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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 141 (1989), S. 461-466 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Evidence in the literature suggests that cancer cell growth in vitro is generally not sensitive to external calcium. A human ovarian carcinoma cell line (SKOV3) retained 60% of its normal growth in Dulbecco modified Eagle's medium (DME) when the calcium concentration was reduced from 3 mM to 10 μM. Chinese hamster ovary cells (CHO) were growth-arrested in media containing less than 500 μM calcium. In low-calcium (10 μM) DME, 10 μM of a calmodulin antagonist W7 inhibited the growth of SKOV3 cells by more than 90%, while 100 μM of its inactive analog W5 was mildly inhibitory (20%). The growth inhibition by W7 was antagonized by increasing calcium concentrations in the culture media, while the inhibition by W5 was calcium-independent. The phorbol ester TPA was also effective in antagonizing W7's growth inhibition in low-calcium DME, suggesting that the W7 effect is mediated via protein kinase C inhibition. SKOV3 total cellular protein kinase C activity was 1.6 times higher than CHO cells when incubated in normal DME. When incubated in low-calcium DME, a large drop in protein kinase C activity in the CHO cells was observed while the enzyme activity was unchanged in the SKOV3 cells. Our data suggest that these human ovarian tumor cells have altered cellular calcium regulatory processes associated with the defective down-regulation of protein kinase C. This defect may confer these cells the ability to proliferate independently of the external calcium concentration. Targeting the cellular signal transduction components may be useful in cancer chemotherapy.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 87 (1976), S. 53-62 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have investigated the effects of 2,4,6-trinitrobenzene sulfonic acid (TNBS), an amino reactive reagent, on passive cation movements in Ehrlich ascites tumor cells. Incubation of tumor cells with TNBS (3 mM) results in a two phase association of TNBS with the cells. An initial, rapid phase, presumably at the level of the membrane, is independent of temperature, while the second phase increases linearly in time and is temperature dependent. Kinetic analyses of Na+ movements indicate that TNBS: (1) inhibits Na+ movement from a slowly exchanging cellular compartment, but is without effect on a more rapidly exchanging compartment; (2) does not alter net Na+ accumulation in transport-inhibited cells; and (3) is without effect on non-exchange Na+ efflux at 0°C. The actions of TNBS on K+ movements depend upon temperature and the continued presence of TNBS in the environment. At 22°C two minute exposure of the cells to TNBS leads to 77% inhibition of K+ efflux. With continued exposure to TNBS, the inhibition is only 42%. Reduction of the temperature to 0°C decreases K+ efflux in control cells by 82%. Two minute exposure to TNBS enhances K+ efflux by 50%, while continuous exposure increases it by 144%. These results suggest: (1) TNBS interacts with several classes of membrane sites which are involved with the regulation of passive cation movements; and (2) passive Na+ and K+ movements across the cell membrane proceed by different pathways.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 125 (1985), S. 499-506 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of heparin on the in vitro growth of rat cervical epithelial cells were examined. Heparin was found to inhbit in a dose dependent fashion the log-phase growth of rat cervical epithelial cells (RCEC) grown in the absence of medium supplements. An inhibition of growth is observed at concentrations as low as 500 ng/ml and 50% inhibition of growth occurs at a concentration of 5 μ/ml. The growth inhibitory activity of heparin is independent of anticoagulant activity since three separate non-anticoagulant preparations of heparin all inhibit growth. Other glycosaminoglycans including chondroitin 4-sulfate, chondroitin 6-sulfate, dermatan sulfate, hyaluronic acid, and keratin sulfate do not inhibit the growth of rat cervical epithelial cells. The ability of heparin to inhibit the log-phase growth of rat cervical epithelial cells is dependent on the composition of the medium in which the cells are grown. The addition of ≥ 7.5 ng/ml epidermal growth factor to epithelial cultures blocks the growth inhibitory activity of heparin. These results suggest that components of the extracellular matrix modulate the growth responses of epithelial cells and may be important in regulating cellular proliferation in normal and pathological states.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 132 (1987), S. 255-262 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The glycosaminoglycan heparin inhibits the growth of a number of different cell types in vitro including smooth muscle cells, mesangial cells, fibroblasts, and rat cervical epithelial cells (RCEC). Studies investigating the antiproliferative effects of heparin on smooth muscle cells have demonstrated the site of the cell cycle block and revealed several metabolic alterations that could be causally associated with growth inhibition. We have investigated these metabolic parameters in RCEC to determine whether they are also associated with the antiproliferative effects of heparin in epithelial cells. Heparin acts rapidly to inhibit RCEC growth with inhibition detectable by autoradiography 7 h after the addition of heparin. Heparin treated RCEC begin to enter S-phase 12 h after the removal of heparin. These findings suggest that heparin blocks RCEC in the early-to-mid G1 phase of the cell cycle rather than late in G1 or early in S-phase as has previously been demonstrated for smooth muscle cells. Unlike smooth muscle cells, the uptake of thymidine and uridine is not inhibited by heparin in RCEC. Treatment of medium with heparin-Sepharose does not reduce the subsequent growth of RCEC; heparin inhibits the growth of RCEC in heparin-Sepharose treated medium in a manner identical to that in nontreated medium. Therefore the growth inhibitory effects of heparin cannot be explained by the inactivation of mitogens present in serum. In contrast to its effects on smooth muscle cells, heparin treatment of RCEC does not result in a reduction in the binding of epidermal growth factor (EGF) to the cells. These results indicate that although heparin inhibits the growth of a variety of cell types, significant differences exist in the responses of the different cells to heparin.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 87 (1976), S. 47-52 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have investigated the effects of La+3 binding to the surface of Ehrlich ascites tumor cells on cell electrophoretic mobility and passive movements of Na+ and K+. Incubation of tumor cells in La+3-containing media results in a La+3 concentration-dependent decrease in net surface charge negativity. At [La+3] greater than 0.5 mM, the net surface charge becomes positive with maximum positivity occurring at [La+3] = 0.9 mM. The effects of La+3 binding on passive Na+ and K+ movements were investigated by following 22Na and K+ losses from ouabain-inhibited cells. Neither low (0.02) nor high (1.0 mM) [La+3] had any effect on the K+ efflux rate coefficient. 22Na losses from control and La+3-treated cells were consistent with washouts from two cellular compartments. Low [La+3] (0.02 mM) was without effect on Na+ loss from the cells. However, higher [La+3] (1.0 mM) resulted in a 48% inhibition of Na+ loss from the more slowly exchanging compartment. These results are not consistent with simple electrostatic interactions exerting a major influence on the passive movements of Na+ and K+. It is suggested that La+3 interacts with sites specific for Na+, perhaps involved in a carrier-mediated exchange system.
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  • 6
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous work from our laboratory has demonstrated that heparin specifically inhibits the proliferation of vascular smooth muscle cells in vivo and in vitro. In this paper, we examine the binding and mode of internalization of heparin by smooth muscle cells. For these studies, radiolabeled and fluoresceinated (FITC) heparin probes were synthesized that retained their antiproliferative capacity. Binding of 3H-heparin to these cells occurs via specific, high-affinity binding sites (Kd = 10-9 M, 100,000 binding sites per cell). Approximately 80% of the heparin bound to the cell surface was shed into the culture medium within 2 hr. The heparin that was left on the cell surface was internalized with biphasic kinetics. Approximately 50% of the bound material was internalized within 2 hr. After this initial rapid uptake, the rate slowed substantially, with the remaining heparin requiring 1-2 days to be internalized. Binding and uptake of FITC heparin was monitored using video image intensification fluorescence microscopy. When smooth muscle cells were exposed to FITC heparin at 4°C, a diffuse surface staining pattern was observed. After warming the cells to 37°C, intensely fluorescent vesicles were seen superimposed over the diffuse surface staining within 2 min. After 15 min at 37°C, numerous large punctate vesicles were seen inside the cell. After 2 hr these vesicles had concentrated in the perinuclear region. This pattern of uptake, when considered along with the presence of specific, high-affinity binding sites and the initial rapid uptake of 3H-heparin, suggests that heparin enters smooth muscle cells by both receptor-mediated and other endocytic pathways.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 135 (1988), S. 435-442 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Calcium-binding (-dependent) proteins (CBPs) associated with the spreading of mammary epithelial cell cultures have been identified as various calelectrins and calpactins (p36). In immunoblot analysis, the CBPs of 30-36 kD and 68-70 KD variously react with different calelectrin and calpactin I monomer/p36 antisera. The same immunoreactive proteins were shown to be present in virgin mammary glands and collagen gel mouse mammary epithelial cell cultures. The mammary CBPs show extensive immunochemical relatedness; however, they fail to show cross-reaction with antiserum to calpactin II (lipocortin) antiserum. These immunoreactive CBPs comigrate in electrophoresis with 35S-methionine-labeled CBPs isolated from mammary epithelial cell cultures. Unlike calmodulin, the mammary CBPs that correspond to calelectrins and calpactin I monomer/p36 are not stable to thermal denaturation. The mammary CBPs bind to epithelial cell membranes in a Ca2+-dependent manner and are differentially released from ruptured cells, compared with calmodulin, suggesting subcellular localization. Phenothiazineagarose and phenylagarose are equivalent in their ability to bind the mammary CBPs. Thus, mammary gland CBPs of 30-36 kD and 68-70 kD have been shown to be related or equivalent to the calelectrins and to calpactin I monomer/p36. Since these proteins are known to bind Ca2+, we conclude that the mammary gland CBPs are also Ca2+-binding proteins. The mammary gland CBPs are immunologically related and probably represent members of a larger family of related proteins.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 98 (1979), S. 359-369 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of Ca+2 on the transport and intracellular distribution of Na+ and K+ in Ehrlich ascites tumor cells was investigated in an effort to establish the mechanism of Ca+2-induced hyperpolarization of the cell membrane. Inclusion of Ca+2 (2mM) in the incubation medium leads to reduced cytoplasmic concentrations of Na+, K+ and Cl- in steady state cells. In cells inhibited by ouabain, Ca+2 causes a 41% decrease in the rate of net K+ loss, but is without effect on the rate of net Na+ accumulation. Net K+ flux is reduced by 50%, while net Na+ flux is unchanged in the transport-inhibited cells. The membrane potential of cells in Ca+2-free medium (-13.9 ± 0.8 mV) is unaffected by the addition of ouabain. However, the potential of cells in Ca+2-containing medium (-23.3 ± 1.2 mV) declines in one hour after the addition of ouabain to values comparable to those of control cells (-15.2 ± 0.7 mV).The results of these experiment are consistent with the postulation that Ca+2 exerts two effects on Na+ and K+ transport. First, Ca+2 reduces the membrane permeability to K+ by 25%. Second, Ca+2 alters the coupling of the Na/K active transport mechanism leding to an electrogenic hyperpolarization of the membrane.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 122 (1985), S. 290-298 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Substrate regulation of System A transport activity in rat H4 hepatoma cells is described. The uptake of several amino acids was tested in the presence of system-specific inhibitors. System A activity was increased in a RNA- and protein synthesis-dependent manner by amino acid deprivation of the cells (adaptive regulation), whereas transport by Systems ASC, N, y+, and L was unaffected. Unlike human fibroblasts, the H4 cells did not require serum to exhibit the depression of System A. At cell densities between 88 × 103 and 180 × 103 cells/cm2, the degree of adaptive regulation was inversely related to cell density. Both transport of AIB and adaptive regulation of System A were nearly abolished if either K+ or Li+ was substituted for Na+ in the medium. The presence of cycloheximide or tunicamycin blocked further increases in starvation-induced activity within 1 hr of addition, suggesting the involvement of a plasma membrane glycoprotein. In contrast, if the medium was supplemented with actinomycin after the stimulation of System A had begun, the activity continued to increase for an additional 2 hr before being slowed by the inhibitor. The contributions of trans-inhibition and repression to the amino acid-induced decay of System A activity were estimated for several representative amino acids. In general, the System A activity in normal rat hepatocytes was much less sensitive to trans-inhibition than the corresponding activity in H4 hepatoma cells. The half-life values for the amino acid-dependent decay of System A ranged from 0.5 to 2.0 hr.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 126 (1986), S. 10-20 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The extended culture of rat cervical epithelial cells can be achieved in the absence of a fibroblast feeder layer by utilizing collagen gels and a complex growth medium. The medium contains a 1:1 mixture of RPMI-1640 and Ham's F12 supplemented with 7.5% porcine serum and epidermal growth factor, cholera toxin, transferrin, insulin, and hydrocortisone, Under these culture conditions the cells show rapid log-phase growth and high saturation densities while retaining the ultrastructural characteristics of immature squamous metaplastic cells of the rat uterine cervix even after extended passage. In a manner similar to epithelial cells from a variety of sources, rat cervical epithelial cells form hemicysts at confluence in vitro when cultured on impermeable substrates. The development of these methods for culturing cervical epithelial cells provides an experimental system for the study of factors important in regulating the growth and differentiation of metaplastic squamous epithelial cells.
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