Search PubMed⌕ Search

Biomedical subjects

V Graef

Publications and source records attributed to V Graef.

At least 55 records · Page 3Linked to original sources
PubMed1977

Hydrolysis of steroid glucuronides with beta-glucuronidase preparations from bovine liver, Helix pomatia, and E. coli.

We determined the enzymic activity of beta-glucuronidase preparations from bovine liver, Helix pomatia, and Escherischia coli with steroid glucuronides and nonsteroid glucuronides as substrates. We also studied the effect of Na2SO4 on the enzymic hydrolysis of several substrates with the three preparations of beta-glucuronidase. Na2SO4 increases the rate of hydrolysis of all substrates with beta-glucuronidase from bovine liver. Hydrolysis of a steroid glucoronide with beta-glucuronidase from Helix pomatia and E. coli is inhibited by Na2SO4. None of the three enzyme preparations gives complete hydrolysis of urinary steroid conjugates, because urine contains inhibitors, which can be removed by absorption chromatography of the urine on a column of neutral polystyrene resin Amberlite XAD-2. But when Amberlite XAD-2 is not used, hydrolysis of urinary glucuronides of androsterone, etiocholanolone, pregnanediol, estriol, and 17-hydroxycorticosteroids proves that, given an incubation time of 24 h, the beta-glucuronidase preparation from bovine liver, in the presence of Na2SO4, is suited for determining all of the above steroids except esriol; the preparation from Helix pomatia is good for determining estriol and 17-hydroxycorticosteroids; the preparation from E. coli is good for determining androsterone, 17-hydroxycorticosteroids, and especially estriol, the glucuronide, of which is maximally hydrolyzed in 2 h.

17-Hydroxycorticosteroids↗
PubMed1976

[Determination of lead in beard hair by atomic absorption spectrometry (author's transl)].

The lead content of hair from the electric razor can be determined by atomic absorption spectrometry, using the micro-sampling technique of Delves. 1--5 mg of the washed and dried hair are partially oxidized with hydrogen peroxide prior to analysis. The method is simple and quick and therefore suited for the serial investigation of persons exposed to lead.

Environmental Exposure↗
PubMed1975

[Decomposition of steroids during incubation with beta-glucuronidase and during storage of urine].

Androsterone, etiocholanolone, pregnanetriol, dehydroepiandrosterone, pregnanediol, tetrahydrocortisol, 5-pregnenolone and 11-beta-OH-androsterone were incubated with beta-glucuronidase preparations (Helix pomatia, bovine liver and E. coli) for 96 hrs at 37 degrees C. After extraction and silylation they were gas-chromatographed. The first 3 steroids were left practically intact. The least decomposition of the last 5 steroids occurred with the liver enzyme. Testosterone and 11-ketoandrosterone without the enzymes showed 74 and 35% recoveries. Cortisol and tetrahydrocortisol, incubated with the first two enzymes for 18 hrs at 37 degrees and 48 degrees C, showed nearly 100% recoveries. The recoveries of 17-OHCS in urines (pH 7.8-8.8), stored for 7 days, was 80% at 20 degrees-25 degrees C and 55% at 25 degrees-30 degrees C. The same samples, brought to pH 1.8-2.8 WITH NaHSO4 before the storage, showed a 100% recovery.

17-Hydroxycorticosteroids↗
PubMed1975

[Studies on the complete enzymatic hydrolysis of steroid conjugates in urine (author's transl)].

The incubation of urine with beta-glucuronidase/arylsuphatase from Helix pomatia results in the incomplete hydrolysis of urinary steroid conjugates, because inhibitors of these enzymes are present in urine; The inhibitors can be separated from the steroid conjugates by chromatography of the urine on a column of Amberlite XAD-2. By this method a complete enzymatic hydrolysis of urinary steroid conjugates is possible in 24 hours at 37 degrees C or in 2 hours at 55 degrees C.

Androsterone↗
PubMed1975

[The metabolism of delta4-3-oxosteroids in rat liver].

The enzymatic reactions are described by which delta4-3-oxosteroids, specially testosterone, are inactivated in rat liver. The delta4-3-oxosteroid-5 alpha-reductase in liver microsomes was studied intensively and it was found that it is an enzyme system. The 5 alpha-reduction of testosterone with NADPH or with NADH depends upon different enzymes or enzyme systems.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗