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Biomedical subjects

G Sangiovanni

Publications and source records attributed to G Sangiovanni.

At least 19 recordsLinked to original sources
PubMed2006

Electron-phonon interaction and antiferromagnetic correlations.

We study effects of the Coulomb repulsion on the electron-phonon interaction (EPI) in the Holstein-Hubbard model, using the antiferromagnetic (AF) dynamical mean-field approximation. AF correlations strongly enhance EPI effects on the electron Green's function with respect to the paramagnetic correlated system, but the net effect of the Coulomb interaction is a moderate suppression of the EPI. Doping leads to additional suppression. In contrast, the Coulomb interaction strongly suppresses EPI effects on phonons, but the suppression weakens with doping.

Journal Article↗
PubMed2005

Electron-phonon interaction close to a Mott transition.

The effect of Holstein electron-phonon interaction on a Hubbard model close to a Mott-Hubbard transition at half filling is investigated by means of dynamical mean-field theory. We observe a reduction of the effective mass that we interpret in terms of a reduced effective repulsion. When the repulsion is rescaled to take into account this effect, the quasiparticle low-energy features are unaffected by the electron-phonon interaction. Phonon features are only observed within the high-energy Hubbard bands. The lack of electron-phonon fingerprints in the quasiparticle physics can be explained interpreting the quasiparticle motion in terms of rare fast processes.

Journal Article↗
PubMed2004

Phase separation close to the density-driven Mott transition in the Hubbard-Holstein model.

The density-driven Mott transition is studied by means of dynamical mean-field theory in the Hubbard-Holstein model, where the Hubbard term leading to the Mott transition is supplemented by an electron-phonon (e-ph) term. We show that an intermediate e-ph coupling leads to a first-order transition at T=0, which is accompanied by a phase separation between a metal and an insulator. The compressibility in the metallic phase is substantially enhanced. At quite larger values of the coupling, a polaronic phase emerges coexisting with a nonpolaronic metal.

Journal Article↗
PubMed1995

Effect of a ubiquinone-like molecule on oxidative energy metabolism in rat cortical synaptosomes at different ages.

Persistent stimulation of energy consumption, induced by depolarization with veratridine, mimics a condition of abnormally enhanced energy demand and causes an increase in the oxygen consumption rate (QO2) and in the interconversion of pyruvate dehydrogenase complex (PDHc) into its active form. Wistar rats at the age of 26 months do not show alterations of QO2 and the ability of veratridine to increase QO2 in comparison with 6 month-old animals whereas the active form of PDHc is slightly but significantly reduced. Idebenone, a ubiquinone-like molecule (1 microM), does not affect the QO2 or PDHc activation state in resting conditions but attenuates the veratridine-challenged increase in QO2 at all the ages tested and attenuates the increase in the percentage of PDHa reaching statistical significance in 26-month-old rats. At higher concentration (10 microM) idebenone totally abolishes the veratridine-induced increase in PDHa also in the 6 month-old rats. At the lower concentration, the drug does not affect the increase in QO2 induced by an uncoupler of oxidative phosphorylation. The results obtained suggest a protective effect of idebenone on the cerebral tissue against stressful conditions; this action may be exerted at the level of some mitochondrial component and/or on the Na+ homeostasis.

Adenosine Triphosphate↗
PubMed1988

Lumbar canal stenosis: results in 40 patients surgically treated.

Authors present the clinical and neuroradiological characteristics of 40 patients treated for lumbar canal stenosis during a 10 years experience. The usefulness of computed tomography in comparison with myelography and plain X-rays of the spine is stressed. The surgical treatment was wide laminectomy involving one or more levels (two to four) plus an eventual foraminotomy but without discectomy. All patients were followed up and in 85% of cases a reduction of clinical symptoms was observed. Residual symptoms were also present in some of the improved patients, they generally accepted them without great dismay.

Adult↗
PubMed1986

[Spontaneous cerebral hematomas. Treatment and follow-up studies].

How to manage spontaneous intracerebral hemorrhage has been in the past years a subject open to discussion. The therapeutic approach, medical or surgical, has constituted a question of debate for the neurosurgeon. The most recent experience, however, attempts to establish the clinical and neuroradiological criteria for medical treatment and clarify the indications, as well as the limitations of surgical treatment. The Authors present 84 cases of spontaneous intracerebral hemorrhage studied by both CT scan and cerebral angiography (October 1980-April 1985). The acute mortality of intracerebral hemorrhage was 17.8%. Determinant for the immediate prognosis was the level of consciousness and the volume of the hematoma. At follow-up, at a median of 3 years after intracerebral hemorrhage, total mortality was 30.9% and 48% had returned work.

Adult↗
PubMed1986

Selected ion monitoring technique for the evaluation of sterols in cerebrospinal fluid: a new approach to desmosterol test for central nervous system tumors.

The desmosterol test for the diagnosis of central nervous system (CNS) tumors is proposed in a simplified form. The procedure is based upon the analysis of sterol profile in cerebrospinal fluid (CSF) by selected ion monitoring (SIM) technique. Applied to 55 patients with tumoral and non tumoral CNS disease, the new test detects average levels of CSF desmosterol in tumor bearing patients that are tenfold higher than in the absence of CNS neoplasia. On an individual basis, a concentration of CSF desmosterol equal to or higher than the mean plus twice the standard deviation for the reference group of patients with no CNS tumor, is considered a positive result. Based on this criterion, a correct diagnosis was made in 73% of cases vs 77% of the former test, which required a 5-day treatment period with a desmosterol-reductase inhibitor in order to increase CSF desmosterol concentration. With this revised procedure CSF desmosterol can be detected in smaller volumes of CSF without any drug pretreatment, thus making the test more suitable for clinical application.

Brain Neoplasms↗
PubMed1986

Three-year neuropsychological follow-up of patients with reversible ischemic attacks.

A short neuropsychological test battery designed to measure language, memory and visuospatial abilities was administered to 217 patients with reversible ischemic attacks. Patients were tested twice: the first time more than one month, but less than one year, from the last ischemic episode, and the second time three years later. A comparison between the first and the second testing session did not disclose any significant worsening. The degree of atherosclerosis and the occurrence of further ischemic episodes during the follow-up period were found to be unrelated to change in performance at the test battery. These results seems to challenge the hypothesis that multi-infarct dementia may follow apparently reversible, or even clinically silent, ischemic episodes.

Follow-Up Studies↗
PubMed1986

Normal-pressure hydrocephalus: twelve years experience.

The authors report on twelve years experience with so-called normal pressure hydrocephalus. If care is taken to make a correct diagnosis and give adequate treatment with a shunt, hydrocephalic dementia has a good prognosis. Such cases should be distinguished from other syndromes, particularly senile dementia and Alzheimer's disease. The occurrence of a syndrome of dementia should compel every neurologist and neurosurgeon to carry out careful investigations in order to determine the favourable time for possible treatment.

Adult↗
PubMed1983

Cyclic nucleotides in experimental and human brain tumors.

It is well known that the system of cyclic nucleotides plays an important role in cell differentiation and proliferation. Cyclic AMP is capable of stimulating cell growth, and cyclic GMP is thought to control cell division and growth. The authors measured adenylcyclase activity (AC) and cGMP content in the tumor latency period and in early neoplastic proliferations in rats with brain tumors induced by transplacental ethylnitrosourea (ENU). AC activity, which is high during the first days of life, decreases until it reaches, at the 60th day, levels lower than those in control animals. Cyclic GMP, on the contrary, increases during the first month in treated animals and remains consistently higher than controls up to the 45th day. In fully developed experimental brain tumors (mixed gliomas, isomorphic and polymorphic oligodendrogliomas) the percentage of reduction in AC activity is significantly higher. AC activity was measured also in human tumoral tissue. In malignant tumors it is markedly lower than in benign tumors. In the same patients cAMP in the cerebrospinal fluid was measured with results similar to those obtained in tissues. These findings confirm that the system of cyclic nucleotides is implicated in all the developmental phases of brain tumors and therefore may reveal how research can clarify the first transformations of tumoral cells.

Adenylyl Cyclases↗
PubMedDate not supplied

Assessment of inter-observer differences in the Italian multicenter study on reversible cerebral ischemia.

A standardized protocol was used for duplicate examination by two neurologists of the clinical history and neurological signs in 55 patients with reversible cerebral ischemia. One trained examiner from each of eight clinical centres involved in the Italian Cooperative Study on reversible cerebral ischemia participated in this research. Duplicate examination were compared in order to evaluate the percentage of agreement achieved in the responses. Several discrepancies relating to either historical data or neurological signs were detected. Possible causes of this disagreement are discussed. The inter-observer differences appear to be an important problem to be faced in cooperative studies on reversible ischemic attacks. The purpose of the study was to estimate these differences in the attempt to increase the degree of agreement by repeated training sessions and discussion between the different examiners. These efforts are needed to improve the quality of clinical investigations on reversible cerebral ischemia and to increase the validity of their results.

Evaluation Studies as Topic↗
PubMedDate not supplied

[Changes in CSF dynamics and performance tests after head injuries (author's transl)].

In a large series of head-injured patients (132 cases), we have selected 30 patients (mean age 43 years) with only primary school education: they have been investigated with isotope cisternography and psycodiagnostic tests. 19 underwent neurosurgical procedures (6 extradural haematomas, 8 subdural haematomas, 5 cerebral lacerations). These investigations have been carried at least six months after the head injury. We have used for isotopic cisternography RISA and In111-DTPA. Raven's Progressive Coloured Matrices and Immediate Memory Tests were performed. Cisternographic pictures were classified as 1) normal, 2) with asymmetrical diffusion, 3) with ventricular reflux and were correlated with the neuropsychological data. We have found ventricular reflux in 10 patients (5 underwent surgical procedures), asimmetrical diffusion in 15 patients (11 operated); in 5 cases cisternographic pictures were normal. Neuropsychological tests give quantitative data about progressive mental deterioration, in full agreement with cisternographic results.

Adult↗
PubMedDate not supplied

Spontaneous intracerebral hemorrhage: medical or surgical treatment.

Eighty-six cases of spontaneous intracerebral haemorrhage, some treated by surgery, some by medical therapy, were studied retrospectively. The two groups, characterized on the basis of numerous parameters were compared: the findings are discussed and interpreted in the hopes of indicating a correct therapeutic strategy.

Cerebral Hemorrhage↗
PubMedDate not supplied

Association of a malignant glioma and an aneurysm of the middle cerebral artery. Report of a case.

A case of association of a malignant glioma of the left frontal lobe and an aneurysm of the middle cerebral artery is reported and the available literature reviewed. The operative mortality of patients with the association of a brain tumor and a cerebral aneurysm is very high (40%). This is the third case reported in the literature in which it was possible to remove the tumor and clip the aneurysm with immediate good surgical results and it is the first case in which the technique of late surgery for malignant glioma was adopted.

Brain Neoplasms↗