Fungal virulence studies come of age

Sophisticated molecular biological research has revealed many virulence attributes in at least four pathogenic fungi, but the future study of fungal virulence requires investigators to distinguish between molecules that directly interact with the host, molecules that regulate these, and molecules that are always required for fungal growth and survival, independent of the host.     

Detection of superoxide anion released extracellularly by endothelial cells using cytochrome c reduction, ESR, fluorescence and lucigenin-enhanced chemiluminescence techniques

Endothelium produces oxygen-derived free radicals (nitric oxide, NO&z.rad;; superoxide anion, O(2)(*-)) which play a major role in physiology and pathology of the vessel wall. However, little is known about endothelium-derived O(2)(*-) production, particularly due to the difficulty in assessing O(2)(*-) when its production is low and to controversies recently raised about the use of lucigenin-enhanced chemiluminescence. We compared four techniques of O(2)(*-) assessment when its production is low. In the present study, we have compared ferricytochrome c reduction, electron spin resonance (ESR) spectroscopy using DMPO as spin trap, hydroethidine fluorescence, and lucigenin-enhanced chemiluminescence to assess O(2)(*-) production in cultured bovine aortic endothelial cells (BAEC). We focused our study on extracellular O(2)(*-) production because the specificity of the signal is provided by the use of superoxide dismutase, and this control cannot be obtained intracellularly. We found that the calcium ionophore A23187 dose-dependently stimulated O(2)(*-) production, with a good correlation between all four techniques. The signals evoked by postconfluent BAEC were increased 2- to 7-fold in comparison to just-confluent BAEC, according to the technique used. Ferricytochrome c 20 microm rather than at 100 microm appears more suitable to detect O(2)(*-). However, in the presence of electron donors such as NADH or NADPH, lucigenin-enhanced chemiluminescence generated high amounts of O(2)(*-). Thus, ferricytochrome c reduction, electron spin resonance (ESR), and hydroethidine fluorescence appear as adequate tools for the detection of extracellular endothelium-derived O(2)(*-) production, whereas lucigenin may be artifactual, even when a low concentration of lucigenin is employed.     

Can Zipf's law be adapted to normalize microarrays?

Background  

Normalization is the process of removing non-biological sources of variation between array experiments. Recent investigations of data in gene expression databases for varying organisms and tissues have shown that the majority of expressed genes exhibit a power-law distribution with an exponent close to -1 (i.e. obey Zipf's law). Based on the observation that our single channel and two channel microarray data sets also followed a power-law distribution, we were motivated to develop a normalization method based on this law, and examine how it compares with existing published techniques. A computationally simple and intuitively appealing technique based on this observation is presented.     

ARTIFICIAL SELECTION ON RELATIVE BRAIN SIZE REVEALS A POSITIVE GENETIC CORRELATION BETWEEN BRAIN SIZE AND PROACTIVE PERSONALITY IN THE GUPPY

Animal personalities range from individuals that are shy, cautious, and easily stressed (a “reactive” personality type) to individuals that are bold, innovative, and quick to learn novel tasks, but also prone to routine formation (a “proactive” personality type). Although personality differences should have important consequences for fitness, their underlying mechanisms remain poorly understood. Here, we investigated how genetic variation in brain size affects personality. We put selection lines of large‐ and small‐brained guppies (Poecilia reticulata), with known differences in cognitive ability, through three standard personality assays. First, we found that large‐brained animals were faster to habituate to, and more exploratory in, open field tests. Large‐brained females were also bolder. Second, large‐brained animals excreted less cortisol in a stressful situation (confinement). Third, large‐brained animals were slower to feed from a novel food source, which we interpret as being caused by reduced behavioral flexibility rather than lack of innovation in the large‐brained lines. Overall, the results point toward a more proactive personality type in large‐brained animals. Thus, this study provides the first experimental evidence linking brain size and personality, an interaction that may affect important fitness‐related aspects of ecology such as dispersal and niche exploration.