The top after-market Nasdaq gainers Monday were PetSmart, Synta Pharmaceuticals Corp, Sycamore Networks Inc, Glu Mobile Inc and PLX Technology Inc.

The top after-market Nasdaq losers were Halozyme Therapeutics Inc, RadiSys Corporation, Body Central Corp, GT Advanced Technologies and Gladstone Holdings.

Gainers

PetSmart (PETM) shares climbed 2.87 percent to $69.50 in post-market trading. The company shares gained after the reports that it would join Standard & Poor’s 500 Index after the close of trading Monday, replacing Sunoco Inc.

Synta Pharmaceuticals Corp (SNTA) shares surged 2.76 percent to $9.67 in post-market trading. The company shares surged over 23 percent Monday in regular trading after the company announced that interim results from a mid-stage study of its experimental cancer drug with a larger patient population showed positive results.

Sycamore Networks (SCMR) shares advanced 2.11 percent to $15.50 in post-market trading. The company stock lost 1.43 percent in regular trading.

Glu Mobile Inc (GLUU) shares rose 1.77 percent to $4.60 in post-market trading. The company shares have a 52-week trading range of $1.80 -$5.90 and a market capitalization of 294.50 million.

PLX Technology Inc (PLXT) shares gained 1.41 percent to $5.75 in post-market trading.

Losers

Halozyme Therapeutics Inc (HALO) shares plunged 25.38 percent to $5.50 in post-market trading.

RadiSys Corporation (RSYS) shares plunged 5.83 percent to $5.83 in post-market trading. The company stock lost over 4 percent in regular trading after it said that its chief executive Michel Dagenais had left the company. The company cut its revenue guidance for the third quarter, citing the weak telecommunications spending.

Body Central Corp (BODY) shares declined 3.78 percent to $11.02 in post-market trading. The company stock gained 9.57 percent in regular trading.

GT Advanced Technologies (GTAT) shares fell 3.36 percent to $5.17 in post-market trading.

Gladstone Investment Corporation (GAIN) shares declined 2.69 percent to $7.59 in post-market trading after the company announced that it planned to sell 4,000,000 shares of common stock in an underwritten public offering.