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Biomedical subjects

S Di Bernardo

Publications and source records attributed to S Di Bernardo.

16 recordsLinked to original sources
PubMed2006

[Transposition of the great arteries: long-term follow-up].

The management of transposition of the great arteries has changed importantly over the last decades. New techniques are employed for the diagnosis and surgical intervention has improved. This has lead to an increasing number of long-term survivors, who require specialised and focussed follow-up, depending on their type of surgical repair Mustard/Senning of arterial Switch. The long-term problems vary for each type of repair and require a specific approach, pharmacotherapy, catheter intervention or surgery. These complex sequellae implicate that transposition patients are never completely cured and probably will have a limited life span.

Cardiac Surgical Procedures↗
PubMed2005

[Treatment of congential heart disease with interventional catheterization].

The development in pediatric interventional cardiology has changed the therapeutic strategy for many patients with congenital heart disease. Interventional catheterization became the first choice for valvuloplasty, angioplasty and collateral vessel occlusion. Effective and safe transcatheter interventions exist for closure of atrial or ventricular septal defects and for patent ductus arteriosus. The progress in the technology used in the catheterization laboratory will permit to continue the expansion of the range of interventions performed without surgery. Pediatric cardiologists and congenital heart surgeons must understand each other's interventional techniques and how they can be used in a coordinated fashion. This interaction is essential for the optimal management of patients with both simple and complex congenital heart disease.

Cardiac Catheterization↗
PubMed2005

[Pediatrics. Advantages of prenatal diagnosis in congenital cardiopathies].

The diagnosis of a congenital heart disease can be made by fetal ultrasound as soon as the 12th week of pregnancy. The main indications for fetal echocardiography are maternal and fetal. Sequential approach is necessary to precise the anatomy and to elaborate a therapeutic strategy for that patient. For severe heart lesions delivery and postnatal care can be programmed, avoiding thus severe hypoxia and acidosis after birth. The prognosis of these children are thus much improved.

Female↗
PubMed2004

Measurement of activated clotting time in children--comparison of the Celite i-STAT ACT with the Medtronic ACT II.

BACKGROUND: To evaluate a recently introduced blood-saving method for the measurement of activated clotting time (ACT), the Celite i-STAT ACT, by comparing the values obtained with those from the widely used Medtronic ACT II device. METHODS: In a prospective clinical study, we compared ACT values from the i-STAT device with the Medtronic ACT II device in 60 paediatric, interventional, cardiac catheterization procedures necessitating prophylactic heparinization. Blood samples were pair-analyzed using two i-STAT analyzers and one Medtronic ACT II device with double-tube-cartridges before and after heparinization. Data were compared using Bland-Altman bias analysis, Student's t-test and simple regression analysis. RESULTS: Bias and precision between the Medtronic ACT II and the i-STAT ACT values was -5.4 +/- 26.3. The i-STAT and Medtronic ACT II values were similar before heparinization (P = 0.22), but i-STAT ACT values became significantly longer than Medtronic ACT II values after heparinization (P = 0.021). The increase of ACT after heparinization was greater (median 86.3; range 40-187 s) in the i-STAT analyzer than in the Medtronic ACT II analyzer (median 73.0; range 19-235.5 s). Increase in ACT values was inversely affected by intraoperative haemoglobin concentration in the Medtronic ACT II analyzer (P = 0.001) but not in the i-STAT analyzer. CONCLUSION: Activated clotting times obtained from the Celite i-STAT ACT and the Medtronic ACT II demonstrated poor agreement. The technical principles are quite different and the two methods showed diverse susceptibility to intraoperative haemoglobin concentration. Users have to be aware of technique-specific ACT target ranges and their confounders, which need to be provided by the manufacturers.

Adolescent↗
PubMed2001

Direct interaction between a membrane domain subunit and a connector subunit in the H(+)-translocating NADH-quinone oxidoreductase.

When Paracoccus denitrificans membranes were treated with a crosslinker, m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), a cross-linked product of M(r) approximately 31 kDa was found which reacted with antibodies against the hydrophobic subunit Nqo7 and the connector subunit Nqo6. NaI treatment of the Paracoccus membranes before, but not after, the crosslinking step prevented the formation of the 31 kDa band. When Nqo7 and Nqo6 were coexpressed in Escherichia coli, both subunits were located in the membrane fraction. MBS treatment of the E. coli membranes generated the 31 kDa band as in the Paracoccus membranes. These results indicate that Nqo7 interacts with probable N2-binding Nqo6.

Antibodies↗
PubMed2001

NADH dehydrogenases: from basic science to biomedicine.

This review article is concerned with two on-going research projects in our laboratory, both of which are related to the study of the NADH dehydrogenase enzyme complexes in the respiratory chain. The goal of the first project is to decipher the structure and mechanism of action of the proton-translocating NADH-quinone oxidoreductase (NDH-1) from two bacteria, Paracoccus denitrificans and Thermus thermophilus HB-8. These microorganisms are of particular interest because of the close resemblance of the former (P. denitrificans) to a mammalian mitochondria, and because of the thermostability of the enzymes of the latter (T. thermophilus). The NDH-1 enzyme complex of these and other bacteria is composed of 13 to 14 unlike subunits and has a relatively simple structure relative to the mitochondrial proton-translocating NADH-quinone oxidoreductase (complex I), which is composed of at least 42 different subunits. Therefore, the bacterial NDH-I is believed to be a useful model for studying the mitochondrial complex I, which is understood to have the most intricate structure of all the membrane-associated enzyme complexes. Recently, the study of the NADH dehydrogenase complex has taken on new urgency as a result of reports that complex I defects are involved in many human mitochondrial diseases. Thus the goal of the second project is to develop possible gene therapies for mitochondrial diseases caused by complex I defects. This project involves attempting to repair complex I defects in the mammalian system using Saccharomyces cerevisiae NDI1 genes, which code for the internal, rotenone-insensitive NADH-quinone oxidoreductase. In this review, we will discuss our progress and the data generated by these two projects to date. In addition, background information and the significance of various approaches employed to pursue these research objectives will be described.

Animals↗
PubMed2001

[Acute respiratory distress syndrome in children].

The acute respiratory distress syndrome (ARDS) encountered in a child may be either due to a primary lung infection or may be secondary to a systemic inflammatory response of varying origin. Therapy is based on: 1) the mechanical ventilation strategy aimed at maintaining the functional residual capacity by alveolar recruitment using positive end expiratory pressure and to limit secondary pulmonary lesions by using small tidal volumes, 2) prone positioning as soon as sufficient stability is achieved; 3) optimizing tissue oxygen delivery by cardiac support; 4) correction of any other organ dysfunction. If this conventional approach is not sufficient experimental therapies may be tempted given the vital risk. For instance inhaled nitric oxide and high frequency oscillation ventilation may be a valuable support. Newer techniques, such as partial liquid ventilation, are being developed and could become useful therapeutic options. After the acute phase a close medical follow-up is mandatory. Because of the possibility of a chronic respiratory insufficiency with negative consequences on the right ventricular function, these patients may need long term oxygen therapy and diuretics. Cardiac echography helps orientation in maintaining or discontinuing this long term therapy by estimating the arterial pulmonary pressure.

Acute Disease↗
PubMed1999

NADH-quinone oxidoreductase: PSST subunit couples electron transfer from iron-sulfur cluster N2 to quinone.

The proton-translocating NADH-quinone oxidoreductase (EC 1.6.99.3) is the largest and least understood enzyme complex of the respiratory chain. The mammalian mitochondrial enzyme (also called complex I) contains more than 40 subunits, whereas its structurally simpler bacterial counterpart (NDH-1) in Paracoccus denitrificans and Thermus thermophilus HB-8 consists of 14 subunits. A major unsolved question is the location and mechanism of the terminal electron transfer step from iron-sulfur cluster N2 to quinone. Potent inhibitors acting at this key region are candidate photoaffinity probes to dissect NADH-quinone oxidoreductases. Complex I and NDH-1 are very sensitive to inhibition by a variety of structurally diverse toxicants, including rotenone, piericidin A, bullatacin, and pyridaben. We designed (trifluoromethyl)diazirinyl[3H]pyridaben ([3H]TDP) as our photoaffinity ligand because it combines outstanding inhibitor potency, a suitable photoreactive group, and tritium at high specific activity. Photoaffinity labeling of mitochondrial electron transport particles was specific and saturable. Isolation, protein sequencing, and immunoprecipitation identified the high-affinity specifically labeled 23-kDa subunit as PSST of complex I. Immunoprecipitation of labeled membranes of P. denitrificans and T. thermophilus established photoaffinity labeling of the equivalent bacterial NQO6. Competitive binding and enzyme inhibition studies showed that photoaffinity labeling of the specific high-affinity binding site of PSST is exceptionally sensitive to each of the high-potency inhibitors mentioned above. These findings establish that the homologous PSST of mitochondria and NQO6 of bacteria have a conserved inhibitor-binding site and that this subunit plays a key role in electron transfer by functionally coupling iron-sulfur cluster N2 to quinone.

Azirines↗
PubMed1999

Localization and mobility of coenzyme Q in lipid bilayers and membranes.

We have studied the mobility of coenzyme Q (CoQ) in lipid bilayers and mitochondrial membranes in relation to the control of electron transfer activities. A molecular dynamics computer simulation in the vacuum yielded a folded structure for CoQ10, with a length of only 21 A. Using this information we were able to calculate diffusion coefficients in the range of 10(-6) cm2/s in good agreement with those found experimentally by fluorescence quenching of pyrene derivatives. To investigate if CoQ diffusion may represent the rate-limiting step of electron transfer, we reconstituted complexes I and III and assayed the resulting NADH-cytochrome c reductase activity in presence of different CoQ10 levels and at different distances between complexes; the experimental turnovers were higher than the collision frequencies calculated using diffusion coefficients of 10(-9) cm2/s but compatible with values found by us by fluorescence quenching. Since the experimental turnovers are independent of the distance between complexes, we conclude that CoQ diffusion is not rate-limiting for electron transfer.

Animals↗
PubMed1999

[Subtotal thrombosis of the juxta-ductal thoracic aorta in a premature 36-week-old infant. Alteplase therapy].

The authors report the case of a neonate, a premature 36 weeks gestation male child who presented with a spontaneous thrombosis of the juxtaduetal aorta at 3 days of age. The clinical presentation mimicked that of severe coarctation with cardiocirculatory failure. The diagnosis was ineffective, the introduction of low dose alteplase (plasma activator of human recombinant plasminogen) with continued anticoagulation resulted in near complete lysis of the clot and avoided surgery. Thromboembolic cerebral and renal complications were observed during treatment. However, 6 months after the acute episode, there were no clinical or echographic sequellae. Global renal function remained normal despite mild atrophy of the parenchyma of the left kidney. This combined treatment represents an alternative to high risk surgery. The follow-up of this form of management should be rigorous in view of the potential renal and cerebral complications.

Aorta, Thoracic↗
PubMed1998

A high diffusion coefficient for coenzyme Q10 might be related to a folded structure.

We measured the lateral diffusion of different coenzyme Q homologues and analogues in model lipid vesicles using the fluorescence collisional quenching technique with pyrene derivatives and found diffusion coefficients in the range of 10(-6) cm2/s. Theoretical diffusion coefficients for these highly hydrophobic components were calculated according to the free volume theory. An important parameter in the free volume theory is the relative dimension between diffusant and solvent: a molecular dynamics computer simulation of the coenzymes yielded their most probable geometries and volumes and revealed surprisingly similar sizes of the short and long homologues, due to a folded structure of the isoprenoid chain in the latter, with a length for coenzyme Q10 of 21 A. Using this information we were able to calculate diffusion coefficients in the range of 10(-6) cm2/s, in good agreement with those found experimentally.

Coenzymes↗
PubMed1996

The role of DT-diaphorase in the maintenance of the reduced antioxidant form of coenzyme Q in membrane systems.

The experiments reported here were designed to test the hypothesis that the two-electron quinone reductase DT-diaphorase [NAD(P)H:(quinone-acceptor) oxidoreductase, EC 1.6.99.2] functions to maintain membrane-bound coenzyme Q (CoQ) in its reduced antioxidant state, thereby providing protection from free radical damage. DT-diaphorase was isolated and purified from rat liver cytosol, and its ability to reduce several CoQ homologs incorporated into large unilamellar vesicles was demonstrated. Addition of NADH and DT-diaphorase to either large unilamellar or multilamellar vesicles containing homologs of CoQ, including CoQ9 and CoQ10, resulted in the essentially complete reduction of the CoQ. The ability of DT-diaphorase to maintain the reduced state of CoQ and protect membrane components from free radical damage as lipid peroxidation was tested by incorporating either reduced CoQ9 or CoQ10 and the lipophylic azoinitiator 2,2'-azobis(2,4-dimethylvaleronitrile) into multilamellar vesicles in the presence of NADH and DT-diaphorase. The presence of DT-diaphorase prevented the oxidation of reduced CoQ and inhibited lipid peroxidation. The interaction between DT-diaphorase and CoQ was also demonstrated in an isolated rat liver hepatocyte system. Incubation with adriamycin resulted in mitochondrial membrane damage as measured by membrane potential and the release of hydrogen peroxide. Incorporation of CoQ10 provided protection from adriamycin-induced mitochondrial membrane damage. The incorporation of dicoumarol, a potent inhibitor of DT-diaphorase, interfered with the protection provided by CoQ. The results of these experiments provide support for the hypothesis that DT-diaphorase functions as an antioxidant in both artificial membrane and natural membrane systems by acting as a two-electron CoQ reductase that forms and maintains the antioxidant form of CoQ. The suggestion is offered that DT-diaphorase was selected during evolution to perform this role and that its conversion of xenobiotics and other synthetic molecules is secondary and coincidental.

Animals↗
PubMed1996

Steady-state kinetics of the reduction of coenzyme Q analogs by complex I (NADH:ubiquinone oxidoreductase) in bovine heart mitochondria and submitochondrial particles.

The reduction kinetics of coenzyme Q (CoQ, ubiquinone) by NADH:ubiquinone oxidoreductase (complex I, EC 1.6.99.3) was investigated in bovine heart mitochondrial membranes using water-soluble homologs and analogs of the endogenous ubiquinone acceptor CoQ10 [the lower homologs from CoQ0 to CoQ3, the 6-pentyl (PB) and 6-decyl (DB) analogs, and duroquinone]. By far the best substrates in bovine heart submitochondrial particles are CoQ1 and PB. The kinetics of NADH-CoQ reductase was investigated in detail using CoQ1 and PB as acceptors. The kinetic pattern follows a ping-pong mechanism; the Km for CoQ1 is in the range of 20 microM but is reversibly increased to 60 microM by extraction of the endogenous CoQ10. The increased Km in CoQ10-depleted membranes indicates that endogenous ubiquinone not only does not exert significant product inhibition but rather is required for the appropriate structure of the acceptor site. The much lower Vmax with CoQ2 but not with DB as acceptor, associated with an almost identical Km, suggests that the sites for endogenous ubiquinone bind 6-isoprenyl- and 6-alkylubiquinones with similar affinity, but the mode of electron transfer is less efficient with CoQ2. The Kmin (kcat/Km) for CoQ1 is 4 orders of magnitude lower than the bimolecular collisional constant calculated from fluorescence quenching of membrane probes; moreover, the activation energy calculated from Arrhenius plots of kmin is much higher than that of the collisional quenching constants. These observations strongly suggest that the interaction of the exogenous quinones with the enzyme is not diffusion-controlled. Contrary to other systems, in bovine submitochondrial particles, CoQ1 usually appears to be able to support a rate approaching that of endogenous CoQ10, as shown by application of the "pool equation" [Kröger, A., & Klingenberg, M. (1973) Eur. J. Biochem. 39, 313-323] relating the rate of ubiquinone reduction to the rate of ubiquinol oxidation and the overall rate through the ubiquinone pool.

Animals↗
PubMed1995

Characterization of 9-aminoacridine interaction with chromatophore membranes and modelling of the probe response to artificially induced transmembrane delta pH values.

We analyze the adsorption of the fluorescent monoamine 9-aminoacridine to the membrane phase of photosynthetic chromatophores, in the physiological interval of pH values ranging from 5.5 to 8.5 and at ionic strengths of 0.005 and 0.150 M. The interaction of the probe with the membrane phase is described with S-shaped isotherms of the Hill type and is modulated by electrostatic effects as modelled with the Gouy-Chapman-Boltzman theory. This description is consistent with different values of the surface change density of the chromatophore membranes decreasing from about 1.3 x 10(-3) to about 0.5 x 10(-3) e-/A2, on changing the pH from 8.5/7.5 to 6.5/5.5, respectively. Furthermore we show that, when the free concentrations of the probe in the inner and outer vesicle compartments are computed from the adsorbing isotherms at the proper pH values, the model considering the equilibrium distribution of the neutral monoamine following the onset of a delta pH is sufficient to describe the dependence of the artificially induced transmembrane delta pH values on the observed quenching of the probe fluorescence.

Aminacrine↗