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Biomedical subjects

R P Taylor

Publications and source records attributed to R P Taylor.

At least 19 recordsLinked to original sources
PubMed1992

In vivo binding and clearance of circulating antigen by bispecific heteropolymer-mediated binding to primate erythrocyte complement receptor.

We have used the avidin/biotin system to construct soluble, cross-linked bispecific heteropolymers containing mAb to both the primate E C receptor and the DNP group. These heteropolymers facilitate in vitro binding of DNP-bovine gamma-globulin (DNP-BGG) to both human and squirrel monkey E. Intravenous injection in squirrel monkeys of DNP-BGG followed by heteropolymer leads to E binding and clearance from the circulation of a significant fraction of both heteropolymer and DNP-BGG, without lysis or clearance of the E. This methodology may potentially be used to treat a variety of infectious diseases and other syndromes associated with blood-borne pathogens.

Animals↗
PubMed1992

Functional characterization of non-human primate erythrocyte immune adherence receptors: implications for the uptake of immune complexes by the cells of the mononuclear phagocytic system.

Erythrocytes from primates express an immune adherence (IA) receptor that binds complement-opsonized immune complexes (IC) both in vivo and in vitro. We have analyzed the immunochemical and functional properties of the IA receptor from erythrocytes from species that have been used for in vivo IC clearance studies and have compared these properties to the human IA receptor (which is called complement receptor type 1, CR1). Erythrocytes from all species (chimpanzee, baboon, rhesus and cynomolgus monkey) bind antibody/double-stranded DNA IC when opsonized with autologous complement. However, IC which are bound to chimpanzee erythrocytes are not released upon addition of chimpanzee serum (which contains factor I activity), while IC bound to baboon erythrocytes and human erythrocytes are released upon addition of autologous serum. Anti-human CR1 monoclonal antibodies (mAb) E11 and HB8592 bind to erythrocytes from all species examined and the number of mAb epitopes per erythrocyte correlated with the number of IC that could bind to the erythrocyte under saturating conditions. However, a number of interesting differences between the species are observed with other mAb. The anti-CR1 mAb 1B4 and 3D9, which block recognition of ligand by CR1, did not bind to chimpanzee erythrocytes and bound partially to rhesus and cynomolgus monkey erythrocytes. In addition, the ability of autologous serum to induce release of erythrocyte-bound IC correlates with the presence of these epitopes. These findings, taken in context with previous clearance studies, suggest that serum-mediated release may not be required for the rapid transfer of the IC from the erythrocyte to the mononuclear phagocytic system.

Animals↗
PubMed1992

E-rosette formation using heteropolymeric monoclonal antibodies.

We have used bispecific, cross-linked monoclonal antibodies (heteropolymers, HP) to facilitate rosette formation between human erythrocytes (EH) and dinitrophenylated sheep erythrocytes (DNP-ES) in the absence of complement. The HP contain monoclonal antibodies (mAbs) specific for both the EH C3b receptor (CR1), and the DNP group, and control experiments with homologous competing non-cross-linked mAbs and naive EH and ES confirm the specificity of the rosetting reaction. These results extend our previous studies, of HP-mediated binding of simple protein antigens to EH CR1, to complex particulate antigens and may eventually allow for the targeting and clearance from the circulation of a variety of pathogens associated with infectious disease.

Animals↗
PubMed1992

Glycated haemoglobin: an assessment of high capacity liquid chromatographic and immunoassay methods.

We have assessed five high-throughput systems for the measurement of glycated haemoglobin and have reviewed published evaluations of individual analysers. All systems offered better precision than a widely used electroendosmosis method. The low pressure chromatography and immunoassay systems demonstrated greater between-batch imprecision than the high performance liquid chromatography analysers, the latter achieving the proposed analytical goal of between-batch coefficients of variation less than 5%. Agreement between all systems measuring HbA1 was good but there was variability amongst observed HbA1c values. The systems were also assessed for their quality of chromatographic separation, simplicity of operation, flexibility, cost and potential for interference by other haemoglobins.

Autoanalysis↗
PubMed1992

A new method for quantification of islets by measurement of zinc content.

The ability to quantify the yield of pancreatic islet tissue after isolation is important for interlaboratory comparisons and for the assessment of islet yield prior to clinical transplantation. Because pancreatic islets contain a much higher concentration of zinc than other tissues, we investigated the analysis of zinc as a measure of islet tissue yield. Rat islets of standard diameter 250 microns were handpicked into samples containing 10-80 islets. The zinc content was measured by EAAS and showed a linear correlation with islet number. A zinc binding fluorescent dye, TSQ, was investigated as a way of simplifying the zinc measurement for routine use. Samples of 10-80 islets of 250 microns were sonicated in 3 ml zinc-free water, 0.18 mumol TSQ was added, and the TSQ-zinc fluorescence was measured at 480 nm. A linear correlation was observed. Exocrine contamination up to 50% barely affected the results. Islet zinc content also was shown to be correlated linearly with islet number for freshly isolated human islets. Measurement of zinc by TSQ fluorescence is a rapid, cheap, and objective measure of islet tissue content.

Animals↗
PubMed1991

Use of heteropolymeric monoclonal antibodies to attach antigens to the C3b receptor of human erythrocytes: a potential therapeutic treatment.

We have prepared bispecific, cross-linked monoclonal antibodies (heteropolymers) with specificity for both targeted antigens and the human erythrocyte (RBC) complement receptor. These heteropolymers facilitate binding of target antigens (human IgG and dinitrophenylated bovine gamma globulin) to human RBCs under conditions that either allow or preclude complement activation. Quantitative analyses of this binding agree well with the number of complement receptors per RBC. In vitro "whole-blood" model experiments indicate heteropolymer-facilitated binding of antigens to RBCs is rapid and stable at 37 degrees C. It may be possible to extend these prototype experiments to the in vivo situation and use heteropolymer-attached RBCs for the safe and rapid binding, neutralization, and removal from the circulation of pathogenic antigens associated with infectious disease.

Antibodies, Monoclonal↗
PubMed1991

Complement-opsonized IgG antibody/dsDNA immune complexes bind to CR1 clusters on isolated human erythrocytes.

We used fluorescence microscopy, quantitative FACS analyses, and radioimmunoassays to examine the distribution of complement (C3b)-opsonized antibody/dsDNA immune complexes (IC) bound to normal human erythrocytes (RBCs) via immune adherence (IA). IC were detected with fluorescent anti-human IgG, and the RBC IA-receptor (CR1) was revealed with monoclonal antibodies (Mabs) to CR1 and fluorescent anti-mouse IgG. Under saturating conditions RBCs exhibit a large heterogeneity in binding; a significant fraction binds no IC. The positions of bound IC coincide with CR1 clusters on RBCs, as predicted by several investigators. FACS experiments indicate an excellent correlation between CR1 number and IC binding within an RBC population. The number of CR1 clusters able to bind IC is proportional to the number of CR1 per RBC. However, IC (fluorescent spots) detected per RBC (on average less than 10) are less than the average number of IC bound (20-30). This suggests that each fluorescent spot represents a small number of aggregated IC bound to a CR1 cluster. These "patches" of aggregated complexes may facilitate transfer of RBC-bound IC to cells of the mononuclear phagocytic system. Finally, not all the CR1 clusters bind IC, suggesting that proper geometric alignment of multiple C3b per IC with several CR1 in the cluster is required for IA.

Antigen-Antibody Complex↗
PubMed1979

Detection of low avidity anti-DNA antibodies in systemic lupus erythematosus.

The binding of sonicated, radiolabeled DNA by systemic lupus erythematosus (SLE) sera was measured by a high sensitivity polyethylene glycol (PEG) precipitation assay. This method is considerably more sensitive than currently used techniques. The results suggest that a significant concentration of low avidity antibodies is present in SLE sera; however, these antibodies are not detected by conventional techniques.

Antibodies, Antinuclear↗
PubMed1979

A polyethylene glycol radioimmunoprecipitation assay for human immunoglobulin G.

A polyethylene glycol (PEG) radioimmunoprecipitation assay for human IgG is described that is sufficiently sensitive to detect 0.5 ng of IgG. This model antibody-antigen system was also used to study the stoichiometries of PEG-precipitated complexes. Our results suggest that the presence of PEG may affect the stoichiometry of the complexes which precipitate from solution.

Chemical Precipitation↗
PubMed1978

Stopped-flow studies on the n equilibrium f transition in serum albumin.

Stopped-flow studies of the refolding of iodoacetamide-blocked bovine serum albumin from the acid unfolded "F" state have been performed. If the protein is incubated with low concentrations of perchlorate anion then the refolding kinetics follow a simple first-order process. The dependence on pH of both the amplitude of the observed transients and the measured rate constants indicates that the N equilibrium F transition is highly cooperative. The results are consistent with the postulated multidomain structure of albumin which has been developed as a result of both sequence work and a variety of physical studies.

Animals↗
PubMed1978

An inexpensive microcomputer-based stopped-flow data acquisition system.

A low-cost (less than $2,500) microcomputer-controlled data acquisition system for use with a stopped-flow instrument is described. Data acquisition, reduction, signal averaging, kinetic modeling, and plotting are performed under software control. Applications to biological and inorganic systems are presented.

Computers↗
PubMed1977

Bovine serum albumin as a catalyst. VI. Specificity of several nucleophilic groups in the protein for N-dansylaziridine.

The reaction of N-dansylaziridine with serum albumin (both bovine and human) results in incorporation of about 3 mol of covalently bound dansyl label per mol protein. This indicates that a number of nucleophilic groups in these proteins (in addition to the free sulfhydryl group) will react with this reagent. The reaction has been studied in detail for bovine serum albumin and the results suggest that one of the sites labelled by the reagent may be at the unusual "catalytic site" responsible for the enzyme-like activity of bovine serum albumin recently described (Taylor, R.P., Chau, V., Bryner, C. and Berga, S. (1975) J. Am. Chem. Soc. 97, 1934-1942). The reaction of N-dansylaziridine with a variety of other proteins indicates a pattern of labelling consistent with high specificity for the sulfhydryl group. The explanation for the unexpected excess reactivity of albumin with the "sulfhydryl specific" reagent N-dansylaziridine must be related to the three-dimensional structure in albumin which enables a number of specific residues to manifest unusually high degrees of nucleophilic reactivity.

Aziridines↗