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B. SHAPIRO
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B. L. PIMSTONE
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Somatomedin (sulphation factor) activity was measured in 26 species by a porcine cartilage bioassay. Although non-dialysable inhibitory factors were present in many species, sulphation factor activity was present in the sera of all the vertebrates studied but was absent from the invertebrates.

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J. Beattie
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D. J. Flint
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The past few years have seen a dramatic increase in knowledge in relation to the molecular structures of both growth hormone(s) (GH) and their polypeptide receptors (GHR). In addition to older data providing the sequences of numerous mammalian and nonmammalian GHs, cDNAs for mouse (Smith et al. 1989), rat (Mathews et al. 1989), rabbit, human (Leung et al. 1987), ovine (Adams et al. 1990), bovine (Hauser et al. 1990) and porcine (Cioffi et al. 1990) GHRs have recently been cloned and sequenced. Further to this, a high resolution X-ray crystal structure for porcine GH has been published (AbdelMeguid et al. 1987), and very recently the cocrystallization of human (h) GH with the extracellular domain of the GHR has been achieved (De Vos et al. 1992). These studies have revealed GHs to be 4α helix bundle proteins with one molecule of GH binding in an asymmetric fashion to two molecules of

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PAMELA M. POVEY
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B. REES SMITH
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R. HALL
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The surface membrane proteins of cultured porcine thyroid cells have been labelled with 125I by the lactoperoxidase method. Evidence that the labelling was restricted to the cell surface was supported by the high viability of the cells in suspension, the high proportion of labelled material in the particulate fraction after homogenization and electronmicroscopic autoradiographic studies. The labelled proteins were analysed by electrophoresis on polyacrylamide gels containing sodium dodecyl sulphate and this indicated the presence of ten major labelled protein bands with approximate molecular weights of 175 000, 155 000, 135 000, 88 000, 80 000, 52 300, 39 000, 30 000, 21 000 and 14 300. Comparison of the electrophoretic patterns obtained with cultured human and porcine thyroid cells suggested that there were species differences in the proportions of lower-molecular-weight proteins.

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JEAN-MICHEL GAREL
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JEAN-PIERRE BARLET
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Laboratoire de Physiologie Comparée, Université Pierre et Marie Curie, 9 quai St Bernard, 75230 Paris Cedex 05, and *Station de Physiopathologie de la Nutrition, I.N.R.A. Theix, 63110 Beaumont, France

(Received 4 March 1975)

Increased calcitonin (CT) secretion has been suggested as a contributory cause of bovine parturient hypocalcaemia (Barlet, 1967; Capen & Young, 1967; Care, Bates, Phillippo, Lequin, Hackeng, Barlet & Larvor, 1970). Plasma concentrations of calcium, inorganic phosphorus, CT and parathyroid hormone (PTH) were measured at intervals before and after parturition. An antibody to porcine CT was selected which cross-reacted significantly with bovine CT in a radioimmunoassay already described (Garel, Care & Barlet, 1974). Calcitonin concentrations were expressed in ng equivalents of porcine CT/ml. An antibody to bovine PTH was obtained by immunizing a goat. Highly purified PTH was used as a Standard and for preparation of 125I-labelled hormone using the chloramine-T method. Purification of labelled PTH was achieved

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JOHN WATSON
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J. T. S. LEASK
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SUMMARY

A method for the continuous superfusion of porcine corpus luteum tissue is described which readily allows both the introduction of regulatory factors to the incubating tissue, and sampling of the tissue. Oestrogen (principally oestradiol) and progestin (principally progesterone) can be measured for up to 24 h in the superfusate from corpora lutea of all ages, and the secretion of both steroids is stimulated by the addition of luteinizing hormone. The pattern of response of both steroids to a pulse of gonadotrophin was similar in that a rapid transient increase in secretion occurred followed some time later by a secondary and more prolonged response. A second pulse of gonadotrophin introduced 6 h after the first also stimulated steroid secretion, indicating that during superfusion in vitro the porcine corpus luteum does not become refractory to the steroidogenic effect of gonadotrophin.

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A. D. CARE
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R. F. L. BATES
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M. PHILLIPPO
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R. M. LEQUIN
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W. H. L. HACKENG
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J. P. BARLET
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P. LARVOR
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An antibody to porcine calcitonin (CT) was selected which cross-reacted completely to bovine CT in a radioimmunoassay using a synthetic porcine CT preparation (CT-s) labelled with 125I (Lequin, Hackeng, Schopman & Care, 1970). With this radioimmunoassay it has been possible to measure CT concentrations in samples of bovine peripheral and thyroid venous plasma. All concentrations of CT reported here are expressed in terms of immunologically active CT-s/ml. The standard error of the CT measurements was ± 50 pg CT-s/ml over the range of concentration 250–2000 pg/ml.

One lobe of the thyroid gland was isolated in situ in each of three calves (33–38 kg body wt) and in one adult Jersey cow (300 kg body wt). The glands were perfused with blood which contained various concentrations of calcium. Glucagon and the kallikrein inhibitor (KI) aprotinin (Zymofren) were also added in an experiment with the cow to give perfusing concentrations of

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D. L. SARSON
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M. G. BRYANT
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S. R. BLOOM
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A sensitive radioimmunoassay for the measurement of human gastric inhibitory polypeptide (GIP), using pure porcine GIP, has been developed. Cross-reactivity of the antiserum with all available mammalian gut peptide preparations was negligible with the exception of glucagon when it was approximately 1%. Two major molecular forms of GIP were detectable in plasma and tissue extracts, one of large molecular size and the other corresponding to the elution coefficient of pure porcine standard.

Concentrations of GIP in plasma from 50 normal subjects after overnight fasting were 9 ± 1·0 (s.e.m.) pmol/l rising to a peak of 34 ± 2·8 pmol/l following the ingestion of a small mixed test meal. Ingestion of glucose or fat resulted in a similar rise of plasma GIP, whereas no change was observed after the ingestion of protein.

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P. A. FIELDS
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L. H. LARKIN
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The present studies indicated that the extensibility of the mouse uterine cervix was significantly increased by administration of as little as one unit of highly purified preparation of porcine relaxin. No significant change in tensile strength of the cervix was noted when doses were administered that caused increased cervical extensibility and formation of the interpubic ligament. A low coefficient of correlation was found between interpubic ligament formation and increased extensibility of the cervix in oestrogen-primed immature female mice.

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W. M. Bennet
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S. F. Hill
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M. A. Ghatei
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S. R. Bloom
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ABSTRACT

Galanin-like immunoreactivity (IR) was measured by radioimmunoassay in extracts of non-tumorous and tumorous human pituitaries and in multiple sites in the human brain. Galanin-IR was present in considerable quantities in the non-tumorous pituitaries (21·4±1·2 pmol/g wet weight; mean ± s.e.m., n = 30). In 25 pituitary tumours, galanin-IR was detectable in extracts of only nine, with a mean concentration of 11·5±4·4 pmol/g. Galanin-IR was undetectable in the remaining 16. Of ten brain sites, galanin-IR was detected only in the hypothalamus, where the concentration was 9·1±1·8 pmol/g (n = 5). On fast protein liquid chromatography of the non-tumorous pituitary extracts, galanin-IR mostly eluted in a peak with a retention time similar to that of synthetic porcine galanin. On gel permeation chromatography, galanin-IR eluted as a peak with an elution coefficient (K av) of 0·72, also similar to that of porcine galanin, with additional preceding (K av 0·62) and following (K av 0·77) peaks of galanin-IR. These results show that healthy human pituitary and hypothalamus contain substantial amounts of galanin, whereas it is present in variable amounts or not at all in pituitary tumours. Chromatographic analysis suggests that pituitary galanin is present in three molecular forms, with the majority corresponding to synthetic porcine galanin.

Journal of Endocrinology (1991) 130, 463–467

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J. Ginsberg
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P. G. Murray
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ABSTRACT

The ability of the non-phorbol protein kinase C (PKC) activator 12-hydroxy-daphnetoxin (mezerein) to modulate differentiated thyroid function was examined in vitro. A dose-dependent inhibition of TSH-stimulated iodide organification was observed in porcine thyroid cells exposed to mezerein. Under identical conditions mezerein caused the translocation of PKC from its inactive cytosolic form to an active membrane-bound form in thyroid cell extracts. The relative biological potencies of mezerein and the phorbol ester, 12-0-tetradecanoylphorbol-13-acetate (TPA), to inhibit thyroid function in vitro corresponded to their abilities to activate PKC. This effect was also observed when dibutyryl cyclic AMP was used, implying a post-receptor site of action. To provide further evidence for this concept, the effects of mezerein and TPA on receptor-related events were studied. Neither mezerein nor TPA had any effect on the binding of radiolabelled TSH to solubilized porcine thyroid membranes. However, both mezerein and TPA were capable of stimulating cyclic AMP (cAMP) production in porcine thyroid cells in the basal state but could not augment TSH or forskolin-activated cAMP release. These data provide evidence that activation of PKC plays a role in the regulation of differentiated thyroid function in vitro and suggest that the effects of PKC are complex, with independent actions on cAMP accumulation and post-receptor events.

J. Endocr. (1988) 118, 199–203

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