Structure and development of the asbestos body

Our plain-English summary of Structure and development of the asbestos body, by Y. Suzuki, J. Churg (The American Journal of Pathology, 1969).

The study

• Authors: Y. Suzuki, J. Churg
• Journal: The American Journal of Pathology
• Published: 1969;55(1):79-107
• Cited by: 85 articles, as counted by NIH iCite
• Read it: PubMed · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001432).

Abstract

Formation of asbestos bodies in the hamster lung from instilled chrysotile asbestos was followed by means of light, phase, and electron microscopy. This process took place in the cytoplasm of certain pulmonary cells, especially the alveolar macrophages, and, to a lesser extent, alveolar epithelial cells and septal cells. The successive steps consisted of: (1) phagocytosis of small fragments (often under 1 μ long and 300 Å in diameter) and incorporation in cytoplasmic phagosomes; (2) appearance of hemosiderin in the cytoplasm of the cells; (3) intracellular transportation of iron micelles from hemosiderin granules into the phagosomes; and (4) progressive concentration of the iron micelles in the vicinity of the fiber and partial clearing of the protein ground substance along the periphery of the phagosome. The central fiber, the coat of hemosiderin, and the investing membrane of the phagosome are considered to be the essential elements of an asbestos body. The presence of uncoated asbestos fibers is noted even after the lapse of 2 years. It is suggested that such fibers, in fact, have undergone phagocytosis, but have been released due to the death of the cell before they became coated with iron. These uncoated fibers probably continue to interact with the cells and may be responsible for the progressive alteration of the lung tissue.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This was an animal experiment. The authors placed 1 mg of soft chrysotile asbestos, suspended in saline, into the windpipes of 24 male hamsters. They examined the lungs with light, phase and electron microscopes at times from 1 day to 24 months afterward. Three hamsters served as controls. In the first days the lungs showed focal acute inflammation and fluid, but the fibers could not be seen by light microscopy. Most fibers found in the air sacs were under 1 micron long, which the authors took to mean that the instilled fibers split and broke up. Lung cells, especially alveolar macrophages, took the fibers into membrane-bound sacs. Iron particles appeared at 16 days and gradually coated the fibers. Typical asbestos bodies were seen at 6 months, along with fibrosis. Uncoated fibers were still present at 2 years. The authors concluded that an asbestos body consists of a central fiber, an iron (hemosiderin) coat and a surrounding membrane. They suggested that uncoated fibers may be responsible for progressive lung changes, and that submicroscopic fibers cause most of asbestos's biologic effects.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Animal experiment (hamsters given asbestos into the windpipe, lungs examined by light, phase and electron microscopy)
• Who was studied: 24 male hamsters weighing 50 to 130 gm. One group was killed at 1, 2, 3, 5, 7, 12 and 16 days and a second group at 6, 12 and 24 months after instillation. There were 3 controls: one given saline only and two untouched. The article does not say how many animals were killed at each time point.
• Exposure: A single dose of 1 mg of soft chrysotile asbestos in 0.1 ml of normal saline, given intratracheally (into the windpipe). The fibers averaged 6 microns in length, a figure that did not count submicroscopic fibers.
• Main results:
  • At 1 to 3 days the lungs showed focal acute inflammation centered on the bronchioles, with edema fluid in the air sacs. The asbestos fibers could not be seen by light microscopy.
  • Most fibers seen in the air sacs were less than 1 micron long, often only one unit fiber thick. The authors took this to suggest that the instilled fibers split lengthwise and broke into short fragments.
  • Iron particles appeared in the cytoplasm of cells containing ingested fibers 16 days after instillation. At the same time they appeared around the fibers inside the phagosomes, forming 'immature' asbestos bodies.
  • After 6 months, typical asbestos bodies were seen in macrophages, along with hypercellularity of the alveolar wall and reticular fibrosis. In later stages, extra- and subpleural fibrosis was seen in some lobes.
  • All asbestos bodies had the same basic structure: a core of asbestos unit fibers, a coat of iron particles, and a surrounding limiting membrane.
  • The lungs of animals killed at 6 to 24 months contained many mature bodies, but also many uncoated fibers and immature bodies.
  • The authors suggested that submicroscopic fibers are responsible for most of the biologic effects of asbestos.
• The authors' conclusion: The authors concluded that the central fiber, the hemosiderin coat and the phagosome membrane are the essential elements of an asbestos body. They suggested that uncoated fibers, released when cells die, probably continue to interact with cells and may be responsible for progressive changes in the lung tissue.
• Limitations the authors state:
  • The enzyme activity of the fiber-containing vacuoles was not examined.
  • The average fiber length of the material used did not take submicroscopic fibers into account.
  • The stimulus that starts and maintains the build-up of iron on the fibers is not known.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Body Formation, Asbestos Bodies, Chrysotile, Alveolar Macrophage, Phagocytosis.

Related studies

• Formation of the asbestos body. A comparative study with three types of asbestos — Y. Suzuki, J. Churg (1970)
• The association among ferruginous body, uncoated fibers, asbestos and non-asbestos fibers in lung tissue in terms of length — T. Suzuki, Y. Sakakibara, et al. (2016)
• The enigmatic asbestos body: its formation and significance in asbestos-related disease — A. Morgan, A. Holmes (1985)
• The mechanism of formation of asbestos bodies — S.K. Botham, P.F. Holt (1968)
• Ferromagnetic contamination in the lungs and other organs of the human body — D. Cohen (1973)
• A comparison of the ferruginous body and uncoated fiber content in the lungs of former asbestos workers — R.F. Dodson, M.G. Williams, et al. (1985)

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