The Los Angeles Business Journal’s weighted index of the largest local public companies closed down for the week ended Sept. 20, even though most companies on the list were up for the week.

The LABJ index closed down 2.4 percent to 114.71, with gainers outpacing decliners 114 to 60.

One of the top gainers was struggling apparel retailer American Apparel Inc., which announced Friday afternoon that NYSE Amex regulators had accepted the Los Angeles company’s updated plan of compliance to avoid delisting. Shares built on earlier gains to close up 27 percent to $1.46.

RadNet Inc. closed up 16 percent to $2.49. The Los Angeles operator of medical imaging centers continued to benefit from last week’s announcement that it was diversifying by acquiring a medical imaging software company.

Cathay General Bancorp rose 11.5 percent to $11.84, after an analyst report suggested that the Los Angeles bank holding company could be an attractive acquisition target.

Los Angeles biotech Cytrx Corp. rose 13 percent to 79 cents as investors reacted to rumors that a large drug company was interested in acquiring RXi Pharmaceuticals Corp., a Worcester, Mass. spinoff in which Cytrx still holds a substantial stake.

Among a handful of large decliners that drove down the index was Camarillo solar inverter company Power-One Inc. which fell 24 percent to $8.33. Shares of the company, which also makes power conversion products, has been up 140 percent so far this year, but slid on investor speculation that its stock has been oversold.

Tix Corp. ended the week down nearly 23 percent to 58 cents after the Studio City ticketing and events promotion company said that it was exploring strategic alternatives, including the possible sale of its live entertainment business segment.