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Biomedical subjects

A Tripodi

Publications and source records attributed to A Tripodi.

At least 127 records · Page 7Linked to original sources
PubMed1989

Familial dysfunction of protein S.

We describe a previously unreported defect of protein S characterized by low levels of cofactor activity for activated protein C contrasting with low normal levels of total and free protein S antigen. The distribution of protein S between the free form and the form complexed with the complement component C4b-binding protein was normal on two-dimensional immunoelectrophoresis. The proband developed juvenile deep-vein thrombosis while taking oral contraceptives. Her defect was transmitted in an autosomal dominant fashion from her asymptomatic mother. Other relatives carrying the same laboratory abnormality (mother, maternal uncle, two sisters and one brother) were also asymptomatic. We postulate that the defect is due to a dysfunctional protein S present in plasma in normal amounts and with normal proportions of the free and complexed forms of the protein.

Adult↗
PubMed1989

Lipid composition and fluidity of liver plasma membranes from rats with chronic dietary iron overload.

Liver plasma membranes isolated from rats with chronic dietary iron overload showed a large modification of their phospholipid fatty acid composition. Specifically, a significant decrease in polyunsaturated fatty acids and a parallel increase in saturated fatty acids was observed. This pattern was consistent with the in vivo occurrence of lipoperoxidative reactions in the liver plasma membranes. However, neither change in the cholesterol/phospholipid molar ratio nor in the lipid/protein ratio was detected. Direct measurement of the plasma membrane fluidity state by electron spin resonance spectrometry did not reveal any difference between control and iron-treated rats. These findings indicate that chronic dietary iron overload can induce lipid peroxidation of rat liver plasma membranes, but this event does not bring about modification in the physical state of the membrane.

Animals↗
PubMed1989

Determinants of bile secretion: effect of bile salt structure on bile flow and biliary cation secretion.

The effect of five bile salts, deoxycholate, chenodeoxycholate, cholate, ursodeoxycholate, and ursocholate, possessing (in decreasing order) different hydrophobicity, on bile flow and biliary secretion of total calcium, magnesium, sodium, and potassium was studied in 10 patients with T-tubes. Each subject was infused intraduodenally with one or two bile salts, given separately, to produce a selective enrichment of biliary bile salts with the infused bile salt. The choleresis induced per 1-mumol increase of bile salt output was greater during the secretion of 7 beta-hydroxylated bile salts, ursodeoxycholate (0.029 ml), and ursocholate (0.027 ml), followed in decreasing order by deoxycholate (0.023 ml), chenodeoxycholate (0.019 ml), and cholate (0.009 ml). Deoxycholate stimulated the greatest increase in cation secretion per unit increase in bile salt output, followed by chenodeoxycholate and cholate. The two 7 beta-hydroxylated bile salts induced greater cation secretion than did their 7 alpha-epimers. Whereas biliary concentration of divalent cations differed depending on the structure and concentration of the infused bile salt, the concentration of monovalent cations was constant for any species and concentration of infused bile salt. Relationships between bile salt and divalent cation concentration indicate that 1 mumol of secreted biliary deoxycholate, the most hydrophobic bile salt, associates with the greatest amount of calcium (0.046 mumol) and magnesium (0.022 mumol), followed by chenodeoxycholate (0.020 and 0.010 mumol, respectively) and cholate (0.012 and 0.008 mumol, respectively). The capacity of ursodeoxycholate and ursocholate to associate with calcium and magnesium seems to be less than that of their 7 alpha-epimers. These data suggest that of the common bile salts, the more hydrophobic bile salts stimulate bile flow and cation secretion better than the more hydrophilic bile salts, whereas ursodeoxycholate and ursocholate are more effective than their more hydrophobic 7 alpha-epimers. Whereas different bile salts seem to influence the secretion of sodium and potassium mainly by virtue of their choleretic properties, the effect of bile salt structure on biliary secretion of calcium and magnesium suggests the presence of a secretory link that might be consistent with cation-bile salt binding.

Bile↗
PubMed1989

Automated amidolytic method for evaluating the activated partial thromboplastin time compared with a conventional coagulation method.

We report studies of the validity and clinical application of a new amidolytic method for evaluating the activated partial thromboplastin time (APTT) compared with a conventional clotting method. The results with the two methods were well correlated for normal plasma and plasma from hemophilia patients. Congenital deficiencies of of the intrinsic coagulation pathway other than hypo- and dysfibrinogenemia detected by the amidolytic method agreed with those detected by the clotting APTT. The results with the two methods for plasma from patients under heparin treatment were statistically different, suggesting a lesser sensitivity of the amidolytic method to heparinization. The use of the amidolytic APTT reagent in combination with factor VIII and IX deficient plasma allowed the measurement of both factors. The results obtained with normal and hemophilic plasma were in agreement with those obtained with the one-stage clotting method in all except two occasions. Even though the amidolytic method demonstrated the presence of the lupus anticoagulant in the majority of tested samples of known lupus subjects, it was less sensitive to the abnormality than the clotting method.

Adult↗
PubMed1988

Antithrombin Milano, single amino acid substitution at the reactive site, Arg393 to Cys.

Antithrombin Milano is an unusual antithrombin variant, exhibiting an abnormal, fast moving component on crossed immunoelectrophoresis (in the absence of heparin). Antithrombin isolated from the propositus could be resolved into two peaks on anion-exchange chromatography; antithrombin Milano peak 1 of Mr approximately 60,000 which could inhibit thrombin, and antithrombin Milano peak 2 of Mr approximately 120,000 which was inactive. The latter component also reacted with antisera to both antithrombin and albumin on immunoblotting. Under reducing conditions, the approximately 120,000 Mr component migrated on SDS-PAGE as two distinct bands with Mr approximately 60,000, one of which reacted with antiserum to antithrombin and the other (of slower mobility) of which reacted with antiserum to albumin only. These and other results established the approximately 120,000 Mr component to be an inactive, disulphide-linked variant antithrombin and albumin complex. The variant antithrombin was isolated, following reduction and S-carboxymethylation, by reverse-phase HPLC and then it was fragmented with CNBr. A major CNBr pool containing the sequence Gly339-Met423 was treated with trypsin, followed by V8 protease. The resulting peptides were analysed by fast atom bombardment mass spectrometry (Fab-MS) mapping. A peptide of molecular mass 1086, corresponding to the normal sequence Ala382-Arg393, was almost absent from the mass spectrum, but an additional peptide of mass number 1772 was present. These results are almost identical to those found in another variant antithrombin, Northwick Park (Erdjument et al., J Biol Chem, 262: 13381, 1987; Erdjument et al., J. Biol Chem, 263: 5589-5593, 1988), indicating the same single amino acid substitution of Arg393 to Cys.

Amino Acid Sequence↗
PubMed1988

Functional assays of protein C: comparison of two snake-venom assays with two thrombin assays.

Protein C (PC) activities measured by two thrombin-based assays have been compared with those obtained by two assays based on snake venom activation of plasma PC followed by measurement of both the amidolytic and anticoagulant activities of activated PC. This study indicates that snake venom assays gave results similar to those of the thrombin assays in 20 healthy subjects, in 16 patients with DIC and in 15 patients with congenital PC deficiency. There was, however, some degree of misclassification of normals and congenitally-deficient patients, with only the clotting snake venom assay resulting in no misclassifications. In 15 patients stabilized on warfarin treatment and in 17 with liver disease, the clotting snake venom assay gave significantly lower values than the other assays, so that it might prove to be more sensitive than the other assays to these defects.

Crotalid Venoms↗
PubMed1988

Frequency of upper gastrointestinal lesions in patients with liver cirrhosis.

The frequency of gastroduodenal lesions has been investigated in 142 patients with liver cirrhosis of various degrees of severity and in 63 patients with mild liver disease (controls) in whom liver biopsy excluded nodular regeneration. Cirrhotic patients were subdivided in three groups according to the Pugh modification of the Child-Turcotte criteria. Although the frequency of peptic ulcer was not different, gastroduodenal erosions were observed more frequently in cirrhotics than in controls (29.6% vs 11.1%, P less than 0.01). The occurrence of erosions was related to the severity of the disease: in Child A and B patients their frequency was 21 and 26% respectively, but rose to 48.4 (15 of 31 vs 7 of 63 in controls, P less than 0.001) in the Child C group. Both mild and severe gastroduodenitis occurred more frequently, although not significantly, in patients with liver cirrhosis. All together one or more endoscopic lesions were observed in almost 60% of cirrhotics but only in 25.4% of controls (P less than 0.001). In conclusion, our data do not show an increased prevalence of peptic ulcer in cirrhotic patients; in contrast, liver cirrhosis is significantly associated with the endoscopic finding of gastroduodenal erosions, especially in the more advanced stages of the disease. These findings would suggest a cautious use, in cirrhotic patients, of drugs which may damage the gastroduodenal mucosa; moreover, long-term administration of antacids or of other drugs with a protective effect on gastroduodenal mucosa might be taken into consideration for Child C patients.

Aspartate Aminotransferases↗
PubMed1988

Inherited factors in thrombosis.

Patients with inherited defects or abnormalities that impair the naturally-occurring anticoagulant and fibrinolytic systems are at risk of developing venous and, more rarely, arterial thromboembolism. The prevalence of inherited thrombophilia in the general population is higher than that of inherited bleeding disorders (ca. 1 in 7500 vs 1 in 20,000). Low levels or dysfunctional forms of antithrombin III, protein C and protein S and abnormal fibrinogens are the most frequent and well-established inherited causes for thrombosis. Less frequent and/or less established causes are low heparin cofactor II and plasminogen and high levels of plasminogen activator inhibitor and histidine-rich glycoprotein. The pathophysiology, genetic and clinical aspects and laboratory diagnosis of inherited thrombotic disorders are reviewed and an approach to prophylaxis and therapy is outlined.

Humans↗
PubMed1987

Purification and further characterization of antithrombin III Milano: lack of reactivity with thrombin.

The functional abnormality of Antithrombin III "Milano", a previously described variant with monomeric and dimeric forms of abnormal AT III, has been further characterized. Affinity chromatography on heparin-Sepharose led to the separation and purification of two distinct fractions: fraction I is identical to normal AT III; fraction II (abnormal AT III) reproduces the abnormalities of the AT III "Milano", i.e. lack of thrombin inhibition, increased mobility by two-dimensional immunoelectrophoresis in the absence of heparin and migration as two bands with molecular weights of 60 K and 120 K by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The interaction of both fractions with purified alpha-thrombin was studied by the formation of complexes as well as by affinity chromatography on thrombin-Sepharose. No thrombin-AT III complexes could be demonstrated with either the monomeric or dimeric forms of purified variant AT III at both concentrations of thrombin used. Similarly, no binding to thrombin-Sepharose was observed, thus indicating that the molecular defect of AT III Milano is related to its absence of reactivity with thrombin.

Antithrombin III↗
PubMed1987

Laboratory screening of inherited thrombotic syndromes.

The prevalence of inherited thrombotic syndromes in the general population (1 in 2,500/5,000) appears to be higher than that of inherited bleeding disorders. The problems of their laboratory diagnosis are reviewed and a screening procedure is proposed. The most important candidates for screening are patients with unexplained venous thromboembolism at ages of less than 40-45 years, particularly when thrombotic episodes are recurrent. Screening must start from the exclusion of common acquired causes of thrombophilia. A negative family history does not exclude inherited thrombophilia, because the defects have a low penetrance and fresh mutations may have occurred in the propositi. Laboratory screening is based on a two-step procedure. The first step is aimed at detecting, preferably with specific functional assays, the most frequent and well established causes of inherited thrombophilia, i.e. deficiencies or dysfunctions of antithrombin III, protein C, protein S, plasminogen and fibrinogen. The tests included in the second step of the screening are aimed at detecting the less common or less well established causes of inherited thrombophilia (low heparin cofactor II, defective release of tissue plasminogen activator, and high plasminogen activator inhibitor). The simplest, more reliable and specific assay methods to be used in laboratory practice are recommended.

Adult↗
PubMed1987

Multicenter comparison of five functional and two immunological assays for protein C.

Five functional assays and two immunoassays for protein C (PC) were evaluated in parallel for the same plasma samples collected from healthy subjects, patients with congenital and acquired PC deficiencies or patients with conditions associated with high PC levels. For 7 patients starting warfarin therapy and for 15 patients during stabilized warfarin therapy, there were significant between-assay differences. For these groups immunoassays gave higher values than most functional assays and the latter also gave varied results, probably depending on their respective capacity for recognizing a carboxylated PC. On the other hand, there were no significant between-assay differences nor discrepancies between PC activity and antigen levels for healthy subjects (n = 39), patients with congenital PC deficiency (n = 10), myocardial infarction (n = 25), chronic liver disease (n = 19), disseminated intravascular coagulation (n = 35), in the post-operative period (n = 20) or in women taking oral contraceptives (n = 20). This comparison of PC assays indicates that PC levels measured by different functional or immunological assays are very close in the majority of clinical conditions, but not for patients on oral anticoagulants.

Blood Coagulation Tests↗
PubMed1987

Evaluation of a fully automated centrifugal analyzer for performance of hemostasis tests.

We have evaluated the performance of a centrifugal analyzer, specifically designed for hemostasis tests, for methods based on clotting time as measured by light scattering, or based on splitting of chromogenic substrates. The results were compared with those obtained with a semiautomated coagulometer (clotting tests) or with a manually operated photometer (chromogenic tests). In general, the results with the centrifugal analyzer were at least as precise as those of the comparative methods, with greater output and ease of operation. Disadvantages of the instrument are its partial incompatibility with some commercial reagents and the relative rigidity of the operational parameters, which hinder its use for research.

Antithrombin III↗
PubMed1986

Characterization of an abnormal antithrombin (Milano 2) with defective thrombin binding.

Four members of an Italian family (two with histories of venous thromboembolism) had a qualitative defect of antithrombin III reflected by normal antigen concentrations and half-normal antithrombin activity with or without heparin. Anti-factor Xa activities were consistently borderline low (about 70% of normal). For the propositus' plasma and serum the patterns of antithrombin III in crossed-immunoelectrophoresis with or without heparin were indistinguishable from those of normal plasma or serum. A normal affinity of antithrombin III for heparin was documented by heparin-sepharose chromatography. Affinity adsorption of the propositus' plasma to human alpha-thrombin immobilized on sepharose beads revealed defective binding of the antithrombin III to thrombin-sepharose. Hence the molecular defect of this variant appears to be at the active site responsible for binding and neutralizing thrombin, thus accounting for the low thrombin inhibitory activity.

Adult↗
PubMed1986

Homozygous protein C deficiency with moderately severe clinical symptoms.

We report a large family with two members homozygotes for protein C deficiency, with activity levels of 5% and 9%. Thirteen additional members were heterozygotes, with protein C activity ranging from 36-66% and equally low levels of protein C antigen. The homozygotes presented with recurrent deep-vein thromboses and pulmonary emboli, but have reached the ages of 26 and 37 years. Hence, protein C levels of 5% appear sufficient to avoid life-threatening clinical symptoms in the neonatal period.

Adolescent↗