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Biomedical subjects

P Pieri

Publications and source records attributed to P Pieri.

At least 19 recordsLinked to original sources
PubMed2006

Microclimate influence on mineral and metabolic profiles of grape berries.

The grape berry microclimate is known to influence berry quality. The effects of the light exposure of grape berry clusters on the composition of berry tissues were studied on the "Merlot" variety grown in a vineyard in Bordeaux, France. The light exposure of the fruiting zone was modified using different intensities of leaf removal, cluster position relative to azimuth, and berry position in the cluster. Light exposures were identified and classified by in situ measurements of berry temperatures. Berries were sampled at maturity (>19 Brix) for determination of skin and/or pulp chemical and metabolic profiles based on (1) chemical and physicochemical measurement of minerals (N, P, K, Ca, Mg), (2) untargeted 1H NMR metabolic fingerprints, and HPLC targeted analyses of (3) amino acids and (4) phenolics. Each profile defined by partial least-square discriminant analysis allowed us to discriminate berries from different light exposure. Discriminant compounds between shaded and light-exposed berries were quercetin-3-glucoside, kaempferol-3-glucoside, myricetin-3-glucoside, and isorhamnetin-3-glucoside for the phenolics, histidine, valine, GABA, alanine, and arginine for the amino acids, and malate for the organic acids. Capacities of the different profiling techniques to discriminate berries were compared. Although the proportion of explained variance from the 1H NMR fingerprint was lower compared to that of chemical measurements, NMR spectroscopy allowed us to identify lit and shaded berries. Light exposure of berries increased the skin and pulp flavonols, histidine and valine contents, and reduced the organic acids, GABA, and alanine contents. All the targeted and nontargeted analytical data sets used made it possible to discriminate sun-exposed and shaded berries. The skin phenolics pattern was the most discriminating and allowed us to sort sun from shade berries. These metabolite classes can be used to qualify berries collected in an undetermined environment. The physiological significance of light and temperature effects on berry composition is discussed.

Amino Acids↗
PubMed2006

Trapped fermions with density imbalance in the Bose-Einstein condensate limit.

We analyze the effects of imbalancing the populations of two-component trapped fermions, in the Bose-Einstein condensate limit of the attractive interaction between different fermions. Starting from the gap equation with two fermionic chemical potentials, we derive a set of coupled equations that describe composite bosons and excess fermions. We include in these equations the processes leading to the correct dimer-dimer and dimer-fermion scattering lengths. The coupled equations are then solved in the Thomas-Fermi approximation to obtain the density profiles for composite bosons and excess fermions, which are relevant to the recent experiments with trapped fermionic atoms.

Journal Article↗
PubMed2005

Extracting the condensate density from projection experiments with Fermi gases.

A debated issue in the physics of the BCS-BEC crossover with trapped Fermi atoms is to identify characteristic properties of the superfluid phase. Recently, a condensate fraction was measured on the BCS side of the crossover by sweeping the system in a fast (nonadiabatic) way from the BCS to the Bose-Einstein condensation (BEC) sides, thus "projecting" the initial many-body state onto a molecular condensate. We analyze here the theoretical implications of these projection experiments, by identifying the appropriate quantum-mechanical operator associated with the measured quantities and relating them to the many-body correlations occurring in the BCS-BEC crossover. Calculations are presented over wide temperature and coupling ranges, by including pairing fluctuations on top of the mean field.

Journal Article↗
PubMed2004

Quantitative comparison between theoretical predictions and experimental results for the BCS-BEC crossover.

Theoretical predictions for the Bardeen-Cooper-Schrieffer-Bose-Einstein condensation crossover of trapped Fermi atoms are compared with recent experimental results for the density profiles of 6Li. The calculations rest on a single theoretical approach that includes pairing fluctuations beyond mean-field. Excellent agreement with experimental results is obtained. Theoretical predictions for the zero-temperature chemical potential and gap at the unitarity limit are also found to compare extremely well with Quantum Monte Carlo simulations and with recent experimental results.

Journal Article↗
PubMed2004

BCS-BEC crossover at finite temperature for superfluid trapped Fermi atoms.

We consider the BCS-BEC (Bose-Einstein-condensate) crossover for a system of trapped Fermi atoms at finite temperature, both below and above the superfluid critical temperature, by including fluctuations beyond mean field. We determine the superfluid critical temperature and the pair-breaking temperature as functions of the attractive interaction between Fermi atoms, from the weak- to the strong-coupling limit (where bosonic molecules form as bound-fermion pairs). Density profiles in the trap are also obtained for all temperatures and couplings.

Journal Article↗
PubMed2004

Pairing fluctuation effects on the single-particle spectra for the superconducting state.

Single-particle spectra are calculated in the superconducting state for a fermionic system with an attractive interaction, as functions of temperature and coupling strength from weak to strong. The fermionic system is described by a single-particle self-energy that includes pairing-fluctuation effects in the superconducting state. The theory reduces to the ordinary BCS approximation in weak coupling and to the Bogoliubov approximation for the composite bosons in strong coupling. Several features of the single-particle spectral function are shown to compare favorably with experimental data for cuprate superconductors.

Journal Article↗
PubMed2003

Derivation of the Gross-Pitaevskii equation for condensed bosons from the Bogoliubov-de Gennes equations for superfluid fermions.

We derive the time-independent Gross-Pitaevskii equation at zero temperature for condensed bosons, which form as bound-fermion pairs when the mutual fermionic attractive interaction is sufficiently strong, from the strong-coupling limit of the Bogoliubov-de Gennes equations that describe superfluid fermions in the presence of an external potential. Three-body corrections to the Gross-Pitaevskii equation are also obtained by our approach. Our results are relevant to the recent advances with ultracold fermionic atoms in a trap.

Journal Article↗
PubMed2002

Magnetic field effect on the pseudogap temperature within precursor superconductivity.

We determine the magnetic-field dependence of the pseudogap closing temperature T* within a precursor superconductivity scenario. Detailed calculations with an anisotropic lattice model with d-wave superconductivity account for a recently determined experimental relation in BSCCO between the pseudogap closing field and the pseudogap temperature at zero field, as well as for the weak initial dependence of T* at low fields. Our results indicate that the available experimental data are fully compatible with a superconducting origin of the pseudogap in cuprate superconductors.

Journal Article↗
PubMed1998

Assessment of myocardial viability by radionuclide imaging.

The differentiation of viable from non viable myocardium is a key issue in the current era of revascularization. Several methods have been used to assess myocardial viability. The radionuclide detection of dysfunctional but viable myocardium depends upon the use of radiotracers whose uptake and trapping are related to presence and amount of living cells. The choice of the diagnostic technique to be applied in clinical practice depends on accuracy of the method and availability of resources. SPECT imaging with TI-201 and Tc-99m-myocardial perfusion tracers are widely available diagnostic tools. Several studies have documented their reliability to detect myocardial segments which may improve in both perfusion and function after revascularization. Positron emission tomography after injection of glucose analogues is a more sophisticated and accurate technology to detect viability, whose utilization is at present limited to few centers due to its high cost. Therefore an accurate selection of patients requiring viability studies is needed in order to identify the most appropriate diagnostic test.

Heart↗
PubMed1995

Assessment of myocardial viability after thallium-201 reinjection or rest-redistribution imaging: a multicenter study. The Italian Group of Nuclear Cardiology.

UNLABELLED: To establish the real nature of 201Tl defects in the assessment of myocardial viability (e.g., fixed versus reversible), 201Tl reinjection was evaluated in a multicenter trial involving 402 consecutive patients with ischemic heart disease and exercise 201Tl defects. METHODS: Twelve hospitals, using the same type of gamma camera and computer software, adopted one of the two most widely used reinjection protocols. In 230 patients (Group A), reinjection was performed immediately after stress-redistribution planar imaging; in 172 patients (Group B), reinjection was performed on a separate day and followed by rest-redistribution imaging. The images were interpreted by three blinded observers in a core laboratory on a five-point qualitative scale; the reproducibility in visual scoring was excellent. RESULTS: Groups A and B had a similar prevalence of myocardial segments with abnormal uptake at stress (39%, 40%), as well as with reversible (16%, 17%), partially reversible (21%, 19%) and irreversible (63%, 64%) defects at redistribution. After reinjection, 201Tl uptake improved in 27% and 36% of both partially reversible and irreversible defects in Groups A and B. No differences were found when comparing early and delayed reinjection imaging in Group B. CONCLUSION: This study confirms the validity of 201Tl reinjection in a large, unselected population, but the discordance with stress/redistribution is less than has been previously reported for both 201Tl reinjection protocols, the prevalence of improved segments after reinjection was higher with the separate day approach.

Exercise Test↗
PubMed1994

Evaluation of myocardial infarct size before and after reperfusion: dual-tracer imaging with radiolabeled antimyosin antibody.

UNLABELLED: Antimyosin antibody is a specific marker of myocardial necrosis that is based on the loss of integrity of the sarcolemmal membrane. Because antimyosin can be labeled with several different radiotracers, gamma imaging performed with antimyosin labeled with two different radionuclides can be used to quantify infarct size before and after an intervention such as reperfusion. METHODS: Twelve open-chested anesthetized dogs were evaluated both at the end of 1.5 hr of occlusion of the left anterior descending coronary artery and following reperfusion. Antimyosin Fab radiolabeled with either 123I or 111In was injected by intracoronary administration over 3 min at the end of the occlusion interval, and the coronary sinus was drained continuously for 7 min to prevent recirculation of the antibody. One hour after reperfusion, a second injection of antimyosin Fab (labeled with a different isotope from the first) was administered as before. Six dogs were given intracoronary trifluoperazine (150 micrograms/kg of body weight) simultaneously with reperfusion, and another six dogs received saline as the control. The infarct size in grams before and after reperfusion was assessed by antimyosin antibody uptake in ex vivo images of 1-cm thick slices of the hearts. The mean infarct sizes before (W1) and after (W2) reperfusion were then calculated as the percent of infarcted myocardium/ventricular myocardial mass. RESULTS: There was a significant increase in the mean percent infarct size after reperfusion in the control group (W2 = 16.73 +/- 4.0, W1 = 14.92 +/- 3.88; p = 0.029). The mean infarct size was uniformly smaller with trifluoperazine intervention (W2 = 12.33 +/- 2.03, W1 = 16.34 +/- 2.78; p = 0.004). The difference between the mean change in the infarct sizes in the two groups was highly significant (p = 0.002). CONCLUSION: Dual imaging of the extent of myocardial necrosis before and after an intervention (reperfusion) in the same animal demonstrated the utility of antimyosin imaging to document changes in the extent of necrosis.

Animals↗
PubMed1993

Characterization of the reinjection thallium image.

The 201TI image after reinjection was characterized by analysis of stress and reinjection data acquired in 204 consecutive patients undergoing planar 201TI cardiac stress tests. In an additional 63 patients, redistribution data were also acquired to determine the effect of washout on the final reinjection image. Maximum count densities for the myocardium, lung and liver were measured, and the ratios between the stress and redistribution and the stress and reinjection sets of data were calculated. In patients with < 5% probability of coronary artery disease (CAD) ("normal" group), the reinjection image was typified by less myocardial activity (initial/reinjection = 1.22), slightly less lung activity (initial/reinjection = 1.05) and greater hepatic activity compared to the initial postexercise image. In male patients with > 5% probability of CAD, peak myocardial activity after reinjection was affected by the following variables: the interval between stress and reinjection, the amount of the initial dose and the 201TI scan results (normal 201TI study: initial/reinjection = 1.16; abnormal = 1.06; p < 0.009). Myocardial activity after reinjection was linearly related to myocardial activity after redistribution (r = 0.82). There was no significant influence by those variables in the 76 women who were studied. In conclusion, myocardial 201TI was decreased after reinjection in normal patients. The results indicate that there is an increased likelihood of underlying CAD in male patients undergoing exercise stress tests when 201TI myocardial activity on reinjection is greater than on the initial image.

Coronary Disease↗
PubMed1991

Myocardial accumulation and clearance of technetium 99m teboroxime at 100%, 75%, 50% and zero coronary blood flow in dogs.

Sequential changes in the regional distribution of technetium 99m Teboroxime (SQ30217) were evaluated in nine dogs with graded coronary artery stenosis, occlusion and reperfusion of either the left anterior descending or left circumflex arteries. 99mTc-Teboroxime accumulation recorded by planar imaging was compared with directly measured coronary blood flow (Doppler) and regional myocardial perfusion (microspheres). Serial images were recorded beginning at the time of injection and continuing for the next 18 min. The data were summed from minutes 2-3, 3-6, 4-8 and 9-18 after injection for comparison with the other parameters. Myocardial clearance of Teboroxime was analysed at each level of blood flow. There was a linear relationship between the Teboroxime activity ratio (abnormal/normal) and coronary blood flow (r = 0.96) and regional myocardial perfusion (r = 0.99). Zones of diminished perfusion were least apparent in the summed images recorded during minutes 2-3. In later images, the lesions were well visualized. The myocardial clearance half-times at 100%, 75% and 50% flow were not significantly different, while clearance half-time at total occlusion was significantly (P less than 0.01) faster. In the 3-6, 4-8 and 9-18 minutes summed images, the Teboroxime activity ratio increased significantly (P less than 0.01) after reperfusion compared with total occlusion.

Animals↗
PubMed1991

Cardiac blood-pool scintigraphy in rats and hamsters: comparison of five radiopharmaceuticals and three pinhole collimator apertures.

Preclinical evaluation of cardiac drugs may require evaluation of cardiac function in intact animals. To optimize the quality of radionuclide measurements of ventricular function in small animals, a comparison was made of gated blood-pool scans recorded with five blood-pool radiopharmaceuticals (99mTc-labeled human polyclonal IgG, 99mTc-human serum albumin labeled by two methods, and red blood cells radiolabeled with 99mTc via in vivo and in vitro methods) in rats and three pinhole apertures in hamsters. The quality of the radiopharmaceuticals was evaluated by comparing count density ratios (LV/BACKGROUND and LV/LIVER) and ejection fractions recorded with each agent. The edge definition of the left ventricle and count rate performance of the 1-, 2-, and 3-mm apertures was evaluated in hamsters. In general, the images obtained with the radiolabeled cells were superior to those obtained with the labeled proteins and no significant differences between the protein preparations were detected. Left ventricular ejection fractions calculated with all five radiopharmaceuticals were not significantly different. The best quality images were obtained with the 1-mm pinhole collimator. Ejection fraction and acquisition time were inversely related to aperture size. A good compromise between resolution and sensitivity was obtained with the 2-mm pinhole collimator.

Animals↗