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Biomedical subjects

A Ruiz

Publications and source records attributed to A Ruiz.

At least 37 records · Page 2Linked to original sources
PubMed2005

Pantak Therapax SXT 150: performance assessment and dose determination using IAEA TRS-398 protocol.

The performance assessment and beam characteristics of the Therapax SXT 150 unit, which encompass both low and medium-energy beams, were evaluated. Dose determination was carried out by implementing the International Atomic Energy Agency (IAEA) TRS-398 protocol and measuring all the dosimetric parameters in order to have a solid, consistent and reliable data set for the unit. Mechanical movements, interlocks and applicator characteristics agreed with specifications. The timer exhibited good accuracy and linearity. The output was very stable, with good repeatability, long-term reproducibility and no dependence on tube head orientation. The measured dosimetric parameters included beam first and second half-value layers (HVLs), absorbed dose rate to water under reference conditions, central axis depth dose distributions, output factors and beam profiles. Measured first HVLs agreed with comparable published data, but the homogeneity coefficients were low in comparison with typical values found in the literature. The timer error was significant for all filters and should be taken into consideration for the absorbed dose rate determination under reference conditions as well as for the calculation of treatment times. Percentage depth-dose (PDD) measurements are strongly recommended for each filter-applicator combination. The output factor definition of the IAEA TRS-398 protocol for medium-energy X-ray qualities involves the use of data that is difficult to measure. Beam profiles had small penumbras and good symmetry and flatness except for the lowest energy beam, for which a heel effect was observed.

Calibration↗
PubMed2005

[Octreotide in the treatment of angiodysplasia in patients with advanced chronic renal failure].

Angiodysplasia is an important cause of gastrointestinal bleeding in patients with chronic renal failure. Octreotide, a long-acting synthetic somatostatin analogue that reduces splachnic blood flow have been used to treat esophageal varicose hemorrhage, but its efficacy for bleeding vascular ecstasies is awaiting support. We present three patients with chronic renal failure (two with diabetic nephropaty and the third with mesangiocapilar glomerulonephritis and hepatic cirrosis), seric creatinine 3-4,5 mg/dl, and recurrent gastrointestinal bleeding due to diffuse angiodysplasia and vascular ecstasies, diagnosed by oral endoscopy, colonoscopy and video capsule. They all were treated with octreotide, administered subcutanesly 0.1 mg twice a day for six months, with significantly decreased blood requirements in all of them, as well as the occurrence of bleeding episodes. It was well tolerated and none side-effects occurred in any subject. In our experience, octreotide is an effective and safe drug in bleeding angiodysplasia and ecstasies vascular of the gastrointestinal tract in patients with chronic renal failure, and it may be a good option especially in patients who are not candidates for surgery or endoscopic treatment due to inaccessible sites, spread of the lesion, old age and/or concomitant disorders.

Adult↗
PubMed2005

[Preoperative use of intravenous iron: a new transfusional therapy].

INTRODUCTION AND OBJECTIVE: Improving preoperative hemoglobin levels reduces transfusion requirements. The availability in Spain of iron sucrose formulas with good safety profiles has added a new therapeutic option for treating anemia. The aim of this study was to demonstrate the usefulness of preoperative intravenous infusion of iron for improving hemoglobin level before elective major orthopedic surgery. PATIENTS AND METHODS: From the beginning of 2003 until July 2004, 27 consecutive patients scheduled to undergo major orthopedic surgery were given preoperative intravenous iron infusions because of intolerance to oral iron administration, poor intestinal absorption, chronic inflammatory anemia, or functional iron deficit. Twenty patients received preoperative intravenous epoetin alfa and iron and 7 received only intravenous iron because epoetin alfa therapy was ruled out due to cardiovascular or thromboembolic disease or because they had pure iron deficiency. Variables studied were age, sex, weight, type of surgery, iron dose, duration of treatment, reason for treatment, blood parameters, hemoglobin levels, and use of transfusions. RESULTS: The preoperative increase in hemoglobin was 1.7 g dL(-1) (range, 10.8-12.5) for patients who received only intravenous iron therapy and half of them were transfused, although inappropriately in 1 case. The increase in the intravenous epoetin alfa plus iron group was 1.7 g dL(-1) (range, 10.9-12.6) and only 25% were transfused. CONCLUSIONS: Intravenous iron therapy improved the preoperative hemoglobin levels in anemic patients scheduled for major orthopedic surgery. This is a new intravenous treatment approach to evaluate.

Aged↗
PubMed2005

Towards single screening tests for brucellosis.

This paper describes an indirect enzyme-linked immunosorbent assay (I-ELISA) and a fluorescence polarisation assay (FPA), each capable of detecting antibody in several species of hosts to smooth and rough members of the genus Brucella. The I-ELISA uses a mixture of smooth lipopolysaccharide (SLPS) and rough lipopolysaccharide (RLPS) as the antigen, and a recombinant protein A/G conjugated with horseradish peroxidase as the detection reagent. When using individually determined cutoff values, the SLPS/RLPS combined-antigen I-ELISA detected antibody in slightly more animals exposed to SLPS or to RLPS than did I-ELISA procedures using each individual antigen separately. Similarly, the assay using combined antigens detected antibody in slightly fewer animals not exposed to Brucella sp. When a universal cutoff of 10% positivity was used (relative to strongly positive control sera of each species), the overall performance index (percentage sensitivity plus percentage specificity) value decreased by 1.0 (from 199.4 to 198.4). In the FPA, it was not possible to use a universal cutoff without significant loss of performance. The overall sensitivity value for the FPA using the combined FPA antigen was 1.0% lower than using the O-polysaccharide (OPS) from SLPS and 9.1% higher than using the core antigen (CORE) from RLPS. When the combined antigen was used, the FPA specificity was slightly higher (1.2%) than from only the OPS, and considerably higher (12.6%) than the CORE. Overall, both the I-ELISA and the FPA with combined antigens were suitable as screening tests for all species of Brucella in the animal species tested.

Animal Diseases↗
PubMed2004

Rapid and sensitive method for determining free amino acids in honey by gas chromatography with flame ionization or mass spectrometric detection.

This paper describes a rapid, sensitive and specific method for determination of free amino acids in honey involving a new reaction of derivatization and gas chromatography (GC) with flame ionization (FID) and mass spectrometric (MS) detection. The method allows the determination of 22 free amino acids in honey samples in a short time: 8 and 5 min for GC-FID and GC-MS, respectively. Quantitation was performed using Norvaline as internal standard, with detection limits ranging between 0.112 and 1.795 mg/L by GC-FID and between 0.001 and 0.291 mg/L by GC-MS in the selected-ion monitoring mode. The method was validated and applied to a set of 74 honey samples belonging to four different botanical origins: eucaliptus, rosemary, orange and heather. The statistical treatment of data shows a correct classification of different origins over 90%.

Amino Acids↗
PubMed2004

Enzyme immunoassay for the diagnosis of brucellosis: chimeric Protein A-Protein G as a common enzyme labeled detection reagent for sera for different animal species.

A recombinant protein combining the immunoglobulin binding sites of Proteins A and G, conjugated with horseradish peroxidase was used as a universal detection reagent for the assessment of antibodies against Brucella spp. The reagent was applied in an indirect enzyme immunoassay for detection of antibodies to smooth lipopolysaccharide antigen in sera from Brucella spp. exposed and non-exposed cattle, sheep, goats and pigs and to antibodies to rough lipopolysaccharide in sheep, dogs and cattle. The results were similar to those obtained when murine monoclonal antibody-enzyme conjugates were used. An added advantage was that a universal cut-off for all tests using the proteins A and G detection reagent could be established, simplifying diagnostic interpretation of the data.

Animals↗
PubMed2004

Phase II study of capecitabine in combination with paclitaxel in patients with anthracycline-pretreated advanced/metastatic breast cancer.

The addition of oral capecitabine to docetaxel improves response rate, time to progression (TTP) and overall survival in anthracycline-pretreated metastatic breast cancer (MBC). This phase II study evaluates the efficacy and safety of a 21-day cycle of oral capecitabine (1000 mg m(-2) twice daily, days 1-14) plus i.v. paclitaxel (175 mg m(-2), day 1) in anthracycline-pretreated advanced/MBC. In all, 73 patients were enrolled at 13 Swedish and Spanish centres. The objective response rate was 52% (95% confidence interval (CI): 40-63%) in the intent-to-treat population, including complete responses in 11%. Disease was stabilised in a further 29%. The median time to disease progression (TTP) was 8.1 months and the median overall survival was 16.5 months. The combination was generally well tolerated with a predictable safety profile. The most common treatment-related nonhaematological adverse events were hand-foot syndrome (42%), alopecia (30%) and diarrhoea (26%). The only treatment-related Grade 3/4 adverse events occurring in >5% of patients were alopecia (22%) and hand-foot syndrome (11%). Grade 3/4 neutropenia and lymphocytopenia were reported in 12 and 14% of patients, respectively. Capecitabine plus paclitaxel is highly active with a favourable safety profile in anthracycline-pretreated MBC.

Adolescent↗
PubMed2004

A theoretical model of the photoabsorption spectra of carbon buckyonions.

A theoretical model has been developed to predict the photoabsorption spectra of spherical carbon buckyonions in the region dominated by the pi-plasmon feature. This model makes use of the microscopic electronic structure of the system, which is provided by an effective Huckel one-electron model. The important screening effects are treated within the random phase approximation, whose form is an extension to the dynamic case of the one derived in a previous work for the static polarizabilities of these species. A systematic analysis as a function of the buckyonion size is performed. We compare the spectra obtained in this way with those derived from a different representation of the electron motion, namely a two-dimensional spherical electron gas, and from a classical dielectric model.

Journal Article↗
PubMed2004

Genetic variability in cysteine protease genes of Haemonchus contortus.

To increase the existent genetic variability in cysteine proteases, a polymorphism study was performed in Haemonchus contortus by comparing 2 different strains of the parasite: North American (NA) and Spanish (SP) strains. For this purpose, the polymorphism of 5 previously reported genes (AC-1, AC-3, AC-4, AC-5 and GCP-7) were analysed by PCR-SSCP and sequencing procedures. Based on the SSCP results, a total of 20 different alleles were identified for the 5 loci assessed. Except locus AC-5, all the loci were polymorphic. Loci AC-1, AC-3, AC-4 and GCP-7 showed 5, 8, 2 and 4 alleles, respectively. The allelic frequencies ranged from 0.0070 to 0.8560 and were significantly different between strains. In addition, nucleotide diversity analyses showed a significant variation within and between strains. The variations in the nucleotide sequence of the different alleles were translated in some cases into changes in the amino acid sequence. Evidence of genetic variability in cysteine proteases from two different strains of H. contortus for the same set of genes had not been previously reported.

Alleles↗
PubMed2004

Physical characteristics of polymer complexes in suspension obtained from cellulosic latexes with ondansetron.

Ondansetron is a carbazol with antiemetic properties. It is used primarily to control nausea and vomiting caused by cytotoxic chemotherapy and radiotherapy, as well as in postoperative vomiting in gynecological surgery. Ondansetron has a half-life of approximately 4 h, hence it is a matter of great interest to determine the ideal conditions for the formation of a drug-polymer complex in order to prolong the duration of the therapeutic action. A stability study of the active drug was first carried out on each of the polymers (Aquateric and Aquacoat). The adsorption of ondansetron on the lattices was determined with respect to time, pH and concentration. The results obtained suggest that both polymers are suitable as drug carriers for the controlled-release formulations obtained. We conclude that an acid pH is evidently fundamental in the adsorption process of this drug in the latexes. Moreover, the Aquateric latex would seem to be the best-suited polymer to use as a vehicle for drug delivery.

Adsorption↗
PubMed2004

Comparison study of MOSFET detectors and diodes for entrance in vivo dosimetry in 18 MV x-ray beams.

The feasibility of dual bias dual metal oxide semiconductor field effect transistors (MOSFETs) for entrance in vivo dose measurements in high energy x-rays beams (18 MV) was investigated. A comparison with commercially available diodes for in vivo dosimetry for the same energy range was performed. As MOSFETs are sold without an integrated build-up cap, different caps were tested: 3 cm bolus, 2 cm bolus, 2 cm hemispherical cap of a water equivalent material (Plastic Water) and a metallic hemispherical cap. This metallic build-up cap is the same as the one that is mounted on the in vivo diode used in this study. Intrinsic precision and response linearity with dose were determined for MOSFETs and diodes. They were then calibrated for entrance in vivo dosimetry in an 18 MV x-ray beam. Calibration included determination of the calibration factor in standard reference conditions and of the correction factors (CF) when irradiation conditions differed from those of reference. Correction factors for field size, source surface distance, wedge, and temperature were determined. Sensitivity variation with accumulated dose and the lifetime of both types of detectors were also studied. Finally, the uncertainties of entrance in vivo measurements using MOSFET and diodes were discussed. Intrinsic precision for MOSFETs for the high sensitivity mode was 0.7% (1 s.d.) as compared to the 0.05% (1 s.d.) for the studied diodes. The linearity of the response with dose was excellent (R2 = 1.000) for both in vivo dosimetry systems. The absolute values of the studied correction factors for the MOSFETs when covered by the different build-up caps were of the same order of those determined for the diodes. However, the uncertainties of the correction factors for MOSFETs were significantly higher than for diodes. Although the intrinsic precision and the uncertainty on the CF was higher for MOSFET detectors than for the studied diodes, the total uncertainty in entrance dose determination, once they were calibrated, was of 2.9% (1 s.d.) while for diodes it was 2.0% (1 s.d.). MOSFETs showed no sensitivity variation with accumulated dose or temperature. When used in the high sensitivity mode, after approximately 50 Gy of accumulated dose MOSFETs could no longer be used as radiation dosimeters. In conclusion, MOSFETs can be used for entrance in vivo dosimetry in high energy x-rays beams if covered by an appropriate build-up cap. Metallic build-up caps, such as those used for in vivo diodes, have the advantage of greater patient comfort and less perturbation of the treatment field than the other build-up caps tested, while keeping the correction factors of the same order.

Body Burden↗
PubMed2004

Comparison of dose calculation algorithms in phantoms with lung equivalent heterogeneities under conditions of lateral electronic disequilibrium.

An extensive set of benchmark measurement of PDDs and beam profiles was performed in a heterogeneous layer phantom, including a lung equivalent heterogeneity, by means of several detectors and compared against the predicted dose values by different calculation algorithms in two treatment planning systems. PDDs were measured with TLDs, plane parallel and cylindrical ionization chambers and beam profiles with films. Additionally, Monte Carlo simulations by means of the PENELOPE code were performed. Four different field sizes (10 x 10, 5 x 5, 2 x 2, and 1 x 1 cm2) and two lung equivalent materials (CIRS, p(w)e=0.195 and St. Bartholomew Hospital, London, p(w)e=0.244-0.322) were studied. The performance of four correction-based algorithms and one based on convolution-superposition was analyzed. The correction-based algorithms were the Batho, the Modified Batho, and the Equivalent TAR implemented in the Cadplan (Varian) treatment planning system and the TMS Pencil Beam from the Helax-TMS (Nucletron) treatment planning system. The convolution-superposition algorithm was the Collapsed Cone implemented in the Helax-TMS. The only studied calculation methods that correlated successfully with the measured values with a 2% average inside all media were the Collapsed Cone and the Monte Carlo simulation. The biggest difference between the predicted and the delivered dose in the beam axis was found for the EqTAR algorithm inside the CIRS lung equivalent material in a 2 x 2 cm2 18 MV x-ray beam. In these conditions, average and maximum difference against the TLD measurements were 32% and 39%, respectively. In the water equivalent part of the phantom every algorithm correctly predicted the dose (within 2%) everywhere except very close to the interfaces where differences up to 24% were found for 2 x 2 cm2 18 MV photon beams. Consistent values were found between the reference detector (ionization chamber in water and TLD in lung) and Monte Carlo simulations, yielding minimal differences (0.4%+/-1.2%). The penumbra broadening effect in low density media was not predicted by any of the correction-based algorithms, and the only one that matched the experimental values and the Monte Carlo simulations within the estimated uncertainties was the Collapsed Cone Algorithm.

Algorithms↗
PubMed2004

[Treatment of hyperphosphatemia with sevelamer in patients with chronic renal failure].

UNLABELLED: Sevelamer is a recent phosphate binder that is mineral-free, and represents a great advance in the treatment of hyperphosphatemia in patients with hypercalcemia and/or gastric intolerance to calcium-based phosphate binders. The communications about the experience with the use of sevelamer in patients non-yet in dialysis is scanty. The aim of our study is to investigate retrospectively the gastrointestinal tolerance of sevelamer, their efficacy as phosphate binder and other parameters in a group of 89 patients with chronic renal failure in predialysis. We have analysed the effects of sevelamer at baseline and after 1, 3 and 6 months on the following data and parameters: calcium, phosphate, intact PTH, venous bicarbonate, urea, creatinine, creatinine clearance, side-effects, number of patients that were discontinued, and co-treatment during the study period with phosphate-based binders, calcitriol, lipid-lowering drugs and sodium bicarbonate. RESULTS: 19 patients (21.3%) refused to continue with sevelamer at the first month (16 patients had digestive intolerance and 3 several symptoms). Serum phosphate fell at 3 months (5 +/- 0.8 mg/dl basal vs 4.8 +/- 0.7 mg/dl, p = 0.02) and 6 months (5 +/- 0.8 mg/dl basal vs 4.7 +/- 0.9 mg/dl, p = 0.07). Serum calcium fell at 6 months (9.8 +/- 0.7 mg/dl basal vs 9.4 +/- 0.6 mg/dl, p = 0.03). Venous bicarbonate and iPTH were unchanged, but the quantity of sodium bicarbonate administered increased significantly. Blood cholesterol fell at 1 months (193 +/- 49 mg/dl basal vs 173 +/- 52 mg/dl, p = 0.001) and 3 months (205 +/- 49 mg/dl basal vs 170 +/- 49 mg/dl, p = 0.004), in spite of a significant reduction of the dose of statins. CONCLUSIONS: Sevelamer is an effective phosphate binder in predialysis patients and also reduces significantly the serum cholesterol, improving the blood lipid profile. The levels of venous bicarbonate remained unchanged, at expenses of an increment in the dose of sodium bicarbonate supplementation.

Acid-Base Equilibrium↗
PubMed2004

Expression of vitamin D3 receptor and retinoid receptors in human breast cancer: identification of potential heterodimeric receptors.

Vitamin D3 (VD) and all-trans-retinoic acid (ATRA) have been postulated as a novel treatment option for breast carcinoma. Since the combined effects of retinoids and VD derivatives are attributed to heterodimeric interactions between members of the nuclear receptor family, the expression patterns of the heterodimers formed by vitamin D3 receptor (VDR) and the retinoid receptors RARs (RAR-alpha, RAR-beta and RAR-gamma) and RXRs (RXR-alpha, RXR-beta and RXR-gamma) have been studied by immunohistochemistry in benign and malignant breast tissues. Present results revealed that immunoexpressions to all receptor types studied were higher in both in situ and infiltrative carcinomas than in benign breast diseases. In a variable number of cases of infiltrative carcinoma, immunostaining appeared in the nucleus, whereas in the other two disorders immunostaining was only cytoplasmic. The correlation established between VDR and the different isoforms of retinoid receptors revealed that VDR seems to select mainly RAR-alpha to form heterodimers and to exert their properties as transcription factor. The results of this study suggest that this heterodimer plays a critical role in cancer malignancy, and its presence indicates those patient groups presenting a better response to adjuvant therapies based on the combination of vitamin D and ATRA.

Adult↗