Mario Gabelli, one of the world’s wealthiest men, put another $3.4 million into Orthovita Inc. (NSDQ:VITA) and dropped $25 million on American Medical Systems Holdings Inc. (NSDQ:AMMD).

Both companies are in the middle of mergers. Orthovita received a $3.85-per-share tender offer from Stryker Corp. (NYSE:SYK) last week; AMMD announced a $2.9 billion acquisition by Endo Pharmaceuticals Holdings Inc. (NSDQ:ENDP) in April.

Gabelli is chairman & CEO of Gamco Investors Inc. (NYSE:GBL), a $14 billion global investment firm based in Rye, N.Y. He’s No. 937 on the Forbes 2010 list of the world’s billionaires.

"We like to buy companies that are ignored and unloved," Gabelli told Bloomberg Television, talking about Gamco’s investment philosophy.

The investment tycoon first unveiled a 5.42 percent stake in Orthovita just days before the announcement of Stryker’s tender offer. The new stock brings Gabelli’s total investment in the Malvern, Pa.-based orthopedic biologics maker to nearly $18.5 million, with 6.58 percent ownership, according to the filing.

Gabelli’s $24 million bought him 6.46 percent of AMMD, which reported modest gains in its first quarter 2011 earnings report.

Gamco had no stake in either company as of its first-quarter holdings report.

Here’s a roundup of other dealflow and investment news:

• CSI files $75 million equity and debt offering
  Cardiovascular Systems Inc. (NSDQ:CSII) registered with the federal SEC to sell up to $75 million in equity and debt securities. The New Brighton, Minn.-based cardiovascular device maker hasn’t announced plans to release the securities into the market.
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• Lumicell lands $2.7 million
  Lumicell Diagnostics Inc., a Waltham, Mass.-based developer of cancer diagnostic devices, announced a $2.7 million equity sale to 4 unnamed investors. The company hopes to rein in another $1.2 million in this round.
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