural injections (5 patients). Epidural injections were performed using the sacral route under fluoroscopic control in patients with lumbar spinal stenosis. Diabetes control had to stable for more than 10 days and the renal function to be preserved. Blood glucose was monitored using a validated continuous measuring device (GMS, Medtronic) the day before and for two days following the injection. Results were expressed in the form of daily glycemic profiles and as by mean, peak and minimal values +/ SD. The urinary excretion of methylprednisolone after the 2 routes of injection was analyzed in 8 patients (4 in each group). Urine samples were cropped one hour before the injections, then 4 times during the first day and 3 times a week for 2 weeks. The measurements included the free and conjugated fraction RESULTS: The glycaemic profile remains unchanged with no significant changes in the group of the 5 diabetic patients receiving epidural injections. On the other end, the average peak and mean values were enhanced up to 3 mmol/l above baseline two days after the infiltration in the groups of the 4 diabetic patients infiltrated intra-articular. The mean urinary excretion of the steroid was about ten times higher in the intra-articular versus epidural group: 7000 ng/ml versus 700 ng/ml. Looking at each individual there were marked differences especially after intra-articular injections. CONCLUSION: This is the first study to show that a single epidural steroid injection of 80 mg depot methylprednisolone had no effect on the glycemic control in diabetic patients. The absence of glycemic control changes correlated well with the very low urinary excretion of the drug after epidural injection. Trial registration NCT01420497.

Genetic variability and differentiation between populations of Rhodnius prolixus and R. pallescens, vectors of Chagas' Disease in Colombia

Enzyme polymorphism in Rhodnius prolixus and R. pallescens (Hemiptera, Reduviidae), principal vectors of Chagas' disease in Colombia, was analyzed using starch gel electrophoresis. Three geographic locations were sampled in order to determine gene flow between populations and to characterize intra- and interspecific differences. Of 25 enzymes assayed 10 were successfully resolved and then used to score the genetic variation. The enzymes PEPD, GPI, PGM and ICD were useful to differentiate these species and PGD, PGM and MDH distinguished between sylvatic and domiciliary populations of R. prolixus. Both polymorphism and heterozygosity indicated greater genetic variability in sylvatic habitats (H = 0.021) compared to domiciliary habitats (H = 0.006) in both species. Gene flow between sylvatic and domiciliary populations in R. prolixus was found to be minimal. This fact and the genetic distance between them suggest a process of genetic isolation in the domiciliary population.

Gestión de recursos en nodos multi-core de memoria compartida

La gestión de recursos en los procesadores multi-core ha ganado importancia con la evolución de las aplicaciones y arquitecturas. Pero esta gestión es muy compleja. Por ejemplo, una misma aplicación paralela ejecutada múltiples veces con los mismos datos de entrada, en un único nodo multi-core, puede tener tiempos de ejecución muy variables. Hay múltiples factores hardware y software que afectan al rendimiento. La forma en que los recursos hardware (cómputo y memoria) se asignan a los procesos o threads, posiblemente de varias aplicaciones que compiten entre sí, es fundamental para determinar este rendimiento. La diferencia entre hacer la asignación de recursos sin conocer la verdadera necesidad de la aplicación, frente a asignación con una meta específica es cada vez mayor. La mejor manera de realizar esta asignación és automáticamente, con una mínima intervención del programador. Es importante destacar, que la forma en que la aplicación se ejecuta en una arquitectura no necesariamente es la más adecuada, y esta situación puede mejorarse a través de la gestión adecuada de los recursos disponibles. Una apropiada gestión de recursos puede ofrecer ventajas tanto al desarrollador de las aplicaciones, como al entorno informático donde ésta se ejecuta, permitiendo un mayor número de aplicaciones en ejecución con la misma cantidad de recursos. Así mismo, esta gestión de recursos no requeriría introducir cambios a la aplicación, o a su estrategia operativa. A fin de proponer políticas para la gestión de los recursos, se analizó el comportamiento de aplicaciones intensivas de cómputo e intensivas de memoria. Este análisis se llevó a cabo a través del estudio de los parámetros de ubicación entre los cores, la necesidad de usar la memoria compartida, el tamaño de la carga de entrada, la distribución de los datos dentro del procesador y la granularidad de trabajo. Nuestro objetivo es identificar cómo estos parámetros influyen en la eficiencia de la ejecución, identificar cuellos de botella y proponer posibles mejoras. Otra propuesta es adaptar las estrategias ya utilizadas por el Scheduler con el fin de obtener mejores resultados.

Thermogenic effect of amrinone in healthy men.

OBJECTIVES: The thermogenic effect of amrinone is unknown and its utilization in patients with severe cardiac failure could potentially increase oxygen requirements and therefore aggravate oxygen debt. Consequently, the present study was undertaken to assess the thermogenic response to amrinone at three different plasma concentrations under controlled conditions and to analyze amrinone's effects on various biochemical variables. DESIGN: A prospective, unblinded, controlled study. The initial control period was followed by three sequential, experimental treatments. SUBJECTS: Ten young, healthy, male volunteers with normal body weight. INTERVENTIONS: Three experimental periods. Amrinone was administered intravenously in progressive doses: a) 0.5 mg/kg followed by 5 micrograms/kg/min; b) 0.5 mg/kg followed by 10 micrograms/kg/min; and c) 1.0 mg/kg followed by 10 micrograms/kg/min. MEASUREMENTS AND MAIN RESULTS: Oxygen consumption (VO2) and CO2 production were continuously measured by means of a computerized indirect calorimeter. At the highest dose, amrinone produced a slight and significant (p < .01) increase in VO2 and in resting metabolic rate (+4.5% and +3.7%, respectively), while no change in CO2 production or in respiratory quotient occurred throughout the study. At the medium and high doses, amrinone increased plasma free fatty acid concentrations by 38% and 53%, respectively (p < .05). No variation in plasma glucose, lactate, insulin, norepinephrine, or epinephrine concentrations was observed during the study. CONCLUSIONS: Amrinone administered intravenously at therapeutic doses has minimal thermogenic and metabolic effects in humans without cardiac failure.

Penicillin tolerance among Beta-hemolytic streptococci and production of the group carbohydrates, hemolysins, hyaluronidases and deoxyribonucleases

Penicillin tolerance among 67 strains of beta-hemolytic streptococci was examined by determining the ratio of the minimal bactericidal concentration to the minimal inhibitory concentration as 32 or greater. Tolerance was demonstrated in 15 group A strains and in 11,7, and 4 of groups B, C and G, respectively. Thereafter the effects of a subminimal inhibitory concentration (1/2MIC) of penicillin on the bacterial products of four tolerant and four nontolerant strains (two of each Lancefield group) were analyzed and compared. The antibiotic caused a marked increase in the expression of the group carbo-hydrates for strains of group B. Penicillin was found to reduce the cell-bound hemolysin activities of the four tolerant strains and to increase the activity of the other (free) form of nontolerant groups A, C and G hemolysins. Penicillin caused an increase in the extracellular hyaluronidase activities of one group A and groups B, C and G streptococci. With added antibiotic the production of deoxyribonuclease by tolerant groups A, C and G was greatly enhanced and that of the group B streptococcus was arrested.

Alteration of brain glycogen turnover in the conscious rat after 5h of prolonged wakefulness.

Although glycogen (Glyc) is the main carbohydrate storage component, the role of Glyc in the brain during prolonged wakefulness is not clear. The aim of this study was to determine brain Glyc concentration ([]) and turnover time (tau) in euglycemic conscious and undisturbed rats, compared to rats maintained awake for 5h. To measure the metabolism of [1-(13)C]-labeled Glc into Glyc, 23 rats received a [1-(13)C]-labeled Glc solution as drink (10% weight per volume in tap water) ad libitum as their sole source of exogenous carbon for a "labeling period" of either 5h (n=13), 24h (n=5) or 48 h (n=5). Six of the rats labeled for 5h were continuously maintained awake by acoustic, tactile and olfactory stimuli during the labeling period, which resulted in slightly elevated corticosterone levels. Brain [Glyc] measured biochemically after focused microwave fixation in the rats maintained awake (3.9+/-0.2 micromol/g, n=6) was not significantly different from that of the control group (4.0+/-0.1 micromol/g, n=7; t-test, P>0.5). To account for potential variations in plasma Glc isotopic enrichment (IE), Glyc IE was normalized by N-acetyl-aspartate (NAA) IE. A simple mathematical model was developed to derive brain Glyc turnover time as 5.3h with a fit error of 3.2h and NAA turnover time as 15.6h with a fit error of 6.5h, in the control rats. A faster tau(Glyc) (2.9h with a fit error of 1.2h) was estimated in the rats maintained awake for 5h. In conclusion, 5h of prolonged wakefulness mainly activates glycogen metabolism, but has minimal effect on brain [Glyc].

Normal glucagon signaling and β-cell function after near-total α-cell ablation in adult mice.

OBJECTIVEEvaluate whether healthy or diabetic adult mice can tolerate an extreme loss of pancreatic α-cells and how this sudden massive depletion affects β-cell function and blood glucose homeostasis.RESEARCH DESIGN AND METHODSWe generated a new transgenic model allowing near-total α-cell removal specifically in adult mice. Massive α-cell ablation was triggered in normally grown and healthy adult animals upon diphtheria toxin (DT) administration. The metabolic status of these mice was assessed in 1) physiologic conditions, 2) a situation requiring glucagon action, and 3) after β-cell loss.RESULTSAdult transgenic mice enduring extreme (98%) α-cell removal remained healthy and did not display major defects in insulin counter-regulatory response. We observed that 2% of the normal α-cell mass produced enough glucagon to ensure near-normal glucagonemia. β-Cell function and blood glucose homeostasis remained unaltered after α-cell loss, indicating that direct local intraislet signaling between α- and β-cells is dispensable. Escaping α-cells increased their glucagon content during subsequent months, but there was no significant α-cell regeneration. Near-total α-cell ablation did not prevent hyperglycemia in mice having also undergone massive β-cell loss, indicating that a minimal amount of α-cells can still guarantee normal glucagon signaling in diabetic conditions.CONCLUSIONSAn extremely low amount of α-cells is sufficient to prevent a major counter-regulatory deregulation, both under physiologic and diabetic conditions. We previously reported that α-cells reprogram to insulin production after extreme β-cell loss and now conjecture that the low α-cell requirement could be exploited in future diabetic therapies aimed at regenerating β-cells by reprogramming adult α-cells.

Infection of Oxydoras kneri Bleecker, 1862 (Pisces, Doradidae) by the acanthocephalan Paracavisoma impudica (Diesing, 1851) Kritcher, 1957

Infection of Oxydoras kneri by the acanthocephalan Paracavisoma impudica is described. The parasites do not penetrate deeply into the host gut wall and do not reach the muscularis layers. Host reaction is minimal, consisting of limited fibrosis around the proboscides. Haemorrhages and lymphocyte infiltration are not observed, and phagocytic cells are only present occasionally. Oxydoras kneri is a newly reported host for Paracavisoma impudica.

Possibilitats i límits de la democràcia deliberativa

La meva investigació s’articula entorn a l’obra del filòsof alemany Jürgen Habermas. L’aportació filosòfica més important de Habermas ha estat l’elaboració d’una racionalitat discursiva. Aquesta nova manera d’entendre la raó com a discurs ha tingut importants repercussions en l’àmbit de la filosofia i de les ciències socials en general. La primera part de la meva investigació analitza l’obra de Habermas, posant èmfasi en el procés de configuració d’aquesta racionalitat discursiva. Aquest primer període culmina amb la presentació de la tesina “Introducció al pensament i l’obra de Jürgen Habermas”. Com a resultat d’aquesta investigació, la meva recerca es centrarà, primer, en les nocions habermasianes de publicitat (Öffentlichkeit) i d’opinió pública (öffentliche Meinung) i, finalment, en l’anomenada democràcia deliberativa. Per tant, la recerca consta de dos part estretament relacionades: (1) un anàlisi del procés de configuració d’una raó discursiva en l’obra de Habermas; (2) una valoració crítica dels límits i les possibilitats de la democràcia deliberativa en les societats contemporànies. Aquesta darrera fase d’investigació –en la qual treballo actualment– s’endinsa en el debat dels “teòrics deliberatius”. Entre d’altres, aprofundeix en les repercussions ètiques i polítiques d’una relació problemàtica entre esfera pública i esfera privada. Desfer aquesta problemàtica passa per repensar l’exigència d’una racionalitat imparcial que, alhora, sigui Desfer aquesta problemàtica capaç de garantir la participació democràtica de la ciutadania en el context actual, on el pluralisme de valors ha esdevingut un dels fenòmens vertebradors de les societats contemporànies.

Using a NPWE model observer to assess suitable image quality for a digital mammography quality assurance programme.

A method of objectively determining imaging performance for a mammography quality assurance programme for digital systems was developed. The method is based on the assessment of the visibility of a spherical microcalcification of 0.2 mm using a quasi-ideal observer model. It requires the assessment of the spatial resolution (modulation transfer function) and the noise power spectra of the systems. The contrast is measured using a 0.2-mm thick Al sheet and Polymethylmethacrylate (PMMA) blocks. The minimal image quality was defined as that giving a target contrast-to-noise ratio (CNR) of 5.4. Several evaluations of this objective method for evaluating image quality in mammography quality assurance programmes have been considered on computed radiography (CR) and digital radiography (DR) mammography systems. The measurement gives a threshold CNR necessary to reach the minimum standard image quality required with regards to the visibility of a 0.2-mm microcalcification. This method may replace the CDMAM image evaluation and simplify the threshold contrast visibility test used in mammography quality.

On problems of calculating energy expenditure and substrate utilization from respiratory exchange data.

Indirect calorimetry based on respiratory exchange measurement has been successfully used from the beginning of the century to obtain an estimate of heat production (energy expenditure) in human subjects and animals. The errors inherent to this classical technique can stem from various sources: 1) model of calculation and assumptions, 2) calorimetric factors used, 3) technical factors and 4) human factors. The physiological and biochemical factors influencing the interpretation of calorimetric data include a change in the size of the bicarbonate and urea pools and the accumulation or loss (via breath, urine or sweat) of intermediary metabolites (gluconeogenesis, ketogenesis). More recently, respiratory gas exchange data have been used to estimate substrate utilization rates in various physiological and metabolic situations (fasting, post-prandial state, etc.). It should be recalled that indirect calorimetry provides an index of overall substrate disappearance rates. This is incorrectly assumed to be equivalent to substrate "oxidation" rates. Unfortunately, there is no adequate golden standard to validate whole body substrate "oxidation" rates, and this contrasts to the "validation" of heat production by indirect calorimetry, through use of direct calorimetry under strict thermal equilibrium conditions. Tracer techniques using stable (or radioactive) isotopes, represent an independent way of assessing substrate utilization rates. When carbohydrate metabolism is measured with both techniques, indirect calorimetry generally provides consistent glucose "oxidation" rates as compared to isotopic tracers, but only when certain metabolic processes (such as gluconeogenesis and lipogenesis) are minimal or / and when the respiratory quotients are not at the extreme of the physiological range. However, it is believed that the tracer techniques underestimate true glucose "oxidation" rates due to the failure to account for glycogenolysis in the tissue storing glucose, since this escapes the systemic circulation. A major advantage of isotopic techniques is that they are able to estimate (given certain assumptions) various metabolic processes (such as gluconeogenesis) in a noninvasive way. Furthermore when, in addition to the 3 macronutrients, a fourth substrate is administered (such as ethanol), isotopic quantification of substrate "oxidation" allows one to eliminate the inherent assumptions made by indirect calorimetry. In conclusion, isotopic tracers techniques and indirect calorimetry should be considered as complementary techniques, in particular since the tracer techniques require the measurement of carbon dioxide production obtained by indirect calorimetry. However, it should be kept in mind that the assessment of substrate oxidation by indirect calorimetry may involve large errors in particular over a short period of time. By indirect calorimetry, energy expenditure (heat production) is calculated with substantially less error than substrate oxidation rates.

Influence of the primary cleft palate closure on the future need for orthognathic surgery in unilateral cleft lip and palate patients.

The aim of the study was to determine the influence of the dissection of the palate during primary surgery and the type of orthognathic surgery needed in cases of unilateral total cleft. The review concerns 58 children born with a complete unilateral cleft lip and palate and treated between 1994 and 2008 at the appropriate age for orthognathic surgery. This is a retrospective mixed-longitudinal study. Patients with syndromes or associated anomalies were excluded. All children were treated by the same orthodontist and by the same surgical team. Children are divided into 2 groups: the first group includes children who had conventional primary cleft palate repair during their first year of life, with extensive mucoperiosteal undermining. The second group includes children operated on according to the Malek surgical protocol. The soft palate is closed at the age of 3 months, and the hard palate at 6 months with minimal mucoperiosteal undermining. Lateral cephalograms at ages 9 and 16 years and surgical records were compared. The need for orthognathic surgery was more frequent in the first than in the second group (60% vs 47.8%). Concerning the type of orthognathic surgery performed, 2- or 3-piece Le Fort I or bimaxillary osteotomies were also less required in the first group. Palate surgery following the Malek procedure results in an improved and simplified craniofacial outcome. With a minimal undermining of palatal mucosa, we managed to reduce the amount of patients who required an orthognathic procedure. When this procedure was indicated, the surgical intervention was also greatly simplified.