磷脂酶D催化反应中的有机溶剂效应

对酶催化反应中的有机溶剂效应进行了深入讨论，引用溶剂化概念解释了有机溶剂对反应平衡状态，反应速率和反应选择性的影响。此外，考察了２４种有机溶剂对磷脂酶Ｄ催化反应的影响，提出了有机溶剂作用机理，即有机溶剂使酶蛋白微粒和底物磷脂表面更具疏水性，从而增加了酶和底物的相互吸引。主题词     

PDE5在ED治疗中的靶向作用

作为细胞内信号传导的第二信使，cAMP和cGMP在细胞的生命活动中有重要的意义，细胞内cAMP和cGMP水平的调控是由环化酶的合成和磷酸二酯酶（PDEs）的水解作用来实现。PDEs能特异性地催化环嘌呤核苷酸的3’，5’-磷酸二酯键，水解生成相应的无活性的5’-GMP或5’-AMP。自1962年Sulherland和Rall首次发现别对细胞内第二信使cGMP和cAMP具有水解活性的PDE以来。     

短杆菌异淀粉酶产生菌选育及酶作用性质研究

研究和讨论了一株短杆菌异淀粉酶的筛选,诱变,产酶条件及部分酶学特性。结果是摇瓶发酵液中酶活单位最高可达520u/ml.酶作用最适pH可低至5.0,最适温度可高至55℃。该酶对多种不同的含α-1,6-葡萄糖苷键的底物皆具有良好的水解作用。水解产物的分子量分布情况类似于假单胞菌异淀粉酶。     

注射用胶原酶对磷脂酶A2活性抑制作用的体外实验研究

目的研究注射用胶原酶对炎性物质磷脂酶A2(PLA2)的水解作用和对其活性的抑制作用。方法制备不连续SDS-PAGE垂直平板凝胶,将3种酶促反应体系的不同酶解时间的反应液样品,进行电泳、固定、染色、脱色。同时在PLA2活性测定体系中,加入定量的胶原酶溶液,测定各反应体系的PLA2活性相当值。以不含胶原酶的PLA2活性测定体系为标准,求出不同活性单位胶原酶体系的PLA2相对活性,并依据实验所获得的数据,绘制Lineweaver-Burk图加以识别。通过对注射用胶原酶在PLA2水解卵磷脂过程中所起的作用,确定注射用胶原酶对PLA2活性的抑制机制。结果注射用胶原酶对PLA2无水解作用,但在体外对PLA2的活性有明显的抑制作用,其抑制类型为竞争性抑制,且抑制作用随胶原酶剂量的增加而增强。结论虽然注射用胶原酶在体外对炎性物质PLA2的活性有明显的抑制作用,但根据酶促反应动力学的基本理论,“针抵患处、酶达底物”是构成化学溶解术这一微创技术的基本要素和应用该技术时必须遵守的基本原则。     

烟雾对灌注和机械通气大鼠肺内血管舒缓素代谢的影响

烟雾吸入不仅能损害肺气体交换功能,还能损害肺内血管性物质的代谢。血管舒缓素是一种在肺内代谢的血管活性物质,具有增强毛细血管通透性及扩张血管作用。作为炎症因子,还能调节内皮细胞功能。肺循环内95％以上的血管舒缓素被肺内皮细胞内酶系统破坏,主要是通经氨基肽酶P和血管紧张素转换酶的水解作用。作者观察了肺烟雾损伤对肺内血管舒缓素代谢的影响。将吸入烟雾大鼠肺脏取下,制成肺脏灌注和机械通气实验装置。灌注液和     

类酶催化反应机理的量子化学的研究

研究了癸酰基－Ｌ－组氨酸催化下的苄酯基－Ｎ－苯丙氨酸对硝基苯酚的类酶催化反应。用ＩＮＤＯ程序计算了底物和催化剂的电荷分布。通过分析，得到了底物和催化剂的活性中心，并提出了一个合理的反应机理。     

休克与蛋白酶

一、蛋白酶休克中蛋白水解作用是很复杂的问题,因为它包含许多器官和机理。首先将描述蛋白酶的术语和分类,区别肽链内切酶与肽链外切酶。特别是肽链内切酶,也叫蛋白酶,更切合它本身的意义。可以鉴别为负责转换细胞蛋白的细胞内蛋白酶,和只引起有限的蛋白水解的血浆蛋白酶。蛋白酶分成四组(表1),每种各有不同的最适pH。休克中特别重要的是丝氨酸和金属蛋白酶。丝氨酸蛋白酶的主要代表是:胰蛋白酶、     

神经元特异性烯醇化酶在小细胞肺癌中的应用

目的:探讨血清肿瘤标记物神经元特异性醇化酶(NSE)对小细胞肺癌诊断及观察疗效的临床价值.方法:采用化学发光法检测46例小细胞肺癌,27例良性肺病患者和50例健康人的血清神经元特异性烯醇化酶,结果:小细胞肺癌组血清神经元特异性醇化酶明显高于良性肺病和健康人对照组.结论:血清神经元特异性烯醇化酶对小细胞肺癌诊断及疗效评估有重要的参考价值.     

经梭状芽胞杆菌胶原酶分解细胞外基质分子释放的活性片段

该文研究旨在探讨细胞外基质(ECM)降解片段在创面愈合中的生物学作用。用梭状芽胞杆菌纯化的胶原酶消化人烧伤焦痂组织得到小分子ECM片段(分子量小于10kDa),进行系列实验以观察所释放具有生物活性的ECM源性的降解片段对坏死组织的酶水解作用。     

有应用前景的前列腺癌相关肿瘤标志物

前列腺癌是男性泌尿系统最常见的恶性肿瘤之一,其病死率为男性癌症死亡的第二位。前列腺癌的早期诊断主要是前列腺特异性抗原筛查,但该指标特异性低。目前有许多敏感性、特异性更高的肿瘤标志物(TM)被发现,现就近年研究较多、有应用前景的几种TM(前列腺癌抗原3、早期前列腺癌抗原、前列腺特异性膜抗原、α-甲酰基辅酶A消旋酶和血管内皮生长因子)予以综述。     

Gastric mucosal pH is associated with initial graft function but is not a predictor of major morbidity after liver transplantation

Gastric mucosal pH reflects splanchnic perfusion. Monitoring gastric mucosal pH might be useful in predicting outcome after liver transplantation. Forty patients were included in the study. Gastric mucosal pH and gastric mucosal pH corrected for systemic pH were compared with regard to initial liver function and morbidity. Eighty percent of the patients had at least one episode with a gastric mucosal pH of <7.32, and 84% of these had a concomitant arterial pH of <7.32. No differences in morbidity were found between patients with a gastric mucosal pH of <7.32 and those with a gastric mucosal pH of >7.32. If gastric mucosal pH was corrected for arterial pH, only 49% of the patients had an episode during transplantation with a corrected gastric mucosal pH of <7.32. Comparing these patients with the group that did not have such an episode, we found that flow in the venovenous bypass system was significantly lower (2.9 v 3.4 L/min; P < .02) in the first group. Also alanine aminotransferase and aspartate aminotransferase levels were higher, antithrombin III levels and lidocaine clearance rates were lower, and prothrombin times were longer in the group with corrected gastric mucosal pH of <7.32. No differences with regard to major morbidity and mortality were noted. Gastric mucosal pH during liver transplantation should be corrected for arterial pH. Patients with a corrected gastric mucosal pH of <7.32 are more likely to develop initial liver function tests disturbances, but morbidity is not different from patients with gastric mucosal pH of >7.32. (Liver Transpl Surg 1997 Nov;3(6):611-6)     

Oesophagitis and pH of refluxate: an experimental and clinical study.

This experimental and clinical study examined the relationship between oesophageal damage and optimal pH of refluxate, and whether 24-h pH monitoring at optimal pH could discriminate the severity of oesophagitis. The rabbit oesophagus was perfused in vivo with pepsin and hydrochloric acid solutions of differing pH for 60 min. Maximal oesophageal damage coincided with peptic solutions at pH 1.5-2.5. Fifty-nine patients with proven gastro-oesophageal reflux disorders were tested for manometric features of the lower oesophageal sphincter (pressure, overall length and abdominal length) and oesophageal exposure to different pH levels. They were classified into four groups according to the endoscopically demonstrated severity of oesophagitis. Supine exposure at the optimal pH level for pepsin activity (pH 1.5-2.5) and overall sphincter length were found to discriminate the severity of oesophagitis reliably in 75 per cent of cases.     

A New Technique for Measurement of Pharyngeal pH: Normal Values and Discriminating pH Threshold

Introduction  Identifying gastroesophageal reflux disease as the cause of respiratory and laryngeal complaints is difficult and depends largely on the measurements of increased acid exposure in the upper esophagus or ideally the pharynx. The current method of measuring pharyngeal pH environment is inaccurate and problematic due to artifacts. A newly designed pharyngeal pH probe to avoid these artifacts has been introduced. The aim of this study was to use this probe to measure the pharyngeal pH environment in normal subjects and establish pH thresholds to identify abnormality. Methods  Asymptomatic volunteers were studied to define the normal pharyngeal pH environment. All subjects underwent esophagram, esophageal manometry, upper and lower esophageal pH monitoring with a dual-channel pH catheter and pharyngeal pH monitoring with the new probe. Analyses were performed at 0.5 pH intervals between pH 4 and 6.5 to identify the best discriminating pH threshold and calculate a composite pH score to identify an abnormal pH environment. Results  The study population consisted of 55 normal subjects. The pattern of pharyngeal pH environment was significantly different in the upright and supine periods and required different thresholds. The calculated discriminatory pH threshold was 5.5 for upright and 5.0 for supine periods. The 95th percentile values for the composite score were 9.4 for upright and 6.8 for supine. Conclusion  A new pharyngeal pH probe which detects aerosolized and liquid acid overcomes the artifacts that occur in measuring pharyngeal pH with existing catheters. Discriminating pH thresholds were selected and normal values defined to identify patients with an abnormal pharyngeal pH environment. This work has been presented at the Digestive Disease Week, San Diego, California, May, 2008. The study was supported by a grant from the Respiratory Technology Corp. T.R. DeMeester is on the scientific advisory board of Respiratory Technology Corp.     

The effect of enteral feeding on gastric pH. Tie for second place Jobst award

To study the effect of jejunal feeding on gastric pH, 13 multiply injured trauma patients having needle catheter jejunostomies were prospectively evaluated. Normal saline and one-half strength Traumacal were infused alternately at 50 cc/hr for 24 hours and gastric pH was measured every other hour. If gastric pH dropped to 4.5 or below, patients received 30 cc of antacid via nasogastric tube. A total of 324 gastric pH determinations were made and 93 doses of antacids were administered. Average gastric pH during Traumacal infusion was 5.34 and did not significantly differ from the average pH (5.37) during saline infusion. Using multivariate analysis to control for antacids, along with diurnal and day-to-day variations, no statistically significant effect of jejunal feeding on gastric pH could be demonstrated. These results suggest that prophylaxis for stress ulceration needs to be maintained in severely injured patients fed via the jejunum.     

Continuous Monitoring of Rumen pH – A Case Study With Cattle

The use of a new pH probe for continuous rumen pH measurement was investigated in a preliminary study in cattle during a 10‐day period. Two cannulated non‐pregnant dairy cows were used together with two autonomous stomach probes, containing a commercial microelectrode and a reference‐electrode with a pressure‐equalizing system. By feeding diets with changing composition it was thought to provoke marked changes in rumen pH. Probes were programmed to sample pH and temperature every 30 s. During the entire experimental period, three daily rumen fluid samples were collected via the cannula as close to the probe as possible. Upon removal of probes, final calibration revealed only minor drifting of electrodes, that was significantly lower than results obtained during previous work with continuous measurement of gastric pH. After drift correction, the calculated absolute error of respective probe measurements for 11 sampling events was on average 0.08 pH for cow 817 (maximum 0.085 pH) and 0.14 pH for cow 686 (maximum 0.146 pH). pH measured by gastric probe was on average lower (i.e. more acid) than pH determined by tube sampling, with a mean difference of 0.33 pH (maximum 0.54) and 0.05 pH (maximum 0.5) for cow 817 and cow 686, respectively. The present prototype may thus play an important role in the development of a telemetric device for continuous monitoring of rumen pH in cattle and potentially other ruminants.     

几种常用的核染色标记物pH 6.0 Citrate和pH 9.0 Tris/EDTA修复液的比较

目的 探讨pH 6.0 Citrate和pH 9.0 Tris/EDTA两种修复液在常用的免疫组化核染色标记物中的染色效果. 方法 选取本科室常用的3种核/浆标记抗体以及22种核标记抗体分别采用pH 6.0 Citrate和pH 9.0 Tris/EDTA微波热修复进行比较. 结果 在25种抗体中,其中有11种分别用pH 6.0 Citrate和pH 9.0 Tris/EDTA微波修复染色效果基本一致,在其余14种抗体中,有11种用pH 9.0 Tris/EDTA微波热修复方法进行修复时,阳性信号明显增强；而有3种抗体用pH 6.0 Citrate微波热修复方法进行修复时,阳性信号稍增强. 结论 对于这25种抗体来说,如果用微波加热的方法进行抗原修复,那么pH 9.0 Tris/EDTA优于PH 6.0 Citrate.     

Spinal Anesthesia in Sheep with Local Anesthetic Solutions at pH 4 and pH 7

Spinal anesthesia was performed in sheep, using five widely-used local anesthetic agents. The durations of sensory and motor block were shortest with procaine and longest with bupivacaine and tetracaine. The durations of block with prilocaine and mepivacaine fell between those of procaine and bupivacaine. These results agree with what we know about the relative durations of action of these agents in man. All solutions were tested at pH 4 and pH 7, but, except for prilocaine, there were no differences in the mean durations of sensory and motor block at the two pH levels. Sensory block with prilocaine solution at pH 7 was about 20% longer than at pH 4. With all the compounds except prilocaine, the frequency of motor block in the hind limbs was lower at pH 7 than at pH 4. We conclude that single injections of unbuffered solutions of these agents at pH 4 are as effective in terms of onset and duration as solutions at pH 7. The results of this study reconfirm the usefulness and reliability of the sheep as a model for evaluating and comparing spinal anesthetics.     

The effect of pH on the in vitro colony forming ability of transitional cell carcinoma cells treated with various chemotherapeutic agents: implications for in vivo therapy.

Extracellular pH may affect the sensitivity of cancer cells to chemotherapy agents. In an attempt to maximize the conditions for chemotherapy treatment of transitional cell carcinoma we tested the effect of pH on sensitivity of MGH-U3 transitional cell carcinoma cell line to thiotepa, doxorubicin, and mitomycin c in vitro. The toxicity of each agent tested varied with pH. There was no variation in cell growth in response to pH alone. The cytotoxic activity of thiotepa was markedly enhanced when cells were treated with a diluent pH of 5.5. Significant differences were also observed after treatment with doxorubicin and mitomycin c with a diluent pH of 7.0. This in vitro assay may be useful for clinical application of pH modulation during intravesical chemotherapy.     

Arteriovenous pH difference--a new index of perfusion

Measurement of the pH of arterial blood may not reflect early stages of anaerobic metabolism. Since a relationship exists between pH and cellular utilization of oxygen, this study sought to determine whether the difference between arterial and venous pH might serve as a more useful index for estimating the adequacy of tissue perfusion. Dogs were made hypovolemic, and hemodynamic profiles including thermodilution cardiac output were obtained while simultaneous arterial and central venous blood samples were analyzed for pH. Arteriovenous pH difference increased as cardiac index fell. Whenever the arteriovenous pH difference became greater than 0.05 pH units, the cardiac index had fallen below 65% of the baseline values. A difference of 0.05 pH units between arterial and venous blood predicted hypoperfusion in 90% of the animals. With deepening shock the gradient widened, and when resuscitation was effective the arteriovenous pH difference returned toward normal. These data suggest that arteriovenous pH difference may reliably predict clinically significant reductions in cardiac output and cellular perfusion. This finding could be useful in pediatric trauma and critical care settings in which invasive monitoring and direct determination of cardiac output are technically difficult.     

Molecular Structure of Human Seminal Coagulum: The Role of Proteolysis

The techniques of SDS-polyacrylamide slab gel electrophoresis and a sensitive fluorescamine-based method were used to study autoproteolysis of human seminal coagulum at various pH. The major protein bands of 72 and 55 Kd were optimally degraded at pH 7.5. Degradation at pH 3.5 was preceded by a lag period of 30 min. When the seminal coagulum was incubated for 5 min at pH 7.5 and then adjusted to pH 3.5, degradation was more rapid and complete than at pH 3.5 only. Autoproteolytic degradation product of discreted sizes were obtained when compared with degradation in the presence of pronase.