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  • GEOPHYSICS  (21)
  • Life and Medical Sciences  (7)
  • 1975-1979  (19)
  • 1970-1974  (9)
  • 1
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mutants of mouse L-cells which are temperature-sensitive for growth have been obtained by using both selective and nonselective isolation procedures on populations treated with the mutagen nitrosoguanidine. Selective isolation was carried out by utilizing a five-day treatment with 3H-TdR and ara-C as selective agents at the nonpermissive temperature. Nonselective isolation was performed by isolating 1400 clones in the absence of selective agents and then testing them for temperature-sensitivity. From this experiment we obtained a minimum estimate of 6 × 10-3 for the frequency of mutants in the mutagentreated population. The mutants were characterized by their plating efficiencies, growth in suspension culture, and uptake of isotopic precursors of DNA, RNA, and protein. A range in phenotypes was observed, and there appeared to be some differences between the mutants obtained by the two types of isolation procedures. In uptake experiments the most marked reductions in the rates of precursor incorporation were seen with 3H-TdR, rather than 3H-UR or 3H-Leu. Different mutant lines showed considerable variation in the rate of cessation of DNA synthesis as well as the time required for termination of cell division. These experiments suggest that both types of isolation procedures are feasible for obtaining temperature-sensitive mutants having a range of phenotypes.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 83 (1974), S. 259-261 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Exposure of early sea urchin embryos to 5-bromodeoxyuridine (at concentrations up to 100 μg per ml) severely decreases the uptake of exogenous 3H-uridine into RNA. However, the actual gross rate of DNA or RNA synthesis in these embryos appears not to be affected by the presence of 5-bromodeoxyuridine.
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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: 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.
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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: 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.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 98 (1979), S. 561-570 
    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.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 100 (1979), S. 39-54 
    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.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 77 (1971), S. 377-384 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The two stages in the uptake of transferrin by rabbit reticulo-cytes were investigated using radioiodine-labeled rabbit transferrin and albumin. The first stage of rapid, temperature-insensitive uptake of transferrin was similar to albumin uptake: uptake of both proteins increased linearly with increasing protein concentration of the incubation medium up to at least 60 mg/ml, was maximal at low ionic strength and pH, and increased in the presence of basic polyamino acids. Transferrin uptake was in part dependent on the reticulocyte concentration of the blood, but albumin uptake was independent of reticulocyte concentration.The second slower, temperature-sensitive stage of transferrin uptake was linearly related to reticulocyte concentration, and was not found with albumin, α1-macroglobulin or γ-globulin. Transferrin uptake was optimal at physiological pH and ionic strength and was unaffected by basic polyamino acids. When the transferrin concentration was raised, uptake increased to reach a maximum at a concentration of 15 mg/ml.It was concluded that the first stage of transferrin uptake was in part or wholly due to non-specific adsorption of transferrin to erythrocytes, while the second stage of uptake was specific for transferrin and reticulocytes and depended upon normal function of the cells.
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  • 8
    Publication Date: 2006-01-16
    Description: A schematic representation of the generation and propagation processes for energetic particles of concern in solar terrestrial predictions is given. Particle precipitation at low, mid, and high altitudes is discussed with emphasis on prediction techniques. Methods given for testing of such techniques include traditional collaborations, enhanced collaborations, simulated prediction schemes, and field tests.
    Keywords: GEOPHYSICS
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 433-440
    Format: text
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  • 9
    Publication Date: 2011-08-16
    Description: Error sources in GEOS-C satellite short arc orbit determination method as determined by altimeter experiment
    Keywords: GEOPHYSICS
    Type: PROC. OF THE GEOS-2 PROGRAM REV. MEETING, VOL. 4 NOV. 1970; P 183-240
    Format: text
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  • 10
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    In:  CASI
    Publication Date: 2016-06-07
    Description: Considerable effort has gone into snow line delineation using available satellite data. Furthermore, increasing emphasis is being put on automated extraction of such information and generation of a useable product for hydrologists. Implications are clear that the impact from future satellite and sensors systems will create an increased demand for computer processing before the data can be used by the hydrologist. If the coarse-resolution, broad spectral band data available from current satellites already create a demand by hydrologists for computer processing of the data, it is obvious there will be an even greater demand for computer analysis and evaluation when the future ERTS data become available.
    Keywords: GEOPHYSICS
    Type: NASA, Washington Intern. Workshop on Earth Resources Surv. Systems, Vol. 2; p 430-440
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