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Biomedical subjects

L Arce

Publications and source records attributed to L Arce.

At least 19 recordsLinked to original sources
PubMed2006

Diversity of LEF/TCF action in development and disease.

Lymphoid enhancer factor/T cell factor proteins (LEF/TCFs) mediate Wnt signals in the nucleus by recruiting beta-catenin and its co-activators to Wnt response elements (WREs) of target genes. This activity is important during development but its misregulation plays a role in disease such as cancer, where overactive Wnt signaling drives LEF/TCFs to transform cells. The size of the LEF/TCF family is small: approximately four members in vertebrates and one orthologous form in flies, worms and hydra. However, size belies complexity. The LEF/TCF family exhibits extensive patterns of alternative splicing, alternative promoter usage and activities of repression, as well as activation. Recent work from numerous laboratories has highlighted how this complexity has important biological consequences in development and disease.

Alternative Splicing↗
PubMed2004

Bioguided extraction of polyphenols from grape marc by using an alternative supercritical-fluid extraction method based on a liquid solvent trap.

The biological activity of polyphenols extracted from grape marc was studied with a view to finding a new use for this winery waste. Polyphenols were extracted by using an alternative supercritical-fluid extraction method based on the use of a liquid trap that allows extracted polyphenols to be retained in a saline buffer, thus avoiding the need for the organic solvent required to elute polyphenols from a solid trap. The major extraction variables influencing the performance of the liquid trap (viz. CO(2) modifier content, flow-rate, extraction time and trap volume) were optimized. The proposed method was applied to the supercritical-fluid extraction extraction of 0.3 g grape marc with CO(2) modified with 3% methanol at 350 bar at 50 degrees C (CO(2) density 0.9 g mL(-1)) for 20 min, using a liquid flow-rate of 0.9 mL min(-1). The polyphenol extracts thus obtained exhibited cytotoxic effects that induced apoptosis in tumour cells.

Apoptosis↗
PubMed2002

Screening of aflatoxins in feed samples using a flow system coupled to capillary electrophoresis.

A method is proposed which presents a new approach to the joint use of capillary electrophoresis (CE) commercial equipment and a flow system. This flow system allows the total determination of several compounds by using a fluorimetric screening system. The individual determination for each analyte is performed by the CE proposed method. The screening procedure uses simple equipment and operations and provides a yes/no binary response that occasionally requires confirmation. A fast, simple, and reliable method has been developed in order to determine the most frequent mycotoxins in feed samples using micellar electrokinetic capillary chromatography (MECC). An extraction step followed by a purification step was carried out on the samples in order to remove interference substances before analysis. A C18 column was chosen to concentrate the mycotoxins, and the analytes were eluted from C18 using methanol. The MECC method allows the separation of six mycotoxins within 50 min with a reproducibility as RSD between 7.45 and 13.06%, and a limit of detection (LOD) between 0.02 and 0.06 mg l(-1) for all the mycotoxins. These LODs were clearly below legal limits (0.05 mg l(-1)).

Aflatoxins↗
PubMed2002

Determination of monoterpene hydrocarbons and alcohols in Majorana hortensis Moench by micellar electrokinetic capillary chromatographic.

Micellar electrokinetic capillary chromatography was used to determine the essential oils obtained by steam distillation of different samples of marjoram (Majorana hortensis Moench) dried leaves and flowers. The electrophoretic method consisted of a running buffer of 10 mM NaH2PO4, 6 mM Na2B4O7, 50 mM SDS, 7 mM gamma-cyclodextrin, and 10% acetonitrile, adjusted to pH 8.0 by the addition of 0.1 M H3PO4. The following monoterpene hydrocarbons and alcohol compounds were extracted from real samples and determined by the method proposed: alpha-pinene, gamma-terpinene, alpha-terpinene, terpinolene, p-cymene, linalool, alpha-terpineol, and terpinen-4-ol. The most prominent component of dried leaves, flowers, and commercial samples was terpinen-4-ol in four of the samples analyzed; only in one sample was alpha-terpineol present as the major compound.

Alcohols↗
PubMed2001

Coupling continuous separation techniques to capillary electrophoresis.

One of the weak points of capillary electrophoresis is the need to implement rigorously sample pretreatment because its great impact on the quality of the qualitative and quantitative results provided. One of the approaches to solve this problem is through the symbiosis of automatic continuous flow systems (CFSs) and capillary electrophoresis (CE). In this review a systematic approach to CFS-CE coupling is presented and discussed. The design of the corresponding interface depends on three factors, namely: (a) the characteristics of the CFS involved which can be non-chromatographic and chromatographic; (b) the type of CE equipment: laboratory-made or commercially available; and (c) the type of connection which can be in-line (on-capillary), on-line or mixed off/on-line. These are the basic criteria to qualify the hyphenation of CFS (solid-phase extraction, dialysis, gas diffusion, evaporation, direct leaching) with CE described so far and applied to determine a variety of analytes in many different types of samples. A critical discussion allows one to demonstrate that this symbiosis is an important topic in research and development, besides separation and detection, to consolidate CE as a routine analytical tool.

Chromatography, High Pressure Liquid↗
PubMed2001

Use of eosin as a fluorophore in capillary electrophoresis with laser detection.

Eosin has been used to generate the background signal for indirect fluorimetric detection of inorganic and organic ions, simultaneously separated by capillary zone electrophoresis (CZE). This reagent provides constant fluorescence over the pH range of 5-10 and is compatible with the excitation by an argon ion laser at 488 nm with emission at 520 nm. The use of esosine as fluorophore, H3BO3, and Na2B4O7 as electrolyte and diethylentriamine as modifier of the electroosmotic flow in CZE were optimised. The analytical potential of the studied buffer was tested on a group of 12 anions, used as model compounds. Both, hydrodynamic and electrokinetic injection mode were optimised. The detection limits determined by the last injection mode, were in the range 0.008-0.037 mg l(-1). By using this method, the quantitation of the common anions in tap and mineral water has been carried out successfully.

Electrophoresis, Capillary↗
PubMed2001

Determination of phenolic constituents in citrus samples by on-line coupling of a flow system with capillary electrophoresis.

Phenolic compounds extracted from different citrus were determined. Calibration, extraction, elution, and introduction into the sample vial was carried out automatically by a continuous flow system (CFS) coupled to capillary electrophoresis (CE) equipment via a programmable arm. The only manual operation was the centrifugation of the sample to remove the pulp. The supernatant solutions were introduced into the CFS-CE system. A C-18 minicolumn coupled into the CFS was used to perform cleanup of the samples. The analytes were eluted from the minicolumn using methanol. Quantitative analysis was carried out by the standard addition method. The method presented allows a fast, quantitative, and reproducible determination of six main phenolic compounds in citrus samples, with precision in the range of 3.0-6.5%, expressed as relative standard deviations.

Citrus↗
PubMed2001

Increased rectal cell proliferation following alcohol abuse.

BACKGROUND: Epidemiological data indicate an increased risk for rectal cancer following chronic alcohol consumption. As chronic ethanol ingestion leads to rectal hyperregeneration in experimental animals, indicating a state of increased susceptibility to carcinogens, we studied cell proliferation in alcohol abusers. METHODS: Rectal biopsies were taken from 44 heavy drinkers and 26 controls. Cell proliferation, including proliferative compartment size, was measured by immunohistological staining for proliferative cell nuclear antigen (PCNA) and Ki67, and by in situ hybridisation for histone H3. Quantification of cell proliferation using PCNA staining was evaluated in 27 alcohol abusers and 12 controls. In addition, immunohistology was performed for cytokeratins and gene products of Rb1, bcl-2, and p53. RESULTS: Heavy drinking resulted in increased cell proliferation of the rectal mucosa, as shown by increased detection of different proliferation markers. However, cell differentiation regarding cytokeratin expression patterns was unchanged as well as regulatory factors involved in carcinogenesis and/or apoptosis. CONCLUSION: Chronic alcohol abuse leads to rectal mucosal hyperproliferation in humans, a condition associated with an increased cancer risk.

Adult↗
PubMed2000

Gene expression array of HTLV type 1-infected T cells: Up-regulation of transcription factors and cell cycle genes.

By utilizing a human cDNA expression array blot (588 genes), we have observed overexpression of various transcription factors, cell cycle regulated kinases, and DNA repair genes in HTLV-1-infected T cells. One of the genes of interest, and focus in this study, is the cyclin-dependent kinase inhibitor, p21/waf1. The p21/waf1 transcription and protein is overexpressed in all HTLV-1-infected cell lines tested as well as ATL and HAM/TSP patient samples. While p21/waf1 has been shown to display a selectivity for G(1)/S cyclin/cdk complexes, we have observed p21/waf1 to be complexed with cyclin A/cdk2. Functionally, the association of p21/cyclin A/cdk2 decreased the histone H1 phosphorylation in vitro, as observed in immunoprecipitations followed by kinase assays, as well as affecting other substrates such as the C-terminus of Rb protein involved in c-Abl and HDAC1 regulation. Wild-type, but not a mutant form (M47) of Tax, was found to be able to transactivate the p21/waf1 promoter in a p53-independent manner. We found that the minimal p21/waf1 promoter (-49 to +49 sequence) was activated by Tax and the minimal promoter contained two E2A transcription factor binding sites located between the TATA box and the initiation site. E2A proteins, E12 and E47, as well as a related helix-loop-helix protein, HEB, are all up-regulated in HTLV-1-infected T cells. When using band shift analysis, we found that only the E1 site (overlapping the transcription start site) was a functional DNA binding site. By using a chromatin immunoprecipitation (ChIP) assay, we observed that histone H4, and not histone H3, was acetylated from the endogenous p21/waf1 promoter in vivo, implying that CBP/p300, and not the SAGA complex, was critical in complexing with E2A in up-regulation of p21/waf1 in HTLV-1-infected cells.

Basic Helix-Loop-Helix Proteins↗
PubMed2000

Determination of pesticides in waters by automatic on-line solid-phase extraction-capillary electrophoresis.

The separation of seven pesticides by micellar electrokinetic capillary chromatography in spiked water samples is described, allowing the analysis of pesticides mixtures down to a concentration of 50 microg l(-1) in less than 13 min. Calibration, pre-concentration, elution and injection into the sample vial was carried out automatically by a continuous flow system (CFS) coupled to a capillary electrophoresis system via a programmable arm. The whole system was electronically coupled by a micro-processor and completely controlled by a computer. A C18 solid-phase mini-column was used for the pre-concentration, allowing a 12-fold enrichment (as an average value) of the pesticides from fortified water samples. Under the optimal extraction conditions, recoveries between 90 and 114% for most of the pesticides were obtained.

Automation↗
PubMed2000

Automatic calibration in capillary electrophoresis.

A direct, completely automated calibration procedure in capillary electrophoresis (CE) is presented. The manual calibration operations involved in analytical methods, such as external calibration, standard addition, and internal standard, were accomplished with a continuous flow system (CFS) coupled to commercial capillary electrophoresis equipment via a programmable arm. The system was managed by the proper CE microprocessor and allowed automatic calibration and direct quantification of the analytes in the sample without any manual pretreatment, therefore avoiding or minimizing manually associated errors. The whole system including peristaltic pumps and the programmable arm was connected via an electronic interface and completely controlled by a computer using a program written in GW-BASIC. The potential of this new CFS-CE arrangement was assessed by applying it to samples containing selected compounds.

Automation↗
PubMed1998

Determination of anti-carcinogenic polyphenols present in green tea using capillary electrophoresis coupled to a flow injection system.

A capillary electrophoresis (CE) method was developed for the simultaneous determination of a number of major ingredients of green tea. The components analysed were caffeine, adenine, theophylline, epigallocatechin-3 gallate, epigallocatechin, epicatechin-3 gallate, (-)-epicatechin, (+)-catechin, gallic acid, quercetin and caffeic acid. Separation was achieved using a fused capillary column with 0.15 M H3BO3 as buffer at a pH of 8.5, UV detection at 210 nm and 20 kV of voltage. Analysis was carried out after treatment (extraction, filtration and dilution) of the samples in a flow injection system which was coupled to a CE equipment via a programmable arm. The procedure allows the determination of these compounds in less than 20 min. Quantitative analysis was performed by the standard addition method. Limits of detection ranged between 0.04 microgram ml-1 for flavonols and 1.2 micrograms ml-1 for caffeine.

Anticarcinogenic Agents↗
PubMed1998

Direct determination of biogenic amines in wine by integrating continuous flow clean-up and capillary electrophoresis with indirect UV detection.

A flow-injection manifold for automating the determination of biogenic amines in wine using capillary electrophoresis (CE) with indirect UV detection was developed. The ensuing method involves clean-up and solid-phase extraction (SPE) of the target analytes in the sample. Various treatments involving different SPE minicolumns were tested and compared. The C18 minicolumn was chosen to concentrate the amines following addition of ammonium chloride and ammonium hydroxide as buffer to neutralize them. Additions of amine standards were used to determine recoveries. Biogenic amines can be separated and detected after SPE with limits of detection in the range 0.05-0.1 microgram ml-1 by using 4 mM copper(II) sulphate, formic acid and 18-crown-6 as running buffer. All the amines studied are eluted within 15 min under the optimum conditions established. The overall process was successfully used to identify biogenic amines in various types of wine from different Spanish regions.

Biogenic Amines↗
PubMed1994

[Circadian aspects of acetylsalicylic acid induced injury and protective effect of ranitidine on the the upper gastrointestinal tract].

Circadian Aspects of Acetylsalicylic Acid Induced Injury and Protective Effect of Ranitidine on the Upper Gastrointestinal Tract. In a randomised parallel double-blind study the gastric and duodenal effects of 300 mg acetylsalicylic acid (ASA, CAS 50-78-2) daily in the presence and absence of 150 mg ranitidine (Zantic, CAS 66357-35-5) daily was evaluated in 32 healthy volunteers undergoing upper gastrointestinal endoscopy. Drugs were taken over a period of 7 days either at 8 a.m. (n = 16) or at 8 p.m. (n = 16). Endoscopic controls were performed at entry and repeated after 7 days of treatment. At entry both groups showed comparable mucosal damages: 8 a.m. group: ASA/placebo 0.8 +/- 0.1 (stomach) and 0.1 +/- 0.1 (duodenum): ASA/ranitidine 1.0 +/- 0.0 (stomach) and 0.07 +/- 0.06 (duodenum). 8 p.m. group: ASA/placebo 0.9 +/- 0.06 (stomach) and 0.1 +/- 0.09 (duodenum). ASA/ranitidine 0.8 +/- 0.08 (stomach) and 0.07 +/- 0.06 (duodenum). After 7 days of treatment the lesions score increased in the ASA/Placebo group in the 8 a.m. group to 9.1 +/- 1.1 (stomach) and 2.7 +/- 1.0 (duodenum), and in the 8 p.m. group to 10.9 +/- 1.1 (stomach) and to 3.9 +/- 0.9 duodenum). The corresponding values in the ASA/ranitidine group were 2.6 +/- 0.8 (stomach) and 0.2 +/- 0.08 (duodenum) (8 a.m.) and 4.8 +/- 0.8 (stomach) and 0.3 +/- 0.1 (duodenum) (8 p.m.). There was no statistical difference between the morning- and the evening dose of ASA. In addition, ranitidine protection was also time-independent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗