Steroid synthesis pathway mnemonic

A 35-year-old Lebanese Christian male was referred to the biochemical laboratory for the study of his mellituria. The urinary sugar had been discovered during a hospitalization for the repair of an inguinal hernia when the patient was 20 years of age, and he was then refused operation because of “diabetes.” Numerous blood sugar analyses were reported normal. The patient was in excellent health and had no symptoms of diabetes, but was concerned about his condition. L- xylulose was present excessively in urine. What is the probable diagnosis?

Depending on the number and character of their functional groups, steroid molecules may show diverse reactivities. Moreover, the reactivity of a functional group varies according to its location within the molecule (for example, esters are formed readily by 3-OH groups but only with difficulty by the 11β-OH group). An important property of steroids is polarity —., their solubility in oxygen-containing solvents (., water and alcohols ) rather than hydrocarbon solvents (., hexane and benzene ). Hydroxyl, ketonic, or ionizable (capable of dissociating to form electrically charged particles) groups in a steroid molecule increase its polarity to an extent that is strongly influenced by the spatial arrangement of the atoms within the molecule.

Isolated hamster granulosa cells and theca from preovulatory follicles were incubated in vitro for 2 and 6 h in the absence/or presence of LH and steroid substrates. The purpose of the experiments was to determine, in theca, the relative activities of the delta 5 and delta 4 pathways under controlled conditions, and to compare the ability of granulosa cells and theca to form progesterone from exogenous pregnenolone. The results of the experiments show that the delta 5 pathway in theca predominates before and up to 2 h after LH stimulation. The delayed effect of LH after 2 h is a switch from delta 5 to delta 4 as the major metabolic pathway. Progesterone formation from exogenous pregnenolone is 7 to 10 times greater in unstimulated granulosa cells than in theca. Acute effects of LH lead to increased conversion of exogenous pregnenolone to progesterone in granulosa cells but not theca. LH does, however, acutely stimulate the thecal conversion of DHEA to androstenedione. The longer term effect of LH in both cell types is to increase pregnenolone conversion to progesterone.

EPA researchers have come a long way in the past few years, developing new assays to target various steps in the thyroid network, as well as other parts of the endocrine system. Once the current effort is complete, however, EPA will need to decide whether its second-tier assays are too slow. With so many of the test chemicals flagged as potential endocrine disruptors—495 potential TPO inhibitors, 404 potential NIS inhibitors, and 225 potential deiodinase inhibitors, among others—EPA may find that those tests will also take decades to complete. Then the race will be on to replace those five second-tier in vivo ecotoxicity tests involving quail, fish, frogs, and rats with high-throughput nonanimal alternatives.

Steroid synthesis pathway mnemonic

steroid synthesis pathway mnemonic

EPA researchers have come a long way in the past few years, developing new assays to target various steps in the thyroid network, as well as other parts of the endocrine system. Once the current effort is complete, however, EPA will need to decide whether its second-tier assays are too slow. With so many of the test chemicals flagged as potential endocrine disruptors—495 potential TPO inhibitors, 404 potential NIS inhibitors, and 225 potential deiodinase inhibitors, among others—EPA may find that those tests will also take decades to complete. Then the race will be on to replace those five second-tier in vivo ecotoxicity tests involving quail, fish, frogs, and rats with high-throughput nonanimal alternatives.

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