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D Suárez

Publications and source records attributed to D Suárez.

At least 19 recordsLinked to original sources
PubMed2006

Predictive factors comparison of complications and recurrences in three tension-free herniorraphy techniques.

Inguinal herniorraphy is one of the most common surgeries performed. Avoiding hernia recurrence is a primary concern. Hence, it is necessary to analyze the predictive factors of postoperative complications and recurrence. To compare the predictive factors of postoperative complications and recurrences of hernias among three tension-free open herniorraphy techniques. Five hundred and fifty-one inguinal hernia patients, operated on with one of three tension-free anterior approach herniorraphy techniques, were included in a cohort study. The three techniques were: Lichtenstein (n=214), Mesh-Plug (n=201) and Prolene Hernia System (PHS, n=136). The patients were evaluated at 15 days, 1 month, 6 months and then every year up to 5 years after hernioplasty. The variables evaluated were recurrences and postoperative complications. Relative risk was estimated from a univariate analysis of the presumable risk values, after which a multivariate analysis was carried out. Complications [n=27, (4.9%)] were more frequently associated with incarcerated hernia, a coexisting disease at the time of operation, hospitalization longer than 1 day, previous herniorraphy, a herniary ring larger than 4.5 cm and a history of postoperative complications. Recurrence was greater for the Mesh-Plug group [n=5 (2.5%), RR: 4.35 (CI: 0.85-22.23)] than for the Lichtenstein [n=2 (0.9%), RR: 0.63 (0.06-3.87)] and PHS [n=0 (0%), RR de 0 (0-2.39)] groups. The presence of coexisting disease during hernioplasty, incarcerated hernia and an extended hospital stay are predictive factors for hernia complications. Previous herniorraphy, a herniary ring larger than 4.5 cm and postoperative complications are predictive factors for hernia recurrence.

Comorbidity↗
PubMed2006

Biochemical and mechanical behavior of ostrich pericardium as a new biomaterial.

We have performed a comparative analysis of glutaraldehyde-preserved ostrich pericardium, as a novel biomaterial, with bovine pericardium. The biochemical characteristics (histology, water content, amino acid composition, and collagen and elastin contents), mechanical properties, and in vivo calcification in a subcutaneous rat model were examined. Ostrich pericardium is slightly thinner and shows a higher water content (70+/-2% vs. 62+/-2%) than bovine pericardium. Additionally, ostrich pericardium presents 1.6-fold lower elastin content and a lower percentage of collagen in reference to the total protein content (68+/-2% vs. 76+/-2%). However, ostrich pericardium shows better mechanical properties, with higher tensile stress at rupture (32.4+/-7.5 vs. 11.5+/-4.6) than calf pericardium. In vivo calcification studies in a rat subcutaneous model show that ostrich pericardium is significantly less calcified than bovine pericardium (23.95+/-13.30 vs. 100.10+/-37.36 mg/g tissue) after 60 days of implantation. In conclusion, glutaraldehyde-stabilized ostrich pericardium tissue shows better mechanical properties than calf tissue. However, calcium accumulation in implanted ostrich tissue is still too high to consider it a much better alternative to bovine pericardium, and anticalcification treatments should be considered.

Animals↗
PubMed2006

Cost-utility of selective serotonin reuptake inhibitors for depression in primary care in Catalonia.

OBJECTIVE: To determine the cost-utility of selective serotonin reuptake inhibitors (SSRIs) for treating depressive disorders prescribed in primary care (PC). METHOD: A total of 301 participants beginning antidepressant treatment with an SSRI were enrolled in a prospective 6-month follow-up naturalistic study. Incremental cost-utility ratios (ICUR) were obtained for several comparisons among different SSRIs. To address uncertainty in the ICUR's sampling distribution, non-parametric bootstrapping was carried out. RESULTS: Taking into account adjusted total costs and incremental quality of life gained, fluoxetine dominated paroxetine and citalopram with 63.4% and 79.3% of the bootstrap replications in the dominance quadrant, respectively. Additionally, fluoxetine was cost-effective over sertraline with 83.4% of the bootstrap replications below the threshold of 33,936 US$/quality-adjusted life year (30,000 euro/QALY). CONCLUSION: Fluoxetine seems to be a better cost-utility SSRI option for treating depressive disorders in PC.

Adolescent↗
PubMed2005

Preoperative progressive pneumoperitoneum in patients with abdominal-wall hernias.

Induction of preoperative progressive pneumoperitoneum is an elective procedure in patients with hernias with loss of domain. A prospective study was carried out from June 2003 to May 2005 at the Hospital de Especialidades, Instituto Mexicano del Seguro Social, Leon, Mexico. Preoperative progressive pneumoperitoneum was induced using a double-lumen intraabdominal catheter inserted through a Veress needle and daily insufflation of ambient air. Variables analyzed were age, sex, body mass index, type, location and size of defective hernia, number of previous repairs, number of days pneumoperitoneum was maintained, type of hernioplasty, and incidence of complications. Of 12 patients, 2 were excluded because it was technically impossible to induce pneumoperitoneum. Of the remaining 10 patients, 60% were female and 40% were male. The patients' average age was 51.5 years, average body mass index was 34.7, and evolution time of their hernias ranged from 8 months to 23 years. Nine patients had ventral hernias and one had an inguinal hernia. Pneumoperitoneum was maintained for an average of 9.3 days and there were no serious complications relating to the puncture or the maintenance of the pneumoperitoneum. One patient who previously had undergone a mastectomy experienced minor complications. We were able to perform hernioplasty on all patients, eight with the Rives technique, one with supra-aponeurotic mesh, and one using the Lichtenstein method for inguinal hernia repair. One patient's wound became infected postoperatively. Preoperative progressive pneumoperitoneum is a safe procedure that is easy to perform and that facilitates surgical hernia repair in patients with hernia with loss of domain. Complications are infrequent, patient tolerability is adequate, and the proposed modification to the puncture technique makes the procedure even safer.

Abdominal Wall↗
PubMed2004

In-plane electronic speckle pattern of interference (ESPI) with optical fibre system applied to the study of the human jaw.

The standard illumination set-up for measurement of in-plane displacement in electronic speckle pattern of interference (ESPI) requires the use of two oblique coherent beams for the illumination of the object. These two beams define a direction in the plane perpendicular to the optical axis in which the displacement can be measured, while in the perpendicular direction the interferometer has no sensitivity. In this paper, a new ESPI system for the measurement of in-plane displacements is used. The novelty presented by this assembly is the use of optical fibres to split and guide the light beams. In this way, it is possible to vary with great precision and ease the direction of the projected beams and, consequently, the direction of the plane in which the displacements undergone by the object can be studied. This set-up makes possible the study of objects with complex geometries, which have deformations with unknown symmetry. We present results obtained with this interferometer applied to the study of the mechanical behaviour of the human jaw.

Algorithms↗
PubMed2003

Neither folic nor folinic acid normalize homocysteine levels in hemodialysis patients.

AIMS: A greater decrease in total homocystein (tHcy) has been reported in patients on hemodialysis (HD) following the administration of reduced forms of folic acid (FA), however, the effect of the administration of moderated doses of oral levofolinic acid has not been compared with that of FA. We decided to perform a study to evaluate the therapeutic effectiveness of oral levofolinic acid, the pharmacologically active form of folinic acid in our population of HD patients already on treatment with oral FA and vitamin B6. MATERIAL AND METHODS: We undertook a prospective study in HD patients who had been receiving oral supplements of both FA 5 mg every 48 hours and vitamin B6 40 mg every 7 days during at least 6 months, with a 17% initial decrease of tHcy levels. Patients matched for age, sex and time on HD were assigned to 1 of 2 groups: Those in group A continued to receive their previous supplements while in group B, FA was substituted by calcium levofolinate 5 mg given orally every 48 hours. The following parameters were measured at baseline and at month 6: urea kinetic model and concentrations of plasma albumin, C-reactive protein, folate, vitamin B12, pyridoxal phosphate and tHcy. RESULTS: Group A: 30 patients aged 63.4 (57.9, 68.9) years, with a time on HD of 23.4 (15.8, 30.8) months, group B: 32 age-matched patients 66.2 (62.1, 70.3) years old, with a time on HD of 23.8 (16.7, 30.9) months. No differences were found either in folate levels (72.7 (47.9, 97.5) vs. 71.9 (44.0. 99.9) ng/ml), tHcy (23.5 (21.1, 25.9) vs. 23.3 (20.8, 25.8) micromol/l), or any other study variables. In the 2 groups a significant reduction in both residual renal function (RRF) and vitamin B12 levels was observed after supplementation, but no changes in tHcy values, folate levels or any of the other parameters were found. The prevalence of hyperhomocysteinemia in group A was 93.3% at study start and 100% at month 6, in group B the corresponding values were 93.8% and 96.9%. After 6 months, multiple regression analysis showed that tHcy levels were not influenced by the type of treatment (p = 0.543). CONCLUSIONS: After 6 months of calcium-levofolinate supplementation tHcy levels did not decrease and were similar to those in patients given the same dose of FA.

Aged↗
PubMed2001

Molecular dynamics simulations of the mononuclear zinc-beta-lactamase from Bacillus cereus complexed with benzylpenicillin and a quantum chemical study of the reaction mechanism.

Herein, we present results from MD simulations of the Michaelis complex formed between the B. cereus zinc-beta-lactamase enzyme and benzylpenicillin. The structural and dynamical effects induced by substrate-binding, the specific role of the conserved residues, and the near attack conformers of the Michaelis complex are discussed. Quantum chemical methods (HF/6-31G* and B3LYP/6-31G*) are also applied to study the hydrolysis reaction of N-methylazetidinone catalyzed by a monozinc system consisting of the side chains of the histidine residues (His86, His88, and His149) complexed with Zn-OH and the side chains of Asp90 and His210. From this model system, we built molecular-mechanics representations of the prereactive complex and transition state configurations docked into the active site. Linear-scaling semiempirical calculations coupled with a continuum solvent model were then performed on these static models. We propose that the experimental rate data for the B. cereus enzyme is compatible with a one-step mechanism for the hydrolysis of beta-lactam substrates in which His210 acts as a proton donor.

Bacillus cereus↗
PubMed2001

A theoretical study of the aminolysis reaction of lysine 199 of human serum albumin with benzylpenicillin: consequences for immunochemistry of penicillins.

Herein, we present results of a computational study on benzylpenicillin attachment to Lys199 of human serum albumin via an aminolysis reaction. The internal geometry of the reactive part of the system was taken from previous work at the B3LYP/6-31+G* level on the water-assisted aminolysis reaction of a penicillin model compound (Díaz, N.; Suárez, D.; Sordo, T. L. J. Am. Chem. Soc. 2000, 122, 6710--6719). The protein environment around Lys199, the 6-acylamino side chain, and the 2-methyl groups of benzylpenicillin were relaxed by carrying out geometry optimizations with a hybrid QM/MM method (PM3/AMBER). Two different mechanistic routes were explored: a one-step water-assisted process and a carboxylate and water-assisted route in which the beta-lactam carboxylate and the ancillary water molecule mediate the proton transfer from the epsilon-amino group of Lys199 to the beta-lactam leaving N atom. The corresponding energy profiles in the protein combine the B3LYP/6-31+G* and PM3 energies of the reactive subsystem (benzylpenicillin + Lys199 side chain + the ancillary water molecule) and semiempirical PM3 energies of the entire system evaluated with a "divide and conquer" linear-scaling method. It is observed that penicillin haptenation to HSA can proceed through the water-assisted concerted mechanism which is calculated to have a high energy barrier of approximately 38 kcal/mol, in agreement with the experimentally observed slow reaction kinetics.

Humans↗
PubMed2001

Quantum chemical study of ester aminolysis catalyzed by a single adenine: a reference reaction for the ribosomal peptide synthesis.

Herein we report the results of a HF/6-31+G** and B3LYP/6-31+G** computational investigation of the title reaction for the peptide bond synthesis catalyzed by a single adenine. This system constitutes a reference reaction to study the basic chemical events that have been proposed to occur at the peptidyl transferase active site of ribosomes on the basis of structural determinations (Science 2000, 239, 920--931). Thus, the analysis of the geometry, charge distribution, and energetics of the critical structures involved in this title reaction yields insight into the catalytic mode of action of RNA molecules. Our computational results give further support to the hypotheses that the activated nucleotide A2451 in the ribosome acts as a base catalyst and that this role is similar to that of the His residue in the catalytic triad of serine proteases.

Acetates↗
PubMed2001

Evaluation of the catalytic mechanism of AICAR transformylase by pH-dependent kinetics, mutagenesis, and quantum chemical calculations.

The catalytic mechanism of 5-aminoimidazole-4-carboxamide ribonucleotide transformylase (AICAR Tfase) is evaluated with pH dependent kinetics, site-directed mutagenesis, and quantum chemical calculations. The chemistry step, represented by the burst rates, was not pH-dependent, which is consistent with our proposed mechanism that the 4-carboxamide of AICAR assists proton shuttling. Quantum chemical calculations on a model system of 5-amino-4-carboxamide imidazole (AICA) and formamide using the B3LYP/6-31G level of theory confirmed that the 4-carboxamide participated in the proton-shuttling mechanism. The result also indicated that the amide-assisted mechanism is concerted such that the proton transfers from the 5-amino group to the formamide are simultaneous with nucleophilic attack by the 5-amino group. Because the process does not lead to a kinetically stable intermediate, the intramolecular proton transfer from the 5-amino group through the 4-carboxamide to the formamide proceeds in the same transition state. Interestingly, the calculations predicted that protonation of the N3 of the imidazole of AICA would reduce the energy barrier significantly. However, the pK(a) of the imidazole of AICAR was determined to be 3.23 +/- 0.01 by NMR titration, and AICAR is likely to bind to the enzyme with its imidazole in the free base form. An alternative pathway was suggested by modeling Lys266 to have a hydrogen-bonding interaction with the N3 of the imidazole of AICAR. Lys266 has been implicated in catalysis based on mutagenesis studies and the recent X-ray structure of AICAR Tfase. The quantum chemical calculations on a model system that contains AICA complexed with CH3NH3+ as a mimic of the Lys residue confirmed that such an interaction lowered the activation energy of the reaction and likewise implicated the 4-carboxamide. To experimentally verify this hypothesis, we prepared the K266R mutant and found that its kcat is reduced by 150-fold from that of the wild type without changes in substrate and cofactor Km values. The kcat-pH profile indicated virtually no pH-dependence in the pH range 6-10.5. The results suggest that the ammonium moiety of Lys or Arg is important in catalysis, most likely acting as a general acid catalyst with a pK(a) value greater than 10.5. The H267A mutant was also prepared since His267 has been found in the active site and implicated in catalysis. The mutant enzyme showed no detectable activity while retaining its binding affinity for substrate, indicating that it plays a critical role in catalysis. We propose that His267 interacts with Lys266 to aid in the precise positioning of the general acid catalyst to the N3 of the imidazole of AICAR.

Binding Sites↗
PubMed2001

Molecular dynamics simulations of the mononuclear zinc-beta-lactamase from Bacillus cereus.

Herein, we report molecular dynamics simulations of the mononuclear form of the Bacillus cereuszinc-beta-lactamase. We studied two different configurations which differ in the presence of a zinc-bound hydroxide or a zinc-bound water and in the protonation state of the essential His210 residue. Contacts of the catalytically important residues (Asp90, His210, Cys168, etc.) with the zinc center are characterized by the MD analyses. The nature of the Zn-OH(2) --> His210 proton transfer pathway connecting the two configurations was studied by means of QM calculations on cluster models while the relative stability of the two configurations was estimated from QM/MM calculations in the enzyme. From these results, a theoretical model for the kinetically active form of the B. cereus metalloenzyme is proposed. Some mechanistic implications and the influence of mutating the Cys168 residue are also discussed.

Bacillus cereus↗
PubMed2001

Molecular dynamics study of the IIA binding site in human serum albumin: influence of the protonation state of Lys195 and Lys199.

The IIA binding site of human serum albumin (HSA) preferentially binds hydrophobic organic anions of medium size (e.g., aspirin, benzylpenicillin, warfarin, etc.) and bilirubin. This binding ability is particularly important for the distribution, metabolism, and efficacy of drugs. In addition, HSA can also covalently link to different IIA substrates owing to the presence of a highly reactive residue, Lys199, which is strategically located in the IIA site. Herein, we present results of three restrained molecular dynamics (MD) simulations of the IIA binding site on the HSA protein. From these simulations, we have determined the influence that the ionization state of the key residue, Lys199, and the nearby Lys195 has on the structure and dynamics of the IIA binding site. When Lys199 is neutral the computed average distances for the most significant interresidue contacts are in good agreement with those estimated from the X-ray coordinates. The analysis of the solvent structure and dynamics indicates that the basic form of Lys199 is likely connected to the acid form of Lys195 through a network of H-bonding water molecules with a donor --> acceptor character. The presence of these water bridges can be important for stabilizing the configuration of the IIA binding site and/or promoting a potential Lys195 --> Lys199 proton-transfer process. These results suggest that both lysine residues located in the IIA binding site of HSA, Lys195 and Lys199, could play a combined and comparable chemical role. Our simulations also give insight into the binding of bilirubin to HSA.

Binding Sites↗
PubMed2001

Multicenter randomized study comparing initial daily induction with high dose lymphoblastoid interferon vs. standard interferon treatment for chronic hepatitis C.

One hundred fifty-five chronic hepatitis C patients were assigned at random to receive natural lymphoblastoid interferon (IFN)alpha-n1, s.c., for 13 months in one of three treatment regimens: initial daily induction with 10 million units (MU) followed (group 1, n = 50) or not (group 2, n = 52) by 1 month of rest and then three times weekly 10 MU (2 months), 5 MU (2 months), and 3 MU (8 months); group 3 (n = 53) received tiw 5 MU (2 months) followed by 3 MU (11 months). By intention-to-treat analysis, ALT normalization at completion of treatment was greater in patients who received continuous IFNalpha-n1 therapy with initial daily induction (group 2: 24/52, 46%) compared with those given intermittent therapy with initial daily induction (group 1: 17/50, 34%) and those who received standard IFNalpha-n1 therapy (group 3, 18/53, 34%; P not significant). The sustained ALT response was 26%, 27% and 21% and the sustained virological response was 20%, 27%, and 19%, in groups 1, 2, and 3, respectively. A trend was observed towards a higher biochemical and virological end-of-treatment response in patients given induction therapy (17%) compared with standard therapy (6%, P = 0.053). Sustained biochemical and virological responses were 20%, 27%, and 17% in groups 1, 2, and 3, respectively. Platelet and leukocyte counts decreased following daily high-dose treatment and remained low until therapy cessation (P < 0.001). The data suggest that daily s.c. induction with 10 MU IFNalpha-n1 followed by intermittent or continuous maintenance therapy for 1 year does not improve the results achieved with the standard 1-year IFNalpha course in the treatment of chronic hepatitis C patients.

Adolescent↗
PubMed2001

New developments in applying quantum mechanics to proteins.

Algorithmic improvements of quantum mechanical methodologies have increased our ability to study the electronic structure of fragments of a biomolecule (e.g. an enzyme active site) or entire biomolecules. Three main strategies have emerged as ways in which quantum mechanics can be applied to biomolecules. The supermolecule approach continues to be utilized, but it is slowly being replaced by the so-called coupled quantum mechanical/molecular mechanical methodologies. An exciting new direction is the continued development and application of linear-scaling quantum mechanical approaches to biomolecular systems.

Algorithms↗
PubMed1999

Myelodysplastic syndrome: a search for minimal diagnostic criteria.

We have evaluated dyshemopoietic features in bone marrow (BM) samples obtained from healthy people aged over 50 without peripheral blood (PB) cytopenia patients and compared them with MDS patients. Control group displayed BM features of dyserythropoiesis and dysgranulopoiesis in up to 15 and 27% of the considered cell elements (P90) respectively, overlapping in part with MDS patients. Interobserver agreement in dyshemopoietic features was highest for BM blast cell and pathological sideroblast counts. An algorithm based on BM blast cell and pathological sideroblast counts that has been verified on 613 patients from different Spanish centers may be of help to improve reproducibility in Myelodysplastic syndrome (MDS) diagnosis.

Cells, Cultured↗
PubMed1999

The mechanical behaviour of human mandibles studied by electronic speckle pattern interferometry.

An understanding of the mechanical behaviour of the human mandible during mastication may be useful in several specific medical fields that examine the maxillofacial area. In this research, the Electronic Speckle Pattern Interferometry Optical Technique was applied to study a dry mandible under external stress. Two images of the mandible, i.e. an image of the relaxed mandible and another of the mandible under stress, were processed using this technique and provided information concerning the most stressed areas of the bone. The advantage of interferometric analysis is that it can be carried out in real time on a mandible to which progressively greater stress has been applied. This research may be of value in maxillofacial surgery, for example, in the diagnosis and treatment of fractured mandibles, and in oral surgery and orthodontics, where it can provide information concerning stress dispersion when an osteointegrated implant or orthodontic appliance is placed in the mouth. One of the most important conclusions to be drawn from the experiments of tension, compression, and in- and out-of-plane deformations is that the capability of the mandible to bend is superior to its capability to stretch. Several quantitative results support this conclusion.

Female↗
PubMed1998

[Intestinal obstruction and necrotizing thyroiditis secondary to Pneumocystis carinii infection in a seropositive hemophiliac patient seropositive for human immunodeficiency virus].

We report a case of bowel infection by Pneumocystis carinii (PC) that presented as an acute obstruction accompanied by intestinal hemorrhage (melena) in a HIV seropositive hemophilic patient. Laparotomy followed by resection of two plaque-like jejunal tumors was performed, and intravenous therapy with pentamidine was initiated. No other organ was found to be affected by PC (not even the lung), with the exception of the thyroid gland. To our knowledge, this is the first reported case in which acute intestinal obstruction was the presenting symptom of extrapulmonary pneumocystosis.

AIDS-Related Opportunistic Infections↗