Shares of

Gene Logic

(GLGC)

were among the worst-performing health-related stocks Thursday, plunging 34% after the provider of drug discovery and development services withdrew its 2006 and 2007 guidance.

The company said that revenue at its genomics division during the second quarter and full year will be significantly lower than expected. What's more, the company said lower-than-expected revenue would hurt operating results at the division for the "foreseeable future." In the meantime, the company is reviewing its genomics division strategy.

Gene Logic also announced the departure of Dennis Rossi, senior vice president and general manager of its genomics unit. The company said Rossi left for personal reasons and to pursue other opportunities. Shares were trading down 68 cents to $1.34.

Celera Genomics

(CRA)

rose 2% after the biotech company said it expects to be profitable by the end of fiscal 2008. For fiscal 2007, meanwhile, the company projects a loss of $28 million to $35 million. The company sees fiscal 2007 revenue of $40 million to $45 million. Looking far into the future, the company said it expects fiscal 2011 revenue of about $160 million to $200 million. End-user sales are expected to be $400 million to $500 million. Operating earnings should be about 15% to 20% of reported revenue, the company said. Shares were trading up 17 cents to $11.34.

Shares of

McKesson

(MCK) - Get Report

traded actively after the health care services company reiterated its fiscal 2007 earnings outlook. For the period ending March 31, 2007, the company continues to forecast earnings of $2.55 to $2.70 a share. Analysts polled by Thomson First Call project earnings of $2.63 a share. The guidance includes previously announced pretax restructuring charges totaling about $25 million. Shares were recently down 82 cents to $45.52.

Orchid Cellmark

(ORCH)

plunged 35% after the genetic testing company posted a wider first-quarter loss and said it expects operating challenges to continue for the rest of the year. The company posted a loss of $6.6 million, or 27 cents a share, on revenue of $12.6 million. During the year-earlier quarter, Orchid Cellmark posted a loss of $1.7 million, or 7 cents a share, on revenue of $14.7 million. "Our first quarter results were, to say the least, extremely disappointing," Orchid Cellmark said. "The company's poor results reflect operational weaknesses in the company that we are now addressing aggressively." Shares were trading down $1.28 to $2.42.

Shares of

MedImmune

(MEDI)

sagged 7% after the drugmaker laid out plans to sell $1 billion in convertible senior notes. The company plans to offer $500 million in notes due 2011 and $500 million in notes due 2013. MedImmune also plans to grant initial purchasers an option to buy up to an additional $75 million in notes for each series to cover over-allotments. The company will use proceeds from the offering to fund the cost of convertible note hedge transactions and for working capital and general corporate purposes. Shares recently had fallen $2.10 to $27.13.

Other health care volume movers included

Teva Pharmaceutical Industries

(TEVA) - Get Report

, down 52 cents to $31.75;

Boston Scientific

(BSX) - Get Report

, down 62 cents to $18.49;

Pfizer

(PFE) - Get Report

, up 3 cents to $22.72;

Merck

(MRK) - Get Report

, up 2 cents to $35.29;

Johnson & Johnson

(JNJ) - Get Report

, down 75 cents to $61.04;

Amgen

(AMGN) - Get Report

, down 91 cents to $64.65;

Millennium Pharmaceuticals

(MLNM)

, down 29 cents to $9.70;

Elan

(ELN)

, down 33 cents to $16.48;

UnitedHealth Group

(UNH) - Get Report

, up 54 cents to $44.61; and

Bristol-Myers Squibb

(BMY) - Get Report

, down 44 cents to $25.28.