Penetration of the Small Intestinal Mucosa by Asbestos Fibers

Our plain-English summary of Penetration of the Small Intestinal Mucosa by Asbestos Fibers, by A.R. Storeygard, A.L. Brown JR (1977).

The study

• Authors: A.R. Storeygard, A.L. Brown JR
• Published: Mayo Clinic Proceedings, Volume 52. December 1977
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This brief report described an animal experiment. The authors placed a salt-water (saline) suspension of amosite asbestos into a tied-off segment of the jejunum, part of the small intestine, in five living rats for 1 hour. Two control rats received saline alone. Under a scanning electron microscope, no fibers were seen in the controls' intestinal lining. Specimens from three of the five exposed rats each contained one to six fibers; the other two had none. Most fibers pierced the lining cells at 45 to 90 degrees. All appeared to enter through the gut-facing surface, and none passed through junctions between cells. Occasional fibers were found in the lamina propria, the layer beneath the lining, at specimen edges or where the lining was missing, apparently damaged during preparation. Fibers in lining cells or lamina propria were 0.4 to 1.4 micrometers wide, with visible portions 5.0 to 30.0 micrometers long. One other fiber, 1.6 by 22.8 micrometers, contained only iron and could not be identified. The authors concluded that their observations provided confirmatory evidence that asbestos fibers can cross the intestinal lining.

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 (brief report): amosite suspension placed in a closed segment of rat jejunum in living rats, with saline-only controls, followed by scanning electron microscopy
• Who was studied: Sprague-Dawley rats weighing 500 to 600 g: five exposed to the amosite suspension and two controls given saline without asbestos
• Exposure: Five grams of finely ground amosite asbestos were added to 1,000 ml of saline. The suspension was left in a closed jejunal segment for 1 hour. Fibers in the suspension ranged from 0.5 to 25 um in length and 0.12 to 1.8 um in diameter.
• Main results:
  • No fibers of any type were seen in jejunal mucosa from the two control rats
  • In the five exposed rats, specimens from three rats each contained one to six fibers, and specimens from the other two contained none
  • Most fibers penetrated the epithelial cells at an angle of between 45 and 90 degrees
  • All of the fibers seemed to enter the cell through its luminal (gut-facing) surface
  • No fibers penetrated the junctions between cells
  • With one exception, microprobe analysis confirmed the fibers as amosite
  • At the edges of specimens where the lamina propria was exposed, an occasional fiber was found enmeshed in that layer
  • In one area where the epithelium was missing, a defect apparently produced during specimen preparation, two fibers were found whose ends appeared to be embedded in the lamina propria
  • In one asbestos-treated rat, a fiber resembling amosite penetrated the epithelium, but analysis showed only iron. Its identity and source were not known.
  • The iron-containing fiber measured 1.6 by 22.8 um
  • Fibers seen in epithelial cells or the lamina propria were 0.4 to 1.4 um in diameter
  • The visible portions of these fibers were 5.0 to 30.0 um long
  • No small fibers, less than 5.0 um in length, were seen in the tissue
  • No changes were seen in the surface membranes of penetrated cells other than a depression where the fiber entered
  • There was no evidence of a preferred cell type or membrane site for fiber penetration
• The authors' conclusion: The authors concluded that their observations provide confirmatory evidence that asbestos fibers can cross the epithelial lining of the intestine. They also concluded that penetration directly through the bodies of the lining cells is at least one way such fibers can reach the lamina propria.
• Limitations the authors state:
  • The authors noted that the absence of small fibers (less than 5.0 um) could have several causes. They also noted that small fibers might penetrate over a different time course than larger fibers.
  • Defects in the epithelium seen in some areas, including one area where fibers appeared embedded in the lamina propria, were apparently produced during specimen preparation

Topics

Medical terms in this study, explained in our Lexicon: Amosite.

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