Shares of Martek Biosciences ( MATK) were among the best-performing health-related stocks Thursday, jumping 18% after the maker of algae-related nutritional products raised its first-quarter sales guidance. The company now sees sales of $62 million to $63 million, up from an earlier view of $58 million to $59 million. Analysts polled by Thomson First Call expected sales of $58.4 million. Martek attributed the revised guidance to growth in sales of its core infant formula. Shares were trading up $5.07 to $33.26. Shares of eResearch Technology ( ERES) slumped 17% after the supplier of technology used by biotech companies posted solid fourth-quarter earnings but warned that first-quarter results would be below forecasts. The company also said its chief executive will retire by the end of the year. For the fourth quarter, eResearch earned $5.3 million, or 10 cents a share, on sales of $25.4 million. Analysts expected earnings of 8 cents a share and sales of $24.5 million. During the year-earlier period, the company earned $7 million, or 13 cents a share, on sales of $27.1 million. Looking ahead, eResearch sees first-quarter earnings of 5 cents to 7 cents a share on sales of $21 million to $23 million. The guidance excludes stock-based compensation costs, which will lower earnings by a penny a share. Analysts project earnings of 10 cents a share and sales of $26.8 million. The company said that Joseph Esposito plans to retire as CEO before the end of 2006. "In addressing the company's future needs for pursuing our next phase of growth and profitability, both the board and I believe it is an opportune time for new leadership to take eResearch to the next level," Esposito said in a prepared statement. Shares were trading down $2.95 to $14.81. Shares of Dendrite ( DRTE) fell 12% after the provider of software and services to the pharmaceutical industry posted fourth-quarter earnings that were below expectations. The company earned $21,000, or less than a penny a share, on sales of $108.4 million. On an adjusted basis, which excludes noncash amortization expense, the company earned $250,000, or 1 cent a share. Analysts expected earnings of 4 cents a share, with sales of $106.4 million. "The fourth quarter was a difficult experience as we did not execute properly and take full advantage of our many growth opportunities," the company said. A year ago, the company posted adjusted earnings of $9.7 million, or 22 cents a share, on sales of $104.8 million. Shares were trading down $1.76 to $12.60.