吲哚乙酸对烟草叶片光合作用和光呼吸的影响

烟草叶面喷施10～100ppm的IAA,光合、光呼吸、CO_2补偿点、乙醇酸合成量、以及RuBp羧化酶/加氧酶和乙醇酸氧化酶活性均提高,而且均随IAA浓度的增加而增高。抗生长素三碘苯甲酸抑制光合和光呼吸,降低CO_2补偿点,降低BuBp羧化酶和乙醇酸氧化酶活性。草甘膦亦降低光合、光呼吸强度和乙醇酸氧化酶活性。亚胺环己酮和放线菌素D亦降低叶片乙醇酸氧化酶活性,并消除由IAA引起的酶活性增强。认为IAA通过提高RuBp羧化酶活性而增强光合作用;通过增加乙醇酸合成和提高乙醇酸氧化酶活性而提高光呼吸。     

光对高等植物乙醇酸氧化酶的诱导

本文阐述了光对高等植物乙醇酸氧化酶活性的影响,分析了白光、光强度、光质等对酶的诱导作用,讨论了前人解释光的作用机制的几种学说,在此基础上提出了另一个光对乙醇酸氧化酶诱导机理的假说,认为光对该酶的诱导有两方面的作用,一是进行光合作用产生乙醇酸,乙醇酸诱导酶蛋白合成;二是光促进体内FMN的生物合成与还原。所合成的酶蛋白再与FMN结合成全酶而表现出催化活性。     

用SDS聚丙烯酰胺凝胶电泳监测细胞色素C的质量

<正> 细胞色素 C 是一种含铁卟啉的色蛋白。在氧化呼吸链中,起传递电子的作用。由猪心分离提取制备。其分子量较大(约为13000),组份亦多,有 C,C_1,C_2,C_3,C_4和 C_5等结构复杂,同时,往往由于制作工艺的局限和操作问题而渗入有异体无活性的大分子物质,给临床使用增加了不安全的因素。因此,考察细胞色素 C的纯度,反映其内在质量是必要的。     

静脉注射白三烯拮抗剂ONO-1078对大鼠血压、心率及呼吸的影响

目的观察静脉注射不同剂量的白三烯受体拮抗剂ONO-1078{pranlnkast,4-氧-8-[对-(4-苯丁氧基)苯甲酰氨基]-2-(5-四唑基)-4H-1-苯并吡喃半水合物}对大鼠血压、呼吸频率和心率的影响,并对静脉注射和静脉缓慢推注两种方法作了比较.方法静脉注射ONO-1078 0.1,1.0,5.0 mg·kg-1,另一组3 h内静脉恒速缓慢推注ONO-1078 5.0 mg·kg-1,以计算机辅助系统PCLab观察、记录3 h内的血压、呼吸频率和心率.结果静脉注射ONO-1078 1.0,5.0 mg·kg-1 引起血压迅速短暂的下降,溶剂50%乙醇1 mL·kg-1也有相同的作用;静脉缓慢推注ONO-1078 5.0 mg·kg-1则无影响.结论静脉注射ONO-1078可短暂影响血压、呼吸,而静脉缓慢推注则无明显影响.可能与其溶剂中所含的乙醇有关.提示改变溶剂成分或静脉滴注可提高安全性.     

十六种β-内酰胺单环衍生物的360兆~1H-NMR化学位移值与取代基物理化学参数间的相关关系

本文对十六种新合成的β-内酰胺单环衍生物测定了360兆~1H-NMR光谱。对β-内酰胺环C_3-H、C_4-H和侧链酰胺N-H的化学位移值与取代基物理化学参数之间进行了逐步回归分析,得出了相应的定量关系式。对该定量关系式进行了讨论,指出了适用范围,并作了校验。     

单环β-内酰胺抗生素衍生物的合成研究

八十年代初氨噻羧单胺菌素(Azthreonam)的问世,使单环β-内酰胺抗生素受到人们普遍的重视。目前业已成为β-内酰胺抗生素的重点研究对象之一。 根据这类化合物的结构特点,若在C_3、C_4位改变各种取代基,特别是电负性大的官能团,可能找到具一定特点的新抗生素。我们以青霉素G(V)、6-APA为原料,经化学转化合成了C_3β-位具酰胺基和不具酰胺基的、C_4-位有不同取代基,不同构型的单环     

类风湿性关节炎患者血清体液免疫水平的观察

目前,有资料认为体液免疫障碍在类风湿性关节炎(RA)的免疫病理机制中只起次要作用,细胞免疫失衡更具重要性。也有否定细胞反应在 RA 发病机制中可能意义的报道。为探讨 RA 的体液免疫水平,我们测定了25例 RA 患者的血清循环免疫复合物(CIC)、IgG,IgA、IgM 和 C_3、C_4、B因子含量,结果报告如下。     

合成短肽与人类相容性佐剂诱导的抗HIV-1蛋白的CTL应答

全球性预防艾滋病的希望寄托于开发有效的疫苗。诱导抗不同人类免疫缺陷病毒( HIV)表位的抗体应答和广泛的细胞毒性 T细胞 ( CTL)应答可消除感染初期宿主体内的病毒。为使机体产生强有力的免疫应答 ,作者使用合成短肽与免疫刺激剂佐剂一同接种转基因小鼠 ,观察了抗 HIV- 1蛋白 CTL应答的诱导情况。　　作者合成了 6种 HIV短肽 ( RT4 76 -484、 p1 777- 85、 gp1 6 0 31 8- 32 7、 RT346 -354、gp4 1 81 4 - 82 3及 RT956 - 96 4) ,将合成肽同 1 4 k Da( D,L-聚乳酸 -乙醇酸共聚物( PL GA)制成微球。微球的大小通过激光散射技术…     

庆大霉素三种C组份对绿脓杆菌抗菌活力的比较

用临床上分离的31株对庆大霉素复合物具有抗性的绿脓杆菌作为试验菌株,测定了庆大霉素三种主要组份C_1、C_(1a)与C_2对这些菌株的抗菌活力。在其中可以比较的27株抗性菌株中,C_(1a)的抗菌活力均大于C_2,C_1抗菌活力大于C_2的占64％,C_(1a)与C_1的抗菌活力相同的菌株占25％,C_(1a)大于C_1或小于C_1的分别占42.8％与32.1％。此外还对4株绿脓杆菌细胞内的钝化酶进行了分析。除了对庆大霉素敏感的Ps85菌株外,其余3株抗性菌株均有使三种组份失去抗菌活力的钝化酶。酶活力的高低与菌株的抗性水平有关。结合文献上报道的LD_(50)值,对庆大霉素三种组份进行了评价,供庆大霉素产生菌选育与发酵时确定三种组份比例的参考。     

齿叶乳香树中乳香酸对人白血病HL-60培养细胞的抑制活性

齿叶乳香树Boswellia serrata为印度传统药,其树脂用于炎症的治疗。有报道称,其树脂乙醇提取物中乳香酸通过5-脂氧化酶抑制白三烯的合成。作者从印度产乳香树脂中分离并鉴定了4种主要三萜酸:β-乳香酸(1)、3-Ο-乙酰基-β-乳香酸(2)、11-酮基-β-乳香酸(3)和3-Ο-乙酰基-11-酮基-β-乳香酸     

几种有机酸和氨基酸对乙醇酸氧化酶活性的影响

本文研究苹果酸、甘油酸、丝氨酸、谷氨酸对菜心(Brassica parachinensis Bailey)叶片乙醇酸氧化酶活性的影响。结果表明,苹果酸、丝氨酸和谷氨酸均对乙醇酸氧化酶起竞争性抑制作用,其中以苹果酸和丝氨酸的抑制作用较强而谷氨酸的抑制作用较弱;测定菜心乙醇酸氧化酶对乙醇酸的Km值为0.36m mol/L,丝氨酸、苹果酸、谷氨酸对乙醇酸氧化酶的Ki值分别为5.5,7.0,13.5m mol/L,甘油酸对乙醇酸氧化酶活性没有明显的影响,讨论了上述几种有机酸和氨基酸在乙醇酸途径代谢调节中的作用。     

Dose-response relationships of hepatic acyl-CoA oxidase and catalase activity and liver mitogenesis induced by the peroxisome proliferator ciprofibrate in C57BL/6N and BALB/c mice.

The dose-response for key hepatic effects of the peroxisome proliferator ciprofibrate, 2-[4-(2,2-dichlorocyclopropyl)phenoxy]-2- methylpropanoic acid, was delineated in mice and strain differences in response were demonstrated. Ciprofibrate was fed at concentrations ranging from 0.1 to 250 ppm to male C57BL/6N and BALB/c mice and the induction of hepatic acyl-CoA oxidase and catalase, peroxisomal enzymes involved in the formation and degradation of hydrogen peroxide, and liver hepatomegaly and mitogenesis were measured. No effect was found for enzyme induction at 5.0 ppm or less in either strain. Likewise, hepatomegaly was not found at 5.0 ppm, but mitogenesis was observed in BALB/c mice at 1.0 ppm. C57BL/6N mice demonstrated greater basal and postexposure acyl-CoA oxidase activity than BALB/c mice, while BALB/c mice demonstrated greater catalase activity and induction of liver mitogenesis. The threshold exposure level for induction of acyl-CoA oxidase activity was approximately the same as that for induction of mitogenesis in C57BL/6N mice; in contrast, the threshold exposure level for induction of acyl-CoA oxidase activity was at least one order of magnitude greater than that required for induction of mitogenesis in BALB/c mice. Thus, the induction of the peroxisomal enzyme involved in the formation of hydrogen peroxide and increased mitogenesis are not mechanistically linked. The differential effects observed in the two mouse strains provide the basis for development of a quantitative model of peroxisome proliferator-induced carcinogenicity in which cellular effects can be related to carcinogenicity.     

氯化钠对小麦幼苗乙醇酸氧化酶活性和叶绿素含量的影响

本文报告氯化钠对小麦幼苗乙醇酸氧化酶的促进作用。试验结果表明,用氯化钠喷施小麦幼苗20小时后,乙醇酸氧化酶活性升高21％,体内蛋白质含量升高24.2％。用0.1、0.2、0.5mol/L的氯化钠培养幼苗,乙醇酸氧化酶活性分别比对照增加23％、61.1％和28.6％;蛋白质含量分别比对照增加12.8％、29.4％和18.1％;叶绿素含量分别下降2.8％、2.8％和22.2％。本文讨论了氯化钠影响乙醇酸氧化酶活性的机理。     

Mechanisms for the induction of oxidative stress in Syrian hamster embryo cells by acrylonitrile.

Chronic administration of acrylonitrile to rats resulted in an increase in the incidence of glial neoplasms of the brain. Recent studies have shown that acrylonitrile induces oxidative stress in rat brain and cultured rat glial cells. Acrylonitrile also induces morphological transformation concomitant with an increase in the formation of oxidized DNA in Syrian Hamster Embryo (SHE) cells in a dose-dependent manner. The mechanism for the induction of oxidative stress in SHE cells remains unresolved. The present study examined the effects of acrylonitrile on enzymatic and nonenzymatic antioxidants in SHE cells. SHE cells were treated with subcytolethal doses of acrylonitrile (0, 25, 50, and 75 microg/ml) for 4, 24, and 48 h. Acrylonitrile (50 microg/ml and 75 microg/ml) increased the amount of reactive oxygen species in SHE cells at all time points. Glutathione (GSH) was depleted and catalase and superoxide dismutase activities were significantly decreased in SHE cells after 4 h of treatment. The inhibition of these antioxidants was temporal, returning to control values or higher after 24 and 48 h. Xanthine oxidase activity was increased following 24 and 48 h treatment with acrylonitrile. 1-aminobenzotriazole, a suicidal P450 enzyme inhibitor, attenuated the effects of acrylonitrile on catalase and xanthine oxidase in SHE cells, suggesting that P450 metabolism is required for acrylonitrile to produce its effects on these enzymes. Additional studies showed that in the absence of metabolic sources acrylonitrile had no effect on either catalase or superoxide dismutase activity. These results suggest that the induction of oxidative stress by acrylonitrile involves a temporal decrease in antioxidants and increase in xanthine oxidase activity that is mediated by oxidative metabolism of acrylonitrile.     

5-Hydroxytryptamine is biotransformed by CYP2C9, 2C19 and 2B6 to hydroxylamine, which is converted into nitric oxide

There is circumstantial evidence suggesting that 5-hydroxytryptamine (5-HT) could be biotransformed by enzymatic systems other than monoamino oxidase A, and that the isoforms of cytochrome P450 may be a source of nitric oxide. This study aimed to assess whether cytochrome P450 contributes to 5-HT biotransformation, and to provide evidence that 5-HT metabolism generates nitric oxide. Addition of 5-HT to cultured hepatocytes yielded 5-hydroxyindol acetic acid, a formation modulated by cytochrome P450 enzyme inducers and inhibitors. Recombinant human CYP2B6, 2C9 and 2C19 biotransformed 5-HT in 5-hydroxyindol acetic acid, but not CYP1A2, 2D6 or 3A4. Cultured hepatocytes with 5-HT generated nitric oxide, the amount of which was altered by cytochrome P450 enzyme inducers and inhibitors. In the presence of CYP2B6, 2C9 and 2C19, 5-HT relaxed precontracted isolated aortic rings, with or without endothelium, an effect prevented by the addition of methylene blue and an inhibitor of catalase, but not by myoglobin. In the absence of catalase, hydroxylamine was always assayed as a byproduct of 5-HT metabolism. In conclusion, CYP2B6, 2C9 and 2C19 biotransform 5-HT, yielding hydroxylamine, which is converted to nitric oxide in the presence of catalase.British Journal of Pharmacology (2004) 141, 407-414. doi:10.1038/sj.bjp.0705632     

CYP isoforms involved in the metabolism of clarithromycin in vitro: comparison between the identification from disappearance rate and that from formation rate of metabolites

To clarify whether CYP2C19 is involved in the overall metabolism of clarithromycin (CAM) or not, in vitro studies using human liver microsomes and recombinant CYPs were performed by an approach based on the disappearance rate of parent compound from the incubation mixture. In addition, the results of disappearance rate were compared with those obtained from the formation rates of the major metabolites of CAM, 14-(R)-hydroxy-CAM and N-demethyl-CAM.The intrinsic clearance (CL(int)) values determined from the disappearance of CAM in nine different human liver microsomes were highly correlated with the testosterone 6beta-hydroxylation activity (r=0.957, p<0.001). The CL(int) of CAM was markedly reduced by selective inhibitors of CYP3A4 (ketoconazole and troleandomycin) and by polyclonal antibodies raised against CYP3A4/5 in human liver microsomes. Among the 11 isoforms of recombinant human CYP, only CYP3A4 revealed the metabolic activity for the disappearance of CAM. These results were fairly consistent with those obtained from the conventional approach based on the formation of major metabolites of CAM. Comparison of the kinetic parameters estimated from the disappearance rate of CAM and the formation rates of 14-(R)-hydroxy-CAM and N-demethyl-CAM indicates that N-demethylation and 14-(R)-hydroxylation account for 65% of CL(int) derived from the disappearance of CAM in human liver microsomes.The findings suggest that CYP3A4 plays a predominant role in the overall metabolic clearance of CAM as well as in the formation of 14-(R)-hydroxy-CAM and N-demethyl-CAM. CYP2C19 does not appear to be involved in the overall metabolism of CAM at least in human liver microsomes. A combination of the disappearance rate of a parent compound and the formation rate of metabolites appears to be a useful approach for estimating the percentage contribution of the formation of metabolites to the overall metabolic clearance of a parent compound in vitro.     

L-amino acid oxidase from Trimeresurus jerdonii snake venom: purification,characterization, platelet aggregation-inducing and antibacterial effects

An L-amino acid oxidase (LAO), designated as TJ-LAO, was purified to homogeneity from the venom of Trimeresurus jerdonii by Sephadex G-100 and Q Sepharose HP chromatography. The molecular weight of this enzyme was 110 kD as estimated by analytical gel filtration and was 55 kD by SDS-polyacrylamide gel electrophoresis, suggesting that the enzyme is composed of two subunits. The enzyme has an absorption spectrum characteristic of flavoproteins, containing 2 moles of FMN per mole of enzyme. The N-terminal sequence of TJ-LAO shares high homology with other viperid snake venom LAOs. Homology with elapid venom LAO is lower. TJ-LAO inhibited the growth of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus megaterium. The antibacterial effect associated with LAO activity was elminated with the addition of catalase. Platelets in platelet-rich plasma aggregated upon the addition of TJ-LAO. The enzyme-induced aggregation was inhibited by catalase, suggesting formation of H2O2 was essential for TJ-LAO to induce platelet aggregation. These results showed H2O2 formation is important for the biological effects of LAO.     

Pluchea lanceolata attenuates cadmium chloride induced oxidative stress and genotoxicity in Swiss albino mice

Cadmium intoxication induces lipid peroxidation and causes oxidative damage to various tissues by altering antioxidant defence system enzymes. At 24 h after treatment with a single intraperitoneal dose of cadmium chloride (5 mg kg-1), Swiss albino mice showed a significant increase in the levels of malanodialdehyde and xanthine oxidase (P<0.001), and a concomitant depletion of renal glutathione, catalase (P<0.001) and other antioxidant enzymes. CdCl2 also led to a simultaneous increase in micronuclei formation (P<0.001) and chromosomal aberrations (P<0.05) in mouse bone marrow cells. Oral pre-treatment with Pluchea lanceolata extract at doses of 100 and 200 mg kg-1 for 7 consecutive days before CdCl2 intoxication caused a significant reduction in malanodialdehyde formation and xanthine oxidase activity (P<0.001). A significant restoration of the activity of antioxidant defence system enzymes such as catalase, glutathione peroxidase (P<0.05), glutathione-S-transferase and glutathione reductase (P<0.001) was observed. A significant dose-dependent decrease in chromosomal aberrations and micronuclei formation was also observed (P<0.05). The results indicate that pre-treatment with P. lanceolata attenuates cadmium chloride induced oxidative stress and genotoxicity by altering antioxidant enzymes and reducing chromatid breaks and micronuclei formation.     

Binding of [14C] allylamine to isolated mitochondria from rat heart and aorta

This study demonstrates specific and saturable binding of [14C] allylamine to mitochondria derived from rat aorta and heart. Specific binding is linear with respect to mitochondrial concentration and has a pH optimum of 7.0. Saturation isotherms reveal anomalous kinetics of specific binding on heart mitochondria with a high affinity site (KD 16 nM) and a lower affinity site (KD 80 nM); Scatchard plots have a common intercept. Exhaustive flow dialysis in the presence of SDS demonstrates that as much as 23.5% of bound radioactive moieties in aorta mitochondria are covalently bound, and as much as 42.6% are covalently bound in heart mitochondria. Hydrolysis of heart mitochondria with phospholipase C markedly enhances saturation of [14C] allylamine, and greatly increases the quantity of covalently bound radioactive ligand. Phospholipase C hydrolysis of heart mitochondria increased monoamine oxidase B activities and unmasked a small amount of benzylamine oxidase activity, whereas hydrolysis of mitochondria with phospholipases A2 and D diminish MAO-B activity. The monoamine oxidase B inhibitor, deprenyl, significantly reduced both specific and covalent binding of the 14C-activity from [14C] allylamine to phospholipase hydrolyzed mitochondria. The benzylamine oxidase inhibitor, phenelzine, significantly decreased specific binding but had no effect on the degree of covalent binding of [14C] allylamine to phospholipase C hydrolyzed mitochondria. The benzylamine oxidase inhibitor, semicarbazide, had no effect in inhibiting [14C] allylamine binding. Covalent binding of 14C-moiety from [14C] allylamine to mitochondria--which express specific binding sites for the [14C] allylamine--and inhibition of binding by monoamine oxidase inhibitors, suggest the formation of highly reactive intermediates.