Identification of sodC encoding periplasmic [Cu,Zn]-superoxide dismutase in Salmonella

Abstract sodC , encoding [Cu,Zn]-cofactored Superoxide dismutase, once thought to be virtually confined to eukaryotes, has now been described in many Gram-negative pathogens that have their primary niche of colonization in the upper respiratory tract. Their role in host-parasite interactive biology is unknown. We here show that members of the major human and animal enteric pathogenic species Salmonella harbour a version of sodC most closely resembling that found in Brucella abortus . The enzyme it encodes is a novel candidate determinant of virulence in Salmonella , an intracellular pathogen potentially exposed to toxic oxygen free radicals within its intracellular niche.     

Which sharks attract research? Analyses of the distribution of research effort in sharks reveal significant non-random knowledge biases

Reviews in Fish Biology and Fisheries - Research effort is unevenly distributed across species, which can cause important biases in our understanding of evolutionary and ecological processes and...     

Nitric oxide (NO) donor 3-morpholinosydnonimine antagonizes cyclosporin A-induced contraction in two in vitro glomerular models

Cyclosporin A induces in vivo a severe nephrotoxicity characterized by a large decrease in renal hemodynamics. The aim of this study is to establish the ability of the known NO donor 3-morpholinosydnomine (SIN-1) to prevent the cyclosporin A-induced contraction by using rat isolated glomeruli and cultured glomerular mesangial cells. Isolated rat glomeruli are obtained from the renal superficial cortex by a sieving method. Mesangial cells are cultured in RPMI 1640 with 15% fetal calf serum. The planar surface area (PSA) of either isolated glomeruli or mesangial cells is assessed using anage analyzer. Each glomerusus or mesangial cell serves as its own control through calculation of the area before any drug incubation and after incubation for 10, 20 and 30 min either in control solution or in control solution with cyclosporin A alone or cyclosporin A and SIN-1. Cyclosporin A (10^–6 mol/L) induces an important time-dependent contraction of either glomerulus or mesangial cell. When pretreated with different concentrations of SIN-1 (10^–4 to 10^–9 mol/L), only a slight size decrease is noted. In conclusion, a direct constrictive effect of cyclosporin A in isolated glomeruli and mesangial cells can be prevented bythe NO donor SIN-1, suggesting an important involvement of the nitric oxide pathway in the cyclosporin A-induced nephrotoxicity.Abbreviations CyA cyclosporin A - SIN-1 3-morpholinosydnonimine - FCS fetal calf serum - PSA planar surface area     

Orientation and foraging movements in a patchy environment by the ant Serrastruma lujae (formicidae-myrmicinae)

Serrastruma lujae ants individually search for collembolans in the leaf litter of humid tropical forests. During the dry season, collembolans aggregate in wet patches randomly scattered in the dry litter where numerous single workers come hunting from their nest. We simulated this situation in the laboratory, and observed that workers seem to be able to use the humidity gradient direction to efficiently orient themselves towards a wet patch. Once the patch has been reached, they exhibit area-concentrated searching,consisting, in particular, of adopting a high sinuosity and a low speed. After capturing a collembolan, the ants return to their nest along nearly straight paths. This ability may rely on a spatial memory of the nest location by means of a path-integration process. In the absence of prey, however, various behaviours were observed after an unsuccessful search. Comparisons between these data and the results obtained with a homogeneously wet environment simulating the rainy season situation showed that these ants do not simply respond to the humidity level but are also sensitive to the degree of patchiness of their environment. They can therefore be said to be able to adapt suitably to the considerable climatic changes they encounter during the year.     

Maximum Likelihood Neural Network Prediction Models

Neural networks have received much attention in recent years mostly by non-statisticians. The purpose of this paper is to incorporate neural networks in a non-linear regression model and obtain maximum likelihood estimates of the network parameters using a standard Newton-Raphson algorithm. We use maximum likelihood estimators instead of the usual back-propagation technique and compare the neural network predictions with predictions of quadratic regression models and with non-parametric nearest neighbor predictions. These comparisons are made using data generated from a variety of functions. Because of the number of parameters involved, neural network models can easily over-fit the data, hence validation of results is crucial.     

Polymorphism due to variable number of repeats in the human involucrin gene.

The coding region of the involucrin gene in higher primates contains a segment consisting of numerous tandem repeats of a 10-codon sequence. The process of repeat addition began in a common ancestor of all higher primates and subsequent repeats were added vectorially. As a result, the principal site of repeat addition has moved in the 3' to 5' direction and the most recently generated repeats (the late region) are close to the 5' end of the segment of repeats. In the human, most of the late region is made up of two different blocks, each consisting of nearly identical repeats. We describe here five polymorphic forms resulting from the addition of differing numbers of repeats to each block. As the variety and nature of the polymorphic alleles are different in different human populations, we postulate that the process of repeat addition is genetically determined.