No officer, director, or employee of any corporation * * * primarily engaged in the issue, flotation, underwriting, public sale, or distribution at wholesale or retail, or through syndicate participation, of stocks, bonds, or other similar securities, shall serve [at] the same time as an officer, director, or employee of any member bank * * *.
12 C.F.R. §250.412
12 U.S.C. 248(i)