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Biomedical subjects

G H Thorpe

Publications and source records attributed to G H Thorpe.

At least 37 records · Page 2Linked to original sources
PubMed1993

A new ultrasensitive chemiluminescent assay for the site-specific quantification of alkaline phosphatase in gingival crevicular fluid.

The search for markers of periodontal disease activity and progression has accelerated over the last decade, in an effort to replace existing subjective clinical measures of periodontal health status. Research is being aimed at establishing more objective and quantitative methodology, capable of rapid diagnosis prior to the appearance of clinical signs of destructive disease. Such tests need to be sensitive enough to evaluate individual periodontal sites in health as well as disease states. We report the development of a new chemiluminescent assay for the enzyme alkaline phosphatase, that is capable of quantifying the enzyme in sub-microliter volumes of gingival crevicular fluid and serum. The technique will measure alkaline phosphatase (ALP) whilst immobilised on paper strips, without the need for an elution stage. It is simple, versatile and amenable to chair-side use. We discuss in detail the assay procedure and have examined levels of ALP in 11 adult volunteers with clinically healthy periodontal tissues. The mean ALP concentration was 2135 IU/L for GCF and 183 IU/L for serum, a 12-fold difference. There also appeared to be an "oral pattern" of enzyme distribution in healthy periodontal sites, with levels being higher in the anterior region of the mouth and highest in the lower anterior region.

Adamantane↗
PubMed1993

Changes in plasma antioxidant status during eccentric exercise and the effect of vitamin supplementation.

Twenty-four healthy students undertook one hour of box-stepping exercise. Prior to exercise eight had received no medication (Group A), eight received 400 mg of vitamin C daily for three weeks before and one week after exercise (Group C) and eight received 400 mg of vitamin E for the same period (Group E). Groups C and E had significantly higher levels of vitamin C (p < 0.01) and vitamin E (p < 0.01) respectively than group A at the commencement of exercise. Plasma total antioxidant capacity rose significantly during exercise in all group (A - p < 0.05; C - p < 0.001; E - p < 0.001). This rise was accounted for by increases in plasma uric acid in all groups. In addition there were significant increases in vitamin C in group C (p < 0.001) and vitamin E in group E (p < 0.05). There were no significant changes in plasma malondialdehyde following exercise in any group. It is concluded that plasma antioxidant capacity rises in response to one hour of eccentric exercise and that the contribution of individual antioxidants to this change can be influenced by vitamin supplementation. The possible mechanisms of the antioxidant changes during exercise and their implications are discussed.

Adolescent↗
PubMed1992

Enzyme-labeled antibodies in bioassays.

Antibody-enzyme conjugates are widely utilized in all spheres of specific analyte detection and measurement, and several trends are evident that will sustain, or even extend, this in the coming years. Of principal importance are the trends toward the development of simplified formats for the rapid and sensitive quantitation of a wide range of analytes without expensive or cumbersome instrumentation, and the exploitation of different types of enzyme and antibody molecules. Advances in hybridoma and recombinant genetics are enabling the practical manipulation of the theoretical repertoire of these reagents, facilitating their availability for a myriad of applications.

Antibodies↗
PubMed1992

Hypophosphatasia: a family study involving a case diagnosed from gingival crevicular fluid.

Hypophosphatasia is an inherited disorder characterized by defective mineralization of the skeletal and dental structures of the body and deficient liver/bone/kidney alkaline phosphatase (L/B/K ALP) activity. There has been a tremendous advance in our knowledge of this condition over the last decade due to the advent of highly specific DNA probes and novel microanalytic techniques. The purpose of this paper is threefold: to review the dental aspects of current literature about this rare condition; to present a case (and family study) that was diagnosed in a 5-yr-old boy from 0.14 microliters of gingival crevicular fluid, using a new ultrasensitive chemiluminescent assay for the enzyme alkaline phosphatase; and to provide strong evidence for an autosomal dominant mode of inheritance.

Adamantane↗
PubMed1992

Comparison of the use of four desktop analysers in six urban general practices.

There is little data on the advantages and disadvantages of using desktop analysers in general practice. This prospective trial compared four of the analysers available in the United Kingdom, in six urban general practices, over a six month period. Of the 2619 tests where the time was noted, 55.8% were performed outside the hours when routine transport to a hospital laboratory was possible (after 12.00 hours). Of the 3530 tests performed the commonest were measurements of cholesterol (14.4 tests per 5000 patients per 30 days), glucose (6.0 tests) and haemoglobin (5.6 tests). Less than 5% of the tests were performed as an emergency despite the speed at which results are available. The main reasons for requesting the tests were screening or case finding (56.9%), with the remainder for monitoring chronic disease, especially diabetes and hypercholesterolaemia. There was evidence that the use of the machines in the four practices reduced requests for hospital laboratory blood tests by 24-40% of pre-study levels. However, there was a considerable increase in testing for cholesterol (three fold) and haemoglobin (eight fold) on the desktop analysers, compared with the number of laboratory tests requested before the study. The cost per test of using such machines is closely related to the level of activity and probably does not compete favourably with hospital testing unless several tests are performed each day. Quality control tests were within the specified limits on at least 98% of occasions, however these tests also identified the need for laboratory back up where a problem was found.

Blood Chemical Analysis↗
PubMed1990

Laboratory testing in, or for, general practice.

Recent technological advances make it possible for general practitioners to do many laboratory tests in the doctor's office. This has advantages and limitations, and a new balance must be found between testing within and outside laboratories. General practitioners will need to decide which tests to do within the practice, and laboratory staff have opportunities to become more involved in the needs and problems of general practice, so that they are able to advise on when and how tests are best performed.

England↗
PubMed1989

An enhanced chemiluminescent enzyme immunoassay for follicle stimulating hormone.

An enhanced chemiluminescent enzyme immunoassay for serum follicle stimulating hormone is described which involves sequential reaction of anti-follicle stimulating hormone antibody immobilised to the inside surface of an opaque microtitre plate with sample, monoclonal anti-alpha thyroid stimulating hormone antibody, and an anti-mouse IgG - horseradish peroxidase conjungate. Bound peroxidase activity was measured using a p-hydroxycinnamic acid enhanced chemiluminescent luminol-hydrogen peroxide reaction. The assay was sensitive (detection limit 0.01 mU/well) precise (intra-assay precision 2.5-8.1%, inter-assay precision 6.7-11.9%) and results obtained with this assay and a competitive radioimmunoassay were in good agreement (correlation coefficient 0.98).

Chorionic Gonadotropin↗
PubMed1989

Chemiluminescent enzyme immunoassay of alpha-fetoprotein based on an adamantyl dioxetane phenyl phosphate substrate.

We have evaluated a new chemiluminescent substrate for the alkaline phosphatase (EC 3.1.3.1) label used in a Hybritech Tandem-E immunoassay of alpha-fetoprotein (AFP). The new substrate, adamantyl 1,2-dioxetane phenyl phosphate (AMPPD), emits light at 477 nm when acted upon by the enzyme. Detection limits for AFP with this method were 33 ng/L (mean of 20 replicates of the zero standard + 2 SD) and 470 ng/L (twice background). Between-batch CVs ranged from 4.31% to 9.60% for AFP in the range 29.1-132.0 micrograms/L. Comparison of results for 49 specimens assayed with use of the chemiluminescent kit and a colorimetric version of the AFP assay gave statistical values as follows: slope = 0.88, intercept = 4.19, and r = 0.94.

Adamantane↗
PubMed1989

Chemiluminescent assay of alkaline phosphatase applied in an ultrasensitive enzyme immunoassay of thyrotropin.

We compared a chemiluminescent assay and a colorimetric endpoint assay for measuring an alkaline phosphatase (EC 3.1.3.1) label in an enzyme immunoassay of thyrotropin (TSH). The substrate in the chemiluminescent assay is a derivative of adamantyl 1,2-dioxetane phosphate. On dephosphorylation, catalyzed by alkaline phosphatase, the 1,2-dioxetane decomposes further and emits a glow of light (lambda max 470 nm). We modified the Hybritech Tandem-E TSH High Sensitivity assay for chemiluminescent detection of bound alkaline phosphatase label by using this substrate (with 20-, 40-, and 60-min incubations). Detection limits (mean +2 SD of zero standard) were 6.0, 5.2, and 4.5 micro-int. units/L for these incubation periods, respectively, vs 20 micro-int. units/L for the conventional colorimetric version of the assay. Comparison of results for 44 clinical specimens assayed by the chemiluminescent (20-min incubation, y) and colorimetric (60-min endpoint, x) TSH immunoassays gave statistical values of: slope = 1.17, intercept = -0.22, and r = 0.98. Hemoglobin, but not bilirubin, lipids, or protein, interfered; but these interferents were removed by the washing steps in the enzyme immunoassay.

Alkaline Phosphatase↗
PubMed1988

An enhanced chemiluminescence enzyme immunoassay for serum oestradiol.

Oestradiol in serum was determined with a simple enhanced chemiluminescent enzyme immunoassay. The assay is based on oestradiol labelled with horseradish peroxidase and the IgG fraction of an oestradiol antiserum coated on a black polystyrene microtitre plate. The enzyme activity of bound label was determined using a p-hydroxycinnamic acid-enhanced chemiluminescent reaction. The assay was sensitive (1.8 fmol/well), precise (intra- and inter-assay CV 4-10% and 8-12%, respectively for sample concentration in the range 122-1330 pmol/L) and showed good agreement with conventional radioimmunoassays (r = 0.99).

Buffers↗
PubMed1986

An enhanced chemiluminescent enzyme immunoassay for serum carcinoembryonic antigen based on a modification of a commercial kit.

A conventional colorimetric peroxidase end-point (ortho-phenylenediamine substrate), used in an enzyme immunoassay for carcinoembryonic antigen, employing plastic beads as solid support, has been replaced by a much faster (30 seconds versus 30 minutes) enhanced chemiluminescent assay for the peroxidase label. Para-iodophenol was used to enhance the light emission from the peroxidase catalysed chemiluminescent reaction between luminol and hydrogen peroxide. Values for precision and carcinoembryonic antigen concentration obtained with the chemiluminescent and colorimetric versions of the immunoassay on 62 serum specimens were in good agreement.

Carcinoembryonic Antigen↗
PubMed1986

Enhanced chemiluminescent reactions catalyzed by horseradish peroxidase.

Enhancement of light emission from the horseradish peroxidase-catalyzed oxidation of diacyl hydrazides on addition of 6-hydroxybenzothiazole or phenol derivatives forms the basis of rapid, specific, and sensitive chemiluminescent assays for peroxidase. The advantages and wide applicability of the technique have been demonstrated in a range of ligand-binding assays. Careful selection of chemiluminescent reagents, enhancer, their relative proportions and reaction conditions, and more detailed knowledge of the mechanism of enhancement should enable further improvements in sensitivity and the intensity or constancy of light emission.

Digoxin↗
PubMed1986

Enhanced luminescent quantitation of horseradish peroxidase conjugates: application in an enzyme immunoassay for digoxin.

A p-iodophenol-enhanced luminescent end-point has been incorporated into a commercially available heterogeneous competitive enzyme immunoassay for digoxin based on a horseradish peroxidase-digoxin conjugate. The luminescent end-point could be completed in less than 1 min and significantly reduced overall assay time. Results for the assay obtained using enhanced luminescence showed good agreement with those obtained using a colorimetric end-point (correlation coefficient 0.98). Both assays gave acceptable precision within the therapeutic range. The incubation time for the luminescent immunoassay was reduced to 15 min and still gave differentiation between sub-therapeutic, therapeutic and toxic levels of digoxin.

Colorimetry↗
PubMed1985

A rapid luminescently monitored enzyme immunoassay for IgE.

A novel halophenol-enhanced luminol-peroxide luminescent detection method for horseradish peroxidase has been tested in an enzyme immunoassay for IgE. The luminescent enzyme immunoassay was reproducible (within-batch CV, 3.9-13.2%) and values obtained on serum samples showed good agreement with those obtained by colorimetric enzyme immunoassay. The major advantages of the luminescent detection method are that it is rapid, 30 s compared with 30 min for the colorimetric assay using o-phenylenediamine, and the luminescent signal is intense and stable for several minutes.

Colorimetry↗