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Biomedical subjects

A M Silva

Publications and source records attributed to A M Silva.

At least 37 records · Page 2Linked to original sources
PubMed2000

Sodium salicylate induces the expression of the immunophilin FKBP51 and biglycan genes and inhibits p34cdc2 mRNA both in vitro and in vivo.

One of the mechanisms proposed to explain the anti-inflammatory activity of sodium salicylate (NaSal) is based, at least in part, on its ability to inhibit nuclear factor-kappaB activation and inhibition of nuclear factor-kappaB-dependent gene expression. On the other hand, little is known about the ability of NaSal to activate gene expression. By differential display reverse transcription polymerase chain reaction, we identified several genes that are modulated upon treatment of mouse fibroblasts with NaSal. From the various cDNA fragments recovered from autoradiograms, we found that NaSal can increase the levels of mRNA for biglycan, the mouse homologue of the human eIF-3 p47 unit, and immunophilin FKBP51. NaSal-induced expression of these genes was time- and dose-dependent. Moreover, FKBP51 gene expression was augmented in vivo, in mice treated orally or intraperitoneally with NaSal. We also found that treating cells with NaSal can inhibit the expression of the p34(cdc2) kinase. The impact this inhibition on cell cycle was evaluated by measuring the content of DNA during the cell cycle. Treatment of cells with NaSal led to a G(2)/M arrest. By investigating the signaling events that regulate the expression of these genes and their biological activities, we can contribute to the understanding of the mechanism of NaSal.

Animals↗
PubMed2000

Xanthones from Calophyllum teysmannii var. inophylloide.

Further study of the wood of Calophyllum teysmannii Miq. var. inophylloide yielded xanthones 7-hydroxy-1,2,8-trimethoxyxanthone, 6-hydroxy-1,2,5-trimethoxyxanthone, and 2-carbomethoxy-6-methoxyxanthone in addition to 3,8-dihydroxy-1,2,4-trimethoxyxanthone, 3-hydroxy-2,4-dimethoxyxanthone, 1,7-dihydroxy-3-methoxyanthone (gentisin) and 2-hydroxyxanthone.

Molecular Structure↗
PubMed2000

[Secondary ionizing radiation generated by digital and analog coronary cineangiographic equipment: influence of external systems of radiologic protection].

BACKGROUND: Exposure to ionizing radiation is a known hazard of radiological procedures. AIM: To compare the emission of secondary ionizing radiation from two coronary angiographic equipment, one with digital and the other with analog image generation. To evaluate the effectiveness of external radiological protection devices. MATERIAL AND METHODS: Environmental and fluoroscopy generated radiation in the cephalic region of the patient was measured during diagnostic coronary angiographies. Ionizing radiation generated in anterior left oblique projection (ALO) and in anterior right oblique projection (ARO) were measured with and without leaded protections. In 19 patients (group 1), a digital equipment was used and in 21 (group 2), an analog equipment. RESULTS: Header radiation for groups 1 and 2 was 1194 +/- 337 and 364 +/- 222 microGray/h respectively (p < 0.001). During fluoroscopy and with leaded protection generated radiation for groups 1 and 2 was 612 +/- 947 and 70 +/- 61 microGray/h respectively (p < 0.001). For ALO projection, generated radiation for groups 1 and 2 was 105 +/- 47 and 71 +/- 192 microGray/h respectively (p < 0.001). During filming the radiation for ALO projection for groups 1 and 2 was 7252 +/- 9569 and 1671 +/- 2038 microGray/h respectively (p = 0.03). Out of the protection zone, registered radiation during fluoroscopy for groups 1 and 2 was 2800 +/- 1741 and 1318 +/- 954 microGray/h respectively (p < 0.001); during filming, the figures were 15,500 +/- 5840 and 18,961 +/- 10,599 microGray/h respectively (NS). CONCLUSIONS: Digital radiological equipment has a lower level of ionizing radiation emission than the analog equipment.

Adult↗
PubMed1999

Experimental infection of sheep with bovine herpesvirus type-5 (BHV-5): acute and latent infection.

We demonstrated that sheep are susceptible to acute and latent infection by bovine herpesvirus type-5 (BHV-5). Lambs inoculated intranasally with two South American BHV-5 isolates replicated the virus with titers up to 10(7.1) TCID50/ml for up to 15 days and showed mild signs of rhinitis. Four lambs in contact with the inoculated animals acquired the infection and excreted virus for up to seven days. One lamb developed progressive signs of neurological disease and was euthanized in extremis. Clinical signs consisted of tremors of the face, bruxism, ptyalism, incoordination, lateral flexion of the neck and head, circling, walking backwards, recumbency and paddling. The virus was detected in the anterior and posterior cerebrum, dorso- and ventro-lateral cortex, cerebellum, pons, midbrain and olfactory bulb. Viral nucleic acids were demonstrated in neurons and astrocytes of the anterior and ventro-lateral cortex by in situ hybridization. Histological changes consisting of non-suppurative meningitis, perivascular mononuclear cuffing, focal gliosis, neuronal necrosis and intranuclear inclusions were observed in the anterior cerebrum, ventro-lateral cortex and midbrain. Dexamethasone treatment at Day 50 pi resulted in reactivation of the latent infection and virus shedding in 13/16 (81%) of the lambs. Together with previous reports of BHV-5 antibodies in sheep, these findings show that sheep are fully susceptible to BHV-5 suggesting that infection by BHV-5 in sheep may occur naturally.

Acute Disease↗
PubMed1999

Expression of serum amyloid A3 mRNA by inflammatory macrophages exposed to membrane glycoconjugates from Trypanosoma cruzi.

Differential display reverse transcriptase-polymerase chain reaction (PCR) was used to identify genes expressed by murine macrophages exposed to glycosylphosphatidylinositol-anchored mucin-like glycoproteins isolated from Trypanosoma cruzi trypomastigotes. Among the different PCR product bands identified in the differential display gel, one showed high homology with the serum amyloid A3 protein (SAA3). Northern blot assays showed augmentation of SAA3 mRNA expression by inflammatory macrophages exposed to live trypomastigotes or parasite glycolipids, as compared to unstimulated macrophages. Our results also showed the expression of SAA3 mRNA, in liver and heart from animals in the acute phase of Chagas disease. It is important that expression of SAA3 mRNA was closely associated with tissue parasitism and presence of inflammatory cells. Together, our findings indicate the possible involvement of SAA3 protein on immunopathology of Chagas disease and establish a new infectious disease model to study the pathophysiological role of this acute-phase protein.

Animals↗
PubMed1999

Identification and partial characterization of FRAG-6, a novel interferon-stimulated gene that is expressed in an IRF-1-INDEPENDENT manner.

In order to identify new interferon-stimulated genes that could help in the better understanding of the mechanism of action of interferons (IFNs), we decided to compare, by differential display RT-PCR (DDRT-PCR), the pattern of gene expression between IFN-alpha treated and untreated mouse embryonic fibroblasts (MEFs). Here we describe the initial characterization of a new cDNA fragment, named FRAG-6, that is expressed only upon IFN stimulation. The IFN-induced expression of this new gene can be observed in both wild-type and IRF-1-deficient MEF. FRAG-6 cDNA hybridizes with an mRNA of 6-9 kb that is induced by IFNs in a time-dependent manner. Analysis of the cloned nucleotide sequence revealed a 174 amino acid (aa) open reading frame (ORF) contained within the 576 bp. No significant homology with known nucleotide or protein sequences was observed. FRAG-6 is induced in vitro upon treatment of wild type or IRF-1-null cells with IFN-alpha or -gamma, but not with TNF or IL-1. Treatment of mice with imiquimod, a potent inducer of IFN, led to induced expression of FRAG-6 mRNA in various organs from wild type or IRF-1-deficient mice, but not from STAT-1 or type I IFN receptor deficient animals. Our results demonstrate that FRAG-6 mRNA induction by interferons is IRF-1-independent and it is likely to be activated by the JAK/STAT pathway. Further characterization of FRAG-6 will help us in the understanding of the mechanism of action of IFNs.

Amino Acid Sequence↗
PubMed1999

Protective effect of bifidus milk on the experimental infection with Salmonella enteritidis subsp. typhimurium in conventional and gnotobiotic mice.

The ability of Bifidobacterium bifidum from a commercial bifidus milk to antagonize Salmonella enteritidis subsp. typhimurium in vivo, and to reduce the pathological consequences for the host, was determined using conventional and gnotobiotic mice. Conventional animals received daily, by gavage, 0.1 ml bifidus milk containing about 10(9) cfu B. bifidum and germ-free animals received a single 0.1 ml dose. The conventional and gnotobiotic groups were challenged orally with 10(2) cfu of the pathogenic bacteria 5 and/or 10 d after the beginning of treatment. Control groups were treated with milk. Bifidus milk protected both animal models against the challenge with the pathogenic bacteria, as demonstrated by survival and histopathological data. However, to obtain the protective effect in gnotobiotic animals, the treatment had to be initiated 10 d before the challenge. In experimental and control gnotobiotic mice, Salm. enteritidis subsp. typhimurium became similarly established at levels ranging from 10(8) to 10(9) viable cells g-1 of faeces and remained at these high levels until the animals died or were sacrificed. It was concluded that the protection against Salm. enteritidis subsp. typhimurium observed in conventional and gnotobiotic mice treated with bifidus milk was not due to the reduction of the intestinal populations of the pathogenic bacteria.

Animals↗
PubMed1999

Application of the differential display RT-PCR strategy for the identification of inflammation-related mouse genes.

The inflammatory response elicited by various stimuli such as microbial products or cytokines is determined by differences in the pattern of cellular gene expression. We have used the differential display RT-PCR (DDRT-PCR) strategy to identify mRNAs that are differentially expressed in various murine cell types stimulated with pro-inflammatory cytokines, microbial products or anti-inflammatory drugs. Mouse embryonic fibroblasts (MEFs) were treated with IFNs, TNF, or sodium salicylate. Also, peritoneal macrophages from C3H/Hej mice were stimulated with T. cruzi-derived GPI-mucin and/or IFN-gamma. After DDRT-PCR, various cDNA fragments that were differentially represented on the sequencing gel were recovered, cloned and sequenced. Here, we describe a summary of several experiments and show that, when 16 of a total of 28 recovered fragments were tested for differential expression, 5 (31%) were found to represent mRNAs whose steady-state levels are indeed modulated by the original stimuli. Some of the identified cDNAs encode for known proteins that were not previously associated with the inflammatory process triggered by the original stimuli. Other cDNA fragments (8 of 21 sequences, or 38%) showed no significant homology with known sequences and represent new mouse genes whose characterization might contribute to our understanding of inflammation. In conclusion, DDRT-PCR has proven to be a potent technology that will allow us to identify genes that are differentially expressed when cells are subjected to changes in culture conditions or isolated from different organs.

Animals↗
PubMed1999

[Angioplasty in acute myocardial infarction. Early and late results].

BACKGROUND: The usefulness of angioplasty in the first hours of an acute myocardial infarction is widely demonstrated. However, its long term effects are less well known. AIM: To report the effects of coronary angioplasty on early and late outcome of patients with acute myocardial infarction. PATIENTS AND METHODS: A non-randomized, consecutive and retrospective analysis of the hospital and late outcome of 70 patients, aged 35 to 85 years, subjected to coronary angioplasty during an acute myocardial infarction. Patients were followed during 12 to 60 months. RESULTS: Angioplasty was performed 5.3 +/- 5 hours after the initial symptoms. Anterior descendent artery was occluded in 63% of patients with a 99.5% luminal occlusion and TIMI 0-1 anterograde flow. An angiographic success was achieved in 83% of procedures with a residual stenosis of 32.3%. Recurrent ischemia was observed in 6% of patients, that were treated with a new revascularization procedure. Thirteen percent of patients died, all due to cardiogenic shock. Severe ventricular failure and failure of revascularization influenced mortality. During the first year of follow up there was a 3.3% mortality and 3.3% of patients required a new revascularization procedure. Eighty percent of patients were asymptomatic and event-free. CONCLUSION: Angioplasty was a useful therapeutic procedure in this group of patients.

Adult↗
PubMed1999

Effect of electrolytic lesion of the median raphe nucleus on behavioral and physiological measures of stress.

The effect of electrolytic lesion of the median raphe nucleus was measured on behavioral and physiological parameters related to stress 24 h after the lesion. In of the elevated plus-maze the lesion decreased the percentage of open arm entries and tended to shorten the time spent on the open arms indicating an increase in anxiety. In contrast, the lesion markedly increased the time spent in the bright (aversive) compartment of the light-dark box and decrease in attempts to cross from the dark toward the bright compartment, an anxiolyic effect. With the exception of plasma prolactin level, which was lowered by the lesion, the physiological measures used in the present study indicate that the lesioned animals are under stress. Thus, death rate and weight loss after the surgery were higher in lesioned than in control animals. In addition, lesioned animals showed higher plasma corticosterone levels, a high incidence of gastric ulcers in the fundus and a depressed immune response to the mitogen concavaline A. These results highlight the importance of the median raphe nucleus in the regulation of stress and anxiety. They also show that behavioral and physiological measures of stress may be dissociated.

Adrenal Cortex Hormones↗
PubMed1998

Control of pulsatile 5-HT/insulin secretion from single mouse pancreatic islets by intracellular calcium dynamics.

1. Glucose-induced insulin release from single islets of Langerhans is pulsatile. We have investigated the correlation between changes in cytosolic free calcium concentration ([Ca2+]i) and oscillatory insulin secretion from single mouse islets, in particular examining the basis for differences in secretory responses to intermediate and high glucose concentrations. Insulin release was monitored in real time through the amperometric detection of the surrogate insulin marker 5-hydroxytryptamine (5-HT) via carbon fibre microelectrodes. The [Ca2+]i was simultaneously recorded by whole-islet fura-2 microfluorometry. 2. In 82 % of the experiments, exposure to 11 mM glucose evoked regular high-frequency (average, 3.4 min-1) synchronous oscillations in amperometric current and [Ca2+]i. In the remaining experiments (18 %), 11 mM glucose induced an oscillatory pattern consisting of high-frequency [Ca2+]i oscillations that were superimposed on low-frequency (average, 0.32 min-1) [Ca2+]i waves. Intermittent high-frequency [Ca2+]i oscillations gave rise to a similar pattern of pulsatile 5-HT release. 3. Raising the glucose concentration from 11 to 20 mM increased the duration of the steady-state [Ca2+]i oscillations without increasing their amplitude. In contrast, both the duration and amplitude of the associated 5-HT transients were increased by glucose stimulation. The amount of 5-HT released per secretion cycle was linearly related to the duration of the underlying [Ca2+]i oscillations in both 11 and 20 mM glucose. The slopes of the straight lines were identical, indicating that there is no significant difference between the ability of calcium oscillations to elicit 5-HT/insulin release in 11 and 20 mM glucose. 4. In situ 5-HT microamperometry has the potential to resolve the high-frequency oscillatory component of the second phase of glucose-induced insulin secretion. This component appears to reflect primarily the duration of the underlying [Ca2+]i oscillations, suggesting that glucose metabolism and/or access to glucose metabolites is not rate limiting to fast pulsatile insulin release.

Animals↗
PubMed1998

[Endovascular stent implantation in the treatment of coronary artery disease: angiographic, and immediate and late clinical results].

BACKGROUND: Coronary revascularization allows a better survival and quality of life in high risk patients with coronary artery disease. AIM: To report the experience in stent placement as treatment for obstructive atherosclerotic coronary artery disease. PATIENTS AND METHODS: A prospective analysis of 105 stent placements. A morphological and quantitative analysis of coronary angiograms, using an electronic caliper, was performed. Patients were followed during their hospital stay and after discharge. RESULTS: In four of 112 coronary lesions, it was not possible to liberate the stent and in 108, it was successfully placed (48 in anterior descending, 19 in circumflex, 36 in right coronary arteries and 5 in saphenous aortocoronary by-pass. Lesions with stent implantation were type A in 11%, B1 in 30%, B2 in 44% and C in 15%. Reference diameter was 3.13 +/- 0.58 mm. After placement, luminal diameter increased from 0.95 +/- 0.43 to 2.99 +/- 0.46 mm, with a final stenosis of 7.2 +/- 10.1%. Angiographic success was obtained in 99% and procedure success in 98%. Hospital mortality was 0.98%. After a mean of eight months follow up, 91% of patients is free of major cardiac events. In 17% angina recurred and 5% required a new revascularization. There were no late cardiac deaths, acute stent thrombosis or infarction in relation to the treated lesion. CONCLUSIONS: In these patients, stent placement has had excellent immediate and late results.

Adult↗
PubMed1998

[Impact of secondary irradiation on operators during coronary arteriography].

BACKGROUND: The activity over cellular genetic pattern of ionizing radiation can produce stochastic and unspecific damages. Interventional cardiology operators have increasing exposure times to ionizing radiation and there is no information about the real protection conferred by simple radiological protection devices. AIM: To assess the magnitude of secondary ionizing radiation exposure of operators during conventional coronary arteriography, evaluating the radiation exposure during different beam projections and the usefulness of leaded aprons. MATERIAL AND METHODS: Ionizing radiation received by operators during coronary arteriography was measured using a Geiger-Müller Victoreen model 490 counter. The device was placed in the ventral region, covered by the leaded apron and in the unprotected dorsal region. Radiation was measured in right and left projections during fluoroscopy and shooting. RESULTS: In right projection, the intensity of ionizing radiation in ventral and dorsal regions was 1.24 +/- 1.1 and 2.9 +/- 4 mR/h respectively (p = 0.08). In left projection, the figures were 2.95 +/- 3 and 7.86 +/- 7.2 mR/h respectively (p = 0.001). During shooting in left projection the radiation exposure in ventral and dorsal regions was 9.66 +/- 6.7 and 32.8 +/- 27 mR/h respectively (p < 0.001). During shooting in right projection that figures were 10.1 +/- 16 and 20.7 +/- 39.8 mR/h respectively (p = 0.09). No correlation between radiation exposure and patients surface area was observed. CONCLUSIONS: Secondary radiation received by operators is higher during shooting and in left projections. Leaded apron confers a partial protection for ventral region, and great fluctuations in the magnitude of radiation exposure were recorded. Unprotected dorsal region receives a greater amount of radiation in left projections.

Age Distribution↗
PubMed1997

Mice lacking the gamma interferon receptor have an impaired granulomatous reaction to Schistosoma mansoni infection.

The egg-induced granulomatous reaction in Schistosoma mansoni-infected individuals develops within the portal system of the liver and is the major pathological finding in schistosomiasis. We have infected mice lacking the gamma interferon (IFN-gamma) receptor with S. mansoni larvae and studied the development of hepatic granulomas in these mutant mice in comparison to that in control wild-type mice. In the absence of IFN-gamma activity, a dramatic reduction in the size and architecture of the granuloma was observed. Granulomas from mutant mice were smaller than those from the control group and showed a significant reduction in the number of infiltrating inflammatory cells. Moreover, they appear to prematurely progress to the chronic phase of the reaction at a time when the control group still has acute inflammation. Our data suggests a pivotal role for IFN-gamma in the early events of the granulomatous reaction in vivo.

Animals↗
PubMed1997

Free radical production by azomethine H: effects on pancreatic and hepatic tissues.

The antimalarial properties of azomethine H represent the basis for its use as a chemotherapeutic agent. This work was carried out in order to verify the biological side effects of azomethine H and to clarify the contribution of reactive oxygen species (ROS) in this process. It was shown that azomethine H increased serum activities of amylase, alanine transaminase (ALT) and the TBARS concentrations, in rats. No changes were observed in glutathione peroxidase and catalase activities. The drug-induced tissue damage might be due to superoxide radicals (O2.-), since Cu-Zn superoxide dismutase activities were increased by azomethine H treatment. This study allows tentative conclusions to be drawn regarding which reactive oxygen metabolites play a role in azomethine H activity. We concluded that (O2.-) maybe produced as a mediator of azomethine H action.

Alanine Transaminase↗
PubMed1996

Real time electrochemical detection of 5-HT/insulin secretion from single pancreatic islets: effect of glucose and K+ depolarization.

We report a highly sensitive electrochemical approach suitable for the real time measurement of insulin release from single islets of Langerhans, the functional endocrine units in the pancreas. The method is based on the detection of the insulin surrogate 5-hydroxytryptamine (5-HT) by carbon fibre microelectrodes implanted in the islets. Based on the combination of this novel approach with the simultaneous microfluorometric recording of cytosolic free Ca2+ concentration ([Ca2+]i), we demonstrate that glucose-stimulated islets secrete 5-HT/insulin in a pulsatile fashion under physiological conditions, and that this activity is encoded by synchronous [Ca2+]i oscillations. The sensitivity to detect variations in minute amounts of secreted materials is partially conferred by the fact that the tracer is released into a relatively confined space (the intraislet interstitial space).

Animals↗