bluuebunny/crossref_metadata_2025_split huggingface dataset:
Translational status of the insulin-like growth factor-I mRNAs in liver of protein-restricted rats
Authors: Thissen J.-P. , Underwood L. E. 
Published: December 2008

ABSTRACT
Dietary protein restriction in young rats decreases serum insulin-like growth factor-I (IGF-I) concentrations and the amount of liver IGF-I mRNA, suggesting that regulation for the liver IGF-I gene expression in this model occurs at a pretranslational level. To determine whether there is also translational control, we assessed the association of the liver IGF-I mRNA transcripts with polysomes in livers of normally fed (15% dietary protein) versus protein-restricted (5% dietary protein) rats. One week of dietary protein restriction reduces serum IGF-I concentrations by 54% and the amount of liver IGF-I mRNA by 35%, with the 7·5 kb size-class of IGF-I mRNA being the most affected (−48%). Protein restriction reduces the amount of the polysomal IGF-I mRNAs by 30%, a value in close agreement with the changes in total IGF-I mRNAs. Protein restriction is not associated with changes in the distribution of IGF-I mRNAs between the polysomal and non-polysomal fractions. All major size-classes of IGF-I mRNA transcripts (7·5, 4·7, 1·7, 0·9–1·2 kb) are associated with the polysomes in both dietary groups, suggesting involvement in the initiation phase of the IGF-I translation. We conclude that no untranslatable pool of IGF-I mRNAs is present in the liver of protein-restricted animals. Protein restriction, however, decreases slightly the mean size of polysomes. This decrease in ribosomal number associated with the IGF-I mRNA could decrease translational efficiency. Our data suggest that dietary protein restriction does not impair the initiation of IGF-I mRNA translation.
Journal of Endocrinology (1992) 132, 141–147
Reproductive effects of placing micro-implants of melatonin in the mediobasal hypothalamus and preoptic area in rams
Authors: Lincoln G. A. , Maeda K.-I. 
Published: December 2008

ABSTRACT
The reproductive effects of placing micro-implants of melatonin in the mediobasal hypothalamus (MBH) and preoptic area (POA) were monitored in Soay rams. Groups of animals were initially conditioned to alternating 16 weekly periods of long days (16 h light:8 h darkness; 16L:8D) and short days (8L:16D) for at least 9 months to entrain the seasonal reproductive cycle. All experiments were then initiated at 10 weeks under long days when the animals were sexually inactive. In experiment 1, rams were exposed to short days for 14 weeks or maintained on long days to illustrate the photoperiodically induced re-activation and regression of the reproductive axis. In experiments 2–4, rams received micro-implants of melatonin in the MBH or POA, or received control treatments (sham-operated or no surgery) for 12–14 weeks while maintained on long days (total of 12 animals/treatment). The melatonin implants consisted of 22-gauge stainless-steel cannulae with melatonin fused inside the tip and were placed bilaterally in the brain. Incubation of the implants in Tricine-buffered saline (pH 8·0) at 37 °C showed that the release rate of melatonin was relatively constant after an initial peak in week 1 (means ± s.e.m.: 3·42 ± 0·43 μg/24 h).
Rams with melatonin implants placed in the MBH, but not in the POA, showed a consistently earlier re-activation of the reproductive axis compared with the control animals in all three experiments (12/12 for MBH vs 2/12 for POA). The mean time to maximum testicular diameter was 12·2 ± 0·9, 21·6 ± 1·8 and 22·3 ± 1·2 weeks for the MBH, POA and combined control groups respectively (MBH vs control, P < 0·01; analysis of variance). The premature growth of the testes in the MBH group was associated with an earlier increase in the blood plasma concentrations of FSH and testosterone, and the appearance of the sexual skin coloration. Removal of the implants resulted in a decline in all reproductive parameters. The melatonin treatments did not cause a detectable increase in the peripheral concentrations of melatonin, or affect the diurnal rhythm in melatonin which reflected the long-day photoperiod. When implants containing 125I-labelled melatonin were introduced into the brain the associated radioactivity was localized to within 1 mm of the implants.
The overall results demonstrate that the constant administration of melatonin into the MBH blocks the effect of the endogenous long-day melatonin signal and induces gonadal redevelopment. This provides the first evidence that melatonin acts within or close to the MBH to relay effects of photoperiod and influence the timing of the reproductive cycle in the ram.
Journal of Endocrinology (1992) 132, 201–215
Influence of the gonad on the degree of suppression induced by an LHRH agonist implant in the marmoset monkey
Authors: Lunn S. F. , Cowen G. M. , Morris K. D. , Fraser H. M. 
Published: December 2008

ABSTRACT
In a previous study pituitary-testicular function was shown to be maintained in a New World primate after the administration of an LHRH agonist implant. In the present study the mechanism of action of the same LHRH agonist (buserelin) on pituitary–gonadal function in the marmoset was investigated and a comparison made between the effects of treatment in three intact males, six adult cyclic females with regular ovulatory cycles, and six long-term ovariectomized animals. These were injected s.c. with an LHRH agonist implant (1·5 mg buserelin in a rod 0·5 cm long). In both the males and intact females, basal plasma LH concentrations were maintained within the normal range throughout the expected duration of agonist action (at least 3 months). Despite this, an absence of response to an LHRH challenge indicated that pituitary desensitization had occurred. In the intact females, ovulation was inhibited in five of six animals, plasma progesterone concentrations initially being maintained but subsequently remaining suppressed until 136 ± 18 (s.e.m.) days after treatment. Responsiveness to administered LHRH returned prior to onset of return to ovarian cycles. In contrast, in ovariectomized marmosets, plasma LH was markedly suppressed to concentrations which were at or below the limit of detection of the assay and were therefore less than those observed in the buserelin-implanted intact animals.
These results show that apparently normal pituitary-gonadal function in this species disguises an underlying pituitary desensitization to LHRH. This allows continuation of testosterone secretion in the male, but in the female ovulation is prevented, presumably as a result of failure of the desensitized pituitary to produce an LH surge. Since LH concentrations in buserelin-implanted ovariectomized animals were suppressed to levels less than those seen in the treated animal, the maintenance of basal LH secretion may be the result of a protective influence of gonadal factors.
Journal of Endocrinology (1992) 132, 217–224
Production of parathyroid hormone-related protein by the mammary gland of the goat
Authors: Ratcliffe W. A. , Thompson G. E. , Caret A. D. , Peaker M. 
Published: December 2008

ABSTRACT
Parathyroid hormone-related protein (PTHRP) has been quantified by sensitive specific immunoassays in mammary venous blood and milk from 7 days before to 7 days after parturition in the goat. A significant venousarterial concentration gradient in plasma PTHRP 1–86 concentrations was demonstrated across the mammary gland, indicating that PTHRP enters the maternal circulation and may have a role in calcium homoeostasis during lactation. Significant and sustained increases in mammary venous and milk PTHRP 1–86 concentrations were found from 1 day before parturition to 7 days afterwards, with peak concentrations of 1·57 ± 0·58 pmol/l (plasma) and 8·69 ±2·95 nmol/l (milk) (mean ± s.e.m.) occurring on day −1 and the day of parturition respectively. Estimates of the mammary output of PTHRP into plasma in four goats averaged 9% (range 1–25%) of that secreted into milk. Suppression of maternal prolactin concentrations by bromocriptine significantly reduced milk yield and the mammary venous PTHRP concentration, without affecting the concentration of PTHRP in milk. In conclusion, parturition in the goat is associated with a sustained increase in secretion of PTHRP into both plasma and milk; the former may be involved in maternal calcium homoeostasis, whereas the latter may have a role in the neonate.
Journal of Endocrinology (1992) 133, 87–93
Effects of insulin-like growth factor-I and insulin on the in-vitro uptake of sulphate by eel branchial cartilage: evidence for the presence of independent hepatic and pancreatic sulphation factors
Authors: Duan C. , Hirano T. 
Published: December 2008

ABSTRACT
The possible roles of insulin-like growth factor-I (IGF-I) and insulin in regulating cartilage growth were studied in the teleost Anguilla japonica. Significant sulphation activity was found in the extracts of pancreas, liver and muscle, but not in those of kidney, intestine or spleen. The hepatic sulphation activity was significantly decreased by hypophysectomy or by fasting for 14 days, suggesting that this activity is regulated by pituitary function and nutritional status. Northern blot analysis revealed that the hepatic IGF-I mRNA in the eel consists of a major 4·0 kb band. This mRNA was GH-dependent and was significantly decreased by fasting for 14 days.
On the other hand, fasting for 14 days had no significant effect on pancreatic sulphation activity. Pancreatic extracts from both intact and hypophysectomized eels exhibited equally significant stimulating activity. Addition of bovine or human insulin (1–250 ng/ml) to the culture medium significantly stimulated sulphate uptake in a dose-dependent manner. Teleost (coho salmon) insulin was as effective as bovine insulin. Bovine insulin was more effective than IGF-I at lower concentrations (1–4 ng/ml) but less effective at higher concentrations (10–250 ng/ml). These results indicate that not only IGF-I but also insulin are likely to be involved in the regulation of cartilage growth in the eel.
Journal of Endocrinology (1992) 133, 211–219
Effect of growth hormone and insulin-like growth factor-I on DNA synthesis and matrix production in rat epiphyseal chondrocytes in monolayer culture
Authors: Ohlsson C. , Nilsson A. , Isaksson O. G. P. , Lindahl A. 
Published: December 2008

ABSTRACT
The influence of various culture conditions was studied on the effect of GH and insulin-like growth factor-I (IGF-I) on DNA and matrix synthesis in epiphyseal rat chondrocytes in monolayer culture.
Chondrocytes from enzymatically digested rat tibia epiphyseal growth plates were seeded in 48-well culture plates and precultured for 10 days in Ham's F-12 medium supplemented with 1% (v/v) newborn calf serum and 1% (v/v) of a serum substitute. After preculture, the medium was changed to Ham's F-12 medium supplemented with 1% serum from hypophysectomized rats, and the effect of GH and IGF-I on DNA synthesis ([3H]thymidine incorporation) and matrix production ([35S]sulphate uptake) was studied during an additional 96-h culture period. Isotopes were present during the last 24 h of culture.
Both hGH and IGF-I stimulated DNA synthesis in a dose-dependent manner. A maximal effect of GH was seen at a concentration of 25 μg/l (60 ± 11% stimulation over control) and for IGF-I at 10 μg/l (162 ± 12%). The stimulatory effects of the same concentrations of human GH (hGH) and IGF-I on [35S]sulphate uptake were 135 ± 25 and 320 ± 42% respectively. In-vitro pulse labelling revealed that GH did not produce a response during the first 3 days of culture (after addition of GH) but was effective during days 4 and 5 of culture. In contrast, IGF-I was effective throughout the culture period. Pretreatment of cells with GH or IGF-I for 2·5 days showed that GH but not IGF-I produced a sustained effect on [3H]thymidine uptake.
In order to study the influence of cell density on the effect of GH and IGF-I on DNA synthesis, the effect of added peptides was evaluated after different preculture periods (5–15 days). A maximal stimulatory effect of hGH was seen at a cell density of 150 000–300 000 cells/cm2. GH had no significant effect at a low (< 100 000 cells/cm2) or a high (>400 000 cells/cm2) cell density. The magnitude of the stimulatory effect of IGF-I was the same at densities between 10 000 and 250 000 cells/cm2, but was reduced at higher cell densities (over 250 000 cells/cm2).
Chondrogenic properties of cells that had been cultured for 15 days were verified in vitro by positive alcian blue staining and identification of type II collagen, and in vivo by development of cartilage nodules in nude mice.
The results from the present study clearly show that GH and IGF-I both stimulate DNA synthesis and matrix production in epiphyseal chondrocytes in monolayer culture. The results also demonstrate that expression of the effect of GH is highly dependent upon the culture conditions.
Journal of Endocrinology (1992) 133, 291–300
Control of protein and matrix-molecule synthesis in isolated ovine fetal growth-plate chondrocytes by the interactions of basic fibroblast growth factor, insulin-like growth factors-I and -II, insulin and transforming growth factor-β1
Authors: Hill D. J. , Logan A. , McGarry M. , De Sousa D. 
Published: December 2008

ABSTRACT
Chondrogenesis is thought to be controlled by interactions between circulating anabolic hormones and locally produced peptide growth factors, and involves ordered changes in matrix composition which ultimately allow endochondral calcification. We have used a model of isolated ovine fetal growth-plate chondrocytes to examine the actions and interactions of basic fibroblast growth factor (basic FGF), insulin-like growth factors-I and -II (IGF-I and -II), insulin and transforming growth factor-β1 (TGF-β1) on total protein, collagen or non-collagenous protein and sulphated glycosaminoglycan synthesis. These parameters were determined by assessment of the incorporation by monolayer cultures of early passage chondrocytes of [3H]leucine, [14C]proline and [35S]sulphate respectively, followed by partial molecular characterization. Basic FGF enhanced total protein synthesis with a half-maximal effective concentration of 270 ± 60 pmol/l (mean ± s.e.m., four animals) and was sixfold more active on a molar basis than IGF-I or insulin, and 28-fold more active that IGF-II which is the endogenously synthesized IGF. The actions of basic FGF were additive to those of IGF-I or insulin. More detailed analysis of extracellular-matrix component synthesis showed that basic FGF, IGF-I and insulin each caused significant increases in the synthesis of collagen and sulphated glycosaminoglycans. TGF-β1 had no effect on total protein synthesis by chondrocytes when present alone at concentrations of 200 pmol/l or less, but was inhibitory at 400 pmol/l. However, the use of this parameter masked a stimulatory action of 50 or 100 pmol TGF-β1 on sulphated glycosaminoglycan synthesis and a relative shift in the ratio of collagen: non-collagenous protein synthesis in favour of the former. A synergistic interaction existed between TGF-β1 (20–100 pmol/l) and basic FGF which potentiated total protein and collagen synthesis, and their actions on sulphated glycosaminoglycan production were additive. The same concentrations of TGF-β1 inhibited the ability of IGF-I or insulin to stimulate total protein or collagen synthesis, but were additive to their stimulatory effects on sulphated glycosaminoglycan synthesis. The results suggest that matrix-molecule composition and the anabolic status of the epiphyseal growth-plate may be modulated in utero by multiple interactions between peptide growth factors produced locally, such as basic FGF, IGF-II and TGF-β1, and circulating hormones such as insulin and IGF-I.
Journal of Endocrinology (1992) 133, 363–373
Preovulatory follicle development and luteal function in ewes immunized against a synthetic peptide sequence of the α subunit of bovine inhibin
Authors: McLeod B. J. , Hunter M. G. , Bleach E. C. L. , Glencross R. G. , Wrathall J. H. M. 
Published: December 2008

ABSTRACT
Immunization against inhibin consistently results in an increase in ovulation rate in sheep, but the effects that this treatment has on follicle development are unknown. In order to determine the influence of inhibin, parameters of follicle development were assessed in ewes that had been actively immunized against a synthetic peptide homologous to the N-terminal sequence (α1–29, Tyr30) of the a subunit of bovine inhibin, a treatment that neutralizes the biological activity of endogenous inhibin. The final stages of preovulatory follicle development that culminate in ovulation were induced in seasonally anoestrous ewes, and follicles were recovered prior to the predicted time of ovulation. After priming with progestagen, inhibin-immunized and control ewes were treated with gonadotrophin-releasing hormone (GnRH) by continuous infusion (200 ng/h). The ovaries were recovered at slaughter 24 h after the start of GnRH treatment and all follicles ≥ 2·0 mm diameter were dissected out and their capacity to produce oestradiol in vitro was assessed. Further groups of similarly treated animals were blood-sampled daily to determine luteal function following GnRH-induced ovulation. The ovaries were recovered from these ewes at slaughter 10 days after the start of GnRH treatment, the corpora lutea were dissected out and their progesterone content was assessed.
There were more (P < 0·01) follicles of 5–6 mm diameter (3·2 ± 0·45 (s.e.m.) compared with 1·1 ± 0·25 follicles/ewe) and more (P < 0·001) follicles of > 6 mm diameter (2·8 ± 0·56 compared with 0·9 ± 0·17 follicles/ewe) in inhibin-immunized than in control ewes. In addition, the mean number of the antral follicles that were oestrogenic was greater (P < 0·05) in immunized than in control ewes (2·8 ± 0·66 compared with 1·3 ± 0·25 follicles/ewe).
In animals slaughtered 10 days after the start of GnRH treatment, mean ovulation rate was greater (3·17 ± 0·65 and 1·14 ± 0·14, P < 0·01) in inhibin-immunized ewes. Although there was more (P < 0·01) total luteal tissue/ewe in the immunized group, both the mean weight and progesterone content (ng/mg tissue) of individual corpora lutea were similar between treatment groups. Mean plasma progesterone levels increased earlier and reached higher (P < 0·01) mean concentrations in immunized than in control ewes.
These results demonstrate that immunization against inhibin increases the number of preovulatory follicles during the follicular phase, and that steroidogenesis within these follicles and the resultant corpora lutea appears to be normal.
Journal of Endocrinology (1992) 133, 413–419
Growth hormone treatment increases oestrogen receptor concentration in the guinea-pig uterus
Authors: Bezecný I. , Bártová J. , Škarda J. 
Published: December 2008

ABSTRACT
Growth hormone does not act as a body growthpromoting hormone during the postnatal period in the guinea-pig. To determine whether it affects uterine and mammary growth, guinea-pigs of 8–9 weeks of age were treated with either recombinant bovine GH (bGH; 0·5 mg per animal) or vehicle for 10 days. Uterine and mammary weights were not changed by treating the animals with bGH. The amount of available cytosolic oestradiol receptor per unit of uterine weight or DNA content, or in whole uteri was increased in bGH-treated animals 7·3 to 14·0-fold) when compared with controls. The nuclear uterine oestradiol receptor concentration was 3·3- to 6·7-fold higher than in controls. The dissociation constant values did not differ between control and bGHtreated animals, suggesting that uterine oestradiol receptors are regulated by GH through changes in the number of binding sites rather than alteration of their binding affinity. Mammary growth and oestradiol receptor levels were unaffected by bGH treatment.
The results of this investigation demonstrate that injected bGH selectively affects the oestradiol receptor level in guinea-pig uterine tissue.
Journal of Endocrinology (1992) 134, 5–9
Antiprogesterone RU486 increases serum immunoreactive inhibin levels and LH:FSH and testosterone:oestradiol ratios in cyclic rats
Authors: Sánchez-Criado J. E. , Uilenbroek J. Th. J. , de Jong F. H. 
Published: December 2008

ABSTRACT
Since administration of the antiprogesterone RU486 to cyclic rats results in a dissociation of basal LH and FSH secretion we studied its effects on peripheral levels of inhibin, oestradiol and testosterone throughout the oestrous cycle. Cyclic rats were given RU486 (2 mg) twice daily (09.00 and 17.00 h) on metoestrus, dioestrus and pro-oestrus. Oil-treated rats were used as controls.
Serum concentrations of immunoreactive inhibin in oil-treated rats increased from metoestrus to prooestrus and decreased at oestrus. RU486-treated rats had serum inhibin concentrations significantly increased over oil-treated rats at dioestrus and prooestrus, but not at oestrus. At both pro-oestrus and oestrus serum concentrations of LH, testosterone and oestradiol were significantly raised in RU486-treated rats compared with oil-treated controls. In contrast, serum FSH concentrations in RU486-treated rats were decreased on both days. Ovaries from RU486-treated rats showed an increased testosterone content at pro-oestrus, mainly in the interstitial tissue.
The results of thepresent study demonstrate that RU486 has a stimulatory effect on inhibin secretion, and offer an explanation for the decrease in basal serum FSH levels. The low FSH secretion on the morning of oestrus in spite of the low levels of inhibin suggests that progesterone is involved in FSH secretion at this time.
Journal of Endocrinology (1992) 134, 51–57
Epidermal growth factor stimulates production of insulin-like growth factor-binding protein-1 in human granulosa-luteal cells
Authors: Angervo M. , Koistinen R. , Seppälä M. 
Published: December 2008

ABSTRACT
Insulin-like growth factor-I (IGF-I) enhances and epidermal growth factor (EGF) inhibits gonadotrophin-induced aromatization in granulosa cells. Our previous studies have shown that human ovarian granulosa cells synthesize insulin-like growth factor-binding protein-1 (IGFBP-1) which inhibits IGF-stimulated DNA synthesis. The present study addresses the effect of EGF and gonadotrophins in the regulation of IGFBP-1 release by human granulosa cells cultured in serum-free medium. At concentrations of 1–100 μg/l EGF was found to stimulate IGFBP-1 secretion. This was not due to cell proliferation, as the viable cell count remained unaffected. Growth hormone and gonadotrophins had no effect on IGFBP-1 secretion when added alone to culture medium. These results suggest that EGF regulates IGFBP-1 secretion in human granulosa-luteal cells.
Journal of Endocrinology (1992) 134, 127–131