The Los Angeles Business Journal’s index of largest local public companies gained for the week, despite Friday’s sell-off in the broader markets over setbacks in “fiscal cliff” negotiations.

The weighted LABJ Stock Index rose nearly 1 percent to close at 135.91 for the week ended Dec. 21. Gainers outpaced decliners 102 to 61, with eight companies unchanged.

The biggest loser was THQ Inc., plunging 70 percent to 40 cents. The Agoura Hills video game developer filed for Chapter 11 bankruptcy as it seeks a buyer.

Among other big decliners was Herbalife Ltd., dropping 39 percent to $27.30. A noted hedge fund trader announced he has been shorting shares of the Los Angeles weight loss and nutritional supplement maker for a year because he considers the company’s multilevel marketing business model an unsustainable “pyramid scheme.”

The biggest gainer was Spark Networks Inc., rising more than 18 percent to $7.73. The Beverly Hills online personals company has been successfully building its subscriber base among Christian singles.

Vitesse Semiconductor Corp. gained more than 17 percent to $2.20. The Camarillo chipmaker completed the sale of 10 million common shares, with underwriters exercising their option to purchase additional shares.