October 18, 1983

International Robert C. McFarlane is President Reagan's new national security adviser. In making the announcement, Mr. Reagan strongly praised Mr. McFarlane, a retired Marine Corps lieutenant colonel who recently served as the President's special Middle East envoy, in an apparent effort to ally concern about the appointment among Republican conservatives. The appointment, which does not require Senate confirmation, took effect at once. (Page A1, Column 6.) Iran's threats to close a waterway in the Persian Gulf region were assailed by Secretary of State George P. Shultz. It was the first time that Mr. Shultz had suggested that the Reagan Administration might be shifting its policy away from neutrality in the Iran-Iraq war. (A1:3.)

''I only wish the election were really next Tuesday rather than a year from now.'' - Senator Paul Laxalt, Republican of Nevada. (A22:3.)

DETECTION of many fetal defects as early as the 10th week of pregnancy may soon become practicle because of a new technique that some experts expect to replace most uses of amniocentesis, currently the standard test for such conditions, within the next several years. The new method is called chorionic villus biopsy. Unlike amniocentesis, which relies on fetal cells found in samples of amniotic fluid taken with a needle through the abdominal wall, chorionic villus biopsy samples fetal tissue directly through the cervix. It is now being tested at several medical centers in the United States and Europe almost a decade after a primitive version of the technique was first tried in China. A small group of experts will meet today at the National Institute of Child Health and Human Development in Bethesda, Md., to discuss the technique. Experts have high hopes for it, but the method has not yet been used widely enough for its safety and efficacy to be evaluated thoroughly. Dr. George G. Rhoads of the institute said the group would discuss optimum ways of answering these questions.

The long-expected battle to revamp the giant Gulf Oil Corporation of Pittsburgh erupted yesterday with the disclosure by T. Boone Pickens Jr., the Texas oilman, that a multimillionaire group he headed had spent $630 million for 8.75 percent of Gulf's stock and was committed to raising its purchases to $1.1 billion - a stake of nearly 15 percent. The purpose, the group told the Securities and Exchange Commission in a 63-page filing, is to bring about ''a significant appreciation'' in Gulf's market value. Wall Street analysts seemed to place considerable importance on the group's plan to break up Gulf into at least two parts, creating a royalty trust to be given to shareholders. The royalty trust would essentially be a collection of Gulf oilfields spun off into a trust that would permit earnings from the fields to escape many corporate taxes. Units in the trust, similar to shares in a corporation, could be traded on the stock exchange and the earnings of the trust would be paid out in the form of royalty payments to the unit holders.

THE three Nobel Prizes in science and medicine have long been the most prestigious of awards. Each year scientists throughout the world compete desperately for them; universities scramble to hire the winners; nations routinely count them up as measures of scientific prowess, and the Nobel laureates become instant celebrities whose advice is sought on everything from research to war and peace. But criticisms of the awards process are being made by a small band of scholars who have been analyzing Nobel choices and records in an effort to evaluate how well the selection committees have done since the first winners were chosen in 1901. These scholars have concluded in particular that restrictions in the will left by Alfred Nobel, the Swedish industrialist who established the prizes, actually freeze out some of the truly towering figures of science - researchers who by almost any definition are more important than many of those who receive the prizes. The critics find evidence that the committees have been swayed by rivalries and jealousies having little to do with scientific merit. Moreover, there are some who believe that the awards do more harm than good.