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Biomedical subjects

R Ferreira

Publications and source records attributed to R Ferreira.

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

An intrinsic but cell-nonautonomous defect in GATA-1-overexpressing mouse erythroid cells.

GATA-1 is a tissue-specific transcription factor that is essential for the production of red blood cells. Here we show that overexpression of GATA-1 in erythroid cells inhibits their differentiation, leading to a lethal anaemia. Using chromosome-X-inactivation of a GATA-1 transgene and chimaeric animals, we show that this defect is intrinsic to erythroid cells, but nevertheless cell nonautonomous. Usually, cell nonautonomy is thought to reflect aberrant gene function in cells other than those that exhibit the phenotype. On the basis of our data, we propose an alternative mechanism in which a signal originating from wild-type erythroid cells restores normal differentiation to cells overexpressing GATA-1 in vivo. The existence of such a signalling mechanism indicates that previous interpretations of cell-nonautonomous defects may be erroneous in some cases and may in fact assign gene function to incorrect cell types.

Anemia↗
PubMed2000

A mutation in the DE loop of the VP1 protein that prevents polyomavirus transcription and replication.

Natural mutants of the DE loop of the Polyomavirus (Py) major coat protein VP1 have been previously shown to display an altered host specificity (L. Ricci, R. Maione, C. Passananti, A. Felsani, and P. Amati, 1992, J. Virol. 66, 7153-7158). To better understand the role of this outfacing loop of the VP1 protein in Py infectivity, we constructed and characterized a Py mutant (Py M17) harboring a deletion of 7 AA within the tip of the DE loop. The mutant virions obtained after DNA transfection were unable to replicate and initiate early transcription in fibroblast cells. Complementation experiments performed to rescue the deficient M17 replication by means of wt functions revealed the cis-dominance of the mutation. In situ cell fractionation experiments demonstrated that the Py mutant, like the Py wt, enters the cells, reaches the nucleus and that both the viral DNA and VP1 protein are found tightly bound to the nuclear matrix. These data suggest that the VP1 protein, associated to the viral DNA, conditions early viral gene expression and that the DE loop of the protein must be involved in this process.

3T3 Cells↗
PubMed2000

CBP/p300 histone acetyl-transferase activity is important for the G1/S transition.

Transforming viral proteins such as E1A which force quiescent cells into S phase have two essential cellular target proteins, Rb and CBP/p300. Rb regulates the G1/S transition by controlling the transcription factor E2F. CBP/p300 is a transcriptional co-activator with intrinsic histone acetyl-transferase activity. This activity is regulated in a cell cycle dependent manner and shows a peak at the G1/S transition, suggesting a function for CBP/p300 in this crucial step of the cell cycle. Here, we have artificially modulated CBP/p300 levels in individual cells through microinjection of specific antibodies and expression vectors. We show that CBP/p300 is required for cell proliferation and has an essential function during the G1/S transition. Using the same microinjection system and GFP-reporter vectors, we demonstrate that CBP/p300 is essential for the activity of E2F, a transcription factor that controls the G1/S transition. In addition, our results suggest that CBP HAT activity is required both for the G1/S transition and for E2F activity. Thus CBP/p300 seems to be a versatile protein involved in opposing cellular processes, which raises the question of how its multiple activities are regulated.

3T3 Cells↗
PubMed2000

On the classes of aminoacyl-tRNA synthetases and the error minimization in the genetic code.

As a consequence of the existence of two classes of aminoacyl-tRNA synthetases (aaRSs), we defined two types of mutations: g (mutations that do not change the class of the involved amino acids) and u (those which change the class). We have found that the mean chemical distance resulting from g mutations is smaller than that corresponding to u mutations, indicating that g mutations are responsible for most of the known minimization of the genetic code. This supports models for the origin and evolution of the code, in which new amino acids were added after duplications or modification of existing aaRSs.

Amino Acids↗
PubMed2000

[Diagnosis of a cardiac mass--a case report].

The authors describe a case of a recidivant pericardial effusion associated to a mass with an unusual, filamentous aspect that involved the upper part of right atrium and surrounded the upper vena cava. Despite the diagnostic techniques employed--transesophageal echocardiography and magnetic resonance imaging, the etiologic diagnosis could not be done, so a biopsy of the mass was made by percutaneous approach using transesophageal echocardiography to control the procedure. The histopathological result was an angiosarcoma of the right atrium. The authors make a brief review of the literature about this rare condition.

Echocardiography, Transesophageal↗
PubMed1999

Docking of 4-oxalocrotonate tautomerase substrates: implications for the catalytic mechanism.

The enzyme 4-oxalocrotonate tautomerase catalyzes the ketonization of dienols, which after further processing become intermediates in the Krebs cycle. The enzyme uses a general acid-base mechanism for proton transfer: the amino-terminal proline has been shown to function as the catalytic base and Arg39 has been implicated as the catalytic acid. We report the results of molecular docking simulations of 4-oxalocrotonate tautomerase with two substrates, 2-hydroxymuconate and 5-carboxymethyl-2-hydroxymuconate. pKa calculations are also performed for the free enzyme. The predicted binding mode of 2-hydroxymuconate is in agreement with experimental data. A model for the binding mode of 5-carboxymethyl-2-hydroxymuconate is proposed which explains the lower catalytic efficiency of the enzyme toward this substrate. The pKa predictions and docking simulations support residue Arg39 as the general acid for the enzyme catalysis.

Aldehydes↗
PubMed1999

Evaluation of the longitudinal musculature of segments of the distal colon interposed following extended jejunum-ileum resection.

Several morbid conditions may necessitate extensive intestinal resection, leading to short-bowel syndrome. When clinical treatment becomes inefficient, a surgical approach is necessary. Distal colon interposition is one of the viable techniques. The interposition of colon segments between remnants of the small bowel improved lifestyle, increased transit time, and diminished diarrhea. The aim of this study is to observe the longitudinal muscular contractions after distal colon interposition. Sixteen male Wistar rats (EPM-1) were submitted to an 80% small bowel resection associated with a partial colectomy of the distal colon immediately after the bifurcation of the middle colic artery followed by a 3-cm isoperistaltic distal colon interposition. After 70 days, the animals were submitted to euthanasia and segments of the jejunum, ileum, remnant colon, and interposed colon were prepared for pharmacological tests. The isometric contractions were measured by a polygraph. After 30 minutes, the dose/effect curves were obtained for both metacholine and barium chloride stimulation through the extraluminal surface (serosa). After this period, we observed a significant increase in the length, diameter, and thickness of the intestinal wall. Regarding the sensibility (pD(2)), no difference was found (interposed colon = 7.21 +/- 0.2; remnant colon = 7.65 +/- 0.1; remnant jejunum 7.46 +/- 0.1; and remnant ileum 7.57 +/- 0.1), even though the animals were submitted to different procedures. In relation to the maximal effect (E(max)), the longitudinal muscle contraction responses (interposed colon = 11.79 +/- 0.1; remnant jejunum = 15.42 +/- 0.2; and remnant ileum = 11.48 +/- 0.2) were lower than those of the remnant colon (E(max) = 22.42 +/- 0.1). This means that there was a possible adaptation of colonic segments to their new location.

Anastomosis, Surgical↗
PubMed1999

Metabolic and ultrastructural effects of cyclosporin A on pancreatic islets.

We investigated the effect of different doses of cyclosporin A (CyA) on glucose and insulin levels, as well as its residual effects on pancreatic islets ultrastructure after discontinuation of the drug. We studied four groups of Wistar rats. One control- (n = 5) and three experimental groups, n = 10 each, were treated with different doses of CyA i.m. for 14 days: group I, 5 mg/Kg; group II, 15 mg/Kg; and group III, 25 mg/Kg. Five animals of each group were sacrificed after 14 days, and the remaining five after 21 days to assess residual CyA effects. On the day of sacrifice, the rats underwent maltose absorption test, and glucose and insulin levels were measured. Pancreatic biopsies were obtained on day 21 to evaluate islets ultrastructure by electron microscopy. As a result, statistically significant, dose dependent (P < 0.05) increases in glucose and insulin levels were observed in CyA-treated groups. Groups II and III showed insulin levels significantly higher after fasting (P < 0.05) on day 14 comparing to the controls, while in groups I and II values returned to normal after CyA discontinuation. Group III showed persistently increased insulin levels on day 21. Pancreatic ultrastructural changes were observed only in group III. We can conclude that CyA effects on glucose and insulin levels were temporary and reversible at low doses. Ultrastructural changes in the pancreatic islets may occur with high doses of CyA.

Animals↗
PubMed1999

Expression of Bacteroides fragilis virulence markers in vitro.

Bacteroides fragilis isolates from intestinal and non-intestinal infections, normal flora and the environment were examined for properties linked with interactions among cells in vitro. Different adhesion molecules were detected in agglutination assays with human erythrocytes and tests for auto-agglutination and adherence to human colon carcinoma cells (HT29). There was no correlation between these properties, indicating that independent molecules are involved. Treatment with trypsin, heat or EDTA inhibited agglutination and adherence, suggesting that these molecules are proteins. The lack of correlation with the origin of the strains did not permit any of these activities to be recognised as virulence markers. The expression of fragilysin, a protease associated with damage to intestinal cells and bacterial translocation, was examined. Only those strains from patients with diarrhoea expressed this protease activity in assays with HT29 cells and this was confirmed by specific PCR for the bft gene. The activity of fragilysin as an enterotoxin was confirmed in the rabbit intestinal ligated loop assay. The association of this property only with strains from intestinal infections indicates that it is too early to suggest this protease as a determinant factor of B. fragilis invasiveness.

Agglutination Tests↗
PubMed1999

[Thrombolysis in pulmonary embolism - initial experience].

UNLABELLED: Pulmonary embolism (PE) is a clinical situation difficult to diagnose, at times of great clinical instability, above all when it is massive, which leads to difficulties in the approach and treatment of patients. The treatment has not had any major innovations in recent years, being conventional the use of heparin and more rarely embolectomy. Recently, some clinical trials have defended the use of thrombolytics. The objéctive of this paper is to present our experience, although the series is still small. From April 1996 to November 1997, 11 patients were admitted to our Cardiac Intensive Care Unit with the clinical suspicion of PE, 5 of which with great hemodynamic instability and suspicion of massive PE. The clinical presentation was sudden dyspnea and loss of consciousness in 2 patients, dyspnea and hypotension in 2 patients and shock and respiratory arrest in one case. Gasimetry revealed acute hypoxemia and hypocapnia in all cases, average partial blood pressure in O2 (pO2) of 59 mm Hg and CO2 (pCO2) of 19 mm Hg. ECC and thorax x-ray contributed to the diagnosis in 3 patients, transthoracic echocardiography was decisive for the diagnosis in 5 cases, with visualisation of the thrombus by transesophageal echocardiography in 3 patients. All patients were monitored by Swan-Ganz catheter, the average systolic pulmonary artery pressure (PAP) was 74 mm Hg. Thrombolysis with rTPA (10 mg bolus followed by 90 mg in perfusion in 2 hrs) was administered in 6 episodes in 5 patients. Only in the case of the patient in shock were other complications related to the use of thrombolytics namely high digestive hemorrhage. There was a clear clinical improvement in all cases with great relief of dyspnea reduction of cyanosis and jugular engurgitation. The patient in shock recovered systemic pressures and improved the hemodynamic state. A significant reduction in PAP was observed (average of 32.5 mm Hg). PE recurred in two cases: with one death and therapeutic thrombolytic was repeated in the other patient with good results. After discharge, all patients remained asymptomatic under oral anticoagulation. IN CONCLUSION: Despite this small series, the results favour the use of thrombolytics in PE with a clear clinical and hemodynamic improvement.

Adult↗
PubMed1999

[Importance of multiplane transesophageal echocardiography in the diagnosis of pulmonary embolism].

Pulmonary thromboembolism (PTE) is a clinical entity difficult to diagnose, its setting is often confused with other pathological entities. The inexistence of isotopic techniques in most centres and the difficulty and delay in performing a pulmonary angiography leads transesophageal echocardiography (TEE) to be, a method of increasing importance for its diagnosis. From January 1996 to November 1997, echocardiographic evaluation was requested for 33 patients due to clinical suspicion of pulmonary thromboembolism. A transthoracic assessment was made previously in 21 patients (average ages 58.3 years, 52% males) which had signs of right overload (dilatation of the right cavities, anomalous movement of the intraventricular septum and pulmonary hypertension) a TEE was performed. The TEE was negative in 10 patients (TEEn) without evidence of thrombi in the trunk and main branches of the pulmonary artery (PA); there was one death on this group for repeated pulmonary microembolisms confirmed by necropsy. The TEE was positive in 11 patients (TEEp) with evidence of thrombi in the PA trunk in 3 patients, bilaterally in both branches in 3 patients and in the right branch in 5 patients. There were dilatations of the right cavities in all patients, paradoxal movement of the interventricular septum and bulging of the intra-auricular septum to the left atria. Foramen ovale was detected in 2 patients. The best visualisation of the PA was achieved in the intermediate planes between 30-70 degrees and between 90-130 degrees (plane for transverse slice of the right branch of the pulmonary artery). In 7 patients with TEEp, PTE was confirmed by CT-scan (visualisation of the thrombi in the trunk and main branches of the PA) and/or ventilation-perfusion scintigraphy and/or pulmonary angiography. In three cases of massive pulmonary embolism in young patients, with severe pulmonary hypertension, thrombolysis was performed with rTPA, under TEE control before and after rTPA in one of the cases. In conclusion, transesophageal echocardiography is an easy technique to be performed in the case of clinical suspicion of PTE. The existence of a negative examination does not invalidate the existence of PTE since only the trunk and the main branches of the PA are accessible by this technique. The detection of thrombi at this level in patients with clinical suspicion of massive pulmonary embolism confirms the diagnosis and supports the indication of thrombolysis.

Adult↗
PubMed1999

[Case report of serious cardiac insufficiency complicated by syncope].

The authors describe a case of a patient with congestive heart failure complicated by syncope, hypotension and a transitory state of vigil coma. The transthoracic and transesophageal echocardiogram showed a huge mass that occupied almost totally the right ventricle causing sever obstruction. The patient was submitted to surgery and a resection of the mass with reconstruction of the free right ventricle wall was done. The histopathology revealed to be a leiomyosarcoma. There was a previous history of an uterine surgery.

Aged↗
PubMed1999

[The nonpharmacological treatment of atrial fibrillation].

The authors describe the main forms of nonpharmacological treatment of atrial fibrillation considering catheter ablation and surgical therapy. A new methodology to modify atrioventricular conduction is discussed as well its long-term results. All studies are non-randomised with selected patients, which makes the development of a therapeutical algorithm difficult. However, the results have shown that it is possible to recover sinus rhythm through surgery or catheter ablation and to control the ventricular rate either by His ablation or modification of atrioventricular conduction.

Aged↗
PubMed1999

[Pulmonary thromboembolism angiographically confirmed: clinical and prognostic aspects].

OBJECTIVE: The aim of this study was to evaluate the clinical profile and prognosis of patients with an angiographically proven thromboembolism. METHODS: Data from 22 consecutive patients (13 males, 9 females; mean age 57.3 +/- 16.8 years) with pulmonary embolism confirmed by pulmonary angiography were reviewed. All our patients were previously submitted to non-invasive diagnostic procedures (blood examinations, EKG, chest x-ray, echocardiography). A V/Q scan was also performed in 5 patients. Fourteen patients were traditionally treated with heparin alone and the rest received thrombolytic therapy and heparin. Two patients had a thromboembolectomy. At discharge, all our patients were submitted to an oral anticoagulant therapy. The mean duration of the follow-up period was 26 +/- 12 months. RESULTS: The majority of the patients were in the 6th decade of life and it was possible to identify a hypercoagulable state in 82%. The most common symptom at the time of presentation was sudden chest pain (64%). The most specific sign in non-invasive procedures were right side cardiac dilatation seen echocardiographically (73%) and the mismatch in the V/Q scan (80%). The most common haemodynamic parameter (91%) observed in the right heart catheterization of these patients was the finding of a gradient between diastolic pulmonary artery and pulmonary capillary wedge pressures. Uneventful angiography was performed in all patients who showed massive pulmonary embolism (86%). Three patients (13.6%) died during the acute phase. At the end of the follow-up period, 10 patients were asymptomatic and 5 had heart failure. Four died, which corresponds to an overall mortality of 31.8% in 2.2 years of follow-up. None of the clinical or haemodynamic parameters analyzed (age, gender, arterial blood gases at presentation, hypercoagulable states, thrombolysis, pulmonary hypertension and extension of the embolism) were related to mortality. CONCLUSION: Angiographically confirmed pulmonary thromboembolism is still a poor outcome situation, even when a lot of diagnostic and therapeutic procedures are available.

Adult↗
PubMed1999

[Should all patients with ventricular pre-excitation of the Wolff-Parkinson-White syndrome type undergo catheter ablation?].

The authors make a concise review concerning clinical, electrocardiographic and electrophysiologic risk stratification in Wolff-Parkinson-White syndrome and present the results of radiofrequency catheter ablation of atrioventricular accessory pathways. The low sensitivity of electrophysiologic criteria for the identification of a high risk profile limits their use in asymptomatic patients with a low incidence of sudden death. The greater risk of ventricular fibrillation in symptomatic patients makes radiofrequency catheter ablation the treatment of choice for these patients. Therefore, the authors do not recommend an electrophysiologic risk stratification in Wolff-Parkinson-White syndrome, but emphasize that catheter ablation should be performed in all symptomatic patients.

Adolescent↗