George R. Evanega has resigned as president and chief executive officer of Gull Laboratories Inc., effective April 6.

Silke Humberg was elected the company's new president and chief executive, according to a Gull press release.Humberg had been senior vice president of international business and development for the intensive care and hemotechnology division of Fresenius AG. She was elected to the Gull board of directors in March.

Gull previously announced that, following its large 1997 loss and related decrease in liquidity, the board had expanded the role of its executive committee to assist in reorganizing its operations.

The company also is discussing with its banks alternative covenants to be put in place in connection with the extension of its line of credit, which comes due in May 1998, and other debt currently outstanding.

Gull Laboratories develops, manufactures and markets diagnostic test kits for the detection of infectious diseases. It is a majority-owned subsidiary of Fresenius AG, an international operating company based in Bad Homburg, Germany.