Increased bile acid pool inhibits cholesterol 7 alpha-hydroxylase in cholesterol-fed rabbits

BACKGROUND & AIMS: Cholesterol feeding unexpectedly inhibits cholesterol 7 alpha-hydroxylase in rabbits. The aim of this study was to explore the mechanism. METHODS: Twenty male New Zealand white rabbits were fed regular chow with and without 2% cholesterol for 10 days followed by 7 days of bile drainage. The activities of hepatic cholesterol 7 alpha-hydroxylase and sterol 27-hydroxylase that control bile acid synthesis in classic and alternative pathways were related to the size and composition of bile acid pool. RESULTS: After feeding cholesterol, plasma and hepatic cholesterol concentrations increased, the bile acid pool doubled (from 254 +/- 44 to 533 +/- 51 mg; P < 0.001), cholesterol 7 alpha-hydroxylase activity decreased 68% (P < 0.01), but sterol 27-hydroxylase activity increased 66% (P < 0.05) with increased cholic acid synthesis (P < 0.01). Bile drainage in the cholesterol-fed rabbits depleted the bile acid pool and stimulated down- regulated cholesterol 7 alpha-hydroxylase activity 11.4-fold (P < 0.001), although hepatic cholesterol remained elevated. Hepatic sterol 27-hydroxylase activity was unaffected. CONCLUSIONS: Feeding cholesterol increased hepatic cholesterol and stimulated sterol 27- hydroxylase and alternative bile acid synthesis, which expanded the bile acid pool and inhibited cholesterol 7 alpha-hydroxylase in rabbits. In distinction, hepatic sterol 27-hydroxylase was insensitive to changes in the bile acid pool. (Gastroenterology 1997 Dec;113(6):1958-65)     

Biliary cholesterol hypersecretion in gallstone-susceptible mice is associated with hepatic up-regulation of the high-density lipoprotein receptor SRBI

Enhanced hepatocellular trafficking of cholesterol to the bile canaliculus and cholesterol hypersecretion appears critical for gallstone formation. Therefore, we studied in more detail the hepatic cholesterol transport pathways in a mouse model of cholesterol gallstone disease. Biliary lipid secretion rates, plasma lipoprotein levels, hepatic expression of lipoprotein receptors, lipid regulatory enzymes, and putative cholesterol transporting proteins were analyzed in gallstone-susceptible C57L/J and gallstone-resistant AKR/J mice, which were fed a lithogenic diet. Biliary cholesterol hypersecretion in C57L mice was associated with decreased plasma high-density lipoprotein (HDL) cholesterol levels and significant hepatic induction of the HDL receptor (SRBI) and cholesteryl ester hydrolase. In response to the lithogenic diet, fatty-acid binding protein of liver (FABPL) was markedly induced in both mouse strains. Caveolin 1 was elevated only in plasma membranes of gallstone-susceptible C57L mice, which also failed to down-regulate cholesterol synthesis. These data suggest a role of the reverse cholesterol transport pathway for genetically determined gallstone susceptibility in the mouse.     

Fallopian tube obstruction: selective salpingography and recanalization. Work in progress

Seven infertile women, in whom interstitial fallopian tube obstruction (IFTO) was suspected at hysterosalpingography and who were recommended for surgical evaluation and treatment, were treated with catheterization techniques. Selective salpingography with ostial injection demonstrated tubal patency in two patients; direct intratubal salpingography demonstrated patency in another patient. Four patients with a true IFTO underwent fallopian tube recanalization: in the first two, a small soft-tipped guide wire was used, and in the other two, a guide wire and 3-F catheter were used. The suggested catheterization techniques have the potential to make evaluation and treatment of IFTO more efficient, safer, and less expensive than presently used methods.     

Large-scale mutation screening in patients with dilated or hypertrophic cardiomyopathy: a pilot study using DGGE

Cardiomyopathies are complex myocardial diseases characterized by inappropriate ventricular hypertrophy (HCM) or dilation (DCM). Both disorders may lead to sudden death or progressive heart failure and exhibit familial aggregation with marked genetic heterogeneity. Many candidate genes were identified by linkage analysis, experimental animal studies, and expression analysis. A systematic assessment of the prevalence of different mutations in these genes requires high-throughput analyses. In this paper, we present a simple and reliable protocol for mutation screening by heteroduplex analysis which reduced costs and workload of sequencing. Employing denaturing gradient gel electrophoresis (DGGE), 11 known and 14 potential candidate genes for HCM and DCM were analyzed. DGGE assays allowed analysis of 286 of the 312 protein coding exons, performing only four alternative polymerase chain reaction protocols and only two different DGGE analysis conditions. Sensitivity for the detection of heteroduplexes proved excellent, even for GC-rich DNA fragments, which were analyzed by a combination of DGGE and constant denaturant gel electrophoresis. To confirm DGGE sensitivity in cases where no variants in our human DNA samples could be observed, we generated heteroduplexes from homologous human and chimpanzee DNA. The platform proved a valuable contribution to elucidating the genetic causes of DCM and HCM as demonstrated by the identification of 17 different known and novel mutations and 98 different polymorphisms in our setting.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Calcification of myocardial necrosis is common in mice

Independent of the severity, phenotypes and clinical outcomes of myocardial infarction may vary considerably in patients, suggesting a strong genetic influence on healing and adaptive processes. Since little is known about these genetic determinants, we examined the tissue response to myocardial injury in seven inbred mouse strains, including those employed for gene targeting or transgenic overexpression. Myocardial necrosis was produced by non-ischemic, trans-diaphragmal freeze–thaw injury in strains C57BL/6, C3H/He, DBA/2, BALB/c, 129S1, FVB/n and A/J. Two days after injury, necrotic cardiomyocytes calcified in C3H/He, DBA/2, BALB/c and 129S1, a phenotype known as dystrophic cardiac calcinosis (DCC). The susceptibility to DCC of 129S1 was determined by Dyscalc1, a locus on chromosome 7, which was identified previously in C3H/He and DBA/2. DCC was also observed in C3H/He following ischemic injury by permanent coronary artery ligation, indicating that DCC was independent of the mode of injury. In contrast, strains C57BL/6, FVB and A/J were resistant to DCC, showing formation of a fibrous scar without calcification. The development of DCC was studied in detail in C3H/He and C57BL/6. In both strains, no calcium deposition and only little structural disintegration were noted in necrotic myocardium 24 h after injury upon calcium-sensitive fluorescence staining. Ultrastructural examination revealed calcified mitochondria in C3H/He that may have served later as a nidus for rapid intracellular calcification of cardiomyocytes. We concluded that the susceptibility to calcification of myocardial necrosis may be common among inbred strains and should be recognised as a strong genetic modifier of experimental myocardial injury.     

Urokinase versus streptokinase in local thrombolysis

In a retrospective analysis, the efficacy of lysis, the degree of systemic thrombolytic effect, and the rate of complications during local thrombolytic therapy with either streptokinase (SK) or urokinase (UK) were compared in 47 patients. There were 24 infusions of each agent; one patient in the UK group received two infusions. The overall efficacy of lysis was better in the UK-treated group (80% vs. 63%). The UK group had a lower frequency of systemic thrombolytic effect and of bleeding complications. SK antibody titers were measured in all patients who received infusions. Patients with high titers who were treated with SK responded poorly (20% lysis); patients with low titers responded at a rate equal to that of UK-treated patients. Three patients with high titers of SK antibodies did not respond to SK, but subsequent successful lysis did occur with UK. In conclusion, UK is believed to be preferable to SK for local thrombolytic therapy due to increased efficacy of lysis and decreased rate of systemic fibrinolytic effect and bleeding complications.     

Growth stimulation of human bone marrow cells in agar culture by vascular cells

Human vascular cells are capable of stimulating granulopoiesis in agar culture of human bone marrow cells. This effect was obtained by including vein fragments in the culture or by using endothelial cells separated from the vein of human umbilical cords as feeder cells. Furthermore, the stimulatory capacity of conditioned medium obtained from cord veins was found to be highly active in comparison to that obtained from peripheral leukocytes. Endothelial cells within the bond marrow cavity are suggested as a local source of factors regulating granulopoiesis in humans in addition to the monocyte.