Diagnostic exercise: suppurative rhombencephalitis and meningitis in a goat.

A 1-year-old female Boer goat was presented for necropsy following spontaneous death and history of acute recumbency, nystagmus, and sialorrhea. A swollen area was grossly observed in the brainstem at the level of the pons. On cut surface, the right cerebellar peduncles were expanded by a focal, pale, poorly demarcated, slightly depressed, and soft area of malacia. Microscopically, this area contained diffuse edema and necrosis, with microabscesses, neuronal necrosis, neuronophagia, axonal spheroids, vasculitis, and perivascular accumulations of lymphocytes, plasma cells, macrophages, and neutrophils. The diagnosis was based on the morphologic findings, fluorescent antibody test results, and special staining.

Carcinogenicity of inhaled vanadium pentoxide in F344/N rats and B6C3F1 mice.

Vanadium pentoxide (V2O5) is a slightly soluble compound found in airborne particle emissions from metallurgical works and oil and coal burning. Because the carcinogenic potential of V2O5 was not known, F344/N rats and B6C3F1 mice (N=50/sex/species) were exposed to V2O5 at concentrations of 0, 0.5 (rats only), 1, 2, or 4 (mice only) mg/m3, by whole-body inhalation for 2 years. The survival and body weights of rats were minimally affected by exposure to V2O5. The survival and body weights of male mice exposed to 4 mg/m3 and body weights of all exposed groups of female mice were lower than the controls. Alveolar/bronchiolar (A/B) neoplasms occurred in male rats exposed to 0.5 and 2 mg/m3 at incidences exceeding the National Toxicology Program (NTP) historical control ranges. A marginal increase in A/B neoplasms was also observed in female rats exposed to 0.5 mg/m3. Increases in chronic inflammation, interstitial fibrosis, and alveolar and bronchiolar hyperplasia/metaplasia and squamous metaplasia were observed in exposed male and female rats. A/B neoplasms were significantly increased in all groups of exposed mice. As with rats, increases in chronic inflammation, interstitial fibrosis, and alveolar and bronchiolar epithelial hyperplasia were observed in mice exposed to V2O5. Thus, V2O5 exposure was a pulmonary carcinogen in male rats and male and female mice. The marginal tumor response in the lungs of female rats could not be attributed conclusively to exposure to V2O5. These responses were noted at and slightly above the OSHA permissible occupational exposure limit of 0.5 mg/m3 (dust) (National Institute for Occupational Safety and Health, NIOSH Pocket Guide to Chemical Hazards, U.S. Department of Health and Human Services, Washington, DC, 1997, p. 328).

Analysis of alpha2u-globulin in rat urine and kidneys by liquid chromatography-electrospray ionization mass spectrometry.

A quantitative method was developed for determination of alpha2u-globulin in urine and kidney samples collected from male rats using liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS). Samples prepared from urine and kidney homogenates using size exclusion filters were subject to reversed-phase liquid chromatography and the effluent passed into an electrospray ionization source. Quantitative analysis using external standard calibration was based upon selected ion monitoring of protonated molecular ions by the mass spectrometer. Linear calibration curves were developed over the range of approximately 4. 6-370 microg of alpha2u-globulin/microL for spiked urine standards and over the range of approximately 4.6-550 microg of alpha2u-globulin/microL for spiked kidney standards. The precision (relative standard deviation) for repeated injection (using urine samples) and intra-assay precision (using both urine and kidney samples) were within +/-10.4% and +/-13.2%, respectively. Using spiked urine standards, inter-assay precision, intra-assay accuracy, and inter-assay accuracy were within +/-20%, +/-20%, and +/-15%, respectively. Using spiked kidney standards, intra-assay accuracy was within +/-15%. The limits of detection (LOD) for the determination of alpha2u-globulin in urine and kidney samples were approximately 0.41 pg/nL (1.0 fmol injected) and 25 pg/nL ( approximately 13 fmol injected), respectively. The limits of quantitation (LOQ) for determination of alpha2u-globulin in urine and kidney samples were calculated as 1.4 pg/nL (3.7 fmol injected) and 83 pg/nL (45 fmol injected), respectively. Applicability of the LC-ESI/MS method was demonstrated by determination of alpha2u-globulin in both urine and kidney samples collected from male Fischer 344/N rats dosed intravenously with cis-Decalin at concentrations of 0, 2.5, 5.0, 10, and 20 mg/kg. A dose-dependent relationship was found between the amount of cis-Decalin administered and alpha2u-globulin accumulation in kidney samples, whereas no significant change in the urinary levels of alpha2u-globulin occurred. These observations are consistent with excessive accumulation of alpha2u-globulin occurring in protein droplets in renal proximal tubule epithelial cells as a result of decreased catabolic activity due to formation of ligand-protein complexs with Decalin and its metabolite(s). This report demonstrates that LC-ESI/MS may be routinely applied for quantitative analysis of alpha2u-globulin in rat urine and kidney samples to address alpha2u-globulin accumulation and its role in the development of nephrotoxicity associated with chemical exposures.

Physiologically based pharmacokinetic model for chronic inhalation of 2-butoxyethanol.

2-Butoxyethanol (2BE) is used extensively in the production of cleaning agents and as a general solvent. It is primarily metabolized in the liver to 2-butoxyacetic acid (2BAA), which is excreted in urine. The objective of this study was to develop a physiologically based pharmacokinetic (PBPK) model describing the toxicokinetic behavior of 2BE and 2BAA in different species following repeated, long-term exposures. The PBPK model was first developed for short-term 2BE exposure to male rats. Allometric scaling was employed to estimate physiological and biochemical model parameters based on body weight. To accommodate differences in 2BE toxicokinetics in female rats, a higher Vmax for 2BE metabolism to 2BAA, higher plasma protein binding sites for 2BAA, and lower Vmax for 2BAA excretion through the kidney were incorporated into the model. For mice, a higher Vmax for 2BE metabolism to 2BAA for both sexes and higher plasma protein binding sites for 2BAA for female mice were also incorporated into the model. Subsequently, the model was expanded to simulate 2BE and 2BAA toxicokinetics for long-term, repeated exposures by incorporating time-dependent changes in model parameters. To reflect physiological/biochemical changes in animals during a chronic exposure, parameters for cardiac output, body composition, metabolic capacity, protein binding, or capacity of renal excretion were adjusted over time depending on species and sex. Sensitivity analysis was performed to better understand how sensitive model responses were to uncertainties in input parameters. The resulting PBPK model was used to simulate toxicokinetic data acquired during a 2-year inhalation toxicity and carcinogenicity study in male and female F344/N rats and B6C3F1 mice.

Toxicokinetics of inhaled 2-butoxyethanol and its major metabolite, 2-butoxyacetic acid, in F344 rats and B6C3F1 mice.

2-Butoxyethanol (2BE) is used extensively in the production of cleaning agents and solvents. It is primarily metabolized in the liver to 2-butoxyacetic acid (2BAA), which is believed to be responsible for 2BE toxicities associated with hemolysis of red blood cells. The objective of the study was to characterize the systemic disposition of 2BE and 2BAA in rats and mice during 2-year 2BE inhalation toxicity studies. Male and female F344 rats and B6C3F1 mice (6-7 weeks old) were exposed to target 2BE concentrations of 0, 31.2, 62.5, or 125 ppm (rats), or 0, 62.5, 125, or 250 ppm (mice), by whole-body inhalation for 6 h/day, 5 days/week for up to 18 months. Postexposure blood samples were collected after 1 day, 2 weeks, and 3, 6, 12, and 18 months of exposure. Postexposure 16-h urine samples were collected after 2 weeks and 3, 6, 12, and 18 months of exposure. A separate set of mice was kept in the control chamber and exposed to 2BE for 3 weeks when they were approximately 19 months old. Postexposure blood samples were collected after 1 day and 3 weeks of exposure and 16-h urine samples were collected after 2 weeks of exposure from these aged mice. Blood samples were analyzed for both 2BE and 2BAA and urine samples were analyzed for 2BAA using GC/MS, and their kinetic parameters were estimated through the curve-fitting method using SAS. Systemically absorbed 2BE was rapidly cleared from blood (t1/2-RAT < 10 min; t1/2-MOUSE < 5 min after the 1-day exposure) independent of exposure concentration. Proportional increases in AUC2BE relative to increases in exposure concentration indicated linear 2BE kinetics. In contrast, the rate of 2BAA elimination from blood decreased as the exposure concentration increased. Nonproportional increases in AUC2BAA also indicated that 2BAA is eliminated following dose-dependent, nonlinear kinetics. Overall, mice eliminated both 2BE and 2BAA from blood faster than rats. Sex-related differences in 2BAA elimination were most significant with rats, in that females were less efficient in clearing 2BAA from the blood. Differences in renal excretion of 2BAA are possibly responsible for the sex-related difference in the 2BAA blood profiles in rats. As exposure continued, the rates of elimination for both 2BE and 2BAA decreased in both species, resulting in longer residence times in the blood. When 19-month-old naive mice were exposed to 125 ppm, 2BE was rapidly cleared from the systemic circulation, exhibiting clearance profiles similar to young mice. However, old mice eliminated 2BAA from blood > 10 times slower than young mice after 1-day of exposure. This delayed elimination of 2BAA in old mice was less obvious after 3 weeks of exposure, suggesting that there might be other factors in addition to the age of animals that could influence the apparent difference in 2BAA kinetics between old and young mice. It was concluded that the elimination kinetics of 2BE and 2BAA following repeated 2BE exposure appear to be dependent on species, sex, age, time of exposure, as well as the exposure concentration.

Effects of water dilution, housing, and food on rat urine collected from the metabolism cage.

The objective of the study reported here was to investigate three factors that may affect the amounts of water consumed and urine excreted by a rat in the metabolism cage: water dilution, housing, and food. Young F344/N rats (eight per group) were used for all experiments. Food was withheld from rats before each 16-h urine collection, then rats were transferred into a metabolism cage. For trial A (water dilution), urine was collected from rats supplied with dyed water (0.05%, vol/vol). This was repeated three times over a 2-week period. Dye in water or urine was quantified, using a spectrophotometer. For trial B (housing), rats were individually housed in wire cages for 3 weeks before the first urine collection. Then they were group housed in the solid-bottom cage (four per cage). After 2 weeks of acclimation, urine collection was repeated. For trial C (food), one group of rats was provided with food, the other was not, during urine collection. About 8% of urine samples of small volume (< or = 3 ml) from trial A were contaminated with drinking water up to 13% of volume. The average urine volume associated with individual housing was approximately twice as large as that associated with group housing. When food was provided during urine collection, rats consumed similar amounts of water but excreted significantly smaller amounts of urine than did rats without food. It was concluded that water dilution of a urine sample from a sipper bottle is relatively small; rats individually housed in wire caging before urine collection can consume and excrete a larger quantity of water, compared with rats group housed in solid-bottom cages; and highly variable urine volumes are, in part, associated with lack of access to food during urine collection.

Comparative absorption of lead from contaminated soil and lead salts by weanling Fischer 344 rats.

A 44-day dosed feed study was performed to compare the bioavailability of lead from contaminated soil versus two lead salts and the effect of soil on gastrointestinal absorption of ingested lead. Male Fischer rats (approximately 4 weeks of age) received lead, 17, 42, or 127 ppm, in the form of lead acetate, lead sulfide, lead-contaminated soil, or combinations thereof in the diet for 7, 15, or 44 days. Control soil was added to the diets of some animals to determine how it might alter lead bioavailability. Blood Delta-aminolevulinic acid dehydratase (Delta-ALAD) and blood, bone, kidney, and liver lead were determined in groups of animals at each time-point. Blood Delta-ALAD was inhibited in a dose-dependent manner and to the greatest degree in the lead acetate and lead acetate/control soil groups, followed by the lead sulfide and lead-contaminated soil groups. Bone and tissue lead levels increased in a dose-dependent manner and were greatest in animals receiving lead acetate and significantly less in animals receiving lead sulfide and lead-contaminated soil. Blood lead levels were generally greatest by 7 days and stabilized at lower levels thereafter. Bone lead concentration-time patterns did not demonstrate the biphasic change seen with tissues and continued to increase in most treatment groups through the course of the study. The presence of soil in the diet clearly attenuated the absorption of lead acetate, but had little effect on the absorption of lead sulfide. Results of these studies confirm previous observations that lead absorption is highly dependent on the form of lead ingested and the matrix in which it is ingested. More important, these studies demonstrate that lead in soil may be significantly less available than estimated by current default assumptions and that the presence of soil may decrease the availability of lead from lead salts on which the default assumptions are based. Results presented here also demonstrate that the weanling rat may represent an appropriate model that could be used to obtain relatively rapid and economical estimates of the availability of lead in complex matrices such as soil.

Bioavailability of arsenic in soil and house dust impacted by smelter activities following oral administration in cynomolgus monkeys.

This study was conducted to determine the extent of arsenic (As) absorption from soil and house dust impacted by smelter activities near Anaconda, Montana. Female cynomolgus monkeys were given a single oral administration via gelatin capsules of soil (0.62 mg As/kg body wt) or house dust (0.26 mg As/kg body wt), or soluble sodium arsenate by the gavage or intravenous route of administration (0.62 mg As/kg body wt) in a crossover design with a minimum washout period of 14 days. Urine, feces, and cage rinse were collected at 24-hr intervals for 168 hr. Blood was collected at specified time points and area under the curves (AUCs) was determined. Arsenic concentrations for the first 120 hr, representing elimination of greater than 94% of the total administered dose for the three oral treatment groups, were < 0.021 to 4.68 micrograms/ml for the urine and < 0.24 to 31.1 micrograms/g for the feces. In general, peak concentrations of As in the urine and feces were obtained during the collection intervals of 0-24 and 24-72 hr, respectively. The main pathway for excretion of As for the intravenous and gavage groups was in the urine, whereas for the soil and dust groups, it was in the feces. Mean absolute percentage bioavailability values based on urinary excretion data were 68, 19, and 14% for the gavage, house dust, and soil treatments, respectively, after normalization of the intravenous As recovery data to 100%. Corresponding absolute bioavailability values based on blood were 91, 10, and 11%. The bioavailability of soil and house dust As relative to soluble As (by gavage) was between 10 and 30%, depending upon whether urinary or blood values were used. These findings suggest that risks associated with the ingestion of As in soil or dust will be reduced compared to ingestion of comparable quantities of As in drinking water.

Styrene inhalation toxicity studies in mice. II. Sex differences in susceptibility of B6C3F1 mice.

Styrene is a commercially important chemical used in the production of plastics and resins. In initial short-term styrene inhalation studies, toxicity was significantly greater in male B6C3F1 mice than in females, suggesting that males may metabolize styrene more extensively and/or may be less able to detoxify reactive metabolites. In addition, a nonlinear dose-response was observed where toxicity and mortality were greater in mice exposed to 250 ppm than in those exposed to 500 ppm. These studies were conducted to investigate potential mechanism(s) for sex differences and the nonlinear dose-response in styrene toxicity by evaluating the effects of repeated styrene exposure on styrene oxide production, hepatic GSH availability, and hepatotoxicity in male and female B6C3F1 mice. Mice (36/sex/dose) were exposed to 0, 125, 250, or 500 ppm styrene 6 hr/day for up to 3 days. Styrene exposure caused increased mortality and hepatotoxicity (centrilobular necrosis, increased serum liver enzymes) in males and females after one or two exposures to 250 and 500 ppm. Hepatic GSH levels were decreased in a dose-dependent manner in males and females. After one exposure, GSH levels in males rebounded above controls in all dose groups. After three exposures to 125 or 250 ppm males appeared to maintain GSH levels; GSH was still decreased in the 500 ppm group. GSH levels in females were decreased after each exposure in all dose groups to lower levels than in males, and did not rebound above controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Styrene inhalation toxicity studies in mice. III. Strain differences in susceptibility.

Inhalation toxicity studies were conducted to evaluate mouse strain differences in the susceptibility to styrene vapors. Male and female B6C3F1, C57BL/6, Swiss, and DBA/2 mice (8 weeks old) were exposed to 0, 125, 250, or 500 ppm styrene 6 hr/day, for 4 days (20/sex/dose). Histopathological changes and changes in liver weights were evaluated as a measure of hepatotoxicity. Styrene uptake and styrene-7,8-oxide (SO) formation were estimated by measuring levels of styrene and SO in blood. An estimate of SO detoxification by conjugation with GSH was obtained by measuring hepatic GSH depletion. In general, mortality, increased liver weights, and hepatocellular necrosis were observed in the 250 and 500 ppm dose groups for all strains and both sexes. Considerable sex and strain differences were observed. Mortality, increased liver weights, and hepatocellular necrosis were greatest in B6C3F1 and C57BL/6 mice in the 250 ppm dose group and in males; hepatotoxicity was similar in both strains. Swiss mice exhibited dose-dependent increases in mortality, liver weights, and in hepatocellular necrosis, with only slight sex differences at early time points. Hepatotoxicity in DBA/2, B6C3F1, and C57BL/6 strains was greater at 250 than 500 ppm; however, toxicity was less severe in DBA/2 than in other strains based on absence of mortality in either sex and less extensive liver necrosis at both 250 and 500 ppm. Blood styrene and SO levels did not correlate well with strain differences in toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental toxicity of inhaled methyl ethyl ketone in Swiss mice.

Methyl ethyl ketone (MEK) is a widely used industrial solvent to which there is considerable human exposure. To assess the potential for MEK to cause developmental toxicity in rodents, groups of Swiss (CD-1) mice were exposed to 0, 400, 1000, or 3000 ppm MEK vapors 7 hr/day on Days 6-15 of gestation. Groups consisted of about 30 bred females each. Exposure of pregnant mice to these concentrations of MEK did not result in overt maternal toxicity although there was a slight, treatment-related increase in relative liver weight which was statistically significant in the 3000 ppm group. Mild developmental toxicity was observed in the 3000 ppm group in the form of a reduction in mean fetal body weight. This reduction was statistically significant for the males only, although the relative decrease from the control values was the same for both sexes. There was no increase in the incidence of resorptions or the number of litters with resorptions among mice exposed to MEK. There was no significant increase in the incidence of any single malformation, but several malformations which were not observed in the concurrent control group or the controls of contemporary studies were present at a low incidence--cleft palate, fused ribs, missing vertebrae, and syndactyly. There was also a significant trend for increased incidence of misaligned sternebrae, a developmental variation. In summary, pregnant Swiss (CD-1) mice were relatively insensitive to the toxic effects of MEK at the inhaled concentrations used in this study. However, the offspring of the mice exhibited significant signs of developmental toxicity at the 3000 ppm exposure level.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of adenylate cyclase by chronic exposure to cannabimimetic drugs.

Previous studies in this laboratory have demonstrated that a cloned neuroblastoma cell line (N18TG2) responds to delta 9-tetrahydrocannabinol (THC), the major psychoactive product of marihuana, with an attenuation of cyclic AMP accumulation that results from an inhibition of adenylate cyclase. The requirement for the Gi regulatory protein, stereoselectivity, pharmacologic specificity and cell selectivity of this response suggest that a receptor for cannabimimetic compounds may be associated with adenylate cyclase in the neuroblastoma cell. Presented here is a comprehensive investigation of cellular effects of chronic exposure to cannabimimetic agents. Short-term exposure to either delta 9-THC or the more potent nantradol analog, desacetyllevonantradol (DALN), at doses up to 100 microM did not compromise the plating efficiency of the cells. Cells that were exposed to 1 microM delta 9-THC (maximally effective for inhibiting cyclic AMP production) for 24 hr in a serum-free medium were shown to accumulate the drug but not to metabolize it. Exposure to 10 microM delta 9-THC or DALN for up to 48 hr failed to significantly affect cell growth rate or protein content per cell. The gross morphology of cannabinoid-treated cells was not altered at the light or the electron microscope level. The cellular organelles and membranes appeared intact, with no remarkable differences from control cells. The inhibition of cyclic AMP accumulation in response to cannabimimetic drugs was diminished in cells treated with delta 9-THC or DALN for 24 hr. This desensitization was homologous because both delta 9-THC and DALN responses were attenuated after exposure to either cannabimimetic drug.(ABSTRACT TRUNCATED AT 250 WORDS)