Intestinal barrier function in response to abundant or depleted mucosal glutathione in Salmonella-infected rats

Background  

Glutathione, the main antioxidant of intestinal epithelial cells, is suggested to play an important role in gut barrier function and prevention of inflammation-related oxidative damage as induced by acute bacterial infection. Most studies on intestinal glutathione focus on oxidative stress reduction without considering functional disease outcome. Our aim was to determine whether depletion or maintenance of intestinal glutathione changes susceptibility of rats to Salmonella infection and associated inflammation.     

Efficient control of transient wave forms to prevent spreading depolarizations

In various neurological disorders spatio-temporal excitation patterns constitute examples of excitable behavior emerging from pathological pathways. During migraine, seizure, and stroke an initially localized pathological state can temporarily spread indicating a transition from non-excitable to excitable behavior. We investigate these transient wave forms in the generic FitzHugh-Nagumo (FHN) system of excitable media. Our goal is to define an efficient control minimizing the volume of invaded tissue. The general point of such a therapeutic optimization is how to apply control theory in the framework of structures in differential geometry by regarding parameter plane M of the FHN system as a differentiable manifold endowed with a metric. We suggest to equip M with a metric given by pharmacokinetic-pharmacodynamic models of drug receptor interaction.     

Absolute versus per unit body length speed of prey as an estimator of vulnerability to predation

To study whether absolute (m/s) or relative (body lengths/s) speed should be used to compare the vulnerability of differently sized animals, we developed a simple computer simulation. Human 'predators' were asked to 'catch' (mouse-click) prey of different sizes, moving at different speeds across a computer screen. Using the simulation, a prey's chances of escaping predation depended on its speed (faster prey were more difficult to catch than slower prey of the same body size), but also on its size (larger prey were easier to catch than smaller prey at the same speed). Catching time, the time needed to catch a prey, also depended on both prey speed and prey size. Relative prey speed (body lengths/s or body surface/s) was a better predictor of catching time than was absolute prey speed (m/s). Our experiment demonstrates that, in contrast to earlier assertions, per unit body length speed of prey may be more 'ecologically relevant' than absolute speed. Copyright 1998 The Association for the Study of Animal Behaviour.     

Migraine aura dynamics after reverse retinotopic mapping of weak excitation waves in the primary visual cortex

 A kinematical model for excitable wave propagation is analyzed to describe the dynamics of a typical neurological symptom of migraine. The kinematical model equation is solved analytically for a linear dependency between front curvature and velocity. The resulting wave starts from an initial excitation and moves in the medium that represents the primary visual cortex. Due to very weak excitability the wave propagates only across a confined area and eventually disappears. This cortical excitation pattern is projected onto a visual hemifield by reverse retinotopic mapping. Weak excitability explains the confined appearance of aura symptoms in time and sensory space. The affected area in the visual field matches in growth and form the one reported by migraine sufferers. The results can be extended from visual to tactile and to other sensory symptoms. If the spatiotemporal pattern from our model can be matched in future investigations with those from introspectives, it would allow one to draw conclusions on topographic mapping of sensory input in human cortex. Received: 25 April 2002 / Accepted: 20 February 2003 / Published online: 20 May 2003 RID="*" ID="*" Present address: M. A. Dahlem Leibniz-Institut für Neurobiologie, Brenneckestr. 6, 39118 Magdeburg, Germany Acknowledgements. We would like to thank V. Zykov for useful discussions on wave Propagation, and one of us (MAD) would like to thank Ed Chronicle for useful discussions on functional excitability. This project was supported by a scholarship Landesstipendium Sachsen-Anhalt to MAD. Correspondence to: M. A. Dahlem (e-mail: dahlem@ifn-magdeburg.de)     

Image processing techniques applied to excitation waves in the chicken retina

Image processing techniques are described in detail that are used to gain information about the dynamics of wave propagation in excitable media. We focus on a phenomenon called spreading depression (SD) observed in the chicken retina, but the techniques described here concern a large variety of excitable systems. Despite the impressive progress both in SD research of the past 50 years and, during nearly the same period, in the theory of self-organization of wave patterns, there is still little mutual overlap. However, the increasing demands for understanding complex systems, like neuronal tissue, require such theoretical concepts. Arguments are given why the chicken retina is a nearly perfect experimental system for assessing and further developing these concepts.     

Rapid and Efficient Zebrafish Genotyping Using PCR with High-resolution Melt Analysis

Zebrafish is a powerful vertebrate model system for studying development, modeling disease, and performing drug screening. Recently a variety of genetic tools have been introduced, including multiple strategies for inducing mutations and generating transgenic lines. However, large-scale screening is limited by traditional genotyping methods, which are time-consuming and labor-intensive. Here we describe a technique to analyze zebrafish genotypes by PCR combined with high-resolution melting analysis (HRMA). This approach is rapid, sensitive, and inexpensive, with lower risk of contamination artifacts. Genotyping by PCR with HRMA can be used for embryos or adult fish, including in high-throughput screening protocols.