甲硝唑氨酸(CM)对受照相对密度生长期V_(79)细胞DNA聚合酶β的抑制与放射增强作用间的关系

借助于DNA聚合酶α专一性抑制剂NEM,观察了CM对受12 Gy照射的相对密度生长期V_(79)细胞核DNA聚合酶β活力的作用。结果表明:在α酶完全被抑制的条件下,除照后即刻CM对β酶活力无明显影响外(p>0.05),保温2-6 h均有抑制作用,其抑制程度随CM浓度和照后保温时间(4 h内)的增加而加强,抑制了DNA的修复,提高了辐射对DNA的损伤效应。其抑制规律,与在相同试验条件下,CM对受照相对密度生长期V_(79)细胞潜在致死损伤修复(PLDR)的抑制规律基本相似,提示CM对PLDR的抑制作用,可能通过抑制DNA修复酶系中的β酶所造成,从而增强了射线对细胞的杀灭效应。

在低盐度胁迫下鲻幼鱼鳃丝Na^+-K^+-ATP酶活性及其β亚基mRNA表达与显微结构变化

探讨在低盐度胁迫下鲻(Mugil cephalus)幼鱼鳃丝Na+-K+-ATP酶活性、Na+-K+-ATP酶β亚基mRNA表达量变化以及对鳃丝组织显微结构的影响.结果表明:在盐度分别为20(对照组),15,10,5和0实验条件下,20d后各低盐度组鳃丝Na+-K+-ATP酶活性均高于对照组;0和5盐度组鳃丝Na+-K+-ATP酶活性在实验过程中表现为持续上升的趋势,前期升高幅度大,后期升高幅度减小;10和15盐度组鳃丝Na+-K+-ATP酶活性在15d后达到峰值,至20d呈现小幅下降趋势.鳃丝Na+-K+-ATP酶β亚基mRNA表达的变化趋势与Na+-K+-ATP酶活性的变化趋势基本保持同步,显示出了其对Na+-K+-ATP酶活性的调控作用.对鳃丝显微结构观察的结果显示,随着盐度的降低,鲻幼鱼鳃小片逐渐变宽,伴随间距缩小,同时泌氯细胞数量逐渐减少,体积缩小,扁平细胞体积增大,黏液细胞数量增多.这表明在低盐度胁迫下鲻幼鱼鳃的生理功能和组织结构具有随外界水体盐度变化的适应能力.

Increase of β -1, 3-Glucanase and Chitinase Activities in Cotton Callus Cells Treated by Salicylic Acid and Toxin of Verticillium dahliae

The different resistance of cotton (Gossypium hirsutum L.) cultivars to crude toxin of Verticillium dah/iae(VD) was correlated with the activities of chitinase and β-1, 3-glucanase in callus cells. The activities of chitinase and β-1, 3-glucanase in the callus cells treated with the VD-toxin were increased to the higher level at earlier time point in resistant cultivars than these in the susceptible cultivars. Exogenous salicylic acid (SA) induced the accumulation of chitinase and β -1,3-glucanase, which resulted in the resistance of callus cells to the VD. toxin. Western blot using a polyclonal antibody against β -1,3-glucanase identified 28 kD protein that was induced by VD-toxin, SA, or VD-toxin plus SA.

Enzymatic Transformation of Notoginsenoside Fe by β-Glucanase

Aim An industrial enzyme β-glucanase was used to transfortn notoginsenoside Fe for the first time. Methods Notoginsenoside Fe was isolated from the leave saponin of Panax notoginseng （Burk.） Chen FH. The enzymatically transformed compounds were detected by HPLC and two transformed compounds were identified as 20 （S） -protopanaxadiol-20- O- α-L-arabinofuranosyl （ 1→6 ） - β-gluco- pyranoside, ginsenoside-Mc） and 20（S）-protopanaxadiol-20-O-β-D-glucopyranoside compound-K （C-K） respectively on the basis of their ^1H NMR and ^13 C NMR spectral data. Results Based on the enzymolytic kinetic curve, the transformation rate of notoginsenoside Fe reached 95% after 24 h. Conclusion The enzymatic transformation pathway of notoginsenoside Fe by β-glucanase has been proposed as notoginsenoside Fe→ginsenoside Mc→C-K.

Endo-Glycanhydrolases Activities in Artemisia sphaerocephala (Asteraceae) Mucilaginous Achene Germination Process

对白沙蒿 (ArtemisiasphaerocephahaKrasch .)种子萌发不同阶段的种胚提取物中几种可能降解果皮外层粘液物质的多糖内切酶进行了检测。研究结果表明 :多聚半乳糖醛酸酶在干燥胚中已存在并具较高的活性 ,但其活性随着种子吸涨及萌发而降低。此酶并不释放到种胚外。β 甘露聚糖内切酶随着种子的吸涨而增加并被萌发的种胚释放到种子外。纤维素酶在种子萌发的过程中不表现出活性。提取物中的所有多糖内切酶都无法降解果皮外层的粘液物质。

Molecular Cloning and Expression of Carotenogenic Genes in Yellowish and Mutant Whitish Loquat (Eriobotrya japonica) Fruits

ObjectiveThe study aimed to explore the factors regulating carotenoid accumulation in flesh color. MethodA loquat mutation （red-or orange-fleshed plant emerged a bud mutation of white-flesh in trunk） was used as material; HPLC analysis of β-carotene content was conducted. ResultThe β-carotene concentration in the flesh of wild and mutant types was 60.9 and 4.6 μg/g fresh weight, respectively. According to the conserved regions of genes from rose family genome, carotenogenic gene fragments in wild and mutant types were obtained. No nucleotide variation of the carotenogenic gene fragments was observed between wild and mutant genome. Real-time quantitative polymerase chain reaction （Q-PCR） was compared and one carotenogenic gene, β-ring hydroxylase （HYB） were considerably suppressed in mature mutant loquat fruits compared with that in wild. The other six carotenogenic genes were also expressed but the expression patterns appeared to be not correlated with the amount of β-carotene concentration in wild loquat flesh. ConclusionThe mutant whitish loquat lacks the ability to synthesize β-carotene because of the transcriptional down-regulation of carotenogenic gene HYB.

Study on the Resistance of Pathogenic Escherichia coli to Ceftiofur

[Objective] Ceftiofur was as the substrate to induce the standard strain of Escherichia coli（E.coli）to be the drug-resistance one.The resistant mechanism of E.coli to ceftiofur was studied.[Method] The sub-inhibitory concentration method was used to induce the standard strains C83907 and C83845.After they were induced for 10 generations,the double disc synergy test（DDST）,NCCLS（National Committee for Clinical Laboratory Standards）confirmatory test and PCR amplification were used to detect the extend spectrum β-lactamases（ESBLs）.The two fold dilution method was used to measure the minimal inhibitory concentration（MIC）of cetiofur to the strain which produced ESBLs.For the drug-resistance strain which produced ESBLs,the two fold dilution method was used to measure the minimal inhibitory concentrations of different proportions of cetiofur and tazobactam sodium.[Result] After they were induced 15 generations,MIC value of ceftiofur to the induced bacteria was during 8-10 μg/ml,and ESBLs was detected.MICs of cetiofur combining tazobactam sodium（the mass ratio was 1∶1-8∶1）to Escherichia coli produced ESBLs reduced 20-22 times than that of cetiofur.[Conclusion] The main mechanism of pathogenic Escherichia coli resistance to ceftiofur was that which produced ESBLs.

Role of Wall-bound β-Glucanases in Regulating Tip-growth of Lilium longiflorum Pollen Tubes

Glucanases were found in the cell wall of Lilium longiflorum Thunb. pollen tubes grown in vitro . The activity of β_glucanases was, in a certain extent, decreased by nojirimycin, an inhibitor of glucosidase. Pollen germination percentage reduced dramatically when nojirimycin was applied in the culture medium. In case that nojirimycin was added at 0 or 1 h after the onset of incubation, the inhibition rate was 99.6% and 91.4%, respectively. When 3 mmol/L of nojirimycin was applied in the liquid medium at 0, 1, 1.5 and 2 h after the onset of incubation, the growth of pollen tubes was interrupted, which resulted in the morphological change of the pollen tubes such as the newly grown portion of pollen tubes being bent, curved and swollen. Tracing the growth pattern of the individual pollen tube grown in semi_solid medium by video microscopy, the authors demonstrated that pollen tube growth rate was strongly inhibited by nojirimycin at concentrations ranged from 0.003 to 3 mmol/L. Moreover, the cytoplasmic arrangement and the morphology of the pollen tubes were also affected by nojirimycin. The growth inhibition brought about by nojirimycin was reversible. These results indicated that β_glucanases, which degrade 1,3_β_glucan and/or 1,4_β_glucan or 1,3:1,4_β_glucan constructed in the cell wall, are involved in pollen germination and pollen tube growth. It provides new insight into an understanding of the contribution of β_glucanases to the cell wall extensibility and the crucial role of cell wall in regards to the regulation of pollen tube growth.

Cloning and Sequence Analysis of ATPase Beta Subunit Gene from Eleutherococcus senticosus

[Objective] This study aimed to clone and analyze the cDNA of ATPase β subunit gene from Eleutherococcus senticosus.[Method] A pair of homologous primers was designed according to the chloroplast ATPase β subunit gene sequences of the known species;then the gene cDNA of E.senticosus were amplified by RT-PCR and compared with that of the known species;its structure was predicted finally.[Result] 1 099 bp of ATPase beta subunit cDNA of E.senticosus which encodes 366 amino acids was amplified by RT-PCR.Sequence comparison and structure prediction showed that amino acids encoded by the ATPase beta subunit gene of E.senticosus shared the highest homology,up to 96.41% with that of Oryza sativa.In the secondary structure,the protein contained 171 alpha helixes accounting for 46.72%,53 extended strands accounting for 14.48%,27 beta sheets accounting for 7.38% and 115 random coils which took up 31.42%.The amino acids 262-271 were the symbolic site of ATPase β subunit.The whole peptide chain had no obvious hydrophobic region and was primarily confirmed as a hydrophilic protein.[Conclusion] The cNDA of ATPase β subunit gene cloned from E.senticosus in this study will provide reference for learning the effect of energy metabolism on secondary metabolism,structure and function of ATPase in E.senticosus.

Effect of Fish Oil on (-Adrenoceptors and the Activity of Adenylate Cyclase on Myocardial Membrane in Rats

Effects of fish oil on β-adrenoceptors as well as the activity of adenylate cyclase (AC) on rat myocardial membrane were investigated.Supplementation with fish oil had no significant effect on basal activity of AC on myocardial membrane whereas it could markedly inhibit the AC activity stimulated by isoproterenol (ISO). Radioligand binding assays showed that supplementation with fish oil had no effect on Bmax and Kd, compared with saline control. However, supplementation with sheep oil could markedly reduce both the Kd and Bmax, compared with saline control. And the Kd of sheep oil group was greatly decreased than that of fish oil group. The results suggested that supplementation with fish oil mainly affected the activation of AC, not β-adrenoceptor itself.

Involvement of cAMP in ABA Signal Transduction in Tobacco Suspension Cells

Abscisic acid (ABA) plays an important role in plant growth and developmental processes. Although some ABA signal molecules, such as cADPR, Ca2+, etc., have been reported, there. was no evidence proving the involvement of cAMP in A-B-A, signal transduction. In this present study, the constructed gene ( rd29A-GUS) was transformed into Nicotiana tabacum, and calli was induced from the transgenic plant. The suspension cells obtained from the callus grew well and uniformly. Treatment of the suspension cells with ABA led to an increase in GUS activity, indicating that these transgenic suspension cells are useful for the study of ABA signaling. Addition of nicotinamide (cADPR inhibitor) or U-73122 (phospholiphase C inhibitor) could only partially inhibit the increase of GUS activity elicited by ABA. The inhibitory effect of nicotinamide was enhanced by application of K252a (inhibitor of protein kinase). Treatment of the suspension cells with 8-Br-cAMP, a membrane-permeable analogue of cAMP, could partially replace the effect of ABA. Furthermore, intracellular addition of IBMX (phosphodiesterase inhibitor) mimicked die effect of exogenous cAMP on the deduction of expression of rd29A promoter. These results suggested that cAMP was an important messenger in ABA signal transduction in tobacco suspension cell.

Expression Activity of CLCuV Bidirectional Promoter in Agrobacterium tumefaciens

Cotton leaf curl virus (CLCuV) belongs to the subgroup III of geminiviruses with single strand DNA genome. Study demonstrated that the bidirectional promoter of CLCuV had activity in Agrobacterium tumefaciens (Smith et Townsend) Conn. This is the first report for the activity of the bidirectional promoter of geminivirus in A. tumefaciens. Results showed that the activity of the complementary sense promoter was stronger than that of virion sense promoter, and was detected 2-fold higher than that of CaMV 35S promoter in A. tumefaciens. Moreover, the promoter 5' deletion analysis indicated that the mean GUS activity driven by a 287 nucleotides complementary sense promoter fragment (from-287 to the translation initiation site) is 4 times higher than that driven by the whole complementary sense promoter in A. tumefaciens. This result suggested that there might exist negative regulatory elements in this deleted fragment. The function of other cis-elements included in CLCuV complementary sense promoter was also discussed in this paper.

Influence of Matrix Attachment Regions from Maize on Transgene Expression Level in Tobacco

The effect of matrix attachment regions (MARs) on foreign gene expression in transgenic plants was studied, The beta-glucuronidase (GUS) gene (uidA) was flanked by the MARs isolated from the genome of maize to form plant expression vector. The vectors with and without MARs were transferred into tobacco ( Nicotiana tabacum L.) through Agrobacterium-mediated transformation procedure. GUS activity assays indicated that MARs could increase expression level of uidA gene. The mean GUS activity could be increased twofold as compared to that of transformants without MARs, and the highest GUS activity of transformant could reach tenfold. The correspondence between GUS activity and mRNA accumulation was positive and indicated that MARs could improve transcription of foreign gene.

β-Amylase Is Predominantly Localized to Plastids in the Developing Tuberous Root of Sweet Potato

Starch degradation in cells is closely associated with cereal seed germination, photosynthesis in leaves, carbohydrate storage in tuber and tuberous roots, and fleshy fruit development. Based on previously reported in vitro assays, β amylase is considered as one of the key enzymes catalyzing starch breakdown, but up to date its role in starch breakdown in living cells remains unclear because the enzyme was shown often extrachloroplastic in living cells. Recently we have shown for the first time that β_amylase is predominantly immuno_localized to plastids in living cells of developing apple fruit. But it remains to know whether this model of β_amylase compartmentation is more widespread in plant living cells. The present experiment, conducted in tuberous root of sweet potato ( Ipomea batatas Lam. cv. Xushu 18) and via immunogold electron_microscopy technique, showed that β amylase visualized by gold particles was predominantly localized in plastids especially at periphery of starch granules, but the gold particles were scarcely found in other subcellular compartments, indicating that the enzyme is subcellularly compartmented in the same zone as its starch substrates. The density of gold particles (β amylase) in plastids was increasing during growing season, but the predominantly plastid_distributed pattern of β amylase in cells was shown unchanged throughout the tuberous root development. These data prove that the enzyme is compartmented in its functional sites, and so provide evidence to support the possible widespread biological function of the enzyme in catalyzing starch breakdown in plant living cells or at least in living cells of plant storage organs.

Inactivation Kinetics of β-N-Acetyl-D-Glucosaminidase from Prawn (Penaeus vannamei) by Formaldehyde

β-N-Acetyl-D-glucosaminidase （NAGase, EC.3.2.1.52） is chitinolytic enzymes and disintegrate dimmer and trimer a composition of oligomers of N-acetyl-β-D-glucosamine （NAG） into monomer. Prawn （P. vannamei） NAGase is involved in digestion and molting processes. Some pollutants in seawater affect the enzyme activity causing loss of the biological function of the enzyme, which affects the exuviating shell and threatens the survival of the animal. The effect of formaldehyde on prawn （P. vannamei） β-N-acetyl-D-glucosaminidase activity for the hydrolysis of pNP-NAG has been studied. The results show that formaldehyde, at appropriate concentrations, can lead to reversible inactivation of the enzyme, and the IC50 is estimated to be 1.05mol· L^-1. The inactivation mechanism obtained from Lineweaver-Burk plots shows that the inactivation of the enzyme by formaldehyde belongs to the competitive type. The inactivation kinetics of the enzyme by formaldehyde has been studied using the progress-of-substrate-reaction method described by Tsou, and the rate constants have been determined. The results show that k＋0 is much larger than k-0, indicating the free enzyme molecule is fragile in the formaldehyde solution.

Synthesis of Hydroxyethylene-based β-Secretase Inhibitors

Aim To discuss in depth the synthesis of hydroxyethylene dipeptide-based β-secretase inhibitors; Methods Organic reactions such as nucleophilic addition and substitution assisted by organometallic agents, catalytic hydrogenation, and classic peptide coupling were used to synthesize peptidomimetic β-secretase inhibitors. Results Ideal reaction conditions and potential problems were investigated, and one of the designed β-secretase inhibitors 13 （as a model） was synthesized successfully; Conclusion This approach might be used to build up the β-secretase inhibitor library and to search for new molecular candidates.

Synthesis and activity of hydroxyethylene peptidomimetic inhibitors of humanβ-secretase

A series of β-secretase peptidomimetic inhibitors with Leu＊Ala hydroxyethylene dipeptide isostere were synthesized and their β-secretase inhibitory activities were measured. The most potent compound N9 showed an inhibitory rate of 59.66% （10 mg/mL）. Compound N9 might be further modified by means of computational chemical methodology.

Expression of β-catenin in hepatocellular carcinoma

AIM: The beta-catenin has been recognized as a critical member of the Wnt signaling pathway and plays an important role in the generation/differentiation of many tissues. Inappropriate activation of this pathway has been implicated in carcinogenesis. The mechanism underlying the development as well as its prognosis of hepatocellular carcinoma (HCC) has remained unclear. The purpose of this study is to analyze the expression of beta-catenin in HCC in relation to histological grades and viral hepatitis backgrounds. METHODS: Thirty-two sections were selected at random from autopsy and surgical cases of HCC. Immuohistologically, the location and positivity of beta-catenin expression in HCC was examined. RESULTS: Normal hepatocytes did not express beta-catenin. In 78% of HCC beta-catenin was expressed at the membrane of the cells, with or without cytoplasmic and/or nuclear expression. The tumor cells with well-and moderately-differentiated grades expressed frequently at the membrane and cytoplasm compared with poorly-differentiated type. Nuclear expression of beta-catenin was prone to occur in the tumor cells of poorly-differentiated grade. There were 15% of hepatitis C virus (HCV) backgrounds with nuclear expression. In contrast, there was 38% with nuclear expression in hepatitis B virus (HBV) backgrounds. In nonB-nonC hepatitis, no case expressed nuclear beta-catenin. CONCLUSION: The beta-catenin expression in HCC cells was heterogenous among types of hepatitis viral infection. Wnt signaling pathway might be deeply involved in less-differentiated HCC and HBV background. (C) 2005 The WJG Press and Elsevier Inc. All rights reserved.

Mutation of DNA polymerase p in esophageal carcinoma of different regions

AIM： To observe the variation of DNA polymerase β （polβ） in esophageal carcinoma. METHODS： Thirty specimens containing adjacent normal epithelial tissues were collected from patients in Linzhou region （a high risk area for esophageal squamous carcinoma） and 25 specimens were from a non-high risk area. Total RNA was extracted from the samples and reverse transcription polymerase chain reaction （RT-PCR） was performed. PCR products were cloned and sequenced to investigate the po1β gene with DNASIS and OMIGA. Statistical significance was evaluated using the X^2 test. RESULTS： High-inddence area group： Polβ gene variation was detected in 13 of 30 esophageal carcinoma tissue specimens, and only one variation was found in 30 corresponding adjacent normal tissue specimens. Non high-incidence area group： po1β gene variation was detected in 5 of 25 esophageal carcinoma tissue specimens, and no variation was found in 25 corresponding adjacent normal tissue specimens. The incidence of po1β gene variation observed in the high-incidence area group was significantly higher than in the non-high incidence area group. Two mutation hot spots （454-466 and 648-670 nt） and a 58 bp deletion （177-234 nt） were found. CONCLUSION： Variations of polβ perform different functions between the high-incidence areas and the other areas, and may play a more important role in the high-incidence areas.

Covalent Assembly of Penicillin Acylase in Mesoporous Silica Based on Macromolecular Crowding Theory

To improve the covalent immobilization of penicillin acylase （PA）, macromolecular crowding theory was applied to its immobilization. Influence of mass ratio of enzyme to the silica, as well as, activation time with glutaraldehyde on the activity of assembled PA, was studied. In the mesopores, the effect of fl-cyclodextrin （β-CD） on the immobilization of the enzyme was also investigated. It was remarkable that the coupled yield and relative activity reached 99.5% and 92.3%, respectively, when penicillin acylase assembled covalently in the mesopores. The results here indicate that mimicked macromolecule crowding could significantly ameliorate the performance of covalently immobilized PA.