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951.
To understand the effect of hydrodynamical process on water phosphorus concentration, wind, wave, and several water quality indices were observed in Meiliang Bay, a shallow and eutrophic bay locates in north of Lake Taihu. During the 7 day observation period, wind speed and significant wave height were recorded more than 3 h per day, and water samples were collected in five water-depth layers once a day. Hydrodynamical disturbance had no significant correlationship with the water quality at the top layer when the significant wave height was smaller than 30 cm, but it significantly increased suspended solids (SS) concentration of the bottom water layer. Concentrations of nutrients showed no positive correlationship with SS concentration in the water body. Intensive sediment resuspension may not have occurred when the hydrodynamic stress on sediment was only a little higher than the critical stress for sediment resuspension. A new method for confirming the critical stress for intensive sediment resuspension and nutrient release still needs to be developed. The range of the water quality indices was quite high during the seven days of observation. High variation seems to be a common character of large shallow lakes like Taihu.  相似文献   
952.
Allelopathic effects of the submerged macrophyte Potamogeton malaianus on Scenedesmus obliquus were assessed using a two-phase approach under controlled laboratory conditions. In the co-culture experiment (phase І), the growth of S. obliquus at two different initial cell densities was significantly inhibited by P. malaianus. Moreover, the growth inhibition was dependent on the biomass density of P. malaianus. Antioxidant enzymes (SOD, CAT and POD), MDA, APA, total soluble protein, protein electrophoretic pattern and morphology of S. obliquus were determined after the co-culture experiment was terminated. The activities of SOD, CAT, POD and APA at the low initial cell density were stimulated, the contents of MDA and total soluble protein were increased, and some special protein bands disappeared in P. malaianus treatments. The macrophyte had no effect on the activities of SOD and APA at the high initial cell density, but significantly influenced other physiological parameters of S. obliquus with the increase of biomass density. The morphology of S. obliquus showed no difference in the macrophyte treatments and the controls, and the cultures were dominated by 4-celled coenobia. The results indicated P. malaianus had significant allelopathic effects on the growth and physiological processes of S. obliquus. Moreover, the allelopathic effects depended on initial algal cell density, biomass density of the macrophyte, and their interaction. In the experiment of P. malaianus culture filtrates (phase II), filtrates from combined culture of plant and S. obliquus at the low initial cell density exhibited no apparent growth inhibitory effect on S. obliquus. The result showed that initial addition of growth-inhibiting plant filtrates had no allelopathic effect on S. obliquus. We concluded that the allelopathic effects on S. obliquus were found in the presence of P. malaianus, but not in P. malaianus filtrates. However, the absence of allelopathic effect on S. obliquus might be due to the very low concentrations of allelochemicals in the filtrates. Handling editor: S. M. Thomas  相似文献   
953.
Zhou QF  Luo XG  Ye L  Xi T 《Current microbiology》2007,54(5):366-370
Perinerin is a small antimicrobial peptide (AMP) isolated from an Asian marine clamworm, Perinereis aibuhitensis Grube. It shows marked activity in vitro against both Gram-negative and Gram-positive bacteria. To obtain it in large amounts, the coding sequence of perinerin was cloned into pET32a(+) vector and expression as a Trx fusion protein in Escherichia coli. The soluble fusion protein collected from the supernatant of the cell lyste was separated by Ni2+-chelating chromatography. The purified protein was then cleaved by Factor Xa protease to release mature perinerin. Final purification was achieved by ion-exchange chromatography. Recombinant perinerin exhibited a similar antimicrobial activity to the native perinerin. These works might provide a significant foundation for the following research on the action of mechanism of marine AMPs.  相似文献   
954.
Asymmetric (N(G),N(G))-dimethylarginine (ADMA) inhibits nitric oxide (NO) synthases (NOS). ADMA is a risk factor for endothelial dysfunction, cardiovascular mortality, and progression of chronic kidney disease. Two isoforms of dimethylarginine dimethylaminohydrolase (DDAH) metabolize ADMA. DDAH-1 is the predominant isoform in the proximal tubules of the kidney and in the liver. These organs extract ADMA from the circulation. DDAH-2 is the predominant isoform in the vasculature, where it is found in endothelial cells adjacent to the cell membrane and in intracellular vesicles and in vascular smooth muscle cells among the myofibrils and the nuclear envelope. In vivo gene silencing of DDAH-1 in the rat and DDAH +/- mice both have increased circulating ADMA, whereas gene silencing of DDAH-2 reduces vascular NO generation and endothelium-derived relaxation factor responses. DDAH-2 also is expressed in the kidney in the macula densa and distal nephron. Angiotensin type 1 receptor activation in kidneys reduces the expression of DDAH-1 but increases the expression of DDAH-2. This rapidly evolving evidence of isoform-specific distribution and regulation of DDAH expression in the kidney and blood vessels provides potential mechanisms for nephron site-specific regulation of NO production. In this review, the recent advances in the regulation and function of DDAH enzymes, their roles in the regulation of NO generation, and their possible contribution to endothelial dysfunction in patients with cardiovascular and kidney diseases are discussed.  相似文献   
955.
Aldehydes are ubiquitous pollutants generated during the combustion of organic materials and are present in air, water, and food. Several aldehydes are also endogenous products of lipid peroxidation and by-products of drug metabolism. Despite well-documented high reactivity of unsaturated aldehydes, little is known regarding their cardiovascular effects and their role in cardiac pathology. Accordingly, we examined the myocardial effects of the model unsaturated aldehyde acrolein. In closed-chest mice, intravenous acrolein (0.5 mg/kg) induced rapid but reversible left ventricular dilatation and dysfunction. In mouse myocytes, micromolar acrolein acutely depressed myofilament Ca(2+) responsiveness without altering catecholamine sensitivity, similar to the phenotype of stunned myocardium. Immunoblotting revealed increased acrolein-protein adducts and protein-carbonyls in both acrolein-exposed myocardium (1.8-fold increase, P < 0.002) and myocytes (6.4-fold increase, P < 0.02). Both the contractile dysfunction and adduct formation were markedly attenuated by pretreatment with the thiol donor N-acetylcysteine (5 mM). Two-dimensional gel electrophoresis and mass-assisted laser desorption/ionization time-of-flight mass spectrometry analysis revealed two groups of adducted proteins, sarcomeric/cytoskeletal proteins (cardiac alpha-actin, desmin, myosin light polypeptide 3) and energy metabolism proteins (mitochondrial creatine kinase-2, ATP synthase), indicating site-specific protein modification that was confirmed by immunohistochemical colocalization. We conclude that direct exposure to acrolein induces selective myofilament impairment, which may be, in part, related to the modification of proteins involved in myocardial contraction and energy metabolism. Myocardial dysfunction induced by acrolein and related aldehydes may be symptomatic of toxicological states associated with ambient or occupational exposures or drug toxicity. Moreover, aldehydes such as acrolein may mediate cardiac dysfunction in pathologies characterized by high-oxidative stress.  相似文献   
956.
目的:探讨大鼠三叉神经节不同直径神经元ATP-激活电流的特征。方法:应用全细胞膜片钳技术进行实验。结果:①92.3%(60/65)的细胞对ATP敏感,有反应的细胞可记录到三种型式的ATP-激活电流:快速激活快速失活型(Fast type,F型)、快速激活缓慢失活型(Intermediate type,I型)和缓慢激活缓慢失活型(Slowtype,S型)。三种电流均具有浓度依赖性。②小直径的细胞多表现为F型特征,大直径的细胞多表现为S型特征,而中等大小的细胞多表现为I型特征。③动力学特征:三种类型的ATP激活电流上升相从10%到90%的时间:F型:(33.6±4.5)ms;Ⅰ型:(62.2±9.9)ms;S型:(302.1±62)ms。去敏感相从10%到90%的时间:F型:(399.4±58.2)ms;S型:>500ms。④I-V曲线:三种电流均表现为内向整流的特性,而且翻转电位均为0~5mV。⑤量-效关系:Ⅰ型的量-效曲线居中间,F型的下移,S型的上移,三种类型电流量-效曲线的EC50非常接近。结论:三种型式的ATP-激活电流可能是由不同亚单位组合的P2X受体各亚型所介导,这些亚型分布于不同大小的三叉神经节神经元,从而传导不同的信息。  相似文献   
957.
阿米洛利抑制NHE-1减轻低氧性肺动脉平滑肌细胞增殖   总被引:1,自引:0,他引:1  
目的:研究Na^+/H^+交换抑制剂阿米洛利对低氧刺激的大鼠肺动脉平滑肌细胞(PASMCs)增殖的影响,以及Na^+/H^+交挟体-l(NHE-1)活性和表达的变化.方法:常氧(21%O2)或低氧(2%O2)条件下培养PASMCs,并分别给予浓度为1.653、3.125、6.25、12.5、25和50μmol/L.等不同浓度的阿米洛利,培养24h,采用MTT比色实验和免疫组化检测PCNA阳性细胞率的方法反映细胞增殖情况,同时采用激光共聚焦检测细胞内pH以反映Na^+/H^+交换体-1活性,RT—PCR法检测Na^+/H^+交换体-1mRNA的表达量.结果:低氧培养的PASMCs细胞内pH升高,NHE—1mRNA的表达增多,而阿米洛利可以降低细胞内pH,减少NHE—1mRNA的表达量。同时低氧较常氧培养MTT光吸收值较常氧培养明显升高。PCNA阳性细胞率明显增高,而给予阿米洛利时上述两个指标随药物浓度增加而逐渐下降。结论:低氧可以激活PASMCs细胞膜上的E—1,增加其mRNA水平表达量,使细胞内碱化,促进细胞增殖,而Na^+/H^+交换抑制剂阿米洛利可以抑制其活性,减少mRNA水平的表达,导致细胞内酸化,从而抑制细胞增殖,并且此抑制作用在3.125~50μmol/L.浓度范围内呈现明显的浓度依赖性。  相似文献   
958.
目的:探讨N-乙酰基-丝氨酰-天门冬酰-赖氨酰-脯氨酰(AcSDKP)对血小板源性生长因子(PDGF)诱导的大鼠心脏成纤维细胞增殖和胶原合成的调节作用。方法:建立新生大鼠心脏成纤维细胞系;采用四甲基偶氮唑(MTT)法和^3H-TdR掺入法检测心脏成纤维细胞的增殖;采用^3H-脯氨酸掺入法检测心脏成纤维细胞胶原的合成。结果:PD3F在1~20ng/ml浓度范围内对心脏成纤维细胞增殖和胶原合成均有促进作用。且随着PDGF浓度的增加,其促细胞增殖和胶原合成作用增强,并在10ng/ml浓度时PDGF的促增殖和胶原合成效应最强。在10^-10~10^-8mol/L浓度范围内,AcSDKP对PDGF介导的心脏成纤维细胞增殖和胶原合成均有抑制作用,并且在10叫mol/L时,AcSDKP抑制心脏成纤维细胞增殖和胶原合成作用最强。结论:AcSDKP对PDGF介导的心脏成纤维增殖和胶原合成均有明显抑制作用,这可能与其抗心脏纤维化的作用相关。  相似文献   
959.
生物信息学在发现新基因方面的应用   总被引:3,自引:0,他引:3  
自生物信息学作为一门交叉学科诞生以来,其在计算机、农业和生命科学等各方面发挥了重要的作用,在后基因组时代,更是成为发现新基因的重要手段。对生物信息学的概况做了回顾与展望,并简述了生物信息学近年在发现新基因方面所取得的成果。  相似文献   
960.
rPA(K)是经过缺失/定点突变技术所获得的t-PA突变体。本实验以IPTG诱导,实现了rPA(K)在原核系统中的表达。实验证明目的产物的表达形式为包涵体,且当以IPTG诱导3h时,表达量最高,为41%。此后对该表达产物进行了初步纯化,即通过对不同超声破碎次数,包涵体洗涤液(脲,Triton X-100,乙醇)的不同浓度对纯化的影响因素进行了摸索。结果表明,超声2次,2M脲,0.5%Triton X-100,20%乙醇对目的蛋白纯化的效果最好,从而为进一步的纯化和复性奠定基础。  相似文献   
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