Chronic toxicity of 1,3,5-trinitrobenzene in Fischer 344 rats.

The chronic toxicity of 1,3,5-trinitrobenzene (TNB) in male and female Fischer 344 (F344) rats was evaluated by feeding a diet containing 0, 5, 60, and 300 ppm of TNB for 2 years. The calculated average TNB intake over 2 years for males and females was 0.22, 2.64, 13.44 and 0.23, 2.68, 13.31 mg/kg body weight (BW)/day respectively. Terminal body weights were decreased and water intake was increased in both sexes (300 ppm), whereas food consumption was decreased in males (60 and 300 ppm groups) only. The relative spleen weights were significantly decreased in both sexes (300 ppm), whereas the relative brain weights were increased in females only (300 ppm). Hematological effects were not observed in animals killed at the 2-year time point, except significant decrease in the mean corpuscular hemoglobin (MCH) in males (300 ppm) and in females (60 and 300 ppm). Methemoglobin levels were increased in both sexes in the high dose group. Histopathological examination showed treatment-related changes in the kidney (hyaline droplets; 60 and 300 ppm) and the spleen (erythroid cell hyperplasia and pigment deposition; 300 ppm) of both sexes. Cytoplasmic hyaline droplets in the kidneys were characterized by immunohistochemistry as alpha-2mu-globulin. We propose a chronic, oral no-observable-adverse-effect level (NOAEL) of 2.68 mg/kg BW/day for TNB in the rat, based on the hematological and renal changes.

Feasibility of micronucleus methods for monitoring genetic damage in two feral species of small mammals.

Peromyscus leucopus (white-footed mouse) and Cryptotis parva (least shrew) possess desirable attributes for biomonitoring contamination of terrestrial ecosystems, but few studies have examined the potential use of these species for monitoring exposure to genotoxic contaminants. The susceptibility of laboratory-reared C. parva, P. leucopus, and Mus musculus (house mouse, strain CD-1) to micronucleus (MN) induction by known clastogens was evaluated. Animals were exposed for 24 hr to methyl methanesulfonate (MMS; 12.5, 25, and 50 mg/kg), 4-nitroquinoline 1-oxide (4-NQO; 7.5, 15, and 30 mg/kg), or mercuric chloride (HgCl2; 6, 12, and 24 mg/kg). Both MMS and 4-NQO induced dose-related increases in micronucleated polychromatic erythrocytes (MNPCE) in all three species, whereas HgCl2 induced a weak response only in P. leucopus. P. leucopus and C. parva were more sensitive than M. musculus to MMS. Similar micronucleus responses to 4-NQO were seen in each of the species. The feasibility of using blood for MN assessment was evaluated by comparing MN frequencies in bone marrow (BM) PCE, and blood PCE and normochromatic erythrocytes (NCE) in untreated animals, and following daily treatment for 1, 2, 3, and 10 days with 0.4 mg/kg triethylenemelamine (TEM). The results indicated that micronucleated erythrocytes were removed from the circulating blood in P. leucopus, but not in C. parva. Measurement of BM and blood MN levels appears feasible for monitoring exposure to genotoxic agents in C. parva and P. leucopus, and for distinguishing between acute and chronic exposure in C. parva.

Fish biliary polycyclic aromatic hydrocarbon metabolites estimated by fixed-wavelength fluorescence: comparison with HPLC-fluorescent detection.

Fixed wavelength fluorescence (FF) was compared to high-performance liquid chromatography with fluorescence detection (HPLC-F) as an estimation of polycyclic aromatic hydrocarbon (PAH) exposure to fish. Two excitation/emission wavelength pairs were used to measure naphthalene- and benzo[a]pyrene (B[a]P)-type metabolites. Early nonmetabolite fluorescent peaks were negligible in HPLC chromatograms of bile of brown bullhead, white sucker, and common carp. Linear regression analysis of FF and HPLC-F data had r2 values between 0.89 and 1.00. Although the linear regression was significant, the absolute HPLC-F and FF values were not equivalent. HPLC-F values for B[a]P-type metabolites were always higher than those determined by FF. For naphthalene-type metabolites there was no consistent relationship between the HPLC-F and FF values. These inequivalencies were possibly due to the variable HPLC-elution patterns caused by the composition of metabolites and the unique fluorescent response exhibited in different solvent concentrations. Nevertheless, mean concentration estimates divided by the value obtained at the reference site were similar by both methods. The FF method can be used to estimate biliary PAH concentrations in these three species and allows PAH metabolites to become a routine measurement end point for environmental assessments.

Fourteen-day toxicity study of 1,3,5-trinitrobenzene in Fischer 344 rats.

Toxic effects of 1,3,5-trinitrobenzene (TNB) in male and female rats were evaluated by feeding powdered certified laboratory chow diet supplemented with varied concentrations of TNB (0, 50, 200, 400, 800 and 1200 mg kg-1 diet) for 14 days. Food intake by female rats in 400, 800 and 1200 mg TNB diet groups was reduced and resulted in a significant decrease in absolute body weights (BW). Food and water consumption by male rats in high-dose groups (800 and 1200 mg TNB kg-1 diet) was also reduced and resulted in a significant decrease in body weight. The calculated average TNB intake (from 1200 mg TNB kg-1 diet) was 92 mg kg-1 BW day-1 for male rats and 80 mg kg-1 BW day-1 for females. A decrease in testicular weight in males and an increase in spleen weight of both sexes in high-dose groups was noted. In addition, histopathological examinations revealed that the susceptible organs for TNB toxicity were kidney (hyaline droplets), spleen (extramedullary hematopoiesis), brain (hemorrhage, malacia and gliosis) and testes (seminiferous tubular degeneration). Hematology and clinical chemistry studies indicated a decrease in red blood cell count and hematocrit, a decrease in alkaline phosphatase, an increase in Heinz bodies and increased methemoglobin concentration as compared to controls in both sexes. A lowest observed adverse effect level of 4.41 mg TNB kg-1 BW day-1 was established based on the findings of this study.

A method for the analysis of biological transduction phenomena.

Biological transduction can be defined as the triggering of a cellular response by the binding of molecules of effector substances to specific cellular sites. An example of biological transduction, analyzed in this report, is the triggering of T-cell proliferation by the binding of T-cell growth factor (TCGF) to specific TCGF-binding sites on responsive T-cells. Sigmoidal or S-shaped curves often result when measurements of biological response are plotted as a function of concentration of effector substance. Such curves suggest that effector molecules must bind a critical number of cellular sites, and this critical number of bound complexes must undergo secondary events (cross-linking, association, internalization, second messenger release, etc.) in order to initiate the biological response. The method described here estimates the critical number of cellular sites (R) and the probability of these secondary events (PS/B) as follows: (1) The total number of cellular sites (N) is estimated from binding data, and the probabilities (PB) of effector molecules binding to a site are estimated from response data. (2) The response data are assumed to follow the summed binomial distribution function, which is equated to the incomplete beta function. (3) R and PS/B are estimated by applying nonlinear regression to the incomplete beta function. The T-cell data to which the method was applied gave N = 15,000, R = 5, and PS/B = 7.22 x 10(-4). These results show that the binding of very few TCGF molecules is required for activation of T-cells and that the probability of the secondary events leading to cell proliferation is much smaller than the probability of TCGF binding to T-cells. The method described can be used to analyze any biological transduction experiments where both binding and biological response data are available.