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Biomedical subjects

G Parisi

Publications and source records attributed to G Parisi.

At least 19 recordsLinked to original sources
PubMed2006

Clinical relevance of colonic lesions in cirrhotic patients with portal hypertension.

BACKGROUND AND STUDY AIMS: This prospective study was conducted in order to evaluate whether the colonic lesions previously described in cirrhotic patients may be of clinical relevance. PATIENTS AND METHODS: Eighty-five patients with cirrhosis of the liver, but without colonic or systemic diseases unrelated to the liver disease, underwent colonoscopy and were followed up for at least 2 years. RESULTS: Colonic varices were observed in 31 % of the patients, portal hypertensive colopathy (PHC; defined as diffuse hyperemia, edema, spider angiomas, and spontaneous bleeding of the colonic mucosa) in 54 %, and normal colonic findings in 18 %. Colonic varices and PHC were present simultaneously in 27 % of the patients. Previous sclerotherapy or band ligation treatment for esophageal varices had been carried out in 27 % and 23 % of the patients, respectively. Portal hypertensive gastropathy was observed in 42 % of the patients. Polyps were found in 12 % of the cirrhotic patients and cancer in 3 %. All of the patients were followed up for at least 2 years; 34 % of them developed upper gastrointestinal hemorrhage (81 % from esophageal varices, 19 % from the stomach), while only 6 % developed lower gastrointestinal bleeding. CONCLUSIONS: Colonic lesions are frequent in cirrhotic patients, but statistical analysis showed that these lesions are not specific for the disease and do not correlate with the etiology and degree of cirrhosis, with the endoscopic treatment of esophageal varices, or with the risk of bleeding from the lower gastrointestinal tract.

Aged↗
PubMed2005

Hypoplastic left heart syndrome associated with left ventricle-coronary artery-pulmonary artery fistula: prenatal diagnosis and histological correlation.

We describe an unusual case of left ventricle-left coronary artery-pulmonary artery fistula associated with hypoplastic left heart syndrome (HLHS) and a ventricular septal defect, in which findings on echocardiography and histological analysis were correlated. The diagnosis was made at 22 weeks of gestation. We speculated that the presence of the fistula was the primary cause of the HLHS due to the existence of the ventricular septal defect that nullified the intraventricular pressure gradient, which is typical of hypoplastic ventricles and thought to be responsible for the secondary development of fistulas in other cases.

Abortion, Therapeutic↗
PubMed2005

[Intraoperative examination in neuropathology: proceedings evaluations].

INTRODUCTION: In the neuropathological intraoperative diagnostic is extremely important having guide lines to obtain a lot of information about the slide. In our study we have considered only the intraoperative the cases diagnosed within a month comparing the histological evaluation using the cryostat and the cytological examination of touch or smear preparation. MATERIALS AND METHODS: Our study includes 7 meningiomas, 2 metastatic carcinomas, 1 anaplastic astrocitoma, 1 mieloplaxis tumor, 1 anaplastic chordoma. For the cytological examination we have got ready 8 touch or smear preparations and we have executed 4 proceedings: stainings with Giemsa, toluidine blue and haematoxylin and eosin, after fixation with 95% alcohol and staining with haematoxylin and eosin after fixation with alcohol and a small quantity of acetic acid. For the histological examination we have got ready 8 preparations, using the cryostat. We have fixed the slides with 95% alcohol or 10% formalin and stained them with haematoxylin and eosin. In the 50% of the cases we have treated the sections with microwave at 400W. RESULTS: Two pathologists have examinated the 192 sections prepared, judging each slide considering the legibility: unsatisfactory, quite good, good and excellent. CONCLUSIONS: Considering the cytological examination, Giemsa and toluidine blue permit the best legibility of nuclear and cytoplasmatic morphological details. Legibility is worse in staining with haematoxylin and eosin. Addition of acetic acid makes variable results. In the histological slides the best result are obtained using 95% alcohol for fixing. Microwave use doesn't determine improvement.

Humans↗
PubMed2005

[Unusual presentation of metastatic osteosarcoma as a giant duodenal polyp. A case report].

INTRODUCTION: Osteosarcoma is a malignant bone neoplasm with an usually high metastatic potential. Besides the common metastatic sites such as lungs, bone, and pleura, metastases to unusual sites such as liver, brain and regional lymph nodes have also been reported with increasing frequency; among them, gastrointestinal metastases represent an extraordinarily rare event in the natural history of this neoplasia. MATERIALS AND METHODS: We describe a case of a 27 year old man, who was diagnosed with a grade IV osteoblastic osteosarcoma of the left tibia and submitted to 5 courses of pre-surgical chemotherapy; later he underwent tibial resection with implantation of a prosthesis, followed by 2 further courses of adjuvant chemotherapy. Five years after the patient presented with melena and acute anemia; during endoscopic examination, a large bleeding duodenal polyp was found, so a surgical resection of the gastric antrum, duodenum, head of the pancreas, main bile ducts and gallbladder was performed. The surgical specimen was formalin fixed and paraffin embedded, and sections obtained by the blocks were stained with haematoxylin-eosin; immunohistochemical and ultrastructural analysis were performed. RESULTS: Microscopically, the tumor mass showed a mostly fasciculated architecture, composed of spindle and epithelioid cells in a scarce fibromyxoid stroma, featuring large areas of coagulative necrosis and small foci of sclerohyalinosis. Tumor cells featured large vesciculous nuclei, with a few prominent nucleoli; no foci of osteoid matrix were detectable. The ultrastructural analysis revealed small calcified electron-dense depots both in the perinuclear cytoplasm and in the extracellular collagen matrix compatible with an "early osteoid formation". Due to alteration of the natural history of the tumor induced by multiagent chemotherapy, the rate of metastases of osteosarcoma to unusual sites has been increasing. We report the 9th case of a gastrointestinal metastasis of osteosarcoma reported thus far, and only the second one arising in the duodenum. Both the histological features and the immunohistochemical findings were not suggestive for osteosarcoma metastases because the tumor appeared dedifferentiated; in our case the combination of electron microscopy and clinical history played a pivotal role to establish the final diagnosis.

Adult↗
PubMed2004

Glutamate-evoked redox state alterations are involved in tissue transglutaminase upregulation in primary astrocyte cultures.

The aim of this study was to evaluate the involvement of oxidative stress in glutamate-evoked transglutaminase (TGase) upregulation in astrocyte cultures (14 DIV). A 24 h exposure to glutamate caused a dose-dependent depletion of glutathione intracellular content and increased the ROS production in cell cultures. These effects were receptor-mediated, as demonstrated by inhibition with GYKI 52466. The pre-incubation with glutathione ethyl ester or cysteamine recovered oxidative status and was effective in significantly reducing glutamate-increased tissue TGase. These data suggest that tissue TGase upregulation may be part of a biochemical response to oxidative stress induced by a prolonged exposure of astrocyte cultures to glutamate.

Animals↗
PubMed2004

Fragility in p-spin models.

We investigate the relation between fragility and phase space properties - such as the distribution of states - in the mean-field p -spin model, a solvable model that has been frequently used in studies of the glass transition. By direct computation of all the relevant quantities, we find that (i) the recently observed correlation between fragility and vibrational properties at low temperature is present in this model and (ii) the total number of states is a decreasing function of fragility, at variance with what is currently believed. We explain these findings by taking into account the contribution to fragility coming from the transition paths between different states. Finally, we propose a geometric picture of the phase space that explains the correlation between properties of the transition paths, distribution of states, and their vibrational properties. However, our analysis may not apply to strong systems where inflection points in the configurational entropy as a function of the temperature are found.

Journal Article↗
PubMed2004

Spin-glass complexity.

We study the quenched complexity in spin-glass mean-field models satisfying the Becchi-Rouet-Stora-Tyutin supersymmetry. The outcome of such study, consistent with recent numerical results, allows, in principle, to conjecture the absence of any supersymmetric contribution to the complexity in the Sherrington-Kirkpatrick model. The same analysis can be applied to any model with a full replica symmetry breaking phase, e.g., the Ising p-spin model below the Gardner temperature. The existence of different solutions, breaking the supersymmetry, is also discussed.

Journal Article↗
PubMed2004

Neurological deterioration after head trauma in patients with colloid cysts of the 3rd ventricle. Two case histories.

The authors report 2 cases of colloid cyst of the 3(rd) ventricle (both patients previously asymptomatic) diagnosed after head trauma. Neurological deterioration due to biventricular hydrocephalus, rendering necessary an urgent bilateral CSF shunting, was observed. The possible relationship between clinical deterioration and head injury in these cases is discussed.

Adult↗
PubMed2003

Near-optimal configurations in mean-field disordered systems.

We present a general technique to compute how the energy of a configuration varies as a function of its overlap with the ground state in the case of optimization problems. Our approach is based on a generalization of the cavity method to a system interacting with its ground state. With this technique we study the random matching problem as well as the mean-field diluted spin glass. As a by-product of this approach we calculate the de Almeida-Thouless transition line of the spin glass on a fixed connectivity random graph.

Journal Article↗
PubMed2003

Phonon interpretation of the 'boson peak' in supercooled liquids.

Glasses are amorphous solids, in the sense that they display elastic behaviour. In crystalline solids, elasticity is associated with phonons, which are quantized vibrational excitations. Phonon-like excitations also exist in glasses at very high (terahertz; 10(12) Hz) frequencies; surprisingly, these persist in the supercooled liquids. A universal feature of such amorphous systems is the boson peak: the vibrational density of states has an excess compared to the Debye squared-frequency law. Here we investigate the origin of this feature by studying the spectra of inherent structures (local minima of the potential energy) in a realistic glass model. We claim that the peak is the signature of a phase transition in the space of the stationary points of the energy, from a minima-dominated phase (with phonons) at low energy to a saddle-point-dominated phase (without phonons). The boson peak moves to lower frequencies on approaching the phonon-saddle transition, and its height diverges at the critical point. Our numerical results agree with the predictions of euclidean random matrix theory on the existence of a sharp phase transition between an amorphous elastic phase and a phonon-free one.

Journal Article↗
PubMed2003

Metastable configurations on the Bethe lattice.

We present a general analytic method to compute the number of metastable configurations as a function of the energy for a system of interacting Ising spins on the Bethe lattice. Our approach is based on the cavity method. We apply it to the case of ferromagnetic interactions, and also to the binary and Gaussian spin glasses. Most of our results are obtained within the replica symmetric ansatz, but we illustrate how replica symmetry breaking can be performed.

Journal Article↗
PubMed2003

[Calcium-phosphate metabolism and bone markers in two patients with Noonan's syndrome treated with growth hormone].

AIM: To evaluate the possible effects of recombinant growth hormone (rhGH) therapy on mineral homeostasis and bone turnover, the authors studied calcium-phosphate metabolism parameters, including some bone markers, in 2 prepubertal subjects with Noonan's syndrome (NS). METHODS: Two prepubertal males suffering from NS, short stature (-3.9 and -5.4 SDS respectively) and low growth velocity (3.9 and 3.3 cm/year), were treated with rhGH (0.85 U/kg/week) for 1 year. Serum levels of total calcium (Ca), inorganic phosphate (P), magnesium (Mg), parathyroid hormone (PTH), calcitonin (CT), 25OH vitamin D, 1.25(OH)(2)D, osteocalcin (BGP), type I procollagen carboxy-terminal propeptide (PICP) and its telopeptide (ICTP) were measured. RESULTS: The baseline values were in the normal range; during the treatment no remarkable difference in the values of every one parameters was detected in the 2 patients studied. In one of them, who responded to GH treatment with significantly improved growth velocity, serum levels of the BGP increased during the first semester, and then progressively declined; conversely, serum levels of the ICTP remained stable during the first 6 months of GH-therapy, whereas increased in the following 6 months. CONCLUSION: The results suggest that in Noonan's syndrome patients responding to GH-therapy, a stimulation of bone turnover, with ensuing increase of height velocity, takes place, at least during the first year of GH-therapy. The authors underline the necessity of confirming their results on a larger group of patients with Noonan's syndrome.

Adolescent↗
PubMed2002

Analytic and algorithmic solution of random satisfiability problems.

We study the satisfiability of random Boolean expressions built from many clauses with K variables per clause (K-satisfiability). Expressions with a ratio alpha of clauses to variables less than a threshold alphac are almost always satisfiable, whereas those with a ratio above this threshold are almost always unsatisfiable. We show the existence of an intermediate phase below alphac, where the proliferation of metastable states is responsible for the onset of complexity in search algorithms. We introduce a class of optimization algorithms that can deal with these metastable states; one such algorithm has been tested successfully on the largest existing benchmark of K-satisfiability.

Journal Article↗
PubMed2002

Width distributions and the upper critical dimension of Kardar-Parisi-Zhang interfaces.

Simulations of restricted solid-on-solid growth models are used to build the width distributions of d=2-5 dimensional Kardar-Parisi-Zhang (KPZ) interfaces. We find that the universal scaling function associated with the steady-state width distribution changes smoothly as d is increased, thus strongly suggesting that d=4 is not an upper critical dimension for the KPZ equation. The dimensional trends observed in the scaling functions indicate that the upper critical dimension is at infinity.

Journal Article↗
PubMed2002

Kob-Andersen model: a nonstandard mechanism for the glassy transition.

We present results reflecting the analogies between the Kob-Andersen model and other glassy systems. Studying the stability of the blocked configurations above and below the transition we also give arguments that support their relevance for the glassy behavior of the model. However, we find, surprisingly, that the organization of the phase space of the system is different from the well known organization of other mean field spin glasses and structural glasses.

Journal Article↗
PubMed2002

[A new technique for foetal brain fixation and extraction].

We performed a new technique for foetal brain fixation and extraction that offers a remarkable reduction in sampling time facilitates specimen handling while conserving high quality. With the new fixation method, it is possible to obtain samples adequate for macroscopic and microscopic observations and immunohistochemical analysis. The technique involves the creation of an ex vacuo phenomenon in the subarachnoideal space prior to injecting the fixative solution. In this manner, the solution is homogenously distributed. Ease, reproducibility and the possibility of standardizing the procedure are the principal advantages. Low costs, reduced wording time and less need for human resources are other advantages. Histologically, we obtained, quickly, high quality slides with routine and immunohistochemical stains. Disadvantages of the technique derive from the use of formaldehyde and glacial acetic acid, rather than water to wash the samples; thus one must work in a well ventilated area, with gloves, protective glasses and an adequate lab coat to avoid skin and respiratory tract damage.

Brain↗