PubMed Health⌕ Search

Biomedical subjects

J C Silva

Publications and source records attributed to J C Silva.

At least 19 recordsLinked to original sources
PubMed2004

Analyses of P-like transposable element sequences from the genome of Anopheles gambiae.

We have identified 50 P element-homologous sequences in the genome of Anopheles gambiae by performing homology searches against the public genome database of A. gambiae using the canonical P element from Drosophila melanogaster as a query sequence. While most of these sequences belong to P subfamilies previously described from anopheline mosquitoes, at least four new subfamilies were identified. One of these A. gambiae P elements, which we termed AgPLS, was analysed in detail. AgPLS consists of three exons and does not have inverted terminal repeats. This element retains several of the structural features of other P-encoded peptides, such as motifs involved in DNA-protein and protein-protein interaction, and a motif involved in GTP utilization. Strong sequence and structural similarity to functional P elements, a number of nonsynonymous substitutions that is smaller than that of synonymous substitutions and the presence of putative nuclear localization signals suggest that the A. gambiae elements may retain the capacity for transposition or its repression. These sequences seem to be most closely related to P elements described from Musca domestica and Lucilia cuprina, the only P element hosts known outside the family Drosophilidae.

Amino Acid Sequence↗
PubMed2003

Conserved fragments of transposable elements in intergenic regions: evidence for widespread recruitment of MIR- and L2-derived sequences within the mouse and human genomes.

We analysed the distribution of transposable elements (TEs) in 100 aligned pairs of orthologous intergenic regions from the mouse and human genomes. Within these regions, conserved segments of high similarity between the two species alternate with segments of low similarity. Identifiable TEs comprise 40-60% of segments of low similarity. Within such segments, a particular copy of a TE found in one species has no orthologue in the other. Overall, TEs comprise only approximately 20 % of conserved segments. However, TEs from two families, MIR and L2, are rather common within conserved segments. Statistical analysis of the distributions of TEs suggests that a majority of the MIR and L2 elements present in murine intergenic regions have human orthologues. These elements must have been present in the common ancestor of human and mouse and have remained under substantial negative selection that prevented their divergence beyond recognition. If so, recruitment of MIR- and L2-derived sequences to perform a function that increases host fitness is rather common, with at least two such events per host gene. The central part of the MIR consensus sequence is over-represented in conserved segments given its background frequency in the genome, suggesting that it is under the strongest selective constraint.

Animals↗
PubMed2001

Seroprevalence of Toxoplasma gondii in captive neotropical felids from Brazil.

Seroprevalence of Toxoplasma gondii was determined in 865 captive neotropical felids from 20 states from Brazil, sampled from September 1995 to April 1997. Sera were tested by the modified agglutination test (MAT) using formalin-fixed whole tachyzoites and mercaptoethanol. Antibodies (MAT> or =1:20) to T. gondii were found in 472 of 865 (54.6%) cats: in 45 of 99 (45.9%) jaguarundis (Herpailurus yagouaroundi), in 97 of 168 (57.7%) ocelots (Leopardus pardalis), in 68 of 131 (51.9%) oncillas (L. tigrinus), in 35 of 63 (55.5%) margays (L. wiedii), in 1 of 8 (12.5%) Pampas-cat (Oncifelis colocolo), in 9 of 12 (75.0%) Geoffroys-cat (O. geoffroyi), in 134 of 212 (63.2%) jaguars (Panthera onca), and in 83 of 172 (48.2%) pumas (Puma concolor). Antibody titers were: 1:20 in 27 felids, 1:25 in 142 felids, 1:40 in 6 felids, 1:50 in 292 felids, and > or =1:500 in 5 felids. The high seroprevalence of T. gondii antibodies found in the present study suggested a widespread exposure of neotropical cats to T. gondii in zoos in Brazil. The results warrant an investigation on the mode of exposure and oocyst shedding by neotropical cats.

Agglutination Tests↗
PubMed2001

Hemodynamic results of femoral vein valve repair.

Our aim was to assess the hemodynamic and clinical responses associated with valve repair surgery in 37 patients with severe chronic venous insufficiency. Patients classified as C(4-6)E(P)A(SDP)P(R) (primary venous dysfunction with skin changes with reflux of superficial, deep and perforating veins) were submitted to a novel procedure combining the closed technique described by Kistner with the Dacron sleeve technique described by Hallberg (mean follow-up = 24 months). A significant improvement in Valsalva test results (P < 0.0001), ambulatory pressure (P = 0.0099), venous refilling time (P < 0.0001), and reflux index (P < 0.0001) was observed. Postoperative reactive hyperemia and gradient tests confirmed absence of venous obstruction signs. On their last visit, 85.3% of the patients had no ulceration, and edema was absent or minimal in over 90%. About 70% of the patients referred partial or complete relief of pain in the affected limb. The combined surgical technique was effective to control venous reflux 24 months after the procedure. A longer follow-up would be necessary to assess long-term results.

Chronic Disease↗
PubMed2001

Whole-genome effects of ethyl methanesulfonate-induced mutation on nine quantitative traits in outbred Drosophila melanogaster.

We induced mutations in Drosophila melanogaster males by treating them with 21.2 mm ethyl methanesulfonate (EMS). Nine quantitative traits (developmental time, viability, fecundity, longevity, metabolic rate, motility, body weight, and abdominal and sternopleural bristle numbers) were measured in outbred heterozygous F3 (viability) or F2 (all other traits) offspring from the treated males. The mean values of the first four traits, which are all directly related to the life history, were substantially affected by EMS mutagenesis: the developmental time increased while viability, fecundity, and longevity declined. In contrast, the mean values of the other five traits were not significantly affected. Rates of recessive X-linked lethals and of recessive mutations at several loci affecting eye color imply that our EMS treatment was equivalent to approximately 100 generations of spontaneous mutation. If so, our data imply that one generation of spontaneous mutation increases the developmental time by 0.09% at 20 degrees and by 0.04% at 25 degrees, and reduces viability under harsh conditions, fecundity, and longevity by 1.35, 0.21, and 0.08%, respectively. Comparison of flies with none, one, and two grandfathers (or greatgrandfathers, in the case of viability) treated with EMS did not reveal any significant epistasis among the induced mutations.

Alleles↗
PubMed2001

Toxoplasma gondii antibodies in exotic wild felids from Brazilian zoos.

Serum samples from 37 captive exotic felids in 12 zoos from six Brazilian states were assayed for antibodies to Toxoplasma gondii by the modified agglutination test using formalin-fixed whole tachyzoites. Titers greater than or equal to 1:20 were considered positive. Antibodies to T. gondii were found in 24 of 37 (64.9%) felids, including one European lynx (Lynx lynx), two jungle cats (Felis chaus), two servals (Leptailurus serval), two tigers (Panthera tigris), three leopards (Panthera pardus), and 14 of 27 lions (Panthera leo). This is the first serologic analysis for T. gondii infection in exotic wild felids from Brazilian zoos.

Animals↗
PubMed2000

Effects of pentoxifylline and nabumetone on the serum levels of IL-1beta and TNFalpha in rats with adjuvant arthritis.

OBJECTIVE AND DESIGN: This study examined whether serum levels of cytokines, IL-1beta and TNFalpha were elevated in rats with adjuvant arthritis in relation to disease progression, and if so, to verify the treatment effects of nabumetone (20 mg/kg, p. o.), a COX-2 inhibitor and pentoxifylline (20 mg/kg, p.o.), a type-4 phosphodiesterase (PDE4) inhibitor, alone or in combination. MATERIALS AND METHODS: Female Wistar rats were used. Freund's complete adjuvant (FCA) was used to induce arthritis. The increment in contralateral hind paw volume (the secondary lesion) was determined by plethysmometry and the serum cytokines were measured by ELISA. RESULTS: In control rats, the serum IL-1beta and TNFalpha levels were greatly elevated on the very first day i.e. 5 h after FCA, and thereupon a progressive decrease in IL-1beta but not TNFalpha was observed until day 30. The secondary arthritic lesion began to increase on day 14 (125+/-26 microl), and attained its peak (330+/-79 microl) on day 21 post-adjuvant injection. The peak arthritic lesion was significantly (p<0.001) less in rats that received nabumetone and pentoxifylline, alone or in combination (20+/-8, 41+/-15 and 65+/-10 microL, respectively). When serum cytokine levels were analysed on day 20 postadjuvant injection, rats treated with pentoxifylline or in association with nabumetone, but not nabumetone alone showed significantly lowered levels of serum TNFalpha. Unlike TNFalpha, serum IL-1beta did not vary significantly. CONCLUSIONS: The drugs nabumetone and pentoxifylline although appearing to produce differential effects on serum cytokine levels, seem to be equally efficacious in attentuating the progression of FCA-induced arthritis. Serum cytokine levels may not accurately reflect the treatment efficacy.

Animals↗
PubMed2000

Managed care organization authorization denials: lack of patient knowledge and timely alternative ambulatory care.

STUDY OBJECTIVE: To assess patient knowledge of managed care organization (MCO) regulations, availability of alternative ambulatory care, and patient outcome after MCO insurance authorization denial for an emergency department visit. METHODS: A medical screening examination and a follow-up structured interview were conducted with patients denied authorization for ED visits. The study was conducted at a large urban hospital with 36,000 annual ED visits and 40% MCO patients. RESULTS: During a 7-month period, 151 patients did not receive MCO authorization for ED care. The interview response rate was 75% (104/138) with 13 patients excluded. Eighty-three percent (86/104) of respondents came to the ED because they believed their problem was an emergency. Four percent (4/104) of the respondents had been instructed to go to the ED but were later denied authorization, whereas 85.6% (89/104) did not know that the MCO could deny payment. Only 37% (38/104) of the respondents reported having received instruction on the MCO preauthorization process, whereas of the 19% who contacted their MCO as instructed, all resulted in scheduling difficulties. Although 57% (59/104) received follow-up within 24 hours, 11% (11/104) of the respondents had a subsequent return visit to the ED with a subsequent admission rate of 4% (4/104). CONCLUSION: Few patients are aware of the need for MCO preauthorization for ED care, and almost half do not receive alternative care within 24 hours. A significant number of patients (11%) returned to the ED with an admission rate of 4%.

Adolescent↗
PubMed2000

Horizontal transfer and selection in the evolution of P elements.

The roles of selection and horizontal transfer in the evolution of the canonical subfamily of P: elements were studied in the saltans and willistoni species groups of the genus Drosophila (subgenus Sophophora). We estimate that the common ancestor of the canonical P: subfamily dates back 2-3 Myr at the most, despite the much older age (more than 40 Myr) of the P: family as a whole. The evolution of the canonical P: subfamily is characterized by weak selection at nonsynonymous sites. These sites have evolved at three quarters the rate of synonymous sites, in which no selective constraints were detected. Their recent horizontal transfer best explains the high degree of similarity among canonical P: elements from the saltans and willistoni species groups. These results are consistent with a model of P:-element evolution in which selective constraints are imposed at the time of horizontal transfer. Furthermore, it is estimated that the spread and diversification of the canonical subfamily involved a minimum of 11 horizontal transfer events among the 18 species surveyed within the past 3 Myr. The presence of multiple P: subfamilies in the saltans and willistoni species groups is likely to be the result of multiple invasions that have previously swept through these taxa in a succession of horizontal transfer events. These results suggest that horizontal transfer among eukaryotes might be more common than anticipated.

Alcohol Dehydrogenase↗
PubMed2000

Determinants of in-hospital mortality in women with acute myocardial infarction who underwent primary coronary angioplasty.

INTRODUCTION: According to recent data, women have a greater risk of dying from an acute coronary event. The determinants of this ominous prognosis are not completely understood. Preliminary analysis of our data suggested that this poorer prognosis is also observed in the subgroup of patients with acute myocardial infarction submitted to direct coronary angioplasty (PTCA). This finding prompted us to investigate gender differences and their determinants in this particular context. OBJECTIVE: To identify risk factors associated with the greater in-hospital mortality of women with acute infarction who underwent PTCA. METHODS: One hundred and forty-five consecutive patients with acute myocardial infarction who underwent direct PTCA in the same hospital were studied retrospectively. Data were collected from the database of the catheterisation laboratory and from clinical files. The following parameters were analysed: in-hospital mortality, age, prevalence of diabetes mellitus, history of coronary heart disease, time elapsed from beginning of symptoms to coronary intervention, peak values of CK and MB-CK, number of coronary arteries with significant disease at angiography, culprit lesion localisation, and prevalence of shock on admission. For statistical analysis, cross-tabulation (Pearson x2) and comparison of means (Student's t test) were employed when appropriate; an error of 5% was admitted for the rejection of the null hypothesis. RESULTS: Women (n = 39) represented 26.9% of sample. In hospital mortality was 28.2% (n = 11) for women and 11.3% (n = 12) for men (p = 0.014). The prevalence of coronary heart disease before the current acute event, the time elapsed from beginning of symptoms to coronary intervention, and maximum values of CK and MB-CK were similar in both genders. Differences between women and men were found as regards the following variables (women vs men): age (61.7 +/- 10 vs 56.1 +/- 12.6 years), prevalence of left main disease (15.3 vs 1.9%) and prevalence of shock (41 vs 17%) and diabetes (38.7 vs 13.6%). Considering women and men who died, only disease severity as evaluated by the number of vessels involved distinguished both genders (p = 0.05). CONCLUSIONS: In our experience, women admitted with acute myocardial infarction and treated by direct PTCA are, on average, older than men and have a greater prevalence of shock at admission, of left main disease and of diabetes, and more severe coronary artery disease. In the present series and as regard in-hospital mortality, disease severity as evaluated by the number of vessels involved is the only variable that discriminates women from men.

Age Factors↗
PubMed1999

Antioestrogenic effect of trans-dehydrocrotonin, a nor-clerodane diterpene from Croton cajucara Benth. in rats.

This study examined trans-dehydrocrotonin (t-DCTN), a nor-clerodane diterpene isolated from the Brazilian medicinal plant Croton cajucara Benth., for a possible antioestrogenic activity using immature rats as a model system for bioassay of oestrogen, and for an antiimplantation effect in regularly cycling rats of proven fertility. In the antioestrogen test, t-DCTN (25 and 50 mg/kg) effectively prevented oestrogen-induced increases of uterine wet weights. In addition, the vaginal openings provoked by oestrogen were completely prevented by t-DCTN. However, blastocyst-implantation was only insignificantly affected in t-DCTN pretreated animals. These results suggest that t-DCTN may be an antioestrogen and warrants further studies with regard to its mechanism of action.

Animals↗
PubMed1999

Intrinsic myenteric denervation: a new model to increase the intestinal absorptive surface in short-bowel syndrome.

INTRODUCTION: Short-bowel syndrome (SBS) is caused by resection of massive portions of the small intestine and is characterized by symptoms related to malabsorption, of which severe weight loss is the most apparent. Surgical treatments for SBS are not yet satisfactory. In rats, the myenteric denervation by benzalkonium chloride (BAC) leads to development of megaileum with visceral dilatation and mucosal hyperplasia and increases the intestinal transit time. Such operation in the remaining intestinal segment after massive small bowel resection could increase the duration of contact between luminal nutrients and ileal mucosal epithelium, and furthermore, it could increase the superficial area of the mucosa. Thus, our aim in this study was to evaluate the epithelial morphology and body weight changes of animals after intrinsic ileal denervation associated with extensive small intestine resection. MATERIAL AND METHODS: Wistar rats were submitted to resection of 80% of small intestinal length (Group R). Another group (B) of animals also received topical serosal application of BAC 0.3%. Control animals were submitted to simulated surgery (Group C). Animals were weighed weekly and sacrificed after 90 days. Intestinal walls were collected for histological procedure and morphometry. RESULTS: At the end of the experimental period all groups showed weight increase, which was reduced in the R group (P < 0.01). Interestingly, the denervated Group B showed a marked increase in weight, similar to the control animals. Morphometric analysis of the mucosal layer area showed a major increase in mucosal surface area, mainly in Group B. CONCLUSIONS: Our results showed that the ileal intrinsic denervation associated with massive intestinal resection induced an increase in the superficial absorptive area and was able to improve the postsurgical conditions for the animals, with accentuated weight increase. This procedure may be a useful model for further studies related to the role of the enteric nervous system on intestinal adaptations after extensive resections and may provide a new approach for the surgical treatment of short-bowel syndrome.

Animals↗
PubMed1999

The rate and risk of heat-related illness in hospital emergency departments during the 1995 Chicago heat disaster.

OBJECTIVES: To conduct an Emergency Department (ED)-based treated prevalence study of heat morbidity and to estimate the rate and risk of heat morbid events for all Chicago MSA EDs (N = 95; 2.7 million visits per year). METHODS: ED patient log data were compiled from 13 randomly selected hospitals located throughout the Chicago MSA during the 2 weeks of the 1995 heat disaster and from the same 2-week period in 1994 (controls). Measurements included: age, sex, date, and time of ED service, up to three ICD-9 diagnoses, and disposition. RESULTS: Heat morbidity for Chicago MSA hospital EDs was calculated at 4,224 (95% CI = 2964-5488) cases. ED heat morbidity increased significantly 5 days prior to the first heat-related death. In 1995, there was an increase in the estimated relative risk for the city = 3.85 and suburbs = 1.89 over the control year of 1994. CONCLUSIONS: Real time ED-based computer automated databanks should be constructed to improve public health response to infectious or noninfectious outbreaks. Rapid area-wide M&M tabulations can be used for advancing the effectiveness of community-based prevention programs, and anticipating hospital ED resource allocation.

Adolescent↗
PubMed1998

In vivo characterization of the type A and B vancomycin-resistant enterococci (VRE) VanRS two-component systems in Escherichia coli: a nonpathogenic model for studying the VRE signal transduction pathways.

Escherichia coli reporter strains modeling the high-level type A and B vancomycin resistances of Enterococcus faecium BM4147 and Ent. faecalis have been developed to study the respective VanR-VanS two-component regulatory systems. PvanH-, PvanRa-, PvanY-, and PvanRb-lacZ fusions report on expression from the vancomycin-resistant enterococci promoters of the type A vanRSHAXYZ and type B vanRSYWHBX gene clusters. These strains also express from single-copy chromosomal genes vanRa, vanRb, or vanRSb behind their respective promoter (PvanRa or PvanRb) or vanSa or vanSb behind the rhamnose-inducible PrhaB. Results show that activation (phosphorylation) of the response regulator VanRa by its sensor kinase VanSa leads to transcriptional activation of both PvanH and PvanRa. Additionally, VanRb activates its cognate promoters PvanY and PvanRb, although this occurs only in the absence of VanSb and presumably is caused by VanRb phosphorylation by an unidentified endogenous E. coli kinase. Thus, VanSb interferes with activation of VanRb, probably by acting as a phospho-VanRb phosphatase. Although both VanRa and VanRb activate their cognate promoters, neither activates the heterologous PvanR, PvanH, or PvanY, arguing against the interchangeability of type A and B two-component regulatory switches in vancomycin-resistant enterococci. VanRa also is activated by the nonpartner kinase PhoR. Because this occurs in the absence of its inducing signal (Pi limitation), PhoR autophosphorylation apparently is regulated in vivo. Furthermore, the activation of VanRa caused by cross talk from PhoR in the absence of a signal allows distinction of cross talk from crossregulation as the latter, but not the former, responds to environmental cues.

Anti-Bacterial Agents↗
PubMed1998

The role of diagnostic laparoscopy in pancreatic and periampullary malignancies.

BACKGROUND: The role of diagnostic laparoscopy before laparotomy in patients with pancreatic or periampullary malignancies remains controversial. We analyzed the value of using diagnostic laparoscopy to avoid laparotomy in these patients. STUDY DESIGN: Between November 1993 and December 1996, 254 patients with pancreatic or periampullary malignancies were treated. In 74 patients, multiple distant metastases precluded further surgical treatment. In all, 180 patients underwent laparotomy for pancreatic cancer (119 patients) or periampullary cancer (61 patients). Preoperatively, all patients underwent computed tomography for staging and to assess resectability of the tumor. Based on the results of the imaging procedure, the patients were scheduled for either tumor resection or a palliative operation. RESULTS: Twenty-one of 180 patients (12%) with pancreatic or periampullary malignancies were scheduled preoperatively for nonresectional operations because of distant metastasis or retroperitoneal tumor infiltration. In none of these patients was the operative strategy changed. In 159 of 180 patients (88%), a pancreatic resection was planned preoperatively; 119 patients underwent pancreatic resection. In the remaining 40 patients preoperatively scheduled for tumor resection, removal of the tumor was not possible. In 24, this resulted from tumor infiltration into the retropancreatic vessels, and in 16 it resulted from liver or peritoneal metastasis detected for the first time intraoperatively. These 16 patients (10%) could have benefited from diagnostic laparoscopy. Similar results were found in the subgroup of 119 patients with pancreatic cancer, of whom 102 were planned for tumor resection and 17 for palliative operation. Of the 102 patients planned preoperatively for tumor resection, 71 patients (70%) underwent pancreatic resection. In the remaining 31 patients scheduled for tumor resection, removal of the tumor was not possible: in 17 because of tumor infiltration into the retropancreatic vessels and in 14 because of liver or peritoneal metastasis detected for the first time intraoperatively. These 14 patients (14%) also would have benefited from laparoscopy. CONCLUSIONS: Preoperative computed tomography is a reliable technique to detect tumor metastasis in patients with pancreatic or periampullary cancer. Unlike other investigators, we found that only 10% of patients with periampullary or pancreatic cancer and 14% of patients with pancreatic cancer might profit from laparoscopy. Because of this low number, laparoscopy cannot generally be recommended for patients with pancreatic or periampullary cancer before laparotomy.

Adult↗
PubMed1998

Metastatic thyroid carcinoma arising from congenital goiter due to mutation in the thyroperoxidase gene.

A very large cervical tumor that extended to the upper mediastinum was seen in a newborn after an uneventful pregnancy. The computed axial tomography scan confirmed the presence of a solid mass with precise limits and scattered foci of calcifications situated in the anterolateral region of the neck. The infant underwent thyroidectomy on the seventh day after birth. Pathological examination revealed a follicular carcinoma of the thyroid and probable dyshormonogenetic hyperplastic goiter. At 5 months of age, whole body scans indicated the presence of lung and bone metastases, which were treated with therapeutic doses of radioiodine. Genomic DNA was obtained from the newborn, her parents, her paternal aunt, and her paternal grandparents. Denaturing gradient gel electrophoresis analysis of PCR fragments corresponding to exon 14 of the thyroid peroxidase (TPO) gene indicated the presence of a mutant TPO allele present in the propositus, her father, and her paternal grandmother. Sequencing of the TPO gene demonstrated a mutation resulting from an insertion of a single extra cytosine in a stretch of seven cytosines at positions 2505-2511. The insertion caused a frame shift and a stop signal in exon 16. This sequence would translate into a structurally modified and probably inactive TPO protein. We conclude that the aggressive thyroid metastatic carcinoma arose from a dyshormonogenetic goiter caused by a defective TPO protein.

Bone Neoplasms↗
PubMed1997

Heterologous expression, isolation, and characterization of versicolorin B synthase from Aspergillus parasiticus. A key enzyme in the aflatoxin B1 biosynthetic pathway.

Aflatoxin B1 is a potent environmental carcinogen produced by certain strains of Aspergillus. Central to the biosynthesis of this mycotoxin is the reaction catalyzed by versicolorin B synthase (VBS) in which a racemic substrate, versiconal hemiacetal, is cyclized to an optically active product whose absolute configuration is crucial to the interaction of aflatoxin B1 with DNA. Attempted over-production of VBS in Escherichia coli led principally to protein aggregated into inclusion bodies but also small amounts of soluble but catalytically inactive enzyme. Comparisons to wild-type VBS by SDS-polyacrylamide gel electrophoresis and after N-glycosidase F treatment revealed that extensive glycosylation accounted for the mass discrepancy (7,000+/-1,500 Da) between the native and bacterially expressed proteins. Several over-expression systems in Saccharomyces cerevisiae were surveyed in which one that incorporated a secretion signal was found most successful. VBS of indistinguishable mass on SDS-polyacrylamide gel electrophoresis and kinetic properties from the wild-type enzyme could be obtained in 50-100-fold greater amounts and whose catalytic behavior has been examined. The translated protein sequence of VBS showed three potential N-glycosylation sites (Asn-Xaa-Ser/Thr) consistent with the modifications observed above and unexpectedly revealed extensive homology to the ADP-binding region prominently conserved in the glucose-methanol-choline (GMC) family of flavoenzymes. Over-production of VBS in yeast marks the first aflatoxin biosynthetic enzyme to be so obtained and opens the way to direct study of the enzymology of this complex biosynthetic pathway.

Aflatoxin B1↗