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Alessandro Desideri

Publications and source records attributed to Alessandro Desideri.

33 records · Page 2Linked to original sources
PubMed2003

The mitochondrial oxoglutarate carrier: structural and dynamic properties of transmembrane segment IV studied by site-directed spin labeling.

The structural and dynamic features of the fourth transmembrane segment of the mitochondrial oxoglutarate carrier were investigated using site-directed spin labeling and electron paramagnetic resonance (EPR). Using a functional carrier protein with native cysteines replaced with serines, the 18 consecutive residues from S184 to S201 which are believed to form the transmembrane segment IV were substituted individually with cysteine and labeled with a thiol-selective nitroxide reagent. Most of the labeled mutants exhibited significant oxoglutarate transport in reconstituted liposomes, where they were examined by EPR as a function of the incident microwave power in the presence and absence of two paramagnetic perturbants, i.e., the hydrophobic molecular oxygen or the hydrophilic chromium oxalate complex. The periodicity of the sequence-specific variation in the spin-label mobility and the O(2) accessibility parameters unambiguously identifies the fourth transmembrane segment of the mitochondrial oxoglutarate carrier as an alpha-helix. The accessibility to chromium oxalate is out of phase with oxygen accessibility, indicating that the helix is amphipatic, with the hydrophilic face containing the residues found to be important for transport activity by site-directed mutagenesis and chemical modification. The helix is strongly packed, as indicated by the values of normalized mobility, which also suggest that the conformational changes occurring during transport probably involve the N-terminal region of the helix.

Animals↗
PubMed2003

Clinical, exercise electrocardiographic, and pharmacologic stress echocardiographic findings for risk stratification of hypertensive patients with chest pain.

Exercise electrocardiography (ECG) is of limited usefulness in hypertensive patients, whereas pharmacologic stress echocardiography can provide diagnostic and prognostic information. The aim of this study was to compare the prognostic value of clinical data, exercise ECG, and pharmacologic stress echocardiography in hypertensive patients with chest pain and to identify the best strategy for their risk stratification. Three hundred sixty-seven hypertensive patients (189 men, age 61 +/- 9 years) with chest pain of unknown origin underwent exercise ECG and pharmacologic stress echocardiography (237 with dipyridamole and 130 with dobutamine) and were followed up for 31 +/- 24 months. Positive exercise ECG (ST-segment shift of > or =1 mm at 80 ms after the J point) and stress echocardiography (new wall motion abnormalities) were found in 130 (35%) and 86 (23%) patients, respectively. During follow-up, there were 13 deaths and 16 myocardial infarctions. Additionally, 43 patients underwent coronary revascularization and were censored accordingly. Of 12 clinical, electrocardiographic, and echocardiographic variables analyzed, a positive result of stress echocardiography was the only multivariate predictor of either death (hazard ratio [HR] 4.7, 95% confidence interval [CI] 1.5 to 14.5, p = 0.007) or hard events (death, myocardial infarction) (HR 4.1, 95% CI 1.8 to 9.3, p = 0.0009). Using an interactive stepwise procedure, stress echocardiography provided additional prognostic information to clinical evaluation and exercise ECG. However, the negative predictive value of the 2 tests was similarly (p = NS) high in assessing 4-year event-free survival. In conclusion, a negative exercise electrocardiographic test identifies low-risk hypertensive patients with chest pain and should be the first-line approach for risk stratification. In contrast, positive exercise ECG is unable to distinguish between patients with different levels of risk. In this case, stress echocardiography provides strong and incremental prognostic power over clinical and exercise electrocardiographic data.

Cardiotonic Agents↗
PubMed2003

Protein concerted motions in the DNA-human topoisomerase I complex.

The collective motions of the core and C-terminal domains of human topoisomerase I (topo I) have been analysed by molecular dynamics simulation of the protein in covalent complex with a 22 bp DNA duplex. The analysis evidenced a great number of correlated movements of core subdomain I and II residues, and a central role for helix 5 in the protein-DNA communication, in particular with the scissile strand downstream of the cleavage site. The flow of information between these core subdomains and DNA suggests that subdomains I and II play an essential role in the DNA relaxation process. In core subdomain III the majority of DNA contacting residues do not communicate with protein regions far from DNA, suggesting that they have a structural role. However, selected core subdomain III residues, involved in the orientation of the active site region, show correlated movements with residues distant from DNA, indicating that the information concerning the catalytic event is also transmitted. The flexibility of two loops formed by residues 519-520 and 580-584 seems indispensable to the dynamic participation of core subdomain III to the DNA cleavage and religation steps. The motion of specific residues has also been found to explain the effect of single point mutations that make topo I resistant to the anticancer drug camptothecin.

Binding Sites↗
PubMed2003

Exercise electrocardiography after acute coronary syndromes: still the first testing modality?

Recent diagnostic and therapeutic advances have been questioning the role of exercise electrocardiography (ECG) for risk stratification of patients recovering from an acute coronary syndrome. The aim of this review was to verify whether evidence still exists supporting the use of exercise ECG as first choice stress testing modality in this clinical setting in the light of the most recent prognostic data and of cost effectiveness considerations. It was concluded that a large body of evidence supports the use of exercise ECG as a cost-effective tool for prognostic purposes and for quality of life assessment following acute coronary syndromes.

Cost-Benefit Analysis↗
PubMed2003

Predischarge exercise electrocardiogram and stress echocardiography can predict long-term clinically driven revascularization following acute myocardial infarction.

BACKGROUND: Predischarge stress testing provides suboptimal prediction of spontaneous hard events following uncomplicated acute myocardial infarction (AMI). HYPOTHESIS: This study was aimed at assessing whether soft cardiac ischemic events requiring late revascularization could be predicted more accurately. METHODS: In all, 428 patients undergoing exercise electrocardiography (ECG) and stress echocardiography (SE, 345 dobutamine and 83 dypiridamole) within 15 days of uncomplicated AMI were followed up for 425 (range 20-2220) days. Soft ischemic events (effort angina>class II [Canadian Cardiovascular Society Classification] and unstable angina) driving late (>6 months) revascularization were regarded as endpoints. RESULTS: A total of 58 events (29 effort and 29 unstable angina with subsequent 47 coronary artery bypass grafts and 11 percutaneous transluminal coronary angioplasties) occurred: 26 in patients with positive exercise ECG and 34 in patients with positive SE. Univariate predictors of revascularizations were positive exercise ECG (p = 0.0001), peak wall motion score index (WMSI) (p = 0.0009), low workload (p = 0.0018), rest WMSI (p = 0.02) and positive SE (p = 0.02). Cox multivariate analysis selected peak WMSI, positive exercise ECG, and low workload positive exercise ECG as independent predictors of late revascularizations. CONCLUSIONS: Predischarge stress testing identifies the long-term occurrence of soft ischemic events driving late revascularization after uncomplicated AMI.

Aged↗
PubMed2003

Cost of strategies after myocardial infarction (COSTAMI): a multicentre, international, randomized trial for cost-effective discharge after uncomplicated myocardial infarction.

AIMS: Risk stratification after uncomplicated acute myocardial infarction is mostly applied by either symptom-limited post discharge exercise electrocardiography or pre-discharge submaximal exercise test. Aim of the present study was to determine if early pharmacological stress echocardiography and discharge within 24 hours of the test in cases without induced myocardial ischemia leads to lower costs and similar clinical outcome during 1 year follow up when compared to clinical evaluation and exercise electrocardiography after discharge. METHODS AND RESULTS: Four-hundred fifty-eight patients from 10 participating centers with a recent uncomplicated myocardial infarction were randomized to pharmacological stress echocardiography on day 3-5 followed by early discharge in the case of negative test result (early discharge strategy) (n=233) or clinical evaluation with hospital discharge on day 7-9 and symptom-limited post-discharge exercise electrocardiography at 2-4 weeks after myocardial infarction (usual care strategy) (n=225). At 1 year follow up there were 63 events (4 deaths, 9 non fatal reinfarctions, 50 chest pains requiring hospitalization) in patients randomized to early discharge, and 69 events (6 deaths, 13 reinfarctions, 50 chest pains requiring hospitalization) in usual care (p=ns). Total median individual costs calculated on the basis of hospitalizations, investigations and interventions during 1 year follow up were 3561 for early discharge strategy vs 3850 for usual care strategy (p<0.05). CONCLUSIONS: Early pharmacological stress echocardiography followed by early discharge in case of negative test result gives similar clinical outcome and lower costs after uncomplicated myocardial infarction than clinical evaluation and delayed post-discharge symptom-limited exercise electrocardiography.

Cardiotonic Agents↗
PubMed2003

Cost-effectiveness analysis of noninvasive strategies to evaluate patients with chest pain.

We evaluated clinical and economic outcomes of diagnostic strategies on the basis of pharmacologic stress echocardiography (PhSE) versus exercise electrocardiography test (EET) in 527 patients with chest pain (274 women; age 59 +/- 10 years) who underwent both EET and PhSE. We investigated 3 strategies, ie, coronary angiography: after positive EET (strategy 1); after positive PhSE (strategy 2); or after a positive PhSE performed after a positive EET (strategy 3). A patient was correctly identified if he or she had negative test results and no events, or had positive test results and abnormal coronaries. The cost per patient correctly identified was calculated as the ratio between the cost of each strategy and the number of patients correctly identified. The accuracy in correctly identifying the patients was 78%, 92%, and 91% with strategies 1, 2, and 3, respectively. The cost of each patient correctly identified was 1572 US dollars, 1097 US dollars, and 1081 US dollars with strategies 1, 2, and 3, respectively. In conclusion, PhSE-based strategies are cost-effective versus EET.

Aged↗
PubMed2003

Myocardial Doppler at rest for the identification of myocardial viability.

BACKGROUND: Echocardiography may permit the detection of a nonviable myocardium. The aim of this study was to test if resting pulsed wave-tissue Doppler imaging (PW-TDI) might yield additional markers. METHODS: Fifty patients (38 males, 12 females, mean age 63 +/- 6 years) with left ventricular dysfunction (ejection fraction 35 +/- 10%) underwent echocardiography. The posterior septum, anterior septum, lateral, inferior, anterior and posterior walls were sampled on the basal segments in the apical views at PW-TDI. The following variables and cardiac phases were tested: 1) the isovolumic contraction phase velocity, polarity or detectability, 2) the ejection phase velocity, a detectable interval between the ejection phase and aortic valve closure, or ejection phase shape, and 3) the isovolumic relaxation phase velocity or ejection velocity/post-systolic shortening ratio. From the tested PW-TDI variables, viable and nonviable patterns were assembled, taking rest-redistribution 201thallium single-photon emission computed tomography as the independent reference for myocardial viability. Patients with significant loading alterations, mitral or aortic valve disease, and arrhythmias were excluded. RESULTS: Out of 219 dyssynergic segments, viability as identified according to conventional rest echocardiographic criteria appeared in 94 (47%), as identified at PW-TDI in 116 (53%), and as identified at nuclear imaging in 105 (48%). The resting PW-TDI variables consistent with absent myocardial viability were as follows: 1) an isovolumic contraction phase velocity equal to the ejection phase velocity +/- 1 cm/s, or absent, 2) an ejection phase velocity < or = 4 cm/s, usually with a gap between the ejection phase and aortic valve closure, or any shape of ejection but the typical single phase, and 3) an isovolumic relaxation phase velocity < 5 cm/s with an ejection phase velocity/isovolumic relaxation phase velocity ratio < 0.8. The accuracy for the identification of myocardial viability was: agreement 73%, kappa 0.44 for echocardiography, and agreement 75%, kappa 0.47 for PW-TDI. CONCLUSIONS: PW-TDI nonviable patterns may be a helpful additional tool for the identification of patients without residual myocardial viability.

Aged↗
PubMed2002

Molecular dynamics simulation of the RNA complex of a double-stranded RNA-binding domain reveals dynamic features of the intermolecular interface and its hydration.

The interaction between double-stranded RNA (dsRNA) and the third double-stranded domain (dsRBD) from Drosophila Staufen protein represents a paradigm to understand how the dsRBD protein family, one of the most common RNA-binding protein units, binds dsRNA. The nuclear magnetic resonance (NMR) structure of this complex and the x-ray structure of another family member revealed the stereochemical basis for recognition, but also raised new questions. Although the crystallographic studies revealed a highly ordered interface containing numerous water-mediated contacts, NMR suggested extensive residual motion at the interface. To address how interfacial motion contributes to molecular recognition in the dsRBD-dsRNA system, we conducted a 2-ns molecular dynamics simulation of the complex derived from Staufen protein and of the separate protein and RNA components. The results support the observation that a high degree of conformational flexibility is retained upon complex formation and that this involves interfacial residues that are critical for dsRBD-dsRNA binding. The structural origin of this residual flexibility is revealed by the analysis of the trajectory of motion. Individual basic side chains switch continuously from one RNA polar group to another with a residence time seldom exceeding 100 ps, while retaining favorable interaction with RNA throughout much of the simulation. Short-lived water molecules mediate some of these interactions for a large fraction of the trajectory studied here. This result indicates that water molecules are not statically associated with the interface, but continuously exchange with the bulk solvent on a 1-10-ps time scale. This work provides new insight into dsRBD-dsRNA recognition and builds upon a growing body of evidence, suggesting that short-lived dynamic interactions play important roles in protein-nucleic acid interactions.

Binding Sites↗
PubMed2002

Stress echocardiography for risk stratification of patients with chest pain and normal or slightly narrowed coronary arteries.

One hundred twenty-five patients (60 +/- 10 years old, 60 women) with known (35, previous myocardial infarction) or suspected (90) coronary artery disease (CAD) and no more than 50% coronary stenoses underwent pharmacologic (48 dipyridamole and 77 dobutamine) stress echocardiography (SE) and prospective follow-up (36 +/- 22 months) for cardiac death, nonfatal infarction, and unstable angina. The ability of clinical and SE variables to predict the outcome was assessed by the Cox model. A significant increase in the global chi-square of the model indicated an incremental prognostic value. Nine events occurred: 2 fatal and 5 nonfatal infarctions and 2 hospitalizations for unstable angina. Hypertension, positive SE, and peak wall motion score index were multivariate predictors of outcome, but SE provided an 87.5% increase in the global chi-square (P <.001). Patients with positive SE had a significantly lower event-free survival compared with those with negative SE. Therefore, we conclude that SE provides incremental prognostic information in patients with chest pain without critical coronary artery disease.

Age Factors↗
PubMed2002

Safety and feasibility of dobutamine and dipyridamole stress echocardiography in hypertensive patients.

OBJECTIVES: To establish whether safety and feasibility of dobutamine and dipyridamole stress echocardiography are affected by history of hypertension. METHODS: Data on 2200 consecutive pharmacologic stress echocardiography (959 dobutamine and 1241 dipyridamole) performed between October 1990 and February 2001 at a single cardiology centre, were analysed. RESULTS: There were two complications (1/480 tests) during dobutamine (one sustained ventricular tachycardia and one severe asthmatic attack following antidote administration) and two (1/620 tests) during dipyridamole (one non-Q wave myocardial infarction and one sustained ventricular tachycardia) stress. Complications or limiting side effects were observed in 83/959 patients (48/430 hypertensives and 35/529 normotensives) with dobutamine and in 34/1241 patients (17/571 hypertensives and 17/670 normotensives) with dipyridamole stress. Therefore, the overall feasibility was 88.8% in hypertensives and 93.4% in normotensives (P = 0.013) for dobutamine, and 97% in hypertensives and 97.5% in normotensives (P = 0.64) for dipyridamole. Dipyridamole was significantly more feasible than dobutamine in both hypertensive (P < 0.0001) and normotensive (P = 0.0006) subjects. Logistic regression analysis failed to identify clinical or echocardiographic predictors of adverse reactions with dipyridamole, while history of hypertension [odds ratio (OR) = 1.8, 95% confidence interval (CI) 1.1-2.8, P = 0.0138] was the only independent predictor of cumulative adverse reactions with dobutamine stress. In addition, history of hypertension (OR = 3.2, 95% CI, 1.2-8.5, P = 0.0166), resting wall motion abnormalities (OR = 1.8, 95% CI, 1.1-3.1, P = 0.0282), and age over 70 years (OR = 4.8, 95% CI, 1.5-15.3, P = 0.0087) predicted hypertensive response, ventricular tachycardia, and atrial fibrillation, respectively. No covariate was associated with hypotensive response during dobutamine test. CONCLUSIONS: Dipyridamole has a slightly better safety profile and significantly higher feasibility than dobutamine stress both in hypertensives and in normotensives. In addition, the history of systemic hypertension is an independent predictor of cumulative adverse effects during dobutamine but not during dipyridamole stress.

Aged↗
PubMedDate not supplied

Substrate-induced conformational changes of the mitochondrial oxoglutarate carrier: a spectroscopic and molecular modelling study.

The structural and dynamic properties of the oxoglutarate carrier were investigated by introducing a single tryptophan in the Trp-devoid carrier in position 184, 190 or 199 and by monitoring the fluorescence spectra in the presence and absence of the substrate oxoglutarate. In the absence of substrate, the emission maxima of Arg190Trp, Cys184Trp and Leu199Trp are centered at 342, 345 and 348 nm, respectively, indicating that these residues have an increasing degree of solvent exposure. The emission intensity of the Arg190Trp and Cys184Trp mutants is higher than that of Leu199Trp. Addition of substrate increases the emission intensity of Leu199Trp, but not that of Cys184Trp and Arg190Trp. A 3D model of the oxoglutarate carrier was built using the structure of the ADP/ATP carrier as a template and was validated with the experimental results available in the literature. The model identifies Lys122 as the most likely candidate for the quenching of Trp199. Consistently, the double mutant Lys122Ala-Leu199Trp exhibits a higher emission intensity than Leu199Trp and does not display further fluorescence enhancement in response to substrate addition. Substitution of Lys122 with Cys and evaluation of its reactivity with a sulphydryl reagent in the presence and absence of substrate confirms that residue 122 is masked by the substrate, likely through a substrate-induced conformational change.

Amino Acid Sequence↗