Maryland Gov. Marvin Mandel was released from Johns Hopkins Hospital in Baltimore yesterday, still in uncertain health, orders from his doctors to rest at home for at least a month.

The exact cause of Mandel's illness continued to elude the team of seven specialists who examined Mandel of Hopkins, where he was brought last week for special tests after 16 days at Prince George's General Hospital. Mandel was hospitalized with complaints of severe headaches and weakness on his right side.

In a statement released by Mandel's press secretary, the governor's doctors said there had been some sort of physical abnormality or disturbance on the left side of the governor's brain, which controls the right side of the body. That condition has shown "distinct improvement," the statement said.

The medical bulletin once again threw into doubt the retrial of the governor and his five codefendants now scheduled for May 11. The political corruption retrial was originally set for April 13, a week before Mandel was admitted to the hospital.

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Shortly thereafter, U.S. District Court Judge Robert Love Taylor granted a motion by Mandel's attorneys to postpone the start of the trial. The case was then rescheduled for May 11.

"I'm coming into Baltimore on the 9th, and I'll find out if the (governor's) attorneys have filed any papers and then I'll just have to read them and decide what to do," Judge Taylor said from his home in Knoxville, Tenn., last night.

"I'm almost helpless when I'm dealing with someone who's sick," the judge added. "I want to go tril. I will go to trial if I feel I can do that without injuring (Mandel's) health and without running any risk.

Mandel's attorneys could not be reached yesterday for comment on whether they will file a new motion for postponement.

During the three-week period that the governor has been hospitalized, Lt. Gov. Blair Lee III has taken over many of the day-to-day duties of government, leaving policy issues for the governor to decide from his hospital bed.

"I'm sure he can continue doing the things he was doing at the hospital," Lee said last night. "His staff was taking him over great stacks of bills to read there."

Lee said he could not speculate on whether these ad hoc arrangements for running state government would continue during state government would continue during the governor's convalescence. "I'll probably go and chat with him some time tomorrow and we'll see where we go from here," he said.

Reporters who saw Mandel leave the hospital at about 3:30 yesterday afternoon said that he looked very tired. He and his wife Jeanne were driven back to the governor's mansion in a state police car.

Mandel's doctors said in their statement yesterday that the possibility that the governor suffered a small stroke remains their "working hypothesis," that is, the most likely bet by available evidence.

After his one-month recovery period, the team of doctors headed by Dr. George B. Udvarhelyi said they felt he should return for more tests.

The doctors also noted that none of the tests had found evidence that concer was the cause of the governor's symptoms. A Harvard medical consultant had hinted two weeks ago that the cause of the governor's illness might be a brain tumor or some other "progressive" problem.

The Johns Hopkins doctors based their opinion on several tests included a cerebral arteriogram - in which dye is injected to make the blood vessels of the brain show up on an x-ray - a spinal puncture for study of spinal fluid and other studies of brain function.

Their final answer was essentially no different from that reached by Mandel's family doctor, Dr. Perry Hookman - with Dr. Marvin Korengold and Dr. Udvarhelyi as consultants - before Mandel's transfer to Johns Hopkins.

These doctors said then that they could not be sure of the cause of his illness, though a stroke seemed the most likely explanation in view of Mandel's symptoms and the lack of any other findings.

A stroke is a blockage or some other kind of interruption in the blood flow of the brain, which kills some brain cells. The effects are felt on the opposite side of the body, as each half or hemisphere of the brain controls the body's opposite side.

If Mandel did suffer a stroke, instead of some more serious condition, he might have a good possibility of looking forward to gradual recovery, like many other stroke patients.

Mandel's doctors said there was evidence of "regression" of the physical problem, "with significant clinical improvement" - that is, gradual return of functions as other brain cells take over the damaged cells work.

Mandel originally went to trial last September on charges of mail fraud and racketeering, but that trial was aborted 13 weeks later after several jurors in the case inadvertently heard news bulletins about attempts to tamper with the trial.

Arrangements have already been made for the retrial to be conducted on a special schedule designed to accommodate the health problems of Irving Kovens, a codefendant whose case was severed from the original trial because of his heart ailment.