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Biomedical subjects

C León

Publications and source records attributed to C León.

At least 19 recordsLinked to original sources

Phenylsulphonyl urenyl chalcone derivatives as dual inhibitors of cyclo-oxygenase-2 and 5-lipoxygenase.

Two series of phenylsulphonyl urenyl chalcone derivatives (UCH) with various patterns of substitution were tested for their effects on nitric oxide (NO) and prostaglandin E2 (PGE2) overproduction in RAW 264.7 macrophages. None of the tested compounds reduced NO production more than 50% at 10 microM but most of them inhibited the generation of PGE2 with IC50 values under the micromolar range. Me-UCH 1, Me-UCH 5, Me-UCH 9, Cl-UCH 1, and Cl-UCH 9 were selected to evaluate their influence on human leukocyte functions and eicosanoids generation. These derivatives selectively inhibited cyclo-oxygenase-2 (COX-2) activity in human monocytes being Me-UCH 5 the most potent (IC50 0.06 microM). Selected compounds also reduced leukotriene B4 synthesis in human neutrophils by a direct inhibition of 5-lipoxygenase (5-LO) activity, with IC50 values from 0.5 to 0.8 microM. In addition, lysosomal enzyme secretion, such as elastase or myeloperoxidase as well as superoxide generation in human neutrophils were also reduced in a similar range. Our findings indicate that UCH derivatives exert a dual inhibitory effect on COX-2/5-LO activity. The profile and potency of these compounds may have relevance for the modulation of the inflammatory and nociceptive responses with reduction of undesirable side-effects associated with NSAIDs.

Animals↗

Influence of vacancy ordering on the percolative behavior of (Li(1)(-x)Na(x))(3y)La(2/3-y)TiO(3) perovskites.

Influence of the vacancy concentration on the Li conductivity of the (Li(1-x)Na(x))(0.2)La(0.6)TiO(3) and (Li(1-x)Na(x)(0.5)La(0.5)TiO(3) perovskite series, with 0 < or = x < 1, has been investigated by neutron diffraction (ND), impedance spectroscopy (IS), nuclear magnetic resonance (NMR), and Monte Carlo simulations. In both series, Li(+) ions occupy unit cell faces, but Na(+) ions are located at A sites of the perovskite. From this fact, the amount of vacant A sites that participate in Li conductivity is given by the expression n(v) = [Li] + square, where square is the nominal vacancy concentration. Substitution of Li by Na decreases the amount of vacancies, reducing drastically the Li conductivity when n(v) approaches the percolation threshold of the perovskite conduction network. In disordered (Li(1-x)Na(x))(0.5)La(0.5)TiO(3) perovskites, the percolation threshold is 0.31; however, in ordered (Li(1-x)Na(x))(0.2)La(0.6)TiO(3) perovskites, this parameter changes to 0.26. Near the percolation threshold, the amount of mobile Li species deduced by (7)Li NMR spectroscopy is lower than that derived from structural formulas but higher than deduced from dc conductivity measurements. Conductivity values have been explained by Monte Carlo simulations, which assume a random walk for Li ions in the conduction network of the perovskite. In these simulations, distribution of vacancies conforms to structural models deduced from ND experiments.

Journal Article↗

Multicenter study of MTT and resazurin assays for testing susceptibility to first-line anti-tuberculosis drugs.

OBJECTIVE: A multicentre evaluation was performed to assess two rapid low-cost methods, MTT (3-[4.5-dimethylthiazol-2-yl]-2.5-diphenyltetrazolium bromide) and resazurin assays, for testing the susceptibility of Mycobacterium tuberculosis to the first-line anti-tuberculosis drugs rifampicin (RMP), isoniazid (INH), ethambutol (EMB) and streptomycin (SM). METHODS: Thirty coded M. tuberculosis strains were sent to seven laboratories located in Latin America, representing six countries. Each site performed the colorimetric assays, MTT and resazurin, blind for the first-line drugs RMP, INH, EMB and SM. The minimum inhibitory concentration results obtained were compared to the conventional proportion method on Lowenstein-Jensen medium. RESULTS: After establishing the breakpoint concentrations, excellent results were obtained for RMP, INH and EMB, with levels of specificity and sensitivity of between 96% and 99%. CONCLUSION: MTT and resazurin assays are promising, accessible new alternative methods for middle- and low-resource countries that need low-cost methods to perform rapid susceptibility testing of M. tuberculosis to key anti-tuberculosis drugs.

Antitubercular Agents↗

Population at risk for eating disorders in a Spanish region.

OBJECTIVE: To estimate the prevalence of adolescent population at risk for eating disorders (EDs), to examine gender differences and their association with non-psychotic mental disorders. METHODS: Cross-sectional study using an anonymous, self-reported questionnaire in the classroom and measurement of weight and height in a representative sample of 4334 teenagers of both sexes. A definition of population at risk for EDs has been established, that differentiates those with dieting criteria and those with binge-purge eating behaviour criteria. This definition includes a combination of weight, behaviour, Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria, and Eating Disorder Inventory (EDI) results. The General Health Questionnaire-28 (GHQ-28) was used to assess non-psychotic mental disorders. RESULTS: The prevalence of population at risk for EDs was 2.2% (95% CI: 1.6-2.8) for men and 15.3% (95% CI: 13.8-16.9) for women. The prevalence rate of combining both ED risk and mental disorder was 0.8% (95% CI: 0.4-1.2) for men and 9.9% (95% CI: 8.6-11.2) for women. Non-psychotic mental disorders were more prevalent in the population at risk for EDs than in the rest of the population. CONCLUSIONS: A considerable proportion of adolescent females have eating problems and non-psychotic mental disorders. Their male counterparts also suffer from these disorders, however, a different pattern is followed.

Adolescent↗

Levofloxacin in the treatment of pneumonia in intensive care unit patients.

In this study, we analyzed 302 patients with pneumonia admitted to the Intensive Care Unit (ICU) who were treated with levofloxacin (LFX) either as monotherapy or combined therapy. Pneumonia was classified as community-acquired in 220 (73%) patients, extra-ICU nosocomial-acquired in 43 (14%), and intra-ICU nosocomial-acquired in 39 (13%) patients. Treatment with LFX was used empirically in 85.7% of the cases. Initial doses of LFX were 500 mg every 24 h in 48.5% of the cases and 500 mg every 12 hours in 48.3%. Treatment was maintained for a mean (SD) of 12.6 (21.9) days. Treatment began as monotherapy in 116 (38.4%) patients and as combination therapy in 186 (61.6%). The factors that influenced the choice of combined treatment were septic shock (odds ratio [OR] 3.03; 95% confidence interval [CI] 1.50-6.12) and the presence of two or more extrinsic factors (OR 1.83; 95% CI 1.04-3.23), while young age was a variable associated with monotherapy (OR 0.98; 95% CI 0.96-0.99). An etiological diagnosis was made in 61.6% of the cases. LFX administration was changed from the intravenous route to oral administration in 85 (28.6%) patients. Satisfactory clinical response (cure and improvement) was achieved in 69.4% of the community-acquired pneumonia, in 55.8% of the extra-ICU nosocomial infection, and in 78.3% of the intra-ICU nosocomial infection. The overall mortality rate was 31.5%. Variables associated with death during ICU stay were combined therapy (OR 3.07; 95% CI 1.23-7.65), septic shock (OR 3.49; 95% CI 1.30-9.39), or therapeutic failure (OR 32.6; 95% CI 13.5-78.9). A total of 15% of the patients experienced adverse effects possibly or probably related the antibiotic given.

Adult↗

Cation mass dependence of the nearly constant dielectric loss in alkali triborate glasses.

Electrical ac conductivity measurements on alkali triborate glasses ( M2O x 3B2O3, M = Li, Na, K, and Rb) were performed at temperatures down to 8 K and frequencies up to 1 GHz. All samples show a nearly constant dielectric loss (NCL), at the limit of high frequencies and/or low temperatures. The magnitude of the NCL is found to decrease as m(-1/3) with increasing alkali ion mass m. This quantitative result for the NCL, closely related to the mean-square displacement of ions, indicates that the origin of the NCL might be related to vibrational relaxation of the ions in the anharmonic potentials that cage them, and the cage is decaying very slowly with time.

Journal Article↗

Direct evidence for block-by-block growth in high-temperature superconductor ultrathin films.

Charge neutrality and stoichiometry impose severe restrictions on the mechanisms of epitaxial growth of complex oxides. The fundamental question arises of what is the minimum growth unit when sample thickness is reduced beyond the size of the unit cell. We have investigated the growth mechanism of YBa2Cu3O7 cuprate superconductor, using a consistent approach based on the growth of noninteger numbers of YBa2Cu3O7 layers in YBa(2)Cu(3)O(7)/PrBa(2)Cu3O7 superlattices. Ex situ chemical and structural analysis evidence a 2D block-by-block mechanism in which the minimum growth units are complete unit cell blocks, growing coherently over large lateral distances.

Journal Article↗

Origin of constant loss in ionic conductors.

We have analyzed the constant loss contribution to the ac conductivity in the frequency range 10 Hz-1 MHz and temperatures down to 8 K, for two Li ionic conductors, one crystalline (Li(0.18)La(0.61)TiO(3)) and the other glassy (61SiO(2);35Li(2)O.3Al(2)O3.P(2)O(5)). As temperature is increased a crossover is observed from a nearly constant loss to a fractional power law frequency dependence of the ac conductivity. At any fixed frequency omega, this crossover occurs at a temperature T such that omega approximately nu(0)exp(-E(m)/k(B)T), where nu(0) is the attempt frequency and E(m) is identified with the barrier for Li+ ions to leave their wells.

Journal Article↗

Acoustic analysis after radiotherapy in T1 vocal cord carcinoma: a new approach to the analysis of voice quality.

PURPOSE: The study of acoustic voice parameters (fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio) in extended vowel production, oral reading of a standard paragraph, spontaneous speech and a song in irradiated patients for Tis-T1 vocal cord carcinoma. METHODS AND MATERIALS: Eighteen male patients irradiated for Tis-T1 vocal cord carcinoma and a control group of 31 nonirradiated subjects of the same age were included in a study of acoustic voice analysis. The control group had been rigorously selected for voice quality and the irradiated group had previous history of smoking in two-thirds of the cases and a vocal cord biopsy. Radiotherapy patients were treated with a 6MV Linac receiving a total dose of 66 Gy, 2 Gy/day, with median treatment areas of 28 cm(2). Acoustic voice analysis was performed 1 year after radiotherapy, the voice of patients in extended vowel production, oral reading of a standard paragraph, spontaneous speech, and in a song was tape registered and analyzed by a Kay Elemetric's Computerized Speech Lab (model CSL# 4300). Fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio were obtained in each case. Mann Whitney analysis was used for statistical tests. RESULTS: The irradiated group presented higher values of fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio. Mann-Whitney analysis showed significant differences for fundamental frequency and jitter in vowel production, oral reading, spontaneous speech, and song. Shimmer only showed differences in vowel production and harmonics-to-noise ratio in oral reading and song. CONCLUSIONS: In our study only fundamental frequency and jitter showed significant increased values to the control group in all the acoustic situations. Sustained vowel production showed the worst values of the acoustic parameters in comparison with the other acoustic situations. This study seems to suggest that more work should be done in this field.

Aged↗

On the Location of Li(+) Cations in the Fast Li-Cation Conductor La(0.5)Li(0.5)TiO(3) Perovskite.

Lithium cations sit in the center of the oxygen "windows" defined by the vertex-sharing TiO(6) octahedra of the title compound (see picture), as shown from neutron diffraction data. The octahedra are tilted to optimize the bond distances between the atoms. The unusual coordination and the partially unoccupied sublattice (occupancy factors 1/6 and (1/2) for Li and La, respectively) account for the high mobility of the Li(+) cations.

Journal Article↗

Amino acid losses during hemodialysis with polyacrylonitrile membranes: effect of intradialytic amino acid supplementation on plasma amino acid concentrations and nutritional variables in nondiabetic patients.

BACKGROUND: Malnutrition is highly prevalent in hemodialysis patients. Amino acid (AA) losses during the dialysis procedure may be a contributing factor. OBJECTIVES: The objectives of this study were 1) to prospectively evaluate AA losses and their effect on plasma AA concentrations during dialysis with polyacrylonitrile at baseline and after administration of AAs by intradialysis and 2) to investigate the effects of intradialytic AA supplementation on nutritional status. DESIGN: Seventeen stable patients without diabetes who were receiving hemodialysis were studied. In the first phase, AA losses were evaluated over 2 wk in 10 patients randomly assigned to receive AA supplementation. AA losses were analyzed during the first week without supplementation and during the second week with AA administration. In the second phase, the patients' nutritional status was investigated after 3 mo of AA supplementation and was compared with those in 7 patients not receiving AAs. RESULTS: Mean +/- SD) AA losses during a 4-h dialysis session were 12 +/- 2 g; there was a significant decrease in plasma AA concentrations (386 +/- 298 micromol/L for essential and 902 +/- 735 micromol/L for nonessential AAs). After administration of AAs, the losses increased to 28 +/- 4 g. However, this procedure produced a positive net balance of AAs (10.6 +/- 5.6 g for total AAs), preventing a reduction in plasma concentrations. After 3 mo of AA administration, there was a significant increase in protein catabolic rate and serum albumin and transferrin. This improvement occurred without any change in the dialysis dose, ruling out the possibility that an increase in dialysis efficiency played a role. CONCLUSIONS: Intradialysis adequately provides AA supplements, prevents reductions in plasma AA concentrations, and favorably affects the nutritional status of patients receiving hemodialysis.

Acrylic Resins↗

Blood ammonia response during incremental and steady-state exercise in military staff.

BACKGROUND: Although in the last few years it has been possible to determine blood ammonia, its application in coaching practice has not yet been fully established. This study was designed to evaluate the blood ammonia response to a laboratory incremental exercise test and three steady-state field tests. METHODS: There were 26 military personnel who performed a submaximal and maximal exercise test on a treadmill, and a field test which included three different constant velocity stages. Gas exchange parameters were monitored throughout the maximal test. Capillary blood samples were obtained from fingertips during the submaximal and field tests for the determination of ammonia and lactate. RESULTS: The ammonia threshold was detected in 23 subjects (88.5%) during the submaximal test. No significant differences were found between the ammonia and lactate thresholds which were shown to be significantly correlated. Blood ammonia levels showed a progressive increase during the last two stages of the field test while lactate levels remained stable at less than 4 mmol x L(-1). CONCLUSIONS: The steady increase in blood ammonia concentration recorded in the field test suggests the possibility of using blood ammonia levels to monitor the duration of exercise although further investigation is required to explore this possibility. Moreover, the assessment of blood ammonia levels during incremental exercise protocols confirms the existence of an ammonia threshold, defined as the intensity of exercise at which ammonia shows a progressive increase.

Adult↗

Antimicrobial susceptibility of Helicobacter pylori determined by the E test using tetrazolium egg yolk agar.

Metronidazole and tetracycline E tests were compared to an agar dilution method for the antimicrobial susceptibility testing of Helicobacter pylori. Sixteen strains were tested by using tetrazolium egg yolk (TEY) agar. The characteristic E test inhibition ellipse was clearer on TEY agar than on standard blood agar and gave results comparable to those of the agar dilution test. The use of TEY medium is preferable to that of blood agar medium in E test MIC determinations for H. pylori.

Agar↗