Morphological changes in tight junctions of Necturus maculosus proximal tubules undergoing saline diuresis.

Tight junctions between epithelial cells are believed to control the paracellular diffusion of substances across epithelia. Epithelia in which tight junctions are poorly developed display a higher paracellular electrical conductance, while those with extensive tight junctions show lower conductance values. We described here a particular epithelium, that of the proximal tubules of the Necturus kidney, in which the development of the tight junctions varies in parallel with a change of paracellular electrical conductance. In control conditions, tight junctions between epithelial cells of the proximal tubules are more developed than in tubules undergoing saline diuresis, a situation which increases the conductance across the paracellular shunt pathway.

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.

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.

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.

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.

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.

Use of a competitive exclusion product (Broilact) to prevent Salmonella colonization of newly hatched chicks.

The study described here was carried out at the request of a French company to utilize the authors' experience of 'competitive exclusion' treatment for poultry. The objective of the study was to determinate the safety and efficacy of a particular treatment product (Broilact) in protecting chicks against Salmonella infection.

Evaluation of a new enrichment broth for the isolation of Salmonella spp. from poultry products.

Four selective enrichment broths were compared for the detection of Salmonella spp. in naturally contaminated poultry products and the recovery of atypical Salmonella strains in suspensions of pure cultures. In analysis of 100 poultry samples, the sensitivities observed were 94.0% for Müller-Kauffmann Tetrathionate-Brilliant Green (MKTBG), 97.6% for Rappaport Vassiliadis (RV), 42.2% for Selenite Cystine (SC) and 97.6% for the new broth KIMAN (Whitley Impedance Broth supplemented with 20 mg/l of novobiocin sodium salt, 10 mg/l of malachite green oxalate and 40 g/l of potassium iodide). The two most efficient broths--RV and KIMAN for recovery of atypical Salmonella strains (gallinarum biotypes gallinarum and pullorum, typhi, paratyphi A) were less toxic than MKTBG but more toxic than s.c. broth. According to these results, the use of RV and KIMAN could be a good combination to assure maximal recovery of Salmonella strains.

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.

Rapid identification of Salmonella from poultry meat products by using 'Mucap Test'.

A study was made in order to improve a new Salmonella identification test (Mucap Test) in which umbelliferone is released, giving a blue fluorescent light under a Wood lamp, after contact with Salmonella colonies. The study concerned 354 colonies, previously isolated from 55 poultry meat samples. Two enrichment media [Tetrathionate Bile Broth (TBB) and Rappaport Vassiliadis (RV)] and two isolation media [Brilliant Green Agar (BGA) and Desoxycholate Agar (DA)] were used, and the results of the test obtained respectively with each association were compared. The sensitivity was consistently good, but the specificity of the test was generally poor. The best association seemed to be RV/DA which gave 85% specificity, against 39% for TBB/BGA, 58% for TBB/DA, and 77% for RV/BGA. The predominant genera responsible for false-positive results were Pseudomonas and Proteus Providencia.

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.

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.

[The risk of transmission of salmonellae in poultry farming: detection and prevention in Europe]. / Risques de transmission des Salmonelles en aviculture: détection et prévention en Europe.

While salmonellas can cause disease problems among poultry, they remain essentially a concern for public health, as a cause of outbreaks of food poisoning. The principal site of multiplication of these bacteria is the digestive tract, particularly the caecum, which may result in widespread contamination of the environment. The pathogenicity of salmonellas depends on the invasive properties and the ability of the bacteria to survive and multiply within cells, particularly macrophages. These properties are the source of vertical transmission which, in the case of survival of the embryo, can result in contamination of a flock or, in the case of embryonic mortality, can result in an explosion of contaminated eggs. Salmonella infection can be diagnosed by isolating the bacteria and/or serological testing of the flock. European Union Directive 92/117/EC, modified by Directive 97/22/EC, stipulates either the destruction of infected flocks of breeding birds, or decontamination of the flock in an effective way, before normal trade in products can be resumed. Noteworthy examples of effective measures suitable for prophylaxis of Salmonella infection in poultry flocks include the slaughter of infected breeding stock, the creation of sanitary barriers at building entrances, heat treatment of feed, the use of competitive exclusion, selection of breeds genetically resistant to Salmonella, and occasional vaccination and antibiotic treatment. However, the most effective means of reducing food poisoning remains adequate cooking of food and maintenance of the cold chain.

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.

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.