As Tenet Healthcare Corp. shares sank to another all-time low November 5, the company's chief executive purchased 100,000 shares at an average cost of $2.68 each. Chief Operating Officer Stephen Newman purchased 30,000 for $2.50 each and general counsel Gary Ruff purchased 10,000 shares for $2.55 each. The moves came a day after the hospital operator posted disappointing third-quarter results and lowered a key full-year earnings target, citing declines in admissions of patients with commercial health plans.