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Biomedical subjects

G Greco

Publications and source records attributed to G Greco.

At least 145 records · Page 8Linked to original sources
PubMed1990

New experimental technique for detecting the effect of low-frequency electric fields on enzyme structure.

A new experimental approach has been developed to determine kinetic and thermodynamic parameters of the inactivation of an enzyme under labile conditions both with and without exposure to electrical currents as sources of perturbation. Studies were undertaken to investigate if low-frequency electric currents can accelerate the thermal inactivation of an enzyme through interactions with dipole moments in enzymatic molecules and through related mechanical stresses. The experiments were conducted with the enzyme acid phosphatase. The enzyme was exposed to a 50-Hz current at different densities (10 to 60 mA/cm2 rms) or to a sinusoidal or square-wave current at an average density of 3 mA/cm2 and frequencies from, respectively, 50 Hz to 20 kHz and 500 pulses per second (pps) to 50,000 pps. Positive-control experiments were performed in the presence of a stabilizer or a deactivator. The results indicate that the technique is sensitive to conformational changes that otherwise may be impossible to detect. However, exposure to electric currents under the experimental conditions described herein showed no effects of the currents.

Acid Phosphatase↗
PubMed1990

Comparison of ketanserin and enalapril in the treatment of mild-to-moderate essential hypertension.

In a double-blind 3-month study in mild-to-moderate essential hypertensive patients over 50 years of age, ketanserin, a selective S2-serotoninergic antagonist with additional alpha 1-adrenergic blocking properties, has been compared with enalapril, an angiotensin-converting enzyme inhibitor. Supine and upright blood pressures and heart rates were recorded for placebo and during active treatment (-4, -2, 0, 2, 4, 6, 8, 10, and 12 weeks). Metabolic profile (plasma glucose, creatinine, sodium, potassium, total and HDL-cholesterol, triglycerides, uric acid) was monitored during treatment with placebo and at the end of the study. Mean blood pressure was equally and significantly (p less than 0.001) lowered by both drugs from 2 weeks of treatment, whereas no changes occurred in mean heart rate or in biochemical variables. Dizziness was observed in three patients on ketanserin and in one patient on enalapril, whereas headache occurred in only one patient on enalapril. These data indicate that ketanserin is as effective and well tolerated as enalapril in hypertensive patients over 50 years of age.

Aged↗
PubMed1990

Baseline and post-atrial pacing release of atrial natriuretic factor in mitral stenosis.

To investigate the release of atrial natriuretic factor (ANF) in mitral stenosis and the influence of the increase on the frequency of atrial contraction or atrial distention on ANF secretion, we studied 10 patients with symptoms of congestive heart failure (New York Heart Association classes II and III) in sinus rhythm, who were undergoing cardiac catheterization as part of an evaluation workup for mitral stenosis. Echocardiographic tracings, repeat determinations of mean pulmonary artery wedge pressure (MPAWP) and mean right atrial pressure, and blood sampling from the pulmonary artery for measurements of ANF were performed at baseline, during atrial pacing (pacing rate of 125 beats/min for 5 minutes), and 5 minutes after the pacing protocol was completed. Baseline ANF levels were closely related to right atrial pressure (r = 0.89; p less than 0.001) and increased markedly after atrial pacing from 205.6 +/- 39.8 (SEM) to 343.9 +/- 57.9 (SEM) pg/ml. A similar pacing-induced increase was shown for MPAWP and left atrial size. Our data indicate that pacing-induced increases in atrial distention and intracavitary pressure further stimulate release of ANF. However, an independent effect of frequency of atrial pacing on plasma ANF in humans could not be identified.

Adult↗
PubMed1990

Echocardiographic detection of aortic valve ring abscesses.

Valve ring abscess complication of infective endocarditis increases the expected morbidity and mortality rates of patients, but is seldom recognized by available noninvasive techniques. In our study, two-dimensional echocardiography successfully detected valve ring abscesses in eight patients with infective endocarditis affecting aortic valve prosthesis. Echocardiography showed the perivalvular abscess as an echo-free space in all patients. Prosthetic vegetations were seen in the only patient who had a biological prosthesis and excessive prosthetic rocking was observed in cases with severe aortic regurgitation. In two patients, the first echocardiographic examination showed an echo-free space without evident clinical signs of endocarditis or significant valve regurgitation. Severe aortic insufficiency and congestive heart failure followed the enlargement of the echo-free space. Valve replacement was required in all but one patient. The echocardiographic findings were confirmed at surgery. In one patient, the extension of the abscess to the interventricular septum was not detected by the echocardiography.

Abscess↗
PubMed1990

[Multiple coronary-pulmonary fistulas: description of a case].

An uncommon case of multiple coronary artery-pulmonary artery fistulas, associated with a mitral valve disease, is reported. The coronary fistulas presence was suspected on the ground of Doppler-echocardiography and the diagnosis was subsequently defined by coronary angiography. The utility of Doppler-echocardiography in the differential diagnosis from patent ductus arteriosus is discussed.

Angiography↗
PubMed1989

Risk factors of female cancers in Ragusa population (Sicily). 2. Breast cancer.

A case-control study on breast, cervix and corpus uteri cancer cases registered in Ragusa between January 1, 1983 and June 30, 1985 has been conducted. Information on risk factors has been obtained by means of a structured questionnaire. Risk factors for breast cancer were: few pregnancies (1-2 vs greater than 4 OR 2.14, 95% CL 1.13-4.04), few children (for postmenopausal only, chi trend 4.84), previous breast disease (OR 1.97, 95% CL 1.20-3.23), family history (OR 3.57, 95% CL 1.92-6.63), alcohol (OR 1.68, 95% CL 1.12-2.53), high socioeconomical status (1 vs 4 OR 2.93, 95% CL 1.22-70.03). A protective role was evident for: early age at first birth (for premenopausal only, less than 20 vs greater than 20 OR 0.11, 95% CL 0.01-0.90), previous ovary disease (OR 0.26, 95% CL 0.08-0.88). Age at menarche, age at menopause, years of fertile life and breast feeding were not found to be related to breast cancer. A different distribution of risk factors among cases with and without family history has been suggested. A synoptic table shows the distribution of the most important risk factors of the three investigated female cancers in the Ragusa population, reported in the present and in an accompanying paper.

Adult↗
PubMed1989

Evidence for a further stimulation of atrial natriuretic factor release by atrial pacing in patients with mitral stenosis.

To investigate the release of atrial natriuretic factor (ANF) in mitral stenosis and the effect of an increased atrial contraction frequency on atrial distension and ANF secretion, we studied 14 patients [New York Heart Association (NYHA) grades II-III] in sinus rhythm, undergoing cardiac catheterization for mitral stenosis. Echocardiographic tracings, repeat determinations of mean pulmonary artery wedge pressure and blood samples from the pulmonary artery for ANF measurements were taken at baseline, during atrial pacing (125 beats/min for 5 min) and 5 min after pacing. After pacing, ANF levels rose markedly with a parallel increase in mean pulmonary artery wedge pressure and left atrial size. These data indicate that atrial pacing is capable of further stimulating ANF release, even in patients with elevated baseline ANF and left atrial pressure and an increased left atrial dimension.

Adult↗
PubMed1982

Further characterization of two mitochondrial populations in tuna heart ventricle.

1. Mitochondria were isolated from the spongy and compact ventricular myocardium of adult Thunnus thynnus thynnus L. 2. Measurement of the succinoxidase activity of phosphorylating mitochondria revealed that those from the spongy had an apparent Km being half of that of the mitochondria from the compact layer. These latter exhibited Km more sensitive to acidic pH values. 3. Succinate-cytochrome c reductase activity was very differently affected by pH and temperature in non-phosporylating mitochondria from the two cardiac layers. 4. The thermostability of the NADH-cytochrome c reductase and the succinate-cytochrome c reductase activities exhibited also marked differences in the two mitochondrial populations. 5. These results, which represent an example of metabolic zonation at the organelle level, are discussed in relation to the homeostatic cooperation of the two myocardial regions of tuna heart.

Animals↗
PubMed1981

[The ventricular myocardium of fish: aspects of comparative morphology, physiology and pharmacology. I) Myocardial architecture and vascularization].

Fish represent a unique natural model for studying the structural arrangement of the ventricular myocardium and its blood supply during phylogeny. The more primitive spongious myocardium, fed by lacunary venous blood, is stepwise transformed into the mixed type of ventricular muscle, in which a compact cortical layer is often fed by oxygenated capillary network. The mixed type of heart muscle--which represents the homologous of the compact myocardium of the homeotherm vertebrates--is found in the most active fishes. The occurrence of this type of myocardium is discussed both in relation to the relative growth of the heart during phylogeny and to the physiological performance of the ventricular wall.

Anatomy, Comparative↗