稀土积累对植物病原细菌生长的影响

本文研究了单一稀土氧化镧（Ｌａ２Ｏ３）在浓度为５０，１００，１５０，２００，２５０，３００，３５０，４００，５００，６００，７００ｐｐｍ时对植物病原细菌（Ｅｒｗｉｎｉａｃｈｒｙｓａｎｔｈｅｍｉ，Ｅｃｈ，Ｘａｎｔｈｏｍｏｎａｓｏｒｙｚａｅｐｖ．ｏｒｙｚａｅ，Ｘｏｏ；Ｐｓｅｕｄｏｍｏｎａｓｓｏｌａｎａｃｅａｒｕｍ，Ａｚ；Ｃｌａｖｉｂａｃｔｅｒｍｉｃｈｉｇａｎｅｎｓｅｓｕｂｓｐ．ｍｉｃｈｉｇａｎｅｎｓｅ，Ｃ３）生长的影响。在平板培养基中，当稀土浓度大于１００ｐｐｍ时，Ｅｃｈ，Ｘｏｏ，Ａｚ三种细菌菌落出现时间均比对照延迟，Ｃ３在所有处理中不生长。稀土浓度越大，菌落出现时间越迟，在５０～３５０ｐｐｍ内，不同菌落出现时间延迟１２～４８小时。随着稀土浓度提高，生长量逐渐减少，至４００ｐｐｍ时，所有菌不生长。在液体培养基中，当稀土浓度小于２００ｐｐｍ，培养时间为２４小时时，可刺激Ｅｃｈ菌的生长。除此之外，不同稀土浓度不同培养时间下，稀土对植物病原细菌均有一定的抑制作用，抑制作用随稀土浓度提高而增加，至３５０ｐｐｍ时，几乎完全抑制病菌生长，其中对Ｃ３的抑制作用最明显。     

镧对青枯假单胞菌生长及若干生化性状的影响

单一稀土氧化镧Ｌａ２Ｏ３对青枯假单胞菌的生长有明显抑制作用。当Ｌａ３＋质量浓度为５０,１００,１５０,２００,２５０,３００,３５０ｍｇ／Ｌ时,与对照相比,固体平板上病菌初生长时间延迟,７天后的菌落直径减小,生长量也减少。液体培养中的生物量也比对照显著下降。当Ｌａ３＋质量浓度大于３５０ｍｇ／Ｌ时,病菌停止生长。浓度为２００ｍｇ／Ｌ的Ｌａ３＋明显刺激该病菌的胞外蛋白酶、果胶酶及纤维素酶活性。     

Toxicity of Lanthanum Against Rhizoctonia solani and Its Effect on Disease-Related Enzymes

Thoroughexperimentsandpracticeaboutrare earth(RE)elementshavebeenconductedsince 1970.ScientistsinChinahavesolvedaseriesofkey technologiesandappliedREelementssuccessfullyin agricultureproduction,andmadeChinabecomethe firstcountryapplyingREasacommercialprod…     

Effects of Neodymium on Growth, Pectinase Activity and Mycelium Permeability of Fusarium oxysporum

The diameter of the colony of Fusarium oxysporum in solid medium, and the mycelium growth, pectinase activity, and mycelium permeability of Fusarium oxysporum in liquid medium under varying concentrations of Nd^3＋ （0, 2, 4, 10, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 300, and 400 mg·L^-1） were measured. The results indicated that the growth of Fusarium oxysporum was stimulated in solid medium when the concentration of Nd^3＋ ranges from 2 to 180 mg·L^-1, whereas it was inhibited when Nd^3 ＋ concentration was greater than 200 mg· L^-1. The colonies were fewer and smaller when Nd^3 ＋ was used in the solid medium. The growth of Fusarium oxysporum was inhibited in liquid medium when Nd^3＋ was used. The inhibition rate showed by the dry weight of mycelium ranged from 4.83% to 52.18% and inereased with Nd^3 ＋ concentration. The pectinase activity decreased compared with that of controls. When the concentration of Nd^3 ＋ was 10 and 400 mg· L^- 1, the pectinase activity decreased by 95 % at both concentrations. Mycelium cell membrane permeability increased when Nd^3 ＋ concentrations ranged from 10 to 400 mg· L^-1 but decreased when Nd^3＋ concentration was 2 mg· L^-1.     

Effect of Europium Chloride on Callus Growth and Cell Ultrastructure of Rheum

Ｒａｒｅｅａｒｔｈｓｈａｖｅｓｔｉｍｕｌａｔｉｖｅｅｆｅｃｔｓｏｎｔｈｅｇｒｏｗｔｈｏｆｐｌａｎｔ，ｐｒｏｄｕｃｔｉｏｎｏｆｃｈｌｏｒｏｐｈｙｌ，ａｂｓｏｒｐｔｉｏｎｏｆｅｌｅｍｅｎｔｓａｎｄｏｕｔｐｕｔｏｆｃｒｏｐｅｔｃ．［１］．Ｂｕｔｔｈｅｒｅ...     

Effect of Lanthanum on Mycelium Growth and Some Pathogenic Factors

Three soil-transmitted pathogenic fungi including Rhizoctonia solani, Fusarium solani, and Pythium sp. were selected to investigate the effect of lanthanum on their growth and the pathogenic enzymes using liquid culture. Variance analysis shows significant differences among treatments with different concentrations of lanthanum （Rhizoctonia solani F = 6.75 〉 F0.01= 5.99; Fusarium solani F = 18.1 〉 F0.01 = 5.99, Pythium sp. F = 23.29 〉 F0.01 = 5.99）. The inhibitory effect of lanthanum on pathogenic fungi increased with an increase in La concentration. The activities of the three pathogenic enzymes per gram mycelium were promoted remarkably. However, the quantity or the activities of the total enzymes were inhibited because of the strong inhibition of mycelium growth by lanthanum. Meanwhile, the effect of lanthanum on toxins of pathogenic fungi were studied using the seed germination experiment. Toxins of pathogenic fungi are influenced by lanthanum and the virulence decreases significantly with the increase of lanthanum concentration.     

La3+对小球藻异养生长及叶绿素含量的影响

０．１～１００ｍｇ·Ｌ－１Ｌａ（ＮＯ３）３均能促进小球藻的异养生长,有助于葡萄糖的利用。异养培养时间≤３６ｈ时,Ｌａ３＋显著抑制小球藻对ＮＯ－３的吸收,之后则加速ＮＯ－３的吸收。Ｌａ３＋还能提高小球藻的叶绿素ａ、叶绿素ｂ及总叶绿素含量,最大促进百分率分别为２３．４％、２７．１％及２４．７％。     

Renal changes after an uncomplicated antireflux operation

Lanthanum had a small effect on the barrier, but did not significantly increase its sodium or potassium permeability. There was no effect on nerve conduction unless the barrier was deliberately damaged. The results lend confidence to the use of lanthanum as an extracellular tracer.     

甲烷磺酸镧在酯化反应中的催化活性

合成了甲烷磺酸镧,用红外、热重分析对其进行表征。热重分析结果表明所合成的甲烷磺酸镧分子中含四个结晶水,La2O3含量的实测值与理论计算值基本相符。以甲烷磺酸镧为催化剂,研究了其催化氯乙酸与异丙醇酯化反应中各种因素对酯化率的影响。反应条件为:醇酸摩尔比1.2∶1,催化剂用量1.0%(以酸的摩尔数计量),反应时间2.5h,反应温度为回流温度,苯作为带水剂,最高酯化率可达95.5%。与其它Lewis酸催化剂比较,甲烷磺酸镧的催化活性最好。     

Extracellular nuclease produced by a marine bacterium. I. Extracellular deoxyribonuclease formation by a marine Vibrio sp

Deoxyribonuclease (DNase) activity was found in the culture fluids of numerous marine bacteria isolated from seawater. Among these ogranisms, marine bacterium, Vibrio sp., strain No. 2, showed the highest deoxyribonucleic acid-hydrolyzing activity. This organism requires salts of seawater for both growth and extracellular DNase formation. The DNase activity could not be detected in the synthetic seawater culture liquid lacking magnesium ion, and DNase activity decreased in a calcium-deficient medium. The optimum temperature for the growth of this organism was between 15 and 25 degrees C. The formation of extracellular DNase was the greatest at 20 degrees C and less activity was found at 10 and 30 degrees C.     

氢氧化镧湿法氟化法合成氟化镧工艺研究

采用了氢氟酸直接氟化氢氧化镧浆液的制备工艺，考察了工艺的可行性。研究了氢氟酸浓度、用量、反应温度、反应时间等因素对产物含氧量、氟化率和制备过程中过滤、洗涤的影响。通过差热分析、扫描电镜、X射线衍射等手段对产品的组成、形貌、结构等进行了研究。制备工艺为固液反应，工艺简单，产品分散性好，易过滤洗涤，质量稳定，工业可操作性强，流程短。     

Selenium and the thioredoxin redox system: effects on cell growth and death

Thioredoxin is a redox protein found overexpressed in some human tumors. Thioredoxin is secreted by tumor cells and enhances the sensitivity of the cancer cells to other growth factors. Redox activity is essential for stimulation of cell growth by thioredoxin. Cells transfected with thioredoxin cDNA show increased tumor growth and decreased apoptosis in vivo and decreased sensitivity to apoptosis induced by a variety of agents both in vitro and in vivo. Cells transfected with a redox-inactive mutant thioredoxin show inhibited tumor growth in vivo. Dietary selenium has been shown to prevent some forms of human cancer. Selenocysteine is an essential component of thioredoxin reductase, the flavoenzyme that is responsible for the reduction of thioredoxin. Selenium added to the culture medium increases thioredoxin reductase activity due to an increase in thioredoxin reductase protein but mostly due to an increase in the specific activity of the enzyme. Some diaryl chalcogenide (selenium and tellurium) compounds have been studied as inhibitors of thioredoxin reductase. The most active were diaryl tellurium compounds, which were noncompetitive inhibitors of thioredoxin reductase with Ki values of 2-10 microM. Several of the compounds inhibited cancer cell colony formation in vitro with IC50s as low as 2 microM.     

Purification and characterization of laccase from Chaetomium thermophilium and its role in humification

Chaetomium thermophilium was isolated from composting municipal solid waste during the thermophilic stage of the process. C. thermophilium, a cellulolytic fungus, exhibited laccase activity when it was grown at 45 degreesC both in solid media and in liquid media. Laccase activity reached a peak after 24 h in liquid shake culture. Laccase was purified by ultrafiltration, anion-exchange chromatography, and affinity chromatography. The purified enzyme was identified as a glycoprotein with a molecular mass of 77 kDa and an isoelectric point of 5.1. The laccase was stable for 1 h at 70 degreesC and had half-lives of 24 and 12 h at 40 and 50 degreesC, respectively. The enzyme was stable at pH 5 to 10, and the optimum pH for enzyme activity was 6. The purified laccase efficiently catalyzed a wide range of phenolic substrates but not tyrosine. The highest levels of affinity were the levels of affinity to syringaldazine and hydroxyquinone. The UV-visible light spectrum of the purified laccase had a peak at 604 nm (i.e., Cu type I), and the activity was strongly inhibited by Cu-chelating agents. When the hydrophobic acid fraction (the humic fraction of the water-soluble organic matter obtained from municipal solid waste compost) was added to a reaction assay mixture containing laccase and guaiacol, polymerization took place and a soluble polymer was formed. C. thermophilium laccase, which is produced during the thermophilic stage of composting, can remain active for a long period of time at high temperatures and alkaline pH values, and we suggest that this enzyme is involved in the humification process during composting.     

Photocatalytic Destruction of Nitrogen Monoxide over La^3＋ and N Co-doped SrTiO3 Powders under Visible Light Irradiation

Lanthanun, and nitrogen co-doped SrTi03 was prepared by a mechanochemical reaction using SrTi03, urea and la203 as the raw materials. The samples were characterized by X-ray diffraction, X-ray photoelectron spectrometer, trans-mission electron microscopy, and nitrogen adsorption-desorption isotherm measurements, lanthanum doping could increase the doping content of nitrogen in the sample. The sample prepared with 0.2 mol% La203, 22 mol% urea and 77.8 mol % SrTi03 by mechanochemical reaction, which has nearly the same nitrogen and lanthanum doping fractions, exhibited high photocatalytic activities. Under the irradiation of light with wavelength larger than 400, and 290 nm, the photocatalytic activity of nitrogen and lanthanum co-doped SrTi03 were 2.6 and 2 times greater than that of pure SrTi03.     

Purification and characterization of a novel thermostable alpha-L-arabinofuranosidase from a color-variant strain of Aureobasidium pullulans

A color-variant strain of Aureobasidium pullulans (NRRL Y-12974) produced alpha-L-arabinofuranosidase (alpha-L-AFase) when grown in liquid culture on oat spelt xylan. An extracellular alpha-L-AFase was purified 215-fold to homogeneity from the culture supernatant by ammonium sulfate treatment, DEAE Bio-Gel A agarose column chromatography, gel filtration on a Bio-Gel A-0.5m column, arabinan-Sepharose 6B affinity chromatography, and SP-Sephadex C-50 column chromatography. The purified enzyme had a native molecular weight of 210,000 and was composed of two equal subunits. It had a half-life of 8 h at 75 degrees C, displayed optimal activity at 75 degrees C and pH 4.0 to 4.5, and had a specific activity of 21.48 mumol min-1. mg-1 of protein against p-nitrophenyl-alpha-L-arabinofuranoside (pNP alpha AF). The purified alpha-L-AFase readily hydrolyzed arabinan and debranched arabinan and released arabinose from arabinoxylans but was inactive against arabinogalactan. The K(m) values of the enzyme for the hydrolysis of pNP alpha AF, arabinan, and debranched arabinan at 75 degrees C and pH 4.5 were 0.26 mM, 2.14 mg/ml, and 3.25 mg/ml, respectively. The alpha-L-AFase activity was not inhibited at all by L-arabinose (1.2 M). The enzyme did not require a metal ion for activity, and its activity was not affected by p-chloromercuribenzoate (0.2 mM), EDTA (10 mM), or dithiothreitol (10 mM).     

Effect of volume expansion on the paracellular flux of lanthanum in the proximal tubule

Although studies of volume expansion (VE) in the Necturus suggest a major role for paracellular flux in reabsorption by the proximal tubule, results from morphologic or electrophysiologic studies of the effect of VE on the rat proximal tubule suggest only a minor role for paracellular transport. In the present study, during in vivo microperfusion, lanthanum was used as an extracellular marker to determine bidirectional paracellular flux in the rat proximal tubule before and during 10% VE. Lanthanum itself did not affect proximal tubule reabsorption (delta 0.7 +/- 3.3 nl/min, LaCl3 versus saline infusion, n = 7). When lanthanum was added to the luminal perfusate, paracellular lanthanum efflux from the lumen to the interstitium was 28.9 +/- 6.6 pg/min per mm, n = 7. Subsequent VE significantly decreased the paracellular lumen-to-interstitium efflux to 12.8 +/- 8.3 pg/min per mm concomitant with a 49% decrease in proximal fluid reabsorption (delta -2.6 +/- 0.9 nl/min per mm, P < 0.05). When lanthanum was infused interstitially, by means of a chronically implanted matrix, there was significant paracellular lanthanum influx from the interstitium into the lumen (143.9 +/- 18.6 pg/min per mm, n = 4). Subsequent VE significantly increased this interstitium-to-lumen influx to 212.1 +/- 29.2 pg/min per mm as proximal reabsorption was significantly decreased by 58% (delta -2.8 +/- 0.8 nl/min per mm, P < 0.05). Thus, VE affects bidirectional paracellular flux in a manner that would decrease proximal reabsorption; paracellular efflux from the lumen to the interstitium was decreased, whereas paracellular influx from the interstitium to the lumen was increased.     

Psychosocial care needs of children with new-onset seizures. 2

Preparations of human cervical mucus were obtained from fifteen female volunteers with or without vaginal candidiasis. Their content of lactoferrin and inhibitory effects on the growth of Candida albicans were estimated. The concentration of lactoferrin in cervical mucus was measured by enzyme linked immunosorbent assay (ELISA). Lactoferrin concentration of the eleven preparations among them was more than 0.2 mg/ml. The effects of these cervical mucus preparations on Candida growth were examined in vitro. Candida growth was not inhibited by the addition of 1/200 diluted cervical mucus alone, however, anti-Candida activity of murine neutrophils was augmented by such an addition. These results suggest that the combination of neutrophils and cervical mucus may have an important role in defense against Candida infection in the vaginal mucosa.     

Alloying Effect of Lanthanum in GCr15 Bearing Steel with Tin and Antimony

Effect of tin and antimony on hot ductility of GCr15 bearing steel as well as interaction between lanthanum and tramp dements, were studied by simulator Gleeble-1500 and the fractures for the tested steels were analyzed using SEM and EDS. The results show that with increasing contents of tin and antimony elements, the hot ductility of GCr15 beating steel was decreased. Lanthanum can reduce the harmful effect of tramp elements on the hot ductility of GCr15, which can react with antimony to form compound and segregate at grain boundary in steel. Lanthanum can refine the recrystallized austenite grains after deformation and subsequent martensite structure.     

An extracellular protease of Streptococcus gordonii hydrolyzes type IV collagen and collagen analogues

Streptococcus gordonii is a frequent cause of infective bacterial endocarditis, but its mechanisms of virulence are not well defined. In this study, streptococcal proteases were recovered from spent chemically defined medium (CDM) and fractionated by ammonium sulfate precipitation and by ion-exchange and gel filtration column chromatography. Three proteases were distinguished by their different solubilities in ammonium sulfate and their specificities for synthetic peptides. One of the enzymes cleaved collagen analogs Gly-Pro 4-methoxy-beta-naphthylamide, 2-furanacryloyl-Leu-Gly-Pro-Ala (FALGPA), and p-phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-Arg (pZ-peptide) and was released from the streptococci while complexed to peptidoglycan fragments. Treatment of this protease with mutanolysin reduced its 180- to 200-kDa mass to 98 kDa without loss of enzymatic activity. The purified protease cleaved bovine gelatin, human placental type IV collagen, and the Aalpha chain of fibrinogen but not albumin, fibronectin, laminin, or myosin. Enzyme activity was inhibited by phenylmethylsulfonyl fluoride, indicating that it is a serine-type protease. Maximum production of the 98-kDa protease occurred during growth of S. gordonii CH1 in CDM containing 0.075% total amino acids at pH 7.0 with minimal aeration. Higher initial concentrations of amino acids prevented the release of the protease without reducing cell-associated enzyme levels, and the addition of an amino acid mixture to an actively secreting culture stopped further enzyme release. The purified protease was stored frozen at -20 degreesC for several months or heated at 50 degreesC for 10 min without loss of activity. These data indicate that S. gordonii produces an extracellular gelatinase/type IV collagenase during growth in medium containing minimal concentrations of free amino acids. Thus, the extracellular enzyme is a potential virulence factor in the amino acid-stringent, thrombotic, valvular lesions of bacterial endocarditis.     

A multisample assay for inhibitors of phosphatidylinositol phospholipase C: identification of naturally occurring peptide inhibitors with antiproliferative activity

A convenient and reliable multisample assay for the screening of inhibitors of the growth factor signalling enzyme phosphatidylinositol specific phospholipase C (PtdInsPLC) has been developed. Three naturally occurring peptide inhibitors of PtdInsPLC have been identified, myroridin K, streptothricin B and edeine, with IC50 values of 8.3, 6.7 and 16.1 microM, respectively. All three peptides inhibited colony formation of HT-29 human colon adenocarcinoma cells, with IC50 values of 7.2, 3.9 and 13.0 microM, respectively. The compounds also inhibited the growth of other human cancer cells in culture. One of the peptides, myroridin K, has previously been reported to have in vivo antitumour activity. It is possible that inhibition of PtdInsPLC is responsible for the cell growth inhibition and antitumour properties of the peptide compounds.