Biomedical subjects
N J Michaud
Publications and source records attributed to N J Michaud.
Corticosterone metabolism and the incorporation of leucine, uridine, and thymidine into fetal mouse brain.
The change in the pattern of biotransformation of [14C]corticosterone in fetal mouse brain between gestational day 14 and 17 increased the proportion of unchanged hormone from 9-75%. A sharp decrease in the in vitro incorporation of [14C]leucine, [3H]uridine, and [3H]thymidine into incubated brain coincided with this change and continued until day 19, when the incorporation of the 3 substrates had fallen to 9, 54, and 16%, respectively, of that on day 14. Injection of dexamethasone reduced values on day 14 to those normally found on days 15-18. Enzymes which metabolize corticosteroids regulate their activity in specific tissues; these data suggest a hormonal influence on developing brain.
Maternal-fetal relationships in corticosteroid metabolism.
Corticosterone in fetal mouse tissues after injection of mothers with 14C-corticosterone was determined by acetylation with 3H-acetic anhydride and cocrystallization to constant specific activity. The corticosterone content of whole fetal tissue varied between gestational days 13 and 17 from 641 to 300 ng/g. Specific activity of fetal hormone remained essentially constant; after a 15-min pulse this was as much as one-quarter that of maternal hormone. Placenta, head and liver showed distinctly different patterns which changed during this time, with a decrease in conversion of corticosterone to 11-dehydrocorticosterone. A sharp increase occurred in the activity of fetal liver 11beta-hydroxysteroid:NADP oxidoreductase activity. This mitochondrial enzyme, pH optimum 6, KM = 33 micrometer, reduced the metabolite, raising the relative amount of corticosterone in the fetus from 16 to 91%. 1 day after removal of maternal adrenals both maternal and fetal corticosterone were normal, indicating ability of fetal adrenals to function. Maternal corticosterone, however, crossed the placenta readily and it is considered likely that, normally, the maternal hormone predominates. Regardless of origin, corticosterone is maintained by enzymatic conversion in a distinct manner in different tissues.
Supervoltage roentgenography with linear accelerator.
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