Toss bread cubes on cookie sheet by baking at 350 degrees F for 10 minutes. Set aside.In a medium skillet, sauté celery, onion and mushrooms in butter. Add salt, sage, thyme, poultry seasoning and pepper.In a large bowl Toss with bread cubes with sautéed vegetables/seasonings until bread is well coated.Add chicken broth to moisten.Pour into a greased 9x13 pan.Bake uncovered at 350 degrees for 35-40 minutes.