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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The chemical stabilities of the adrenal-scanning agents, 6beta-iodo-methyl-19-norcholest-5(10)-en-3beta-ol (6-iodomethylnorcholesterol) and 19-iodocholest-5-en-3beta-ol (19-iodocholesterol), and several of their derivatives were examined by 13C nuclear magnetic resonance. Neat 6-iodomethylnorcholesterol, sealed in glass under nitrogen and stored at 0 degrees C, remains 98 mole% chemically pure for 3 months. Neat 19-iodocholesterol, stored in the dark at 25 degrees C, remains 98 mole% chemically pure for 3 months. Either 6-iodomethylnorcholesterol-125I or-131I, informulation and stored at 5 degrees C, will remain greater than 97% radiochemically pure for at least 15 days. Labelled 19-iodocholesterol, formulated and stored under the same conditions, shows 20% decomposition after 3 weeks and 40% after 6 weeks.
Steroids 1977 Oct
PMID:Chemical and radiochemical stability of the adrenal-scanning agents, 6beta-iodomethyl-19-norcholest-5(10-en-3beta-ol and 19-iodocholest-5-en-3beta-ol. 60 58

21-Amino-5-pregnene-3,20-dione bisethylene ketal was obtained in good yield by lithium aluminum hydride reduction of 21-azido-5-pregnene-3,20-dione bisethylene ketal. The azido bisethylene ketal was synthesized by the sequence: deoxycorticosterone leads to deoxycorticosterone 21-p-toluene-sulfanate leads to 21-azidoprogesterone leads to 21-azido-5-pregnene-3, 20-dione bisethylene ketal. The structure of the title compound was confirmed by its conversion to the known 21-acetylaminoprogesterone. 21-Amino-5-pregnene-3,20-dione bisethylene ketal is a stable aminosteroid which is a useful intermediate for the synthesis of C-21 nitrogen derivatives of progesterone.
Steroids 1977 Dec
PMID:Synthesis of 21-amino-5-pregnene-3,20-dione bisethylene ketal. 61 37

Steroids exert no beneficial effect upon acute pulmonary dysfunction created by nitrogen tetroxide inhalation and may worsen small airway obstruction in the early phases of injury. Treatment, therefore, is still largely symptomatic and supportive.
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PMID:The use of steroids in inhalation injury. 89 76

The inhibition of the conversion of [4-14C] cholesterol to [4-14C] pregnenolone by a number of steroids has been studied in bovine adrenocortical mitochondrial acetonedried preparations. At equimolar substrate and inhibitor concentrations (3.3 muM) the most potent inhibitors were cholesterol derivatives containing a nitrogen function at c-22, followed by derivatives containing oxygen functions at c-22 or c-20 or both. The presence of a hydroxyl group at c-17 or the replacement of the 3beta-hydroxyl group by fluorine reduced the inhibitory efficacy. In the presence of inhibitors that were also relatively good substrates of the cholesterol side-chain cleavage system, such as some cholesterol derivatives hydroxylated in the side-chain,the rate of [4-14C] pregnenolone formation increased with time as the inhibitor was consumed. (20S)-20,21-Dihydroxycholesterol exerted such an effect on the kinetics of [4-14C]pregnenolone formation, and yielded 21-hydroxypregnenolone which was identified by gas chromatography-mass spectrometry. The synthesis of (20R)-22-ketocholesterol, of (20R,22R)-22hydroxycholesterol, (20R,22S)-hydroxycholesterol, and of (20S)-desmosterol is described.
Steroids 1976 Mar
PMID:Inhibition of the conversion of cholesterol to pregnenolone in bovine adrenocortical preparations. 126 98

When methanolic solutions of tritiated 11-deoxycorticosterone or corticosterone (0.1 to 300 ng) were evaporated to dryness with a stream of nitrogen in soda-lime test tubes only 8-24% of the radioactivity was recovered as the parent steroid. Evaporation in borosilicate test tubes led to a recovery of 90% or more. With ethyl acetate as solvent no decomposition occured in soda-lime test tubes.
Steroids 1976 Apr
PMID:Decomposition of 11-deoxycorticosterone and corticosterone in soda-lime glass. 127 98

Metabolism of steroid hormones by dehydrogenases is an important mechanism for regulating steroid hormone action. Analysis of recently reported amino acid sequences of 11 beta-hydroxysteroid dehydrogenase, 17 beta-hydroxysteroid dehydrogenase, and 3 alpha, 20 beta-hydroxysteroid dehydrogenase reveals that they are descended from a common ancestor. Unexpectedly, this superfamily of dehydrogenases has other interesting relatives: 15-hydroxyprostaglandin dehydrogenase, proteins found in nitrogen-fixing bacteria, and enzymes important in the synthesis of antibiotics. The novel lineage of these proteins and the actions of flavonoids in regulating gene transcription in nitrogen-fixing bacteria and mammals provide new insights into the evolution of regulation of gene transcription by intercellular signals in multicellular animals.
Steroids 1991 Jul
PMID:Genealogy of regulation of human sex and adrenal function, prostaglandin action, snapdragon and petunia flower colors, antibiotics, and nitrogen fixation: functional diversity from two ancestral dehydrogenases. 178 Sep 51

Liver cytochrome P450 monooxygenases (P450), a group of isozymes that catalyze the reductive cleavage of molecular oxygen, dominate hepatic metabolism of xenobiotic lipophilic substances. These P450 enzymes exhibit broad and overlapping substrate specificities, in contrast to the P450 isozymes of the steroid biosynthetic pathways, which are highly substrate specific. Hepatic heme pigments, N-alkylated porphyrins, accumulate following the self-catalyzed destruction of P450 by the metabolic activation of 17 alpha-ethynyl steroids. Acetylenic substituted steroidal aromatase inactivators, norethisterone (NET), and 10-(2-propynyl)estr-4-ene-3,17-dione (MDL 18,962) were administered to rats to determine if the acetylenic substituent was activated by hepatic P450 mixed-function oxidases. This metabolism could result in the formation of a reactive species that would alkylate a pyrrole nitrogen atom of heme. Male Sprague-Dawley rats were treated with 0, 10, 30, or 100 mg/kg NET or MDL 18,962 intraperitoneally. Four hours later, these animals received 40 mg/kg sodium pentobarbital and their sleeping times were recorded. On arousal, the rats were killed and their livers were taken for determination of P450 content and formation of N-alkylated porphyrins (green pigments). Norethisterone inhibited hepatic P450 isozymes, resulting in a dose-related increased sleeping time (89.2 +/- 3.5 to 156.3 +/- 7.6 minutes) and decreased P450 levels (maximum 25% decrease at 100 mg/kg), and the amount of green pigments increased with doses of 10 to 100 mg/kg. In contrast, MDL 18,962 treatment did not increase sleeping time and caused only a 15% decrease in hepatic P450 content at 100 mg/kg, with no detectable green pigments.(ABSTRACT TRUNCATED AT 250 WORDS)
Steroids 1991 Apr
PMID:Regioselectivity of metabolic activation of acetylenic steroids by hepatic cytochrome P450 isozymes. 187 82

Effects of carbon monoxide, nitrogen, ferricytochrome c and p-hydroxymercuribenzoate were studied on cholesterol 7 alpha-hydroxylase activity of swine hepatic microsomes. The results suggest that a microsomal electron transport system is involved in hepatic microsomal cholesterol 7 alpha-hydroxylation in swine. Cholesterol 7 alpha-hydroxylation is inhibited by superoxide dismutase in the standard assay system containing a NADPH generating system. Superoxide dismutase also inhibited cholesterol 7 alpha-hydroxylation in the system where superoxides were generated by enzymatic or nonenzymatic means in the absence of NADPH-generating system. The current study suggests that superoxide anion may be an important factor in the cholesterol 7 alpha-hydroxylation of swine.
Steroids 1980 Apr
PMID:Effects of superoxide dismutase on cholesterol 7 alpha-hydroxylation in swine. 624 63

Human female reproductive tract tissues were analysed for estrogen and progestogen receptor content in the presence or absence of sodium molybdate immediately after removal at surgery. Other fractions of the tissue were stored in liquid nitrogen and similarly analysed after 2, 4, 6 and 8 weeks storage. The results showed that at all times the apparent receptor content for both steroids was significantly higher (P less than 0.001) and Kd values were significantly lower (P less than 0.02) in assays carried out with 10 mM molybdate added to the buffer systems. Furthermore, as soon as either whole tissue or tissue cytosol was frozen for storage, receptors were "lost" with values decreasing by approximately 30% for both steroid receptors. However, once frozen in liquid nitrogen tissue receptor content remained stable over the eight weeks of study. It is recommended that laboratories standardize techniques to allow valid comparisons of results.
Steroids 1982 Aug
PMID:The effect of storage time and molybdate on steroid receptors in gynaecological tissues. 715 51

Amino acid sequence comparisons have revealed that mammalian 11 beta-hydroxysteroid and 17 beta-hydroxysteroid dehydrogenases and bacterial 3 alpha, 20 beta- and 3 beta-hydroxysteroid dehydrogenases are homologs; that is, these enzymes are descended from a common ancestor. These steroid dehydrogenases are also homologous to human 15-hydroxyprostaglandin dehydrogenase and to proteins found in Rhizobia, bacteria that form nitrogen-fixing nodules in the roots of legumes. We constructed a multiple sequence alignment of these proteins, which, when combined with the recently determined tertiary structure of Streptomyces hydrogenans 3 alpha, 20 beta-hydroxysteroid dehydrogenase and a homologous enzyme, rat dihydropteridine reductase, identifies segments and residues that are likely to be structurally important in the functioning of these enzymes especially regarding specificity for NADPH and NADH.
Steroids 1994 Apr
PMID:Sequence analysis of steroid- and prostaglandin-metabolizing enzymes: application to understanding catalysis. 807 79


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