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  • activity assay  (2)
  • Adenosine receptors  (1)
  • 2010-2014
  • 1990-1994  (3)
  • 1965-1969
  • 1
    Electronic Resource
    Electronic Resource
    Development of Activity Assays for High-Volume Evaluation of Human Immunodeficiency Virus (HIV) Protease Inhibitors in Rat Serum: Results with Ditekiren (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 562-566 
    Details
    ISSN: 1573-904X
    Keywords: rat ; serum ; human immunodeficiency virus protease inhibitor ; activity assay ; scintillation proximity assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We showed previously that a commercially available synthetic tetradecapeptide, Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Leu-Val-Tyr-Ser, produces authentic angiotensin I (Ang I) upon incubation with the HIV-1 protease (S. K. Sharma et al., Anal. Biochem. 198:363, 1991). Therefore, we developed an Ang-I based activity assay for HIV protease inhibitors based on the technology developed earlier (M. J. Ruwart et al., Pharm. Res. 7:407, 1990; S. K. Sharma et al., Anal. Biochem. 186:24, 1990) for tracking renin inhibitors in rat sera. Ditekiren was either extracted from sera with ethyl acetate or assayed after the interfering substances in sera were precipitated with acetonitrile. Purified recombinant HIV-1 protease was added to extracted rat serum and the enzymatic reaction was initiated in the presence of the tetradecapeptide substrate. The inhibition of Ang I production was measured by a commercially available RIA kit. The cleanup methodology also enabled a commercially available Proteinase Scintillation Proximity Assay (SPA, Amersham) to quantify ditekiren in rat serum through the addition of recombinant HIV-1 protease and cleavage of substrate from SPA beads. Results were confirmed by HPLC or by the renin assay for ditekiren, which inhibits both aspartyl proteases. These technologies should prove useful for assessing serum levels of HIV protease inhibitors in rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018950003185
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence for the presence of A1 and A2 adenosine receptors in the ventral aorta of the dogfish shark, Squalus acanthias (1992)
    Springer
    Journal of comparative physiology 162 (1992), S. 179-183 
    Details
    ISSN: 1432-136X
    Keywords: Adenosine receptors ; Aortic smooth muscle ; dogfish shark, Squalus acanthias
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Isolated, endothelium-free rings of vascular smooth muscle (VSM) from the ventral aorta of the dogfish shark, Squalus acanthias, were used to examine the vasoactive effects of various adenosine agonists. Cumulative addition of 2-chloroadenosine (2 Cl-ADO) over the concentration range 10 nM–1 mM resulted in a biphasic response, with a significant increase in tension at 1 μM and a more significant decline in tension at 100 μM and 1 mM, suggesting that this tissue may possess both A1 and A2 adenosine receptors. N6-Cyclopentyladenosine (N-6 CPA) and N6-(2-phenylisopropyl)adenosine, R(-)isomer (R-PIA), generally considered to be more A1 specific, also produced slight, but significant increases in tension, but only at relatively high concentrations. The more specific A1 agonist, N6-(25)-[2-endo-norbonyl] adenosine [(S)-ENBA] produced a significant increase in tension at 1 pM, reaching 28% above control at 10 nM. The response to (S)-ENBA was also biphasic, with a fall in tension at 10 μM. The relatively non-specific agonist 5′-N-ethylcarboxamidoadenosine (NECA) produced a small, but significant, increase in tension at 1 μM, with no subsequent decline in tension at higher concentrations. These results allow us to assign a tentative structure-activity relationship (SAR) for an increase in tension of (S)-ENBA≫R-PIA≥2-Cl ADO=N-6 CPA=NECA; for the decrease, the SAR is (S)-ENBA〉2-Cl ADO〉R-PIA〉N-6 CPA=NECA. These SARs are consistent with the hypothesis that the VSM from the ventral aorta of this elasmobranch fish contains both A1 and A2 adenosine receptors. This is the first such description of both adenosine receptors in fish VSM. The role of a putative release of adenosine from the fish heart on branchial hemodynamics remains to be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398345
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  • 3
    Electronic Resource
    Electronic Resource
    Development of a Sensitive Activity Assay for High-Volume Evaluation of Human Renin Inhibitory Peptides in Rat Serum: Results with U-71,038 (1990)
    Springer
    Pharmaceutical research 7 (1990), S. 407-410 
    Details
    ISSN: 1573-904X
    Keywords: human renin inhibitory peptide ; rat ; activity assay ; angiotensin I ; serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A sensitive activity assay for high volume evaluation of human renin inhibitory peptides (RIPs) in rat sera (range 2–80 ng/ml) was developed based on the low affinity of RIPs to rat renin and their high affinity to human renin. The utility of this activity assay was tested by measuring concentrations of a human RIP, U-71,038 (BOC-Pro-Phe-N-MeHis-Leu Ψ [CHOHCH2]Val-Ile-Amp), in rat sera, determined by the activity assay, by a sensitive radioimmunoassay (RIA), and by tracking tritiated drug. Rats were given radiolabeled drug as an intravenous bolus, and blood samples were collected at various times after dosing. The serum level of U-71,038 equivalents was determined by the three techniques. Whole blood was also counted for total radioactivity to evaluate the potential for U-71,038 incorporation into red blood cells. Results from the three serum assays indicate good agreement between the calculated U-71,038 equivalents for the 30 min and 1 hr collection times. The 2 and 4 hr collection times show excellent agreement for the activity assay and RIA; [3H]-U-71,038 determinations gave substantially higher values. Serum levels for U-71,038 determined 30 min after dosing averaged less than 300 ng equivalents/ml suggesting that less than 1% of the administered dose was in the systemic circulation at that time. Thus, U-71,038 was rapidly cleared. At the 4 hr collection time, the level of U-71,038 equivalents, as determined by activity assay and RIA, was ten times the in vitro IC50 for the renin inhibitory activity of U-71,038. Analysis of whole blood levels of 3[H]-U-71,038 indicated little or no incorporation of drug related material into red blood cells. In addition to predicting pharmacological response, the activity assay can be used to quantify human RIPs in rat serum when biotransformation is absent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015883709275
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