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  • 1
    Electronic Resource
    Electronic Resource
    Interaction between monensin and lysosomotropic amines in the regulation of the processing of epidermal growth factor by BALB/c 3T3 cells (1987)
    Springer
    Molecular and cellular biochemistry 73 (1987), S. 1-9 
    Details
    ISSN: 1573-4919
    Keywords: Chloroquine ; methylamine ; lysosomes ; pH gradients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Monensin, like the lysosomotropic amines Chloroquine and methylamine, caused a large accumulation of 125I-EGF in BALB/c-3T3 cells that was due to specific increases in the amount of intracellular intact hormone. However using a pulse-chase paradigm of 125I-EGF accumulation, marked differences were observed between monensin and the amines. When EGF was accumulated in the presence of monensin, there was a gradual loss of cell-bound radioactivity during a chase in the absence of the drug, and the labeled material recovered in. the medium primarily consisted of degraded hormone. The continued presence of monensin in the chase medium substantively prevented the loss of cell bound material, and what little was recovered in the medium consisted of intact 125I-EGF. In contrast, when 125I-EGF was accumulated in the presence of methylamine, predominately intact peptide was lost from the cells at a relatively high rate during the chase whether or not methylamine remained in the medium. When monensin was present in the chase medium following accumulation in the presence of either Chloroquine or methylamine, the loss of intracellular 125I-EGF was essentially blocked.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229370
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  • 2
    Electronic Resource
    Electronic Resource
    SV40 T antigen alone drives karyotype instability that precedes neoplastic transformation of human diploid fibroblasts (1990)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 42 (1990), S. 13-31 
    Details
    ISSN: 0730-2312
    Keywords: immortalization ; chromosome damage ; SV40 ; simian virus 40 ; large T antigen ; karyotype instability ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: To define the role of SV40 large T antigen in the transformation and immortalization of human cells, we haye constructed a plasmid lacking most of the unique coding sequences of small t antigen as well as the SV40 origin of replication. The promoter for T antigen, which lies within the origin of replication, was deleted and replaced by the Rous sarcoma virus promoter. This minimal construct was co-electroporated into normal human fibroblasts of neonatal origin along with a plasmid containing the neomycin resistance gene (neo). Three G418-resistant, T antigen-positive clones were expanded and compared to three T antigen-positive clones that received the pSV3neo plasmid (capable of expressing large and small T proteins and having two origins of replication). Autonomous replication of plasmid DNA was observed in all three clones that received pSV3neo but not in any of the three origin minus clones. Immediately after clonal expansion, several parameters of neoplastic transformation were assayed. Low percentages of cells in T antigen-positive populations were anchorage independent or capable of forming colonies in 1% fetal bovine serum. The T antigen-positive clones generally exhibited an extended lifespan in culture but rarely became immortalized. Large numbers of dead cells were continually generated in all T antigen-positive, pre-crisis populations. Ninety-nine percent of all Tantigen-positive cells had numerical or structural chromosome aberrations. Control cells that received the neo gene did not have an extended life span, did not have noticeable numbers of dead cells, and did not exhibit karyotype instability. We suggest that the role of T antigen protein in the transformation process is to generate genetic hypervariability, leading to various consequences including neoplastic transformation and cell death.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240420103
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  • 3
    Electronic Resource
    Electronic Resource
    Chloroquine allows the secretion of internalized 125I-epidermal growth factor from fibroblasts (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 125 (1985), S. 215-222 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Incubation of cells with labelled hormone in the presence of the lysosomotropic agent chloroquine produces an enhanced intracellular accumulation of hormone and receptor. Using a pulse-chase paradigm in which cell surface receptors were labelled with 125I-EGF at 4°C, it was found that when 100 μM chloroquine was present in the 37°C chase medium intact hormone was accumulated in the medium. Without chloroquine, low molecular weight (mw) degradation products were found in the medium. The processes of receptor-mediated endocytosis and subcellular distribution of 125I-EGF-receptor complexes were unchanged by chloroquine. The source of the intact hormone accumulating in the medium was therefore an intracellular compartment(s). The 125I-EGF released from the cells could rebind to surface receptors and be re-internalized; rebinding was inhibited by unlabelled EGF or Concanavalin A in the incubation medium. The concentration of unlabelled EGF required to inhibit rebinding was more than three orders of magnitude greater than the amount of 125I-EGF whose rebinding was inbibited. Thus, the 125I-EGF whose rebinding was inhibited. Thus, the 125I-EGF released from intracellular sites was rebound preferentially over exogenous EGF. The possible pathways for secretion of intact 125I-EGF and mechanisms of its preferential rebinding are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041250207
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  • 4
    Electronic Resource
    Electronic Resource
    Late G1 amino acid restriction point in human dermal fibroblasts (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 124 (1985), S. 433-438 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human dermal fibroblasts arrested in G0 by maintenance in medium supplemented with 0.1% serum were not restimulated to divide when fresh medium containing 10% dialyzed serum but lacking group B amino acids (cystine, isoleucine, lysine, phenylalanine and tyrosine) was added. Unlike rodent cells, the addition of fresh serum-supplemented medium lacking only isoleucine did not cause a growth arrest. The amino acid sensitive growth arrest in human fibroblasts was dependent both on presynchronization in G0 as well as a prestarvation for amino acids prior to stimulation with high serum.When cells were restimulated in the absnece of amino acids, they arrested predominantly in G1, although a small percentage of cells entered early S phase. When medium containing a complete complement of amino acids was then added, cells initiated DNA synthesis following a minimum lag of 2-3 hr. Growth arrested cells initiated DNA synthesis even when complete unsupplemented medium was added, although the addition of high concentrations of insulin or 10% serum increased the rate of entry.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041240311
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of the rebinding of 125I-epidermal growth factor released from BALB/c-3T3 cells following accumulation in the presence of chloroquine (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 134 (1988), S. 387-395 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Lysosomotropic amines, such as chloroquine and methylamine, increase the intracellular accumulation of 125I-EGF by inhibiting lysosomal degradation. It has been shown previously that BALB/c-3T3 cells, prelabeled at 4°C with 125I-EGF for 3 h and subsequently chased at 37°C in the presence of chloroquine, internalized the surface bound 125I-EGF which was subsequently released into the extracellular medium in a high molecular weight form which co-migrated with native 125I-EGF. The secreted 125I-EGF rebound to the cells from which it was released more efficiently than does peptide in the extracellular media. We now show that when the BALB/c-3T3 cells were prelabeled at 37°C for 2 h in the presence of chloroquine, the internalized 125I-EGF released into the medium was in a high molecular weight form which co-migrated with native 125I-EGF and did not rebind anymore efficiently than did peptide in the extracellular media. This lack of rebinding was not due to an alteration in the 125I-EGF molecule since it was still capable of rebinding to naive A431 cells, nor was it due to the exhaustion of EGF receptors on the BALB/c-3T3 cells. The inhibition of rebinding was observed only when the cells were treated with EGF in the presence of chloroquine, and was not due to a general down-regulation of membrane receptors. The differences between the rebinding of 125I-EGF at 4°C and 37°C suggest that EGF may be processed via different pathways in the cell.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041340309
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