Use of fluidizing bed aerosol generators to establish a dust mixture of two substances at a fixed ratio for inhalation toxicity studies.

A method was developed to use two fluidizing bed generators to deliver a mixture of 1 mg cobalt + 15 mg tungsten carbide/m3 to an inhalation exposure chamber with the output from the cobalt generator split to provide the same cobalt concentration to a cobalt-only chamber. To provide a more uniform delivery of material and to minimize the amount of starting dust needed, a subsystem that produced timed bursts of compressed air was used to prevent the accumulation of dust along the aerosol transport tubes. The addition of an electrostatic precipitator placed in the exhaust lines reduced the amount of dust delivered to the high-efficiency particulate air filters, thereby reducing the number of filter changes.

Chloropentafluorobenzene: short-term inhalation toxicity, genotoxicity and physiologically-based pharmacokinetic model development.

Ten Fischer 344 rats and six B6C3F1 mice of each sex were exposed to air, 0.25, 0.80, or 2.50 mg chloropentafluorobenzene (CPFB)/liter of air for three weeks, excluding weekends. Exposure to 2.50 mg/liter caused a reduction in the growth rate of rats but did not affect the growth rate of mice. Following the exposure there was reduced SGOT activity in the blood serum of exposed rats and a dose related increase in liver weights. Increased liver weights were observed in mice as well; the response in the female groups was clearly dose dependent. Histologically the livers of both rats and mice presented single cell necrosis. In exposed mice hepatocytes exhibited mild hepatocytomegaly with increased granular eosinophilic cytoplasm. In evaluations for its potential to induce chromosomal damage following this exposure regimen, CPFB did not alter the rate of bone marrow cellular proliferation. Assessment of the micronucleated polychromatic erythrocytes and normochromatic erythrocyte populations during the inhalation exposures indicated a general absence of genotoxic activity.

The determination of the repeated oral toxicity of halocarbon oil, series 27-S.

Halocarbon 27-S (HC 27-S), a polymer of chlorotrifluoroethylene (CTFE), is used as a lubricating oil for pumps in hyperbaric chambers. Although monomeric CTFE has been shown to produce renal lesions in rats, the toxicity of CTFE polymers have not been investigated. To assess the toxicity of repeated exposure to HC 27-S, three groups (N = 6/group) of male and female Fischer-344 rats were dosed with 2.5 g HC 27-S/kg for 7 or 21 consecutive days. Groups were sacrificed at 7, 21, and 35 days (14 days after the 21-day dosing). Corresponding control groups (N = 6) were dosed with deionized water. Decreased water consumption and urine output were apparent in all test groups. Statistically significant increases in fluoride excretion were noted in 24-hr urine samples assessed periodically during the study. Neurotoxic signs were observed in female rats but not in male rats. Significant increases in liver and kidney weights were seen in all rats, regardless of number of dosing days. The increased fluoride burden in treated animals appeared sufficient to alter bone calcium/phosphate ratios in male rats but not female rats. Gross liver enlargement and hepatocellular cytomegaly indicated that the liver was probably the primary target organ following repeated administration of HC 27-S.

The impact of inhaled acrolein on hypertension-sensitive and resistant rats.

The Dahl selected rat lines, one susceptible to salt-induced hypertension (DS) and the other resistant to salt-induced hypertension (DR), were subchronically exposed to filtered air, 0.4, 1.4, or 4.0 ppm acrolein. All of the DS rats exposed to 4.0 ppm acrolein died within the first 11 days, while 60% of the DR animals survived. Neither dose dependent blood pressure changes nor altered behavioral characteristics were evident following acrolein exposure. Exposure to 4.0 ppm acrolein increased the level of several serum enzymes. This concentration of acrolein also led to pulmonary edema and a significant increase in lung connective tissue. There was a marked difference in the pulmonary pathology observed in DS and DR rats exposed to 4.0 ppm acrolein. The lungs of the DS rats exhibited severe airway epithelial necrosis with edema and hemorrhage, while surviving DR rats primarily showed a proliferative change. Following exposure to 0.4 to 1.4 ppm acrolein, both rat lines displayed similar pathologic change. Epithelial hyperplasia and/or clusters of macrophages were usually found near terminal bronchiolar areas. These findings suggest that further investigation of the physiopathologic sensitivity of the DS rat line may elucidate a model for investigating the underlying characteristics of stress susceptible populations.

Altered lung function and structure in the rat after subchronic exposure to acrolein.

Lung mechanics and diffusion and associated structural correlates were evaluated in groups of 24 male Fischer-344 rats exposed 62 days (6 h/day, 5 days/wk) to 0, 0.4, 1.4, or 4.0 ppm acrolein. Exposure to 4.0 ppm resulted in depressed flow-volume curves, leftward shifts of the compliance curve, and enlarged lung volumes, suggesting airway obstruction. Air-flow dysfunction correlated with the presence of focal peribronchial lesions and lung elastin concentrations. In contrast, the flow-volume dynamics of the 0.4 ppm rats were significantly enhanced without corresponding lung histologic and compositional changes. Rats exposed to 1.4 ppm were not functionally different from control animals, but did have infrequent bronchiolar lesions and marginally increased collagen. All exposure groups exhibited increases in DLCO that correlated with lung tissue surface area, apparently related to alveolar hyperinflation and possibly lung tissue growth. Acrolein produces distinct functional lesions at 0.4 and 4.0 ppm, which, when present at an intermediate exposure challenge, appear to sum algebraically and obscure the presence of disease.

Pulmonary changes resulting from subchronic exposure to cadmium chloride aerosol.

Fischer-344 rats were exposed to 0.0, 0.3, 1.0, or 2.0 mg Cd/m3 as CdCl2 aerosol for 6 h/d, 5 d/wk, for 62 exposure days. Exposure to 2.0 mg Cd/m3 resulted in rapid weight loss, and all of the animals died within the first 45 exposure days. As a group, female rats survived significantly longer than the males. Exposure to Cd resulted in dose-dependent increases in lung weight. The increased weight was the result of additional tissue mass rather than edema. Both connective-tissue components, elastin and collagen, were significantly increased in the 1.0-mg/m3 group when these components were expressed on the basis of dry weight. Dose-dependent changes at the terminal bronchioles consisted of hyperplasia and flattening of type II cells, inflammation, and the proliferation of fibroblasts. Exposure to Cd also resulted in the development of intralymphatic microgranulomas in the perivascular and peribronchiolar lymphoid tissues.

Changes in rat lung structure and composition as a result of subchronic exposure to acrolein.

Groups of Fischer-344 rats were exposed to either filtered air, 0.4, 1.4, or 4.0 ppm acrolein for 62 days (6 h/day, 5 days/week). Mortality was observed only in the 4.0 ppm chamber, where 32 of 57 male rats died, but none of the 8 exposed females died. The lungs of the 4.0 ppm group were heavier than those of the larger control animals. Relative to controls, there was a 20% increase in total dry lung weight while the percent dry weight decreased 1.5% in the high dose group. This increased dry weight and the absence of significant changes in the DNA and protein content per unit dry weight indicated that the greater lung weight observed in this group was in part due to increased cellularity. Lung connective tissue content was increased as a result of subchronic acrolein exposure. The amount of elastin per unit dry weight was 173% of control values in the animals exposed to 4.0 ppm acrolein. Collagen levels were elevated in both the 1.4 and 4.0 ppm groups, 113 and 137%, respectively, of control values. Histologically, the 4.0 ppm animals demonstrated bronchiolar epithelial necrosis and sloughing, bronchiolar edema with macrophages, and focal pulmonary edema. Exposure related lesions were observed in only 3 of the 31 rats examined from the 1.4 ppm chamber and in none of the animals exposed to 0.4 ppm acrolein.

Synthesis of 4-[18F]fluoroantipyrine and its biodistribution in mice.

The synthesis of 4-[18F]fluoroantipyrine (1) and its biodistribution in mice are described. Compound 1 was synthesized either by direct fluorination of antipyrine with [18F]F2 or CH3CO2 18F, or by an isotopic exchange method. While direct fluorination of antipyrine with [18F]F2 gave compound 1 in about a 20% yield, the isotopic exchange method gave compound 1 in only a 1%-2% yield. The biodistributions of compound 1 and 4-[131I]iodoantipyrine (3) in mice indicated that both compounds reached apparent equilibrium concentration in the bloodstream at approximately 0.5 min postinjection and compound 1 was found in higher concentrations than the iodinated analog in the well-perfused tissues. The 18F activity in the mouse brain persisted for about 2 min. The ratio of activity in the brain to bone was approximately 2:1. After 10 min, the 18F activity in the brain decreased markedly while the 18F activity in bones rose sharply resulting in a brain to bone ratio of approximately 1:2. This would suggest that compound 1 defluorinated in vivo to give fluoride as one of the metabolites. The mean octanol/pH 7 buffer solution partition coefficients of 4-[18F]fluoroantipyrine and 4-[131I]iodoantipyrine were 5.18 +/- 0.10 and 11.34 +/- 0.28, respectively.

Selected responses of hypertension-sensitive and resistant rats to inhaled acrolein.

The Dahl selected rat lines, one susceptible to salt-induced hypertension (DS) and the other resistant to salt-induced hypertension (DR), were exposed to filtered air, 0.4, 1.4, or 4.0 ppm acrolein for 6 h/day, 5 days/week for 62 days. All of the DS rats exposed to 4.0 ppm acrolein died within the first 11 days, while 60% of the DR animals survived the duration of the study. Neither dose dependent blood pressure changes nor altered behavioral characteristics were evident in either rat strain following acrolein exposure. Exposure to 4.0 ppm acrolein increased the level of several serum enzymes in the DR rats which survived. This concentration of acrolein also led to pulmonary edema and a significant increase in lung connective tissue in these animals. There was a marked difference in the pulmonary pathology observed in DS and DR rats exposed to 4.0 ppm acrolein. The lungs of moribund DS rats exhibited severe airway epithelial necrosis with edema and hemorrhage, while surviving DR rats primarily showed a proliferative change. Following exposure to 0.4 and 1.4 ppm acrolein, both rat lines displayed similar pathologic changes. Epithelial hyperplasia and/or clusters of macrophages were usually found near terminal bronchiolar areas. These findings suggest that further investigation of the physiopathologic sensitivity of the DS rat line may elucidate a model for investigating the underlying characteristics of stress susceptible populations.

Effects of sulfur dioxide and ozone on hypertension sensitive and resistant rats.

Two lines of Dahl rats, one resistant to salt-induced hypertension (DR) and one susceptible to salt-induced hypertension (DS) were subchronically exposed to SO2 (50 ppm, 6 hr/d, 5 d/wk for 31 weeks) or ozone (2.0 ppm, 6 hr/d, 5 d/wk for 20 weeks). Subgroups of rats were maintained on either high or low salt diets. In rats not expected to develop hypertension, exposure to SO2 caused a slight but consistent decrease in blood pressure. In DS rats on a high salt diet exposure to SO2 resulted in an increase in blood pressure over that of their air exposed counterparts. All exposure-related differences in blood pressure disappeared after the last exposure to SO2. Exposure to ozone was fatal to all DS rats, regardless of the amount of salt in the diet. The DR rats were more resistant to ozone, with most animals surviving the 20-week exposure. Ozone-exposed rats exhibited a decrease in both growth rate and blood pressure in all groups when compared to their air-exposed counterparts. It is not known if exposure-related blood pressure differences would persist after ending ozone exposures. After brief exposures, ozone caused increased lung weights in both groups, but there were no consistent changes in pulmonary nonprotein sulfhydryl groups. Hepatic nonprotein sulfhydryl levels were consistently, but not significantly, lower in ozone-exposed rats.

The biodistribution and metabolic fate of [11C]acrylic acid in the rat after acute inhalation exposure or stomach intubation.

Rats were nose-exposed to an atmosphere containing gaseous [11C]acrylic acid for 1 min and sacrificed 1.5 and 65 min later. At 1.5 min 28% of the administered radiolabel was associated with the snout of the exposed animal. The biodistribution data indicated the gastrointestinal tract as the major site of absorption of acrylic acid after inhalation exposure. Therefore, rats were also stomach intubated with an aqueous solution of [11C]acrylic acid and sacrificed at 1.5, 10, 20, 40, and 65 min after intubation. The absorption of acrylic acid from the stomach was rapid, as was its subsequent metabolism. Carbon-11 was rapidly eliminated from both nose-exposed and stomach-intubated animals as 11CO2, with about 60% of the administered dose eliminated 1 h after administration. A portion of the radiolabel was also eliminated via the renal system.

The biodistribution and metabolic fate of inhaled 11C-octanal in the rat after acute exposure.

Rats were nose exposed to an atmosphere containing 11.4 ppm of 11C-octanal for 2 min. Inhaled octanal was absorbed from the lungs in a biphasic manner and the greatest concentration of octanal occurred in most tissues at 5 min. Tissue activities calculated on the basis of the administered dose and on the radiolabel retained until the animal was killed indicated a redistribution of the radiolabel as metabolic products after 20 min. The labeled carbon was eliminated in a biphasic manner as 11CO2, which accounted for essentially all of the activity lost by the exposed rats.

Biodistribution and excretion of [11C]benzaldehyde by the rat after two-minute inhalation exposures.

1. Based on the decay characteristics of short-lived gamma-emitting radioisotopes a new acute exposure method was developed for studying the kinetics and biodistribution of inhaled toxic agents. Such body-penetrating radiation allows direct, non-invasive determination of the radiation in the animal at any time. 2. Rats exposed to 11C-labelled benzaldehyde for 2 min accumulated an average of 2.5 micrograms of this aldehyde. 3. Inhaled benzaldehyde was rapidly absorbed and at 1.5 min after exposure only 0.8% of the administered dose was resident in the lungs. This aldehyde was quickly distributed with the peak radioactivity in the organs occurring at 1.5 min after exposure. Subsequent loss of radiolabel from tissues was rapid and paralleled the removal from the blood. The adipose tissue cleared most slowly. 4. Benzaldehyde was rapidly excreted via the renal system with the kidneys containing 17% of the total administered activity at 5 min. The excreted radiolabelled compound co-chromatographed with hippuric acid on t.l.c.

Metabolic changes in Crithidia fasciculata accompanying physiological adaptation to growth in the presence of carbonyl cyanide m-chlorophenylhydrazone.

1. Crithidia fasciculata adapted to growth in the presence of 10(-5) M carbonyl cyanide m-chlorophenylhydrazone (CCCP), an uncoupler of oxidative phosphorylation, maintained adenosine phosphate pools and an adenylate energy charge comparable to those of control cells. 2. CCCP-adapted cells in the presence of the uncoupler respire endogenous substrate at a greater rate than control cells and this effect of CCCP appears readily reversible. 3. CCCP-treated, adapted cells, supporting high endogenous respiration rates, were not responsive to added substrates which significantly stimulated the oxygen utilization of normal C. fasciculata. 4. CCCP-adapted cells, provided with [U-14C]-labeled proline, utilize this substrate at 67% the rate of control cells, but divide the isotopic label between CO2 and protein in a ratio identical to that of normal cells. 5. The transport of alanine and proline by adapted C. fasciculata was severely impaired, while the transport of tyrosine and leucine was unaffected.