Brain Quinolinic Acid in Huntington''s Disease

Concentrations of the endogenous neurotoxic tryptophan metabolite, quinolinic acid (QA), were measured in postmortem brain tissue obtained from patients with Huntington's disease (HD) and matched controls, using a gas chromatography/mass spectrometry method. There was no significant difference in either the putamen or the frontal cortex between the HD and control groups. These results do not support the hypothesis that increased QA is responsible for neuronal degeneration in HD.     

Generalized N-Acetylneuraminic Acid Storage Disease: Quantitation and Identification of the Monosaccharide Accumulating in Brain and Other Tissues

Abstract: Brain and other tissues from a patient with extensive neonatal as-cites and clinical symptoms suggestive of a severe neurovisceral storage disorder were examined following autopsy for the accumulation of oligosaccharides. This carbohydrate analysis revealed the presence of large amounts (3–21 μmol/g fresh weight) of sialic acid in brain, liver, and kidney tissue as the major abnormality. Exhaustive characterization of the accumulating material by gel filtration, gas-liquid chromatography, thin-layer chromatography, and GLC-mass spectrometry positively identified the saccharide as free N -acetylneuraminic acid. Based on the accumulation of only free N -acetylneuraminic acid in the tissue of this patient, and normal activities of lysosomal enzymes involved in the catabolism of cellular glycoproteins, this storage disorder appears to result from a previously unreported defect in glycoconjugate metabolism.     

Auxins of non-flowering plants. I. Occurrence of 3-indoleacetic acid and phenylacetic acid in vegetative and fertile fronds of the ostrich fern (Matteucia struthiopteris)

Gas chromatography-mass spectrometry evidence is presented for the presence of both phenylacetic acid (PAA) and 3-indoleacetic acid (IAA) in vegetative and fertile tissues of the sporophyte of the ostrich fern [ Matteucia struthiopteris (L.) Todaro]. 3-Indolepropionic acid, tryptamine and 3-indoleacetonitrile were not found in tissue extracts, although small amounts of 3-indolebutyric acid and tryptophol may have been present. PAA was present in amounts higher than those found in flowering plants, while LAA levels fall within the angiosperm range. The levels of both auxins were higher in the younger vegetative tissues than in mature vegetative or fertile pinnae. Recent evidence for the occurrence of angiosperm growth hormones in ferns is discussed.     

Norepinephrine Metabolism in Man Using Deuterium Labeling: Turnover of 4-Hydroxy-3-Methoxymandelic Acid

Abstract: 4-Hydroxy-3-methoxymandelic acid (HMMA; VMA) labeled with three deuterium atoms was used to study the turnover and fate of HMMA following intravenous injection. Five healthy men were given a pulse dose of 5.0 μmol of labeled HMMA. Plasma and urinary levels of both endogenous and labeled HMMA were subsequently followed by gas chromatography-mass spectrometry using selected ion detection. The kinetic parameters were determined both with and without compensation for the pool expansion caused by the injection of labeled HMMA. The urinary recovery of labeled HMMA was 85 × 10% (mean ± SD). No conversion of HMMA t o 4-hydroxy-3-methoxyphenyl glycol (HMPG) occurred. The biological half-life of HMMA was 0.54 ± 0.22 h. The apparent volume of distribution was 0.36 ± 0.11 L/kg. The production rate or body turnover was 1.27 ± 0.51 μmol HMM/h and urinary excretion rate was 0.82 ± 0.22 μmol/h. These results show that HMMA is turning over rapidly in a relatively small volume of distribution and that, unlike HMPG, it is an end metabolite of norepinephrine in man.     

Determination of anandamide and other fatty acyl ethanolamides in human serum by electrospray tandem mass spectrometry

We developed a new selective liquid chromatography-electrospray ionization-tandem mass spectrometry method for the identification and quantification of anandamide (AEA), an endogenous cannabinoid receptor ligand, and other bioactive fatty acid ethanolamides (FAEs) in biological samples. Detection limit (0.025 pmol for AEA and 0.1 pmol for palmitoylethanolamide (PEA) and oleoylethanolamide (OEA)) and quantification limit (0.2 pmol for AEA and 0.4 pmol for OEA and PEA) were in the high fmol to low pmol range for all analytes. Linear correlations (r(2)=0.99) were observed in the calibration curves for standard AEA over the range of 0.025-25 pmol and for standard PEA and OEA over the range of 0.1-500 pmol. This method provides a time-saving and sensitive alternative to existing methods for the analysis of FAEs in biological samples.     

Determination of 1-Methylimidazole-4-Acetic Acid in Brain Tissue from Rat and Mouse

The concentration of the histamine metabolite 1-methylimidazole-4-acetic acid was determined in brain tissue from rat and mouse with a gas chromatographic-mass spectrometric method. Mouse brain contained 1.7-3.2 nmol/g, depending on the strain. The concentration in cerebrum from Sprague-Dawley rats was 1.2 nmol/g, whereas cerebellum contained 0.24 nmol/g. The concentration of tele-methylhistamine in mouse brain was 1.4-2.2 nmol/g. The concentration of 1-methylimidazole-4-acetic acid in rat brain after death did not change significantly during 2 h at room temperature.     

气相色谱质谱联用技术对栝楼籽油亚麻酸和亚油酸含量的分析

通过皂化法和尿素包合法对热榨、冷榨栝楼（Trichosanthes kirilowii）籽油进行提取,采用气相色谱-质谱联用（GC-MS）技术检测分析栝楼籽油中亚麻酸、亚油酸成分、含量。结果表明,热榨栝楼籽油中亚麻酸相对含量为4.16%～11.58%,亚油酸相对含量为68.62%～95.84%。冷榨栝楼籽油中不含亚麻酸成分。此方法适用于栝楼籽油的成分分析。     

Identification and Determination of 1-Methylimidazole-4-Acetic Acid in Human Cerebrospinal Fluid by Gas Chromatography-Mass Spectrometry

Abstract: A method for the quantification of 1-methylimidazole-4-acetic acid in human CSF was developed. Methylimidazole-acetic acid was identified and quantitated in CSF. The method involves concentration of the compound on a cation exchanger, extraction of the methyl ester with ethyl acetate, and preparation of a heptafluorobutyryl derivate of the methyl ester, which is finally purified by chromatography on silica gel and quantitated by gas chromatography-mass spectrometry with the deuterated analogue as internal standard. The coefficient of variation at 1 ng/ml was 13%. The limit of sensitivity was about 0.2 ng/ml. The concentration of methylimidazole-acetic acid in lumbar CSF from healthy volunteers was below 1 ng/ml. Ventricular CSF contained higher concentrations than lumbar fluid. The existence of a rostrocaudal concentration gradient was established. There was a correlation between the concentration of methylimidazole-acetic acid and tele-methylhistamine in CSF. The concentration of methylimidazole-acetic acid in lumbar CSF from schizophrenic patients, patients with subarachnoidal haemorrhage, or patients with rheumatic disease was in the range of that in healthy volunteers.     

A capillary gas chromatography/mass spectrometric method for the quantification of hydroxysteroids in human plasma

A specific and sensitive methodology for the quantitative determination of hydroxysteroids dehydroepiandrosterone and pregnenolone and their main metabolites in human plasma is described. Hydroxysteroids were extracted using methanol and steroids were further separated by reverse-phase high-performance liquid chromatography, allowing for minimization of the possible chromatographic interferences. Eluted fractions were collected, pooled, and analyzed by gas chromatography-mass spectrometry as trimethylsilyl ether derivatives. The quantification was performed with single-ion monitoring of the highly abundant m/z 129 or m/z 358 fragments. The combination of the chromatographic characteristics to the specific fragments ensured the selectivity and specificity of the method. Under these conditions the method was linear (typical R2 is superior to 0.98 for all hydroxysteroids studied) over the concentration range of 2 x 10(-9) to 10(-6)M with good precision and accuracy.     

Norepinephrine Metabolism in Man Using Deuterium Labelling: Origin of 4-Hydroxy-3-Methoxymandelic Acid

A double isotope labelling technique was used to simultaneously determine the in vivo turnover rates of 4-hydroxy-3-methoxyphenylglycol (HMPG) and 4-hydroxy-3-methoxymandelic acid (HMMA, VMA) and the rate of HMPG oxidation to HMMA. Six healthy men were given intravenous injections of [2H3]HMPG and [2H6]HMMA and their plasma and urine samples analysed by gas chromatography--mass spectrometry (GC/MS) for the protium and deuterium species. HMPG and HMMA production rates were calculated by isotope dilution. The rate of HMPG oxidation to HMMA was obtained from the fraction of [2H3]HMPG recovered as [2H3]HMMA. The results showed that the entire production of HMMA, 1.11 +/- 0.21 mumol/h (mean +/- SE), could be accounted for by oxidation of HMPG, 1.49 +/- 0.31 mumol/h. In another experiment designed to avoid expansion of the HMPG body pool, a tracer dose of [14C]HMPG was given to the same subjects. The levels of [14C]HMPG and [14C]HMMA were measured in urine after extraction and separation by thin layer chromatography. Urinary excretion of endogenous HMPG and HMMA was determined by GC/MS. The results showed that the endogenous HMMA fraction of the total HMPG and HMMA urinary excretion rate, 0.57 +/- 0.04, was the same as the fraction of [14C]HMPG oxidized to [14C]HMMA, 0.62 +/- 0.01. Thus, HMPG is the main intermediate in the metabolic conversion of norepinephrine and epinephrine to HMMA in man.     

Differences in metabolite profile between blood plasma and serum

In metabolomic research, blood plasma and serum have been considered to possess similar compositions and properties. Their perceived equivalence has resulted in researchers choosing arbitrarily between serum and plasma for analysis. Here, routine serum and plasma were prepared and their low-molecular-weight compounds were determined using gas chromatography/time-of-flight mass spectrometry. Principal components analysis was applied to process the acquired data, and marked differences in metabolite profiles were observed between serum and plasma. Of the 72 identified compounds, 36 (50%) discriminate serum from plasma, with 29 and 7 metabolites showing a significantly higher abundance (t test, P < 0.05) in serum and plasma, respectively. Incubation of blood had distinct effects on the analyte peak areas, with the effects being more pronounced for plasma than for serum and more pronounced for a shorter incubation than for a longer incubation. These results highlight the importance in choosing serum or plasma as the analytical sample and in stipulating the incubation time. Because incubation affected the analyte peak areas less in serum than in plasma, we recommend serum as the sample of choice in metabolomic studies.     

GC/MS分析血浆中丁丙诺啡

目的:建立血浆中丁丙诺啡GC/MS分析方法。方法:血浆中丁丙诺啡,加入内标长春西汀,加pH 7缓冲溶液,用三氯甲烷提取,提取物经BSTFA衍生化后进行GC/MS分析。结果:方法的线性范围为2～100 g·L~(-1),检出限为1g·L~(-1)。结论:该方法灵敏度高,可用于涉毒案件血浆中丁丙诺啡的分析。     

Determination of N-Acetylaspartic Acid in Human Cerebrospinal Fluid by Gas Chromatography–Mass Spectrometry

N-Acetyl-L-aspartic acid was identified and determined in human cerebrospinal fluid. The concentration in lumbar fluid was about 2 nmol/ml and about 20 nmol/ml in ventricular fluid. There was no difference between healthy subjects and schizophrenic patients.     

超高效液相色谱-质谱联用法测定人尿液中5-羟吲哚乙酸浓度方法学验证

目的:采用超高效液相色谱-质谱联用法(UPLC-MS/MS)建立人尿液中5-羟吲哚乙酸(5-HIAA)的检测方法。方法:采用人工尿液UR-N-CONTROL LEVEL 2 NP配制标准曲线,质控样品采用人工尿液和天然尿液配制而成,以5-HIAA的同位素氘标记物5-HIAA-d5为内标,尿液样品采用乙腈进行稀释处理后,采用UPLC-MS/MS检测。色谱柱为Waters HSS T3(100×2.1 mm,1.8μm),流动相A为含0.02%乙酸的2 m M醋酸铵水溶液,B相为:含0.02%乙酸的乙腈溶液,在2.5 min内使用5%的B相至100%的B相进行梯度洗脱,流速为0.5 m L/min,进样量3.0μL,柱温50℃;采用电喷雾负离子模式电离,5-HIAA和5-HIAA-d5内标的监测离子分别为m/z 190.1→146.2和m/z 195.1→151.0。结果:该方法测定的5-HIAA在0.0500至50.0μg/m L范围内线性良好,r≥0.9948,最低定量限(LLOQ)为0.0500μg/m L。5-HIAA批内、批间准确度在89.3%~99.8%之间,精密度(CV)≤8.4%。平均回收率为100.3%~102.3%。结论:该方法专属性强、灵敏度高,快速。人工尿液和天然尿液在定量分析时无差异,适合于人尿液中5-HIAA的浓度测定。     

Mass Spectrometric Identification of 13C‐Labeled Metabolites During Anaerobic Propanoic Acid Oxidation

Biowaste digestion is a possibility to gain biogas as a renewable fuel source. However, the anaerobic food chain may be disrupted by, e.g., substrate overload or by inhibitors, leading to the accumulation of volatile fatty acids (VFAs), predominantly of propanoic acid (PA). VFA Accumulation may cause a rapid pH decrease, less biogas production, or even a total inhibition. To maintain high biogas productivity or to prevent a collapse of methanogenesis, metabolic properties of the degrading microorganisms must be elucidated, e.g., by investigation of the established pathways for degradation of VFAs. A Dani 3950 headspace system (HS), a Varian 431 gas chromatograph (GC), and a Varian 210 mass spectrometer (MS) have been combined to quantify and specifically identify metabolites of PA oxidation. The use of [1‐¹³C]‐labeled PA as a carbon source for microorganisms allows differentiation between the methyl‐malonyl‐CoA or the C(6)‐dismutation pathway, both resulting in AcOH production. Appearance of the ¹³C‐moiety either in the COO or Me group of AcO can easily be detected by MS. The methyl‐malonyl‐CoA pathway was successfully identified as the only pathway of PA degradation by organisms in a lab‐scale anaerobic digester. A similar approach can be applied to any degradation pathway involving VFAs.     

Determination of hexahydrophthalic anhydride adducts to human serum albumin

Hexahydrophthalic anhydride (HHPA) is a highly sensitizing industrial chemical that is known to covalently bind to endogenous proteins. The aim of this study was to determine the binding sites of HHPA to human serum albumin (HSA). Conjugates between HSA and HHPA, at two different molar ratios, were synthesized under physiological conditions. The conjugates were digested with trypsin and Pronase E to obtain specific peptides and amino acids, which were separated by liquid chromatography (LC). Fractions containing modified peptides were detected through quantification of hydrolysable HHPA using LC coupled to a triple quadrupole mass spectrometer with electrospray ionization. Modified residues in albumin were identified by sequence analyses using nanoelectrospray quadrupole time-of-flight mass spectrometry. A total of 36 HHPA adducts were found in the HSA-HHPA conjugate with 10 times molar excess of added HHPA. In the conjugate with a molar ratio of 1:0.1 of added HHPA, seven HHPA adducts were found bound to Lys¹³⁷ (domain IB), Lys¹⁹⁰, Lys¹⁹⁹ and Lys²¹² (domain IIA), Lys³⁵¹ (domain IIB), and Lys⁴³² and Lys⁴³⁶ (domain IIIA). Moreover, several of these adducted albumin peptides were detected in nasal lavage fluid from one volunteer exposed to HHPA. The binding sites of HHPA to HSA have been determined, thus identifying potential allergenic chemical structures. This knowledge generates the possibility of developing methods for the biological monitoring of HHPA exposure by analysing tryptic peptides including these binding sites.     

Determination of hexahydrophthalic anhydride adducts to human serum albumin

Hexahydrophthalic anhydride (HHPA) is a highly sensitizing industrial chemical that is known to covalently bind to endogenous proteins. The aim of this study was to determine the binding sites of HHPA to human serum albumin (HSA). Conjugates between HSA and HHPA, at two different molar ratios, were synthesized under physiological conditions. The conjugates were digested with trypsin and Pronase E to obtain specific peptides and amino acids, which were separated by liquid chromatography (LC). Fractions containing modified peptides were detected through quantification of hydrolysable HHPA using LC coupled to a triple quadrupole mass spectrometer with electrospray ionization. Modified residues in albumin were identified by sequence analyses using nanoelectrospray quadrupole time-of-flight mass spectrometry. A total of 36 HHPA adducts were found in the HSA–HHPA conjugate with 10 times molar excess of added HHPA. In the conjugate with a molar ratio of 1:0.1 of added HHPA, seven HHPA adducts were found bound to Lys¹³⁷ (domain IB), Lys¹⁹⁰, Lys¹⁹⁹ and Lys²¹² (domain IIA), Lys³⁵¹ (domain IIB), and Lys⁴³² and Lys⁴³⁶ (domain IIIA). Moreover, several of these adducted albumin peptides were detected in nasal lavage fluid from one volunteer exposed to HHPA. The binding sites of HHPA to HSA have been determined, thus identifying potential allergenic chemical structures. This knowledge generates the possibility of developing methods for the biological monitoring of HHPA exposure by analysing tryptic peptides including these binding sites.     

Identification and Determination of Tele-Methylhistamine in Cerebrospinal Fluid by Gas Chromatography-Mass Spectrometry

Abstract: The presence of tele-methylhistamine in human cerebrospinal fluid has been established. The concentration was determined with the use of deuterated tele-methylhistamine. The preparation of the deuterated standard is described. The concentration range in samples from neuropsychiatric patients was 0.1-2.5 ng/ml. The structure of the pentafluoropropionyl derivative used for gas chromatography was studied with the aid of proton nuclear magnetic resonance spectroscopy.     

Fabrication and characterization of noble crystalline silver nanoparticles from Pimenta dioica leave extract and analysis of chemical constituents for larvicidal applications

The current works report the bio-efficacy of Pimenta dioica leaf derived silver nanoparticles (Pd@AgNPs) and leaf extract obtained trough different solvents against the larvae of malaria, filarial and dengue vectors. Synthesis of silver nanoparticles (AgNPs) was done by adding 10 ml of P. dioica leaf extract into 90 ml of 1 mM silver nitrate solution, a slow colour change was observed depicting the formation of AgNPs. Further, Pd@AgNPs was confirmed through Ultraviolet–visible spectroscopy which exhibited characteristic absorption peak at 422 nm wavelength. X-ray diffraction and selected area electron diffraction analysis confirmed monodispersed and crystalline nature of Pd@AgNPs with 32 nm an average size. Scanning electron microscopy and transmission electron microscopy showed the most of Pd@AgNPs were spherical and triangular in shape and energy-dispersive X-ray spectroscopy revealed silver elemental nature of nanoparticles. Zeta potential of Pd@AgNPs is highly negative which confirmed its stable nature. Pd@AgNPs showed prominent absorption peaks at 1015, 1047, 1243, 1634, 2347, 2373, 2697 and 3840 cm^?1 which are corresponding to following compounds polysaccharides, carboxylic acids, water, alcohols, esters, ethers, amines, amides and phenol, respectively as reported by Fourier-transform infrared spectroscopy analysis. Gas chromatography–mass spectrometry and Liquid chromatography–mass spectrometry analysis revealed 39 and 70 compounds, respectively, which might be contributed for bio-reduction, capping, stabilization and larvicidal behavior of AgNPs. A comparable lethality (LC₅₀ and LC₉₀) was observed in case of Pd@AgNPs over leaf extract alone. The potential larvicidal activity of Pd@AgNPs was observed against the larvae of Aedes aegypti,(LC_50, 2.605; LC_90, 5.084 ppm) Anopheles stephensi (LC_50, 3.269; LC_90, 7.790 ppm) and Culex quinquefasciatus (LC_50, 5.373; LC_90, 14.738 ppm without affecting non-targeted organism, Mesocyclops thermocyclopoides after 72 hr of exposure. This study entails green chemistry behind synthesis of AgNPs which offers effective technique for mosquito control and other therapeutic applications.     

Identification of Human Plasma Metabolites Exhibiting Time-of-Day Variation Using an Untargeted Liquid Chromatography–Mass Spectrometry Metabolomic Approach

Although daily rhythms regulate multiple aspects of human physiology, rhythmic control of the metabolome remains poorly understood. The primary objective of this proof-of-concept study was identification of metabolites in human plasma that exhibit significant 24-h variation. This was assessed via an untargeted metabolomic approach using liquid chromatography–mass spectrometry (LC-MS). Eight lean, healthy, and unmedicated men, mean age 53.6 (SD?±?6.0) yrs, maintained a fixed sleep/wake schedule and dietary regime for 1 wk at home prior to an adaptation night and followed by a 25-h experimental session in the laboratory where the light/dark cycle, sleep/wake, posture, and calorific intake were strictly controlled. Plasma samples from each individual at selected time points were prepared using liquid-phase extraction followed by reverse-phase LC coupled to quadrupole time-of-flight MS analysis in positive ionization mode. Time-of-day variation in the metabolites was screened for using orthogonal partial least square discrimination between selected time points of 10:00 vs. 22:00?h, 16:00 vs. 04:00?h, and 07:00 (d 1) vs. 16:00?h, as well as repeated-measures analysis of variance with time as an independent variable. Subsequently, cosinor analysis was performed on all the sampled time points across the 24-h day to assess for significant daily variation. In this study, analytical variability, assessed using known internal standards, was low with coefficients of variation <10%. A total of 1069 metabolite features were detected and 203 (19%) showed significant time-of-day variation. Of these, 34 metabolites were identified using a combination of accurate mass, tandem MS, and online database searches. These metabolites include corticosteroids, bilirubin, amino acids, acylcarnitines, and phospholipids; of note, the magnitude of the 24-h variation of these identified metabolites was large, with the mean ratio of oscillation range over MESOR (24-h time series mean) of 65% (95% confidence interval [CI]: 49–81%). Importantly, several of these human plasma metabolites, including specific acylcarnitines and phospholipids, were hitherto not known to be 24-h variant. These findings represent an important baseline and will be useful in guiding the design and interpretation of future metabolite-based studies. (Author correspondence: Jooern.Ang@icr.ac.uk or Florence.Raynaud@icr.ac.uk)