K-ras and p53 mutations in colonic lavage fluid of patients with colorectal neoplasias

Background: The adenoma-carcinoma sequence has its molecular basis in several gene mutations of which K-ras and p53 are of paramount importance. The aims of this study were to evaluate whether these genetic alterations can be detected in colonic lavage fluid from patients with colorectal adenomas and carcinomas. Methods: In 45 patients with adenomas, 20 patients with colorectal carcinomas and 38 patients with non-neoplastic and noninflammatory diseases of the colon p53 and K-ras mutations were evaluated in colonic lavage fluid employing single-strand confirmation polymorphism analysis and dot-blot hybridization, respectively. Results: Mutations of the K-ras and the p53 gene were found in 15.6% (p = 0.065) of patients with adenomas, in 25.0% (p = 0.016) of patients with carcinomas and in 2.6% in the control group. Conclusion: Genetic alterations in the colonic lavage fluid could be an additional diagnostic tool for the surveillance of patients with colorectal neoplasias. Copyright (C) 2001 S. Karger AG, Basel

Electron exchange model potential: Application to positronium-helium scattering

The formulation of a suitable nonlocal model potential for electron exchange is presented, checked with electron-hydrogen and electron-helium scattering, and applied to the study of elastic and inelastic scattering and ionization of ortho positronium (Ps) by helium. The elastic scattering and the $n = 2$ excitations of Ps are investigated using a three-Ps-state close-coupling approximation. The higher ($n\ge 3$) excitations and ionization of Ps atom are treated in the framework of Born approximation with present exchange. Calculations are reported of phase shifts, and elastic, Ps-excitation, and total cross sections. The present target elastic total cross section agrees well with experimental results at thermal to medium energies.Comment: 16 latex pages, 7 postscript figure