Comparison of diversities of Escherichia coli O157 shed from a cohort of spring-born beef calves at pasture and in housing

A cohort of spring-born beef calves demonstrated limited genetic and phenotypic diversity of Escherichia coli O157 when kept in a state of isolation. Despite this, there was a difference in the pulsed-field gel electrophoresis and phage types of isolates shed by cattle at pasture compared with those shed by the same cattle when weaned and housed.     

Establishment and characterization of continuous hematopoietic progenitors-derived pig normal mast cell lines

Mast cells (MCs) are tissue resident, hematopoietic stem cells-derived elements, distributed throughout the body. They are the pivotal mediating cells of allergic reactions. In addition, in mice, MCs play a critical role in the defense against several pathogens, such as bacteria, parasites and viruses. Whereas the biology of rodent and human MCs has been extensively studied using in vitro derived populations, the role of MCs in pigs has not yet been evaluated, given the very low availability of pure porcine MCs populations. In the present report, we describe an original method to obtain continuous factor-dependent normal pig MCs (PMC) lines from fetal hematopoietic progenitors. These Stem Cell Factor (SCF) and Interleukin-3- (IL-3)-dependent PMC lines retain their capacity to growth after conventional freezing methods and exhibit most of the morphological and biochemical properties of normal, although immature, MCs, including metachromatic granules containing sulfated polysaccharides, the expression of c-kit and high-affinity IgE receptors (FcepsilonRI), and the ability to store histamine that is released upon cross-linking of FcepsilonRI. In vitro derived PMC lines might thus be valuable tools to further investigate the reactivity of these elements towards several parasites frequently encountered in pig, such as, but not limited to, Ascaris suum, Trichinella spiralis or Trichuris suis, or towards antigens derived from these pathogens.     

Evaluation of two DNA probes specific for Leishmania infantum in the diagnosis of canine leishmaniasis

This study reports on the evaluation of two L. infantum specific DNA probes for the diagnosis of canine leishmaniasis. The probes presented very satisfying performances in terms of specificity (100%) and predictive value of the positive result (100%). However, their sensitivity (35.3%) and the clinical complexity of canine infections render their use difficult in epidemiological surveys of visceral leishmaniasis aiming at measuring the prevalence of the dog infection by L. infantum. The sensitivity of these tools has improved (66.7%) when dogs presenting patent leishmaniasis were considered. Such probes constitute appropriate tools to confirm suspected cases of leishmaniasis. Unlike the classical parasitological and serological tools, this kind of tools allows a concomitant detection and identification of the causative agent. Therefore, despite their low sensitivity, these probes can still be of importance in epidemiological investigations.     

Superacidic Electrospun Fiber‐Nafion Hybrid Proton Exchange Membranes

A novel type of hybrid membrane has been fabricated by incorporating superacidic sulfated zirconia (S‐ZrO₂) fibers into recast Nafion for proton exchange membrane fuel cells (PEMFCs). With the introduction of electrospun superacidic fiber mats, a large amount of protogenic groups aggregated in the interfacial region between S‐ZrO₂ fibers and the ionomer matrix, forming continuous pathways for facile proton transport. The resultant hybrid membranes had high proton conductivities, which were controlled by selectively adjusting the fiber diameter and fiber volume fraction. Consequently, the superacidic S‐ZrO₂ electrospun fibers are promising filler materials and hybrid membranes containing S‐ZrO₂ fiber mats can be potentially used in high‐performance fuel cells.     

Laboratory Study on Individual and Combined Effects of Cobalt- and Zinc-Spiked Sediment on Meiobenthic Nematodes

Free-living nematodes are the most abundant taxa among the meiobenthos and the predominant prey for bottom-feeding fishes. They are able to accumulate toxicants from sediments which explain their use in this study as possible tools in nutritional quality assessment of fishes. Nematodes from sediments of Ghar El Melh lagoon (Tunisia) were subjected to cobalt and/or zinc enrichment in a microcosm experiment for 30?days. Three levels (low, medium, and high) of each treatment were used. Nematode abundance and diversity significantly decreased, and the taxonomic structure was altered. Results from multivariate analyses of the species abundance data revealed that all treatments were significantly different from the control. Both univariate and multivariate analyses of the data showed that the differential response occurred in all treatments, but the assemblages from microcosms contaminated with zinc alone were much more negatively affected compared with those exposed to cobalt alone. The presence of cobalt simultaneously with zinc seems to reduce its impact on nematode species composition. Such a result is suggestive of antagonistic interactions between these two metals. The responses of nematode species to the cobalt and zinc treatments were varied. Oncholaimellus mediterraneus, Oncholaimus campylocercoides, and Neochromadora trichophora were significantly affected with cobalt contamination but, they were not eliminated. Exposed to zinc, Hypodontolaimus colesi was eliminated and seemed to be an intolerant species versus this metal. Some of these species, "cobalt-sensitive" or "zinc-sensitive", were also affected by the metal combination even at low dose: O. mediterraneus, N. trichophora, and H. colesi. Differential sensitivity to cobalt and/or zinc may result in a subsequent competitive release of more tolerant species. A list of this kind of species was established to be used as a possible preventive tool versus contaminated fish. This was most evidently the case in Marylynnia stekhoveni and O. campylocercoides which increased at all doses of cobalt and zinc, respectively. These two resistant species have also the opportunity to dominate the nematode assemblage when the studied metals were added together. The level of health risk is probably higher for humans assimilating additional amount of cobalt and zinc, especially heavy smokers and/or patients using some medications including salts of these metals.     

Biocontrol of root-knot nematode infected banana plants by some marine algae

Root-knot nematodes are serious pests that cause losses of a wide range of different crops. Nematodes are controlled mainly by nematicides which cause pollution and have serious effects on all living organisms including human beings. Therefore, discovering alternative methods to control plant parasitic nematodes was attempted during the last few years to avoid pesticides hazards. Four species of marine algae (Ulva lactuca, Jania rubens, Laurencia obtusa and Sargassum vulgare) were tested to control root-knot nematode, (Meloidogyne spp.) infecting banana plants (Musa spp.). All the treatments significantly (p ≤ 0.05) reduced the rate of build-up compared with the check. U. lactuca alga gave the best results in reducing the number of galls (73.68%) and the final population of nematode (56.78%). The chemical analysis of all tested materials revealed that U. lactuca had the highest amount of phenolics (10.39 mg GAE/g dry wt). This may explain the remarkable high capability of U. lactuca to control root-knot nematode infections. Also, the same alga was the best treatment and showed maximum growth when compared with other algae and the check. For instance, shoot weight of U. lactuca surpassed the other treatments, even that of non-nematizied check one, giving high increase percentage.     

Impacts of permethrin contamination on nematode density and diversity: A microcosm study on benthic meiofauna from a Mediterranean coastal lagoon

A microcosm experiment was used to examine the response of nematode in terms of density and diversity at different levels of permethrin contamination. The sediments were contaminated with three permethrin concentrations [P1: low (5 mg kg⁻¹), P2: medium (25 mg kg⁻¹) and P3: high (250 mg kg⁻¹)] and the effects were evaluated after 30 days. The results from univariate and multivariate analyses showed significant differences between nematode assemblages from uncontaminated control and those from permethrin treatments. All univariate indices changed significantly at all the levels of permethrin contamination. In fact, the total nematode abundance (I), Shannon-Weaner index (H′), species richness (d), evenness (J′) and number of species (S) decreased significantly in all the contaminated microcosms. In addition, the results from multivariate analyses of the species abundance data demonstrated that permethrin affects the responses of nematode species. These significant modifications in nematode community structures with response to permethrin contamination were the consequences of a different specific tolerance to this pesticide. Thus, Araeolaimus bioculatus, Calomicrolaimus honestus, Oncholaimus campylocercoides and Theristus pertenuis characterized by increased abundances in all treated replicates, appeared to be “permethrin-resistant” species. Daptonema trabeculosum was eliminated in all the doses tested and seemed to be a very sensitive species to permethrin contamination.     

Molecular approach to the epidemiology of urinary schistosomiasis in France

BackgroundThe diagnosis of urogenital schistosomiasis is based on the complementarity of serological technique and microscopic examination (ME). Between 2015 and 2019, the number of urinary schistosomiasis tests received in our laboratory increased sharply from 300 to 900 per year.Therefore, we wanted to evaluate the reliability of urine microscopic examination (ME, reference and routine technique) from urine sample by comparing it to other techniques (antigenic technique and PCR). To this end, we optimized two real-time PCRs targeting respectively Schistosoma haematobium (Sh) and Schistosoma mansoni (Sm).Methodology/Principal findings914 urine samples from 846 patients suspected of urogenital schistosomiasis were prescribed and analyzed by PCR and also by antigenic technique for the first 143 samples. The antigenic technique evaluated was Schisto POC-CCA, Rapid Medical Diagnostics. These results (antigenic technique and PCR) were compared to ME which was performed from all urines.The percentage of 14% (128/914) positive cases with the PCR technique and the percentage of 6.0% (54/914) positive cases with ME is significantly different (Chi 2 test, p<0.001). These 128 positive PCRs correspond to 120 different patients, 88.3% (106/120) of them were young migrants and 11.7% (14/120) were French patients returning from travel. Among these migrants, more than 75% (80/106) came from French-speaking West Africa.In addition, the Schisto POC-CCA showed a specificity of 39% (46/117), too poor to be used as a screening tool in low or non-endemic areas.Conclusion/SignificanceTargeted Sh and Sm PCRs in urine are reliable techniques compared to ME (reference technique). In view of our results, we decided to screen urinary schistosomiasis by direct ME always coupled by the PCR technique, which has shown better reliability criteria.     

[3H]Epibatidine Photolabels Non-equivalent Amino Acids in the Agonist Binding Site of Torpedo and ��4��2 Nicotinic Acetylcholine Receptors

Nicotinic acetylcholine receptor (nAChR) agonists, such as epibatidine and its molecular derivatives, are potential therapeutic agents for a variety of neurological disorders. In order to identify determinants for subtype-selective agonist binding, it is important to determine whether an agonist binds in a common orientation in different nAChR subtypes. To compare the mode of binding of epibatidine in a muscle and a neuronal nAChR, we photolabeled Torpedo α₂βγδ and expressed human α4β2 nAChRs with [³H]epibatidine and identified by Edman degradation the photolabeled amino acids. Irradiation at 254 nm resulted in photolabeling of αTyr¹⁹⁸ in agonist binding site Segment C of the principal (+) face in both α subunits and of γLeu¹⁰⁹ and γTyr¹¹⁷ in Segment E of the complementary (−) face, with no labeling detected in the δ subunit. For affinity-purified α4β2 nAChRs, [³H]epibatidine photolabeled α4Tyr¹⁹⁵ (equivalent to Torpedo αTyr¹⁹⁰) in Segment C as well as β2Val¹¹¹ and β2Ser¹¹³ in Segment E (equivalent to Torpedo γLeu¹⁰⁹ and γTyr¹¹¹, respectively). Consideration of the location of the photolabeled amino acids in homology models of the nAChRs based upon the acetylcholine-binding protein structure and the results of ligand docking simulations suggests that epibatidine binds in a single preferred orientation within the α-γ transmitter binding site, whereas it binds in two distinct orientations in the α4β2 nAChR.Nicotinic acetylcholine receptors (nAChRs)³ are prototypical members of the Cys loop superfamily of neurotransmitter-gated ion channels that mediate the actions of the neurotransmitter acetylcholine (1). nAChRs from vertebrate skeletal muscle and the electric organs of Torpedo rays are heteropentamers of homologous subunits with a stoichiometry of 2α:β:γ(ϵ):δ that are arranged pseudosymmetrically around central cation-selective ion channels (1, 2). There are 12 mammalian neuronal nAChR subunit genes: nine neuronal α subunits (α2–α10) and three neuronal β subunits (β2–β4). The α4β2 nAChR is the most abundant and widely distributed nAChR subtype expressed in the brain and is a major target for potential therapeutic agents for neurological diseases and conditions, including nicotine dependence and Alzheimer and Parkinson diseases (3, 4). Although the ratio of α4 to β2 subunit in vivo is uncertain, expressed receptors containing either three α4 or three β2 subunits have distinct pharmacological properties (5, 6).The agonist binding sites (ABS) of nAChRs are located within the amino-terminal extracellular domain at the interface of adjacent subunits (α-γ and α-δ in the Torpedo nAChR), and different nAChR subunit combinations form ABS with distinct physical and pharmacological properties (3, 7). Affinity labeling studies with Torpedo nAChR and site-directed mutational analyses of muscle and neuronal nAChRs identified key amino acids delineating the ABS from three noncontiguous stretches of the α subunit (Segments A-C, the principal component (+ face)) and three noncontiguous regions of the non-α subunit (Segments D–F, the complementary component (− face)) (8, 9). The three-dimensional structure of the ABS in the absence and presence of nAChR agonists or competitive antagonists has been determined for snail acetylcholine-binding proteins (AChBPs) that are soluble homopentamers homologous to the extracellular (amino-terminal) domain of a nAChR (10–12). In the AChBP, four aromatic amino acids from Segments A–C that are conserved within α subunits, along with a conserved Trp in Segment D, form a core aromatic “pocket” with a dimension optimal for accommodation of a trimethylammonium group. The other amino acids in the non-α subunits closest to the aromatic pocket, which are generally not conserved among γ, δ, or neuronal β subunits, are on three antiparallel β strands. The AChBP structure was used to refine the structure of the Torpedo nAChR in the absence of agonist to 4 Å resolution (13). In this structure, there is a reorientation of Segments A–C, resulting in the absence of a well defined core aromatic binding pocket.Analysis of agonist interactions with mutant nAChRs containing fluorine-substituted core aromatic residues provides evidence that cation-π interactions, particularly with αTrp¹⁴⁹ in Segment B, are important determinants of agonist binding affinity (14) and for the higher affinity binding of nicotine to α4β2 nAChRs compared with α₂βγδ nAChRs (15). Mutational analyses and molecular docking calculations have also provided evidence that two molecules of very similar structure may actually bind to a single receptor in very different orientations, as seen for two high affinity antagonists, d-tubocurarine and its quaternary ammonium analog metocurine, binding to the AChBP and to the muscle nAChR (16, 17).Photoaffinity labeling provides an alternative means to identify amino acids contributing to a drug binding site (18, 19) and has been used to determine the orientation of drugs bound in the ABS of Torpedo nAChR (20). Epibatidine binds with very high affinity (∼10 pm) to heteromeric neuronal nAChRs (e.g. α4β2) and with nanomolar affinity to α7 and muscle-type/Torpedo nAChRs (3). Utilizing a photoreactive analogue of epibatidine (azidoepibatidine; Fig. 1) and mass spectrometry, Tomizawa et al. (21) identified photolabeled amino acids in the Aplysia AChBP (Tyr¹⁹⁵ in Segment C and Met¹¹⁶ in Segment E), establishing an orientation for bound azidoepibatidine consistent with the orientation of epibatidine in an AChBP crystal structure (12).Open in a separate windowFIGURE 1.Structure of [³H]epibatidine (top) and azidoepibatidine (bottom).In this report, we use [³H]epibatidine as a photoaffinity reagent to identify the amino acids photolabeled in an expressed α4β2 nAChR and in the Torpedo α₂βγδ nAChR. Comparisons of the labeled amino acids seen in the Torpedo nAChR α-γ binding site and in the α4β2 nAChR, in conjunction with the results of docking calculations for epibatidine binding to homology models of the α₂βγδ and α4β2 nAChRs, suggests that epibatidine binds in a single orientation in the α-γ site but in two orientations in the α4β2 ABS.