Distribution of mRNAS of fibrinogen polypeptides and albumin in free and membrane-bound polyribosomes and induction of alpha-fetoprotein mRNA synthesis during liver regeneration after partial hepatectomy

To study the effect of regenerative response of the liver following partial hepatectomy on the synthesis of major plasma proteins (secretory proteins), we have determined the sequence contents and the distribution of albumin and fibrinogen polypeptide mRNAs in rat liver at intervals after partial hepatectomy and sham operation. Using a quantitative technique for the isolation of polyribosomes, we demonstrated that the distribution of RNA between free and membrane-bound polyribosomal fraction was unchanged in these experiments. There was no shift in the polyribosomal population to favor free polyribosomes after partial hepatectomy. However, there was a dramatic increase (5-6-fold) of the fibrinogen polypeptide mRNA concentration during the first 24 h after resection. In contrast, the albumin mRNA concentration decreased (2-3-fold). There were no alpha-fetoprotein mRNA sequences detectable in any liver RNA fraction in these experimental animals. In sham-operated rats with intact livers, similar changes of fibrinogen polypeptide and albumin mRNA concentrations as described in regenerating liver after partial hepatectomy, were observed. These results suggest that albumin and fibrinogen synthesis after partial hepatectomy is reciprocally regulated at the mRNA level and represents a nonspecific acute phase response to surgical trauma.     

Distribution of mRNAs of fibrinogen polypeptides and albumin in free and membrane-bound polyribosomes and induction of α-fetoprotein mRNA synthesis during liver regeneration after partial hepatectomy

To study the effect of regenerative response of the liver following partial hepatectomy on the synthesis of major plasma proteins (secretory proteins), we have determined the sequence contents and the distribution of albumin and fibrinogen polypeptide mRNAs in rat liver at intervals after partial hepatectomy and sham operation. Using a quantitative technique for the isolation of polyribosomes, we demonstrated that the distribution of RNA between free and membrane-bound polyribosomal fraction was unchanged in these experiments. There was no shift in the polyribosomal population to favor free polyribosomes after partial hepatectomy. However, there was a dramatic increase (5–6-fold) of the fibrinogen polypeptide mRNA concentration during the first 24 h after resection. In contrast, the albumin mRNA concentration decreased (2–3-fold). There were no α-fetoprotein mRNA sequences detectable in any liver RNA fraction in these experimental animals. In sham-operated rats with intact livers, similar changes of fibrinogen polypeptide and albumin mRNA concentrations as described in regenerating liver after partial hepatectomy, were observed. These results suggest that albumin and fibrinogen synthesis after partial hepatectomy is reciprocally regulated at the mRNA level and represents a nonspecific acute phase response to surgical trauma.     

Elf Electromagnetic Fields Affect Gene Expression of Hegenerating Rat Liver Following Partial Hepatectomy

Pulsed extremely-low-frequency magnetic fields (ELF-PEMFs) influence the expression of oncogenes c-myc and c-ras and of ornithine decarboxylase (ODC) in the regenerating rat liver following partial hepatectomy. In fact, while the mRNA's encoding both oncogenes are present in very low amounts in the normal liver, their concentration is dramatically increased during regeneration. Ornithine decarboxylase and c-myc mRNA's reach a maximum during the early phases of regeneration (3 hours after surgery) and decrease thereafter. c-ras mRNA reaches a maximum 40 hours after the operation. Treatment with ELF-PEMFs delivered to the animals immediately after the operation and every 12 hours thereafter increases The concentration of both oncogenes and of ornithine decarboxylase mRNA' s at 3 hours (c-myc and ODC) and at 40 hours (c-ras) respective-ty.     

Cloning and characterization of a mouse liver-specific gene mfrep-1, up-regulated in liver regeneration

Human fibrinogen-related protein-1/liver fibrinogen-related protein-1 (HFREP-l/LFIRE-1), a liver-specific protein, is a member of fibrinogen superfamily that exerts various biological activities. However, the function of HFREP-l/LFIRE-1 in liver remains unknown. Here we isolated its mouse ortholog gene-mouse fibrinogen-related protein-1 (mfrep-1), which encoded 314 amino acids, exhibiting 80.4% similarity to HFREP-l/LFIRE-1. Northern blot analysis revealed that 1.2-kb mfrep-1 mRNA was detected selectively in mouse liver. To explore the function of MFREP-1, we examined the levels of mfrep-1 mRNA during regeneration after 70% partial hepatectomy (PHx) in mice, mfrep-1 mRNA increased in the regenerating liver and reached the first shoulder peak at 2-4 h after PHx. Cycloheximide pretreatment could suppress the induction of mfrep-1, indicating the up-regulation of this gene need de novo protein synthesis. Its mRNA continued to elevate at 6 h thereafter and reached the second peak at 24 h. The enhanced express     

Sequence content of alpha-fetoprotein, albumin and fibrinogen polypeptide mRNAs in different organs, developing tissues and in liver during carcinogenesis in rats

To investigate the variable gene activities of alpha-fetoprotein, albumin and fibrinogen polypeptides as markers of 'liver specific proteins' in different developing organs or tissues, we have used specific complementary DNA probes to detect and to quantitate alpha-fetoprotein, albumin and fibrinogen polypeptide mRNA, respectively, in RNA fractions, prepared from various tissues of rats at different stages of fetal and postnatal development and from hepatomas induced by diethylnitrosamine. The results indicate that there is no consistent relationship between sequence content of alpha-fetoprotein, albumin and fibrinogen polypeptide mRNA in different developing tissues. Intestines which are like the liver also of endodermal origin do not contain alpha-fetoprotein, albumin and fibrinogen polypeptide mRNAs, while kidneys which are mesodermal in origin were found to be alpha-fetoprotein, albumin and fibrinogen polypeptide mRNA producers in neonatal life. In yolk sac, only alpha-fetoprotein and fibrinogen polypeptide mRNA could be detected. In the liver, the increased level of albumin and fibrinogen polypeptide mRNA during fetal and neonatal development is accompanied with a diminished amount of alpha-fetoprotein mRNA. The neosynthesis of alpha-fetoprotein mRNA in the liver during carcinogenesis occurred without a decreased content of albumin and fibrinogen polypeptide mRNAs. These findings suggest that complex mechanisms of gene regulation are involved in variable gene activities of alpha-fetoprotein, albumin and fibrinogen polypeptides in cells of different organs or tissues developed from a single cell.     

Cloning and characterization of a mouse liver-specific gene mfrep-1, up-regulated in liver regeneration

Human fibrinogen-related protein-1/liver fibrinogen-related protein-1 (HFREP-1/LFIRE-1), a liver-specific protein, is a member of fibrinogen superfamily that exerts various biological activities. However, the function of HFREP-1/LFIRE-1 in liver remains unknown. Here we isolated its mouse ortholog gene-mouse fibrinogen-related protein-1 (mfrep-1), which encoded 314 amino acids, exhibiting 80.4% similarity to HFREP-1/LFIRE-1. Northern blot analysis revealed that 1.2-kb mfrep-1 mRNA was detected selectively in mouse liver. To explore the function of MFREP-1, we examined the levels of mfrep-1 mRNA during regeneration after 70% partial hepatectomy (PHx) in mice. mfrep-1 mRNA increased in the regenerating liver and reached the first shoulder peak at 2-4 h after PHx. Cycloheximide pretreatment could suppress the induction of mfrep-1, indicating the up-regulation of this gene need de novo protein synthesis. Its mRNA continued to elevate at 6 h thereafter and reached the second peak at 24 h. The enhanced expression of mfrep-1 maintained high until 72 h and then declined slowly to the basal level. Immunohistochemistry assessment confirmed the up-regulated expression of MFREP-1 protein in parenchymal cells during liver regeneration. These data suggested that MFREP-1 might play an important role in liver regeneration and be involved in the regulation of cell growth.     

alpha-Fetoprotein and albumin mRNA levels in liver regeneration and carcinogenesis

Using a titration procedure, we measured the proportion of alpha-fetoprotein (AFP) and albumin mRNA in normal, regenerating, and preneoplastic rat livers. AFP mRNA constitutes approximately 0.006% of the polysomal polyadenylated RNA of normal livers and this proportion increases only slightly before the onset of DNA synthesis in liver regeneration induced by partial hepatectomy or CCl4 injury. In either model of liver regeneration, the proportion of AFP mRNA in polysomal RNA is highest approximately 24 h after the peak of DNA synthesis. The increase in the proportion of AFP mRNA in polysomal RNA is relatively small during liver regeneration (2-4-fold) but is larger (30-50-fold) in preneoplastic livers of rats fed a choline-deficient diet containing 0.1% ethionine. In contrast to those changes in AFP mRNA, albumin mRNA levels remain unchanged during liver regeneration and double in preneoplastic livers. Our results indicate that the concept of "retrodifferentiation" as it applies to liver regeneration and certain types of hepatic neoplasia needs reevaluation.     

Sequence content of α-fetoprotein, albumin and fibrinogen polypeptide mRNAs in different organs, developing tissues and in liver during carcinogenesis in rats

To investigate the variable gene activities of α-fetoprotein, albumin and fibrinogen polypeptides as markers of ‘liver specific proteins’ in different developing organs or tissues, we have used specific complementary DNA probes to detect and to quantitate α-fetoprotein, albumin and fibrinogen polypeptide mRNA, respectively, in RNA fractions, prepared from various tissues of rats at different stages of fetal and postnatal development and from hepatomas induced by diethylnitrosamine. The results indicate that there is no consistent relationship between sequence content of α-fetoprotein, albumin and fibrinogen polypeptide mRNA in different developing tissues. Intestines which are like the liver also of endodermal origin do not contain α-fetoprotein, albumin and fibrinogen polypeptide mRNAs, while kidneys which are mesodermal in origin were found to be α-fetoprotein, albumin and fibrinogen polypeptide mRNA producers in neonatal life. In yolk sac, only α-fetoprotein and fibrinogen polypeptide mRNA could be detected. In the liver, the increased level of albumin and fibrinogen polypeptide mRNA during fetal and neonatal development is accompanied with a diminished amount of α-fetoprotein mRNA. The neosynthesis of α-fetoprotein mRNA in the liver during carcinogenesis occurred without a decreased content of albumin and fibrinogen polypeptide mRNAs. These findings suggest that complex mechanisms of gene regulation are involved in variable gene activities of α-fetoprotein, albumin and fibrinogen polypeptides in cells of different organs or tissues developed from a single cell.     

mRNA差别显示研究肝再生调控基因

以正常肝和再生肝为对比材料,利用mRNA差别显示技术,研究肝再生过程中基因的差别表达,旨在从基因选择性表达水平上探讨肝再生调控机理. 得到4种未知肝再生相关cDNA,完成其克隆与序列分析,一例在再生肝中的表达低于正常肝,余者则高于正常肝. 这些序列均已在EMBL(Europe Molecular Biology Laboratory)数据库中登录,登录号分别为X95721、X95722、X95723、X97973.     

mRNA差别显示技术对肝再生调控基因的研究

以正常肝和再生肝为对比材料,利用mRNA差别显示技术,研究肝再生过程中基因的差别表达,旨在从基因选择性表达水平上探讨肝再生调控机理。得到4种未知肝再生相关cDNA,完成其克隆与序列分析,其一在再生肝中的表达低于正常肝,余者则高于正常肝。这些序列均已在EMBL(Europe Molecular Biology Laboratory)数据库中登录,登录号分别为X95721、X95722、X95723、X97973。     

Mechanism of T cell proliferation in vivo: analysis of IL-2 receptor expression and activation of c-myc and c-myb oncogenes during lymphatic regeneration

The mechanism of T cell proliferation was studied using in vivo lymphatic regeneration as the model. Lymphatic regeneration was induced by injecting a sublethal dose (300 mg/kg) of cyclophosphamide (Cy) into mice. Majority of the regenerating splenic T cells were found to be in the cell cycle, nearly 30% being found in S/G2+M phases resembling the ratio obtained for mitogen activated T cells in vitro. Expression of interleukin-2 receptor (IL-2R) was defined by the monoclonal anti-IL-2R antibody, AMT-13. Only 1-3% of regenerating T cells were IL-2R positive (while about 30% of the in vitro activated T cells were IL-2R positive). Accordingly, these cells did not respond to IL-2 in vitro. However, when the freshly isolated regenerating T cells were cultured in the presence of Con A or PMA + ionophore A 23187, IL-2R was readily induced. The regenerating T cells were further analyzed for the expression of the cellular oncogenes c-myc and c-myb. These cells expressed about three times more c-myb mRNA than Con A-stimulated T cells and the levels were comparable to those seen in thymocytes. By contrast, the amount of c-myc mRNA was similar in the regenerating T cells and in Con A-activated T cells, but weak or barely detectable in splenocytes and thymocytes. Taken together, our results imply that the vigorous T cell proliferation during cyclophosphamide-induced lymphatic regeneration is independent of the IL-2/IL-2R hormone system, like T-cell precursor proliferation in the thymus, and is characterized by both high c-myb expression typical for thymocytes and high c-myc expression typical for in vitro proliferation-activated T cells.