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Biomedical subjects

R E Jordan

Publications and source records attributed to R E Jordan.

At least 73 records · Page 4Linked to original sources
PubMed1982

Heparin with two binding sites for antithrombin or platelet factor 4.

A new, highly discriminating affinity chromatographic technique has been developed which employs antithrombin and concanavalin A-Sepharose to fractionate heparin species of all molecular sizes. This methodology is able to subdivide the active mucopolysaccharide pools of molecular weight 6,000 to 8,000 (LMW) or 18,000 to 22,000 (HMW) into various species with descending affinities for antithrombin as well as decreasing anticoagulant potencies. The upper 10% of these two pools, either LMW or HMW highly active heparin, appears to be relatively homogeneous with respect to interactions with antithrombin and possessed anticoagulant potencies of 350 units/mg and 731 units/mg, respectively. The HMW highly active heparin has been examined by analytic ultracentrifugation. It exhibited a charge-connected weight-average molecular weight of 22,000 +/- 2,000 with minimal size heterogeneity. The stoichiometries of interaction of antithrombin and platelet factor 4 with HMW highly active heparin as determined by fluorescence spectroscopy indicated that 2 molecules of either protein are able to bind to 1 molecule of the mucopolysaccharide. These studies also reveal that the binding of antithrombin to HMW highly active heparin is characterized by KDISSHAT = 5.0 X 10(-8) M and KDISSHAT2 = 1.0 x 10(-7) M, respectively. The avidity of platelet factor 4 for HMW highly active heparin could not be quantitated but appears to be at least 10 to 100 times greater than that of antithrombin for mucopolysaccharide.

Antithrombins↗
PubMed1982

Clinical management of non-carious enamel defects.

Enamel defects not caused by decay may occur singly or may be generalized over the entire tooth surface. In the past, treatment of these aesthetic problems required large cavity preparations or full crown coverage of the affected teeth. Now, with the advent of various resin restorative materials capable of bonding to enamel, new techniques are being developed which are less radical. By etching the surface of the enamel with varying concentrations of dilute phosphoric acid, sufficient porosity is produced to allow the resin to adhere to it. Thus, by removing a minimal amount of tooth structure, the affected area can be masked with a thin layer of resin material after the surface has been properly prepared. If the fault in the enamel is generalized, the whole surface of the tooth may be restored using this technique, effectively covering the tooth with an aesthetic veneer. The new resin filling materials offer good colour stability as well as resistance to abrasive wear. Tests have revealed that this mode of treatment has a successful retention rate of over 92 per cent after 5 years. Lightly discoloured or stained defects of the enamel may be treated by bleaching the affected area with no adverse effect on the pulp tissue. Those teeth not improved by bleaching can be conservatively managed by veneering their surfaces with smooth finishing plastic materials.

Acid Etching, Dental↗
PubMed1980

The binding of low molecular weight heparin to hemostatic enzymes.

A low molecular weight preparation of porcine heparin (specific anticoagulation activity = 125 units/mg) was fractionated to obtain a mucopolysaccharide product of 6500 daltons (specific anticoagulant activity = 373 units/mg) that is homogeneous with respect to its interaction with antithrombin. This material was treated with fluorescamine in order to introduce a fluorescent tag into the mucopolysaccharide. Initially, we showed that the fluorescamine-heparin conjugate and the unlabeled mucopolysaccharide interacted with antithrombin in a virtually identical fashion. Subsequently, we demonstrated that labeled heparin could be utilized in conjunction with fluorescence polarization spectroscopy to monitor the binding of mucopolysaccharide to thrombin, factor IXa, factor Xa, and plasmin. The interaction of this complex carbohydrate with thrombin exhibited a stoichiometry of 2:1 with KH1T DISS = KH2T DISS = 8 x 10(-7) M. The formation of mucopolysaccharide . factor IXa complex is characterized by a stoichiometry of 1:1 with KHIXa DISS = 2.58 x 10(-7) M. The binding of heparin to factor Xa or plasmin occurred with low avidity. Therefore, the stoichiometries of these processes could not be established. However, our experimental data were compatible with a single-site binding residue with KHXa DISS = 8.73 x 10(-6) M and KHPL DISS = approximately 1 x 10(-4) M, respectively.

Animals↗
PubMed1980

The kinetics of hemostatic enzyme-antithrombin interactions in the presence of low molecular weight heparin.

The kinetics of inhibition of four hemostatic system enzymes by antithrombin were examined as a function of heparin concentration. Plots of the initial velocity of factor Xa-antithrombin or plasmin-antithrombin interaction versus the level of added mucopolysaccharide exhibit an ascending limb and subsequent plateau regions. In each case, the kinetic profile is closely correlated with the concentration of the heparin . antithrombin complex formed within the reaction mixture. A decrease in the velocity of inhibition is not observed at high levels of added mucopolysaccharide despite the generation of significant quantities of heparin-enzyme interaction products. The second-order rate constants for the neutralization of factor Xa or plasmin by the mucopolysaccharide . inhibitor complex are 2.4 x 10(8) M-1 min-1 and 4.0 x 10(6) M-1 min-1, respectively. These parameters must be contrasted with the similarly designated constants obtained in the absence of heparin which are 1.88 x 10(5) M-1 min-1 and 4.0 x 10(4) M-1 min-1, respectively. Plots of the initial velocity of the factor IXa-antithrombin or the thrombin-antithrombin interaction versus the level of added mucopolysaccharide exhibit an ascending limb, pseudoplateau, descending limb, and final plateau regions. In each case, the ascending limb and pseudoplateau are closely correlated with the concentration of heparin c antithrombin complex formed within the reaction mixture. Furthermore, the descending limb and final plateau of these two processes coincide with the generation of increasing amounts of the respective mucopolysaccharide-enzyme interaction products. The second-order rate constants for the neutralization of factor IXa or thrombin by the heparin . antithrombin complex are 3.0 x 10(8) M-1 min-1 and 1.7 x 10(9) M-1 min-1, respectively. The second-order rate constants for the inhibition of mucopolysaccharide-factor IXa or mucopolysaccharide-thrombin interaction products by the heparin . antithrombin complex are 2.0 x 10(7) M-1 min-1 and 3.0 x 10(8) M-1 min-1, respectively. These kinetic parameters must be contrasted with similarly designated constants obtained in the absence of mucopolysaccharide which are 2.94 x 10(4) M-1 min-1 and 4.25 x 10(5) M-1 min-1, respectively. Thus, our data demonstrate that binding of heparin to antithrombin is required for the mucopolysaccharide-dependent enhancement in the rates of neutralization of thrombin, factor IXa, factor Xa, or plasmin by the protease inhibitor. Furthermore, a careful comparison of the various constants suggests that the direct interaction between heparin and antithrombin may be largely responsible for the kinetic effect of this mucopolysaccharide.

Antithrombins↗
PubMed1979

Circulating immune complexes in cutaneous vasculitis. Detection with C1q and monoclonal rheumatoid factor.

To investigate the pathogeneic significance of immune complexes in cutaneous vasculitis, 107 patients with various forms of cutaneous vasculitis, including 59 patients with necrotizing (leukocytoclastic) vasculitis (group 1), and 48 patients with lymphocytic vasculitis, or a predominately lymphocytic perivascular infiltrate (group 2), were studied. Immunoglobulins or complement components in cutaneous blood vessels were detected by direct immunofluorescence in high frequency in both groups (91 and 88%, respectively). Using two radioassays for circulating immune complexes, Clq or monoclonal rheumatoid factor (mRF) reactive material was detected in 68% of the patients with necrotizing vasculitis but only 44% of the patients in the lymphocytic-perivascular group. The mRF radioassay was elevated in 58% of the first group of patients and 41% of the patients in group 2, although Clq binding activity was increased in 54% of the patients with necrotizing vasculitis but only in 9% of the patients with a lymphocytic vasculitis or lymphocytic perivascular infiltrate. By using both sucrose density gradient ultracentrifugation and Sepharose 6B gel filtration, the Clq and mRF reactive material detected in some patients with necrotizing vasculitis eluted in high molecular weight fractions that were also anticomplementary. In one patient with necrotizing vasculitis and hepatitis B antigenemia, these heavy molecular weight Clq and mRF reactive fractions contained a two- to three-fold increase in hepatitis B surface antigen when compared with lighter molecular weight fractions. Heavy and light molecular weight mRF reactive material could be detected in selected patients in the lymphocytic-perivascular group as well as in the necrotizing vasculitis group. These studies suggest that cutaneous vasculitis, including acute necrotizing (leukocytoclastic) vasculitis and some forms of lymphocytic vasculitis, and perhaps some diseases characterized by a lymphocytic perivascular infiltrate, may represent cutaneous expressions of immune complex disease.

Antigen-Antibody Complex↗