Simultaneous stimulation of ex vivo pancreatic islets with dynamic oxygen and glucose is a critical technique for studying how hypoxia alters glucose-stimulated response, especially in transplant environments. Standard techniques using a hypoxic chamber cannot provide both oxygen and glucose modulations, while monitoring stimulus-secretion coupling factors in real-time. Using novel microfluidic...

Preconditioning stimulus: Preconditioning is an adaptive response, whereby a small dose of a harmful substance protects the brain from a subsequent damaging insult (Dirnagl et al., 2009). The concept of preconditioning was first described in an ischemic heart model, it was observed that brief ischemic episodes protect against a subsequent ischemic insult (Murry et al., 1986). Consequently, seve...

We present augmented Lagrangian Schur complement preconditioners and robust multigrid methods for incompressible Stokes problems with extreme viscosity variations. Such systems arise, instance, upon linearization of nonlinear viscous flow problems, they can have severely inhomogeneous anisotropic coefficients. Using an formulation the incompressibility constraint makes easier to approximate but...

BACKGROUND Anesthetic and ischemic preconditioning share similar signal transduction pathways. The authors tested the hypothesis that the beta1-adrenergic signal transduction pathway mediates anesthetic and ischemic preconditioning in vivo. METHODS Pentobarbital-anesthetized (30 mg/kg) rabbits (n = 96) were instrumented for measurement of systemic hemodynamics and subjected to 30 min of coron...

Ischemic preconditioning is a well-established phenomenon first described in experimental preparations in which brief episodes of ischemia/reperfusion applied prior to a longer coronary artery occlusion reduce myocardial infarct size. There are ample correlates of ischemic preconditioning in the clinical realm. Preconditioning mimetic agents that stimulate the biochemical pathways of ischemic p...

BACKGROUND Activation of protein kinase C epsilon (PKC-epsilon) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) are important for cardioprotection by preconditioning. The present study investigated the time dependency of PKC-epsilon and ERK1/2 activation during desflurane-induced preconditioning in the rat heart. METHODS Anesthetized rats were subjected to regional myocardial ische...

The Jacobi–Davidson (JD) algorithm was recently proposed for evaluating a number of the eigenvalues of a matrix. JD goes beyond pure Krylov-space techniques; it cleverly expands its search space, by solving the so-called correction equation, thus in principle providing a more powerful method. Preconditioning the Jacobi–Davidson correction equation is mandatory when large, sparse matrices are an...

We consider deflation and augmentation techniques for accelerating the convergence of Krylov subspace methods for the solution of nonsingular linear algebraic systems. Despite some formal similarity, the two techniques are conceptually different from preconditioning. Deflation (in the sense the term is used here) “removes” certain parts from the operator making it singular, while augmentation a...

background: the aim of this study was to investigate the effects of high-intensity interval training (hiit) on nitric oxide metabolites (no2 - , no3 - ) and myocardial infarct size after ischemia/reperfusion (i/r) injury in healthy male rats. methods: a total of 44 wistar rats were randomly divided into 4 groups including hiit (n=8), hiit + ir protocol (n=14), control (n=8), and control + ir (n...

objective: ischemic preconditioning (ipc) is an endogenous phenomenon that can induce ischemic tolerance (it) in variety of organs such as brain. in this study, we examined the intermittent and prolonged normobaric hyperoxia (ho) on neurologic deficit scores, infarct volume, and superoxide dismutase activity. materials and methods: the rats were divided to four main groups. first two main grou...