bluuebunny/crossref_metadata_2025_split huggingface dataset:
Insulin-like growth factor-I production and action in porcine thyroid follicular cells in monolayer: regulation by transforming growth factor-β
Authors: Beere H. M. , Soden J. , Tomlinson S. , Bidey S. P. 
Published: December 2008

ABSTRACT
The regulation of thyroid follicular cell growth in vitro involves autocrine or paracrine actions of insulin-like growth factor-I (IGF-I), which are partially suppressed by transforming growth factor-β (TGF-β). Using subconfluent monolayers of porcine thyroid follicular cells, the aims of this study were to establish whether the actions of TGF-β involve changes in the synthesis of, or response to, IGF-I. We also investigated the extent to which inhibitory actions of iodide on IGF-I-dependent proliferation of thyroid follicular cells may be attributable to the production of TGF-β by follicular cells, as opposed to iodide-mediated autoregulation events.
Exposure of porcine thyroid follicular cells in subconfluent monolayer culture to TGF-β over a 7-day period reduced both IGF-I release and the incorporation of [met hyl-3H]thymidine into trichloroacetic acidprecipitable cellular material, while preincubation of cells with NaI (0 ·1 mmol/l) for 24 h prior to the addition of TSH reduced the stimulatory effect of the latter on IGF-I release over the following 7 days. Preincubation of cells with iodide also reduced basal (i.e. autonomous) [methyl-3H]thymidine incorporation. This effect was partially reversed when, following initial exposure to follicular cells, iodide-containing preincubation medium was immunoadsorbed with a neutralizing TGF-β antiserum, and subsequently readded to the cells. Furthermore, similar immunoadsorption of iodide-free preincubation medium resulted in an enhancement of the control level of [methyl-3H]thymidine incorporation when the treated medium was returned to the original cultures. The results of this study are consistent with the hypothesis that IGF-I and TGF-β are both produced by subconfluent thyroid follicular cells in vitro, and that the inhibitory action of TGF-β on follicular cell growth may involve a decrease in the thyroidal production of IGF-I. While the attenuating action of iodide on follicular cell proliferation may, in part, reflect an increased autocrine production of TGF-β, and a reduction by TGF-β of the growth response to IGF-I, these studies also provide evidence that the intrathyroidal actions of TGF-β include an attenuation of IGF-I biosynthesis.
Journal of Endocrinology (1991) 130, 3–9
Increased secretion of insulin-like growth factor-binding proteins and decreased secretion of insulin-like growth factor-II by muscle from growth-retarded neonatal rats
Authors: Frampton R. J. , Jonas H. A. , Larkins R. G. 
Published: December 2008

ABSTRACT
Insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) may be important factors in the control of neonatal growth. We have examined the production, in vitro, of IGFBPs and IGFs by hindlimb skeletal muscle from normal and small-for-gestational age (SGA) neonatal rats. Conditioned medium was collected from muscle strips after incubation at 37 °C for 2 h in Ham's F-12 medium. The conditioned medium was subjected to acid-gel permeation chromatography to separate IGFBPs from IGFs. The binding of 125I-labelled IGF-I to IGFBPs from both control and SGA muscle was displaced equipotently by IGF-I and IGF-II and not at all by insulin. IGFBPs from control and SGA muscles bound IGF-I with comparable affinities (Kd = 0·071 and 0·069 nmol/l respectively). When IGF-II was used as tracer, neither IGF-I nor insulin competed for binding. Western ligand blots of IGFBPs in conditioned media from both control and SGA muscles showed three bands of radioactivity at molecular masses equivalent to 24, 30 and 40 kDa. When the release of IGFBPs by muscle tissue in vitro was quantified by measuring the number of IGF-I binding sites in acid-fractionated medium it was apparent that the muscles from SGA pups secreted significantly more IGFBPs (39·3±7·5 fmol/mg muscle protein per 2 h) than the muscles from control pups (17·8±2·7 fmol/mg protein per 2 h; P < 0·05). In contrast to the IGFBPs, more IGF activity was secreted by the muscles from the control pups (61·1±15·6 fmol/mg muscle protein per 2 h) than the muscles from the SGA pups (12·6±5·8 fmol/mg muscle protein per 2 h; P < 0·05). Analysis of the IGF activity with assays specific for IGF-I and IGF-II showed that both SGA and control muscles secreted predominantly IGF-II with approximately 10% of the total IGF activity measurable as IGF-I. This differential secretion of IGFBPs and IGFs may be associated with the reduced growth potential of the SGA neonate.
Journal of Endocrinology (1991) 130, 33–42
Binding and bioactivity of ovine and porcine prolactins in porcine mammary tissue
Authors: Jerry D. J. , Griel L. C. , Kavanaugh J. F. , Kensinger R. S. 
Published: December 2008

ABSTRACT
Differential binding of homologous and heterologous prolactin was investigated in porcine mammary tissue. Specific binding of ovine prolactin to porcine mammary membranes or tissue slices was significantly greater than specific binding of the homologous porcine prolactin. Ovine prolactin was also more potent than porcine prolactin in stimulating proliferation of Nb2 cells. In contrast, stimulation of glucose metabolism in porcine mammary explants by porcine prolactin was greater than that by ovine prolactin. Differences in specific binding were probably not due to damage during iodination, as low concentrations of iodinated prolactins were similar to unlabelled prolactins in their abilities to stimulate proliferation of Nb2 cells. Furthermore, electrophoretic analysis of medium from binding reactions suggested that differences in specific binding were not due to proteolytic cleavage of the homologous prolactin into large (> 10 kDa) fragments. These studies suggest that ovine prolactin either binds to sites in addition to the authentic lactogenic receptor in porcine mammary tissue or that a significantly higher affinity of ovine prolactin for the porcine lactogenic receptor has little effect on its biological activity.
Journal of Endocrinology (1991) 130, 43–51
Somatostatin partially impedes the stimulatory effects of thyrotrophin-releasing hormone and dibutyryl cyclic AMP on prolactin release: prolactin release through multiple routes
Authors: Shin S. H. , Heisler R. L. , Szabo M. S. 
Published: December 2008

ABSTRACT
Patterns of prolactin release were examined using stimulating and inhibiting agents. Primary cultured pituitary cells primed with oestrogens were used for perifusion experiments. TRH (100 nmol/l) increased the peak prolactin concentration to 360% of the basal concentration, while TRH, under inhibition by 1 nmol somatostatin/l, raised the peak prolactin concentration to 185% of the basal levels. When the somatostatin concentration was increased to 10, 100 and 1000 nmol/l, TRH still stimulated prolactin release to 128%, 121% and 140% respectively, indicating that concentrations of somatostatin of 10 nmol/l or higher did not further suppress the stimulatory effect of TRH. TRH (1 μmol/l) stimulated prolactin release under the influence of 0 (control), 1, 10, 100 and 1000 nmol dopamine/l (plus 0·1 mmol ascorbic acid/l) to 394, 394, 241, 73 and 68% of the basal concentration respectively, showing that the dopamine concentrations and peak prolactin concentrations induced by TRH have an inverse linear relationship in the range 1–100 nmol dopamine/l. The stimulatory effect of dibutyryl cyclic AMP (dbcAMP) on prolactin release was also tested. The relationship between dbcAMP and somatostatin was similar to that between TRH and somatostatin. When adenohypophyses of male rats were used for perifusion experiments, somatostatin (100 nmol/l) did not inhibit basal prolactin release from the fresh male pituitary in contrast with the primary cultured pituitary cells, but dopamine (1 μmol/l) effectively inhibited prolactin release.
In conclusion, (1) oestrogen converts the somatostatin-insensitive route into a somatostatin-sensitive route for basal prolactin release, (2) TRH-induced prolactin release passes through both somatostatin-sensitive and -insensitive routes, (3) dopamine blocks both somatostatin-sensitive and -insensitive routes and (4) cAMP activates both somatostatin-sensitive and -insensitive routes.
Journal of Endocrinology (1991) 130, 79–86
Testicular oxytocin: effects of intratesticular oxytocin in the rat
Authors: Nicholson H. D. , Guldenaar S. E. F. , Boer G. J. , Pickering B. T. 
Published: December 2008

ABSTRACT
The long-term effects of oxytocin administration on the testis were studied using intratesticular implants. Adult male rats had an Accurel device containing 20 μg oxytocin (releasing approximately 200 ng/day) implanted into the parenchyma of each testis; control animals received empty devices. The animals were killed at weekly intervals for 4 weeks. Some animals were perfused and the testes processed for light and electron microscopy. Blood was collected from the remaining animals for the measurement of testosterone, dihydrotestosterone, LH, FSH and oxytocin; epididymal sperm counts were measured and the testes were extracted and radioimmunoassayed for testosterone, dihydrotestosterone and oxytocin.
Long-term administration of oxytocin resulted in a significant reduction in testicular and plasma testosterone levels throughout the 4-week period examined and, after 14 days of treatment, lipid droplets were seen in the Leydig cells of treated but not control animals. Concentrations of dihydrotestosterone in the plasma and testes of the oxytocin-treated animals, however, were significantly elevated after 7 and 14 days and at no time fell below control values. Plasma FSH levels were also lower in the oxytocin-treated animals. Intratesticular oxytocin treatment did not affect LH or oxytocin concentrations in the plasma, epididymal sperm counts or the number of Leydig cells in the testis. Empty Accurel devices had no effect on testicular morphology.
This study provides the first evidence that oxytocin in vivo can modify steroidogenesis in the testis.
Journal of Endocrinology (1991) 130, 231–238
Progesterone receptor in the mammary tissue of pregnant and lactating gilts and the effect of tamoxifen treatment during late gestation
Authors: Lin C. L. , Buttle H. L. 
Published: December 2008

ABSTRACT
An isotope exchange assay using [3H]progesterone was used to examine progesterone receptor moieties in cytosolic extracts obtained from mammary tissue of gilts over the course of pregnancy and lactation, and during treatment of pregnant gilts with tamoxifen. Scatchard analysis was used to determine the concentrations and dissociation constants of progesterone receptors. The concentration of progesterone receptor was high at the onset of pregnancy (1394 fmol/mg DNA), fell to a nadir at 45 days (36 fmol/mg DNA), increased to a second maximum at 75 days (1232 fmol/mg DNA) and declined thereafter till parturition: the dissociation constant (Kd) of progesterone for its receptor remained stable during pregnancy with a mean Kd of 0·78 nmol/l. Progesterone receptors were not identifiable at day 21 of lactation. Treatment of pregnant gilts with tamoxifen (100 mg or 1·0 g/gilt per day orally ≡ 0·70 or 7·0 mg/kg per day) did not affect the development of mammary structures or the ability to lactate at parturition; however, mammary progesterone receptor content in tamoxifen-treated animals tended to be lower than the controls at day 90 of pregnancy (15·7±1·56 vs 27·0±3·75 fmol/mg protein respectively). The results show that a temporal relationship exists between oestrogen concentrations in the circulation of pregnant gilts with progesterone receptor content in mammary tissue.
Journal of Endocrinology (1991) 130, 251–257
Effect of the entero-pancreatic hormones, gastric inhibitory polypeptide and glucagon-like polypeptide-1(7–36) amide, on fatty acid synthesis in explants of rat adipose tissue
Authors: Oben J. , Morgan L. , Fletcher J. , Marks V. 
Published: December 2008

ABSTRACT
The effect of gastric inhibitory polypeptide (GIP), glucagon-like peptide-1(7–36) amide, (GLP-1(7–36) amide), glucagon-like peptide-2 (GLP-2), glucagon and insulin on fatty acid synthesis in explants of rat adipose tissue from various sites was investigated. GIP, GLP-1(7–36) amide and insulin stimulated fatty acid synthesis, as determined by measuring the incorporation of [14C]acetate into saponifiable fat, in a dose-dependent manner, over the concentration range 5–15 ng/ml (0·87–2·61 nmol/l) for insulin and 0·5–7·5 ng/ml for GIP (0·10–1·50 nmol/l) and GLP-1(7–36) amide (0·15–2·27 nmol/l). Insulin and GIP caused a significantly greater stimulation of [14C]acetate incorporation into fatty acids in omental adipose tissue than in either epididymal or subcutaneous adipose tissue. Both GIP and GLP-1(7–36) amide had the ability to stimulate fatty acid synthesis within the physiological range of the circulating hormones. At lower concentrations of the hormones, GLP-1(7–36) amide was a more potent stimulator of fatty acid synthesis than GIP in omental adipose tissue culture; the basal rate of fatty acid synthesis was 0·41±0·03 pmol acetate incorporated/mg wet weight tissue per 2 h; at 0·10 nmol hormone/l 1·15±0·10 and 3·40±0·12 pmol acetate incorporated/mg wet weight tissue per 2 h for GIP and GLP-1(7–36) amide respectively (P < 0·01). GLP-2 and glucagon were without effect on fatty acid synthesis in omental adipose tissue. The study indicates that GIP and GLP-1(7–36) amide, in addition to stimulating insulin secretion, may play a direct physiological role in vivo, in common with insulin, in promoting fatty acid synthesis in adipose tissue.
Journal of Endocrinology (1991) 130, 267–272
Administration of growth hormone to pigs alters the relative amount of insulin-like growth factor-I mRNA in liver and skeletal muscle
Authors: Grant A. L. , Helfericht W. G. , Kramer S. A. , Merkel R. A. , Bergen W. G. 
Published: December 2008

ABSTRACT
The relative amount of insulin-like growth factor-I (IGF-I) mRNA was determined in the liver and skeletal muscle of market weight crossbred barrows (castrated male pigs) using a solution hybridization–nuclease protection assay. Pigs were given either 50 μg recombinant porcine GH per kg body weight or vehicle daily for 24 days i.m. They were fed corn–soybean meal diets containing either 140 or 200 g crude protein/kg (low or high protein). The percentage of muscle in the carcasses of pigs given GH was greater (P <0·01) than that of controls. Relative to controls, GH increased (P <0·05) the amount of liver IGF-I mRNA by 2·7-fold in pigs fed the low protein diet and 3·0-fold in pigs fed the high protein diet. The amount of IGF-I mRNA in the muscles of GH-treated pigs was 77% and 84% of control pigs in those fed the low and high protein diets respectively (P <0·08). GH increased (P <0·001) the serum concentration of IGF-I 1·6-fold in pigs fed the low protein diet and 2·0-fold in those fed the high protein diet. These results indicate that the administration of GH to pigs influences the relative amount of liver IGF-I mRNA. The increased amount of liver IGF-I mRNA and the increased serum IGF-I concentrations suggest that IGF-I plays an endocrine role in mediating GH-induced muscle hypertrophy in pigs.
Journal of Endocrinology (1991) 130, 331–338
Transplacental passage of a human relaxin administered to rhesus monkeys
Authors: Cossum P. A. , Hill D. E. , Bailey J. R. , Anderson J. H. , Slikker W. 
Published: December 2008

ABSTRACT
A synthetic version of the human relaxin encoded by the human gene 2 (hRlx-2) was administered to pregnant rhesus monkeys (Macaca mulatta) on gestational days 141–158. Monkeys (three per group) received doses of 100 μg/kg or 2000 μg/kg as a continuous i.v. infusion over 2 h into a radial vein. One monkey in the low-dose group received, along with the unlabelled hRlx-2, 25·5 μCi/kg of the test material internally labelled with [35S]cysteine. Immunoreactive hRlx-2, as measured by enzyme-linked immunosorbent assay, appeared in all fetuses within 30 min (the first sampling time) of beginning the infusions. Peak fetal plasma levels of hRlx-2 were only 0·8–1·5% of the maternal values. Only 8–15% of the fetal serum radioactivity was hRlx-2. Radioactivity from maternal urine pooled over the 4-h experiment did not elute at the volume corresponding to hRlx-2, but near the column volume.
Journal of Endocrinology (1991) 130, 339–345
Facile separation of the subunits of ovine and bovine gonadotrophins by high-performance liquid chromatrography: microheterogeneity and biological activity
Authors: Sairam M. R. 
Published: December 2008

ABSTRACT
The α and β subunits of ovine and bovine gonadotrophins which undergo instant dissociation in 0·1% (v/v) trifluoroacetic acid in water could be separated into their multiple components by reverse-phase high-performance liquid chromatography on analytical and preparative scales. Several batches of highly purified ovine LH (oLH) separated into four α components (α1 to α4) and five β components (β1 to β5). While the major α component (α3) remained the same in all, the β subunit was variable in all these prepartions of oLH of equal biological and immunoreactivity. Various manipulations, such as prolonged incubation in dilute acid or alkali or conditions prone to air oxidation, did not change elution patterns or produce interconversions among the α or β components, suggesting that microheterogeneity arose in the pituitary itself or during its collection. The subunits obtained on a preparative scale were of high yield and quality and recombined (100%) to produce fully active LH or FSH. Chemical deglycosylations in which 75–80% of the peripheral sugars were removed shifted the elution of all components (a as well as β) slightly but modifications to the protein backbone by other reagents changed the profile of the α subunit. Obtaining the various α and β components in high yield would permit a complete analysis of gonadotrophin microheterogeneity.
Journal of Endocrinology (1991) 130, 415–424
Adhesion molecule expression by the FRTL-5 rat thyroid cell line
Authors: Tandon N. , Dinsdale C. , Tamatani T. , Miyasaka M. , Weetman A. P. 
Published: December 2008

ABSTRACT
We have examined the expression and function of rat CD54, a homologue of human intercellular adhesion molecule-1 (ICAM-1), by the continuously growing rat thyroid cell line FRTL-5. Approximately 10% of FRTL-5 cells express CD54 under basal conditions and this is not influenced by thyrotrophin. Expression of CD54 is increased by cytokines (γ-interferon, tumour necrosis factor, interleukin-1) and by an activator of C-kinase, phorbol 12-myristate 13-acetate. Blocking ICAM-1 with a monoclonal antibody directed against this molecule significantly (P <0·01) reduced the binding of splenic lymphocytes to FRTL-5 cells but inhibition was consistently greater (P <0·01) in the presence of antibodies against a rat homologue of lymphocyte function-associated antigen-1, the receptor on T cells for ICAM-1. In no case was complete blocking of cluster formation observed. These results show that a pure line of rat thyroid cells can express an ICAM-1 homologue and this is directly enhanced by cytokines. Expression of this homologue is partially responsible for lymphocyte adhesion to thyroid cells, which is likely to be a major event in T cell recognition of thyroid antigens in autoimmune thyroiditis.
Journal of Endocrinology (1991) 130, 451–456
Interaction between cortisol and arachidonic acid on the secretion of LH from ovine pituitary tissue
Authors: Nangalama A. W. , Moberg G. P. 
Published: December 2008

ABSTRACT
In several species, glucocorticoids act directly on the pituitary gonadotroph to suppress the gonadotrophin-releasing hormone (GnRH)-induced secretion of the gonadotrophins, especially LH. A mechanism for this action of these adrenal steroids has not been established, but it appears that the glucocorticoids influence LH release by acting on one or more post-receptor sites. This study investigated whether glucocorticoids disrupt GnRH-induced LH release by altering the liberation of arachidonic acid from plasma membrane phospholipids, a component of GnRH-induced LH release. Using perifused ovine pituitary tissue, it was established that exposure of gonadotrophs to 1–1000 nmol cortisol/l for 4 h or longer significantly reduced GnRH-stimulated LH release with the maximal inhibitory effect being observed after 6 h of exposure to cortisol. This suppressive effect of cortisol could be reversed by administration of arachidonic acid, which in its own right could stimulate LH release from ovine pituitary tissue. Furthermore, the inhibitory effect of cortisol on GnRH-stimulated LH release could be directly correlated with decreased pituitary responsiveness to GnRH-stimulated arachidonic acid liberation, consistent with our hypothesis that glucocorticoids can suppress GnRH-induced secretion of LH by reducing the amount of arachidonic acid available for the exocytotic response of GnRH.
Journal of Endocrinology (1991) 131, 87–94
Changes in insulin-like growth factor-binding proteins in bovine mammary secretions associated with pregnancy and parturition
Authors: Skaar T. C. , Vega J. R. , Pyke S. N. , Baumrucker C. R. 
Published: December 2008

ABSTRACT
The bovine mammary gland accumulates large quantities of insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) during late gestation which are secreted at parturition. The present study was conducted to determine the changes in the profiles of IGFBPs secreted by the mammary gland and in blood during late gestation and early lactation in dairy cows.
Ligand blotting of serum and mammary secretions showed that IGFBPs of Mr 25 000, 30000, 34000, 42 000, 46 000 and > 200 000 were present in both fluids. The binding activity of the 42–46 000 Mr IGFBP predominated in prepartum mammary secretions and colostrum but was reduced postpartum. The binding activities of the 30 000 and 34 000 Mr IGFBPs, relative to other IGFBPs, were increased postpartum. Concentrations of IGF-I and IGF-II in mammary secretions declined from 347·1 and 181·1 nmol/litre 1 week prepartum to 0·7 and 0·3 nmol/litre 1·5 weeks postpartum. The volume of mammary secretions obtained was 0109 litre and 6·690 litres at 1 week prepartum and 1·5 weeks postpartum respectively. In prepartum serum, the greatest binding activity was at Mr 42–46 000. The activity at this Mr decreased at parturition but was restored postpartum. The binding activities of the 30 000 and 34 000 Mr IGFBPs were increased around parturition. The 25 000 Mr IGFBP had minor activity during all periods. IGF-I concentrations decreased from 10·6 nmol/litres 1 week prepartum to 4·7 nmol/litres 1·5 weeks postpartum but IGF-II concentrations remained constant.
In conclusion, IGFBP activity secreted by the mammary gland shifts from primarily Mr 42–46 000 prepartum to Mr 30 000 postpartum. The 42–46 000 Mr IGFBP activity in serum was not abolished during late gestation as reported in several monogastric species.
Journal of Endocrinology (1991) 131, 127–133