Gains from sales of property and a federal income tax credit due for previous loses enabled B.F. Saul Real Estate Investment Trust to report a net profit of $2.7 million (45 cents a share) for the first quarter of fiscal 1983.

The Saul REIT, which lost $1.1 million (18 cents) in the same period a year ago, reported gross revenues slipped from $14.38 million to $14.32 million and the quarter's deficit from operations increased to $984,000 from $130,000.

But the trust earned a $296,000 profit on condominium conversions, posted gains of $3.87 million from sales of other properties and took advantages of tax write-offs totaling $1.24 million from previous losses that produced $2,731,000 in earnings for the three months ended Dec. 31.

U.S. Design Corp., a Lanham computer company, reported its revenues jumped from $21,000 to $905,000 and losses slid to $439,000 (16 cents a share) from $466,000 (17 cents) for the quarter ended Dec. 31.

Chairman William R. Anderson Jr. said USDC "is continuing to sustain losses as a result of our continued heavy investment in facilities and personnel necessary to produce our products in larger volumes."

Sales of the firm's information storage systems jumped 70 percent from the previous quarter's $537,000, and the firm has signed an agreement for marketing its products in Europe, he added.