bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of the ovine stem cell factor gene during folliculogenesis in late fetal and adult ovaries
Authors: Tisdall D J , Quirke L D , Smith P , McNatty K P 
Published: December 2004

ABSTRACT
Two ovine stem cell factor (oSCF) cDNAs (822 bp and 738 bp) were generated from ovarian follicle mRNA by RT-PCR. Nucleotide sequencing revealed that the oSCF 822 bp cDNA encodes a precursor protein of 274 amino acids. An amino acid change 109E to 109Q was the only sequence difference from that previously described for this species. The smaller (738 bp) oSCF cDNA was shown by nucleotide sequencing to be an mRNA splice variant, equivalent to that found in other mammals, in which an exon (84 bp) encoding a potential proteolytic cleavage site is removed. Northern analysis revealed a single transcript of approximately 6·5 kb in follicles, corpora lutea and stroma of mid-luteal sheep ovaries. In situ hybridization was used to detect oSCF mRNA within ovaries of fetal sheep on days 90, 100, 120 and 135 of gestation (term=147) and of adult sheep within the breeding season. In fetal and adult ovaries, oSCF mRNA was detected in the granulosa cells of follicles at all stages of follicle growth (primordial through to antral). The SCF gene was also expressed in granulosa cells of atretic follicles but appeared to be down-regulated in the cumulus cells surrounding the oocyte at more advanced stages of atresia. In fetal ovaries at day 90 of gestation (90DG), oSCF was expressed in the subepithelial mesenchymal cells of the ovarian cortex. By 100DG the gene expression in the subepithelial cells became restricted to a narrow region below the epithelium, and areas of expression were observed in groups of cells around isolated oocytes, primordial and primary follicles. oSCF gene expression also occurred in the surface epithelial cells of 90DG ovaries, the expression was absent from these cells by 135DG and in adult ovaries. Localization of oSCF mRNA was observed in the ovarian rete and endothelial cells of blood vessels of fetal ovaries. These results suggest that oSCF may have an important and continuous role in the development and/or maintenance of germ cells during follicle growth and atresia in sheep.
Sequences in the ligand-binding domains of the human androgen and progesterone receptors which determine their distinct ligand identities
Authors: Vivat V , Gofflo D , Garcia T , Wurtz J-M , Bourguet W , Philibert D , Gronemeyer H 
Published: December 2004

ABSTRACT
The natural ligands of the progesterone (PR) and androgen (AR) receptors, progesterone and testosterone, differ only by their 17β-substitution. To identify within the AR and PR ligand-binding domains (LBDs) the sequences responsible for the differential recognition of these ligands, chimeric LBDs assembled from five homologous AR/PR 'cassettes' linked to the GAL4-DNA binding domain were constructed, and their ligand binding and transactivation characteristics were determined. Replacing the central cassette 3 of PR by that of AR generated a progesterone- and testosterone-responsive PR LBD with the AR residues 788-RHLS-791 being specifically involved in testosterone recognition, while the introduction of the C-terminal PR cassette 5 into AR conferred progestin responsiveness onto the AR LBD. These results suggest that residues within AR 788-RHLS-791 interact with the testosterone 17β-OH, while PR cassette 5 apparently contains the amino acid(s) specifically involved in the recognition of the progesterone 17β-acetyl group. However, ligand binding and transactivation by these chimeras were significantly decreased compared with those of the parental LBDs, indicating that residues located outside of these cassettes contribute to the proper positioning of the steroids in the AR and PR ligand-binding pockets (LBPs). Indeed, certain AR/PR chimeras acquired efficient ligand binding, but were unable to transactivate, indicating that the ligand was improperly bound in the chimeric LBP and could not induce the conformational changes leading to a transcriptionally competent activation function (AF-2) within the LBD. The properties of the various LBD chimeras are discussed in view of the recently solved three-dimensional structures of the retinoid X receptor α apo- and retinoic acid receptor γ holo-LBDs.
Effects of withdrawal of dopamine on translocation of protein kinase C isozymes and prolactin secretion in rat lactotroph-enriched pituitary cells. Modulation of substance P-mediated responses
Authors: Mau S E 
Published: December 2004

ABSTRACT
The present study deals with the effects of withdrawal of dopamine (DA) on the translocation of protein kinase C (PKC) isozymes and release of prolactin (Prl) in resting- and substance P (SP)-stimulated cultures of enriched rat pituitary lactotrophs.
Following a brief tonic input (10 min), DA withdrawal induced a redistribution of PKC α- and β-immunoreactivity (IR) to the particulate fraction with maximal levels, attained after 5 min, remaining translocated for 20 min. DA withdrawal prolonged the effect of SP-induced translocation of PKC α-and β-IR. Similar effects were detected when the catalytic activity of PKC in response to DA withdrawal was evaluated. Thus, DA washout redistributed PKC catalytic activity and prolonged the effect of SP on catalytical PKC translocation to the particulate fraction. Pretreatment of cells with the protein kinase A inhibitor, rp-adenosine-3′,5′-cyclic monophosphothionate (rp-cAMP), reduced the amount of PKC α- and β-IR redistributed after DA withdrawal. Furthermore, this treatment also reduced the DA withdrawal effect on SP-mediated translocation of PKC α- and β-IR. Methoxyverapamil, a blocker of voltage-gated Ca2+ channels, completely inhibited the redistribution of PKC isozymes after DA withdrawal, but also reduced the potentiating effect of DA withdrawal on SP-induced redistribution of PKC isozyme-IR.
In perifused enriched lactotrophs, DA withdrawal induced a release of Prl that lasted 45-55 min and prolonged the effect of SP on Prl secretion. rp-cAMP did not significantly affect Prl release due to DA removal, but the prolonging effect of DA withdrawal on SP-induced Prl secretion was abolished. Methoxyverapamil completely abolished the rebound release of Prl after DA withdrawal, and the potentiating effect of DA removal on SP-mediated Prl release was also diminished. Readdition of DA after DA withdrawal was able to suppress the translocation of PKC isozyme-IR and catalytic activity and to reduce the release of Prl to baseline levels. Moreover, readdition of DA reduced the potentiating effects of DA withdrawal on the same parameters after SP-stimulation of cells.
On the basis of these results it is concluded that in resting cells following DA withdrawal prolactin is released and specific PKC isozymes and concomitant catalytic activity are translocated to the particulate fraction in enriched lactotrophs. While cAMP/PKA and influx of Ca2+ seem to work in concert in translocating PKC, influx of Ca2+ is the primary mechanism responsible for the rebound release of Prl after DA withdrawal. DA withdrawal exerts a potentiating effect on SP-induced PKC translocation and Prl release. It is suggested that the biochemical events involved in these processes are cAMP/PKA and Ca2+ influx.
Transcriptional and post-transcriptional regulation of prolactin during the turkey reproductive cycle
Authors: Tong Z , Pitts G R , Foster D N , El Halawani M E 
Published: December 2004

ABSTRACT
The present study examined turkey prolactin (PRL) transcription and PRL mRNA stability during different reproductive stages. Nuclear run-on transcription assays were performed using isolated nuclei from pituitaries of turkeys at different reproductive stages. Meanwhile, cytoplasmic PRL mRNA and plasma PRL were measured by slot blot and RIA respectively. The PRL transcription, pituitary cytoplasmic PRL mRNA abundance and plasma PRL levels increased after photostimulation and peaked at the incubating stage (P<0·05). A decrease in PRL transcription, pituitary cytoplasmic PRL mRNA and plasma PRL (P<0·05) was observed during the transition from incubation to photorefractoriness. Nest-deprivation reduced circulating PRL (P<0·05), whereas pituitary cytoplasmic PRL mRNA and PRL transcription were not significantly altered from those in incubating birds (P>0·05). The half-life of PRL mRNA was determined in pituitaries of non-photostimulated, laying, incubating and photorefractory hens. Primary pituitary cell cultures were treated with the transcription inhibitor actinomycin-D and the decay of the pre-existing PRL mRNA was quantified using Northern blot analysis. The PRL mRNA half-life was 1·5- and 1·4-fold greater in incubating and laying birds respectively than in non-photostimulated turkeys (P<0·05). The half-life of PRL mRNA in photorefractory and incubating hens was similar in spite of great differences in pituitary PRL mRNA steady-state levels and PRL transcription. Our data suggest that photoinduced changes in pituitary PRL mRNA and plasma PRL are due to changes in both PRL transcription and PRL mRNA stability. Nest-deprivation inhibits the PRL releasing mechanism(s) independently of PRL transcription in turkeys.
Cloning of glucocorticoid-regulated genes in C6/ST1 rat glioma phenotypic reversion
Authors: Valentini S R , Armelin M C S 
Published: December 2004

Abstract
The C6 rat glioma cell line is responsive to glucocorticoid hormones. C6 variants that are hyper-responsive (ST1) and resistant (P7) to hormone treatment have been derived previously. Glucocorticoid treatment of ST1 cells leads to complete reversion of the transformed phenotype and loss of tumorigenic potential. Production of C type retrovirus particles is also induced by glucocorticoids in ST1 cells. Cloning of the genes regulated by glucocorticoids in this cell system was used here as a strategy to uncover the gene products involved in the transformed-to-normal phenotypic change. Construction of a cDNA library from glucocorticoid-treated ST1 cells and screening by differential hybridization resulted in the isolation of three cellular sequences that code for rat metallothioneins (C27 and C41) and α1-acid glycoprotein (C36). Northern blot analysis revealed that expression of these genes was dramatically induced by hydrocortisone in ST1 but not in P7 cells. Viral genomic RNA was used to isolate and characterize retrovirus-related sequences that could also be responsible for the phenotypic reversion phenomenon.
Journal of Endocrinology (1996) 148, 11–17
Regional differences and up-regulation of progesterone receptors in adipose tissues from oestrogen-treated sheep
Authors: Mayes J S , McCann J P , Ownbey T C , Watson G H 
Published: December 2004

Abstract
Differing risk factors between men and women for a number of vascular and metabolic diseases have been linked to regional obesity. The differences in the distribution of adipose tissues between men (abdominal or upper-body obesity) and women (gluteal/femoral or lower body obesity) suggest a role for sex steroids in the regional distribution of fat. Previous work from this laboratory has shown the presence of oestrogen receptor (ER) in gluteal, perirenal and omental adipose tissues of ewes with similar physical characteristics to the ER in uterine tissue. The concentration profile for adipose ER was gluteal> perirenal>omental. In this report, we determined the physiological significance of adipose ERs by showing an up-regulation of the progesterone receptor (PR) in adipose tissues after oestrogen treatment in a fashion similar to that seen in a major responsive tissue such as uterus. Using PR antibodies (PR-6 and C-262), Western blot analysis of PR from oestrogen-treated sheep indicated that PR was induced in uterus>>>gluteal adipose>perirenal adipose consistent with the concentration of ER contained in these tissues. PR could not be detected by Western blotting in omental adipose tissue from oestrogen-treated animals or in gluteal, perirenal and omental adipose tissues from untreated animals. Sucrose gradient profiles of progestin (R-5020) binding from uterus and gluteal adipose tissues of oestrogen-treated ewes showed specific binding in both the 5S and 9S regions of the gradient, while perirenal and omental adipose tissue had only the 5S peak. The amount of specific binding was increased with oestrogen treatment in all the tissues. When gluteal adipose tissue cytosol was preincubated with PR antibody (C-262) to prevent binding of ligand and subjected to sucrose gradient analysis, both the 5S and 9S regions were diminished, suggesting that both peaks contained PR. Dilution of uterine cytosol resulted in an increase in the ratio of the 5S to the 9S peak, indicating that the 9S PR complex dissociates at low concentrations; this may be the reason why only the 5S peak was observed in perirenal and omental adipose tissues. These data offer further support for a direct role of sex steroids in regional adipose accretion and metabolism.
Journal of Endocrinology (1996) 148, 19–25
The proliferative responses of porcine thyroid follicular cells to epidermal growth factor and thyrotrophin reflect the autocrine production of transforming growth factor-β1
Authors: Cowin A J , Heaton E L , Cheshire S H , Bidey S P 
Published: December 2004

Abstract
The present study has investigated an involvement of autocrine transforming growth factor-β1 (TGF-β1) in regulating the proliferative response of porcine thyroid follicular cells (TFCs) to epidermal growth factor (EGF) and TSH. Primary monolayer TFC cultures exposed to EGF over the range 0–0·4 nmol/l showed a dose-dependent increase in [methyl-3H]thymidine incorporation, whereas higher EGF doses were associated with a reduction in the level of [methyl-3 H]thymidine incorporation. TGF-β immunoneutralisation had little effect on the stimulatory action of low EGF doses, but led to an increase in [methyl-3H]thymidine incorporation at higher EGF levels. In TFC cultures exposed to TSH, the level of [methyl-3H]thymidine incorporation attained at a dose of 1 U TSH/1 was enhanced in the presence of TGF-β1 antiserum, although the similar stimulatory effect of 8-bromo cAMP was unaffected. Treatment of TFCs with phorbol 12-myristate 13-acetate (8 nmol/l) to activate protein kinase C (PKC) led to an enhanced incorporation of [methyl-3H]thymidine which was increased further after neutralisation of endogenous TGF-β1. While confirming, therefore, a role for autocrine TGF-β1 in maintaining control of TFC DNA synthesis in vitro, these findings provide evidence that an increase in the availability of autocrine TGF-β1 effected by EGF and TSH may play an instrumental role in limiting the cellular hyperplasia induced by these factors within the thyroid follicular microenvironment. Moreover, the present data also suggest that the availability of active autocrine TGF-β1 to TFCs under such conditions may be dependent upon a PKC-mediated mechanism.
Journal of Endocrinology (1996) 148, 87–94
IGF-II and IGF-binding proteins increase dramatically during rabbit pregnancy
Authors: Nason K S , Binder N D , Labarta J I , Rosenfeld R G , Gargosky S E 
Published: December 2004

Abstract
During pregnancy, changes in the IGF axis are associated with changes in maternal metabolism and nutrient repartitioning which are necessary to meet the demands of a growing conceptus. The aim of this study was to assess the IGF axis, maternal weight changes and food intake in female New Zealand White rabbits (n=7) prior to breeding (day 0) and serially throughout pregnancy until term (day 30-31).
The total weight of the pregnant does progressively increased from 4·03±0·06 kg (mean ± s.e.m.) on day 0 to 4·47 ±0·07 kg on day 30 (P<0·001). Maternal tissue mass (total weight minus estimated conceptus weight) increased until day 18, plateaued to day 22/23, and then significantly declined. On day 30, the maternal tissue mass was not significantly different from the non-pregnant value, such that the final increase in total weight was due to conceptus growth. Although the does were fed ad libitum, food intake did not change until day 29 when it decreased to approximately 50% of previous intake (P<0·01).
Maternal serum IGF-I was 499 ± 32 ng/ml on day 0, reached a peak of 832 ± 160 ng/ml on day 21 (P<0·02), and then declined to 341 ± 49 ng/ml on day 30. In contrast, serum IGF-II increased dramatically from a non-pregnant level of 85 ±14 ng/ml to 16 295 ± 2488 ng/ml on day 23 (P<0·001), and then rapidly declined (3335 ± 954 ng/ml, day 30). Changes in serum IGF-binding proteins (IGFBPs) followed a pattern similar to IGF-II, as assessed by Western-ligand blotting. All IGFBPs, especially the 45–40 kDa IGFBP-3 doublet, increased dramatically between days 12 and 24 of pregnancy, and then declined towards term.
In conclusion, we observed unique and dramatic changes in the maternal serum IGF axis that corresponded to periods of maternal weight gain and loss. The tissue source of IGFs and IGFBPs remains undetermined, although it is of note that the time when major changes in the IGF axis were first observed coincided with the time of functional change from yolk sac to placenta in the rabbit.
Journal of Endocrinology (1996) 148, 121–130
Effects of hormone replacement therapy on platelet membrane fatty acid composition
Authors: Ranganath L R , Christofides J A , Wright J W , Marks V 
Published: December 2004

Abstract
Oestrogen replacement therapy has been shown to protect postmenopausal women from ischaemic heart disease, strokes and hypertension. The mechanism of protection conferred by oestrogen, although partly attributable to changes in serum lipoproteins, is not fully understood. The present study was undertaken to assess the effect of hormone replacement therapy on the composition of platelet membrane fatty acids in postmenopausal women. These were analysed by gas-liquid chromatography before and six weeks after continuous conjugated equine oestrogen therapy (0·625 mg daily) combined with cyclical therapy with 75 μg l-norgestrel from day 17 to 28 of a 28-day cycle. Each subject acted as her own control. The principal findings of the study were that, following treatment, there was a 16·2% reduction in platelet membrane polyunsaturated fatty acids (P<0·001), an increase of 9·1 and 7·1% in saturated fatty acids and monounsaturated fatty acids respectively (P<0·001) and a 17·8% reduction in arachidonic acid (P<0·003). There was no correlation between changes in membrane fatty acids and serum lipoproteins. This suggests that the changes in membrane composition noted in this study may be a primary effect of hormone replacement therapy, especially oestrogen.
Journal of Endocrinology (1996) 148, 207–212
Peripheral and ovarian IGF-I concentrations during the ovine oestrous cycle
Authors: Leeuwenberg B R , Hudson N L , Moore L G , Hurst P R , McNatty K P 
Published: December 2004

Abstract
IGF-I was measured by RIA in plasma samples collected 8-hourly for 24 days which included two consecutive preovulatory surges of LH. In a separate study, ovarian venous blood was collected from animals undergoing ovariectomy on day 10 of the oestrous cycle, or 36 h later after being treated with prostaglandin with or without steroid-free bovine follicular fluid. Jugular venous blood samples were collected before, during and after surgery. Follicles were dissected from ovaries of these animals and sorted into categories of small, intermediate and large, non-atretic or atretic, and the follicular fluid was pooled and assayed for IGF-I. From another population of ovaries recovered from the slaughterhouse, granulosa, theca and corpora lutea were isolated, homogenized and assayed for IGF-I. Finally ovarian corpora lutea and granulosa cells were each incubated with tritiated amino acids overnight at 37 °C. Thereafter the tissues and media were sonicated, IGF-I extracted from the supernatant and tritiated IGF-I precipitated using a specific IGF-I antibody.
The absence of any significant change in peripheral IGF-I concentrations following ovariectomy and the finding that the ovarian venous IGF-I concentrations (161 ± 10 μg/l) were not significantly different from levels seen in peripheral blood (157 ± 10 μg/l) indicated that the ovary is not a net exporter of IGF-I. However, the ovary does synthesize IGF-I, as evidenced by granulosa and luteal synthesis, but probably not in quantities in excess of that utilized by ovarian tissues per se. Although the plasma IGF-I levels increased around the second preovulatory LH surge, the results overall indicated that the IGF-I concentrations in plasma are not strictly related to any major ovarian event during the oestrous cycle in the sheep. This view is based on the findings that the concentration of IGF-I in follicular fluid was not related to follicular health but correlated with those in peripheral plasma and that the ovarian venous concentrations did not vary between left and right ovaries irrespective of whether the ovaries contained a corpus luteum, dominant follicle or neither. Collectively, these results are consistent with the notion that IGF-I of ovarian origin fulfils an autocrine/paracrine function and does not have an endocrine role. Moreover, the results show that the concentrations of IGF-I in follicular fluid reflect those in peripheral plasma.
Journal of Endocrinology (1996) 148, 281–289