Ultrastructure of the lung in the rat following exposure to crocidolite asbestos and quartz

Our plain-English summary of Ultrastructure of the lung in the rat following exposure to crocidolite asbestos and quartz, by K. Miller, I. Webster, R.I. Handfield, et al (The Journal of Pathology, 1978).

The study

• Authors: K. Miller, I. Webster, R.I. Handfield, M.I. Skikne
• Journal: The Journal of Pathology
• Published: 1978;124(1):39-44
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Lung tissue from rats that had inhaled U.I.C.C. crocidolite asbestos or quartz particles showed thickening of the interstitial tissue and the presence of collagen fibres. Aggregates of macrophages in the alveolar spaces were a dominant feature of all the sections examined from asbestos exposed rats. According to the ultrastructural studies described here, all the macrophages were mature cells, indicating that the ingested crocidolite asbestos was non-toxic. Lung sections of rats exposed to quartz particles were significantly different. Single cells were found in the alveolar spaces and many macrophages showed a characteristic pattern of vacuole formation. Other cells contained intracellular membranous lamellated bodies, similar to those found in Type II pneumocytes. Cells containing lamellated bodies were also found in the interstitial tissue. These findings suggest that the two mineral dusts have quite different biological effects on the macrophage and that the development of pulmonary fibrosis may, to some extent, be caused by a different mechanism in each instance.

In plain English

In this animal experiment from South Africa, 24 adult male Wistar rats breathed either UICC crocidolite asbestos (1350 fpcc) or quartz particles (11 mg/m3) for 8 hours a day, 5 days a week. Unexposed rats served as controls. The article did not say how many rats were in each group. After 5 to 7 months the lungs were examined, mainly by electron microscope. Both dust groups showed thickened interstitial (supporting) tissue and collagen fibres compared with controls. In crocidolite rats, clumps of macrophages (scavenger cells) in the air spaces were a dominant feature, many containing fibres, and all appeared mature. The authors took this to indicate that crocidolite was non-toxic to these cells. In quartz rats, the cells were not clumped, many macrophages had vacuoles, and cell debris was often present. Type II pneumocytes increased more obviously than in the asbestos rats, and plasma cells lay beside areas of collagen. The authors concluded that the two dusts affect macrophages quite differently and that lung fibrosis may, to some extent, develop by different mechanisms.

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 inhalation experiment, with lung tissue examined by transmission electron microscopy and routine histology
• Who was studied: 24 adult male outbred Wistar rats, placed in inhalation chambers at 6 months of age, plus age- and weight-matched unexposed control rats; National Research Institute for Occupational Diseases, Johannesburg, South Africa. The number of rats in each dust group is not stated.
• Exposure: Inhalation of either U.I.C.C. crocidolite asbestos at 1350 fpcc or Dowson and Dobson quartz particles at 11 mg/m3, 8 hours a day and 5 days a week; animals were killed after 5 to 7 months
• Main results:
  • Lungs of all exposed rats (both crocidolite and quartz) showed thickening of the interstitial tissues and collagen fibres compared with non-dusted rats
  • Crocidolite-exposed rats: aggregates of macrophages in the alveolar spaces were a dominant feature of all lung sections examined, and many macrophages had taken up crocidolite particles or fibres
  • Crocidolite-exposed rats: according to the authors, all macrophages in the alveolar spaces were mature cells
  • Quartz-exposed rats: cells in the alveolar spaces were not aggregated and many macrophages showed a characteristic pattern of vacuole formation
  • Quartz-exposed rats: alveolar spaces often contained cell debris and myelin figures, unlike asbestos-exposed rats
  • Mast cells and increased Type II pneumocytes were seen in both exposed groups, but the increase in Type II pneumocytes was far more obvious in quartz-exposed rats
  • Quartz-exposed rats: plasma cells were found in the interstitial tissue of all sections examined, generally next to areas of collagen deposition, which the authors suggested pointed to a local immune reaction
• The authors' conclusion: The authors concluded that crocidolite and quartz have quite different biological effects on the macrophage and that pulmonary fibrosis may, to some extent, develop by a different mechanism for each dust. They interpreted the mature macrophages as indicating that crocidolite was non-toxic to macrophages.
• Limitations the authors state:
  • Some cells containing lamellated bodies could not be classified on appearance alone as macrophages or Type II pneumocytes; the authors state that histochemical techniques would be needed
  • Lung sections containing quartz were difficult to cut, and the quartz was often masked by tearing of the sections
  • The effect of the mature macrophages on lung tissue was not known

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Interstitial, Collagen, Macrophage, Pulmonary Fibrosis.

Related studies

• Kinetics of the bronchoalveolar leucocyte response in rats during exposure to equal airborne mass concentrations of quartz, chrysotile asbestos, or titanium dioxide — K. Donaldson, R.E. Bolton, et al. (1988)
• On the defensive action of glutamate against the cytotoxicity and fibrogenicity of quartz dust — K.I. Morosova, G.V. Aronova, et al. (1982)
• A spin label study of the effects of asbestos, quartz, and titanium dioxide dusts on the bovine erythrocyte membrane — W. Leyko, E. Gendek (1985)
• Cytotoxic effects of quartz and chrysotile asbestos: in vitro interspecies comparison with alveolar macrophages — J. Schimmelpfeng, A. Seidel (1991)
• The effect of different mineral dusts on the mechanism of phagocytosis: a scanning electron microscope study — K. Miller, R.I. Handfield, et al. (1978)
• Fibrogenic effect of wollastonite compared with asbestos dust and dusts containing quartz — M. Cambelová, A. Juck (1994)

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