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  • 1
    ISSN: 0730-2312
    Keywords: fatty acid-binding protein ; mechanism of action ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Mammary-derived growth inhibitor (MDGI), a polypeptide growth inhibitor isolated from lactating bovine mammary tissue, previously shown to have extensive sequence homology with fatty acid-binding proteins, was demonstrated to meet the criteria of a fatty acid-binding protein. The protein was found to bind [3H]palmitic acid in a saturable manner and to be complexed with endogeneous free fatty acids. [3H]palmitic acid, when bound to the protein, was more rapidly taken up by the target cells (human mammary carcinoma cells [MaTu]) than was free [3H]palmitic acid, suggesting a lipid carrier function for the inhibitor. It is suggested that the fatty acid-binding properties of MDGI may relate to its ability to inhibit cell growth in vitro and to regulate other cellular functions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0730-2312
    Keywords: epidermal growth factor receptor ; breast cancer ; immunohistochemistry ; cell proliferation ; receptor phosphorylation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The prognostic significance of the epidermal growth factor receptor status (EGF-R-status) for certain human tumors requires the development of antibodies useful for clinical application. We used purified receptor preparations to generate monoclonal antibodies immunoreactive with the EGF-R purified from placenta membranes and A431 tumors. Four of the hybridomas contained antibodies (R2, R3, R5, and R9) which recognized both antigens. Antibody R3 was shown to display the following properties: it binds with a KD value of about 10-9-10-10 M to the receptor, a half maximal inhibition of EGF-binding is achieved at 5 × 10-8 M, and in Western blots of cell membranes R3 specifically detects the EGF-R at 0.1 μ/ml. R3 inhibits EGF-dependent clonogenic growth of NRK cells and completely blocks EGF stimulated autophosphorylation of the receptor. Moreover, R3 also detects EGF-R in paraffin-embedded tissue sections taken from human salivary gland, term placenta, and adult skin and mammary carcinomas. Thus, R3 can be used in retrospective diagnostic clinical studies and might help to develop new immunotherapeutic intervention.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Conditions have been established for the separation of viable mouse lymphoid cells by continuous free-buffer film preparative electrophoresis. The detailed electrophoretic distribution profiles of T and B lymphocytes from mouse spleen and thoracic duct have been determined. Cell surface θ-antigen was used as a marker for T cells, and high surface-density of immunoglobulin as a marker for B cells. Spleen cells from athymic “nude” mice were also studied.In the unselected normal spleen cell populations B lymphocytes are heterogeneous, about 60% being of low mobility with the remainder distributing broadly, and extending into the highest mobility fractions. T lymphocytes are predominantly of high mobility. Lymphoid cells lacking markers of either the B or T lineage are of intermediate mobility. There is only partial separation of T and B cells because of the extensive overlap between the populations.The high mobility B cells, which separate along with T cells, include a substantial proportion of large cells, and include cells with high surface density of immunoglobulin. The majority of these large B cells can be selectively eliminated by their adherence on passage through a glass-bead column.By pre-selecting the 50% non-adherent lymphocytes from spleen as the starting material, a very sharp and more extensive separation of B and T cells can be achieved, with 100% pure B cells and 90% pure T cells in many fractions. However these samples are not representative of the total T and B cell populations of spleen.In thoracic duct lymph high mobility B-cells are absent, there is little overlap between T and B cell mobility. 100% pure T and B cells can be isolated.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 136 (1988), S. 194-197 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When quiescent cells in monolayer culture are stimulated to proliferate with growth factor, the entry into S-phase or mitosis appears to follow first-order kinetics, with a probability to enter the cell cycle that depends on growth factor concentration (Smith and Martin, 1973). Suboptimal growth factor concentrations also lead to a decreased fraction of the cell population that responds to the stimulation (Brooks et al., 1984). Using flow cytometry, we have re-investigated this dual effect of growth factor concentration on cultures of quiescent normal human skin fibroblasts, stimulated with submaximal concentrations of fetal calf serum, epidermal growth factor, and platelet-derived growth factor. The size of the responding population decreased with decreasing concentration of growth factor, but the time course of cell division within this responding population was identical for all growth factor concentrations. This is in conflict with previous concepts and indicates that the entry into the proliferative state is based on a decision mechanism that cannot be adequately described using transition probabilities determined by mitogen concentration.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 146 (1991), S. 191-196 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When quiescent normal skin fibroblasts are stimulated by mitogens such as epidermal growth factor (EGF), the proportion of cells entering a division cycle decreases with increasing cell density. The presence of a synthetic double-stranded RNA (poly I:C) enhances this density-related restriction. Fetal calf serum (FCS) as well as human serum (HS) and human platelet-poor plasma (HPPP) completely abrogate the inhibiting effect of cell density on EGF mitogenicity, both in the presence and absence of poly I:C. HS and HPPP are up to ten times more potent than FCS in overcoming density-related restriction of EGF mitogenicity in human skin fibroblasts, whereas the mitogenic potencies of FCS, HS and HPPP in the absence of EGF are identical. Thus the mitogenic activity of FCS, HS and HPPP and their ability to overcome the density-related restriction of EGF-induced proliferation may be due to different molecules. Addition of FCS or HS at various times after EGF exposure reveals two distinct control points within the prerepli-cative phase: one within the first 2 hours and the other between 10 and 20 hours after the beginning of EGF exposure. Thus, the interactions of EGF, serum, and poly I:C reveal the kinetics of a cell density-related mechanism of negative proliferation control.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 139 (1989), S. 531-537 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The growth, in vitro of the murine myeloid cell line FDC-P1 depends on the presenc of serum and a murine hemopoietic growth factor (either granulocyte/ macrophage colony-stimulating factor (GM-CSF) or multipotential colony-stimu-lating factor (multi-CSF, IL3)). To determine the differential roles of serum and colony-stimulating factor (CSF) during the growth of FDC-P1 cultures, we investigated the kinetics of proliferation and death after withdrawal of serum or CSF, using flow cytometry to quantitate the numbers of vital and dead cells. After withdrawal of CSF, the cells died without entering a quiescent state. The life span of cultures lacking CSF increased with increasing concentrations of serum (〉 50 h at 30% serum), and the cells kept dividing until they died. During the period of population death caused by the absence of CSF, the re-addition of CSF immediately prevented further cells from dying. After the withdrawal of serum in the presence of CSF, the cells continued to live and proliferate for weeks, but required high cell densities (〉〉 105/ml), which suggests that the cells produced an active substance that can substitute for serum. Serum as well as serum-free conditioned medium from dense cultures made the survival and growth of FDC-P1 cultures independent of cell density. Without sufficient quantities of this activity, all cells of the population died within an interval that was much shorter than one cell cycle, which indicates that the factor acts throughout most of the cell cycle. The results suggest that both the CSF and the serum factor act together to permit cell survival, rather than to drive proliferation.
    Additional Material: 8 Ill.
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  • 7
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The aim of the present study was to investigate the expression of the mammary derived growth inhibitor (MDGI) and the subcellular localization of MDGI related antigens in bovine mammary glands. Cell-free translation of poly (A+) = RNA, immunoprecipitation with rabbit anti-MDGI-antibodies, and estimation of the relative contents of MDGI by a radioimmunoassay in mammary tissue of different functional statess revealed that the 13 kDa MDGI was dramatically increased in terminally differentiated mammary tissue compared with the proliferating tissue from pregnant animals. To address the question of tissue localizationl, polyclonal anti-MDGI antibodies and antibodies directed aganist a sythetic peptide corresponding ot residues 69 to 78 of MDGI were used. Western blotting of tissue fractions revealed the cytosolic and microsomal localization of MDGI. Additionally, both types of antibodies a 70-kDa antigeninthe unclear fractionof differentiated mammary glands. Salt extraction and DNase I digestion of isolated unclei, as well as chromatin purification, indicated an association of the 70-kDa antigen with the chromatin. By means of the immunogold technique, MDGI-related antigens were localized within euchromatic unclear regions of epithelial cells in the intact differentiated mammary gland. The immunostaining was markedly diminished in the proliferating tissue. This finding raises the possibility that MDGI and the 70-kDa antigen influence cell proliferation by acting on geneexpression within the unclei of mammary glands.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 155 (1993), S. 79-88 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cell density negative control (CDNC) of normal human fibroblast proliferation occurs after stimulation by mitogens with different signal transduction mechanism. Delayed exposure to agents that interfere with CDNC, such as doublestranded RNA and vanadate, reveals the existence of a biochemical event, involved in CDNC, that occurs 5-8 hr after the beginning of mitogenic stimulation. This is earlier than the point of “mitogenic commitment,” defined by the duration of mitogen exposure required for cell cycle entry (8-18 hr). Phosphorylation of the retinoblastoma gene product (pRB) begins 8-10 hr after mitogen stimulation and is nearly complete at 18 hr, just as the first cells enter S-phase. CDNC prevents pRB phosphorylation. Interferon β delays pRB phosphorylation by up to 20 hr but has little effect on the timing of mitogenic commitment. Thus mitogenic commitment is located in time between CDNC and pRB phosphorylation. When agents that cause a release from CDNC are applied to dense, negatively controlled cultures after 18 hr of EGF stimulation, pRB phosporylation occurs 6-8 hr after release. This suggests that the negatively controlled cells process the mitogenic signal but accumulate at a restriction point. The relatively early timing of CDNC-related events in the prereplicative phase raises the possibility that pRB phosphorylation is a consequence rather than a prerequisite for release from cell density negative control. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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