Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more  or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram.  [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography .  :10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. 
The metabolism of propionate in adipose tissue and its effect on lipogenesis was investigated. Fasting induced changes in propionate metabolism of adipose tissue, drastically reducing higher fatty acid synthesis and increasing glyceride-glyerol formation from low concentrations of propionate ( mM). Propionate also promoted lipogenesis from acetate-1-(14)C in tissues of fasted rats, while it inhibited lipogenesis and CO(2) formation from acetate in the fed animal. Treatment with actinomycin D or ethionine abolished both the increased glyceride-glycerol formation from propionate and the promoting effect on lipogenesis from acetate. Synthesis of long-chain fatty acids from propionate-1-(14)C was increased by actinomycin treatment. The change in propionate metabolism induced by fasting is, however, not entirely due to its conversion to glyceride-glycerol, since the latter was almost completely blocked by malonate while part of the promoting effect on fatty acid synthesis persisted.
TCDF reporter assay . TCDF treatment in Ahr –/– mice was confirmed using the mouse hepatoma reporter cell line. After killing the Ahr –/– mice, 50 mg of liver was extracted using the Folch method ( Folch et al. 1957 ), lyophylized, and reconstituted in 20 μL of DMSO; μL of the DMSO-reconstituted extracted was used for the reporter assay. The Hepa mouse hepatoma cell line containing the stably integrated pGudluc luciferase reporter construct was obtained from M. Denison (University of California, Davis). The Hepa mouse hepatoma cell line was maintained in α-modified essential media (Sigma-Aldrich) supplemented with 8% fetal bovine serum (Hyclone Laboratories) and 100 IU/mL penicillin/100 μg/mL streptomycin (Sigma-Aldrich). Cells were cultured at 37°C in a humidified atmosphere composed of 95% air and 5% CO 2 . The reporter cells (Hepa ) were seeded in 12-well plates and cultured to approximately 90% confluence. The AHR responsiveness of extracts was examined after treatment for 4 hr, followed by lysing with 400 μL lysis buffer.