The Los Angeles Business Journal’s index of the largest local public companies closed down for the week ended Sept. 10 even though the overall market rose late in the week following encouraging economic news.

The weighted LABJ index closed down nearly 4 percent to 113.23, with gainers outpacing decliners 99 to 78.

Despite no market-moving announcements, the top gainer was Genius Products Inc., a Santa Monica home entertainment products company that acquires, produces, and licenses a library of motion pictures, television programming and other entertainment. Shares jumped 35 percent to $6.95.

RadNet Inc, gained 28 percent to $2.39 after the Los Angeles company said it was buying five imaging centers in northern New Jersey and taking a 50 percent stake in a sixth center.

Mission Valley Bancorp, the Sun Valley parent of Mission Valley Bank, gained 17 percent to $3.99 after announcing that it had moved its TARP federal recovery capital into the Community Development Capital Initiative program, which will help it make more investments in economically distressed San Fernando Valley markets.

Motorcar Parts of America Inc. rose more than 15 percent to $8.08 after the Los Angeles manufacturer and distributor of aftermarket auto parts received an analyst upgrade.

Among the largest decliners was Manhattan Beach footwear maker Skechers U.S.A., which fell 16 percent to 22.84 on an analyst’s downgrade.

Monrovia unmanned aircraft maker AeroVironment Inc. fell 8 percent to $22.08 despite reporting a narrower-than-expected quarterly loss.