The top after-market NASDAQ Stock Market gainers are: Ultra Clean Holdings, Calamos Asset Management, ACADIA Pharmaceuticals, Veeco Instruments, and Cubist Pharmaceuticals. The top after-market NASDAQ Stock Market losers are: Express Scripts, Netflix, Rent-A-Center, L & L Energy, and MIND C.T.I.

Gainers

Ultra Clean Holdings Inc. (UCTT) stock jumped 11.33 percent to $11.45 in the after-market trading, as it guided second quarter above Street view. The company expects second quarter earnings of 26 cents to 29 cents a share and revenue of $128 million to $133 million, while Street predicts profit of 24 cents a share on revenue of $125.24 million. The company expects tax rate of 26 percent. Moving ahead to the second quarter of 2011 we anticipate a continued increase in overall demand as well as continued progress in penetrating the HB-LED market, said Clarence Granger, Chief Executive Officer of Ultra Clean.

Ultra Clean Holdings reported first quarter earnings of $5.8 million or 25 cents a share, up from $3.9 million or 17 cents a share last year. Revenue rose to $126.7 million from $98.5 million. Analysts had expected profit of 21 cents a share on revenue of $121.65 million.

Calamos Asset Management Inc. (CLMS) stock grew 4.98 percent to $16.24 in the after-market trading. Standard & Poor's, a subsidiary of The McGraw-Hill Companies Inc. (MHP), said SmallCap 600 constituent Catalyst Health Solutions Inc. (CHSI) will replace AirTran Holdings Inc. (AAI) in the S&P MidCap 400 index, and Calamos Asset will replace Catalyst Health in the S&P SmallCap 600 index after the close of trading on May 2.

ACADIA Pharmaceuticals, Inc. (ACAD) stock gained 4.76 percent to $2.86 in the after-market trading.

Veeco Instruments Inc. (VECO) stock increased 4.75 percent to $50.25 in the after-market trading, as its first quarter earnings and revenue exceeded Street view. Adjusted profit was $56.55 million or $1.33 a share, up from $17.59 million or $0.42 a share last year. Revenue improved 89 percent to $254.67 million. Analysts had expected profit of $1.21 a share on revenue of $246.68 million.

Veeco Instruments expects second quarter adjusted earnings of $1.20 to $1.45 a share and revenue of $255 million to $285 million, while Street analysts predict profit of $1.34 a share on revenue of $270.88 million. Veeco's $530 million in backlog, combined with our forecasted Q2 revenue increase and very positive order outlook give us even greater confidence in our full year 2011 guidance of over $1 billion in revenues and adjusted earnings of greater than $5.00 a share, said Chief Executive John Peeler. Analysts expect earnings of $5.17 a share on revenue of $1.07 billion for the full year 2011.

Cubist Pharmaceuticals Inc. (CBST) stock rose 4.26 percent to $35 in the after-market trading.

Losers

Express Scripts Inc. (ESRX) stock plunged 6.36 percent to $51.85 in the after-market trading, as its first quarter earnings and revenue missed Street view. Profit was $326.5 million or 61 cents a share, up from $260.2 million or 47 cents a share last year. Adjusted earnings were 66 cents a share, up from 55 cents a share last year. Revenue declined to $11.09 billion from $11.14 billion. Analysts had expected profit of 69 cents a share on revenue of $11.56 billion. The company still expects 2011 adjusted earnings of $3.15 to $3.25 a share, while Street predicts $3.22 a share.

Separately, Express Scripts said it intends to begin a public offering of a benchmark amount of senior notes some time within the next few weeks. The company currently plans to use the net proceeds from the debt offering to repurchase its common stock under its existing share repurchase program, or for other general corporate purposes.

Netflix, Inc. (NFLX) stock fell 5.27 percent to $238.40 in the after-market trading, as it guided second quarter earnings below Street view. The company expects second quarter earnings of $50 million to $62 million or $0.93 to $1.15 a share. The company expects domestic revenue of $762 million to $778 million and international revenue of $16 million to $20 million. Street analysts predict profit of $1.19 a share on revenue of $763.01 million. The company expects total domestic subscribers of 24.0 million to 24.8 million and international subscribers of 0.9 million to 1.05 million.

Looking forward, our prior period comps for net adds are going to get tougher, and while we expect our net adds the rest of this year to continue to exceed those of the prior year, it won't be at a pace of nearly 2X like in Q1, Netflix said in a statement.

Netflix reported first quarter earnings of $60.23 million or $1.11 a share, up from $32.27 million or $0.59 a share last year. Revenue rose to $718.55 million from $493.67 million. Analysts had expected profit of $1.08 a share on revenue of $703.60 million.

Rent-A-Center Inc. (RCII) stock tumbled 5.27 percent to $32.70 in the after-market trading, as its first quarter earnings and revenue missed Street view. Profit was $44.2 million or 69 cents a share, down from $51.5 million or 77 cents a share last year. Adjusted earnings were 79 cents a share, up from 77 cents a share last year. Revenue rose 3.3 percent to $742.18 million. Analysts had expected profit of 85 cents a share on revenue of $754.58 million. Same-store sales for the quarter were 0.1 percent.

Rent-A-Center expects second quarter earnings of 68 cents to 74 cents a share and revenue of $694 million to $709 million, while Street predicts profit of 77 cents a share on revenue of $706.46 million. The company expects full year 2011 earnings of $2.90 to $3.10 a share and revenue of $2.868 billion to $2.928 billion, while Street predicts profit of $3.06 a share on revenue of $2.89 billion.

L & L Energy, Inc. (LLEN) stock slid 4.12 percent to $6.98 in the after-market trading.

MIND C.T.I., Ltd. (MNDO) stock declined 4.07 percent to $3.30 in the after-market trading.