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Biomedical subjects

S Scalia

Publications and source records attributed to S Scalia.

49 records · Page 3Linked to original sources
PubMed1990

Persistent arteriolar constriction in microcirculation of the terminal ileum following moderate hemorrhagic hypovolemia and volume restoration.

A stable in vivo preparation of moderate hypovolemia with prompt volume restoration was produced in anesthetized rats. The microcirculation of the terminal ileum was observed in vivo videomicroscopy, and changes in mean arterial pressure (MAP) as well as arteriolar diameters were recorded after a 30-min period in which the MAP was reduced by 50% by bleeding. Volume was restored with shed blood alone (control); dextran 70 alone (dextran); or dextran + hypertonic (7.5%) saline (dextran + HS). A final group of rats was pretreated with allopurinol 5 mg/kg and then treated identically to the control group to assess the role of the xanthine oxidase system in microcirculation changes following hemorrhage. MAP was restored to normal by return of shed blood in control animals, but inflow arterioles (A1) remained significantly constricted. MAP was significantly higher and A1 arteriolar dilation was observed in the dextran + HS group. Responses in allopurinol-pretreated animals were not different from the responses seen in control animals. We conclude that persistent arteriolar constriction is produced by moderate hypovolemia and this effect is ameliorated by volume restoration with dextran + HS.

Allopurinol↗
PubMed1990

An improved purification procedure for conjugated bile acids using octadecyl-bonded silica cartridges.

A rapid procedure for the extraction of conjugated bile acids from human fluids using pre-packed octadecyl-bonded silica cartridges is described. The method was compared with the other procedures reported in the literature and was found to produce a higher degree of sample purification and to achieve satisfactory accuracy and reproducibility. The present procedure is applicable to the high-performance liquid chromatographic assay of bile acid conjugates in human bile, gastric juice, serum and urine.

Bile↗
PubMed1989

Controlled proteolysis of mouse epidermal growth factor. An RP-HPLC and 1H-n.m.r. study.

Tryptic digestion of the mouse epidermal growth factor (mEGF) and the chromatographic separation of its proteolytic fragments by RP-HPLC affords the isolation of the pure hormone, of its 1-48 (Des(49-53)mEGF) and 1-45 (Des(46-53)mEGF) derivatives, and of the carboxyl-terminal pentapeptide W49-W50-E51-L52-R53. Kinetics of mEGF proteolytic degradation follows a two-state time-course: native mEGF being converted into Des(49-53)mEGF with an apparent half-time of 10 min; and Des(49-53)mEGF subsequently hydrolyzed to Des(46-53)mEGF with an apparent half-time of 7 h. Native mEGF and its proteolytic fragments have been characterized by 1H-n.m.r. spectroscopy. In the aromatic and aliphatic regions, the 1H-n.m.r. spectrum proved to be a sufficiently sensitive probe for following controlled proteolysis, and for analyzing the influence of the carboxyl-terminal sequence on the hormone conformation and stability.

Amino Acid Sequence↗
PubMed1988

Simultaneous determination of free and conjugated bile acids in human gastric juice by high-performance liquid chromatography.

A high-performance liquid chromatographic procedure has been developed for the simultaneous assay of the major free bile acids and the corresponding glycine and taurine conjugates in man. No preliminary fractionation into the free, glyco- and tauro-conjugated forms was required. An Ultrasphere ODS column with UV detection at 210 nm and methanol-acetate buffer gradient elution were used. The retention volume of the conjugates was dependent on the sodium acetate concentration in the mobile phase. The method is applicable to the quantification of intragastric bile acids with satisfactory sensitivity, selectivity and precision. Unconjugated and conjugated bile acids present in the gastric juice of patients with bile reflux gastritis were determined directly after Sep-Pak C18 cartridge purification.

Bile Acids and Salts↗
PubMed1988

HPLC assay of conjugated bile acids in gastric juice during ursodeoxycholic acid (Deursil) therapy of bile reflux gastritis.

A rapid high-performance liquid chromatographic method for the direct assay of the taurine and glycine conjugated bile acids in human gastric juice is described. After extraction with Sep-Pak C(18) cartridges, compounds are baseline resolved on a reversed-phase column and detected by UV absorption. The procedure is linear from 10 micromol l(-1) to 1200 micromol l(-1), with recovery rates ranging from 87 to 100%. The present method is applicable to the quantification of bile acid conjugates in human gastric bile with satisfactory sensitivity, selectivity and precision. Intragastric bile acid compositions in 10 patients with bile reflux gastritis during Deursil or placebo treatment are presented.

Journal Article↗
PubMed1987

Inhibition of serine proteinases by tetra-p-amidinophenoxy-neo-pentane: thermodynamic and molecular modeling study.

The inhibitory effect of the aromatic tetra-benzamidine derivative tetra-p-amidinophenoxy-neo-pentane (TAPP) on the catalytic properties of beta-trypsin (EC 3.4.21.4), alpha-thrombin (EC 3.4.21.5), factor Xa (EC 3.4.21.6), Lys77-plasmin (EC 3.4.21.7) and beta-kallikrein-B (EC 3.4.21.35) was investigated (between pH 2 and 8, I = 0.1 M; T = 37 +/- 0.5 degrees C), and analyzed in parallel with that of benzamidine, commonly taken as a molecular inhibitor model of serine proteinases. Over the whole pH range explored, TAPP and benzamidine show the same values of the dissociation inhibition constant (Ki) for beta-trypsin; at variance with the affinity of TAPP for alpha-thrombin, factor Xa, Lys77-plasmin and beta-kallikrein-B which is higher than that found for benzamidine association around neutrality, but tends to converge in the acidic pH limb. On lowering the pH from 5.5 to 3.0, values of Ki for TAPP binding to beta-trypsin as well as for benzamidine association to all the enzymes investigated decreased thus reflecting the pK-shift, upon inhibitor binding, of a single ionizing group. Over the same pH range, values of Ki for TAPP binding to alpha-thrombin, factor Xa, Lys77-plasmin and beta-kallikrein-B may be described as depending on the pK-shift, upon inhibitor association, of two equivalent proton-binding amino acid residues. Considering the X-ray three-dimensional structures and the computer-generated molecular models of serine proteinases: TAPP and :benzamidine adducts, the observed binding behaviour of TAPP and benzamidine to the enzymes considered has been related to the inferred stereochemistry of proteinase: inhibitor contact region(s).

Amidines↗
PubMed1986

Proton NMR and photochemically induced dynamic nuclear polarization studies of peptide fragments obtained by controlled proteolysis of mouse epidermal growth factor.

Controlled proteolysis of epidermal growth factor from the mouse leads to fragments of mouse epidermal growth factor containing residues 1-48 and 1-45. The COOH-terminal pentapeptide appears to play a crucial role in determining the hydrophobic interactions between the hormone and the stationary phase during gel chromatography on TSK-125 gel. Proton NMR studies indicate that the overall structure of mouse epidermal growth factor is retained in the protein devoid of the COOH-terminal pentapeptide, while subsequent cleavage of the peptide bond between Arg-45 and Asp-46 starts to perturb the proton resonances most characteristic of the tertiary structure of the hormone, especially those from the aromatic ring protons of Tyr-37. Consequently, photochemically induced dynamic nuclear polarization experiments show an increased exposure of Tyr-37 in the fragment of mouse epidermal growth factor containing residues 1-48. Nuclear Overhauser data suggest that structural changes do occur on fragmentation but seem to be localized in the tiered-beta-sheet domain which contains Tyr-37.

Amino Acid Sequence↗
PubMed1986

Gabexate mesylate inhibition of serine proteases: thermodynamic and computer-graphics analysis.

The inhibitory effect of gabexate mesylate, which is used therapeutically in the treatment of pancreatitis and disseminated intravascular coagulation, and as a regional anticoagulant agent for hemodialysis, has been measured on bovine factor Xa, bovine alpha-thrombin, human Lys77-plasmin, human urinary kallikrein, human urokinase, porcine pancreatic beta-kallikrein-B, and bovine beta-trypsin catalyzed hydrolysis of p-nitrophenyl esters of N-alpha-carbobenzoxy-L-arginine and N-alpha-carbobenzoxy-L-lysine. On the basis of enzyme:gabexate mesylate affinities, the serine proteases can be arranged as follows: human urinary kallikrein approximately porcine pancreatic beta-kallikrein-B much less than bovine beta-trypsin approximately bovine factor Xa approximately human Lys77-plasmin approximately human urokinase approximately bovine alpha-thrombin. The mode of binding of gabexate mesylate to the serine proteases conforms to the active-reactive site geometries observed in their complexes with natural and synthetic inhibitors. Differences in gabexate mesylate affinities for these proteases reflect structural differences at their primary specificity subsite, which have been investigated by comparative analysis of amino acid sequences and by computer-graphics techniques.

Animals↗
PubMed1986

Guanidinophenyl derivatives of pyrazole: synthesis and inhibitory effect on serine proteinases, blood coagulation and platelet aggregation.

Guanidinophenyl derivatives of pyrazole have been synthesized. Their inhibitory effects on (i) bovine trypsin, bovine thrombin, porcine pancreatic kallikrein catalyzed hydrolysis of p-nitro anilide of N alpha -benzoyl-arginine and (ii) blood coagulation and platelet aggregation, were investigated. The kinetic behaviour of all compounds conformed to that of a reversible competitive inhibition pattern, and they were also found to act in vitro as inhibitors of platelet aggregation induced by ADP.

Animals↗
PubMed1985

Ethyl esters of N-(3- and N-(4-amidinobenzoyl)(-L-)amino acids: synthesis and antiproteolytic activity towards bovine trypsin and porcine pancreatic kallikrein.

Ethyl esters of N-(3- and N-(4-amidinobenzoyl)(-L-)amino acids (namely, glycine, alanine, valine, leucine and phenylalanine) were synthesized and their inhibitory effect on the bovine trypsin and porcine pancreatic kallikrein catalyzed hydrolysis of p-nitroanilides of amino acids was investigated, at pH 8.1 and 37 degrees, in parallel with the effect of ethyl and/or methyl esters of N-benzoyl(-L-)amino acids and benzamidine. For both proteinases, the inhibitory effect of ethyl esters of N-(3- and N-(4-amidinobenzoyl)(-L-)amino acids is independent of the aminoacidic side chain, is closely similar to that of benzamidine (which binds at the S1 subsite of the proteinases examined and is commonly taken as a molecular inhibitor-model), and is higher by at least 10-fold than that of ethyl and/or methyl esters of N-benzoyl(-L-)amino acids (depending on the aminoacidic residue). On structural grounds, the peculiar inhibitory behaviour of ethyl esters of N-(3- and N-(4-amidinobenzoyl)(-L-)amino acids has been related to the interaction of the positively charged substituent at the N-position with the Asp189 residue present in the primary specificity subsite (S1) of bovine trypsin and porcine pancreatic kallikrein. The consistently lower affinity for porcine pancreatic kallikrein of all the inhibitors considered, as compared to bovine trypsin, may be related to the marked structural differences of the primary specificity subsite of these two serine proteinases.

Amidines↗
PubMedDate not supplied

Reversed-phase HPLC study on the in vitro enzymic degradation of dermorphin.

A high-performance liquid chromatographic (HPLC) method for the separation of the opioid heptapeptide dermorphin and related fragments has been developed. The chromatographic system was applied in the study of the kinetics of degradation of dermorphin (Der) in various tissues. Der was found to be extremely resistant to human and rat plasma (T 1/2 greater than 180 min). Upon incubation with homogenates of rat brains and kidneys, Der was cleaved with a half-life of 20.8 +/- 2.2 min and 2.4 +/- 0.3 min respectively. The catabolite formed was identified, in both tissues, as the N-terminal tetrapeptide H-Tyr-D-Ala-Phe-Gly-OH. The stability to rat kidney and brain of the N-terminal hexa- and pentapeptides and of the [4 psi 5, NHCO] Der analogue was also investigated. The nature of the enzyme systems involved in the in vitro degradations is discussed.

Analgesics, Opioid↗