Norihiko Kohyama

Analysis of Asbestos Fibers in Lung Parenchyma, Pleural Plaques, and Mesothelioma Tissues of North American Insulation Workers

Asbestos fibers and ferruginous bodies (FBs) in lung parenchyma, lung cancer tissues, pleural plaques, and pleural and peritoneal mesothelioma tissues from 13 North American insulation workers were analyzed and quantified using an analytical transmission electron microscope and a polarized microscope. Diseases from which these workers suffered included asbestosis, lung cancer, and mesothelioma. They had been occupationally exposed to materials containing chrysotile and amosite; their pathological diagnoses, occupational and cigarette smoking histories, and clinical summaries have been reported. Large numbers of FBs were found in the lungs and small numbers found in extrapulmonary sites. Most of the FBs had cores of amosite fibers. In all instances, lung parenchyma and lung cancer tissues showed chrysotile and amosite fibers in high concentrations (63.1 x 10(6) and 150.2 x 10(6) fibers/g dry tissue as mean values, respectively). Crocidolite fibers were seen in seven of the 13 cases, but in much smaller numbers. Other amphiboles were rarely found. In pleural plaques and in pleural and peritoneal mesothelioma tissues, amosite fibers were markedly fewer in number, whereas chrysotile fibers were seen in similar numbers as in the lungs. No significant differences in the size distribution of asbestos fibers were seen in the different sites. However, the mean widths of chrysotile fibers were thinner than those of amosite fibers. These results strongly suggest that translocation of inhaled asbestos fibers from the lung to other tissues, such as the pleura and the peritoneum, occurs frequently, and that chrysotile may be more actively translocated from the lung, compared to amosite or amphibole asbestos. The likelihood of translocation seems to be strongly related to the thinness of the fibers. Translocated chrysotile fibers may play an important role in the induction of either malignant mesothelioma and/or hyaline plaques, since the asbestos fibers detected in both these sites were mainly chrysotile.

Characteristics and modifying factors of asbestos-induced oxidative DNA damage

Respiratory exposure to asbestos has been linked with mesothelioma in humans. However, its carcinogenic mechanism is still unclear. Here we studied the ability of chrysotile, crocidolite and amosite fibers to induce oxidative DNA damage and the modifying factors using four distinct approaches. Electron spin resonance analyses revealed that crocidolite and amosite containing high amounts of iron, but not chrysotile, catalyzed hydroxyl radical generation in the presence of H2O2, which was enhanced by an iron chelator, nitrilotriacetic acid, and suppressed by desferal. Natural iron chelators, such as citrate, adenosine 5′‐triphosphate and guanosine 5′‐triphosphate, did not inhibit this reaction. Second, we used time‐lapse video microscopy to evaluate how cells cope with asbestos fibers. RAW264.7 cells, MeT‐5 A and HeLa cells engulfed asbestos fibers, which reached not only cytoplasm but also the nucleus. Third, we utilized supercoiled plasmid DNA to evaluate the ability of each asbestos to induce DNA double strand breaks (DSB). Crocidolite and amosite, but not chrysotile, induced DNA DSB in the presence of iron chelators. We cloned the fragments to identify break sites. DSB occurred preferentially within repeat sequences and between two G:C sequences. Finally, i.p. administration of each asbestos to rats induced not only formation of nuclear 8‐hydroxy‐2′‐deoxyguanosine in the mesothelia, spleen, liver and kidney but also significant iron deposits in the spleen. Together with the established carcinogenicity of i.p. chrysotile, our data suggest that asbestos‐associated catalytic iron, whether constitutional or induced by other mechanisms, plays an important role in asbestos‐induced carcinogenesis and that chemoprevention may be possible through targeting the catalytic iron. (Cancer Sci 2008; 99: 2142–2151)

Iron overload signature in chrysotile-induced malignant mesothelioma†

Exposure to asbestos is a risk for malignant mesothelioma (MM) in humans. Among the commercially used types of asbestos (chrysotile, crocidolite, and amosite), the carcinogenicity of chrysotile is not fully appreciated. Here, we show that all three asbestos types similarly induced MM in the rat peritoneal cavity and that chrysotile caused the earliest mesothelioma development with a high fraction of sarcomatoid histology. The pathogenesis of chrysotile‐induced mesothelial carcinogenesis was closely associated with iron overload: repeated administration of an iron chelator, nitrilotriacetic acid, which promotes the Fenton reaction, significantly reduced the period required for carcinogenesis; massive iron deposition was found in the peritoneal organs with high serum ferritin; and homozygous deletion of the CDKN2A/2B/ARF tumour suppressor genes, the most frequent genomic alteration in human MM and in iron‐induced rodent carcinogenesis, was observed in 92.6% of the cases studied with array‐based comparative genomic hybridization. The induced rat MM cells revealed high expression of mesoderm‐specific transcription factors, Dlx5 and Hand1, and showed an iron regulatory profile of active iron uptake and utilization. These data indicate that chrysotile is a strong carcinogen when exposed to mesothelia, acting through the induction of local iron overload. Therefore, an intervention to remove local excess iron might be a strategy to prevent MM after asbestos exposure. Copyright

Sedimentary history and chemical characteristics of clay minerals in cores from the distal part of the Bengal Fan (ODP 116)

Abstract The purpose of this study is to clarify the sedimentary history and chemical characteristics of clay minerals found in sediments deposited in the distal part of the Bengal Fan since the Himalayas were uplifted 17 m.y. ago. A total of seventy-eight samples were collected from three drilled cores which were to be used for the clay mineral analyses by means of XRD and ATEM. The results obtained from the analyses show that individual clay mineral species in the sediment samples at each site have similar features when the samples are of the same age, whereas these species have different features in samples of differing geological ages. Detrital clay minerals such as illite and chlorite were deposited in greater amounts than kaolinite and smectite during the Early to Middle Miocene. This means that the Himalayan uplift was vigorous at least until the Middle Miocene. In the Pliocene chemical weathering was more prevalent so that instead, in the distal part of the Bengal Fan, kaolinite shows the highest concentrations. This would accord with weaker uplift in the Himalayas. In the Pleistocene period, vigorous Himalayan uplift is characterized by illite-rich sediment in place of kaolinite. In the Holocene, smectite shows the highest concentration in place of the illite and kaolinite which were the predominant clay minerals of the earlier periods. Increasing smectite concentration suggests the Himalayan uplift to have been stable after the Pleistocene period. The smectite analyzed here is found to be dioctahedral Fe-beidellite, and it originated largely from the augite-basalt on the Indian Deccan Traps. The tri-octahedral chlorite is subdivided into three sub-species, an Fe-type, a Mg-type and an intermediate type. The mica clay mineral can be identified as di-octahedral illite which is rich in potassium. The chemical composition and morphology of each clay mineral appears to exhibit no change with burial depth in the sedimentary columns. This implies that there was no systematic transformation of clay minerals with time.

Cenozoic sedimentation and clay mineralogy in the northern part of the Magellan Trough, Central Pacific Basin

Abstract Assemblages of clay-sized minerals in twelve deep-sea cores from the northern part of the Magellan Trough in the Central Pacific Basin clearly show that authigenic smectite together with clinoptilolite formed subsea in situ and predominated throughout Palaeogene time. Clastic clay minerals such as chlorite, illite and kaolinite increased at the expense of smectite in sediments deposited since the Pliocene. Most of the authigenic smectites are of the di-octahedral, iron-rich type. The most probable origin of the authigenic smectites is formation from precursors such as volcanic glass. As part of this process biogenic silica evidently contributed to the formation of smectite and zeolites as clinoptilolite. The presence of a tri-octahedral saponite and the TEM morphology of some smectites, on the other hand, suggests that not all of the smectite studied was formed subsea in situ but that some had an allogenic origin. Systematic vertical changes in the assemblage of clay-sized minerals suggest that the authigenesis of submarine smectite and clinoptilolite prevailed in conditions of reduced aridity and weak wind activity throughout the Palaeogene in the study area. However, allogenic clay minerals such as chlorite and illite increased since the Olduvai event under conditions of severe aridity and strong wind activity caused by global climatic change. The west-northwest movement of the Pacific plate must have partly played a role in deposition of the clastic clay-sized minerals from the Asian continent by westerlies in the study area. The widespread occurrence of Cenozoic hiatuses in the study area is attributed to the influence of Antarctic Bottom Water (AABW). The latter must have influenced non-deposition of the clay-sized minerals at times during the Cenozoic.

Mesothelioma in a worker who spun chrysotile asbestos at home during childhood

BACKGROUND Malignant mesothelioma has a long latency period and more commonly found in those exposed to amphibole than chrysotile asbestos. METHOD A 35 years old asbestos worker in an asbestos textile plant in Chongqing, China, developed mesothelioma after only 4 years of employment. He was born and bred in a company residence of an asbestos plant and manually spun asbestos thread during school age. In the plant, not amphibole but only chrysotile has been used. RESULTS Diagnosis of malignant mesothelioma was confirmed by comprehensive approaches including gross appearance, histology, histochemistry, and immunocytochemistry. In the lung and tumor tissues, huge number of tremolite with exceptional chrysotile was observed despite the reverse proportion in the work environment. DISCUSSION Residential exposure and home spinning of asbestos seemed contributed to the early development of mesothelioma in this subject. Although only chrysotile was used and contamination of tremolite was low in the work environment, chrysotile seemed to be cleared leaving tremolite remain in the tissue. CONCLUSION Chrysotile with little contamination of tremolite can lead to early development of malignant mesothelioma when heavily exposed from childhood at a company residence with household exposure. There can be several mechanisms for tremolite to remain in the lung tissue, far exceeding chrysotile in number.

Mineralogical notes of apatite in urinary calculi.

SummaryApatite in some samples of common urinary calculi consisting mainly of apatite or of calcium oxalate and apatite was subjected to X-ray and thermal analysis and electron microscopic investigation. The X-ray analysis has determined the lattice parameters agreeing with hydroxyapatite, and the mean crystallite size normal to the basal plane in a range of 200–800 Å. The thermal analysis is given by differential thermal analysis (DTA) and thermogravimetric (TG) curves. From the TG curve of a mixed apatite-calcium oxalate calculus, an approach is given to estimate the proportions of the constituent materials; the result is as follows: whewellite, 51.7%; weddellite, 16.6%; apatite, 19.1%; and organic materials, 12.6%. Analysis with the scanning electron microscope with energy dispersive X-ray spectrometer has shown that apatite is found as tiny spherules (5–10 µm in diameter) with fluffy surfaces resulting from projecting fine fibers or needles (about 0.5 µm in length). The fibers are considered to be mosaic aggregates of crystallites. The spherules fill interspaces of well-formed oxalate crystals or are included sporadically in individual crystals. Occasionally well-formed crystal-shaped oxalates are bordered with narrow bands consisting of apatite spherules (often as hemispheres) linked in a row.

The vertical change in clay mineral composition and chemical characteristics of smectite in sediment cores from the southern part of the Central Pacific Basin

Abstract Clay mineral composition and chemical characteristics of smectite in five piston core samples collected from different sedimentary provinces in the Central Pacific Basin were studied using XRD and ATEM. The results show that submarine authigenic smectite occurs as the most abundant constituent in four clay mineral assemblages throughout the Neogene, whereas it was diluted by continental clastic clay minerals, such as illite, chlorite and kaolinite, which were transported to the ocean in Quaternary time. The submarine authigenic smectite is characterized as di-octahedral iron-rich beidellite, its morphology comprising the fleecy or lath forms which are considered to have been formed by submarine volcanism or hydrothermal reactions.

Comparative Cytotoxicity Study of Rock Wool and Chrysotile by Cell Magnetometric Evaluation

Rock wool (RW), a type of man-made mineral fiber (MMMF), is a building material used as an asbestos substitute for heat insulation, fire resistance, and reinforcement. RW is included in group 3 of the IARC classification. In the present study, the cytotoxicity of RW was investigated by cell magnetometry, enzyme assay, DNA ladder detection, and electron microscopic morphological evaluation in comparison with chrysotile fibers (CF). Specimens were prepared by 18-h incubation of Fischer rat alveolar macrophages in the presence of RW fibers as the study material, CF as positive control, and phosphate-buffered saline (PBS) as negative control, together with a relaxation indicator, Fe3O4, except for morphological evaluation, followed by additional procedures of external magnetization and subsequent 20-min remanent magnetic field measurement for magnetometric evaluation, and macrophage DNA extraction for evaluating possible apoptosis by DNA ladder detection. In magnetometry, relaxation, a marker of cytotoxicity, was rapid in both the RW- and PBS-treated groups, while it was delayed in both the long and short CF-treated groups. Differences in percent lactate dehydrogenase (LDH) release between the RW-treated group and PBS-treated group were not significant, but those between the RW-treated group and short CF-treated group were statistically significant. A DNA ladder was not detected in any of the study groups. Electron micrographs showed that RW did not cause any change, but CF caused changes in macrophages. Thus, magnetometric measurements suggested no cytotoxicity of RW. We plan, in the future, to evaluate the safety of RW by magnetometric measurement and morphological observation of the lungs in in vivo inhalation experiments.

Selective detection of airborne asbestos fibers using protein-based fluorescent probes

Fluorescence microscopy (FM) is one of the most important analytical tools in modern life sciences, sufficiently sensitive to allow observation of single molecules. Here we describe the first application of the FM technique for the detection of inorganic environmental pollutants-airborne asbestos fibers that can cause asbestosis, mesothelioma, and lung cancer. In order to assess FM capabilities for detecting and counting asbestos fibers, we screened E. coli lysate for proteins that bind to amphibole asbestos. In combination with the previously discovered E. coli protein DksA (Kuroda et al., Biotechnol. Bioeng. 2008, 99, 285-289) that can specifically bind to chrysotile, the newly identified GatZ protein was used for selective and highly sensitive detection of two different asbestos types. Our novel FM-based method overcomes a number of limitations of the commonly used phase-contrast microscopy (PCM) method, offering a convenient alternative to PCM for airborne asbestos monitoring.