PubMed Health⌕ Search

Biomedical subjects

S L Jeffcoate

Publications and source records attributed to S L Jeffcoate.

At least 19 recordsLinked to original sources
PubMed1992

Analysis of therapeutic growth hormone preparations: report of an interlaboratory collaborative study on growth hormone assay methodologies.

Recombinant DNA-derived human growth hormone (somatotropin) is widely used to treat growth hormone-deficient children. The potency of this product is determined by in-vivo bioassay in hypophysectomized rats, which is imprecise, costly and invasive, and there have been suggestions that it could safely be replaced with in-vitro or physico-chemical alternatives. In this report we present the results of a collaborative study designed to test this proposal. Somatotropin was modified by mild or severe proteolysis, mild or severe oxidation or treatment at high pH, and compared in a multi-centre collaborative study with unmodified somatotropin or with dimerized somatotropin. Participating laboratories included manufacturers and national control laboratories, and pharmacopoeial bioassays were compared with in-house in-vitro and physico-chemical bioassays. Although performing adequately with untreated somatotropin, for degraded samples the in-vivo bioassays were relatively unresponsive to changes in the growth hormone molecule. In contrast, the physico-chemical assays, in particular the reverse-phase HPLC, performed with a high degree of selectivity. We conclude that in the case of somatotropin, the in-vivo bioassay can be removed from the routine product specification with an acceptable degree of security. This however does not obviate the requirement rigorously to demonstrate biological activity in-vivo during product development, nor may the conclusions of this study be applied to other therapeutic recombinant proteins without similar collaborative investigations.

Animals↗
PubMed1989

The production and characterisation of monoclonal antibodies against human prolactin and the development of a two-site immunoradiometric assay.

Monoclonal antibodies against human prolactin (PRL) have been produced and characterised and used to develop a sensitive two-site immunoradiometric assay (IRMA). Nine anti-PRL monoclonal antibodies were assessed for reactivity in immunoblotting experiments with PRL, hPL, hGH and pituitary gland extract. There was no detectable crossreactivity with hPL or hGH. In liquid phase radioimmunoassay (RIA) studies using three of the antibodies there was no detectable crossreaction from hPL or hGH. Five antibodies were positive in immunocytochemical studies using sections of human pituitary gland. Using FPLC purified monoclonal antibodies, a two-site IRMA was developed that could assay PRL over the range 17.5-3500 mIU per litre and was readily adapted to assaying serum samples from patients. The two-site IRMA could be performed within one day without loss of sensitivity and has potential as a rapid and simple method for screening clinical samples.

Antibodies, Monoclonal↗
PubMed1989

International Standards for human prolactin: calibration by international collaborative study.

Three ampouled preparations of purified human prolactin were assessed by 20 laboratories in eight countries for their suitability to serve as International Standards for the estimation of human prolactin in serum. Bioassays (pigeon crop sac assays and NB2 cell assays) were carried out in two laboratories, radioreceptor assays by one laboratory and radioimmunoassays by 17 laboratories. By physicochemical analysis the preparations appeared similar. Each preparation contained small amounts of contaminants and/or prolactin variants. No major differences among the three preparations were detected by immunoassay although, in one radioreceptor assay system, one of the preparations was found to differ from the other two. On the basis of all the available information, the Expert Committee on Biological Standardization of the World Health Organization (ECBS) in 1986 established the preparation in ampoules coded 83/562 as the Second International Standard for Prolactin and in October 1988 established the preparation in ampoules coded 84/500 as the Third International Standard for Prolactin. A value of 0.053 IU (53 mIU) prolactin activity/ampoule was assigned to both the Second and Third IS on the basis that this unitage would, insofar as possible, maintain continuity of the IU defined by the First International Reference Preparation of Prolactin, human, for Immunoassay (coded 75/504).

Amniotic Fluid↗
PubMed1989

Three methods compared for estimating the fraction of testosterone and estradiol not bound to sex-hormone-binding globulin.

Here we propose and validate, both theoretically and experimentally, a new technique for measuring the percentage of non-sex-hormone-binding globulin (SHBG) bound to testosterone and estradiol. In this method, SHBG is saturated with 1 mumol of 5 alpha-dihydrotestosterone per liter and the non-protein-bound fraction is subsequently measured in treated and untreated samples by centrifugal ultrafiltration dialysis (CUFD). We compared this technique with two previously published methods for measuring the percentage of albumin-bound steroid--ammonium sulfate precipitation and heat denaturation of SHBG followed by CUFD--and also with previously published computer predictions. The ammonium sulfate precipitation gave results closest to the computer-predicted percentage of albumin-bound testosterone and estradiol. Of the two techniques involving CUFD, the 5 alpha-dihydrotestosterone saturation method was the more reproducible. Results by both CUFD methods were higher than the computer-based predictions for albumin-bound steroid in pregnancy serum, in part perhaps because the CUFD measurements represent the non-SHBG-bound fraction rather than that which is albumin-bound alone.

Ammonium Sulfate↗
PubMed1988

The inhibitory effects of danazol, danazol metabolites, gestrinone, and testosterone on the growth of human endometrial cells in vitro.

Danazol and gestrinone are effective drugs in the treatment of endometriosis. Their mechanism of action remains uncertain, but may be related to their androgenic activity. The authors examined the effect of danazol on human endometrial cells cultured in vitro, its two major metabolites, ethisterone and 2 hydroxymethyl ethisterone, gestrinone, and testosterone (T) at 1X and 10X expected plasma concentrations. Danazol and T suppressed growth by 20.8 and 25.0% (P less than 0.01), respectively, at the lower dose, and by 26.9 and 35.5% (P less than 0.01), respectively, at the 10-fold higher dose. No significant suppression of growth occurred with gestrinone, ethisterone, or 2 hydroxymethyl ethisterone. The results provide further evidence that danazol and T (but not gestrinone) may act by a direct effect on endometrial tissue.

Cell Division↗
PubMed1988

The effects of aminoglutethimide and hydrocortisone, alone and combined, on androgen levels in post-orchiectomy prostatic cancer patients.

Aminoglutethimide has been used in combination with hydrocortisone in patients with advanced prostatic cancer with the rationale that it causes a 'medical adrenalectomy'. Both objective and subjective responses have been recorded. We have examined the effect of AG and HC alone and in combination on plasma androgen levels throughout the day in two studies on 11 such patients. Whilst AG combined with HC led to a significant suppression of both testosterone and androstenedione levels, the suppression with HC alone was significantly greater, indicating that any beneficial clinical effects of AG in these patients is not due to its suppression of adrenal androgen secretion.

Aged↗
PubMed1988

Inappropriate ACTH concentrations in two patients with functioning adrenocortical carcinoma.

Two female patients with functioning adrenocortical carcinomas had plasma ACTH detectable by RIA at presentation. In both patients there was evidence for biological activity of ACTH. There was no evidence for an ectopic source of ACTH, nor for a pituitary tumour. Urinary steroid analysis showed patterns of multiple hormone secretion characteristic of adrenocortical carcinomas. The finding of detectable ACTH concentrations in a patient with Cushing's syndrome does not exclude the presence of an adrenocortical tumour.

Adrenal Gland Neoplasms↗
PubMed1988

Suppression of postmenopausal ovarian steroidogenesis with the luteinizing hormone-releasing hormone agonist goserelin.

Twenty-one postmenopausal women with advanced breast cancer were treated with monthly 3.6-mg sc injections of the LHRH agonist goserelin [D-Ser-(But)6, Azgly10-LHRH] to determine whether the resultant endocrine changes could provide an explanation for the clinical responses that occur during therapy with this agent. After 4 weeks, serum gonadotropin levels were less than 10% of pretreatment levels, whereas serum PRL levels did not change. A significant decrease in serum testosterone occurred in 19 of 20 patients; this fall was associated with a 22% fall in serum estradiol levels. Serum androstenedione levels also decreased, but serum estrone and dehydroepiandrosterone sulfate (DHAS) levels did not. The lack of fall in serum DHAS levels indicates that the changes in androgen levels were a result of reduced ovarian secretion, and the reduced estradiol levels were a consequence of reduced precursor (i.e. testosterone) availability. The continued dependence of ovarian androgen secretion on gonadotropin stimulation after the menopause may explain the responses of some patients to LHRH agonists and some other therapeutic agents of unknown or uncertain modes of action.

Aged↗
PubMed1987

Use of the aromatase inhibitor 4-hydroxyandrostenedione in postmenopausal breast cancer: optimization of therapeutic dose and route.

4-Hydroxyandrostenedione (4-OHA) is a potent inhibitor of estrogen production by aromatase and causes suppression of plasma estradiol levels and disease regression in postmenopausal breast cancer patients. Groups of patients were given p.o. or parenteral 4-OHA, and plasma estradiol and 4-OHA levels were measured to enable the delineation of the minimal effective dose and optimal therapeutic regimen. A single injection of 500 mg i.m. suppressed estradiol levels to a mean 36.3 +/- 3.3% (SE) (n = 14) of base line after 4 to 7 days and maintained this suppression in six of seven patients for greater than 14 days. The half-life of 4-OHA was approximately 8 days, and when the level had fallen to less than 3 ng/ml, estradiol levels began to rise. Similar suppression was achieved by a single i.m. injection of 125 mg of 4-OHA and by 500 mg of 4-OHA p.o. daily after 1 wk, but escape from suppression was more rapid.

Administration, Oral↗