Heart and red blood cell antioxidant status and plasma lipid levels in the spontaneously hypertensive and normotensive Wistar-Kyoto rat

Heart and red blood cell endogenous antioxidant status and plasma lipids were investigated in hypertensive, 14-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats fed a standard commercial rat chow. Specific heart and red blood cell antioxidant enzyme activities, as well as the susceptibility of tissues to H2O2-induced glutathione (GSH) depletion and lipid peroxidation, were measured. Systolic blood pressure in SHR was greater than in WKY rats at 13 weeks of age (197 +/- 12 vs. 132 +/- 14 mmHg (1 mmHg = 133.3 Pa); p < or = 0.05), confirming the presence of hypertension in SHR. Red blood cell catalase (CAT) and superoxide dismutase (SOD) activities were greater (p < or = 0.05) in SHR than WKY rats. Red blood cell CAT activity was positively correlated (r = +0.634; p = 0.026) with SOD, which in turn was correlated (r = +0.709; p = 0.049) with systolic blood pressure. Heart SOD activity was higher (p < or = 0.05) in SHR, while glutathione reductase (GSSG-Red) activity was lower (p < or = 0.05) than in WKY rats. This reduced ability to recycle GSH in the heart coincided with greater (p < or = 0.05) levels of H2O2-induced lipid oxidation products in SHR. Plasma total cholesterol and triacylglycerol levels were lower (p < or = 0.05) in SHR than WKY rats, with no visible signs of atherosclerosis in either SHR or WKY rats. In summary, hypertension in SHR was associated with alterations in antioxidant enzyme profiles of red blood cells and heart, with the latter showing an increased susceptibility to in vitro lipid oxidation. Although hypertension is a recognized factor in the development of human atherosclerosis, spontaneously hypertensive rats did not exhibit signs of aortic plaque, reflecting the resistance of this species to the development of atherosclerosis.     

Differential effects of 15-HPETE and 15-HETE on BHK-21 cell proliferation and macromolecular composition

Arachidonate and/or linoleate metabolites have been implicated in modulating cell growth, replication and cell transformations. In studies with BHK-21 cells, we found lipoxygenase and cyclooxygenase inhibitors (NDGA and indomethacin, respectively) to be antiproliferative. Studies on the metabolism of arachidonic acid in BHK-21 cells have demonstrated that prostaglandin D2 is the major cyclooxygenase product, and 15-hydroxyeicosatetraenoic acid (15-HETE) is the major lipoxygenase product. Addition of D2 showed a significant decrease in the BHK-21 cell number showing antiproliferative action. Addition of lipoxygenase products, on the other hand, showed differential effects in that 15-HPETE decreased the cell number while 15-HETE increased. NDGA and 15-HPETE decreased DNA, RNA and protein contents, while 15-HETE significantly increased them. 5-HPETE and 5-HETE also showed similar results but were less potent than 15-H(P)ETEs. The differential effects of 15-HPETE and 15-HETE could be due to the generation of free radicals by the hydroperoxide and mitogenic response by hydroxide.     

粉末冶金压制成形受力情况的研究

本文将多台阶的零件拆分为多个简单圆柱体,并结合圆柱体压坯的有关实验,对原零件做了压制前的受力分析,预先了解到了多台阶零件压制时的受力情况,为粉末冶金产品的压制提供了理论参考。