Protective effect of ischemic preconditioning on hepatic ischemia-reperfusion injury by advancing the expressive phase of survivin in rats

BACKGROUND: Survivin is a new and important gene in the regulation of apoptosis. It is very important to explore the effect of the expression of survivin protein caused by ischemia-reperfusion (IR) injury. The effect of IR injury caused by ischemic preconditioning (IP) on the liver in rats and the relation between the protective effect of IP and the expression of survivin are unclear. METHODS: One hundred and fifty male Wistar rats (weighing 190-210 g, aged 6-7 weeks) were divided into three groups at random: ischemic preconditioning (IP), ischemia-reperfusion (IR) and sham-operation (SO). Sample specimens were collected from each group at 6, 12, 24, 48, and 72 hours after reperfusion. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured by an automatic biochemical analyzer. Malondialdehyde (MDA) in liver tissue was measured. Pathological changes in the liver and immunohistochemical staining for survivin were determined with an optical microscope. RESULTS: The ALT levels in the IP and IR groups after reperfusion at each time were higher than those in the SO group (P<0.05), whereas after reperfusion for 6 and 12 hours, the ALT levels in the IP group were lower than those in the IR group (P<0.05). The AST levels in all IP and IR groups were higher than those in the SO group (P<0.05), whereas after reperfusion for 12, 24, 48 and 72 hours, the AST levels in the IP group were lower than those in the IR group (P<0.05). The MDA concentrations after reperfusion in the IP group were lower than those in the IR group (P<0.05), though the MDA concentrations in the IP and IR groups increased in contrast to those in the SO group after reperfusion at each time (P<0.05). After reperfusion for 12, 24, 48 and 72 hours, the number of survivin-positive cells was larger in the IP and IR groups than in the SO group (P<0.05). After reperfusion for 12, 24, and 48 hours the number of survivin-positive cells in the IP group increased compared with that in the IR group (P<0.05). CONCLUSIONS: IR increases the protein expression of survivin in liver tissue. IP inhibits the accumulation of MDA, advances the expressive phase of survivin protein in hepatic tissue, and improves liver function.

Geometrical Modeling by NURBS Surface and RCS Computing by Visualization for Complex Targets

A novel approach to compute the high frequency radar cross-section (RCS) of complex targets is described in this paper.From the three views or the sectional views of the target, target is geometrically modeled by non-uniform rational B-spline (NURBS) parametric surfaces using the software CNFEOV developed by oneself which constructs NURBS representation of complex target from engineering orthographic views. RCS is obtained through PO, PTD, MEC and IBC techniques. When calculating RCS of the target, it is necessary to get the unit normal vector to surface illumi- nated by radar and the value Z which is the distance from the point on the surface to radar. ln this novel approach, the unit normal vector to the surface can be obtained either by the Phong rendering model, in which the color components (RGB) of every pixel on the image are equal to the coordinate components of the normal, or by the NURBS expressions. The value Z can be achieved by software or hardware Z-buffer. The effects of the size of image on the RCS of target are discussed and the correct method is recommended. The RCS of the perfect conducting sphere, cylinder and dihedral as well as the coated cylinder, as some examples, are computed. The accuracy of the method is verified by comparing the numerical results with those obtained by using other methods.