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  • 1995-1999  (3)
  • Human P450  (1)
  • IDDQ testing  (1)
  • Key words Cytochrome P450   (1)
  • 1
    Electronic Resource
    Electronic Resource
    Roles of CYP2A6 and CYP2B6 in nicotine C-oxidation by human liver microsomes (1999)
    Springer
    Archives of toxicology 73 (1999), S. 65-70 
    Details
    ISSN: 1432-0738
    Keywords: Key words Nicotine ; CYP2A6 ; CYP2B6 ; Human P450 ; Liver microsomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Nicotine C-oxidation by recombinant human cytochrome P450 (P450 or CYP) enzymes and by human liver microsomes was investigated using a convenient high-performance liquid chromatographic method. Experiments with recombinant human P450 enzymes in baculovirus systems, which co-express human nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH)-P450 reductase, revealed that CYP2A6 had the highest nicotine C-oxidation activities followed by CYP2B6 and CYP2D6; the K m values by these three P450 enzymes were determined to be 11.0, 105, and 132 μM, respectively, and the V max values to be 11.0, 8.2, and 8.6 nmol/min per nmol P450, respectively. CYP2E1, 2C19, 1A2, 2C8, 3A4, 2C9, and 1A1 catalysed nicotine C-oxidation only at high (500 μM) substrate concentration. CYP1B1, 2C18, 3A5, and 4A11 had no measurable activities even at 500 μM nicotine. In liver microsomes of 16 human samples, nicotine C-oxidation activities were correlated with CYP2A6 contents at 10 μM substrate concentration, whereas such correlation coefficients were decreased when the substrate concentration was increased to 500 μM. Contribution of CYP2B6 (as well as CYP2A6) was demonstrated by experiments with the effects of orphenadrine (and also coumarin and anti-CYP2A6) on the nicotine C-oxidation activities by human liver microsomes at 500 μM nicotine. CYP2D6 was found to have minor roles since quinidine did not inhibit microsomal nicotine C-oxidation at both 10 and 500 μM substrate concentrations. These results support the view that CYP2A6 has major roles for nicotine C-oxidation at lower substrate concentration and both CYP2A6 and 2B6 play roles at higher substrate concentrations in human liver microsomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050588
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Cytochrome P450-dependent drug oxidation activities in liver microsomes of various animal species including rats, guinea pigs, dogs, monkeys, and humans (1997)
    Springer
    Archives of toxicology 71 (1997), S. 401-408 
    Details
    ISSN: 1432-0738
    Keywords: Key words Cytochrome P450  ;  CYP  ;  Species  ;   Drug metabolism  ;  Liver microsomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Levels of cytochrome P450 (P450 or CYP) proteins immunoreactive to antibodies raised against human CYP1A2, 2A6, 2C9, 2E1, and 3A4, monkey CYP2B17, and rat CYP2D1 were determined in liver microsomes of rats, guinea pigs, dogs, monkeys, and humans. We also examined several drug oxidation activities catalyzed by liver microsomes of these animal species using eleven P450 substrates such as phenacetin, coumarin, pentoxyresorufin, phenytoin, S-mephenytoin, bufuralol, aniline, benzphetamine, ethylmorphine, erythromycin, and nifedipine; the activities were compared with the levels of individual P450 enzymes. Monkey liver P450 proteins were found to have relatively similar immunochemical properties by immunoblotting analysis to the human enzymes, which belong to the same P450 gene families. Mean catalytic activities (on basis of mg microsomal protein) of P450-dependent drug oxidations with eleven substrates were higher in liver microsomes of monkeys than of humans, except that humans showed much higher activities for aniline p-hydroxylation than those catalyzed by monkeys. However, when the catalytic activities of liver microsomes of monkeys and humans were compared on the basis of nmol of P450, both species gave relatively similar rates towards the oxidation of phenacetin, coumarin, pentoxyresorufin, phenytoin, mephenytoin, benzphetamine, ethylmorphine, erythromycin, and nifedipine, while the aniline p-hydroxylation was higher and bufuralol 1′-hydroxylation was lower in humans than monkeys. On the other hand, the immunochemical properties of P450 proteins and the activities of P450-dependent drug oxidation reactions in dogs, guinea pigs, and rats were somewhat different from those of monkeys and humans; the differences in these animal species varied with the P450 enzymes examined and the substrates used. The results presented in this study provide useful information towards species-related differences in susceptibilities of various animal species regarding actions and toxicities of drugs and xenobiotic chemicals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050403
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    A Low-Loss Built-In Current Sensor (1999)
    Springer
    Journal of electronic testing 14 (1999), S. 39-48 
    Details
    ISSN: 1573-0727
    Keywords: Built-in current sensor ; IDDQ testing ; low-voltage LSIs ; multiple power supplies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper presents a novel built-in current sensor that uses two additional power supply voltages besides the system power supply voltage, and that is constructed by using a current mirror circuit to pick up an abnormal IDDQ. It is activated only by an abnormal quiescent power supply current and minimizes the voltage drop at the terminal of the circuit under test. Simulation results showed that it could detect 16-μA IDDQ against 0.03-V voltage drop at 3.3-V VDD and that it reduced performance degradation in the circuit under test. It is therefore suitable for testing low-voltage integrated circuits. Moreover, we verified the behavior of the sensor circuit implemented on the board by using discrete devices. Experimental results showed that the real circuit of the sensor functioned properly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008393104650
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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