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See detailMicroPET Focus 120 scanner use at high-­‐count rate
Bahri, Mohamed Ali ULg; Warnock, Geoffrey ULg; Taleb, Dounia ULg et al

Poster (2012, September)

Kinetic modeling of physiological processes using imaging techniques requires an accurate measurement of the time-activity curve of the tracer in plasma, known as the arterial input function (IF). The IF ... [more ▼]

Kinetic modeling of physiological processes using imaging techniques requires an accurate measurement of the time-activity curve of the tracer in plasma, known as the arterial input function (IF). The IF can be obtained by manual blood sampling, can be derived from PET images, or continuously measured by the use of small counting systems such as beta microprobes [1]. However, some beta microprobe systems can suffering from high background counts and low sensitivity compared to PET can obligate the use of activities higher than those typical for the imaging system. In the present study, the NEMA NU4-2008 image quality (IQ) phantom [2] was used to evaluate the image quality of the microPET Focus 120 at high activity values. Attenuation correction was obtained from transmission measurement using 57Co point source. Eight emission scans of 20 minutes were performed at decreasing activity starting from 109 MBq to 3.7 MBq (total activity in the field-of-view). To study the effect of normalization in high count rate studies, several normalization scans were performed using activities ranging between 18 and 212 MBq. Images were reconstructed with all corrections using Fourier rebinning and filtered backprojection. The mean activity and the coefficients of variation of the uniform slices were measured. All high activity reconstructed images showed a detector-block-patterned artifact with an overestimation of the counts when normalization activity is higher than that used in the IQ phantom and underestimation of the counts when normalization activity is below the activity used in the IQ phantom. Using the same high activity for acquisition and normalization considerably reduces the patterned-artifact but does not eliminate it entirely. The observed artifact is due to pulse pile-up in the detectors at high count-rates. A dedicated rejection of the pulse pile-up does not appear to have been implemented for the microPET Focus 120. An alternative would be to re-calibrate the detectors with higher activity values to prevent any pile-up effect or to create an attenuation volume into which phantoms or small animals could be inserted thus decreasing the artifact. This latter option is under development. References: [1] G. Warnock et al, European Journal of Nuclear Medicine and Molecular Imaging Research, 1-13 (2011) [2] NEMA Standards Publication NU4-2008. Rosslyn, VA: National Electrical Manufacturers Association; (2008). [less ▲]

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See detailSmall animal imaging with human PET
Bahri, Mohamed Ali ULg; Tombuloglu, S; Warnock, Geoffrey ULg et al

Poster (2012, September)

PET studies provide valuable information in the assessment of animal models for human diseases. MicroPET systems provide the high resolution needed to explore small organs but suffer from a reduced axial ... [more ▼]

PET studies provide valuable information in the assessment of animal models for human diseases. MicroPET systems provide the high resolution needed to explore small organs but suffer from a reduced axial FOV. Multiple bed positions are then used to obtain whole body scans resulting in increased scan time and incomplete dynamic data. In contrast, human PET systems have larger axial FOV but a lower resolution. In this study, an image-based model of the scanner spatial response function combined with a 3D-OSEM reconstruction algorithm were used to improve spatial resolution of the Siemens ECAT EXACT HR+ PET scanner. A stationary double Gaussian model [1] of the ECAT EXACT HR+ point spread function was derived from 18F point source measurements performed at different radial and axial locations in the scanner FOV. This model was used in a 3D-OSEM reconstruction (3D-OSEM-RM). Sinograms were normalized and attenuation and scatter corrected using the Siemens ECAT tools before reconstruction. Both NEMA NU 2-1994 performance phantoms and NEMA NU4-2008 image quality phantom mimicking small animals were used to evaluate the accuracy of corrections for physical effects and the overall image quality. A 50 min dynamic FDG rat study was conducted on the ECAT HR+ and reconstructed with 3D-OSEM-RM. The images were used to compute the metabolic rate of glucose (MRglu) in multiple brain structures. These images were also visually compared to the static image obtained with a FOCUS 120 microPET immediately after the HR+ dynamic scan. The standard deviations of the two Gaussians used to model the transaxial (axial) resolution in a central FOV of 5 cm radius were σ1 = 1.6 (2.75) mm and σ2 = 3.66 (4.16) mm, and the ratio of the weights between the first and second Gaussians was ρ = 0.2 (0.7). Image uniformity and accuracy of scatter and attenuation corrections, evaluated following NEMA NU 2-1994, were found to be very similar between 3D-OSEM, 3D-OSEM-RM, 2D- and 3D-FBP reconstructed images. When using the NEMA NU4-2008 image quality phantom a significant increase of the hot rod recovery coefficient was observed. This effect was rod size dependent and amounted to 17-35% for the 3D-OSEM-RM compared to the 3D-OSEM and to 35-62% compared to the FBP reconstructions. Nevertheless the values obtained with 3D-OSEM-RM were around 20-35% lower than those obtained with the FOCUS 120 microPET scanner. Most of the small brain structures observed on microPET images were also visible on the images obtained with the HR+ scanner and 3D-OSEM-RM. Rat cerebral MRglu values calculated on 3D-OSEM-RM images were in the range of published values [2] (e.g. whole brain = 25.34 μmol/min/100g). Using an approximate model of the ECAT EXACT HR+ spatial response in 3D-OSEM resulted in sufficient image quality for dynamic whole body scans of small rodents, despite the large FOV, and resulted in improved contrast compared to images generated using the built-in software. This methodology will be applied for future small animal dosimetry and modeling studies in our laboratory. [1] Comtat et al. IEEE Nucl Sci Symp Conf Record. pp. 4120-4123 (2008) [2] Schiffer et al. J Nucl Med 48:277-287 (2007) [less ▲]

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See detailDosimetry for 6-[18F]Fluoro-L-DOPA in humans based on in vivo microPET scans and ex vivo tissue distribution in mice
Bretin, Florian ULg; Warnock, Geoffrey ULg; Bahri, Mohamed Ali ULg et al

Poster (2012, September)

Radiation dosimetry of new radiopharmaceuticals generally starts with studies in small animals such as mice and rats. The traditional technique has long been ex vivo measurement of the biodistribution ... [more ▼]

Radiation dosimetry of new radiopharmaceuticals generally starts with studies in small animals such as mice and rats. The traditional technique has long been ex vivo measurement of the biodistribution over time using harvested organs at different times post administration of the radiopharmaceutical. Since this approach requires a significant amount of animals, dynamic microPET studies, where the biodistribution of the tracer over time can be determined in vivo in a single scan, are an invaluable alternative. Due to known imaging artifacts and limitations, such as partial volume effect, a hybrid technique combining harvesting organs (post-scan) and dynamic imaging was introduced to achieve a cross-calibration to account for these limitations. Since 6-[18F]Fluoro-L-DOPA is a widely used PET tracer to study the dopaminergic system in neurology and oncology and there is no sound published dosimetry data, absorbed doses for major organs in humans were estimated using the traditional ex vivo technique and by dynamic microPET imaging in mice, allowing direct comparison of the results from the two techniques. The tissue distribution over time of 6-[18F]Fluoro-L-DOPA was determined by radioassay of harvested organs at 2, 5, 10, 30, 60, 120 minutes post administration (n=5 at each time point) in isoflurane-anaesthetized mice. Dynamic PET images were acquired with a FOCUS 120 microPET for 120 minutes after injection of 6-[18F]Fluoro-L-DOPA followed by radioassay of harvested organs (n=4). A bladder voiding scenario was used to simulate excretion every 2 h. The organ time-activity-curves (TACs) from both methods were extrapolated from a simulated 35 g standard mouse to a 70 kg standard male human using a technique based on organ to bodyweight ratios. The absorbed doses in major human organs were calculated with the commercially available human dosimetry software OLINDA/EXM (Version 1.1) using the extrapolated TACs. The extrapolated organ TACs obtained using the two methods showed a high correlation (average r = 0.94 ± 0.05, p < 0.001). However, TACs from PET alone under- or overestimated the activity in individual organs in contrast to TACs obtained using the cross-calibration of the PET data with the activity in post-scan dissected organs. Those organs in the excretion pathways, comprising bladder wall, kidneys and liver, received the highest organ doses. The total body absorbed dose was 0.0118 mGy/MBq for both the imaging based and harvesting based methods. The effective dose was 0.0193 mSv/MBq for the hybrid imaging-harvesting technique and 0.0189 mSv/MBq for the pure harvesting technique. Scaling errors in the PET TACs are likely caused by quantification errors such as partial volume effects and image artifacts. The use of a hybrid imaging technique to cross-calibrate the TACs improved the accuracy of the imaging-based dosimetry estimates. Therefore the hybrid technique combining dynamic imaging and harvesting organs (post-scan) is a suitable alternative to the gold standard ex vivo radioassay method. It yields comparable results yet reduces significantly the amount of animals needed in the study and can accelerate data acquisition. [less ▲]

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See detailPET In Conscious Rodents - Quantification of Stress During The Training Process
Warnock, Geoffrey ULg; Bahri, Mohamed Ali ULg; Bretin, Florian ULg et al

Poster (2012, September)

Recently several methods for performing PET studies in conscious rodents have been developed [1-3]. These methods have the potential to greatly improve the translational nature of PET studies in rodents ... [more ▼]

Recently several methods for performing PET studies in conscious rodents have been developed [1-3]. These methods have the potential to greatly improve the translational nature of PET studies in rodents. One of the most easily implemented methods is the training of a rat to tolerate head fixation in a restraining device. Training consists of intervals of restraint over several days. However, the stress induced by this training procedure has not been quantified in detail. Limited changes in plasma corticosterone have been reported, but this data may be confounded by sample timing and baseline levels. An implantable telemetry system (Telemetry Research) was used to remotely measure blood pressure, heart rate and core temperature during training. Transmitters were implanted in the abdominal cavity under isoflurane anesthesia, with the blood pressure sensor fixed in the abdominal aorta. Training was started after a recovery period of at least 1 week. Training consisted of a 5 min period of acclimatization in the cage containing the restraining device, followed by increasing durations of restraint in the device on subsequent training days (15, 30, 45, 60, 90 min). Telemetry data was acquired from 5 min prior to acclimatization to 60 minutes post-training. In this initial pilot study, a single rat was trained, without head fixation, for 4 consecutive days and again on day 7. All reported values are mean ± SEM across the five training days. In the home cage, prior to acclimatization, baseline heart rate (HR) was 294 ± 15 bpm. During the acclimatization period, HR was elevated to 411 ± 7 bpm. Immediately after starting training, HR was 419 ± 16 bpm. During the training period HR showed a tendency to decrease, with raised periods at undefined intervals. After return to the home cage, HR remained elevated for 15-20 min before returning to a value (313 ± 9 bpm) close to baseline. A similar pattern was seen in blood pressure (mean; BP). Baseline BP was 76 ± 7 mmHg, increasing to 94 ± 9 mmHg during acclimatization. After commencing training, a peak in BP was reached at 102 ± 8 mmHg. After the 15-20 min recovery interval, BP returned to a baseline of 77 ± 9 mmHg. The HR and BP responses to acclimatization and to the training protocol persisted throughout all training days, with the main noticeable difference being the number of bouts of increased HR, which increased with training duration. Core body temperature (baseline: 37.45 ± 0.21 °C) increased during restraint training, with a subsequent post-training peak (38.21 ± 0.03 °C). Measurement of core temp is complicated during longer training sessions by the need to charge the transmitter. This early data indicates that stress induced by the training procedure for conscious PET persists after several days of training. In subsequent studies the head will be fixed and the effect of the training on plasma corticosterone and central glucose metabolism (using [18F]FDG) will be examined. [1] Momosaki et al. (2004) Synapse 54:207–213 [2] Wyss et al. (2009) NeuroImage 48:339–347 [3] Itoh et al. (2009) J Nucl Med 50:749–756 [less ▲]

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See detailSynthesis of two new alkyne-bearing liners used for the preparation of siRNA for labeling by click chemistry with fluorine-18
Flagothier, Jessica ULg; Kaisin, Geoffroy ULg; Mercier, Frederic et al

in Applied Radiation & Isotopes (2012), 70(8), 1549-1557

Oligonucleotides (ONs) and more particularly siRNAs are promising drugs but their pharmacokinetics and biodistribution are widely unknown. Positron Emission Tomography (PET) using fluorine-18 is a ... [more ▼]

Oligonucleotides (ONs) and more particularly siRNAs are promising drugs but their pharmacokinetics and biodistribution are widely unknown. Positron Emission Tomography (PET) using fluorine-18 is a suitable technique to quantify these biological processes. Click chemistry (Huisgen cycloaddition) is the current method for labeling siRNA. In order to study the influence of a linker bearing by [18F]labeled ONs, on the in vivo pharmacokinetic and metabolism, we have developed two modified ONs by two news linkers. Here we report the synthesis of two alkyne-bearing linkers, the incorporation onto a ONs and the conjugation by click chemistry with a [18F]prosthetic group. [less ▲]

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See detailAutomatic multiclass classification of 18FDG-PET scans for the distinction between Parkinson’s disease and atypical parkinsonian syndromes
Phillips, Christophe ULg; Schrouff, Jessica ULg; Luxen, André ULg et al

Poster (2012, June 10)

Part of the difficulty in the early diagnosis of Parkinson’s disease (PD) is in differentiating it from atypical parkinsonian disorders (APS) that have a poorer prognosis such as multiple system atrophy ... [more ▼]

Part of the difficulty in the early diagnosis of Parkinson’s disease (PD) is in differentiating it from atypical parkinsonian disorders (APS) that have a poorer prognosis such as multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS). 18flurodeoxyglucose (FDG) positron emission tomography (PET) has been recommended for the early differentiation between PD and APS [1]. Here, 120 FDG PET scans (42, 31, 26 and 21 for the PD, MSA, PSP and CBS resp.) were acquired on average 3.5 years after symptoms onset (because the initial clinical features were outside the prevailing perception for PD) to look, without any a priori assumption, for cerebral FDG uptake patterns that discriminate either between the PD and APS classes, or between the four PD, MSA, PSP and CBS classes. The diagnostic used to label the scans was defined by clinical criteria on average 4.5 years after PET assessment. [less ▲]

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See detailImaging Guided Proteomics Unveils Heterogeniety in Colorectal Carcinoma Liver Metastases – Implications for Targeted Therapies.
blomme, Arnaud; Turtoi, Andrei ULg; Delvaux, David ULg et al

in Proceedings Giga Day 2012 (2012, May 04)

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See detailSynthesis and evaluation of boronic acids as inhibitors of Penicillin Binding Proteins of classes A, B and C
Zervosen, Astrid ULg; Sauvage, Eric ULg; Bouillez, André ULg et al

Poster (2012, April 18)

The widespread use of beta-lactam antibiotics has lead to the worldwide appearance of drug-resistant strains. Bacteria have developed resistance to beta-lactams by three main mechanisms: the production of ... [more ▼]

The widespread use of beta-lactam antibiotics has lead to the worldwide appearance of drug-resistant strains. Bacteria have developed resistance to beta-lactams by three main mechanisms: the production of beta-lactamases that catalyze hydrolysis of beta-lactams, the production of low-affinity, drug resistant Penicillin Binding Proteins (PBPs) and the over expression of resistant PBPs. PBPs are interesting targets because they catalyse the last steps of the biosynthesis of peptidoglycan, which is unique in bacteria and has no mammalian analogs, outside the cytoplasmic membrane. Various non-ß-lactam inhibitors of PBPs have been developed with the objective of attempting to stall the development of ß-lactam resistance. Boronic acids are potent beta-lactamase inhibitors and have been shown to display some specificity for soluble transpeptidases and PBPs, but their potential as inhibitors of the latter enzymes is yet to be widely explored. Recently, a (2, 6-dimethoxybenzamido)methylboronic acid was identified as being a potent inhibitor of Actinomadura sp. R39 transpeptidase (IC50: 1.3 µM). Here, we will discuss the synthesis of a number of acylaminomethylboronic acids, analogs of (2, 6-dimethoxybenzamido)methylboronic acid, and their potential as inhibitors of PBPs. Several boronic acids of this library were able to inhibit PBPs of classes A, B and C from penicillin sensitive strains. Thus (2-nitrobenzamido)methylboronic acid was identified as a good inhibitor of class A PBP (PBP1b from S. pneumoniae, IC50 = 26 µM), class B PBP (PBP2xR6 from S. pneumoniae, IC50 = 138 µM) and class C PBP (R39 from Actinomadura sp., IC50 = 0.6 µM). Crystal structures of complexes of R39 and PBP1b with boronic acid analogs of our library have already been solved and allowed an interpretation of results. We believe that this work opens new avenues towards the development of molecules that will inhibit PBPs, and eventually display bactericidal effect, on distinct bacterial species. [less ▲]

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See detailNEMA NU4-2008 Performance Evaluation for the MicroPET FOCUS 120 and Iodine-124
Taleb, Dounia ULg; Bahri, Mohamed Ali ULg; Warnock, Geoffrey ULg et al

in IEEE proceedings of ANIMMA 2011 (2012, March 12)

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See detailNeural Correlates of Performance Variabilty during Motor Sequence Acquisition
Albouy, Geneviève ULg; Sterpenich, V.; Vandewalle, Gilles ULg et al

in NeuroImage (2012), 60(1), 324-331

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See detailInfluence of acute sleep loss on the neural correlates of alerting, orientating and executive attention components
Muto, Vincenzo ULg; Shaffii, Anahita ULg; Matarazzo, Luca et al

in Journal of Sleep Research (2012), 21(6), 648-58

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See detailCircadian preference modulates the neural substrate of conflict processing across the day
Schmidt, Christina ULg; Peigneux, Philippe ULg; Leclercq, Yves ULg et al

in PLoS ONE (2012), 7(1), 29658

Human morning and evening chronotypes differ in their preferred timing for sleep and wakefulness, as well as in optimal daytime periods to cope with cognitive challenges. Recent evidence suggests that ... [more ▼]

Human morning and evening chronotypes differ in their preferred timing for sleep and wakefulness, as well as in optimal daytime periods to cope with cognitive challenges. Recent evidence suggests that these preferences are not a simple by-product of socio-professional timing constraints, but can be driven by inter-individual differences in the expression of circadian and homeostatic sleep-wake promoting signals. Chronotypes thus constitute a unique tool to access the interplay between those processes under normally entrained day-night conditions, and to investigate how they impinge onto higher cognitive control processes. Using functional magnetic resonance imaging (fMRI), we assessed the influence of chronotype and time-of-day on conflict processing-related cerebral activity throughout a normal waking day. Sixteen morning and 15 evening types were recorded at two individually adapted time points (1.5 versus 10.5 hours spent awake) while performing the Stroop paradigm. Results show that interference-related hemodynamic responses are maintained or even increased in evening types from the subjective morning to the subjective evening in a set of brain areas playing a pivotal role in successful inhibitory functioning, whereas they decreased in morning types under the same conditions. Furthermore, during the evening hours, activity in a posterior hypothalamic region putatively involved in sleep-wake regulation correlated in a chronotype-specific manner with slow wave activity at the beginning of the night, an index of accumulated homeostatic sleep pressure. These results shed light into the cerebral mechanisms underlying inter-individual differences of higher-order cognitive state maintenance under normally entrained day-night conditions. [less ▲]

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See detailThe fate of incoming stimuli during NREM sleep is determined by spindles and the phase of the slow oscillation
Schabus, M.; Dang Vu, Thien Thanh ULg; Heib, D. P. J. et al

in Frontiers in Neurology (2012), 3(40), 1-11

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See detailThe neural correlates of recollection and familiarity during aging
Angel, Lucie; Bastin, Christine ULg; Genon, Sarah ULg et al

in Frontiers in Human Neuroscience (2012)

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See detailThe Neural Substrates of Memory Suppression: A fMRI Exploration of Directed Forgetting
Bastin, Christine ULg; Feyers, Dorothée ULg; Majerus, Steve ULg et al

in PLoS ONE (2012), 7(1), 29905

The directed forgetting paradigm is frequently used to determine the ability to voluntarily suppress information. However, little is known about brain areas associated with information to forget. The ... [more ▼]

The directed forgetting paradigm is frequently used to determine the ability to voluntarily suppress information. However, little is known about brain areas associated with information to forget. The present study used functional magnetic resonance imaging to determine brain activity during the encoding and retrieval phases of an item-method directed forgetting recognition task with neutral verbal material in order to apprehend all processing stages that information to forget and to remember undergoes. We hypothesized that regions supporting few selective processes, namely recollection and familiarity memory processes, working memory, inhibitory and selection processes should be differentially activated during the processing of to-be-remembered and to-be-forgotten items. Successful encoding and retrieval of items to remember engaged the entorhinal cortex, the hippocampus, the anterior medial prefrontal cortex, the left inferior parietal cortex, the posterior cingulate cortex and the precuneus; this set of regions is well known to support deep and associative encoding and retrieval processes in episodic memory. For items to forget, encoding was associated with higher activation in the right middle frontal and posterior parietal cortex, regions known to intervene in attentional control. Items to forget but nevertheless correctly recognized at retrieval yielded activation in the dorsomedial thalamus, associated with familiarity-based memory processes and in the posterior intraparietal sulcus and the anterior cingulate cortex, involved in attentional processes. [less ▲]

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See detailDevelopment of new drugs for an old target — the penicillin binding proteins.
Zervosen, Astrid ULg; Sauvage, Eric ULg; Frère, Jean-Marie ULg et al

in Molecules (2012), 17(11), 12478-505

The widespread use of β-lactam antibiotics has led to the worldwide appearance of drug-resistant strains. Bacteria have developed resistance to β-lactams by two main mechanisms: the production of β ... [more ▼]

The widespread use of β-lactam antibiotics has led to the worldwide appearance of drug-resistant strains. Bacteria have developed resistance to β-lactams by two main mechanisms: the production of β-lactamases, sometimes accompanied by a decrease of outer membrane permeability, and the production of low-affinity, drug resistant Penicillin Binding Proteins (PBPs). PBPs remain attractive targets for developing new antibiotic agents because they catalyse the last steps of the biosynthesis of peptidoglycan, which is unique to bacteria, and lies outside the cytoplasmic membrane. Here we summarize the “current state of the art” of non-β-lactam inhibitors of PBPs, which have being developed in an attempt to counter the emergence of β-lactam resistance. These molecules are not susceptible to hydrolysis by β-lactamases and thus present a real alternative to β-lactams. We present transition state analogs such as boronic acids, which can covalently bind to the active serine residue in the catalytic site. Molecules containing ring structures different from the β-lactam-ring like lactivicin are able to acylate the active serine residue. High throughput screening methods, in combination with virtual screening methods and structure based design, have allowed the development of new molecules. Some of these novel inhibitors are active against major pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and thus open avenues new for the discovery of novel antibiotics. [less ▲]

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See detailModulation of brain activity during a Stroop inhibitory task by the kind of cognitive control required
Grandjean, Julien ULg; D'Ostilio, Kevin ULg; Phillips, Christophe ULg et al

in PLoS ONE (2012), 7(7), 41513

This study used a proportion congruency manipulation in the Stroop task in order to investigate, at the behavioral and brain substrate levels, the predictions derived from the Dual Mechanisms of Control ... [more ▼]

This study used a proportion congruency manipulation in the Stroop task in order to investigate, at the behavioral and brain substrate levels, the predictions derived from the Dual Mechanisms of Control (DMC) account of two distinct modes of cognitive control depending on the task context. Three experimental conditions were created that varied the proportion congruency: mostly incongruent (MI), mostly congruent (MC), and mostly neutral (MN) contexts. A reactive control strategy, which corresponds to transient interference resolution processes after conflict detection, was expected for the rare conflicting stimuli in the MC context, and a proactive strategy, characterized by a sustained task-relevant focus prior to the occurrence of conflict, was expected in the MI context. Results at the behavioral level supported the proactive/reactive distinction, with the replication of the classic proportion congruent effect (i.e., less interference and facilitation effects in the MI context). fMRI data only partially supported our predictions. Whereas reactive control for incongruent trials in the MC context engaged the expected fronto-parietal network including dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex, proactive control in the MI context was not associated with any sustained lateral prefrontal cortex activations, contrary to our hypothesis. Surprisingly, incongruent trials in the MI context elicited transient activation in common with incongruent trials in the MC context, especially in DLPFC, superior parietal lobe, and insula. This lack of sustained activity in MI is discussed in reference to the possible involvement of item-specific rather than list-wide mechanisms of control in the implementation of a high task-relevant focus. [less ▲]

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See detailExploration of the chemical space of novel naphthalene-sulfonamide and anthranilic acid-based inhibitors of penicillin-binding Proteins
Sosic, Izidor; Turk, Samo; Sinreih, Masa et al

in Acta Chimica Slovenica (2012), 59(2), 380-388

Penicillin-binding proteins are a well established, validated and still a very promising target for the design and development of new antibacterial agents. Based on our previous discovery of several ... [more ▼]

Penicillin-binding proteins are a well established, validated and still a very promising target for the design and development of new antibacterial agents. Based on our previous discovery of several noncovalent small-molecule inhibitor hits for resistant PBPs we decided to additionally explore the chemical space around these compounds. In order to clarify their structure-activity relationships for PBP inhibition two new series of compounds were synthesized, characterized and evaluated biochemically: the derivatives of anthranilic acid and naphthalene-sulfonamide derivatives. The target compounds were tested for their inhibitory activities on three different transpeptidases: PBP2a from methicillin-resistant Staphylococcus aureus (MRSA) strains, PBP5fm from Enterococcus faecium strains, and PBP1b from Streptococcus pneumoniae strains. The most promising results for both of these series of compounds were obtained against the PBP2a enzyme with the IC50 values in the micromolar range. Although these results do not represent a significant breakthrough in the field of noncovalent PBP inhibitors, they do provide useful structure-activity relationship data, and thus a more solid basis for the design of potent and noncovalent inhibitors of resistant PBPs. [less ▲]

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