July 18, 1983

Inside Jorge Diaz Serrano's home in a fashionable Mexico City neighborhood, the trappings are of comfort and success; outside, they are of an armed camp. Mr. Diaz Serrano, the head of Mexico's national oil company under former President Jose Lopez Portillo, has become the first ''big fish'' of the new Government's effort to show it is committed to restraining corruption in high places. While other cases have been brought since Miguel de la Madrid Hurtado became President last December, none has matched the impact of linking the former director of Petroleos Mexicanos with a fraud of $34 million involving the purchase of two tankers. Followed by a Helicopter The Government is serious about not letting this one get away. Gun-toting men dart about on his street, and each time Mr. Diaz Serrano travels these days, according to his lawyer, he is followed by an entourage of six unmarked cars, a pickup truck equipped for off-the-road travel, two motorcycles and occasionally a helicopter.

The summer season, the hectic season, is under way at Pennsylvania Station in Manhattan. Seven days a week more than half a million people pass through the railroad station, one of the nation's busiest. Many are commuters traveling to and from homes as far away as Pennsylvania. Thousands more are vacationers, loaded down with luggage, coolers and tennis rackets. And travelers are not the only people there, of course. It's a city of its own. People work, eat, shop and even live at the station. Some people play the horses at the Offtrack Betting parlor. Others stop in to get out of the hot sun. Some nights businessmen are stranded after missing their last train. For Debbi Hoeler, an information clerk, summer in Penn Station means answering hundreds of questions a day, many from abusive customers. For Brad Rubin, a baker at a bagel store in the station, it means a full shift working near a 500-degree oven on an already hot day. For Michael P. Harmon, a police officer, it means controlling the derelicts and homeless people who wander the terminal at night.

It was 50 years ago that Congress erected barriers between commercial banks and other types of financial institutions to protect the banks from the kind of excessive risktaking that led to bank failures during the Depression. In recent years, however, a kind of de facto deregulation has been under way as aggressive bank managers have tried to expand into new areas. Congress is beginning to consider proposals for overhauling banking regulations, but there is still disagreement over what is appropriate. Treasury Secretary Donald T. Regan will testify Monday on behalf of an Administration bill to speed the pace of deregulation, by allowing banks to expand into real estate, insurance and some securities activities. Paul A. Volcker, chairman of the Federal Reserve Board, has in principle endorsed the Administration's proposal. But as a first step he has also urged that Congress impose a temporary freeze on crossindustry acquisitions, to give legislators more time to establish policy.

Senior Administration officials said today that they hoped to work out with President Amin Gemayel of Lebanon this week a new formula toward ending the impasse with Syria over the withdrawal of foreign troops from Lebanon. But Lebanese and United States officials offered differing evaluations of the likelihood of any early movement toward a solution of the problem. Foreign Minister Elie Salem of Lebanon, who is in Washington in advance of Mr. Gemayel's arrival on Wednesday, expressed optimism today that Syria's adamant refusal so far to negotiate a withdrawal was only a temporary, tactical move. No Fear of Partition Mr. Salem also said he had no fear that either Israel or Syria had plans for any permanent partition of his country. ''I am confident that we will break the stalemate and then we will have progress and phases that will show encouragement and then we can regain a momentum that I think we have lost in the past two months,'' Mr. Salem said.

The Presidents of four Latin American countries tonight expressed ''profound concern for the rapid deterioration'' of the situation in Central America. They called for the removal of foreign military bases and advisers, a freeze on arms shipments and establishment of international border patrols as key steps to achieving peace in the region. The four leaders, Miguel de la Madrid Hurtado of Mexico, Luis Herrera Campins of Venezuela, Belisario Betancur of Colombia and Ricardo de la Espriella of Panama, made their appeal after five hours of meetings at this resort island. It was part of a broader program that built upon six meetings held by their foreign ministers earlier this year.