Roles for T and NK cells in the innate immune response to Shigella flexneri

Shigella flexneri, an enteroinvasive Gram-negative bacterium, is responsible for the worldwide endemic form of bacillary dysentery. The host response to primary infection is characterized by the induction of an acute inflammation, which is accompanied by polymorphonuclear cell (PMN) infiltration, resulting in massive destruction of the colonic mucosa. However, PMN play a major role in the recovery from primary infection, by restricting the bacterial infection at the intestinal mucosa. In this study, we assessed the roles for T and NK cells in the control of primary S. flexneri infection, using an alymphoid mouse strain (Rag null gamma(c) null) devoid of B, T, and NK cells. Using the mouse pulmonary model of Shigella infection, we showed that alymphoid Rag null gamma(c) null mice were highly susceptible to S. flexneri infection in comparison with wild-type (wt) mice. Whereas PMN recruitment upon infection was similar, macrophage recruitment and production of proinflammatory cytokines were significantly decreased in Rag null gamma(c) null mice compared with wt mice. Upon selective engraftment of Rag null gamma(c) null mice with polyclonal alphabeta T cells, but not with alphabeta T cells from IFN-gamma null , S. flexneri infection could be subsequently controlled. Rag null mice devoid of B and T cells but harboring NK cells could control infection. Local IFN-gamma production by T and NK cells recruited to the lung was demonstrated in S. flexneri-infected wt mice. These data demonstrate that both alphabeta T cells and NK cells contribute to the early control of S. flexneri infection through amplification of an inflammatory response. This cellular lymphocyte redundancy assures IFN-gamma production, which is central to innate immunity against Shigella infection.     

Asparagine endopeptidase is not essential for class II MHC antigen presentation but is required for processing of cathepsin L in mice

Class II MHC molecules survey the endocytic compartments of APCs and present antigenic peptides to CD4 T cells. In this context, lysosomal proteases are essential not only for the generation of antigenic peptides but also for proteolysis of the invariant chain to allow the maturation of class II MHC molecules. Recent studies with protease inhibitors have implicated the asparagine endopeptidase (AEP) in class II MHC-restricted Ag presentation. We now report that AEP-deficient mice show no differences in processing of the invariant chain or maturation of class II MHC products compared with wild-type mice. In the absence of AEP, presentation to primary T cells of OVA and myelin oligodendrocyte glycoprotein, two Ags that contain asparagine residues within or in proximity to the relevant epitopes was unimpaired. Cathepsin (Cat) L, a lysosomal cysteine protease essential for the development to CD4 and NK T cells, fails to be processed into its mature two-chain form in AEP-deficient cells. Despite this, the numbers of CD4 and NK T cells are normal, showing that the single-chain form of Cat L is sufficient for its function in vivo. We conclude that AEP is essential for processing of Cat L but not for class II MHC-restricted Ag presentation.     

Discriminatory power of RAPD,PCR-RFLP and southern blot analyses of ureCD or ureA gene probes on Helicobacter pylori isolates

The genetic diversity of 33 Nigerian Helicobacter pylori isolates were studied using RAPD, PCR-RFLP and Southern blot analysis of ureA or ureCD gene probes. RAPD was able to distinguish the following number of isolates using the primers 3880: 5'-AAGAGCCCGT-3' (28), 3881 :5'-AACGCGCAAC-3' (33) and OPH8 :5'-GAAACACCCC-3' (25). Southern blot analysis using the ureCD probe was also able to distinguish the 12 isolates tested into ten different patterns. The PCR-RFLP technique distinguished all 33 isolates into six types. In conclusion, considering typeability, discriminatory power, and convenience, RAPD with the 3881 primer was considered the most useful technique.     

Influence of an arbuscular mycorrhizal fungus on the interaction of a binucleate Rhizoctonia species with Myc+ and Myc- pea roots

A binucleate Rhizoctonia (BNR) species was isolated from a clay loam soil on the Epoisses experimental station of INRA, Dijon and identified as belonging to the anastomosis Group A (AG-A). The BNR was inoculated to a Myc- Pisum sativum mutant (P53, sym30 locus) and its wild-type parent (cv Frisson) in the presence or absence of the arbuscular mycorrhizal fungus Glomus mosseae. The BNR had no significant effect on plant weight. Myc+ and Myc- roots were equally susceptible towards BNR and showed no localized cellular defense responses. The presence of BNR decreased significantly the percentage of root length colonized by G. mosseae and, inversely, G. mosseae reduced the number of BNR monilioid chains formed in root epidermal cells of the two pea genotypes. The pisatin concentration was increased significantly by BNR in both Myc+ and Myc- roots and by G. mosseae in the wild-type pea plants. The highest accumulation of pisatin was observed in Myc+ roots when both fungi were present.     

Dystrophin and Utrophin Complexed with Different Associated Proteins in Cardiac Purkinje Fibres

Abnormal dystrophin expression is directly responsible for Duchenne and Becker muscular dystrophies. In skeletal muscle, dystrophin provides a link between the actin network and the extracellular matrix via the dystrophin-associated protein complex. In mature skeletal muscle, utrophin is a dystrophin-related protein localized mainly at the neuromuscular junction, with the same properties as dystrophin in terms of linking the protein complex. Utrophin could potentially overcome the absence of dystrophin in dystrophic skeletal muscles. In cardiac muscle, dystrophin and utrophin were both found to be present with a distinct subcellular distribution in Purkinje fibres, i.e. utrophin was limited to the cytoplasm, while dystrophin was located in the cytoplasmic membrane.In this study, we used this particular characteristic of cardiac Purkinje fibres and demonstrated that associated proteins of dystrophin and utrophin are different in this structure. We conclude, contrary to skeletal muscle, dystrophin-associated proteins do not form a complex in Purkinje fibres. In addition, we have indirect evidence of the presence of two different 400kDa dystrophins in Purkinje fibres.     

Density-dependence across dispersal stages in a hermaphrodite land snail: insights from discrete choice models

Dispersal movements, i.e. movements leading to gene flow, are key behaviours with important, but only partially understood, consequences for the dynamics and evolution of populations. In particular, density-dependent dispersal has been widely described, yet how it is determined by the interaction with individual traits, and whether density effects differ between the three steps of dispersal (departure, transience, and settlement), remains largely unknown. Using a semi-natural landscape, we studied dispersal choices of Cornu aspersum land snails, a species in which negative effects of crowding are well documented, and analysed them using dispersal discrete choice models, a new method allowing the analysis of dispersal decisions by explicitly considering the characteristics of all available alternatives and their interaction with individual traits. Subadults were more dispersive than adults, confirming existing results. In addition, departure and settlement were both density dependent: snails avoided crowded patches at both ends of the dispersal process, and subadults were more reluctant to settle into crowded patches than adults. Moreover, we found support for carry-over effects of release density on subsequent settlement decisions: snails from crowded contexts were more sensitive to density in their subsequent immigration choices. The fact that settlement decisions were informed indicates that costs of prospecting are not as important as previously thought in snails, and/or that snails use alternative ways to collect information, such as indirect social information (e.g. trail following). The observed density-dependent dispersal dynamics may play an important role in the ability of C. aspersum to successfully colonise frequently human-disturbed habitats around the world.     

Variable Cross-Resistance to Cry11B from Bacillus thuringiensis subsp. jegathesan in Culex quinquefasciatus (Diptera: Culicidae) Resistant to Single or Multiple Toxins of Bacillus thuringienisis subsp. israelensis

A novel mosquitocidal bacterium, Bacillus thuringiensis subsp. jegathesan, and one of its toxins, Cry11B, in a recombinant B. thuringiensis strain were evaluated for cross-resistance with strains of the mosquito Culex quinquefasciatus that are resistant to single and multiple toxins of Bacillus thuringiensis subsp. israelensis. The levels of cross-resistance (resistance ratios [RR]) at concentrations which caused 95% mortality (LC₉₅) between B. thuringiensis subsp. jegathesan and the different B. thuringiensis subsp. israelensis-resistant mosquito strains were low, ranging from 2.3 to 5.1. However, the levels of cross-resistance to Cry11B were much higher and were directly related to the complexity of the B. thuringiensis subsp. israelensis Cry toxin mixtures used to select the resistant mosquito strains. The LC₉₅ RR obtained with the mosquito strains were as follows: 53.1 against Cq4D, which was resistant to Cry11A; 80.7 against Cq4AB, which was resistant to Cry4A plus Cry4B; and 347 against Cq4ABD, which was resistant to Cry4A plus Cry4B plus Cry11A. Combining Cyt1A with Cry11B at a 1:3 ratio had little effect on suppressing Cry11A resistance in Cq4D but resulted in synergism factors of 4.8 and 11.2 against strains Cq4AB and Cq4ABD, respectively; this procedure eliminated cross-resistance in the former mosquito strain and reduced it markedly in the latter strain. The high levels of activity of B. thuringiensis subsp. jegathesan and B. thuringiensis subsp. israelensis, both of which contain a complex mixture of Cry and Cyt proteins, against Cry4- and Cry11-resistant mosquitoes suggest that novel bacterial strains with multiple Cry and Cyt proteins may be useful in managing resistance to bacterial insecticides in mosquito populations.     

Nouvelles données histochimiques et ultrastructurales sur les photorécepteurs «branchiaux» de Dasychone bombyx (Dalyell) (Annélide Polychète)

Résumé L'il composé «branchial» de Dasychone bombyx est constitué de plusieurs yeux élémentaires. Chacun d'eux est associé à une cellule pigmentaire qui forme un manchon autour de sa base, les deux extrémités de la cellule se rejoignant après en avoir fait le tour. La cellule photoréceptrice comprend une partie distale: le «bâtonnet» qui contient des structures lamellaires d'origine ciliaire et supportant probablement le pigment photosensible. Le corps même de la cellule est en relation avec le bâtonnet par un isthme ménagé au niveau d'affrontement des extrémités de la cellule pigmentaire. Le cristallin, situé immédiatement au-dessus du bâtonnet, est extracellulaire et en continuité avec la cuticule. Il semble être en relation avec une formation en cupule, de structure apparemment semblable, située à la base du bâtonnet. Il est entouré, successivement, par une cellule «pericristallinienne» en anneau et par la cellule pigmentaire.

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Summary Each photoreceptor unit of Dasychone bombyx consists of a photoreceptor cell and a lens both enclosed in a collar composed of a «cellule pericristallinienne» and a pigmented cell. The rod which is supposed to be the photosensitive part of the photoreceptor cell is situated inside the pigmented cup and is connected by a narrow channel to the body of the cell, situated outside the pigmented cup. The rod is composed of membranous sacs of ciliary origin. The lens is extracellular and continuous with the cuticle. It seems to be connected with an extracellular cupule of the same morphological structure, located at the base of the rod.

     

Niches and routes of transmission of <Emphasis Type="Italic">Xanthomonas citri</Emphasis> pv. <Emphasis Type="Italic">fuscans</Emphasis> to bean seeds

Aims

Seeds are vectors of a diversified microbiota including plant pathogens. To better understand transmission of common bacterial blight (CBB) agents to bean seeds, we analyzed the role of non-pathogenic xanthomonads on seed transmission efficiency and investigated the location of Xanthomonas citri pv. fuscans (Xcf) into seeds and plantlets.

Methods

Competition between CBB and NP strains was initially assessed in vitro and then extended in planta to monitor the impact of co-inoculation on Xcf seed transmission. Moreover, location of Xcf strains in seeds and seedlings was visualized using a combination of gfp-tagged strain and DOPE-FISH/CSLM.

Results

Whereas CBB agent growth was inhibited in vitro by some seed-borne non-pathogenic xanthomonads strains, these strains did not transmit efficiently to seed through floral pathway and did not affect Xcf seed transmission. Xcf cells were observed entering seed through vascular elements and parenchyma of funiculus, but also micropyle and testa. Xcf cells were observed, moreover, among other bacteria on radicle surfaces, especially tip, in cotyledons, and plumules.

Conclusions

CBB agents are more efficient than non-pathogenic xanthomonads in using the floral route to colonize seeds. CBB agents are located within different niches in the seed tissues up to the embryonic axis.

     

Stress, behaviour and reproductive performance in female cattle and pigs

Female farm animals are exposed to a great variety of environmental and management related stressors. As a consequence, their reproductive and maternal abilities may be compromised through mechanisms acting on the hypothalamic, pituitary, ovarian and uterine function. Responses to short- and long-term stressors may differ as short-term stressors often fail to affect reproduction or even may have stimulatory effects. Thus, the stress response induces diverse neuroendocrine reactions that can either increase or decrease the probability of an animal reproducing depending on the specific situation. The aim of the present review is to summarise the current knowledge on the stress concept and its implications on behaviour and reproductive performance in cows and female pigs as phenomena reported in laboratory animals are unable to explain all effects encountered in domesticated farm animals.