Modulation of K؉ conductance of the inner mitochondrial membrane has been proposed to mediate preconditioning in ischemia-reperfusion injury. The mechanism is not entirely understood, but it has been linked to a decreased activation of mitochondrial permeability transition (mPT). In the present study K ؉ channel activity was mimicked by picomolar concen- A short non-injurious ischemic insult can greatly reduce the severity of a subsequent prolonged ischemia, a phenomenon generally referred to as preconditioning or ischemic tolerance (1-3). This adaptive response can be seen as a general biological phenomenon by which organisms respond with protective mechanisms to potentially recurring challenges (4). A low dose of one type of stressful stimulus can also induce resistance to another, e.g. prior transient hyperthermia can protect against subsequent forebrain ischemia (5). Understanding and controlling these seemingly general endogenous survival responses might enable a clinical therapeutic opportunity to reduce tissue damage after cerebral or cardiac ischemia (4, 6, 7). Ischemic preconditioning mediates both a rapid adaptive response coming into effect within minutes to hours as well as an induced tolerance occurring over a longer time frame requiring gene activation and de novo protein synthesis. The former is extensively studied in cardiac ischemia and the latter in cerebral ischemia (6, 7). Various physiological and chemical triggers can induce preconditioning, and whereas several mediating pathways have been characterized, the final causal effectors remain more obscure (7).The inner mitochondrial membrane has been proposed to contain ATP-sensitive potassium channels (mitoK ATP ), 2 which are pharmacologically distinct from plasma membrane K ATP and may mediate as well as be end-effectors of the preconditioning effect. Although there is substantial support for mitoK ATP activation in preconditioning, the evidence comes almost exclusively from studies with pharmacological compounds, mainly diazoxide and 5-hydroxydecanoate (7,8). Ischemic preconditioning can be closely mimicked by the K ATP opener diazoxide, which shows a concentration-dependent selectivity for mitoK ATP over plasma membrane K ATP (9, 10). Both ischemic and diazoxide-mediated preconditioning can be blocked by 5-hydroxydecanoate, which is believed to inhibit the diazoxide-induced opening of mitoK ATP (11). A role of mitoK ATP is also implicated in different models of cerebral ischemia where pretreatment with diazoxide mediates neuronal protection in a 5-hydroxydecanoate-sensitive manner (12,13

No abstract

Two-dimensional SDS-PAGE gel electrophoresis using post-run staining is widely used to measure the abundances of thousands of protein spots simultaneously. Usually, the protein abundances of two or more biological groups are compared using biological and technical replicates. After gel separation and staining, the spots are detected, spot volumes are quantified, and spots are matched across gels. There are almost always many missing values in the resulting data set. The missing values arise either because the corresponding proteins have very low abundances (or are absent) or because of experimental errors such as incomplete/over focusing in the first dimension or varying run times in the second dimension as well as faulty spot detection and matching. In this study, we show that the probability for a spot to be missing can be modeled by a logistic regression function of the logarithm of the volume. Furthermore, we present an algorithm that takes a set of gels with technical and biological replicates as input and estimates the average protein abundances in the biological groups from the number of missing spots and measured volumes of the present spots using a maximum likelihood approach. Confidence intervals for abundances and p-values for differential expression between two groups are calculated using bootstrap sampling. The algorithm is compared to two standard approaches, one that discards missing values and one that sets all missing values to zero. We have evaluated this approach in two different gel data sets of different biological origin. An R-program, implementing the algorithm, is freely available at http://bioinfo.thep .lu.se/MissingValues2Dgels.html.

No abstract

Using a decapitation ischemia model, we studied translocation of proteins to and from the cytosol in normothermic (NT) and hypothermic (HT) rat brains. 2D gel analysis identified 74 proteins whose cytosolic level changed significantly after 15 min of ischemia. HT preserved the cytosolic levels of several glycolytic enzymes, as well as many plasticity related proteins, otherwise decreased following NT ischemia. The levels of redox-related proteins was lower in HT than in NT. Our results indicate that translocation of proteins to and from the cytosol is an important issue during ischemia.