bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of phorbol ester on protein kinase C activity and effects of depletion of its activity on thyrotrophin, forskolin and 8′-bromoadenosine 3′,5′-cyclic monophosphate-induced [3H]thymidine incorporation in rat FRTL-5 cells
Authors: Akiguchi I. , Izumi M. , Nagataki S. 
Published: December 2008

ABSTRACT
Protein kinase C (PKC) activity was measured in rat FRTL-5 cells cultured in medium containing insulin and transferrin (2H medium), in cells treated with phorbol 12,13-dibutyrate (PDBu), an activator of PKC, and in cells treated with 4α-12,13-phorbol didecanoate (4α-PDD), an inactive phorbol ester, in order to study the translocation and down-regulation of its activity. Provided the PDBu induced translocation and down-regulation of PKC activity, we used the down-regulated cells to study the roles played by PKC in DNA synthesis induced by stimuli which increase cyclic AMP (cAMP) and a cAMP analogue. Cytosolic preparations obtained from cells cultured in 2H media were fractionated on a DEAE-cellulose column, and fractions were assayed for PKC activity. PKC activity was eluted at concentrations between 0·06 and 0·15 mol NaCl/l with a peak at 0·1 mol/l. Exposure of cells to PDBu (100 ng/ml) resulted in 53% loss of initial PKC activity in the cytosolic fraction in concert with reciprocal augmentation of PKC activity in the particulate fraction that peaked at 321% of the initial level at 15 min of exposure.
When cells were stimulated with 100 ng PDBu/ml for 15 min, three- and 1·9-fold greater PKC activity appeared in the particular and total cellular (cytosol plus particulate) fractions respectively than was the case for stimulation with 10 ng PDBu/ml. The total cellular PKC activity transiently increased at 15 min to 137% and subsequently decreased to 74, 40 and 25% of the initial level at 1, 12 and 24 h respectively. However, translocation of PKC activity to the particulate fraction was not observed in cells treated for 15 min with either 10 or 100 ng 4α-PDD/ml and total cellular PKC activity was modestly reduced, to 97% of the initial level in cells exposed to 4α-PDD (100 ng/ml) for 24 h.
[3H]Thymidine incorporation was measured in cells whose PKC activity was stimulated by TSH, forskolin or 8-bromoadenosine cAMP simultaneously with PDBu (100 ng/ml), and also in cells whose PKC activity had been down-regulated by pretreatment with PDBu prior to the addition of each stimulant. The [3H]thymidine incorporation induced by each of the stimulants was inhibited in cells whose PKC activity was subjected to simultaneous stimulation, but was enhanced in cells whose PKC activity had previously been depleted. This potentiating effect of PDBu pretreatment on subsequent TSH-induced [3H]thymidine incorporation was not observed in cells exposed to PDBu for less than 12 h, but was observed in cells exposed for 24 h or longer.
These findings support the hypothesis that PKC regulates TSH-induced DNA synthesis in an inhibitory fashion at sites both proximal and distal to the cAMP generation process in FRTL-5 cells, and that a critical amount of activity must be present for this inhibition to occur.
Journal of Endocrinology (1993) 138, 379–389
The influence of endocrine factors on the serum concentrations of insulin-like growth factor-I (IGF-I) and IGF-binding proteins
Authors: Sugisaki T. , Yamada T. , Takamatsu K. , Noguchi T. 
Published: December 2008

ABSTRACT
Serum insulin-like growth factor-I (IGF-I) levels in lit (isolated GH deficiency), dw (panhypopituitarism), hyt (hypothyroidism) and cog (congenital goiter) mutant mice were found to be significantly lower than in control mice. In addition, liver and kidney IGF-I concentrations in mutants were also found to be significantly reduced compared with controls. These differences in IGF-I concentration were not observed in pg (genetic IGF receptor or post-receptor defect?) mice. These results indicated that serum IGF-I production is induced by thyroid hormones as well as by GH. Western blot analysis of serum IGF-binding protein (IGFBP) fractions revealed the following differences among the five mutants: the triplet of IGFBP-3 (42, 45 and 49 kDa) and IGFBP-4 (24 kDa) levels were significantly reduced. IGFBP-2 (32 kDa) levels were also reduced in the lit, hyt and cog mice, although the level in serum of dw mice was found to be greatly elevated. No differences in serum IGFBP levels were found in the pg mouse. Consequently, the ratio of IGFBP-3%: IGFBP-2% (the percentage of IGFBP-3 fraction of total IGFBP (IGFBP-3%) divided by that of IGFBP-2 (IGFBP-2%)) was decreased in GH-deficient mice but increased in hypothyroid mice, suggesting that IGFBP-3 and IGFBP-2 production in the liver is induced by GH and thyroid hormones respectively.
Journal of Endocrinology (1993) 138, 467–477
Tumour necrosis factor-α modulates oestradiol responsiveness of MCF-7 breast cancer cells in vitro
Authors: Danforth D. N. , Sgagias M. K. 
Published: December 2008

ABSTRACT
We studied the effect of tumour necrosis factor-α (TNF) on oestradiol regulation of growth and metabolism of MCF-7 breast cancer cells to determine whether TNF altered the oestradiol responsivness of these cells. We found that TNF antagonized oestradiol stimulation of cell growth in a dose-dependent manner, with partial inhibition at 1·0 U/ml and complete inhibition at 1000 U/ml. TNF inhibited cell cycle progression, increasing cells in the G0G1 phase and blocking oestradiol-stimulated progression into the S phase. We examined the effect of TNF on three oestrogen-regulated proteins, the oestrogen receptor (ER), the progesterone receptor (PR) and insulin-like growth factor-I (IGF-I). TNF down-regulated the ER and up-regulated the PR. Both of these processes were enhanced by the addition of oestradiol. The effects of TNF on the ER and PR were dose-dependent and occurred without a change in the Kd of the receptor. TNF did not change the respective steady-state mRNA levels. In addition, TNF did not alter secretion of IGF-I either in the absence or presence of oestradiol, indicating that the effects of TNF on oestrogen-regulated proteins is selective. These findings indicate an important interaction between the immune and endocrine systems. The cytokine TNF has a prominent effect on oestradiol stimulation of MCF-7 cells, blocking its proliferative response and enhancing certain metabolic effects. These actions may be mediated in part through modulation of the ER, although other pathways appear to be involved.
Journal of Endocrinology (1993) 138, 517–528
Androgen regulation of circulating insulin-like growth factor-I during puberty in male hypogonadal mice
Authors: Crawford B. A. , Singh J. , Simpson J. M. , Handelsman D. J. 
Published: December 2008

ABSTRACT
This study aimed at determining the relationship of sex steroids, particularly in the perinatal period, to the pubertal insulin-like growth factor-I (IGF-I) surge in male mice. We used hypogonadal (hpg) mice, which have a major deletion in the gonadotrophin-releasing hormone (GnRH) gene, in order to have a model lacking all GnRH-induced gonadotrophin and sex steroid secretion throughout pre- and postnatal life. Cross-sectional data on body weights and weights of testes, seminal vesicles, kidneys, liver and spleen from 9 to 77 days of age were obtained in male hpg, heterozygous (Hz) and homozygous normal (N/N) littermates (n = 75–78/group). These data did not reveal any difference between Hz and N/N mice. Hpg mice had decreased body weights which by 70–77 days of age were approximately 18% less than normal controls. Testes and seminal vesicles of hpg mice did not demonstrate any significant postnatal growth. Relative to body weight, kidney weights were also markedly reduced in hpg mice (P<0·0001), deviating significantly from normal by 28–35 days of age, reflecting the impact of androgen deficiency on a non-reproductive organ. From the cross-sectional data it was concluded that puberty commenced soon after weaning (21 days) in the male and that maturity was achieved within 4–5 weeks. Longitudinal study showed that, compared with normal controls, untreated hpg mice had an exaggerated pubertal IGF-I surge (P<0·005) which peaked in mid-puberty. This, together with their reduced body weights (P<0·05), were normalized by treatment from 21 to 70 days of age with two 1 cm s.c. implants of testosterone (n=6) or dihydrotestosterone (n=7). There was no difference in IGF-I levels or in weights of testes, seminal vesicles, kidney, liver or spleen between testosterone and dihydrotestosterone treatments (P>0·05). Prolonged high levels of androgen also restored testicular and seminal vesicle weights to 40% of phenotypically normal controls, while kidney, liver and spleen weights were also significantly increased. The pubertal IGF-I surge in mice does not, therefore, require androgens in either the pre- or postnatal periods, and it is exaggerated in androgen-deficient male mice and dampened to normal regardless of aromatization.
Journal of Endocrinology (1993) 139, 57–65
Effects of recombinant bovine somatotrophin, insulin-like growth factor-I and insulin on the proliferation of bovine granulosa cells in vitro
Authors: Gong J. G. , McBride D. , Bramley T. A. , Webb R. 
Published: December 2008

ABSTRACT
Treatment of heifers with recombinant bovine somatotrophin (BST) significantly increases the population of small ovarian follicles and peripheral concentrations of somatotrophin, insulin-like growth factor-I (IGF-I) and insulin. To investigate the possible mechanism(s) involved in the action of BST on ovarian follicles, the effects of BST, IGF-I and insulin, given alone or in combination with either FSH or LH, on the proliferation of bovine granulosa cells in vitro were examined using a serum-free culture system. Bovine granulosa cells were obtained from antral follicles classified into three size categories according to diameter: small <5 mm; medium-sized 5–10 mm and large >10 mm. The proliferation of granulosa cells was assessed by the incorporation of [3H]thymidine into the cultured cells.
Both FSH and LH (1–1000 ng/ml) inhibited the proliferation of bovine granulosa cells obtained from all three size classes of follicles in a dose-dependent manner. BST, at doses ranging from 1 to 1000 ng/ml, had no effect on the proliferation of granulosa cells from small and medium-sized follicles, but inhibited the division of granulosa cells from large follicles in a dose-dependent manner. Treatment with either IGF-I (10–3000 ng/ml) or insulin (0·5–1000 ng/ml) stimulated, in a dose-dependent manner, the proliferation of granulosa cells obtained from all three size categories of follicles. No synergistic interaction between BST (30 ng/ml) and either FSH (50 ng/ml) or LH (5 ng/ml) was observed in granulosa cells from all three size classes of follicles. In contrast, physiological concentrations of both IGF-I (100 ng/ml) and insulin (1 ng/ml) acted in synergy with both FSH (50 ng/ml) and LH (5 ng/ml) to stimulate the proliferation of granulosa cells from small follicles, whilst no such synergistic interactions were observed in granulosa cells from medium-sized and large follicles.
It was concluded that the increase in the number of small ovarian follicles induced by BST treatment in heifers may be mediated by increased peripheral concentrations of IGF-I and/or insulin, possibly acting in synergy with gonadotrophins. Furthermore, insulin probably acts through its own receptor rather than acting via the type-I IGF receptor, as it can stimulate the proliferation of bovine granulosa cells at physiological concentrations.
Journal of Endocrinology (1993) 139, 67–75
Interactions between growth hormone and nutrition in hypophysectomized rats: body composition and production of insulin-like growth factor-I
Authors: Bates P. C. , Loughna P. T. , Pell J. M. , Schulster D. , Millward D. J. 
Published: December 2008

ABSTRACT
Hypophysectomy of adult rats results in a loss of body growth which can be reversed by treatment with GH. The increased growth caused by administration of GH is accompanied by an increase in food consumption. The effects of GH and interactions with nutrition were investigated by treating hypophysectomized rats with GH and either providing unrestricted food or preventing the increased food consumption by pair-feeding with the same intake as that of the hypophysectomized animals.
Over the 7-day experimental period, the GH-treated animals grew significantly when food was available ad libitum but did not gain body weight when an increase in food intake was prevented. However, there was a significant interaction between GH and nutrition on body composition; GH significantly decreased body fat and increased the protein: fat ratio only in the animals with the restricted intake. Gastrocnemius muscle weight was increased by GH regardless of food intake, but heart weight did not increase and liver weight was actually decreased by GH teatment when food intake was restricted. Serum concentrations of insulin and insulin-like growth factor-I (IGF-I) were increased by GH in the rats with food available ad libitum but not in the pair-fed rats. However, the liver concentration of IGF-I and its mRNA were increased by GH although the increase in IGF-I mRNA was modulated by the restricted food intake. The decreased weight of the liver in the pair-fed GH-treated rats, despite the increase in IGF-I mRNA, suggests that IGF-I does not influence liver growth. In the gastrocnemius muscle, however, GH increased IGF-I mRNA concentration similarly in both rats with food available ad libitum and in pair-fed rats. Decreased nutrition therefore modulated the action of GH but emphasized its nutrient partitioning effect, thus increasing the anabolic drive towards skeletal muscle growth; this appeared to be mediated by the local production of IGF-I within the muscle.
Journal of Endocrinology (1993) 139, 117–126
Rat placental lactogen-I binds to the choroid plexus and hypothalamus of the pregnant rat
Authors: Pihoker C. , Robertson M. C. , Freemark M. 
Published: December 2008

ABSTRACT
Recent findings suggest that placental lactogen has a role in the regulation of hypothalamic function during pregnancy. To explore the mechanisms by which placental hormones may exert effects in the maternal central nervous system, we have examined the binding of rat placental lactogen-I (rPL-I) to brain slices from pregnant rats at mid- and late gestation. The binding of rPL-I to maternal rat brain was compared with that of human GH (hGH). Radiolabelled rPL-I bound specifically to ependymal cells of the choroid plexus in the lateral ventricles and in the roof of the third ventricle. The binding of 125I-labelled rPL-I was inhibited by unlabelled rPL-I, hGH or rat prolactin but not by rat GH, indicating that rPL-I and rat prolactin interact with a common binding site in maternal rat brain. Radiolabelled hGH bound to the choroid plexus and to ependymal cells lining the third ventricle in the region of the arcuate nucleus. In addition, hGH bound specifically to the ventromedial nuclei and to the medial preoptic area of the hypothalamus. The binding of radiolabelled hGH to all brain regions was inhibited by unlabelled rPL-I as well as hGH, indicating that rPL-I competes for lactogenic binding sites in the hypothalamus as well as the choroid plexus of the pregnant rat. These findings suggest potential mechanisms by which placental hormones may exert direct effects on the maternal central nervous system during pregnancy. The precise functions and roles of the PL-I binding sites in maternal choroid plexus and hypothalamus remain to be explored.
Journal of Endocrinology (1993) 139, 235–242
Nutritional regulation of insulin-like growth factor-I mRNA expression in salmon tissues
Authors: Duan C. , Plisetskaya E. M. 
Published: December 2008

ABSTRACT
In salmonids, nutritional insufficiency leads to retarded growth and reduced hepatic GH receptors, but increased circulating GH levels. To understand the endocrine mechanism underlying the retarded growth in starved fish better, we investigated the effect of food deprivation and refeeding on circulating levels of GH and insulin, as well as insulin-like growth factor-I (IGF-I) mRNA expression in different tissues of juvenile coho salmon (Oncorhynchus kisutch). Deprivation of food for 2–4 weeks resulted in cessation of growth and a significant decrease in condition factor (an indicator of fish body shape). No difference in circulating insulin or glucose levels were found between starved and fed fish, whereas starvation increased the plasma GH levels. After 4 weeks of starvation, the plasma GH level rose to 9 ng/ml, which was four times as high as that of the fed fish. In spite of elevated circulating GH, hepatic IGF-I mRNA levels were significantly reduced after 4 weeks of starvation. No significant difference in IGF-I mRNA levels of fed and starved fish was found in other tissues, including kidney, spleen, ovary, gill filament and gut. Two weeks of refeeding significantly increased hepatic IGF-I mRNA levels and growth and reduced plasma GH levels. These results suggest that food deprivation primarily reduces IGF-I mRNA expression in the liver which results, most probably, in a decline in systemic IGF-I levels and consequently leads to the retarded growth of salmon.
Journal of Endocrinology (1993) 139, 243–252
Prolonged intermittent but not continuous administration of oestradiol-17β increases bone volume in the rat
Authors: Tobias J. H. , Gallagher A. , Chambers T. J. 
Published: December 2008

ABSTRACT
We have previously found that administration of oestradiol-17β (OE2) to intact adult female rats of 19 days stimulates cancellous bone formation. However, this effect is not observed following longer periods of OE2 treatment, suggesting that the responsiveness of the skeleton to oestrogen's anabolic action is reduced after prolonged administration. A possible explanation for this is that oestrogen also suppresses bone resorption, which is an important stimulus for bone formation. We therefore investigated the effect of omitting OE2 for short periods, on the proximal tibial metaphysis of intact female rats. We found that, unlike continuous treatment with OE2 (40 pg/kg) for 56 days, omission of OE2 for 4 days out of every 20 was associated with a significant increase in cancellous bone volume. Although continuous and intermittent OE2 were both associated with a reduction in osteoclast surface, a decrease in the proportion of double fluorochrome-labelled surface was only seen after continuous OE2 treatment. We then studied the effects of longer periods of OE2 omission by giving OE2 (40 pg/kg) for three repeated cycles of: (1) OE2 for 16 days/vehicle for 4 days, (2) OE2 for 12 days/vehicle for 8 days, (3) OE2 for 8 days/vehicle for 12 days, or (4) OE2 for 4 days/vehicle for 16 days. We found a significant increase in cancellous bone volume when OE2 was stopped for either 4 or 8 days at a time. However, longer periods of OE2 omission did not affect bone volume, possibly because these were associated with an increase in bone resorption and/or a reduction in bone formation during the OE2-free period. In conclusion, we observed an increase in cancellous bone volume after prolonged treatment with oestrogen only if OE2 was omitted for short periods. This may be due, at least in part, to bone formation being maintained at a higher rate by such treatment than by either continuous OE2 administration or by intermittent administration where OE2 is discontinued for longer periods.
Journal of Endocrinology (1993) 139, 267–273
Stimulation of placental, fetal and neonatal growth by thyroxine administration to pregnant rats
Authors: Spencer G. S. G. , Robinson G. M. 
Published: December 2008

ABSTRACT
The effects of daily thyroxine (T4) administration to pregnant rats on the growth of their fetuses and placentae were examined. Additional trials examined the effect of such treatment on the postnatal growth of the offspring. Injection of 10 μg T4 into the mother caused a tenfold elevation in maternal plasma T4 concentration, which remained elevated for more than 12 h, but returned to basal levels by 24 h after injection. Despite the increase in maternal T4 concentrations, no increase in fetal plasma T4 was found. A greater weight of both the fetuses (20·1%; P<0·001) and placentae (14·6%; P<0·05) was found in the young of T4-treated mothers compared with those from control mothers at delivery by hysterotomy on day 20 of gestation. In trials where mothers delivered naturally, birth weights of the young from mothers treated with T4 (10, 20 or 50 μg daily) were also significantly heavier than controls, and continued to grow faster postnatally. These data suggest that maternal thyroid hormone status is important for fetal growth, and further indicate that stimulation of the thyroid hormone axis during pregnancy could provide a method for improving postnatal growth.
Journal of Endocrinology (1993) 139, 275–279
Serum unmasks the binding of thyroid-stimulating hormone to endogenous and transfected receptors: evidence for a soluble form of the receptor in human thyroid
Authors: Willey K. P. , Hunt N. , Abend N. , Northemann W. , Ivell R. , Leidenberger F. 
Published: December 2008

ABSTRACT
A specific homologous radioligand receptor assay for thyroid-stimulating hormone (TSH) using bovine thyroid membranes was adapted for use with human thyroid. Specific 125I-labelled TSH binding was detected in the 3000 g membrane pellet from bovine thyroid but predominantly in the 3000 g supernatant of the human thyroid homogenate. Both assays required incubation in the presence of 10% serum, whilst the assay using human thyroid could only be precipitated using polyethylene glycol (PEG). The serum requirement transcended a possible role as carrier protein and unmasked specific TSH binding. Molecular sieving determined that the active fraction of the serum had an apparent size of 30 000–100 000. The requirement for PEG-assisted precipitation of the TSH receptor assay was a consequence of the TSHbinding entity from Graves' thyroid behaving like a soluble 'receptor': it did not sediment with the membranes, passed a 0·2 μm filter and, upon molecular sieving, had an apparent size of 300 000–1 000 000. A full-length TSH receptor cDNA was cloned from a human Graves' thyroid library and stably transfected cell lines expressing the TSH-receptor protein were constructed using human HeLa and murine 3T3 cells. Specific TSH binding was unmasked by serum in the human cell lines, as observed for the human thyroid TSH receptor, whereas serum hindered TSH binding in the murine cell lines. A soluble form of the receptor was not released from the cells and was not produced in conditions which demonstrated a soluble receptor-like binding component in human thyroid tissue.
Journal of Endocrinology (1993) 139, 317–328