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

A rapid, precise, and accurate photometric method for determining free and esterified fecal 3 alpha-hydroxy bile acids is described. Feces are homogenized and (a) extracted with boiling absolute ethanol, or (b) lyophilized and extracted with chloroform:methanol 2:1 (v/v). Hydrolyzed and nonhydrolyzed crude extracts are prepared and aliquots treated with a reagent containing nitro blue tetrazolium (NBT), 3 alpha-hydroxysteroid oxidoreductase, beta-nicotinamide adenine dinucleotide (beta-NAD) and diaphorase. The reagent first oxidizes bile acid 3 alpha-hydroxyls to 3-oxo groups and 3 beta-hydrogen is transferred to beta-NAD yielding beta-NADH. beta-NADH in turn reduces NBT (yellow) to its diformazan (blue). Absorbance is measured at 540 nm and is proportional to the 3 alpha-hydroxy bile acid titer of fecal extract aliquots. Fecal pigments present in crude extracts do not interfere with the assay since they absorb minimally at 540 nm.
Steroids 1983 Jun
PMID:Rapid photometric determination of free and esterified 3 alpha-hydroxy fecal bile acids. 666 19

A rapid, accurate, precise method for determining human fecal bile acids is reported. Feces are homogenized and then briefly extracted with boiling absolute ethanol. A portion of the extract is evaporated to dryness and the residue heated with mild alkali to hydrolyze bile acid 3 alpha-hydroxyl esters. Aliquots of hydrolyzed crude extract are treated with resazurin reagent which effects a series of enzyme catalyzed reactions in which bile acid free 3 alpha-hydroxyls are first oxidized to 3-oxo-groups in a reaction catalyzed by 3 alpha-hydroxysteroid dehydrogenase. Resulting protons are transferred to beta-nicotinamide adenine dinucleotide, yielding reduced beta-nicotinamide adenine dinucleotide (beta-NADH). beta-NADH then reduces nonfluorescent resazurin to fluorescent resorufin in a reaction catalyzed by diaphorase. Developed fluorescence, which is proportional to the extract aliquots bile acid content, is excited at 565 nm and read at 580 nm, wavelengths which lie in a spectral region in which there is minimal fecal pigment absorption. 3-Oxo-bile acids and bile acid 3 alpha-sulfates are extracted in the procedure but reduction and/or solvolysis is necessary before quantification.
Steroids 1981 Sep
PMID:Rapid analysis of human fecal bile acids. 730 34

22R-Hydroxycholesterol is an intermediate in the steroid biosynthesis pathway shown to exhibit a neuroprotective property against beta-amyloid (1-42) (Abeta) toxicity in rat PCl2 and human NT2N neuronal cells by binding and inactivating Abeta. In search of potent 22R-hydroxycholesterol derivatives, we assessed the ability of a series of naturally occurring entities containing the 22R-hydroxycholesterol structure to protect PC12 cells against Abeta-induced neurotoxicity, determined by measuring changes in membrane potential, mitochondrial diaphorase activity, ATP levels and trypan blue uptake. 22R-Hydroxycholesterol derivatives sharing a common spirost-5-en-3-ol or a furost-5-en-3-ol structure were tested. Although some of these compounds were neuroprotective against 0.1 microM Abeta, only three protected against the 1-10 microM Abeta-induced toxicity and, in contrast to 22R-hydroxycholesterol, all were devoid of steroidogenic activity. These entities shared a common structural feature, a long chain ester in position 3 and common stereochemistry. The neuroprotective property of these compounds was coupled to their ability to displace radiolabeled 22R-hydroxycholesterol from Abeta, suggesting that the Abeta-22R-hydroxycholesterol physicochemical interaction contributes to their beneficial effect. In addition, a 22R-hydroxycholesterol derivative inhibited the formation of neurotoxic amyloid-derived diffusible ligands. Computational docking simulations of 22R-hydroxycholesterol and its derivatives on Abeta identified two binding sites. Chemical entities, as 22R-hydroxycholesterol, seem to bind preferentially only to one site. In contrast, the presence of the ester chain seems to confer the ability to bind to both sites on Abeta, leading to neuroprotection against high concentrations of Abeta. In conclusion, these results suggest that spirost-5-en-3-ol naturally occurring derivatives of 22R-hydroxycholesterol might offer a new approach for Alzheimer's disease therapy.
Steroids 2004 Jan
PMID:Identification of naturally occurring spirostenols preventing beta-amyloid-induced neurotoxicity. 1471 72