Midday Leaders and Laggards: Nasdaq 100

The index, which includes 100 of the largest nonfinancial securities listed on the Nasdaq Stock Market, gained 8.84 points to 1,845.93 in midday trading. The broader Nasdaq composite fell 2.59 points to 2,290.39.

Crude oil stayed on investors' minds during the session, remaining above $142 per barrel on the New York Mercantile Exchange.

Meanwhile, the Institute for Supply Management said manufacturing unexpectedly grew in June, but the data also shows that fuel and material prices are rising even as demand shrinks.

Shares of Petsmart Inc. rose 94 cents, or 4.7 percent, to $20.89. A Deutsche Bank analyst kept a "Buy" rating on the company Tuesday after a review of sector pricing.

Shares of University of Phoenix operator Apollo Group Inc. gained $1.83, or 4.1 percent, to $46.09. A BMO Capital Markets analyst said Tuesday a bill signed by President Bush that includes $63 billion over a decade for college scholarship programs for veterans who served after Sept. 11, 2001 may help the sector.

Shares of Celgene Corp. added $2.63, or 4.1 percent, to $66.50. A competitor said Tuesday its bone marrow drug failed in a late-stage European clinical trial.

On the falling side, shares of United Airlines operator UAL Corp. slipped 55 cents, or 10.5 percent, to $4.67. Earlier in the session, shares touched a 52-week low of $4.67. The profitability of airline operators is closely linked to jet-fuel costs.

Shares of Millicom International Cellular SA fell $6.12, or 5.9 percent, to $97.38.

Shares of Leap Wireless International Inc. shed $2.53, or 5.9 percent, to $40.64.