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Biomedical subjects

L Araujo

Publications and source records attributed to L Araujo.

At least 19 recordsLinked to original sources
PubMed1992

Detection of coronary artery disease with positron emission tomography and rubidium 82.

Myocardial blood flow was evaluated in 31 subjects with not only visual but also, for the first time, circumferential profile analysis of rubidium 82 (82Rb) images acquired with positron emission tomography. Fifteen were control subjects and 16 subjects had significant coronary artery disease, defined as 50% or greater diameter stenosis in a major coronary artery or a first-order branch. Simultaneous 82Rb images at three myocardial levels were obtained before and after intravenous dipyridamole plus handgrip stress. In patients with significant coronary artery disease, visual analysis correctly identified significant disease in 26 (76%) of 34 arteries and its absence in 12 (86%) of 14 normal arteries. According to circumferential profile analysis, these numbers were 91% and 86%, respectively. Thus circumferential analysis of 82Rb images, obtained before and after intravenous dipyridamole plus handgrip stress, yielded improved sensitivity and comparable specificity compared with visual analysis.

Coronary Disease↗
PubMed1991

Effects of oxyfedrine on regional myocardial blood flow in patients with coronary artery disease.

Medical treatment of angina pectoris is largely based on the use of beta-blocking agents, calcium antagonists, and nitrates. Oxyfedrine, an amino ketone derivative and partial agonist at beta receptors, has been shown to have potent antianginal properties and to increase coronary blood flow in normal and ischemic myocardial regions in experimental studies. We assessed the effects of intravenous oxyfedrine on regional myocardial blood flow, using positron emission tomography (15-oxygen water), in six patients with chronic stable angina, positive exercise tests, and documented coronary artery disease. Myocardial blood flow was measured in all patients before (baseline) and 10 minutes after the intravenous administration of a single bolus (0.11-0.13 mg/kg) of oxyfedrine. Compared to baseline, heart rate and systolic blood pressure remained almost unchanged after the administration of oxyfedrine. Mean baseline myocardial blood flow was 0.90 +/- 0.15 ml/g/min in areas supplied by arteries with significant coronary stenosis and 1.08 +/- 0.19 ml/g/min in areas supplied by nonstenotic coronary vessels (p less than 0.05). After the administration of oxyfedrine, myocardial blood flow increased significantly in both the regions supplied by stenotic vessels (by 25%; from 0.90 +/- 0.15 to 1.20 +/- 0.31 ml/g/min; p = 0.002) and in areas supplied by angiographically normal coronary vessels (by 22%; from 1.08 +/- 0.19 to 1.38 +/- 0.49 ml/g/min; p less than 0.05). The results of this study indicate that in patients with coronary artery disease, intravenous oxyfedrine significantly increases regional myocardial blood flow, both in areas supplied by critically obstructed vessels and in areas supplied by normal or less severely narrowed coronary arteries.

Aged↗
PubMed1991

Positron emission tomography demonstrates that coronary sinus retroperfusion can restore regional myocardial perfusion and preserve metabolism.

Positron emission tomography was used to image blood flow and metabolic tracers in risk zone myocardium after left anterior descending coronary artery occlusion during synchronized coronary venous retroperfusion. Six control and seven intervention open chest dogs had occlusion of the mid left anterior descending coronary artery. Synchronized retroperfusion commenced 25 min later. Flow tracers (rubidium-82 and nitrogen-13 ammonia) were injected retrogradely. Three hours after coronary occlusion, fluorine-18 (F-18) deoxyglucose uptake in the control and treatment groups was compared. At 200 min of occlusion, infarct size was assessed. Retrograde flow tracer uptake was observed in the risk zone in the seven intervention dogs. Fluorine-18 deoxyglucose uptake in the risk zone was increased in five of the six intervention dogs but was reduced in five of the six control dogs. The risk zone to normal zone F-18 deoxyglucose count ratio was higher in the intervention than the control group (1.13 +/- 0.39 vs. 0.59 +/- 0.51; p less than 0.05). The endocardial subsegment risk zone to normal zone F-18 deoxyglucose count ratio was also significantly higher in the intervention group. Percent infarction in the risk zone was 70% lower in the group treated with synchronized retroperfusion than in the control group (18.4 +/- 22.6% vs. 61.2 +/- 25.4%; p less than 0.02). Thus, positron emission tomography revealed that retroperfusion could deliver oxygenated blood and maintain metabolism in risk zone myocardium. Infarct size was limited to 30% of that of control. In acute closure of the left anterior descending coronary artery, synchronized retroperfusion might be considered for maintaining viability of the jeopardized myocardium if the artery cannot be reopened rapidly.

Animals↗
PubMed1991

[Obstetric care and perinatal mortality in a rural area of northeastern Brazil].

This paper examines deliveries in a rural community of northeastern Brazil served by midwives who had received training that included the referral of pregnancies with complications; such training is essential to improve obstetrical care in rural areas of less developed countries. Data were collected on 1,661 women, of whom 62% gave birth in their homes and 38% in hospitals. The women referred to hospital were more likely to be primigravidas, to experience complications during labor, or to have had a stillbirth in the past. The parturients who were sent straight to hospital were more likely to have completed primary schooling or to have obtained prenatal care. The infant mortality rate was 32/1,000 births and the early neonatal mortality rate 14/1,000. For referred pregnancies these mortalities rose to 128 and 24, respectively. The factors significantly associated with perinatal mortality were advanced maternal age, the presence of prenatal pathology, abnormal presentation, complications in labor, and previous stillbirth. The low rate of perinatal mortality for young women and nulliparas and the disproportionally high number of nulliparas with deliveries in hospitals suggest that the midwives and health professionals providing prenatal care are aware of the problems associated with the first delivery and hence are providing prompt and appropriate care to these parturients. Family planning is recommended, especially for grand multiparas and older mothers. The early detection of abnormal presentation and the transfer of these women to surgical facilities should improve perinatal prognosis.

Adolescent↗
PubMed1990

A study of infant mortality and causes of death in a rural north-east Brazilian community.

In 1984 a prospective study of 1645 women and 1677 births in a rural community in north-eastern Brazil showed the infant mortality rate to be 65 per 1000 live births. Neonatal, post-neonatal and infant mortality are analysed to determine the most important risk factors for each period. Post-neonatal survival depends largely on factors relating to child care, while neonatal deaths are more likely to be associated with biological factors. The principal cause of death, diarrhoeal disease, was responsible for a third of the deaths.

Brazil↗
PubMed1990

A community detection program for abdominal aortic aneurysm.

This study aimed to discover the prevalence of undiagnosed abdominal aortic aneurysm in the community in men aged sixty-five to seventy-four. All 1,392 men in this age group registered with twenty general medical practitioners were invited for free health screening at hospital and 746 attended. The abdominal aorta was imaged by ultrasound and its anteroposterior diameter measured. An abdominal aortic aneurysm was present in 6.3% and the aneurysm was 4.0 cm or more in diameter in 2%.

Aged↗
PubMed1989

Sustained nonoxidative glucose utilization and depletion of glycogen in reperfused canine myocardium.

Ischemically injured reperfused myocardium is characterized by increased 18F-fluorodeoxyglucose uptake as demonstrated by positron emission tomography. To elucidate the metabolic fate of exogenous glucose entering reperfused myocardium, D-[6-14C] glucose and L-[U-13C] lactate were used to determine glucose uptake, glucose oxidation and the contribution of exogenous glucose to lactate production. The pathologic model under investigation consisted of a 3 h balloon occlusion of the left anterior descending coronary artery followed by 24 h of reperfusion in canine myocardium. The extent and severity of myocardial injury after the ischemia and reperfusion were assessed by histochemical evaluation (triphenyltetrazolium chloride and periodic acid-Schiff stains). Thirteen intervention and four control dogs were studied. The glucose uptake in the occluded/reperfused area was significantly enhanced compared with that in control dogs (0.40 +/- 0.14 versus 0.15 +/- 0.10 mumol/ml, respectively). In addition, a significantly greater portion of the glucose extracted immediately entered glycolysis in the intervention group (75%) than in the control dogs (33%). The activity of the nonoxidative glycolytic pathway was markedly increased in the ischemically injured reperfused area, as evidenced by the four times greater lactate release in this area compared with the control value. The dual carbon-labeled isotopes showed that 57% of the exogenous glucose entering glycolysis was being converted to lactate. Exogenous glucose contributed to greater than 90% of the observed lactate production. This finding was confirmed by the histochemical finding of sustained glycogen depletion in the occlusion/reperfusion area. The average area of glycogen depletion (37%) significantly exceeded the average area of necrosis (17%). These data demonstrate enhanced and sustained activity of the nonoxidative glycolytic pathway after a prolonged occlusion with reperfusion in canine myocardium. Because glycogen stores remain depleted, exogenous glucose becomes an important myocardial substrate under these pathologic conditions.

Animals↗
PubMed1989

How fast do very small abdominal aortic aneurysms grow?

Fifty patients with abdominal aortic aneurysms from 2.5 to 5.0 cm in anteroposterior diameter (median 3.1 cm, mean +/- S.E. 3.3 +/- 0.1 cm) were initially offered non-operative treatment. Two patients have subsequently undergone successful elective aneurysm resection because of increase in aneurysm size, and a third has died. The median annual growth rate of the aneurysm has been 0.22 cm and 77.8% increased in size between 6 monthly ultrasound examination. For aneurysms less than 4.0 cm the maximum 6 monthly increment in diameter was 0.7 cm. Even the smallest abdominal aortic aneurysms usually progressively increase in size and 6 monthly ultrasound remeasurement of aneurysm diameter is an essential component of non-operative management.

Aged↗
PubMed1989

Rabbit myocardial 82Rb kinetics and a compartmental model for blood flow estimation.

Quantification of regional myocardial blood flow (MBF) with rubidium-82 (82Rb) and positron emission tomography (PET) requires the validation of a tracer kinetic model that adequately describes the kinetics of 82Rb in tissue. We performed 134 82Rb kinetic experiments in 24 isolated, arterially perfused rabbit interventricular septa at different flow rates (0.5-4.5 ml.min-1.g-1) and under the following conditions: varied concentrations of glucose (2.8-11 mM), insulin (0-5 mU/ml), and potassium (5-8 mM); varied pH (7.2-7.8); varied workload; and the addition of acetylstrophanthidin (1.0 microM). The measured 82Rb tissue time-activity curves consisted of two exponential components, with half times inversely related to MBF. The size of the slow component decreased as MBF increased (from 70% at 0.3 ml.min-1.g-1 to 30% at 2.0 ml. min-1.g-1). The kinetics were not strongly dependent on the conditions studied and were consistent with a compartmental model containing two communicating compartments. The volume of the fast exchangeable compartment and the transport rate constant from the fast to the slow compartment were found to be independent of MBF. Values of MBF were estimated with the compartmental model from 82Rb kinetics, and they correlated well with the directly measured MBF (r = 0.91; slope = 1.03).

Animals↗
PubMed1988

Oxford screening programme for abdominal aortic aneurysm in men aged 65 to 74 years.

824 men aged 65 to 74 were invited for ultrasound screening of the aorta and 426 (51.7%) attended. An abdominal aortic aneurysm was discovered in 23 (5.4%), and in 10 (2.3%) the aneurysm was 4.0 cm or more in diameter. 2 other patients had a common iliac artery aneurysm. The 36 men who had objective evidence of occlusive arterial disease of the lower limbs were twice as likely to be tobacco smokers and accounted for 5 (20%) of the aneurysms discovered. Extension of this screening programme to England and Wales could be expected to identify 52,500 men with an abdominal aortic aneurysm. If elective surgical replacement of the aneurysm were to be accepted by 60% of those with aneurysms 4 cm or more in diameter, 6000 unnecessary deaths from aortic aneurysm rupture could be prevented.

Aged↗
PubMed1988

A community screening programme for abdominal aortic aneurysms.

Three-hundred and sixty-nine unselected men aged 65-79 years were invited for screening for abdominal aortic aneurysm. One hundred and forty-one men were examined and 4 aneurysms detected. 43.2% of men aged 65-74 attended for examination in response to a single unsolicited letter of explanation with the date of an appointment, but only 29.1% of those aged 75-79 years. It is suggested that community mortality from ruptured aortic aneurysm could be reduced by ultrasound screening of the aorta in men aged 65-74 years and early selective aneurysm surgery.

Aged↗
PubMed1988

Validation of PET-acquired input functions for cardiac studies.

To validate the determination of the arterial input function by noninvasive dynamic PET imaging, measurements of blood-pool activity in canine LV by PET were compared to beta probe measurements of arterial blood withdrawn directly from the LV. PET scans were done during intravenous bolus injections of [13N]ammonia or 82Rb, while the activity of blood withdrawn continuously from a catheter inserted in the LV was measured with a beta probe. PET determinations of LV blood-pool activity were compared with dispersion-corrected beta probe time-activity curves. In 15 experiments involving four dogs under a wide range of physiologic conditions, LV time-activity curves obtained with PET matched well in shape with those obtained with the beta probe. Linear regression yielded slopes within 10% of unity (95% confidence interval) and high correlation (r greater than 0.968, p less than 0.001). We conclude that noninvasive measurement of the arterial input function by dynamic PET imaging is valid.

Ammonia↗
PubMed1987

Antibodies to a surface membrane marker from human mammary carcinoma cell line.

A tumor surface antigen (BTA-BT20-68K) was isolated from a human mammary carcinoma cell line (BT-20). The antigen (Mr 68,000) induced the formation of high titer antibodies which recognized BTA-BT20-68K as a cell surface marker by the immune adherence hemagglutination test and recognized the soluble antigen by solid phase radioimmunoassay. The antibodies which failed to recognize human beta-2-microglobulin, alpha-fetoprotein, and carcinoembryonic antigen were cytotoxic to the parent BT-20 tumor cells at high serum dilutions. The antibodies recognized a similar tumor surface marker isolated directly from human breast adenocarcinomas, but failed to recognize human lymphocyte antigens isolated from BT-20 cells or bound to human lymphocytes bearing human lymphocyte antigen markers in common with those of BT-20 cells. Added to BT-20 tumor cells in culture and in the absence of complement, antibody-dose-related inhibition of tumor cell growth was documented. In the presence of complement, the antibodies were highly cytotoxic to the parent cells. These results demonstrate the presence of a unique tumor surface marker with chemical and immunological properties in common with that isolated directly from human breast adenocarcinomas.

Adenocarcinoma↗
PubMed1986

Myocardial glucose utilization in ischaemic heart disease: preliminary results with F18-fluorodeoxyglucose and positron emission tomography.

Regional myocardial utilization of glucose can be assessed non-invasively in man with the sugar analogue F18-2-fluoro-2-deoxyglucose (FDG) and positron emission tomography (PET). The preliminary observations made in patients with different clinical forms of ischaemic heart disease using FDG and PET are reported. In patients with stable angina pectoris at rest, regional myocardial glucose utilization was comparable to that in normal volunteers whilst an increased utilization of glucose was found in the recovery from exercise-induced ischaemia in the regions that showed an abnormal perfusion during the stress test. These metabolic changes persisted in the recovery phase when all the parameters that were altered during the exercise, including myocardial perfusion, had normalized. In patients with unstable angina, characterized by repeated episodes of spontaneous ST depression, myocardial glucose utilization was regionally or globally increased already at rest in the absence of symptoms or signs of ischaemia at the time of study and most often without evident perfusion abnormalities. In patients with a recent infarction, two different patterns of glucose utilization in the infarcted area have been described: a concordant decrease of myocardial perfusion and glucose utilization; a disproportionately increased glucose utilization relative to perfusion interpreted as an index of the presence of ischaemic, but still viable myocardium.

Angina Pectoris↗
PubMed1986

Local coronary supersensitivity to diverse vasoconstrictive stimuli in patients with variant angina.

It has been shown in different groups of patients with variant angina that coronary spasm can be reproduced by physiologic maneuvers and pharmacologic agents. It is not known, however, to what extent different stimuli can induce spasm in the same patient. To investigate whether coronary arterial spasm results from specific abnormal agonist-receptor interactions or from a local nonspecific coronary supersensitivity to different stimuli, 28 patients with vasospastic angina were submitted to a series of diverse vasoconstrictive stimuli known to provoke coronary spasm. Ergonovine, hyperventilation, handgrip, cold pressor, and exercise-tests, were carried out in all 28 patients. In the last 15 patients histamine was also administered. Spasm was provoked by ergonovine in 96% of patients, by hyperventilation in 54%, by histamine in 47%, by exercise in 46%, and by the cold pressor and handgrip tests in 11% and 7%, respectively. No significant differences were found in the responses to provocative tests of patients with normal coronary arteries or nonsignificant stenoses and those with significant lesions. In the same individual, spasm was induced by at least two vasoconstrictive stimuli, although with a different mechanism of action, in 82% of patients and spasm was induced by three or more stimuli in 39%. Tests were repeated in at least 23 patients and short-term reproducibility paralleled sensitivity. These results suggest that in patients with variant angina, a local nonspecific supersensitivity rather than an abnormal specific agonist-receptor interaction plays a major role in the genesis of coronary arterial spasm.

Adult↗