Effects of a platelet-activating factor antagonist,CV-6209, on Gastric mucosal lesions induced by ischemia-reperfusion

Recent research was shown that oxygen-derived free radicals are involved in the pathogenesis of various diseases, including ischemia-reperfusion injury. We have also reported that oxygen-derived free radicals and lipid peroxidation may play an important role in gastric mucosal injury induced by ischemia-reperfusion. The hypoxanthinexanthine oxidase system and neutrophils are considered important sources of oxygen-derived free radicals in this process. In recent years, it also has been shown that serum platelet-activating factor (PAF) levels increased during ischemia-reperfusion, and that induction of superoxide generation by neutrophils is one of the important biological effects of PAF. In the present study, we examined the effect of CV-6209, a specific PAF receptor antagonist, on gastric mucosal injury induced by ischemia-reperfusion, to shed some light on the possible involvement of PAF in such lesions. CV-6209 significantly attenuated the gastric mucosal injury induced by ischemia-reperfusion, and inhibited both an increase of thiobarbituric acid reactive substances and a decrease of α-tocopherol in gastric mucosa after ischemia-reperfusion. However, CV-6209 had no effect on gastric mucosal blood flow during ischemiano effect on gastric mucosal blood flow during ischemia-reperfusion. These results suggest that endogenous PAF may play an important role in gastric mucosal injury induced by ischemia-reperfusion, and that CV-6209 exerts its beneficial effect mainly by inhibiting neutrophil superoxide production induced by PAF. Based in part on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Phase relations in silicon and germanium nitrides up to 98 GPa and 2400°C

Phase relations in silicon and germanium nitrides (Si₃N₄ and Ge₃N₄) were investigated using a Kawai-type multianvil apparatus and a laser-heated diamond anvil cell combined with a synchrotron radiation. The pressure-induced phase transition from the β to γ (cubic spinel-type structure) phase was observed in both compositions. We observed the coexistence of the β and γ phases in Si₃N₄ at 12.4 GPa and 1800°C, while the appearance of single phase γ-Ge₃N₄ was observed at pressures above 10 GPa. Our observations under higher pressures revealed that γ-Si₃N₄ and γ-Ge₃N₄ have wide stability fields and no postspinel transition was observed up to 98 GPa and 2400°C in both compositions. Using the room-temperature compression curves of these materials, the bulk moduli (K₀) and their pressure derivatives (K′₀) were determined: K₀ = 317 (16) GPa and K′₀ = 6.0 (8) for γ-Si₃N₄; K₀ = 254 (13) GPa and K′₀ = 6.0 (7) for γ-Ge₃N₄.