天然溴化:酶、底物和溴化机制

溴在自然界主要以可溶或不可溶的溴化物形式存在,溴化物在农业、化工、医药等领域具有广泛的应用潜力。动植物和微生物也可以利用溴化酶合成天然有机溴化物。随着越来越多的溴化酶被发现,溴化现象被认为是生物合成与代谢途径中的修饰策略之一。本文从以下五个方面综述了天然溴化研究领域的最新进展,包括:(1) 溴化物的分布;(2) 天然溴化物的生物学功能及其对生态环境的影响;(3) 天然溴化物的临床应用潜力;(4) 溴化酶的分类与作用机理;(5) 近期报道的溴化酶。最后,讨论了溴化酶研究领域未来急需解决的科学问题。

Bromophenacyl bromide,a phospholipase A_2 inhibitor attenuates chemically induced gastroduodenal ulcers in rats

AIM: To study the effect of bromophenacyl bromide (BPB), a phospholipase A2 inhibitor on gastric secretion and to protect chemically induced gastric and duodenal ulcers in rats. METHODS: Acid secretion studies were undertaken in pylorus-ligated rats with BPB treatment (0, 5, 15 and 45 mg/kg). Gastric and duodenal lesions in the rats were induced by ethanol and cysteamine respectively. The levels of gastric wall mucus, nonprotein sulfhydryls (NP- SH) and myeloperoxidase (MPO) were also measured in the glandular stomach of rats following ethanol induced gastric lesions. RESULTS: BPB produced a dose-dependent inhibition of gastric acid secretion and acidity in rats. Pretreatment with BPB significantly attenuated the formation of etha- nol induced gastric lesion. BPB also protected intestinal mucosa against cysteamine-induced duodenal ulcers. The antiulcer activity of BPB was associated with signifi- cant inhibition of ethanol-induced depletion of gastric wall mucus, NP-SH and MPO. These findings pointed towards the mediation of sulfhydryls in BPB induced gas- trointestinal cytoprotection. CONCLUSION: BPB possesses significant antiulcer and cytoprotective activity against experimentally induced gastroduodenal lesions.

Role of neuronal nitric oxide synthase and inducible nitric oxide synthase in intestinal injury in neonatal rats

AIM： TO investigate the dynamic change and role of neuronal nitric oxide synthase （nNOS） and inducible nitric oxide synthase （iNOS） in neonatal rat with intestinal injury and to define whether necrotizing enterocolitis （NEC） is associated with the levels of nitric oxide synthase （NOS） in the mucosa of the affected intestine tissue. METHODS： Wistar rats less than 24 h in age received an intraperitoneal injection with 5 mg/kg lipopolysaccharide （LPS）. Ileum tissues were collected at 1, 3, 6, 12 and 24 h following LPS challenge for histological evaluation of NEC and for measurements of nNOS and iNOS. The correlation between the degree of intestinal injury and levels of NOS was determined. RESULTS： The LPS-injected increase in injury scores pups showed a significant versus the control. The expression of nNOS protein and mRNA was diminished after LPS injection. There was a negative significant correlation between the nNOS protein and the grade of median intestinal injury within 24 h. The expression of iNOS protein and mRNA was significantly increased in the peak of intestinal injury. CONCLUSION： nNOS and iNOS play different roles in LPS-induced intestinal injury. Caution should be exerted concerning potential therapeutic uses of NOS inhibitors in NEC.

PMA-ddPCR法检测活的非可培养状态高产乙醇肺炎克雷伯菌

目的建立活的非可培养(VBNC)状态高产乙醇肺炎克雷伯菌的绝对定量方法。方法诱导高产乙醇肺炎克雷伯菌进入VBNC状态,评价乙醇产量。建立PMA-ddPCR方法通过单拷贝基因来计数高产乙醇肺炎克雷伯菌VBNC状态的活细胞基因拷贝数。进一步在VBNC状态粪便模拟中,评价ddPCR对低浓度样品检测的灵敏度和适应性。结果对高产乙醇肺炎克雷伯菌梯度稀释液进行定量时ddPCR的检测下限是qPCR的10倍。在低温、低营养状态,高产乙醇肺炎克雷伯菌第45天进入VBNC状态,通过PMA-ddPCR对VBNC状态细胞进行定量结果为(5.46±0.05)log10 DNA 拷贝数/ml。VBNC状态的乙醇产量为<2.2 mmol/L,复苏后恢复产乙醇能力。VBNC状态粪便模拟样品中ddPCR最低检测下限为3.2 log10 DNA拷贝数/ml。结论建立VBNC状态高产乙醇肺炎克雷伯菌的ddPCR检测方法灵敏度和适应性良好,可用于临床样品中VBNC状态细胞的检测。