Health and industrial sciences company PerkinElmer Inc. said Thursday that its profit fell by half in the second quarter compared with a year ago, when it bought part of a joint venture with Danaher Corp.

In the three months ended July 3, PerkinElmer said its profit declined 50 percent to $28.6 million, or 25 cents per share, from $57.6 million, or 49 cents per share. The company said it earned 42 cents per share excluding amortization costs and purchase accounting adjustments.

Its revenue grew 14 percent, to $479.5 million from $421.6 million.

Analysts expected a profit of 40 cents per share and $477.6 million in revenue, according to FactSet.

In the second quarter of 2010, PerkinElmer reported a $25.6 million gain on an acquisition of half of a scientific instrument joint venture with Danaher.

In the latest quarter, PerkinElmer said revenue from its human health business grew 11 percent to $219.2 million, and environmental health revenue rose 16 percent to $260.2 million.

PerkinElmer raised its annual profit forecast, saying it expects to earn between $1.64 and $1.68 per share. It had estimated a profit of $1.62 to $1.67 per share.

Analysts are forecasting a profit of $1.67 per share on average.

Shares of PerkinElmer declined 5.8 percent to $21.39 Thursday as the markets stumbled. The stock fell an additional $1.97, or 9.2 percent, to $19.42 in after-hours trading following the earnings release.