Preparation of radiolabeled bioactive asbestos fibers

Our plain-English summary of Preparation of radiolabeled bioactive asbestos fibers, by T.J. Tewson, M.P. Francsechini, R.K. Scheule, et al (International Journal of Radiation Applications and Instrumentation. Part A, Applied Radiation and Isotopes, 1991).

The study

• Authors: T.J. Tewson, M.P. Francsechini, R.K. Scheule, A. Holian
• Journal: International Journal of Radiation Applications and Instrumentation. Part A, Applied Radiation and Isotopes
• Published: 1991;42(6):499-502
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We have developed an efficient procedure to radiolabel asbestos fibers while retaining the bioactivity of the fibers. The fibers are labeled with 68Ge. The 68Ge decays into 68Ga, which then can be detected by its characteristic positron emission. Both chrysotile and crocidolite asbestos, a serpentine and an amphibole, respectively, were radiolabeled successfully. Mild reaction conditions and short reaction times were found under which approximately 90% of the added 68Ge and 68Ga bound to the fibers. The radiolabel was retained even after washing the fibers extensively with physiologic buffers. The effects of the labeling on the bioactivity of the fibers were evaluated in an in vitro assay using guinea pig alveolar macrophages as a target cell. Labeled chrysotile fibers were found to retain greater than 95% of their ability to stimulate these cells. The labelling procedure described in this study should be useful in preparing labeled fibers to investigate both in vitro and in vivo phenomena.

In plain English

This laboratory study described a method for attaching a radioactive tag to asbestos fibers, so they could be tracked, while trying not to change how the fibers act on cells. The authors labeled chrysotile and crocidolite asbestos with germanium-68, which decays into gallium-68, the substance actually counted. They tested several chemical conditions. When fibers were suspended in sodium hydroxide and acid containing germanium-68 was added, 44% of the germanium bound to chrysotile but only 12% bound to crocidolite. When fibers suspended in the acid were neutralized with ammonia or imidazole solution, the fibers bound about 90% of both germanium and gallium, and washing removed no more than 1% of the label. To check biological activity, chrysotile was put through the same treatments without the radioactive tag. It was then tested on lung cells (alveolar macrophages) from guinea pigs by measuring their superoxide production. Chrysotile neutralized with imidazole for 1 minute gave more than 95% of the control level. The other treatments gave 32% to 64%. The authors concluded that the labeled fibers should be useful for studying fiber-cell interactions and tracking fibers in animal lungs.

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 (in vitro) methods-development study of a radiolabeling procedure for asbestos fibers, with a cell-based bioactivity test
• Who was studied: Asbestos fiber samples (1-2 mg each) and alveolar macrophages isolated from male Hartley guinea pigs; laboratory work at the University of Texas Health Science Center at Houston. The number of animals is not given.
• Exposure: Chrysotile (Union Carbide sample) and crocidolite (UICC standard reference) labeled with germanium-68 and gallium-68 under various acid, base and buffer conditions. Only chrysotile was tested for effects on macrophage superoxide production.
• Main results:
  • With fibers suspended in 0.5 M sodium hydroxide and germanium-68 in acid added, 44% of the germanium bound to chrysotile and 12% to crocidolite. For chrysotile, 24% of the gallium bound under these conditions.
  • When the conditions were reversed (chrysotile suspended in the acid containing germanium-68), less than 3% of either metal bound to the chrysotile.
  • With 0.1 M phosphate buffer, about 60% of the gallium-68 bound to the asbestos but less than 3% of the germanium-68.
  • With fibers suspended in the germanium acid solution and neutralized with 1 M ammonia or 1 M imidazole, the fibers bound about 90% of both germanium and gallium. Washing with buffer removed no more than 1% of the label, and repeated washings removed typically about 1/100 of 1%.
  • In chrysotile treated under the labeling conditions without germanium-68, guinea pig macrophage superoxide production as a percentage of control was 32% (ammonium hydroxide, final pH 9, 10 min), 51% (ammonium hydroxide, pH 7, 10 min), 64% (imidazole, 10 min) and more than 95% (imidazole, 1 min).
  • Chrysotile neutralized with imidazole for 1 minute showed bioactivity indistinguishable from untreated control fibers.
• The authors' conclusion: The authors concluded that imidazole appeared to be the preferred base of those tested, giving good labeling yields with unimpaired ability to stimulate macrophages. They suggested the labeled fibers should be useful for studying asbestos-macrophage interactions and for following fiber distribution in animal lungs by positron emission tomography.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Crocidolite, Serpentine Group, Amphibole Group, Alveolar Macrophage.

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