bluuebunny/crossref_metadata_2025_split huggingface dataset:
The expression of c-myc during follicular growth and luteal formation in the rat ovary in vivo
Authors: Piontkewitz Y , Sundfeldt K , Hedin L 
Published: December 2004

The processes of folliculogenesis and formation of corpora lutea involve proliferation and differentiation of the follicular cells. The expression of several oncogenes is associated with the proliferative phase in many cell types. The present study examined the expression and hormonal regulation of the c-myc proto-oncogene during follicular development and the luteal phase of pseudopregnancy. Follicular development was initiated by pregnant mare's serum gonadotropin (PMSG) in immature rats followed two days later by the injection of human chorionic gonadotropin (hCG) to induce ovulation and luteal formation. Ovaries were collected at different time points and the content and distribution of c-myc mRNA/protein were examined. C-myc increased rapidly after the administration of both PMSG and hCG, but the effect of PMSG was less pronounced. The increase after PMSG was transient and localized primarily to the granulosa cells of developing follicles. The ovulatory dose of hCG resulted in a rapid and substantial increase of c-myc mRNA and protein with maximal levels at 1 h and 2–4 h respectively. At this stage, the c-myc protein was localized to the follicular cells, the surface epithelium and, to some extent, to the interstitial tissue. There was a subsequent decrease prior to ovulation. The luteal phase was characterized by decreasing levels of c-myc with increasing luteal age.
In order to examine the involvement of specific hormones in the regulation of c-myc, hypophysectomized, immature rats were injected sequentially with estradiol (E2) and follicle-stimulating hormone (FSH). Hypophysectomy resulted in a decrease of c-myc compared with intact animals. The administration of E2 resulted in an increase of c-myc mRNA and protein. The subsequent treatment with FSH did not result in a further increase and the levels remained at the same level as with E2 only. However, an ovulatory dose of hCG to E2 and FSH primed animals resulted in an additional increase of c-myc mRNA and protein. The levels after E2 and FSH were considerably lower compared with those of untreated ovaries of intact, immature animals, suggesting the involvement of other endocrine and paracrine factors.
The presence of proliferating cell nuclear antigen in cell extracts indicated that the expression of c-myc was associated with phases of increased proliferation of follicular cells after hormonal stimulation.
The results demonstrate that c-myc is regulated by hormones (E2, gonadotropins) in the rat ovary during follicular development to the preovulatory stage. The pronounced increase prior to ovulation also suggests a role for c-myc in the regulation of proliferative events involved in luteal formation.
Journal of Endocrinology (1997) 152, 395–406
Effects of maternal iodine deficiency and thyroidectomy on basal neuroendocrine function in rat pups
Authors: Kondo K , Levy A , Lightman S L 
Published: December 2004

We have used in situ hybridization histochemistry to investigate the effects of maternal thyroidectomy and chronic maternal iodine deficiency on basal neuroendocrine function in rat pups. Specifically, we have measured hypothalamic thyrotrophin-releasing hormone (TRH) and pituitary thyroid-stimulating hormone (TSH) expression together with circulating levels of tri-iodothyronine (T3) in rat pups delivered from and suckled by thyroidectomized or iodine-deficient dams. Because of the close interaction between the thyroid, adrenal and growth hormone axes, we have also examined hypothalamic corticotrophin-releasing hormone (CRH) and growth hormone-releasing hormone (GRH) transcripts at the same time points: birth, 1 month and 2 months of age.
Three weeks after surgical thyroidectomy, adult female Sprague–Dawley rats proved unable to carry pups to term and lactate successfully. Pups delivered from thyroidectomized dams given a small replacement dose of T3 during pregnancy were significantly lighter than controls (84 ± 3%) and had markedly depressed plasma T3 levels (36 ±6% of control). Hypothalamic CRH and GRH transcript levels were significantly decreased in pups at birth (to 8±2·5% and 24 ± 8% of control respectively) but had returned to normal by 1 month after delivery. Pituitary TSH transcript levels and hypothalamic levels of TRH transcripts, however, were similar to those of controls.
Only one of seven dams fed a low-iodine diet for 6 months produced live pups, and these were too few in number to produce significant data. Dams fed a lowiodine diet from 4 months before mating, however, did produce live pups and although they were not significantly lighter than control pups at birth, by 1 month after birth, they were significantly lighter (72 ± 3% of controls). Circulating T3 levels were not significantly different from control at any time point examined. Hypothalamic TRH levels were significantly elevated at birth (451 ± 138% of control), but this difference was not maintained at 1 or 2 months after birth despite the lactating dams being maintained on the low-iodine diet. Pituitary TSH levels showed an upward trend at all time points that reached significance at 1 month after birth (204 ± 19%; P<0·05). Hypothalamic CRH and GRH transcript levels were not different from controls at any time point.
In summary, chronic iodine deficiency or thyroidectomy with low-level T3 replacement in Sprague–Dawley rats markedly impaired fertility and the ability to carry pups to term, and produced an unexpectedly modest up-regulation of the hypothalamo–pituitary–thyroid axis and down-regulation of the hypothalamo–pituitary–adrenal axis.
Journal of Endocrinology (1997) 152, 423–430
Continuous intracerebroventricular administration of a corticotropin releasing hormone antagonist amplifies spontaneous growth hormone pulses in the rat
Authors: Mounier F , Pellegrini E , Kordon C , Epelbaum J , Bluet-Pajot M T 
Published: December 2004

Involvement of endogenous corticotropin releasing hormone (CRH) in the regulation of spontaneous growth hormone (GH) secretion was investigated. A CRH antagonist, α helical CRH 9–41, was intracerebroventricularly infused for 36 h at a rate of 1 μg/0·5 μl/h to freely moving, cannulated adult male rats. Serial blood samples were drawn every 20 min for the last 8 hours of α helical CRH 9–41 infusion. The treatment induced a marked increase in GH peak amplitude without affecting either trough levels or numbers of peaks. In parallel, levels of growth hormone releasing hormone (GHRH) mRNA in the arcuate nucleus, but not of somatotropin release inhibiting hormone (SRIH) mRNA in the periventricular and arcuate nuclei, were increased. These data suggest that, in addition to its action in the stress-induced inhibition of GH secretion through regulation of periventricular SRIH neurons, CRH can also act as a modulator of endogenous GH secretion through regulation of arcuate GHRH neurons. Whether the modulatory effects of CRH on GHRH neurons are direct or indirect remains to be established.
Journal of Endocrinology (1997) 152, 431–436
Ethanol, growth hormone and testosterone in peripubertal rats
Authors: Tentler J J , LaPaglia N , Steiner J , Williams D , Castelli M , Kelley M R , Emanuele N V , Emanuele M A 
Published: December 2004

The deleterious effects of ethanol on the hypothalamic pituitary growth hormone axis in adult male humans and animals have been well documented. It is also well established that ethanol has toxic effects on testicular function in adult humans and animals. Much less is known, however, about the effects of ethanol on the growth hormone (GH) axis and testicular function in adolescence. Recent studies have established that adolescent problem drinking is a widespread and growing threat to the health of young people in the United States. In the present study, therefore, we investigated if acute ethanol exposure in peripubertal male Sprague–Dawley rats altered normal pituitary and testicular function.
Serum levels of GH and testosterone were measured at 1·5, 3, 6, and 24 h after a single i.p. injection of either saline or 3 g/kg body weight ethanol. Histologic analysis as well as serum testosterone levels allowed us to assign animals to either early puberty (35-day-old animals), mid-puberty (41-day-old animals), or young adult (51- and 66-day-old animals) status. Ethanol produced significant decrements in serum testosterone in the 51-and 66-day-old animals, with a trend toward suppression in the 41-day-old group. Furthermore acute ethanol administration significantly decreased serum GH (P< 0·0001 by 3 way ANOVA) demonstrating a significant effect of ethanol on serum GH in all age groups and at all time points studied when compared with saline injected controls (P<0·01 by Tukey's studentized range test). Despite this significant fall in peripheral GH levels, there was no decrease in either GH mRNA or growth hormone-releasing factor (GRF) mRNA levels nor in hypothalamic concentration of GRF peptide.
We conclude that, as in adult animals, acute exposure to ethanol causes a prolonged and severe decrement in serum GH which is possibly mediated at the level of secretion. In addition, there is attenuation in testosterone secretion. These data are all the more important since GH and testosterone play critical roles in organ maturation during this stage of development.
Journal of Endocrinology (1997) 152, 477–487
Differential effect of insulin treatment on islet amyloid polypeptide (amylin) and insulin gene expression in streptozotocin-induced diabetes in rats
Authors: Mulder H , Ahrén B , Sundler F 
Published: December 2004

Islet amyloid polypeptide (IAPP) is a β cell hormone, which forms islet amyloid in non-insulin-dependent diabetes mellitus and may oppose insulin action and release. Therefore, the previously observed relative overexpression of IAPP compared with insulin in streptozotocin-treated rats could be unfavourable if it occurs in diabetes. Using quantitative in situ hybridization, we examined whether insulin treatment affected IAPP and insulin gene expression and their ratio at day 8 and 20 after induction of streptozotocin diabetes (plasma glucose ∼ 30 mm). Total islet IAPP mRNA levels were less reduced than those of insulin at both time points. Differential regulation of the two hormones was further reflected by mean IAPP mRNA levels in the remaining islet cells being unaffected by streptozotocin treatment, whereas those of insulin were reduced. At both time points, insulin treatment decreased total islet levels of IAPP and insulin mRNA even more, IAPP mRNA levels being less reduced. Mean insulin mRNA levels, but not IAPP mRNA levels, in the remaining islet cells were reduced by insulin treatment. Between time points, total islet mRNA levels were higher at day 20, while mean mRNA levels in the remaining islet cells were unchanged, suggesting that regeneration of β cells had occurred. In contrast, insulin gene expression was the same at both time points in insulin-treated rats, suggesting that insulin impaired insulin expression. To summarize, we found that IAPP and insulin were differentially expressed in experimental diabetes and that insulin treatment inhibited insulin, but not IAPP, gene expression. It is therefore unlikely that insulin will protect against amyloid formation and metabolic perturbations which may arise as a consequence of IAPP overexpression.
Journal of Endocrinology (1997) 152, 495–501
MATERNAL DIABETES INDUCES UPREGULATION OF HEPATIC INSULIN-LIKE GROWTH FACTOR BINDING PROTEIN-1 MRNA EXPRESSION, GROWTH RETARDATION AND DEVELOPMENTAL DELAY AT THE SAME STAGE OF RAT FETAL DEVELOPMENT
Authors: Rajaratnam Veeraramani S. , Webb Peggy J. , Fishman Renata B. , Streck Randal D. 
Published: December 2004

ABSTRACT
Since maternal diabetes is associated with fetal growth abnormalities in humans and rats, effects of maternal diabetes on fetal expression of genes regulating growth are of interest. Increased expression of Insulin-Like Growth Factor Binding Protein-1 (IGFBP-1) is associated with several examples of growth retardation and is upregulated in response to diabetes. As we have shown previously, IGFBP-1 expression is upregulated in gestational day (GD) 14 rat fetuses in response to maternal diabetes. Here we analyze the effect of streptozotocin-induced maternal diabetes on IGFBP-1 mRNA expression during GD12-16 of rat fetal development, using in situ hybridization. IGFBP-1 mRNA was more abundant in GD12-14 fetal livers from diabetic dams than in livers of age-matched controls. This upregulation is not due to the approximately 1-day fetal developmental delay associated with maternal diabetes, as there is no gross difference in the level of IGFBP-1 mRNA in GD13 vs GD12 or GD14 vs GD13 control fetal livers. At GD15-16, however, we detected little difference in IGFBP-1 expression between experimental and control fetuses. This transient period of maternal diabetes-stimulated IGFBP-1 mRNA expression (GD12-14) is coincident with the sensitive period for maternal diabetes-induced defects in fetal growth and development, suggesting that IGFBP-1 is involved in the regulation of fetal growth and development in response to the maternal condition.
Thyroid hormone and glucocorticoid regulation of pituitary growth hormone-releasing hormone receptor gene expression
Authors: Korytko A I , Cuttler L 
Published: December 2004

Abstract
The GH-releasing hormone receptor (GHRH-R) is a critical link between hypothalamic GH-releasing hormone (GHRH) and pituitary GH secretion. However, the factors that regulate GHRH-R are not well understood. Despite the importance of thyroid hormone and glucocorticoids in influencing the GH axis in vivo, it is not known whether these hormones act directly at the pituitary to regulate expression of GHRH-R. We tested the effects of T3 and hydrocortisone on GHRH-R gene expression in primary pituitary cell cultures of adult male rats. Pituitary cells were treated for 24 h with increasing concentrations of T3 (0.06-60 nM) or hydrocortisone (2.8 nM-2.8 μM). GHRH-R mRNA levels were assessed by ribonuclease protection assay. T3 caused a striking dose-dependent increase in GHRH-R mRNA, reaching levels 5.1 ± 0.5 fold over controls (P<0·001). Hydrocortisone also stimulated a marked dose-dependent increase in GHRH-R mRNA, reaching levels 5.6 ± 0.7 fold over controls (P<0·001). Combined treatment with both hormones did not cause further augmentation of GHRH-R mRNA levels. These data indicate that T3 and hydrocortisone act directly at the pituitary as potent regulators of GHRH-R gene expression.
Two oxytocin-binding site subtypes in rat kidney: pharmacological characterization, ontogeny and localization by in vitro and in vivo autoradiography
Authors: Arpin-Bott M P , Waltisperger E , Freund-Mercier M J , Stoeckel M E 
Published: December 2004

Abstract
The localization of oxytocin (OT)-binding sites in the developing rat kidney and their pharmacological characterization were investigated by means of autoradiographic techniques. The cellular localization was studied by application of the histoautoradiographic technique to (1) frozen sections and semithin sections from kidney slices incubated in vitro in the presence of a 125I-labelled OT antagonist and (2) frozen and semithin sections from kidneys after in vivo systemic infusion of the radioligand. Pharmacological characteristics were determined in competition experiments by using quantitative film autoradiography.
Specific OT-binding sites were first detected at embryonic day 17 (E17) in the cortex. At early stages up to postnatal days (PN30), the cortical OT-binding sites were highly concentrated on the juxta- and paraglomerular portion of the distal tubule; in the adult they were restricted to the macula densa. In the medulla, OT-binding sites were first detected at E19 when this region is forming; they were localized on the thin limb of Henle's loop. These data obtained by in vitro binding were confirmed by in vivo binding at PN30 which showed, in addition, the presence in one rat of OT-binding sites in the inner stripe of the outer medulla.
At all stages examined (PN15 to PN90), cortical OT-binding sites had a higher selectivity for OT versus vasopressin (IC50=0·78 ± 0·04 nm and 8 ± 0·5 nm respectively at PN90) than medullary sites (IC50= 1·9 ± 0·27 nm and 2±1·13 nm respectively at PN90). These data suggest that the OT-binding sites of the macula densa and thin Henle's loop, detected in the rat kidney, represent two subtypes of OT receptors which could mediate distinct effects of OT on kidney function.
Journal of Endocrinology (1997) 153, 49–59
Solid-phase assay for insulin-like growth factor (IGF) binding to IGF-binding protein-3: application to the study of the effects of antibodies and heparin
Authors: Koedam J A , Hoogerbrugge C M , van Buul-Offers S C , Van den Brande J L 
Published: December 2004

Abstract
The availability and activity of insulin-like growth factors (IGF-I and IGF-II) are largely determined by a group of IGF-binding proteins (IGFBPs). We have developed a new assay to characterize the interaction between the IGFs and IGFBP-3. In this assay, recombinant IGFBP-3 (5 ng) was immobilized on plastic microtitre wells, after which radiolabelled IGF-I or -II was allowed to bind. The assay is highly specific, since neither IGF bound to control wells blocked with albumin. By constructing both saturation and competition binding curves, equivalence of binding between the radiolabelled and native IGF ligands could be demonstrated. From these curves, reliable specific activities of the tracers were calculated. Scatchard plots of both types of data produced identical results for dissociation constants and number of binding sites. The affinity of IGF-II was twice as high as the affinity of IGF-I (dissociation constants of 44 and 102 pm respectively).
The assay was used to show that polyclonal anti-IGFBP-3 antibodies could block binding of IGF. Alkylating agents and NaCl were without effect, but chaotropic salts such as CaCl2 and NaSCN decreased IGF binding to IGFBP-3. IGFBP-1 and IGFBP-3, but not an N-terminal fragment of IGFBP-3, could effectively block binding of both IGF-I and IGF-II to the solid-phase IGFBP-3. Increasing concentrations of heparin had little or no effect on IGF-I binding, but strongly inhibited IGF-II binding. This was shown to be a consequence of a decrease in both the affinity and the number of binding sites. Possibly, the interaction of IGFBP-3 with heparin or heparin-like structures in vivo can lead to the selective release of IGF-II from this binding protein. Our results with heparin also suggest that the binding sites on IGFBP-3 for IGF-I and IGF-II are not completely identical.
This assay can be applied to the study of various aspects of the interaction between the IGFs and IGFBP-3, such as the effects of interfering substances and structure–function relationships of both moieties of the complex.
Journal of Endocrinology (1997) 153, 87–97
Immunoneutralization of interleukin-1, tumor necrosis factor, interleukin-6 or interferon does not prevent the LPS-induced sick euthyroid syndrome in mice
Authors: Boelen A , Platvoet-ter Schiphorst M C , Wiersinga W M 
Published: December 2004

Abstract
The sick euthyroid syndrome is a state of altered thyroid hormone metabolism which occurs during illness. The pathogenesis is incompletely understood but recent studies indicate a role of cytokines. It is unknown if cytokines released during illness are directly responsible for the changes in thyroid hormone metabolism. Therefore we studied if previous immunoneutralization of cytokines can prevent endotoxin (lipopolysaccharide LPS), induced sick euthyroid syndrome.
LPS administration resulted in systemic illness, an increase in serum tumor necrosis factor (TNFα) and interleukin (IL)-6 and a decrease in serum triiodothyronine (T3) and thyroxine (T4). Immunoneutralization of the effects of cytokines was accomplished by administration of monoclonal antibodies against mouse IL-1 type-1 receptor (IL-1R), TNFα, IL-6 or interferon (IFNα) prior to LPS. The LPS-induced release of cytokines was affected by previous immunoneutralization as compared with control experiments with normal immunoglobulin (IgG): anti-IL-1R did not affect serum TNFα but decreased serum IL-6, anti-TNFα decreased serum TNFα but not IL-6, anti-IL-6 did not affect serum TNFα but hugely increased IL-6 and anti-IFNγ decreased both serum TNFα and IL-6. Specific immunoneutralization of IL-1, TNFα or IFNγ did not prevent the LPS-induced decrease in serum T3, T4 and liver 5′-deiodinase mRNA. However, immunoneutralization of IL-6, although not preventing the fall in serum T3 and T4, did mitigate the LPS-induced decrease in liver 5′-deiodinase mRNA.
In view of possible non-specific effects of the huge dose of immunoglobulins (1 mg), used only in the immunoneutralization of IL-6, we repeated the experiment with F(ab′)2 fragments of anti-IL-6 antibodies. Compared with F(ab′)2 fragments of control IgG, anti-IL-6 F(ab′)2 did not affect the LPS-induced rise in serum TNFα or the decrease in serum T3 and T4 and liver 5′-deiodinase mRNA. Serum IL-6 levels induced by LPS were, however, cleared more rapidly from the circulation when anti-IL-6 F(ab′)2 fragments rather than intact anti-IL-6 were administered. In conclusion, immunoneutralization of IL-1, TNFα or IFNγ did not prevent the LPS-induced sick euthyroid syndrome in mice; immunoneutralization of IL-6, however, transiently inhibits the LPS-induced decrease of liver 5′-deiodinase mRNA.
Journal of Endocrinology (1997) 153, 115–122
Parathyroid hormone/parathyroid hormone-related protein receptor expression in nude mice with a transplantable canine apocrine adenocarcinoma (CAC-8) and humoral hypercalcaemia of malignancy
Authors: Gröne A , McCauley L K , Capen C C , Rosol T J 
Published: December 2004

Abstract
The effect of humoral hypercalcaemia of malignancy (HHM) on parathyroid hormone/parathyroid hormonerelated protein (PTH/PTHrP) receptor expression was investigated in nude mice with subcutaneous transplantation of an adenocarcinoma line (CAC-8) which produces PTHrP. Serum calcium and PTHrP concentrations were analysed by colorimetric assay and a two-site IRMA respectively. Mice were hypercalcaemic (3·3 ±0·1 mmol/l) compared with non-tumour-bearing control mice (2·1 ± 0·1 mmol/l) and had elevated serum PTHrP concentrations (30·4 ±3·4 pmol/l) compared with non-tumour-bearing control mice (0·7 ±0·1 pmol/l. Lumbar vertebrae were analysed by histomorphometry. Tumourbearing mice had a significant (P<0·01) increase in resorptive perimeter, increased numbers of osteoclasts/mm endosteum and increased endosteal bone-forming perimeter. Total RNA was isolated from calvarium, humerus and kidney and analysed for PTH/PTHrP receptor expression by Northern blot analysis. There was no significant difference between PTH/PTHrP receptor mRNA expression in the kidneys and humeri of tumourbearing mice compared with non-tumour control mice, but a significant increase in PTH/PTHrP receptor expression in calvaria. Kidneys and vertebral bodies were stained for PTH/PTHrP receptor protein by immunohistochemistry. Renal proximal tubules (especially the basolateral regions) and endosteal osteoblasts of control and tumourbearing mice stained positive for PTH/PTHrP receptor. These results demonstrated that HHM induced by increased serum PTHrP concentrations did not result in down-regulation of PTH/PTHrP receptor mRNA or protein expression in vivo.
Journal of Endocrinology (1997) 153, 123–129