By Barbara Kollmeyer, MarketWatch

MADRID (MarketWatch) -- U.S. stock futures posted moderate gains on Tuesday, a day after Wall Street suffered heavy losses, with Citigroup Inc. and Johnson & Johnson each posting better-than-expected financial results ahead of the opening bell.

Futures for the S&P 500 index (SPZ4) rose 10 points to 1,874.60, while those for the Dow industrials (DJZ4) climbed 59 points to 16,290. Futures for the Nasdaq 100 index (NDZ4) gained 18 points to 3,817. Stock futures had earlier slipped into negative after downbeat German sentiment data.

Futures held to gains after the National Federation of Independent Business said its small-business optimism index fell 0.8 points to 95.3, which is 5 points below the pre-recession average.

Extending last week's equity losses, volatile trading on Monday ended with the S&P 500 (SPX) dropping 1.6% to 1,874.74. Like other major benchmarks, the S&P 500 is now trading below its 200-day moving average of 1,900. Vote here: Does this stock slump have further to go?

James Hughes, chief market analyst for Alpari U.K., said he's wary because he sees traders targeting old stories, such as concerns over slow global growth and its effect on earnings. "When traders look for excuses for why the market is falling, [it] is always a worrying time and would point to me as an indication that we could see much more negativity to come," he said in a note.

Earnings in focus: The tide could change with Tuesday's earnings batch, the first busy day in the third-quarter reporting season. Ahead of the bell, J.P. Morgan Chase & Co. (JPM) swung to a third-quarter profit as the bank rebounded from a year-earlier period in which it was hit by big legal charges. The bank's profit per share was $1.36 and revenue rose to $24.2 billion, against expectations for per-share earnings of $1.38 on revenue of $24 billion, according to analysts surveyed by FactSet.

The earnings were scheduled to be released around 7 a.m. Eastern Time, but showed up on the Internet several hours earlier on a third-party website. J.P. Morgan shares eased 0.4% in early premarket trading.

Citi (C) shares popped up 2.6% before the bell after third-quarter profit and revenue rose from the year-earlier period. Citi also plans to pare back from retail banking in smaller countries. Meanwhile, Wells Fargo & Co. (WFC) shares slipped 0.5% as the bank's quarterly profit met expectations but revenue beat estimates.

Johnson & Johnson (JNJ) shares picked up 1.4% premarket after quarterly earnings climbed nearly 30% on higher pharmaceutical sales.

Domino's Pizza Inc. (DPZ) was up 0.4% ahead of the bell after the chain delivered better-than-expected results.

Among other stocks in focus, Versar Inc. (VSR) was surging nearly 40% in premarket trading. Its PPS unit makes hazmat suits and mobile decontamination shelters. Other stocks linked to concerns over the Ebola virus continued a pattern of pushing higher. Lakeland Industries Inc. (LAKE) and Alpha Pro Tech Ltd. (APT) were trending higher. Ebola stock trading volumes should raise red flags

Other markets:European stocks fell after a key sentiment survey out of Germany turned negative. Burberry Group PLC shares dropped after the luxury-goods maker posted a rise in sales, but cited unfavorable foreign exchange headwinds and Chinese weakness. U.K. inflation fell to a five-year low. The European Court of Justice has begun holding a hearing on the European Central Bank's Outright Monetary Transactions bond-buying program.

In Asia, the Nikkei 225 index sank 2.4%, falling below the 15,000 level and skidding to two-month lows.

Crude-oil prices(CLX4) drifted lower, and gold(GCZ4) inched up, while the dollar ((USDJPY) pulled back from an overnight slip against the Japanese yen.

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