G. L. Finch

THE ACUTE TOXICITY OF INHALED BERYLLIUM METAL IN RATS

We exposed rats once by nose only for 50 min to a mean concentration of 800 micrograms/m3 of beryllium metal (initial lung burden, 625 micrograms) to characterize the acute toxic effects within the lung. Histological changes within the lung and enzyme changes within bronchoalveolar lavage (BAL) fluid were evaluated at 3, 7, 10, 14, 31, 59, 115, and 171 days postexposure (dpe). Beryllium metal-exposed rats developed acute, necrotizing, hemorrhagic, exudative pneumonitis and intraalveolar fibrosis that peaked at 14 dpe. By 31 dpe, inflammatory lesions were replaced by minimal interstitial and intraalveolar fibrosis. Necrotizing inflammation was observed again at 59 dpe which progressed to chronic-active inflammation by 115 dpe. This inflammation worsened progressively, as did alveolar macrophage and epithelial hyperplasia, becoming severe at 171 dpe. Low numbers of diffusely distributed lymphocytes were also present but they were not associated with granulomas as is observed in beryllium-induced disease in man. Throughout the experiment, total numbers of cells were elevated within the BAL samples due primarily to increased numbers of neutrophils. Lymphocytes were not elevated in BAL samples collected from beryllium-exposed rats at any time after exposure. Lactate dehydrogenase (LDH), beta-glucuronidase, and protein levels were elevated in BAL fluid from 3 through 14 dpe but returned to near normal levels by 31 dpe. LDH increased once again at 59 dpe and remained elevated at 171 dpe. beta-Glucuronidase and protein levels were slightly, but not significantly, elevated from 31 through 171 dpe. Results indicate that inhalation of beryllium metal by rats results in severe, acute chemical pneumonitis that is followed by a quiescent period of minimal inflammation and mild fibrosis. Progressive, chronic-active, fibrosing pneumonitis is observed later. Chronic beryllium lung disease of man is an immunologically mediated granulomatous lung disease, whereas beryllium-induced lung lesions in rats appear to be due to direct chemical toxicity and foreign-body-type reactions.

Effects of concurrent ozone exposure on the pathogenesis of cigarette smoke-induced emphysema in B6C3F1 mice.

Episodic elevation of air pollutants may exacerbate respiratory distress associated with chronic obstructive pulmonary disease (COPD), yet few experiments have been performed to determine how continuously polluted atmospheres may contribute to the etiology of COPD, in general and pulmonary emphysema in particular. This study describes the effects of concurrent exposure to ozone (O 3) in the pathogenesis of cigarette smoke (CS)-induced emphysema in the mouse. Female B6C3F 1 mice were whole-body exposed either to filtered air (FA) or to mainstream CS at a concentration of 250 mg total particulate material/m 3 for 6 h/day, 5 days/wk for 15 or 32 wk. Concurrently, mice were exposed either to FA or to O 3 at 0.3 ppm for 8 h/night, 5 nights/wk for the same time periods. At necropsy, mouse lungs were lavaged, and bronchoalveolar lavage fluid (BALF) was analyzed for inflammatory cell numbers, total protein, lactate dehydrogenase (LDH) and alkaline phosphatase (AP) activities, superoxide production by isolated alveolar macrophages, glutathione content, inflammatory cytokines, and proteolytic activity. Other lungs were inflated at constant pressure for 6 h with formalin for fixation, routine histopathology, and stereology. After 32 wk of exposure, CS with or without concurrent O 3 exposure produced stereologic evidence of emphysema as previously described. Concurrent O 3 exposure did not worsen any of these parameters, nor did O 3 by itself cause stereologic changes that were consistent with emphysema. The O 3 exposure caused only slight elevations of BALF macrophages, while CS exposure caused marked increases in the numbers of both BALF macrophages and neutrophils. Neutrophils in the BALF in response to CS exposure were also more numerous at 32 wk than at 15 wk. Exposure to CS caused an increase in BALF total protein, LDH, AP, and interleukin (IL)-1β. After 32 wk, CS exposure was associated with decreased superoxide production from isolated alveolar macrophages. The CS exposure elevated BALF total glutathione primarily at 15 wk. Overall, O 3 had little effect on endpoints that were significantly affected by CS exposure. We conclude that concurrent O 3 exposure has no effect on the induction of emphysema by CS in this animal model.

Effect of Chronic Cigarette Smoke Exposure on Lung Clearance of Tracer Particles Inhaled by Rats

Cigarette smoking can influence the pulmonary disposition of other inhaled materials in humans and laboratory animals. This study was undertaken to investigate the influence of cigarette smoke exposures of rats on the pulmonary clearance of inhaled, relatively insoluble radioactive tracer particles. Following 13 weeks of whole-body exposure to air or mainstream cigarette smoke for 6 hr/day, 5 days/week at concentrations of 0, 100, or 250 mg total particulate matter (TPM)/m3, rats were acutely exposed pernasally to 85Sr-labeled fused aluminosilicate (85Sr-FAP) tracer particles, then air or smoke exposures were resumed. A separate group of rats was exposed to the 85Sr-FAP then serially euthanized through 6 months after exposure to confirm the relative insolubility of the tracer particles. We observed decreased tracer particle clearance from the lungs that was smoke concentration-dependent. By 180 days after exposure to the tracer aerosol, about 14, 20, and 40% of the initial activity of tracer was present in control, 100 mg TPM/m3, and 250 mg TPM/m3 groups, respectively. Body weight gains were less in smoke-exposed rats than in controls. Smoke exposure produced lung lesions which included increased numbers of pigmented alveolar macrophages distributed throughout the parenchyma and focal collections of enlarged alveolar macrophages with concomitant alveolar epithelial hyperplasia and neutrophilic alveolitis. The severity of the lesions increased with smoke exposure duration and concentration to include interstitial aggregates of pigmented macrophages and interstitial fibrosis. Our data confirm previous findings that exposure to cigarette smoke decreases the ability of the lungs to clear inhaled materials. We further demonstrate an exposure-concentration related magnitude of effect, suggesting that the cigarette smoke-exposed rat constitutes a useful model for studies of the effects of cigarette smoke on the disposition of inhaled particles.

Clearance, Translocation, and Excretion of Beryllium following Acute Inhalation of Beryllium Oxide by Beagle Dogs

Beagle dogs inhaled radiolabeled beryllium oxide (7BeO) particles that were calcined at either 500 or 1000 degrees C, resulting in either high (mean of 50 micrograms/kg body wt) or low (mean of 17 micrograms/kg body wt) initial lung burdens (ILBs) of both preparations of BeO. Levels of beryllium in whole body, tissue, and excreta were measured by external gamma-ray counting. Dogs were euthanized in pairs at 8, 32, 64, and 180 days after exposure to determine beryllium distribution in tissues. Beryllium oxide calcined at 1000 degrees C was retained more tenaciously in the lungs (62% of the ILB retained at 180 days after exposure) than BeO calcined at 500 degrees C (14% of the ILB retained at 180 days after exposure). Most of the beryllium that was cleared from the lungs and not excreted was translocated to the tracheobronchial lymph nodes, skeleton, liver, and blood. More beryllium was translocated to the skeleton and liver at 180 days after inhalation of BeO prepared at 500 degrees C than at 1000 degrees C. The predominant mode of excretion at early times after exposure was through the feces, with urinary excretion assuming predominance at later times. These data are important for interpreting the toxic effects of beryllium in the exposed dogs. Furthermore, because little is known concerning the retention and clearance of inhaled beryllium in man, these results provide information that may be used to understand the disposition of beryllium in accidentally exposed humans.

The Induction of Chromosome Damage in CHO Cells by Beryllium and Radiation Given Alone and in Combination

Studies were conducted to determine the effects of BeSO4 or X rays, alone and in combination, on cell cycle kinetics, cell killing, and the production of chromosome aberrations in Chinese hamster ovary (CHO) cells. The concentration of BeSO4 required to kill 50% of CHO cells exposed to BeSO4 for 20 h was determined to be 1.1 mM with 95% confidence intervals of 0.72 to 1.8 mM. During the last 2 h of the 20-h beryllium treatment (0.2 and 1.0 mM), cells were exposed to 0.0, 1.0, or 2.0 Gy of X rays. Exposure to either BeSO4 or X rays produced a change in cell cycle kinetics which resulted in an accumulation of cells in the G2/M stage of the cell cycle. However, combined exposure to both agents resulted in a block similar to that observed following exposure to X rays only. The background level of chromosome damage was 0.05 +/- 0.015 aberrations/cell in the CHO cells. Seven hours after the end of exposure to 0.2 and 1.0 mM beryllium, 0.03 +/- 0.003 and 0.09 +/- 0.02 aberrations/cell, respectively, were observed. The data for chromosome aberrations following X-ray exposure were fitted to a linear model with a coefficient of 0.14 +/- 0.01 aberrations/cell/Gy. When beryllium was combined with the X-ray exposure the interactive response was predicted by a multiplicative model and was significantly higher (P less than 0.05) than predicted by an additive model. The influence of time after radiation exposure on the interaction between beryllium and X rays was also determined. No interaction between beryllium and X-ray exposure in the induction of chromosome-type aberrations (P greater than 0.05) was detected. The frequency of chromatid-type exchanges and total aberrations was significantly higher (P less than 0.05) in the radiation plus beryllium-exposed cells when compared to cells exposed to X rays only, at both 9 and 12 h after X-ray exposure. These data suggest that the multiplicative interaction may be limited to cells in the S and G2 stages of the cell cycle.

The comparative pulmonary toxicity of beryllium metal and beryllium oxide in cynomolgus monkeys

Inhalation of beryllium (Be) may result in an immune-mediated, chronic granulomatous pulmonary disorder known as chronic beryllium disease (CBD). The physicochemical form of Be may affect the incidence and severity of CBD. We exposed cynomolgus monkeys, by bronchoscopic, intrabronchiolar instillation, to either beryllium oxide (BeO; heat-treated at 500 degrees C) or Be metal at concentrations selected to achieve equimolar concentrations of available Be2+ ions dissolving from the particles. Monkeys underwent bronchoalveolar lavage of the right and left diaphragmatic lobes at 14, 30, 60, 90, and 120 days post exposure (dpe). Monkeys were sacrificed at 80 and 180 dpe for evaluation of histopathological pulmonary changes. Numbers of lymphocytes from lung lobes of Be metal-exposed, but not BeO-exposed, monkeys were increased at 14, 30 and 90 dpe. Lung lymphocytes were increased for BeO exposed monkeys only at 60 dpe. In vitro, Be-specific, lung lymphocyte proliferation occurred at 14, 60, and 90 dpe for lymphocytes from Be metal-exposed lung lobes only. At no time were values from BeO-exposed lung lobes different from values from control lobes. Lung lesions in Be metal-exposed monkeys were characterized by focally intense, interstitial fibrosis, marked Type II cell hyperplasia, and variable lymphocyte infiltration. Some Be-metal-exposed monkeys had discrete immune granulomas consisting of tightly organized lymphocytic cuffs surrounding nodular aggregates of epithelioid macrophages. Lesions were rarely present in BeO-exposed monkeys and were much less severe. These data suggest that Be metal produces more severe pulmonary lesions than does BeO and that these lesions are accompanied by Be-specific immune responses.

Release of Aerosols during Sawing and Milling of Beryllium Metal and Beryllium Alloys

Abstract In spite of stringent standards for occupational exposure of workers to airborne beryllium, new cases of chronic beryllium disease continue to occur. Many of these cases are among workers involved in the machining of beryllium metal. Although the exposure history of most individuals recently diagnosed as having chronic beryllium disease included exposures above the current occupational standard (2 μg/m3), there are limited data on the source of beryllium aerosols and on the inhalation toxicology of beryllium metal. Similar information is lacking on the source terms and toxicology of beryllium metal alloys. Although no cases of chronic beryllium disease have been diagnosed among machinists working exclusively with beryllium alloys, it is not clear whether this results from a lower probability for inhalation exposures above the occupational limits or from an intrinsically lower toxicity of beryllium in dilute alloys. The work reported here was undertaken to better define the potential aerosol sourc...

Responses of Rat Lungs to Low Lung Burdens of Inhaled Beryllium Metal

AbstractThe linkage between acute and chronic toxic responses to inhaled beryllium (Be) is not well understood. This study described (1) the lowest lung burdens of Be that would induce acute pulmonary toxicity, (2) the progression of acute to chronic toxic responses, and (3) the effects of Be exposure on lung clearance. We simultaneously exposed groups of male F344/N rats by single, brief, nose-only inhalation to a mixed aerosol consisting of Be metal and radioactive tracer particles. Lung burdens of Be achieved were 0.32, 1. B, 10, and 100 μg; control rats received the tracer particles alone. The purpose of the tracer particle exposure was to compare lung clearance of these particles between groups. Groups of rats were sacrificed at 8, 16, 40, 90, 210, and 365 days after exposure for histopathologic examination and for bronchoalveolar lavage. No lesions were observed in controls or in animals receiving lung burdens of 0.32 μg Be. At the 1.8 μg lung burden of Be, only late-occurring, minimal chronic infla...

Effects of cigarette smoke on the glutathione status of the upper and lower respiratory tract of rats

AbstractEndogenous antioxidants, like the tripeptide glutathione (CSH), protect the respiratory airways from potentially injurious agents within inhaled pollutants like cigarette smoke. The purpose of this study was to determine the effects of cigarette smoke exposure on respiratory tract tissue. Twenty-four F344/N male rats were exposed to cigarette smoke (249 mg total particulate matter/m3) or filtered air for 6 h/day for 9 days. Rats were sacrificed 1 day or 14 days after the last exposure. The most dramatic changes in CSH concentrations occurred in the tissues of the nasal cavity 1 day following exposure, with tissues from the proximal nasal airways showing the greatest response. These same proximal nasal airway tissues also had the greatest histopathological changes. Within 2 wk after exposure, the CSH concentrations in the nasal tissues from smoke-exposed rats were similar to air-exposed controls, and there was only minimal histopathological evidence of tissue alteration. CSH concentrations were not...

Immunologic Specificity of Lymphocyte Cell Lines from Dogs Exposed to Beryllium Oxide

We have reported that dogs exposed twice to aerosols of beryllium oxide (BeO) developed Be-specific immune responses within the lung, along with granulomatous and fibrotic lung lesions. To evaluate the specificity of the immune response, lymphocytes from lungs and blood of BeO-exposed dogs were co-cultured over an irradiated blood monocyte layer, alternately with interleukin 2 and BeSO4. Resultant cell lines were then tested for their response to different metal cations, common canine recall antigens, and BeSO4 in an in vitro cell proliferation assay. The cell lines responded to BeSO4 in a dose-dependent fashion, with mean stimulation indices of 7, 58, 119, and 112 at concentrations of 0.01, 1.0, 10, and 100 microM BeSO4 respectively. Cells not proliferate when incubated with ZnSO4 or NiSO4, or with canine distemper, leptospira, adenovirus 2, parvovirus, or parainfluenza antigens. Lymphocytes from normal vaccinated dogs proliferated markedly when cultured with these antigens. Cells from the cultured cell lines (91%) stained with Thy-1 (a pan T-cell marker) and 96% stained with DT2 (a helper T-cell marker). Furthermore, the Be-induced proliferative response was restricted by major histocompatibility (MHC) class II antigens. These data reinforce the premise that inhalation exposure of dogs to BeO produces lung lesions and MHC class II restricted immunologic responses mediated by Be-specific, helper T-Cells. These data further confirm the hypothesis that antigen localized to the lung results in the recruitment of T-cells to the lung, followed by localized antigen-specific, cell-mediated immune responses.