The Los Angeles Business Journal’s index of largest local public companies dropped sharply for the week ended Sept. 23, in line with a sell off in the markets over recession fears.

The weighted LABJ index fell 7.5 percent to close at 102.96. Decliners outpaced gainers 150 to 17 and nine companies were unchanged.

Analyst speculation about Power-One Inc.’s future earnings prompted the Camarillo power management company to drop nearly 25 percent to $5.23.

Stocks across a wide variety of industries fell, even for companies with positive news to report. PC Mall Inc. dropped 22 percent to $4.87. The Torrance technology online retailer recently launched a new e-mailed daily deals service.

Sylmar construction company Tutor Perini Corp. split off its electrical and mechanical contractors into a new specialty contractors group that is expected to generate revenue of more than $1 billion over the next four quarters. But the company ended the week down nearly 19 percent to close at $11.54.

Los Angeles engineering company Aecom Technology Corp. fell more than 15 percent to $18.06 despite announcing a contract to supervise the construction of a Russian highway.

Among a small handful of double-digit gainers was Iris International Inc., which gained 12 percent to $9.66. The Chatsworth developer of medical diagnostics tests received U.S. Food and Drug Administration clearance to market a new prostate cancer test.

MannKind Corp. ended the week up 10 percent to $3.74. Instead of issuing new shares, the Valencia biotech plans to sell about $370 million in senior secured discount notes to help pay for additional drug trials that the FDA is requiring before approving its experimental insulin inhaler Afrezza.