MARKET PULSE-Yum Brands, Krispy Kreme, Tesla, Conatus Pharma, Oncomed

(For more market insights, including options activity, click on ; for the Day Ahead newsletter http://link.reuters.com/mex49s; for the Morning News Call newsletter, http://link.reuters.com/nex49s) U.S. stock index futures fell on Tuesday indicating the S&P 500 may fall for a third consecutive day on concerns a scale-back in stimulus by the Federal Reserve may be on the horizon.

Dow Jones industrial average futures were down 0.39 percent at 15,936, S&P 500 futures were down 0.28 percent at 1,794.7 and Nasdaq 100 futures were down 0.11 percent at 3,479.

** APPLE INC (NasdaqGS: AAPL - news) , Monday close $551.23, +0.94 pct premarket

The i-Phone maker has acquired social media search and analytics startup Topsy, an unusual purchase for a hardware-focused company that has made few forays into social networking.

** TWITTER INC (NYSE: TWTR - news) , Monday close $40.78, -0.44 pct premarket

Some of the five lead underwriters of the social media company's initial public offering said it might not achieve Facebook (NasdaqGS: FB - news) -like scale and its stock may not rise much.

** POTASH CORP OF SASKATCHEWAN INC, Monday close $31.71

The world's largest potash producer by capacity said it would cut 18 percent of its workforce as it struggled with slumping demand and weak prices for the crop ingredient.

** ONCOMED PHARMACEUTICALS INC (NasdaqGS: OMED - news) , Monday close $14, +83.21 pct premarket

** CELGENE CORP (Munich: CG3.MU - news) , Monday close $163.11

OncoMed said Celgene would develop and market six of its anti-cancer stem cell experimental drugs for an upfront payment of $155 million.

** YUM BRANDS INC, Monday close, $77.71, -1.80 pct after market

The company forecast a return to earnings per share growth in 2014 but said November sales at established KFC restaurants in China, its top market, failed to grow despite a successful half-priced chicken promotion.

** KRISPY KREME DOUGHNUTS INC (NYSE: KKD - news) , Monday close $24.55, -13.85 pct premarket

The doughnut chain forecast fiscal 2015 earnings below analysts' estimates, saying it expected international franchise same-store sales to remain negative. Krispy Kreme forecast adjusted earnings of 71-76 cents per share for its year ending January 2015. Analysts on average were expecting 77 cents per share, according to Thomson Reuters I/B/E/S.

** TESLA MOTORS INC (Xetra: A1CX3T - news) , Monday close $124.17, +5.86 pct premarket

The electric-car maker said Germany's vehicle regulatory agency would pursue "no further measures" after concluding a review of recent Tesla Model S fires in the United States and Mexico.

Morgan Stanley (Xetra: DWD.DE - news) named the stock its top pick.

** MICROSOFT CORP, Monday close $38.45

U.S. antitrust regulators have approved Microsoft (Hanover: 870747 - news) 's deal to buy Nokia Corp's mobile phone business, the Federal Trade Commission said on Monday.

** ASCENA RETAIL GROUP INC, Monday close $20.88, +4.2 pct after market

The women's apparel retailer reported a 5 percent rise in first-quarter sales as more customers shopped at its Lane Bryant and Justice brand stores.

** CONATUS PHARMACEUTICALS INC (NasdaqGM: CNAT - news) , Monday close $6.14, +26.06 pct premarket

The biotechnology company said the U.S. health regulator granted an orphan drug status to its experimental drug, emricasan, for the treatment of liver transplant recipients with a type of scarring that could be irreversible and lead to end-stage liver disease.

Orphan status is granted to drugs that treat conditions or diseases that affect fewer than 200,000 people in the United States. The status usually comes with a seven-year marketing exclusivity if the drug is approved for sale.

** LEXICON PHARMACEUTICALS INC (NasdaqGS: LXRX - news) , Monday close $2.32, -11.64 pct premarket

The company said its experimental irritable bowel syndrome drug, LX1033, failed the main goal of showing improvements in stool consistency over a placebo in an initial mid-stage study. However, there were positive effects on abdominal pain in the treated group that warrant further study, Lexicon said in a statement.

The drug was granted fast-track status by the U.S. health regulator in December last year.

** CBOE HOLDINGS INC (NasdaqGS: CBOE - news) , Monday close $52.98, -1.32 pct after market

The operator of the biggest U.S. stock-options market reported an 8 percent fall in trading volume in VIX (Volatility Index) futures to 2.5 million contracts. November exchange-wide trading volumes at CFE, a unit of CBOE, totaled about 2.6 million contracts.

** CME GROUP INC (NasdaqGS: CME - news) , Monday close $81.39, -9.87 pct premarket

The largest U.S. futures exchange operator reported a 7 percent fall in its CME Group (Kuala Lumpur: 7018.KL - news) foreign exchange average volume to 718,000 contracts per day. The company said total volume in November was more than 241 million contracts, of which 87 percent was traded electronically.

** 3D SYSTEMS CORP, Monday close $76.89, +1.44 pct premarket

** STRATASYS LTD (NasdaqGS: SSYS - news) , Monday close $118.84, +0.68 pct premarket

FBR started coverage on shares of the two 3D printer makers with "outperform" rating, according to Theflyonthewall.com.

** WESTERN GAS PARTNERS LP (NYSE: WES - news) , Monday close $63.41, -3.69 pct premarket

The company, which processes and transports oil and gas, announced on Monday an underwritten public offering of 4.5 million common units. The company said it expected to use the net proceeds from the offering to repay outstanding borrowings under its revolving credit facility.

** NRG YIELD INC (NYSE: NYLD - news) , Monday close $36.11

The renewable energy company said it entered an agreement to acquire the assets of privately held thermal energy supplier Energy Systems Co for $120 million in cash.

** THOR INDUSTRIES INC (NYSE: THO - news) , Monday close $54.25

The recreational vehicle (RV) maker reported lower-than-expected revenue for the first quarter, partly due to lower sales of towable RVs.

** ENVIVIO INC (NasdaqGS: ENVI - news) , Monday close $2.88, +8.33 pct premarket

The video delivery company reported a 62 percent rise in third-quarter revenue on Monday, helped by orders from Tier 1 customers.

** GT ADVANCED TECHNOLOGIES INC (NasdaqGS: GTAT - news) , Monday close $9.94, -5.94 pct premarket

The solar and LED equipment maker said on Monday that it would offer $125 million worth of senior notes to raise working capital and for general corporate purposes, including acquisitions and capital expenditures.

** MEDALLION FINANCIAL CORP (NasdaqGS: TAXI - news) , Monday close $17.54, -9.12 pct premarket

The specialty finance company said it commenced public offering of 2.9 million shares of its common stock. The company said it planned to use the proceeds for lending to and making investments in companies and for other general corporate purposes.

** NCR CORP (NYSE: NCR - news) , Monday close $34.19

The ATM maker said it would buy Digital Insight Corp, a provider of online and mobile banking technology, from private equity firm Thoma Bravo LLC for $1.65 billion to boost its financial services business.

** RIO TINTO PLC (LSE: RIO.L - news) , Monday close $52.37, +0.69 pct premarket

The miner plans to halve capital spending to $8 billion by 2015 from last year's level to cut debt, in the latest move by a major miner to slash outlays as commodities prices remain fragile. The cuts are sharper than some investors had expected and deeper than those made by Rio Tinto (Xetra: 855018 - news) 's major rivals. [ID: nL4N0JI081]

** GOLDMAN SACHS GROUP INC, Monday close $169.72, -0.37 pct premarket

** JPMORGAN CHASE & CO (NYSE: JPM - news) , Monday close $56.98, -0.14 pct premarket

The U.S. Federal Reserve on Monday said that it approved new capital plans by Goldman Sachs (NYSE: GS-PB - news) and JPMorgan, after initially ordering the banks to fix flaws in their capital planning processes.

** SOUTHWEST AIRLINES CO (NYSE: LUV - news) , Monday close $18.61

The U.S. Federal Aviation Administration on Monday proposed fining the Dallas-based airline $325,000, saying it operated an aircraft with improper modifications.

** CVS CAREMARK CORP, Monday close $66.65

The company agreed to pay $4.25 million to settle allegations it failed to reimburse Medicaid for patients' drug costs that should have been paid by private health plans administered under the company's pharmacy benefit management unit, the U.S. Justice Department said on Monday. [ID: nL2N0JH1YA]

** VALE SA, Monday close $14.89, +1.61 pct premarket

The world's No. 2 mining company lowered its investment budget for a third straight year as it bolstered efforts to focus expansion on its main iron ore business.

** BARRICK GOLD CORP, Monday close $15.54, +0.39 pct premarket

The world's largest gold producer is poised to announce a board shuffle and name a new chief operating officer, according to several sources familiar with the situation. (Compiled by Avik Das in Bangalore; Editing by Kirti Pandey)