January 17, 1984

Federal regulators, in a move to reduce the losses of the two Federal deposit insurance funds, voted tentatively today to limit the availability of insurance on deposits placed by brokers, but ran into unexpected - and potentially fatal - opposition from the Treasury Department. Although the target of the curb appears to be the growing corps of financial middlemen known as money brokers, Wall Street executives said that the action, if it becomes final, would make it all but impossible for stockbrokers to offer their customers federally insured money market accounts. In separate but coordinated actions, both the Federal Deposit Insurance Corporation and the Federal Home Loan Bank Board proposed regulations that, if made final, would deny insurance to deposits in excess of $100,000 placed by any broker at any one insured bank or savings association. The bank board manages the Federal Savings and Loan Insurance Corporation, which insures deposits at savings associations.

The simple little sea urchin with its bristly coat is providing important new insights into one of nature's best-kept secrets: how a single fertilized egg cell gives rise to the millions of specialized cells that compose an adult organism. Using advanced techniques of molecular biology, scientists have recently learned, to their surprise, that in terms of the diversity of genetic information actually put into action, a ''simple'' fertilized egg is far more complex than any cell in the adult animal. This probably holds true for human beings as well as sea urchins, they believe. Moreover, genetic products inherited through the egg - and therefore from the mother alone - exert powerful control over embryonic development. Biologists have also observed, for the first time, that some genes turn on rapidly as an embryo develops, other genes turn off slowly and some continue to be used throughout embryonic life. Thus, the patterns of gene activity that underlie the building of the embryo are complex and of more kinds than one.

In the last four days the nation's nuclear energy industry has been rocked by what many analysts say are two stunning and potentially destructive precedents. First, a nuclear power plant was scrapped nearer to completion and with more money invested in it than ever before. Second, the Federal Government for the first time denied a utility permission to operate a newly completed nuclear plant. Last Friday, a Federal Nuclear Regulatory Commission licensing board told the Commonwealth Edison Company that it could not operate the nearly completed $3.35 billion Byron Nuclear Power Station near Rockford, Ill., because of inadequate quality controls during its construction.

France announced today that it had reached an arms sales agreement of about $4.5 billion to provide Saudi Arabia a mobile system of antiaircraft missiles for the protection of its oilfields and other important ground installations. The order, worth nearly 40 billion francs, is the largest France hasever received from an arms customer, the Government said. Far larger was the $8.5 billion American sale of Awacs radar planes to Saudi Arabia, which was approved by the Senate in 1981. The order for the French air defense system was signed Jan. 11 by Defense Minister Charles Hernu and his Saudi counterpart, Prince Sultan, after a year and a half of negotiations.

WITH a national debate now raging over the quality of American education, high schools in New York City have developed an ''Academic Index'' to measure educational excellence through an objective formula. The index rates individual schools on the basis of such factors as the number of students who take and pass Regents Examinations and the number who take difficult courses in basic academic subjects. ''Numbers drive a school system, and the index is a way to rate schools,'' said Aaron N. Maloff, the Senior Superintendent for High School Curriculum and Instruction, who developed the system. ''More important, it is a diagnostic tool that focuses clearly on the components of a school and helps it to become better.'' The new approach differs from the usual method of judging schools by the performance of their students on standardized tests. Mr. Maloff said the new technique could be readily adapted by any school system ''with access to an external test such as the Regents Examinations.''