The relationship of biochemical and morphological information in the central nervous system: The problem of sampling

The histology of the central nervous system (CNS) is complex, consisting of membranes derived from a number of cell types as well as specialized membranes associated with structural modifications of the neuron. The cell structure, and thus the membrane content, of the CNS varies with age and from area to area; in no instance is it possible to isolate a single cell type without special microdissection techniques. Neurological disease often involves specific areas of the CNS attacking one or all of the cellular elements in that region. In other instances, damage may be wide‐spread, but at the histological level it may be restricted to a single cell type or even to a single membrane. The latter situation is particularly applicable to diseases that attack the myelin sheath. The biochemical investigation of changes in the lipid content of the brain resulting from neurological disease is hampered not only by the morphological complexity of nervous tissue, but by the tendency of destructive processes to be accompanied by proliferation of other cellular elements, both during the acute phase of disease and during the process of repair, which may mask significant abnormalities. Thus, in order to decide which changes in the structural lipids of the diseased brain are meaningful, a knowledge of the histopathology of the disorder is essential. When the morphological changes that accompany a neurological disorder are known, one may choose an appropriate tissue sample for study. Isolation of specific structural or functional subunits of the CNS, dissection of small groups of cells, isolation of single cells and separation of specific membranes are techniques available to sample nervous tissue. These are discussed, and their applicability to the biochemical study of specific neurological diseases is evaluated.