Shares of Rita Medical Systems ( RITA) were among the worst-performing health-related stocks Wednesday, falling 7% after the medical device company cut its third-quarter sales estimate.

The company now expects sales of $11.1 million to $11.3 million, below its prior view of $12 million to $12.3 million. Rita continues to expect a loss of 2 cents to break-even. "Although we achieve third-quarter domestic sales growth of approximately 19% compared with last year, sales were lower than expected due in part to the impact of Hurricane Katrina on our customers located in the southeastern U.S.," the company said. Analysts surveyed by Thomson First Call projected sales of $11.4 million. Shares were trading down 25 cents to $3.22.

Vical ( VICL) fell 20% after the company laid out plans to sell $22.6 million in stock. The company plans to sell 4.7 million shares of stock at $4.80 apiece, which represents a 21% discount to Tuesday's closing price of $6.05. The stock sale is expected to close on Oct. 17. On Tuesday, shares of Vical rose 13% after the company said a National Institutes of Health HIV vaccine moved into a phase II trial. The vaccine, developed by scientists, is manufactured by Vical. Shares recently traded down $1.19 to $4.86.

Shares of Conmed ( CNMD) fell 16% after the surgical equipment company warned that third- and fourth-quarter results would fall short of expectations. The company expects adjusted earnings of $9.3 million to $9.6 million, or 31 cents to 32 cents a share, on sales of $150 million. Previously, the company said that it would post adjusted earnings of 41 cents to 44 cents a share on sales of $153 million to $156 million; analysts had been expecting earnings of 42 cents a share and sales of $154.5 million. "While the third quarter sales tend to be our weakest due to the seasonal nature of elective surgeries, our reports from the field suggest that this quarter was especially weak," the company said.

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