Every year there are over 2,000 new cases of mesothelioma diagnosed in the United States because of asbestos exposure. This fact has been a major force behind the research aimed at better understanding the disease and someday finding a cure. One important study is called, Electron Miscroscopical Investigation of Asbestos Fibers by Arthur M. Langer, Anne D. Mackler, and Fred D. Pooley - Environmental Health Perspectives Vol. 9, pp 68-80, 1974. Here is an excerpt: Abstract - Examination of asbestos fibers by electron microscopical techniques enables the observer to distinguish among the fiber types by morphological and structural characteristics. Chrysotile asbestos fibers are composed of bundles of fibrils. Fibers are often curvilinear with splayed ends. Individual fibrils consist of a central capillary defined by an electron dense crystalline wall. With increasing time of electron bombardment, the capillary wall decreases in thickness, deforms, and is encapsulated in an electron translucent material. The chan ge in electron opacity is considered to be a product of structural disruption brought about by dehydroxylation due to electron radiation. A well recognized sequential deformation pattern may be used for identification purposes. Amphibole fibers tend to be straight, splintery, and electron-opaque, although curved fibers are occasionally observed. Diffraction contrast figures are visible as dark bands moving parallel and at right angles to the fiber axis. Crocidolite forms the shortest and thinnest fibers, followed in size by amosite and anthophyllite. Size distribution characteristics of the amphibole fiber types are different. The selected area electron diffraction pattern for chrysotile is unique. Reflections range in forms from streaked to arcuate. Reflection intensity and shape are related to the degree of openness of the fiber bundle and the extent of physical degradation of the fiber. The amphibole asbestos fibers possess diffraction patterns having similar characteristics prohibiting individual identifi cation. Microchemical analysis is required for identification in such cases. A discussion of the industrial hygiene threshold limit values for ampliphibole asbestos fibers is presented. The discussion is based on their differing size distribution characteristics.
Another interesting study is called, Comparison of alveolar and interstitial macrophages in fibroblast stimulation after silica and long or short asbestos by Adamson, I.Y.R. ; Bowden, D.H. University of Manitoba, Winnipeg - Journal Volume: 5:5; Conference: 75. annual meeting of the Federation of American Societies for Experimental Biology (FASEB), Atlanta, GA (United States), 21-25 Apr 1991. Here is an excerpt: Pulmonary fibrosis in response to particles has been attributed to secretion of fibroblast growth factors (FGF) by alveolar macrophages (AM). However, since fibrosis is interstitial and is associated with particle retention by interstitial macrophages (IM), the authors have now compared the secretory activity of FGF by rat alveolar (AM) and interstitial macrophages (IM) in response to silica and to long or short asbestos fibers. AM were obtained by broncho-alveolar lavage, and IM by collecting macrophages that migrate from explants of a previously lavaged and perfused lung. Isolated Am and IM from fib rotic lungs, 6 weeks after instilling silica, secreted equal amounts of FGF. Six weeks after giving short asbestos fibers in vivo, lavaged AM secreted FGF in vitro, but there was no change in fibroblast growth and no fibrosis in vivo. After giving long fibers, which reach the interstitium, isolated IM secreted FGF and collagen levels were increased in whole lung. When macrophages were isolated from normal rats and exposed to particles in vitro, Am and IM supernatants contained equal amounts of FGF. The results show that these macrophage populations respond equally to particles with respect to FGF secretion. The fibrotic reaction seen in vivo is likely due to the close proximity to fibroblasts to particle-laden macrophages within the interstitium allowing more efficient transfer of growth factors.
If you found any of these excerpts interesting, please read the studies in their entirety. We all owe a debt of gratitude to these researchers.
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