Atlasing the frontal lobe connections and their variability due to age and education: a spherical deconvolution tractography study.

In neuroscience, there is a growing consensus that higher cognitive functions may be supported by distributed networks involving different cerebral regions, rather than by single brain areas. Communication within these networks is mediated by white matter tracts and is particularly prominent in the frontal lobes for the control and integration of information. However, the detailed mapping of frontal connections remains incomplete, albeit crucial to an increased understanding of these cognitive functions. Based on 47 high-resolution diffusion-weighted imaging datasets (age range 22-71 years), we built a statistical normative atlas of the frontal lobe connections in stereotaxic space, using state-of-the-art spherical deconvolution tractography. We dissected 55 tracts including U-shaped fibers. We further characterized these tracts by measuring their correlation with age and education level. We reported age-related differences in the microstructural organization of several, specific frontal fiber tracts, but found no correlation with education level. Future voxel-based analyses, such as voxel-based morphometry or tract-based spatial statistics studies, may benefit from our atlas by identifying the tracts and networks involved in frontal functions. Our atlas will also build the capacity of clinicians to further understand the mechanisms involved in brain recovery and plasticity, as well as assist clinicians in the diagnosis of disconnection or abnormality within specific tracts of individual patients with various brain diseases.

Connectivity between right inferior frontal gyrus and supplementary motor area predicts after-effects of right frontal cathodal tDCS on picture naming speed.

BACKGROUND: Cathodal transcranial direct current stimulation (tDCS) of the right frontal cortex improves language abilities in post-stroke aphasic patients. Yet little is known about the effects of right frontal cathodal tDCS on normal language function. OBJECTIVE/HYPOTHESIS: To explore the cathodal tDCS effects of the right-hemispheric homologue of Broca's area on picture naming in healthy individuals. We hypothesized that cathodal tDCS improves picture naming and that this effect is determined by the anatomical and functional connectivity of the targeted region. METHODS: Cathodal and sham tDCS were applied to the right inferior frontal gyrus in 24 healthy subjects before a picture-naming task. All participants were studied with magnetic resonance imaging at pre-interventional baseline. Probabilistic tractography and dynamic causal modeling of functional brain activity during a word repetition task were applied to characterize anatomical and functional connectivity. RESULTS: Subjects named pictures faster after cathodal relative to sham tDCS. The accelerating effect of tDCS was explained by a reduced frequency of very slow responses. tDCS-induced acceleration of picture naming correlated with larger volumes of the tract connecting the right Broca's area and the supplementary motor area (SMA) and greater functional coupling from the right SMA to the right Broca's area. CONCLUSIONS: The results support the notion that the after-effects of tDCS on brain function are at least in part determined by the anatomical and functional connectivity of the targeted region.

Evaluation of a French ELISA for the detection of Salmonella Enteritidis and Salmonella Typhimurium in flocks of laying and breeding hens.

In France, the regular and compulsory detection of Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) in flocks of breeding and laying hens is based on bacteriological examination of environmental swabs and faeces samples. The aim of this study was to compare this bacteriological examination with a serological method (ELISA) developed in our laboratory. This ELISA was first evaluated by use of artificially infected hens. During these experimental infection studies, several groups of hens were inoculated with SE, ST, different vaccines and different Salmonella serovars to calculate the experimental parameters of our ELISA. Then, in a field study, 43 flocks were followed monthly using two bacteriological samples (environmental swab and pool of faeces) and 20 serological samples (sera or yolks). Twenty-seven flocks without SE or ST gave a negative serological response throughout their surveillance. Among the 10 various serovars different from SE and ST isolated in this study, S. Heidelberg, S. Agona and S. Hadar gave seropositive results in seven flocks. Consequently, this ELISA was not specific of SE and ST as it detected serovars sharing or not common antigens with SE and ST. Seropositive results were also obtained each month for two flocks where no Salmonella could be isolated. Finally, in seven flocks found infected with SE or ST, the positive ELISA results appeared later than the bacteriological detection. Therefore, for the detection of chicken flocks recently infected with SE or ST, bacteriological examination currently used in France seems to be more appropriate than this ELISA.

Use of avilamycin for growth promotion and avilamycin-resistance among Enterococcus faecium from broilers in a matched case-control study in France.

We assessed the putative link between avilamycin-resistant Enterococcus faecium carriage and avilamycin consumption in broilers. As part of the French programme of monitoring for antimicrobial resistance, broilers sampled at slaughterhouse in 1999 and 2000 and carrying avilamycin-resistant E. faecium were matched by slaughterhouse, slaughter month and production type (free-range, standard, light) with control broilers carrying avilamycin-susceptible strains. History of antibiotics consumption (either for growth promotion or therapeutic purpose) in the broiler flocks sampled was collected from the monitoring programme and consumption of each antibiotic class was screened as a potential risk factor. Avilamycin was a risk factor for avilamycin-resistant E. faecium carriage: OR=2.3.

Potentials of radio-frequency field gradient NMR microscopy in environmental science.

An understanding of transport, flow, diffusivity and mass transfer processes is of central importance in many fields of environmental biotechnology such as biofilm, bioreactor and membrane engineering, soil and groundwater bioremediation, and wastewater treatment. Owing to its remarkable sensitivity to molecular displacements and to its noninvasive and nondestructive character, pulsed field gradient (PFG) nuclear magnetic resonance (NMR) can be a valuable tool for investigating such processes. In conventional NMR microscopy, spatial encoding is achieved by using static magnetic field gradients (B0 gradients). However, an interesting alternative is to use radio-frequency magnetic field gradients (RF or B1 gradients). Although the latter are less versatile than the former, RF field gradient microscopy is particularly suitable for dealing with heterogeneous systems such as porous media because of its quasi-immunity to background static magnetic field gradients arising from magnetic susceptibility inhomogeneities, unlike the B0 gradients microscopy. Here, we present an overview of basic principles and the main features of this technique, which is still relatively unused. Different examples of diffusion imaging illustrate the potentialities of the method in both micro-imaging and the measurement of global or local diffusion coefficients within membranes and at liquid-solid interfaces. These examples suggest that a number of environmental problems could benefit from this technique. Different future prospects of application of B1 gradient NMR microscopy in environmental biotechnology are considered.

Potentials of radio-frequency field gradient NMR microscopy in environmental science.

An understanding of transport, flow, diffusivity and mass transfer processes is of central importance in many fields of environmental biotechnology such as biofilm, bioreactor and membrane engineering, soil and groundwater bioremediation, and wastewater treatment. Owing to its remarkable sensitivity to molecular displacements and to its noninvasive and nondestructive character, pulsed field gradient (PFG) nuclear magnetic resonance (NMR) can be a valuable tool for investigating such processes. In conventional NMR microscopy, spatial encoding is achieved by using static magnetic field gradients (B(0) gradients). However, an interesting alternative is to use radio-frequency magnetic field gradients (RF or B(1) gradients). Although the latter are less versatile than the former, RF field gradient microscopy is particularly suitable for dealing with heterogeneous systems such as porous media because of its quasi-immunity to background static magnetic field gradients arising from magnetic susceptibility inhomogeneities, unlike the B(0) gradients microscopy. Here, we present an overview of basic principles and the main features of this technique, which is still relatively unused. Different examples of diffusion imaging illustrate the potentialities of the method in both micro-imaging and the measurement of global or local diffusion coefficients within membranes and at liquid-solid interfaces. These examples suggest that a number of environmental problems could benefit from this technique. Different future prospects of application of B(1) gradient NMR microscopy in environmental biotechnology are considered.

Characterization of fibrosurfin, an interfibrillar component of sea urchin catch connective tissues.

The Sea URchin Fibrillar (SURF) domain is a four-cysteine module present in the amino-propeptide of the sea urchin 2alpha fibrillar collagen chain. Despite numerous international genome and expressed sequence tag projects, computer searches have so far failed to identify similar domains in other species. Here, we have characterized a new sea urchin protein of 2656 amino acids made up of a series of epidermal growth factor-like and SURF modules. From its striking similarity to the modular organization of fibropellins, we called this new protein fibrosurfin. This protein is acidic with a calculated pI of 4.12. Eleven of the 17 epidermal growth factor-like domains correspond to the consensus sequence of calcium-binding type. By Western blot and immunofluorescence analyses, this protein is not detectable during embryogenesis. In adult tissues, fibrosurfin is co-localized with the amino-propeptide of the 2alpha fibrillar collagen chain in several collagenous ligaments, i.e., test sutures, spine ligaments, peristomial membrane, and to a lesser extent, tube feet. Finally, immunogold labeling indicates that fibrosurfin is an interfibrillar component of collagenous tissues. Taken together, the data suggest that proteins possessing SURF modules are localized in the vicinity of mineralized tissues and could be responsible for the unique properties of sea urchin mutable collagenous tissues.

Development of a complete ELISA using Salmonella lipopolysaccharides of various serogroups allowing to detect all infected pigs.

Although poultry is recognized as the major source of food-poisoning caused by Salmonella, pork also contributes to human infections. This study was therefore undertaken in order to develop a reliable serological method for the evaluation of the Salmonella status of piglets. A complete ELISA was performed using lipopolysaccharides of Salmonella Typhimurium, Anatum, Hadar and Infantis because these serovars were representative of the serogroups isolated from 30 contaminated fattening farms. S. Enteritidis was also added because of its importance in human infection and to include the O:9 antigen. This method potentially detects 100% of infected pigs. A significant correlation was found between this serological method and the bacteriological data from mesenteric lymph nodes (p = 0.01). In addition, both sensitivity and specificity were high (97% and 94% respectively). The ELISA test was therefore used in a cross-sectional study on 4 farms to evaluate when pigs became contaminated: seropositive pigs were only found for the 20 week old finishing pigs. The antibody response to Salmonella in piglets was also investigated: maternal antibodies persisted until 7 weeks of age and post-Salmonella contamination seroconversion was detected from 8 weeks of age onwards.

Changes in culturability and virulence of Salmonella typhimurium during long-term starvation under desiccating conditions.

The survival of Salmonella typhimurium under desiccation and starvation conditions commonly associated with farm buildings was investigated in a desiccation model system: filtration onto polycarbonate membranes placed in a sealed desiccator with 0.0067 g/m3 absolute humidity. Heterogeneities within bacterial populations in relation to time of desiccation were investigated on a single-cell basis by epifluorescence microscopy coupled with an image analysis system in conjunction with fluorescent dyes Chemchrome V6 and DAPI. Changes in cellular states were compared to the results of plate counts (colony forming units, CFU) on selective (modified semi-solid Rappaport Vassiliadis (MSRV)) and non-selective (nutrient agar (NA) and R2A agar) media, and to the measurements of infectivity and virulence using two animal models (chicks and mice). During 9 weeks of experimental desiccation, total cell counts (DAPI) of starved S. typhimurium remained stable, as did esterase activity (Chemchrome V6), but DAPI fluorescence intensity decreased slowly. Bacterial cells entered gradually into non-culturable states (decrease of CFU counts on MSRV, NA and R2A agar media) and the total loss of culturability on NA (defined as probability of presence of 1 CFU on the membrane inferior to 10 (-6)) was obtained after 9 weeks. Loss of chick infectivity and mice virulence in animal models occurred more rapidly, within three weeks of experimental desiccation.

Some safety aspects of Salmonella vaccines for poultry: in vivo study of the genetic stability of three Salmonella typhimurium live vaccines.

Live vaccine strains of Salmonella should be avirulent, immunogenic and genetically stable. Some isolates of three commercially available live vaccine strains of Salmonella typhimurium, sampled during a study on their persistence in a vaccinated flock of chickens, were analyzed for genetic stability using macrorestriction analysis of their genome. Two out of the three vaccine strains showed genetic instabilities. Two of the 51 isolates of Zoosaloral vaccine strain and nine of the 32 analyzed isolates of chi(3985), a genetically modified organism, were variants and showed different macrorestriction profiles.

Some safety aspects of salmonella vaccines for poultry: distribution and persistence of three Salmonella typhimurium live vaccines.

The purpose of this study was to analyze the safety characteristics of three commercially available live Salmonella vaccine strains (vacT, Zoosaloral, and X3985) in relation to their persistence in individual animals but also within a flock and in the environment. In a first experiment, the digestive and systemic distributions in chickens were followed for 10 days in individually reared chickens that were orally inoculated at 1 day of age. Strain X3985 quickly disappeared from the digestive tract but remained in the liver until the end of this experiment, whereas strains vacT and Zoosaloral colonized the liver as well as the gut for 10 days. In the second trial, behavior of the vaccine strains was studied in groups of 20 chickens during 10 wk after a single oral administration to individual birds. Strain vacT remained in the environment of inoculated animals for 4-5 wk. Six weeks after the inoculation, vacT was not recovered from internal organs such as liver and spleen, and vacT disappeared from the digestive tract between the sixth and the 10th weeks. Comparatively, both Zoosaloral and X3985 vaccine strains persisted longer in the environment (8 wk at least). Of the vaccine strains, X3985 showed the greatest colonization of both systemic and digestive organs.

Maps of self-diffusion coefficients by radiofrequency field gradient NMR microscopy

The methods of measurement of spatially resolved diffusion coefficients using radiofrequency field gradient (E. Mischler et al., J. Magn. Reson. B 106, 32, 1995; R. Kimmich et al., J. Magn. Reson. A 112, 7, 1995) produce 1D profiles whose amplitude is not only a function of the local self-diffusion coefficient but also is modulated by cosine functions of spatial coordinates. Due to this modulation diffusion-weighted images cannot be obtained unless cumbersome data processing is used. Here, we present a new sequence which avoids this modulation and yields in a straightforward manner true self-diffusion coefficient maps; this is in contrast with conventional methods which use static field gradients and which are therefore altered by background gradients. The feasibility and the reliability of the method are demonstrated with phantoms; it is also applied to different systems of interest such as solvent swelled rubber, membranes, and plants. Copyright 1999 Academic Press.

Nuclear longitudinal relaxation time images by radiofrequency field gradients.

Combination of the Super Fast Inversion Recovery (SUFIR) method (D. Canet, J. Brondeau, and K. Elbayed, J. Magn. Reson. 77, 483 (1988)) and imaging procedures by radiofrequency field gradients (P. Maffei, P. Mutzenhardt, A. Retournard, B. Diter, R. Raulet, J. Brondeau, and D. Canet, J. Magn. Reson. A 107, 40 (1994)) provides spatially resolved maps of longitudinal relaxation times (T1). In addition to accurate T1 values, enhanced spatial resolution is obtained.

Measurement of the residual contamination of post-weaning facilities for pigs and related risk factors.

A survey was designed in France to assess residual contamination in post-weaning rooms within the 2 h prior to restocking when all the pigs of the previous batch had been removed (all in-all out) and after application of the 'in use' cleaning procedures. The protocol was based on the results of a pilot study and was considered 'a good compromise'. Special agar plates (Rodac plates) with a prominent agar medium surface were prepared and used to collect the bacteria. They were applied by impression onto the floors and the partitions between the pens. In all, 24 plates were applied per room. The culture medium was VRBG which mainly permits the growth of enterobacteria. The plates were incubated for 24 h (37 degrees C) and the Colony-Forming Units (CFU) counted. After sampling, measurements were made and information collected from the farmer to obtain potential explanations for the resulting microbiological data. The same scientist sampled 129 post-weaning rooms with slatted floors. Of the 3045 plates, 18.4% were negative and 12.8% were heavily colonized (> 300 CFU). A score combining six criteria based on the counts was produced, and indicated a wide spread of the rooms. The profile of circumstances associated with the different levels of the score was extracted. The following points should be respected to achieve low residual contamination: removal of the slurry from the pit below the slatted floor; damping to be started soon after pig removal; prolonged damping; thorough washing; disinfecting soon after washing; and attention to the recommended dosage of disinfectant. Smooth surfaces were found to be less contaminated than rough ones. It is concluded that cleaning and disinfecting operations must not be considered as minor tasks and should clearly be integrated into the process of pig production.

Diffusion measurements using radiofrequency field gradient: artifacts, remedies, practical hints

The two major advantages of experiments carried out with radiofrequency (RF) field-gradient NMR are the instrumental simplicity and the insensitivity to background static magnetic field gradients. These features combined with large RF gradients, which became available only recently, should make this technique especially attractive for molecular translational diffusion studies. However, a critical evaluation of the method shows that under some circumstances (small and/or heterogeneous samples, weak diffusion coefficients, very short relaxation times) the quality of measurements may be affected by a number of artifacts. Their origin has been investigated and several remedies have been considered; in particular, a new improved sequence is presented. The success of various experimental tests demonstrates the efficiency of the proposed solutions which thus open the way to much wider application fields. Copyright 1998 Academic Press.

Development of a new culture medium for the rapid detection of Salmonella by indirect conductance measurements.

The main difficulties in conductance medium development are to allow Salmonella to grow and produce a conductance signal while impeding growth of related species such as Escherichia coli and Citrobacter freundii. Various selective agents were screened for these capacities and a new medium was derived, named KIMAN (Whitley Impedance Broth basal medium supplemented with three selective components: novobiocin, malachite green and potassium iodide). This medium supported the growth of Salmonella serotypes and inhibited non-salmonella strains in pure cultures.

Self-Diffusion Measurements by Carbon-13 NMR Using Radiofrequency Field Gradients

This paper demonstrates the feasibility of self-diffusion measurements by radiofrequency field gradients with equipment tuned to the carbon-13 resonance frequency (i.e., 50 MHz for a field of 4.7 T). For the first time, self-diffusion coefficients of carbon disulfide and carbon tetrachloride are measured by NMR. The agreement with results from tracer methods is excellent. Copyright 1998 Academic Press. Copyright 1998 Academic Press

Vaccination du pigeon contre Salmonella typhimurium.

Les salmonclles constituent l'une des preoccupations majeures des eleveurs de pigeons. Aussi, afin de diminuer le portage et d'assurer la protection des animaux ainsi que celle des consommateurs, des moyens de detection et de prevention doivent etre developpes. Dans ce cadre, il a ete mis au point une technique ELISA pour detecter les anticorps anti-Salmonella typhimurium chez des pigeons recevant un autovaccin. Le vaccin a entraine une protection de 85% des pigeons vaccines a 7 et 11 semaines et de 50% des sujets vaccines a 11 semaines, alors que les temoins non vaccines sont tous morts apres l'epreuve a 13 semaines. La vaccination n'exclut pas le portage ni l'excretion.

A selective medium for the rapid detection by an impedance technique of Pseudomonas spp. associated with poultry meat.

A new medium for detecting and enumerating Pseudomonas spp. associated with poultry meat spoilage by a rapid impedance technique was developed, after testing potential growth promoters for eight Pseudomonas strains and inhibitors against eight competing strains (Enterobacteriaceae) able to grow on the medium of Mead and Adams (1977). Four basal media (brain heart infusion, brucella broth, Shaedler broth and Whitley impedance broth (WIB)) and a synthetic medium were evaluated. Whitley impedance broth was the best basal medium for detecting variations in impedance in relation to Pseudomonas growth. The efficiency of WIB was improved by adding compounds which enhanced the growth of Pseudomonas on the synthetic medium. Among the incubation temperatures tested, 22 degrees C proved to be the best compromise between growth of Pseudomonas associated with poultry meat spoilage and inhibition of competitors. Among the 15 inhibitory substances evaluated against Pseudomonas competitors, five were chosen for inclusion in the final medium: metronidazole, carbenicilline, cetrimide, cycloheximide and diamide (MCCCD medium). Preliminary results obtained from experiments with beef and pork meat showed that this medium could also be used without diamide and at an incubation temperature of 25 degrees C. The impedance technique using MCCCD medium was then compared with an official method which uses the medium of Mead and Adams (1977) on 106 samples of poultry neck skin. The linear regression coefficient between the two techniques was approximately r = 0.85. Impedance was able to detect 10(3) Pseudomonas g-1 within less than 19 h making it a promising technique for predicting poultry meat spoilage.

Bacteriological monitoring of Salmonella enteritidis carrier birds after decontamination using enrofloxacin, competitive exclusion and movement of birds.

Two hundred and forty, four-week-old laying birds naturally infected with Salmonella enteritidis PT33 (Pasteur Institute phage typing system) were randomly divided twice (before and during the treatments) to obtain four separately housed groups of 60 birds and to study the efficacy of three decontamination treatments: enrofloxacin either with or without the movement of birds to a clean area, and enrofloxacin combined with movement of birds and a competitive exclusion treatment. The control group remained untreated. In each group contamination with S enteritidis was checked bacteriologically, every week from two months before until two months after the treatments began. All the samples taken from all the birds before the treatments began were S enteritidis-positive. After the treatments it was not possible to isolate salmonella either from the environment or from the faeces of the three treated groups. All the birds were humanely sacrificed at 22 weeks of age and samples of liver, spleen, ovaries and caeca were analysed for the presence of salmonella. The results demonstrated that although antibiotic therapy, the movement of birds into a clean house and competitive exclusion, either combined or not, had some efficacy in reducing infection levels, it was not possible to decontaminate all the birds completely.