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  • fibroblasts  (2)
  • transepithelial electrical resistance  (2)
  • 1
    Electronic Resource
    Electronic Resource
    UVB radiation affects the mobility of epidermal growth factor receptors in human keratinocytes and fibroblasts (1996)
    Springer
    Bioscience reports 16 (1996), S. 227-238 
    Details
    ISSN: 1573-4935
    Keywords: Ultraviolet light B ; reactive oxygen species ; EGF receptors ; keratinocytes ; fibroblasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Growth factor receptors transmit biological signals for the stimulation of cell growth in vitro and in vivo and their autocrine stimulation may be involved in tumorigenesis. It is therefore, of great value to understand receptor reactions in response to ultraviolet (UV) light which certain normal human cells are invaribly exposed to during their growth cycle. UV irradiation has recently been shown to deplete antioxidant enzymes in human skin. The aims of the present study were a) to compare the lateral mobility of epidermal growth factor receptors (EGF-R) in cultured human keratinocytes and human foreskin fibroblasts, b) to investigate effects of ultraviolet B radiation on the mobility of EGF-R in these cells, and c) study the response of EGF-R on addition of antioxidant enzymes. The epidermal growth factor receptors were labeled with rhodaminated EGF, the lateral diffusion was determined and the fraction of mobile EGF-R assessed with the fluorescence recovery after photobleaching (FRAP). We found that human keratinocytes display a higher basal level of EGF-R mobility than human skin fibroblasts, viz. with diffusion coefficients (D ± standard error of the mean, SEM) of 4.2±0.2 × 10−10 cm2/s, and 1.8±0.2 × 10−10 cm2/s, respectively. UVB-irradiated fibroblasts showed an almost four-fold increase in the diffusion coefficient; D was 6.3±0.3 × 10−10 cm2/s. The keratinocytes, however, displayed no significant increase in receptor diffusion after irradiation; D was 5.1±0.8 × 10−10 cm2/s. In both cell types the percentage of EGF-R fluorescence recovery after photobleaching, i.e. the fraction of mobile receptors, was significantly increased after irradiation. In keratinocytes it increased from 69% before irradiation to 78% after irradiation. Analogous figures for fibroblasts were 61% and 73%. The effect of UVB on fibroblast receptors was abolished by prior addition of superoxide dismutase (SOD) and catalase (CAT). It is concluded that UVB radiation of fibroblasts and keratinocytes can affect their biophysical properties of EGF-R. The finding that addition of antioxidant enzymes prevented the UVB effect in fibroblasts may indicate the involvement of reactive oxygen metabolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01207337
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Studies with wortmannin and cytochalasins suggest a pivotal role of phosphatidylinositols in the regulation of tight junction integrity (1996)
    Springer
    Bioscience reports 16 (1996), S. 265-272 
    Details
    ISSN: 1573-4935
    Keywords: Wortmannin ; cytochalasin B ; dihydrocytochalasin B ; MDCK-I cells ; transepithelial electrical resistance ; F-actin ; phosphatidylinositols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Wortmannin, a selective inhibitor of phosphatidylinositol 3-kinase (P13K), was found to give a dose and time-dependent, bimodal effect-initial increase, followed by decrease on the tight junction integrity of MDCK-1 monolayers, as assessed by electrical resistance measurement of the epithelia. Moreover, dihydrocytochalasin B inhibited the wortmannin-induced alteration, whereas cytochalasin B had a negligible influence on the wortmannin effect. Wortmannin was also found to cause changes in the cytoskeleton structure. These alterations were also seen when wortmannin was combined with cytochalasin B. However, in accordance with the electrical resistance measurements, dihydrocytochalasin B was able to abolish wortmannin-induced filamentous (F-) actin changes. These findings suggest that the P13K, phosphatidylinositols, and filamentous actin rearrangements, in combination, play an important role in the modulation of the junctional integrity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01207340
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  • 3
    Electronic Resource
    Electronic Resource
    Modulation of the junctional integrity by low or high concentrations of cytochalasin B and dihydrocytochalasin B in associated with distinct changes in F-actin and ZO-1 (1996)
    Springer
    Bioscience reports 16 (1996), S. 313-326 
    Details
    ISSN: 1573-4935
    Keywords: cytochalasin B ; dihydrocytochalasin B, MDCK-I cells ; transepithelial electrical resistance ; ZO-1 ; F-actin ; tight junction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In a study of Necturus gallbladder epithelium Benzel et al. (Benzel et al., 1980) found that low (0.2–1.2 μM) and higher concentrations (1.5 μM and more) of cytochalasin B (CB) caused an increase and decrease in the transepithelial electrical resistance (TER), respectively. Moreover, there were slight changes in the height and complexicity of tight junction (TJ) strands, as visualized by freeze-fracture and freeze-etching. To elucidate the mechanisms of these findings, we first demonstrated that the effect is also present in monolayers of Madin-Darby Canine Kidney strain I (MDCK-I) cells. Thus, a low concentration (0.1 ng/ml) cytochalasin B (CB) strengthened the permeability barrier, as evidenced quantitatively by increases in TER on transepithelial electrical measurements. Furthermore, indirect immunofluorescence and confocal microscopy demonstrated that this effect was paralleled with an accumulation of F-actin and the tight junction marker protein, ZO-1, at the level of TJ. Equimolar concentrations of dihydrocytochalasin B (dhCB), on the other hand, did not lead to a tightening of the epithelium. Confirming previous studies, there was a general decrease in epithelial resistance after treatment with high concentrations (1 μg/ml) of CB and dhCB, which was accompanied by distinct changes in the F-actin network and distribution of ZO-1. We speculate that the divergent effects of CB and dhCB on the F-actin and ZO-1 organization might be due to specific effects on the transport of monosaccharides across the plasma membrane, or that CB and dhCB in distinct ways involve the turnover of phosphatidylinositols in the membrane, thereby modulating junctional permeability and F-actin structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01855015
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Lateral diffusion of plasma membrane receptors labelled with either platelet-derived growth factor (PDGF) or wheat germ agglutinin (WGA) in human polymorphonuclear leukocytes and fibroblasts (1989)
    Springer
    Bioscience reports 9 (1989), S. 63-73 
    Details
    ISSN: 1573-4935
    Keywords: diffusion ; membrane receptors ; platelet-derived growth factor (PDGF) ; wheat germ agglutinin (WGA) ; polymorphonuclear leukocytes (PMNL) ; fibroblasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The aims of the present investigation were (a) to compare the lateral mobility of membrane receptors of human fibroblasts and polymorphonuclear leukocytes (PMNL) labelled with either platelet-derived growth factor (PDGF), or the lectin wheat germ agglutinin (WGA), and (b) to study effects of serum or PDGF on the mobility of these receptor molecules in human fibroblasts. Human foreskin fibroblasts (AG 1523) were grown on coverslips either under standard (10%) or under serum-free conditions yielding “normal” and “starved” cells, respectively. The receptor mobility was studied in response to exposure to PDGF, or serum, in short time or prolonged incubations. Human polymorphonuclear leukocytes (PMNL) were adhered to microscope slides by clotting drops of blood. They were stained with rhodaminated PDGF or fluoresceinated WGA. The diffusion of labelled receptors was assessed with fluorescence recovery after photobleaching (FRAP). It was found that (a) fibroblasts grown at normal serum concentration had a lower diffusion coefficient (D=3×10−10 cm2 s−1) for the PDGF-receptor and a slightly lower mobile fraction (R=60%) than starved cells (D=5×10−10 cm2s−1 and R=73%), (b) addition of serum to starved cells increased both D and R for the PDGF receptor to 12×10−10 cm2 s−1 and 96%, respectively, (c) a similar pattern was obtained for WGA-labelled glycoconjugates indicating general membrane effects of serum-induced cell stimulation, and (d) in PMNL the PDGF receptor displayed motility characteristics (D=3–4×10−10 cm2 s−1 and R=59%) similar to those in fibroblasts, possibly suggesting equivalent anchorage mechanisms in the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01117512
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    Paper (German National Licenses)
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