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In this paper we will attempt to provide some explanations for the organ selectivity of four different pneumotoxicants (monocrotaline, naphtalene, 3-methylindole, and 4-ipomeanol)

Human mitogen-stimulated lymphocytes, cultured in the presence of amosite asbestos (AS), demonstrated a slight increase in aryl hydrocarbon hydroxylase (AHH) activity compared with non-induced (control) cultures (P = 0.005). A much greater increase in enzyme activity occurred following addition of the inducers benzanthracene (BA) or cigarette tars (CT) to cell cultures (P less than 0.001 in both instances). Significant enzyme induction also occurred when AS fibers were first preincubated with CT or BA, washed with acetone, then added to lymphocyte cultures (P less than 0.003 in all instances). This increase in AHH activity was not as great, however, as the induction observed when BA or CT was added to cell cultures. No further increase in enzyme activity was noted when AS and CT or AS and BA were simultaneously added to culture lymphocytes (P greater than 0.070 in all instances). The results demonstrate that polycyclic aromatic hydrocarbons (PAH), such as BA and other components of CT, are adsorbed and transported by amosite AS particles. These AS-PAH complexes are capable of inducing AHH in cultured human lymphocytes.

5S ond study consisted of 70 golden syrian hamsters: 54 experimental and 16 control animals. The implantation of the thread in the trachea induced a regenerative basal cell hyperplasia of the epithelium. We Ibund squamous metaplasia and progressive intraepithelial neoplasia (lEN) prior to the development of squamous cell carcinoma (CA). In the experimental guinea pigs, only one invasive CA was found at 265 days postoperation. In the experimental hamsters, the first CA was seen at 55 days postoperation, and 65% of the animals sacrificed between 120 and 250 days developed CA. Most of the hamsters with CA also developed spindle cell tumors in the tracheal stroma. The control hamsters and guinea pigs did not develop lEN, and the mature respiratory epithelium was reconstituted. We conclude that this method reliably produces localized, readily accessible preneoplastic and neoplastic lesions in the trachea of hamsters and, to a lesser extent, in that of guinea pigs. This model of squamous cell bronchogenic carcinoma should prove useful in the study of tumor ultrastructure, the immunologic response to cancer, and the relationship of diet to cancer.

Asbestos bodies represent the product of the macrophage's attempt to detoxify inhaled asbestos fibers. The process of asbestos body maturation was examined by scanning electron microscopy of material isolated from lungs of former asbestos workers. The results suggest that the progression from a membrane-bound, smooth coating of the fiber, to the typically beaded form may be caused by cracking and subsequent erosion due to the inspiratory and expiratory forces of the lung on the asbestos body.