Hemosiderin Granules in the Choroid Plexus

Since the first light microscope descriptions of the choroid plexus by Faivre (1) and Luschka (2), numerous kinds of granules and vacuoles have been described as components of epithelial cells of the choroid plexus, such as slightly pigmented, os-miophilic granules (3), hyaline-like granules (4), and fuchsinophilic and basophilic granules (5). These observations were promptly interpreted as evidence of secretory activity. Evidence in partial support of this interpretation was not lacking. Cappelletti (6) had found that injection of pilocar-pine increased the flow of spinal fluid while Pettit and Girard (4), later confirmed by Meek (7), showed that after the injection of ether, theobro-mine, muscarine, or pilocarpine, the apical ends of the choroidal epithelial cells became more watery and increased in height. Later, Dandy and Black-fan (8) produced a unilateral hydrocephalus by plugging the foramen of Monro on one side, and Flexner (9) showed that energy is required for the production of spinal fluid. Today, production ot the cerebrospinal fluid by the choroid plexus is generally accepted as the most plausible theory. A few investigators, however, have strongly opposed this theory, believing instead , that the spinal fluid is produced by the parenchyma of the brain and percolates via peri-neuronal and pericapillary spaces into the ven-tricles and subarachnoid space. Foremost in holding this theory were Hassin (10-13) and Has-sin, Oldberg, and Tinsley (14). These men considered the choroid plexus to be an organ of absorption , and believed that it removed noxious and waste substances from the blood. They insisted that what other observers had interpreted as secretion granules and vacuoles in the cytoplasm of the choroid epithelial cells were actually catabolic products which had been picked up by these cells for disposal. In the course of a comparative study of the ultrastructure of the choroid plexus in the rat, rabbit , guinea pig, opossum, dog, and hamster, "frothy" bodies of varying size were observed constantly in the guinea pig but were not found in any of the other animals. The animals reported on here are two groups of adult guinea pigs in apparent good health. The first group consisted of three animals and the second group, sacrificed 18 months after the first, contained two animals. All animals were sacrificed in the same manner by being placed under deep anesthesia with nembutol and, after reflecting the scalp and temporalis muscles laterally, were beheaded to allow rapid exsanguination of the brain, and the …