Estudi del procés de neurodegeneració

Les anomenades malalties neurodegeneratives tenen una simptomatologia i unes manifestacions clíniques molt diferents entre elles. No obstant, totes elles convergeixen en el mateix procés final, la neurodegeneració, que es manifestarà en diferents localitzacions o tipus cel·lulars del sistema nerviós. Nosaltres, plantegem la hipòtesi de que els processos moleculars i cel·lulars subjacents a la neurodegeneració són comuns per totes elles. Després de dur a terme un procés de selecció, es decideix treballar amb la malaltia de Parkinson, la d’Alzheimer, l’Esclerosi lateral amiotròfica i l’esclerosi múltiple. Hem pogut determinar que hi ha set processos moleculars o cel·lulars que estan associats al procés de neurodegeneració i que són comuns a totes elles. Havent-les estudiat per separat s’observa que el procés de neurodegeneració consisteix en una fallada en cadena de diferents sistemes moleculars i cel·lulars que tenen com a punt d’origen l’estrès oxidatiu. A aquest estrès s’hi pot arribar de diferents maneres. Una d’elles és l’exposició excessiva a certs metalls, que provoca la pèrdua dels sistemes antioxidants cel·lulars. Degut a això, els mitocondris reben un impacte oxidatiu massa gran i comencen a fallar. El fet que aquest orgànul actuï com a tampó del calci intracel·lular en provoca la seva desregulació, alterant d’aquesta manera el senyal nerviós. En resposta a l’estrès oxidatiu i tèrmic que genera la disfunció mitocondrial, s’activen les Proteïnes de Xoc Tèrmic (HSP) que actuant de citocines i presentadores d’antígens, inicien la resposta immunològica contra les cèl·lules danyades. Paral·lelament, s’observa un increment de la permeabilitat de la barrera hematoencefàlica degut a la pèrdua de les adhesions cel·lulars estretes per l’alta presència d’espècies reactives. Com a conseqüència de l’afebliment o el trencament de la barrera hematoencefàlica, es pot produir una entrada al SNC de diferents substàncies neurotòxiques i de cèl·lules del sistema immunitàri que, en condicions normals tenen l’accés restringit. Juntament amb aquestes cèl·lules immunològiques, també s’activen les cèl·lules del sistema immunitari innat residents al cervell, la micròglia, i totes elles secreten citocines proinflamatòries que contribueixen al procés de neurodegeneració. Nosaltres presentem els mecanismes pels quals aquesta inflamació, lluny d’atenuar-se, es cronifica per l’acció de certs bucles de retroalimentació positiva. Les diferents peculiaritats de cada malaltia contribueixen en aquest procés de diferents maneres, com és el cas dels pèptids β-amilides en la malaltia d’Alzheimer, l’α-sinucleina en el Parkinson, la superòxid dismutasa (SOD) en l’esclerosi lateral amiotròfica, o l’infiltració de leucòcits al cervell degut a la resposta autoimmune de l’esclerosi múltiple.Deixant de banda aquestes diferències, si el procés és comú entre totes elles, l’estudi a fons d’aquest procés hauria de poder permetre identificar dianes tarapèutiques que siguin comunes per les quatre malalties.

Azole resistance by loss of function of the sterol Δ⁵,⁶-desaturase gene (ERG3) in Candida albicans does not necessarily decrease virulence.

The inactivation of ERG3, a gene encoding sterol Δ⁵,⁶-desaturase (essential for ergosterol biosynthesis), is a known mechanism of in vitro resistance to azole antifungal drugs in the human pathogen Candida albicans. ERG3 inactivation typically results in loss of filamentation and attenuated virulence in animal models of disseminated candidiasis. In this work, we identified a C. albicans clinical isolate (VSY2) with high-level resistance to azole drugs in vitro and an absence of ergosterol but normal filamentation. Sequencing of ERG3 in VSY2 revealed a double base deletion leading to a premature stop codon and thus a nonfunctional enzyme. The reversion of the double base deletion in the mutant allele (erg3-1) restored ergosterol biosynthesis and full fluconazole susceptibility in VSY2, confirming that ERG3 inactivation was the mechanism of azole resistance. Additionally, the replacement of both ERG3 alleles by erg3-1 in the wild-type strain SC5314 led to the absence of ergosterol and to fluconazole resistance without affecting filamentation. In a mouse model of disseminated candidiasis, the clinical ERG3 mutant VSY2 produced kidney fungal burdens and mouse survival comparable to those obtained with the wild-type control. Interestingly, while VSY2 was resistant to fluconazole both in vitro and in vivo, the ERG3-derived mutant of SC5314 was resistant only in vitro and was less virulent than the wild type. This suggests that VSY2 compensated for the in vivo fitness defect of ERG3 inactivation by a still unknown mechanism(s). Taken together, our results provide evidence that contrary to previous reports inactivation of ERG3 does not necessarily affect filamentation and virulence.

Lack of MRI neurohypophyseal bright signal in a child with congenital nephrogenic diabetes insipidus

Congenital nephrogenic diabetes insipidus (CNDI) is a rare disease characterized by the inability of the kidney to respond to arginine vasopressin (AVP). The absence of the neurohypophyseal 'bright signal' on T1 sequence magnetic resonance imaging (MRI) is considered as an argument in favour of the diagnosis of central diabetes insipidus (CDI). This observation is challenged as we hereby present a case of a child diagnosed with CNDI and who did not present MRI pituitary bright signal. A 6-month-old male presented with failure to thrive, polyuria and polydypsia. Family history revealed that the mother, 35 years of age, had been presenting polydypsia and polyuria, and she was investigated at the age of 6 years with no concluding diagnosis. The patient's physical exam showed a weight of 5215 g (−3 DS) and clinical signs of dehydration. The patient's plasma sodium level was 155 mmol/L, osmolality 305 mOsm/kg and urine osmolality 150 mOsm/kg. Brain MRI showed in T1 sequences the absence of the posterior pituitary bright signal suggesting the diagnosis of CDI (Figure 1). The child was treated with synthetic AVP analogue 1-desamino-8-d-arginine vasopressin (DDAVP) without improvement, which led to the consideration of CNDI. The diagnosis was confirmed by an elevated serum level of AVP of 214 pmol/L (reference value ≤4.34 pmol/L) and by genetic analysis demonstrating and T106C mutation in the V2R (X-linked CNDI). The child was treated with thiazide diuretic and increased fluids with restricted sodium intake. This resulted in catch-up growth and improved neurological development. A follow-up MRI was performed 6 months after the start of therapy with the same technique. At that time, the child's weight had improved to 9310 g (−1.5 DS) corresponding to a gain of 22 g per day, and he did not present any clinical signs of dehydration and had a normal plasma level of sodium (140 mmol/L). MRI showed that the bright signal was still absent.

Decreased glucose-induced thermogenesis after weight loss in obese subjects: a predisposing factor for relapse of obesity?

Glucose-induced thermogenesis (GIT) after a 100-g oral glucose load was measured by continuous indirect calorimetry in 32 nondiabetic and diabetic obese subjects and compared to 17 young and 13 middle aged control subjects. The obese subjects were divided into three groups: A (n = 12) normal glucose tolerance, B (n = 13) impaired glucose tolerance, and C (n = 7) diabetics, and were studied before and after a body weight loss ranging from 9.6 to 33.5 kg consecutive to a 4 to 6 months hypocaloric diet. GIT, measured over 3 h and expressed as percentage of the energy content of the load, was significantly reduced in obese groups A and C (6.2 +/- 0.6, and 3.8 +/- 0.7%, respectively) when compared to their age-matched control groups: 8.6 +/- 0.7 (young) and 5.8 +/- 0.3% (middle aged). Obese group B had a GIT of 6.1 +/- 0.6% which was lower than that of the young control group but not different from the middle-aged control group. After weight loss, GIT in the obese was further reduced in groups A and B than before weight loss: ie, 3.4 +/- 0.6 (p less than 0.001), 3.7 +/- 0.5 (p less than 0.01) respectively, whereas in group C, weight loss induced no further diminution in GIT (3.8 +/- 0.6%). These results support the concept of a thermogenic defect after glucose ingestion in obese individuals which is not the consequence of their excess body weight but may be one of the factors favoring the relapse of obesity after weight loss.

Dinor-oxo-phytodienoic acid: a new hexadecanoid signal in the jasmonate family.

Jasmonic acid and its precursors are potent regulatory molecules in plants. We devised a method for the simultaneous extraction of these compounds from plant leaves to quantitate changes in the levels of jasmonate family members during health and on wounding. During our study, we identified a novel 16-carbon cyclopentenoic acid in leaf extracts from Arabidopsis and potato. The new compound, a member of the jasmonate family of signals, was named dinor-oxo-phytodienoic acid. Dinor-oxo-phytodienoic acid was not detected in the Arabidopsis mutant fad5, which is incapable of synthesizing 7Z,10Z, 13Z-hexadecatrienoic acid (16:3), suggesting that the metabolite is derived directly from plastid 16:3 rather than by beta-oxidation of the 18-carbon 12-oxo-phytodienoic acid. Simultaneous quantitation of jasmonate family members in healthy leaves of Arabidopsis and potato suggest that different plant species have different relative levels of jasmonic acid, oxo-phytodienoic acid, and dinor-oxo-phytodienoic acid. We term these profiles "oxylipin signatures." Dinor-oxo-phytodienoic acid levels increased dramatically in Arabidopsis and potato leaves on wounding, suggesting roles in wound signaling. Treatment of Arabidopsis with micromolar levels of dinor-oxo-phytodienoic acid increased the ability of leaf extracts to transform linoleic acid into the alpha-ketol 13-hydroxy-12-oxo-9(Z) octadecenoic acid indicating that the compound can regulate part of its own biosynthetic pathway. Tightly regulated changes in the relative levels of biologically active jasmonates may permit sensitive control over metabolic, developmental, and defensive processes in plants.

IL-12-mediated STAT4 signaling and TCR signal strength cooperate in the induction of CD40L in human and mouse CD8(+) T cells.

CD40L is one of the key molecules bridging the activation of specific T cells and the maturation of professional and nonprofessional antigen-presenting cells including B cells. CD4(+) T cells have been regarded as the major T-cell subset that expresses CD40L upon cognate activation; however, we demonstrate here that a putative CD8(+) helper T-cell subset expressing CD40L is induced in human and murine CD8(+) T cells in vitro and in mice immunized with antigen-pulsed dendritic cells. IL-12 and STAT4-mediated signaling was the major instructive cytokine signal boosting the ability of CD8(+) T cells to express CD40L both in vitro and in vivo. Additionally, TCR signaling strength modulated CD40L expression in CD8(+) T cells after primary differentiation in vitro as well as in vivo. The induction of CD40L in CD8(+) T cells regulated by IL-12 and TCR signaling may enable CD8(+) T cells to respond autonomously of CD4(+) T cells. Thus, we propose that under proinflammatory conditions, a self-sustaining positive feedback loop could facilitate the efficient priming of T cells stimulated by high affinity peptide displaying APCs.

A Fast Gradient Approximation for Nonlinear Blind Signal Processing

When dealing with nonlinear blind processing algorithms (deconvolution or post-nonlinear source separation), complex mathematical estimations must be done giving as a result very slow algorithms. This is the case, for example, in speech processing, spike signals deconvolution or microarray data analysis. In this paper, we propose a simple method to reduce computational time for the inversion of Wiener systems or the separation of post-nonlinear mixtures, by using a linear approximation in a minimum mutual information algorithm. Simulation results demonstrate that linear spline interpolation is fast and accurate, obtaining very good results (similar to those obtained without approximation) while computational time is dramatically decreased. On the other hand, cubic spline interpolation also obtains similar good results, but due to its intrinsic complexity, the global algorithm is much more slow and hence not useful for our purpose.

EEG signal analysis via a cleaning procedure based on multivariate empirical mode decomposition

Artifacts are present in most of the electroencephalography (EEG) recordings, making it difficult to interpret or analyze the data. In this paper a cleaning procedure based on a multivariate extension of empirical mode decomposition is used to improve the quality of the data. This is achieved by applying the cleaning method to raw EEG data. Then, a synchrony measure is applied on the raw and the clean data in order to compare the improvement of the classification rate. Two classifiers are used, linear discriminant analysis and neural networks. For both cases, the classification rate is improved about 20%.

Malarial hemozoin is a Nalp3 inflammasome activating danger signal.

BACKGROUND: Characteristic symptoms of malaria include recurrent fever attacks and neurodegeneration, signs that are also found in patients with a hyperactive Nalp3 inflammasome. Plasmodium species produce a crystal called hemozoin that is generated by detoxification of heme after hemoglobin degradation in infected red blood cells. Thus, we hypothesized that hemozoin could activate the Nalp3 inflammasome, due to its particulate nature reminiscent of other inflammasome-activating agents. METHODOLOGY/PRINCIPAL FINDINGS: We found that hemozoin acts as a proinflammatory danger signal that activates the Nalp3 inflammasome, causing the release of IL-1beta. Similar to other Nalp3-activating particles, hemozoin activity is blocked by inhibiting phagocytosis, K(+) efflux and NADPH oxidase. In vivo, intraperitoneal injection of hemozoin results in acute peritonitis, which is impaired in Nalp3-, caspase-1- and IL-1R-deficient mice. Likewise, the pathogenesis of cerebral malaria is dampened in Nalp3-deficient mice infected with Plasmodium berghei sporozoites, while parasitemia remains unchanged. SIGNIFICANCE/CONCLUSIONS: The potent pro-inflammatory effect of hemozoin through inflammasome activation may possibly be implicated in plasmodium-associated pathologies such as cerebral malaria.

NR2A at CA1 synapses is obligatory for the susceptibility of hippocampal plasticity to sleep loss.

A loss in the necessary amount of sleep alters expression of genes and proteins implicated in brain plasticity, but key proteins that render neuronal circuits sensitive to sleep disturbance are unknown. We show that mild (4-6 h) sleep deprivation (SD) selectively augmented the number of NR2A subunits of NMDA receptors on postsynaptic densities of adult mouse CA1 synapses. The greater synaptic NR2A content facilitated induction of CA3-CA1 long-term depression in the theta frequency stimulation range and augmented the synaptic modification threshold. NR2A-knock-out mice maintained behavioral response to SD, including compensatory increase in post-deprivation resting time, but hippocampal synaptic plasticity was insensitive to sleep loss. After SD, the balance between synaptically activated and slowly recruited NMDA receptor pools during temporal summation was disrupted. Together, these results indicate that NR2A is obligatory for the consequences of sleep loss on hippocampal synaptic plasticity. These findings could advance pharmacological strategies aiming to sustain hippocampal function during sleep restriction.

Signal transduction by the cloned glucagon-like peptide-1 receptor: comparison with signaling by the endogenous receptors of beta cell lines.

Glucagon-like peptide-1 (GLP-1) is a gastrointestinal hormone that potentiates glucose-induced insulin secretion by pancreatic beta cells. The mechanisms of interaction between GLP-1 and glucose signaling pathways are not well understood. Here we studied the coupling of the cloned GLP-1 receptor, expressed in fibroblasts or in COS cells, to intracellular second messengers and compared this signaling with that of the endogenous receptor expressed in insulinoma cell lines. Binding of GLP-1 to the cloned receptor stimulated formation of cAMP with the same dose dependence and similar kinetics, compared with the endogenous receptor of insulinoma cells. Compared with forskolin-induced cAMP accumulation, that induced by GLP-1 proceeded with the same initial kinetics but rapidly reached a plateau, suggesting fast desensitization of the receptor. Coupling to the phospholipase C pathway was assessed by measuring inositol phosphate production and variations in the intracellular calcium concentration. No GLP-1-induced production of inositol phosphates could be measured in the different cell types studied. A rise in the intracellular calcium concentration was nevertheless observed in transfected COS cells but was much smaller than that observed in response to norepinephrine in cells also expressing the alpha 1B-adrenergic receptor. Importantly, no such increase in the intracellular calcium concentration could be observed in transfected fibroblasts or insulinoma cells, which, however, responded well to thrombin or carbachol, respectively. Together, our data show that interaction between GLP-1 and glucose signaling pathways in beta cells may be mediated uniquely by an increase in the intracellular cAMP concentration, with the consequent activation of protein kinase A and phosphorylation of elements of the glucose-sensing apparatus or of the insulin granule exocytic machinery.

Revision to the SUDAS Traffic Signal Design Guide, TR-546, 2009

Changes in technology have an impact on standard practice, materials, and equipment. The traffic signal industry is constantly producing more energy-efficient and durable equipment, better communications, and more sophisticated detection and monitoring capabilities. Accordingly, this project provides an update to the traffic signal content within the Statewide Urban Design and Specifications (SUDAS) Design Manual and Standard Specifications. This work was completed through a technical advisory committee with a variety of participants representing contractors, the Iowa Department of Transportation, cities, consultants, vendors, and university research and support staff.

Improved Methods for Determining Wind Loads on Highway Sign and Traffic-Signal Structures, TR-559, 2007

The main objective of the proposed study is to use Computational Fluid Dynamics (CFD) tools to determine the wind loads by accurate numerical simulations of air flow characteristics around large highway sign structures under severe wind speeds conditions. Fully three-dimensional Reynolds- Averaged Navier-Stokes (RANS) simulations are used to estimate the total force on different panels, as well as the actual pressure distribution on the front and back faces of the panels. In particular, the present study investigates the effects of aspect ratio and sign spacing for regular panels, the effect of sign depth for the dynamic message signs that are now being used on Iowa highways, the effect induced by the presence of back-to-back signs, the effect of the presence of add-on exit signs, and the effect of the presence of trucks underneath the signs potentially creating “wind tunnel” effect.

Autonomous Measurements of Bridge Pier and Abutment Scour using Motion-Sensing Radio Transmitters, TR-595, 2010

Two portable Radio Frequency IDentification (RFID) systems (made by Texas Instruments and HiTAG) were developed and tested for bridge scour monitoring by the Department of Civil and Environmental Engineering at the University of Iowa (UI). Both systems consist of three similar components: 1) a passive cylindrical transponder of 2.2 cm in length (derived from transmitter/responder); 2) a low frequency reader (~134.2 kHz frequency); and 3) an antenna (of rectangular or hexagonal loop). The Texas Instruments system can only read one smart particle per time, while the HiTAG system was successfully modified here at UI by adding the anti-collision feature. The HiTAG system was equipped with four antennas and could simultaneously detect 1,000s of smart particles located in a close proximity. A computer code was written in C++ at the UI for the HiTAG system to allow simultaneous, multiple readouts of smart particles under different flow conditions. The code is written for the Windows XP operational system which has a user-friendly windows interface that provides detailed information regarding the smart particle that includes: identification number, location (orientation in x,y,z), and the instance the particle was detected.. These systems were examined within the context of this innovative research in order to identify the best suited RFID system for performing autonomous bridge scour monitoring. A comprehensive laboratory study that included 142 experimental runs and limited field testing was performed to test the code and determine the performance of each system in terms of transponder orientation, transponder housing material, maximum antenna-transponder detection distance, minimum inter-particle distance and antenna sweep angle. The two RFID systems capabilities to predict scour depth were also examined using pier models. The findings can be summarized as follows: 1) The first system (Texas Instruments) read one smart particle per time, and its effective read range was about 3ft (~1m). The second system (HiTAG) had similar detection ranges but permitted the addition of an anti-collision system to facilitate the simultaneous identification of multiple smart particles (transponders placed into marbles). Therefore, it was sought that the HiTAG system, with the anti-collision feature (or a system with similar features), would be preferable when compared to a single-read-out system for bridge scour monitoring, as the former could provide repetitive readings at multiple locations, which could help in predicting the scour-hole bathymetry along with maximum scour depth. 2) The HiTAG system provided reliable measures of the scour depth (z-direction) and the locations of the smart particles on the x-y plane within a distance of about 3ft (~1m) from the 4 antennas. A Multiplexer HTM4-I allowed the simultaneous use of four antennas for the HiTAG system. The four Hexagonal Loop antennas permitted the complete identification of the smart particles in an x, y, z orthogonal system as function of time. The HiTAG system can be also used to measure the rate of sediment movement (in kg/s or tones/hr). 3) The maximum detection distance of the antenna did not change significantly for the buried particles compared to the particles tested in the air. Thus, the low frequency RFID systems (~134.2 kHz) are appropriate for monitoring bridge scour because their waves can penetrate water and sand bodies without significant loss of their signal strength. 4) The pier model experiments in a flume with first RFID system showed that the system was able to successfully predict the maximum scour depth when the system was used with a single particle in the vicinity of pier model where scour-hole was expected. The pier model experiments with the second RFID system, performed in a sandbox, showed that system was able to successfully predict the maximum scour depth when two scour balls were used in the vicinity of the pier model where scour-hole was developed. 5) The preliminary field experiments with the second RFID system, at the Raccoon River, IA near the Railroad Bridge (located upstream of 360th street Bridge, near Booneville), showed that the RFID technology is transferable to the field. A practical method would be developed for facilitating the placement of the smart particles within the river bed. This method needs to be straightforward for the Department of Transportation (DOT) and county road working crews so it can be easily implemented at different locations. 6) Since the inception of this project, further research showed that there is significant progress in RFID technology. This includes the availability of waterproof RFID systems with passive or active transponders of detection ranges up to 60 ft (~20 m) within the water–sediment column. These systems do have anti-collision and can facilitate up to 8 powerful antennas which can significantly increase the detection range. Such systems need to be further considered and modified for performing automatic bridge scour monitoring. The knowledge gained from the two systems, including the software, needs to be adapted to the new systems.