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  • interaction  (2)
  • moxalactam  (2)
  • Microdissected nephron segment  (1)
  • 1
    ISSN: 1432-2013
    Keywords: Renal gluconeogenesis ; Chronic metabolic acidosis ; Potassium depletion ; Microdissected nephron segment ; Superficial nephron ; Juxtamedullary nephron ; Nephron heterogeneity ; Substrate specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The intra- and inter-nephron heterogeneity of renal gluconeogenesis within rat proximal tubules and the effects of chronic metabolic acidosis and chronic potassium(K)-depletion were studied using isolated proximal tubules of rats by directly measuring glucose synthesized. The gluconeogenic activity from pyruvate and glutamine in control rats was almost limited to within the early proximal tubule (S1: 45.4±5.7 pmol/mm/60 min from pyruvate; 58.0±6.0 from glutamine). Very low, but detectable gluconeogenesis was observed in the middle portion of the proximal tubule (S2:9.9±2.2 from pyruvate; 4.8±1.1 from glutamine). The rate of glucose production in the terminal proximal tubule (S3) was negligible. Furthermore, gluconeogenesis from glutamine of superficial (SF) nephrons was significantly higher than that of juxtamedullary (JM) ones, whereas no difference was seen in gluconeogenesis from pyruvate. In acidotic and K-depleted rats, significant increase could be seen in S1 and S2, but the increase in S3 was not significant. By the serial determination in acidosis, the glucose production from both substrates was found to be the highest at the second 1 mm segment from the glomerulus, and it decreased downward along the proximal tubule. In acidosis, glucose production from both substrates in SF nephrons and that from glutamine in JM ones were elevated significantly compared with the control, but that from pyruvate in JM nephrons did not change. These results suggest that S1 of the SF nephron plays the most important role in gluconeogenesis in the control, whereas S1 of the JM nephron and S2 contribute to gluconeogenesis in acidotic and/or possibly K-depleted rats.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 7 (1990), S. 364-369 
    ISSN: 1573-904X
    Keywords: moxalactam ; epimerization ; frozen plasma ; frozen urine ; electrolyte ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The epimerization of moxalactam (LMOX) in frozen urine and plasma samples was studied during long-term storage. The R/S ratio at equilibrium [(R/S)eq] at −10°C was similar in urine and in rat and human plasma ultrafiltrate but differed from that in water. The (R/S)eq values in human plasma and its ultrafiltrate differed slightly, while they were the same in rat plasma and in its ultrafiltrate. The difference for the human plasma and ultrafiltrate may result from differences in plasma protein binding between R- and S-epimers in the liquid region of the frozen plasma. The change of R/S ratio in frozen human plasma continued below the collapse temperature of LMOX aqueous solution, where the liquid region appeared still to exist as determined by NMR measurement. Consequently, the biological LMOX samples should be preserved at or below −70°C to prevent changes in the R/S ratio.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: moxalactam ; epimerization ; frozen solution ; ice ; activation energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The epimerization rate constants of R- and S-epimers of moxalactam (LMOX) in a frozen aqueous solution decreased as the temperature decreased. The reaction proceeded in the unfrozen region remaining in the frozen solution, without being affected by the ice. The reaction stopped completely below the collapse temperature of the LMOX aqueous solution. The ratio of R- and S-epimers at equilibrium, which was equal to the ratio of the epimerization rate constant, increased as the temperature decreased. This change in the ratio at equilibrium could be ascribed to the difference in the activation energy between the two epimers.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 643-649 
    ISSN: 0899-0042
    Keywords: ibuprofen ; stereoselective ; binding ; HSA ; interaction ; fluorescent ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Binding of ibuprofen (IB) enantiomers to human serum albumin (HSA) was studied using a chiral fluorescent derivatizing reagent, which enabled the measurement of IB enantiomers at a concentration as low as 5 × 10-8 M. Scatchard analyses revealed that there were two classes of binding sites for both enantiomers. For the high affinity site, the number of the binding sites was one for both enantiomers, and the binding constant of R-IB was 2.3-fold greater than that of S-IB. The difference in the affinity at the high affinity site may result in the stereoselective binding of IB enantiomers at therapeutic concentrations. It was confirmed that the high affinity site of IB enantiomers is Site II (diazepam binding site) by using site marker ligands. Also, significant enantiomer-enantiomer interactions were observed in the binding. The binding data were quantitatively analyzed and a binding model with an assumption of competitive interactions only at the high affinity site simulated the binding characteristics of IB enantiomers fairly well. Chirality 9:643-649, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 201-206 
    ISSN: 0899-0042
    Keywords: carbenicillin ; stereoselective ; binding ; HSA ; interaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Binding of carbenicillin (CBPC) epimers to human serum albumin (HSA) was found to be stereoselective. Epimer-epimer interaction was also observed in the binding to HSA. There were at least three binding sites on HSA for CBPC epimers, one of which (stereoselective site) was more in favor of S-CBPC than R-CBPC. At the stereoselective site, the binding constant of S-CBPC was approximately 4-fold greater than that of R-CBPC. The affinities to other binding sites (non-stereoselective sites) were similar between the epimers, and the affinity of S-CBPC of the non-stereoselective sites was much smaller than that for the stereoselective site.R-CBPC and S-CBPC appeared to displace each other at all the binding sites, i.e., the binding of the epimers was competitive at the non-stereoselective sites as well as at the stereoselective site. By using site marker ligands, it was revealed that CBPC epimers may bind to Site I (warfarin binding site), but not to Site II (diazepam binding site). A binding model with an assumption of competitive interactions at all the binding sites simulated the binding characteristics of CBPC epimers fairly well. © 1996 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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