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Biomedical subjects

J Silva

Publications and source records attributed to J Silva.

At least 73 records · Page 4Linked to original sources
PubMed2000

Auditory event-related potentials in poor readers.

Although poor readers (PR) are considered the major group among reading-disabled children, there are not event-related potentials (ERP) studies reported of PR on the subject. In this study, attentional and memory processes were studied in an auditory oddball task in PR and normal controls. ERP to auditory stimuli were recorded in 19 leads of the 10/20 system, using linked earlobes as references, in 20 normal children (10 female) and 20 PR (10 female) of the same age (10-12 years old). Two pure tones (1000 and 3000 Hz) were used in an oddball paradigm. No significant differences were observed in the amplitudes and latencies of N100 between the groups. However, N200 to frequent stimuli and P200 to both frequent and infrequent stimuli were of higher amplitude in poor readers than in normal children. There were no differences between groups in the latency and amplitude of P300. The results suggest that PR use more attentional resources in the components occurring before P300 to both frequent and infrequent stimuli than the normal children, and this finding is particularly marked for PR girls.

Child↗
PubMed2000

[Midterm results of coronary bypass surgery exclusively with arterial revascularization].

INTRODUCTION AND OBJECTIVES: In recent years, the exclusive use of arterial grafts in coronary surgery has been the surgical option to achieve maximum survival and minimum recurrence of coronary events. The aim of this study was to analyze the surgical results and follow up of this approach. PATIENTS AND METHODS: Over a period of six and a half years, 87 patients underwent coronary surgery using arterial grafts alone for revascularization. The mean age of the patients was 62 +/- 1 years with 78 men and 9 women; 22 patients (25%) were clinically unstable. The number of vessels affected per patient was 1.83 +/- 0.1, and the number of patients with one, two and three affected vessels, were 38 (44%), 26 (30%) and 23 (26%), respectively. The mean ejection fraction was 63 +/- 1.6. Emergency surgery was carried out in 13 cases (16%). RESULTS: A total of 1.9 +/- 0.1 grafts were implanted per patient and complete revascularization was achieved in 65 cases (75%). The left mammary artery was used in 87 cases (100%), the right mammary artery in 31 (35.6%) and the radial artery in 20 cases (23%). Hospital mortality was 1.1% (one case). During the postoperative period, 3 patients (3.4%) presented myocardial infarction, 12 (13.8%) atrial fibrillation and there were 3 cases of sternal dehiscence.A total of 86 patients (98.9%) were followed over a mean period of 24.5 +/- 0.5 months. Survival, angina-free period and period free of any coronary event at 5 years were 97 +/- 0.05%, 89 +/- 0.1% and 87 +/- 0.1% respectively (mean +/- standard error, CI 95%). On multivariate analysis, the presence of peripheral vascular disease (p < 0.015) and the development of low cardiac output (p < 0.04) or atrial fibrillation (p < 0.04) during the postoperative period were predictive factors for the appearance of coronary events during follow-up. CONCLUSIONS: Surgery exclusively with arterial grafts achieves good medium term results in relation to survival and time free of coronary events.

Arteries↗
PubMed2000

Genotyping of Bacteroides fragilis isolates from stool specimens by arbitrarily-primed-PCR.

In order to determine genetic relatedness of Bacteroides fragilis isolates from different clinical sources, arbitrarily primed polymerase chain reaction (PCR) (AP-PCR) was used to compare 17 strains isolated from patients with inflammatory bowel disease (IBD) and 20 strains isolated from foals with diarrhea. Three reference ATCC strains were also analyzed. Eighteen unique types were identified with a 22-mer arbitrary primer (ERIC-2) among the 20 patient isolates. Types 1 (enterotoxigenic) and 9 (nonenterotoxigenic), were each found in the stools of two patients. All other isolates showed a distinct and unique DNA banding pattern indicating a high degree of genotypic variability. Eleven types were identified among the foal isolates. Type 20, a nonenterotoxigenic type, was present in 30% of the foals. No correlation was found between the human and horse isolates. No clear relationship between a disease state (diarrhea or IBD) and specific types was observed. AP-PCR will be useful as a rapid method to determine genetic relatedness and in future epidemiologic studies of diarrheal diseases due to B. fragilis.

Animals↗
PubMed2000

Clinicopathological characteristics of breast carcinomas with allelic loss in the p73 region.

p73, a new member of the p53 family, has been mapped to chromosome 1p 36, a region where loss of heterozygosity (LOH) is frequently observed in primary human tumors. Allelic loss studies involving the 1p arm in breast carcinomas offer rates ranging from 13% to 75%, depending on the genetic interval being studied. We investigated LOH in an intragenic microsatellite marker, and those centromerically flanking the p73 gene, at 1p 36, and their correlations with patient age and 10 pathologic parameters in a series of 193 breast carcinomas. The LOH analysis was performed by amplifying DNA by PCR, using the five markers of the 1p 36 region (p73P1, D1S2694, D1S214, D1S2666 and D1S450). LOH was found in at least one of these markers in 27% of tumors. When we established the comparison between tumors with and without LOH and the distribution of the 10 pathologic parameters considered, we observed statistically significant differences in association with higher histologic grade (p = 0.02), more advanced pathological stage (p = 0.02), peritumoral vessel involvement (p = 0.04) and poorly differentiated carcinomas (p = 0.01), as well as in tumors that concomitantly exhibited lymph node metastases, peritumoral vessel involvement and absence of steroid receptors (p = 0.02). These data suggest that LOH in the p73 region could be pathogenically related to breast cancer and possibly to a poor tumor prognosis.

Adult↗
PubMed2000

Cocaine increases beta-myosin heavy-chain protein expression in cardiac myocytes.

BACKGROUND: As many as 47% of chronic cocaine users develop cardiac ventricular hypertrophy. The presence and degree of cocaine-induced ventricular hypertrophy is not correlated with the use of other substances of abuse such as alcohol or cigarettes. Moreover, this hypertrophy occurs in individuals without sustained increases in arterial blood pressure or heart rate, or increases in the plasma concentration of renin, aldosterone, norepinephrine, or cortisol. Therefore, we investigated whether cocaine, in concentrations commonly found in cocaine users, has any direct effects on the protein content in cardiac ventricular myocytes. We compared the effects of cocaine with norepinephrine, which increases the total protein content, especially beta-myosin heavy-chain contractile protein (beta-MHC), in cardiac ventricular myocytes. METHODS: Experiments were performed on 30-day-old rat ventricular myocytes suspended in culture media and cultured in flasks. In 12 suspension-culture experiments, cocaine or norepinephrine, in doses of 0 (control) or 10(-6) mol/L was added to each culture and the cells were harvested on day 5. In 16 flask-culture experiments, cocaine or norepinephrine was added to each culture on day 7 in doses of 0 (control-vehicle), 10(-7), or 10(-6) mol/L and the cells were harvested on day 10. The total protein content and the myosin protein expression of the myocytes in each culture were determined. Juvenile and adult rat cardiac myosin protein is predominately alpha-myosin heavy-chain protein (alpha-MHC), whereas beta-MHC occurs primarily in fetal rat hearts. RESULTS: In the suspension-culture experiments, cocaine, 10(-6) mol/L, increased the cardiomyocyte total protein concentration by 29% +/- 2% (P <.001) and the beta-MHC expression by 81% +/- 10% (P <.01) in comparison with the control myocytes. Cocaine slightly decreased cardiomyocyte alpha-MHC. Norepinephrine increased the total protein concentration by 21% +/- 3% (P <.001) and the beta-MHC expression by 59% +/- 10% (P <.01), but did not increase alpha-MHC expression. In the flask-culture experiments, cocaine, 10(-6) mol/L, maximally increased the total protein concentration by 28% (P <.001), the protein/cell ratio by 57% +/- 10% (P <.01), and the beta-MHC expression by 85% +/- 8% (P <.01). Cocaine slightly decreased alpha-MHC. Norepinephrine, 10(-6) mol/L, maximally increased the total protein concentration by 35%, the protein/cell ratio by 63% +/- 9% (P <.01), and the expression of beta-MHC by 78% +/- 11% (P <. 01). Norepinephrine did not increase alpha-MHC expression. In 18 separate flask-culture experiments, cocaine, 10(-6) mol/L, was added to the cardiomyocyte cultures after the addition of phentolamine (n = 9), in concentrations of 10(-7) to 10(-5) mol/L, or metoprolol (n = 9), in concentrations of 10(-7) to 10(-5) mol/L. Neither phentolamine nor metoprolol inhibited the cocaine-induced increase in cardiomyocyte total protein content or the expression of beta-MHC. CONCLUSION: Cocaine, similar to norepinephrine, significantly increases the total protein content and the expression of beta-MHC in cardiac ventricular myocytes. In this manner, cocaine may cause cardiac ventricular hypertrophy. This process is not inhibited by alpha- or beta-adrenergic receptor blockade.

Animals↗
PubMed2000

Early attachment of anaerobic bacteria may play an important role in biliary stent blockage.

BACKGROUND: In vitro studies have demonstrated that ciprofloxacin suppresses Escherichia coli attachment on stents, and ciprofloxacin has been shown to prolong stent patency in cats. However, clinical studies with antibiotic prophylaxis have produced conflicting results. The aim of this study was to isolate and identify the bacteria that attach early on unblocked stents removed from patients and to study their enzyme activities. METHODS: Eighteen unblocked biliary stents were removed from 17 patients (benign obstruction in 14 and malignant obstruction in 4). All patients received antibiotic prophylaxis (mean of 6 days). Stents were in place for a mean of 33 days. The inside of stents was scraped and sludge was cultured aerobically and anaerobically. Identification of isolated bacteria and measurement of beta-glucuronidase and phospholipase C activities were performed by using standard techniques. Gastric and duodenal juice from 18 patients with no biliary diseases was used as control samples. RESULTS: All stents were patent and only 6 had visible sludge. There were 19 anaerobes isolated from 16 stents (Clostridium perfringens 13, Clostridium bifermentans 4 and Bacteroides fragilis 2). Phospholipase C was detected in all Clostridium species. beta-Glucuronidase was produced only by 12 of 13 C perfringens isolates. Sixteen aerobes including Enterococcus species and Bacillus species were isolated but none produced beta-glucuronidase or phospholipase C. There were no aerobic gram-negative bacteria isolated from stents. Clostridium species and B fragilis were not recovered from the control samples. CONCLUSIONS: In patients who had received antibiotic prophylaxis against gram-negative bacterial infection, anaerobic bacteria may play a role in initiating stent blockage.

Adult↗
PubMed2000

Persistence of an endemic (toxigenic) isolate of Clostridium difficile in the environment of a general medicine ward.

The epidemiology of Clostridium difficile-associated diarrhea (CDAD) in an endemic setting was investigated by use of DNA typing methods to determine the strain identity of C. difficile isolates. Two predominant toxigenic clones were found in the environment and accounted for 29.8% (type 1) and 15.5% (type 2) of CDAD cases, respectively. In endemic settings, the environment and cross-transmission may play a role in acquisition of CDAD.

Clostridioides difficile↗
PubMed2000

Analysis of the pathogenicity locus in Clostridium difficile strains.

The genes for Clostridium difficile toxins A and B (tcdA and tcdB) are part of a 19.6-kb pathogenicity locus (PaLoc) that includes the genes tcdD, tcdE, and tcdC. To determine whether the C. difficile PaLoc is a stable and conserved genetic unit in toxigenic strains, a multiplex polymerase chain reaction was used to analyze 50 toxigenic, 39 nontoxigenic, and 2 toxin-defective isolates. The respective amplicons were identified for tcdA-E in the toxigenic isolates; these were absent in the nontoxigenic isolates. C. difficile P-829 lacked at least a fragment of tcdD, tcdB, tcdE, and tcdC, but tcdA was present. C. difficile 8864 had deletions in the tcdA and tcdC genes. These data suggest that the PaLoc is highly stable in toxigenic C. difficile, nontoxigenic isolates lack the unit, and isolates with a defective PaLoc can still cause clinical disease. Further studies are needed to define the role of individual genes in the pathogenesis of C. difficile-associated diarrhea.

Bacterial Proteins↗
PubMed2000

Monte Carlo calculation of dose rate conversion factors for external exposure to photon emitters in soil.

The dose rate conversion factors D(CF) (absorbed dose rate in air per unit activity per unit of soil mass, nGy h(-1) per Bq kg(-1)) are calculated 1 m above ground for photon emitters of natural radionuclides uniformly distributed in the soil. Three Monte Carlo codes are used: 1) The MCNP code of Los Alamos; 2) The GEANT code of CERN; and 3) a Monte Carlo code developed in the Nuclear Technology Laboratory of the Aristotle University of Thessaloniki. The accuracy of the Monte Carlo results is tested by the comparison of the unscattered flux obtained by the three Monte Carlo codes with an independent straightforward calculation. All codes and particularly the MCNP calculate accurately the absorbed dose rate in air due to the unscattered radiation. For the total radiation (unscattered plus scattered) the D(CF) values calculated from the three codes are in very good agreement between them. The comparison between these results and the results deduced previously by other authors indicates a good agreement (less than 15% of difference) for photon energies above 1,500 keV. Antithetically, the agreement is not as good (difference of 20-30%) for the low energy photons.

Health Physics↗
PubMed2000

Loss of heterozygosity at the ACTBP2 locus in lung cancer detected on Elchrom precast Spreadex gels.

One of the most important goals in the continuous struggle against cancer is early detection of the disease by a simple method that can be used in routine laboratory practice. According to several recent reports, early detection may be achieved by monitoring alterations at several microsatellite loci containing tri- and tetranucleotide repeats. The method relies on comparison of the intensity of allele bands in cancer tissue, plasma, and lymphocytes of a patient. Microsatellite instability is typically detected by labeling the DNA with a radioactive probe or a fluorescent dye followed by electrophoresis on 20-40-cm-long denaturing polyacrylamide gels. In this study, we show that loss of heterozygosity at the ACTBP2 locus in lung cancer patients can be detected using the Elchrom electrophoresis system and just 4-cm-long precast Spreadex gels.

Actins↗
PubMed2000

TLA-1: a new plasmid-mediated extended-spectrum beta-lactamase from Escherichia coli.

Escherichia coli R170, isolated from the urine of an infected patient, was resistant to expanded-spectrum cephalosporins, aztreonam, ciprofloxacin, and ofloxacin but was susceptible to amikacin, cefotetan, and imipenem. This particular strain contained three different plasmids that encoded two beta-lactamases with pIs of 7.0 and 9.0. Resistance to cefotaxime, ceftazidime, aztreonam, trimethoprim, and sulfamethoxazole was transferred by conjugation from E. coli R170 to E. coli J53-2. The transferred plasmid, RZA92, which encoded a single beta-lactamase, was 150 kb in length. The cefotaxime resistance gene that encodes the TLA-1 beta-lactamase (pI 9.0) was cloned from the transconjugant by transformation to E. coli DH5alpha. Sequencing of the bla(TLA-1) gene revealed an open reading frame of 906 bp, which corresponded to 301 amino acid residues, including motifs common to class A beta-lactamases: (70)SXXK, (130)SDN, and (234)KTG. The amino acid sequence of TLA-1 shared 50% identity with the CME-1 chromosomal class A beta-lactamase from Chryseobacterium (Flavobacterium) meningosepticum; 48.8% identity with the VEB-1 class A beta-lactamase from E. coli; 40 to 42% identity with CblA of Bacteroides uniformis, PER-1 of Pseudomonas aeruginosa, and PER-2 of Salmonella typhimurium; and 39% identity with CepA of Bacteroides fragilis. The partially purified TLA-1 beta-lactamase had a molecular mass of 31.4 kDa and a pI of 9.0 and preferentially hydrolyzed cephaloridine, cefotaxime, cephalothin, benzylpenicillin, and ceftazidime. The enzyme was markedly inhibited by sulbactam, tazobactam, and clavulanic acid. TLA-1 is a new extended-spectrum beta-lactamase of Ambler class A.

Amino Acid Sequence↗
PubMed2000

Isolation and molecular characterization of Clostridium difficile strains from patients and the hospital environment in Belarus.

Toxigenic Clostridium difficile is the most common etiologic agent of hospital-acquired diarrhea in developed countries. The role of this pathogen in nosocomial diarrhea in Eastern Europe has not been clearly established. The goal of this study was to determine the prevalence of C. difficile in patients and the hospital environment in Belarus and to characterize these isolates as to the presence of toxin genes and their molecular type. C. difficile was isolated from 9 of 509 (1.8%) patients analyzed and recovered from 28 of 1,300 (2. 1%) environmental sites cultured. A multiplex PCR assay was used to analyze the pathogenicity locus (PaLoc) of all isolates, and strain identity was determined by an arbitrarily primed PCR (AP-PCR). The targeted sequences for all the genes in the PaLoc were amplified in all C. difficile strains examined. A predominantly homogeneous group of strains was found among these isolates, with five major AP-PCR groups being identified. Eighty-three percent of environmental isolates were classified into two groups, while patient isolates grouped into three AP-PCR types, two of which were also found in the hospital environment. Although no data on the role of C. difficile infection or epidemiology of C. difficile-associated diarrhea (CDAD) in this country exist, the isolation of toxigenic C. difficile from the hospital environment suggests that this pathogen may be responsible for cases of diarrhea of undiagnosed origin and validates our effort to further investigate the significance of CDAD in Eastern Europe.

Adolescent↗
PubMed2000

Anaerobic bacteria and intrahepatic stones: detections of Clostridium sp. and Bacteroides fragilis.

OBJECTIVE: To detect anaerobic bacteria Clostridium sp. and Bacteroides fragilis in intrahepatic stones by molecular genetic method. METHODS: DNA was extracted from 59 stone samples and subjected to polymerase chain reaction (PCR) amplification targeting the 16S rRNA gene of Clostridium sp. and the glutamine synthetase gene of Bacteroides fragilis. Single-strand conformational polymorphism (SSCP) analysis was performed to identify the Clostridium sp. RESULTS: 16S rRNA gene sequences for Clostridium sp. were identified in 49 stones (83%, 49/59). The two most common groups were detected in 19 (41%) and 17 (37%) of the 46 samples using SSPC analysis, and 25/59 (42%) stones were tested positive for Bacteroides fragilis. CONCLUSIONS: Anaerobes such as Clostridium sp. and Bacteroides fragilis present in intrahepatic stones and may play a role in stone formation. PCR is a useful technique to detect fastidious pathogens, which are difficult to culture. SSCP of PCR products is a rapid method in differentiating bacterial species.

Adult↗
PubMed1999

Phenotypic and genotypic diversity of human neuroblastoma studied in three IGR cell line models derived from bone marrow metastases.

Metastatic stage IV neuroblastoma tumors, as well as cell lines derived from them, are highly malignant and rapidly fatal. To determine whether malignant potential of these cells might be influenced by stromal tissue at sites frequently involved in metastasis, we initiated primary cultures from bone marrow of three patients (331, 337, and 91) with stage IV neuroblastoma. All three explants contained two distinct cell populations, malignant neuroblasts (Nb-type) and substrate adherent stromal-like (Str-type) cells. The cell types were separated at the first passage and studied by cytogenetic, molecular, and immunocytochemical methods. Karyotypic analyses after 3-6 passages in vitro revealed the presence of unique chromosomal abnormalities in Nb-type cells of all three lines: (1) der(1)t(1;7) (p32;q11) and der(5)t(5;17)(q35;q21) in pseudodiploid IGR-N-331 neuroblasts; (2) der(1)t(1;17)(p35;q21-22) x 2 and der(7)t(7;7)(p21;q21) in IGR-N-337 hyperdiploid neuroblasts; and (3) more than six rearranged chromosomes in two related subpopulations of hypodiploid IGR-N-91 neuroblasts. Neuroblastic cells from all three tumors amplified MYCN 25- to 50-fold (with amplified genes visible as dmin or, in one IGR-N-91 subline, as an hsr(14)[q32]) and expressed N-CAM. Str-type cells from tumors 331 and 337 had a normal diploid karyotype, did not express either N-CAM or S-100, and are probably normal bone marrow fibroblasts. By contrast, S-100 negative Str-type IGR-N-91 cells were hypodiploid and shared at least two unbalanced translocations, der(4)t(1;4)(q12;p15) and der(2)t(2;10;17)(p14;q11;q22), with neuroblastic counterparts, indicating that "stromal" cells and malignant neuroblasts had a common tumor cell origin. Thus, the Str-type cells of IGR-N-91 are examples of S-type phenotypic variants frequently described for long-term human neuroblastoma cells lines in vitro, but not previously observed in vivo.

Bone Neoplasms↗
PubMed1999

Do specific EEG frequencies indicate different processes during mental calculation?

EEG recordings during mental calculation and a control task (with presentation of stimuli with similar physical characteristics to the arithmetic symbols) were obtained in 10 subjects. Narrow band analyses of the EEG and distributed sources for each EEG frequency were calculated using variable resolution electromagnetic tomography. Significant differences between the sources for arithmetic and control tasks were observed at 3.9 Hz within Broca's and left parietotemporal cortices, suggesting that this frequency may be related with the production of internal speech, storage and rehearsal of verbal working memory. Differences at 5.46 Hz within the right dorsolateral prefrontal cortex were considered to be associated to sustained attention. The decrease at 12.46 Hz within the left parietal cortex was interpreted as a sign of retrieval of arithmetic facts from long term memory.

Adult↗