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Biomedical subjects

A Maseri

Publications and source records attributed to A Maseri.

At least 379 records · Page 21Linked to original sources
PubMed1982

Evidence for a direct stimulatory effect of prostacyclin on renin release in man.

THE OBJECTIVES OF THIS INVESTIGATION WERE: (a) to characterize the time and dose dependence of the effects of prostacyclin (PGI(2)) on renin release in healthy men; (b) to define whether PGI(2)-induced renin release is secondary to hemodynamic changes; (c) to determine the plasma and urine concentrations of 6-keto-PGF(1alpha) (the stable breakdown product of PGI(2)) associated with renin release induced by exogenous or pharmacologically enhanced endogenous PGI(2). Intravenous PGI(2) or 6-keto-PGF(1alpha) infusions at nominal rates of 2.5, 5.0, 10.0, and 20.0 ng/kg per min were performed in each of six normal human subjects; in three of them, PGI(2) infusion was repeated after beta-adrenergic blockade and cyclooxygenase inhibition. PGI(2), but not 6-keto-PGF(1alpha), caused a time- and dose-dependent increase of plasma renin activity, which reached statistical significance at 5.0 ng/kg per min and was still significantly elevated 30 min after discontinuing the infusion. Although combined propranolol and indomethacin treatment significantly enhanced the hypotensive effects of infused PGI(2), it did not modify the dose-related pattern of PGI(2)-induced renin release. Plasma 6-keto-PGF(1alpha) levels rose from undetectable levels (<7.5 pg/ml) in a stepwise fashion during increasingly higher infusion rates of PGI(2) or 6-keto-PGF(1alpha). The threshold concentration of plasma 6-keto-PGF(1alpha) associated with a statistically significant stimulation of renin release was approximately 200 pg/ml. Upon discontinuing PGI(2) or 6-keto-PGF(1alpha) infusion, the disappearance of 6-keto-PGF(1alpha) from blood showed an identical biphasic behavior, the initial phase having an apparent t((1/2)) of 3.2 min. The intravenous infusion of furosemide, which is known to stimulate renin release via a cyclooxygenase-dependent mechanism, caused a three-to fourfold increase of urinary 6-keto-PGF(1alpha) excretion rate, concomitant with the elevation of plasma renin activity levels, in six healthy women. 6-Keto-PGF(1alpha) remained undetectable in peripheral venous plasma throughout the study. WE CONCLUDE THAT IN HUMAN SUBJECTS: (a) PGI(2)-induced renin release occurs with a dose and time dependence similar to its reported platelet effects; (b) PGI(2)-induced renin release is not mediated by adrenergic stimuli or cyclooxygenase-dependent mechanisms secondary to hemodynamic changes; (c) furosemide-induced renin release is associated with increased renal PGI(2) formation; and (d) PGI(2) appears to act as a local modulator rather than a circulating hormone in controlling juxtaglomerular function.

6-Ketoprostaglandin F1 alpha↗
PubMed1982

[The role of spasm in angina pectoris, myocardial infarction and sudden death. Indications for future research and treatment].

Recent concepts on the role of coronary artery spasm and other forms of vasoconstriction in coronary artery disease are studied with particular reference to episodes of transient ischemia and their therapeutic implications. The possible contribution of spasm and other obstructive mechanisms such as platelet agregation, to the different forms of angina, myocardial infarction and sudden death, is analysed in the light of clinical observations, some of which have not previously been reported. Based on these concepts and clinical considerations, new orientations for future research and treatment are suggested. In our series, long term treatment of coronary artery disease with the association of nitrate derivatives are suggested. In our series, long term treatment of coronary artery disease with the association of nitrate derivatives and calcium antagonists has led to a reduction in mortality and in the incidence of myocardial infarction over periods ranging from 2 to 4 years.

Angina Pectoris↗
PubMed1982

[Myocardial imaging with 99mTC albumin microspheres for the simultaneous assessment of contraction and perfusion in man].

Radiolabeled human albumin microspheres (HAM) have been used in the past, in order to visualize coronary flow distribution in man. In order to obtain information both on myocardial perfusion and contractility, we applied R-wave synchronized reconstruction of the cardiac cycle in cine mode to HAM imaging. In 20 patients with angina pectoris and coronary stenosis of variable severity and in 1 patient with congestive cardiomyopathy we injected 4 millions of HAM (mean diameter 15 microns) labeled with 15-20 mCi of 99mTc, into the left ventricle during routine cardiac catheterization. Data were collected by a gamma camera, and by the use of a high resolution collimator and were electronically restricted to the cardiac area (64 X 64 matrix). The reconstruction of the cardiac cycle was made according to the technique developed in our laboratory for gated blood pool imaging. From the displayed images we evaluated myocardial flow distribution at the time of injection and regional wall motion (by cine mode) at any subsequent time, with a temporal resolution of 2 to 4 mins. The patterns of contractility of myocardial walls with normal or reduced perfusion were in agreement with those observed by means of contrast ventriculography. Advantages of the technique are: a) simultaneous information on flow and contractility; b) prolonged time for wall motion observation (4 to 6 hours); c) high quality pictures, since the signal to background ratio is much more favourable than with other isotope techniques. The technique appears to be promising from the results obtained in the number of patients included in this study.

Adult↗
PubMed1981

Prostacyclin does not affect insulin secretion in humans.

The effects of Prostacyclin (PGI2) infusion on insulin secretion and glucose tolerance were investigated in 7 healthy subjects. PGI2 infusion caused no statistically significant changes of either glucose or insulin concentration, over the range 2.5-20 ng/Kg/min. A constant PGI2 infusion (10 ng/Kg/min) did not inhibit acute insulin responses to a glucose (20 g i.v.) pulse (response before PGI2 = 612 +/- 307%; during PGI2 = 515 +/- 468%, mean +/- SD, mean change 3-5 min insulin, % basal; P=NS). Glucose disappearance rates were similar after the first and second glucose pulse. Thus, in contrast to PGE2, PGI2 does not affect insulin secretion nor glucose disposal at doses producing platelet and vascular changes. It is hypothesized that an altered PGI2/PGE2 balance in diabetes may represent a link between vascular, platelet and metabolic changes.

6-Ketoprostaglandin F1 alpha↗
PubMed1981

A simplified method of quantitating organ uptake using a gamma camera.

A simplified method of absolute quantitation of activity in any region of the body is presented utilizing a series of views acquired with a scintillation camera linked to a computer. An accuracy of +/- 6% may be achieved. No additional programming needs to be added to the standard nuclear medicine computer software and a knowledge of the attenuation coefficients involved and the shape or position of the organs examined is not presupposed or estimated. Attention correction is performed using a transmission image as one of the sequence of camera. The phantom measurements used to evaluate the technique are described and some clinical results presented.

Gamma Rays↗
PubMed1981

[Hourly distribution of episodes of angina at rest. Effect of medical treatment].

Aim of the study was to evaluate whether frequency of myocardial ischemic attacks at rest (IA) had any identifiable distribution during 24-hour periods. Two ECG leads were continuously recorded by an Oxford 4-24 tape recorder for a total of 148 days in 10 patients admitted to CCU because of frequent spontaneous anginal attacks. During 48 days, in absence of therapy, 682 IA were recorded (2.03 per patient per day). They showed a symmetrical bell-shaped distribution curve in the 24 hour periods with a peak occurring at 5 a.m. and 43% of IA from 0 to 6 a.m. Only 25% of IA was symptomatic with the lowest values (10%) between 2 and 6 a.m. Distribution of IA was independent from their distinctive electrocardiographic feature [ST (71%) or T changes]. During 100 days with therapy [Verapamil and/or Isosorbide dinitrate ointment) a marked reduction of episodes was observed (0.64 per patient per day), while their distribution, the incidence of different electrocardiographic patterns and percentage of symptomatic IA remained unchanged. Attenuated incidence, but inalterated distribution of IA with therapy suggest its possible effect on the threshold response of coronary smooth muscle to vasoconstrictor stimuli rather than its primary effect on pathogenetic factors.

Adult↗
PubMed1981

[Diagnosis of transient acute myocardial ischemia in man by M-mode echocardiography (author's transl)].

Under basal conditions the echocardiographic findings in anginal patients (pts.) without previous myocardial infarction appears usually normal. Consequently, the usefulness of the ultrasounds evaluation in angina pectoris has been commonly considered poor and the utilization of this technique in coronary artery disease has been restricted to the detection of myocardial infarction in its acute phase or to its chronic mechanical alterations. The purpose of this study was to assess the possibility offered by M-mode echocardiography to detect changes caused by transient myocardial ischemia at rest in man, in view of the possible diagnostic application of this technique. The reported results were obtained from 25 ischemic attacks (13 spontaneous and 12 ergonovine induced) with ST segment elevation or pseudonormalization of a basally negative T wave at rest. The semiautomatic computerized analysis of echocardiograms continuously recorded during these attacks showed a reduction of motion and of systolic thickening, accompanied by a diastolic thinning of the wall involved by the ischemia. These changes occur very early: they appear few seconds before ECG changes and are accompanied by a reduction of contraction and relaxation dP/dt and precede the onset of chest pain; moreover, they are followed by an increase in left ventricular internal diameters. In conclusion M-mode echocardiography is a sensitive technique capable to detect transient myocardial ischemia in the course of spontaneous or induced angina with ST segment elevation or positivity of negative T wave. This approach could be helpful in the diagnostic evaluation of patients with atypical chest pain and/or aspecific ECG changes and it can be complementary to other non invasive techniques such dynamic ECG and nuclear cardiology techniques.

Acute Disease↗
PubMed1980

Some clinical considerations regarding the relation of coronary vasospasm to coronary atherosclerosis: a hypothetical pathogenesis.

This study explores the relation between coronary arterial spasm and the development of coronary atherosclerosis. The clinical history and coronary angiographic and electrocardiographic data in 212 consecutive patients with ischemic heart disease were correlated. These patients were classified into four groups: Group 1, patients without angiographic evidence of atherosclerosis; Group 2, patients with single vessel disease; Group 3, patients with double vessel disease; and Group 4, patients with significant narrowing of major coronary arteries. Although spontaneous angina occurred in all four groups, it was more common (55 percent) in the patients in Group 1, who were predominantly female and young. Spontaneous angina was confirmed in Group 1 with several techniques, including thallium-201 scintigraphy, ergonovine administration and electrocardiography during attacks of pain. Prior myocardial infarction was present with similar frequency in all four groups. A patient is discussed whose spontaneously occurring coronary arterial spasm later progressed to fixed arteriosclerotic narrowing requiring coronary bypass surgery. These observations and a review of the literature lend support to the hypothesis that coronary arterial spasm can be a possible antecedent leading to the later development of fixed atherosclerotic coronary arterial obstruction.

Adult↗