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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 83 (2002), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Urotensin-II (U-II), a peptide with multiple vascular effects, is detected in cholinergic neurons of the rat brainstem and spinal cord. Here, the effects of U-II on [Ca2+]i was examined in dissociated rat spinal cord neurons by fura 2 microfluorimetry. The neurons investigated were choline acetyltransferase-positive and had morphological features of motoneurons. U-II induced [Ca2+]i increases in these neurons with a threshold of 10−9 m, and a maximal effect at 10−6 m with an estimated EC50 of 6.2 × 10−9 m. The [Ca2+]i increase induced by U-II was mainly caused by Ca2+ influx from extracellular space, as the response was markedly attenuated in a Ca2+-free medium. Omega-conotoxin GVIA (10−7 m), a N-type Ca2+ channel blocker, largely inhibited these increases, whereas the P/Q Ca2+ channel blocker, omega-conotoxin GVIIC (10−7 m) and the l-type Ca2+ channel blocker, verapamil (10−5 m) had minimal effects. Down-regulation of protein kinase C by 4-α-phorbol 12-myristate 13-acetate (10−6 m) or enzyme inhibition using the specific inhibitor bisindolylmaleimide I (10−6 m) did not inhibit the observed effects. Similarly, inhibition of protein kinase G with KT5823 (10−6 m) or Rp-8-pCPT-cGMPS (3 × 10−5 m) did not modify U-II-induced [Ca2+]i increases. In contrast, protein kinase A inhibitors KT5720 (10−6 m) and Rp-cAMPS (3 × 10−5 m) reduced the response to 25 ± 3% and 42 ± 8%, respectively. Present results demonstrate that U-II modulates [Ca2+]i in rat spinal cord neurons via protein kinase A cascade.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 0269-3879
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: One of the most important problems for the use of liposomes as a drug delivery system is the modification of the vesicle induced by the liquid medium in which they are introduced (blood plasma for in vivo studies and the saline buffer solution for in vitro studies).Using thin-layer chromatography (TLC) we compared the behaviour of phosphatidylcholine (used for liposomes preparation) to that of the following unfilled liposomes: multilamellar liposomes (MLV); small unilamellar vesicles (SUV); and reverse phase evaporation vesicles (REV), before and after storage for 15 min in Krebs-Henseleit solution (37°C, pH 7.4, aereated continuously with 95% O2 + 5% CO2). All variants contained the same amount of phosphatidylcholine.Thin-layer chromatography was performed on silica gel 60 as adsorbant. Two types of solvents were tested: one based on chloroform/alcohol (n-butanol or n-propanol or methanol)/water mixture (in different ratios) and another based on alcohol/alcohol/water mixture (n-butanol/n-propanol/water in 4/3/3 volume ratio). In all variants of chloroform containing solvents no differences were found between phosphatidylcholine and all types of liposomes.When using as solvent n-butanol/n-propanol/water significant differences were found between all types of liposomes before and after storage in Krebs-Henseleit solution. Their presence, after TLC treatment, was shown in electron microscopy studies.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 9 (1995), S. 175-178 
    ISSN: 0269-3879
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The thin-layer chromatographic (TLC) behaviour of liposomes containig inositol phosphates (IPs) was studied. The liposomes contained different concentrations of D-myo-inositol 1, 4, 5-trisphosphate (IP3), D-myo-inositol 1, 2, 6-trisphosphate (α-trinositol, PP 56, a novel Perstorp Pharma derivative), D-myo-inositol 1, 3, 4, 5-tetrakisphosphate (IP4), D-myo-inositol 1, 3, 4, 5, 6-pentakisphosphate (IP5) and D-myo-inositol 1, 2, 3, 4, 5, 6-hexakisphosphate (IP6). Migration of all liposome batches was compared to that of control liposomes (containing only triple-distilled water), and to that of free phosphatidylcholine (PC); the same amount of lipid was used in all situations.Thin-layer chromatography was performed on silica gel as adsorbent. As solvent we used an n-buthanol: ethanol: water mixture in a 4:3:3 volume ratio. Significant differences were found between PC and all liposome batches, as well as between control liposomes and the ones containing IP3, α-trinositol, IP4, or IP5, in various concentrations. Liposomes containing IP6 migrate completely differently compared not only to phosphatidylcholine and control liposomes, but also to the ones containing other IPs (〈10-3 M). Unlike the other IPs studied, liposome-entrapped IP6 elicits dose-independent contractions of the isolated rat aorta. This suggests that liposomes loaded with IP6 undergo, during or after their preparation, physico-chemical alterations that eventually change their drug-delivery capacity.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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