Biomedical subjects

Ana González

Publications and source records attributed to Ana González.

13 recordsLinked to original sources

PubMed2006

Retrospective analysis of surgical complications following cadaveric kidney transplantation in the modern transplant era.

BACKGROUND: Risk factors for surgical complications (SCs) following kidney transplantation in the modern transplant era need to be identified to perform appropriate prophylactic interventions. METHODS: Records from 870 consecutive adult cadaveric kidney transplants done at a single centre were reviewed. SCs were classified into four groups: (i) vascular (12%, thrombosis or stenosis); (ii) haemorrhagic (12%); (iii) ureteral (7.5%, leaks and stenosis) and (iv) wound (16%, lymphocoeles or dehiscences). RESULTS: One or more SCs occurred in 299 (34%) patients, with multiple SCs in 65 (7.4%). By logistic regression analysis, recipient vessel atherosclerosis and delayed graft function (DGF) were significantly associated with both thrombotic complications [odds ratio (OR) 4, 95% confidence interval (CI), 1.4-11, P = 0.010 and OR 3.8, 1.3-12, P < 0.00001, respectively] and graft artery stenosis (OR 2.9, 1.2-6.8, P = 0.015 and OR 5.6, 2.3-13.4, P < 0.0001, respectively). Acute rejection increased the risk of graft artery or ureteral stenosis by 2.5 (CI 1.02-6.4, P = 0.045) and 3.3 (CI 1.1-10, P = 0.034), respectively. Older recipients were related to urinary leak (OR 1.04, CI 1.01-1.07, P = 0.011). Difficult bench surgery, DGF and the use of antiplatelet drugs increased the risk of bleeding by 3.6 (CI 1.9-6.4, P < 0.0001), 2.7 (CI 1.5-4.7, P < 0.0001) and 1.8 (CI 1.03-3.29, P = 0.038), respectively. Each month on dialysis increased the risk by 1.02 (CI 1.01-1.03, P = 0.002). Sirolimus increased the risk for wound SCs by 4.1 (CI 2.1-8.3, P < 0.0001) and obesity, retransplant and acute rejection were additional risk factors. CONCLUSIONS: Adult renal transplant recipients at risk for SCs can be identified by age, DGF, graft vessel and recipient atheromatosis, difficult bench surgery, obesity, rejection and the use of antiplatelet drugs and rapamycin.

Adolescent↗

PubMed2006

[Effect of different bronchial washing sequences on diagnostic yield in endoscopically visible lung cancer].

OBJECTIVE: Aspiration of bronchial wash fluid is commonly used in conjunction with brushing and forceps biopsy to diagnose endoscopically visible lung cancer. However, the optimal sequence of these procedures is subject to debate. The objective of this study was to determine if the order in which bronchial washing is performed relative to bronchial brushing and forceps biopsy has any effect on the diagnostic yield. PATIENTS AND METHODS: A prospective, cross-sectional study was carried out on patients with endoscopically visible lung cancer who underwent video-assisted fiberoptic bronchoscopy for diagnostic purposes. Aspiration of bronchial wash fluid was performed on all patients both before and after bronchial brushing and forceps biopsy. The results were analyzed separately for each type of endobronchial lesion and for both together. RESULTS: The study included 75 patients, with a mean age of 63.3 years; 81% were men. Bronchoscopy was diagnostic in 71 (94.7%) cases. Findings from bronchial washing fluid were positive in 40 (53.3%) patients when washing was performed prior to brushing and forceps biopsy; when washing was performed after these procedures, findings were positive in 43 (57.3%) patients (P=.6). The combined diagnostic yield of washing before and after brushing and forceps biopsy was 69.3%, a significantly better result than either washing before (P=.001) or after (P=.004) the other sampling techniques. In cases where findings from washing done after brushing and forceps biopsy were negative (14 of 32, 43.7%), blood in the aspirated sample interfered with cytology. In comparison, when washing was performed prior to brushing and biopsy, that problem arose in only 3 of the 35 cases (8.5%) (P=.002). CONCLUSIONS: The order in which bronchial washing is performed in relation to other sampling techniques for diagnosing bronchial tumors does not influence the diagnostic yield. This is probably because the aspirated fluid sample is more likely to contain excessive blood when washing is performed after brushing and forceps biopsy. However, the diagnostic yield can be significantly increased by combining the findings from bronchial washings performed both before and after other sample collection procedures.

Aged↗

PubMed2005

Pneumococcal phosphorylcholine esterase, Pce, contains a metal binuclear center that is essential for substrate binding and catalysis.

The phosphorylcholine esterase from Streptococcus pneumoniae, Pce, catalyzes the hydrolysis of phosphorylcholine residues from teichoic and lipoteichoic acids attached to the bacterial envelope and comprises a globular N-terminal catalytic module containing a zinc binuclear center and an elongated C-terminal choline-binding module. The dependence of Pce activity on the metal/enzyme stoichiometry shows that the two equivalents of zinc are essential for the catalysis, and stabilize the catalytic module through a complex metal-ligand coordination network. The pH dependence of Pce activity toward the alternative substrate p-nitrophenylphosphorylcholine (NPPC) shows that k(cat) and k(cat)/K(m) depend on the protonation state of two protein residues that can be tentatively assigned to the ionization of the metal-bound water (hydrogen bonded to D89) and to H228. Maximum activity requires deprotonation of both groups, although the catalytic efficiency is optimum for the single deprotonated form. The drastic reduction of activity in the H90A mutant, which still binds two Zn2+ ions at neutral pH, indicates that Pce activity also depends on the geometry of the metallic cluster. The denaturation heat capacity profile of Pce exhibits two peaks with T(m) values of 39.6 degrees C (choline-binding module) and 60.8 degrees C (catalytic module). The H90A mutation reduces the high-temperature peak by about 10 degrees C. Pce is inhibited in the presence of 1 mM zinc, but this inhibition depends on pH, buffer, and substrate species. A reaction mechanism is proposed on the basis of kinetic data, the structural model of the Pce:NPPC complex, and the currently accepted mechanism for other Zn-metallophosphoesterases.

Binding Sites↗

PubMed2005

Insights into pneumococcal pathogenesis from the crystal structure of the modular teichoic acid phosphorylcholine esterase Pce.

Phosphorylcholine, a specific component of the pneumococcal cell wall, is crucial in pathogenesis. It directly binds to the human platelet-activating factor (PAF) receptor and acts as a docking station for the family of surface-located choline-binding proteins (CBP). The first structure of a complete pneumococcal CBP, Pce (or CbpE), has been solved in complex with the reaction product and choline analogs. Pce has a novel modular structure, with a globular N-terminal module containing a binuclear Zn(2+) catalytic center, and an elongated choline-binding module. Residues involved in substrate binding and catalysis are described and modular configuration of the active center accounts for in vivo features of teichoic acid hydrolysis. The hydrolysis of PAF by Pce and its regulatory role in phosphorylcholine decoration of the bacterial surface provide new insights into the critical function of Pce in pneumococcal adherence and invasiveness.

Binding Sites↗

PubMed2005

Two-wavelength MAD phasing and radiation damage: a case study.

Radiation damage affects MAD experiments in two ways: (i) increased absorption by the crystal at the wavelengths of interest for the experiment results in faster crystal deterioration; (ii) lack of isomorphism induced by radiation damage causes problems when scaling and merging data at different wavelengths and can prevent accurate measurement of anomalous and dispersive differences. In an attempt to overcome these problems in the case of radiation-sensitive crystals of vinculin, two-wavelength MAD data were collected at the Se absorption-edge inflection and at high-energy remote wavelengths. Although this strategy resulted in a lower total absorbed dose compared with a standard three-wavelength experiment using the peak wavelength, an increase in the unit-cell volume and other effects attributable to radiation damage were still observed. In an effort to extract the maximum information available from the data, different data-processing and scaling procedures were compared. Scaling approaches involving local scaling of unmerged reflections were consistently successful and most ordered Se sites could be located. Subsequent use of these sites for phasing resulted in an interpretable electron density map. This case demonstrates the feasibility of two-wavelength MAD in the presence of moderate radiation damage using conventional data collection strategies and widely available standard software.

Crystallization↗

PubMed2005

Crystallization and preliminary X-ray diffraction studies of the pneumococcal teichoic acid phosphorylcholine esterase Pce.

The pneumococcal phosphorylcholine esterase (Pce or CbpE) is a modular protein that hydrolyses the phosphorylcholine residues present in the teichoic and lipoteichoic acids of the pneumococcal cell wall. Pce has been crystallized using the hanging-drop vapour-diffusion method at 291 K. Diffraction-quality monoclinic crystals belong to space group C2, with unit-cell parameters a = 169.82, b = 57.26, c = 67.44 A, beta = 112.60 degrees. A 2.7 A resolution SAD data set from a non-isomorphous Gd-HPDO3A Pce derivative was collected at the gadolinium L(III) absorption edge using synchrotron radiation.

Amino Acid Sequence↗

PubMed2004

Docetaxel plus fractionated cisplatin is a safe and active schedule as first-line treatment of patients with advanced non-small cell lung cancer: results of a phase II study.

This phase II trial evaluated the efficacy and safety of docetaxel 85 mg/m(2) (day 1) and cisplatin 80 mg/m(2) (administered as 40 mg/m(2) doses each on days 1 and 2) every 3 weeks as first-line treatment of patients with advanced non-small cell lung cancer (NSCLC). Forty-two NSCLC patients were enrolled, most of them with stage IV disease (74%). A total of 195 chemotherapy cycles were administered (median 6, range 1-6). All patients were considered evaluable for efficacy and toxicity in an intention-to-treat (ITT) analysis. The overall response rate was 48% (95% CI, 33-64), including one CR (3%) and 19 PRs (45%). Stable disease was found in 6 patients (14%). The median time to disease progression was 4.9 months (95% CI, 4.0-5.7) and the median overall survival was 10.5 months (95% CI, 5.1-16.0). The survival rates at 1 and 2 years were 36.0% (95% CI, 19.9-52.0) and 18.0% (95% CI, 3.9-32.1), respectively. Overall, the combination showed an excellent safety profile. Severe hematological toxicities were uncommon: neutropenia (5% of patients, 1% of cycles) and febrile neutropenia (2% of patients, 0.5% of cycles). Asthenia (12%) was the only grade 3/4 non-hematological toxicity that affected more than 10% of patients. There were no toxic deaths. In conclusion, docetaxel plus fractionated cisplatin as first-line treatment of advanced NSCLC patients showed similar efficacy as the same combination with higher doses of docetaxel but where cisplatin was administered in a single dose. This new schedule shows promise in its excellent hematological and non-hematological toxicity profile. A randomized phase III trial is needed to confirm these results.

Adult↗

PubMed2003

Optimizing data collection for structure determination.

The ultimate purpose of diffraction data collection is to produce a data set which will result in the required structural information about the molecule of interest. This usually entails collecting a complete and accurate set of reflection intensities to as high a resolution as possible. In practice, the characteristics of the crystal and properties of the X-ray source can be limiting factors to the data-set quality that can be achieved and a careful strategy has to be used to extract the maximum amount of information from the data within the experimental constraints. In the particular case of data intended for phasing using anomalous dispersion, the synchrotron beamline properties are relevant to determine how many wavelengths (one or more) should be used for the experiment and what the wavelength values should be. This will in turn affect the detailed strategy for data collection, including decisions about the data-collection sequence and how much data to collect at each wavelength. Collection of multiwavelength anomalous dispersion (MAD) data at three different wavelengths can provide very accurate experimental phases. Two-wavelength MAD experiments may offer the best compromise between phase quality and minimizing the effects of radiation damage to the sample. However, MAD experiments are demanding in terms of beamline wavelength range, easy tunability, stability and reproducibility. When the beamline cannot fulfill these demands, single-wavelength experiments may be a better option.

Crystallography, X-Ray↗

PubMed2003

The 0.93A crystal structure of sphericase: a calcium-loaded serine protease from Bacillus sphaericus.

We have previously isolated sphericase (Sph), an extracellular mesophilic serine protease produced by Bacillus sphaericus. The Sph amino acid sequence is highly homologous to two cold-adapted subtilisins from Antarctic bacilli S39 and S41 (76% and 74% identity, respectively). Sph is calcium-dependent, 310 amino acid residues long and has optimal activity at pH 10.0. S41 and S39 have not as yet been structurally analysed. In the present work, we determined the crystal structure of Sph by the Eu/multiwavelength anomalous diffraction method. The structure was extended to 0.93A resolution and refined to a crystallographic R-factor of 9.7%. The final model included all 310 amino acid residues, one disulfide bond, 679 water molecules and five calcium ions. Although Sph is a mesophilic subtilisin, its amino acid sequence is similar to that of the psychrophilic subtilisins, which suggests that the crystal structure of these subtilisins is very similar. The presence of five calcium ions bound to a subtilisin molecule, as found here for Sph, has not been reported for the subtilisin superfamily. None of these calcium-binding sites correlates with the well-known high-affinity calcium-binding site (site I or site A), and only one site has been described previously. This calcium-binding pattern suggests that a reduction in the flexibility of the surface loops of Sph by calcium binding may be responsible for its adaptation to mesophilic organisms.

Amino Acid Sequence↗

PubMed2003

Structure of Rhodoferax fermentans high-potential iron-sulfur protein solved by MAD.

The crystal structure of Rhodoferax fermentans high-potential iron protein (HiPIP) has been solved by MAD methods using the anomalous signal from the Fe atoms in the [Fe(4)S(4)] cluster present in the protein and refined to a resolution of 1.45 A. The peptide chain is well defined except in the N- and C-terminal areas. The structure of the protein reveals the presence of three helical fragments, a small beta-sheet and several turns, with the [Fe(4)S(4)] cluster being located close to a surface patch containing several well conserved aromatic residues. The protein fold is very similar to the structures of other known HiPIPs, especially in the region proximal to the [Fe(4)S(4)] cluster, while the largest differences are observed on the opposite side of the protein, which is rich in positive charges and has no sequential homology to other HiPIP families.

Bacterial Proteins↗

PubMed2003

Faster data-collection strategies for structure determination using anomalous dispersion.

Many macromolecular structures are being determined using anomalous dispersion phasing methods. Different data-collection strategies at one, two, three or more wavelengths can be used for these experiments. The choice of strategy can determine the success or failure of the experiment and should be based on a clear understanding of the advantages and disadvantages of each approach given the experimental constraints and goals. In this paper, several sets of three-wavelength MAD experiment data were reanalyzed using one, two and three wavelengths and systematically removing reflections from the data sets to determine the minimum amount of data required to yield an automatically traceable map as a function of the number of wavelengths used in phasing. In the cases studied here, two-wavelength MAD consistently required fewer data than three-wavelength MAD, as long as the unique data completeness was high at each wavelength. It was also found in some instances that using one wavelength for phasing required as much or more data as using two wavelengths. These results can help with the design of adequate data-collection strategies which maximize the phasing power from the minimal data collected. This is particularly important for minimizing the effects of radiation damage on phasing while taking sample characteristics, beamline properties and experimental goals into account.

Crystallography, X-Ray↗

PubMed2003

Rapid progression of midventricular obstruction in adults with double-chambered right ventricle.

OBJECTIVE: The purpose of this study was to determine the rate of progression of midventricular obstruction in adolescents and adults with double-chambered right ventricle. METHODS: Clinical and echocardiographic findings in 45 patients (mean age 26 +/- 6 years, range 15-44) diagnosed with double-chambered right ventricle were retrospectively analyzed. Twenty patients underwent surgical repair before the age of 15 years. The relationship between Doppler midventricular pressure gradient and patient age was analyzed in 25 patients without previous repair. Sequential change in midventricular obstruction was determined for patients with 2 or more Doppler echocardiographic examinations performed within at least a 2-year interval. RESULTS: Right midventricular pressure gradient in nonrepaired patients was 70 +/- 38 mm Hg (range 25-150). A significant relationship between midventricular obstruction and patient age (r = 0.64, P <.001) was found. Midventricular pressure gradient at initial evaluation was 32 +/- 27 mm Hg in 16 patients < 25 years and 73 +/- 45 mm Hg in 9 patients >/= 25 years (P <.03). After the initial study, 5 patients underwent surgical repair and 13 patients without repair were followed up for a period of 6.1 +/- 2.7 years (range 2-9), in which midventricular pressure gradient increased from 32 +/- 26 mm Hg to 67 +/- 35 mm Hg (P <.001). The slope of the change in midventricular pressure gradient was 6.2 +/- 3 mm Hg per year of follow-up. Seven more patients underwent surgical repair during follow-up due to progression of the obstruction. There was no mortality nor residual midventricular obstruction in surgically repaired patients. CONCLUSIONS: Mild right midventricular obstruction shows a fast rate of progression in adolescents and young adults. Thus, close clinical and echocardiographic follow-up is advised, and surgical repair should be considered if significant progression of obstruction is detected.

Adolescent↗

PubMed2002

Predisposing conditions for atrial fibrillation in atrial septal defect with and without operative closure.

The aims of this study were to determine the prevalence and predisposing conditions for atrial fibrillation (AF) in adults with atrial septal defect (ASD) and to evaluate the influence of age at surgical repair. The study population consisted of 286 adults with ASD (mean age 39.5 +/- 19 years). All patients had >or = 1 follow-up visit and a Doppler echocardiographic study. One hundred ninety-two of the patients underwent surgical closure 1 to 34 years before the study. Analyzed variables were entered into univariate (Mann-Whitney U) and multivariate (stepwise logistic regression) models to assess independent predictors for AF. The prevalence of AF was similar in surgically treated patients (15.6%) and in the nonsurgical group (13.8%) (p = 0.69). Multivariate analysis showed that current age (RR 1.9 per each decade of age, 95% confidence interval [CI] 1.3 to 2.7, p = 0.001), mitral regurgitation (RR 3.0 per each degree of regurgitation, 95% CI 1.6 to 5.8, p = 0.001), left atrial enlargement (RR 2.8 per each 10 mm increase in size, 95% CI 1.5 to 5.2, p = 0.001), and tricuspid regurgitation (RR 1.9 per each degree of regurgitation, 95% CI 1.0 to 3.7, p = 0.04) were independent predictors of AF; however, gender, anatomic type, defect size, Qp:Qs, pulmonary artery pressure, right ventricular dimension, left ventricular shortening fraction, and prior surgical repair were not related to late AF development. In the surgical group, age >25 years at the time of surgery was the only predictor for AF independent of age at the time of the study (p = 0.02).

Adolescent↗