Most of Sudan's doctors stopped working and said they will resign in a week unless the government acts to end shortages of basic medical supplies. Abdul Rahman Abul Kul, chief of the Physicians' Assn. of Sudan, led 1,000 of the striking physicians on a march through Khartoum, the capital, to the Ministry of Health. The physicians said they are protesting the lack of such supplies as disposable syringes, antibiotics and medications such as insulin. Abul Kul said the East African country needs to spend at least $24 million in the next six months to upgrade health conditions.