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Biomedical subjects

J G Ratcliffe

Publications and source records attributed to J G Ratcliffe.

At least 145 records · Page 8Linked to original sources
PubMed1976

The radioimmunoassay of 3,3',5' - triiodothyronine (reverse T3) in unextracted human serum.

A specific, sensitive and simple double antibody radioimmunoassay for total serum 3,3',5'-triiodothyronine (reverse T3, rT3) in small volumes of unextracted human serum is described. High titre antisera were raised in rabbits using dl=rT3 or l-rT3 conjugated to bovine serum albumin. The selected antisera cross reacted less than 0-003% with triiodothyronine (T3) and 0-14% with thyroxine (T4). A stable high activity rT3 tracer was prepared by iodination of 3,3"-diiodo-l-thyronine by the chloramine-T method, and purified by column chromatography on Sephadex LH-20. Binding of rT3 to endogenous serum proteins was blocked by including 8-anilino-1-naphthalene sulphonic acid (ANS) in the assay. Mean rT3 levels in healthy euthyroid adults are 0-27 nmo1/1 (range 0-21-1-18); in cord sera 3-67 nmo1/1 (range 2-30-7-45) and in amniotic fluid taken during the second trimester 4-70 nmo1/1 (range 2-22-8-00). In approximately half the hypothyroid subjects, rTO levels were undetectable ( less than0-05 nmo1/1) and in the remaining subjects the mean rT3 level was 0-10 nmo1/1 (range 0-05-0-25).

Anilino Naphthalenesulfonates↗
PubMed1976

Adrenocorticotrophin and glucocorticoid response to exchange transfusion.

Plasma adrenocorticotrophin (ACTH) and glucocorticoid concentrations were measured during and for 3 hours after exchange transfusion in four groups of infants. Transfusion with ACD blood via the umbilical artery were performed on 10 infants of 35--40 weeks gestation and 11 infants of 27 to 33 weeks gestation. Ten transfusions via the umbilical vein were performed with ACD blood and 9 with heparin blood on infants of 32 to 41 weeks gestation. In all four types of transfusion there was a significant washing out of ACTH and glucocorticoids from the baby. An associated rise of plasma ACTH and glucocorticoid levels indicated increased secretion in the larger infants transfused with ACD blood via the umbilical artery. Equivocal results were obtained in the other groups. After all types of transfusion plasma glucocorticoid levels remained relatively constant for one hour and then doubled and then doubled in the second and third hour. The results suggest that (a) exchange transfusion via the umbilical artery is more stressful than that via the umbilical vein, (b) the glucocorticoid response of premature infants to exchange transfusion is similar to that of mature ifants, (c) an unspecified stimulus, which is not solely hypoglycaemia nor the metabolic reaction to a citrate load, results in a rise in plasma glucocorticoid levels 2-3 hours after all types of transfusion.

Adrenal Cortex↗
PubMed1976

Observations on the automated calculation of radioimmunoassay results.

Radioimmunoassay standard curves derived by four different automated calculation methods are compared with those derived manually for five assays of clinical importance (thyroxine, triiodothyronine, thyrotrophin, alphafetoprotein, and human growth hormone). The three curve fitting methods (linear or cubic regression on log x versus logit y, cubic regression on log x versus y) produced considerable distortion of the manually derived curves, which in some cases could have impaired the accuracy of an estimate in a clinical sample and altered the clinical interpretation. Distortion patterns varied with the particular antigen assayed and with experimental conditions. In contrast, a simple linear interpolation method produced little distortion and gave results which were close to those derived manually in each assay examined.

Autoanalysis↗
PubMed1975

Effect of lithium on hypothalamic-pituitary-thyroid function in patients with affective disorders.

Hypothalamic-pituitary-thyroid (H.P.T.) function was assessed in 17 patients on maintenance doses of lithium carbonate for a mean period of 21 months (range 1-67 months) and by serial studies on four patients from the start of lithium treatment for a maximum of six months. An exaggerated thyrotrophin (TSH) response to intravenous thyrotrophin-releasing hormone (TRH) occurred in 14 of the 17 patients on maintenance treatment, though basal TSH levels were raised in only three. Two of the three patients were clinically and biochemically hypothyroid and showed a delayed recovery of normal H.P.T. function after lithium was stopped. There were no significant differences in thyroid hormone or basal TSH levels between the euthyroid lithium-treated.

Adult↗
PubMed1975

Semi-automated radioimmunoassays for total serum thyroxine and triiodothyronine.

Single stage semi-automated radioimmunoassays for total serum thyroxine (T4) and triiodothyronine (T3) are described which employ an automatic pipetting station, automatic gamma counter, and a programmable calculator with paper tape reader and printing facility. Both assays require only a small volume of unextracted serum, and are specific and sensitive. Their sample capacity, precision, speed, and cost are comparable with the measurement of serum protein-bound iodine. Both assays therefore have significant advantages over previous methods for the assessment of thyroid function in the diagnostic laboratory. A Simple method of automating the calculation of results is described, which is applicable to any radioimmunoassay in which the standard curve is approximately linear on a plot of the free/bound fraction against the antigen concentration. In addition, a general method is reported which reveals the relative contributions of intrinsic, systematic, and random error to radioimmunoassay precision.

Analysis of Variance↗
PubMed1975

A semi-automated serum alphafetoprotein radioimmunoassay for prenatal spina bifida screening.

A simple, reliable, semi-automated and inexpensive radioimmunoassay for serum alphafetoprotein (AFP) is described which fulfils the requirements for a screening test for open neural tube defects. The normal range for serum AFP throughout pregnancy has been determined in 1534 samples. In a retrospective study of 15 samples of maternal serum taken from nine pregnant women carrying a fetus affected with a neural tube defect, the serum AFP level was found to be above the 95th centile in four of the five cases of open defect sampled between 15 and 20 weeeks gestation. Preliminary results of a prospective study are reported in which two cases of nencephaly were detected among 671 unselected pregnancies sampled between 15 and 20 weeks gestation.

Adolescent↗
PubMed1975

Thyroid function during exchange transfusion.

The changes in plasma thyroid hormone concentration were studied during exchange transfusion performed for haemolytic disease. 24 transfusions were performed using blood preserved with acid-citrate and dextrose and in 11 cases 10 or 50 mug glucagon was added to the donor blood. Plasma tri-iodothyronine (T3), thyroxine (T4), thyrotropin (TSH), thyroid hormone binding capacity, and free thyroxine index were measured in the donor blood and in the infant at the start and at intervals during the transfusion. Before transfusion the plasma TSH levels of the infants fell as postnatal age indreased and plasma T3 and T4 were correlated with one another. In 20 transfusions the mean infant/donor ratio of TSH was approximately 10, of T4 3, and of T3 2. During these transfusions there was a progressive fall in the infant's plasms TSH, T4, and T3 concentration. In 3 transfusions in which the donor plasma TSH was greater than that of the infant, plasma TSH levels rose during the transfusion and in 2 cases this was associated with a late rise in plasma T3 levels. The addition of glucagon to donor blood had no effect on thyroid hormone levels. It is concluded that erythroblastotic infants have normal thyroid function and that they became biochemically hypothyroid during transfusion. Acute changes in plasma thyroid hormone and glucagon concentration do not induce TSH responses by the neonatal pituitary during the period of the exchange transfusion.

Erythroblastosis, Fetal↗
PubMed1975

Development and validation of a radioimmunoassay for peptides related to beta-melanocyte-stimulating hormone in human plasma: the lipotropins.

A radioimmunoassay is described for the measurement of human "beta-melanocyte-stimulating hormone" ("betah-MSH"). Two antisera have been used, one of which cross-reacts with synthetic betah-MSH as well as with the two larger pituitary peptides betah- and gammah-lipotropin (betah- and gammah-LPH) and the other mainly with betah-MSH and gammah-LPH. The sensitivity and reliability of the assay have been improved by employing a simple plasma extraction procedure, and the shelf-life of the iodinated betah-MSH tracer has been increased more than five-fold by storage in a concentrated human serum albumin solution. Using a 5 ml plasma sample the detection limit is 6 pg/ml. The mean resting "betah-MSH" level in normal subjects is 21 pg/ml (range 13-38 pg/ml) at 9 AM and 12 pg/ml (range 6-20 pg/ml) at 9 PM. Levels are considerably elevated (51-12,000 pg/ml) in patients with Addison's disease. Nelson's syndrome, Cushing's disease and the "ectopic" ACTH syndrome. After administration of insulin or pyrogen, the concentration of plasma "betah-MSH" increases in parallel with that of ACTH and they are approximately equivalent on a molar basis. The stability of purified betah- and gammah-LPH and endogenous "betah-MSH" when incubated in vitro in fresh blood or plasma are similar, in contrast to the less stable peptide synthetic betah-MSH. It is suggested that "betah-MSH" immunoreactivity in human plasma is due to betah- and gammah-LPH rather than betah-MSH.

Addison Disease↗
PubMed1975

Thyroid function in patients in clinical remission after medical treatment of thyrotoxicosis.

This paper described the changes in the levels of serum triiodothyronine, serum thyroxine,serum thyrotrophin and other indices of thyroid function between 2-5 y after completion of antithyroid drug therapy in 35 patients who were euthyroid on clinical criteria. There was a small but significant elevation of the mean triiodothyronine and thyroxine levels with a relative hypersecretion of Triiodothyronine. No correlation was found between the levels of either thyroid hormone measured or their ratio and the radioiodine uptakes and clearance rate, the plasma inorganic iodine level, the absolute iodine uptake or the serum TSH level. There was no case of clinical hypothyroidism but in one patient the TSH level was at the upper limit of the nrmal range and an exaggerated TSH response to TRH was found.

Adult↗