Good performances by its laboratory and research animals groups, lower interest expenses and a decline in the effective tax rate helped push first-quarter earnings at Mazleton Laboratories Corp. to a record level.

The Vienna company, which provides services for the life and environmental sciences industry, reported that net income for the quarter ended Sept 30 increased 19 percent over last year's earnings to $312.000 (16 cents a share) compared with $263.000 (16 cents).Revenues rose 21 percent to $7.9 million from the $6.5 million recorded for the first quarter last year.

On Nov. 1, Mazleton completed the acquisition of the Environmental Sciences Group of Nalco Chemical Co. Mazleton purchased the net assets of the Group, valued at about $3 million, for 207,551 shares of its common stock. Now known as Mazleton Environmental Sciences Corp., the company is involved in environmental studies for a variety of industries.

Riviere Realty Trust's net operating income increased 40 percent during the third quarter and jumped 57 percent for the nine months ended Sept. 30. Third-quarter net income was $138.509 (18 cents a share) compared with $98.952 (13 cents) for the third quarter of 1977. For the nine month period, the trust's net income before a gain on the sale of a rental property was$368.10 (47 cents) compared with $235.184 (30 cents) for the comparable period last year. Total net income for the nine months, including the $34,528 gain, amounted to $402.628 (51 cents a share).

Chairman Joseph D. Riviere announced that the trust recently sold a 3.2-acre parcel of undeveloped land in Nags Head, N.C. for $365,000. The sale will not result in a gain or loss to the trust, but Riviere added that it has converted a non-earning asset into a productive one.

Natural Energy Corp., a marketer of solar energy products and systems, registered its first profitable quarter since it began marketing operations in mid-1977. Third-quarter earnings totalled $9,256 on sales of $237,210. For the nine months ended Sept. 30, the firm posted a loss of $109,170 on sales of $458,102.

All the profits in the third quarter were produced by the company's mechanical contracting operations recently established in the Caribbean, according to James P. Ince, chief executive officer. Both domestic and Caribbean units have contract backlogs extending into next year.

RPS Products Inc. of Baltimore reported net income of $92,000 (7 cents a share) on sales of $9.8 million for the first quarter ended Sept. 30. This is down from the previous year's third quarter earnings of $153.000 (12 cents) and total income of $93,000 before extra-ordinary tax credit, or 7 cents a share, on $9.5 million in sales. For the fiscal year ended June 30, RPS had a next income of $475.000 (37 cents) and $427,000 income before extraordinary tax credit, or 33 cents a share, on sales of $36.8 million.

Government Services Savings & Loan Inc. announced record earnings for its second quarter and first six months of the fiscal year ended Sept. 30. For the quarter, earnings totaled $821,263 (95 cents a share), up 35 percent from the $607,312 (71 cents) recorded during the second quarter of the previous fiscal year. Earnings for the first fiscal half rose 29 percent to $1.5 million ($1.72 a share) over the $1.15 million ($1.34), reported for the first six months of 1977.

Total assets as of Sept. 30 were $314.9 million, up 13 percent from $278.9 million year ago. Savings deposits were $274 million, an increase of 11 percent over the $247.8 million on Sept. 30, 1977. Loans outstanding were $267.9 million, a 13 percent gain from the $236.3 million at the end of September 1977.

Providence Savings and Loan Association of Baileys Crossroads reported earnings of $877,365 ($4 a share) for the nine months ended Sept. 30, an increase of 7 percent from $816,424, ($3.75) for the same period last year after adjustment of a 10 percent stock dividend on Aug. 15.

Total assets at Providence were $112.6 million on Sept. 30, up 15 percent from the year ago figure of $98.3 million. Savings deposits of $102.7 million were up 14 percent from last year and mortgage loans rose more than 13 percent during the same period to $100.9 million.

First Financial of Virginia Corp., a savings and loan holding company, reported record earnings of $670,000 ($1.41 share) for its first fical quarter ended Sept. 30. This represents a 25 percent increase over last year when earnings were $537,000 ($1.13). A substantial increase in loan volume at First Financial's subsidiary. Washington-Lee Savings and Loan Association, was cited as one of the reasons for the corporation's recored performance.

Second National Building and Loan Inc. of Salisbury announced third quarter earnings of $143,589, versus $88,580 for the comparable quarter a year earlier, an increase of 62 percent. The association earned $404,384, ($3.84 a share) during the nine months ended Sept. 30 compared to $251,405 ($2.81), for the same period in 1977. Loan volume was up 41 percent and assets stood at $67.6 million, up 37 percent from last year.

Doughtie's Foods Inc., a Portsmouth-based processing and distribution firm, earned a record $472,000 (69 cents a share) on sales of $23.4 million for the nine months ended Sept. 30. That compares to earnings of $463,000 (68 cents) on $20.2 million in sales for the same period in 1977. Three month earnings ended Sept. 30 totaled $150,000, (22 cents) on sales of $8.6 million, down from earnings of $194,000 (28 cents) on sales of $7 million, for the corresponding quarter last year.

Universal Security Instruments Inc. of Owings Mills, Md. posted a net operating loss of $148,749 on sales of $1.24 million for the quarter ended Sept. 30, versus earnings of $215,453 (14 cents a share) on sales of $2.9 million for the same period last year. Sales and earnings for the six months ended Sept. 30 dropped sharply. Sales decreased to $2.9 million from $7 million and operating losses amounted to $317,850 against year ago earnings of $754,962.

James River Corp. of Virginia reported earnings of $3.93 million for the second quarter ended Oct. 29 nearly triple the $1.37 million reported for the same period last year. Earnings per share were $1.35, up 128 percent over the 59 cents reported in the second quarter of 1977. For the first half ended Oct. 29, net income increased almost three fold to $6 million.