Bronchogenic and alveologenic tumors in mice induced by N-nitrosopiperidine

The aim of this study was to explore the histogenesis and carcinogenesis of pulmonary cancer induced by N-nitrosopiperidine (NPIP) in mice. NPIP is a form of N-nitrosamine found in tobacco smoke, which has been shown to be a genotoxic chemical as well as a mutagenic compound for inducing chromosome aberrations and severe clastogenicity. In this study, 80 BALB/C strain mice were injected with 0.2 mmol/kg NPIP intraperitoneally for 8 weeks, and experiments were conducted for a further 16 weeks. For the control group, 40 mice were injected with an equal volume of 0.9% NaCl. Pulmonary tissues and tumors in the NPIP-treated group were examined by light microscopy and transmission electron microscopy and compared with the control group at 4-week intervals. The mRNA levels of p53 (mutant), bcl-2, c-myc, ras, and subunits of telomerase - telomerase reverse transcriptase (TERT) and an RNA component, TR - were assayed by mPCR or RT-PCR. Twenty-two mice in the experimental group were found to develop pulmonary tumors, but none in the control group. All tumors found in the experimental group originated from alveolar type II epithelial cells. In addition, 6 of the 22 mice also developed tumors of bronchogenic origin. The expression of p53, bcl-2, c-myc, ras, and the subunits of telomerase were found to increase in all pulmonary tissues and tumors formed thereafter upon NPIP treatment. In summary, NPIP-induced mouse lung tumors exhibited morphological changes during carcinogenesis, which may be the consequence of overexpression of some genes associated with the development of carcinoma and changes in subunits of telomerase. This mouse model of lung tumor formation may be a useful tool to delineate the histogenesis and carcinogenesis of human pulmonary cancer.

Single- and multi-wall carbon nanotubes versus asbestos: are the carbon nanotubes a new health risk to humans?

Carbon nanotubes (CNT), since their discovery, have become one of the most promising nanomaterials in many industrial and biomedical applications. Due to their unique physicochemical properties, interest is growing in the manufacture of CNT-based products and their subsequent marketing. Since their discovery, the prospect of possible undesirable human health effects has been a focus of many scientific studies. Although CNT possess unique physical properties that include (1) nanoscale diameter, (2) a wide length distribution ranging from tens of nanometers to several micrometers, and (3) high aspect ratio, the fibrous-like shape and durability suggest that their toxic properties may be analogous to those observed with other fibrous particles, such as asbestos. The present study provides a summary of published findings on CNT bioactivity, such as the potential of CNT, especially of multi-wall carbon nanotubes (MWCNT), to activate signaling pathways modulating transcription factor activity, induce apoptosis, induce DNA damage, and initiate biological responses. Assessment of risks to human health and adoption of appropriate exposure controls is critical for the safe and successful introduction of CNT -based products for future applications.

Microscopic analysis of the chromium content in the chromium-induced malignant and premalignant bronchial lesions of the rat

OBJECTIVE

Our previous studies demonstrated that the frequency of gene instability in lung cancer of chromate workers was very high, but the frequencies of the p53 and ras gene mutations were low. To clarify the carcinogenesis of chromate in the lung, we established a chromate-induced cancer model in the rat proximal airway and examined the relationship between chromium accumulations and the chromium-induced cancer and premalignant bronchial lesions of the rat.

METHODS

Fifteen male, bred, 12-week-old Jcl-Wister rats were used. A pellet of strontium chromate were inserted into the bronchus of the rats. The rats were sacrificed 9 months after the pellet was inserted. We pathologically examined the region of the bronchi to which the pellet was attached. We quantified the amount of chromium accumulation in the bronchial lesions using a microscopic X-ray fluorescence analyzer.

RESULTS

Of the 15 rats, 1 rat had a lesion of squamous cell carcinoma (SCC), 7 rats had carcinoma in situ (CIS) or dysplasia, 8 rats had squamous metaplasia, and 5 rats had goblet cell hyperplasia. The amounts of chromium accumulation in normal epithelium (n=24), goblet cell hyperplasia (n=14), squamous metaplasia (n=8), and dysplasia plus CIS plus SCC (n=9) were 500+/-1354, 713+/-1062, 941+/-1328, and 3511+/-4473 (mean+/-SD) counts/s/mA, respectively. The amount of chromium accumulation was significantly increased according to the progression of malignant change of the bronchial epithelium (Spearman's correlation coefficient by ranks, rs=0.454, P<0.01).

CONCLUSIONS

The amount of chromium accumulation was significantly increased according to the progression of malignant change of the bronchial epithelium. Examining the genetic alterations of histologic changes in this model was helpful in elucidating the process of carcinogenesis of chromium in the lung.

[Chemoprevention of bronchogenic carcinoma]

Lung cancer is the leading cause of cancer-related deaths in many developed countries. Understanding its carcinogenesis is critical for the development of rational approaches to cancer prevention. The concept of chemoprevention is based on the idea that the diffuse injury of the respiratory epithelium results from chronic carcinogen exposure. Chemoprevention agents should reverse or suppress the development of premalignant and malignant changes by different mechanisms. In the future, the clinical application to risk groups of patients could lead to substantially decreased frequency of the lung cancer. The results of ongoing trials are eagerly awaited.

3-Methylcholanthrene triggers the differentiation of alveolar tumor cells from canine bronchial basal cells and an altered p53 gene promotes their clonal expansion

Alveolar type II cells arising in canine bronchial autografts following exposure to 3-methylcholanthrene (MCA) give rise to carcinomas of varying glandular and squamous growth patterns. To study the role of the tumor suppressor gene p53 in this process, sections from progressive lesions were immunostained for p53 protein; microdissected regions were screened for p53 mutations. Adjacent sections were examined for type II cell expression [cuboid cell shape, large roundish nucleus, cytoplasmic staining for surfactant protein A (SP-A)] and proliferating cell nuclear antigen expression. Evidence for an altered p53 function (nuclear staining, missense mutations) was found in most carcinomas of all histologic types and in all grades of bronchial dysplasia, but not in hyperplastic or normal bronchial epithelium. It was primarily associated with the hyperplastic type II cell populations present in the basal zone of the lesions. In addition, we found SP-A staining in hyperplastic (but not in normal) bronchial basal cells. These data suggest that MCA initiates type II cell differentiation through phenotypic selection (basal cells). Inactivation of the p53 gene promotes the clonal expansion of the type II cells into discernible populations of (squamous or glandular) alveolar tumor cells. This in vivo study is the first to show that p53 is involved in a specific pathway leading to bronchogenic carcinoma.

Histogenesis of adenosquamous bronchogenic carcinoma

In our hamster lung cancer model studies, among 463 non-small-cell lung cancers (NSCLC), there were 47 adenosquamous neoplasms. In 24 of 27 lesions with diameters of less than 3.0 mm, the adenocarcinoma and the squamous cell carcinoma components arose as separate, spatially discrete lesions, but these were separate in only 7 of 20 lesions with diameters of 30 mm or greater. Co-infiltration of the components became more frequent as tumor size increased. The usual adenosquamous variety of NSCLC is likely a collision tumor, with each component possessing separate biological characteristics. Thus, future prognostically directed studies of this variety of NSCLC must recognize that these neoplasms have two components, each of which needs to assessed.

Bronchial carcinoma mortality in the German chromate-producing industry: the effects of process modification

This study updates a 1982 report on mortality at two German chromate-producing factories. The main objective of the study was to establish whether the change-over to a production process using lime-free conversion of chromite ore, thus eliminating the formation of calcium chromate, had resulted in a distinct reduction in bronchial carcinoma mortality among workers exposed for the first time after the change-over (completed in 1958 in Leverkusen and 1964 in Uerdingen). A total of 1417 workers with at least 1 year of exposure were enrolled in the study. The observation period ended on 31 December 1988. The expected number of deaths was calculated using population statistics for North Rhine-Westphalia. The risk was determined in the form of a standardised mortality ratio (SMR), i.e. the ratio of observed deaths to expected deaths. In the group of 739 workers exposed before the process change-over was completed, 432 died during the observation period, 66 of them from bronchial carcinoma. This significant excess produced an SMR of 2.27 (95% confidence interval: 1.78-2.85). Where the cause of death was unknown, cases were allocated to a cause of death on the basis of the percentage occurrence of various causes of death in the specific subcohort. The cohort of 678 workers first exposed after the process modification had been completed had a slightly increased SMR for lung cancer of 1.26 (95% confidence interval: 0.58-2.38) based on nine cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical detection of pulmonary cytochrome P450IA and metabolic activities associated with P450IA1 and P450IA2 isozymes in lung cancer patients

The main polycyclic aromatic hydrocarbon-inducible cytochrome P450 was studied in lung tissue from 57 lung cancer patients by immunohistochemistry, using a monoclonal antibody (1-7-1) that recognizes P450IA1 and P450IA2 isozymes. The intensity of immunostaining was compared with the pulmonary activity of a P450IA1-dependent enzyme, aryl hydrocarbon hydroxylase (AHH), and with P450IA2-related metabolic activity estimated from the ratio of caffeine metabolites in urine. Immunostaining was not observed in peripheral lung tissue of nonsmokers or ex-smokers but was seen in the bronchiolar and alveolar epithelium of all patients who were smokers and had a peripheral carcinoma (16/16) and of 60% (10/17) of those who had a bronchial carcinoma. AHH activity was positively related to the intensity of immunostaining, and an almost 2-fold increase due to smoking was detected in the ratios of caffeine metabolites. These results demonstrate that tobacco smoke induces P450IA1 in the lung and probably P450IA2 in the liver, and suggest a role for certain metabolic phenotypes of P450IA1 in peripheral pulmonary carcinoma.

Variable regression of experimental bronchial preneoplasia during carcinogenesis

It has been thought that squamous severe atypical metaplasia of the bronchus is reliably precancerous. The canine subcutaneous bronchial autograft model for studying the progression of epidermoid carcinogenesis (normal----regular squamous metaplasia----mild, moderate, and severe atypical metaplasia----squamous cell carcinoma) provides evidence that severe atypical metaplasia of the bronchial epithelium is reversible. Among 148 subcutaneous bronchial autografts that had serial sampling of the epithelium and exposure to implants of methylcholanthrene, severe atypical metaplasia was noted in 28 that received only a single implant. During the total carcinogen exposure (median 24.5 months), 9 of 28 (32%) developed squamous cell cancer, and 19 of 28 (68%) regressed toward normal. Severe atypical metaplasia was noted in 34 subcutaneous bronchial autografts that received two or more carcinogen implants: epidermoid cancer developed in 26 of 34 (76.5%), and regression toward or to normal occurred in 8 of 34 (23.5%). Severe atypical metaplasia was not detected in 53 subcutaneous bronchial autografts: 19 that received only a single implant and 34 that received two or more implants. Progression and regression occurred among these subcutaneous bronchial autografts in proportions similar to those found in subcutaneous bronchial autografts wherein severe atypical metaplasia was seen. Among 33 subcutaneous bronchial autografts initially studied after 6 months of exposure to carcinogen, progression to severe atypical metaplasia was seen 3 months later in 19 of 33 that had additional exposure; in the same interval regression of epithelial abnormalities occurred in 14 of 33 subcutaneous bronchial autografts that had no additional exposure (p less than 0.05). We have presented evidence that severe atypical metaplasia includes at least three cell populations: one committed to cancer without further stimulus, one that regresses despite further carcinogen exposure, and one that requires additional carcinogen to progress to cancer. At least in this model, severe atypical metaplasia is not inexorably precancerous. The subcutaneous bronchial autograft model is suitable for seeking biologic indicators of irreversibility.

[Familial clustering of asbestos-related diseases]

This article describes the case histories of four individuals in the same family, all of whom developed asbestos-related disease. Special emphasis is placed upon the case of a woman, who after seemingly minimal exposure to asbestos, in the form of cleaning her husband's working clothes, developed a malignant mesothelioma. The incidence of asbestos-related disease has increased steadily over the past ten years. This probably reflects the extensive use of asbestos in Norway since World War II, and the long latency period of the disease. The authors recommend obtaining an in-depth history of exposure when asbestos-related disease is suspected.

[Asbestos-induced lung diseases]

Asbestos fibres have potent cancerogenic and fibrogenic properties and may lead to development of cancer and fibrosis in the lung parenchyma and pleura. The Danish Ministry of Employment has established rules which should prevent development of disease when working with asbestos in future but, on account of the very long latent period between exposure and development of asbestos-related disease, these conditions will still occur during the next 30-40 years. Primarily, the more benign pleural plaques will be concerned but serious disease such as bronchial carcinoma and pleural mesothelioma will occur in the future. When patients are encountered who present symptoms or objective/paraclinical findings which are compatible with disease produced by asbestos, it is important to remember that exposure to asbestos may be many decades ago and, particularly where the malignant conditions are concerned, exposure need not have been particularly massive or prolonged. All cases where asbestos-related disease is suspected should be notified to the insurance administration.

Cancer after exposure to metronidazole

We assessed the risk of occurrence of cancer associated with exposure to metronidazole in the 771 female residents of Rochester, Minnesota, who were treated with metronidazole for vaginal trichomoniasis during the period 1960 through 1969 and were followed up for a total of 12,628 person-years. Standardized morbidity and mortality ratios were determined by using an expected number calculated by applying age-specific incidence rates from Rochester studies and Cancer Surveillance, Epidemiology, and End-Results Reporting (SEER) data to the person-years of follow-up. The overall standardized morbidity ratios for cancer at all sites were 1.4 (Rochester, 1978 through 1983), 1.5 (SEER data for Iowa, 1978 through 1981), and 1.2 (SEER data for Connecticut, 1978 through 1981). By site of the cancers, the standardized morbidity ratios greater than unity were those for malignant lesions of the lung, breast, thyroid, bladder, brain, kidney, nasopharynx, and oral cavity, as well as for multiple myeloma and malignant melanoma; however, the only significantly elevated standardized morbidity ratio was that for bronchogenic carcinoma. After adjustment for smoking status, the standardized morbidity ratio for bronchogenic cancer was 2.5 (95% confidence interval of 1.3 to 4.4). The standardized mortality ratio for cancer at all sites was 1.4 (95% confidence interval of 0.9 to 2.2). The analysis of these data suggests no significant increase in cancer-related morbidity or mortality for women exposed to metronidazole for treatment of vaginal trichomoniasis.

Increased chromium and nickel content in lung tissue and bronchial carcinoma

In 25 random autopsies, chromium (Cr) and nickel (Ni) in lung tissue and regional lymph nodes were analysed by means of flameless atomic absorption spectrometry (AAS). The subjects originate from Bochum in the Ruhr District, which is defined as a particular pollution area with locally high Cr and Ni emissions. The subjects examined from Bochum (BO) and vicinity have Cr and Ni concentrations about 5 and 6 times higher than those in a previous series form Münster (MS) and vicinity (outside the particular pollution area), which is used for comparison purposes. BO and MS data showed an age-dependent increase of chromium and nickel in the lung, and in both data sets as well as in the combined, the Cr and Ni values showed extremely high correlations (r greater than 0.9). The Cr and Ni concentrations (BO) in lung (3.47 +/- 2.53 micrograms Cr/g, 1.09 +/- 1.43 micrograms Ni/g dry weight) and lymph node tissue (6.30 +/- 3.72 micrograms Cr/g, 1.00 +/- 0.58 micrograms Ni/g dry weight) do not show any correlation. The BO data contained four cases of bronchial carcinoma (all male), three of which showed pulmonary Cr and Ni concentrations that lie clearly above the predicted level. One case of bronchial carcinoma had extremely high Cr and Ni values; an occupational exposure as dental laboratory technician is taken into consideration.

Lung neoplasms in rodents after chronic administration of dimethyl hydrogen phosphite

Dimethyl hydrogen phosphite (DMHP), an intermediate in the production of insecticides or herbicides, was administered by p.o. gavage for 2 yr to male Fischer 344/N rats and male and female B6C3F1 mice at doses of 0, 100, or 200 mg/kg and to female Fischer 344/N rats at doses of 0, 50 or 100 mg/kg. Dose related toxicity was seen in the lungs of treated male and female rats. The lung lesions were most prevalent in the high dose male rat group which received a dose twice that given to the high dose female rats. Lung lesions included alveolar epithelial hyperplasia, chemically related pneumonia, alveolar-bronchiolar adenoma, alveolar-bronchiolar carcinoma, and squamous cell carcinoma. DMHP also caused neoplastic and nonneoplastic lesions of the forestomach in male rats; a similar but less pronounced effect was observed in female rats. Nonneoplastic lesions associated with administration of DMHP included mineralization of the cerebellum in male rat and focal calcification of the testis in male mice. Under the conditions of this study, there was clear evidence for carcinogenicity for male rats, equivocal evidence for carcinogenicity in female rats, and no evidence for carcinogenicity in either male or female mice. DMHP caused the highest incidence of lung tumors in the male rat of all chemicals studied to date in the National Cancer Institute-National Toxicology Program Carcinogenesis Testing Program.

Reversibility of bronchial cell atypia

Various degrees of cellular atypia were induced in the bronchial epithelium of dogs by means of repeated submucous 20-methylcholanthrene injections. Thereafter, the 20-methylcholanthrene treatment was stopped, and the outcome of the bronchial cell atypias in individual dogs was studied using cytomorphological and cytochemical methods. The results suggest that the various degrees of 20-methylcholanthrene-induced cellular atypias, including those cytologically interpreted as malignant, may reflect reversible cellular alterations which disappear after removal of the carcinogen. Similar observations were made in a group of cigarette smokers who, after malignant-appearing cells were observed in the sputum material, stopped smoking or significantly reduced their cigarette consumption.

Chromate lung cancer with special reference to its cell type and relation to the manufacturing process

The manufacturing process of the chromate industry can be classified into five steps. The main hazardous pollutants of the first step are trivalent chromate compounds, and those of the second and third steps are hexavalent chromate compounds. Analysis of the detailed working history of chromate workers with bronchogenic carcinoma, yielded the following results: the work history of chromatic lung cancer patients in the first step, which produced mainly trivalent chromate dust, was rather short. Patients with small cell carcinoma were engaged mainly in the second step (98.1% of the total working months), where they were heavily exposed to hexavalent chromate dusts. Patients with squamous cell carcinoma were engaged rather evenly in the second and fourth steps, and somewhat longer in the third step. Comparisons of the exposure periods revealed that the working history of small cell carcinoma patients was significantly shorter than that of squamous cell carcinoma patients. There were many more heavy smokers among the squamous cell carcinoma group as compared to the small cell carcinoma patients. Based on these results, it is concluded that the cell type of occupational lung cancer was mainly small cell carcinoma when the exposure to carcinogenic agents was heavy, and that the carcinogenicity of chromate was derived mainly from hexavalent chromate rather than trivalent compounds.

[Is there a relation between occupational exposure of the welder and the formation of bronchial cancer?]

From 1961 to 1979 844 men with a bronchogenic carcinoma have been operated in the Pulmological Department of the Wittenberg-Apollensdorf hospital. 63 patients (7.5%) were younger than 45, 781 (92.5%) were older than 45 years of age. Those who are employed in the metal industry are at the top of the occupational index in both age groups, whereas those employed in the chemical industry are only on place 5, although the district of Halle from which the patients mostly are coming is the centre of the chemical industry in the GDR. In our investigations it is remarkable that the group of welders, and heating fitters is to be found on place 2 among the younger patients, whereas the older ones occupy place 11.

Studies of neoplastic development in respiratory tract epithelium

The dynamics of neoplastic development in conducting airways were studied in an animal model using morphologic and tissue culture techniques. Evidence for the regression of many metaplastic-dysplastic lesions, including advanced "preneoplastic" lesions, was provided. This regression of lesions is not synonymous with reversion of the neoplastic process. The number of "carcinogen-altered" cells and the number of cells with neoplastic potential continued to increase as a function of time after carcinogen exposure. With the cell culture methods developed for these studies, it is possible to analyze qualitatively and quantitatively the progression of the neoplastic process as it takes place in vivo and to detect and enumerate the progenitor cells of later-appearing cancers. The investigations also provide strong evidence suggesting that carcinogen-exposed organs contain many more cells with neoplastic potential. This expression may, however, be sharply enhanced when permissive or promoting conditions prevail. The investigations open up new avenues to develop means for detection of preneoplastic cell populations and for therapeutic intervention during early phases of the neoplastic disease process.

Lung carcinoma induction in BD rats after a single intratracheal instillation of an arsenic-containing pesticide mixture formerly used in vineyards

A single intratracheal 0.1-ml instillation of a calcium-arsenate containing vineyard pesticide induced multi-focal bronchogenic adenocarcinomas and bronchiolar-alveolar-cell carcinomas in nine out of 15 treated BD rats. This seems to be the first experimental confirmation of carcinogenicity of arsenic-containing pesticides used formerly in vineyards.

Detection, localization, and treatment of occult bronchogenic carcinoma in nickel workers

Asymptomatic men exposed to nickel sulfide prior to 1963 were studied prospectively to investigate cytologic abnormalities in the sputum. We discovered a considerably greater incidence of squamous cell tumors that would have been expected from subjects exposed only to cigarette smoke.

Statistical analysis of epidemiological data from a chromium chemical manufacturing plant

A statistical analysis was performed on reported bronchogenic carcinoma incidence in a group of chromium chemical manufacturing workers over the period 1929 to 1977. The purpose was to determine if post-1950 process improvements corresponded to favorable trends in morbidity. Because the paucity of data on the population at risk prevented meaningful calculations of SMR's, a recently developed method called "probability window analysis" was used to evaluate for statistically valid changes in the "numerators" or number of reported cases. A significant downward trend in reported bronchogenic carcinoma was found which coincided with major process improvements made in 1951 and 1961. Although adjustment for all competing risk factors was not possible because of insufficient data on the population at risk, the improved working environment has to be considered a major contributing factor to the favorable trend.

Is the role of the environment in carcinogenesis overestimated?

The dominant role of the physical and chemical environment in the development of cancer is challenged. Analyses of the etiology of skin, bladder, respiratory and gastric cancers are presented which demonstrate the considerable extent to which one's health status may modify the initiation and promotion of environmentally associated cancers. It is concluded that although environmental factors may initiate and/or promote 85 to 90 percent of all cancers this is misleading since it neglects the critical role of the individual's health status as a factor modifying carcinogenesis.

Lung cancer in Japanese chromate workers

We have treated ten patients with lung cancer among workers in a chromate factory between 1972 and 1976. Four further cases were also found through death certificates and medical records. Most were smokers and all were men. The average duration of exposure to chromate was 24 years (range 10 to 36). The cell type in our ten patients was squamous in seven and small anaplastic type in three. The primary sites were all in large bronchi. The incidence (person per year) calculated from the number of employees, duration of factory activity, number of cancer patients, and shortest duration of labour period among the patients was 657.9 per 100,000 compared to 13.3 per 100,000 in Japan as a whole.

A method for experimental induction of bronchogenic carcinoma in subcutaneously implanted bronchial autograft in dogs

A method for induction of carcinoma in subcutaneously implanted bronchial autografts in dogs is described. Four to 6 weeks after successful bronchial autografting, 30 to 90 mg. amounts of 3-MC or B(a)P suspended in sterile saline solution containing 1 percent CMC was injected into the lumen of the graft. The mucosal changes were followed histologically by excision of biopsy specimens and cytologically by needle aspiration biopsies. Three dogs developed squamous cell carcinomas invading deep into the submucosal area as early as 13 to 30 weeks after the first carcinogen treatment. The remaining eight experimental dogs showed various grades of squamous cell metaplasia with atypia within 30 weeks. Subsequently examined specimens revealed atypical metaplastic and proliferative changes further advanced than those seen in the initial biopsy specimens. The advantages of this method for a better understanding of the development of bronchogenic carcinomas are discussed.

Effect of systemic administration of BCG cell walls on bronchogenic carcinoma in hamsters

Systemic injection of BCG cell walls was evaluated for effects on the development of respiratory tract tumors induced by intratracheal instillation of benzo[a]pyrene plus Fe2O3 in Syrian hamsters. Only 74% of animals developed respiratory tract tumors at the dose level of benzo[a]pyrene used. Treatment with BCG cell walls reduced the incidence of respiratory tract tumors to 50%. A similar effect of treatment with BCG cell walls was found when only malignant tumors of the respiratory tract were considered. Both single and multiple injections of BCG cell walls effectively reduced the incidence of respiratory tract tumors.

Techniques for localized injections and topical applications of carcinogens at specific endobronchial sites in dogs

We seek to create a canine lung cancer model with sharply localized carcinomas analogous to human lung cancers. Toward this goal techniques for recurrent endobronchial transbronchoscopic submucosal injections and topical applications of the carcinogens 3,4-benzo(a)pyrene and N-methyl-nitrosourea have been developed. After 2 years of experience with 2,868 endoscopic manipulations and varying dosage schedules in 59 dogs, safe effective techniques for recurrently delivering carcinogens and sequential biopsies of the same sites have evolved. Predominantly during the first year of experience, 10 dogs died as a consequence of technical problems such as exsanguinations after 1 mm. punch biopsies. There were also 39 instances of nonlethal technical complications of endoscopy in the face of immunosuppression and local irritation caused by the carcinogens. By the techniques and dosage schedules described, it has now become possible reliably and safely to create impressive localized bronchial preneoplasia with squamous metaplasia and atypia among the prominent features.

The biological effects of mineral fibres, especially asbestos, as seen from in vitro and in vivo studies

Two in vitro models have been extensively used to compare the biological action of different types of asbestos fibres: the haemolytic effect and the cytotoxic one on macrophages grown in cell culture. The use of both techniques as led towards a better understanding of the chemical reactions which occur between fibres and the biological membranes of cells or intracellular organelles. Studies on the prevention of haemolysis and cytotoxicity have also been of use in explaining how asbestos acts a the cellular and molecular levels. Regarding in vivo studies, useful comparisons have been made of the fibrogenic and carcinogenic effects of different types of fibres in man and experimental animals. Both the in vitro and the in vivo aspects of the problem are discussed in some detail and an attemps is made to provide a reasonably unified concept for both.

The respiratory effects of chloromethyl methyl ether

A prospective study of 125 chemical workers was carried out for ten years to investigate the incidence of lung cancer. Some of the men were exposed to chloromethyl methyl ether containing bis(chloromethyl) ether as an impurity. Bronchogenic carcinoma was markedly increased among them, with a strong dose-response relationship. An unexpected inverse relationship was noted between smoking and the incidence of lung cancer. The neoplasms (all small-cell carcinomas) occurred in relatively young men. Symptoms of chronic bronchitis were reported more often among men exposed to chloromethyl ether, and a dose-response relationship was apparent, with smoking a cofactor. Ventilatory function was not significantly affected by chemical exposure. Periodic screening over the first five years of the study showed a decrease in chronic coughing and an increase in dyspnea while chemical exposure was diminishing.

Association of asbestos and bronchogenic carcinoma in a population with low asbestos exposure

Quantitative counts of ferruginous bodies were performed on digests of lungs from 100 control and 30 lung cancer patients. It was found that the lung cancer group had significantly higher levels, although only 1 patient was known to be occupationally exposed to asbestos. It is suggested that even extremely low levels of asbestos exposure may have a carcinogenic effect.

Investigations on the carcinogenic burden by air pollution in man. XII. Early pathological alterations of the bronchial epithelium in syrian golden hamsters after intratracheal instillation of benzo(a)pyrene

The ultrastructural alterations occurring in the bronchial epithelium of Syrian golden hamsters treated once weekly for life with 0.63 mg BP were examined during the first 20 weeks of treatment. It was demonstrated that epithelial cells penetrated the basement membrane thus finally forming small bronchogenic tumours (adenomata) composed of ciliated, nonciliated and a few basal cells. No squamous metaplasis occurred.

Background documentation of evaluation of occupational exposure to airborne asbestos

This review presents background information and literature documentation to supplement the "Recommended Procedures for Sampling and Counting Asbestos Fibers: Procedures for the Evaluation of Occupational Exposure to Airborne Asbestos" prepared by the joint ACGIH-AIHA Aerosol Hazards Evaluation Committee. It reviews the nature of the inhalation hazard associated with asbesots fibers, the sampling and analytic methods which have been used, and a rationale for the selection of the membrane filter sampling-optical phase microscope identification and assay methodology which is recommended.

Diagnosis of experimentally induced bronchogenic tumours in the european hamster with bronchographs

Four groups of European hamsters were treated subcutaneously once weekly for life with 1/20 or 1/40 the diethylnitrosamine LD 50. Three animals from each treatment group and the two control groups were examined every three weeks by means of bronchographic technique. In four of the animals the bronchograms showed early neoplastic alterations of the bronchial system. The results demonstrate that bronchography is a suitable method for the diagnosis of bronchogenic tumours in the European hamster and that it also allows for the detection of displacing neoplasms of non-bronchogenic origin in the region of the tracheal bifurcation.