It was an up and down week on Wall Street as oil prices continued their upward spiral. The Dow Jones industrial average closed Friday at 10,629.67, down 1.3 percent for the week. The Nasdaq finished the week off 1.7 percent at 2,007.79, its lowest close of the year. At one point during the week, the Nasdaq dropped below 2,000 for the first time in more than four months. Among the reasons cited for its decline was a warning from Radio Shack that cell-phone sales may be slowing. Amid its well-chronicled woes, IPG's shares fell almost 5 percent in Monday's trading, then dropped only slightly over the next few days to close at $11.76, down 6 percent for the week. Omnicom shares zig-zagged but closed down only a quarter, at $88. WPP, trading on the Nasdaq as American Depository Receipts, also saw little movement, closing at $59.52, up 1.3 percent for the week.