Heat wok or skillet at 375 degrees for 2 to 3 minutes; add oil, and heat 1 minute. Add cabbage, green pepper, bean sprouts, bamboo shoots, and water chestnuts; stir-fry 5 minutes. Cover and cook over low heat for 3 to 5 minutes. Stir in spinach, soy sauce, and salt; stir-fry bout 2 minutes or until spinach wilts.