PubMed Health⌕ Search

Biomedical subjects

A Ríos

Publications and source records attributed to A Ríos.

At least 73 records · Page 4Linked to original sources
PubMed2001

Determination of nonsteroidal anti-inflammatory drugs in biological fluids by automatic on-line integration of solid-phase extraction and capillary electrophoresis.

A new, automatic method for the clean-up, preconcentration, separation, and quantitation of nonsteroidal anti-inflammatory drugs (NSAIDs) in biological samples (human urine and serum) using solid-phase extraction coupled on-line to capillary electrophoresis is proposed. Automatic pretreatment is carried out by using a continuous flow system operating simultaneously with the capillary electrophoresis equipment, to which it is linked via a laboratory-made mechanical arm. This integrated system is controlled by an electronic interface governed via a program developed in GWBasic. Capillary electrophoresis is conducted by using a separation buffer consisting of 20 mM NaHPO4, 20 mM beta-cyclodextrin and 50 mM SDS at pH 9.0, an applied potential of 20 kV and a temperature of 20 degrees C. The analysis time is 10 min and the detection limits were between 0.88 and 1.71 microg mL(-1). Automatic clean-up and preconcentration is accomplished by using a C-18 minicolumn and 75% methanol as eluent. The limit of detection of NSAIDs can be up to 400-fold improved when using sample clean-up. The extraction efficiency for these compounds is between 71.1 and 109.7 microg mL(-1) (RSD 2.0-7.7%) for urine samples and from 77.2 to 107.1 microg mL(-1) (RSD 3.5-7.1%) for serum samples.

Anti-Inflammatory Agents, Non-Steroidal↗
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

Automated flow-injection spectrophotometric determination of nitrosamines in solid food samples.

A spectrophotometric method using a flow-injection system is proposed for the determination of nitrosamines in foods (cured-meats). The method is based on the photochemical cleavage of the N-NO bond of the nitrosamine to yield the corresponding amine and nitrite. The nitrite is then detected spectrophotometrically, at 542 nm, by use of its reaction with a modified Griess reagent. Different linear ranges between 0.8 and 2000 ng mL(-1) are obtained for the method, depending on the time of exposure of the sample to the UV radiation. The relative standard deviation varies between 2.0 and 3.9% and the sample throughput is between three and seven samples per hour, depending on the experimental conditions. The proposed method was successfully applied to the analysis of N-nitrosodimethylamine in cured ham and loin, bacon, and sausages.

Animals↗
PubMed2001

Antibiotic prophylaxis in incisional hernia repair using a prosthesis.

Antibiotic prophylaxis in clean surgery with implantation of prosthetic material is widely accepted, although there are no studies on its use in abdominal incisional hernia repair. The objective was to evaluate antibiotic chemoprophylaxis in incisional herniorrhaphy with the implantation of prosthetic material. A prospective non-randomized study (1990-1998) was conducted to analyse 216 patients undergoing surgery for abdominal incisional hernia who required a prosthesis (polypropylene) in the reconstruction and who met the criteria for clean surgery. Risk factors were observed in 31.5%, the most frequent being diabetes and obesity. The incisional hernia was located mostly in the abdominal midline and in 64.4% measured over 10 cm. Antibiotic prophylaxis was administered in 140 patients (64.8%) via the systemic route, the antibiotics being first- or second-generation cephalosporins or amoxicillin-clavulanic acid. Surgical wound infection occurred in 39 patients (18.1%), 19 who had received antibiotic prophylaxis (13.6%) and 20 who had not (26.3%). In multivariate analysis using logistic regression, the variables with statistical significance for local septic infection were antibiotic prophylaxis and number of risk factors. We can conclude therefore that antibiotic chemoprophylaxis is useful in abdominal incisional herniorrhaphy surgery with implantation of prosthetic material for reducing local septic complications.

Aged↗
PubMed2001

Determination of fat in leather by the use of supercritical fluid extraction combined with on-line piezoelectric detection.

Leather samples were prepared and characterized as 'in house' matrix standards for the determination of fat. The Soxhlet standard method was used to establish the reference fat content in every standard sample. Sample homogeneity and stability were examined under specific storing conditions. The materials were subsequently used as matrix standards for the determination of fat in leather samples, using supercritical fluid extraction (SFE) with on-line piezoelectric detection. Real samples were weighed in the extraction SFE thimble, previously loaded with 1 g of diatomaceous earth. A temperature of 45 degrees C and a CO2 fluid density of 0.85 g ml-1 were used for extraction. The linear calibration range thus achieved was 0.001-0.040% m/m total fat (related to the weight of the leather) and the relative standard deviation +/- 3% (n = 11; P = 0.05). The results were compared with those obtained with the Soxhlet method and no significant differences were found.

Journal Article↗
PubMed2001

Familial papillary carcinoma of the thyroid: report of three families.

OBJECTIVE: To report our experience of the clinical characteristics, treatment and outcome of familial papillary carcinoma. DESIGN: Descriptive study. SETTING: Tertiary referral centre, Spain. PATIENTS: Eight patients from three families. INTERVENTIONS: Treatment for familial papillary carcinoma of thyroid. MAIN OUTCOME MEASURES: Age, sex, reason for consultation, preoperative investigation, indication for operation and type, variety of papillary carcinoma and characteristics (size, adenopathies, multicentricity and bilaterality), treatment with 131I, and outcome. RESULTS: The mean (SD) age was 46 (14) years, and seven were women. In all but one patient, who was admitted for hypercalcaemia and operated on for primary hyperparathyroidism, cervical palpation and ultrasound showed a thyroid nodule. Needle aspiration suggested papillary carcinoma in 6/7, who were all treated by total thyroidectomy. Four patients with enlarged nodes also had bilateral neck disection. All the papillary carcinomas were well-differentiated, mean (SD) diameter was 1.5 (1) cm and in four were microcarcinomas. Three patients presented with invaded nodes. They were all treated postoperatively with 131I, except the patient with hyperparathyroidism who had a microcarcinoma of 0.5 cm. After a median (range) follow-up of 1 (0, 6-7) years the patients are well, except one had a high thyroglobulin concentration seven years later; however clinical exploration and morphological screening were within normal limits and he was treated with 131I 5.6 x 10(9) Bq. CONCLUSIONS: About a third of familial papillary carcinomas of the thyroid have lymph node involvement at the time of diagnosis, and have a relatively good prognosis if treated in accordance with the stage of the disease.

Adult↗
PubMed2001

Cavernous hemangioma of the thyroid.

Most current vascular alterations of the thyroid are connected with the organization of a thyroid hematoma after fine-needle aspiration (FNA). Cavernous hemangioma is a benign congenital vascular malformation that occasionally affects the thyroid. This article presents two cases of this rare thyroid pathology unrelated to FNA.

Biopsy↗
PubMed2001

Has the incidence of perforated peptic ulcer decreased over the last decade?

BACKGROUND: The therapeutic use of new drugs for inhibiting gastric secretion together with Helicobacter pylori antimicrobe therapy has given rise to controversy over the current incidence of perforated peptic ulcer (gastroduodenal peptic ulcer, GDPU). The aim of this study is to analyze the incidence of ulcer perforation over the last 12 years in our health area and the influence of new medical treatments. MATERIAL AND METHODS: Our series includes 246 patients operated on for perforated peptic ulcer during a 12-year period (January 1987 to December 1998) in our health area. The mean patient age was 55.2 +/- 18.1 (16-93) years, and there was a predominance of males (199/246; 80.9%). The ulcer was located fundamentally in the pylorus (48.3%) and duodenal bulb (39.1%), and the most frequent surgical technique was bilateral truncal vagotomy associated with pyloroplasty (85.3%). RESULTS: During the 1987-1992 period, 152 patients underwent surgery, whereas 94 patients were operated on between 1993 and 1998, which reveals a statistically significant difference (p < 0.001). Furthermore, if we divide the study into four 3-year periods (1987-1989, 1990-1992, 1993-1995 and 1996-1998), we see that there were 74 and 78 GDPUs in the first two periods, with no statistical differences between each other, and 48 and 46 cases in the last two periods, also with no statistical differences between each other, but statistically significant when compared to the first two periods. CONCLUSION: The incidence of perforated GDPU has dropped by half over the last 6 years due fundamentally to the use of proton pump inhibitors.

Adolescent↗
PubMed2000

Automatic on-line coupling of supercritical fluid extraction and capillary electrophoresis.

An interface for the automatic coupling of a supercritical fluid extractor (SFE) with capillary electrophoretic (CE) equipment, both commercially available, was developed with a view to improving sample treatment, which is a crucial step in capillary electrophoresis. Extracted analytes were collected in a trap following depressurization in the SFE and were transferred to the CE equipment across the interface. The key elements of the experimental assembly are a laboratory-made programmable arm and the autosampler of the CE equipment, both of which are controlled by a built-in microprocessor using an appropriate electronic interface and customized software. This combined system was successfully used to determine cresols and chlorophenols in liquid samples (river water and human urine) with increased precision, throughput, and automatability. The proposed arrangement opens up interesting prospects for the direct determination of analyte traces in solid samples without human intervention.

Journal Article↗
PubMed2000

Automatic microgravimetric determination of fats in milk products by use of supercritical fluid extraction with on-line piezoelectric detection.

An on-line supercritical fluid extraction-piezoelectric detection system was developed and applied to the quantitative gravimetric determination of total fat in food samples (skimmed milk and cocoa). The proposed assembly provides all the advantages of an on-line system as regards automation, in addition to acceptable sensitivity and precision. Its strength lies in the design of the interface between the supercritical fluid extractor and the piezoelectric detector. Samples of skimmed milk and cocoa are weighed in the extraction thimble, previously loaded with I g of diatomaceous earth. A temperature of 100 degrees C and a CO2 fluid density of 0.60 mg/ml are used for extraction. The linear calibration range thus achieved is 0.005-0.07% w/w total fat, and the relative standard deviation is +/-2.3% (n=11; P=0.05). The throughput is six samples h(-1) (for the overall process). The proposed method was used to determine the total fat in food samples (milk, cocoa), the results being competitive with those of the Soxhlet methods for the same purpose.

Animals↗
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↗
PubMed2000

Flow injection spectrophotometric determination of ascorbic acid in soft drinks and beer.

Two spectrophotometric methods, a photochemical and a non-photochemical, for the determination of ascorbic acid in soft drinks and beer using a flow-injection system are proposed. The non-photochemical method is based on the redox reaction that takes place between ascorbic acid and Fe(III), yielding dehydroascorbic acid and Fe(II). Fe(II) reacts with 1,10-phenantroline, originating the reddish orange Fe(phen)3(2+) complex (ferroin). This complex is spectrophotometrically monitored at 512 nm, and the signal is directly related to the concentration of ascorbic acid in the sample. The photochemical method has the same basis, nevertheless, uses the irradiation with visible light to enhance the redox reaction and so achieve higher sensitivities in the analysis. The non-photochemical method shows a linear range between 5 and 80 microg mL(-1), with a relative standard deviation of 1.6% (n = 11), a detection limit of 2.7 microg mL(-1) and a sample throughput of 60 samples h(-1). The photochemical method shows a linear range between 1 and 80 microg mL(-1), with a relative standard deviation of 1.0% (n = 11 ), a detection limit of 0.5 microg mL(-1) and a sample throughput of 40 samples h(-1).

Ascorbic Acid↗
PubMed2000

Experimental ulcerative colitis impairs antioxidant defense system in rat intestine.

Increasing attention has been given recently to the role of free radicals in the pathogenesis of ulcerative colitis, since the inflamed intestine is exposed to oxidative stress generated by infiltrating macrophages and neutrophils within the lamina propia. The overall goal of this study was to evaluate whether experimental ulcerative colitis induces significant changes in the antioxidant defense system in an experimental model induced by the intrarectal administration of 2,4,6-trinitrobenzenesulfonic acid. Twenty rats were treated with 80 mg/kg body weight of trinitrobenzenesulfonic acid and 20 with the same volume of 0.9% NaCl. Rats were killed at one and two weeks after treatment to evaluate colon damage by light and electron transmission microscopy. The degree of tissue injury and inflammation was determined by measuring alkaline phosphatase, gamma-glutamyltranspeptidase, and myeloperoxidase activities and prostaglandin E2 and leukotriene B4. Glutathione levels and the activity of the enzymes of the antioxidant defense system were determined. Enzymatic markers of colon injury showed higher activities in rats with ulcerative colitis. Concentrations of prostaglandin E2 and leukotriene B4 were higher in the groups treated for one week with trinitrobenzenesulfonic acid and markers decreased after two weeks of treatment. All antioxidant enzyme activities were higher at one and two weeks after treatment; however, a significant decrease in total glutathione content was also observed. In conclusion, ulcerative colitis induced by trinitrobenzenesulfonic acid damages the intestinal mucosa and is accompanied by a shift in the antioxidant enzyme activities, and low levels of glutathione. This deficiency in glutathione could be a target for new therapies to treat ulcerative colitis.

Alkaline Phosphatase↗
PubMed2000

Chronic diarrhea impairs intestinal antioxidant defense system in rats at weaning.

The aim of the present study was to evaluate the influence of severe protein-energy malnutrition on the antioxidant defense system in the small and large intestine in rats at weaning. Chronic diarrhea and the subsequent malnutrition were induced by oral intake of a lactose-enriched diet. Twenty rats were weaned at 21 days of age, and the control group was fed a semipurified synthetic diet for two weeks. The malnourished group was fed the same diet but carbohydrates were replaced by lactose, and they developed diarrhea one day after. Rats were killed, and macroscopic and histological features were analyzed, DNA content was measured, and alkaline phosphatase, myeloperoxidase, and gamma-glutamyltranspeptidase activities were determined to assess the degree of intestinal injury. Glutathione levels as well as the activities of intestinal glutathione transferase, glutathione reductase, total glutathione peroxidase, selenium-dependent glutathione peroxidase, superoxide dismutase, and catalase were measured to study the antioxidant defense system. Malnourished rats showed loss of body weight and an increase in length and weight in jejunum and ileum, while no significant changes were observed in colon. Epithelial cells showed fewer and shorter microvilli, larger mitochondria with low inner density and loss of cristae, dilated endoplasmic reticulum, and Golgi apparatus. The protein-to-DNA ratio was higher in the jejunum, ileum, and colon of malnourished rats. Glutathione levels decreased 40% in jejunum and 50% in colon of malnourished rats. A 40-50% decrease in the activity of all the enzymes of the antioxidant defense system was observed in the jejunum and ileum of malnourished rats, while only catalase and glutathione transferase activities decreased 50% in colon. These results suggest that early chronic diarrhea and severe protein-energy malnutrition impair the antioxidant defense system in both the small and large intestine, which may have a role in the pathogenesis and maintenance of the vicious circle of malabsorption-diarrhea-malnutrition in infancy.

Animals↗
PubMed2000

Use of supported liquid membranes incorporated in a flow system for the direct determination of eugenol in spice samples.

A method for the determination of eugenol in spice samples based on the use of supported liquid membranes coupled to a flow system was developed. The solid sample is placed directly in the membrane unit without any treatment and the analyte is extracted from the sample, passes through the membrane and is conducted to the flow cell by the acceptor stream. This stream flows through the detector, allowing the measurement of the analyte by using a PVC-graphite composite electrode, versus Ag/AgCl/3 M KCl at +0.3 V, placed in a well-jet flow cell as amperometric detector. The method allowed the determination of eugenol in the range 0.5-30 micrograms ml-1 with a relative standard deviation of 5%. Results provided by the proposed procedure when applied to clove and seasoning samples agreed well with those obtained by a reference method.

Electrochemistry↗
PubMed1999

Enantiomeric separation of D- and L-carnitine by integrating on-line derivatization with capillary zone electrophoresis.

A new capillary zone electrophoretic method has been developed for the enantiomeric separation and quantification of enantiomers of carnitine, D- and L-carnitine were derivatized with 9-fluorenylmethyl chloroformate in a flow system, working on-line with the capillary electrophoretic equipment. The separation was performed using a selective chiral buffer containing 2,6-dimethyl-beta-cyclodextrin (heptakis). Triethanolamine was used as electroosmotic modifier and the separation was carried out in a uncoated capillary. Under the optimal conditions the resolution between D- and L-carnitine was 1.2 and the limits of detection for both isomers were about 5.0 microM. The proposed method was applied to the determination of D-carnitine in excess of L-carnitine in synthetic samples, and the results demonstrated that the maximal D-:L-carnitine ratio determined was approximately 1:100.

Carnitine↗