Biomedical subjects

V Graef

Publications and source records attributed to V Graef.

At least 37 records · Page 2Linked to original sources

PubMed1984

Rat liver 3-oxo-5 alpha-steroid delta 4-dehydrogenase. Modulation of enzyme activity by changes in phosphorylation state.

3-Oxo-5 alpha-steroid: NAD+ delta 4-oxidoreductase ("NADH-5 alpha-reductase", EC 1.3.1.?) is rapidly inactivated in the presence of 17 beta-hydroxy-4-androsten-3-one (testosterone). This activation is prevented by increasing the phosphate concentration. When the enzyme assay is carried out in Tris-HCl, only a small activity (1.7 nmol X min-1 X mg-1) is observed which may be further decreased by addition of phosphatases. Addition of the phosphatase inhibitor dextran sulphate or ATP, Mg++ and c-AMP results in a significant increase of activity (228% and 273%, respectively) compared with the Tris-HCl control. Glycerol 2-phosphate and glycerol 3-phosphate have a stabilizing effect on 3-oxo-5 alpha-steroid: NAD+ delta 4-oxidoreductase by decreasing the Km towards the substrate testosterone from 1.2 X 10(-5) mol/l to 3.3 X 10(-6) mol/l. V remains unchanged. Half maximal velocity (testosterone reduction) is achieved with 20 mumol/l glycerol 2-phosphate and glycerol 3-phosphate. Addition of c-AMP dependent protein kinase (EC 2.7.1.37) to a microsomal preparation pretreated with alkaline phosphatase (EC 3.1.3.1) results in a significant increase of 3-oxo-5 alpha-steroid: NAD+ delta 4-oxidoreductase activity compared with the control.

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

PubMed1984

Plasma aldosterone, cortisol and electrolyte concentrations in physical exercise after magnesium supplementation.

Plasma aldosterone, cortisol, sodium (Na), potassium (K), calcium (Ca), magnesium (Mg) as well as urine and sweat Na, K, Ca and Mg concentrations were measured in nine male healthy persons during an one hour ergometer exercise before and after a fourteen day magnesium aspartate (Mg) supplementation. The usual aldosterone and cortisol increase during exercise was not observed and cortisol concentration was significantly lower after Mg supplementation. Na and K in plasma increased during the exercise; these changes were not affected by Mg. The Mg concentration was elevated in plasma and erythrocytes after Mg supplementation. During the ergometer course plasma Mg was unchanged but decreased significantly in the red blood cells. Mg and K concentration in sweat decreased during the exercise. No influence of Mg on urinary electrolyte excretion was observed.

Adolescent↗

PubMed1984

[The effect of allopurinol on testosterone metabolism].

Plasma testosterone, dehydroepiandrosterone, 17-hydroxy-progesterone and estrogens were diminished in male renal stone patients under treatment with allopurinol, whereas urinary testosterone glucuronide was elevated. Since plasma LH (luteinizing hormone) was diminished it is concluded that allopurinol decreases the plasma testosterone level via an inhibition of LH secretion. Also in male rats treated with allopurinol, plasma testosterone and LH concentrations were diminished. The activities of NADPH-5 alpha-reductase and the testosterone hydroxylases in rat liver microsomes were decreased, UDP-glucuronyl transferase activity was elevated. delta 5-3 beta-Hydroxysteroid dehydrogenase/delta 4,5-isomerase and 17 beta-hydroxysteroid dehydrogenase in rat testes were unchanged.

Allopurinol↗

PubMed1983

[5-S-cysteinyldopa determination in the urine. Its value for monitoring in melanoma patients].

In case of uncharacteristic patient complaints or slightly pathologic BSR or liver enzyme levels in patients, suffering from melanoma, the determination of 5-S-cysteinyldopa in the 24-h-urine may be of great diagnostic value. If the complaints and the pathologic values are early symptoms and signs of generalized metastases being clinically not yet manifest, the excretion of 5-S-cysteinyldopa in the urine is often increased. In such cases, a thorough and possibly invasive search for metastases is indicated.

Cysteinyldopa↗

PubMed1982

Further evidence for the participation of 5 beta-steroids in the development of a porphyria induced by hexachlorobenzene.

Adult female rats were fed with a diet containing hexachlorobenzene to induce a porphyria. 5 alpha/5 beta-ratios of androstane steroids in blood were 0.61 +/- 0.13 in porphyric rats and 1.05 +/- 0.35 in normal rats. Etiocholanolone treatment of rats was ineffective in generation of a porphyria. The activity of microsomal glucuronyltransferase increased from 0.20 +/- 0.04 mU/mg to 0.77 +/- 0.23 mU/mg by this treatment. Administration of Flutamide (4'-nitro-3'-trifluoromethylisobutyranilide) to porphyric rats resulted in a decline of porphyrin excretion by 55%. The hepatic NADH-5 beta-reductase was strongly inhibited by this drug, whereas NADPH-5 beta-reductase displayed a slightly increased activity. These findings are further evidence for the involvement of 5 beta-steroids in the formation of porphyria.

Animals↗

PubMed1982

Affinity labeling of rat liver microsomal NADH-5 alpha-reductase with a nucleoside analogue.

A time dependent irreversible loss of rat liver microsomal NADH-5 alpha-reductase activity is caused by incubation of microsomes with the nucleoside 5'-p-fluorosulfonylbenzoyladenosine (FSA). The decrease of activity is dependent on FSA concentration and shows first order kinetics. Presence of NADH partially stabilizes the NADH-5 alpha-reductase. Thioglycerol present before incubation prevents loss of activity, and stops decrease of activity when added during incubation. NADPH-5 alpha-reductase (E.C. 1.3.1.4) and NADPH-cytochrome c reductase (E.C. 1.6.2.4) are not influenced while NADH-cytochrome c reductase (E.C. 1.6.99.3) is inhibited by FSA. Evidently FSA causes inactivation of the enzymes by binding to the NADH-binding site. Affinity labeling by FSA thus clearly distinguishes between NADH- and NADPH-dependent 5 alpha-reductases from rat liver microsomes.

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

PubMed1982

Urinary free and conjugated 5-S-cysteinyldopa in normal subjects and in patients with melanoma.

We measured free and total 5-S-cysteinyldopa excretion in 24-h urine specimens from nine patients with malignant melanoma and forty-five controls, and found that the levels of 5-S-cysteinyldopa excretion (measured by a fluorometric method) were greatly increased in the melanoma patients. The conjugates were hydrolysed by enzymatic treatment with beta-glucuronidase/arylsulphatase, and we found that the percentage of conjugated 5-S-cysteinyldopa was higher in urines with a low content of free 5-S-cysteinyldopa than in those with a higher concentration.

Adult↗

PubMed1981

NADPH: 4-ene-3-oxosteroid-5 alpha-reductase and NADH: 4-ene-3-oxosteroid-5 alpha-reductase in liver microsomes of different species of animals.

Explore the source record for details and available documents.

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

PubMed1981

Urticaria in association with etiocholanolone fever.

A 17-year-old girl is reported with a history of recurrent febrile episodes during her menstrual bleeding accompanied by a generalised exanthem. Increased plasma levels of unbound etiocholanolone were noticed during the febrile attacks. Both the fever and the skin eruption could be suppressed by oral contraceptives.

Adolescent↗

PubMed1980

[5-S-cysteinyldopa in the urine - a "tumor test" for malignant melanoma? Comparison with the usual laboratory examinations].

In a total of 1,828 determinations, urinary excretion of 5-S-Cysteinyldopa was studied over a period of three years in 384 patients treated for melanoma or with metastases of malignant melanoma. By serial investigations the excretion of 5-S-Cysteinyldopa was compared to the course of the disease. In the case of small and circumscribed metastases which could be eliminated by surgical treatment, the excretion of 5-S-Cysteinyldopa remained normal. When the disease became generalized, an increase of the urinary excretion of 5-S-Cysteinyldopa prior to the clinical manifestation of the metastases was observed in only four out of 26 cases. In the remaining cases, the increase of 5-S-Cysteinyldopa coincided with the manifestation of metastases, or the excretion of the substance became pathological when the metastases were already conspicuous. In five patients, the urinary excretion of 5-S-Cysteinyldopa remained normal inspite of widespread disease. Therefore, its diagnostic value seems to be similar to that of the "common" laboratory investigations the results of which are only pathological when the disease has already become generalized. Our investigations demonstrate that serial investigations of the urinary excretion of 5-S-Cysteinyldopa only rarely indicate melanoma metastases prior to their clinical manifestation. In cases of early metastasing melanoma, all common laboratory investigations are of limited value. BSR and GGT levels which become pathological very early in the course of the disease are so sensitive that slightly pathological levels may be ambiguous. In these cases, however, pathological levels of 5-S-Cysteinyldopa most probably will indicate a widespread disease.

BCG Vaccine↗

PubMed1980

The involvement of porphyrogenic steroids in the development of experimental porphyria.

Hexachlorobenzene alters the hepatic steroid metabolism, and it was suggested that a porphyria was induced by overproduction of 5 beta-H-steroids. Structurally similar chlorinated hydrocarbons (pentachlorobenzene, pentachlorophenol, 2,4,5-trichlorophenol) without porphyrogenic activity did not affect the steroid metabolism in rat liver.