Search Results
You are looking at 1 - 10 of 17 items for
- Author: W. R. Robertson x
- Refine by access: All content x
Search for other papers by R. B. Lomax in
Google Scholar
PubMed
Search for other papers by W. R. Robertson in
Google Scholar
PubMed
ABSTRACT
Hypo- and hyperthyroidism have been associated with changes in the activities of mitochondrial enzymes in homogenates of skeletal muscles, but it is unclear whether such changes were due to changes in single fibre enzyme activities or to previously documented changes in relative numbers of fibres. In this study the activities of the mitochondrial enzymes α-glycerol phosphate dehydrogenase (m-αGPDH) and succinate dehydrogenase (SDH) were measured in single fibres of the soleus and gastrocnemius muscles of the rat by cytochemical assays.
In the soleus muscles of hypothyroid animals there was a decrease in the mean percentage (± s.d.) of type II fibres from 8·0 ± 6·0 to 0·8 ± 1·9% (P < 0·05) and decreases in SDH activities in all fibre types (P < 0·005). In the gastrocnemius muscles of these animals there were no changes in fibre composition but type IIB fibres had reduced (P < 0·05) m-αGPDH activities. In the hyperthyroid animals, in which body weight had increased relative to the euthyroid animals, there were increases in the percentages of type IC and type II fibres in the soleus from 4·3 ± 1·7 to 13·1 – 9·0% (P < 0·05) and from 9·6 ± 7·2 to 33·4 ± 9·6% (P < 0·005) respectively and an increase in the percentage of type IIA fibres in the gastrocnemius from 92·9 ± 2·3 to 97·0 ± 2·9% (P < 0·05). However, there were no increases in single fibre mitochondrial enzyme activities. It is therefore suggested that the administration of moderate, growth-promoting doses of thyroid hormones to euthyroid animals can cause changes in muscle fibre composition without stimulating the activities of mitochondrial enzymes.
Journal of Endocrinology (1992) 133, 375–380
Search for other papers by N. LOVERIDGE in
Google Scholar
PubMed
Search for other papers by W. R. ROBERTSON in
Google Scholar
PubMed
Division of Cellular Biology, The Mathilda and Terence Kennedy Institute of Rheumatology, Bute Gardens, London, W6 7DW
(Received 24 April 1978)
It is well established (Chayen, Daly, Loveridge & Bitensky, 1976) that segments of guineapig adrenal gland can be maintained in vitro and will respond to low concentrations (0·005– 5·0 pg/ml) of corticotrophin (ACTH). The response measured in the cytochemical bioassay of ACTH is the loss of ascorbate from the zona reticularis (Chayen, Loveridge & Daly, 1972), which is directly related to secretion of cortisol by these segments (Chayen, Bitensky, Chambers, Loveridge & Daly, 1974). However, because both major zones of the adrenal cortex are involved in steroidogenesis (see, e.g., Symington, 1969; Hyatt, Bell, Gould, Tait & Tait, 1976), the lack of a response in the zona fasciculata seems to be anomalous. To test whether the cells of the zona fasciculata in guinea-pig adrenal segments can respond to low concentrations
Search for other papers by A. Lambert in
Google Scholar
PubMed
Search for other papers by R. Mitchell in
Google Scholar
PubMed
Search for other papers by W. R. Robertson in
Google Scholar
PubMed
ABSTRACT
The effect of etomidate (an anaesthetic), epostane (WIN 32729; an inhibitor of ovarian and adrenal steroidogenesis) and cyproterone acetate (an antiandrogen) on testosterone secretion from mouse Leydig cells stimulated with LH (5 i.u./l) was tested. The concentration of drug which inhibited testosterone secretion by 50% was 11·5±1·1 (s.e.m.) μmol/l for cyproterone acetate, 1·2 ± 0·2 μmol/l for etomidate and 0·23 ± 0·03 μmol/l for epostane.
The effect of all three drugs on testicular steroidogenesis was completely reversible. Thus testicular cells which had been washed after exposure to a >95% inhibitory dose of drug responded in a similar manner to hormone stimulation as cells similarly washed and which had not been exposed to the drug.
The sites of the antisteroidogenic effect of epostane, etomidate and cyproterone acetate were established using a method based on the sequential stimulation by the exogenous precursor steroids of the various steps leading to the biosynthesis of testosterone. It was concluded that etomidate acts at the sequence between LH binding and pregnenolone production, epostane acts at 3β-hydroxysteroid dehydrogenase and cyproterone acetate inhibits 3β-hydroxysteroid dehydrogenase and C17,20-lyase.
J. Endocr. (1987) 113, 457–461
Search for other papers by S. C. J. READER in
Google Scholar
PubMed
Search for other papers by J. R. DALY in
Google Scholar
PubMed
Search for other papers by W. R. ROBERTSON in
Google Scholar
PubMed
The effect of plasma on the bioactivity of ACTH was investigated with the cytochemical section bioassay. Levels of ACTH in normal human plasma were underestimated if the plasma concentration in the incubation medium exceeded 2%, and if the plasma ACTH level was > 2 ng/l. A retrospective analysis of 250 plasma ACTH assays revealed that the ACTH concentration was consistently underestimated in the 1: 100 dilution compared with the 1: 1000 dilution, although not to the extent that any assay would be rejected for non-parallelism. The extent of the underestimation increased as the ACTH concentration increased.
Guinea-pig adrenal sections responded faster to 1: 10 or 1: 50 dilutions of human plasma (containing 2 ng ACTH/l) than to either 1: 100 or 1: 1000 dilutions of that same plasma, or to ACTH (over the range 0·005–5 ng/l) in the absence of plasma. This faster response could also be seen in the absence of plasma by increasing the ACTH concentration above 5 ng/l. It seems that plasma contains factors which potentiate the biological effect of ACTH in the cytochemical assay system.
Search for other papers by G. Edwards in
Google Scholar
PubMed
Search for other papers by W. R. Robertson in
Google Scholar
PubMed
Search for other papers by I. D. Morris in
Google Scholar
PubMed
ABSTRACT
The Leydig cells repopulating the adult rat testis after destruction by a single injection of the cytotoxic ethylene-1,2-dimethanesulphonate (EDS) were investigated. After 14 days, serum concentrations of LH and FSH were significantly raised and concentrations of testosterone in the serum and testis reduced. At 21 days, hormone concentrations had returned to within the normal range. Binding of 125I-labelled human chorionic gonadotrophin (hCG) to testis homogenate, however, was still less than 10% of normal. After 21 or 28 days the 125I-labelled hCG binding profiles of isolated Leydig cells from EDS-treated rats, separated on a Percoll gradient, showed a single peak similar to that of immature (25 days old) rats. After 49 days, 125I-labelled hCG binding resolved into two peaks more like that of normal adult rats. Using a quantitative cytochemical method, 3β-hydroxysteroid dehydrogenase activity in individual Leydig cells of unfixed testis sections was determined. Activity was increased by 70% (P < 0·05) in repopulating Leydig cells 21 days after EDS treatment compared with cells from vehicle-treated rats. In addition, Leydig cells were still capable of further 'in-vivo' stimulation by pharmacological doses of hCG. These data indicate that Leydig cells repopulating the testis are homogenous. Fewer cells from the newly formed population are capable of maintaining normal serum concentrations of testosterone and must thus be individually more active in secreting testosterone. In these respects, the Leydig cells repopulating the adult rat testis after EDS treatment more closely resemble those of the fetal rat testis.
J. Endocr. (1988) 117, 11–18
Search for other papers by S. P. Bidey in
Google Scholar
PubMed
Search for other papers by A. Lambert in
Google Scholar
PubMed
Search for other papers by W. R. Robertson in
Google Scholar
PubMed
Department of Medicine and Department of Cell and Structural Biology, University of Manchester, Stopford Building, Oxford Road, Manchester m139pt
*Department of Clinical Biochemistry, Clinical Sciences Building, Hope Hospital, Eccles Old Road, Salford m6 8hd
received 14 April 1988
Introduction
An understanding of the mechanisms underlying the differentiation of mammalian cells represents one of the most challenging aspects of modern cell biology, and the success of investigations into such processes has been greatly influenced by the availability of experimental in-vitro systems in which the cellular environment closely resembles that encountered by the cells in vivo. For any particular cell type, however, the successful implementation of such experimental models is also dependent upon the isolation of long-term, stable cell lines having a normal phenotype and the differentiation characteristics of cells within the parent tissue.
In the absence of a stable, characterized line of thyroid epithelial cells, early studies of thyroid
Search for other papers by N. R. W. TAYLOR in
Google Scholar
PubMed
Search for other papers by J. A. LORAINE in
Google Scholar
PubMed
Search for other papers by H. A. ROBERTSON in
Google Scholar
PubMed
1. The ACTH concentration has been estimated in lyophilized pituitary tissue from five adults, seven infants and eight foetuses. Results are expressed in terms of the international standard. Adult pituitaries contain more ACTH than infantile glands, and infantile glands more than foetal ones.
2. ACTH activity was detected in foetal pituitaries at a period of gestation as early as 16 weeks.
3. The accuracy of the Sayers test was considerably improved when the time interval between hypophysectomy and assay was increased from 24 to 48 hr.
Search for other papers by S. C. J. READER in
Google Scholar
PubMed
Search for other papers by J. ALAGHBAND-ZADEH in
Google Scholar
PubMed
Search for other papers by J. R. DALY in
Google Scholar
PubMed
Search for other papers by W. R. ROBERTSON in
Google Scholar
PubMed
Plasma ACTH and corticosteroid levels were measured in normal subjects during constant infusion of either 0·9% (w/v) NaCl solution or cortisol, and during insulin-induced hypoglycaemia. During infusions of 0·9% NaCl solution the secretion of ACTH and corticosteroids was episodic. Fast, rate-sensitive, negative feedback inhibition of ACTH secretion was observed during cortisol infusions, when the corticosteroid levels were within the physiological range (200–750 nmol/l) and were rising at a rate of between 5 and 10 nmol/l per min for 30 min or longer. When plasma corticosteroid levels were in a steady state, the initial fast feedback effects were abolished and ACTH secretion resumed. However, this recovery of ACTH secretion was not seen when the corticosteroid levels were persistently above 800 nmol/l. It appears that corticosteroid-induced negative feedback in man may be both rate- and level-sensitive. During insulin stress tests ACTH secretion fell at a time when the plasma corticosteroid level was rising rapidly (> 5 nmol/l per min) despite persistent hypoglycaemia.
Search for other papers by A. Tsatsoulis in
Google Scholar
PubMed
Search for other papers by K. Mavroudis in
Google Scholar
PubMed
Search for other papers by J. Frost in
Google Scholar
PubMed
Search for other papers by A. Lambert in
Google Scholar
PubMed
Search for other papers by S. M. Shalet in
Google Scholar
PubMed
Search for other papers by W. R. Robertson in
Google Scholar
PubMed
ABSTRACT
The degree of stability in vitro of bioactive and immunoreactive LH in human blood, plasma and serum was examined. Bioactivity and immunoreactivity of LH were assayed by the dispersed mouse Leydig cell assay and by standard radioimmunoassay respectively, using the same reference preparation (first international reference preparation for human pituitary LH 68/40 for immunoassay).
Bioactive and immunoreactive LH were stable in blood and plasma at 22 °C for up to 4 and 24 h respectively, and in blood at 4 °C for up to 24 h. There was no loss of biological or immunological LH activity in plasma which had been either snap-frozen and stored at −70 °C, allowed to freeze at −20 °C and stored at that temperature or kept at 4 °C for 24 h and then stored at − 70 °C. Likewise, the levels of LH in plasma and serum which had been stored at either − 20 or − 70 °C and then thawed and refrozen up to four times remained unchanged. In addition, the biological and immunological activity of LH was not affected after vortexing samples of plasma or serum for up to 60 s. Bioactive LH was also stable in plasma samples after prolonged storage (up to 9 months) at either −70 or −20 °C.
We conclude that LH bioactivity and immunoreactivity are stable in blood and plasma following a variety of treatments commonly experienced during normal handling of a blood sample after venepuncture.
J. Endocr. (1988) 117, 139–145
Search for other papers by A.M. Wood in
Google Scholar
PubMed
Search for other papers by S.P. Bidey in
Google Scholar
PubMed
Search for other papers by J. Soden in
Google Scholar
PubMed
Search for other papers by W.R. Robertson in
Google Scholar
PubMed
ABSTRACT
We have studied the chronic effects of TSH (100μU/ml) and insulin (10μg/ml) on intracellular pH (pHi) in FRTL-5 cells using the pH sensitive probe 2′7-bis (2-carboxyethyl-5′-6′) carboxyfluorescein. FRTL-5 cells were cultured on Petri dishes either in the presence of 4H, ie. Coons F-12 containing cortisol (10nM), transferrin (0.5μg/ml), glycyl-histidyl lysine acetate (10ng/ml) and somatostatin (10μg/ml), or with 4H+insulin (5H), 4H+TSH, or 4H+TSH+insulin (6H). pHi was measured in small groups of cells by microspectrofluorimetry both in the presence and absence of bicarbonate ions after cells had been deprived of serum for at least a day. In
