The plasma level of 7α-hydroxy-4-cholesten-3-one reflects the activity of hepatic cholesterol 7α-hydroxylase in man

AbstractCirculating levels of 7α-hydroxy-4-cholesten-3-one have been compared with activities of the rate-limiting enzyme in bile acid synthesis, microsomal cholesterol 7α-hydroxylase, measured in liver biopsies obtained from patients undergoing surgery for gallstone disease. Some patients were treated with cholestyramine or bile acids prior to operation in order to alter the feed-back inhibition of the enzyme. The levels of the sterol were similar in untreated patients and in patients treated with ursodeoxycholic acid (median concentration 17 and 13 ng/ml, respectively), and so were the activities of the enzyme (median activity 7.0 and 5.5 pmol/min/mg protein, respectively). The sterol levels and enzyme activities were significantly increased in patients treated with cholestyramine (91 ng/ml and 45 pmol/min/mg protein) and decreased in patients treated with chenodeoxycholic acid (<2.0 ng/ml and 0.7 pmol/min/mg protein). There was a strong positive correlation (r=0.90, P<0.00001) between levels of 7α-hydroxy-4-cholesten-3-one in plasma and the activities of cholesterol 7α-hydroxylase in the whole patient group. The results show that analysis of 7α-hydroxy-4-cholesten-3-one in plasma is a sensitive and convenient method to determine relative rates of bile acid production in man

Triggered fault slip on June 17, 2000 on the Reykjanes Peninsula, SW-Iceland captured by radar interferometry

Dynamically triggered seismicity followed shortly after a M-s 6.6 earthquake in Iceland on June 17, 2000. Smaller earthquakes occurred on the Reykjanes Peninsula up to 100 km from the mainshock rupture. Using interferometric analysis of Synthetic Aperture Radar images (InSAR), we measure crustal deformation associated with three triggered deformation events. The largest of these occurred at Lake Kleifarvatn, 85 km west of the mainshock epicenter. Modeling of the InSAR data reveals strikeslip on a north-striking fault, with a geodetic moment of 6.2 x 10(17) Nm, equivalent to magnitude M-w 5.8 earthquake. A seismological estimate of the moment is not yet available, because the seismic signature of this event is partly hidden by the mainshock waveform. The paucity of aftershocks on the triggered rupture plane suggests some aseismic slip there, compatible with a thin seismogenic crust, high heat-flow, hydrothermal alteration and the presence of fluids in the area