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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 29 (1991), S. 238-244 
    ISSN: 1040-452X
    Keywords: IGF-IA ; Long 3′-end ; Expression ; Transcripts sizes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A cDNA clone of 525 bp corresponding to the 3′-untranslated region of insulin-like growth factor-I was isolated from a human placenta library. The sequence of this clone extended 200 nucleotides downstream from the previously reported 3′-end of IGF-IA cDNA, indicating the existence of IGF-IA transcripts having an even larger 3′-untranslated region. By using this clone for RNA transfer blot hybridization, it was shown that this longer 3′-untranslated region is included in the 7.5- and 5.0-kb transcripts, but not in the 1.1- and 0.9-kb transcripts. It is also apparent that transcripts bearing the extended 3′-untranslated sequence are highly expressed in human placenta.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 45 (1991), S. 49-53 
    ISSN: 0730-2312
    Keywords: Trypanosoma brucei ; ornithine decarboxylase ; in vivo half-life ; PEST hypothesis ; DL-α-Difluoromethylornithine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: DL-α-Difluoromethylornithine (DFMO), a suicide inhibitor of eukaryotic ornithine decarboxylase (ODC), has therapeutic activities against African trypanosomiasis. The Ki, value of DFMO for ODC of Trypanosoma brucei is somewhat higher than that for mouse ODC. The therapeutic efficacy of DFMO cannot therefore be attributed to a preferential inhibition of the parasite enzyme. The T. brucei gene encoding ODC was cloned and sequenced, and the derived amino acid sequence has 61.5% homology with that of mouse ODC, except that the C-terminal 36 amino acids of the mouse enzyme are missing from the parasite enzyme. The cloned T. brucei and mouse ODC genes were expressed in ODC-deficient Chinese hamster ovary cells (CHO) where the T. brucei enzyme was stable, but mouse ODC was unstable. Thus, the observed difference in intracellular stability is a property of the ODC protein itself, rather than of the cellular environment in which it is expressed. A chimeric ODC composed of the amino terminus of trypanosome ODC and the C-terminus of mouse ODC also was rapidly degraded in CHO cells, suggesting that peptide sequences in the mouse ODC carboxy-terminus determine its stability.The relatively slow turnover of the parasite enzyme constitutes the basis of selective antitrypanosomal action of DFMO. By this same token, many other proteins known to perform crucial functions in bacteria, fungi, protozoa, helminths, etc., also may have shorter half-lives in the mammalian hosts than in parasites. Suicide inhibitors of these proteins may have desirable characteristics as good chemotherapeutic agents. This new approach could provide an additional strategy for controlling infectious diseases.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 58 (1995), S. 393-402 
    ISSN: 0730-2312
    Keywords: adipocytes ; bone morphogenetic proteins ; differentiation ; bone marrow stromal cells ; transforming growth factor β ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The bone morphogenetic proteins were originally identified based on their ability to induce ectopic bone formation in vivo and have since been identified as members of the transforming growth factor-β gene superfamily. It has been well established that the bone morphogenetic cytokines enhance osteogenic activity in bone marrow stromal cells in vitro. Recent reports have described how bone morphogenetic proteins inhibited myogenic differentiation of bone marrow stromal cells in vitro. In vivo, bone marrow stromal cells differentiate along the related adipogenic pathway with advancing age. The current work reports the inhibitory effects of the bone morphorphogenetic proteins on adipogenesis in a multipotent murine bone marrow stromal cell line, BMS2. When exposed to bone morphogenetic protein-2, the pre-adipocyte BMS2 cells exhibited the expected induction of the osteogenic-related enzyme, alkaline phosphatase. Following induction of the BMS2 cells with adipogenic agonists, adipocyte differentiation was assessed by morphologic, enzymatic, and mRNA markers. Flow cytometric analysis combined with staining by the lipophilic fluorescent dye, Nile red, was used to quantitate the extent of lipid accumulation within the BMS2 cells. By this morphologic criteria, the bone morphogenetic proteins inhibited adipogenesis at concentrations of 50 to 500 ng/ml. This correlated with decreased levels of adipocyte specific enzymes and mRNAs. The BMS2 pre-adipocytes constitutively expressed mRNA encoding bone morphogenetic protein-4 and this was inhibited by adipogenic agonists. Together, these findings demonstrate that bone morphogenetic proteins act as adipogenic antagonists. This supports the hypothesis that adipogenesis and osteogenesis in the bone marrow microenvironment are reciprocally regulated.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The blast cells in acute myeloblastic leukemia (AML) respond to many of the same regulatory mechanisms that control normal hemopoiesis. These include the growth factors that bind to membrane receptors and steroid hormones or vitamins that have intracellular receptors. We report the effects in culture of the steroid glucocorticoid hydrocortisone on freshly explanted AML blasts from patients and on two continuous AML cell lines. Only small changes in clonogenic cell numbers in suspension cultures were seen in the presence of hydrocortisone. The most striking effect of the hormone was on the sensitivity of blasts cells to cytosine arabinoside (ara-C). In contrast to the response of AML blast cells to retinoic acid, a ligand for intracellular steroid receptors that sensitizes some blast populations to ara-C, hydrocortisone reduced the toxic effects of the drug. The protective action of hydrocortisone was not mediated through the cell cycle since exposure of blasts to hydrocortisone did not affect the percentage of cells in DNA synthesis as measured with the tritlated thymidine (3HTdR) “suicide” technique. The hydrocortisone effect could be demonstrated using a pulse (20 min) exposure protocol. Blasts pulsed with increasing specific activities of 3HTdR showed the usual response pattern with an initial loss in plating efficiency to about 50% of control, followed by a plateau, regardless of whether the cells had been exposed to hydrocortisone. Control blasts exposed to increasing ara-C concentrations gave very similar dose-response curves; in striking contrast, blast cells cultured in hydrocortisone, then pulsed with ara-C did not lose colony-forming ability even though the same population was sensitive to 3HTdR. The hydrocortisone effect was dose and time related; protection from ara-C increased from 10-8 to 10-5 M and was seen after 4 hr exposure but required 8 hr to reach a maximum. We conclude that hydrocortisone can protect blasts from the lethal effects of ara-C even while the cells are in active DNA synthesis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 193 (1992), S. 152-163 
    ISSN: 0002-9106
    Keywords: Cerebral endothelium ; Development ; Immunocytochemistry ; Rat ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A constant supply of blood-borne glucose is vital to cerebral metabolism. Although transport of glucose into the nervous tissue, effectively separated from the blood by a functional barrier (the blood-brain barrier, BBB), is one of the essential properties of the cerebral endothelium, little is known about its metabolic regulation and developmental expression in the BBB. In this study we provide evidence by immunocytochemistry that the pattern of the brain endothelial glucose transporter in rat brains (BBB-GT), immunologically homologous with the human hepatoma (G2), human erythrocyte transporter (Glut 1), changes with BBB maturation. While the neuroepithelium at embryonic days 12 and 13 shows a high incidence of immuno-detectable BBB-GT, vascularisation of the cerebral anlage and subsequent development of vascular tightness, as evidenced by intravascularly applied horseradish peroxidase and fluorescinated dextrans, is accompanied by a significant reduction BBB-GT expression in neuroepithelial cells and confinement of BBB-GT expression to the cerebral endothelium. Immunoblots and Northern blots of embryonic brain homogenates corroborate this change in BBB-GT expression in the brain anlage at the time of BBB maturation. However, low molecular weight glucose transporters, presumed to be of non-endothelial origin, are less dramatically reduced. The development of BBB tightness, therefore, seems to play a pivotal role in the pattern of BBB-GT expression during brain differentiation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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