Separation and simultaneous determination of nalidixic acid, hydroxynalidixic acid and carboxynalidixic acid in serum and urine by micellar electrokinetic capillary chromatography

Separation in capillary electrophoresis is governed by various factors, including buffer type, buffer concentration, pH, temperature, voltage and micelles. Through proper adjustment of these parameters, nalidixic acid and its two major metabolites, 7-hydroxynalidixic and 7-carboxynalidixic, could be separated by micellar electrokinetic capillary chromatography using an electrophoretic electrolyte consisting of 50 mM borate buffer (pH 9) containing 25 mM sodium dodecyl sulphate and 10% acetonitrile. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.15–100 μg ml⁻¹, with a correlation coefficient greater than 0.999 and detection limits in the 0.2–0.7 ng ml⁻¹ range. Intra- and inter-day precision values of about 0.8–1.2% RSD (n=11) and 1.3–2.0% RSD (n=30), respectively, were obtained. The method has been applied to the analysis of nalidixic acid and its two major metabolites in serum and urine with limits of sensitivity lower than 0.8 ng ml⁻¹.     

酚酸类物质对三七幼苗的化感影响

该文研究了不同浓度的阿魏酸、对香豆酸、丁香酸、对羟基苯甲酸、香草酸5种酚酸类物质对三七幼苗生长和生理的影响。结果表明:处理后,三七幼苗的苗高、根长、可溶性蛋白质含量、根系活力、CAT以及POD活性均有所降低。其中,阿魏酸各处理组幼苗的苗高及POD活性均显著降低,50、100 mg·L~(-1)的对香豆酸以及100 mg·L~(-1)的香草酸处理组幼苗苗高也分别比对照显著降低16.19%、16.67%和29.29%;对香豆酸、丁香酸以及对羟基苯甲酸各处理组幼苗根长均显著低于对照;香草酸处理组幼苗的根系活力也显著低于对照,且幼苗的CAT活性在10、50、100 mg·L~(-1)丁香酸、对羟基苯甲酸以及香草酸处理下也达到了显著降低水平。此外,1 mg·L~(-1)阿魏酸以及100 mg·L~(-1)香草酸处理组幼苗的叶绿素含量也均显著降低;中高浓度的阿魏酸、对香豆酸、丁香酸、对羟基苯甲酸增加了三七幼苗的MDA含量,而香草酸在0.1、1、10、100 mg·L~(-1)浓度下显著降低幼苗的MDA含量;丁香酸、香草酸、对羟基苯甲酸以及中高浓度的对香豆酸增加了三七幼苗的SOD活性,且香草酸各处理组均达到了显著性水平。综上结果表明,5种酚酸类物质对三七幼苗均具有一定的化感抑制作用,但各酚酸物质的作用方式及强度并不完全一致,阿魏酸的化感影响较大,这为进一步研究三七的化感自毒作用提供了一定的理论参考。     

氨基酸分析仪测定饲料添加剂——叶酸的方法

用６ｍｏｌ／Ｌ盐酸于１１０℃条件下水解饲料添加剂——叶酸,使之游离出谷氨酸,用氢氧化钠中和调节ｐＨ到２,氨基酸分析仪测定谷氨酸含量,经与标准叶酸水解样品比较,计算出叶酸的纯度。该方法重现性好,变异系数ＣＶ＝０．０８％,平均回收率为９８．３４％,浓度与峰面积呈线性相关,相关系数ｒ＝０．９９８７,可随氨基酸分析同时进行,不需改变任何分析条件。     

Comparative acid stress response of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella Typhimurium after habituation at different pH conditions

AIMS: The aim of the study was to evaluate the effect of habituation at different pH conditions on the acid resistance of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella enterica serotype Typhimurium, and to identify potential differences between the adaptive responses of the three pathogens. METHODS: Stationary phase cells of L. monocytogenes, E. coli O157:H7 and S. Typhimurium, grown in glucose-free media, were exposed to pH 3.5 broth directly or after habituation for 90 min at various pH conditions from 4.0 to 6.0. Survivors at pH 3.5 were determined by plating on tryptic soy agar and incubating at 30 degrees C for 48 h. The kinetics (death rate) of the pathogens at pH 3.5 was calculated by fitting the data to an exponential model. RESULTS: Habituation to acidic environments provided protection of the pathogens against lethal acid conditions. This acid protection, however, was found to be pH dependent. For example, for E. coli O157:H7 an increased acid resistance was observed after habituation at a pH range from 4.0 to 5.5, while the maximum acid tolerance was induced at pH 5.0. Furthermore, the effect of low pH habituation was different among pathogens. For L. monocytogenes, E. coli O157:H7 and S. Typhimurium, the pH range within which habituation resulted to increased acid resistance was 5.0-6.0, 4.0-5.5 and 4.0-5.0, respectively, while the maximum acid tolerance was induced after habituation at pH 5.5, 5.0 and 4.5, respectively. SIGNIFICANCE: Acid stress conditions are common within current food processing technologies. The information on adaptive responses of L. monocytogenes, E. coli O157:H7 and S. Typhimurium after habituation to different pH environments provided in the present study, could lead to a more realistic evaluation of food safety concerns and to a better selection of processes in order to avoid adaptation phenomena and to minimize the potential for food safety risks.     

Triterpene acids from Salvia and Teucrium species

The pentacyclic triterpene acids ursolic acid, oleanolic acid, micromeric acid, maslinic acid and 3-epi-maslinic acid have been isolated from several Salvia and Teucrium species.     

Temperature regulates tuber-inducing lipoxygenase-derived metabolites in potato (Solanum tuberosum)

Temperature is one of the major environmental factors affecting potato tuberization. It has been suggested that lipoxygenase (LOX) mediates between temperature and tuber induction. In this study, the contents of the LOX-derived metabolites hydroperoxylinolenic acid (HPOT), jasmonic acid (JA), tuberonic acid (TA) and tuberonic acid glucoside (TAG) were analyzed in leaves of potatoes growing at different temperatures. At low, tuber-inducing temperature, endogenous levels of JA, TA and TAG rise, indicating their crucial role in tuber induction. The concentration of 13(S)-HPOT seems not to be directly affected by temperature. Instead, the molecule has only a short half-life in leaves and is readily metabolized.     

Effects of flaxseed,raw soybeans and calcium salts of fatty acids on apparent total tract digestibility,energy balance and milk fatty acid profile of transition cows

Oilseeds offer some protection to the access of ruminal microorganisms and may be an alternative to calcium salts of fatty acids (FA), which are not fully inert in the ruminal environment. This study aimed to evaluate the effects of different sources of FA supplementation on apparent total tract nutrient digestibility, milk yield and composition, and energy balance (EB) of cows during the transition period and early lactation. We compared diets rich in C18:2 and C18:3 FA. Multiparous Holstein cows were randomly assigned to receive one of the four diets: control (n=11); whole flaxseed (WF, n=10), 60 and 80 g/kg (diet dry matter (DM) basis) of WF during the prepartum and postpartum periods, respectively; whole raw soybeans (WS, n=10), 120 and 160 g/kg (diet DM basis) of WS during the prepartum and postpartum periods, respectively; and calcium salts of unsaturated fatty acids (CSFA, n=11), 24 and 32 g/kg (diet DM basis) of CSFA during the prepartum and postpartum periods, respectively. Dry cows fed WF had higher DM and net energy of lactation (NE_L) intake than those fed WS or CSFA. The FA supplementation did not alter DM and NDF apparent total tract digestibility, dry cows fed WF exhibited greater NDF total tract digestion than cows fed WS or CSFA. Feeding WS instead of CSFA did not alter NE_L intake and total tract digestion of nutrients, but increased milk fat yield and concentration. Calculated efficiency of milk yield was not altered by diets. FA supplementation increased EB during the postpartum period. Experimental diets increased long-chain FA (saturated and unsaturated FA) in milk. In addition, cows fed WS and CSFA had higher C18:1 trans-11 FA and C18:2 cis, and lower C18:3 FA in milk than those fed WF. Furthermore, cows fed CSFA had higher C18:1 trans-11 and cis-9, trans-11 FA than cows fed WS. Although supplemental C18:2 and C18:3 FA did not influence the milk yield of cows, they positively affected EB and increased unsaturated long-chain FA in milk fat.     

硬枝树花中抑制H_22荷瘤小鼠肿瘤的活性成分研究

研究了从硬枝树花中提取得到的4个单体化合物松萝酸(usnic acid)、去甲环萝酸(evernic acid)、巴尔巴地衣酸(barbatic acid)和水杨嗪酸(salazinic acid)对H22荷瘤小鼠的抑瘤作用,并且对抑瘤率、胸腺指数、脾指数及小鼠白介素-2含量等各个指标的进行检测,以说明此4种化合物对小鼠肿瘤生长的抑制效果。结果表明,松萝酸高、中剂量组,去甲环萝酸高、中剂量组,巴尔巴地衣酸低剂量组,水杨嗪酸高剂量组对小鼠肿瘤有较好的抑制效果,与阴性对照组比较有极显著差异(P0.01),并且这些组的H22荷瘤小鼠血清中白介素-2的含量显著增加,与抑制肿瘤活性具有相关性。     

Determination of aromatic metabolites in ruminant urine by high-performance liquid chromatography

A method based on reversed-phase HPLC is reported for the separation and quantification of various urinary aromatic metabolites: hippuric, phenylaceturic, salicyluric, benzoic, phenylacetic, salicylic. 3-phenylpropionic and cinnamic acids and several phenols in ruminant urine. In this method, a Nova-Pak C₁₈ (4 μm) 150×3.9 mm I.D. column, two solvents [A: 15°b methanol in 20 mM acetic acid (pH 3.3); B: methanol] in a gradient mode at a flow-rate of 0.8 ml/min, and UV detection at 210 nm were used. Quantification of the total (free and conjugated) benzoic, phenylacetic and salicylic acids present in urine was achieved by hydrolysis of the samples in 3 M HCl at 100°C for 24 h prior to HPLC analysis. The lowest detection concentration was 50 μmol/I. This method is useful for scanning the profile of aromatic metabolites in urine of ruminants, which provides information on the diets the animals receive.     

Characterization of Transgenic Rice Plants Expressing an Arabidopsis FAD7

Fatty acid -3 desaturase (FAD) is the key enzyme catalyzing the formation of trienoic fatty acids. We utilized an Arabidopsis FAD7 gene and the seven independent transgenic rice plants harbouring 1 to 3 copies of this gene were generated. The expression of FAD7 mRNA was different among independent transgenic lines regardless of the copy number. The total linolenic acid (18:3) contents reduced by about 7 – 32 % in transgenic rice plants but the linoleic acid (18:2) content increased accordingly. With or without wounding treatments, the jasmonate content was higher in transgenic lines than in wild-type rice plant. The transgenic lines overproducing jasmonate also showed increased expression of PR1b mRNA and allene oxide synthase inresponse to wounding.     

Determination of hexahydrophthalic acid and methylhexahydrophthalic acid in plasma after derivatisation with pentafluorobenzyl bromide using gas chromatography and mass spectrometric detection

A method for the simultaneous determination of hexahydrophthalic acid (HHP acid) and methylhexahydrophthalic acid (MHHP acid) in human plasma was developed. The procedure was a rapid, single step extractive derivatisation with pentafluorobenzyl bromide as the derivatisation agent. The formed pentafluorobenzyl esters were analysed by gas chromatography-mass spectrometry in negative ion chemical ionisation mode with ammonia as the moderating gas. Deuterium-labeled HHP acid and MHHP acid were used as internal standards. The detection limit was 0.4 ng/ml for HHP acid (m/z 153) and 0.3 ng/ml for MHHP acid (m/z 365). The within-day precision of the method was between 2 and 3% and the between-day precision was between 3 and 12%. The overall recovery was between 65 and 83%. A comparison between HHP acid determinations with a previous and this method showed that the methods gave similar results. The method was applicable for analysis of plasma from occupationally exposed workers.     

Determination of ascorbic and dehydroascorbic acids in blood plasma and serum by liquid chromatography

A liquid-chromatography (LC) method with ultraviolet detection for measuring ascorbic (AA) and dehydroascorbic acid (DHA) in human blood and serum was studied. The method used an ODS reversed-phase column and cetyltrimethylammonium bromide as an ion-pairing agent. AA was measured before and after the reduction of DHA with dithiothreitol. The absene of interferences resulting from hemolysis products was verified and also the stability of the ascorbic acid in metaphosphoric acid extracts. The analytical parameters, linearity (1–80 μg/ml), accuracy (recovery, 96.7–100.7%) and precision (C.V.=3.1%), show that the method is reliable and adequate for measuring the total vitamin C content in serum and plasma.     

Degradation of substituted benzoic acids by a Micrococcus species

Abstract a Micrococcus sp. isolated by isophthalate enrichment, utilized 8 of the 13 substituted benzoic acids tested as the sole source of carbon and energy. The organism degraded benzoic acid and anthranilic acid through the intermediate formation of catechol. While salicylate is metabolized through genetisic acid, p -hydroxybenzoic acid is degraded through protocatechuic acid. The organism grew well on isophthalate but failed to utilize phthalate and terphthalate. Catechol disoxygenase, gentisate dioxygenase and protocatechuate dioxygenase activities were shown in the cell-free extracts. Catechol and protocatechuate are further metabolized through an ortho -cleavage pathway.     

Genetic loci associated with circulating levels of very long-chain saturated fatty acids

Very long-chain saturated fatty acids (VLSFAs) are saturated fatty acids with 20 or more carbons. In contrast to the more abundant saturated fatty acids, such as palmitic acid, there is growing evidence that circulating VLSFAs may have beneficial biological properties. Whether genetic factors influence circulating levels of VLSFAs is not known. We investigated the association of common genetic variation with plasma phospholipid/erythrocyte levels of three VLSFAs by performing genome-wide association studies in seven population-based cohorts comprising 10,129 subjects of European ancestry. We observed associations of circulating VLSFA concentrations with common variants in two genes, serine palmitoyl-transferase long-chain base subunit 3 (SPTLC3), a gene involved in the rate-limiting step of de novo sphingolipid synthesis, and ceramide synthase 4 (CERS4). The SPTLC3 variant at rs680379 was associated with higher arachidic acid (20:0 , P = 5.81 × 10⁻¹³). The CERS4 variant at rs2100944 was associated with higher levels of 20:0 (P = 2.65 × 10⁻⁴⁰) and in analyses that adjusted for 20:0, with lower levels of behenic acid (P = 4.22 × 10⁻²⁶) and lignoceric acid (P = 3.20 × 10⁻²¹). These novel associations suggest an inter-relationship of circulating VLSFAs and sphingolipid synthesis.     

Excitatory Amino Acid Agonist-Antagonist Interactions at 2-Amino-4-Phosphonobutyric Acid-Sensitive Quisqualate Receptors Coupled to Phosphoinositide Hydrolysis in Slices of Rat Hippocampus

Studies were carried out to define the relative affinities and intrinsic activities of excitatory amino acid agonists that activate receptor sites coupled to phosphoinositide hydrolysis in brain. Slices of rat hippocampus were prelabeled with myo-[3H]inositol, and agonist stimulation was indexed by measuring the accumulation of [3H]inositol monophosphate [( 3H]IP) in the presence of Li+. It was observed that ibotenic (IBO) and quisqualic (QUIS) acids both elicit highly significant, concentration-dependent stimulation of phosphoinositide hydrolysis. Whereas maximal stimulation by IBO (10(-3) M) was four- to fivefold over basal values, the maximal effect of QUIS (10(-4) M) was less (about twofold). Based on the relative concentrations required for 50% maximal stimulation, QUIS was 20 times more potent than IBO. Stimulation of phosphoinositide hydrolysis by either IBO or QUIS was additive to the effects of nonexcitatory amino acid agonists (carbachol and norepinephrine) in this tissue. However, the stimulatory effects of IBO plus QUIS were not additive. At greater than or equal to 10(-4) M, QUIS significantly inhibited phosphoinositide hydrolysis by a maximal stimulatory concentration of IBO (10(-3) M) to a level observed with QUIS alone. Other excitatory amino acid agonists, including kainate, N-methyl-D-aspartate, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), had no stimulatory effects at concentrations as high as 10(-3) M. The D,L or L forms of 2-amino-4-phosphonobutyric acid (AP4), but not D-AP4, significantly enhanced [3H]IP levels to approximately 135% of basal values.(ABSTRACT TRUNCATED AT 250 WORDS)     

氨基酸转运载体研究进展

氨基酸转运载体是介导氨基酸跨膜转运的膜蛋白,在氨基酸营养机体细胞和神经调节过程中起着重要作用;而且,其功能异常会导致严重的氨基酸吸收和代谢障碍性疾病,也具有重要的病理学意义。本文就近年来关于中性氨基酸、酸性氨基酸和碱性氨基酸转运载体家族成员及其组织分布、分子生物学特征、生理功能和病理学意义等研究进展进行了综述。