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Sökning: swepub > Umeå universitet > (1990-1994) > Liu Y X

  • Resultat 1-7 av 7
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1.
  • Liu, Y X, et al. (författare)
  • Coordinated regulation of tissue type plasminogen activator and plasminogen activator inhibitor type-1 gene expression in hypophysectomized rat ovaries during GnRHa-induced ovulation.
  • 1994
  • Ingår i: Science in China. Series B, Chemistry, life sciences & earth sciences. - 1001-652X. ; 37:7, s. 820-30
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study we have demonstrated that both granulosa and theca-interstitial cells of hypophysectomized rat ovaries are capable of synthesizing tPA and PAI-1. Injection of a GnRH agonist can markedly induce these gene expressions in the ovary in a cell-specific and time-coordinated manner, so that a surge of tPA mRNA and its activity in both granulosa and theca-interstitial cells was obtained just prior to ovulation. Theca-interstitial cells make PAI-1 become the most active in the ovary. Both the amount PAI-1 mRNA and its activity in the cells reach the maximum level 6 h before the tPA peak. By contrast, granulosa cells produce only a little amount of PAI-1 (most increase tPA activity), and both PAI-1 mRNA and activity in the cells reach the maximum after ovulation. The coordinated regulation of tPA and PAI-1 in the ovary may fine-tune the peak of tPA activity which may be important for the regulation of the ovulatory process. The changes of tPA and PAI-1 in the ovarian cells of hypophysectomized rats during GnRHa-induced ovulation are similar to that in intact rats during hCG-induced ovulation, suggesting that the ovulatory process can be modulated by different regulatory signals mediated by influencing the coordinated expression of both tPA and PAI-1.
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2.
  • Liu, Y X, et al. (författare)
  • Hormonal regulation of expression of tissue type plasminogen activator and plasminogen activator inhibitor type 1 in cultured rat granulosa cells.
  • 1994
  • Ingår i: Science in China. Series B, Chemistry, life sciences & earth sciences. - 1001-652X. ; 37:3, s. 271-9
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present study, gonadotropin and gonadotropin-releasing hormone (GnRH) regulation of tPA and PAI-1 expression in PMSG-primed granulosa cells has been investigated. (i) Addition of gonadotropins (FSH and LH) and GnRH agonist (GnRHa) or PMA to the culture increases tPA activity; FSH (or LH) plus GnRHa (or PMA) in the culture further enhances the enzyme production to such an extent that a more obvious effect than the additive effect caused by these hormones used alone has been observed; (ii) in contrast, FSH and LH decrease PAI-1 activity, whereas GnRHa and PMA alone markedly increase PAI-1 mRNA level and PAI-1 activity. Because FSH and LH stimulate tPA production and have no significant effect on PAI-1 mRNA induction, the observed inhibition of PAI-1 activity by gonadotropins may be due to the occurrence of neutralization of PA and PAI-1 proteins in the conditioned media by the formation of complexes between PA and PAI-1; (iii) increases in PAI-1 mRNA level and activity by GnRH and PMA are completely inhibited by the co-addition of FSH or LH to the culture. It is, therefore, suggested that the mechanism of gonadotropin and GnRHa regulation of tPA and PAI-1 expression in granulosa cells is different.
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3.
  • Liu, Y X, et al. (författare)
  • Hormonal regulation of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 gene expression in cultured mouse Sertoli cells.
  • 1993
  • Ingår i: Science in China. Series B, Chemistry, life sciences & earth sciences. - 1001-652X. ; 36:3, s. 319-328
  • Tidskriftsartikel (refereegranskat)abstract
    • We have demonstrated for the first time that (i) mouse Sertoli cells predominantly secrete tPA under the action of FSH and cAMP-generating agents, whereas Leydig cells mainly produce uPA; (ii) Sertoli cells are also capable of secreting PAI-1, as well as FSH, growth factors and GnRH increase PAI-1 gene expression; (iii) the increases in tPA and PAI-1 activities by different hormones in the conditioned media of Sertoli cells correspond to the increases in the levels of tPA and PAI-1 mRNA in the cultured cells, suggesting that the synthesis of the activator-inhibitor in mouse Sertoli cells is regulated at a transcriptional level and the tPA secreted by Sertoli cells may be involved in the spermatogenesis.
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5.
  • Liu, Y X, et al. (författare)
  • Tissue-specific and time-coordinated hormone regulation of plasminogen-activator-inhibitor type I and tissue-type plasminogen activator in the rat ovary during gonadotropin-induced ovulation.
  • 1991
  • Ingår i: European Journal of Biochemistry. - 0014-2956 .- 1432-1033. ; 195:2, s. 549-55
  • Tidskriftsartikel (refereegranskat)abstract
    • The plasminogen-activator system provides proteolytic activity in many biological processes. The regulation of plasminogen activation may occur at many levels including the synthesis and secretion of plasminogen activators (PA) and the specific inhibition of PA activity by inhibitors. PA-inhibitor type-1 (PAI-1) is an efficient inhibitor of tissue-type PA (tPA) and urokinase-type PA (uPA) that may therefore be instrumental for the control of plasminogen activation. To investigate if coordinated regulation of PA and PA inhibitors take place in vivo in response to physiological signals, we have examined the regulation of PAI-1 and tPA in the ovary during gonadotropin-induced ovulation. We found that PAI-1, as well as tPA activity and mRNA levels, were coordinately regulated by gonadotropins in a time-dependent and cell-specific manner, such that a surge of PA-activity was obtained just prior to ovulation. Both theca-interstitial and granulosa cells synthesized PAI-1, but their maximal PAI-1 expression occurred at different times during the periovulatory period, ensuring inhibition of proteolytic activity in ovarian extra cellular compartments both before and after ovulation. The coordinated regulation of tPA and PAI-1 in the ovary may fine-tune the peak of PA activity which may be important for the regulation of the ovulatory process.
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  • Resultat 1-7 av 7
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tidskriftsartikel (5)
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refereegranskat (7)
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Liu, Y. X. (7)
Ny, Tor (6)
Peng, X R (6)
Liu, K. (2)
Ohlsson, M (2)
Hsueh, A.J.W. (2)
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Jia, X C (2)
Feng, Q. (1)
Du, Q. (1)
Hsueh, A J (1)
Ny, Tor, 1949- (1)
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