December 26, 1986

Asserting that new Medicare provisions in a law adopted this year would discriminate against the elderly and the disabled, the American Medical Association has asked a Federal judge to declare the law unconstitutional. The A.M.A., in a lawsuit filed Wednesday, is also seeking a preliminary injunction to stop the law's Medicare provisions from taking effect until the recipients are given more information about the changes. The provisions on Medicare, which finances health care for 28 million elderly people and 3 million disabled people, are to take effect Jan. 1, a week from today. The suit was filed by the association, which represents 272,000 physicians, and several other parties in Federal District Court in Lubbock, Tex., against Dr. Otis R. Bowen, the Secretary of Health and Human Services, whose department is charged with carrying out the new provisions.

Richard Keating recalls with wonder those hectic days after he first moved to Houston from Chicago as a young architect in 1976. Those were days of wild Texas growth, when a 20-story building was a small job, when he and his ambitious young colleagues often worked all night, fueled on take-out pizzas and the sheer excitement of building a dazzling new city, with their dogs curled up under the drafting tables. A few months ago Mr. Keating, who cut a tall figure in Houston in his aviator glasses, 40-foot sailboat and Porsche Cabriolet, transferred to Los Angeles to take over the busy Skidmore Owings & Merrill architectural office there. Departing with him were about a dozen other architects from the Houston office who, he said, felt that they ''want to go where the action is.'' Vanguard of Outflow The group was in the vanguard of a small but growing outflow of professionals - architects, lawyers, writers, scholars, bankers - from Texas as its oil economy slows. They are part of a larger demographic shift in which, for the first time, more people are moving out of Texas than into it.

The defeat suffered by the chairman of the Federal Home Loan Bank Board on his proposal to extend a limit on real estate investments by thrift institutions signaled a major shift in the balance of power at the agency, industry experts said this week. The inability of Edwin J. Gray to muster support from the agency's two other members, both Reagan appointees, may have even neutralized his tough regulatory stance on the industry's widespread problems, some experts said. In the agency's packed boardroom last Thursday, Mr. Gray had argued for a two-year extension of a measure limiting direct investment in real estate ventures to 10 percent of a thrift institution's assets. But after two hours of debate, he lamented: ''Ladies and gentlemen, there has been some consultation as to where the various board members are coming out. I have indications that the other two members do not want to extend it. So it seems somewhat ridiculous for me to make that motion.''

The pro-democracy demonstrations by university students over the last several weeks have revealed a depth of discontent among the elite of China's youth that was unsuspected until now. That university students, the chosen young, should demonstrate in such numbers in favor of political principles closely associated in the minds of Chinese with the non-Communist West, particularly the United States, has raised disturbing questions among many here about the direction of economic and political change in China. The largest rallies were in Shanghai last weekend, where close to 50,000 people were estimated to have gathered on Sunday alone. But they also occurred in Beijing and about half a dozen other cities. Today there were reports that 3,000 students demonstrated in the port city of Tianjin to show their solidarity with the Shanghai protests.

An Iraqi airliner was hijacked yesterday and later crashed and burned on a remote desert airstrip in Saudi Arabia, killing 62 people, Jordanian officials said. The Jordanian Government said the Iraqi Airways jetliner en route from Baghdad to Amman had been commandeered by gunmen shortly after takeoff. Witnesses said that unidentified armed men set off least one hand grenade in the cabin before the Boeing 737 hit the ground and that a fire on board spewed smoke through the cabin. One witness said that when the plane, Flight 163, hit the ground, the fuselage split apart. Emergency Landing The plane crashed during an emergency landing at Arar, 60 miles south of the Saudi-Iraqi border and 250 miles southwest of Baghdad in northern Saudi Arabia, the Saudi Defense Ministry said.

The United States Ambassador to Costa Rica helped secure initial Costa Rican permission to build a secret airstrip for the Nicaraguan rebels early this year and was deeply involved in overseeing its use, according to a senior Government official in Central America. According to United States Government and Nicaraguan rebel officials, the Ambassador, Lewis A. Tambs, as well as other officials in the American Embassy in Costa Rica, maintained close contact with others involved in a so-called private supply network for the rebels that was set up by Lieut. Col. Oliver L. North of the White House National Security Council. The supply operation was established at a time when Congress had made it illegal to send military supplies to the rebels, known as contras, who are seeking the overthrow of the Nicaraguan Government. Ambassador Denies Report Early this month, asked about a published report linking him to secret arms shipments to the contras, Mr. Tambs denied that he had had anything to do with such an operation. But he declined a request for an interview for this article and efforts to reach him by telephone for comment were unsuccessful.

PATRICK MAHONEY said he wouldn't swear to it but he had been told that in Los Angeles they had limousines 40 feet long ''with a midget who serves drinks, and a hot tub.'' He sounded the way Easterners do when they talk about excesses indulged in by residents of that other coast. Considering the vagaries of New York winter weather, it would seem more logical to have a limo hot tub, if indeed there is such a thing, in cars here but, alas, the Big Apple's fast lane apparently still hasn't caught up with all of life's refinements. But just so no one thinks the city is somewhere on the back track when it comes to transportation, it should be known that there is at least one 40-foot beauty in Manhattan - a white Lincoln with a red interior that has three bars, two television sets, two video-cassette recorders and one laser disk. It is so popular that an identical car, except that its interior will be gray, is expected any day.

An Iranian secret agent and arms smuggler went to the South Bronx in 1981 to meet with the top officials of the Wedtech Corporation in an unsuccessful effort to purchase spare parts sought by the Iranian army, according to company officials. The discussions fell through, Wedtech officials said, when they became suspicious of the agent -who they originally thought was a wealthy Arab investor. They hired a private investigator to check out his background, and discovered his links to Iran. ''After obtaining a report on him, they concluded that his past was nefarious, that he had some contacts to Iran,'' said Wedtech's corporate counsel, Martin Pollner. ''They did not want to get involved with him. There was no contract, no deal, and nothing was ever consummated.''

The television networks and Hollywood studios may be headed for a showdown over the often-hefty profits from rerun rights to prime-time shows. The issue is among the most contentious in the entertainment business today. For the most part, the networks are now barred by Federal regulations from owning shows or sharing in the proceeds from the syndication of reruns. But the rule prohibiting the networks from producing more than a small amount of their own programming is set to expire in 1990. And when that rule, the one of most immediate concern to the Hollywood studios, runs out, the networks effectively will gain the right to share in some syndication revenues - largely at the studios' expense.

A lawyer for a victim in the racial attack in Howard Beach, Queens, last week said yesterday that his client wanted to cooperate with prosecutors but was not yet well enough to do so. The lawyer, Alton H. Maddox Jr., also said he telephoned the Queens District Attorney, John J. Santucci, on Wednesday to explain that the victim's injuries had kept him from viewing a police lineup earlier in the week and would prevent him from meeting with prosecutors in the next few days. Mr. Maddox said Mr. Santucci did not return his calls. Mr. Santucci said that he had called back, but that Mr. Maddox had not been in his office. Mr. Santucci also said the lawyer had not responded to repeated messages left with Mr. Maddox's secretary. On Wednesday, the day the calls were being made, Mr. Santucci asserted that second-degree-murder charges against three white teen-agers would be ''tough to prosecute'' without the cooperation of the victim, Cedric Sandiford, 36 years old, of Brooklyn.

International Japan's Government approved an austere preliminary budget that calls for total spending of $336 billion in the 1987 fiscal year, an increase of $75 million, the smallest rise in three decades. Besides providing for virtually no growth from the current year's budget, the proposed budget includes a drop of 2 percent in the important category of public works. The spending restraint could be a concern to Japan's major trading partners, especially the United States, which has urged Japan to bolster its economy to stimulate demand for American goods. [ Page D1. ]

Good times are coming to an end for the only part of the American steel industry that has been consistently profitable. For the last five years, while the major steel producers' losses mounted, steel service centers flourished as one of the few oases of profit in the beleaguered industry. As the industry's middlemen, the centers buy steel from both domestic and foreign mills, then cut and shape it to customers' specifications. The rise of steel service centers resulted as manufacturers became more and more skittish about keeping huge inventories of steel products in their warehouses. Playing an increasingly vital role in inventory control, the centers began to profit by allowing manufacturers in the automobile, appliance and machinery industries to have the steel parts they needed when they were needed.