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P Pedroni

Publications and source records attributed to P Pedroni.

At least 19 recordsLinked to original sources
PubMed2006

Measurement of the Gerasimov-Drell-Hearn Integrand for 2H from 200 to 800 MeV.

A measurement of the helicity dependence of the total inclusive photoabsorption cross section on the deuteron was carried out at MAMI (Mainz) in the energy range 200<Egamma<800 MeV. The experiment used a 4pi detection system, a circularly polarized tagged photon beam and a frozen-spin target which provided longitudinally polarized deuterons. The contribution to the Gerasimov-Drell-Hearn sum rule for the deuteron determined from the data is 407+/-20(stat)+/-24(syst) mu b for 200<Egamma<800 MeV.

Journal Article↗
PubMed2005

Measurement of helicity-dependent photoabsorption cross sections on the neutron from 815 to 1825 MeV.

Helicity-dependent total photoabsorption cross sections on the deuteron have been measured for the first time at ELSA (Bonn) in the photon energy range from 815 to 1825 MeV. Circularly polarized tagged photons impinging on a longitudinally polarized LiD target have been used together with a highly efficient 4pi detector system. The data around 1 GeV are not compatible with predictions from existing multipole analyses. From the measured energy range an experimental contribution to the GDH integral on the neutron of [33.9 +/- 5.5(stat) +/- 4.5(syst)] microb is extracted.

Journal Article↗
PubMed2004

Experimental check of the Gerasimov-Drell-Hearn sum rule for 1H.

For the first time we checked the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the proton experimentally in the photon energy range from 0.2-2.9 GeV with the tagged photon facilities at MAMI (Mainz) and ELSA (Bonn). New data of the doubly polarized total cross section difference are presented in the energy range from 1.6 to 2.9 GeV. The contribution to the GDH integral from 0.2-2.9 GeV yields [254+/-5(stat)+/-12(syst)] microb with negative contributions in the Regge regime at photon energies above 2.1 GeV. This trend supports the validity of the GDH sum rule.

Journal Article↗
PubMed2004

How to study boron biodistribution in liver metastases from colorectal cancer.

The purpose of this study was to evaluate boron distribution for a safe and effective BNCT (Boron Neutron Capture Therapy) of liver metastases. Samples both from healthy and tumour liver parenchyma were analysed, after i.v. boron administration, by: alpha particles counting under neutron irradiation; morphological analysis by standard haematoxylin-eosin staining; neutron autoradiography. Our method was unaffected by the cytological heterogeneity inside tumour nodules; it demonstrated selective boron distribution in tumour tissue and predicted estimated mean therapeutic doses in tumour and safety doses in healthy tissue. The time interval for efficient BNCT was 2 to 4 hours after i.v. boron administration.

Animals↗
PubMed2003

First Measurement of the Gerasimov-Drell-Hearn Sum Rule for 1H from 0.7 to 1.8 GeV at ELSA.

To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] microb.

Journal Article↗
PubMed2002

Helicity amplitudes A1/2 and A3/2 for the D13(1520) resonance obtained from the gamma-->p-->-->ppi(0) Reaction.

The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes.

Journal Article↗
PubMed2000

Helicity dependence of gammap --> Npi below 450 MeV and contribution to the Gerasimov-Drell-Hearn sum rule.

The helicity dependence of the single pion photoproduction on the proton has been measured in the energy range from 200 to 450 MeV for the first time. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a frozen-spin target. The data obtained provide new information for multipole analyses of pion photoproduction and determine the main contributions to the Gerasimov-Drell-Hearn sum rule and the forward spin polarizability gamma(0).

Journal Article↗
PubMed1997

[Non-invasive evaluation of coronary reperfusion. Analysis of the ST segment before and after thrombolysis in acute myocardial infarct].

BACKGROUND: The aim of this study was to determine the role of the ST segment elevation resolution > 50% between the ECG before and 2 hours after thrombolytic therapy as a predictor of acute myocardial infarction (AMI)-related artery patency, assessed by a coronary angiography performed 1 month after AMI. MATERIALS AND METHODS: This study enrolled 95 patients, 75 men and 20 women, 58 years mean aged, admitted to the coronary care unit with diagnosis of AMI. Patients were treated with thrombolysis within 6 hours from the onset of chest pain, according to the GUSTO trial. RESULTS: The findings showed a significant prevalence of ST segment elevation resolution > 50% in inferior AMI (p < 0.01). It has been observed that the ST segment resolution is correlated with lower (p < 0.01) and earlier (p < 0.05) peak in serum creatinekinase (CK) and CK MB release and with less damage of left ventricular ejection fraction assessed by ventriculography (p < 0.01). All these findings indicated a lower extensive myocardial damage. Patients with ST segment resolution presented a prevalence of one or two-coronary vessel disease, with an infarct-related vessel narrowing like that observed in the other patients without ST resolution. Nevertheless a TIMI grade 2 or 3 flow was observed more frequently, but not significantly, in the subjects with ST resolution; a significant prevalence was limited to TIMI 3 grade flow (p < 0.05). In the present study ST segment elevation resolution > 50% represented a highly sensitive and a poor specific predictor of vessel patency in inferior AMI, but with a poor sensitivity and specificity in anterior AMI. CONCLUSIONS: Personal experience suggested that the thrombolytic therapy has a less favourable effect on the artery patency assessed 1 month after AMI, rather than in the acute phase as reported in previous studies. Dynamic changes of flow or a following worsening in atherosclerotic plaque could be probably responsible of reocclusion of an initially reperfused coronary artery.

Electrocardiography↗
PubMed1996

The [Ni-Fe] hydrogenase from the thermophilic bacterium Acetomicrobium flavidum.

Biochemical analysis of the soluble hydrogenase from the thermophilic organism Acetomicrobium flavidum revealed that the enzyme is an alpha 2 beta 2 tetramer, with the alpha and beta subunits having a molecular mass of 50 kDa and 25 kDa, respectively. The most important biochemical properties of the enzyme are a specific activity of 77 mumol min-1 (mg protein)-1, a Km for methylviologen of 0.2 mM, a pH optimum of 7.5 and a T50 of about 70 degrees C. In addition, the enzyme is remarkably stable to oxygen inactivation, retaining full activity after 24 h exposure to air. By using oligodeoxynucleotides designed on the basis of the N-terminal sequences of the two subunits, the corresponding genes have been isolated and sequenced. When compared to the other hydrogenases so far characterized, the A. flavidum hydrogenase appears to be a typical [Ni-Fe] enzyme. The hydrogenase was expressed in Escherichia coli at high levels in a soluble form but it was not active. The analysis of the recombinant large subunit showed that it was not post-translationally processed at its C-terminus.

Amino Acid Sequence↗
PubMed1995

Characterization of the locus encoding the [Ni-Fe] sulfhydrogenase from the archaeon Pyrococcus furiosus: evidence for a relationship to bacterial sulfite reductases.

The hydBGDA genes, which encode the four subunits beta, gamma, delta and alpha of the [Ni-Fe] hydrogenase from the archaeon Pyrococcus furiosus, have been isolated and sequenced using a PCR/IPCR-based strategy. From the sequence analysis it appears that the four structural genes are tightly linked and organized in a single transcription unit. The hydD and hydA gene products are related to the small and the large subunits of several archaeal and eubacterial [Ni-Fe] hydrogenases with an overall degree of sequence relatedness ranging from 35% to 50% (identity + similarity). In particular, the amino acid sequence motifs involved in the accommodation of nickel and iron-sulfur clusters are conserved. In addition, the database search revealed that the hydB and hydG gene products are homologous to the asrA- and asrB-encoded subunits of the sulfite reductase enzyme from Salmonella typhimurium. This is particularly interesting in view of the recent finding that the P. furiosus hydrogenase appears to be a bifunctional enzyme endowed with both proton- and sulfur-reducing activities.

Amino Acid Sequence↗
PubMed1991

Sympathetic and vagal influences on rate-dependent changes of QT interval in healthy subjects.

Dependence of QT interval duration on cardiac heart rate has been well established and is considered to be an intrinsic property of ventricular myocardium. Conclusive results of autonomic influences on such phenomena are lacking. To evaluate whether rate-dependent changes of QT interval are conditioned by the autonomic nervous system, 28 normal subjects with no heart disease and a normal QT interval were electrophysiologically assessed. The QT interval was calculated at 6 paced cycle lengths (600, 540, 500, 460, 430 and 400 ms) during the basal state, and after beta blockade (propranolol 0.2 mg/kg) and autonomic blockade (propranolol plus atropine 0.04 mg/kg). Because of atrioventricular nodal conduction limits, intrapatient cross-comparisons were performed in 10 subjects (aged 42 +/- 15 years). Single regression lines, evaluated in each subject, showing correlation between pacing cycle length and QT duration at each of the 3 states were analyzed. The mean slope observed after autonomic blockade (b = 0.10 +/- 0.04) was significantly lower than that seen during the basal state (b = 0.22 +/- 0.12, p less than 0.05) and after beta blockade (b = 0.23 +/- 0.08, p less than 0.05); nonsignificant differences were found between slopes during the basal state and after beta blockade. Results showed that vagal tone increased intrinsic dependence of QT at increasing cycle length, whereas sympathetic tone did not seem to interfere significantly. Since (in each subject) beta blockade was performed--or achieved--before atropine administration, the vagal influences are likely to be directly exerted on the ventricular electrophysiologic substrate.

Adult↗
PubMed1991

Expression of Bordetella pertussis fimbrial (fim) genes in Bordetella bronchiseptica: fimX is expressed at a low level and vir-regulated.

To identify the elements involved in Bordetella pertussis fimbriae regulation and to determine whether fimX is an expressed gene, the promoter regions of fimX, fim2 and fim3 from strain BPSA1 were isolated and linked to the promoterless CAT gene in pLAFR2. By following CAT activity in Bordetella bronchiseptica vir+ and vir- strains we established that the fimX promoter, like those for fim2 and fim3, is active, although at a low level, and vir-regulated. This suggests that the fimX protein might be produced in minute quantities which are not detectable by conventional methods. Comparison of the three fim promoter sequences and transcriptional activities identifies two conserved elements necessary for transcription in the -60 to -20 region: the 'fim box' and the 'C-stretch'. Mutations in these two sequences drastically reduce transcription and alter the interaction with vir components, suggesting a role for the two elements in the regulation of fim genes. Finally, we suggest that the apparent constitutive nature of fim3 in BPSA1 is due to a modification in the length of the 'C-stretch'.

Base Sequence↗
PubMed1990

Calcium sensitivity of isometric tension in intact papillary muscles and chemically skinned trabeculae in different models of hypertensive hypertrophy.

STUDY OBJECTIVE - The aim was to examine the contractile state, the inotropic response to [Ca2+]e and the Ca2+ sensitivity of the contractile proteins in different models of hypertensive hypertrophy in an early stage of evolution (3-4 weeks). DESIGN - Renal hypertension was induced by placing a silver clip around the left renal artery. The contralateral kidney was either removed (1K-1C) or left untouched (2K-1C). Hypertension through sodium overload was produced by administration of deoxycorticosterone and 1% NaCl drinking water. (DOCA rats). Active and passive length-tension curves were performed to evaluate basal contractility at Lmax and passive stiffness of cardiac muscle. The inotropic responsiveness to [Ca2+]e and the Ca2+ sensitivity of the contractile proteins were also evaluated. EXPERIMENTAL MATERIAL - Papillary muscles and skinned trabeculae from the left ventricle of male Wistar hypertensive and age matched normotensive rats were used. MEASUREMENTS AND RESULTS - Cardiac hypertrophy was similar in all hypertensive groups. In 2K-1C and 1K-1C rats, basal contractility was not significantly different from controls. In DOCA rats, developed tension and time to peak tension (TTP) were significantly greater than controls. The inotropic response to [Ca2+]e was depressed in 2K-1C and increased in DOCA rats. In DOCA rats, increasing [Ca2+]e produced an increase in TTP greater than in controls. No differences were detected in muscle passive stiffness or in Ca2+ sensitivity of the contractility proteins among the different groups. CONCLUSIONS - In the earlier stages of hypertensive hypertrophy, differences in basal contractile state and/or inotropic responsiveness appear to be more related to the initiating cause of hypertensive hypertrophy than to the degree of hypertrophy itself. These differences cannot be attributed to changes in Ca2+ sensitivity of the contractile system.

Animals↗