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Biomedical subjects

G Signorini

Publications and source records attributed to G Signorini.

At least 19 recordsLinked to original sources
PubMed1991

Electroretinographic changes in aged pigeons.

Photopic electroretinograms, either to full-field light flashes (FERGs) or to contrast-reversal of square-wave gratings (PERGs) have been recorded in pigeons aged 2 years old (n = 5) and 10 years old (n = 5). Mydriatic pupil diameter, ophthalmoscopic appearance of the retinal fundus and optic media, and refractive state were comparable in the two groups. V/log I functions of individual FERG components (a-wave, b-wave and oscillatory potentials) displayed significantly lower slopes in the old birds than in the young, which suggests a reduction in retinal gain. PERG amplitude also was significantly lower in the older birds over a wide range of spatial frequencies (0.2-8.8 c/deg). Estimated visual acuity based on the extrapolated high-frequency cut off was 18 c/deg in the younger birds and 7.8 c/deg in the older birds. These results are in agreement with psychophysical data and retinal age-related losses in visual acuity, photoreceptors and retinal ganglion cells. Since these findings are comparable to those reported for humans, the results suggest that pigeons may serve as a useful model for human visual aging.

Aging↗
PubMed1990

[Effects of low-dose diltiazem on isovolumetric relaxation and contraction].

Calcium entry blockers are commonly believed to have a direct negative inotropic effect, but systolic function of the left ventricle (LV) can be improved when the peripheral vasodilator activity of the drug is present. The aim of our study was to evaluate the effect of diltiazem (D) on isovolumic contraction (IC) and relaxation (IR) at a dosage which is not effective on the peripheral vascular bed. We infused 10 micrograms/Kg/min i.v. of D for a 30 min period in to 12 pigs, anesthetized with ethyl urethane (1250 mg/Kg) and under artificial ventilation. The following variables were evaluated: left ventricular systolic (LVSP) and end-diastolic (LVEDP) pressure, peak - and + dP/dt, mean arterial pressure (MAP), heart rate (HR) and double product. The recordings were obtained in the control condition and 5, 10, 15, 20, 25 and 30 minutes after beginning the infusion. The statistical analysis was performed using the one-way ANOVA test. Our results show: 1) a maximal increase in the peak + dP/dt from 2228 +/- 501 to 2448 +/- 576 mmHg/sec (p less than or equal to 0.01) and of the peak . dP/dt from 1262 +/- 260 to 1348 +/- 272 mmHg/sec (p less than or equal to 0.05); 2) and increase in LVSP from 86 +/- 13 to 90 +/- 10 mmHg (p less than or equal to 0.01) and 3) no changes in HR, PAM, LVEDP and double product. As the indices representing afterload and preload (PAM and LVEDP) remained unchanged during the infusion, we suggest that the increase in dP/dt + and - are due to a direct effect of diltiazem on myocardial function.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1989

Serotonin depletion modifies the pigeon electroretinogram.

Significant amounts of endogenous serotonin have been detected in the retina of many nonmammalian vertebrates. In the pigeon retina, serotonin-like immunoreactivity has been localized within a subpopulation of bipolar and amacrine cells, and serotonin-containing terminals have been found to be segregated in different laminae of the inner plexiform layer. In the current experiments 5,7-dihydroxytryptamine was injected intravitreally in the pigeon eye in order to examine the effect of serotonin depletion on the functional activity of the retina. The physiological modifications induced by the serotonin depletion were examined by recording electroretinographic responses to light flashes of different intensity under conditions of light and dark adaptation. Our results show that 5,7-dihydroxytryptamine treatment selectively increases b-wave amplitude and modifies the function relating b-wave amplitude to Log flash intensity without affecting the peak latency and the amplitude of oscillatory potentials. These results can be interpreted in terms of a possible inhibitory role of serotonin on b-wave generators.

5,7-Dihydroxytryptamine↗
PubMed1988

[First seconds after acute experimental ischemic: changes in isovolumic contraction and relaxation].

The purpose of this study was to answer the following questions: 1) are isovolumic contraction and relaxation affected in a different way by LAD occlusion? 2) Does proximal and distal LAD coronary occlusion induce different changes in isovolumic contraction and relaxation? In 22 pigs, LAD coronary artery was dissected free right after the first or third diagonal branch and occluded by ligation. The following variables were evaluated: left ventricular systolic and end-diastolic pressure; peak - and + dP/dt, mean arterial and pulmonary pressure. All our data were obtained in the first minute following the occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1988

[Digital radiology in the study of the lacrimal ducts].

The authors emphasize the usefulness of digital dacryocystography (DCG), as compared with various current techniques. Utilizing a radiographic unit equipped with a video-fluoroscopic system and interfaced to a digital video-processor, several digitalized images are acquired before, during and after the injection of contrast medium. Final images are obtained by subtraction of suitable pairs of source frames. Twenty-six patients affected by epiphora have been examined so far. In 21 cases digital subtraction DCG allowed an accurate visualization of the lacrimal system; in the other five patients the amount of information was acceptable. This methodology allows the assessment of both the normal anatomy of the lacrimal passages and their pathological patterns, such as obstructions, stenoses, fistulas, chronic dacryocystitis, lacrimal stones. The examination is easy and quick to perform, with no discomfort for the patient. Digital subtraction DCG proves thus to be a very valuable technique thanks to its possible electronic elaboration--i.e. the subtraction and the magnification of images--to its better contrast resolution, and to the possibility it yields of dynamic studies under radioscopic control.

Humans↗
PubMed1988

[Incidence of aortic recoarctation in 161 patients after a mean follow-up of 8 years. The usefulness of pressure gradient measurement at rest and following exercise and of digital angiography].

The incidence of aortic recoarctation has been evaluated after a mean follow-up period of 8.2 years in 161 patients aged from 2 to 54 years at the time of the operation. To this aim, blood pressure levels in the upper and lower limbs were measured at rest and after bicycle ergometer exercise. Patients whose systolic pressure gradient was significant (either above 20 mmHg at rest or 35 mmHg after exercise) underwent aortic digital angiography. Aortic coarctation was diagnosed when the ratio of the aortic area at the site of the operation was less than 40% of that at diaphragmatic level (Frederiksen's index III). Thus the overall incidence of recoarctation was 10.1%. All patients with a significant gradient at rest also showed a significant gradient after exercise. This suggests that it is worthwhile performing digital angiography directly, without exercise testing, in these patients. However, 39.8% of the patients without significant rest gradients displayed a significant gradient after exercise. On the whole, only 21.4% of the patients with a significant gradient after exercise had signs of recoarctation on digital angiography.

Adolescent↗
PubMed1986

Cystic meningiomas--an update.

Eighteen unusual cases of intracranial meningioma associated with a cyst are considered. Three patients were operated upon before the introduction of computed tomography scanning, and the discovery of a peritumoral cyst was unexpected. Among 15 patients studied with computed tomography, 8 had a peritumoral cyst, 6 had an intratumoral cyst, and 1 had a totally cystic meningioma (hypodense on computed tomography). Computed tomography permitted a correct preoperative diagnosis only in four cases. In six additional cases diagnosis was reached by selective angiographic studies. In the remaining cases diagnosis was impossible or incorrect. Different pathogenetic mechanisms underlie different radiologic patterns. The authors comment on the complex processes that lead to cyst formation in meningiomas and stress the necessity of an accurate preoperative study to avoid misdiagnosis.

Adult↗
PubMed1983

Prostacyclin effect on heart rate in the pig.

The purpose of this study was to assess the hemodynamic response after prostacyclin infusion into the venous system and into the carotid artery in the pig. During the study the following circulatory variables were studied: mean systemic arterial pressure, mean pulmonary arterial pressure, wedge pressure, heart rate, cardiac output, systolic and diastolic left ventricular pressure, stroke volume, total systemic resistance, total pulmonary resistance, left ventricular stroke work. Our results confirm that prostacyclin is a powerful hypotensive agent. The hypotensive effect seems to be due to a peripheral vasodilatation of arterial and venous vessels. Venous infusion caused only 19% tachycardia, as opposed to 36% caused by arterial infusion for the same percentage of blood pressure reduction. This suggests that prostacyclin probably stimulates cardiopulmonary vagal receptors. The effect of prostacyclin on heart rate, therefore, may be twofold and in opposite directions: one action causing tachycardia secondary to hypotension, and the other inviting bradycardia through direct vagal stimulation.

Animals↗
PubMed1982

[Pharmacological effects of the combination of a spasmolytic (otilonium) with a benzodiazepine (diazepam)].

The pharmacological effects of an association represented by a myolitic agent (otilonium bromide) and a benzodiazepine (diazepam) were investigated on different in vitro preparations and on one in vivo test. In the isolated preparations both drugs administered alone showed a remarkable inhibitory effect on the motility of different areas of the digestive system both spontaneous and evoked by different stimulatory agents. Association of the two compounds gave rise to additive effects or actually to a potentiating effect according to the different tissues and animal species. Negative interference was never observed. The same was true also in the in vivo preparation ("in situ" rat pylorus). The significance and the importance of these observations are discussed also in the light of the relevant clinical implications.

Acetylcholine↗
PubMed1979

Surgical treatment of thoracic disc protrusion.

The Authors report on nine cases of thoracic disc hernia operated on through Carson's posterolateral approach. Several steps were taken to protect the spinal cord, and to remove completely disc fragments and any calcifications. The importance of the combined use of the operating microscope and the posterolateral approach are emphasized, and the longterm results are evaluated.

Adolescent↗