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M Bolognesi

Publications and source records attributed to M Bolognesi.

At least 109 records · Page 6Linked to original sources
PubMed1996

Short-term effects of transcatheter arterial chemoembolisation on metabolic activity of the liver of cirrhotic patients with hepatocellular carcinoma.

BACKGROUND: Transcatheter arterial chemoembolisation, a procedure for the treatment of hepatocellular carcinoma, provokes a pronounced but transient increase in hepatic cytolysis parameters. A definite evaluation of the impairment of liver function after this treatment, performed by adequate techniques, is still lacking. AIMS: To assess and quantify the impairment of liver metabolic activity after arterial chemoembolisation in patients with cirrhosis. The variations of hepatic vein pressure gradient provoked by this procedure were evaluated. PATIENTS: 15 patients with cirrhosis (Child's class A and B) and hepatocellular carcinoma. METHODS: 17 transcatheter arterial chemoembolisations with epirubicin, iodised oil, and gelfoam were performed; liver function was assessed before, the following day, and after seven days measuring galactose elimination capacity; aminopyrine breath test was also performed in six patients before the procedure and seven days after. In 10 patients intrinsic hepatic clearance of indocyanine green and hepatic vein pressure gradient were measured by hepatic vein catheterisation before and 30 minutes after chemoembolisation. RESULTS: Intrinsic hepatic clearance of indocyanine green decreased significantly from (mean (SEM)) 355 (140) ml/min to 277 (98) ml/min after the procedure (p = 0.0007). Galactose elimination capacity did not show significant changes, being 4.00 (0.90) mg/min/kg body weight at baseline, 4.20 (0.90) mg/min/kg body weight after one day, and 3.95 (0.87) mg/min/kg body weight seven days after chemoembolisation. Aminopyrine breath test was 2.31 (1.09)% and remained unchanged after treatment, being 2.39 (2.04)% at day 7. Baseline hepatic vein pressure gradient was 17.0 (5.5) mm Hg, and 14.4 (3.7) mm Hg 30 minutes after chemoembolisation (p = 0.09). CONCLUSIONS: A single transcatheter chemoembolisation in cirrhotic patients was detected by galactose elimination capacity and aminopyrine breath test one and seven days after the procedure. Therefore it can be considered a safe therapeutic tool for hepatocellular carcinoma in Child's class A and B cirrhotic patients.

Adult↗
PubMed1996

Left ventricular diastolic function in liver cirrhosis.

BACKGROUND: Left ventricular systolic abnormalities have been reported in liver cirrhosis (LC). Diastolic function in cirrhotics, on the contrary, does not seem to have been studied so far. METHODS: Diastolic function was evaluated in 42 cirrhotic patients and in 16 controls by means of Doppler echocardiography. RESULTS: Compared with the controls, cirrhotics had increased left ventricular end-diastolic and left atrial volume, stroke volume, late diastolic flow velocity (peak A) (71 + or - 17 cm/sec versus 56 +/- 18; p <0.01), time from onset of mitral inflow to the early peak (time E) (86 + or - 11 msec versus 72 +/- 14; p < 0.003), and deceleration time (DT) (194 +/- 40 msec versus 159 +/- 27; p < 0.001) and decreased ratio of peak E to peak A filling velocities (1.02 +/ - 0.35 versus 1.22 +/- 0.25; p < 0.02). Patients with tense ascites had a higher E/A ratio (p < 0.03) and a shorter DT (p < 0.03) than patients with mild or no ascites. CONCLUSIONS: The impaired left ventricular relaxation in the presence of high stroke volume suggests a myocardial involvement in LC. The pseudo normalization of the E/A ratio and DT in patients with tense ascites could reflect loading conditions masking the relaxation abnormality.

Ascites↗
PubMed1996

[Physiopathologic basis of medical therapy of portal hypertension in cirrhosis].

The in-depth study of the pathophysiology of portal hypertension is the basis for a correct medical treatment. The backward-flow theory of portal hypertension stresses the importance of increased hepatic vascular resistance, while the forward-flow theory of portal hypertension underscores generalized vasodilation, the hyperdynamic circulation and increased portal inflow. The role of expanded plasma volume has been emphasized in recent studies. The aim of drug therapy is to normalize each one of these components. Vasoconstrictor agents, i.e. vasopressin, triglycyl-lysin-vasopressin, non selective beta-blockers, somatostatin and octreotide, try to normalize the increased portal inflow and to decrease porto-collateral blood flow. Venous vasodilators, e.g. nitrates, mainly act by decreasing portal blood outflow resistance. Spironolactone has been proposed to decrease plasma volume. The use of a combination of a vasoconstrictor agent and a vasodilator or spironolactone has been proposed to increase the efficacy of medical treatment.

Humans↗
PubMed1995

Inhibition of bovine beta-trypsin by the active site titrant N alpha-(N,N-dimethylcarbamoyl)-alpha-azaornithine p-nitrophenyl ester: a kinetic and X-ray crystallographic study.

Kinetics of the bovine beta-trypsin (trypsin) reaction with the active site titrant N alpha-(N,N-dimethylcarbamoyl)- alpha-aza-ornithine p-nitrophenyl ester (Dmc-azaOrn-ONp) was obtained at pH 6.2 and 21.0 degrees C. The results are consistent with the minimum three-step catalytic mechanism of serine proteinases involving a stable acyl.enzyme adduct. Dmc-azaOrn-ONp binds stoichiometrically to trypsin and allows the reliable determination of the active enzyme concentration between 1.0 x 10(-6) M and 3.0 x 10(-4) M. The three-dimensional structure of the trypsin.Dmc-azaOrn acyl.enzyme adduct has been solved by X-ray crystallography at 1.8 A resolution (R = 0.153). The Dmc-azaOrn moiety of the active site titrant is accommodated in the serine proteinase active center, occupying the S1 specificity subsite, and is covalently linked to the OG atom of the Ser195 catalytic residue.

Animals↗
PubMed1995

Crystallization and preliminary X-ray analysis of pyruvate kinase type I from Escherichia coli.

Crystals of the fructose-l,6-bisphosphate-dependent pyruvate kinase from Escherichia coli have been grown using the hanging-drop vapour-diffusion technique. The space group was found to be C222(1) with cell dimensions a = 76.8, b = 247.5, c = 132.6 A. Diffraction data to 3.0 A resolution have been recorded and the enzyme molecular symmetry analysed through inspection of the self-rotation function. The crystallized protein is in the allosterically inactive T state.

Journal Article↗
PubMed1995

Crystal structure of Escherichia coli pyruvate kinase type I: molecular basis of the allosteric transition.

BACKGROUND: Pyruvate kinase (PK) plays a major role in the regulation of glycolysis. Its catalytic activity is controlled by the substrate phosphoenolpyruvate and by one or more allosteric effectors. The crystal structures of the non-allosteric PKs from cat and rabbit muscle are known. We have determined the three-dimensional structure of the allosteric type I PK from Escherichia coli, in order to study the mechanism of allosteric regulation. RESULTS: The 2.5 A resolution crystal structure of the unligated type I PK in the inactive T-state shows that each subunit of the homotetrameric enzyme comprises a (beta/alpha)8-barrel domain, a flexible beta-barrel domain and a C-terminal domain. The allosteric and active sites are located at the domain interfaces. Comparison of the T-state E. coli PK with the non-allosteric muscle enzyme, which is thought to adopt a conformation similar to the active R-state, reveals differences in the orientations of the beta-barrel and C-terminal domains of each subunit, which are rotated by 17 degrees and 15 degrees, respectively. Moreover, the relative orientation of the four subunits differs by about 16 degrees in the two enzymes. Highly conserved residues at the subunit interfaces couple these movements to conformational changes in the substrate and allosteric effector binding sites. The subunit rotations observed in the T-state PK induce a shift in loop 6 of the (beta/alpha)8-barrel domain, leading to a distortion of the phosphoenolpyruvate-binding site accounting for the low substrate affinity of the T-state enzyme. CONCLUSIONS: Our results suggest that allosteric control of PK is accomplished through remarkable domain and subunit rotations. On transition from the T- to the R-state all 12 domains of the functional tetramer modify their relative orientations. These concerted motions are the molecular basis of the coupling between the active centre and the allosteric site.

Allosteric Regulation↗
PubMed1995

Evidence for breaking of the active site dimetal cluster in Cu,Co superoxide dismutase upon copper reduction: a polarized absorption spectra study.

The polarized absorption spectra of the cobalt chromophore in orthorhombic crystals of bovine Cu,Co superoxide dismutase (SOD), bearing the copper ion in both the oxidized and the reduced states, are reported together with the calculated isotropic spectrum. All the absorption bands are polarized and a spectral shift, from 598 nm to 588 nm, is observed in only one of them upon copper reduction. This shift, previously described in solution studies, is unequivocally assigned to the detachment of the copper side from the imidazolate bridging copper and cobalt ions in the oxidized catalytic center. At variance with a recent X-ray diffraction investigation on Cu(I),Zn SOD, this result indicates that reduction of copper in Cu,Co SOD is associated to the breaking of the dimetal cluster also in the crystalline state.

Animals↗
PubMed1995

Modulation of the catalytic rate of Cu,Zn superoxide dismutase in single and double mutants of conserved positively and negatively charged residues.

The catalytic rate of four single and three double mutants of Xenopus laevis Cu,Zn superoxide dismutase B, neutralized at Lys120, Asp130, Glu131, and Lys134, has been determined by pulse radiolysis as a function of ionic strength. Neutralization of Glu131 increases the catalytic rate by 80% at low ionic strength, but the effect is reduced to 50% at physiological ionic strength. The rate is unperturbed upon neutralization of Asp130, while neutralization of either of the two lysines drastically decreases the enzyme activity. The Lys120Leu-Lys134Thr and Lys134Thr-Asp130Gln double mutations have an additive and a compensative effect, respectively, on the activity values, while neutralization of the Glu131-Lys134 pair, which also has a compensative effect, gives rise to a faster enzyme at any ionic strength value. The effects observed in the single Asp130Gln and Lys120Leu mutants differ from those reported on human or bovine enzymes [Getzoff et al. (1992) Nature (London) 358, 347-351; Sines et al. (1990) Biochemistry 29, 9403-9412], indicating that some residues occupying the same position in the linear sequence of different Cu,Zn superoxide dismutases have a different functional weight. Our results also suggest that the strategy of multiple charge mutation may be a promising approach in order to increase the catalytic rate of Cu,Zn SODs independently of ionic strength.

Animals↗
PubMed1995

Active site titration of bovine beta-trypsin by N alpha-(N,N-dimethylcarbamoyl)-alpha-aza-lysine p-nitrophenyl ester: kinetic and crystallographic analysis.

Kinetics of bovine beta-trypsin (trypsin) with the N alpha-(N,N-dimethylcarbamoyl)-alpha-aza-lysine p-nitrophenyl ester (Dmc-azaLys-ONp) was obtained at pH 6.2 and 21.0 degrees C. Dmc-azaLys-ONp shows the characteristics of an optimal active site titrant in that it (i) gives titrations in a short time, (ii) is a stable and soluble compound with a stoichiometric reaction that is easily and directly detectable, and (iii) allows titrations over a wide range of enzyme concentration. Moreover, the three-dimensional structure of the trypsin.N alpha-(N,N-dimet hylcarbamoyl)-alpha-aza-lysine acyl.enzyme adduct has been solved by X-ray crystallography at 2.0 A resolution (R = 0.145). The Dmc-azaLys moiety of the active site titrant is sited in the serine proteinase reaction center, and is covalently linked to the OG atom of the Ser195 catalytic residue.

Animals↗
PubMed1995

Formate binding to ferric wild type and mutant myoglobins thermodynamic and X-ray crystallographic study.

The X-ray crystal structure of the formate derivative of ferric loggerhead sea turtle (Caretta caretta) Mb has been determined at 2.0 A resolution (R = 0.164) by difference Fourier techniques. Formate, sitting in the central part of the heme distal site, is coordinated to the heme iron as unidentate ligand, through the O1 oxygen atom, and is hydrogen bonded to the distal His64(E7) NE2 atom through O2. Thermodynamics for formate binding to ferric loggerhead sea turtle Mb, sperm whale Mb, Aplysia limacina Mb, as well as to the VR and VRS mutants of sperm whale Mb were obtained between pH 4.5 and 8.5, at 20.0 degrees C. These results, representing the first structure of a ferric hemoprotein:formate complex solved by X-ray crystallography, outline the role of amino acid residues at positions E7, F8 and E10 in modulating ligand binding properties of oxygen carrying proteins.

Animals↗
PubMed1995

Relationship between portal blood flow measured by image-directed Doppler ultrasonography and hepatic blood flow measured by indocyanine green constant infusion in patients with cirrhosis.

The validity of portal blood flow measurement in image-directed Doppler ultrasound (PBF-IDU) is still under debate. In this study PBF-IDU has been compared with hepatic blood flow measured by the indocyanine green constant infusion technique (HBF-ICG), which is the reference invasive method with which to measure total hepatic blood flow in man (ie, the sum of hepatic artery and portal vein blood flow). In 27 cirrhotic patients with hepatopetal portal blood flow, PBF-IDU was measured by multiplying the portal vein cross-sectional area by the averaged mean velocity of blood in the vessel. About 1 hour later HBF-ICG was measured during hepatic vein catheterization performed to evaluate portal hypertension. In 19 of 27 patients, intrahepatic arterial resistance indices were also measured. PBF-IDU and HBF-ICG were 1.010 +/- 0.555 L/min (M +/- SD) and 1.496 +/- 0.731 L/min, respectively. Blood flow measured by the two methods showed a close correlation (r = 0.80, p < 0.001). The regression line showed that HBF-ICG was systematically higher than PBF-IDU (mean difference +29 +/- 30%). The hepatic artery component of HBF-ICG probably accounted for the difference. An inverse correlation was found between the differences between the two procedures and intrahepatic arterial resistance indices (r = -0.52, p = 0.04), which may be considered indirect parameters of arterial supply. It can be concluded that image-directed Doppler ultrasound is a sufficiently accurate method to measure portal blood flow in cirrhotics.

Adult↗
PubMed1995

Hepatic arterial resistance in cirrhosis with and without portal vein thrombosis: relationships with portal hemodynamics.

BACKGROUND/AIMS: Little information is available on hepatic arterial hemodynamics in cirrhosis because of the invasiveness of methods. Hepatic arterial resistance indexes were evaluated noninvasively by Doppler ultrasonography and were correlated with portal hemodynamics evaluated both noninvasively and invasively. METHODS: Hepatic arterial resistance indexes, portal blood flow velocity and volume, and portal vein congestion index were evaluated in 31 controls and 171 cirrhotic patients with (n = 13) or without (n = 158) portal vein thrombosis. Resistance to portal blood flow was also calculated in 15 patients from hepatic venous pressure gradient, measured by hepatic vein catheterization, and portal blood flow. RESULTS: Resistance indexes were significantly higher in cirrhotics without portal thrombosis than in controls (pulsatility index, 1.30 +/- 0.29 vs. 0.89 +/- 0.09; P < 0.001; resistive index, 0.71 +/- 0.07 vs. 0.59 +/- 0.04; P < 0.001). In patients with portal thrombosis, the pulsatility index (1.86 +/- 0.39) and resistive index (0.81 +/- 0.06) were significantly higher than in controls (P < 0.001) and in patients without thrombosis (P < 0.001). Resistance indexes directly correlated with portal resistance (P < 0.01), the congestion index (P < 0.01), and the degree of esophageal varices (P < 0.01). CONCLUSIONS: Hepatic arterial resistance indexes increase in cirrhosis, particularly with portal vein thrombosis. The pathophysiology of the increase in hepatic arterial resistance seems to be parallel to that of portal resistance.

Adult↗
PubMed1995

Inhibition of bovine beta-trypsin, human alpha-thrombin and porcine pancreatic beta-kallikrein-B by 4',6-diamidino-2-phenylindole, 6-amidinoindole and benzamidine: a comparative thermodynamic and X-ray structural study.

The inhibitory effect of 4',6-diamidino-2-phenylindole (DAPI) and 6-amidinoindole on the catalytic properties of bovine beta-trypsin (trypsin), human alpha-thrombin (thrombin) and porcine pancreatic beta-kallikrein-B (kallikrein) was investigated (between pH 3.0 and 7.0, I = 0.1 M; T = 30.0 +/- 0.5 degrees C), and analyzed in parallel with that of benzamidine, commonly taken as a molecular inhibitor model of serine proteinases. Next, the X-ray crystal structure of the trypsin:DAPI complex was solved at 1.9 A resolution (R = 0.161). Over the whole pH range explored, values of the association inhibition constant (Ki) for DAPI and 6-amidinoindole binding to trypsin, thrombin and kallikrein are higher than those found for benzamidine association, suggesting a binding mode of DAPI to the enzyme primary specificity pocket-based on the indole moiety of the inhibitor. On lowering the pH from 5.5 to 3.0, the decrease in affinity for DAPI, 6-amidinoindole and benzamidine binding to trypsin, thrombin and kallikrein reflects the acidic pK shift of the Asp189 invariant residue, present at the bottom of the primary specificity subsite of the serine proteinases considered, from 4.5, in the free enzyme, to 3.7, in the proteinase:inhibitor complexes. Inspection of the refined crystal structure of the trypsin:DAPI complex, however, does not allow a unique interpretation of the inhibitor binding mode. The present data were analysed in parallel with those reported for related serine (pro)enzyme/inhibitor systems.

Animals↗
PubMed1995

Effect of 8-day therapy with propionyl-L-carnitine on muscular and subcutaneous blood flow of the lower limbs in patients with peripheral arterial disease.

The efficacy of propionyl-L-carnitine in increasing walking capacity in patients with peripheral arterial disease is primarily due to the metabolic effect of the drug, but a direct vasoactive action is also hypothesized. Muscular and subcutaneous blood flow of lower limbs were separately evaluated using the 133-Xenon washout technique in 10 patients with peripheral arterial disease of moderate degree, before and after 8-days of treatment with propionyl-L-carnitine (1 g orally b.i.d.). After treatment, muscular blood flow slightly increased, from 10.7 +/- 13.4 to 14.1 +/- 14.0 ml kg-1 min-1. This increase was not statistically significant (T = -1.6568, P = 0.136). Subcutaneous blood flow was not affected by the treatment (from 26.2 +/- 16.9 to 26.1 +/- 12.5 ml kg-1 min-1, T = 0.0141, P = 0.95). In conclusion, in patients with peripheral arterial disease, short-term therapy with propionyl-L-carnitine had no clinical significant effect on muscular and subcutaneous blood flow of the lower limbs. Therefore, this study suggests that the beneficial effect of this drug on the walking capacity of patients with peripheral arterial disease is not due to a direct vasoactive action. Oral administration of propionyl-L-carnitine was found to be safe, as it did not cause any change in heptic, renal or metabolic functional parameters.

Administration, Oral↗
PubMed1995

Paraumbilical vein patency in cirrhosis: effects on hepatic hemodynamics evaluated by Doppler sonography.

Doppler sonographic portal vein parameters are used for the noninvasive evaluation of portal hypertension in cirrhosis. The patency of a paraumbilical vein is a rather frequent finding in cirrhosis, which may affect hepatic hemodynamics and function. We evaluated portal and hepatic arterial parameters in 184 cirrhotic patients with and without a patent paraumbilical vein and the relationships with paraumbilical blood flow. A patent paraumbilical vein was found in 33.7% of patients. The prevalence was higher (56.8%) in Child C patients. Portal blood flow velocity (PBV) (10.8 +/- 2.2 vs. 9.8 +/- 2.4 cm/sec; P < .01) and volume (PBF) (995.0 +/- 383.8 vs. 811.6 +/- 318.7 mL/min; P < .001) was significantly higher, and effective portal liver perfusion (PLP) (portal blood flow--paraumbilical blood flow) (621.3 +/- 420.8 vs. 811.6 +/- 318.7 mL/min; P < .001) was significantly lower in patients with a patent paraumbilical vein than in those without. These differences were more evident in Child C patients (10.7 +/- 2.0 vs. 8.3 +/- 2.3 cm/sec; 935.7 +/- 378.3 vs. 680.6 +/- 239.4 mL/min; 369.0 +/- 282.0 vs. 680.6 +/- 239.4 mL/min). Portal vein diameter, the congestion index (CI) of the portal vein, hepatic arterial resistance indexes, and the severity of esophageal varices did not differ between the two groups. In patients with a patent paraumbilical vein, the Child-Pugh score and the prevalence of ascites were significantly higher than in those without. In conclusion, the evaluation of PBV and PBF in cirrhotic patients can provide misleading results if a paraumbilical vein is patent, underestimating the degree of portal hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Identification of L-methionine oxidation products in tripeptides, in Met-enkephalin and in the bovine basic pancreatic trypsin inhibitor: 1H and 13C NMR study.

L-methionine (Met) oxidation products in tripeptides, in Met-enkephalin and in the bovine basic pancreatic trypsin inhibitor have been identified by 1H and 13C NMR spectroscopy. The oxidation of Met residues by stoichiometric amounts of chloramine-B, H2O2 and I2 yields a mixture of L-methionine sulfoxide (Met (O)) and dehydro-L-methionine (DH-Met), Met (O) and DH-Met, respectively, at pH 7.0 and 25.0 degrees C. The formation of DH-Met occurs only if the amino-group of Met is not derivatized. The analysis of 1H and 13C NMR spectra allows us to quantitate Met oxidation products, to ascertain the relative proportion of the R and S forms of Met (O) and DH-Met, and to reveal the presence of a Met residue at the N-terminal position in peptides and proteins.

Animals↗
PubMed1995

Duplex Doppler ultrasonography allows a multiorgan noninvasive approach to splanchnic pharmacodynamics in patients with cirrhosis.

UNLABELLED: Duplex Doppler ultrasonography (DDU) is a suitable method to evaluate acute splanchnic hemodynamic effects of vasoactive drugs. It allows the contemporary evaluation of arterial and venous splanchnic parameters. Forty-six cirrhotic patients with esophageal varices were investigated by DDU. Portal blood flow mean velocity (PBV) (cm/s), portal blood flow volume (PBF) (ml/min), pulsatility index (PI) [(maximum-minimum)/mean velocity] in the superior mesenteric artery, in intrahepatic arteries (main branches), in an instrasplenic artery, and in interlobar arteries of the kidneys were measured before and 120-180 min after the administration of nadolol (80 mg p.o.) in 24 patients, and before and 120 min after placebo administration in 9 patients. In 13 patients who were chronically treated with nadolol, DDU parameters were evaluated before and 90 min after the administration of isosorbide-5-mononitrate (20 mg p.o.). RESULTS: placebo caused no hemodynamic change. After nadolol, heart rate decreased (-22 +/- 8%), and so did PBV and PBF (8.8 +/- 3.4 vs. 10.9 +/- 3.2, -20 +/- 17%, p < 0.0001; 660 +/- 347 vs. 852 +/- 371, -24 +/- 18%, p < 0.0001). Mesenteric PI increased (2.72 +/- 0.67 vs. 2.28 +/- 0.56, +21 +/- 25%, p = 0.005). Hepatic, splenic, and renal PIs showed slight, not significant changes (1.42 +/- 0.41 vs. 1.38 +/- 0.32, p = NS; 1.05 +/- 0.23 vs. 0.99 +/- 0.21, p = NS; 1.24 +/- 0.26 vs. 1.19 +/- 0.20, p = NS, respectively). After the administration of isosorbide-5-mononitrate, PBV decreased (8.2 +/- 2.0 vs. 9.4 +/- 2.3, -12 +/- 13%, p = 0.006), while PBF did not modify (648 +/- 189 vs. 711 +/- 209, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗