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Dipolar interactions among nuclear magnetic moments embedded in rigid solids are examined. Substitutional disorder in lattices is shown to modify the statistical properties of the distributions of the absolute values of dipolar coupling constants. Numerical studies reveal that a crossover in the average of the coupling constants in dilute spin networks occurs as a function of the random fractional occupancy in the lattice. The origin of this crossover is related to an interplay between the statistical weights of the coupling constants and their values which are distributed over many orders of magnitude. Two different regimes of behavior are observed for the average of the coupling constants as a function of dilution; one regime is dominated by the most probable value of the distribution of coupling constants, while in the other regime, the arithmetic mean prevails. For a macroscopic sample of 1022 sites, the crossover between regimes is predicted to occur when 1011 sites are occupied. Averaging over the s...

Since the invention of cancer radiotherapy, its primary goal has been to maximize lethal radiation doses to the tumor volume while keeping the dose to surrounding healthy tissues at zero. Sadly, conventional radiation sources (γ or X rays, electrons) used for decades, including multiple or modulated beams, inevitably deposit the majority of their dose in front or behind the tumor, thus damaging healthy tissue and causing secondary cancers years after treatment. Even the most recent pioneering advances in costly proton or carbon ion therapies can not completely avoid dose buildup in front of the tumor volume. Here we show that this ultimate goal of radiotherapy is yet within our reach: Using intense ultra-short infrared laser pulses we can now deposit a very large energy dose at unprecedented microscopic dose rates (up to 10 11 Gy/s) deep inside an adjustable, well-controlled macroscopic volume, without any dose deposit in front or behind the target volume. Our infrared laser pulses produce high density avalanches of low energy electrons via laser filamentation, a phenomenon that results in a spatial energy density and temporal dose rate that both exceed by orders of magnitude any values previously reported even for the most intense clinical radiotherapy systems. Moreover, we show that ( i ) the type of final damage and its mechanisms in aqueous media, at the molecular and biomolecular level, is comparable to that of conventional ionizing radiation, and ( ii ) at the tumor tissue level in an animal cancer model, the laser irradiation method shows clear therapeutic benefits.

Reaching the full potential of magnetic resonance imaging (MRI)-positron emission tomography (PET) dual modality systems requires new methodologies in quantitative image analyses. In this study, methods are proposed to convert an arterial input function (AIF) derived from gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) in MRI, into a (18)F-fluorodeoxyglucose ((18)F-FDG) AIF in PET, and vice versa. The AIFs from both modalities were obtained from manual blood sampling in a F98-Fisher glioblastoma rat model. They were well fitted by a convolution of a rectangular function with a biexponential clearance function. The parameters of the biexponential AIF model were found statistically different between MRI and PET. Pharmacokinetic MRI parameters such as the volume transfer constant (K(trans)), the extravascular-extracellular volume fraction (ν(e)), and the blood volume fraction (ν(p)) calculated with the Gd-DTPA AIF and the Gd-DTPA AIF converted from (18)F-FDG AIF normalized with or without blood sample were not statistically different. Similarly, the tumor metabolic rates of glucose (TMRGlc) calculated with (18) F-FDG AIF and with (18) F-FDG AIF obtained from Gd-DTPA AIF were also found not statistically different. In conclusion, only one accurate AIF would be needed for dual MRI-PET pharmacokinetic modeling in small animal models.

Purpose The aims of this study were to compare in vitro magnetic resonance imaging (MRI) characteristics of keratinocytic skin cancer assessed by a 7-tesla (T) MRI with histopathology, and to describe MRI features of skin tumors. Methods This prospective study included 30 skin tumors treated by surgery. MR images of skin samples were acquired on a 7-T MR scanner using a fast spin-echo T2-weighted and an isotropic 3D gradient-echo T1-weighted sequence. Length, width, Breslow index and margins of the lesions were measured. The presence or absence of the following was noted: healthy margins, ulceration of the dermis, in situ lesions, superficial and deep dermis involvement, subcutaneous involvement, superficial and intratumoral keratin. MR results were compared to histopathology. Results Interclass correlation coefficient (ICC) was very good for the evaluation of the width (ICC = 0.86) and Breslow index (ICC = 0.87). The ICC was good for the evaluation of the margins (ICC = 0.70) but for length, ICC was lower (ICC = 0.67). Mean bias between MRI and histopathology was inferior to 1 mm for width, Breslow index and margin. Conclusion In vitro 7-T MRI of keratinocytic skin cancer allows delineation of lesions with good correlation with histopathology. After in vivo confirmation it could have a diagnostic role regarding the delineation of surgical margins but its actual limitations prevent its practical adoption at this time.

This paper presents the first characterization of aquatic particles and particulate organic matter (POM) by attenuated total reflectance infrared spectroscopy (ATR-FTIR) using particles deposited on filters. Particles from 30 water samples from the St. Lawrence System (Canada) were analyzed. ATR-FTIR spectra revealed changes in numerous organic and inorganic functional group contents. Particles from marine waters contained POM enriched in amide, N-H, and aliphatic groups, while terrigenous POM had more COO(-)/COOH and aromatic groups. The spectra showed the selective degradation of amide, N-H, aliphatic, and carbohydrate-like structures during the sinking of the particles. Partial least-squares (PLS) regression of the ATR-FTIR spectra was used to quantify 12 important elemental and molecular parameters, such as amino acids, bacterial biomarkers, and degradation indices. Most parameters were quantified with good accuracy compared to conventional methods (15% error). The spectral regions leading to the best quantifications and the PLS loadings revealed that aromatic cycles, other unsaturated structures, and COO(-)/COOH groups were degraded at a much slower rate than N-molecules, such as amino acids, and carbohydrates. Marine POM was enriched in CH(3) groups. CH(3) groups appeared highly labile and abundant in bacterial POM. ATR-FTIR represents a new and powerful method for a rapid, inexpensive, and nondestructive characterization of particles collected by filtration revealing important biogeochemical processes involving POM.

Objective We studied whether magnetic resonance imaging (MRI) could be used to detect placental inflammation before the detection of irreversible tissue damage. Next, we tested whether this early detection would enable the administration of treatment (ie, interleukin-1 receptor antagonist [IL-1Ra]) in a realistic clinical time after diagnosis. Study Design Pregnant rats were injected intraperitoneally with lipopolysaccharide with/without delayed IL-1Ra. MRI was performed at different time after the injection, and placentas were collected for comparison. Placental inflammation was assessed by determination of the levels of inflammatory cytokines. Results Placental inflammation was detected by MRI as early as 3 hours after maternal administration of lipopolysaccharide, concomitantly to IL-1β up-regulation. This was observed before any tissue damage, which appeared only at 24 hours after the administration of lipopolysaccharide. Delayed IL-1Ra administration (after MRI diagnosis) protected the placenta, as seen by the preserved tissue integrity and limited macrophages infiltration in the placental parenchyma. Conclusion These findings established a noninvasive diagnostic method for early in utero detection of placental inflammation that would allow the administration of placentoprotective intervention within a clinically relevant delay after diagnosis.

Objective.To describe early rheumatologic management for newly diagnosed rheumatoid arthritis (RA) in Canada.Methods.A retrospective cohort of 339 randomly selected patients with RA diagnosed from 2001–2003 from 18 rheumatology practices was audited between 2005–2007.Results.The most frequent initial disease-modifying antirheumatic drugs (DMARD) included hydroxychloroquine (55.5%) and methotrexate (40.1%). Initial therapy with multiple DMARD (15.6%) or single DMARD and corticosteroid combinations (30.7%) was infrequent. Formal assessment measures were noted infrequently, including the Health Assessment Questionnaire (34.6%) and Disease Activity Score for 28 joints (8.9%).Conclusion.Initial pharmacotherapy is consistent with guidelines from the period. The infrequent reporting of multiple DMARD combinations and formal assessment measures has implications for current clinical management and warrants contemporary reassessment.

Background Extravasation of circulating cancer cells is a key event of metastatic dissemination that is initiated by the adhesion of cancer cells to endothelial cells. It requires interactions between adhesion receptors on endothelial cells and their counter-receptors on cancer cells. Notably, E-selectin, a major endothelial adhesion receptor, interacts with Death receptor-3 present on metastatic colon carcinoma cells. This interaction confers metastatic properties to colon cancer cells by promoting the adhesion of cancer cells to endothelial cells and triggering the activation of the pro-migratory p38 and pro-survival ERK pathways in the cancer cells. In the present study, we investigated further the mechanisms by which the E-selectin-activated pathways downstream of DR3 confer a survival advantage to colon cancer cells. Methods Cell survival has been ascertained by using the WST-1 assay and by evaluating the activation of the PI3 kinase/NFκB survival axis. Apoptosis has been assayed by determining DNA fragmentation by Hoechst staining and by measuring cleavage of caspases-8 and -3. DR3 isoforms have been identified by PCR. For more precise quantification, targeted PCR reactions were carried out, and the amplified products were analyzed by automated chip-based microcapillary electrophoresis on an Agilent 2100 Bioanalyzer instrument. Results Interaction between DR3-expressing HT29 colon carcinoma cells and E-selectin induces the activation of the PI3K/Akt pathway. Moreover, p65/RelA, the anti-apoptotic subunit of NFκB, is rapidly translocated to the nucleus in response to E-selectin. This translocation is impaired by the PI3K inhibitor LY294002. Furthermore, inhibition of the PI3K/Akt pathway increases the cleavage of caspase 8 in colon cancer cells treated with E-selectin and this effect is still further increased when both ERK and PI3K pathways are concomitantly inhibited. Intriguingly, metastatic colon cancer cell lines such as HT29 and SW620 express higher levels of a splice variant of DR3 that has no trans-membrane domain and no death domain. Conclusion Colon cancer cells acquire an increased capacity to survive via the activation of the PI3K/NFκB pathway following the stimulation of DR3 by E-selectin. Generation of a DR3 splice variant devoid of death domain can further contribute to protect against apoptosis.

Here, we report that intense ultra-short laser pulses produce a plasma of low energy electrons (LEEs) by the inverse Bremsstrahlung effect and multiphoton ionization process. The phenomena show five striking characteristics. First, the self-focusing of ultra-short laser pulses creates a plasma of LEEs (6.5 eV), which is concentrated in filaments through an avalanche process. Second, kinetically hot 6.5 eV electrons interact with surrounding molecules resulting in reactive radical species. Third, the dose rate reaches an enormous level of ~2.8 × 10 11 Gy/s as determined by a cericcerous sulfate dosimetry and this leads to an ultra-high deposition of energy of between 4.6 × 10 7 to 8.16 × 10 7 keV/μm. Fourth, filaments of variable length are produced by femtosecond pulses depending on the pulse duration as determined by a tissue-equivalent radiation polymer gel dosimeter and imaged by magnetic resonance imaging (MRI). These results reveal that one of the very interesting novelty of filamentation is the very low entrance dose, similar to proton irradiation. Lastly, filamentary irradiation results in the decomposition of thymidine in the absence and the presence of oxygen similar to the radiolysis of water.

Treatment of breast tumours frequently involves irradiating the whole breast to reach malignant microfoci scattered throughout the breast. In this study, we determined whether irradiation of normal tissues could increase the invasiveness of breast cancer cells in a mouse model.Non-irradiated MC7-L1 mouse mammary carcinoma cells were injected subcutaneously in irradiated and non-irradiated thighs of Balb/c mice. The invasion volume, tumour volume, blood vessel permeability and interstitial volumes were monitored by magnetic resonance imaging (MRI). Slices of normal tissue invaded by cancer cells were examined by histology. Activity of matrix metalloproteinase -2 and -9 (MMP -2 and -9) in healthy and irradiated tissues was determined, and the proliferation index of the invading cancer cells was evaluated.Three weeks after irradiation, enhancement of MC7-L1 cells invasiveness in irradiated thighs was already detected by MRI. The tumour invasion volume continued to extend 28- to 37-fold compared to the non-irradiated implantation site for the following three weeks, and it was associated with an increase of MMP-2 and -9 activities in healthy tissues. The interstitial volume associated with invading cancer cells was significantly larger in the pre-irradiated sites; while the blood vessels permeability was not altered. Cancer cells invading the healthy tissues were proliferating at a lower rate compared to non-invading cancer cells.Implantation of non-irradiated mammary cancer cells in previously irradiated normal tissue enhances the invasive capacity of the mammary cancer cells and is associated with an increased activity of MMP-2 and -9 in the irradiated normal tissue.

Some statistical properties of the distributions of dipolar coupling constants and their products are discussed in the context of nuclear magnetic resonance (NMR) of solids. Transformations of the distributions (absolute values and their logarithms) reveal new statistical properties. The ‘‘relative fluctuations’’ of the absolute value distributions, i.e., (second absolute central moment)1/2/(first absolute moment) are shown to scale as N+1/2, where N is the number of spins. The ratio (first absolute moment)/(most probable value) is shown to diverge as N+3/2. Products of the absolute values of dipolar coupling constants follow lognormal distributions in large spin networks. The relative fluctuations of these products also scale with N+1/2. Numerical studies of spin systems, with 10≤N≤105, in one‐, two‐, and three‐dimensional crystalline lattices support several of these results. Some implications for multiple quantum NMR spectroscopy are presented.

Pre-clinical bone cancer pain models mimicking the human condition are required to respond to clinical realities. Breast or prostate cancer patients coping with bone metastases experience intractable pain, which affects their quality of life. Advanced monitoring is thus required to clarify bone cancer pain mechanisms and refine treatments. In our model of rat femoral mammary carcinoma MRMT-1 cell implantation, pain onset and tumor growth were monitored for 21 days. The surgical procedure performed without arthrotomy allowed recording of incidental pain in free-moving rats. Along with the gradual development of mechanical allodynia and hyperalgesia, behavioral signs of ambulatory pain were detected at day 14 by using a dynamic weight-bearing apparatus. Osteopenia was revealed from day 14 concomitantly with disorganization of the trabecular architecture (µCT). Bone metastases were visualized as early as day 8 by MRI (T(1)-Gd-DTPA) before pain detection. PET (Na(18)F) co-registration revealed intra-osseous activity, as determined by anatomical superimposition over MRI in accordance with osteoclastic hyperactivity (TRAP staining). Pain and bone destruction were aggravated with time. Bone remodeling was accompanied by c-Fos (spinal) and ATF3 (DRG) neuronal activation, sustained by astrocyte (GFAP) and microglia (Iba1) reactivity in lumbar spinal cord. Our animal model demonstrates the importance of simultaneously recording pain and tumor progression and will allow us to better characterize therapeutic strategies in the future.

The stimulation of subsurface microbial metabolism often associated with engineered bioremediation of groundwater contaminants presents subsurface microorganisms, which are adapted for slow growth and metabolism in the subsurface, with new selective pressures. In order to better understand how Geobacter species might adapt to selective pressure for faster metal reduction in the subsurface, Geobacter sulfurreducens was put under selective pressure for rapid Fe(III) oxide reduction. The genomes of two resultant strains with rates of Fe(III) oxide reduction that were 10-fold higher than those of the parent strain were resequenced. Both strains contain either a single base-pair change or a 1 nucleotide insertion in a GEMM riboswitch upstream of GSU1761, a gene coding for the periplasmic c-type cytochrome designated PgcA. GSU1771, a gene coding for a SARP regulator, was also mutated in both strains. Introduction of either of the GEMM riboswitch mutations upstream of pgcA in the wild-type increased the abundance of pgcA transcripts, consistent with increased expression of pgcA in the adapted strains. One of the mutations doubled the rate of Fe(III) oxide reduction. Interruption of GSU1771 doubled the Fe(III) oxide reduction rate. This was associated with an increased in expression of pilA, the gene encoding the structural protein for the pili thought to function as microbial nanowires. The combination of the GSU1771 interruption with either of the pgcA mutations resulted in a strain that reduced Fe(III) as fast as the comparable adapted strain. These results suggest that the accumulation of a small number of beneficial mutations under selective pressure, similar to that potentially present during bioremediation, can greatly enhance the capacity for Fe(III) oxide reduction in G. sulfurreducens. Furthermore, the results emphasize the importance of the c-type cytochrome PgcA and pili in Fe(III) oxide reduction and demonstrate how adaptive evolution studies can aid in the elucidation of complex mechanisms, such as extracellular electron transfer.

Chunking of single movements into integrated sequences has been described during motor learning, and we have recently demonstrated that this process involves a dopamine-dependant mechanism in animal (Levesque et al. in Exp Brain Res 182:499-508, 2007; Tremblay et al. in Behav Brain Res 198:231-239, 2009). However, there is no such evidence in human. The aim of the present study was to assess this question in Parkinson's disease (PD), a neurological condition known for its dopamine depletion in the striatum. Eleven PD patients were tested under their usual levodopa medication (ON state), and following a 12-h levodopa withdrawal (OFF state). Patients were compared with 12 healthy participants on a motor learning sequencing task, requiring pressing fourteen buttons in the correct order, which was determined by visual stimuli presented on a computer screen. Learning was assessed from three blocks of 20 trials administered successively. Chunks of movements were intrinsically created by each participant during this learning period. Then, the sequence was shuffled according to the participant's own chunks, generating two new sequences, with either preserved or broken chunks. Those new motor sequences had to be performed separately in a fourth and fifth blocks of 20 trials. Results showed that execution time improved in every group during the learning period (from blocks 1 to 3). However, while motor chunking occurred in healthy controls and ON-PD patients, it did not in OFF-PD patients. In the shuffling conditions, a significant difference was seen between the preserved and the broken chunks conditions for both healthy participants and ON-PD patients, but not for OFF-PD patients. These results suggest that movement chunking during motor sequence learning is a dopamine-dependent process in human.

The precise role of maternal bacterial infection and inflammation occurring at the end of gestation is a controversial matter. Although it is recognized as an independent risk factor for neurodevelopmental diseases such as cerebral palsy, mental deficiency, and autism, it remains unclear whether it is causal or simply associated with the diseases. In this study, we demonstrate that IL-1 plays a key role in mediating severe placental damage and neurodevelopmental anomalies in offspring. Our results show that end of gestation exposure of pregnant rats to systemic microbial product (LPS) triggers placental inflammation and massive cell death, fetal mortality, and both forebrain white matter and motor behavioral alterations in the offspring. All these effects are alleviated by the coadministration of IL-1 receptor antagonist with LPS, suggesting a possible protective treatment against human placental and fetal brain damage.

In humans, sensory afferences are combined and integrated by the central nervous system (Ernst MO, Bülthoff HH (2004) Trends Cogn. Sci. 8: 162-169) and appear to provide a holistic representation of the environment. Empirical studies have repeatedly shown that vision dominates the other senses, especially for tasks with spatial demands. In contrast, it has also been observed that sound can strongly alter the perception of visual events. For example, when presented with 2 flashes and 1 beep in a very brief period of time, humans often report seeing 1 flash (i.e. fusion illusion, Andersen TS, Tiippana K, Sams M (2004) Brain Res. Cogn. Brain Res. 21: 301-308). However, it is not known how an unfolding movement modulates the contribution of vision to perception. Here, we used the audio-visual illusion to demonstrate that goal-directed movements can alter visual information processing in real-time. Specifically, the fusion illusion was linearly reduced as a function of limb velocity. These results suggest that cue combination and integration can be modulated in real-time by goal-directed behaviors; perhaps through sensory gating (Chapman CE, Beauchamp E (2006) J. Neurophysiol. 96: 1664-1675) and/or altered sensory noise (Ernst MO, Bülthoff HH (2004) Trends Cogn. Sci. 8: 162-169) during limb movements.

In this paper, we will cover the bonus-malus system in automobile insurance. Bonus-malus systems are based on the distribution of the number of car accidents. Therefore, the modelling and fitting of that distribution are considered. Fitting of data is done using the Poisson inverse Gaussian distribution, which shows a good fit. Building the bonus system is done by minimizing the insurer's risk, according to Lemaire's (1985) bonus system.

Studies investigating the specificity hypothesis have not always demonstrated that reliance on a specific source of feedback increases with practice. The goal of the present study was to address this inconsistency by having participants practice a throwing task with or without vision at incremental levels (10, 50, 100, or 200 acquisition trials). Following acquisition, all participants in the present experiment performed 10 trials in a no-vision transfer condition. Our results demonstrated that, given a sufficient number of acquisition trials, feedback reliance increased as a function of time engaged in practice. Our results also suggest that increased reliance on a specific source of feedback occurs only after the control strategy for a task is optimized.

Treatment of malignant glioma with chemotherapy is limited mostly because of delivery impediment related to the blood-brain barrier (BBB). One approach for transporting drugs across the BBB involves the activation of bradykinin-B2 receptors (BK-B2R). Our objective was to pharmacologically characterize the BBB permeability induced by the synthetic biostable BK-B2R analogue [Phe(8)psi(CH(2)NH)Arg(9)]-BK (R523) in F98 glioma-implanted Fischer rats. On day 10 post-inoculation, we detected the presence of B2R in the tumor cells and the peritumoral microvasculature (RT-PCR and immunohistochemistry). We assessed BBB permeability before and after the intracarotid (i.c.) infusion of R523 (0.1ml/min for 5min; 2.5, 10, and 50nmol/kg/min) using non-invasive dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with the different sized-contrast agents Gd-DTPA (0.5kDa) and Gadomer (17kDa) (0.25mmol/kg via the caudal vein). T(1)-weighted images were analyzed for the presence or absence of contrast enhancement within and surrounding the tumor area and mathematically processed to yield a contrast agent distribution volume (CADV), which was used as an indicator of vascular permeability. Our results showed that the agonist R523 increased, in a dose-dependent manner, the CADV indexes of Gd-DTPA and Gadomer, with a maximum 2-fold increase in brain uptake of both CA. The increase in CADV induced by R523 (10nmol/kg/min) was prevented by the B2R antagonist HOE140 (20nmol/kg/min, i.c.) and the nitric oxide synthase inhibitor L-NA (5mg/kg, i.v.) but not by the B1R antagonist R892 (20nmol/kg/min, i.c.) or the cyclooxygenase inhibitor Meclofenamate (5mg/kg, i.v.). The BBB permeabilizing effect of R523 (10nmol/kg/min) lasted for1h and was accompanied by a dose-related fall in arterial blood pressure. We concluded that R523 allows the extravasation of hydrophilic macromolecular agents (17kDa) into tumor tissues by inducing selective tumor BBB permeability via B2R- and NO-dependent mechanisms.

Objective Treatment of malignant gliomas is hampered by several factors, one of which is the blood-brain barrier (BBB). Thus, innovative strategies to cross the BBB have been developed, such as the BBB disruption procedure. Although it has been studied extensively, details regarding the physiology of the procedure remain obscure. This study was undertaken to clarify these issues. Methods Forty Wistar rats were imaged with a 7T animal magnetic resonance imaging scanner in dynamic acquisitions during BBB disruption. Gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) was injected to visualize and characterize the permeability of the BBB at different time points after disruption. The concentration of Gd-DTPA in the brain parenchyma was determined as a function of time after injection. Results A typical pattern of signal change as a function of time was observed in the treated hemisphere of all animals. Initially, a slight signal decrease was observed in T1-weighted images followed by a strong increase corresponding to the injection of Gd-DTPA. Two different mechanisms seemed responsible for the distribution of Gd-DTPA within the parenchyma: 1) a direct diffuse increase in capillary permeability, and 2) a diffusion process in the interstitial compartment. Initial results showed that the barrier opens immediately after the procedure and for at least 30 minutes. Conclusion The methodology described in this article allows monitoring of the dynamics of the BBB disruption process and characterization of its physiology in vivo, and represents a marked advantage over postmortem static studies.

The nervous system is extraordinarily complex and exposed to various trauma and degenerative diseases that remain difficult to treat. To facilitate its study, in vitro models were developed by culturing neurons and glial cells in monolayer cultures, or through organotypic cultures of brain or spinal cord slices. These in vitro models were, and are still very helpful for the advancement of neurosciences. However, they are for some studies, either overly simplified, or too complex. The application of tissue engineering to neurosciences offers a new and highly versatile approach to develop accurate models of the nervous system. These models can be engineered in three-dimensions while choosing for each individual component, cellular and molecular, that will compose it. The level of complexity of the model can be adjusted from the simplest to the more complete as needed. For example, through the use of a three-dimensional tissue-engineered model of the spinal cord, it was possible to reproduce the process of myelin sheath formation around motor neuron axons for the first time in vitro. This breakthrough shows the promising potential of tissue engineering in the development of powerful in vitro models of the nervous system. The combination of these models with the use of human adult neurons and glial cells obtained from the differentiation of neural precursor cells isolated from accessible tissues from patients (skin, fat, bone marrow), opens promising perspectives to better understand -neurodegenerative diseases.

Members of the Amt/Rh family of transporters are found almost ubiquitously in all forms of life. However, the molecular state of the substrate (NH(3) or NH(4)(+)) has been the subject of active debate. At least for bacterial Amt proteins, the model emerging from computational, X-ray crystal and mutational analysis is that NH(4)(+) is deprotonated at the exterior, conducted through the membrane as NH(3), and reprotonated at the cytoplasmic interface. A proton concomitantly is transferred from the exterior to the interior, although the mechanism is unclear. Here we discuss recent evidence indicating that an important function of at least some eukaryotic and bacterial Amts is to act as ammonium sensors and regulate cellular metabolism in response to changes in external ammonium concentrations. This is now well documented in the regulation of yeast pseudohyphal development and filamentous growth. As well, membrane sequestration of GlnK, a PII signal transduction protein, by AmtB has been shown to regulate nitrogenase in some diazotrophs, and nitrogen metabolism in some gram-positive bacteria. Formation of GlnK-AmtB membrane complexes might have other, as yet undiscovered, regulatory roles. This possibility is emphasized by the discovery in some genomes of genes for chimeric Amts with fusions to various regulatory elements.

In the photosynthetic bacterium Rhodobacter capsulatus, the post-translational regulation of the MoFe nitrogenase is deficient in a strain with a kanamycin insertion in amtB, a gene coding for an ammonium channel (Yakunin and Hallenbeck, 2002). GlnB and GlnK, two homologues of the PII protein, are also involved in this regulatory process since there is no nitrogenase switch-off in a glnB-/glnKdouble mutant strain (Drepper et al., 2003). Here, we have examined the effect of single mutations in either GlnB or GlnK on nitrogenase regulation. There was no nitrogenase switch-off in the glnB strain when subjected to the addition of 200 M NH4. When ADP-ribosylation of the Fe protein in response to a 50 mM NH4 addition was examined, only a moderate response after 80 min was noted for the glnB strain, whereas the wild-type strain showed appreciable Fe-protein modification after 40 min, and even more substantial modification after 80 min. Thus, GlnB appears necessary for nitrogenase switch-off and Fe-protein modification in R. capsulatus.

For women with early stage breast cancer, the primary tumour is removed by conservative surgery. However, malignant microfoci are often scattered in the breast. To eliminate these cells radiotherapy is designed to irradiate the whole breast. But the dose is not calculated to eliminate all residual cancer cells but rather to optimize long-term results with minimal complications to normal tissues such as fibrosis. These complications are mainly caused by the induction of an inflammation, associated with the upregulation of the cyclooxygenase-2 (COX-2). Furthermore the inhibition of COX-2 decreases matrix metalloproteinases (MMPs) expression, such as MMP-2 and MMP-9, both playing a central role in breast cancer cell invasion. The aim of this study is to further improve radiotherapy of breast cancer by preventing radiation-enhancement dermatitis and breast cancer cell invasion with the administration of NS-398, a COX-2 specific inhibitor. Female Balb/c mice were irradiated on a healthy thigh followed by the s.c. injection of MC7-L1 mammary cancer cells. NS-398 was injected i.p. before and after irradiation. Controls without irradiation and without cancer cells were also performed. For 3 and 6 weeks the degree of skin inflammation was scored and cancer cell invasion was monitored by contrast-enhanced magnetic resonance imaging. Tumors and surrounding tissues were subsequently removed and processed for histological analysis and zymography. We have shown that radiation actually enhances the invasiveness of breast cancer cells. MC7-L1 cells grown mainly under the skin in non irradiated thighs but invaded into the muscle fibers in irradiated thighs. These patterns were distinct 4 weeks after irradiation, but more pronounced on the 6th week. The calculated apparent invasion tumor volume was significantly greater in irradiated thighs. The activity of MMP-2 and -9 were enhanced in muscle and skin after irradiation. Our preliminary results with the COX-2 inhibitor NS-398 demonstrated an improvement of skin tolerance and a decrease of the invasion marker MMP-2 in the irradiated area. The NS-398 seemed also to reduce cancer cells proliferation and invasion. Our promising preliminary data showed that the NS-398, a specific COX-2 inhibitor, might improve the efficacy of radiotherapy for breast cancer by preventing radiation-induced dermatitis and radiation-enhancement of cancer cell invasion.

A series of Rhodobacter capsulatus AmtB variants were created and assessed for effects on ammonia transport, formation of AmtB-GlnK complexes, and regulation of nitrogenase activity and NifH ADP-ribosylation. Confirming previous reports, H193 and H342 were essential for ammonia transport and the replacement of aspartate 185 with glutamate reduced ammonia transport. Several amino acid residues, F131, D334, and D335, predicted to be critical for AmtB activity, are shown here for the first time by mutational analysis to be essential for transport. Alterations of the C-terminal tail reduced methylamine transport, prevented AmtB-GlnK complex formation, and abolished nitrogenase switch-off and NifH ADP-ribosylation. On the other hand, D185E, with a reduced level of transport, was capable of forming an ammonium-induced complex with GlnK and regulating nitrogenase. This reinforces the notions that ammonia transport is not sufficient for nitrogenase regulation and that formation of an AmtB-GlnK complex is necessary for these processes. However, some transport-incompetent AmtB variants, i.e., F131A, H193A, and H342A, form ammonium-induced complexes with GlnK but fail to properly regulate nitrogenase. These results show that formation of an AmtB-GlnK complex is insufficient in itself for nitrogenase regulation and suggest that partial ammonia transport or occupation of the pore by ammonia is essential for this function.

The encapsulation of molecules into nanocarriers is studied for its potential in delivering a high dose of anticancer drugs to a tumor, while minimizing side effects. Most systems either release their content in a non-specific manner or under specific environmental conditions such as temperature or pH. We have synthesized a novel class of photo-controllable polymer micelles that can stably encapsulate a hydrophilic compound and subsequently release it upon absorption of UV light. Here, we describe an in vitro magnetic resonance imaging assay that can evaluate the state of incorporation of a small Gd-based contrast agent. Our results indicate that the contrast agent alone can diffuse through a filter, but that the same agent incorporated into micelles cannot. After exposure to UV light, the micelles released the contrast agent, which could then diffuse through the filter.

Modification of 2'-deoxycytidine (dCyd) by hydroxyl radicals and direct ionization leads to the formation of various oxidation products, including dCyd 5,6-glycols, 5-hydroxy-2'-deoxycytidine, and ring fragmentation products. The mechanism of oxidation is complex and poorly understood. In the present work, we have prepared four cis- and trans-diastereomers of N'-(2-deoxy-β-D-erythro-pentofuranosyl)-I -carbamoyl-2-oxo-4,5-dihydroxyimidazolidine by bromination of dCyd followed by peroxidation of the resulting dCyd bromohydrins. The structure and stereochemistry of each product were determined by 'H NMR, 13 C NMR, and 2D NOE analyses. The formation of imidazolidine products involves rearrangement of initial 5(6)-hydroxy-6(5)-hydroperoxides to C6-C2 endoperoxides, which subsequently decompose by a concerted pathway to imidazolidine products. A remarkable feature of the four diastereomers was their ability to interconvert via single and successive cycles of ring-chain tautomerism at N1-C5 and N3-C4, leading to epimerization of C5 and C4, respectively. The rate of isomerization was greater for cis-diastereomers compared to trans-diastereomers, and the rate sharply increased with pH (pH 9.0 > 7.0 > 5.5).

Background Sex differences exist for many spatial tasks. This is true for circular vection, field dependence, and perception of veridical vertical with body tilt. However, explanations for these sex differences is lacking in the literature. In this study, we investigated the nature of individual differences in the perception of self-orientation in humans. Male and female participants were asked to identify their Morphological Horizon (i.e., line perpendicular to saggital plane at eye-level) in different body orientations relative to gravity (i.e., 45 deg and 135 deg body pitch) with and without prior whole body rotation. Results Sex explained the observed differences in the perception of self-orientation only when blood distribution was least altered (i.e., 45 deg body pitch) and without prior whole body rotation. Specifically, females presented a more footward bias than males in these conditions. Conclusion These results add to the literature on sex differences for spatial orientation tasks. As the differences were only observed with static conditions and when blood distribution was least affected, we concluded that sex differences in the perception of self-orientation are associated with gravireceptors (e.g., otoliths).

Two pathways for para -cresol ( p -cresol) degradation by anaerobic bacteria have been elucidated; one involves fumarate addition at the methyl group of p -cresol by a hydroxylbenzylsuccinate synthase protein while the other utilizes a methylhydroxylase protein (PCMH) to catalyze hydroxylation of the methyl group of p -cresol. In Geobacter metallireducens , in vitro enzymatic assays showed that p -cresol is degraded via the methylhydroxylation pathway. However, prior to this study these results had not been confirmed by genetic analyses. In this work, the gene coding for benzylsuccinate-CoA dehydrogenase ( bbsG ), an enzyme required for toluene degradation by G. metallireducens that is homologous to the p -hydroxybenzylsuccinyl-CoA dehydrogenase involved in p -cresol degradation by Desulfobacula toluolica Tol2 via fumarate addition, and the gene encoding the alpha prime subunit of PCMH ( pcmI ), were deleted to investigate the possibility of co-existing p -cresol degradation pathways in G. metallireducens . The absence of a functional PcmI protein, completely inhibited p -cresol degradation, while deletion of the bbsG gene had little impact. These results further support the observation that G . metallireducens utilizes a PCMH-initiated pathway for p -cresol degradation.

The specificity of practice hypothesis predicts the development of a sensorimotor representation specific to the afferent feedback available during skill acquisition (Proteau, 1992; Proteau, Marteniuk, Girouard, & Dugas, 1987). In the present investigation, we used the specificity of practice hypothesis to test whether skill acquisition through visual imagery would lead to the development of a sensory-specific movement representation similar to one resulting from actual practice. To accomplish this objective, participants practiced walking a 12-m linear path in one of three practice conditions, full-vision (FV), no-vision (NV), or visual imagery (VI), for either 10 or 100 trials. Knowledge of spatial and/or temporal results (KR) was provided to participants following each trial during this phase. Following acquisition, participants completed 10 NV trials without KR. An analysis of root-mean-squared-error (RMSE) indicated NV participants were more accurate than both FV and VI participants in the transfer condition. We believe the equivalence in transfer RMSE between FV and VI suggests that there are similarities between the movement representations attained by FV and VI practice.

The development of a new pharmacological strategy, the angiostatic therapy, to inhibit solid tumor progression has increased the need of powerful in vitro models to screen the angiostatic potential of new drug candidates. We produced an endothelialized reconstructed connective tissue (ERCT) that promotes the spontaneous formation of a human capillary-like network by coculture of human endothelial cells isolated from umbilical cord or from newborn foreskin, with dermal fibroblasts in a collagen sponge. Three inhibitors of angiogenesis, tamoxifen, ilomastat, and echistatin, were used to assess the efficiency of our ERCT to discriminate, in vitro, an angiostatic potential. The capillary-like structures were characterized by their immunoreactivity to human platelet-endothelial cellular adhesion molecule-1 antibodies and were quantified on histological cross-sections of biopsies taken after 10, 17, 24, and 31 days of culture. A dose-response significant inhibition of the capillary-like formation was detected when increasing concentrations of tamoxifen, ilomastat, or echistatin were added for 1 week to the culture medium of the ERCT. Tamoxifen was found to be angiogenic at 10 microM and to have a cytotoxic effect at 40 microM 1 week after drug removal. Echistatin induced a rapid, slight, and reversible inhibition of capillary-like formation, whereas ilomastat caused a very precocious, strong, and reversible inhibition of angiogenesis. In addition, a 16-h hypoxia promoted the formation of 10 times larger vessels (>300 microm(2)), compared with normoxic condition. These results suggest that our model could be efficiently used to study the long-term angiostatic potential of drugs in vitro in a very physiological environment.

There is a lack of data about the practice effect and test-retest reliability (TRR) on many attentional and executive tests in neuropsychology. In this study, 37 subjects aged 52 to 80 were tested three times with an inter-assessment interval of 14 days. The battery included the Rey Auditory Verbal Learning Test, the Stroop interference test, the Letter-Number Sequencing test, Wechsler Adult Intelligence Scale-III (WAIS-III), the Ruff 2 and 7 Selective Attention Test, the Tower of London, the Verbal Fluency test, and simple, choice, and sequential reaction time tests. The results showed that tasks were generally subject to a practice effect, except for those with alternate forms. In all tests, there were a number of scores demonstrating good TRR, but others, although largely used in clinical practice, failed to reach acceptable TRR standards. Usually, time derived scores were associated with the best TRR.

Over the last century, investigators have developed a number of models to explain the relation between speed and accuracy in target-directed manual aiming. The models vary in the extent to which they stress the importance of feedforward processes and the online use of sensory information (see D. Elliott, W. F. Helsen, & R. Chua, 2001, for a recent review). A common feature of those models is that the role of practice in optimizing speed, accuracy, and energy expenditure in goal-directed aiming is either ignored or minimized. The authors present a theoretical framework for understanding speed-accuracy tradeoffs that takes into account the strategic, trial-to-trial behavior of the performer. The strategic behavior enables individuals to maximize movement speed while minimizing error and energy expenditure.

Basic region-helix1-loop-helix2-leucine zipper (b/H 1 LH 2 /LZ) transcription factors bind specific DNA sequence in their target gene promoters as dimers. Max, a b/H 1 LH 2 /LZ transcription factor, is the obligate heterodimeric partner of the related b/H 1 LH 2 /LZ proteins of the Myc and Mad families. These heterodimers specifically bind E-box DNA sequence (CA CG TG) to activate (e.g. c-Myc/Max) and repress (e.g. Mad1/Max) transcription. Max can also homodimerize and bind E-box sequences in c-Myc target gene promoters. While the X-ray structure of the Max b/H 1 LH 2 /LZ/DNA complex and that of others have been reported, the precise sequence of events leading to the reversible and specific binding of these important transcription factors is still largely unknown. In order to provide insights into the DNA binding mechanism, we have solved the NMR solution structure of a covalently homodimerized version of a Max b/H 1 LH 2 /LZ protein with two stabilizing mutations in the LZ, and characterized its backbone dynamics from 15 N spin-relaxation measurements in the absence of DNA. Apart from minor differences in the pitch of the LZ, possibly resulting from the mutations in the construct, we observe that the packing of the helices in the H 1 LH 2 domain is almost identical to that of the two crystal structures, indicating that no important conformational change in these helices occurs upon DNA binding. Conversely to the crystal structures of the DNA complexes, the first 14 residues of the basic region are found to be mostly unfolded while the loop is observed to be flexible. This indicates that these domains undergo conformational changes upon DNA binding. On the other hand, we find the last four residues of the basic region form a persistent helical turn contiguous to H 1 . In addition, we provide evidence of the existence of internal motions in the backbone of H 1 that are of larger amplitude and longer time-scale (nanoseconds) than the ones in the H 2 and LZ domain. Most interestingly, we note that conformers in the ensemble of calculated structures have highly conserved basic residues (located in the persistent helical turn of the basic region and in the loop) known to be important for specific binding in a conformation that matches that of the DNA-bound state. These partially prefolded conformers can directly fit into the major groove of DNA and as such are proposed to lie on the pathway leading to the reversible and specific DNA binding. In these conformers, the conserved basic side-chains form a cluster that elevates the local electrostatic potential and could provide the necessary driving force for the generation of the internal motions localized in the H 1 and therefore link structural determinants with the DNA binding function. Overall, our results suggests that the Max homodimeric b/H 1 LH 2 /LZ can rapidly and preferentially bind DNA sequence through transient and partially prefolded states and subsequently, adopt the fully helical bound state in a DNA-assisted mechanism or induced-fit.

With their eyes initially on either the home, midline, or final end position, 30 participants practiced a 2-target aiming movement. After 120 acquisition trials, participants performed a retention test and were then transferred to each of the other 2 eye conditions. During acquisition, all groups improved over practice, but the home group showed the greatest improvement. The temporal improvement was most pronounced in the times spent after peak velocity. Retention and transfer tests indicated that participants performed best under eye-movement conditions that were the same as the 1 they had practiced in. There was also positive transfer of training between conditions in which the oculomotor information was similar. Thus, to optimize learning, one should practice under the same afferent and oculomotor conditions that will be required for the final performance.

The present experiment was conducted to explore the effect of practice on the one-target advantage in manual aiming, as well as asymmetries in intermanual transfer of training. Reaction and movement times for the first movement were longer in the 2-target than in the 1-target task, regardless of the amount of practice, hand preference and practice hand. When two movements were required, peak velocity was lower and, proportionally, more time was spent after peak velocity. Our kinematic results suggest that the one-target advantage is related to both predefined strategies as well as movement implementation processes during execution. Therefore, an integration of advance planning and on-line explanations for the one-target advantage is suggested. Regarding manual asymmetries, right-handers showed more transfer of training from the left to the right hand than vice versa. Left-handers exhibited a reversed pattern of asymmetric transfer of training to right-handers, but they were more disadvantaged using their non-dominant hand. These latter two findings have implications for models of manual asymmetry and upper limb control.

Objective To evaluate the safety and efficacy of long-term intraarticular (IA) steroid injections for knee pain related to osteoarthritis (OA). Methods In a randomized, double-blind trial, 68 patients with OA of the knee received IA injections of triamcinolone acetonide 40 mg (34 patients) or saline (34 patients) into the study knee every 3 months for up to 2 years. The primary outcome variable was radiologic progression of joint space narrowing of the injected knee after 2 years. Measurements of minimum joint space width were performed by an automated computerized method on standardized fluoroscopically guided radiographs taken with the patient standing and with the knee in a semiflexed position. The clinical efficacy measure of primary interest was the pain subscale from the Western Ontario and McMaster Universities OA Index (WOMAC). Efficacy measures of secondary interest were the total score on the WOMAC, physician's global assessment, patient's global assessment, patient's assessment of pain, range of motion (ROM) of the affected knee, and 50-foot walking time. Clinical symptoms were assessed just before each injection. Results At the 1-year and 2-year followup evaluations, no difference was noted between the two treatment groups with respect to loss of joint space over time. The steroid-injected knees showed a trend toward greater symptom improvement, especially at 1 year, for the WOMAC pain subscale, night pain, and ROM values (P = 0.05) compared with the saline-injected knees. Using area under the curve analyses, knee pain and stiffness were significantly improved throughout the 2-year study by repeated injections of triamcinolone acetonide, but not saline (P < 0.05). Conclusion Our findings support the long-term safety of IA steroid injections for patients with symptomatic knee OA. No deleterious effects of the long-term administration of IA steroids on the anatomical structure of the knee were noted. Moreover, long-term treatment of knee OA with repeated steroid injections appears to be clinically effective for the relief of symptoms of the disease.

Participants made perceptual judgments about the length of, and manual aiming movements to the opposite end of, formerly visible Muller-Lyer stimuli. The Muller-Lyer illusion affected both perceptual judgments and aiming amplitude. Manipulations of stimulus duration (10 ms or 3,000 ms) and memory delay length (10 ms or 3,000 ms) had no impact on the illusory effect. Aiming movements executed with vision of the hand were less affected by the illusion than movements executed without vision of the hand. The effect of the illusion on aiming amplitude remained the same between peak velocity and the end of the movement even though participants were engaged in on-line control between peak deceleration and the end of the movement. This latter finding was counter to the predictions of a hypothesis (Glover 2002) stating that illusions should only affect the early (planning) stages of movement and not the late (control) stages of movement. We conclude that a single visual representation is used for perception, motor planning, and motor control.

A simple method based on diffuse reflectance coupled with infrared Fourier transform spectroscopy (DRIFTS) has been developed for the quantification and the characterization of sedimentary (or soil, peat, etc.) humic substances. Under optimized conditions, the quantification of humic substances or total organic matter is possible with DRIFTS at a frequency of 2930 cm(-1) using whole dry sediment samples. A study of the operational parameters that affect the DRIFTS signal shows the importance of normalizing analysis conditions, especially the diffuse reflectance accessory alignment, the particle size and compaction, and the homogeneity of the powdered samples, to obtain reproducible quantitative analyses. The quantification of total humic substances by DRIFTS correlates well with the concentrations determined using classical extraction methods. DRIFTS analysis requires only a few minutes instead of tedious extractions of humic substances. Moreover, the distribution of total organic matter and of fulvic acids, humic acids, and humin can also be obtained. Analysis of natural samples indicates that a calibration using humic material representative of the studied area provides the most accurate quantification. The fast screening of organic matter fractions by DRIFTS on intact natural samples provides useful quantitative and qualitative information that can be used in environmental or monitoring studies.

Introduction La barriere hemato-encephalique (BHE) de par sa presence limite l’acheminement d’agents therapeutiques au systeme nerveux central (SNC). La presence de pompes a efflux au niveau de la BHE constitue un important mecanisme d’exclusion d’agents lipophiles tentant t’atteindre le SNC. La glycoproteine-P (p-gp), l’une de ses pompes a efflux, est exprimee a la BHE et par les cellules tumorales et a pour substrats plusieurs agents de chimiotherapie. Il a ete demontre que l’ouverture osmotique de la BHE (OBHE) est efficace pour acheminer des agents n’etant pas des substrats de la PGP. Cependant, il n’a pas ete demontre que l’OBHE permet d’augmenter egalement l’acheminement d’agents antineoplasiques substrats de la PGP. Cette etude a ete mise sur pied afin de determiner si l’OBHE permet d’augmenter l’acheminement de substrats de la PGP. Materiels et methode Trois groupes d’animaux etaient a l’etude : 1 : OBHE, 2 : temoin positif (Tariquidar, inhibiteur specifique de la PGP), 3 : radiotraceur seul, a raison de 6 animaux par groupe. Le 11C-carvedilol, substrat de la PGP, a ete administre durant la 1re minute de l’acquisition par tomographie d’emission par positrons. La captation du 11C-carvedilol a ete calculee pour deux regions d’interets : le volume tumoral et un volume equivalent dans l’hemisphere controlateral. Resultats Aucune difference significative n’a ete observee pour les courbes temps–activite dans l’hemisphere controlateral pour tous les groupes etudies. Il n’y a que dans le groupe 2 que la captation du 11C-carvedilol est augmentee au niveau de la tumeur. Ces resultats suggerent que l’OBHE n’affecte pas l’activite de la PGP. Conclusion Si ces resultats se confirment, la procedure d’OBHE ne serait pas utile lorsque son utilisation est combinee a l’administration d’agents therapeutiques substrats de les p-gp.