A novel nitric oxide scavenger decreases liver injury and improves survival after hemorrhagic shock

We tested the ability of a nitric oxide (NO) scavenger to reduce tissue injury in a rodent model of hemorrhagic shock. Rats were hemorrhaged to a mean arterial blood pressure (MAP) of 40 mmHg and then resuscitated when either 30% of their shed blood had been returned ( group 1) or after 100 min of continuous shock ( group 2). Selected animals were treated with the NO scavenger NOX (30 mg ⋅ kg−1 ⋅ h−1) infused over 4 h. Hemorrhaged rats had a lower MAP after resuscitation compared with sham-shock control rats. NOX treatment significantly increased MAP after resuscitation from hemorrhage. Hemorrhagic shock also increased liver injury as reflected by elevated ornithine carbamoyltransferase (OCT) plasma levels, and NOX treatment significantly reduced OCT release. In addition, NOX was associated with significantly decreased hepatic neutrophil infiltration and improved 24-h survival ( n = 8 of 9) compared with saline-treated shock animals ( n = 3 of 9). These data suggest that excess NO mediates shock-induced tissue injury and that suppression of NO availability with NO scavengers may reduce the pathophysiological sequelae of severe hemorrhage.

The compressible vortex pair

We consider the steady self-propagation with respect to the fluid at infinity of two equal symmetrically shaped vortices in a compressible fluid. Each vortex core is modelled by a region of stagnant constant-pressure fluid bounded by closed constant-pressure, constant-speed streamlines of unknown shape. The external flow is assumed to be irrotational inviscid isentropic flow of a perfect gas. The flow is therefore shock free but may be locally supersonic. The nonlinear free-boundary problem for the vortex-pair flow is formulated in the hodograph plane of compressible-flow theory, and a numerical solution method based on finite differences is described. Specific results are presented for a range of parameters which control the flow, namely the Mach number of the pair translational motion and the fluid speed on each vortex bounding streamline. Perturbation-theory predictions are developed, valid for vortices of small core radius when the pair Mach number is much less than unity. These are in good agreement with the hodograph-plane calculations. The numerical and the perturbation-theory results together confirm the recently discovered (Barsony-Nagy, Er-El & Yungster 1987) existence of continuous shock-free transonic compressible flows with embedded vortices. For the vortex-pair geometry studied, solution branches corresponding to physically acceptable flows that could be calculated using the present hodograph-plane numerical method were found to be terminated when either the flow on the streamline of symmetry separating the vortiqes tends to become superonic or when limiting lines appear in the hodograph plane giving a locally multivalued mapping to the physical plane.

Continuity of Shock and Level of Aversiveness in Shuttlebox-Avoidance Behavior

4 groups of 16 rats each were given standard shuttlebox-avoidance training. 2 groups were trained with a continuous shock which, depending on the scrambling arrangement, could be characterized as relatively more or less aversive, respectively. 2 groups were trained with a discontinuous shock which, depending on duration and frequency, could be characterized as relatively more or less aversive. Superior performance was obtained with the less aversive discontinuous shock compared with a more aversive discontinuous shock, and a continuous aversive shock led to better performance than a continuous less aversive shock. The results partially support Dieter's (1976) continuity of shock explanation.