Autopsy samples from eight former shipyard workers were collected from lung parenchyma, tracheal lymph nodes, and pleural plaques. The tissue from each respective area was prepared by a modified bleach digestion technique, and the residue was collected on a 0.2-micron pore polycarbonate or 0.22-micron mixed cellulose ester filter. Quantitation of ferruginous bodies and uncoated fibers was done by light and transmission electron microscopy, respectively. Differences in the asbestos burden were noted for each site. Ferruginous bodies were observed in both parenchyma and nodes but not in plaques. Three subjects were found to have more ferruginous bodies per gram dry weight in their lymph nodes than in their lung parenchyma. Likewise, all subjects were found to have more uncoated fibers per gram in the nodes than in the parenchyma. Amphibole and chrysotile fibers were noted in the lung and extrapulmonary sites, with chrysotile being the predominant asbestiform in plaques. The majority of the uncoated fibers in both the nodes and the plaques were less than or equal to 5 microns in length. However, some fibers with dimensions conforming to the "Stanton hypothesis" reached both areas. These residual patterns most likely reflect the impact of clearance on lung burden as opposed to the eventual accumulation and stasis in the extrapulmonary areas.

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Spores of Clostridium sp. Ni are characterized by numerous broad ribbon-like appendages attached to one end. The appendages are two to three times the length of the spore and, at their maximal dimension, may be two-thirds the width of the spore. They are attached to the spore body by a common trunk which is continuous with the outer spore coat. Each appendage is a multilayered structure and is enclosed in an amorphous material. Details of spore and appendage formation are described, and appendage ultrastructural features are presented. The function of the appendages is not known.

Two distinct spore appendage types of Clostridium bijermentans, a pinlike appendage and a tubular appendage, were studied by electron microscopy. The pinlike appendage is characterized by a shaft, about 100 A in diameter, which has a lobed caplike structure. The tubular appendage, 500 to 600 A in diameter, is characterized by a hirsute region consisting of small filaments or fibrils. Gross morphology and ultrastructural features of both types are described. Recently, we reported the occurrence of four distinct spore appendage types among 12 strains of Clostridium bifermentans examined (9). In that report, we characterized two of the appendage types, one a smooth tubular appendage (strain 9-SDH) and the other a featherlike appendage (strain 1A-SDH). In the present report, we characterize the remaining two appendage types, a pinlike appendage (strain U-11) and a hirsute tubular appendage (strain FDA-1). In addition, some ultrastructural features of the previously reported smooth tubular appendage of strain 9-SDH are described. MATERIALS AND METHODS The experimental approach and procedures used in the present investigation were identical with those detailed in a previous report (9), and thus only an abbreviated account of these methods is given here. Three strains of C. bifermenttanis were used. Strains U-li and FDA-i were received from Stanley M. Harmon, Food and Drug Administration,

Background The potential for asbestos exposure among members of the general population is appreciable, considering its widespread use in many products. This study examined tissue burden of asbestos in such a population. Methods A group of 33 individuals who had no work history of occupational exposure to asbestos were included in the study. Tissue sections from areas adjacent to those sites sampled for digestion were found to be without ferruginous bodies (FB) or histopathology consistent with asbestos‐induced changes. All individuals had 20 or less FBs per gram of digested wet lung, a number considered to reflect general population levels. Tissue analysis of uncoated fiber burden was carried out by analytical electron microscopy. There was a trend of a higher likelihood of FB and asbestos fiber content correlated with age. Results The data are not consistent with the findings that chrysotile is readily found in lung tissue from the general population, in that none was found in 19 of the cases. It was almost as likely that one would find anthophyllite (12 of 33 cases) in this study. The commercial amphiboles (amosite and crocidolite) were occasionally found in the tissue from the general population and, when observed, were few in numbers. Twenty‐six of the patients had no FBs and ten had no uncoated asbestos fibers within the limits of detectability in this study. Conclusions The total tissue burden of asbestos in this study is much less than earlier reported observations from other general populations. Am. J. Ind. Med. 35:281–286, 1999. © 1999 Wiley‐Liss, Inc.

The ability of amosite cored asbestos bodies isolated from human lungs to catalyse damage to qpX174 RFI DNA in vitro was measured and compared with that of uncoated amosite fibres with a similar distribution of length. Asbestos bodies (5000 bodies) suspended for 30 minutes in 50 mM NaCl containing 0 5 ug qX174 RFI DNA, pH 7.5, did not catalyse detectable amounts of DNA single strand breaks. Addition of the reducing agent ascorbate (1 mM), however, resulted in single strand breaks in 10% of the DNA. Asbestos bodies in the presence of a low molecular weight chelator (1 mM) and ascorbate catalysed the formation of single strand breaks in 21% of the DNA with citrate or 77% with ethyl-

A comprehensive scheme is described for isolating amosite asbestos and ferruginous bodies from fixed and unfixed human lung tissue and sputum. This qualitative procedure avoids many of the problems associated with previous isolation techniques and illustrates the advantages of brief bleach digestions. The samples are digested in prefiltered Wright laundry bleach (9.2% sodium hypochlorite), collected on 0.2-microns Nucleopore filters by vacuum filtration, rinsed with distilled water and absolute ethanol, and examined visually for excessive residue. If organic residues are suspected or are known to occur, the sample is treated sequentially with 2% potassium permanganate, 8% oxalic acid, and 9.2% sodium hypochlorite, and rinsed with distilled water and absolute ethanol. The ethanol, potassium permanganate, and oxalic acid steps can be repeated as often as needed until the desired sample volume has been filtered. The entire procedure allows large volumes to be filtered and yields filters that have extremely clean backgrounds. Filtration can be completed in as little as 15 min, as opposed to the hours or days recommended for other procedures. The technique is applicable to specimens fixed in Saccomanno's fixative or glutaraldehyde, and to those in an unfixed state. The procedure does not appear to damage the gross morphology of the amosite fibers, and it does not produce a detectable change in their elemental composition when determined by energy-dispersive X-ray analysis.