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A substitution naturally determines a directed graph with an ordering of the edges incident at each vertex. We describe a simple method by which any primitive substitution can be modified (without materially changing the bi-infinite fixed points of the substitution) so that points in the substitution minimal shift are in bijective correspondence with one-sided infinite paths on its associated directed graph. Using this correspondence, we show that primitive substitutive sequences in the substitution minimal shift are precisely those sequences represented by eventually periodic paths. We use directed graphs to show that all measures of cylinders in a substitution minimal shift lie in a finite union of geometric sequences, confirming a conjecture of Boshernitzan. Our methods also yield sufficient conditions for a geometric realization of a primitive substitution to be "almost injective. [ABSTRACT FROM AUTHOR]

Objective: A high plasma cholesterol level is a major predisposing factor for coronary artery disease, and new treatments are currently under consideration. Supported by the close relationship between cholesterol and bile acid metabolism, recent studies have reported a hypocholesterolaemic effect of the bile acid ursodeoxycholic acid (UDCA) in patients with primary biliary cirrhosis but, unfortunately, no data are available in primary hypercholesterolaemia. We performed this study to evaluate the effects of oral administration of UDCA on serum lipoprotein patterns in patients with primary hypercholesterolaemia. Design and Setting: A double-blind, placebo-controlled, crossover study with a 4-week washout period carried out at an outpatient clinic at a university hospital. Study Participants: Twelve individuals with a total serum cholesterol level >5.17 mmol/L. Intervention: Patients were assigned to receive UDCA (8 to 10 mg/kg/day) or placebo for 28 days. They then crossed over to receive the other treatment after a 4-week washout period. Main Outcome Measures and Results: Serum total, low density lipoprotein (LDL), high density lipoprotein (HDL), very low density lipoprotein (VLDL) cholesterol and apoprotein A and B were determined before and after 28-day UDCA and placebo administration. After UDCA administration, the mean (±SD) total serum cholesterol level decreased significantly from 6.37 ± 1.01 mmol/L to 6.06 ± 0.97 mmmol/L (F = 5.7, p = 0.041); no significant differences from baseline were observed in LDL, HDL, VLDL cholesterol, apoprotein A and B. No significant changes in serum lipid parameters occurred after the placebo period. When compared with placebo, the UDCA-induced decrease in total serum cholesterol levels was statistically significant (F = 5.5, p = 0.043). Conclusion: This study shows that UDCA reduces total serum cholesterol levels in patients with mild to moderate hypercholesterolaemia. This effect suggests that the administration of UDCA may improve cholesterol metabolism in these individuals. [ABSTRACT FROM AUTHOR]

Investigates the descendants of primitive substitutions designated s. Evidence that the set of all descendants of s is finite for each primitive substitution; Proof contradicting previous studies which state than an interval exchange transformation defined over a quadratic field has only finitely many descendants; Nonperiodic sequence fixed by s.

The localization of angiotensin converting enzyme (ACE) in the gonads of the normal rabbit was studied by immunofluorescence and immunoelectron microscopy. The enzyme is present in the cytoplasm of testicular spermatids and of epididymal and ejaculated spermatozoa, and on the surface of follicular and tubal cocytes. These findings support the hypothesis that ACE has a role in gamete maturation and in fertilization. [ABSTRACT FROM AUTHOR]