Fine structural aspects of the influence of lymphatic blockage on cold injury of the brain and skin, and the effects of benzo-pyrones.

The fine structural changes of cold injury, lymphoedema, or both have been studied in the cerebral cortices and facial skin of rats, with and without treatment by a mixture of two benzo-pyrones (coumarin and rutin sulphate salts). It was found that cold injury opens the endothelial junctions of the blood vessels and injures their plasma membranes, thus allowing plasma protein and fluid to enter the tissues, producing oedema. Hence the lymphatics of the skin and the prelymphatics of the brain become dilated, contain excess protein, and the junctions of the former become opened. Macrophages (together with astrocytes in the brain) appear to phagocytise some of the protein. Apart from the injuries to the blood vessels, lymphostasis causes similar effects. The two injuries in combination considerably enhance the effects of either by itself. The benzopyrones greatly reduce the amounts of protein and fluid, particularly in the tissues: the lymphatics lag behind these, especially if they are obstructed.