The exact biological function of vitamin E in humans is unknown, although the vitamin is believed to act as an antioxidant. It has been postulated that vitamin E protects cellular membranes and other oxygen-sensitive substances such as vitamin A and ascorbic acid (vitamin C) from oxidation. Coenzyme Q, selenium, synthetic antioxidants, and some sulfur-containing amino acids can prevent vitamin E deficiency syndromes in animals. Most, but not all, studies have found that vitamin E decreases platelet aggregation. Vitamin E deficiency does not cause specific disease in adults; in premature neonates, irritability, edema, thrombosis and hemolytic anemia may be caused by vitamin E deficiency. Creatinuria, ceroid deposition, muscle weakness, decreased erythrocyte survival or increased in vitro hemolysis by oxidizing agents has been identified in adults and children with low serum tocopherol concentrations. Administration of vitamin E completely reverses the signs of vitamin E deficiency.