A fine structural study of the tissue channels' numbers and dimensions in normal and lymphoedematous tissues.

The numbers and effective radii were estimated for the tissue channels in the intersitial tissue of rats in the cerebral cortex and the facial subcutaneous tissue. Normal animals and some with acute (3 days) abd chronic (12 months) lymphoedema were used. It was found that the numbers and sizes of the channels corresponded well to those obtained by other techniques, however it was possible that in the oedematous animals the largest channels may have been artefactually counted as a number of smaller ones, thus reducing the hydraulic conductivity calculated. It is unlikely that this error was important for the normal tissue. In acute lymphoedema the numbers of both the small and the larger channels increased markedly, as did the radii of the largest channels. In chronic lymphoedema the numbers of the smaller channels fell to some extent. It was noted that, especially in lymphoedema and especially in the brain, there were many extra channels in the basement membrane regions of the capillaries. It is concluded that this new technique will be of considerable use in investigating the tissue channels in human patients since it can be applied to biopsy specimens.