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Biomedical subjects

M M Silva

Publications and source records attributed to M M Silva.

At least 19 recordsLinked to original sources

Attention-memory interactions in scene perception.

The perception of natural scenes relies on the integration of pre-existing knowledge with the immediate results of attentional processing, and what can be remembered from a scene depends in turn on how that scene is perceived and understood. However, there are conflicting results in the literature as to whether people are more likely to remember those objects that are consistent with the scene or those that are not. Moreover, whether any discrepancy between the likelihood of remembering schema-consistent or schema-inconsistent objects should be attributed to the schematic effects on attention or on memory remains unclear. To address this issue, the current study attempted to directly manipulate attention allocation by requiring participants to look at (i) schema-consistent objects, (ii) schema-inconsistent objects, or (iii) to share attention equally across both. Regardless of the differential allocation of attention or object fixation, schema-consistent objects were better recalled whereas recognition was independent of schema-consistency, but depended on task instruction. These results suggest that attention is important both for remembering low-level object properties, and information whose retrieval is not supported by the currently active schema. Specific knowledge of the scenes being viewed can result in the recall of non-fixated objects, but without such knowledge attention is required to encode sufficient detail for subsequent recognition. Our results demonstrate therefore that attention is not critical for the retrieval of objects that are consistent with a scene's schematic content.

Attention↗

Pediatric liver transplantation: fourteen years of experience at the children institute in São Paulo, Brazil.

This study reports the 14-year experience of a single center on 206 liver transplantations from living and cadaveric donors performed in 179 pediatric patients. Biliary atresia (57.2%) and fulminant hepatitis (9.8%) were the most frequent indications. The mean age of the recipients was 3 years, 7 months (9 months to 18 years) and mean weight was 14 kg (7 to 57 kg). The allografts were distributed as 82 (39.8%) whole cadaveric, 76 (36.9%) reduced-size cadaveric, 46 (22.3%) living donor liver transplants, and 2 (0.9%) ex situ split livers. The waiting periods were 25 days for living donors and 2.5 years for cadaveric donors (P <.001). Twenty-seven children were retransplanted with hepatic artery thrombosis the most frequent indication. The postoperative complications were: primary nonfunction (12.2%), biliary stenosis (28.8%), hepatic artery thrombosis (12.2%), portal vein stenosis (4.9%), hepatic vein stenosis (6.9%), and lymphoproliferative disorder (5.9%). The diagnosis of biliary stenosis was obtained by liver biopsy and transhepatic cholangiography and treated by balloon dilatation, although four children (3.9%) required a redo hepaticojejunostomy. The venous stenoses were percutaneously dilated with five-children (4.9%) requiring venous stents. The incidence of hepatic vein stenosis was 15.6% among living donor and 2.5% in cadaveric liver transplantation (P <.05). The overall 5-year patient and graft survivals were 70.2% and 65.1%. Liver transplantation provides excellent long-term survival. The use of grafts from living donors decreases the waiting periods but increases the incidence of hepatic vein stenosis.

Brazil↗

Basiliximab-chimeric anti-IL2-R monoclonal antibody in pediatric liver transplantation: comparative study.

Basiliximab is a monoclonal antibody that binds to the alpha subunit (CD(25)) of the interleukin-2 receptor of activated T lymphocytes. The advantage of basiliximab in organ transplantation is the reduce possibility to calcineurin inhibitor dosages to avoid nephrotoxicity. Basiliximab has significantly reduced the incidence of acute rejection (AR) in renal transplant recipients; however, the results are uncertain in liver transplantation (LT). The objective of this investigation was to assess the effect of basiliximab to prevent AR in the first 6 months after pediatric LT. From March 2000 to October 2001, 32 recipients of a primary orthotopic cadaveric or living donor LT were given basiliximab by intravenous bolus injection on the day of transplantation (day 0) and on day 4. Four children who received one dose were excluded from the study. The rate and the intensity of AR episodes, the incidence of chronic rejection, serum creatinine level, incidence of infections, adverse side effects, and daily oral dosage of cyclosporine (Neoral) to maintain the target blood level of 850 to 1000 mg/dL at C2, 2 hours after the administration, were analyzed in the remaining 28 recipients. Results were compared to those obtained from a matched historical group (n = 28) of similar age, weight, and hepatic diseases distribution. None of the analyzed parameters was statistically significant (P >.05) except for the daily oral dose of cyclosporine (7 to 13 mg/kg/dose, P <.05). In our series, the addition of basiliximab to the immunosuppressive therapy did not reduce the incidence of AR in pediatric LT.

Adolescent↗

A polyethylenetherephthalate (PET) device for sampling freshwater benthic macroinvertebrates.

A new device to sample freshwater benthic macroinvertebrates was used in a low and sandy stretch of a Brazilian sub-tropical river (the River Cai, Triunfo, RS) and in one of its small tributaries, Bom Jardim brook (Arroio Bom Jardim). In this study, the effectiveness of this device, a PET sampler, was tested at different sites in the river and the brook throughout the four seasons between 2001-2002. Comparisons were made by PCA and ANOVA, both employing a bootstrap procedure based on similarity matrices. The PET sampler proved to be a reliable tool for detection of seasonal and spatial differences in richness, total abundance of organisms, and Shannon's diversity index in both river and brook and is therefore recommended for use in the monitoring of macroinvertebrate communities in this system.

Analysis of Variance↗

The role of phospholipase A(2) and cyclooxygenase in renal toxicity induced by microcystin-LR.

We have shown previously that exposure to microcystin-LR (MCLR) causes renal toxic effects in isolated perfused rat kidney. That study was extended further to approach the perspective of pharmacological blockade of renal toxic effects by MCLR through the use of experimental therapeutic agents. An isolated kidney perfusion system was utilized and samples of urine and perfusate were collected at 10min intervals to determine the levels of inulin, sodium, potassium and osmolality. Dexamethasone (20microg ml(-1)) and indomethacin (10microg ml(-1)) were administered in the beginning of the perfusion and MCLR was employed in a dose of 1microg ml(-1) after an internal control of 30min to evaluate the perfusion pressure (PP), renal vascular resistance (RVR), glomerular filtration rate (GFR) and urinary flow (UF). Dexamethasone and indomethacin antagonized the toxic effects of MCLR on PP, RVR, GFR and UF. Histologic analysis of dexamethasone and indomethacin treated groups did not show any vascular or interstitial alterations. MCLR potentially impairs the renal function, probably causing vascular and glomerular lesions and, promoting renal alterations through direct or indirect actions. These data seem to indicate that the renal alterations promoted by MCLR involves also phospholipase A(2) and arachidonic acid-derived mediators.

Analysis of Variance↗

Optic pathway hypothalamic gliomas in children under three years of age: the role of chemotherapy.

OBJECTIVES: Optic pathway/hypothalamic gliomas (OPHGs) tend to occur in young children. Treatment options consist of surgical resection, radiation therapy (RT) and chemotherapy. Due to complications induced by surgery and RT, chemotherapy has gained significant recognition for the treatment of OPHG in young children. Chemosensitivity of OPHG in very young children under 3 years of age has not been well documented. We analyzed 14 patients who were treated with chemotherapy with or without surgery. MATERIALS AND METHODS: Fourteen children younger than 3 years (median age of 10 months) with OPHG were treated between 1988 and 1998. Magnetic resonance imaging was obtained in all cases. Hydrocephalus was present in 8 patients and diencephalic syndrome was noted in 6. Only 3 of these had evidence of neurofibromatosis-1. Five patients had partial tumor resection and 4 had endoscopic biopsy at the time of ventriculoperitoneal shunt placement. Pathological examination revealed low-grade astrocytoma in 5 and juvenile pilocytic astrocytoma in 4. All patients received chemotherapy: carboplatin in 8, a combination of carboplatin and vincristine in 4 and a combination of other agents in 2. RESULTS: Eight (57%) of 14 patients had a sustained reduction of tumor during the follow-up time between 15 months and 8 years. The 5-year progression-free survival was 63%. These tumor reductions were often accompanied by clinical improvements. Diencephalic syndrome responded to chemotherapy alone in 4 of 6 patients. However, 5 others had progressive disease; 3 during the treatment and 2 following the treatment (9 months and 2 years, respectively). All these 5 patients had a partial tumor resection prior to chemotherapy. CONCLUSION: A majority of OPHGs responds to chemotherapy. Due to slow progression of these tumors and adverse effects of other therapeutic modalities, we recommend chemotherapy as a primary treatment for OPHGs. Our present data indicates that partial surgical resection does not enhance chemotherapy effectiveness for OPHGs in infants or children younger than 3 years.

Antineoplastic Combined Chemotherapy Protocols↗

Functional phage display of leech-derived tryptase inhibitor (LDTI): construction of a library and selection of thrombin inhibitors.

The recombinant phage antibody system pCANTAB 5E has been used to display functionally active leech-derived tryptase inhibitor (LDTI) on the tip of the filamentous M13 phage. A limited combinatorial library of 5.2 x 10(4) mutants was created with a synthetic LDTI gene, using a degenerated oligonucleotide and the pCANTAB 5E phagemid. The mutations were restricted to the P1-P4' positions of the reactive site. Fusion phages and appropriate host strains containing the phagemids were selected after binding to thrombin and DNA sequencing. The variants LDTI-2T (K8R, I9V, S10, K11W, P12A), LDTI-5T (K8R, I9V, S10, K11S, P12L) and LDTI-10T (K8R, I9L, S10, K11D, P12I) were produced with a Saccharomyces cerevisiae expression system. The new inhibitors, LDTI-2T and -5T, prolong the blood clotting time, inhibit thrombin (Ki 302 nM and 28 nM) and trypsin (Ki 6.4 nM and 2.1 nM) but not factor Xa, plasma kallikrein or neutrophil elastase. The variant LDTI-10T binds to thrombin but does not inhibit it. The relevant reactive site sequences of the thrombin inhibiting variants showed a strong preference for arginine in position P1 (K8R) and for valine in P1' (I9V). The data indicate further that LDTI-5T might be a model candidate for generation of active-site directed thrombin inhibitors and that LDTI in general may be useful to generate specific inhibitors suitable for a better understanding of enzyme-inhibitor interactions.

Amino Acid Sequence↗

Management of biliary atresia in the liver transplantation era: a 15-year, single-center experience.

BACKGROUND/PURPOSE: The aim of this study was to address the perioperative aspects of hepatoportoenterostomy (HPE) for biliary atresia (BA), through the study of a 15-year, single-center experience of the management of this disease. METHODS: One hundred twenty-seven patients were divided into three groups, depending on the variant of HPE performed: group A (n = 53) underwent HPE with external diversion of the Roux-en-Y anastomosis; group B (n = 54) underwent HPE with a long (35 to 40 cm) Roux-en-Y anastomosis, without diversion; and group C (n = 20) underwent the same kind of HPE as group B, but with a modified, "super extensive" dissection of the porta hepatitis. Eleven children in group B had an intussusception type antireflux valve in the Roux-en-Y loop. The porta hepatitis of 105 children was histologically classified in types I to III and correlated with rate of postoperative bile flow and age at surgery. Liver transplantation was performed after HPE in 20 patients. RESULTS: Overall, biliary drainage was achieved in 72.5% of the children after HPE and 26.8% of all patients became jaundice free. Porta hepatitis type III was associated with a significantly higher rate of biliary drainage post-HPE then types I and II. There was no difference in the rate of bile drainage, relative number of jaundice-free patients, and mean number of episodes of cholangitis per year among surgical groups A, B, C. In group A, 43.7% of the patients had complications related to the stoma. The actuarial survival of children who underwent HPE followed by liver transplantation was 85%. CONCLUSIONS: (1) There is no correlation between type of porta hepatis and age at surgery for BA; (2) type III porta hepatis is associated with higher rates of bile drainage post-HPE; (3) children older than 16 weeks with BA should still be considered for HPE; (4) in these older patients, factors other than the type of porta hepatis, possibly the degree of liver damage, play a role in the lower rate of bile drainage observed; (5) external diversion of the Roux-en-Y in HPE is not beneficial and is detrimental because of stoma-related complications; (6) an antireflux valve in the Roux-en-Y loop does not reduce the incidence of cholangitis post-HPE; (7) Surgical reexploration does not restore biliary drainage; and (8) sequential therapy with HPE followed by liver transplantation remains the treatment of choice for BA.

Actuarial Analysis↗

[Isolation of rabies virus from an insectivorous bat, Nyctinomops macrotis, in southeast Brazil].

The rabies virus was isolated from an insectivorous bat, Nyctinomops macrotis, trapped in Diadema, SP, Brazil, in a public building near a water supply reservoir. Fluorescent antibodies against rabies virus were detected in cerebral tissue and the viral isolation was made after the inoculation of cerebral tissue and salivary gland suspension in mice. There have been no recorded cases of animal rabies in Diadema since 1982, and this is the first isolation of the rabies virus in an insectivorous bat in the city.

Animals↗

Refinement and comparisons of the crystal structures of pig cytosolic aspartate aminotransferase and its complex with 2-methylaspartate.

Two high resolution crystal structures of cytosolic aspartate aminotransferase from pig heart provide additional insights into the stereochemical mechanism for ligand-induced conformational changes in this enzyme. Structures of the homodimeric native structure and its complex with the substrate analog 2-methylaspartate have been refined, respectively, with 1.74-A x-ray diffraction data to an R value of 0.170, and with 1.6-A data to an R value of 0.173. In the presence of 2-methylaspartate, one of the subunits (subunit 1) shows a ligand-induced conformational change that involves a large movement of the small domain (residues 12-49 and 327-412) to produce a "closed" conformation. No such transition is observed in the other subunit (subunit 2), because crystal lattice contacts lock it in an "open" conformation like that adopted by subunit 1 in the absence of substrate. By comparing the open and closed forms of cAspAT, we propose a stereochemical mechanism for the open-to-closed transition that involves the electrostatic neutralization of two active site arginine residues by the negative charges of the incoming substrate, a large change in the backbone (phi,psi) conformational angles of two key glycine residues, and the entropy-driven burial of a stretch of hydrophobic residues on the N-terminal helix. The calculated free energy for the burial of this "hydrophobic plug" appears to be sufficient to serve as the driving force for domain closure.

Acetic Acid↗

Using the ICSOoL to measure the impact of lower urinary tract symptoms on quality of life: evidence from the ICS-'BPH' Study. International Continence Society--Benign Prostatic Hyperplasia.

OBJECTIVE: To present and describe the validity and reliability of the International Continence Society-Benign Prostatic Hyperplasia study quality-of-life (ICSQoL) instrument, a new set of questions to assess the impact of lower urinary tract symptoms (LUTS) on quality of life (QoL) in middle-aged and elderly men. PATIENTS AND METHODS: The study comprised 1271 consecutive men over the age of 45 years, attending urology departments in 12 countries, with LUTS and possible benign prostatic obstruction who were recruited to the ICS-'BPH' study (the clinic group); 423 ambulant men were recruited from a general practice in the UK to provide a community group. Each individual completed the ICS-'BPH' study questionnaire which includes six items addressing general and specific aspects of QoL (the ICSQoL). Content and construct validity were assessed by interviews with patients and by testing hypotheses within the study groups, e.g. the relationships with age, individual LUTS (as measured on the ICSmale questionnaire) and generic health status, as measured by the Short Form (SF-36) and EuroQol instruments. Reliability was assessed by measures of internal consistency and a test-retest analysis. RESULTS: The ICSQoL items were easily understood by patients, were completed with low levels of missing data, and address some (but not all) concerns about the impact of LUTS on QoL. The ICSQoL items have good construct validity, showing expected differences between community and clinic samples, and expected relationships with each other and individual LUTS. Items had good test-retest reliability, but their internal consistency was poor, confirming that ICSQoL questions should not be combined into a score. General ICSQoL items were closely related with most domains of the SF-36 and the EuroQol. CONCLUSION: ICSQoL items may be used individually or as a group in research studies or in clinical practice.

Aged↗

Refined crystal structures of unligated adenylosuccinate synthetase from Escherichia coli.

Crystal structures of unligated adenylosuccinate synthetase from Escherichia coli in space groups P2(1) and P2(1)2(1)2(1) have been refined to R-factors of 0.199 and 0.206 against data to 2.0 and 2.5 A, respectively. Bond lengths and angles deviate from expected values by 0.011 A and 1.7 degrees for the P2(1) crystal form and by 0.015 A and 1.7 degrees for the P2(1)2(1)2(1) crystal form. The fold of the polypeptide chain is dominated by a central beta-sheet, which is composed of nine parallel strands and a tenth antiparallel strand. Extending off from this central beta-sheet are four subdomains. The four subdomains contribute loops of residues that are disordered or have high thermal parameters. At least three of these loops (residues 42 to 52, 120 to 131 and 298 to 304) contribute essential residues to the putative active site of the synthetase. In the absence of ligands, much of the active site of the synthetase exists in an ill-defined conformational state. Two, nearly independent regions contribute residues to the interface between polypeptide chains of the synthetase dimer. A pair of helices (H4 and H5) interact with their symmetry-equivalent mates by way of residues that are not conserved amongst the known sequences of the synthetase. The second interface region involves conserved residues belonging to structural elements that connect strands of the central beta-sheet. Residues putatively involved in the binding of IMP lie at or near the interface between polypeptide chains of the dimer. Of the four sequence elements putatively common to all GTP hydrolases, the synthetase has only the guanine recognition element and a glycine-rich loop (P-loop). Although the base recognition element is essentially identical with those of the p21 ras and G alpha proteins, the P-loop of the synthetase is extended in size relative to the P-loops of other GTP hydrolases. The P-loop has two acid residues (Asp13 and Glu14), which are found in the P-loops of only the synthetase family. Glu14 may be involved in the stabilization of the enlarged P-loop of the synthetase, whereas Asp13 may play a role in catalysis and in the coordination of Mg2+. The structural elements of the p21 ras and G alpha proteins responsible for binding Mg2+ are either absent from the synthetase or unavailable for the coordination of metal cations.

Adenylosuccinate Synthase↗

[Isolation of rabies virus from the insectivorous bat Myotis nigricans].

The following is a case study of the natural infection by the rabies virus of an insectiverous bat belonging to the species Myotis nigricans in the municipality of Ribeirão Pires, Greater S. Paulo. Diagnosis was made by means of immunofluorescence and intracerebral innoculation of mice with nervous and intrascapular muscular tissues.

Animals↗

[Rabies in insectivorous (Mollossidae) bats of southeastern Brazil].

Four rabid bats belonging to three species of Molossidae (one Molossus molossus, one Nyctinomops laticaudatus and two N. macrotis) were captured in the State of S. Paulo, southeastern Brazil. Three of these bats were found during the day in unusual, visible places and the other came flying through a window in the evening. A descriptive table containing data on 19 similar cases, belonging to eight species, is presented and suggests that bats with atypical behavior must dearly be suspected of being sick, possibly as having rabies.

Animals↗

[Lumbar spinal stenosis. Significance of neurophysiologic tests].

The authors review Lumbar Spinal Stenosis discussing the diagnostic criteria, the etiopathogenesis, and clinical manifestations. Imaging and neurophysiological investigations are also discussed. EMG, Sensory Evoked Potencials and Motor Stimulation are described stressing their role in differential diagnosis. The therapeutic approach is briefly commented.

Diagnosis, Differential↗