September 16, 1986

Because of a computer processing error, the Weather Report in some copies on Saturday repeated the previous day's listing of temperatures and forecasts for United States cities. Readers wishing a corrected list may write to the news desk, The New York Times, 229 West 43d Street, New York, N.Y. 10036.

The London Stock Exchange plans to merge with a group of international securities dealers in a bold bid to form a central electronic marketplace for trading leading international stocks when their home markets are closed and to compete with those markets when they are open, according to sources close to the exchange. The move by the exchange and the dealers' group, the International Securities Regulatory Association, would be the most important development to date in the evolution toward 24-hour global trading of major American and international stocks. The exchange will also seek to change its name to the International Stock Exchange, according to the sources, who said the actions would be announced this week. ''It's a formidable combination that may well attract business in U.S. stocks that normally might wait until the American market opens,'' said Gordon Macklin, president of the National Association of Securities Dealers, which oversees trading in over-the-counter stocks in the United States.

A new round of low-interest-rate incentive plans pushed new-car sales to record highs in the first 10 days of September, the seven major manufacturers in the United States reported today. Car sales were up 36.9 percent, on the basis of daily sales of 46,084 autos, the highest in history for early September and the second-highest rate for any 10-day period. The record was set in late September 1972, when cars sold at a rate of 53,959 a day. Light-truck sales soared 69.6 percent in the same period, bringing light-vehicle sales - cars and light trucks - to 516,219 units, up 44.9 percent. The changes are computed on the basis of daily sales, with eight selling days in the period this year against seven in September 1985.

VIRUSES of the common cold have been halted in their disease-producing attacks by a novel strategy that does not touch the viruses at all, but blocks their entrance into human cells. The strategy, called receptor blockade, was first tested on human cells growing in the laboratory. It prevented infection of the cells by rhinoviruses, the main causes of the common cold. Later, the same method prevented rhinovirus infection in chimpanzees. The method was then tried in a group of human volunteers. Some volunteers were given nose drops containing high concentrations of special antibodies designed to attach to the same receptors on the nasal tissues' cell surfaces that the virus seeks out to begin its invasion. The intention was to use the antibodies as a shield to keep the viruses from attaching to cells of the nasal passages where cold viruses ordinarily multiply. If the virus cannot attach to the cell it cannot penetrate and multiply. Infection is thwarted.

An unarmed, submarine-launched Soviet missile misfired during a test last week and apparently landed in northeastern China, Defense Department and White House sources said today. The sources said they believed that the dummy warhead, from a missile that United States officials call an SS-N-8, was more than 1,500 miles off course when it landed. They said the cause of the misfiring was not known. But one official said that ''something went wrong with the guidance.''