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1.
Food Chem ; 340: 128156, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33011465

RESUMO

The Berthelot reaction for ammonia is revisited with the aim of miniaturization and addressing interferences as encountered with food and water samples. Headspace single drop microextraction of ammonia in phosphoric acid served to attain selectivity in complex matrices, and liquid-liquid microextraction of red or blue indophenol species into 1-octanol-isooctane (60:40, v/v) resulted into high sensitivity. Fiber-optics-based cuvetteless micro-spectrophotometry has been used for colorimetric determination on microliter volumes of extract. The linear dynamic range, limit of detection and enrichment factor have been found to be 0.2-3 mg kg-1, 0.14 mg kg-1 and 38, respectively, measuring red species for milk, cheese and beer (4.9-5.5% error; 4.8-6.3% RSD; n = 5); and 5-400 µg L-1, 0.4 µg L-1 and 137, respectively, measuring blue species for water samples (3.3-5.7% error; 3.6-6.8% RSD; n = 5). A plausible reaction scheme has been proposed for nitroprusside catalysis in indophenol reaction.


Assuntos
Amônia/análise , Indofenol/química , Espectrofotometria/métodos , Água/química , Amônia/isolamento & purificação , Cerveja/análise , Tecnologia de Fibra Óptica , Análise de Alimentos/métodos , Limite de Detecção , Microextração em Fase Líquida , Teoria Quântica
2.
Anal Chem ; 90(11): 6431-6435, 2018 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-29730934

RESUMO

The development of a multipurpose integrated syringe-pump-based environmental-water analyzer ( iSEA) and its application for spectrophotometric determination of ammonium is presented. The iSEA consists of a mini-syringe pump equipped with a selection valve and laboratory-programmed software written by LabVIEW. The chemistry is based on a modified indophenol method using o-phenylphenol. The effect of reagent concentrations and sample temperatures was evaluated. This fully automated analyzer had a detection limit of 0.12 µM with sample throughput of 12 h-1. Relative standard deviations at different concentrations (0-20 µM) were 0.23-3.36% ( n = 3-11) and 1.0% ( n = 144, in 24 h of continuous measurement, ∼5 µM). Calibration curves were linear ( R2 = 0.9998) over the range of 0-20 and 0-70 µM for the detection at 700 and 600 nm, respectively. The iSEA was applied in continuous real-time monitoring of ammonium variations in a river for 24 h and 14 days. A total of 1802 samples were measured, and only 0.4% was outlier data (≥3 sigma residuals). Measurements of reference materials and different aqueous samples ( n = 26) showed no significant difference between results obtained by reference and present methods. The system is compact (18 cm × 22 cm × 24 cm), portable (4.8 kg), and robust (high-resolution real-time monitoring in harsh environments) and consumes a small amount of chemicals (20-30 µL/run) and sample/standards (2.9 mL/run).


Assuntos
Compostos de Amônio/análise , Monitoramento Ambiental/instrumentação , Análise de Injeção de Fluxo/instrumentação , Água Doce/análise , Compostos de Bifenilo/química , Desenho de Equipamento , Indofenol/química , Limite de Detecção , Rios/química , Seringas
3.
Sci Rep ; 7(1): 10304, 2017 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-28871132

RESUMO

Ammonia is a fundamental aspect of metabolism spanning all of phylogeny. Metabolomics, including metabolic tracing studies, are an integral part of elucidating the role of ammonia in these systems. However, current methods for measurement of ammonia are spectrophotometric, and cannot distinguish isotopologues of ammonia, significantly limiting metabolic tracing studies. Here, we describe a novel LC-MS-based method that quantitatively assesses both 14N-and 15N-isotopologues of ammonia in polar metabolite extracts. This assay (1) quantitatively measures the concentration of ammonia in polar metabolite isolates used for metabolomic studies, and (2) accurately determines the percent isotope abundance of 15N-ammonia in a cell lysate for 15N-isotope tracing studies. We apply this assay to quantitatively measure glutamine-derived ammonia in lung cancer cell lines with differential expression of glutaminase.


Assuntos
Amônia/química , Cromatografia Líquida , Marcação por Isótopo , Espectrometria de Massas , Amônia/metabolismo , Glutaminase/metabolismo , Glutamina/química , Glutamina/metabolismo , Humanos , Indofenol/química , Indofenol/metabolismo , Metabolômica/métodos , Estrutura Molecular
4.
Metab Brain Dis ; 32(6): 1929-1934, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28795258

RESUMO

Tourette syndrome (TS) is a neurological disorder characterized by highest familial recurrence rate among neuropsychiatric diseases with complicated inheritance. Recurrence of Tourette syndrome was frequently observed in clinical. Unexpectedly, the mechanism of recurrence of Tourette syndrome was failure to elucidate. Here, we first shown that lipopolysaccharide(LPS) may played an important role in the recurrence of Tourette syndrome. The TS model in rats was induced by DOI (the selective 5-HT2A/2C agonist 1-(2, 5-dimethoxy-4-iodophenyl) -2- aminopropane). The rats were randomly divided into 4 groups:(1)Control;(2) Control + LPS; (2)TS; (3)TS + LPS. The results demonstrated that the LPS treatment significantly increased stereotypic score and autonomic activity. LPS treatment also significantly increased inflammatory cytokines such as interleukin-6 (IL-6), interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) in serum and striatum. Also, highly expressed TLR4, MyD88, P-NF-κBp65, P-IκBα in TS rats were increased respectively by LPS treatment as indicted in western blot analysis and immunohistochemistry analysis. Thus, it was supposed that lipopolysaccharide(LPS) may played an important role in the recurrence of Tourette syndrome and its mechanism was related to TLR/NF-κB pathway.


Assuntos
Corpo Estriado/metabolismo , Indofenol/análogos & derivados , Lipopolissacarídeos , Agonistas do Receptor de Serotonina , Síndrome de Tourette/induzido quimicamente , Animais , Citocinas/metabolismo , Modelos Animais de Doenças , Masculino , Ratos , Ratos Wistar , Recidiva , Síndrome de Tourette/metabolismo
5.
Anal Chem ; 88(7): 3775-80, 2016 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-26938207

RESUMO

The prevalently used immunoassays for fast screening of aftatoxins (AFs) usually cannot meet the requirement for simultaneous determination of total AFs (aflatoxin B1 + aflatoxin B2 + aflatoxin G1 + aflatoxin G2) due to the deficiency of highly group-specific antibodies. This paper describes a two-step chromogenic reaction based method to quantitatively detect total AFs in rice using colorimetric measurement without antibody. In the method, colorless AFs transform into green-colored indophenol products through the reaction with sodium hydroxide and 2,6-dibromoquinone-4-chloroimide (DBQC) successively, allowing selectively determining total AFs up to 3.9 µg/kg over other competitive mycotoxins under optimal conditions by a UV-vis spectrophotometer. In addition, the colorimetric measurement results of the rice samples agree well with that of a standard HPLC method, demonstrating the good reliability and applicability of the method. Uniquely, the method has potential for on-site detection of total AFs in rice when using a nylon membrane-based device.


Assuntos
Aflatoxinas/análise , Colorimetria/métodos , Oryza/química , Aflatoxinas/química , Indofenol/análogos & derivados , Indofenol/síntese química , Limite de Detecção , Quinonas/química , Hidróxido de Sódio/química
6.
Talanta ; 143: 374-380, 2015 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-26078173

RESUMO

We describe a highly sensitive colorimetric method for the determination of nanomolar concentrations of ammonium in seawater based on the indophenol reaction with o-phenylphenol [(1,1'-biphenyl)-2-ol, abbreviated as OPP]. OPP is available as non-toxic, stable flaky crystals with no caustic odor and has some advantages over phenol in practical use. The method was established by using a gas-segmented continuous flow analyzer equipped with two types of long path liquid waveguide capillary cell, LWCCs (100 cm and 200 cm) and an UltraPath (200 cm), which have inner diameters of 0.55 mm and 2 mm, respectively. The reagent concentrations, flow rates of the pumping tubes, and reaction path and temperature were determined on the basis of a manual indophenol blue method with OPP (Kanda, Water Res. 29 (1995) 2746-2750). The sample mixed with reagents that form indophenol blue dye was measured at 670 nm. Aged subtropical surface water was used as a blank, a matrix of standards, and the carrier. The detection limits of the analytical systems with a 100 cm LWCC, a 200 cm LWCC, and a 200 cm UltraPath were 6, 4, and 4 nM, respectively. These systems had high precision (<4% at 100 nM) and a linear dynamic range up to 200 nM. Non-linear baseline drift did not occur when using the UltraPath system. This is due to the elimination of cell clogging because of the larger inner diameter of the UltraPath compared to the LWCCs. The UltraPath system is thus more suitable for long-term measurements compared with the LWCC systems. The results of the proposed sensitive colorimetry and a conventional colorimetry for the determination of seawater samples showed no significant difference. The proposed analytical systems were applied to underway surface monitoring and vertical observation in the oligotrophic South Pacific.


Assuntos
Compostos de Amônio/análise , Compostos de Bifenilo/química , Indofenol/química , Água do Mar/análise , Compostos de Amônio/química , Espectrofotometria/métodos
7.
Mol Genet Metab ; 115(2-3): 95-100, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25936660

RESUMO

Quantification of ammonia in whole blood has applications in the diagnosis and management of many hepatic diseases, including cirrhosis and rare urea cycle disorders, amounting to more than 5 million patients in the United States. Current techniques for ammonia measurement suffer from limited range, poor resolution, false positives or large, complex sensor set-ups. Here we demonstrate a technique utilizing inexpensive reagents and simple methods for quantifying ammonia in 100 µL of whole blood. The sensor comprises a modified form of the indophenol reaction, which resists sources of destructive interference in blood, in conjunction with a cation-exchange membrane. The presented sensing scheme is selective against other amine containing molecules such as amino acids and has a shelf life of at least 50 days. Additionally, the resulting system has high sensitivity and allows for the accurate reliable quantification of ammonia in whole human blood samples at a minimum range of 25 to 500 µM, which is clinically for rare hyperammonemic disorders and liver disease. Furthermore, concentrations of 50 and 100 µM ammonia could be reliably discerned with p = 0.0001.


Assuntos
Amônia/sangue , Análise Química do Sangue/métodos , Amônia/química , Humanos , Hiperamonemia/sangue , Indofenol/química
8.
PLoS One ; 10(3): e0121612, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25816248

RESUMO

Cytidine is an industrially useful precursor for the production of antiviral compounds and a variety of industrial compounds. Interest in the microbial production of cytidine has grown recently and high-throughput screening of cytidine over-producers is an important approach in large-scale industrial production using microorganisms. An enzymatic assay for cytidine was developed combining cytidine deaminase (CDA) and indophenol method. CDA catalyzes the cleavage of cytidine to uridine and NH3, the latter of which can be accurately determined using the indophenol method. The assay was performed in 96-well plates and had a linear detection range of cytidine of 0.058-10 mM. This assay was used to determine the amount of cytidine in fermentation flasks and the results were compared with that of High Perfomance Liquid Chromatography (HPLC) method. The detection range of the CDA method is not as wide as that of the HPLC, furthermore the correlation factor of CDA method is not as high as that of HPLC. However, it was suitable for the detection of large numbers of crude samples and was applied to high-throughput screening for high cytidine-producing strains using 96-well deep-hole culture plates. This assay was proved to be simple, accurate, specific and suitable for cytidine detection and high-throughput screening of cytidine-producing strains in large numbers of samples (96 well or more).


Assuntos
Bactérias/metabolismo , Citidina/análise , Ensaios Enzimáticos/métodos , Ensaios de Triagem em Larga Escala/métodos , Citidina Desaminase/metabolismo , Fermentação , Indofenol/química , Reprodutibilidade dos Testes , Uridina/química
9.
Microb Biotechnol ; 8(2): 230-8, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25580842

RESUMO

Adenosine is a major local regulator of tissue function and industrially useful as precursor for the production of medicinal nucleoside substances. High-throughput screening of adenosine overproducers is important for industrial microorganism breeding. An enzymatic assay of adenosine was developed by combined adenosine deaminase (ADA) with indophenol method. The ADA catalyzes the cleavage of adenosine to inosine and NH3 , the latter can be accurately determined by indophenol method. The assay system was optimized to deliver a good performance and could tolerate the addition of inorganic salts and many nutrition components to the assay mixtures. Adenosine could be accurately determined by this assay using 96-well microplates. Spike and recovery tests showed that this assay can accurately and reproducibly determine increases in adenosine in fermentation broth without any pretreatment to remove proteins and potentially interfering low-molecular-weight molecules. This assay was also applied to high-throughput screening for high adenosine-producing strains. The high selectivity and accuracy of the ADA assay provides rapid and high-throughput analysis of adenosine in large numbers of samples.


Assuntos
Adenosina/análise , Ensaios Enzimáticos/métodos , Ensaios de Triagem em Larga Escala/métodos , Adenosina Desaminase/metabolismo , Amônia/metabolismo , Bactérias/metabolismo , Indofenol/metabolismo , Inosina/metabolismo , Reprodutibilidade dos Testes , Coloração e Rotulagem
11.
Appl Biochem Biotechnol ; 172(1): 289-97, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24078189

RESUMO

In this study, an enzymatic procedure for the determination of glycine (Gly) was developed by using a column containing immobilized glutamate dehydrogenase (GDH) on glyoxal agarose beads. Ammonia is produced from the enzymatic reactions between Gly and GDH with NAD(+) in phosphate buffer medium. The indophenol blue method was used for ammonia detection based on the spectrophotometric measurements of blue-colored product absorbing at 640 nm. The calibration graph is linear in the range of 0.1-10 mM of Gly concentrations. The effect of pH, temperature, and time interval was studied to find column stability, and also the interference effects of other amino acids was investigated. The interaction between GDH and glyoxal agarose beads was analyzed by Fourier transform infrared (FTIR) spectroscopy. The morphology of the immobilized and non-immobilized agarose beads were characterized by atomic force microscopy (AFM).


Assuntos
Técnicas Biossensoriais/métodos , Enzimas Imobilizadas/química , Glutamato Desidrogenase/química , Glicina/análise , Glioxilatos/química , Microesferas , Sefarose/química , Água/química , Enzimas Imobilizadas/metabolismo , Glutamato Desidrogenase/metabolismo , Ácido Glutâmico/análise , Ácido Glutâmico/química , Glicina/química , Concentração de Íons de Hidrogênio , Indofenol/química , Soluções , Temperatura , Fatores de Tempo
12.
Rev. lab. clín ; 6(4): 168-171, oct.-dic. 2013.
Artigo em Espanhol | IBECS | ID: ibc-118166

RESUMO

Introducción. Los niveles de paracetamol se miden habitualmente en los laboratorios de urgencias ante la evidencia o sospecha de una intoxicación para predecir la posible hepatotoxicidad aguda por este fármaco. Sin embargo varios estudios han reportado un falso incremento en la concentración de paracetamol medida por métodos enzimáticos en plasmas ictéricos, circunstancia que ocurre frecuentemente en casos de fracaso hepático. Material y métodos. Para evaluar la influencia de la bilirrubina en la medición de paracetamol en el analizador Dimension(R) EXL(TM) (Siemens Healthcare Diagnostics Inc.(R)) se preparó una solución primaria de interferente a una concentración de 800 mg/dl (13.680 μmol/l) que se añadió a una solución de control comercial con altos niveles de paracetamol hasta obtener una mezcla con una concentración de bilirrubina de 40 mg/dl (684 μmol/l) realizando la medición de paracetamol en esta mezcla y en una de referencia. Comprobada la existencia de interferencia se procedió a cuantificarla diluyendo la solución primaria hasta obtener mezclas con 20; 10; 5; 2,5; 1,25 y 0,625 mg/dl de bilirrubina (342; 171; 85,5; 42,75; 21,37 y 19,69 μmol/l). Se obtuvo el interferograma representando la desviación de la medida frente a la mezcla de referencia frente a las distintas concentraciones de interferente. Resultados. Las distribuciones fueron gaussianas, por lo que se pudo aplicar la t de Student para el cálculo de las significaciones estadísticas. Se demostró la existencia de una interferencia significativa negativa a partir de 5 mg/dl (85,5 μmol/l) de bilirrubina, lo que muestra que las mediciones de paracetamol deben interpretarse con cautela en casos de hiperbilirrubinemia (AU)


Background. Blood levels of acetaminophen (paracetamol) are measured routinely in large acetaminophen overdoses or when poisoning is suspected, in order to predict the likelihood of hepatotoxicity. However some cases of spurious acetaminophen levels have been reported in jaundiced patients. Material and methods. The interference of bilirubin in acetaminophen measurements was studied on the Dimension(R) EXL(T)M by preparing a primary mixture of bilirubin at 800 mg/dL, which was spiked to a quality control solution with high acetaminophen concentration in order to get a bilirrubin concentration of 40 mg/dl on the mixture. Acetaminophen concentration was measured in the mixture with bilirubin and in reference solution without bilirubin. Interference was assessed and quantified by diluting the bilirubin solution to achieve final concentrations of 20, 10, 5, 2.5, 1.25 and 0.625 mg/dl (342, 171, 85.5, 42.75, 21.37 and 19.69 μmol/l). A graph of the interference was obtained showing the bias of acetaminophen concentrations with reference solution vs. increasing bilirubin concentrations. Results. Acetaminophen concentrations in both solutions followed Gaussian distributions. The t test showed significant negative interference at bilirubin concentrations higher to 5 mg/dl (85.5 μmol/l), which means that blood acetaminophen concentrations must be interpreted with caution in cases of hyperbilirubinemia (AU)


Assuntos
Humanos , Masculino , Feminino , Hiperbilirrubinemia/diagnóstico , Acetaminofen , Indofenol/análise , Indofenol , Receptores de Superfície Celular/análise , Receptores de Superfície Celular/metabolismo , Intervalos de Confiança , Bilirrubina/análise , Bilirrubina , Colorimetria/métodos , Colorimetria/normas , Colorimetria
13.
Int J Neuropsychopharmacol ; 16(10): 2145-63, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23809188

RESUMO

Non-competitive NMDA receptor antagonists are widely used as pharmacological models of schizophrenia due to their ability to evoke the symptoms of the illness. Likewise, serotonergic hallucinogens, acting on 5-HT(2A) receptors, induce perceptual and behavioural alterations possibly related to psychotic symptoms. The neurobiological basis of these alterations is not fully elucidated. Data obtained in recent years revealed that the NMDA receptor antagonist phencyclidine (PCP) and the serotonergic hallucinogen 1-(2,5-dimethoxy-4-iodophenyl-2-aminopropane; DOI) produce a series of common actions in rodent prefrontal cortex (PFC) that may underlie psychotomimetic effects. Hence, both agents markedly disrupt PFC function by altering pyramidal neuron discharge (with an overall increase) and reducing the power of low frequency cortical oscillations (LFCO; < 4 Hz). In parallel, PCP increased c-fos expression in excitatory neurons of various cortical areas, the thalamus and other subcortical structures, such as the amygdala. Electrophysiological studies revealed that PCP altered similarly the function of the centromedial and mediodorsal nuclei of the thalamus, reciprocally connected with PFC, suggesting that its psychotomimetic properties are mediated by an alteration of thalamocortical activity (the effect of DOI was not examined in the thalamus). Interestingly, the observed effects were prevented or reversed by the antipsychotic drugs clozapine and haloperidol, supporting that the disruption of PFC activity is intimately related to the psychotomimetic activity of these agents. Overall, the present experimental model can be successfully used to elucidate the neurobiological basis of schizophrenia symptoms and to examine the potential antipsychotic activity of new drugs in development.


Assuntos
Comportamento Animal , Encéfalo/fisiopatologia , Indofenol/análogos & derivados , Fenciclidina , Córtex Pré-Frontal/fisiopatologia , Esquizofrenia/induzido quimicamente , Psicologia do Esquizofrênico , Núcleos Talâmicos/fisiopatologia , Animais , Antipsicóticos/farmacologia , Comportamento Animal/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Modelos Animais de Doenças , Humanos , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Esquizofrenia/tratamento farmacológico , Esquizofrenia/metabolismo , Esquizofrenia/fisiopatologia , Núcleos Talâmicos/efeitos dos fármacos , Núcleos Talâmicos/metabolismo
14.
J Urol ; 189(5): 1982-8, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23159275

RESUMO

PURPOSE: We examined the effects of the 5-HT2A/2C receptor agonist DOI on micturition in chronic spinal cord injured rats. MATERIALS AND METHODS: Female Sprague-Dawley® rats were used. Spinal cord injury was produced by transection at the T10 level. A cystometric study was performed 8 to 12 weeks after transection. Cystometrograms were done using urethane anesthesia in all rats. The selective 5-HT2A antagonist ketanserin was administered after each DOI dose-response curve. All drugs were administered intravenously. RESULTS: Compared to controls, spinal cord injured rats had higher bladder capacity and post-void residual urine volume, and lower voiding efficiency. In spinal cord injured rats DOI (0.01 to 0.3 mg/kg) induced significant dose dependent increases in micturition volume and decreases in residual volume, resulting in increased voiding efficiency. Cystometrogram measurements showed a dose dependent increase in high frequency oscillation activity, evident as an increased number of small oscillation per voiding. This correlated with the improved voiding efficiency. Ketanserin (0.1 mg/kg) partially or completely reversed the DOI induced changes. CONCLUSIONS: High frequency oscillation seems to reflect external urethral sphincter burst activity during voiding. Bladder voiding efficiency and high frequency oscillation activity were decreased in spinal cord injured rats. High frequency oscillation activity can be enhanced by 5-HT2A receptor agonism, improving voiding efficiency. To our knowledge it remains to be studied whether these results may have implications for the future treatment of voiding dysfunction in patients with spinal cord injury.


Assuntos
Indofenol/análogos & derivados , Agonistas do Receptor 5-HT2 de Serotonina/farmacologia , Traumatismos da Medula Espinal/fisiopatologia , Micção/efeitos dos fármacos , Animais , Doença Crônica , Feminino , Indofenol/farmacologia , Ratos , Ratos Sprague-Dawley
15.
J Am Soc Mass Spectrom ; 22(10): 1737-43, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21952887

RESUMO

The recently discovered sample plug formation and injection operational mode of a continuous flow, coaxial tube geometry, liquid microjunction surface sampling probe (LMJ-SSP) was further characterized and applied for concentration and mixing of analyte extracted from multiple areas on a surface and for nanoliter-scale chemical reactions of sampled material. A transparent LMJ-SSP was constructed and colored analytes were used so that the surface sampling process, plug formation, and the chemical reactions could be visually monitored at the sampling end of the probe before being analyzed by mass spectrometry of the injected sample plug. Injection plug peak widths were consistent for plug hold times as long as the 8 min maximum attempted (RSD below 1.5%). Furthermore, integrated injection peak signals were not significantly different for the range of hold times investigated. The ability to extract and completely mix individual samples within a fixed volume at the sampling end of the probe was demonstrated and a linear mass spectral response to the number of equivalent analyte spots sampled was observed. Using the color and mass changing chemical reduction of the redox dye 2,6-dichlorophenol-indophenol with ascorbic acid, the ability to sample, concentrate, and efficiently run reactions within the same plug volume within the probe was demonstrated.


Assuntos
Hidrodinâmica , Espectrometria de Massas por Ionização por Electrospray/métodos , Ácido Ascórbico/química , Clorofenóis/química , Corantes/química , Desenho de Equipamento , Indofenol/química , Oxirredução , Espectrometria de Massas por Ionização por Electrospray/instrumentação , Propriedades de Superfície
16.
Talanta ; 85(3): 1448-52, 2011 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-21807208

RESUMO

A miniaturized method based on liquid-phase microextraction (LPME) in combination with microvolume UV-vis spectrophotometry for monitoring ammonia in waters is proposed. The methodology is based on the extraction of the ion pair formed between the blue indophenol obtained according to the Berthelot reaction and a quaternary ammonium salt into a microvolume of organic solvent. Experimental parameters affecting the LPME performance such as type and concentration of the quaternary ammonium ion salt required to form the ion pair, type and volume of extractant solvent, effect of disperser solvent, ionic strength and extraction time, were optimized. A detection limit of 5.0 µg L(-1) ammonia and an enrichment factor of 30 can be attained after a microextraction time of 4 min. The repeatability, expressed as relative standard deviation, was 7.6% (n=7). The proposed method can be successfully applied to the determination of trace amounts of ammonia in several environmental water samples.


Assuntos
Amônia/análise , Amônia/isolamento & purificação , Microextração em Fase Líquida/métodos , Espectrofotometria/métodos , Amônia/química , Água Potável/análise , Água Doce/análise , Indofenol/química , Íons/química , Águas Minerais/análise , Miniaturização , Nascentes Naturais/análise , Compostos de Amônio Quaternário/química , Reprodutibilidade dos Testes , Abastecimento de Água/análise , Poços de Água/análise
17.
J Food Sci ; 76(2): T59-64, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21535796

RESUMO

Meat products are packaged in polymer films designed to protect the product from exterior contaminants such as light, humidity, and harmful chemicals. Unfortunately, there is almost no data on ammonia permeability of packaging films. We investigated ammonia permeability of common meat packaging films: low-density polyethylene (LDPE; 2.2 mil), multilayer polyolefin (MLP; 3 mil), and vacuum (V-PA/PE; 3 mil, 0.6 mil polyamide/2.4 mil polyethylene). The films were fabricated into 10 × 5 cm pouches and filled with 50 mL deionized water. Pouches were placed in a plexiglass enclosure in a freezer and exposed to 50, 100, 250, or 500 ppm ammonia gas for 6, 12, 24, and 48 h at -17 ± 3 °C and 21 ± 3 °C. At freezing temperatures, no ammonia residues were detected and no differences in pH were found in the water. At room temperature, ammonia levels and pH of the water increased significantly (P < 0.05) with increasing exposure times and ammonia concentrations. Average ammonia levels in the water were 7.77 ppm for MLP, 5.94 ppm for LDPE, and 0.89 ppm for V-PA/PE at 500 ppm exposure for 48 h at 21 ± 3 °C. Average pH values were 8.64 for MLP, 8.38 for LDPE, and 7.23 for V-PA/PE (unexposed ranged from 5.49 to 6.44) at 500 ppm exposure for 48 h. The results showed that temperature influenced ammonia permeability. Meat packaging materials have low ammonia permeability and protect meat products exposed to ammonia leaks during frozen storage.


Assuntos
Amônia/análise , Amônia/química , Embalagem de Alimentos/métodos , Carne , Animais , Conservação de Alimentos , Congelamento , Concentração de Íons de Hidrogênio , Indofenol/análise , Permeabilidade , Polienos/química , Polietileno/química , Vácuo , Água
18.
J Neurotrauma ; 27(10): 1805-18, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20698759

RESUMO

Autonomic dysreflexia consistently develops in patients and in rats after severe upper thoracic spinal cord injury (SCI) as a result of exaggerated spinal sympathetic excitation. In this study we induced episodic hypertension in rats after varying degrees of SCI severity to investigate the contribution of serotonergic bulbospinal axons to the development of autonomic dysreflexia after SCI. Female Wistar rats (250-300 g) were used in all experiments in the following groups: (1) uninjured, (2) clip compression at T4 of 20, 35, or 50 g, (3) spinal cord transection at T4, and (4) intrathecal 5,7-dihydroxytryptamine creatinine sulfate (5,7-DHT). Immunohistochemistry for choline acetyl transferase and serotonin (5-HT) was performed on T8-T12 spinal segments to identify sympathetic preganglionic neurons, and to assess 5-HT-containing axons in the intermediolateral cell column (IMLC), respectively. Testing for autonomic dysreflexia was conducted by measuring mean arterial pressure (MAP) at rest and after colon distension-induced hypertension. We observed that the magnitude of the pressor response seen after colon distension correlated with SCI severity and density of 5-HT-immunoreactive axons in the IMLC. Intrathecal administration of the 5-HT(2A) agonist dimethoxy-4-iodamphetamine increased resting MAP and blocked colon distension-induced hypertension, whereas the 5-HT(2A) antagonist ketanserin decreased resting MAP and was permissive to the colon distension-induced pressor response in SCI rats. These results suggest that the SCI-induced loss of serotonergic inputs into the spinal cord IMLC is proportional to the pathogenesis of autonomic dysreflexia and hypotension seen after SCI. We thus conclude that sparing of serotonergic axons beyond a critical threshold preserves cardiovascular regulation and prevents the development of autonomic dysreflexia.


Assuntos
Disreflexia Autonômica/etiologia , Disreflexia Autonômica/fisiopatologia , Axônios/metabolismo , Serotonina/metabolismo , Traumatismos da Medula Espinal/complicações , Análise de Variância , Animais , Disreflexia Autonômica/metabolismo , Axônios/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Colina O-Acetiltransferase/metabolismo , Feminino , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Imuno-Histoquímica , Indofenol/análogos & derivados , Indofenol/farmacologia , Injeções Espinhais , Ketanserina/farmacologia , Atividade Motora/fisiologia , Ratos , Ratos Wistar , Antagonistas da Serotonina/farmacologia , Agonistas do Receptor de Serotonina/farmacologia , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/fisiopatologia
19.
J Food Sci ; 75(2): T35-9, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20492264

RESUMO

Regulations and publications about food contaminated during ammonia refrigerant leaks provide limited information and recommendations, which means that contaminated products are often held for an indeterminate period or condemned. Moreover, the scientific literature offers little guidance on disposing of products exposed to low levels of ammonia refrigerant gas. We evaluated meat contaminated with low levels of ammonia under frozen storage conditions. Fresh beef semitendinosus muscles were trimmed of external fat; fabricated into 10 x 5 x 2.3 cm (height x width x depth) steaks; and exposed to 50, 100, 250, and 500 ppm ammonia gas (85 mL/min) in a plexiglass enclosure contained in a freezer for 6, 12, 24, and 48 h at -17 +/- 3 degrees C. Ammonia content in meat was analyzed by the indophenol method, and pH was measured according to AOAC official method 981.12. Ammonia levels and pH values increased significantly (P < 0.05) in the exposed meat with increasing exposure times and ammonia concentrations. Ammonia levels were 34.2, 51.5, 81.1, and 116 ppm, and pH values ranged from 5.56 to 5.75 (control range 5.31 to 5.43) when the meat was exposed to 50, 100, 250, 500 ppm for 48 h. Our results showed that meat ammonia content was low even with ammonia exposures as high as 500 ppm at freezing temperatures.


Assuntos
Amônia/análise , Contaminação de Alimentos , Manipulação de Alimentos/métodos , Conservação de Alimentos/métodos , Congelamento , Carne/análise , Animais , Bovinos , Concentração de Íons de Hidrogênio , Indofenol/análise , Fatores de Tempo
20.
Zh Evol Biokhim Fiziol ; 46(6): 485-8, 2010.
Artigo em Russo | MEDLINE | ID: mdl-21268878

RESUMO

Kinetic analysis of the activating effect of substrate on the cholinesterase catalysis is performed. There are determined values of coefficient of activation A in the pH zone 5.0-7.5 for the process of hydrolysis of acetylcholine, indophenylacetate (IPA), and 2,6-dichlorophenolindophenylacetate (DIPA) by cholinesterase (ChE) of horse blood serum, as well as of IPA and DIPA by ChE of optical ganglia of the Pacific squid Todarodes pacificus. The phenomenon of activation has not been revealed at hydrolysis of phenylacetate by the horse blood serum ChE. The conclusion is made that the cause of the activating effect of substrate on the process of enzymatic hydrolysis by ChEs of different origin is the presence of the onium grouping in the structure of substrates.


Assuntos
Acetilcolina/química , Colinesterases/química , Indofenol/análogos & derivados , Compostos de Amônio Quaternário/química , Animais , Decapodiformes , Ativação Enzimática , Cavalos , Concentração de Íons de Hidrogênio , Hidrólise , Indofenol/química , Especificidade por Substrato
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