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Biomedical subjects

P Rossi

Publications and source records attributed to P Rossi.

At least 91 records · Page 5Linked to original sources
PubMed2001

Generalized crossover in multiparameter Hamiltonians.

Many systems near criticality can be described by Hamiltonians involving several relevant couplings and possessing many nontrivial fixed points. A simple and physically appealing characterization of the crossover lines and surfaces connecting different nontrivial fixed points is presented. Generalized crossover is related to the vanishing of the renormalization group function Z(-1)(t). An explicit example is discussed in detail based on the tetragonal Landau-Ginzburg-Wilson Hamiltonian.

Journal Article↗
PubMed2001

Signaling through extracellular signal-regulated kinase is required for spermatogonial proliferative response to stem cell factor.

In vitro addition of stem cell factor (SCF) to c-kit-expressing A(1)-A(4) spermatogonia from prepuberal mice stimulates their progression into the mitotic cell cycle and significantly reduces apoptosis in these cells. SCF addition results in a transient activation of extracellular signal-regulated kinases (Erk)1/2 as well as of phosphatidylinositol 3-kinase (PI3K)-dependent Akt kinase. These events are followed by a rapid re-distribution of cyclin D3, which becomes predominantly nuclear, whereas its total cellular amount does not change. Nuclear accumulation of cyclin D3 is coupled to transient activation of the associated kinase activity, assayed using the retinoblastoma protein (Rb) as a substrate. These events were followed by a transient accumulation of cyclin E, stimulation of the associated histone H1-kinase activity, a delayed accumulation of cyclin A2, and Rb hyper-phosphorylation. All the events associated with SCF-induced cell cycle progression are inhibited by the addition of either a PI3K inhibitor or a mitogen-activated protein-kinase kinase (MEK) inhibitor, indicating that both MEK and PI3K are essential for c-kit-mediated proliferative response. On the contrary, the anti-apoptotic effect of SCF is not influenced by the separate addition of either MEK or PI3K inhibitors. Thus, SCF effects on mitogenesis and survival in c-kit expressing spermatogonia rely on different signal transduction pathways.

Animals↗
PubMed2001

Theta-frequency bursting and resonance in cerebellar granule cells: experimental evidence and modeling of a slow k+-dependent mechanism.

Neurons process information in a highly nonlinear manner, generating oscillations, bursting, and resonance, enhancing responsiveness at preferential frequencies. It has been proposed that slow repolarizing currents could be responsible for both oscillation/burst termination and for high-pass filtering that causes resonance (Hutcheon and Yarom, 2000). However, different mechanisms, including electrotonic effects (Mainen and Sejinowski, 1996), the expression of resurgent currents (Raman and Bean, 1997), and network feedback, may also be important. In this study we report theta-frequency (3-12 Hz) bursting and resonance in rat cerebellar granule cells and show that these neurons express a previously unidentified slow repolarizing K(+) current (I(K-slow)). Our experimental and modeling results indicate that I(K-slow) was necessary for both bursting and resonance. A persistent (and potentially a resurgent) Na(+) current exerted complex amplifying actions on bursting and resonance, whereas electrotonic effects were excluded by the compact structure of the granule cell. Theta-frequency bursting and resonance in granule cells may play an important role in determining synchronization, rhythmicity, and learning in the cerebellum.

4-Aminopyridine↗
PubMed2001

Dependence of 13C NMR chemical shifts on conformations of rna nucleosides and nucleotides.

Cross-polarization magic-angle spinning solid-state NMR spectroscopy has been used to investigate the dependence of (13)C sugar chemical shifts on specific conformational parameters of a variety of ribonucleotides and ribonucleosides. Solid-state NMR is a valuable tool for nucleoside and nucleotide structural studies since it provides the means to acquire spectra that correspond to single conformations, as opposed to (13)C solution NMR methods. The distinct effects of sugar puckering on the C1', C4', and C5' resonances of C2' endo (S type) and C3' endo (N type) furanoid conformations allow us to separate them into two groups. Further analysis of each group reveals an additional dependence of the C1' and C5' resonances on the glycosidic and C4'-C5' exocyclic torsion angles, respectively. However, it is found that the glycosidic conformation cannot independently be determined from sugar (13)C chemical shift data. The statistical methods of exploratory data analysis and discriminant analysis are used to construct two canonical coordinates-linear combinations of chemical shifts which give the statistically optimal determination of the conformation from the NMR data.

Carbohydrate Conformation↗
PubMed2001

Calculation of 13C chemical shifts in rna nucleosides: structure-13C chemical shift relationships.

Isotropic 13C chemical shifts of the ribose sugar in model RNA nucleosides are calculated using SCF and DFT-GIAO ab initio methods for different combinations of ribose sugar pucker, exocyclic torsion angle, and glycosidic torsion angle. Idealized conformations were obtained using structures that were fully optimized by ab initio DFT methods starting with averaged parameters from a collection of crystallographic data. Solid-state coordinates of accurate crystal or neutron diffraction structures were also examined directly without optimization. The resulting 13C chemical shifts for the two sets of calculations are then compared. The GIAO-DFT method overestimates the shifts by an average of 5 ppm while the GIAO-SCF underestimates the shifts by the same amount. However, in the majority of cases the errors appear to be systematic, as the slope of a plot of calculated vs experimental shifts is very close to unity, with minimal scatter. The values of the 13C NMR shifts of the ribose sugar are therefore sufficiently precise to allow for statistical separation of sugar puckering modes and exocyclic torsion angle conformers, based on the canonical equation model formulated in a previous paper.

Algorithms↗
PubMed2001

Fatigue in multiple sclerosis is associated with abnormal cortical activation to voluntary movement--EEG evidence.

Converging evidence is consistent with the view that fatigue in Multiple Sclerosis is independent from pyramidal tract involvement, suggesting a possible involvement of frontal areas. During voluntary movement, changes of the EEG rhythms can be observed over sensorimotor areas. Event-related desynchronization (ERD) of the 10 and 20 Hz frequency bands occurs during motor planning and execution and is followed after movement termination by event-related synchronization (ERS), expressing cortical idling or inhibition. We evaluated the pattern of cortical activation to voluntary movement in MS patients complaining of fatigue assessed using the Fatigue Severity Scale. Fifteen MS patients complaining of fatigue, 18 MS patients without fatigue, and 14 normal controls were studied. The two patients groups were similar for age, sex, disease duration, and were not disabled (score <1.5 at the Expanded Disability Status Scale). Twenty-nine channel EEG was recorded during about 60 self-paced extensions of the right thumb. The onset latency and amount of the contralateral sensorimotor (C3 electrode) 10 and 18--22 Hz ERD were similar in the three groups. ERD was more widespread anteriorly in the fatigue group compared with normal controls (P < 0.01 over Fz electrode). Postmovement contralateral sensorimotor 18--22 Hz ERS was significantly lower in fatigue MS patients compared with normal subjects (P < 0.005) and with nonfatigue MS patients (P = 0.02). These findings are consistent with a central origin of fatigue in MS and indicate cortical dysfunction even during a simple motor task, resulting in hyperactivity during movement execution and failure of the inhibitory mechanisms intervening after movement termination.

Adult↗
PubMed2001

Physiopathology and treatment of fatigue in multiple sclerosis.

Fatigue is a common symptom of patients with multiple sclerosis (MS). It is reported by about one-third of patients, and for many fatigue is the most disabling symptom. Fatigue may be associated with motor disturbances and/or mood disorders, which makes it very difficult to determine whether the fatigue is an aspect of these features or a result per se of the disease. Although peripheral mechanisms have some role in the pathogenesis of fatigue, in MS there are clear indications that the more important role is played by "central" abnormalities. Neurophysiological studies have shown that fatigue does not depend on involvement of the pyramidal tracts and implicate impairment of volitional drive of the descending motor pathways as a physiopathological mechanism. Metabolic abnormalities of the frontal cortex and basal ganglia revealed by positron-emission tomography and correlations between fatigue and magnetic resonance imaging lesion burden support this hypothesis. Some recent studies also suggest that pro-inflammatory cytokines contribute to the sense of tiredness. No specific treatments are available. Management strategies include medications, exercise, and behavioural therapy; in most cases a combined approach is appropriate.

Antidepressive Agents↗
PubMed2001

RNF4 is a growth inhibitor expressed in germ cells but not in human testicular tumors.

The RING-finger protein RNF4 modulates both steroid-receptor-dependent and basal transcription and interacts with a variety of nuclear proteins involved in cell growth control. RNF4 is expressed at very high levels in testis and at much lower levels in several other tissues. We show that in germ cells RNF4 expression is strongly modulated during progression of spermatogonia to spermatids, with a peak in spermatocytes. Analysis of human testicular germ cell tumors shows that RNF4 is not expressed in all tumors analyzed including seminomas, the highly malignant embryonal carcinomas, yolk sac, and mixed germ cell tumors. We also show that the ectopically expressed RNF4 gene inhibits cell proliferation of both somatic and germ cell tumor-derived cells. Mutation of critical cysteine residues in the RING finger domain abolished the RNF4 growth inhibition activity. Our results suggest that the lack of RNF4 expression may play a role in the progression of testicular tumors.

Animals↗
PubMed2001

Cutaneous afferents mediating the cutaneous silent period in the upper limbs: evidences for a role of low-threshold sensory fibres.

OBJECTIVES: To evaluate the contribution of the low-threshold afferents to the production of the cutaneous silent period (CSP) in the upper limbs. METHODS: The CSP was studied in 10 healthy adults and 4 patients with Friedreich's ataxia. The following neurophysiological aspects were studied: (a) relationship between sensory threshold (ST), sensory action potential (SAP) amplitude and CSP parameters; (b) habituation and recovery cycle of the CSP at different stimulus intensities (2xST and 8xST); (c) pattern of responses in distal and proximal muscles at different stimulus intensities (2xST and 8xST). RESULTS: (a) The CSP occurred at low intensities (1xST and 2xST) and increased abruptly between 3.5xST and 4xST (corresponding to the pain threshold). The SAP amplitude was saturated before CSP saturation. In the patients with Friedreich's ataxia, the CSP appeared only at higher stimulus intensities (6xST-8xST). (b) The CSP evoked at 2xST showed a fast habituation and slow recovery cycle whereas the opposite behaviour was found at 8xST. (c) Low-threshold stimuli induced an inhibitory response restricted to the distal muscles. High-intensity stimulation produced an electromyographic suppression, significantly increasing from proximal to distal muscles. CONCLUSIONS: Our findings support the notion that low-threshold afferents participate in the production of the CSP in the upper limbs. The different afferents may activate different central neural networks with separate functional significance.

Action Potentials↗
PubMed2001

Neuropeptide degradation in naive and steroid-treated allergic saliva.

The hydrolysis of neuropeptides and possible variations in hydrolysis following steroidal treatment, were examined in the presence of saliva collected from allergic volunteers; data obtained were compared to those obtained with a age and sex-matching group of healthy controls. The results reported indicate the presence of a statistically significant increase in the hydrolysis of the model substrate in allergic as compared to control saliva, and a reduction of substrate hydrolysis in treated as compared to naive allergic saliva. Total enzyme activity, the relative activity of the three classes of substrate-active enzymes (aminopeptidases, dipeptidylaminopeptidases, and dipeptidylcarboxypeptidases), the allergy-associated variations of these activities, and the variations associated to therapy were found to be different in male and female saliva. Specifically, in the controls, the lower level of hydrolysis evident in female as compared to male saliva appeared to be principally induced by lower activity of aminopeptidases. Under allergic conditions, a sex-different increase in the activity of all three classes of substrate-active enzymes modified the hydrolysis pattern differently in samples obtained from male and female donors. Finally, pharmacological treatment induced opposite effects on the enzymes present in each sex: in male saliva, the activity of all three classes of substrate-active enzymes--and, thus, of substrate hydrolysis--was reduced near to the levels measured in the controls. In female saliva, the reduction in the activity of aminopeptidases was coupled with an increase in the activity of dipeptidylaminopeptidases, causing substrate hydrolysis to remain near the levels measured in naive allergic, rather than control, saliva.

Adult↗
PubMed2001

Percutaneous liver biopsy using an ultrasound-guided subcostal route.

Percutaneous biopsy is considered one of the most important diagnostic tools to evaluate diffuse liver diseases. The introduction and widespread diffusion of ultrasounds in medical practice has improved percutaneous bioptic technique, while reducing postoperative complications. Although ultrasonography has become almost ubiquitous in prebiopsy investigation, only one third of biopsies are performed under ultrasound control. Moreover, the one-day procedure, reported in several studies to be safe and cost effective, accounted for only 4% of biopsies done. We report our experience of 142 percutaneous US-guided biopsies performed on 140 patients affected by chronic diffuse liver disease over a four-year period. Liver biopsies were performed under US guidance at the patient's bed using an anterior subcostal route. We evaluated postoperative pain, modifications of blood pressure and red cell count, hospital stay, morbidity and mortality rates, and adequacy of specimens for histologic examination. There was no operative mortality. As for major complications, one case of hemobilia occurred. As for minor complications, two cases of persistent postoperative pain required analgesic therapy. Patients were discharged the day following the procedure in all cases but two, who were discharged on the third and fifth postoperative days. Liver specimens were suitable for histologic diagnosis in all but one case, in which there were no portal spaces. According to our experience, we believe that hepatic biopsy guided by ultrasonography could replace blinded biopsy in the diagnosis of diffuse liver disease. The procedure is suitable to be performed safely on an outpatient basis.

Biopsy↗
PubMed2001

Defective dendritic cell maturation in a child with nucleotide excision repair deficiency and CD4 lymphopenia.

We report a case of a combined immunodeficiency (CID) in a child affected by trichothiodystrophy (TTD) characterized by an altered response to ultraviolet (UV) light due to a defect in the XPD gene. The XPD gene encodes a subunit of the transcription factor II H (TFIIH), a complex involved in nucleotide-excision repair (NER) and basal transcription. Our patient showed neurological and immune system abnormalities, including CD4 + lymphopenia never previously reported in TTD patients. In vitro immunological studies revealed a marked reduction in T-cell proliferation in response to mitogens and CD3 cross-linking which was partially recovered by the addition of anti-CD28 antibody or exogenous interleukin-2. The patient's T cells displayed alterations in T-cell receptor (TCR/CD3) proximal signalling characterized by marked reduction in Lck kinase activity coupled with a constitutive hyperactivation of Fyn kinase. Despite these alterations, normal levels of Lck and Fyn proteins were detected. The role of antigen-presenting cells (APCs) in the pathogenesis of the T-cell defect was investigated by analysing dendritic cells (DCs) generated from the patient's blood monocytes. In these cells, flow cytometry revealed significantly reduced expression of the CD86 co-stimulatory molecules and HLA glycoproteins. In addition, the patient's DCs showed a decreased ability to stimulate naive T lymphocytes. Overall, the results of our study suggest that a defective TFIIH complex might result in alterations in T cells and DC functions leading to a severe immunodeficiency.

CD4-Positive T-Lymphocytes↗
PubMed2001

Assessment of trans, trans-muconic acid in human seminal plasma.

Trans, trans-muconic acid (tt-MA) is one of the most important metabolites of benzene, a pollutant ubiquitously distributed in ambient air and classified in 1982 as a group I carcinogen. For its sensitivity and specificity, tt-MA excreted in urine is considered a good biological marker of benzene exposure. In this study, seminal tt-MA levels in occupationally nonexposed subjects (n = 32) have been determined. The seminal fluid of normozoospermic subjects contained an average tt-MA concentration (170 +/- 100 ng ml-1) significantly lower than that of teratozoospermic (310 +/- 180 ng ml-1; P < 0.01), oligozoospermic (400 +/- 180 ng ml-1; P < 0.001), and oligoasthenozoospermic (430 +/- 230 ng ml-1; P < 0.01) subjects. A negative correlation existed between tt-MA levels and sperm concentration (r = - 0.62; P < 0.001), percentage of normal spermatozoa (r = - 0.41; P < 0.05), and percentage of vital spermatozoa (r = - 0.89; P < 0.001). Average tt-MA levels detected in seminal plasma were higher in smokers (350 +/- 160 ng ml-1) than in nonsmokers (280 +/- 210 ng ml-1). These results show that seminal plasma tt-MA content could be an important biological indicator for evaluating the negative effects of benzene on spermatogenesis.

Adult↗
PubMed2001

Self-administered pain-relieving manoeuvres in primary headaches.

We investigated the use of self-administered pain-relieving manoeuvres on a sample of 400 patients with primary headaches--represented by an even distribution of migraine without aura (MO), migraine with aura (MA), episodic tension-type headache (TH), and cluster headache (CH)--consecutively seen at Padua and Parma Headache Centres. Manoeuvres on various regions of the head were used by 258 patients (65% of the cases). The most applied procedures were: compression (114 out of 382 manoeuvres; 30%), application of cold (27%), massage (25%) and application of heat (8%). A significant (P < 0.001) relationship was found between headache diagnoses and type of manoeuvre. In MO patients the application of cold (38% of the manoeuvres) and compression (36%), used mainly on the forehead and temples, prevailed; compression, mainly on the temples, was the most frequent procedure (44%) in MA patients. Massage on the temples and nape was the predominant manoeuvre (43%) in TH patients, whereas in the CH group, which more often required heterogeneous procedures, none of the above-mentioned manoeuvres was prevalent. Compression, as a diagnostic criterion for MO, had a sensitivity of 33% and a specificity of 86%; for the application of cold the figures were 36% and 84%, respectively. Massage had a sensitivity of 33% and a specificity of 80% for TH. The efficacy of the self-administered manoeuvres in reducing pain was scarce. Only 8% of the manoeuvres, in fact, resulted in a good or excellent pain control. Moreover, the efficacy of the manoeuvre was often momentary, wearing off when the manoeuvre stopped. In spite of this, 46% of the subjects used the manoeuvres constantly, at each attack.

Adolescent↗
PubMed2001

Sonographic prenatal diagnosis of intracranial fetus in fetu.

A case of sonographic prenatal diagnosis of a complex intracranial mass, with features of a fetus in fetu at 17 weeks' gestation, is reported. This diagnosis is reserved for a highly organized tumor containing a vertebral column and recognizable fetal parts and should be differentiated from a teratoma.

Adult↗
PubMed2001

Discrepancy between polymerase chain reaction assay and Western blot analysis in the assessment of CagA status in dyspeptic patients.

BACKGROUND: Infection with CagA-positive Helicobacter pylori may be diagnosed by detecting cagA gene by polymerase chain reaction assay (PCR) or serum antibodies against CagA by Western blot analysis. The aim of this study is to evaluate whether results of PCR and Western blot analysis are in agreement in CagA status assessment. PATIENTS AND METHODS: Thirty-six dyspeptic patients with unknown H. pylori status underwent upper gastrointestinal endoscopy to assess the presence of mucosal lesions and to collect six gastric biopsies (three from the antrum and three from the body) for evaluation of H. pylori infection (rapid urease test, histology and PCR for ureA gene) and gastritis. CagA status was assessed by PCR (cagA gene) on two biopsy specimens and by Western blot analysis of serum (CagA-antibodies) in each patient. RESULTS: At endoscopy, nine patients showed normal mucosa, 15 a duodenal ulcer and 12 antral erosions. Twenty-eight patients were found to be H. pylori-positive and eight H. pylori-negative. Of the 28 H. pylori-positive patients, 17 were CagA-positive and five were CagA-negative by both methods, five were CagA-positive by Western blot analysis but not by PCR and one was CagA-positive by PCR but not by Western blot analysis. Of the eight H. pylori-negative patients, none was CagA-positive by PCR, while six were CagA-positive by Western blot analysis. Therefore, the two tests agreed in only 24 patients (67%). In those patients in whom the PCR and Western blot analysis were not in agreement, the histological features appear to suggest that the results of the Western blot analysis should be considered false positives or false negatives. CONCLUSIONS: PCR and Western blot analysis failed to provide comparable data in many cases. Western blot analysis seems to be more likely to give misleading results than PCR. Thus, PCR seems to be the method of choice to assess CagA status.

Adult↗
PubMed2001

Magnetic resonance imaging findings in piriformis syndrome: a case report.

Piriformis syndrome (PS) is an unusual cause of sciatica that, because of the lack of strict diagnostic criteria, remains a controversial clinical entity. The diagnosis of PS is still primarily clinical because no diagnostic tests have proven to be definitive. We report the case of a 30-year-old woman, affected by a severe scoliosis, who developed a persistent buttock pain resembling that of PS. The clinical suspicion was confirmed by magnetic resonance imaging (MRI) of the pelvis, which showed an enlargement of the left piriformis muscle with an anterior isplacement of the sciatic nerve. The role of MRI in the diagnosis, clinical definition, and therapeutic approach to PS is discussed.

Adult↗