铝胁迫下小麦根部苹果酸和柠檬酸的直接测定

铝的有害性严重制约了约占世界可耕地面积40％的酸性土壤中的作物生产。从植物的培养液巾发现从根部分泌出的有机酸与铝结合从而实现无毒化是其抗铝逆性机理的重要依据。而本文直接测定了铝胁迫下培育的小麦根中的铝和有机酸含量,确认了主要积累的是苹果酸和柠檬酸。发现随着提高培养液中的铝浓度,根部的铝含量也相应增加。同时,虽然根中的柠檬酸含量无明显变化,但苹果酸被诱导增加。通过对有机酸与铝的络合能力的调查,探讨了对植物抗铝逆性强弱的影响。     

Liquid chromatographic determination of free and conjugated 3-methoxy-4-hydroxyphenylethylene glycol with wide-ranging substances related to monoamine metabolism

A simple and sensitive procedure was developed for the simultaneous determination of substances metabolically related to monoamine transmitters including 3-methoxy-4-hydroxy-phenylethylene glycol (MOPEG) in dissected brain regions of rats using high-performance liquid chromatography combined with electrochemical detection. The tissue sample was homogenized in HCl solution. The homogenate was divided into two portions, of which one was used for the assay of MOPEG after enzymatic hydrolysis with sulfatase. A butanol extraction process was performed on the remaining portion to obtain the sample of monoamine transmitters, precursor amino acids, and acidic metabolites. The monoamines and precursor amino acids were finally recovered in HCl solution, while the acidic metabolites shifted into the alkaline buffer from the organic layer. The basic and neutral substances were separated with a 0.1 M sodium citrate/citric acid buffer system (pH 4.0) containing 1% tetrahydrofuran, and the acidic ones with 0.075 M sodium citrate/citric acid buffer (pH 3.5) containing 1% tetrahydrofuran, 10% methanol, and 12% acetic acid. The steady-state concentrations of three monoamine transmitters (noradrenaline, dopamine, and 5-hydroxytryptamine) were determined together with their precursors and metabolites. Changes in the concentrations of these substances were examined for various drugs, of which the effects had been previously confirmed. The changes reflected putative drug effects and demonstrated that the procedure was applicable to the regional determination of monoamines and their metabolically related substances.     

Influence of S-ethyl Dipropylthiocarbamate (EPTC) on the Fatty Acid Composition of Wheat Leaf Galactolipids

Winter wheat (Triticum sativum L. cv. Nisu) was grown in sand which contained 0, 0.25, 0.5 and 1.0 mg S-ethyl dipropylthiocarbamate (EPTC) per kg air dry sand. The galactolipids of leaves of 21-day-old seedlings were isolated by preparative thin layer chromatography. The fatty acids of the mono- and digalactosyl diglycerides were analysed by gas liquid capillary chromatography. The major fatty acids of the wheat leaf galactolipids were palmitic, palmitoleic, stearic, oleic, vaccenic, linoleic and linolenic acids (in the monogalactosyl diglyceride fraction of untreated plants 22.5, 2.4, 3.1, 5.2, 2.5, 51.1 and 1526.6 μg and in the digalactosyl diglyceride fraction 108.8, 2.3, 10.4, 9.9, 8.2, 42.3 and 1120.7 μg/g leaf fresh weight, respectively). Total fatty acid content of the mono- and digalactosyl diglyceride fractions was decreased by 85 and 87%, respectively, at 1 mg EPTC/kg sand, while decrease in the fresh weight of the leaves was 79%. The content of linoleic and linolenic acids/g fresh weight of the leaves was decreased in the monogalactosyl diglyceride fraction by 27 and 43%, respectively, while the content of all other fatty acids was increased. In the digalactosyl diglyceride fraction the content of both linoleic and linolenic acids/g leaf fresh weight was decreased by 55%. The content of palmitic and vaccenic acids was also decreased, whereas the content of other fatty acids remained at the level of the untreated samples. The general quality of the fatty acids in the mono- and digalactosyl diglyceride fractions was altered slightly by EPTC.     

Purification and characterization of phospholipase A2 from rat stomach

Phospholipase A2, which is localized in the mucosal part of the corpus of rat stomach (Hirohara et al. (1987) Biochim. Biophys. Acta 919, 231-238), was purified 990-fold from the supernatant of a tissue homogenate by heat treatment at acidic pH, ammonium sulfate fractionation, ion-exchange chromatography, gel-filtration and reverse-phase high-performance liquid chromatography (reverse-phase HPLC). The purified enzyme gave a single protein band on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis with a molecular mass of approx. 17 kDa. The enzyme had a pH optimum of 8.0 and hydrolyzed the 2-arachidonoyl residue of phosphatidylcholine preferentially to the 2-oleoyl residue, the Vmax and Km values for the two being 227 and 29 mumol/min per mg protein and 0.037 and 0.019 mM, respectively. The activity was calcium-dependent and was markedly increased by SDS and dimethyl sulfoxide (DMSO). The enzyme showed typical product inhibition. Free unsaturated fatty acids (oleic, arachidonic and docosahexaenoic acids), which are supposedly the main enzymatic products in vivo, inhibited the activity. Arachidonic acid caused noncompetitive inhibition and its concentration for its maximal inhibition (50% inhibition) was 5 x 10(-5) M. Lysophosphatidylcholine, free saturated fatty acids (palmitic and stearic acids) and arachidonic acid metabolites (leukotrienes and prostaglandins) had no effect on the activity.     

Nature and Amount of Auxin in Algae : IAA from Extracts of Caulerpa paspaloides (Siphonales)

Evidence for the occurrence of indole 3-acetic acid in Caulerpa paspaloides extracts was obtained by bioassay, by high-performance liquid chromatography with an electrochemical detector, and by capillary gas chromatography combined with mass spectrometry. The amount of indole 3-acetic acid present was estimated to be about 1 milligram per kilogram fresh weight, with an error limit of one order of magnitude. This is in the range reported from angiosperms.     

Roles of Organic Acids and Nitrate in the Long-Distance Transport of Cobalt in Xylem Saps of <Emphasis Type="Italic">Alyssum murale</Emphasis> and <Emphasis Type="Italic">Trifolium subterraneum</Emphasis>

Roles of organic acids and nitrate in the long-distance transport of cobalt (Co) in xylem saps of hyperaccumulator Alyssum murale and non-hyperaccumulator Trifolium subterraneum were studied under hydroponic conditions. Organic acids (oxalic, malic, malonic, citric, and fumaric) and nitrate in xylem sap samples were separated and determined simultaneously by reversed-phase high performance liquid chromatography after solid-phase extraction with nanosized hydroxyapatite. Results indicated that Co treatment significantly increased the concentrations of xylem oxalic and malic acids for the hyperaccumulator A. murale compared to the control but significantly decreased the concentrations of xylem nitrate and malonic acid; concentrations of citric acid in xylem sap samples did not show significant difference between the control and Co treatments. By analyzing the relationship between the concentrations of organic acids, nitrate, and concentrations of Co in xylem saps, it could be concluded that oxalic and malic acids in xylem saps seemed to participate in the long-distance Co translocation process, and citric acid did not relate to the xylem Co transport of A. murale and T. subterraneum. Our work might be very useful for understanding the mechanism of long-distance transport of heavy metals in hyperaccumulator.     

Augmenting effect of acetic acid for acidification on bactericidal activity of hypochlorite solution

AIMS: Bactericidal activity of chlorine solution is enhanced by weak acidification. We compared the effects of various acids on the bactericidal activity of hypochlorite solution to establish a method for safe and effective use of an acidic hypochlorite solution. METHODS AND RESULTS: The bactericidal activities of acidic hypochlorite solutions that had been adjusted to pH 5.0 with hydrochloric acid, acetic acid, citric acid, lactic acid, formic acid, phosphoric acid or sulphuric acid against Bacillus subtilis spores were compared. The acidic solutions prepared with hydrochloric acid and acetic acid showed the highest bactericidal activity, and all of the spores (5 x 106 cfu ml(-1)) were killed within 10 min. On the other hand, the solutions prepared with citric acid and lactic acid showed no bactericidal activity against any bacterial strains tested in this study despite the low pH. The amount of chlorine gas produced by the preparation using acetic acid was sixfold less than that produced from the preparation using hydrochloric acid. CONCLUSIONS: Acetic acid is the most suitable and safe acid for the preparation of an acidic hypochlorite solution. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provide useful information for establishing a method for safe and effective use of an acidic hypochlorite solution.     

Root excretion of carboxylic acids and protons in phosphorus-deficient plants

Phosphorus deficiency-induced metabolic changes related to exudation of carboxylic acids and protons were compared in roots of wheat (Triticum aestivum L. cv Haro), tomato (Lycopersicon esculentum L., cv. Moneymaker), chickpea (Cicer arietinum) and white lupin (Lupinus albus L. cv. Amiga), grown in a hydroponic culture system. P deficiency strongly increased the net release of protons from roots of tomato, chickpea and white lupin, but only small effects were observed in wheat. Release of protons coincided with increased exudation of carboxylic acids in roots of chickpea and white lupin, but not in those of tomato and wheat. P deficiency-induced exudation of carboxylic acids in chickpea and white lupin was associated with a larger increase of carboxylic acid concentrations in the roots and lower accumulation of carboxylates in the shoot tissue compared to that in wheat and tomato. - Citric acid was one of the major organic acids accumulated in the roots of all investigated species in response to P deficiency, and this was associated with increased activity and enzyme protein levels of PEP carboxylase, which is required for biosynthesis of citrate. Accumulation of citric acid was most pronounced in the roots of P-deficient white lupin, chickpea and tomato. Increased PEP carboxylase activity in the roots of these plants coincided with decreased activity of aconitase, which is involved in the breakdown of citric acid in the TCA cycle. In the roots of P-deficient wheat plants, however, the activities of both PEP carboxylase and aconitase were enhanced, which was associated with little accumulation of citric acid. The results suggest that P deficiency-induced exudation of carboxylic acids depends on the ability to accumulate carboxylic acids in the root tissue, which in turn is determined by biosynthesis, degradation and partitioning of carboxylic acids or related precursors between roots and shoot. In some plant species such as white lupin, there are indications for a specific transport mechanism (anion channel), involved in root exudation of extraordinary high amounts of citric acid. This revised version was published online in June 2006 with corrections to the Cover Date.     

Urinary profiles of volatile and acid metabolites in germfree and conventional rats

Qualitative and quantitative differences in the urinary excretion of volatile and acidic metabolites in germfree and conventional rats were examined by capillary gas chromatography and gas chromatography/mass spectrometry. A number of carbonyl compounds, including several short-chain aliphatic ketones and acetophenone, were higher in the conventional urines, while many heterocyclic compounds (furan derivatives, benzothiazole and others) were lower. Both qualitative and quantitative differences were observed in the urinary excretion of acidic metabolites. Three meta-hydroxy phenolic acids appeared only in the conventional rat urines, while levels of many other aromatic and aliphatic acids were also higher.     

Substances Isolated from Woody Cuttings of Salix atrocinerea and Their Growth Properties

A study of the cuttings of Salix atrocinerea Brot. was made by extraction with methanol, paper chromatography and Avena coleoptile straight growth test. In the acidic fraction, indole-3-acetic acid (IAA; about 15 μg per kg fresh weight) and p-hydroxybenzoic acid (PHB; about 850 μg per kg fresh weight) were isolated and identified. The growth activity of the different zones is explained by their content of these two compounds. The watersoluble residue, insoluble in ether, showed growth Stimulating activity, which probably is due to a bound auxin (IAA-sugar); alkaline breakdown of this aqueous residue, giving PHB, vanillic and p-coumaric acids, suggests the presence (in the cuttings of Salix atrocinerea) of glycosides with aglycones similar to rhamnacine and scutellareine.     

罗勒籽脂肪酸及其对蛋白酪氨酸磷酸酯酶1B(PTP1B)抑制作用的研究

利用索氏提取法提取罗勒籽油,向罗勒籽油加入氢氧化钾甲醇溶液后并用水浴加热,加入正已烷和蒸馏水萃取,上清液即为罗勒籽油中脂肪酸,用气相色谱质谱法(CC/MS)对脂肪酸进行鉴定.共鉴定出了4种脂肪酸,其中α-亚麻酸为62.88％、亚油酸为20.66％、棕榈酸为10.67％、硬脂酸为5.79％.对罗勒籽脂肪酸进行PTP1B的抑制作用研究,结果表明脂肪酸对PTP1B有较强的抑制作用,其IC50为11.12 μg/mL.该研究为深入研究罗勒籽的药理作用提供了科学依据.     

土霉素残留对蔬菜发酵过程微生物群落演替及代谢产物的影响

【目的】探究土霉素残留对蔬菜自然发酵过程中微生物群落演替和代谢产物动力学的影响,为评估抗生素残留对蔬菜发酵的影响提供理论基础。【方法】超高效液相色谱-串联质谱法测定土霉素残留;高效液相色谱法测定有机酸、电子鼻和气相色谱-质谱联用测定挥发性成分和高通量技术测定微生物种类。【结果】蔬菜自然发酵过程中,土霉素残留从4.00 mg/L下降到2.53 mg/L;不含抗生素残留的蔬菜发酵含有同型和异型乳酸发酵,而土霉素残留的蔬菜发酵仅含有同型乳酸发酵;同时,其特征微生物由Lactobacillus pentosus和Lactobacillus plantarum转变为Lactobacillus paratarrginis、Lactobacillus buchneri和Lactobacillus kisonensis;土霉素残留明显影响了乳酸、柠檬酸、乙酸、香茅醇、3-辛醇、异硫氰酸烯丙酯、乙酸香叶酯、乙烯基硬脂醚和异硫氰酸苯乙酯等代谢产物的含量。【结论】土霉素残留影响了蔬菜乳酸发酵的类型、微生物群落的演替、有机酸和挥发性化合物的形成过程,因此应将抗生素残留纳入发酵蔬菜原料的质量控制指标。     

Unpolluted fractionation of wheat straw by steam explosion and ethanol extraction

An unpolluted process of wheat straw fractionation by steam explosion coupled with ethanol extraction was studied. The wheat straw was steam exploded for 4.5 min with moisture of 34.01%, a pressure of 1.5 MPa without acid or alkali. Hemicellulose sugars were recovered by water countercurrent extraction and decolored with chelating ion exchange resin D412. The gas chromatography (GC) and high-performance liquid chromatography (HPLC) analysis results indicated that there were organic acids in the hemicellulose sugars and the ratio of monosaccharides to oligosaccharides was 1:9 and the main component, xylose, was 85.9% in content. The total recovery rate of hemicellulose was 80%. Water washed materials were subsequently extracted with ethanol. The optimum extraction conditions in this work were 40% ethanol, fiber/liquor ratio 1:50 (w/v), severity log(R)=3.657 (180 degrees C for 20 min), 0.1% NaOH. The lignin yield was 75% by acid precipitation and 85% ethanol solvent was recovered. The lignin was purified using Bj?rkman method. Infrared spectrometry (IR) results indicated that the lignin belonged to GSH (guaiacyl (G) syringyl (S) and p-hydroxyphenyl (H)) lignin and its purity rate reached 85.3%. The cellulose recovery rate was 94% and the results of electron spectroscopy for chemical analysis (ESCA) and infrared spectrometry (IR) showed that hemicellulose and lignin content decreased after steam explosion and ethanol extraction.     

Radioimmunological determination of serum 3 beta-hydroxy-5-cholenoic acid in normal subjects and patients with liver disease.

A radioimmunoassay for the determination of 3 beta-hydroxy-5-cholenoic acid in human serum has been developed, using 3 beta-hydroxy-5-cholenoyl-thyroglobulin as immunogen and 3 beta-hydroxy-5-cholenoylglycyl-125I histamine as radioactive ligand. The association constant was 6.3 X 10(8) l/mol. Cross reactivity with other bile acids of human serum was not detectable, but was 5.6% with cholesterol. Serum sample preparation included extraction of 3 beta-hydroxy-5-cholenoic acid from serum, solvolysis of sulfates, hydrolysis of conjugates, and separation from cholesterol by thin-layer chromatography. Serum concentrations of 3 beta-hydroxy-5-cholenoic acid were 0.23 +/- SD 0.12 mumol/l and 0.21 +/- SD 0.09 mumol/l in healthy males and females, respectively. In patients with primary biliary cirrhosis the serum concentration of 3 beta-hydroxy-5-cholenoic acid and the quotient 3 beta-hydroxy-5-cholenoic acid over total 3 alpha-hydroxy-bile acids (measured enzymatically) were significantly higher (P less than 0.02) than in patients with chronic active hepatitis or alcoholic cirrhosis. Analysis of 17 sera with elevated concentration of 3 beta-hydroxy-5-cholenoic acid by radioimmunoassay and capillary gas-liquid chromatography showed a close correlation (r = 0.91, slope = 0.97) between the results of the two methods.     

Determination of tryptophan and metabolites in rat brain and pineal tissue by reversed-phase high-performance liquid chromatography with electrochemical detection

Tryptophan and many of its indole metabolites were separated using reversed-phase high-performance liquid chromatography (HPLC) and determined using electrochemical detection. This was accomplished isocratically using an acetate—citric acid eluent with various amounts of methanol. Brain and pineal tissue was analyzed for several tryptophan metabolites. Tissue preparation required only homogenization in acidic solution and centrifugation prior to application to the HPLC column. Detection limits in the low picogram range were found for those indoles separated.     

Fatty Acid Profiling of Commercially Important Raw and Boiled Seer Fish <Emphasis Type="Italic">Scomberomorus commerson</Emphasis> (Lacepede, 1800) (Scombridae,Teleostei, Pisces)

The present study aims to determine the fatty acid profiling of commercially important fresh and boiled Scomberomorus commerson. Fatty acids in fresh and boiled fish were separated and quantitatively determined by gas chromatography–mass spectrophotometer using standard methods. The findings revealed that the predominant fatty acids in fresh S. commerson were octadecanoic acid methyl ester, octanoic acid, 1,2-benzenedicarboxylic acid and 3-cyclopentylpropionic acid representing respectively 45.91, 5.69, 6.75 and 8.65% of total fatty acids. Boiled S. commerson showed predominant changes in their fatty acid profiles. In the omega-3 and omega-6 families the dominant fatty acids were doconexent, 3-cyclopentylpropionic acid, octadeconoic acid methyl ester and Hexadecane representing respectively 3.87, 12.08, 44.26 and 3.11% of total fatty acids. After boiling, some fatty acids present in fresh fish are damaged and formed new fatty acids which belonged to ω-3 polyunsaturated fatty acids (PUFA). Boiling increased the concentration of PUFAs from 73.25 to 80.37% of total fatty acids and also formed new fatty acids.     

Ethanol administration and the relationship of malonyl-coenzyme A concentrations to the rate of fatty acid synthesis in rat liver

1. The effect of ethanol on liver fatty acid synthesis was studied in vivo in 24h-starved and ;meal-fed' rats (i.e. fed for 3h per day and not ad libitum). 2. In the fed animal (3)H(2)O was incorporated into fat at a rate of 0.46mumol of C(2) units/min per g wet wt. of liver. Administration of either ethanol (3.2g/kg) or equicaloric amounts of glucose had no effect on the rate of (3)H(2)O incorporation into lipid. 3. In the 24h-starved animal, administration of the same dose of ethanol produced an increase in the rate of (3)H(2)O incorporation from 0.06 to 0.12mumol of C(2) units/min per g fresh wt. after 3h whereas [malonyl-CoA] increased from 0.006 to 0.009mumol/g. Glucose given in amounts equicaloric to ethanol was significantly more lipogenic, increasing both the (3)H(2)O incorporation from 0.06 to 0.20mumol of C(2) units/min per g and the malonyl-CoA content from 0.006 to 0.013 mumol/g wet wt. at 3h. 4. The decrease in the redox state of free cytoplasm NAD or NADP couples or the changes in content of citrate, glucose 6-phosphate and pyruvate of liver after ethanol administration had no measurable effect on the rate of fatty acid synthesis in vivo. 5. Under the conditions of the experiments there was no significant difference, among any of the groups, in the activity of liver fatty acid synthetase measured in vitro. A double-reciprocal plot of the rate of (3)H(2)O incorporation and the total tissue malonyl-CoA concentrations showed a striking relationship. It has been concluded that the rate of fatty acid synthesis in vivo is determined principally by the V(max.) of fatty acid synthetase and the concentration of free malonyl-CoA. 6. It has also been concluded that under the conditions of the present study, the synthesis of fatty acids de novo is unlikely to be an important factor in the increased liver lipid content associated with ethanol administration.     

The aconitate hydratase family from <Emphasis Type="Italic">Citrus</Emphasis>

Background  

Research on citrus fruit ripening has received considerable attention because of the importance of citrus fruits for the human diet. Organic acids are among the main determinants of taste and organoleptic quality of fruits and hence the control of fruit acidity loss has a strong economical relevance. In citrus, organic acids accumulate in the juice sac cells of developing fruits and are catabolized thereafter during ripening. Aconitase, that transforms citrate to isocitrate, is the first step of citric acid catabolism and a major component of the citrate utilization machinery. In this work, the citrus aconitase gene family was first characterized and a phylogenetic analysis was then carried out in order to understand the evolutionary history of this family in plants. Gene expression analyses of the citrus aconitase family were subsequently performed in several acidic and acidless genotypes to elucidate their involvement in acid homeostasis.     

Proton nuclear magnetic resonance of human muscle extracts

High resolution proton nuclear magnetic resonance (NMR) spectra of normal and diseased human muscle extracts were recorded at 470 MHz. Resonances from lactic acid, creatine, glucose, ribose, purine and pyrimidine bases were identified. The longitudinal relaxation times of these resonances were determined to allow quantitation of muscle metabolites. With aid of a standardized reference capillary, inserted into the NMR tube containing the muscle extracts, the lactic acid and total creatine content of the extracts was determined. After 5 h of incubation at 37 degrees C, normal muscles contained on average 103 mumol lactic acid and 36 mumol creatine/173 mg of noncollagenous protein, equivalent to 1.0 g of fresh muscle. The lactic acid and creatine contents decreased slightly in scoliosis and idiopathic scoliosis and they decreased significantly in cerebral palsy. In an extract of a patient whose illness was diagnosed as 'scoliosis' no creatine was present, and in an extract of a patient with unknown diagnosis the creatine content was reduced to 2 mumol/173 mg of noncollagenous protein. The short time (1.7 sec to 6.5 min) and the small amount of tissue (300 mg) needed for an analysis add to the potential of proton NMR as a new technique for the characterization of muscular diseases.