色氨酸残基在磷酸烯醇式丙酮酸羧化酶催化功能中的作用

在pH7.5条件下,用NBS对PEP羧化酶中色氨酸残基进行共价修饰表明,PEP羧化酶中48个色氨酸残基均能被NBS修饰。用邹承鲁图解法求得,其中4个残基为酶表现催化活性所必需的。 PEP羧化酶的变构效应剂G6P、Gly及Mal分别与酶预保温后,再经NBS修饰,前两种处理中,同样浓度的NBS所用修饰的色氨酸残基数和处理后的残存酶活与对照相比有很大的差异,而用Mal处理的,两者与对照相差无几。     

马齿苋叶片PEP羧化酶的分子特性

马齿苋叶片PEPCase由四个相同的亚基组成,亚基分子量为83kD。远紫外CD光谱分析表明,此酶含有36.6％α—螺旋结构。马齿苋叶片PEPCase可被G6P激活,但不能被Gly、Ser激活。G6P可防止酶的尿素变性和枯草杆菌蛋白酶的作用。这种保护效应与G6P诱导的酶构象变化有关。 从酶对低温、高温及尿素的反应来看,马齿苋叶片PEPCase的稳定性高于高粱叶片PEP—Case,两者的免疫特性和电泳特性亦不同。     

银额果蝇的B染色体研究 2.昆明群体的生活力和B染色体的关系

本文分析了钮额果蝇的生活力和B染色体的关系。结果表明,银额果蝇的B染色体在其生长和发育过程中具双重性调节作用。一方面,B染色体以单一的形式存在于单雌系核型中,即1B或2Bs,可刺激生长、发育,增强生活力。另一方面,在单雌系的细胞中存在多条B染色体,并形成核型多态性,这似乎对生长和发育又有一定的抑制作用而减弱其生活力。     

去甲肾上腺素在大鼠缰核引起的心血管效应及其机制

在乌拉坦麻醉的大鼠,研究了去甲肾上腺素(NE)在缰核(Hb)引起的心血管效应及其机制。Hb内微量注射NE使平均动脉压和心率呈剂量依赖性增加。用α受体阻断剂酚妥拉明预处理Hb,可明显减弱NE在Hb引起的心血管效应,但β受体阻断剂心得安或生理盐水不引起任何影响。Hb内微量注射海人酸使平均动脉压和心率明显增加,但Hb内微量注射利多卡因则不能引起明显的心血管效应。上述结果表明,Hb内NE在调节心血管活动中起重要作用,而这种效应可能是通过激活α受体使Hb兴奋的结果。     

NO—样松驰因子在大鼠止血带休克中的作用

为探讨NO-样松驰因子(NO-LRF)在休克中的效应及其病理生理意义,本工作在大鼠止血带休克(ToS)模型上发现离体灌流的主动脉环对去甲肾上腺素的反应性降低,组织cGMP含量增加。用NO前体L-精氨酸(L-Arg)或NO合成阻断剂L-NNA,可溶性乌苷酸环化酶抑制剂亚甲蓝灌流,分别增强或减轻ToS动物主动脉的上述变化,而且这些药物的作用不受血管内皮是否存在的影响。实验结果提示非内皮细胞源的NO-LRF是引起ToS动物血管低反应性的因素之一。体内实验表明 L-Arg治疗缓解,而L-NNA恶化ToS病程,提示NO-LRF可能参与机体的适应保护机制。     

一个拖延了半个多世纪的研究课题的总结汇报

本文是汤佩松教授为北京植物生理学会1992年年会准备的发言稿,并以庆祝中国植物生理学会成立30周年。后“北京年会”因故未开,本刊应汤老要求按原样发表于此(并附英文摘要),以飨读者。     

Sensitization of low-dose-rate irradiation by nonlethal hyperthermia

To assess whether hyperthermia could radiosensitize cells irradiated at a low dose rate, Chinese hamster V79 cells were simultaneously heated and irradiated at 0.86 Gy/h. The data showed that heat treatments at 39 and 40 degrees C, which did not induce heat killing alone or high-dose-rate radiosensitization, resulted in enhanced cell killing with low-dose-rate irradiation. The dose-modification factor (ratio of the slopes of the curves for low dose rate and high dose rate) was reduced to 1.8 at 39 degrees C and 1.4 at 40 degrees C, compared to a value of 2.1 at 37 degrees C. These data indicate that nonlethal heat treatments can cause enhanced radiosensitization under low-dose-rate conditions. The implications of these results for interstitial thermoradiotherapy are discussed.     

Changes in pulmonary Cu−Zn contents in superior mesenteric artery occlusion shock of rabbit

Contents of Cu and Zn of into-pulmonary blood (IPB), out-pulmonary blood (OPB), Lung tissue, and supernatant and macrophages of Lung Lavage were determined in superior mesenteric artery occlusion (SMAO) shock of rabbits. Zn of pulmonary tissue was 11.42 +/- 0.60 and 14.52 +/- 1.78 (micrograms/g wet wt) in SMAO shock and control groups, respectively. Content of Zn was found to be lower, Cu was not changed, and Cu/Zn ratio increased in lung tissue in SMAO shock. Contents of Cu and Zn in other samples were not changed. The results suggest that lower Zn in lung tissue related to acute lung injury.     

Randomised controlled trial of short term treatment to eradicate Helicobacter pylori in patients with duodenal ulcer.

OBJECTIVE--To determine whether one week''s drug treatment is sufficient to eradicate Helicobacter pylori in patients with duodenal ulcer. DESIGN--Single blind, randomised controlled trial. SETTING--Specialised ulcer clinic in a teaching hospital. PATIENTS--155 patients with H pylori and a duodenal ulcer verified endoscopically which had either bled within the previous 24 hours or was causing dyspepsia. INTERVENTIONS--Patients were allocated randomly to receive either omeprazole for four weeks plus bismuth 120 mg, tetracycline 500 mg, and metronidazole 400 mg (all four times a day) for the first week (n = 78), or omeprazole alone for four weeks (n = 77). Further endoscopy was performed four weeks after cessation of all drugs. MAIN OUTCOME MEASURES--Presence or absence of H pylori (by urease testing, microscopy, and culture of antral biopsy specimens), duodenal ulcer, and side effects. RESULTS--Eradication of H pylori occurred in 70 (95%) patients taking the four drugs (95% confidence interval 86% to 97%) compared with three (4%) patients taking omeprazole alone (1% to 11%). Duodenal ulcers were found in four (5%) patients taking the four drugs (2% to 12%) and in 16 (22%) patients taking omeprazole alone (14% to 32%). Mild dizziness was the only reported side effect (six patients in each group) and did not affect compliance. CONCLUSIONS--A one week regimen of bismuth, tetracycline, and metronidazole is safe and effective in eradicating H pylori and reduces the number of duodenal ulcers four weeks after completing treatment.