Shares of several biotech companies developing stem cell-based therapies rose Wednesday on news that a Missouri measure protecting stem-cell research narrowly passed Tuesday.

The state constitutional amendment drew national attention after actor Michael J. Fox, who has Parkinson's disease, appeared in a television ad endorsing the bill.

Shares of Palo Alto, Calif.-based StemCells Inc. rose 21 cents, or 6.8 percent to $3.28 in morning trading on the Nasdaq as volume surged. The company is focusing its research on treating major organ systems using stem cells.

Geron Corp., based in Menlo Park, Calif., rose 17 cents, or 2 percent, to $8.55 on the Nasdaq as volume doubled. Geron is developing possible treatments for a variety of diseases based on stem-cell technology.

Cambridge, Mass.-based ViaCell Inc. caught a slight boost from the news, rising 5 cents to $5.56 in morning trading. The company develops umbilical cord and adult-derived stem-cell treatment candidates for cancer, cardiac disease and diabetes.

The Missouri legislation allows any federally allowed stem-cell research and treatment to occur in the state. Bank of America analyst Frank H. Pinkerton considered the vote a much needed candidate for Invitrogen Corp., which makes kits used by researchers and companies to speed up gene cloning. In June the company licensed patents related to human embryonic stem cells from Geron.

"There are still questions regarding intellectual property ownership, economic returns, and funding has also slowed the research process; however, we view this as a step toward loosening funds that could accelerate Invitrogen's sales," he said in a note to investors.

Shares of Carlsbad, Calif.-based Invitrogen rose 37 cents to $57.74 in the morning Nasdaq session.