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Biomedical subjects

J Ferreira

Publications and source records attributed to J Ferreira.

At least 19 recordsLinked to original sources
PubMed1998

Antioxidant activity of gallates: an electrochemical study in aqueous media.

The electron-donating ability of gallates, which are food and pharmaceutical antioxidants, is quantitatively assessed on the basis of their electrochemical characteristics. Gallic acid and the propyl, i-propyl, butyl, i-butyl, pentyl and i-pentyl gallate derivatives were electrochemically oxidized on the glassy carbon electrode by using differential pulse voltammetry, cyclic voltammetry and hydrodynamic voltammetry on the rotating disk electrode. All the compounds under study were easily oxidized in acidic and neutral solutions. Electrochemical oxidation occurs via two electron-transfer steps; however good resolution for the second wave was obtained only by using hydrodynamic conditions. The oxidation process results to be irreversible, diffusion controlled and pH-dependent. The introduction of the alkyl groups seems to affect the intensities of the semiquinone gallate radicals as can be ascribed from the observed differences in i(II)d/i(I)d ratio obtained from hydrodynamic voltammetric experiments for the different derivatives. We have found that the intensity of the gallate radicals follows the sequence GA > or = i-PG > PG > i-BG > BG > i-PeG > PeG. From the pH-dependence of the peak current it is possible to affirm that pH 2 is the better condition for the oxidative activity showing that the antioxidant behaviour of these compounds are important in the stomach acid.

Antioxidants↗
PubMed1998

Effects of the Kupffer cell inactivator gadolinium chloride on rat liver oxygen uptake and content of mitochondrial cytochromes.

The effect of gadolinium chloride (GdCl3) on the content of rat liver mitochondrial cytochromes was investigated in relation to the basal rate of O2 uptake and Kupffer cell functioning, assessed in liver perfusion studies. (1) A single dose of GdCl3 (10 mg/kg) produced a significant diminution in Kupffer cell functioning, evidenced by the decreases in colloidal carbon uptake and in carbon-induced O2 uptake observed at 6-24 h after treatment, without changes in the sinusoidal lactate dehydrogenase efflux as index of tissue viability; at 48 h after GdCl3 administration, carbon phagocytosis was recovered to control values, whereas carbon-induced O2 uptake remained lower than control values. (2) GdCl3 also caused a 34% decrease in the basal rate of O2 consumption of the liver at 24 h after treatment, which returned towards control values at 48 h. (3) The content of mitochondrial cytochromes c1 and c at 24 h after GdCl3 treatment was significantly reduced by 40 and 32%, respectively, which returned to control values at 48 h, without changes in that of cytochromes b and a+a3. It is concluded that GdCl3-induced decrease in liver O2 consumption is a reversible phenomenon that seems to be due to a diminution in the content of mitochondrial cytochromes c1 and c.

Animals↗
PubMed1998

Occluding aortic endoluminal stent graft combined with extra-anatomic axillofemoral bypass as alternative management of abdominal aortic aneurysms for patients at high risk with complex anatomic features: a preliminary report.

PURPOSE: To describe an exclusion endoluminal technique for management of abdominal aortic aneurysms among high-risk patients with complex anatomic features. METHODS: From January 1995 to December 1996, among 143 patients with infrarenal abdominal aortic aneurysm treated by means of endograft placement, 9 (6.3%) had complex aortic or aortoiliac morphologic features. For these patients, the endograft was delivered through a femoral cutdown in an occluding aortoiliac configuration. The contralateral iliac artery was occluded with an iliac endograft. Axillofemoral bypass grafting was performed. Computed tomographic scans were obtained regularly. RESULTS: There was 1 postoperative death of severe arrhythmia. All aneurysms were found to be affected by thrombosis on immediately postoperative computed tomographic scans, except in 1 patient with a proximal leak, which was managed successfully with angiographic embolization. The mean follow-up time was 12 months. Aortic aneurysm diameter decreased from 2 mm at 6 months (2 patients) to 6 mm at 12 months (6 patients). All axillofemoral bypass grafts are patent. CONCLUSIONS: Placement of an occluding endograft associated with axillofemoral bypass grafting is a good alternative for patients at high risk with complex anatomic features. Longer-term follow-up study is needed to evaluate this endoluminal technique.

Aged↗
PubMed1998

Adventitial cystic disease of the popliteal artery communicating with the knee joint. A case report.

We describe the case of a patient with adventitial cystic disease of the popliteal artery in which a direct anatomic communication between the cysts and the nearby knee joint was demonstrated by magnetic resonance imaging and confirmed by surgery. This unusual observation could shed some light on the much debated question of the cause, the pathogenesis, and the management of the affection. Moreover, it emphasizes the importance and the role of magnetic resonance imaging in the diagnosis of adventitial cystic disease of the popliteal artery.

Adult↗
PubMed1998

Diagnosis of stroke by the nonneurologist. A validation study.

BACKGROUND AND PURPOSE: The first medical contact of an acute stroke victim is often a nonneurologist. Validation of stroke diagnosis made by these medical doctors is poorly known. The present study seeks to validate the stroke diagnoses made by general practitioners (GPs) and hospital emergency service physicians (ESPs). METHODS: Validation through direct interview and examination by a neurologist was performed for diagnoses of stroke made by GPs in patients under their care and doctors working at the emergency departments of 3 hospitals. RESULTS: Validation of the GP diagnosis was confirmed in 44 cases (85%); 3 patients (6%) had transient ischemic attacks and 5 (9%) suffered from noncerebrovascular disorders. Validation of the ESP diagnosis was confirmed in 169 patients (91%); 16 (9%) had a noncerebrovascular diagnosis. Overall, the most frequent conditions misdiagnosed as stroke were neurological in nature (cerebral tumor, 3; subdural hematoma, 1; seizure, 1; benign paroxysmal postural vertigo, 1; peripheral facial palsy, 2; psychiatric condition, 6; and other medical disorders, 7). CONCLUSIONS: In the majority of cases, nonneurologists (either GPs or ESPs) can make a correct diagnosis of acute stroke. Treatment of acute stroke with drugs that do not cause serious side effects can be started before evaluation by a neurologist and CT scan.

Adult↗
PubMed1998

Helical CT of aorta after endoluminal stent-graft therapy: value of biphasic acquisition.

OBJECTIVE: We report our prospective study evaluating biphasic helical CT of the aorta after endoluminal stent-graft placement. SUBJECTS AND METHODS: Biphasic helical CT scans in 95 patients with abdominal and thoracic aortic aneurysms who had undergone endoluminal stent-graft placement were reviewed. After a test bolus injection of 15 ml of contrast media at a rate of 3.5 ml/sec for the measurement of the optimal start delay, the aorta was scanned using the following parameters: collimation of 5 mm, table speed of 7 mm per rotation, tube rotation time of 0.75 sec, 120 kV, and 295 mA. A delayed helical CT scan was obtained 15 sec after the initial acquisition using the same parameters. RESULTS: Biphasic helical CT scans showed perigraft leakage in 45 (47%) of 95 patients. Leakage was shown only on arterial phase CT in eight patients and only on the delayed scans in three patients. In two patients, leakage shown on the delayed acquisition was retrospectively seen on the first scan. Leakage and outflow vessels were most visible on the arterial phase acquisition in 17 patients and on the second acquisition in six patients. Overall, biphasic acquisition was superior to arterial phase acquisition alone in 15 (16%) of 95 patients. CONCLUSION: The diagnostic value of biphasic helical CT is superior to arterial phase acquisition alone for the evaluation of the aorta after endoluminal stent-graft therapy.

Aged↗
PubMed1998

[The role of season in the incidence of deep venous thrombosis].

INTRODUCTION: The question of the role of season as a predisposing factor for development of venous thromboembolic disease still remains a matter of debate. Actually, most reports described a higher incidence of thrombotic disorders in winter, while a recent study showed no seasonal variation in the incidence of deep vein thrombosis (DVT). These data led us to study the seasonal distribution of all outpatients with DVT admitted to our Department over a period of 14 years. METHODS: Retrospective review of the files of all outpatients with confirmed (venography or ultrasound) DVT of the legs admitted from Jan. 1st 1982 to Dec. 31st 1995 (n = 512; mean age 59.4 years; 49.4% women). RESULTS: DVT occurred in spring in 135 (26.4%), in summer in 104 (20.3%), in autumn in 142 (27.7%) and in winter in 131 (25.6%) patients. This distribution appears to be similar to an expected uniform distribution [chi 2(3) df = 6.48; p = 0.090 (NS)]. CONCLUSIONS: In our study, by investigating retrospectively 512 outpatients with confirmed DVT, no correlation was found between season and development of thrombosis, suggesting that cold seasons do not represent a predisposing factor for DVT. Further large prospective studies are needed in order to validate our data and to investigate the clinical implications and the precise role of the season in the risk of occurrence of venous thrombosis.

Adolescent↗
PubMed1998

[Role of auxiliary diagnostic tests in the clarification of the etiology of syncope: experience at an arrhythmia center].

UNLABELLED: Syncope is a syndrome caused by a reversible reduction of blood to the brain. Three hemodynamic abnormalities can cause syncope: an acute decrease in cardiac output, an acute increase in cerebrovascular resistance and a fall in systemic blood pressure due to ineffective control of peripheral vascular resistance. We made a retrospective study of 121 patients with syncope history, 67 males, and 57 females, with mean age 48 +/- 14 years, and at least six months of clinical follow-up. Twelve patients had valvular disease, two patients had hypertrophic cardiomyopathy, eight patients had dilated cardiomyopathy, 14 patients had ischemic disease, three patients had congenital disease; 82 patients did not have cardiac disease. Syncope etiology was arrhythmic in 69 patients: 47 patients had tachyarrhythmia (supraventricular--in 27 patients and ventricular in 20 patients) and 15 patients had bradyarrhythmia (seven patients had sinus node disease and eight patients had atrioventricular block). Non arrhythmic etiology of syncope was identified in 29 patients (neurologic disease--ten patients, metabolic disease--one patient and iatrogenic--two patients; vasodepressor syncope--14 patients, and hypertrophic cardiomyopathy--two patients). It was not possible to determine the syncope etiology in 30 patients. The assessment of patients who present syncope depends on establishing the basis for the symptoms. The initial step is differentiating patients with normal cardiovascular systems from those with heart disease. In the former, tilt-table testing proved to be the most productive from a diagnostic perspective; in the latter group, electrophysiologic evaluation was the most elucidative from a diagnostic perspective. The ultimate goal is to obtain a sufficiently strong correlation between syncopal symptoms and detected abnormalities to permit an accurate assessment of prognosis and to develop an effective treatment plan. CONCLUSIONS: It is very important to establish the etiology of syncope for optimal management of patients and it is therefore possible to control the symptoms in the majority of them. The patients who present syncope require a complete history and a physical examination for an appropriate workup to be initiated. Tilt-table testing was the most accurate for the diagnosis of vasodepressor syncope while electrophysiologic testing provides an accurate method for assessing the etiology of tachyarrhythmic syncope.

Adult↗
PubMed1997

Spatial organization of large-scale chromatin domains in the nucleus: a magnified view of single chromosome territories.

We have analyzed the spatial organization of large scale chromatin domains in chinese hamster fibroblast, human lymphoid (IM-9), and marsupial kidney epithelial (PtK) cells by labeling DNA at defined stages of S phase via pulsed incorporation of halogenated deoxynucleosides. Most, if not all, chromosomes contribute multiple chromatin domains to both peripheral and internal nucleoplasmic compartments. The peripheral compartment contains predominantly late replicating G/Q bands, whereas early replicating R bands preferentially localize to the internal nucleoplasmic compartment. During mitosis, the labeled chromatin domains that were separated in interphase form a pattern of intercalated bands along the length of each metaphase chromosome. The transition from a banded (mitotic) to a compartmentalized (interphasic) organization of chromatin domains occurs during the late telophase/early G1 stage and is independent of transcriptional activation of the genome. Interestingly, generation of micronuclei with a few chromosomes showed that the spatial separation of early and late replicating chromatin compartments is recapitulated independently of chromosome number, even in micronuclei containing only a single chromosome. Our data strongly support the notion that the compartmentalization of large-scale (band size) chromatin domains seen in the intact nucleus is a magnified image of a similar compartmentalization occurring in individual chromosome territories.

Animals↗
PubMed1997

Endovascular aortic stent-grafts: transcatheter embolization of persistent perigraft leaks.

PURPOSE: To assess efficacy of transcatheter embolization of peri prosthetic leaks from aortic stent-grafts MATERIALS AND METHODS: Eight patients with a long-standing (3-13 months) perigraft leak after stent-graft implantation underwent transcatheter embolization. Leakage was demonstrated at helical computed tomography (CT). Angiography was performed for evaluation of outflow vessels and transcatheter embolization. All patients underwent helical CT follow-up after the procedure and every 3 months. RESULTS: Embolization was successful in seven patients and resulted in aneurysmal sac thrombosis. A second procedure was necessary in one patient to complete occlusion of the aneurysm. No further aneurysmal growth was detected during 4-9 months follow-up. Right leg paresis was observed in one patient immediately after the procedure, but symptoms disappeared completely after 8 days. Another patient had a minor sensory deficit in the region of the right crural nerve. CONCLUSION: Transcatheter embolization of perigraft leaks appears to be an effective technique to achieve aneurysmal thrombosis.

Aged↗
PubMed1997

Genome replication in early mouse embryos follows a defined temporal and spatial order.

The spatial and temporal organisation of replication sites during early mouse embryogenesis was analysed using high resolution confocal and video fluorescence microscopy. The results show that distinct replication patterns occur in the transcriptionally inactive pronuclei of 1-cell embryos as well as in the transcriptionally active nuclei from 2- and 16/32-cell embryos. This indicates that specific chromatin regions are replicated at different times during S-phase and provides the first evidence that mechanisms controlling the temporal and spatial replication of DNA are already present in the haploid pronuclei of the mammalian zygote. Furthermore the data demonstrate that the male and female pronuclei in one-cell embryos replicate their genomes asynchronously. Finally, we observe changes in the dynamics of embryonic genome replication during early development which correlate with gross chromatin structure transitions detected at the electron microscope level. Taken together these results indicate that DNA synthesis in the mouse zygote follows a defined four-dimensional order which may evolve during development and differentiation.

Animals↗
PubMed1997

[The prognostic significance of late potentials in patients with chronic coronary disease].

OBJECTIVE: The prognostic value of late potentials (LP) in the subacute phase of myocardial infarction (MI) is well known, but its prognostic value in long-standing coronary disease (LSCD) has not yet been established. In a population with LSCD we searched for a relation between the presence of LP in signal-averaged ECG (SAECG) performed before cardiac catheterization, and the incidence of cardiac events. METHODS: Based on our department's casuistics, we selected 50 consecutive patients with coronary disease confirmed by an angiogram and LP, and a control group without LP, in SAECG. We selected 91 men and nine women with an average age of 59 +/- 8 years. None of the patients had had ischemic events or revascularization procedures, in the 3 month period before catheterization. The follow-up was made between the time of the SAECG and the last medical visit. The events recorded were: ventricular arrhythmia, cardiac death, coronary angioplasty, coronary artery by-pass graft, MI or unstable angina. RESULTS: During a follow-up period of 20.1 +/- 8 months, we found no statistically significant difference between the two groups, regarding the incidence of such events. However, there was a higher incidence of ventricular arrhythmic events in the group with LP (four patients with ventricular tachycardia against none in the control group). All patients with ventricular tachycardia had had a previous MI. CONCLUSIONS: In this study, the presence of LP in SAECG did not have the same prognostic value found in the subacute phase of MI, but a higher incidence of arrhythmic events was observed in the group with LP and a previous MI.

Adult↗
PubMed1997

[Prevalence of several cardiovascular risk factors in a population in the municipality of Viseu].

STUDY OBJECTIVE: To assess the prevalence of the main changeable cardiovascular risk factors (hypertension, hypercholesterolemia and smoking) in the population of the Viseu municipality. MATERIAL AND METHODS: The population was obtained through a publicity campaign in local radios and on lighted placards in the town of Viseu. We chose a set of volunteers above 20 years of age, who answered a questionnaire about smoking habits, academic qualifications, profession and residence. After the inquiry, the total cholesterol and blood pressure were determined. We considered hypertension (HBP) values > or = 140/90 mmHg and hypercholesterolemia > 200 mg/dl. RESULTS: 1852 persons were inquired (3.2% of the population of the Viseu municipality) 1173 of which were females. According to the age groups, we verified that the ages between 50 and 69 years represented 47.9% of the total amount of volunteers. In what concerns smoking habits, we found a prevalence of 9.1% (15.9% in males and 5.2% in females). In the study of the prevalence of HBP we found a value of 38.5%, higher in males (42.8%) than in females (35.9%). The prevalence of hypercholesterolemia found was 34.9% (no significant differences between the sexes). CONCLUSION: In comparison with other studies carried out in the Portuguese population, a low prevalence of smoking habits, high hypertension and similar hypercholesterolemia were found.

Adult↗
PubMed1996

The topography of chromosomes and genes in the nucleus.

At present several lines of evidence indicate that the nucleus is functionally compartmentalized into discrete structures with defined properties. For instance, it is well established that the molecular machines involved in replication, transcription, and RNA processing assemble into morphological entities but it remains unclear whether these correspond to autonomous "organelles" or rather represent temporary accumulations of either active factors recruited onto DNA templates or inactive factors stored in the vicinity of genes. According to the latter view, the spatial distribution of genes during interphase should play a major role in the subnuclear organization of nonchromatin components such as replication, transcription, and processing factors, and in this article we discuss current ideas on the functional compartmentalization of chromosomes and genes within the nucleus.

Binding Sites↗
PubMed1996

Nuclear morphogenesis and the onset of transcriptional activity in early hamster embryos.

Coiled bodies and interchromatin granules are distinct subnuclear domains that contain splicing small nuclear ribonucleoproteins (snRNPs) and protein-splicing factors. Here we have studied the morphogenesis of coiled bodies and clusters of interchromatin granules in relation to the onset of transcriptional activity in early hamster embryos. The results indicate that major embryonic transcription by RNA polymerase II is first detected during the early two-cell stage (15-20 h post-fertilization), whereas RNA polymerase I activity and nucleologenesis are only observed in late two-cell embryos (30-40 h postfertilization). Splicing snRNPs and heterogeneous nuclear RNP (hnRNP) proteins are shown to be imported into the pronuclei following fertilization, and prominent clusters of interchromatin granules containing the splicing factor SC-35 are already observed in both maternal and paternal pronuclei of one-cell embryos. Interestingly, these large clusters of interchromatin granules do not appear to concentrate splicing snRNPs. In contrast, coiled bodies are first detected during the two-cell stage after the onset of transcription, and they are clearly enriched in snRNPs. Taken together with results previously obtained in mouse embryos, these data suggest that the assembly of coiled bodies and clusters of interchromatin granules is independent from the onset of embryonic transcriptional activity, and that coiled bodies represent the major snRNP-enriched subnuclear domain in the early mammalian embryo.

Animals↗
PubMed1996

A nuclear cap-binding complex binds Balbiani ring pre-mRNA cotranscriptionally and accompanies the ribonucleoprotein particle during nuclear export.

In vertebrates, a nuclear cap-binding complex (CBC) formed by two cap- binding proteins, CBP20 and CBP80, is involved in several steps of RNA metabolism, including pre-mRNA splicing and nuclear export of some RNA polymerase II-transcribed U snRNAs. The CBC is highly conserved, and antibodies against human CBP20 cross-react with the CBP20 counterpart in the dipteran Chironomus tentans. Using immunoelectron microscopy, the in situ association of CBP20 with a specific pre-mRNP particle, the Balbiani ring particle, has been analyzed at different stages of pre-mRNA synthesis, maturation, and nucleo-cytoplasmic transport. We demonstrate that CBP20 binds to the nascent pre-mRNA shortly after transcription initiation, stays in the RNP particles after splicing has been completed, and remains attached to the 5' domain during translocation of the RNP through the nuclear pore complex (NPC). The rapid association of CBP20 with nascent RNA transcripts in situ is consistent with the role of CBC in splicing, and the retention of CBC on the RNP during translocation through the NPC supports its proposed involvement in RNA export.

Animals↗