Collagen biosynthesis enzymes in lung tissue and serum of rats with experimental silicosis

The activities of prolyl 4-hydroxylase, galactosylhydroxylysyl glucosyltransferase (GGT) and lysyl oxidase (three enzymes catalysing post-translational modifications of collagen) were measured in the lungs of rats exposed to silica (DQ12). Circulatory levels of GGT were also estimated. Rats were killed after 24 h and at 6, 12 and 24 weeks after a single intratracheal instillation of either 12.5 or 25 mg of silica (DQ12). Control animals received saline. The total activity of the three enzymes in the lungs of the exposed animals was significantly increased at all times (P less than 0.05). The circulatory levels of GGT were also increased though some differences failed to reach significance. Thus increased activities of enzymes of collagen biosynthesis correlated with the development of silicosis and occurred within 24 h of treatment. This suggests that the changes responsible for the eventual development of fibrosis are operative within hours of dust exposure.

Erionite exposure and mesotheliomas in rats

Epidemiological and environmental surveys in the Cappadocian region of Turkey have linked the high incidence of pleural and peritoneal mesothelioma in the occupants of some villages with the zeolite fibres released from the locally occurring volcanic tuff. In view of the low ambient fibre concentrations and the extraordinary incidence of mesothelioma a study to test the hypothesis of high biological activity for the zeolite fibres was required. Experimental studies using both intrapleural inoculation and inhalation techniques have been undertaken with the erionite from this region and from Oregon in the United States. Additionally a non-fibrous zeolite from Japan and a synthetic non-fibrous zeolite of similar chemical composition to erionite have been included in the experiments. In these studies the samples from Oregon and Turkey produced a very high incidence of tumours. All the rats inoculated intrapleurally with Oregon erionite and almost all those inoculated with the Turkish fibre died with a mesothelioma. Inhalation of the Oregon erionite induced a similar effect. No other dusts we have investigated have produced this high incidence of tumours particularly following inhalation. These studies demonstrate that we now have a valuable new fibre for experimental study and a possible hazard to man in regions other then Turkey.

Comparison of tumour markers in malignant mesothelioma and pulmonary adenocarcinoma

Immunohistological methods were used to investigate the presence of carcinoembryonic antigen, beta 1 pregnancy specific glycoprotein, beta subunit of human chorionic gonadotrophin, human placental lactogen, calcitonin, and keratin in formalin fixed tissue from 29 malignant mesotheliomas and 27 pulmonary adenocarcinomas. Malignant mesotheliomas were negative for tumour markers except for the beta subunit of human chorionic gonadotrophin and keratin, one and 13 cases respectively being positive for these. Pulmonary adenocarcinomas, however, were frequently positive for tumour markers--namely, carcinoembryonic antigen, beta 1 pregnancy specific glycoprotein, beta subunit of human chorionic gonadotrophin, human placental lactogen, calcitonin, and keratin. The presence of carcinoembryonic antigen and beta 1 pregnancy specific glycoprotein within an intrathoracic tumour is strong evidence against its being of mesothelial origin.

Mortality of factory workers in east London 1933-80

The mortality of 3000 male factory workers, 1400 laggers, and 700 women factory workers in east London has been studied. The men were first employed between 1933 and 1964, the women between 1936 and 1942. Textiles were produced until the late 1950s as well as other asbestos products. Laggers were employed on contract in increasing numbers in later years. Crocidolite asbestos was used until the late 1950s as well as asmosite and chrysotile. Exposure of workers was graded according to the job into two categories, low/moderate and severe, and subdivided by duration of employment up to two years or longer. Mesothelial tumours accounted for 7.5% of the total mortality in men, and 9% in women with their longer follow up period. Lung cancer accounted for 20% of deaths in men and 14% in women. Both mesothelial tumours and lung cancer showed a dose response relationship. Histopathological examination of a series of predominantly postmortem specimens showed 22% of adenocarcinomas of lung among men and 21% in women. There was an excess of gastrointestinal tumours but no dose response relationship could be shown. Among severely exposed male factory workers there was an excess of deaths from cancer of the larynx and among severely exposed women of carcinoma of the breast and ovary. Twenty four deaths (2%) were due to asbestosis. There is an indication that the incidence of mesothelial tumours is declining but a further period of observation is required for confirmation.

Enhanced theophylline clearance secondary to phenytoin therapy

This report describes two cases in which theophylline clearance accelerated markedly with concomitant phenytoin administration. Maximum calculated theophylline clearance ranged from 2 1/2 to 3 1/2 times baseline. Onset of the interaction began within five days of beginning concurrent therapy. With combined use, clinicians should be aware, when phenytoin is added, of the potential for reexacerbation of pulmonary symptomatology due to lowered serum theophylline concentrations.

Mast cells and inhalation of asbestos in rats

Mast cell counts were performed on sections taken from the lungs of rats exposed by inhalation to different UICC samples of asbestos fibres for periods ranging from a few days to two years. A comparison of mast cell counts with grades of fibrosis showed that there is a sevenfold increase when there is interlobular linking of the fibrotic lesions (grade 5). Submesothelial mast cells showed a trend of increasing numbers with increasing exposure and with increasing subpleural thickening. Each type of asbestos produced a steady increase in mast cell numbers with increasing exposure. Two samples from animals exposed to chrysotile and two from animals exposed to amphiboles (crocidolite and amosite respectively) had 10 times as many cells as the control group after six and 24 months' exposure. Another amphibole, anthophyllite, produced 50 times more cells than were present in the control specimen appropriate for the heaviest exposure. These results are briefly discussed in relation to further exposure, smoking, and characteristics of the dusts.

Pluripotential nature of mesotheliomata induced by inhalation of erionite in rats

Mesotheliomata can be induced more rapidly and more frequently by inhalation of erionite than by asbestos inhalation. Erionite-induced tumours have in general a similar ultrastructural appearance to inoculum-induced pleural and peritoneal mesotheliomata. Unusual features of these tumours were the presence of dense-cored vesicles and cells staining positively for neuron-specific enolase which indicated the presence of endocrine cells. In addition, one tumour showed differentiation towards bone-forming cells. The expression of both epithelial and mesodermal characteristics demonstrates the pluripotential nature of mesothelial cells under certain circumstances.

The effect of fibre size on the in vivo activity of UICC crocidolite

Standard (UICC) crocidolite was subjected to ball milling to reduce the length of the fibre. These milled materials and the original standard sample were injected into the pleural cavity of rats to determine their ability to induce mesothelioma. Previous in vitro work on the same materials had suggested that biological activity was related to fibres greater than 6.5 microns in length and that the material milled for 4 and 8 h did not contain fibres in this range and was biologically inactive. The results of the animal work, however, did not follow this pattern; mesotheliomas occurred in rats in all treatment groups including the 4 and 8 h milled samples. Examination of the tissues and the dust recovered from them showed the presence of fibres greater than the suggested threshold. Attention is drawn to the problems associated with drawing conclusions from size distributions and in vitro studies without considering in vivo mechanisms.

Falsely elevated aminoglycoside serum levels in jaundiced patients

Two cases in which hyperbilirubinemia produced falsely elevated aminoglycoside concentrations, using the Emit assay, are described. Patients' sera were analyzed by both the Emit and a microbiologic assay. The first patient had a 26-percent greater tobramycin concentration with the Emit assay, as compared with the microbiologic assay, when the total bilirubin was 20.1 mg%. For the same patient, there was essentially no difference between the two assays when the total bilirubin was 4 mg%. The Emit concentrations in the other patient were 34-percent elevated with a total bilirubin of 9.7 mg%. Pharmacokinetic analysis also was performed on serum levels reported by each method. Calculated kinetic parameters and dosage regimens varied greatly. Patients with total bilirubin concentrations greater than 4 mg% may need to have aminoglycoside serum levels assayed by a method other than the Emit assay.

Angiotensin converting enzyme in the serum of rats with experimental silicosis

The development of silicosis in rats given an intratracheal dose of silica was followed both by normal histological procedures and by measuring the level of angiotensin converting enzyme in the serum. The histological changes demonstrated a variable response due to the uneven deposition of material given by the intratracheal route. While the enzyme activity in the serum increased in the treated group it was not well correlated with the histological changes.

Post-mortem study of emphysema in coalworkers and non-coalworkers

A post-mortem survey of emphysema in coalworkers and non-coalworkers was carried out in men aged 50-70 years dying of ischaemic heart disease (IHD). It was determined that in such men selection for necropsy was similar in coalworkers and non-coalworkers. All lungs were examined in a standard way and the amounts of centrilobular and panacinar emphysema were scored on numerical scales. Emphysema in men dying of IHD was significantly more frequent in coalworkers than in non-coalworkers even after age and smoking habits were accounted for by stratification. In the coalworkers, the severity of emphysema was related to the amount of dust in simple foci in the lungs. Because both groups were selected similarly from their parent populations the relative frequency of emphysema found in this study reflects that in the whole populations of coalworkers and non-coalworkers in the study area and confirms an excess of emphysema in coalworkers. This excess is likely to be due to occupational factors.

Mesotheliomas and asbestos type in asbestos textile workers: a study of lung contents

The asbestos contents of the lungs of former employees of an asbestos textile factory were determined at necropsy using a transmission electron microscope. Those who had died of mesothelioma were compared with a matched sample of those who had died of other causes. The predominant fibre processed in the factory was chrysotile, but crocidolite had also been used. The lung content was consistent with the known exposure to chrysotile, but the crocidolite content was also high, being about 300 times that of the general population of the United Kingdom. The lungs of those with mesothelioma did not contain more of either chrysotile or crocidolite than the lungs of the controls, so no particular type of asbestos could be implicated in causing the mesotheliomas. The evidence of substantial exposure to crocidolite means that the mesotheliomas that occurred in this factory could not be attributed with any certainty to the exposure to chrysotile.

Histology and ultrastructure of serially transplanted rat mesotheliomas

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Biological effects of tremolite

Tremolite is an amphibole which has been implicated in a variety of disease patterns in different parts of the world. It occurs in a number of phases, which are chemically identical but have specific physical characteristics. In an attempt to clarify the epidemiological findings, tremolite fibres of 3 specific forms--A, B and C--were characterized and studied for biological activity by: (i) in vivo intrapleural injection of rats (2 separate experiments--1 with poor survival). (ii) in vitro enzyme release from mouse peritoneal macrophages (iii) in vitro giant-cell formation in A549 cultures (iv) in vitro cytotoxicity for V79-4 cells. Sample C, which contained more long thin fibres than A and B, was alone in producing mesotheliomas. C, but not A or B, induced LDH and B-glucuronidase enzyme release, and induced giant cells. A was not cytotoxic, B moderately cytotoxic and C as highly cytotoxic as UICC crocidolite. The in vivo studies were marred by being split between 2 experiments, of which the second had poor survival. We are aware of the weakness of our in vivo data, but as Tremolite C was being considered for commercial use on the European market we felt it timely to submit our findings for publication.

Presence of fibronectin in pneumoconiotic lesions

During the last 10 years our investigations have confirmed that collagen is not the major protein material in the lesions of progressive massive fibrosis of coal workers. In previous studies it was demonstrated that a substance similar in composition to fibrin was an important component in these masses. We report immunohistochemical studies on the lungs of seven coalworkers which show that the complex extracellular material in six of the lesions of massive fibrosis contains fibronectin. Preliminary observations indicate that fibronectin is also present in the lesions of silicosis and asbestosis.

Preliminary observations of the effect of inhalation of PVC in man and experimental animals

Attention has been focussed, both in man and experimental animals, on the effects of inhalation of the gas monomer, vinyl chloride. Recently, note is being taken of the possible effects of the inhalation of the polymer in man. The particles in question are those produced commercially as paste polymer or dispersion polymer or having an average diameter of 0.15 micrometers, and accounting for more than 10% of the production in Britain. There are now strict regulations for the control of the monomer gas, but the particles are regarded as nuisance dust and their emission is not covered by specific legislation. Our studies on rats, where both inhalation and implantation methods of exposure have been used, and examination of tissue from human cases exposed to paste polymers, indicate that these small particles can only be regarded as evidence of exposure, and on present evidence there is no indication of causation of significant pulmonary disease. Techniques have been developed by which these particles can be demonstrated in ordinary histological preparations and by transmission electron microscopy.

Emphysema in smoking and non-smoking coalworkers with pneumoconiosis

The relationships between coalworkers' pneumoconiosis, cigarette smoking and emphysema in a group of 139 deceased coalminers, 19 of whom were non or ex-smokers of 10 years standing, were studied from available clinical and morphological evidence. There was 95 cases of simple pneumoconoiosis and 44 cases with early (Cat. A) progressive massive fibrosis (PMF). The objects were to compare the amounts and types of emphysema in the smokers and non-smokers and also their ventilatory findings. The emphysema content of all the 139 cases of smokers and non-smokers was measured by a standard method and the amounts compared. In addition, the emphysema content of the 19 non- and ex-smokers plus 32 appropriate control cases drawn from the smoking group were measured afresh by a new method devised by the pathologists for the estimation of the extent and type of both emphysema and coalworkers, pneumoconiosis, from large paper lung sections and histological preparations. Both methods compared well in estimating emphysema content and both indicated that the amounts of emphysema in the smoking and non-smoking groups were similar. These findings still applied when both the life-long non-smokers and the cases with simple pneumoconiosis only were looked at separately. It was found that centrilobular emphysema was much commonest type encountered in both smokers and non-smokers. The non-smokers were less disabled in terms of impairment of FEV1.0 than the smokers, although the difference was not statistically significant. The relationship between the centrilobular emphysema and coalworkers' pneumoconiosis is discussed.

Silica-induced malignant histiocytic lymphoma: incidence linked with strain of rat and type of silica

It has already been established that a single intrapleural inoculation of crystalline silica (quartz) produces malignant lymphomas of histiocytic type (MLHT) in Wistar-derived rats. It has now been shown that after treatment with Min-U-Sil, rats of the Alderley Park strain have a tumour incidence of 35%, whereas the incidence in Agus rats is 5% and in PVG 8%. There was also a significant difference in the incidence of MLHT caused by injecting different samples of crystalline silica, particularly of tridymite. There was correlation between cytotoxicity to mouse peritoneal macrophages and tumour incidence, except for one dust (DQ12). Zeta potential, number of particles and their size range were considered, but the incidence does not show a clear correlation with these measurements. The results are discussed.