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Biomedical subjects

I D Walker

Publications and source records attributed to I D Walker.

At least 163 records · Page 9Linked to original sources
PubMed1985

The polypeptide structure and assembly of Ly-2/3 heterodimers.

Mild reduction of mature, thymic Ly-2/3 heterodimers of Mr 67 000 resulted in dissociation into three individual polypeptide chains, alpha, alpha', and beta, of respective Mr values 38 000, 35 000, and 30 000. The alpha and alpha' chains were both immunoprecipitated by a monoclonal antibody directed to the Ly-2.1 epitope whereas the Ly-3.1 antibody bound only the beta chain. The possibility that the alpha and beta chains of each heterodimer established their interchain links within a labile precursor protein in which alpha and beta segments were fused was considered but discounted by the finding that in mice heterozygous for both Ly-2 and Ly-3 loci, the Ly-2 product of one chromosome was not exclusively joined to Ly-3 structures coded by the same chromosome. By utilizing ionic detergents which selectively alter the charge of intrinsic membrane proteins, both Ly-2 and Ly-3 polypeptides were shown to have membrane insertion sites. It is suggested that as a consequence of their likely synthesis on membrane-bound polysomes, newly synthesized Ly-2 and Ly-3 structures accumulate within the same subcellular compartment - the membranes of the rough endoplasmic reticulum. Their elevated concentration within this space may facilitate a low affinity binding interaction between Ly-2 and Ly-3 which is later stabilized by interchain disulfide bond formation.

Animals↗
PubMed1985

The Ly-15 alloantigenic system: a genetically determined polymorphism of the murine lymphocyte function-associated antigen-1 molecule.

Serological and biochemical studies using monoclonal antibodies have demonstrated that the Ly-15 cell membrane alloantigens are polymorphic sites on the lymphocyte function-associated antigen-1 (LFA-1) molecule. Ly-15.2 and LFA-1 show identical tissue distributions, being present on all thymocytes, lymphocytes, and neutrophils, and flow cytofluorometric analysis indicated identical cell surface expression of these molecules. Identity of Ly-15.2 and LFA-1 was confirmed by immunochemical analysis. The Ly-15.2 and LFA-1 molecules have an identical heterodimeric structure of Mr 180,000 alpha chain and Mr 94,000 beta chain, which coelectrophorese on two-dimensional NaDodSO4/PAGE. Furthermore, anti-Ly-15.2 and anti-LFA-1 antibodies coprecipitate the same molecule from thymocyte lysates, and peptide mapping studies show that the Ly-15.2 and LFA-1 alpha chains are identical, as are the beta chains.

Animals↗
PubMed1984

Acylated streptokinase--plasminogen complex in patients with acute myocardial infarction.

BRL 26921 is the p- anisoyl derivative of the primary streptokinase-human plasminogen complex in which the acyl group is specifically located at the catalytic centre of the enzyme. Doses of BRL 26921 ranging from 5 mg to 25 mg were given intravenously or into a coronary artery to 12 patients with acute myocardial infarction. The complex was well tolerated and produced no serious bleeding. Coronary artery reperfusion was demonstrated angiographically in three patients. In most patients, fibrinogen, plasminogen, alpha 2 antiplasmin and alpha 2 macroglobulin levels fell and the level of fibrinogen degradation products increased acutely post treatment indicating systemic fibrinolytic activation. The degree of this activation was variable but was profound in some. It appeared to be dose related and modified by the presence of streptokinase antibodies. BRL 26921 appears less "selectively" thrombolytic in patients than had been expected from animal models.

Adult↗
PubMed1984

Comparison of thymic and peripheral T cell Ly-2/3 antigens.

Major structural differences occur between the thymic and peripheral T cell forms of the Ly-2/3 antigen. Thymus Ly-2/3 consists of similar amounts of two types of disulfide-linked heterodimer, alpha beta and alpha' beta (Mr alpha = 38000, Mr alpha' = 35000, Mr beta = 30000). In contrast material from peripheral T cells consists almost exclusively of alpha beta dimers. The alpha chains of thymus and peripheral T cells differ also in isoelectric point with the thymic alpha chain being the more acidic. Based on peptide mapping experiments the alpha and alpha' chains of thymus are likely to be alternatively modified forms of the same polypeptide backbone. Individual T cell clones or T cell tumors propagated in vitro exhibit either a typical thymus or a typical peripheral T cell Ly-2/3 polypeptide pattern indicating that the synthesis of both alpha and alpha' chains can occur in the same cell. The heterogeneity of thymic Ly-2/3 can be considerably reduced by removal of sialic acid residues, and after desialylation the alpha chains of thymus and a cloned cytotoxic T lymphocyte (CTL) line cannot be electrophoretically distinguished. If Ly-2 structures affected the antigen specificity of CTL, a different structural variant would be expected in individual clones. The electrophoretic identity of desialylated thymus and CTL alpha chains suggests that Ly-2 does not exhibit clonal variation in polypeptide structure and, therefore, cannot contribute to antigen specificity.

Animals↗
PubMed1984

Two-dimensional gel analysis demonstrates no structural alteration of HLA-B27 polypeptides between patients with ankylosing spondylitis and healthy individuals.

After precipitation of the HLA-B27 antigen from the surface of peripheral blood lymphocytes (PBL) by means of an anti-HLA-B27 allospecific monoclonal antibody 2-dimensional gel electrophoresis was used to compare the structure of the B27 antigens derived from 5 patients with ankylosing spondylitis with that of healthy HLA-B27 positive counterparts. No significant difference in polypeptide structure was noted, which suggests that the pathogenesis of ankylosing spondylitis does not involve a structural alteration in cell surface HLA-B27 molecules.

Chemical Phenomena↗
PubMed1984

Evaluation of an automated prothrombin assay using a chromogenic substrate.

The performance of a commercially available assay for the determination of prothrombin by a chromogenic substrate method has been evaluated for use on an automated clinical analyser. The method was rapid and simple; accuracy, precision and sensitivity were satisfactory, while carry-over was negligible. Determinations were performed on 170 plasma samples from patients on long-term oral anticoagulant therapy, using the automated amidolytic method; comparison of the prothrombin levels with results obtained by the prothrombin time and Thrombotest methods provided highly significant correlations.

Autoanalysis↗
PubMed1983

The H-2dm1 mutation and Qa antigens.

The effect of the H-2dm1 mutation on Qa-m2 expression was examined. The mutant strain B10.D2-H-2dm1 showed a fourfold increase in Qa-m2 expression when compared with the parental strain B10.D2. Qa-m2 molecules immunoprecipitated from B10.D2-H-2dm1, C57BL/10, and B10.D2 spleen cells were identical by two-dimensional (2-D) gel electrophoresis [isoelectric focusing (IEF) followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE]). It is likely therefore that the increased Qa-m2 expression is not due to gross structural alterations of the Qa-m2 molecule; in the present study, alternative explanations are discussed.

Animals↗
PubMed1983

Effects of dazoxiben on transcardiac thromboxane levels and haemodynamics in coronary heart disease.

1 Plasma thromboxane levels were obtained from both the coronary sinus and aorta in patients with stable angina pectoris paced to angina, and in unstable angina patients before and after dazoxiben 100 mg. 2 Although there was a wide range of values in the different groups, dazoxiben significantly reduced plasma thromboxane levels in all patients. 3 Dazoxiben had no adverse effect on coronary and systemic haemodynamics, and atrial pacing time to angina was increased from 245 +/- 41 to 308 +/- 48s (P less than 0.01).

Adult↗
PubMed1983

Freeze dried cryoprecipitate: a clinical evaluation.

Freeze dried cryoprecipitate was used in the treatment of 14 patients with haemophilia A. The in vivo recovery was 91.2% which is comparable to that reported from other parts of Europe. The product was efficacious and no adverse effects were reported. Freeze dried cryoprecipitate is the high yield product of a low technology process and as such may be of value in reducing any possible shortfall in the factor VIII requirements of the haemophiliac population of the UK.

Chemical Precipitation↗
PubMed1982

A search for messenger RNA molecules bearing immunoglobulin VH nucleotide sequences in T cells.

Expression of VH-coded mRNA molecules in T cells, antigen-specific T cell lines, or T cell hybridomas was not detected using four different VH DNA probes under conditions that permitted cross-hybridization between distantly related VH genes. In contrast, VH gene expression was readily detected in two B cell lymphomas and in splenic B cells. Less than one molecule per cell of RNA, exactly complementary to the DNA probes used, would have been detected in these T cell populations. The results thus seriously question the proposition that T cells use the B cell VH repertoire to code for antigen receptors.

Animals↗
PubMed1982

Prostacyclin in cardiopulmonary bypass operations.

The effects of prostacyclin (PGI2) on postoperative blood loss and on the deposits which are known to form on filters in the bypass circuit were studied in patients undergoing operations with cardioopulmonary bypass. In this double-blind, randomized study, PGI2 or a placebo solution was administered to 56 patients undergoing elective cardiac operations. At the end of cardipulmonary bypass, the arterial line filter was removed from the circuit and blood losses were accurately recorded. There was no statistically significant difference in either the amount or the pattern of postbypass bleeding between the PGI2 and the control patients. However, the changes in weight of the arterial line filters and their electron microscopic appearances suggest that PGI2 can reduce the deposition of platelets and fibrin on the filter mesh, and in this role it may be of value in reducing visceral injury during cardiac operations.

Adult↗
PubMed1982

Maintenance control of oral anticoagulant therapy by an automated chromogenic substrate assay of factor X.

An amidolytic assay of factor X based on the new chromogenic peptide substrate S 2337 (Kabi Diagnostica) was adapted for use with the Kem-o-Mat (Coulter Electronics) automated substrate analyser. Factor X was assayed in 25 healthy controls and in 375 patients on Warfarin therapy. The results in the control group correlated well with a one stage coagulation factor X assay. A good correlation was also found when the S 2337 factor X assay was compared with Thrombotest (Nyegaard & Co.) results in the patients. From the regression line of the S 2337 factor X assay on the Thrombotest results, the comparable range for factor X amidolytic activity in well controlled anticoagulated patients was found to be 22.5-37.5% with this method. Concordant classification of patients by both tests according to proposed therapeutic ranges demonstrated fully concordant information in 76% and fully discordant information in none. This study demonstrates that chromogenic substrate assays for anticoagulant control can be readily automated. Amidolytic assays of factor X based on the S 2337 substrate, therefore, warrant further clinical investigation as a potential method for controlling maintenance oral anticoagulant therapy.

Adult↗
PubMed1981

Contact sensitivity to azobenzenearsonate and its inhibition after interaction of sensitized cells with antigen-conjugated cells.

Painting mice on the skin with the diazonium salt of p-arsanilic acid elicited two types of T cell activity. One was restricted by the I region of the major histocompatibility complex and was responsible for the transfer of azobenzenearsonate (ABA) sensitivity to naive mice. The other was H-2K restricted and could be demonstrated by its ability to interact specifically with ABA-coupled cells in vitro and to inhibit nonspecifically the transfer of sensitivity by cells sensitized either to ABA or to another antigen. Free antigen, or antibody directed against the cross-reactive idiotype on the anti-ABA antibodies of A/J mice, could inhibit the H-2K-restricted suppressive activity induced in the ABA immune A/J cells.

Animals↗