Document bBR0B4GdeywKNqRGpk0xG7k7Z

"FERRUGINOUS BODIES" IN GUINEA FIGS--DAVIS ET AL MS Thomson had assumed that all the bod ies found in his cases were caused by asbestos, but anthracosis bodies have been known for a long time from the lungs of coal miners. Gloyne, in 1949,'* reported bodies similar to asbestos bodies in the lungs of workers exposed to graphite. This indicated that the process of body forma tion was not limited to asbestos, although, since the coal and graphite bodies had dark central cores, it was thought that they could not be confused with genuine asbestos bodies. In 1968, however, Gross et al15 reported that structures indistin guishable from asbestos bodies could be formed in experimental animals by the injection of such materials as aluminum silicate needles, silicon carbide whiskers, and fine glass fiber. Because all the bodies contained iron, it was suggested that they and asbestos bodies should be given the general name of "ferruginous bodies." Since minerals of similar size range to those used in these experiments are ubiquitous, it now seems very likely that many of the bodies seen in the lungs of the normal urban population result from minerals other than asbestos. The deposition of a coating containing iron around a variety of different min eral fibers indicates that a very general process is involved, and it is of great im portance, therefore, to elucidate the bio chemical conditions required for body formation. As a first step, an electron microscope study of a variety of experi mentally produced ferruginous bodies was undertaken to see if all these bodies have the same ultrastructure, and whether this is exactly the same as asbestos bodies. Asbestos bodies from guinea pigs and one human had previously been examined by Davis in 1965," ,s and it was reported that these structures were always formed in tracellular]}' within macrophages or giant cells. The body coating consisted of small granules approximately 60 A in diameter and it was suggested that these might be ferritin. Ihe body coating was sometimes deposited as a single layer but could con sist of a number of layers of variable thickness and density. Sometimes the outermost layer consisted of radially ar ranged fine filaments about 60 A in di ameter, and it was suggested that these represented some form of calcium deposit. It has now been shown that the fine struc ture of apatite crystals is very similar to these asbestos body filaments, and it now seems likely that the outer layer of some asbestos bodies is made up of this material. In the experimental studies of ferrugi nous bodies, the following minerals were used: ceramic aluminum silicate, silicon carbide whiskers, and fine glass fiber. In addition to this, a commercial prepara tion of elastin was also tested to check on the structural similarity between elastosis bodies and other ferruginous bodies. Materials and Methods In the first experiments, mineral samples were Injected intratracheaUy into hamsters as reported by Gross et a) " in 1968. It was found, however, that although the resulting ferruginous bodies were common enough to be easily found with the light microscope, they were too dispersed to be found with the electron microscope except on rare occasions. It was known, however (Davis, unpublished data), that the intrapleural injec tions of asbestos dust into guinea pigs resulted in the production of large granulomas which contained many asbestos bodies after as little as two weeks. For this reason it was decided to use the intrapleural technique with other minerals. For these experiments. 25 mg of test material was suspended in 1 ml of physiological saline and injected into the right lower thoracic cavity of guinea pigs. The animals were killed between two and six weeks after injection and the result ing granulomas were divided into two segments. One was fixed in formol saline for light micro scope examination and the other was fixed in buffered osmium tetroxide for electron micro scope study. The light microscope sections were stained by Perl's method for iron. This stains the coating material of the ferruginous bodies a dense blue, making them easily visible against the back ground of a pale, neutral red counterstain. The material for electron microscopy was embedded in epoxy resin and stained with lead citrate. The injected materials were as follows: 1. Glass fiber, a commercial sample with an average fiber diameter of 0.05m to 0.99m. Initially Arch Path--Vol 8$, April 1910 8005 1449 PRODUCED BY FORD