After two weeks of slight losses, the Los Angeles Business Journal's index of the 200 largest public companies was hit hard this week, dropping 4.8 percent as 164 companies lost ground or stayed flat.

Falling the most was Carson-based auto parts supplier U.S. Auto Parts Network Inc., which reported poor fourth quarter earnings and saw shares shed a whopping 41 percent for the week nearly all on Friday. Shares closed the week at $2.94.

Also dropping was Santa Monica-based real estate investment trust Anworth Mortgage Asset Corp., which shed 38 percent after being downgraded by an investment firm. Shares closed at $6.

Long Beach-based prescription skincare products maker Obagi Medical Products Inc. was hit by poor earnings, dropping the 35 percent to $10.29.

But there were some bright spots. Shares in Chad Therapeutics Inc. surged 35 percent after the Chatsworth-based medical device manufacturer announced it had finalized the sale of a business unit. Shares closed at 42 cents per share.

Shares in North Hollywood-based IPC The Hospitalist Company Inc. gained 11 percent after the new issue had coverage initiated on it by an investment firm. Shares closed at $21.34.

Shares in Chatsworth-based biotech company Iris International Inc. gained 7 percent after the company announced it was buying back $15 million worth of stock. Shares closed at $11.17.

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