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Biomedical subjects

M Bolognesi

Publications and source records attributed to M Bolognesi.

At least 199 records · Page 11Linked to original sources
PubMed1988

Reassessment of copper stoichiometry in ascorbate oxidase.

A very pure ascorbate oxidase solution was obtained by dissolving a crystalline sample of the enzyme. The ratio between 280 and 610 nm absorbancies was 22.5. It contained 8.0 +/- 0.2 Cu ions, 50% EPR detectable, per dimeric molecule (140,000 M.W.) with a molar extinction coefficient of 10,000 cm-1 at 610 nm. Two Cu ions were removed by treatment with N,N-diethyldithiocarbamate. The optical blue absorption band was unaffected, while two EPR detectable Cu ions were lost, with disappearance of the type 2 Cu signal. It is concluded that native ascorbate oxidase contains two type 1, two type 2, and four type 3 Cu ions.

Ascorbate Oxidase↗
PubMed1988

Nicotinic acetylcholine receptor: a structural model for alpha-subunit peptide 188-201, the putative binding site for cholinergic agents.

A peptide corresponding to amino acid sequence 188-201 of the alpha-subunit of Torpedo AChR binds alpha-Bgtx. The S-S bridge between Cys 192 and 193 is essential for the binding as Tyr in position 189. The same sequence 188-201 corresponding to human AChR, which instead of Tyr has a Thr in position 189, binds alpha-Bgtx with a much lower efficiency. Monoclonal antibodies raised against Torpedo peptide 188-201 recognize Torpedo AChR and antibodies against Torpedo AChR recognize peptide 188-201 indicating that the synthetic peptide and the corresponding sequence in the native molecule share some immunological epitopes. With computer graphics and energy refinement a molecular model of this peptide has been elaborated.

Amino Acid Sequence↗
PubMed1988

Zymogen activation: effect of peptides sequentially related to the bovine beta-trypsin N-terminus on Kazal inhibitor and benzamidine binding to bovine trypsinogen.

The activating effect of peptides sequentially related to the Ile 16-Val17-Gly18 N-terminus of bovine beta-trypsin (namely Ile-Val-Gly, Ile-Val, Ile-Leu, Ile-Ala, Val-Val, Leu-Val, and Val-Leu) on the thermodynamic parameters for the binding of the porcine pancreatic secretory trypsin inhibitor (Kazal inhibitor) and benzamidine to bovine trypsinogen was investigated at pH 5.5 (Bis tris-HCl buffer, I = 0.1 M) and T = 21 +/- 0.5 degrees C. Thermodynamic parameters for Kazal inhibitor and benzamidine association to the binary peptide/zymogen adducts are more favorable than those observed for ligand binding to the proenzyme alone, although never as much as those reported for the formation of bovine beta-trypsin/Kazal inhibitor and bovine beta-trypsin/benzamidine adducts. Analogously, the affinity of activating peptides for the binary proenzyme/Kazal inhibitor and binary proenzyme/benzamidine complexes is higher than that observed for peptide binding to free bovine trypsinogen. Differences in affinity for ligand binding to free bovine trypsinogen, to its binary adducts and to bovine beta-trypsin suggest the presence of different activation levels of the proenzyme, none of which structurally coincide with that achieved in bovine beta-trypsin. The existence of different discrete states suggests that the zymogen-to-active enzyme transition should not be considered as a two-state process but as a multistep event.

Amidines↗
PubMed1988

Structural alignment and analysis of two distantly related proteins: Aplysia limacina myoglobin and sea lamprey globin.

Two new globin structures have recently been determined at high resolution: the globin from the mollusc Aplysia limacina at 1.6 A resolution and a new refinement of the structure from sea lamprey. Two amino acid sequences of these homologous molecules have only 30% residue identity in an optimal alignment. We discuss some of the problems arising in the alignment of Aplysia globin with other globins of known structure, a challenging problem because of the distant relationship. Four independent approaches were applied to the alignment of the Aplysia and lamprey globins, including those based on individual sequence comparisons, structural analysis, and the relatively new method of templates or fingerprints derived for an entire family of proteins. We also compare these two new structures with what is already known about the globin family. A detailed description of the two structures shows that the two molecules contain the main structural features common to all the globins so far studied, with several minor but interesting hitherto unobserved variations.

Amino Acid Sequence↗
PubMed1988

Long-term effect of nadolol on quantitative liver function tests in patients with cirrhosis.

Nadolol, a non-cardioselective beta adrenoreceptor blocking agent, has been reported to decrease portal pressure without affecting liver function in cirrhotic patients treated for 1 month. There were no data about the long-term effects of nadolol on liver function. In 11 patients with cirrhosis and portal hypertension galactose eliminating capacity, aminopyrine metabolic capacity, ICG clearance and IGC intrinsic hepatic clearance according to the "parallel tube" model were measured before and after 6 months of treatment with nadolol at a dose reducing resting heart rate by approximately 25%. No significant variation in any of these parameters was found. Thus 6 months of continuous oral administration of nadolol did not further impair liver function in cirrhotics.

Adult↗
PubMed1988

Hemodynamic changes of systemic, hepatic, and splenic circulation following triglycyl-lysin-vasopressin administration in alcoholic cirrhosis.

Triglycyl-lysin-vasopressin is a long-acting vasopressin derivative which is under consideration for the treatment of acute variceal bleeding in cirrhosis. However, its splanchnic hemodynamic effects have not been investigated thoroughly. In 11 patients with alcoholic cirrhosis, systemic and splanchnic hemodynamics were evaluated before and 20-40 min after intravenous administration of 2 mg triglycyl-lysin-vasopressin. Following the drug administration, heart rate decreased by 10% and cardiac index by 22% on the average, respectively; mean arterial pressure increased by 14% and systemic vascular resistence index by 48%. Hepatic venous pressure gradient showed a marked and persistent fall, averaging 31%. Hepatic and splenic blood flow decreased by 31% and 56%, respectively. A significant correlation was found between the decrease in hepatic venous pressure gradient and in splenic blood flow. By contrast, the decrease in the hepatic venous pressure gradient was not significantly correlated to the decrease in hepatic blood flow or in cardiac index. We conclude that in patients with alcoholic cirrhosis, triglycyl-lysin-vasopressin decreases portal pressure as well as hepatic and splenic blood flows. The decrease in portal pressure was due to the decrease in splanchnic blood inflow and not to the decrease in cardiac index.

Adult↗
PubMed1988

Effect of inositol hexakisphosphate on the spectroscopic properties of the nitric oxide derivative of ferrous naturally glycated human hemoglobin HbA1c.

The effect of inositol hexakisphosphate (IHP) on the spectroscopic (EPR and absorbance) properties of the nitric oxide derivative of ferrous naturally glycated human hemoglobin HbA1c (HbA1cNO) has been investigated quantitatively. The results obtained show that 1) both in the absence and presence of IHP, the EPR and absorbance spectra of HbA1cNO show the same basic characteristics described for the nitrosyl derivative of ferrous HbA0, the nonglycated major component of human hemoglobin (HbA0NO); and 2) HbA1cNO binds IHP with an apparent dissociation equilibrium constant (upsilon = 1.8 x 10(-2) M), which is at least four orders of magnitude higher than that estimated for the polyphosphate interaction with HbA0NO (less than or equal to 3 x 10(-6) M). These data provide further independent evidence that interaction(s) of polyphosphates at the specific cleft between beta-chains along the dyad-axis is sterically hindered in HbA1c by the presence of the two glucose residues covalently bound to the N-termini of beta-chains, this finding being in agreement with the reduced effect of polyanions on HbA1c spectral and ligand-binding properties.

Electron Spin Resonance Spectroscopy↗
PubMed1988

The calcium-channel blocker, verapamil, does not improve portal pressure in patients with alcoholic cirrhosis.

1. Recently the calcium-channel blocker, verapamil, has been reported to decrease portal pressure in rats with experimental cirrhosis and in patients with liver cirrhosis. 2. In eight patients with alcoholic cirrhosis the effect of verapamil (5 mg i.v.) on systemic and splanchnic haemodynamics was investigated. 3. Mean arterial pressure, wedged hepatic venous pressure, hepatic venous pressure gradient, and verapamil plasma concentrations were measured before and at 10, 20, 30 min following 5 mg i.v. administration of verapamil. At 30-40 min cardiac output, systemic vascular resistance and hepatic blood flow were also measured. 4. Verapamil plasma concentrations averaged 47.9 +/- 52.0, 36.5 +/- 36.3, 31.3 +/- 33.9 ng ml-1 at 10, 20, 30 min respectively: mean arterial pressure and systemic vascular resistance decreased significantly (-9% and -14% respectively), and cardiac index increased significantly (+8%). Wedged hepatic venous pressure and hepatic venous pressure gradient remained unchanged, variations never exceeding 0.2 kPa. Hepatic blood flow increased significantly by 12%. 5. These results show that i.v. administration of 5 mg verapamil does not decrease portal pressure in alcoholic cirrhosis. This lack of effect is probably the consequence of a balance between decrease in porto-hepatic vascular resistance and increase in splanchnic blood inflow.

Adult↗
PubMed1988

Binding of the recombinant proteinase inhibitor eglin c from leech Hirudo medicinalis to human leukocyte elastase, bovine alpha-chymotrypsin and subtilisin Carlsberg: thermodynamic study.

The effect of pH and temperature on the apparent association equilibrium constant (Ka) for the binding of the recombinant proteinase inhibitor eglin c from leech Hirudo medicinalis to human leukocyte elastase (EC 3.4.21.37), bovine alpha-chymotrypsin (EC 3.4.21.1) and subtilisin Carlsberg (EC 3.4.21.14) has been investigated. On lowering the pH from 9.5 to 4.5, values of Ka for eglin c binding to the serine proteinases considered decrease thus reflecting the acid-pK shift of the invariant histidyl catalytic residue (His57 in human leukocyte elastase and bovine alpha-chymotrypsin, and His64 in subtilisin Carlsberg) from congruent to 6.9, in the free enzymes, to congruent to 5.1, in the enzyme:inhibitor adducts. At pH 8.0, values of the apparent thermodynamic parameters for eglin c binding are: human leukocyte elastase - Ka = 1.0 x 10(10) M-1, delta G phi = -13.4 kcal/mol, delta H phi = +1.8 kcal/mol, and delta S phi = +52 entropy units; bovine alpha-chymotrypsin -Ka = 5.0 x 10(9) M-1, delta G phi = -13.0 kcal/mol, delta H phi = +2.0 kcal/mol, and delta S phi = +51 entropy units; and subtilisin Carlsberg - Ka = 6.6 x 10(9) M-1, delta G phi = -13.1 kcal/mol, delta H phi = +2.0 kcal/mol, and delta S phi = +51 entropy units (values of Ka, delta G phi and delta S phi were obtained at 21 degrees C; values of delta H phi were temperature independent over the range explored, i.e. between 10 degrees C and 40 degrees C; 1 kcal = 4184J).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

[Liver metabolism of indocyanine green and aminopyrine in liver cirrhosis: relations with functioning liver cell mass].

Hepatic clearance of indocyanine green, a drug with a high hepatic extraction rate, and breath tests with aminopyrine, a drug with a low hepatic extraction ratio, were calculated in 26 patients with liver cirrhosis. In addition galactose elimination capacity was calculated as an index of functional liver cell mass. All these parameters resulted significantly correlated with each other. These results confirm the view that during liver cirrhosis, metabolism of drugs with high and low hepatic extraction rates can be described according to the intact hepatocyte theory.

Adult↗
PubMed1987

Binding of the bovine pancreatic secretory trypsin inhibitor (Kazal) to bovine serine (pro)enzymes.

The effect of temperature and pH on the association equilibrium constant (Ka) for the binding of the bovine pancreatic secretory trypsin inhibitor (bovine PSTI, type I; Kazal inhibitor) to bovine beta-trypsin, bovine alpha-chymotrypsin and bovine trypsinogen has been investigated. The results suggest that serine (pro)enzyme inhibitor interaction involves both rigorous spatial configuration and molecular flexibility.

Amino Acid Sequence↗
PubMed1987

Crystal structure of the trigonal form of bovine beta-lactoglobulin and of its complex with retinol at 2.5 A resolution.

The structure of the trigonal crystal form of bovine beta-lactoglobulin has been determined by X-ray diffraction methods. An electron density map, calculated with phases obtained by the multiple isomorphous replacement method, served as a starting point for alternate cycles of model building and restrained least-squares refinement. The model of the molecule fitted to the initial Fourier map was the one built for the orthorhombic crystal form of beta-lactoglobulin, solved at 2.8 A resolution (1 A = 0.1 nm). The final R factor for 1456 atoms (1276 non-hydrogen protein atoms and 180 solvent atoms) is 0.22, including 5245 reflections from 6.0 to 2.5 A. The molecule shows significant differences in the two crystal forms mentioned, mainly due to different packing. In the trigonal form, the species crystallized does not appear to be dimeric, but a linear polymer with tight intermolecular contacts. A difference electron density map between the complex of beta-lactoglobulin with retinol and the native protein shows no significant peaks in the cavity which, in the similar retinol-binding protein, binds the chromophore. Instead, differences are found at a surface pocket, which is limited almost completely by hydrophobic residues.

Animals↗
PubMed1987

Binding of the Ile-Val and Val-Val effector dipeptides to the binary adducts of bovine trypsinogen with Kunitz and Kazal inhibitors as well as the acylating agent p-nitrophenyl p-guanidinobenzoate. A thermodynamic and kinetic study.

Thermodynamics and kinetics of binding of the Ile-Val and Val-Val effector dipeptides to the binary adducts of bovine trypsinogen with the bovine basic pancreatic trypsin inhibitor (BPTI, Kunitz inhibitor), the porcine pancreatic secretory inhibitor (PSTI, Kazal inhibitor) and the acylating agent p-nitrophenyl p-guanidinobenzoate have been investigated at pH 7.4 and 21(+/- 0.5) degrees C. The affinity of both effector dipeptides for bovine trypsinogen: BPTI and bovine trypsinogen: PSTI binary adducts is higher than that observed for the formation of the dipeptide: bovine trypsinogen: p-guanidinobenzoate ternary complexes; moreover, the affinity of Ile-Val for the zymogen binary adducts is higher than that observed for Val-Val association. Binding of Ile-Val and Val-Val to the bovine trypsinogen binary complexes conforms to the induced-fit model, which consists of a fast pre-equilibrium followed by intramolecular isomerization change(s), the latter fast pre-equilibrium followed by intramolecular isomerization change(s), the latter representing the rate-limiting first-order process. For the three bovine trypsinogen systems considered, the rate of the intramolecular isomerization change(s) is essentially independent of the nature of the dipeptide and of the proenzyme binary complex.

Animals↗
PubMed1987

The use of human albumin millimicrospheres tagged with 99mTc in the evaluation of the removal capacity of the reticuloendothelial system.

Liver uptake kinetics of 99mTc labelled millimicrospheres of human serum albumin (MM) was studied in 16 subjects. Every subject received four doses of MM intravenously. The uptake constant decreased progressively with increasing dose. The maximum liver removal capacity, a parameter which is independent of liver blood flow, was calculated according to the method of Iio and Wagner (1963). From these data we conclude that MM are taken up by the reticuloendothelial system (RES) with saturable kinetics, and they are suitable for clinical use to evaluate RES function in man.

Adult↗
PubMed1987

Renal effects of nadolol in cirrhosis.

The effects of nadolol on renal haemodynamics and function, and on the renin-angiotensin-aldosterone system and on renal prostaglandin production were studied in eighteen cirrhotics. After 1 month of treatment, nadolol had significantly decreased cardiac output by 25% without affecting arterial pressure, renal plasma flow or renal vascular resistance. Glomerular filtration rate, filtration fraction and the proportion of the cardiac output delivered to the kidneys were significantly increased. The renin-angiotensin-aldosterone system was suppressed and urinary PGE2 excretion was slightly increased. The latter effects were not correlated with those on renal haemodynamics and function.

Cardiac Output↗
PubMed1987

Effects of isosorbide dinitrate on portal hypertension in alcoholic cirrhosis.

It has recently been reported that vasodilators lower portal pressure in patients with cirrhosis. This effect, however, is not definitively proven. The effect of isosorbide dinitrate (5 mg sublingually) on splanchnic and systemic hemodynamics was investigated in 13 patients with alcoholic cirrhosis and portal hypertension. The administration of isosorbide dinitrate reduced hepatic venous pressure gradient by 34% (P less than 0.001), mean arterial pressure by 30% (P less than 0.001), cardiac index by 17% (P less than 0.001) and systemic vascular resistance by 11% (P = 0.05). Hepatic blood flow was not affected by the treatment. Significant correlations were found between the decrease in hepatic venous pressure gradient and that of cardiac index (P less than 0.05) and mean arterial pressure (P less than 0.05). These data indicate that isosorbide dinitrate lowers portal pressure in patients with cirrhosis. Decrease in cardiac output, rise in splanchnic arterial vascular resistance and decrease in porto-hepatic resistance seem to participate in determining the effect.

Adult↗
PubMed1987

Long-term effects of beta-adrenergic blockade with nadolol on hepatic and renal haemodynamics and function in cirrhotics.

Non-cardioselective beta-blockers are used for prevention of re-bleeding from oesophageal varices in cirrhotics with portal hypertension. Nadolol, a non-cardioselective beta-blocker with a low liposolubility and a low hepatic metabolism, has been demonstrated to decrease portal pressure in cirrhotic patients. Since cirrhotics need long-term treatment, we investigated long-term effects of beta-adrenergic blockade with nadolol on hepatic and renal haemodynamics and function in a group of patients with cirrhosis and portal hypertension. In 19 patients with cirrhosis, after one and six months of treatment with nadolol hepatic venous pressure gradient showed a significant and persistent decrease, averaging 19% and 22%, respectively. Hepatic function and renal haemodynamics and function remained unaffected. Oesophageal varices severity was lowered in 11/19 patients after one month, in 9/16 after six months, in 8/14 after 12 months and in 5/10 after 18 months. Our results showed that, also after long-term treatment, nadolol decreases portal pressure and, in approximately 50% of patients, oesophageal varices severity, without side-effects on liver and renal function.

Adult↗