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K. Yang, G. L. Hammond, and J. R. G. Challis


Fetal sheep tissues possess glucocorticoid receptors (GR), and these change in number during the last two-thirds of gestation. There is, however, no information about developmental changes in tissue GR mRNA levels which might account for alterations in fetal GR content. We have therefore cloned and sequenced a 942 bp GR cDNA from a sheep liver cDNA library, and used it to study the relative abundance of GR mRNA in fetal and neonatal sheep tissues. Analysis of the cDNA revealed a partial sequence of the ovine GR which displayed over 80% identity with residues 143–453 in human GR and 163–472 in rat GR. Furthermore, the first zinc finger motif in these receptors was perfectly conserved among species. The relative abundance of GR mRNA was studied in hypothalami, anterior pituitary glands and adrenals in fetuses at days 60–70, 100–110, 125–130 and at term (approximately 145 days), and in newborn lambs. Total RNA extracts (20 μg) were analysed by Northern blot analysis. A single 5.6kb transcript was detected in all three fetal tissues, and its relative abundance did not change significantly throughout gestation. However, in newborn lambs, levels of GR mRNA increased significantly in the hypothalamus and pituitary gland but decreased to undetectable levels in the adrenal. These tissue-specific changes in the relative abundance of GR mRNA did not correlate with alterations in GR content in fetal tissues, which suggests that the latter may reflect alterations in GR mRNA translation, subsequent modifications and/or GR turnover. In addition, the pattern of developmental changes in GR mRNA content of the adrenal differs from that of the hypothalamus and pituitary gland in neonatal lambs, and indicates that tissue-specific factors may influence GR gene expression in neonatal sheep.

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K Yang, S G Matthews, and J R G Challis


To examine the role of 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) in the control of glucocorticoid actions in the ovine pituitary during development, we have sought developmental changes in the distribution and the level of 11β-HSD1 mRNA by in situ hybridization. In the pars distalis, 11β-HSD1 mRNA was present by day 60; its amount did not change significantly until term (days 145–147) when it increased dramatically. The level of 11β-HSD1 mRNA increased further during the postnatal period. In contrast, 11β-HSD1 mRNA in the pars intermedia was not detectable until day 135; it increased in amount at days 140–143, but did not change significantly thereafter through to adulthood.

We have also measured levels of both dehydrogenase and reductase activities of 11β-HSD1 in the pars distalis of fetal sheep at day 140 and term, and of postnatal sheep at 1–2 months of age, to determine whether changes in 11β-HSD1 mRNA are reflected in the levels of enzyme activities. There were progressive increases in both dehydrogenase and reductase activities from day 140 to 1–2 months postnatally, although dehydrogenase activity was consistently higher than reductase activity.

Finally, we have determined the effect of short-term intrafetal cortisol infusion (5 μg/min for 12 h) on levels of pituitary 11β-HSD1 mRNA by in situ hybridization. There was no effect of cortisol infusion on 11β-HSD1 mRNA expression.

The present results demonstrate that 11β-HSD mRNA and enzyme activity in the pars distalis of fetal sheep increase dramatically at term when plasma levels of both ACTH and cortisol are elevated. This suggests that 11β-HSD1 may contribute to the proposed resetting of cortisol negative feedback within the fetal pituitary at that time.

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F Lü, K Yang, V K M Han, and J R G Challis


Activation of the fetal pituitary-adrenal axis is crucial for fetal organ maturation and the onset of parturition in sheep. Many factors including corticotrophin-releasing hormone (CRH) and arginine vasopressin secreted from the hypothalamus, and growth factors produced within the pituitary may be involved in the regulation of maturation of the fetal pituitary gland. IGFs have mitogenic and differentiation-promoting capacities in a variety of organs and are synthesized as paracrine factors within developing tissues. However, there is little information concerning the synthesis, distribution, regulation and function of IGFs in the fetal pituitary gland at different times during pregnancy. Therefore, we have localized IGF-I and IGF-II mRNAs and peptides, and determined the effect of cortisol on the level of IGF-II mRNAs in the pituitary glands of developing sheep fetuses. We examined the possible effects of IGFs on corticotroph function in cultures of adenohypophysial cells from term fetuses.

Seven species of IGF-II transcripts of 1·2–6·0 kb were identified by Northern blot analysis in the pituitary gland of fetuses between day 60 of gestation and term (day 145). The levels of IGF-II mRNAs did not change significantly during pregnancy, although there was a trend for the presence of higher levels of IGF-II mRNAs at day 60 of gestation. IGF-I mRNA was not detectable. By in situ hybridization, IGF-II mRNA was localized to non-endocrine cells and to cells lining the blood vessels of the pars distalis, to some presumed endocrine cells in the pars distalis and pars intermedia, and to clusters of cells in the pars nervosa. In contrast, IGF-I and IGF-II peptides were detected in the presumed endocrine cells in the pars distalis and pars intermedia but not in the pars nervosa. Incubation of adenohypophysial cells from term fetuses with IGF-I, but not IGF-II, for 48 h increased specific 125I-Tyr-ovine CRH binding. However, neither IGF-I nor IGF-II had any significant effects on the basal or CRH-stimulated immunoreactive (ir)-ACTH output, the level of POMC mRNA or the number of ir-ACTH positive cells. Infusion of cortisol to fetuses starting at day 96 of gestation for 100 h or at days 120–125 of gestation for 84 h did not affect the level of IGF-II mRNAs in the pars distalis but decreased the levels of POMC mRNA.

These results are consistent with IGFs having the potential to influence fetal pituitary function, although probably on cell types other than the corticotrophs. The likely sources of IGFs may be predominantly local (IGF-II) or from extrapituitary sources (IGF-I).

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M Tamura, S Sebastian, S Yang, B Gurates, Z Fang, K Okamura, and SE Bulun

We previously reported that human malignant endometrial epithelial cell conditioned medium (MECM) up-regulated cyclooxygenase (COX)-2 mRNA and protein levels in human normal endometrial stromal cells (ESC). Here we showed that pretreatment with a selective inhibitor of the extracellularly regulated kinase (ERK)1/2 signaling pathway blocked the MECM-induced COX-2 expression in ESC. Transient transfection assays indicated critical roles of a cAMP response element (CRE,-59/-53 bp) and a nuclear factor for interleukin (IL)-6 expression (NF-IL6) site (-132/-124 bp) in the regulation of basal and MECM-induced activity of COX-2 gene promoter in ESC. Employing electrophoretic mobility shift assays, we demonstrated that increased functional binding of CCAAT/enhancer binding protein (C/EBP)alpha, C/EBPbeta and upstream stimulatory factor-2 to the CRE and C/EBPalpha and C/EBPbeta to the NF-IL6 site were, at least in part, responsible for MECM-induced COX-2 expression in ESC. Moreover, overexpression of C/EBPalpha and C/EBPbeta significantly induced COX-2 promoter activity in ESC. Collectively, these results suggest that the basal and MECM-induced transcription of the COX-2 gene in ESC is regulated through a combination of the CRE and the NF-IL6 site by functional interactions of C/EBPalpha and C/EBPbeta.

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M Nakamura, S Morimoto, Q Yang, T Hisamatsu, N Hanai, Y Nakamura, I Mori, and K Kakudo

Receptor activity modifying proteins (RAMPs) act as receptor modulators that determine the ligand specificity of receptors for the calcitonin (CT) family. The purpose of this study was to analyze the expression of RAMPs in osteoclast-like cells using the laser capture microdissection (LCM) technique. Mouse bone marrow and spleen cells were co-cultured on a film designed for LCM. After 10 days, 250 osteoclast-like cells were captured using the LCM system. Total RNA from these cells was used to synthesize cDNA and RT-PCR analysis was performed. Osteoclast-like cells expressed CT receptor (CTR), CT receptor-like receptor (CRLR) and RAMP2, but did not express RAMP1 or RAMP3. These results indicated (1) that a pure population of osteoclast-like cells can be prepared by LCM and gene expression of this population can be analyzed by RT-PCR and (2) that RT-PCR shows that osteoclast-like cells express RAMP2, CTR and CRLR, suggesting the potential for adrenomedullin binding to osteoclast-like cells. This is the first report that osteoclast-like cells express RAMP2.

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W M Liu, Y J Cao, Y J Yang, J Li, Z Hu, and E-K Duan

The expression of tetraspanin CD9 was found on blastocysts in mice and endometrium epithelial cells in human and bovine. However, it remains unknown how CD9 is involved in the precise dialogue between embryo and uterus during early pregnancy. This study was designed to investigate the functional roles of CD9 in the embryo implantation with monoclonal antibody against CD9 protein (anti-CD9 mAb) and antisense oligonucleotide against CD9 gene (AS-CD9). Our results showed that intrauterine injection of anti-CD9 mAb on day 4 of pregnancy significantly increased the number of embryos implanted (7.24±0.39 versus 4.04±0.38). In vitro, anti-CD9 mAb or AS-CD9 significantly enhanced embryo-outgrowth ability on the monolayer of uterus epithelial cells in a dose-dependent manner. However, the attachment of blastocysts to epithelial cells was unaffected. Furthermore, we found that anti-CD9 mAb or AS-CD9 stimulated matrix metalloproteinase 2 (MMP-2) production of blastocysts on Fibronectin. LY294002, a specific inhibitor of phosphoinositide 3-kinase, was able to counteract the effect of anti-CD9 mAb and AS-CD9 on outgrowth ability and production of MMP-2. Our results indicated that CD9 played a role of inhibiting embryo implantation. CD9 was able to impair embryo invasion and the production of MMP-2 through the phosphoinositide 3-kinase signaling pathway.