Oxygen Radical Production by a Red Tide Flagellate Chattonella and its Ichthyotoxicity

只有当死亡发生时，过氧化氢浓度（[H_2O_2]）才升高至约100 mg/L。1.5在黄尾鱼（Seriola quinqueradiata）开始暴露于查顿氏菌（Chattonella）后，立即将其浓度降低至μ mol/l。在鱼存活的情况下，H_2O_2在整个实验过程中没有检测到。鱼没有表现出生理干扰响应[H_2O_2]的5 μ mol/L添加到周围的水。因此，过氧化氢本身不是造成查顿氏菌鱼死亡的原因。颊部和鳃盖部的[H_2O_2]无明显差异。当用OH自由基清除剂甘露醇处理时，鱼的存活时间延长，表明OH自由基参与了查顿氏菌对鱼的致死机制。然而，与黄尾鱼不同的是，在7小时的暴露期间没有鱼被杀死。苏的区别 ...更多信息 比较了黄尾鱼、真鲷和比目鱼鳃中过氧化氢酶（CAT）和超氧化物歧化酶（SOD）的活性。过氧化氢酶的Vmax显着低于在比目鱼比黄尾，红鲷显示中间活动。过氧化氢酶和超氧化物歧化酶的Km值在3种植物间差异不显著。组织学检查表明，在暴露于查顿氏菌的早期，鳃中的过氧化氢酶活性的差异可能是导致黄尾鱼对查顿氏菌更敏感的原因。在这些鳃样品中观察到的唯一组织学变化是粘液阻塞了间隙。卡通氏菌产生氧自由基与粘液分泌的关系有待进一步研究。少

Only when mortality occurred, hydrogen peroxide concentration ([H_2O_2]) increased up to ca. 1.5 mumol/l immediately after the onset of exposure of the yellowtail, Seriola quinqueradiata, to Chattonella. In cases where fish survived, H_2O_2 was not detected throughout the experiment. Fish showed no physiological perturbations in response to [H_2O_2] of 5 mumol/l added to ambient water. Thus, hydrogen peroxide per se was not responsible to fish kill by Chattonella. There was no detectable difference in [H_2O_2] between samples collected from buccal and opercular cavities. When the effect of mannitol, known as an OH radical scavenger, was tested, survival of fish was prolonged, suggesting the involvement of OH radical in fish kill mechanism by Chattonella.When the Japanese flounder, Paralichthys olivaceus, were exposed to Chattonella, blood Po_2 rapidly declined as was the case in the yellowtail. Unlike yellowtail, however, no fish was killed during 7 hr of exposure. The difference in su … More sceptibility to Chattonella between these two fish species was considered to be attributable to difference in hypoxia tolerance between them.We then compared the activities of catalase and superoxide dismutase (SOD) in the gills of the yellowtail, red sea bream, and flounder. The Vmax of catalase was significantly lower in the flounder than in the yellowtail, red sea bream showing an intermediate activity. The Km of catalase as well as activity of superoxide dismutase was not significantly different between the three species. This difference in catalase activity in the gills may also be responsible to the higher susceptibility of the yellowtail to Chattonella.Histological examination revealed that there were no edema formation in the gills when the initial Po_2 drop occurred early in Chattonella exposure. The only histological change observed in those gill samples was blockage of interfilamental spaces by mucus. Relationship between oxygen radical production by Chattonella and mucus secretion needs to be elucidated in the future research. Less