Department of Clinical Medicine, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka. harshaninr@yahoo.com. Institute of Biochemistry, Molecular Biology and Biotechnology, University of Colombo, Colombo, Sri Lanka. Department of Clinical Medicine, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka. Department of Pharmacology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka.