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Cook DB, Bustamam AA, Brotherick I, Shenton BK, Self CH. Lectin ELISA for the c-erb-B2 tumor marker protein p185 in patients with breast cancer and controls. Clin Chem 1999; 45:292-5. [PMID: 9931057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Affiliation(s)
- D B Cook
- Departments of Clinical Biochemistry, University of Newcastle upon Tyne, NE2 4HH, United Kingdom
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2
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Fleming SC, Smith S, Knowles D, Skillen A, Self CH. Increased sialylation of oligosaccharides on IgG paraproteins--a potential new tumour marker in multiple myeloma. J Clin Pathol 1998; 51:825-30. [PMID: 10193323 PMCID: PMC500976 DOI: 10.1136/jcp.51.11.825] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIMS To investigate whether changes in carbohydrate structure of IgG are related to malignancy and stage of disease in myeloma and monoclonal gammopathy of uncertain significance (MGUS). METHODS 61 patients were studied at diagnosis: 14 with MGUS, nine with stage I multiple myeloma, 11 with stage II, 21 with stage III, and five with solitary plasmacytoma. IgG was extracted from serum by protein G affinity chromatography. Oligosaccharides were cleaved from the protein backbone enzymatically by N-glycosidase F. Oligosaccharide analysis was performed by high pressure anion exchange chromatography with pulsed electrochemical detection (HPAE-PED). RESULTS Up to 15 oligosaccharide peaks were identified in three major fractions: neutral, monosialylated, and disialylated. Patients with myeloma showed an increase in the proportion of sialylated oligosaccharides in comparison with patients with MGUS. The ratio of neutral to sialylated oligosaccharides (N:S) was reduced at all stages of myeloma compared with MGUS: MGUS, 11.35; myeloma stage I, 7.6 (p = 0.047); stage II, 5.20 (p = 0.035); stage III, 3.60 (p = 0.0002); plasmacytoma, 7.5 (p = 0.046). The N:S ratio was independent of paraprotein concentration (r = 0.05). CONCLUSIONS The ratio of neutral to sialylated oligosaccharides may act as a new marker of malignancy in IgG paraproteinaemia and warrants further investigation.
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Affiliation(s)
- S C Fleming
- Department of Clinical Biochemistry, University of Newcastle upon Tyne, UK
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3
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Farajollahi MM, Cook DB, Self CH. Major improvement of lectin-based assays through choice of cation and optimization of cation concentration. Anal Biochem 1998; 261:118-21. [PMID: 9683521 DOI: 10.1006/abio.1998.2563] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- M M Farajollahi
- Medical School, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne, NE2 4HH, U.K
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4
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Wicks B, Cook DB, Barer MR, O'Donnell AG, Self CH. A sandwich hybridization assay employing enzyme amplification for termination of specific ribosomal RNA from unpurified cell lysates. Anal Biochem 1998; 259:258-64. [PMID: 9618205 DOI: 10.1006/abio.1998.2643] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We have employed the power of the cyclic NAD-based enzyme amplification system to the determination of 16S rRNA. This generally applicable system employs two oligonucleotide probes, one of which is captured on a microtiter well surface and the other labeled with alkaline phosphatase. The detection of very low levels of hybridization of the capture probe is then achieved by the means of the ultrasensitive enzyme-amplified assay system, resulting in a highly sensitive, convenient, and rapid technology which can be directly employed on unpurified samples. We have been able to demonstrate the detection of 20 amol (10(7) molecules) of pure rRNA, and specific signals from as few as 2000 bacterial cells have also been demonstrated. The total procedural time can be short-5 to 18 h-depending on the dynamic range and sensitivity required. RNA target in the range of 10(12)-10(8) molecules can be assayed within 5 h. Extending the substrate incubation time enables between 10(11) and 10(7) molecules to be determined within 18 h. The system has great potential use with respect to studying the distribution and physiological states of cellular organisms.
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Affiliation(s)
- B Wicks
- Department of Microbiology, University of Newcastle upon Tyne, Tyne, NE2 4HH, United Kingdom
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5
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Abstract
The human placenta synthesizes and secretes large amounts of corticotropin-releasing hormone (CRH) which has been implicated in the triggering of parturition. The placental CRH was found to act in a paracrine manner to stimulate secretion of ACTH and beta-endorphin. In view of this we sought to characterize CRH binding sites in the human placenta. The specific binding of 125I-tyrosyl-ovine CRH (125I-oCRH) to placental membranes was dependent on time, temperature, pH, divalent cations and was reversible on addition of excess oCRH. Scatchard analysis revealed a high afinity binding site with a dissociation constant of approximately 0.7 nmol/L and maximum number of binding sites approximately 44 fmol/mg protein. Disuccinimidyl suberate, a chemical cross-linker, was used to covalently attach 125I-oCRH to placental membranes. The labelled placental membranes were analyzed by SDS-PAGE and autoradiography. A major radioactively labelled band with a molecular weight of 55,000 Da was identified. In this study we have identified placental binding sites for CRH with properties similar to CRH receptors described in a number of human and animal tissues and with a molecular weight similar to that of the brain CRH receptor. These binding sites may be involved in the regulation of the placental CRH/ACTH-beta-endorphin axis during pregnancy and parturition.
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Affiliation(s)
- B O Saeed
- Department of Clinical Biochemistry, Medical School, University of Newcastle-upon-Tyne, England
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6
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Winger LA, Dessi JL, Self CH. Enhanced specificity for small molecules in a convenient format which removes a limitation of competitive immunoassay. J Immunol Methods 1996; 199:185-91. [PMID: 8982361 DOI: 10.1016/s0022-1759(96)00182-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Anti-complex immunoassay systems for small molecules permit the exquisite specificity achievable with monoclonal antibodies to be expressed to an extent which is not possible with competitive format immunoassay. While our previously reported anti-complex system is superior to competitive systems in terms of sensitivity, precision and specificity we have found that this specificity may be enhanced dramatically by simply interposing a wash step between the addition of sample and that of the labelled anti-complex antibody. When such a wash step was attempted with the competitive format system, after addition of sample but before addition of the labelled component, assay performance was degraded to the extent of making it unusable. We suggest, therefore, that the inherent flexibility of the anti-complex approach for small molecule assay creates an opportunity for remarkable enhancement of the functional specificity of primary antibody.
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Affiliation(s)
- L A Winger
- Department of Clinical Biochemistry and Metabolic Medicine, The Medical School, University of Newcastle upon Tyne, UK.
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7
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Abstract
Abstract
New immunometric forms of immunoassay are much more flexible to use than competitive-format immunoassays for small molecular analytes. An example of the utility of this flexibility is the ability to wash the capture antibody after it has been exposed to analyte but before addition of the labeled reagent. This simple maneuver has a large impact on the specificity obtained from already highly specific assays. We also show that specificity can be further increased by means of our multiple binding assay approach, in which the final reading reflects analyte binding to two different primary capture monoclonal antibodies.
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Affiliation(s)
- C H Self
- Department of Clinical Biochemistry, Royal Victoria Infirmary and Associated Hospitals, NHS Trust, The University of Newcastle upon Tyne, UK
| | - J L Dessi
- Department of Clinical Biochemistry, Royal Victoria Infirmary and Associated Hospitals, NHS Trust, The University of Newcastle upon Tyne, UK
| | - L A Winger
- Department of Clinical Biochemistry, Royal Victoria Infirmary and Associated Hospitals, NHS Trust, The University of Newcastle upon Tyne, UK
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8
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Self CH, Dessi JL, Winger LA. Ultra-specific immunoassays for small molecules: roles of wash steps and multiple binding formats. Clin Chem 1996; 42:1527-31. [PMID: 8787724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
New immunometric forms of immunoassay are much more flexible to use than competitive-format immunoassays for small molecular analytes. An example of the utility of this flexibility is the ability to wash the capture antibody after it has been exposed to analyte but before addition of the labeled reagent. This simple maneuver has a large impact on the specificity obtained from already highly specific assays. We also show that specificity can be further increased by means of our multiple binding assay approach, in which the final reading reflects analyte binding to two different primary capture monoclonal antibodies.
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Affiliation(s)
- C H Self
- Department of Clinical Biochemistry, Royal Victoria Infirmary and Associated Hospitals, NHS Trust, The University of Newcastle upon Tyne, UK
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9
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Abstract
The ability to activate biological macromolecules remotely, at specific locations and times, will allow the manipulation of a wide range of cellular activities and give rise to many practical applications. Interest has been shown in the theoretical possibility of accomplishing this by means of photochemical approaches. Photochemical changes of the guest-binding cavity of cyclodextrins has been suggested; however, these changes require organic solvent. What is needed is a widely and readily applicable method allowing activation under physiological conditions. We have developed such a method. This is based on our demonstration that relatively large amounts of the a-methyl substituted 2-nitrobenzyl alcohol, namely, 1-(2-nitrophenyl)ethanol (NPE) can be coupled to proteins using diphosgene. Previous work involved "caging" of small molecules such as ATP (ref. 5-9) and blocking amino acids in peptide synthesis with 2-nitrobenzyl compounds. For large molecules, site-specific reversible inactivation of T4-lysozyme has been reported following introduction of an aspartyl beta-nibenzyl ester into its active site by mutagenesis. In contrast, the present simple procedure allows an existing protein to be deactivated and then, when and where required, reactivated by exposure to ultraviolet-A (UV-A) light. We have employed antibodies as models for both receptors and ligands and have successfully modulated: antibody binding sites for antigen; antigen binding sites for antibody, and antibody Fc binding sites for Protein A.
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Affiliation(s)
- C H Self
- Department of Clinical Biochemistry, University of Newcastle upon Tyne, Medical School, UK
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10
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Abstract
Major developments continue to be reported in key areas of immunoassay technology. Following the development of excellent signal generation methods, attention has shifted to the development of immunochemical methods and instrumentation to provide convenient systems of high performance. Important advances have been made in the design of immunochemical approaches that permit the replacement of competitive format assays for small molecules, such as drugs, metabolites and pollutants, with non-competitive formats, bringing advantages previously seen only with large molecular analytes. Bispecific antibodies and recombinant proteins are also beginning to impact immunodiagnostics, with the promise of even more highly specified reagents. Improvements in automation have brought the facility of homogeneous systems to high-throughput and high-performance heterogeneous systems. Similarly, 'point of need' testing continues to progress. Through all of these advances, systems are evolving according to the needs of users in terms of operator convenience, accuracy, specificity, speed, robustness, and sensitivity.
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Affiliation(s)
- C H Self
- Department of Clinical Biochemistry, University of Newcastle upon Tyne, UK
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11
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Thompson S, Fawcett MC, Spoors JA, Self CH. The modulation of protein A-IgG(Fc) binding by the reversible addition of 2-nitrobenzyl groups. Biochem Soc Trans 1995; 23:155S. [PMID: 7672186 DOI: 10.1042/bst023155s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- S Thompson
- Department of Clinical Biochemistry, Medical School, University of Newcastle Upon Tyne
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12
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Affiliation(s)
- C H Self
- Department of Clinical Biochemistry, Medical School, Newcastle Upon Tyne
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13
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Self CH, Dessi JL, Winger LA. High-performance assays of small molecules: enhanced sensitivity, rapidity, and convenience demonstrated with a noncompetitive immunometric anti-immune complex assay system for digoxin. Clin Chem 1994. [DOI: 10.1093/clinchem/40.11.2035] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
We report the first clinical application of a noncompetitive immunometric assay system that provides advantages for the rapid and robust assay of small molecules similar to those realized for larger molecules with two-site immunometric assays. This anti-immune complex assay is based on the interaction of a receptor such as a primary antibody with its ligand, such that new binding sites, recognizable by a secondary antibody, are formed. In this report the system is applied to the measurement of digoxin in serum. Utilizing an anti-complex antibody that recognizes a digoxin-bound primary antibody with affinity > 2000-fold over its binding to the primary antibody alone, we show that this anti-complex assay system provides a high-performance assay for serum samples, being conveniently simple (immobilized primary antibody binds digoxin and then labeled secondary antibody so that when excess unbound label is washed away the immunometric readout reflects the digoxin concentration), rapid (incubation time 1-10 min), sensitive (detection limit 30 ng/L), precise (3-4% within-run CV, 1-8% total CV), and free from interference from digoxin-like immunoreactive factors.
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Affiliation(s)
- C H Self
- Department of Clinical Biochemistry, Royal Victoria Infirmary, Newcastle upon Tyne, UK
| | - J L Dessi
- Department of Clinical Biochemistry, Royal Victoria Infirmary, Newcastle upon Tyne, UK
| | - L A Winger
- Department of Clinical Biochemistry, Royal Victoria Infirmary, Newcastle upon Tyne, UK
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14
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Self CH, Dessi JL, Winger LA. High-performance assays of small molecules: enhanced sensitivity, rapidity, and convenience demonstrated with a noncompetitive immunometric anti-immune complex assay system for digoxin. Clin Chem 1994; 40:2035-41. [PMID: 7955375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We report the first clinical application of a noncompetitive immunometric assay system that provides advantages for the rapid and robust assay of small molecules similar to those realized for larger molecules with two-site immunometric assays. This anti-immune complex assay is based on the interaction of a receptor such as a primary antibody with its ligand, such that new binding sites, recognizable by a secondary antibody, are formed. In this report the system is applied to the measurement of digoxin in serum. Utilizing an anti-complex antibody that recognizes a digoxin-bound primary antibody with affinity > 2000-fold over its binding to the primary antibody alone, we show that this anti-complex assay system provides a high-performance assay for serum samples, being conveniently simple (immobilized primary antibody binds digoxin and then labeled secondary antibody so that when excess unbound label is washed away the immunometric readout reflects the digoxin concentration), rapid (incubation time 1-10 min), sensitive (detection limit 30 ng/L), precise (3-4% within-run CV, 1-8% total CV), and free from interference from digoxin-like immunoreactive factors.
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Affiliation(s)
- C H Self
- Department of Clinical Biochemistry, Royal Victoria Infirmary, Newcastle upon Tyne, UK
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15
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Abstract
As elevated levels of glycated IgG have been detected in the plasma of patients with diabetes mellitus, a disease associated with increased susceptibility to infection, we have investigated whether glycation of MoAbs affects the kinetics and/or affinity of antigen binding. Three mouse MoAbs were incubated with 0.5 M glucose at pH 7.4 for 14-21 days at 37 degrees C. Control MoAbs were incubated using identical conditions but with no added glucose. Using a surface plasmon resonance technique we found that glycation significantly increased the rate of dissociation (kdiss) of the antigen-antibody complex for all three MoAbs (P < 0.05, n = 4), but had no significant effect on the rate of association (kass). For one of the MoAbs, against human IgG (Fab), we also measured kdiss by an alternative method utilizing radiolabelled antigen, which confirmed that glycation of the antibody significantly increases kdiss (P < 0.001, n = 8). We also found using an ELISA-based method that glycation of the same MoAb significantly increased the equilibrium dissociation constant (Kd) (P < 0.05, n = 6). A significant increase in kd was observed after glycation using glucose concentrations consistent with those found in poorly controlled diabetics (P < 0.02, n = 5). We conclude that in vitro glycation can significantly lower the affinity of an antibody for its antigen, and significantly increases the rate of dissociation of the antigen-antibody complex.
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Affiliation(s)
- D M Kennedy
- Department of Clinical Biochemistry, University of Newcastle upon Tyne, UK
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16
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Abstract
We have developed methods to allow the reversible binding of up to 15 nitrobenzyl residues per bovine serum albumin molecule and show 95% of these residues can be removed by exposure to UV light for 10 min. The general non-specific coating method is presented by means of a model system but is applicable to a wide range of proteins with important biological functions. Potentially, any protein could be coated with sufficient photo-removable groups to inhibit its biological function. Its activity may then be restored at will by exposure to UV light removing the coupled 2-nitrobenzyl groups.
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Affiliation(s)
- S Thompson
- Department of Clinical Biochemistry, Medical School, Newcastle Upon Tyne, United Kingdom
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17
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Mann AC, Record CO, Self CH, Turner GA. Monosaccharide composition of haptoglobin in liver diseases and alcohol abuse: large changes in glycosylation associated with alcoholic liver disease. Clin Chim Acta 1994; 227:69-78. [PMID: 7955423 DOI: 10.1016/0009-8981(94)90136-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Liver damage through prolonged intake of high amounts of alcohol is a serious problem that affects many members of the population. The aim of this study was to investigate changes in the glycosylation of haptoglobin (Hp) resulting from alcoholic liver diseases. The monosaccharide composition was measured in Hp isolated from 48 healthy individuals, 15 alcohol abusers (AA); 25 patients with alcoholic liver disease, including those with alcoholic cirrhosis (ALD/AC), and 17 other patients with either chronic active hepatitis (AH) or primary biliary cirrhosis (BC). Fucose was elevated per mol of Hp in 70%, 44%, and 33% of the individuals in the ALD/AC, BC and AA groups, respectively. Fucose was not elevated in the AH group. N-acetylglucosamine was also elevated in the ALD/AC group. Expressing results per 3 mol of mannose suggested the presence of higher branching with increased fucose content in Hp from all the abnormal groups except the AH group. More structural information is required to develop the diagnostic potential of carbohydrate measurements of Hp in alcoholic liver diseases.
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Affiliation(s)
- A C Mann
- Department of Clinical Biochemistry, Medical School, Newcastle upon Tyne, UK
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18
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Abstract
As elevated levels of glycated IgG have been detected in the plasma of diabetics we have investigated whether glycation of IgG affects its vascular clearance rate, using a mouse model system. Polyclonal mouse IgG was aseptically incubated for 14-19 days with 0.5 M glucose in 0.1 M phosphate buffer (pH 7.4) at 37 degrees C. As control, IgG was incubated under identical conditions but with no added glucose. After incubation, both forms were labelled with 125I and injected intravenously into BALB/c mice. The rate of vascular clearance of the glycated IgG was found to be significantly higher than the control IgG in the periods 5-24 h (P < 0.001, n = 6) and 24-48 h (P < 0.01, n = 6) after injection. After 2-3 days the mice were killed and the major organs were harvested. With glycated IgG there was a significant increase in the 125I accumulated in the kidney (P < 0.02). In later experiments, dual labelling with 131I and 125I allowed mixtures of glycated and unglycated IgG to be injected into the same mouse so that the vascular clearance of both forms of IgG could be followed simultaneously. These experiments confirmed that glycation of the IgG significantly increases its vascular clearance rate.
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Affiliation(s)
- D M Kennedy
- Department of Clinical Biochemistry, Medical School, University of Newcastle Upon Tyne, UK
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19
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Kennedy DM, Skillen AW, Self CH. Colorimetric assay of glycoprotein glycation free of interference from glycosylation residues. Clin Chem 1993; 39:2309-11. [PMID: 7693374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have developed a colorimetric assay for determining the degree of glycation of serum proteins that is unaffected by glycosylation residues. This was accomplished by reducing the proteins with sodium borohydride prior to periodate oxidation. Previous periodate-based methods, which offer several advantages over other glycation assays, cannot determine glycoprotein glycation because interference from sialic residues in the glycan chain can lead to overestimation of the amount of glycation products. Without reduction, glycation of fetuin was double that of asialofetuin glycated under identical conditions. We found that borohydride reduction before periodate oxidation increases the amount of formaldehyde released in proportion to the extent of glycation, irrespective of the degree of glycosylation. Using two glycoproteins and an unglycosylated protein, we showed how measurement of the formaldehyde increase enables the extent of glycoprotein glycation to be determined without removal of interfering sugars.
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Affiliation(s)
- D M Kennedy
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK
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20
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Abstract
Abstract
We have developed a colorimetric assay for determining the degree of glycation of serum proteins that is unaffected by glycosylation residues. This was accomplished by reducing the proteins with sodium borohydride prior to periodate oxidation. Previous periodate-based methods, which offer several advantages over other glycation assays, cannot determine glycoprotein glycation because interference from sialic residues in the glycan chain can lead to overestimation of the amount of glycation products. Without reduction, glycation of fetuin was double that of asialofetuin glycated under identical conditions. We found that borohydride reduction before periodate oxidation increases the amount of formaldehyde released in proportion to the extent of glycation, irrespective of the degree of glycosylation. Using two glycoproteins and an unglycosylated protein, we showed how measurement of the formaldehyde increase enables the extent of glycoprotein glycation to be determined without removal of interfering sugars.
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Affiliation(s)
- D M Kennedy
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK
| | - A W Skillen
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK
| | - C H Self
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK
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21
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Abstract
Abstract
Enzyme amplification has proved to be a highly sensitive quantification technique for immunoassays. We have shown that by using a fluorescent end-point, even more sensitive enzyme amplification assays can be generated than hitherto reported. We describe some general properties of this system and demonstrate its application in an assay for human proinsulin in plasma. The detection system can be used to measure less than one thousandth of an attomole (1 zeptomole) of alkaline phosphatase, equivalent to about 350 molecules of alkaline phosphatase per well of a microtiter plate. We have used this system to construct a proinsulin assay with a sensitivity of 0.017 pmol/L.
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Affiliation(s)
- D B Cook
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK
| | - C H Self
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK
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22
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Cook DB, Self CH. Determination of one thousandth of an attomole (1 zeptomole) of alkaline phosphatase: application in an immunoassay of proinsulin. Clin Chem 1993; 39:965-71. [PMID: 8504565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Enzyme amplification has proved to be a highly sensitive quantification technique for immunoassays. We have shown that by using a fluorescent end-point, even more sensitive enzyme amplification assays can be generated than hitherto reported. We describe some general properties of this system and demonstrate its application in an assay for human proinsulin in plasma. The detection system can be used to measure less than one thousandth of an attomole (1 zeptomole) of alkaline phosphatase, equivalent to about 350 molecules of alkaline phosphatase per well of a microtiter plate. We have used this system to construct a proinsulin assay with a sensitivity of 0.017 pmol/L.
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Affiliation(s)
- D B Cook
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK
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23
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Milton NG, Self CH, Hillhouse EW. Effects of pyrogenic immunomodulators on the release of corticotrophin-releasing factor-41 and prostaglandin E2 from the intact rat hypothalamus in vitro. Br J Pharmacol 1993; 109:88-93. [PMID: 8495249 PMCID: PMC2175569 DOI: 10.1111/j.1476-5381.1993.tb13535.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
1. The actions of the following pyrogens: lipopolysaccharide (LPS), polyinosinic:polycytidylic acid (Poly-I:C), human interleukin (IL)-1 alpha and IL-1 beta, human IL-6 and rat interferon (INF) on corticotrophin-releasing factor-41 (CRF-41) and prostaglandin E2 (PGE2) release from the intact rat hypothalamus in vitro have been studied. 2. Rat hypothalami were incubated in vitro in an artificial cerebrospinal fluid. Immunoreactive (ir)-CFR-41 and PGE2 released into the medium were measured by two-site enzyme amplified immunometric assay (EAIA) and radioimmunoassay (RIA) respectively. 3. Human IL-6 (1 to 10,000 IU ml-1) caused a dose-dependent release of irCRF-41, rising to a maximal 3-4 fold increase over basal at the highest dose tested. Human IL-1 alpha (1 to 1000 IU ml-1), human IL-1 beta (1 to 1000 IU ml-1), poly-I:C (10 pg ml-1 to 100 micrograms ml-1) and rat INF (1 to 10,000 IRu ml-1) all failed to alter irCRF-41 release. 4. LPS (1 mg ml-1) caused a 35% decrease in irCRF-41 release; however, over the dose-range of 0.1 microgram ml-1 to 100 micrograms ml-1, LPS failed to alter irCRF-41 release. The decreased irCRF-41 release in response to LPS (1 mg ml-1) was accompanied by a decrease in the subsequent 56 mM KCl stimulation of irCRF-41. 5. Human IL-1 alpha and IL-1 beta (1000 IU ml-1) were able to stimulate the release of irPGE2 from intact hypothalami, causing a 2 fold increase over basal release. Poly-I:C (100 microg ml-1), LPS (0.1 microg ml-1 to 1 mg ml-1), rat INF (10,000 IRu ml-1) and human IL-6 (1 to 10,000 iu ml-1) all failed to alter irPGE2release.6. In conclusion, these results suggest that the in vitro release of CRF-41 and PGE2, in response to pyrogens, are mediated via different cytokines. In view of this it is possible that different cytokines may mediate the temperature, prostaglandin and hypothalamo-pituitary-adrenocortical axis activation seen during pyrogenic stimulation in vivo.
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Affiliation(s)
- N G Milton
- Department of Clinical Biochemistry, University of Newcastle upon Tyne
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24
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Mann AC, Thompson S, Record CO, Self CH, Turner GA. Monosaccharide composition of haptoglobin purified from alcoholic cirrhotic and control sera determined by HPAE. Biochem Soc Trans 1993; 21:214S. [PMID: 8359464 DOI: 10.1042/bst021214s] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- A C Mann
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne
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25
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Abstract
Abstract
We describe an amplified enzyme-linked immunoassay of human proinsulin in serum that detects intact proinsulin and both the 32/33 and 65/66 split forms. The method uses the IgG fraction of a polyclonal antibody raised in a guinea pig against intact proinsulin, which we used to coat plastic microtiter plates. A sandwich was formed with proinsulin by using a monoclonal antibody against C-peptide labeled with alkaline phosphatase. We quantified the reaction by using the enzyme amplification procedure, which detected as little intact proinsulin as 0.1 pmol/L. We found no cross-reactivity with C-peptide in the assay, and decreased recovery attributable to the presence of insulin could be demonstrated only with a 30-fold excess of this hormone over proinsulin.
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Affiliation(s)
- F J Dhahir
- Department of Clinical Biochemistry and Supra-Regional Assay Service Laboratory, Medical School, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne, NE2 4HH,U.K
| | - D B Cook
- Address correspondence to this author
| | - C H Self
- Department of Clinical Biochemistry and Supra-Regional Assay Service Laboratory, Medical School, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne, NE2 4HH,U.K
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Dhahir FJ, Cook DB, Self CH. Amplified enzyme-linked immunoassay of human proinsulin in serum (detection limit: 0.1 pmol/L). Clin Chem 1992; 38:227-32. [PMID: 1541005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We describe an amplified enzyme-linked immunoassay of human proinsulin in serum that detects intact proinsulin and both the 32/33 and 65/66 split forms. The method uses the IgG fraction of a polyclonal antibody raised in a guinea pig against intact proinsulin, which we used to coat plastic microtiter plates. A sandwich was formed with proinsulin by using a monoclonal antibody against C-peptide labeled with alkaline phosphatase. We quantified the reaction by using the enzyme amplification procedure, which detected as little intact proinsulin as 0.1 pmol/L. We found no cross-reactivity with C-peptide in the assay, and decreased recovery attributable to the presence of insulin could be demonstrated only with a 30-fold excess of this hormone over proinsulin.
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Affiliation(s)
- F J Dhahir
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, U.K
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McNeil CJ, Greenough KR, Weeks PA, Self CH, Cooper JM. Electrochemical sensors for direct reagentless measurement of superoxide production by human neutrophils. Free Radic Res Commun 1992; 17:399-406. [PMID: 1337538 DOI: 10.3109/10715769209083144] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Electrochemical sensors based on immobilised cytochrome c or superoxide dismutase for the measurement of superoxide radical production by stimulated neutrophils are described. Cytochrome c was immobilised covalently at a surface-modified gold electrode and by passive adsorption to novel platinised activated carbon electrodes (PACE). The reoxidation of cytochrome c at the electrode surface upon reduction by superoxide was monitored using both xanthine/xanthine oxidase and stimulated neutrophils as sources of the free radical. In addition, bovine Cu/Zn superoxide dismutase was immobilised to PACE by passive adsorption and superoxide, generated by xanthine/xanthine oxidase, detected by oxidation of hydrogen peroxide produced by the enzymic dismutation of the superoxide radical. A biopsy needle probe electrode based on cytochrome c immobilised at PACE and suitable for continuous monitoring of free radical production was constructed and characterised.
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Affiliation(s)
- C J McNeil
- Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK
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Milton NG, Nicholson SA, Self CH, Hillhouse EW. The effects of rat corticotrophin-releasing factor-41 Peptide fragments on bioassay and immunoassay determination of corticotrophin-releasing factor-41 levels. J Neuroendocrinol 1990; 2:897-901. [PMID: 19215435 DOI: 10.1111/j.1365-2826.1990.tb00657.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Abstract Peptide fragments of rat corticotrophin-releasing factor-41 (CRF-41) containing amino-acid residues 21-33 antagonized the 5 nmol/l CRF-41-stimulated adrenocorticotrophin secretion from the adult rat pituitary gland in vitro. The CRF 6-33 sequence had antagonistic effects at equimolar (5 nmol/l) concentrations which were not observed at high (50 nmol/l) concentrations whilst the CRF 21-41 sequence had effects only at high (50 nmol/l) concentrations. Similar effects were observed with CRF 6-33 on basal release of adrenocorticotrophin. Peptide fragments elevated radioimmunoassay measurement of CRF-41 whilst inhibiting measurement of CRF-41 in a two-site enzyme amplified immunometric assay. The inhibitory effects of peptide fragments in the enzyme amplified immunometric assay could be removed by dilution to within the lower end of the standard curve or by increasing the concentration of antibody bound to the solid phase. These inhibitory effects mimic those of peptide fragments on basal adrenocorticotrophin release seen in a rat pituitary gland in vitro bioassay indicating that such two-site immunoassay determinations bear closer relation to bioactivity than those obtained using radioimmunoassay.
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Affiliation(s)
- N G Milton
- Department of Medicine, King's College School of Medicine, Bessemer Road, London SE5 9PJ, UK
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Milton NG, Hillhouse EW, Fuller JQ, Self CH. Corticotrophin-releasing factor-41 in the human and rat-utility of a highly sensitive enzyme amplified immunometric assay. J Neuroendocrinol 1990; 2:889-95. [PMID: 19215434 DOI: 10.1111/j.1365-2826.1990.tb00656.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Abstract We have developed a highly sensitive and specific immunoassay for human/rat corticotrophin-releasing factor-41 (CRF-41) to enable determination of immunoreactive CRF-41 levels in biological samples. To achieve high specificity, sensitivity and speed we have used two antisera in a sandwich enzyme immunoassay combined with enzyme amplification. The assay has a sensitivity of 0.08 fmol/well compared with radioimmunoassay sensitivities of 0.5 fmol/tube and is highly specific for the intact CRF-41 molecule. Measurement of samples is complete within 24 h compared with the 5 days required to obtain sensitive radioimmunoassay measurement. The assay has been used to measure both rat hypothalamic CRF-41 tissue content and release in vitro with good correlation when compared to radioimmunoassay measurement using antisera rC70 (0.983) or R1 (0.953). The assay only measures immunoreactive CRF-41 coeluting with human/rat CRF-41 and its oxidized form Met [O(21,38)]CRF-41 in human and rat tissue extracts separated by high-performance liquid chromatography. The ability to measure immunoreactive CRF-41 in unextracted plasma allows rapid measurement and eliminates multiple extraction steps.
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Affiliation(s)
- N G Milton
- Department of Medicine, King's College School of Medicine, Bessemer Road, London SE5 9PJ, UK
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Milton NG, Hillhouse EW, Nicholson SA, Self CH, McGregor AM. Production and utilization of monoclonal antibodies to human/rat corticotrophin-releasing factor-41. J Mol Endocrinol 1990; 5:159-66. [PMID: 2248688 DOI: 10.1677/jme.0.0050159] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Murine monoclonal antibodies against human/rat corticotrophin-releasing factor-41 (CRF-41) were produced and characterized for use in the immunological and biological characterization of CRF-41. Spleen cells from BALB/c mice immunized with CRF-41 conjugated to bovine gamma-globulin were fused with a BALB/c-derived non-secretor X-63 myeloma line. Hybridomas were selected for CRF antibody production by enzyme-linked immunosorbent assay, and positive hybridomas cloned twice. Three monoclonal antibodies were obtained (KCHMB001, KCHMB002 and KCHMB003) and characterized as IgG1, IgG1 and IgG2a isotypes respectively, with affinity constants for rat CRF-41 of 30, 53 and 34 nmol/l respectively. All three monoclonal antibodies recognize an epitope contained between residues 34 and 41 of the human/rat sequence. The antibodies were able to neutralize the ACTH-releasing activity of rat CRF-41, applied to rat pituitary fragments in vitro, in a dose-dependent manner. Isoelectric focusing showed that KCHMB003 detected bands of synthetic rat CRF-41 and rat [Met(O)21,38]-CRF-41 at pH 7.1 and 6.8 respectively. Use of KCHMB003 in a two-site enzyme-amplified immunoassay showed that this antibody recognizes both synthetic rat CRF-41 and immunoreactive CRF-41 in rat hypothalamic tissue extracts.
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Affiliation(s)
- N G Milton
- Department of Medicine, King's College School of Medicine and Dentistry, London
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Zaidi M, Seth R, Girgis SI, Self CH. Development and performance of a highly sensitive and specific two-site immunometric assay of calcitonin gene-related peptide. Clin Chem 1990. [DOI: 10.1093/clinchem/36.7.1288] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Calcitonin gene-related peptide (CGRP), a potent endogenous circulating vasodilator, is produced by the alternative splicing of the calcitonin/CGRP gene and is expressed mainly in neural and cardiovascular tissues. We recently reported a highly sensitive radioimmunoassay of CGRP, based on an antiserum recognizing the C-terminus of the molecule. We have also found that circulating immunoreactive CGRP is heterogeneous; thus we are unable to measure selectively the intact molecule with our one-site competitive approach. We therefore attempted to construct a two-site immunometric assay involving two antibodies, one that detects the C-terminus and another that recognizes the midregion of the molecule. To enhance assay sensitivity, we applied a colorimetric amplification system to this assay. This rapid, robust, and reproducible assay provides more nearly accurate estimates of circulating CGRP and offers a sensitive and more specific alternative to the radioimmunoassay, with advantages in speed, simplicity, and convenience.
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Affiliation(s)
- M Zaidi
- Department of Cellular and Molecular Sciences, St. George's Hospital Medical School, Tooting, London, U.K
| | - R Seth
- Department of Cellular and Molecular Sciences, St. George's Hospital Medical School, Tooting, London, U.K
| | - S I Girgis
- Department of Cellular and Molecular Sciences, St. George's Hospital Medical School, Tooting, London, U.K
| | - C H Self
- Department of Cellular and Molecular Sciences, St. George's Hospital Medical School, Tooting, London, U.K
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Zaidi M, Seth R, Girgis SI, Self CH. Development and performance of a highly sensitive and specific two-site immunometric assay of calcitonin gene-related peptide. Clin Chem 1990; 36:1288-94. [PMID: 2197033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Calcitonin gene-related peptide (CGRP), a potent endogenous circulating vasodilator, is produced by the alternative splicing of the calcitonin/CGRP gene and is expressed mainly in neural and cardiovascular tissues. We recently reported a highly sensitive radioimmunoassay of CGRP, based on an antiserum recognizing the C-terminus of the molecule. We have also found that circulating immunoreactive CGRP is heterogeneous; thus we are unable to measure selectively the intact molecule with our one-site competitive approach. We therefore attempted to construct a two-site immunometric assay involving two antibodies, one that detects the C-terminus and another that recognizes the midregion of the molecule. To enhance assay sensitivity, we applied a colorimetric amplification system to this assay. This rapid, robust, and reproducible assay provides more nearly accurate estimates of circulating CGRP and offers a sensitive and more specific alternative to the radioimmunoassay, with advantages in speed, simplicity, and convenience.
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Affiliation(s)
- M Zaidi
- Department of Cellular and Molecular Sciences, St. George's Hospital Medical School, Tooting, London, U.K
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Seth R, Motté P, Kehely A, Wimalawansa SJ, Self CH, Bellet D, Bohuon C, MacIntyre I. A sensitive and specific two-site enzyme-immunoassay for human calcitonin using monoclonal antibodies. J Endocrinol 1988; 119:351-7. [PMID: 3058855 DOI: 10.1677/joe.0.1190351] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A highly sensitive, specific and rapid two-site enzyme-immunometric assay (EIA) for the measurement of immunoreactive (ir) human calcitonin (hCT) in human plasma was developed using high-affinity monoclonal antibodies. The assay was validated in terms of sensitivity, specificity and reproducibility and its performance compared with that of a radioimmunoassay (RIA) employing a polyclonal antiserum. The sensitivity of the overnight EIA (2 pmol/l) was comparable with the long-incubation (7 days) RIA. The overnight RIA had a sensitivity of 10 pmol/l. The inter- and intra-assay variations of the EIA were less than 12%. Some related and non-related peptides were compared with synthetic hCT for cross-reactivity in the assay and were found to be negative. The mean recovery of added synthetic hCT from plasma of normal volunteers was 96%. Both RIA and EIA have been applied to the measurement of ir-hCT in normal volunteers and in patients with medullary carcinoma of the thyroid. In both groups, the level of ir-hCT measured by EIA was found to be lower than that measured by RIA, presumably due to the ability of the more specific EIA to detect only the 'mature' form of the hormone. EIA offers an attractive alternative to the more cumbersome and lengthy RIA in current usage, with the added advantage of employing a non-isotopic label.
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Affiliation(s)
- R Seth
- Department of Chemical Pathology, Royal Postgraduate Medical School, London
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Seth R, Zaidi M, Fuller JQ, Self CH. A highly specific and sensitive enzyme-immunometric assay for calcitonin gene-related peptide based on enzyme amplification. J Immunol Methods 1988; 111:11-6. [PMID: 3260611 DOI: 10.1016/0022-1759(88)90053-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Calcitonin gene-related peptide (CGRP) is an important member of the peptide family encoded by the calcitonin gene. It has been found to be a potent vasodilator in man and a major circulating gene product (Girgis et al., 1985). The present study reports the development of a sensitive and rapid two-site immunoassay for CGRP based on enzyme amplification (Self, 1985). The assay has been easy to construct, taking advantage of available antisera raised for other purposes. Nevertheless it has been found to be clearly superior to our previous radioimmunoassay in terms of sensitivity, specificity, speed and convenience.
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Affiliation(s)
- R Seth
- Department of Chemical Pathology, Royal Postgraduate Medical School, London, U.K
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Abstract
A colorimetric enzyme amplification system was used to develop an immunoassay for human calcitonin (hCT) with a sensitivity of 6 pmol/l, and intra- and inter-assay CVs of 12% and 11.8% respectively for the low pool, and 10% and 11.2% for the high pool. The mean recovery of added synthetic hCT (58.5 pmol) from the plasma of 10 patients was 110% (64.4 pmol). The correlation coefficient between radioimmunoassay (RIA) and amplified enzymo-immunoassay was found to be 0.96 (p 0.001). The assay was successfully applied to the measurement of elevated calcitonin levels in plasma from patients with medullary carcinoma of the thyroid (MCT). AEIA offered a reliable and sensitive alternative to RIA for calcitonin determination with the added advantage of convenience as the label employed was much more stable.
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Affiliation(s)
- C Lynch
- Department of Chemical Pathology, Royal Postgraduate Medical School, Hammersmith Hospital, London, U.K
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Moss DW, Self CH, Whitaker KB, Bailyes E, Siddle K, Johannsson A, Stanley CJ, Cooper EH. An enzyme-amplified monoclonal immunoenzymometric assay for prostatic acid phosphatase. Clin Chim Acta 1985; 152:85-94. [PMID: 2414044 DOI: 10.1016/0009-8981(85)90179-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
An immunoassay for prostatic acid phosphatase is described in which a high degree of specificity for the prostatic isoenzyme, obtained by the use of monoclonal antibodies, is combined with great sensitivity, made possible by enzyme-amplified measurement of the combination of the isoenzyme with its antibody. The increase in sensitivity thus achieved is of the order of 170 times that of conventional methods of measurement. The advantages of the enzyme-amplified method have been shown to be particularly useful in detecting and monitoring small abnormalities of prostatic acid phosphatase levels in patients with prostatic cancer.
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Abstract
Enzyme immunoassays (EIA) are now used for the quantitation of a wide range of clinically important analytes and have, in many cases, replaced radioimmunoassays, though without improving on the sensitivity of the latter technique. We describe a general enzyme-amplification method which can be used to increase both the speed and the sensitivity of EIA. In this method, the enzyme label is used to catalyse the dephosphorylation of nicotinamide adenine dinucleotide phosphate (NADP+); the NAD+ so formed then catalytically activates an NAD+-specific redox cycle, yielding an intensely coloured formazan dye. The application of this new enzyme detection method has made possible an assay for human thyroid-stimulating hormone (TSH) with a sensitivity of 1 X 10(-5) IU/1 and a progesterone assay which takes only 15 min to complete.
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Girgis SI, Macdonald DW, Stevenson JC, Bevis PJ, Lynch C, Wimalawansa SJ, Self CH, Morris HR, MacIntyre I. Calcitonin gene-related peptide: potent vasodilator and major product of calcitonin gene. Lancet 1985; 2:14-6. [PMID: 2861456 DOI: 10.1016/s0140-6736(85)90059-5] [Citation(s) in RCA: 148] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In addition to calcitonin and katacalcin, the human calcitonin gene encodes a novel peptide--calcitonin gene-related peptide (CGRP)--a potent vasodilator. A sensitive and specific radioimmunoassay was developed to study plasma levels of CGRP in normal subjects. CGRP circulates at five times the concentration of calcitonin, suggesting that it may be an important physiological regulator of vascular tone and blood flow.
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Self CH, Wimalawansa SJ, Johannsson A, Bates DL, Girgis SI, Macintyre I. A new sensitive and fast peptide immunoassay based on enzyme amplification used in the determination of CGRP and the demonstration of its presence in the thyroid. Peptides 1985; 6:627-30. [PMID: 3906592 DOI: 10.1016/0196-9781(85)90164-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
An enzyme amplified immunoassay for rCGRP based on cofactor cycling has been found to be clearly superior to a comparable radioimmunoassay employing the same antiserum in terms of sensitivity, speed and convenience. Correlation between the two methods was very good. With the enzyme amplified immunoassay we have been able to demonstrate the existence of rCGRP in thyroid extract.
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Johannsson A, Stanley CJ, Self CH. A fast highly sensitive colorimetric enzyme immunoassay system demonstrating benefits of enzyme amplification in clinical chemistry. Clin Chim Acta 1985; 148:119-24. [PMID: 3888455 DOI: 10.1016/0009-8981(85)90221-9] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A method for greatly enhancing the sensitivity of assays employing enzyme labels is described which offers advantages in assays for a wide range of analytes. The principle of the new approach is that the enzyme label gives rise to a catalytic activator for a specific secondary detection system, the activity of which is measured and related back to the amount of label present and thus of the analyte it is being used to determine (C.H. Self, Eur. Pat. Appl. 80303478.4, 15.4.81 exclusively licenced to IQ (Bio) Ltd.). The general principle of enzyme amplification is illustrated by using alkaline phosphatase as the labelling enzyme and nicotinamide adenine dinucleotide phosphate (NADP) as its substrate. The nicotinamide adenine dinucleotide (NAD) formed catalytically activates a strictly NAD specific redox cycle which produces a coloured formazan as the end product. The measured absorbance is at least two orders of magnitude greater than that achieved by conventional methods. The application of this method to immunoassay is demonstrated by a sensitive, rapid and precise assay for human prostatic acid phosphatase (PAP). Some of the many other applications of this methodology are discussed.
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Abstract
A method is described in which enzyme amplification is used for the quantitative determination of placental alkaline phosphatase. In this particular application, placental alkaline phosphatase is captured on a solid surface by means of a monoclonal antibody. The enzyme is then determined by dephosphorylation of NADP to NAD which activates a strictly NAD-dependent redox cycle leading to the formation of a coloured product.
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Self CH, Van der Riet FJ. A general method for the rapid separation and specific detection of antigenic meterial by immunoelectrofiltration using multispecific antisera. J Immunol Methods 1976; 13:235-9. [PMID: 64569 DOI: 10.1016/0022-1759(76)90070-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A general technique is described for the separation and detection of specific antigens from complex antigen mixtures, by their electrophoresis through antibody-containing gels. The method does not require purified reagent antigen or fuctionally monospecific antisera and should have a wide applicability in the detection, quantification and characterization of various antigens.
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Tew JG, Self CH, Harold WW, Stavitsky AB. The spontaneous induction of anamnestic antibody synthesis in lymph node cell cultures many months after primary immunization. J Immunol 1973; 111:416-23. [PMID: 4717987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Self CH, Parker MG, Weitzman DJ. The isocitrate dehydrogenases of Acinetobacter lwoffi. Studies on the regulation of a nicotinamide-adenine dinucleotide phosphate-linked isoenzyme. Biochem J 1973; 132:215-21. [PMID: 4146835 PMCID: PMC1177580 DOI: 10.1042/bj1320215] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Of the two NADP-linked isocitrate dehydrogenases in Acinetobacter lwoffi the higher-molecular-weight form, isoenzyme-II, is reversibly stimulated sixfold by low concentrations of glyoxylate or pyruvate. Kinetic results indicate that this stimulation of activity involves both an increase in V(max.) and a decrease in the apparent K(m) values for substrates, most markedly that for NADP(+). Other changes brought about by glyoxylate or pyruvate include a shift in the pH optimum for activity and an increased stability to inactivation by heat or urea. Mixtures of glyoxylate plus oxaloacetate, known to inhibit isocitrate dehydrogenases from other organisms, produce inhibition of both A. lowffi isoenzymes, and do not reflect the stimulatory specificity of glyoxylate for isoenzyme-II. Isoenzyme-II is also stimulated by AMP and ADP, but the activation by glyoxylate or pyruvate is shown to be quite independent of the adenylate activation. Differential desensitization of the enzyme by urea to the two types of activator further supports the view that the enzyme possesses two distinct allosteric regulatory sites. The metabolic significance of the activations is discussed.
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Stavitsky AB, Tew JG, Self CH. Antibody responses in cell cultures from draining and non-draining rabbit lymph nodes primed with native or polymerized human albumin. Adv Exp Med Biol 1973; 29:675-82. [PMID: 4211811 DOI: 10.1007/978-1-4615-9017-0_98] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Self CH, Weitzman PD. The isocitrate dehydrogenases of Acinetobacter lwoffi. Separation and properties of two nicotinamide-adenine dinucleotide phosphate-linked isoenzymes. Biochem J 1972; 130:211-9. [PMID: 4144072 PMCID: PMC1174318 DOI: 10.1042/bj1300211] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Two isoenzymes of NADP-linked isocitrate dehydrogenase have been identified in Acinetobacter lwoffi and have been termed isoenzyme-I and isoenzyme-II. The isoenzymes may be separated by ion-exchange chromatography on DEAE-cellulose, by gel filtration on Sephadex G-200, or by zonal ultracentrifugation in a sucrose gradient. Low concentrations of glyoxylate or pyruvate effect considerable stimulation of the activity of isoenzyme-II. The isoenzymes also differ in pH-dependence of activity, kinetic parameters, stability to heat or urea and molecular size. Whereas isoenzyme-I resembles the NADP-linked isocitrate dehydrogenases from other organisms in having a molecular weight under 100000, isoenzyme-II is a much larger enzyme (molecular weight around 300000) resembling the NAD-linked isocitrate dehydrogenases of higher organisms.
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Stavitsky AB, Self CH. In vitro regulation of the anamnesic antibody response upon addition of heterologous antigens to primed lymphoid cells. Immunol Commun 1972; 1:491-506. [PMID: 4680355 DOI: 10.3109/08820137209022959] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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