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Biomedical subjects

S V Pizzo

Publications and source records attributed to S V Pizzo.

At least 289 records · Page 16Linked to original sources
PubMed1979

Vessel occlusion with transcatheter electrocoagulation: initial clinical experience.

Transcatheter electrocoagulation (TCEC) was used for vessel occlusion in combination with embolization by Gelfoam and/or Ivalon in six patients in whom other interventional or surgical techniques were considered dangerous or unfeasible. The technique was effective in decreasing or obliterating the blood supply to variously located lesions in all cases. The only complications were small skin burns in one patient and a small ulceration of the upper lip in another.

Adult↗
PubMed1979

Demonstration and characterization of specific binding sites for factor VIII/von Willebrand factor on human platelets.

The presence of specific Factor VIII/von Willebrand factor (FVIII/vWF) binding sites on human platelets has been demonstrated by using 125I-FVIII/vWF and washed human platelets. Binding is ristocetin-dependent and increases in proportion to the concentration of ristocetin from 0.2 to 1 mg/ml. Binding of 125I-FVIII/vWF to platelets can be competitively inhibited by unlabeled human or bovine FVIII/vWF, but not by human thrombin, fibrinogen, alpha 2-macroglobulin, equine collagen, or a lectin of Ricinus communis. Scatchard analysis of binding data indicated that the dissociation constant of FVIII/vWF receptors is 0.45--0.5 nM. There are 31,000 binding sites per platelet at 1 mg/ml of ristocetin concentration. The optimal pH range for binding is from 7.0 to 7.5. At a concentration of 2 mM, EGTA inhibits 86% of the binding; however, 20 mM of Ca++, Mg++, or EDTA have little effect. Binding sites for FVIII/vWF were found only on platelets, and no significant binding was detected with human erythrocytes or polymorphonuclear leukocytes.

Binding Sites↗
PubMed1978

Carbohydrate on human factor VIII/von Willebrand factor. Impairment of function by removal of specific galactose residues.

Human factor VIII/von Willebrand factor protein containing 120 +/- 12 nmol of sialic acid and 135 +/- 13 nmol of galactose/mg of protein was digested with neuraminidase. The affinity of native factor VIII/von Willebrand factor and its asialo form for the hepatic lectin that specifically binds asialoglycoproteins was assessed from in vitro binding experiments. Native factor VIII/von Willebrand factor exhibited negligible affinity while binding of the asialo derivative was comparable to that observed for asialo-alpha1-acid glycoprotein. Incubation of asialo-factor VIII/von Willebrand factor with Streptococcus pneumoniae beta-galactosidase removed only 62% of the galactose but abolished binding to the purified hepatic lectin. When the asialo derivative was incubated with purified beta-D-galactoside alpha2 leads to 6 sialyltransferase and CMP-[14C]NeuAc, only 61% of the galactose incorporated [14C]NeuAc. From the known specificites of these enzymes, it is concluded that galactose residues important in lectin binding are present in a terminal Gal/beta1 leads to 4GlcNAc sequence on asialo-factor VIII/von Willebrand factor. The relative ristocetin-induced platelet aggregating activity of native, asialo-, and agalacto-factor VIII/von Willebrand factor was 100:38:12, respectively, while procoagulant activity was 100:100:103.

Animals↗
PubMed1978

Hepatic receptor that specifically binds oligosaccharides containing fucosyl alpha1 leads to 3 N-acetylglucosamine linkages.

Evidence is presented suggesting that hepatocytes contain a receptor that binds glycoproteins specifically through fucose in alpha1-->3 linkage to N-acetylglucosamine. Human lactoferrin, which contains this type of linkage, is rapidly cleared from the circulation of mice after intravenous injection, and greater than 90% of the injected material is found in hepatocytes. Binding of lactoferrin is mediated through its carbohydrate groups, since its clearance is prolonged after periodate oxidation or after its oligosaccharide groups are extensively degraded with glycosidases. In addition, glycopeptides from lactoferrin inhibit lactoferrin clearance. That lactoferrin clearance is mediated through binding to its fucosyl groups is suggested for several reasons. First, transferrin and asialotransferrin, whose oligosaccharide groups are essentially structurally identical to those of lactoferrin but devoid of fucose, are not cleared on intravenous injection. Second, when fucose is incorporated into asialotransferrin by alpha1-->3 N-acetylglucosamine fucosyl transferase, the resulting fucosylated derivative is cleared rapidly. Neither mannan nor derivatives of orosomucoid that are cleared by binding to receptors for galactose, N-acetylglucosamine, or mannose, inhibit clearance of lactoferrin although clearance is inhibited by fucoidin. Finally, glycoproteins containing fucose in alpha1 --> 2 linkage to galactose or alpha1 --> 6 linkage to N-acetylglucosamine do not inhibit lactoferrin clerance by the liver. Since clearance of other glycoproteins, such as human lactoperoxidase, also appears to be mediated through binding to the same hepatocyte receptor as lactoferrin, it is concluded that the fucose-specific receptor studied here may fulfill other functions than binding lactoferrin. Preliminary studies with liver homogenates and detergent extracts of liver show binding in vitro.

Acetylglucosamine↗
PubMed1976

Characterization of fragment E from fibrinogen and cross-linked fibrin.

Fragment E, a terminal plasmin digestion product of fibrinogen or fibrin, contains portions of the alpha, beta, and gamma chains linked by disulfide bonds. In this study, Fragment E from fibrinogen and fully cross-linked fibrin were purified by gel filtration of the soluble fraction from heated plasmin digests of either fibrinogen or fibrin or by step-wise chromatography of terminal plasmin digests of fibrinogen or cross-linked fibrin on DEAE-cellulose. Fibrinogen Fragment E and fibrin Fragment E migrated as single bands with identical mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis or on polyacrylamide gel electrophoresis at pH 3.2 or pH 8.6. After reduction by beta-mercaptoethanol, the two Fragment E species had very similar patterns on sodium dodecyl sulfate gel electrophoresis; each contained three subunits which had molecular weights ranging from 5,000 to 12,000. Only the subunit polypeptide derived from the gamma chain in either Fragment E contained carbohydrate. The two Fragment E species had identical sedimentation coefficients and identical molecular weights by equilibrium ultracentrifugation. The amino acid compositions were indistinguishable. Partial NH2-terminal sequence analyses of fibrinogen Fragment E and fibrin E were identical, indicating that plasmin had cleaved the NH2-terminal regions of the Aalpha or alpha and Bbeta or beta chains of both Fragment E Species.

Amino Acid Sequence↗
PubMed1976

Comparison of ancrod and heparin as anticoagulants following endarterectomy in the dog.

An experimental model of surgically-induced arterial thrombosis was devised using the femoral arteries of dogs. Within 7 days, 67% of the arteries became completely thrombosed and only 12% remained compeletly patent. In the group of dogs that received low-dose heparin, 69% of the vessels were completely thrombosed and 6% remained completely patent. In the group of dogs treated with low-dose Ancrod to induce partial defibrination, 75% remained completely patent while only 19% of their femoral arteries were completely thrombosed. Although the ancrod was effective in preventing arterial thrombosis, 88% of the wounds showed moderate to severe separations. Most likely the absence of a fibrin lattice, necessary for the securement and growth of fibroblasts as the wound heals, explains this latter effect. Thus while Ancrod may become useful as an anticoagulant in certain clinical situations, it should not be used in proximity to surgery. Finally, in these studies of acute arterial thromboses, low-dose heparin therapy offered no protective effect.

Ancrod↗
PubMed1973

The subunit structure of normal and hemophilic factor VIII.

Human factor VIII from normals and hemophiliacs was partially purified by ethanol and polyethylene glycol precipitations. Final purification was achieved by gel filtration on 2 or 4% agarose or ion exchange chromatography on diethylaminoethyl cellulose. Comparable amounts of highly purified protein were obtained from normal and hemophilic plasma following the agarose chromatography step. Highly purified factor VIII was not dissociated by 6 M guanidine hydrochloride or 1% sodium dodecyl sulfate. However, when reduced by beta-mercaptoethanol and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, a single subunit species with an estimated 195,000 molecular weight was found for both normal and hemophilic factor VIII. By sedimentation equilibrium analysis, the normal factor VIII subunit was homogeneous and had an estimated molecular weight of 202,000. The subunit polypeptides from normal or hemophilic factor VIII contained carbohydrate. Each was homogeneous by isoelectric focusing. Immunodiffusion of purified normal and hemophilic factor VIII against rabbit antiserum to purified normal human factor VIII showed a single line of precipitation. Very low concentrations of purified human thrombin initially increased the activity of normal factor VIII about threefold and then progressively destroyed activity by 3 h. Only minimal activation occurred with hemophilic factor VIII. Both the activation and inactivation of normal and hemophilic factor VIII were unaccompanied by detectable changes in subunit molecular weight. These findings may have implications for the definition of the molecular defect in hemophilic factor VIII.

Amino Acids↗
PubMed1972

Mechanism of ancrod anticoagulation. A direct proteolytic effect on fibrin.

Fibrin formed in response to ancrod, reptilase, or thrombin was reduced by beta-mercaptoethanol and examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It was found that ancrod progressively and totally digested the alpha-chains of fibrin monomers at sites different than plasmin; however, further digestion of fibrin monomers by either reptilase or thrombin was not observed. Highly purified ancrod did not activate fibrin-stabilizing factor (FSF); however, the reptilase preparation used in these experiments, like thrombin, activated FSF and thereby promoted cross-link formation. Fibrin, formed by clotting purified human fibrinogen with ancrod, reptilase, or thrombin for increasing periods of time in the presence of plasminogen, was incubated with urokinase and observed for complete lysis. Fibrin formed by ancrod was strikingly more vulnerable to plasmin digestion than was fibrin formed by reptilase or thrombin. The lysis times for fibrin formed for 2 hr by ancrod, reptilase, or thrombin were 18, 89, and 120 min, respectively. Evidence was also obtained that neither ancrod nor reptilase activated human plasminogen. These results indicate that fibrin formed by ancrod is not cross-linked and has significantly degraded alpha-chains: as expected, ancrod-formed fibrin is markedly susceptible to digestion by plasmin.

Anticoagulants↗