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Biomedical subjects

G Urban

Publications and source records attributed to G Urban.

64 records · Page 4Linked to original sources
PubMed1978

[Biochemical and hematological measures for determination of folate status in humans. 2. Comparative determination of folate in blood and in erythrocytes].

Criteria to judge the folate supply have been evaluated in previous studies. The present study is examining parameters to estimate the degree of folate deficiency. Serum folate levels and erythrocyte folate concentrations were measured in 116 volunteers (patients). The erythrocyte folate is to a large extend independent of exterior supply and is lowered only in severe chronic deficiency. Low levels of erythrocyte folate indicate longstanding undersupply. Our experiments show that folate concentration of greater than 250 ng per ml erythrocytes indicate adequate supply. Concentrations below this limit are characteristic for chronic folate deficiency. To confirm this statement further studies will take into account the urine concentration of formiminoglutamic acid.

Adult↗
PubMed1975

[Female constitution and tolerance of pills (author's transl)].

In a retrospective study on 526 patients in a family-planning clinic the significance of physical constitution type and pill-tolerance was examined. If only one type of pill was administered statistically significant differences in the tolerance were not evident. When several types of pills were tried because of undesirable side-effects of a single pill a significantly higher tolerance of pills with a balanced hormone-composition could be demonstrated. The latter kind of pills was better tolerated by students than by salaried employees. This could be explained by an increased readiness for family-planning among undergraduate students. A correlation between physical constitution and pill tolerance could not be found in this statistical analysis and the widespread use of this criterion is questioned by the authors.

Body Constitution↗
PubMedDate not supplied

Metabolism of the chlorofluorocarbon substitute 1,1-dichloro-2,2,2-trifluoroethane by rat and human liver microsomes: the role of cytochrome P450 2E1.

1,1-Dichloro-2,2,2-trifluoroethane (HCFC-123) has been developed as a substitute for ozone-depleting chlorofluorocarbons. The atmospheric lifetime of HCFC-123 is expected to be much shorter than those of chlorofluorocarbons; however, due to its lower stability and the presence of carbon-hydrogen bonds, metabolism of HCFC-123 in mammals and metabolism-dependent toxicity is likely. We compared the metabolism of HCFC-123 and its analog halothane in rat and human liver microsomes. 19F-NMR studies showed that trifluoroacetic acid is a major metabolite of HCFC-123. Besides trifluoroacetic acid, chlorodifluoroacetic acid and inorganic fluoride were identified as products of the enzymatic oxidation of HCFC-123 in rat and human liver microsomes by 19F-NMR and mass spectrometry. The metabolites were not detected in incubations with halothane. HCFC-123 and halothane were transformed by liver microsomes from untreated rats at low rates. Microsomes from ethanol-and pyridine-treated rats metabolized both HCFC-123 and halothane at much higher rates. These microsomes also exhibited high rates of p-nitrophenol oxidation. p-Nitrophenol is a model substrate mainly oxidized by P450 2E1 to p-nitrocatechol. Samples of human liver microsomes showed considerable differences in the extent of HCFC-123, p-nitrophenol oxidation, and chlorzoxazone hydroxylation. In human liver microsomes, rabbit anti-rat P450 2E1 IgG recognized a single protein band corresponding in apparent molecular weight to human P450 2E1. Immunoblot analysis revealed considerable heterogenity in the P450 2E1 protein content of the human liver samples. Trifluoroacetic acid formation from HCFC-123 and halothane and p-nitrocatechol formation from p-nitrophenol were significantly reduced by the P450 2E1 inhibitor diethyldithiocarbamate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Gas-uptake pharmacokinetics of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123).

The in vivo metabolic rate constants for the metabolism of the chlorofluorocarbon replacement 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) were determined for both male and female rats with a physiologically based pharmacokinetic model. Uptake studies with 500-5,000 ppm HCFC-123 indicated that a single saturable component was involved in both sexes, and no significant differences were observed in in vivo metabolic rate constants between male and female rats. The in vivo metabolic rate constants obtained from computer simulation studies were: for male rats--KM = 1.2 mg liter-1 (7.85 mumol liter-1) and Vmaxc = 7.20 +/- 0.28 mg kg-1 hr-1 (47.1 +/- 1.83 mumol kg-1 hr-1); for female rats--KM = 1.2 mg liter-1 (7.85 mumol liter-1) and Vmaxc = 7.97 +/- 0.30 mg kg-1 hr-1 (52.1 +/- 1.96 mumol kg-1 hr-1). The physiologically based pharmacokinetic model failed to simulate the reduction in HCFC-123 uptake in female rats at 2,000-5,000 ppm. The production and excretion of trifluoroacetic acid, the major urinary metabolite of HCFC-123, was also predicted by the physiologically based pharmacokinetic model with in vivo metabolic rate constants obtained in the gas-uptake simulation studies. Diallyl sulfide, a selective, mechanism-based inhibitor of cytochrome P450 2E1, inhibited the metabolism of HCFC-123, as indicated by a decreased uptake of HCFC-123 and by a lowered urinary excretion of trifluoroacetic acid in diallyl sulfide-treated rats.

Administration, Oral↗
PubMedDate not supplied

[Miniature thin layer biosensors which are sensitive to glutamate and glutamine].

Integrated thin film biosensors for simultaneous measurement of L-glutamine and L-glutamate in a micro-flow cell were developed. Due to a novel glutaminase with an activity optimum in the neutral pH range a direct monitoring of glutamine in mammalian cell culture medium could be performed. The glutamine bienzyme sensor was prepared by coimmobilization of glutaminase with glutamate oxidase within a photo patterned poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel membrane. The sensor response is linear in the concentration range of 55 mmol to 10 mmol glutamine/l. Additionally a glutamate biosensor is integrated on the sensor chip for difference measurement of possible glutamate interferences. The sensor chip can be used for at least 300 measurements without any alteration in the performance of its sensors. A new sensor chip with an integrated flow cell provides the possibility of simultaneous measurement of four different parameters at a cell volumina of 1 ml. Completing the microsystem a battery operated surface mounted device (SMD) potentiostat was developed to get a "lab on chip".

Biosensing Techniques↗