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Biomedical subjects

G Monchaux

Publications and source records attributed to G Monchaux.

36 records · Page 2Linked to original sources
PubMed1983

Incidence of various types of thoracic malignancy induced in rats by intrapleural injection of 2 mg of various mineral dusts after inhalation of 222Ra.

After inhalation of 222Ra at equilibrium with radon daughters, male Sprague-Dawley rats were inoculated intrapleurally with 2 mg of unleached or acid-leached asbestos fibres or glass fibres or quartz. The additive co-carcinogenic effects of this type of insult were demonstrated by the increased incidence of malignant thoracic tumours. In rats given mineral materials, bronchopulmonary carcinomas and mixed carcinomas were observed, as well as typical mesotheliomas and combined pulmonary pleural tumours, whereas in control rats inhaling radon alone, only bronchopulmonary carcinomas occurred. No significant differences in tumour incidence were observed between the groups of animals given the different types of dusts, but statistically significant differences were noted in survival times, according to the histological type of tumour. The co-carcinogenic effects of an insult of the pleura by mineral dusts following inhalation of radon are discussed in relation to a possible tumour-promoting effect by these agents.

Animals↗
PubMed1981

Mesotheliomas in rats following inoculation with acid-leached chrysotile asbestos and other mineral fibres.

The carcinogenicity of untreated UICC chrysotile A, of acid (oxalic and hydrochloric)-leached UICC chrysotile A, of crocidolite and of JM 104 glass fibres has been studied by intrapleural injection into rats. This experiment, carried out on 304 animals, demonstrated that when more than 80% of the Mg had been leached from chrysotile fibres by either hydrochloric or oxalic acid, the proportion of pleural mesotheliomas was either nil or dramatically lower than that obtained with untreated chrysotile. The carcinogenic effect of crocidolite was higher than that of 43.7% oxalic acid-leached chrysotile. The proportion of mesotheliomas observed in animals injected with JM 104 glass fibres was similar to that in animals injected with fibres from which 63.8% had been leached with oxalic acid. These results indicate that with regard to the induction of pleural carcinogenicity by chrysotile fibres, not only size characteristics but also parameters such as chemical composition and physiochemical properties must intervene.

Animals↗
PubMed1980

Mesothelioma induced by intrapleural injection of different types of fibres in rats; synergistic effect of other carcinogens.

Intrapleural injections of 20 mg of various mineral fibres were made to rats. Three types of fibres (chrysotile, crocidolite and glass fibres) were untreated; other chrysotile fibres were leached to different degrees. The results show that chrysotile is the most toxic of the three: animals died sooner and presented mesotheliomas earlier. With increased leaching, toxicity and carcinogenic effect decreased. Crocidolite is less toxic than untreated chrysotile but later produces as many mesotheliomas; with glass fibres, some mesotheliomas are observed. Small groups of animals were exposed to two types of irradiation before intrapleural injection of 2 mg of chrysotile. Whole-body irradiation was delivered to a third group of animals which were given asbestos-contaminated food. The paper analyses the synergistic action of these two insults.

Animals↗
PubMed1980

Experimental demonstration of the penetration of asbestos fibres into the gastrointestinal tract.

Evidence for a no-threshold concentration-effect relationship for many environmental carcinogens, and especially for asbestos fibres, has been substantiated. Thus, the risk for humans of low concentrations of fibres in the diet could be predicted if the absorption of fibres through the gut could be measured. In this study, the behaviour of ingested fibres (asbestos and attapulgite) has been investigated by the collection of lymph, as described by Bollman et al. (1948). Fibres were found to cross the gut wall and to circulate in the abdominal lymph at 2-24 hours after feeding. The kinetics of the fibre passage could be measured: 50% of the total load absorbed was found in the lymph within the first six hours. The greatest fibre passage was observed with long asbestos fibres, which reached 2.1 X 10(-4) of the ingested load. Selection of the longest fibres was observed when size distributions were compared in the lymph and in the diet. negative results were obtained consistently in controls and in some of the treated animals. Lymph collection was found to be the most appropriate method for detecting intestinal absorption.

Animals↗
PubMed1979

Human and experimental data on translocation of asbestos fibers through the respiratory system.

The translocation of fibrous dusts through the respiratory system is discussed on the basis of human and experimental data obtained with the transmission electron microscope. Comparison of the characteristics (numerical and mass concentrations, sizes, types) of asbestos fibers retained in different locations of the respiratory system in humans exposed to asbestos has shown that there is no relationship between the numerical concentrations in lung parenchyma and those in parietal pleura. Moreover, almost al fibers encountered in the pleura were ultimate, short fibrils of chrysotile. The animal data are from rats injected intrapleurally with different types of fibers (chrysotile, crocidolite and glass fibers) and sacrificed at different times. There was a progressive increase in the number and mass of fibers translocated into lung parenchyma from the pleural cavity that was particularly obvious after 90 days. After this time, the mean length of fibers, especially chrysotile, increased, indicating that more long fibers are retained in alveolar tissue than short fibers.

Animals↗
PubMed1975

Topographic distribution of asbestos fibres in human lung in relation to occupational and non-occupational exposure.

A topographic study of asbestos fibre content of lung and pleura of diversely exposed cases has been carried out. For heavily exposed cases with lung fibrosis, this study has stressed the distinctive behaviour of the peripheral lower lobe in the retention of asbestos fibres in the lung. In these areas were found the smallest asbestos concentrations but the largest fibres. For cases without lung fibrosis, the results clearly demonstrated an accumulation of asbestos fibres, especially of chrysotile type, in peripheral areas. These findings are to be related to the incidence of pleural mesothelioma associated with moderate or low exposure. The small variation of fibre concentration in the pleural plaques of diversely exposed subjects is pointed out.

Adult↗
PubMedDate not supplied

[Topographical variations of pulmonary and pleural asbestos fiber concentrations in variously exposed subjects].

The authors study three groups of subjects with different exposures to asbestos dust. The lung content in asbestos fibres is measured by optical and electron microscopy, the latter technique revealing preferential concentration of asbestos fibres in the peripheral zones of the lung, in particular in individuals subject to a moderate degree of professional exposure.

Asbestos↗