N-乙酰-L-半胱氨酸溶液氧化反应速率常数的测定

目的测定N-乙酰-L-半胱氨酸(NAC)在水溶液中氧化反应的速率常数。方法在一定温度下,向反应液中持续通入空气,以维持溶解氧浓度恒定,利用氧电极测定氧的浓度;采用碘量法测定NAC在水溶液中不同时刻的浓度,计算氧化反应降解速率常数。结果试验温度下,在pH9.0、pH6.8的缓冲溶液中,NAC与氧的反应均为表观零级反应,298.2 K时平均表观反应速率常数分别为8.03×10-3、0.08 mmol.L-.1h-1;而在pH4.0的缓冲溶液中,NAC与氧的反应为表观一级反应,298.2 K时,平均表观反应速率常数为0.02 h-1。结论弱碱性和中性条件下反应速率较慢,NAC的抗氧化能力较强;在弱酸性条件下反应速率较快,抗氧化能力较弱。在NAC溶液的初始浓度及pH相同条件下,温度升高,表观反应速率常数增大。     

抗氧剂L-半胱氨酸盐酸盐在水溶液中的氧化反应速率常数

目的 测定抗氧剂L-半胱氨酸盐酸盐在水溶液中与氧反应的速率常数,并评价其抗氧化能力.方法 在25℃、35℃、45℃下,向反应液中持续通入空气以维持溶解氧浓度恒定,并用氧电极测定其浓度;用碘量法测定L-半胱氨酸盐酸盐在水溶液中不同时刻的浓度,做出降解曲线,计算各温度下的氧化降解速率常数.结果 25℃时,L-半胱氨酸盐酸盐在pH4.0、pH6.8缓冲溶液中与氧的反应均为表观零级反应,而在pH9.0缓冲溶液中为表观一级反应.3个不同pH条件下的表观反应速率常数分别为7.78、30.1μmol·L-1·h-1、5.03×10-2 h-1.结论 L-半胱氨酸盐酸盐在弱酸性条件下,反应速率较慢,抗氧化能力较弱;在中性和弱碱性条件下反应速率较快,抗氧化能力较强.     

抗氧剂L-抗坏血酸在水溶液中氧化反应速率常数的测定

目的测定抗氧剂L-抗坏血酸在3种缓冲溶液中与氧反应的速率常数。方法反应液中持续通入空气,在保证溶液中氧浓度恒定的情况下,用碘量法测定不同时刻抗坏血酸溶液的浓度,作出降解曲线,拟合降解公式并计算降解速率常数。结果抗坏血酸在中性和弱碱性溶液中为表观一级反应,氧化反应速率常数分别为(9.24±0.8)×10-3h-1,(100±1)×10-3h-1;在弱酸性溶液中为表观1/2级反应,氧化反应速率常数为(8.73±0.14)×10-5mol1/2·L-1/2·h-1。结论在弱碱性条件下L-抗坏血酸反应速率较快,抗氧化能力较弱;在中性和弱酸性条件下反应速率较慢,抗氧化能力较强。     

对尼莫地平注射液在4种常用输液中的稳定性探讨

尼莫地平(Nimodipine,NMDP)可用于治疗缺血性脑血管病。鉴于本品在输液中的稳定性尚无报道,本文作者以HPLC内标法测定NMDP为主要手段,研究了其在4种常用输液中的稳定性及其对光稳定性。结果表明:NMDP对漫射光、避光条件下在5％GS和NS输液中较稳定,漫射光与避光对其稳定性影响无差异(p>0.1),而在6％右旋糖酐40葡萄糖注射液和6％低分子羟乙基淀粉氯化钠注射液中稳定性较差;阳光照射下NMDP在4种输液中均不稳定,光解较快,光解反应呈表观一级反应,相关系数r>—0.9900。上述结果提示:临床应用含NMDP输液,选用5％GS和NS为宜,并应尽量避开阳光。     

2-羟丙基-β-环糊精对金银花挥发油的增溶作用研究

目的:研究2-羟丙基-β-环糊精(HP-β-CD)对金银花挥发油的增溶作用及包合物的稳定常数。方法:运用相溶解度法进行增溶试验,采用气相色谱内标法测定金银花挥发油的浓度。结果:随着HP-β-CD浓度的增加,金银花挥发油的溶解度增加。中性条件下,金银花油与HP-β-CD形成的包合物表观稳定常数为40.79,在pH值为3时,金银花油的溶解度可达到最大,且包合物性质稳定,受温度影响小。结论:对于金银花挥发油,HP-β-CD是较理想的增溶剂。     

竹叶黄酮在大鼠肠道的吸收动力学

目的:研究竹叶黄酮在肠道中的吸收部位和吸收机制。方法:通过对大鼠的十二指肠、空肠、回肠分别进行在体肠吸收实验,用紫外-分光光度法测定竹叶黄酮的含量,计算出竹叶黄酮的吸收速率常数Ka和表观吸收系数Papp,从而反映竹叶黄酮的吸收部位和吸收机制。结果:灌流速度不同,Ka和Papp差异有显著性(P<0.05);药物浓度不同,Ka和Papp差异无显著性(P>0.05);在相同的灌流速度及质量浓度下,竹叶黄酮在大鼠空肠和回肠的吸收速率常数Ka和表观吸收系数Papp无显著性差异(P>0.05),而两者与十二指肠的Ka和Papp之间差异存在显著性(P<0.05);在不同的pH值条件下,竹叶黄酮在大鼠十二指肠的吸收速率常数Ka和表观吸收系数Papp差异无显著性(P>0.05)。结论:竹叶黄酮在全肠段均有吸收,竹叶黄酮的吸收不受其质量浓度、pH的影响,提示其吸收机制主要为被动扩散吸收。     

甲醛合次硫酸氢钠氧化反应速率常数的测定

目的测定甲醛合次硫酸氢钠在水溶液中与氧反应的反应速率常数。方法在不断通入空气的情况下,采用碘量法测定甲醛合次硫酸氢钠在水溶液中不同时刻的浓度,作出降解曲线,并计算反应速率常数。结果甲醛合次硫酸氢钠在溶液中为假一级反应,在碱性、中性和弱酸性条件下反应速率常数分别为5.185×10-4h-1、4.404×10-4h-1和4.909×10-3h-1。结论甲醛合次硫酸氢钠在弱酸性条件下抗氧能力较强,在中性和弱碱性条件下较弱。     

抗坏血酸注射液稳定性的研究——Ⅲ.25%抗坏血酸注射液浓度变化规律的探讨

探讨了25%抗坏血酸注射液在98°、90°、80℃绝氧降解的浓度变化规律,其绝氧降解都是假零级反应,降解速度常数在注射液浓度约为初浓度的85%之上与下,略有差异。以5%的注射液在98℃和12.5%的注射液在90℃的绝氧降解作对照,二者都是假一级反应,其速度常数在注射液浓度约为初浓度的75%之上与下,也略有差异。不含抗氧剂的25%抗坏血酸溶液在98℃的绝氧降解也是假零级反应。     

阿洛西林钠水溶液的降解动力学(英文)

应用高效液相色谱法研究了在35℃、μ=0.6条件下,阿洛西林钠在pH4.9～10.3水溶液中的降解动力学。降解速率常数测定表明:为表观一级反应,并受酸、碱催化的影响。原盐效应研究指出.在pH4.9,5.5和6.0中呈现负效应;pH9.2呈正效应。测定了不同 pH溶液中阿洛西林钠降解的表观活化能。pH-K_(ob),全视图显示pH5.5时最稳定。     

布洛芬/羟丙基-β-环糊精体系的Caco-2细胞转运研究

目的:考察羟丙基-β-环糊精(HP-β-CD)超分子体系对布洛芬细胞转运的影响.方法:运用相溶解度法考察超分子体的表观稳定常数(K);运用Caco-2细胞模型考察各类超分子体中布洛芬的表观渗透系数(P<,app>)以及跨膜电阻(TEER)的变化.结果:随HP-β-CD的浓度增加,布洛芬的溶解度不断提高;在0%～5%HP-β-CD的范围内,布洛芬的表观渗透系数随HP-β-CD的浓度增加逐渐下降;布洛芬三元体系表观稳定常数的变化趋势与布洛芬的表观渗透系数变化趋势相反.结论:布洛芬的细胞转运与体系中HP-β-CD浓度、超分子体系的稳定常数有密切关系.HP-β-CD浓度升高可显著增加布洛芬的溶解度,但过量的HP-β-CD不利于布洛芬的渗透转运;布洛芬、HP-β-CD通过与适量泊洛沙姆188(Poloxamer 188)、聚山梨酯-80(Tween-80)、十二烷基硫酸钠(SDS)组成的三元体系,可影响布洛芬、HP-β-CD之间的相互作用,改善布洛芬的表观渗透系数.     

Efficacy of gut lavage,hemodialysis, and hemoperfusion in the therapy of paraquat or diquat intoxication

Clinical and in vitro investigations were carried out to test the efficacy of gut lavage, hemodialysis, and hemoperfusion in the treatment of poisoning with paraquat or diquat. In a patient suffering from diquat intoxication 130 times more diquat was removed by gut lavage 30 h after ingestion than was removed by complete aspiration of the gastric contents.Determination of in vitro clearances for paraquat and diquat by hemodialysis showed that, at serum concentrations of 1–2 ppm, such as are frequently encountered in poisoning in man, toxicologically relevant quantities of herbicide cannot be removed from the body. At a concentration of 20 ppm, on the other hand, hemodialysis proved to be effective, the clearance being 70 ml/min at a blood flow rate of 100 ml/min. The efficacy of hemoperfusion with coated activated charcoal was on the whole better. Especially at concentrations around 1–2 ppm, the clearance values for hemoperfusion were some 5–7 times higher than those for hemodialysis.In a patient suffering from paraquat poisoning, both hemodialysis as well as hemoperfusion were carried out. The in vitro results could be confirmed: At serum concentrations of paraquat less than 1 ppm no clearance could be obtained by hemodialysis while by hemoperfusion with activated charcoal quite high clearance values were measured and the serum level dropped down to zero.

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Zusammenfassung Klinische Untersuchungen und Laboratoriumsversuche wurden durchgeführt, um die Wirksamkeit von Darmspülung, Hämodialyse und Hämoperfusion bei Paraquat- und Deiquat-Vergiftungen zu prüfen.Bei einem Patienten wurde 30 Std nach Deiquat-Aufnahme durch Darmspülung 130mal mehr Deiquat entfernt als durch vollständige Aspiration des Mageninhaltes. In vitro-Versuche ergaben, daß bei Blutserumkonzentrationen von 1–2 ppm, die bei Vergiftungen oft gemessen werden, durch Hämodialyse keine toxikologisch relevanten Paraquat- oder Deiquat-Mengen entfernt werden können. Dagegen erwies sich die Hämodialyse bei 20 ppm und einer Blutumlaufgeschwindigkeit von 100 ml/min mit einer Clearance von 70 ml/min als wirksam. Die Hämoperfusion mit beschicheter Aktivkohle war in diesen Versuchen aber eindeutig überlegen, denn insbesondere bei Konzentrationen um 1–2 ppm waren die Clearance-Werte 5–7mal höher als bei der Hämodialyse.Die in vitro-Ergebnisse wurden bei einem Patienten mit einer Paraquat-Vergiftung bestätigt: Bei Konzentrationen unter 1 ppm war die Hämodialyse wirkungslos, während durch Hämoperfusion relativ hohe Clearance-Werte erreicht wurden, so daß der Serumspiegel rasch unter die Nachweisgrenze abfiel.

     

In vitro studies on sterically stabilized liposomes (SL) as enzyme carriers in organophosphorus (OP) antagonism

This study describes a new approach for organophosphorous (OP) antidotal treatment by encapsulating an OP hydrolyzing enzyme, OPA anhydrolase (OPAA), within sterically stabilized liposomes. The recombinant OPAA enzyme was derived from Alteromonas strain JD6. It has broad substrate specificity to a wide range of OP compounds: DFP and the nerve agents, soman and sarin. Liposomes encapsulating OPAA (SL)* were made by mechanical dispersion method. Hydrolysis of DFP by (SL)* was measured by following an increase of fluoride ion concentration using a fluoride ion selective electrode. OPAA entrapped in the carrier liposomes rapidly hydrolyze DFP, with the rate of DFP hydrolysis directly proportional to the amount of (SL)* added to the solution. Liposomal carriers containing no enzyme did not hydrolyze DFP. The reaction was linear and the rate of hydrolysis was first order in the substrate. This enzyme carrier system serves as a biodegradable protective environment for the recombinant OP-metabolizing enzyme, OPAA, resulting in prolongation of enzymatic concentration in the body. These studies suggest that the protection of OP intoxication can be strikingly enhanced by adding OPAA encapsulated within (SL)* to pralidoxime and atropine.     

Synthesis,Cytotoxicity and Antileishmanial Activity of Some N-(2-(indol-3-yl)ethyl)-7-chloroquinolin-4-amines

We report herein the condensation of 4,7-dichloroquinoline (1) with tryptamine (2) and D-tryptophan methyl ester (3) . Hydrolysis of the methyl ester adduct (5) yielded the free acid (6) . The compounds were evaluated in vitro for activity against four different species of Leishmania promastigote forms and for cytotoxic activity against Kb and Vero cells. Compound (5) showed good activity against the Leishmania species tested, while all three compounds displayed moderate activity in both Kb and Vero cells.     

Steroidal sapogenin contents in some domestic plants

In order to find out the values of the steroid resources for the future use. the compositions and contents of steroidal sapogenins from 13 domestic plants have been investigated. As a result,Dioscorea nipponica, D. quinqueloba andSmilax china were found to have large amount of diosgenin. And pennogenin inTrillium kamtschaticum andParis verticillata, yuccagenin inAllium fistulosum, hecogenin inAgave americana and neochlorogenin inSolanum nigum were appeared to be major steroidal sapogenins.     

Aquatic Insects and Trace Metals: Bioavailability,Bioaccumulation, and Toxicity

Abstract

The uptake of metals from food and water sources by insects is thought to be additive. For a given metal, the proportions taken up from water and food will depend both on the bioavailable concentration of the metal associated with each source and the mechanism and rate by which the metal enters the insect. Attempts to correlate insect trace metal concentrations with the trophic level of insects should be made with a knowledge of the feeding relationships of the individual taxa concerned. Pathways for the uptake of essential metals, such as copper and zinc, exist at the cellular level, and other nonessential metals, such as cadmium, also appear to enter via these routes. Within cells, trace metals can be bound to proteins or stored in granules. The internal distribution of metals among body tissues is very heterogeneous, and distribution patterns tend to be both metal and taxon specific. Trace metals associated with insects can be both bound on the surface of their chitinous exoskeleton and incorporated into body tissues. The quantities of trace meals accumulated by an individual reflect the net balance between the rate of metal influx from both dissolved and particulate sources and the rate of metal efflux from the organism. The toxicity of metals has been demonstrated at all levels of biological organization: cell, tissue, individual, population, and community. Much of the literature pertaining to the toxic effects of metals on aquatic insects is based on laboratory observations and, as such, it is difficult to extrapolate the data to insects in nature. The few experimental studies in nature suggest that trace metal contaminants can affect both the distribution and the abundance of aquatic insects. Insects have a largely unexploited potential as biomonitors of metal contamination in nature. A better understanding of the physico-chemical and biological mechanisms mediating trace metal bioavailability and exchange will facilitate the development of general predictive models relating trace metal concentrations in insects to those in their environment. Such models will facilitate the use of insects as contaminant biomonitors.