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Biomedical subjects

G F Read

Publications and source records attributed to G F Read.

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

Simultaneous plasma and saliva steroid measurements as an index of control in congenital adrenal hyperplasia (CAH). A longitudinal study.

A detailed study involving simultaneous measurements of plasma and saliva 17OH-progesterone (17OHP), and plasma testosterone concentrations was performed at frequent intervals over a 3-year period in 16 patients with congenital adrenal hyperplasia (CAH). There was a close correlation between the results of these three biochemical measurements over a wide range of concentrations. The practical application of a sensitive saliva 17OHP radioimmunoassay permitted detailed monitoring of patients receiving various glucocorticoid preparations through repeated frequent saliva sampling over the whole day. When the results of serial steroid measurements were analysed in relation to growth velocity in prepubertal patients, it was possible to device upper limits of 40 nmol/l, 0.8 nmol/l and 1,500 pmol/l for plasma 17OHP, plasma testosterone and saliva 17OHP concentrations, respectively, in well-controlled patients. Applying these guidelines from the early onset of treatment should ensure normal growth potential in treated CAH children, at least until puberty.

Adolescent↗
PubMed1982

Radioimmunoassay for salivary estriol, with use of an 125I radioligand and a solid-phase separation technique.

This simple, rapid radioimmunoassay for salivary unconjugated estriol in the third trimester of pregnancy is based on use of a Sepharose-coupled antiserum and a radioiodinated tracer, and requires only a 15-min incubation. Estriol conjugates are shown not to be present in saliva in significant concentrations; therefore a preliminary extraction is unnecessary. Determinations of unconjugated estriol in matched specimens of plasma and saliva correlate well (r = 0.95). A provisional normal range for 30 weeks to term agrees closely with those reported by others. This assay can give results quickly for the large numbers of specimens generated by weekly or daily sampling regimes.

Cross Reactions↗
PubMed1981

A radioimmunoassay for ethinyl oestradiol in plasma incorporating an immunosorbent, pre-assay purification procedure.

A radioimmunoassay for plasma ethinyl oestradiol, featuring an immunosorbent extraction procedure, is described. Ethinyl oestradiol (EE2) was extracted using a non-specific, anti-oestrogen serum, raised to an oestradiol-17-hemisuccinate conjugate. The antiserum, coupled to microcrystalline cellulose, selectively extracted EE2 but not norethisterone ( NE), thus conferring specificity on a radioimmunoassay which has previously exhibited unacceptably high cross-reactivity with the synthetic progestagen, norethisterone, often used concomitantly with ethinyl oestradiol. This radioimmunoassay was shown to fulfil accepted assay validation criteria. Levels in subjects not receiving EE2 were less than 25 pmol/l. Circulating concentrations of EE2 could therefore be accurately determined in patients receiving low-dose combined preparations (EE2 35 micrograms; NE 500 micrograms).

Antigen-Antibody Complex↗
PubMed1981

A sensitive, specific, solid-phase enzymeimmunoassay for plasma progesterone.

A homologous enzymeimmunoassay (EIA) for plasma progesterone, using a horseradish peroxidase conjugate as enzyme label and an antiserum raised against a progesterone-11 kappa-hemisuccinyl/BSA conjugate, is described. The antiserum was covalently linked to microcrystalline cellulose to facilitate separation of bound and free steroid; this solid-phase antiserum was stable for at least nine months when stored at 4 degrees C. the freeze-dried enzyme label is also stable, having retained both enzymic and immunological activity for about four years. The EIA developed was specific and had the sensitivity (4.8 pg/tube) required for determining progesterone concentrations in in plasma samples collected at any time during the menstrual cycle. EIA of plasma samples provided results which were in good agreement with a well validated radioimmunoassay (RIA). The specificity and inter- and intra-assay coefficients of variation in the EIA were strictly comparable with those of the RIA. The method described has been in use for two years and has been assessed in external quality assurance programme established by the World Health organization and the United Kingdom Department of Health and Social Security.

Cross Reactions↗
PubMed1981

Enzyme immunoassay for specific determination of the synthetic estrogen, ethynyl estradiol, in plasma.

In this enzyme immunoassay for ethynyl estradiol, a conjugate of the 3-(O-carboxymethyl)ether with horseradish peroxidase is used as the label and a conjugate of the 6-(O-carboxymethyl)oxime with bovine serum albumin as the immunogen. A solid-phase antibody procedure is used in separating antibody-bound and free steroid. The lower limit of sensitivity of the assay is 2 pg per assay tube. Interference by synthetic progestagens was minimized by extracting the sample with an anti-estrogen serum before assay. Results obtained with a comparison radioimmunoassay and this procedure agreed well (r greater than 0.98).

Contraceptives, Oral↗
PubMed1981

Measurement of diethylstilbestrol in plasma from patients with cancer of the prostate.

A specific radioimmunoassay has been developed for diethylstilbestrol (DES), using an antiserum raised against DES monocarboxymethyl ether and a tritium-labeled radioligand. Prior to radioimmunoassay, a fraction enriched in DES is obtained from a dichloroethane extract of plasma using Sephadex LH-20. The specificity of the assay is good, and the sensitivity (130 pg/ml) is adequate for accurate determination of DES in plasma from prostatic cancer patients treated with the drug. The precision is satisfactory, with an interassay coefficient of variation of approximately 10% at concentrations of approximately 1 ng/ml, and the blank values are negligible. Excellent agreement (r = 0.96) is observed between data obtained by radioimmunoassay and those obtained by a procedure using gas chromatography-high-resolution mass spectrometry. DES concentrations in the plasma of six treated (1 mg DES three times daily) patients were in the range 0.15 to 6.0 ng/ml. Increases in plasma concentration were observed within 2 hr of administration, with secondary rises occurring 5 to 6 hr later. Plasma testosterone concentrations were low in four of the patients; in a single subject, relatively high levels of testosterone were further elevated following administration of luteinizing hormone-releasing hormone.

Circadian Rhythm↗
PubMed1980

Improvement of antisera for cortisol immunoassay by reduction of endogenous hormone concentrations.

Markedly elevated concentrations of endogenous steroids in antisera may reduce the potential sensitivity of immunoassays. Attempts to raise antisera containing reduced amounts of cortisol by adrenalectomy, or concomitant administration of synthetic corticosteroid during immunisation, have met with indifferent success. Removal of cortisol, using dextran-coated charcoal in buffer of optimum molarity, may increase the average affinity constant of the antiserum, and improve the assay sensitivity and specificity.

Animals↗
PubMed1980

A sensitive solid phase enzymeimmunoassay for norethisterone (norethindrone) in saliva and plasma.

A sensitive, solid phase enzymeimmunoassay suitable for determining norethisterone in small aliquots of plasma (10 microliters) and saliva (100 microliters) has been developed. A solid phase antiserum raised against a norethisterone-11 alpha-hemisuccinyl/bovine serum albumin conjugate was prepared by coupling to cyanogen bromide activated cellulose. A norethisterone/horseradish peroxidase conjugate was used as enzyme label, o-phenylenediamine/hydrogen peroxide being the substrate for colour development. The assay had a lower limit of sensitivity of 3 pg/assay tube and satisfied accepted validation criteria. Norethisterone concentrations determined by enzymeimmunoassay and by a well established radioimmunoassay were in excellent agreement in both plasma (r = 0.993, n = 20) and saliva (r = 0.989, n = 15). Plasma and salivary norethisterone concentrations determined in healthy volunteers reached peak values at about 1 hour after administering a norethisterone-containing oral contraceptive preparation. The maximum values achieved in saliva (775--1430 pmol/l) were only approximately 3% of those observed in plama. Since salivary norethisterone concentrations reflected those in plasma, they may be useful in fertility control programmes and pharmacokinetic studies.

Administration, Oral↗
PubMed1980

Assessment of testicular function by the radioimmunoassay of testosterone in saliva.

A sensitive RIA (500 fg/tube) has been developed for assay of testosterone in male saliva and extensively validated. In normal male saliva samples, morning concentrations (368 +/- 167 pmol/l) were significantly higher than evening samples (212 +/- 132 pmol/l). The circadian rhythm was confirmed by COSINOR analysis. Levels of testosterone in saliva, in response to HCG stimulation, accurately reflected the increase observed in matched plasma samples. Synacthen administration, although increasing circulating cortisol levels, caused no significant change in plasma and salivary testosterone concentrations. Prostatic cancer patients on diethylstilboestrol therapy had low salivary (47--122 pmol/l) and plasma (1.0--2.8 nmol/l) testosterone concentrations. Correct assessment of testicular function following stimulation and treatment regimens requires multiple sampling. Since saliva samples are easily collected by non-invasive techniques they represent an attractive alternative to plasma for evaluation of androgenicity.

Adolescent↗
PubMed1980

A simple direct solid-phase enzymeimmunoassay for cortisol in plasma.

A simple, direct solid-phase enzyme-labelled immunoassay for plasma cortisol was established using horseradish peroxidase/cortisol 21-hemisuccinate conjugate as "enzyme label. The antiserum, raised against a cortisol 21-hemisuccinate/bovine serum albumin conjugate, was coupled to cellulose to facilitate separation of free and bound steroid. Solvent extraction was avoided by the use of heat denaturation of the cortisol-binding globulin. This assay had a lower limit of sensitivity of 16.6 nmol/l and satisfied the standard criteria of accuracy and precision. Cortisol concentrations determined by enzymeimmunoassay were in excellent agreement with a gas liquid chromatography/mass spectrometry procedure (r=0.98, n=19) and also with the radioimmunoassay in current use (r=0.95, n=20). Cortisol levels after ACTH stimulatin and dexamethasone suppression in various subjects are presented. This enzymeimmunoassay is particularly applicable to the routine determination of plasma cortisol in small clinical laboratories or in those with a fluctuating workload.

Adrenocorticotropic Hormone↗
PubMed1980

Salivary steroid assays for screening endocrine function.

Current assessment of endocrine function requires multiple sampling regimens. Salivary studies have the advantage of collection by non-invasive techniques, ease of repetition and findings which accurately reflect circulating steroid concentrations. Since hormone concentrations in saliva are low, these investigations require development of highly sensitive, specific immunoassay techniques. Salivary studies may prove useful in assessing the influence of endocrine factors in depression and sexual dysfunction. Clinical and research applications are being rapidly developed.

Adolescent↗
PubMed1979

A sensitive solid phase enzymeimmunoassay for testosterone in plasma and saliva.

A sensitive, solid phase enzymeimmunoassay suitable for determining testosterone concentrations in samll aliquots of plasma (20 microliter) and saliva (200 microliter) has been developed. A solid phase antiserum raised against a testosterone-11 alpha-hemisuccinate/bovine serum albumin conjugate was prepared by coupling to cyanogen bromide activated cellulose. The "enzyme label" was a covalently linked testosterone/horseradish peroxidase conjugate. The assay had a lower limit of sensitivity of 4pg/assay tube and satisfied accepted criteria of specificity and precision. Testosterone concentrations determined by enzyme-immunoassay were in excellent agreement not only with a gas liquid chromatography/mass spectrometry procedure (r=0.96, n=12) but also with the radioimmunoassay in routine use (r=0.95, n=12). The EIA can therefore replace RIA in both the small clinical laboratory and high throughput service centres for determining plasma and salivary testosterone concentrations. In normal males salivary testosterone concentrations reflected circulating steroid levels and indicated the possibility of assaying saliva rather than plasma in clinical studies.

Antibody Specificity↗
PubMed1979

A simple robust assay for testosterone in male plasma using an 125I-radioligand and a solid-phase separation technique.

A radioimmunoassay for testosterone in male plasma utilising a gamma-emitting radioligand and a solid-phase antiserum is described. The radioligand is testosterone-3-(O-carboxymethyl)-oxime coupled to 125I-iodohistamine, and the solid-phase antiserum is prepared by coupling antitestosterone-3-bovine serum albumin to cyanogen bromide activated cellulose. The new procedure retains much of the specificity associated with a published, specific radioimmunoassay using an antiserum raised against testosterone-11 alpha-BSA and a tritium radioligand and incorporating a dextra-coated charcoal separation procedure; values obtained by the two procedures are in excellent agreement (r = 0.98, n = 20). The combination of an 125I-radioligand and a solid-phase separation technique greatly increases sample throughput and has the further advantage of reduced running costs and a greater potential for automation. The method gives satisfactory levels of sensitivity, precision, and accuracy.

Animals↗
PubMed1979

A simple, direct radioimmunoassay for plasma cortisol, featuring a 125I radioligand and a solid-phase separation technique.

A simple, direct radioimmunoassay for cortisol in human serum and plasma is described. An antiserum, raised in sheep to a cortisol-3-(O-carboxymethyl)oxime/bovine serum albumin conjugate, is coupled to microcellulose. No extraction is required because plasma samples and standards are incubated with the antiserum and an 125I radioligand in a low-pH buffer, which denatures cortisol-binding globulins. The assay satisfies accepted validation criteria. In addition, results from the radioimmunoassay compare well with those obtained by a gas chromatographic-mass spectrometric technique (r = 0.968; FRIA = 0.97 FGCMS + 2.0 nmol/L). The latter procedure features the very high intrinsic specificity obtained by selected ion monitoring at high mass-spectrometric resolution (M/deltaM = 8500) with a Varian MAT-731 instrument. The simplicity of the radioimmunoassay procedure, with use of reagents prepared "in house," makes this a very practical and economical assay for use in the medium or large endocrine laboratory.

Chromatography, Gas↗