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  • 1
    Electronic Resource
    Electronic Resource
    Glucocorticoids enhance the mitogenic action of insulin in serum-free cultures of chick embryo cells (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 98 (1979), S. 561-570 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Addition of insulin to nonproliferating serum-free cultures of secondary chicken embryo (CE) cells caused a 30% to 50% increase in cell number. Addition of any one of several glucocorticoids (dexamethasone, cortisol, or corticosterone) to the cultures two days before insulin addition increased the mitogenic effect of insulin by about twofold at each insulin concentration tested. This glucocorticoid stimulation of cell proliferation was “permissive” because in the absence of insulin glucocorticoids caused little increase in cell number (usually less than 15%). Glucocorticoids were maximally active at low concentrations (e.g., 10-10 M dexamethasone). Steroids without glucocorticoid activity were inactive over a wide range of concentrations. Glucocorticoids increased the mitogenic response to insulin largely by increasing the percentage of cells that insulin stimulated to synthesize DNA.The maximum mitogenic effect of insulin upon CE cells rapidly decreased after the cells were serially subcultured. After only nine population doublings (4 passages) in culture, the response to insulin was diminished by about 70%. The mitogenic effect of insulin plus dexamethasone declined similarly during serial subculture, and was always about twofold greater than the effect of insulin alone. The cells maintained their mitogenic responsiveness to serum as these responses decreased.In contrast to the growth promoting influence of glucocorticoids in the presence of insulin, glucocorticoids inhibited the mitogenic response of CE cells to serum. This result may resolve our above findings with reports that glucocorticoids inhibit the proliferation of CE cells.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040980314
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  • 2
    Electronic Resource
    Electronic Resource
    Characteristics of concanavalin A-resistant Chinese hamster ovary cells and certain revertants (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 100 (1979), S. 39-54 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Clones of Chinese hamster ovary (CHO) cells were isolated by single-step selection for resistance to killing by Concanavalin A (ConA) and certain cellular and membrane properties were examined. The ConA-resistant isolates were only about 2-fold more resistant than wild type cells to the selecting lectin, but exhibited pleiotropic temperature-sensitivity for growth, markedly altered morphology and adherence, and significant differences in susceptibility to other agents such as colchicine. Two revertants to full temperature-resistance were isolated from different ConA-resistant mutants. One revertant clone had reacquired wild type sensitivity to ConA while the other revertant remained ConA-resistant. The two series of wild type, ConA-resistant, and temperature revertant clones were analyzed for altered mobility of cell surface glycoproteins using lactoperoxidase/125I and galactose oxidase/[3H]borohydride labelling procedures. The ConA-resistant clones showed increased mobility on polyacrylamide gels of three classes of labelled proteins, in the molecular weight ranges 225,000, 200,000, and 130,000 daltons. These changes persisted in the temperature-revertant that remained ConA-resistant, while two of the altered protein classes were restored to wild type mobility in the revertant that regained ConA-sensitivity. Cell hybridization experiments indicated that the temperature-sensitive phenotypes of different ConA-resistant isolates are recessive and noncomplementing, implying that the same gene is affected in each case. The reversions to temperature resistance appear to be recessive suppressor mutations in different genes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041000105
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  • 3
    Electronic Resource
    Electronic Resource
    Growth enhancement of myogenic tumor cells by conditioned medium from embryo fibroblastsThis research was supported by grants from the Cancer Council of Western Australia and the National Health and Medical Research Council. (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 86 (1975), S. 321-326 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Growth medium was conditioned by incubation on mouse embryo cells in vitro. Supplementation of agar suspension cultures with conditioned medium from primary cells, but not from established lines, readily enhanced colony development by mouse tumor cells. Only cells with the properties of myoblasts responded to conditioned medium. Other fibroblastoid cells and virus-transformed cell lines were not affected. Myogenic cells in agar cultures grew in the presence of conditioned medium but did not differentiate. Soluble collagen at 400 m̈g/ml possessed little colony-stimulating activity by comparison with fresh conditioned medium.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040860403
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  • 4
    Electronic Resource
    Electronic Resource
    Control of granulopoiesis in man. III. Inhibition of colony formation by dense leukocytesSupported by Grant 263, The Ontario Cancer Treatment and Research Foundation. (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 86 (1975), S. 337-342 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cellular feeder layers, prepared from normal blood leukocytes, usually stimulate human marrow to form colonies. A significant increase in the stimulating activity of unseparated leukocyte feeder layers is brought about following the removal of dense leukocytes in a manner which avoids enrichment of any remaining cell type. Restoration of dense leukocytes to a dense leukocyte depleted leukocyte feeder layer results in the reduction of stimulating activity to that of an unseparated leukocyte feeder; however, addition of dense leukocytes to unseparated leukocyte feeder layers has no effect on the stimulatory activity, over the range of concentrations used in this study.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040860405
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  • 5
    Electronic Resource
    Electronic Resource
    Isolation and characterization of the nuclear matrix from the male xenopus laevis following estrogen administration: Kinetics of [3H] uridine incorporationThis is Contribution Number 520 of the Departments of Cell and Molecular Biology, Medical School of Georgia. (1979)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 12 (1979), S. 471-479 
    Details
    ISSN: 0091-7419
    Keywords: nuclear matrix ; estrogen ; RNA ; uridine ; Xenopus laevis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: At various times following estorgen administration, the nuclear matrix was isolated from the liver of male Xenopus laevis by sucrose gradient centrifugation of nuclei treated with a high-salt buffer and DNase I in the presence of a proteolytic inhibitor (PMSC - phenylmethyl sulfonyl chloride). Electron micrographs of the nuclear matrix demonstrate a sponge-like network attached to a well-defined inner envelope with a ribosome-free outer envelope. Chemical analyses show that the HSB-DNase-treated nuclei consist of 16% DNA, 2% RNA, and 82% protein, a composition that is consistent with that of nuclear matrices isolated from other species. The specific activity of the matrix-associated RNA following estrogen treatment appears to be maximally enhanced after 5 h and decreases until approximately 12 h, when the activity begins to increase again.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400120407
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanisms of thrombin-stimulated cell division (1979)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 11 (1979), S. 259-267 
    Details
    ISSN: 0091-7419
    Keywords: cell surface receptors ; proteolysis of receptors ; positive or negative regulation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Addition of highly purified thrombin t o cultures of several kinds of nondividing fibroblasts brings about cell division. This stimulation occurs in serum-free medium, permitting studies on its mechanism under chemically defined conditions. Previous studies have shown that action of thrombin a t the cell surface is sufficient to cause cell division and that the proteolytic activity of thrombin is required for its mitogenic effect. These results prompted experiments which showed that there is a cell surface receptor for thrombin and that thrombin must hind to its receptor and cleave it to stimulate cell division. Some of the thrombin that hinds to its receptors becomes attached to them by a linkage that appears to be covalent. However, it is presently unknown whether this direct thrombin receptor complex plays a role in the stimulation.These results raise a number of question that should be explored in future studies. They also provide a foundation on which to build hypotheses about tentative molecular mechanisms that might be involved in the stimulation. Knowledge that thrombin must cleave its receptor to bring about cell division suggests two alternative mechanisms for stimulation by proteolysis. In one the receptor is a negative effector which prevents cell division when it is intact, but not after it has been cleaved. Alternatively, a fragment of the receptor could be a positive effector. In this mechanism, proteolysis by thrombin would produce a specific receptor fragment which brings about cell proliferation. If every protease which cleaves the receptor also stimulates cell division, the receptor is probably a negative effector. In contrast, if certain proteases cleave the receptor but do not stimulate the cells, a fragment of the receptor is likely a positive effector. With negative regulation by the receptor, the controlling events would occur before proteolysis of it, and it might be possible to find putative regulatory molecules by identification of nearest neighbors of the receptor. This should be possible by using bifunctional crosslinking reagents. If a fragment of the thrombin receptor turns out to be a positive effector, it should be possible to identify and study fragments by analyzing the metabolic fate of the receptor. Techniques are now available for this kind of analysis and it should also be possible to determine whether receptor fragments remain in the membrane or whether they are translocated to specific sites within the cell. A critical question to be asked is which of these events and interactions involving the thrombin receptor are necessary for stimulation of cell division. It now appears that the best way to answer this question is to examine these events in a large number of cloned cell populations that are responsive or unresponsive to the mitogenic action of thrombin. If a thrombin-mediated event occurs in all responsive clones but is altered or absent in sonie unresponsive clones, it is probably necessary for stimulation of cell division.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400110215
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  • 7
    Electronic Resource
    Electronic Resource
    An electron microscopic and enzymic study of rat liver peroxisomal nucleoid core and its association with urate oxidase (1977)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 7 (1977), S. 419-434 
    Details
    ISSN: 0091-7419
    Keywords: peroxisome ; microbody ; nucleoid core ; urate oxidase ; starvation effects ; rat liver enzymes ; catalase ; cell organelle ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The appearance of the characteristic crystalloid core of rat liver peroxisomes is emulated by the electron microscopic (EM) appearance of highly purified urate oxidase prepared from the same tissue. The purity of the enzyme preparation was established by gel electrophoresis under various conditions and the specific enzyme activity was at least as high as any previously reported. The amino acid composition of urate oxidase was determined. As additional evidence for close association of the peroxisomal core with urate oxidase, it was demonstrated that the biphasic changes in rat liver urate oxidase activity in response to prolonged starvation were paralleled by changes in the EM appearance of peroxisomes. Under comparable conditions catalase, another peroxisomal enzyme, did not show the same changes in activity as did urate oxidase. Evidence for the possible identity of urate oxidase with the peroxisomal crystalloid of rat liver has been presented, all materials having been obtained from, and experiments performed with, the rat.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400070313
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  • 8
    Electronic Resource
    Electronic Resource
    Glucocorticoid-mediated alteration in growth factor binding and action: Analysis of the binding change (1978)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 9 (1978), S. 69-77 
    Details
    ISSN: 0091-7419
    Keywords: dexamethasone ; epidermal growth factor ; human diploid fibroblasts ; cell proliferation ; permissive effect ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The addition of the glucocorticoid analog dexamethasone (DX) to serum-free cultures of human fibroblasts caused a twofold enhancement of the mitogenic response to epidermal growth factor (EGF), although DX by itself was not mitogenic. A basis for this effect was suggested by studies showing that DX also increased the cellular binding of 125I-EGF. DX increased the ability of the cells to bind 125I-EGF only at low physiological concentrations of this polypeptide. Thus, data from 125I-EGF binding to cells incubated without DX produced a linear Scatchard plot, whereas the data from 125I-EGF binding to DX-treated cells led to an upwardly curvilinear Scatchard plot. Measurements of 125I-EGF association with the cell surface and cytoplasm indicated that this binding change involved an alteration of cell surface EGF receptors. The binding change appeared not to involve negatively cooperative interactions between EGF receptors, nor a change in the number of receptors. The binding alteration could be explained by a model in which DX converted 25-30% of the cell surface EGF receptors to a form having a fourfold increased affinity.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400090108
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  • 9
    Electronic Resource
    Electronic Resource
    Inhibition by protease inhibitors of binding of adrenal and sex steroid hormones (1978)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 9 (1978), S. 421-426 
    Details
    ISSN: 0091-7419
    Keywords: aldosterone ; dexamethasone ; dihydrotestosterone ; estrogen ; progesterone ; steroid hormone receptor ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Binding of steroid hormones is inhibited by protease inhibitors and substrates. The protease inhibitors phenylmethyl sulphonylfluoride, tosyl-lysine chloromethyl ketone, and tosylamide-phenylethyl-chloromethyl ketone and the protease substrates tosyl arginine methyl ester and tryptophan methyl ester eliminate specific binding of aldosterone, dexamethasone, dihydrotestosterone, estrogen, and progesterone to their respective receptors. These protease inhibitors and substrates also inhibit binding of progesterone to the 20,000 molecular weight mero-receptor formed from the progesterone receptor in chick oviduct. The binding of estradiol to rat alpha-fetoprotein is inhibited by the protease inhibitors and substrates but not by tryptophan or tryptophan amide, indicating the importance of an ester structure in the inhibition of steroid binding. Our results suggest that all steroid hormone receptors have a site with both common structural features and a role in the regulation of steroid hormone binding.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400090312
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  • 10
    Electronic Resource
    Electronic Resource
    Direct linkage of thrombin to its cell surface receptors in different cell types (1979)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 12 (1979), S. 245-257 
    Details
    ISSN: 0091-7419
    Keywords: thrombin receptors ; epidermal growth factor receptors ; cell proliferation ; normal and transformed cells ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: When 125I-thrombin was incubated with foreskin fibroblasts, cervical carcinoma cells or fibrosarcoma cells of human origin, or with secondary chick embryo cells or Chinese hamster lung cells, it became directly linked to its cell surface receptors. The thrombin-receptor complex (TH-R) was derived exclusively from a pool of 125I-thrombin that had become specifically bound to the cell surface. The linkage was probably covalent, since the complex was resistant to boiling in sodium dodecyl sulfate and 2-mercaptoethanol. Raising the pH to 12 disrupted TH-R, but did not affect a similar complex between epidermal growth factor and its receptor, suggesting that the linkage of these mitogens to their receptors was different. Mild trypsin treatment removed the ability of cells to form TH-R; however, after a 24-h incubation in serum-free medium, trypsin-treated cells recovered the capacity to form TH-R, suggesting that TH-R resulted from interaction of 125I-thrombin with a cellular rather than a serum component. The mitogenic response of cells to thrombin was inversely related to the fraction of specifically bound 125I-thrombin represented by TH-R. The role of TH-R in mitogenesis may be clarified in future studies by obtaining clones of Chinese hamster lung cells that vary in their capacities to form TH-R and to respond to the mitogenic action of thrombin.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400120209
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