Oxygen incineration and electron microscope x-ray microanalysis of mineral particles in biological tissues

Our plain-English summary of Oxygen incineration and electron microscope x-ray microanalysis of mineral particles in biological tissues, by W.J. Henderson, C. Melville-Jones, D.W. Wilson, et al (The Journal of Histochemistry and Cytochemistry, 1978).

The study

• Authors: W.J. Henderson, C. Melville-Jones, D.W. Wilson, K. Griffiths
• Journal: The Journal of Histochemistry and Cytochemistry
• Published: 1978;26(12):1087-93
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Techniques employed for the recovery from biological tissues of noncombustible fine particles such as asbestos, talc, kaolin and diatomaceous material were assessed by electron microscope x-ray microanalysis. Recovery procedures which have been proven successful for lung tissue were found to be impracticable for more solid types of tissues. Digestion techniques employing acids, alkalis or enzymes and standard incineration procedures were found to be unsatisfactory for human adrenal, cervix, liver and ovarian tissues when the resultant residues were examined by electron microscope microanalysis. The recovered particles were often completely masked with residues which were shown to be composed of organic elements. The use of oxygen during the incineration process completely removed this contaminating material in nearly all cases studied. When such procedures were used, clearly defined particles were recovered from the tissue, thereby permitting x-ray analysis. A quantitative analysis could then be made to estimate the particle content in a variety of tissues.

In plain English

This 1978 laboratory methods paper from Cardiff, Wales, tested ways of recovering mineral particles such as asbestos and talc from human tissues for identification by electron microscope x-ray microanalysis. Standard heat-ashing followed by acid washing left most particles from ovarian tissue hidden under carbon-like residue. A total of 90 human ovaries were assessed in these tests of established methods. In tests on reference samples, hydrochloric acid affected only chrysotile, which lost magnesium and iron. Concentrated nitric acid left talc and crocidolite unaffected, but chrysotile was the most severely affected. An alkali digestion had not dissolved ovarian tissue after 7 days. Oxygen ashing, evaluated on 26 ovaries, completely removed the residue in nearly all cases studied. Particles from one ovarian sample were typical of talc. A worked example for one cystic ovary gave 8374 particles per gram of wet tissue. The authors concluded the oxygen method avoids acid treatment and allows semiquantitative counting. They noted uneven particle distribution on grids and that the best statistical design was still under investigation.

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 methods study comparing techniques for recovering mineral particles from tissue, assessed by electron microscope x-ray microanalysis
• Who was studied: Human tissues, mainly ovaries. 90 human ovaries were used in tests of established procedures and 26 in the oxygen-ashing evaluation; the article does not say whether these groups overlap. Adrenal, cervix and liver tissue were also mentioned, including liver from an aborted fetus. The work was done at the Tenovus Institute, Cardiff, Wales.
• Exposure: No human exposure was studied. The authors tested recovery methods (ashing, acid, alkali and solvent treatments, and oxygen incineration) and checked their effect on UICC reference samples of talc, crocidolite, chrysotile and amosite.
• Main results:
  • In ovarian residue prepared by standard ashing, most particles were covered by what appeared to be carbonaceous material.
  • Washing in 2N hydrochloric acid affected only chrysotile, which lost magnesium and iron. The degree depended on how long the acid wash lasted.
  • Over 2600 individual reference particles of various sizes were assessed in this part of the study.
  • Talc and crocidolite were unaffected by concentrated nitric acid treatment.
  • Under nitric acid treatment chrysotile was the most severely affected. After prolonged exposure, the structure of both amosite and chrysotile was destroyed.
  • Potassium hydroxide digestion (the Gold technique) did not digest ovarian tissue even after 7 days at room temperature.
  • Raising the ashing temperature (500 to 1000 degrees C) and time (7 to 14 hr) also failed to give a clean preparation.
  • Solid tissues such as ovary or adrenal were ashed in oxygen at 550 degrees C, with an oxygen flow of 250 ml/min for 5 hr, for samples of about 500 mg wet weight.
  • Oxygen ashing was evaluated on 26 ovaries.
  • Oxygen during incineration completely removed the contaminating residue in nearly all cases studied.
  • Particles shown from one ovarian sample after oxygen ashing had an elemental composition typical of talc.
  • Particle counts per gram were calculated using the wet weight of the original tissue.
  • A worked example of the counting method, for one ashed human cystic ovary (0.696 g wet weight), gave 8374 particles per gram of tissue.
  • In liver from an aborted fetus, a gold particle was seen between two iron particles after oxygen ashing.
• The authors' conclusion: The authors concluded that incinerating tissue in oxygen at 550 degrees C removes the need for acid treatment and is a more efficient mineral extraction technique. They said it is suitable for microanalysis and for semiquantitative assessment of particle content.
• Limitations the authors state:
  • The best statistical design for counting (the number of grid squares examined) was still under investigation.
  • Particles clustered on some grids instead of being spread randomly, and this must be taken into account when counting.
  • Oxygen ashing removed the contaminating material in nearly all cases studied, not in all of them.

Topics

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

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