Comparison of rhapidosomes and asbestos microfibrils

Our plain-English summary of Comparison of rhapidosomes and asbestos microfibrils, by W.G. Hutchison, R.I. Harker, M.M. Allen (Science, 1978).

The study

• Authors: W.G. Hutchison, R.I. Harker, M.M. Allen
• Journal: Science
• Published: 1978;200(4348):1401-3
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Rhapidosomers (cylindrical nucleoprotein rods of bacterial origin) show great structural similarity to the microfibrils of chrysotile asbestos when negatively stained and observed with the electron microscope. If the negative stain is omitted, the asbestos retains its structural detail whereas the rhapidosomes appear to be unstructured bodies. When the microscope is adjusted into a selected area diffraction mode, the asbestos shows characteristic electron diffraction patterns whereas the rhapidosomes appear to be amorphous to electron diffraction.

In plain English

This was a short laboratory report based on electron microscopy. While studying bacteria, the authors found rod-shaped bodies on their grids that resembled rhapidosomes, hollow rods of bacterial origin. They concluded that the rods were, at least in part, contamination that resembled chrysotile asbestos microfibrils. A grid placed where an asbestos glove had been tossed onto a bench showed many such rods. A control grid prepared in another laboratory showed only one. The authors then compared rhapidosomes of Spirulina with freshly milled asbestos from the Johns-Manville Jeffrey mine in Quebec. The chrysotile microfibrils they examined measured 23 to 63 nm across. Staining with 1 percent uranyl acetate greatly enhanced rhapidosome images, which looked unstructured without stain, but did not improve the asbestos images. Chrysotile gave its characteristic electron diffraction patterns, but no equivalent patterns could be obtained from rhapidosomes. The authors concluded that chrysotile asbestos and negatively stained rhapidosomes are too similar to identify reliably from electron micrographs of negatively stained specimens alone. They suggested that some rods previously described as rhapidosomes could be chrysotile asbestos.

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: Laboratory comparison by electron microscopy (stained and unstained specimens, and electron diffraction) of bacterial rhapidosomes and chrysotile asbestos microfibrils; no people were studied
• Who was studied: Known rhapidosomes of Spirulina prepared in the biology laboratory of Wellesley College, compared with freshly milled asbestos from the Johns-Manville Jeffrey mine in Quebec Province; no human subjects
• Exposure: Chrysotile asbestos microfibrils (freshly milled asbestos from the Jeffrey mine, Quebec), plus asbestos contamination of laboratory surfaces from an asbestos glove
• Main results:
  • A single grid placed on the bench where an asbestos glove had been dropped showed many rod-shaped bodies of the kind first suspected to be rhapidosomes (the scanned count reads 'over 106'). A control grid prepared in another laboratory showed only one rod-shaped structure on its entire surface.
  • After a bacterial culture was passed through filters of decreasing pore size, the filtrate from the smallest-pore filter still showed as many of the large rods as the original suspension.
  • The diameters of the known chrysotile asbestos microfibrils examined in this study ranged from 23 to 63 nm.
  • Improper focusing of the electron microscope gave a clear but greatly distorted image of an asbestos fiber, which closely resembled a stained rhapidosome.
  • Negative staining with 1 percent uranyl acetate greatly enhanced rhapidosome images. Without staining, the rhapidosomes appeared as unstructured bodies.
  • Staining did not improve the clarity or structural detail of asbestos microfibrils. One microfibril photographed before and after staining gave indistinguishable micrographs.
  • In electron diffraction, the chrysotile fibers gave their characteristic patterns. No equivalent patterns could be obtained from the rhapidosomes, even at voltages as low as 10 percent of normal.
  • Under high magnification, rhapidosomes occasionally showed a braided or spiral appearance. This was not observed in chrysotile asbestos, stained or unstained.
  • The authors suggested it seemed possible that some rod-shaped bodies previously described as rhapidosomes could be chrysotile asbestos.
• The authors' conclusion: The authors concluded that chrysotile asbestos and negatively stained rhapidosomes are too similar to be identified reliably from electron micrographs of negatively stained specimens alone. They also stated that unequivocal results can be obtained with a standard electron microscope.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec

All asbestos mines

Topics

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

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