Biomedical subjects

A Marín

Publications and source records attributed to A Marín.

At least 19 recordsLinked to original sources

PubMed2006

Leptonic and charged kaon decay modes of the phi meson measured in heavy-ion collisions at the CERN super proton synchrotron.

We report on results of a measurement of meson production in central Pb-Au collisions at E(lab) = 158A GeV. For the first time in the history of high energy heavy-ion collisions, phi mesons were reconstructed both in the K+K- and the dilepton decay channels in the same experiment. This measurement yields rapidity densities near midrapidity, from the two decay channels, of 2.05 +/- 0.14(stat) +/- 0.25(syst) and 2.04 +/- 0.49(stat) +/- 0.32(syst), respectively. The shape of the measured transverse momentum spectrum is also in close agreement in both decay channels. The data rule out a possible enhancement of the phi yield in the leptonic over the hadronic decay channel of a factor 1.6 or larger at the 95% C.L. This rules out the discrepancy reported in the literature between measurements of the hadronic and dimuon decay channels by two different experiments.

Journal Article↗

PubMed2006

Dose escalation with three-dimensional conformal radiotherapy for prostate cancer. Is more dose really better in high-risk patients treated with androgen deprivation?

AIMS: To determine the effect of radiation dose on biochemical control in prostate cancer patients treated in a single institution with three-dimensional conformal radiotherapy (3DCRT) and the additional effect of androgen deprivation in prostate cancer patients. MATERIALS AND METHODS: In total, 363 men with T1-T3b prostate cancer treated in a sequential radiation dose-escalation trial from 66.0 to 84.1 Gy (International Commission Radiation Units and Measurement [ICRU] reference point) between 1995 and 2003, and with a minimum follow-up of 24 months, were included in the analysis. One hundred and forty-eight (41%) men were treated with 3DCRT alone; 74 (20%) men received neoadjuvant androgen deprivation (NAD) 4-6 months before and during 3DCRT; and 141 (39%) men received NAD and adjuvant androgen deprivation (AAD) 2 years after 3DCRT. Univariate, stratified and multivariate analyses were carried out separately for defined risk groups (low, intermediate and high) to determine the effect of radiation dose on biochemical control and its interaction with hormonal manipulation and clinical prognostic variables. RESULTS: The median follow-up was 59 months (range 24-147 months). The actuarial biochemical disease-free survival (bDFS) at 5 years for all patients was 75% (standard error 3%). For low-risk patients, the bDFS was 82% (standard error 5%), for intermediate-risk patients it was 64% (standard error 6%) and for high-risk patients it was 77% (standard error 3%) (P = 0.031). In stratified and multivariate analyses, high-dose 3DCRT for all risk groups, and for high-risk patients, the use of long-term AAD vs NAD, contributed independently and significantly to improve the outcome of prostate cancer patients. CONCLUSION: The present study indicates an independent benefit on biochemical outcome of high-dose 3DCRT for low-, intermediate- and high-risk patients and of long-term AAD in high-risk prostate cancer patients.

Aged↗

PubMed2006

[Effectiveness and efficiency of a specialized unit in the care of patients with chronic obstructive pulmonary disease and respiratory insufficiency].

OBJECTIVE: In the absence of a clear health care model for the management of patients with chronic obstructive pulmonary disease and chronic respiratory insufficiency, we evaluated the effectiveness and efficiency of a specialized outpatient unit for these patients managed by the hospital s respiratory medicine department. PATIENTS AND METHODS: This was a 1-year prospective study of a group of patients for whom historical control data were available. The mean (SD) descriptive data for the 124 patients (105 men) were as follows: age, 69 (7) years; forced vital capacity, 64.6% (16.1%); forced expiratory volume in the first second (FEV1), 35.6% (12.8%); PaO2, 56.6 (8.3) mm Hg; PaCO2, 49.8 (6.7) mm Hg. Forced spirometry and arterial blood gas analysis were performed at 3-monthly visits. Participants completed a quality-of-life questionnaire (Guyatt's Chronic Respiratory Disease Questionnaire) at the beginning and end of the study. The following variables were analyzed: forced spirometry, arterial blood gases, quality of life, number of emergency visits and hospital admissions, mean length of stay in hospital, reduction in the number of inpatient bed-days, mean cost of emergency visits, mean cost of hospital stays for both the Catalan Health Service (CHS) and the hospital, mean total cost per patient for the CHS and the hospital, and aggregate cost for the CHS and the hospital. The results were compared with data for the preceding year taken from the hospital records. RESULTS: Significant improvement was found in forced vital capacity and PaO2 (which went from 56.6 [8.2] mm Hg to 59.1 [8.9] mm Hg during the prospective part of the study); FEV1 also tended to improve (875 [282] mL as against 912 [321] mL), but this change was not significant (P= .17). A significant reduction was observed in the following variables: PaCO2; hospital admissions, 1.16 (1.15) in the historical control period compared to 0.67 (1.17) during the prospective study; emergency visits, 2.06 (1.9) as against 1.5 (2.1); mean length of stay in hospital, 14.2 (19) compared to 8.1 (16) days; total number of inpatient bed-days (756 inpatient bed-days were saved in the study period); mean cost of emergency visits and hospital stays for both the hospital (2246 euros [3007 euros] in the historical period as against 1297 euros [2639 euros] with the new management system) and for the CHS; and the aggregate cost both for the hospital (40,011 euros in the historical control period as against 6048 euros with the new model) and the CHS (238,513 euros as against 152,312 euros). The quality-of-life score improved, but the change was not significant. CONCLUSIONS: The change in the health care model used to manage these patients led to an improvement in care (effectiveness) as well as a marked reduction in costs (greater efficiency) for both the funding entity (CHS) and for the care provider (the hospital). No change was observed in the quality of life as reported by the patients.

Aged↗

PubMed2006

[Transcutaneous measurement of partial pressure of carbon dioxide and oxygen saturation: validation of the SenTec monitor].

OBJECTIVE: To validate a monitor for transcutaneous measurement of oxygen saturation (SpO2) and partial pressure of carbon dioxide (TcPCO2). PATIENTS AND METHODS: This observational study included 140 Caucasian nonsmokers without jaundice. Patients underwent forced spirometry, measurement of SpO2 and TcPCO2 with the SenTec monitor, and arterial blood gas analysis (readings with 2 devices) during the stabilization phase of the monitor. In the statistical analysis, values from the 2 devices for measuring arterial blood gases were compared by mean differences for PaCO2 and oxygen saturation (SaO2). The arithmetic mean of the 2 blood gas measurements was calculated and relations between them and the SpO2 and TcPCO2 were assessed by the Pearson correlation coefficient (r) and the intraclass correlation coefficient (ICC) as a measure of agreement. Bland-Altman analysis was used to test data dispersion. RESULTS: Ten patients were excluded due to a systematic error in the gas calibrator. The mean (SD) time to stabilization of the monitor before reading was 13.9 (2.4) minutes. The forced expiratory volume in the first second was greater than 80% in 40 patients, between 60% and 79% in 23, between 40% and 59% in 30, and less than 40% in 37. The mean (SD) differences between arterial blood gas measurements were 0.28 (1.0) mm Hg for PaCO2, -0.06% (0.86%) for SaO2, and -0.9 (2.7) mm Hg for PaO2. In the tests for correlation and agreement, r was 0.74 and ICC was 0.73 for SaO2 and SpO2; r was 0.92 and ICC was 0.92 for PaCO2 and TcPCO2. The subgroup analyses did not show any noteworthy differences. The Bland Altman analysis showed no significant dispersion. It was observed that the SenTec monitor underestimated oxygen saturation values by around 1% with respect to SaO2 and overestimated carbon dioxide pressure by 1 mm Hg with respect to PaCO2 values. CONCLUSIONS: The stabilization time recommended for the SenTec monitor before taking a reading is 20 minutes. The overestimates and underestimates by the monitor are not clinically relevant. Finally, the values for SpO2 and TcPCO2 measured by the validated monitor are reliable.

Blood Gas Monitoring, Transcutaneous↗

PubMed2005

Systematic comparison of different functionality columns for a classical pharmaceutical problem.

The performance of five reversed-phase columns which included a standard C18 phase, a polar embedded phase (amide group), a polyethyleneglycol phase, a cyano phase, and a perfluorinated phase, all coming from the same manufacturer, have been studied. They were systematically compared with a test mixture containing basic, neutral and acidic compounds of very different polarities, as well as different functional groups (acetaminophen, phenylephrine hydrochloride or phenylpropanolamine hydrochloride, chlorpheniramine maleate, 4-aminophenol, 4-chloracetanilide and 4-nitrophenol) at three pH levels (2.5, 4.6 and 7.0) and three proportions of buffer/acetonitrile (80:20, 50:50 and 20:80, v/v). The results obtained have permitted our group to develop unique applications with these columns, as these compounds are not only a test mixture, due to their chemical characteristics, but they are also usually contained in pharmaceutical formulations for the relief of common cold symptoms and have been selected as a real-life case study. Moreover, after observing the reversed-phase and normal-phase-like characteristics for certain analytes on the perfluorinated phase, a systematic study was developed in this column to understand the chromatographic behaviour of these compounds at three pH (2.5, 4.6 and 7.0) and seven different organic proportions from 20 to 80% acetonitrile. The predominant electrostatic interactions observed on the perfluorinated phase could explain its special behaviour and the high retention at higher percentages of organic solvent, especially for amine compounds, which makes this column very advantageous in working with LC/MS. Different applications with volatile buffers, such as TFA at pH 2.5 and ammonium acetate at pH 4.6 and 7.0, were also considered. Some results have been related to parameters frequently employed for column description.

Acetaminophen↗

PubMed2005

Comparative gene expression profile of mouse carotid body and adrenal medulla under physiological hypoxia.

The carotid body (CB) is an arterial chemoreceptor, bearing specialized type I cells that respond to hypoxia by closing specific K+ channels and releasing neurotransmitters to activate sensory axons. Despite having detailed information on the electrical and neurochemical changes triggered by hypoxia in CB, the knowledge of the molecular components involved in the signalling cascade of the hypoxic response is fragmentary. This study analyses the mouse CB transcriptional changes in response to low PO2 by hybridization to oligonucleotide microarrays. The transcripts were obtained from whole CBs after mice were exposed to either normoxia (21% O2), or physiological hypoxia (10% O2) for 24 h. The CB transcriptional profiles obtained under these environmental conditions were subtracted from the profile of control non-chemoreceptor adrenal medulla extracted from the same animals. Given the common developmental origin of these two organs, they share many properties but differ specifically in their response to O2. Our analysis revealed 751 probe sets regulated specifically in CB under hypoxia (388 up-regulated and 363 down-regulated). These results were corroborated by assessing the transcriptional changes of selected genes under physiological hypoxia with quantitative RT-PCR. Our microarray experiments revealed a number of CB-expressed genes (e.g. TH, ferritin and triosephosphate isomerase) that were known to change their expression under hypoxia. However, we also found novel genes that consistently changed their expression under physiological hypoxia. Among them, a group of ion channels show specific regulation in CB: the potassium channels Kir6.1 and Kcnn4 are up-regulated, while the modulatory subunit Kcnab1 is down-regulated by low PO2 levels.

Adrenal Medulla↗

PubMed2005

New approaches with two cyano columns to the separation of acetaminophen, phenylephrine, chlorpheniramine and related compounds.

The development of new pharmaceutical forms with classical active compounds generates new analytical problems. That is the case of sugar-free sachets of cough-cold products containing acetaminophen, phenylephrine hydrochloride and chlorpheniramine maleate. Two cyanopropyl stationary phases have been employed to tackle the problem. The Discovery cyanopropyl (SUPELCO) column permitted the separation of the three actives, maleate and excipients (mainly saccharine and orange flavour) with a constant proportion of aqueous/ organic solvent (95:5, v/v) and a pH gradient from 7.5 to 2. The run lasted 14 min. This technique avoids many problems related to baseline shifts with classical organic solvent gradients and opens great possibilities to modify selectivity not generally used in reversed phase HPLC. On the other hand, the Agilent Zorbax SB-CN column with a different retention profile permitted us to separate not only the three actives and the excipients but also the three known related compounds: 4-aminophenol, 4-chloracetanilide and 4-nitrophenol in an isocratic method with a run time under 30 min. This method was validated following ICH guidelines and validation parameters showed that it could be employed as stability-indicating method for this pharmaceutical form.

Acetaminophen↗

PubMed2005

Major degradation product identified in several pharmaceutical formulations against the common cold.

Different pharmaceutical preparations against the common cold containing acetaminophen, phenylephrine hydrochloride, and chlorpheniramine have been studied. An unidentified degradation product has been discovered in these preparations after short- and long-term stability studies, with increasing concentration at increasing storage temperatures and times. LC/MS was employed to identify and obtain molecular weights of the degradation products using an electrospray ionization interface. To obtain detailed structural information on the major degradation product, its isolation by SPE followed by HPLC was required. Final isolation was accomplished by using a new pentafluorophenyl stationary phase. Once the major degradation product was isolated, MS/MS, 1H NMR, 13C NMR, COSY, HMBC, and HSQC techniques permitted the complete characterization of this new compound formed under the usual stability conditions at climatic chambers. Its origin was also established as a result of the interaction between two of the components in the formulation. It is important to remark that this compound has not been described in the literature up to now and that, moreover, it has been identified in several commercial preparations containing phenylephrine hydrochloride and chlorpheniramine maleate.

Chromatography, High Pressure Liquid↗

PubMed2005

[Dose escalation with three dimensional conformal radiotherapy for prostate cancer: more is better?].

PURPOSE: The present study was undertaken to determine the effect of radiation dose on biochemical control and morbidity in prostate cancer patients. MATERIALS AND METHODS: Between 1995 and 2003, 360 patients with T1-T3b prostate cancer were treated in a sequential radiation dose escalation trial from 66.0 to 82.6 Gy. These patients were prospectively assigned to 1 of 3 prognostic groups according to risk factors: a) low risk patients were treated with 3DCRT alone; b) intermediate risk patients were allocated to receive neoadjuvant AD (NAD) 4-6 months prior and during 3DCRT; and c) high-risk received NAD and adjuvant AD (AAD) 2 years after 3DCRT. RTOG/EORTC toxicity score was used to analyze late complications RESULTS: Median follow-up was 48 months (12-138). The actuarial biochemical disease free survival (bDFS) at 4 years for low risk, intermediate risk and high risk patients was 88%, 68% and 79% respectively. Stratified and multivariate analysis showed that higher radiation dose (>76 Gy) (p=0.0053) and the use of AAD for high risk patients (p=0.0046) correlated significantly with an improvement of bDFS for all patients. The incidence of late grade 2 rectal and urinary bleeding were 7% and 11% respectively. CONCLUSION: The present study confirms an independent benefit of high-dose (> 76 Gy) radiation therapy and long-term AAD in high-risk prostate cancerpatients.

Aged↗

PubMed2004

LC/MS for the degradation profiling of cough-cold products under forced conditions.

Heat, acid, base, UV radiation and oxidation stress methods were applied to study the stability of cough-cold products containing acetaminophen, phenylephrine or phenylpropanolamine hydrochloride and chlorpheniramine maleate. Liquid chromatography coupled with mass spectrometry was used to analyze the degraded samples and obtain molecular weights information. Different volatile buffers (ammonium bicarbonate and ammonium acetate) were assayed in LC/MS methods and retention times of the analytes were compared with those obtained in HPLC with UV detection employing a conventional sodium phosphate buffer to establish the possibility of results transference between the two systems.

Acetaminophen↗

PubMed2004

CE versus HPLC for the dissolution test in a pharmaceutical formulation containing acetaminophen, phenylephrine and chlorpheniramine.

A new polar reverse phase stationary phase has permitted our group to develop and validate an isocratic HPLC method for the simultaneous determination of acetaminophen, phenylephrine and chlorpheniramine in capsules as pharmaceutical formulation after their dissolution test. Final optimised chromatographic conditions employed a Supelco Discovery HS PEG column (polyethylene glycol), 5 microm, 15 cm x 0.46 cm. The mobile phase was 20 mM phosphate buffer at pH 7.0/acetonitrile 80:20 (v/v) at a flow rate of 1 ml/min. UV detection was performed at 210 nm for phenylephrine and chlorpheniramine and at 305 nm for acetaminophen. On the other hand, to evaluate the capability of CE to work in a routine analytical method fulfilling the pharmaceutical requirements and to study the behaviour of the technique with these compounds, we developed a CE method with the same objective. Normal and reverted polarity, the pH and concentration of the buffer, and the presence and concentration of surfactants were assayed. Forty millimolar phosphate buffer at pH 6.20 with 0.5 mM SDS at 30k V in an uncoated silica capillary provided a runtime of 4.5 min to separate the three analytes and the excipients. Moreover, parameters affecting precision in CE, such as the injection of buffer after the sample to refill the capillary were also tested. After development, the validation was performed in parallel for HPLC and CE with the same standards and samples to avoid differences due to the manipulation. The validation parameters of both techniques were adequate for the intended purpose.

Acetaminophen↗

PubMed2004

Assessment of potential (inhalation and dermal) and actual exposure to acetamiprid by greenhouse applicators using liquid chromatography-tandem mass spectrometry.

New analytical methods based on liquid chromatography with electrospray tandem mass spectrometry (LC-MS/MS) have been developed and validated for assessing the exposure of greenhouse workers to acetamiprid. Both ambient (potential inhalation and dermal exposure) and internal dose (biological monitoring of urine samples) measurements were carried out. Potential inhalation exposure was assessed using Chromosorb 102 cartridges connected to air personal samplers. Potential dermal exposure was estimated by using whole body dosimetry. The measurement of actual exposure was done by analyzing the parent compound in urine samples of the applicators, after a solid-phase extraction (SPE) step. The methods showed a good accuracy (72-92%), precision (2-13%) and lower limits (few microg l(-1)). The validated approaches have been applied to assess potential and actual exposure of agricultural workers spraying acetamiprid in greenhouses. The results shown the need to wear personal protective equipment (suits) in order to reduce the absorbed dose of acetamiprid.

Chromatography, Liquid↗

PubMed2004

Semihard scattering unraveled from collective dynamics by two-pion azimuthal correlations in 158A GeV/c Pb+Au collisions.

Elliptic flow and two-particle azimuthal correlations of charged hadrons and high-p(T) pions (p(T)>1 GeV/c) have been measured close to midrapidity in 158A GeV/c Pb+Au collisions by the CERES experiment. Elliptic flow (v(2)) rises linearly with p(T) to a value of about 10% at 2 GeV/c. Beyond p(T) approximately 1.5 GeV/c, the slope decreases considerably, possibly indicating a saturation of v(2) at high p(T). Two-pion azimuthal anisotropies for p(T)>1.2 GeV/c exceed the elliptic flow values by about 60% in midcentral collisions. These nonflow contributions are attributed to nearside and back-to-back jetlike correlations, the latter exhibiting centrality dependent broadening.

Journal Article↗

PubMed2003

Enhanced production of low-mass electron-positron pairs in 40-AGeV Pb-Au collisions at the CERN SPS.

We report on first measurements of low-mass electron-positron pairs in Pb-Au collisions at the CERN SPS beam energy of 40 AGeV. The observed pair yield integrated over the range of invariant masses 0.2 e(+)e(-) annihilation with a modified rho propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the rho are more driven by baryon density than by temperature.

Journal Article↗

PubMed2003

Poly(ethyleneglycol) column for the determination of acetaminophen, phenylephrine and chlorpheniramine in pharmaceutical formulations.

New polar reversed-phase stationary phases in HPLC provide specific selectivities which can help to solve traditional chromatographic problems related to the development of chromatographic methods with widely different retention times for the sample components. One such case is the analysis of pharmaceutical formulations against the common cold. Acetaminophen, phenylephrine and chlorpheniramine, compounds with different polarities, are frequently associated in these drugs. An isocratic and rapid HPLC method for the simultaneous determination of the three compounds, acetaminophen, phenylephrine and chlorpheniramine, in capsules as pharmaceutical formulations, including the separation of impurities (4-aminophenol and 4-chloracetanilide) and excipients, has been developed and validated. The final chromatographic conditions employed a Supelco Discovery HS PEG column poly(ethyleneglycol) 15x0.46 cm, 5 microm. The mobile phase was 20 mM phosphate buffer, pH 7.0-acetonitrile (90:10, v/v) at a flow-rate of 1 ml/min. UV detection was performed at 215 nm for all the compounds except acetaminophen, which was measured at 310 nm. Validation parameters permit us to consider this method suitable.

Acetaminophen↗

PubMed2003

Universal pion freeze-out in heavy-ion collisions.

Based on an evaluation of data on pion interferometry and on particle yields at midrapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda(f) reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from the Alternating Gradient Synchrotron to the Relativistic Heavy Ion Collider.

Journal Article↗

PubMed2003

Long-term effects of almitrine bismesylate in COPD patients with chronic hypoxaemia.

BACKGROUND: Almitrine bismesylate (AB) is a peripheral chemoreceptor agonist which is believed to improve oxygenation of COPD patients with chronic hypoxaemia, probably by improving the ventilation perfusion mismatch. We studied the long-term effects of AB in COPD patients with chronic hypoxaemia. METHODS DESIGN: Prospective, randomised, double-blind, placebo-controlled trial. SETTING: Eight hundred bed teaching hospital with a catchment population of 350,000 inhabitants. PATIENT RECRUITMENT: COPD outpatients consulting between September 95 and September 99. INCLUSION CRITERIA: (1) COPD (FEV1 < 50%). (2) PaO2 < or = 65 mmHg. (3) Stable arterial blood gases (ABG), spirometry (S) and clinical state. EXCLUSION CRITERIA: Asthma, restrictive disease, sleep apnoea syndrome, advanced renal or hepatic disease, peripheral neuropathy, use of respiratory stimulants or psychotrophic drugs. TREATMENT: AB 1 mg/kg/day (weight < 75 kg = 50 mg/day; weight > or = 75 kg = 100 mg/day) in an intermittent schedule with resting periods of 1 month after the third, 6th and 9th months during 1 year. INSTRUMENTATION: Stabilisation period: S, ABG. Run-in period: S, ABG, 6-min walking test (WT), nocturnal pulse oximetry (NP) and quality of life evaluation (CRQ). Third, 6th and 9th months: S, ABG. End of the study: S, ABG, WT, NP, CRQ. STATISTICS: ANOVA for repeated measurements. RESULTS: Two hundred and eighty-nine patients were evaluated and 81 were included in the study. Sixty-six were followed for 6 months, 53 for 9 months and 42 for 1 year. Almitrine and placebo groups did not present significant differences in ABG and S in the 6th, 9th and 12th months. Evolution in WT, NP and CRQ were similar in the two groups. No relevant side-effects were detected: only two patients stopped treatment (one placebo and one AB). CONCLUSION: In an intermittent schedule, although well tolerated, at doses of 1 mg/kg/day, AB was not effective in long-term treatment of chronic hypoxemia in COPD patients.

Aged↗

PubMed2002

Validation of a HPLC quantification of acetaminophen, phenylephrine and chlorpheniramine in pharmaceutical formulations: capsules and sachets.

Acetaminophen, phenylephrine and chlorpheniramine are frequently associated in pharmaceutical formulations against the common cold. Their quantification presents several problems. A HPLC method for the simultaneous determination of these compounds in pharmaceutical formulations such as capsules and sachets, including the separation of impurities and excipients has been developed and validated. The selectivity of the method was also tested to be used if phenylpropanolamine hydrochloride were employed instead of phenylephrine. Final chromatographic conditions were a gradient elution, being solvent A: phosphate buffer 40 mM at pH 6.0 and solvent B: acetonitrile. At t=0, the mobile phase consisted of 92% A and 8% B and it changed with a linear gradient during 8 min to 75% A and 25% B. At min 8, it changed to 30% A and 70% B for 5 min and at t=15 min, it returns to the initial conditions (92% A and 8% B) during 1 min remaining at this composition until t=20 min. UV detection was performed at 215 nm for phenylephrine and chlorpheniramine, because at this wavelength sensitivity was higher than in other more characteristic wavelengths and it was necessary for the detection of minor compounds. For acetaminophen 280 nm was employed. Validation parameters permit to consider the method adequate.

Acetaminophen↗