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L Marquez

Publications and source records attributed to L Marquez.

15 recordsLinked to original sources
PubMed2001

Molecular epidemiology of a multiresistant Pseudomonas aeruginosa outbreak in a paediatric intensive care unit.

After isolation of multiresistant (MR) Pseudomonas aeruginosa from 3 hospitalized patients in a paediatric intensive care unit (PICU), a prospective surveillance programme was established to detect infected and/or colonized patients in the hospital. Isolates were examined by means of outer membrane protein (OMP) profiles, serotyping and DNA genomic analysis using pulsed-field gel electrophoresis (PFGE). Fifty-five P. aeruginosa strains were isolated from 23 hospitalized patients during September and October 1997. The median hospital stay before isolation of P. aeruginosa was 8 d. PFGE demonstrated that the same clone infected 14 patients, 4 of whom were not hospitalized in the PICU. Susceptibility patterns and OMP profiles correlated with PFGE results in 37.8% and 36.4% of cases, respectively. Serotype O11 correlated with pattern A in 77% of cases and serotype O4 correlated with unrelated strains in 75% of cases but did not discriminate between outbreak and unrelated isolates. Extensive investigation of cultures failed to identify a reservoir of P. aeruginosa. PFGE was superior to OMP analysis and serotyping for discriminating between strains. The possible mode of acquisition for most of the patients infected with the same clone was cross-contamination.

Adolescent↗
PubMed1998

Quality supervision.

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Developing Countries↗
PubMed1994

Mechanism of manganese peroxidase compound II reduction. Effect of organic acid chelators and pH.

The effect of oxalate, malonate, lactate, and succinate chelators on the reduction of Phanerochaete chrysosporium manganese peroxidase compound II by MnII was investigated using stopped-flow techniques. All rate data were collected from single-turnover experiments under pseudo-first-order conditions. With oxalate, the reduction of compound II by MnII exhibited saturation behavior when the observed pseudo-first-order rate constants were plotted against oxalate concentration. The plots passed through the origin, indicating that the reduction by MnII is irreversible at all concentrations of oxalate. Maximal stimulation of the rate of compound II reduction occurred at 2 mM oxalate, the concentration of oxalate found in the extracellular medium of agitated cultures of this fungus. In contrast, maximal stimulation of the reduction of compound II by MnII only was observed at high (> 20 mM) nonphysiological concentrations of malonate and lactate. Furthermore, at low concentrations of malonate and lactate, the reduction of compound II appeared to be reversible. These results suggest that at physiological concentrations oxalate chelates and stabilizes MnIII, enhancing its efficient removal from the enzyme. The rate constants for compound II reduction exhibited bell-shaped curves as a function of pH and had optima at pHs 5.0-5.4. In the presence of succinate, triphasic kinetics were observed for compound II reduction by MnII. In contrast to the reduction of compound II by MnII, various chelators had no observable effect on the formation of compound I. However, they did affect the steady-state oxidation of 2,6-dimethoxyphenol.

Basidiomycota↗
PubMed1990

Lignin peroxidase compounds II and III. Spectral and kinetic characterization of reactions with peroxides.

Stopped-flow techniques were used to investigate the kinetics of the reaction of lignin peroxidase compounds II and III (LiPII and LiPIII) with peroxides. Rate data were obtained from single-turnover experiments under pseudo-first-order conditions. LiPII reacts with H2O2 or peracetic acid (AcOOH) to form a modified LiPIII, designated as LiPIII*, via a biphasic reaction. During the first phase, LiPIII is formed as an intermediate. Kinetic analysis also indicates a LiPII-peroxide complex. The first-order dissociation rate constants for the reaction of LiPII with H2O2 and AcOOH are 7.9 +/- 0.5 and 4.9 +/- 0.6 s-1, respectively. The rate of the H2O2 reaction is approximately 500 times the rate of the comparable reaction with horseradish peroxidase, suggesting it is physiologically significant. The activation energy for the formation of LiPIII is 23 kJ mol-1. During the second phase, the intermediate LiPIII is converted to LiPIII*, confirmed by analyzing the reaction of exogenously prepared LiPIII with peroxides. The second-order rate constants for the reaction of LiPIII with H2O2 and AcOOH are (3.7 +/- 0.2) x 10(2) M-1 s-1 and (2.9 +/- 0.2) x 10(2) M-1 s-1, respectively. The conversion of LiPIII to LiPIII* is reversible; the first-order rate constant for the reverse reaction is approximately (6.6 +/- 0.6) x 10(-2) s-1. The rates of both LiPIII and LiPIII* formation decrease markedly above pH 4.0. The pH dependence of these reactions is controlled by a heme-linked ionizable group of pK alpha congruent to 4.2.

Basidiomycota↗
PubMed1989

Cytochrome c peroxidase activity of a protease-modified form of cytochrome c-552 from the denitrifying bacterium Pseudomonas perfectomarina.

Protease activity present in aerobically grown cells of Pseudomonas perfectomarina, protease apparently copurified with cytochrome c-552, and trypsin achieved a limited proteolysis of the diheme cytochrome c-552. That partial lysis conferred cytochrome c peroxidase activity upon cytochrome c-552. The removal of a 4000-Da peptide explains the structural changes in the cytochrome c-552 molecule that resulted in the appearance of both cytochrome c peroxidase activity (with optimum activity at pH 8.6) and a high-spin heme iron. The oxidized form of the modified cytochrome c-552 bound cyanide to the high-spin ferric heme with a rate constant of (2.1 +/- 0.1) X 10(3) M-1 s-1. The dissociation constant was 11.2 microM. Whereas the intact cytochrome c-552 molecule can be half-reduced by ascorbate, the cytochrome c peroxidase was not reducible by ascorbate, NADH, ferrocyanide, or reduced azurin. Dithionite reduced the intact protein completely but only half-reduced the modified form. The apparent second-order rate constant for dithionite reduction was (7.1 +/- 0.1) X 10(2) M-1 s-1 for the intact protein and (2.2 +/- 0.1) X 10(3) M-1 s-1 for the modified form. In contrast with other diheme cytochrome c peroxidases, reduction of the low-spin heme was not necessary to permit ligand binding by the high-spin heme iron.

Amino Acid Sequence↗
PubMed1988

Spectroscopic and kinetic properties of the oxidized intermediates of lignin peroxidase from Phanerochaete chrysosporium.

Stopped-flow rapid scan techniques were used to obtain a spectrum of nearly homogeneous lignin peroxidase compound I (LiPI) under pseudo-first order conditions at the unusually low pH optimum (3.0) for the enzyme. The LiPI spectrum had a Soret band at 407 nm with approximately 60% reduced intensity and a visible maximum at 650 nm. Under steady-state conditions a Soret spectrum for lignin peroxidase compound II (LiPII) was also obtained. The Soret maximum of LiPII at 420 nm was only approximately 15% reduced in intensity compared to native LiP. Transient state kinetic results confirmed the pH independence of LiPI formation over the pH range 3.06-7.39. The rate constant was (6.5 +/- 0.2) x 10(5) M-1 S-1. Addition of excess veratryl alcohol to LiPI resulted in its reduction to LiPII with subsequent reduction of LiPII to the native enzyme. Reactions of LiPI and LiPII with veratryl alcohol exhibited marked pH dependencies. For the LiPI reaction the rate constants ranged from 2.5 x 10(6) M-1 S-1 at pH 3.06 to 4.1 x 10(3) M-1 S-1 at pH 7.39; for the LiPII reaction, 1.6 x 10(5) M-1 S-1 (pH 3.06) to 2.3 x 10(3) M-1 S-1 (pH 5.16). These single turnover experiments demonstrate directly that the pH dependence of these reactions dictates the overall pH dependence of this novel enzyme. These results are consistent with the one-electron oxidation of veratryl alcohol to an aryl cation radical by LiPI and by LiPII.

Agaricales↗
PubMedDate not supplied

Cardiac catheterization: the patients' perspective.

OBJECTIVE: To identify the patients' experience of cardiac catheterization. DESIGN: Descriptive, qualitative, phenomenologic. SETTING: Large southeastern teaching hospital with an active cardiac catheterization laboratory and research center. PATIENTS: Ten men, between 44 and 73 years of age, who had undergone their first cardiac catheterization. RESULTS: The participants described feelings of loss of control of physical and personal self; an increased fear of the unknown during the test and especially of outcomes that might affect their future; a focus on time and its relationship to complication; a need not to be alone and not to be isolated after the test; and an awareness of spiritual belief in the good of others, trusting in their competencies. CONCLUSIONS: This study suggests the need for more attention to the psychologic aspects of the test, especially to the outcomes, negative as well as positive, and how they may affect the patient.

Adaptation, Psychological↗
PubMedDate not supplied

Vascular trauma: late sequelae and treatment.

58 patients presenting with late manifestations of vascular trauma underwent operative correction at an average of 37.2 months from the date of injury. False aneurysms alone were seen in 23 patients, arteriovenous fistulae in another 35, and both lesions concurrently in 6 patients. Excellent results were achieved in 54 patients, fair results in 4 patients, and only 3 patients required later reoperation despite the chronic nature of these lesions.

Adolescent↗