The top after-market NYSE gainers Tuesday were Blyth Inc, Knight Capital Group, Delphi Automotive, Mine Safety Appliances and Box Ships Inc. The top after-market NYSE losers were Energen Corp, Tenet Healthcare, Unit Corp, Lender Processing Services and Abercrombie & Fitch.

Gainers

Blyth Inc. (BTH) shares climbed 9.88 percent to $20.36 in post-market trading. Blyth announced Tuesday that it and other members of ViSalus have reached an agreement whereby Blyth increased its ownership in ViSalus to more than 80% for a payment of $57.4 million to the other members of ViSalus.

Knight Capital Group Inc. (KCG) shares surged 4.80 percent to $3.49 in post-market trading. Getco Holding Company LLC will buy Knight Capital for about $2 billion after sweetening its offer for the equities market-making firm to beat out rival Virtu Financial LLC, Reuters reported citing people close to the deal.

Delphi Automotive Plc. (DLPH) shares surged 4.47 percent to $35.99 in post-market trading. Delphi will replace Titanium Metals Corp in the S&P 500 after the close of trading Friday, Dec. 21.

Mine Safety Appliances Co. (MSA) shares gained 2.83 percent to $42.18 in post-market trading. The stock has a 52-week low of $32.32, a 52-week high of $44.34 and $1.52 billion in market capitalization.

Box Ships Inc. (TEU) shares rose 2.75 percent to $4.27 in post-market trading. The company stock plunged nearly 5 percent in regular trading.

Losers

Energen Corp. (EGN) shares plunged 5.58 percent to $42.77 in post-market trading. The company currently expects its fiscal 2012 net profit to be in a range of $3.15 to $3.25 per share and, down from its prior estimation of $3.15 to $3.55 per share and also fell short of analysts' estimation of $3.45 per share.

Tenet Healthcare Corp. (THC) shares plunged 4.29 percent to $31.08 in post-market trading. The company stock surged more than 4 percent in regular trading after it was initiated with “overweight” rating at JPMorgan Chase with a price target of $41.00.

Unit Corp. (UNT) shares declined 3.95 percent to $44.60 in post-market trading. The stock has a 52-week low of $32.08, a 52-week high of $50.90 and $2.25 billion in market capitalization.

Lender Processing Services Inc. (LPS) shares declined 3.51 percent to $24.80 in post-market trading. The stock has a 52-week low of $14.09, a 52-week high of $30.88 and $2.18 billion in market capitalization.

Abercrombie & Fitch Co. (ANF) shares fell 3.51 percent to $47.27 in post-market trading. The company stock surged nearly 4 percent in regular trading.