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  • 1
    Electronic Resource
    Electronic Resource
    Calcitriol effect on natural killer cells from hemodialyzed and normal subjects (1995)
    Springer
    Calcified tissue international 56 (1995), S. 113-117 
    Details
    ISSN: 1432-0827
    Keywords: Calcitriol ; Chronic renal failure ; Cytotoxicity ; Natural killer ; PTH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Patients with chronic renal failure have a decreased secretion of calcitriol (CTR). They also show an impaired cellular immune response including a defective natural killer (NK) cell-mediated activity. The aim of this study was to analyze, in vivo and in vitro, the effect of CTR on NK cell cytotoxicity in healthy control subjects and in hemodialyzed (HD) patients. Our results show that HD patients had baseline-depressed NK cell activity when compared with controls (P〈0.001), which increased significantly after 1 month of oral CTR treatment (0.5 μg/day) (P〈0.001). Calcitriol treatment also induced a significant increase in CTR serum levels (P〈0.001) and a significant decrease (P〈0.001) in total parathyroid hormone (PTH). In vitro CTR treatment (10-7 M) of peripheral blood mononuclear cells (PBMC) increased NK cell-mediated cytotoxicity after 24 hours of incubation with a maximum at 48 hours (P〈0.001). In vitro CTR treatment at doses of 10-11 and 10-9 M did not significantly increase NK cytotoxic activity. The enhanced NK activity after CTR treatment was not the consequence of increased numbers of CD56 positive cells, nor to lymphocyte activation, as tested by the expression of the interleukin 2 receptor p55 α chain (CD25) on their surface. In vitro treatment of PBMC from HD patients with CTR (10-7 M, during 48 hours) also induced a strong increase in NK cell cytotoxicity (P〈0.001). These results demonstrate a positive role of CTR in the stimulation of NK cell activity and support the hypothesis of a direct steroid-mediated action of CTR on NK cells, although an indirect effect mediated by the CTR-induced PTH decrease in vivo cannot be excluded. Our data also raise the possibility for potential therapeutic uses of this hormone in immunomodulation of patients with depressed NK cell activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296341
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ascorbate Increases the 1,25 Dihydroxyvitamin D3-Induced Monocytic Differentiation of HL-60 Cells (1996)
    Springer
    Calcified tissue international 59 (1996), S. 277-282 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Ascorbate — Calcitriol — 1,25 Dihydroxyvitamin D3— Leukemia — HL-60 — Cell Differentiation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. 1,25 Dihydroxyvitamin D3 (calcitriol) induces differentiation of HL-60 leukemia cells. We studied the in vitro effect of a physiological concentration of ascorbate as potentiator of 1,25 dihydroxyvitamin D3 [(OH)2D3] activity by determining different markers of differentiation: nitroblue tetrazolium reduction, nonspecific esterase activity, and the expression of CD11b and CD14 surface antigens. Nitroblue tetrazolium reduction and nonspecific esterase activity increased up to 50% in the presence of both 1,25 (OH)2D3 plus 0.2 mM ascorbate (ASC), compared with (OH)2D3 as a unique agent. ASC also increased the expression of specific surface antigens (CD11b and CD14) during differentiation induced by 1,25 (OH)2D3, the effect being more pronounced after 48 hours of treatment with 10−8 M 1,25 (OH)2D3. Furthermore, 1,25 (OH)2D3 alone increased intracellular cAMP level during differentiation, and the addition of ASC increased its concentration from 60 to 100% above the level reached with 1,25 (OH)2D3 as unique agent. ASC did not enhance the antiproliferative effect of calcitriol, suggesting that it only affects the ability of 1,25 (OH)2D3 to promote differentiation of HL-60 cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900123
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  • 3
    Electronic Resource
    Electronic Resource
    Aminopropyl-silica as an advantageous alternative to nonpolar sorbents for continuous cleanup/preconcentration of vitamin D3 metabolites (1998)
    Springer
    Chromatographia 47 (1998), S. 367-372 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Aminopropyl-silica sorbent ; Continuous cleanup/preconcentration ; Hydroxyvitamin D3 metabolites ; Flow injection analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new procedure for continuous cleanup and concentration of hydroxyvitamin D3 metabolites prior to their separation by HPLC and UV-detection is reported. The process is based on the use of aminopropyl-silica as solid-phase sorbent as an alternative to the use of nonpolar sorbents. The improvement thus achieved has been tested by comparing the results with those obtained using octadecyl-C18 as non-polar sorbent. The comparison has been based on the calibration graphs (linear range, detection and quantitation limits), precision and multiple standard addition method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466466
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    Paper (German National Licenses)
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