Review of the significance of fibre size in fibre-related lung disease: a centrifuge cell for preparing accurate microscope-evaluation specimens from slurries used in inoculation studies

Our plain-English summary of Review of the significance of fibre size in fibre-related lung disease: a centrifuge cell for preparing accurate microscope-evaluation specimens from slurries used in inoculation studies, by V. Timbrell (The Annals of Occupational Hygiene, 1989).

The study

• Author: V. Timbrell
• Journal: The Annals of Occupational Hygiene
• Published: 1989;33(4):483-505
• Type of article: Review
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Intratracheal, intrapleural and intraperitoneal inoculation studies in animals are widely used for identifying important factors in the pathogenicity of fine fibrous particles and estimating the potential of new materials to produce human pulmonary disease. Evidence on the significance of fibre size is reviewed, with emphasis on direct data derived from airborne fibres in asbestos mines and fibres retained in the mineworkers' lungs. This evidence indicates a need in mesothelioma-related inoculation experiments for means of measuring fibres down to 0.01 microns in diameter. A test cell, developed for preparing microscope-evaluation specimens from injection slurries, has a sector-shaped sedimentation chamber and is used in a swing-rotor centrifuge. To minimize re-formation of aggregates that are dispersed by shearing forces during sedimentation, a sample of the slurry is diluted beforehand to a degree indicated by the length of the longest fibres seen in the light microscope. Fibres and other particles are collected as a uniform deposit on a collodion film enveloping a microscope cover-glass. Current techniques are used to prepare specimens from films for light microscopy, scanning electron microscopy and the transmission electron microscopy which is so necessary for measurement of very fine fibres. Applications of the cell to fibre samples from other sources are outlined.

In plain English

This article combined a review with a laboratory methods report. The review part discussed published evidence on how fibre size relates to fibre-related lung disease, with emphasis on data from airborne fibres in asbestos mines and fibres retained in mineworkers' lungs. The author argued that fibres finer than 0.1 micrometres in diameter are probably biologically important, particularly for mesothelial tumours. The author then described a sector-shaped centrifuge cell for making uniform microscope specimens from the liquid slurries injected into animals. In a test with a suspension of UICC crocidolite, fibre counts along one line across the specimen fitted a uniform distribution well. Counts along a second line fitted badly because clumps of fibres had not fully dispersed. Counts at the edges were low on both lines because particles were lost into a gap in the cell, so edge areas were excluded. Tests with polystyrene spheres showed no significant difference between calculated and expected concentrations. The author concluded that the cell collects particles of all sizes and shapes. The author noted that the trial suspension was too concentrated to ensure a clump-free specimen.

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: Review of evidence on fibre size, combined with a description and laboratory performance testing of a new centrifuge cell for preparing microscope specimens
• Who was studied: No human or animal subjects were studied directly. The performance trial used a specimen made from a liquid suspension of UICC crocidolite. Further tests used other fibrous materials, polystyrene spheres and man-made filaments.
• Exposure: UICC standard reference samples of asbestos (Transvaal amosite, Finnish anthophyllite, NW Cape crocidolite, Rhodesian chrysotile, Canadian chrysotile), used to illustrate the test cell. The performance trial used UICC crocidolite.
• Main results:
  • On the first (V-series) traverse of the UICC crocidolite specimen, the 22 fibre counts from the second to the 23rd totalled 1416 (mean 64.36, variance 61.39). The chi-squared value was 20.03, with p between 0.5 and 0.7, which the author described as an excellent fit to a uniform distribution.
  • On the second (H-series) traverse, the 22 counts totalled 1386 (mean 63.00, variance 104.38). The chi-squared value was 34.79, with p between 0.02 and 0.05, a bad fit. The author attributed this to agglomerates that had not fully dispersed, affecting counts 15 to 21.
  • On both traverses, the first and 24th (edge) counts were much lower than the others. This was caused by particles moving into the unsealed gap between the chamber housing and the cover-glass and being lost at unloading.
  • Three further trials at the same crocidolite concentration each gave counts with a good fit to a uniform distribution.
  • With a variety of fibrous materials, the edge deficiency was confined to a zone less than 0.25 mm wide. The author recommended counting only within a central 5 x 5 mm area, which is 70% of the specimen.
  • In experiments with monodisperse polystyrene spheres, no significant difference was found between the concentration calculated from the counts and that estimated from the mass, density and diameter of the spheres.
• The authors' conclusion: The author concluded that the probable biological importance of fibres under 0.1 micrometres in diameter, particularly for mesothelial tumours, makes it necessary to have specimen-preparation methods that allow TEM measurement of very fine fibres. The author stated that the cell can completely collect particles of all sizes and shapes from a liquid suspension.
• Limitations the authors state:
  • The crocidolite concentration used in the trial was too high to ensure a specimen free of agglomerates.
  • The acceptable concentration for crocidolite gives poor guidance for other fibrous materials of different fibre size.
  • TEM specimens could not be used for the uniformity trial because of grid bars and holes in the carbon film.
  • A sector angle greater than 5 degrees harms specimen uniformity, so increasing cell volume requires a larger centrifuge rotor.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM).

Related studies

• Solubility of asbestos and man-made mineral fibers in vitro and in vivo: its significance in lung disease — A. Morgan, A. Holmes (1986)
• Mesotheliomas in rats following inoculation with acid-leached chrysotile asbestos and other mineral fibres — G. Monchaux, J. Bignon, et al. (1981)
• Effects of fiber characteristics on lung deposition, retention, and disease — M. Lippmann (1990)
• Cases of alleged asbestos-related disease: a radiologic re-evaluation — R.B. Reger, W.S. Cole, et al. (1990)
• Lung dust analysis in the assessment of past exposure of man-made mineral fibre workers — J.C. McDonald, B.W. Case, et al. (1990)
• Comparing biological effects of mineral fibres — J.M. Meijers (1990)

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