US STOCKS-Dow, S&P 500 lower on oil prices; Morgan Stanley weighs

(Corrects paragraph 7 to remove reference to Amazon.com (NasdaqGS: AMZN - news) as a Dow Jones industrials component; the error appeared in earlier versions)

* Morgan Stanley (Xetra: 885836 - news) leads weak results on Monday

* Exxon, Chevron (Swiss: CVX.SW - news) drag down S&P 500, Dow

* Weight Watchers soars after Oprah takes stake

* China Q3 GDP data weighs on commodities

* Dow down 0.14 pct, S&P down 0.15 pct, Nasdaq (NasdaqGS: NDAQ - news) up 0.22 pct

By Abhiram Nandakumar

Oct (HKSE: 3366-OL.HK - news) 19 (Reuters) - A swathe of weak quarterly results led by Morgan Stanley and a slide in commodity prices weighed on the Dow and S&P 500 indexes, while a rebound in healthcare and biotech stocks sent the Nasdaq composite higher.

The energy index fell 2.0 percent as Brent crude slid more than 3 percent to $48.80 on renewed worries about demand from China. Copper prices slipped 1.5 percent.

Exxon and Chevron fell 2 percent and were the biggest drags on the S&P 500 and the Dow Jones industrial average.

Morgan Stanley's shares fell as much as 6.9 percent to $31.60 after the bank's profit fell for the second straight quarter, capping mostly downbeat quarterly results from major U.S (Other OTC: UBGXF - news) . banks. The stock recorded its biggest results-day decline since 2009.

"You've got a market that's really somewhat directionless because you don't have a lot of data points out there that can drive the market up or down," said John Roberts, director of research at Hilliard Lyons.

At 12:23 p.m. ET (1623 GMT), the Dow was down 23.81 points, or 0.14 percent, at 17,192.16, the S&P 500 was down 2.95 points, or 0.15 percent, at 2,030.16 and the Nasdaq composite index was up 10.69 points, or 0.22 percent, at 4,897.37.

Investors will continue scrutinizing company reports this week with several Dow components posting quarterly results, including Caterpillar (NYSE: CAT - news) , Boeing (NYSE: BA - news) and Coca-Cola .

S&P 500 companies are expected to show a 3.9 percent fall in third-quarter profit, according to Thomson Reuters (Dusseldorf: TOC.DU - news) data.

Data on Monday showed China's economic growth slowed to 6.9 percent between July and September, but still ahead of the 6.8 percent forecast.

U.S. homebuilder sentiment improved in October, with the NAHB/Wells Fargo Housing Market index rising to 64, ahead of the 62 expected.

Halliburton (Hanover: HAL.HA - news) fell 2.0 percent to $37.05 after reporting a bigger-than-expected drop in quarterly revenue.

Weight Watchers surged 93 percent to $13.11 after it said Oprah Winfrey will buy a 10 percent stake in the company and join the board.

PMC-Sierra jumped nearly 14.1 percent to $11.68 after the chipmaker received a buyout offer from Microsemi , valuing the company at $2.4 billion.

IBM (NYSE: IBM - news) reports quarterly results after the close.

Declining issues outnumbered advancing ones on the NYSE by 1,630 to 1,332. On the Nasdaq, 1,355 issues rose and 1,297 fell.

The S&P 500 index showed 17 new 52-week highs and three new lows, while the Nasdaq recorded 44 new highs and 26 new lows. (Reporting by Abhiram Nandakumar in Bengaluru; Editing by Don Sebastian)