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  • 1
    Electronic Resource
    Electronic Resource
    Glucocorticoids promote development of the osteoblast phenotype by selectively modulating expression of cell growth and differentiation associated genes (1992)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 50 (1992), S. 425-440 
    Details
    ISSN: 0730-2312
    Keywords: osteocalcin ; osteopontin ; collagen ; c-fos ; oncogene ; histone ; fibronectin ; alkaline phosphatase ; collagenase ; steroid hormone ; growth control ; osteoblast differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: To understand the mechanisms by which glucocorticoids promote differentiation of fetal rat calvaria derived osteoblasts to produce bone-like mineralized nodules in vitro, a panel of osteoblast growth and differentiation related genes that characterize development of the osteoblast phenotype has been quantitated in glucocorticoid-treated cultures. We compared the mRNA levels of osteoblast expressed genes in control cultures of subcultivated cells where nodule formation is diminished, to cells continuously (35 days) exposed to 10 -7 M dexamethasone, a synthetic glucocorticoid, which promotes nodule formation to levels usually the extent observed in primary cultures. Tritiated thymidine labelling revealed a selective inhibition of internodule cell proliferation and promotion of proliferation and differentiation of cells forming bone nodules. Fibronectin, osteopontin, and c-fos expression were increased in the nodule forming period. Alkaline phosphatase and type I collagen expression were initially inhibited in proliferating cells, then increased after nodule formation to support further growth and mineralization of the nodule. Expression of osteocalcin was 1,000-fold elevated in glucocorticoid-differentiated cultures in relation to nodule formation. Collagenase gene expression was also greater than controls (fivefold) with the highest levels observed in mature cultures (day 35). At this time, a rise in collagen and TGFβ was also observed suggesting turnover of the matrix. Short term (48 h) effects of glucocorticoid on histone H4 (reflecting cell proliferation), alkaline phosphatase, osteopontin, and osteocalcin mRNA levels reveal both up or down regulation as a function of the developmental stage of the osteoblast phenotype. A comparison of transcriptional levels of these genes by nuclear run-on assay to mRNA levels indicates that glucocorticoids exert both transcriptional and post-transcriptional effects. Further, the presence of glucocorticoids enhances the vitamin D3 effect on gene expression. Those genes which are upregulated by 1,25(OH)2D3 are transcribed at an increased rate by dexamethasone, while those genes which are inhibited by vitamin D3 remain inhibited in the presence of dexamethasone and D3. We propose that the glucocorticoid promote changes in gene expression involved in cell-cell and cell-extracellular matrix signaling mechanism that support the growth and differentiation of cells capable of osteoblast phenotype development and bone tissue-like organization, while inhibiting the growth of cells that cannot progress to the mature osteoblast phenotype in fetal rat calvarial cultures. © 1992 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240500411
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  • 2
    Electronic Resource
    Electronic Resource
    Acidic fibroblast growth factor modulates gene expression in the rat thyroid in vivo (1992)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 50 (1992), S. 392-399 
    Details
    ISSN: 0730-2312
    Keywords: thyroid function ; c-fos ; type I 5′ deiodinase ; histone ; cathepsin D ; throid peroxidase ; thyroglobulin ; acti ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have recently demonstrated that the iv administration of acidic fibroblast growth factor(a-FGF) to rats for 6 days results in a marked increase in thyroid weight colloid accumulation and flat, quiescent follicular cells. Whereas a-FGF administration consistently increases thyroid weight, there are only minor alterations in serum TSH and thyroid hormones, and no change in intrathyroidal metabolism of 125l metabolism. In the present work, we studied the effects of 1 or 6 daily injections of a-FGF (60 μ/kg BW) or vehicle on the mRNA levels for histone, c-fos, actin, type I 5′ deiodinase (5′D-1), thyroid peroxidase, and thyroglobulin and cathepsin D in the thyroid, liver and bone. Rats were sacrificed 0.5, 2, 4, 8 and 24 h after the 1st or the 6th a-FGF injection and thyroid, liver and calvarium were removed. The relative amounts of mRNAs were determined by slot blot analysis. There was a 43% increase in thyroid weight in rats treated with a-FGF for 6 days compared to vehicle-treated rats. We observed an increase in c-fos mRNA content in the thyroid gland 0.5 to 4 h after 1 or 6 injections of a-FGF. In contrast, treatment with a-FGF for 1 or 6 days did not affect histone mRNA content, a marker of proliferative activity or actin mRNA levels. Treatment with a-FGF caused a marked decrease in thyorid 5′ D-I mRNA content in the thyroid. The decrease was present 2 h after the first injection and reached a nadir 8 h. After 6 daily injections, the decrease in 5′ D-I mRNA was present throughout the whole day. In the liver, there was a significant decrease in 5′ D-1 mRNA only 2 and 4 h after the 6daily injection of a-FGF. There was no effect of a-FGF treatment on the mRNA content of thyorid peroxidase, thyroglobulin, or a marker of lysosomal activity, cathepsin D. These data indicate that a-FGF induces colloid accumulation in the rat thyroid without changes in proliferative or lysosomal activites, or alteration in the regulation of the thyroid specific genes thyroid peroxidase and thyroglobulin. Modification in gene expression and induction are reflected by the upregulation of the early response gene c-fos. The marked and persistent decrease in 5′ deiodinase mRNA content after a-FGF treatment suggests that a-FGF may be involved in the regulation of 5′ D-1 activity in the thyroid. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240500408
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  • 3
    Electronic Resource
    Electronic Resource
    Apoptosis during bone-like tissue development in vitro (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 31-49 
    Details
    ISSN: 0730-2312
    Keywords: Bax ; Bcl-2 ; Bcl-X ; bone ; programmed cell death ; p53 ; c-fos ; Msx-2 ; differentiation ; IRF-1 ; IRF-2 ; collagenase gene expression ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We present evidence of cell death by apoptosis during the development of bone-like tissue formation in vitro. Fetal rat calvaria-derived osteoblasts differentiate in vitro, progressing through three stages of maturation: a proliferation period, a matrix maturation period when growth is downregulated and expression of the bone cell phenotype is induced, and a third mineralization stage marked by the expression of bone-specific genes. Here we show for the first time that cells differentiating to the mature bone cell phenotype undergo programmed cell death and express genes regulating apoptosis. Culture conditions that modify expression of the osteoblast phenotype simultaneously modify the incidence of apoptosis. Cell death by apoptosis is directly demonstrated by visualization of degraded DNA into oligonucleosomal fragments after gel electrophoresis. Bcl-XL, an inhibitor of apoptosis, and Bax, which can accelerate apoptosis, are expressed at maximal levels 24 h after initial isolation of the cells and again after day 25 in heavily mineralized bone tissue nodules. Bcl-2 is expressed in a reciprocal manner to its related gene product Bcl-XL with the highest levels observed during the early post-proliferative stages of osteoblast maturation. Expression of p53, c-fos, and the interferon regulatory factors IRF-1 and IRF-2, but not cdc2 or cdk, were also induced in mineralized bone nodules. The upregulation of Msx-2 in association with apoptosis is consistent with its in vivo expression during embryogenesis in areas that will undergo programmed cell death. We propose that cell death by apoptosis is a fundamental component of osteoblast differentiation that contributes to maintaining tissue organization. J. Cell. Biochem. 68:31-49, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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