U.S. Securities and Exchange Commission Chairman Mary Schapiro testifies before the Senate Banking Committee on Capitol Hill in Washington, June 22, 2009.    REUTERS/Jim Young      By Jonathan Spicer
NEW YORK, Aug 24 (Reuters) – Senator Ted Kaufman on Monday asked U.S. regulators to undertake a comprehensive review of several “questionable” developments in the structure of capital markets, the latest lawmaker to weigh in on so-called dark pools, flashes, and high-frequency trading.