Subchronic,Reproductive, and Developmental Toxicity of a Fluorotelomer-Based Urethane Polymeric Product

A commercial fluorotelomer-based urethane polymeric dispersion, consisting of polymer, surfactant, and water, was evaluated in subchronic, reproduction, and developmental toxicity studies. The dispersion was administered daily by gavage to rats at dosages of 0, 50, 250, or 1000 mg polymer/kg/day or with 70 mg/kg/day of the sulfonate surfactant. Dose levels of 0, 50, 250, or 1000 mg polymer/kg/day were also used for the reproductive and developmental studies. Nasal olfactory epithelial degeneration and necrosis occurred in all dose groups in the 90-day study. Nasal adhesions were observed only in rats administered surfactant alone. Liver-enzyme alterations at 250 and 1000 mg/kg were considered to be potentially adverse effects. The subchronic no-observed-adverse-effects level (NOAEL) was 50 mg/kg. For the reproduction study, rats were dosed for 10 weeks prior to cohabitation and throughout mating, gestation, and lactation. There were no effects on reproductive function in males or females at any dosage. Thyroid weight was decreased in the 250 and 1000 mg/kg day F₁ groups unaccompanied by microscopic effects. In the developmental toxicity study, female rats were dosed from gestation days 6–20; there was no test-substance-related embryolethality, nor was there any dose-related increase in either fetal malformations. Fetal weight was minimally decreased at 1000 mg/kg/day in the presence of slight maternal toxicity; the NOAEL for developmental parameters was 250 mg/kg/day. The polymeric product was not a specific developmental or reproductive toxin.     

Chronic Toxicity, Oncogenic Potential, and Reproductive Toxicity of p-Nitroaniline in Rats

Chronic Toxicity, Oncogenic Potential, and Reproductive Toxicityof p-Nitroaniline in Rats. NAIR, R. S., AULETTA, C. S., SCHROEDER,R. E., AND JOHANNSEN, F. R. (1990). Fundam. Appl. Toxicol 15,607–621. Dose levels for these studies were selected mainlyon the basis of subchronic studies, although consideration wasalso given to workplace exposure levels and proposed mechanismof tumor formation with structurally similar compounds. Forthe chronic study, groups of 60 male and 60 female Sprague—DawleyCD (Registered Trademark of Charles River Breeding Laboratories,Portage, Ml) rats were given 0, 0.25, 1.5, or 9.0 mg/kg/daypara-nitroaniline (PNA) by gavage in corn oil for a period of2 years. Parameters monitored included clinical observations,ophthalmoscopic exams, body weights, food consumption, hematology,clinical chemistry, and urinalysis at regular intervals throughoutthe study. All gross lesions and over 40 tissues were examinedhistologically for all control and high-dosage-level animals.Gross lesions, spleens, and livers of low- and mid-dosage groupswere also examined histologically. For the reproduction study,groups of 15 male and 30 female rats, designated as F₀ generation,were given PNA at the same levels as the chronic study for 14weeks prior to mating and during mating, gestation, and lactation.Selected groups of 15 male and 30 female rats of the F₁ generationreceived the same dose of PNA for 18 weeks prior to mating andduring mating, gestation, and lactation. F₂ pups were observedthrough weaning at which time they were euthanized. Observationsmade during the study included body weights, food consumption,mating and fertility indices, pup and litter survival indices,and histopathology of selected tissues. In the chronic study,except for a slight decrease in survival of high-dose male ratslate in the study, survival in all treated groups was comparableto controls. Blood methemoglobin levels were elevated in themid- and high-dosage groups, while slight anemia was observedin the high-dosage group also. Spleen weights were significantlyincreased in the high-dosage groups. An accumulation of brownpigment was observed in the cytoplasm of the sinusoidal macrophagesor littoral cells of the liver and in the reticuloendothelialcells of the spleen. No treatment-related increase in tumorincidence was observed. In the reproduction study, no consistentpattern of effect from treatment between the F₀ and F₁ generationwas seen in mating, pregnancy, or fertility indices. Thus, administrationof PNA at levels which produced significant methemoglobin-emiaand low-level anemia in the rat and histological changes inthe spleen produced no tumors or reproducible effects on reproductiveperformance.     

Subchronic Toxicity and Teratogenicity of 2-Chloro-1,1,1,2-tetrafluoroethane (HCFC-124)

Inhalation studies were conducted to determine the potentialtoxicity of HCFC–124. Groups of rats and mice were exposedto HCFC-124 6 hr/day, 5 days/week for 13 weeks at 0, 5000, 15,000,and 50,000 ppm. Subgroups of rats and mice were held for a 1–monthrecovery period. A functional observational battery (FOB) wasconducted on rats at 0, 4, 8, 13, and 16 weeks. Clinical pathologyevaluations were conducted at 7, 13, and 17 weeks. Thirteenor 17 weeks after study initiation, rats and mice underwentgross and microscopic evaluation, and livers were evaluatedfor hepatic beta–oxidation activity. In addition, groupsof female rats and rabbits were exposed to HCFC-124 by inhalationduring gestation to 0, 5000, 15,000, or 50,000 ppm. Exposureof rats and mice to HCFC-124 caused minimal compound–relatedeffects. Compound–related changes occured in several clinicalpathology parameters in rats and mice. Hepatic beta–oxidationactivity was significantly higher in 5000, 15,000, and 50,000ppm male mice; however, there were no compound–relatedeffects on beta–oxidation activity in rats. During thedaily exposures, rats, mice, and rabbits exposed to 50,000 ppmwere less responsive to auditory stimuli or less active comparedto controls. At the 13–week FOB, male rats exposed to15,000 or 50,000 ppm had decreased arousal. There were no compound–relatedeffects on mortality, clinical signs, ocular tis sues, hematologyparameters, organ weights, and tissue morphol ogy at any concentrationin rats or mice. Maternal toxicity in rats was evident by asignificant decrease in weight gain and food consumption at50,000 ppm. Similarly, 50,000 ppm pregnant rab bits had lowerfood consumption. However, for both rats and rab bits, therewas no evidence of fetal toxicity at any concentration.     

Toxicity of N-Methyl-2-pyrrolidone (NMP): Teratogenic, Subchronic, and Two-Year Inhalation Studies

Toxicity of N-Methyl-2-pyrrolidone (NMP): Teratogenic, Subchronic,and Two-Year Inhalation Studies. LEE, K. P., CHROMEY, N. C.,CULIK, R., BARNES, J. R., AND SCHNEIDER, P. W. (1987). Fundam.Appl Toxicol. 9,222–235. Pregnant rats were exposed toN-methyl-2-pyrrolidone (NMP) at atmospheric concentrations of0.1 and 0.36 mg/liter for 6 hr/day on Days 6 through 15 of gestation.Except for sporadic lethargy and irregular respiration in severalrats the first 3 days of exposure, there were neither abnormalclinical signs nor pathological lesions in the maternal rats.Exposure did not affect either the outcome of pregnancy or embryonalgrowth rate. No abnormal development was detected in the vitalorgans and skeletons of the fetuses. Rats were exposed to anaerosol-vapor mixture of NMP at concentrations of 0,0.1, 0.5,and 1.0 mg/liter for 6 hr/day, 5 days/week for 4 weeks. At 0.1and 0.5 mg/liter exposure levels, rats did not show any significantclinical signs or pathological lesions. However, lethargy, respiratorydifficulty, and excessive mortality were found in rats exposedto 1.0 mg/liter. These rats had focal pneumonia, bone marrowhypoplasia, and atrophy of lymphoid tissue in the spleen andthymus. These lesions were reversible in surviving rats following2 weeks of recovery. Increases in the relative and absolutenumbers of neutrophils were observed during exposure at 1.0mg/ liter, but returned to normal limits after 2 weeks of recovery.Rats were exposed to vapor of NMP at concentrations of 0, 0.04,or 0.4 mg/liter for 6 hr/day, 5 days/week for 2 years. Malerats at 0.4 mg/liter showed slightly reduced mean body weight.No life-shortening toxic or carci nogenic effects were observedin rats exposed for 2 years to 0.04 or 0.4 mg/liter of NMP.     

Toxicity of PCB 77 (3,3',4,4'-Tetrachlorobiphenyl) and PCB 118 (2,3',4,4',5-Pentachlorobiphenyl) in the Rat Following Subchronic Dietary Exposure

The toxicity of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) and 2,3',4,4',5-pentachlorobiphenyl(PCB 118) was investigated in rats following subchronic dietaryexposure. Groups of 10 male and 10 female weanling Sprague-Dawleyrats were administered PCB 77 In the diet at 0, 10, 100, 1000,or 10,000 ppb for 13 weeks. PCB 118 was administered to malesin the diet at 0, 10, 100, 1000, and 10,000 ppb, while the femalegroups received 0, 2, 20, 200, or 2000 ppb of the congener for13 weeks. Growth rate and food consumption were not affectedby treatment. No clinical signs of toxicity were observed. Increasedspleen weight occurred in male rats fed 1000 or 10,000 ppb PCB77. Male rats receiving 10,000 ppb PCB 118 had increased liverweight and hepatic ethoxyresorufin O-deethylase (EROD) activity.Increased hepatic EROD activity but not liver weight was observedin female rats given the 2000-ppb PCB 118 diet. Increased ERODactivity was also noted in male rats given 10,000 ppb and infemale groups receiving 1000 or 10,000 ppb PCB 77. Male ratsexposed to 10,000 ppb PCB 77 had decreased vitamin A in theliver and lung and elevated levels in the kidney. Liver vitaminA of both 1000- and 10,000-ppb PCB 77 female groups was decreased.PCB 118 had no effects on tissue vitamin A at the levels studied.No hematological changes or serum biochemical changes were seenin any of PCB 118- and PCB 77-treated groups, nor were liveruroporphyrin levels altered. A reduction in dopamlne and homovanillinicacid in the substantia nigra region of the brain was observedin female rats fed 2000 ppb PCB 118, while 10,000 ppb PCB 77was associated with an elevation in 3,4-dihydroxyphenylaceticacid in the nucleus accumbens region of male rat brains. Mildto moderate changes were observed in the liver and thyroid ofrats given PCB 77 or PCB 118. PCB 118 accumulated in a dose-dependentmanner in fat and to a much lesser extent in liver. In contrast,very low levels of PCB 77 residue were found in the tissuesexamined. Based on the above data It was concluded that theNOAEL of PCB 77 is 100 ppb in diet or 8.7 sglkg and that ofPCB 118 is 200 ppb in diet or 17 µg/kg body wt/day.     

A Subchronic, Teratologic, and Dominant Lethal Study of 2-Methylresorcinol in Rats: I. Subchronic Toxicity

A Subchronic, Teratologic, and Dominant Lethal Study of 2-Methylresorcinolin Rats. I. Subchronic Toxicity. RE, T.A., LOEHR, R.F., RODRIGUEZ,S.C, GILMORE, C.E., AND BURNETT, C.M. (1986). Fundam. Appl.Toxicol. 7, 287–292.2-methylresorcinol (2-MR) was administeredto groups of 40 male and 35 female Sprague-Dawley rats by admixturewith diets at levels of 0.1, 0.4, and 1.5% for periods up to6 months. Methemoglobin levels were determined after 6 weeks.After 90 days 10 animals/sex/group were killed for clinicalpathological and histopathologic determinations. The 25 remainingfemales and 20 males per group were utilized in teratology anddominant lethal studies presented in Part II (T. A. Re, R.F.Loehr, S.C. Rodriguez, D.E. Rodwell, C.M. Burnett, 1986, Fundam.Appl. Toxicol. 7, 293-298). Ten additional males were killedafter 6 months of exposure for additional clinical pathologicdeterminations and gross pathologic observations. The 20 males/groupused in the dominant lethal study (Part II) were also killedafter 6 months to serve as a comparison recovery group (grossexamination of organs). Feeding 2-MR at a level of 1.5% in thediet was associated with a significant reduction in body weightgains. Females fed at a level of 0.4% also weighed significantlyless than the control. No pathological effects were noted aftereither 90 or 180 days of feeding.     

Subchronic Toxicity of Orally Administered (Gavage and Dosed-Feed) Theophylline in Fischer 344 Rats and B6C3F2 13 Mice

Subchronic Toxicity of Orally Administered (Gavage and Dosed-Feed)Theophylline in Fischer 344 Rats and B6C3F, Mice.COLLINS, J.J., ELWELL, M. R., LAMP, J. C, IV, MANUS, A. C, HEATH, J. E.,and MAKOVEC, G. T. (1988). Fundam Appl Toxicol. 11, 472—484.Theophylline, a methylated xanthine closely resembling caffeineand theobromine, is a widely used pharmaceutical agent for thetreatment of respiratory disorders and certain acute cardiovascularconditions. The National Toxicology Program has conducted 13-weeksubchronic toxicity studies in F344 rats and B6C3F₁ mice (10animals/group) following administration of theophylline viathe diet or by gavage. Administration of theophylline in thefeed (0, 1000, 2000, and 4000 ppm) resulted in no mortalityor body weight effects in F344 rats, but did induce periarteritisof the arteries adjacent to mesenteric lymph nodes and the pancreas,particularly arterioles in the latter. Also observed in ratsdosed with theophylline via the diet was an increased severityof chronic nephropathy in males, especially at the high dose.Administration of theophylline at the same concentrations inthe feed to B6C3Fi 2 mice resulted in no mortality, but terminalbody weights were significantly decreased in all dosed groups.An increased incidence of hepatocellular glycogen depletionwas observed in male and female mice, and this change is believedto represent a physiological alteration exacerbated by the administrationof theophylline. Administration of theophylline by gavage toF344 rats (0, 37.5, 75, and 150 mg/kg) resulted in the earlydeath of one high-dose male and female and significantly decreasedor increased terminal body weights of high-dose males and females,respectively. Similar to the results of the dosed-feed study,male and female rats receiving theophylline by gavage demonstrated a dose-related increase in the incidence and severityof perivascular inflammation of mesen teric arteries. Gavageadministration of theophylline to B6C3F, mice (0, 75, 150, and300 mg/kg) resulted in the early death of all high-dose femalesand 3/10 high-dose males and significant depres sion of terminalbody weights in high- and mid-dose males and low-dose females.As in the dosed feed study, the primary histopathologk changein the mouse subchronic gavage study was hepatocel lular glycogendepletion, although in this case it was seen only in females.In summary, the major target organs for orally administeredtheophylline in 13-week subchronic toxicity studies appear tobe the mesenteric arteries in F344 rats and the liver in B6C3F₁mice. On the basis of organ weight changes and/or minor histopathologiceffects, many other tissues were also affected, particularlythe kidneys in dosed-feed male rats and the uterus in gavage-dosedfemale rats.     

Comparison of Subchronic Neurotoxicity of 2-Hydroxyethyl Acrylate and Acrylamide in Rats

The comparative neurotoxicity of subchronic exposure to 2-hydroxyethylacrylate (HEA) and acrylamide (ACR) was evaluated using a functionalobservational battery (FOB) and neuropathology. Three dose levelsof each compound (HEA: 3, 20, 60 mg/kg; ACR: 1, 4, 12 mg/kg)were administered intraperitoneally to male and female Long-Evansrats (n = 10/sex/dose level), 5 days/week for 13 weeks. Twovehicle control groups were also included. The FOB, which includeshome-cage and open-field observations and interactive testsof sensory, neuromuscular, and autonomic function, was administeredbefore dosing, at monthly intervals, and on the day after thelast dose. Subsets of rats (n = 6/sex/dose level) were thenperfused and tissues from the brain, spinal cord, and peripheralnerve were prepared for light microscopic evaluation. Therewere clear differences between the effects of HEA and ACR. ACRproduced time- and dose-related changes in FOB measures of muscletone and equilibrium, and produced axonal degeneration in peripheralnerves and within long tracts of the spinal cord. HEA exposurewas also associated with changes in muscular function on FOBtesting, but the magnitude of the effects was not as great aswith ACR and not dose related. In addition, no neuropathologicalchanges were detected after HEA exposure. Thus, the effectsof HEA did not resemble those of ACR. The FOB data were summarizedin domains of neurobehavioral functions. Using a composite scoreanalysis, ACR was shown to produce prominent effects in theneuromuscular domain whereas HEA was largely without effect.When the data are analyzed in this manner, the neurotoxic potentialof HEA appears to be minimal.     

Evaluation of the Potential Developmental Toxicity of Cyclododecatriene (CDDT)

Abstract

The potential maternal and developmental toxicity of cyclododecatriene (CDDT) was assessed in rats. Groups of 22 time-mated female Crl:CD® (SD) BR rats were exposed by inhalation (whole-body, 6 h/day) to either 0 (control), 10, 25, or 67 ppm CDDT over days 6–20 of gestation (days 6–20 G); the day of copulation plug detection was designated day 0 G. The dams were euthanized on day 21 G, and their abdominal and thoracic viscera were examined grossly. The fetuses were weighed, sexed, and examined for external, visceral, and skeletal alterations. Evidence of maternal toxicity was seen at 25 and 67 ppm. There were compound-related reductions in maternal body weight and food consumption parameters as well as increased occurrences of wet and stained fur at these exposure levels. Developmental toxicity evident as reduced mean fetal weight and delayed skeletal ossification was seen only at 67 ppm. There was no evidence of either maternal or developmental toxicity at 10 ppm. Thus, the no-observed-effect level (NOEL) for maternal toxicity was 10 ppm, and the NOEL for developmental toxicity was 25 ppm. Because developmental toxicity was observed only after exposures that also produced signs of maternal toxicity, CDDT was not considered to be a selective developmental toxicant in the rat.     

Nasal Toxicity of Manganese Sulfate and Manganese Phosphate in Young Male Rats Following Subchronic (13-Week) Inhalation Exposure

Growing evidence suggests that nasal deposition and transport along the olfactory nerve represents a route by which inhaled manganese and certain other metals are delivered to the rodent brain. The toxicological significance of olfactory transport of manganese remains poorly defined. In rats, repeated intranasal instillation of manganese chloride results in injury to the olfactory epithelium and neurotoxicity as evidenced by increased glial fibrillary acidic protein (GFAP) concentrations in olfactory bulb astrocytes. The purpose of the present study was to further characterize the nasal toxicity of manganese sulfate (MnSO₄) and manganese phosphate (as hureaulite) in young adult male rats following subchronic (90-day) exposure to air, MnSO₄ (0.01, 0.1, and 0.5 mg Mn/m³), or hureaulite (0.1 mg Mn/m³). Nasal pathology, brain GFAP levels, and brain manganese concentrations were assessed immediately following the end of the 90-day exposure and 45 days thereafter. Elevated end-of-exposure olfactory bulb, striatum, and cerebellum manganese concentrations were observed following MnSO₄ exposure to ≥0.01, ≥0.1, and 0.5 mg Mn/m³, respectively. Exposure to MnSO₄ or hureaulite did not affect olfactory bulb, cerebellar, or striatal GFAP concentrations. Exposure to MnSO₄ (0.5 mg Mn/m³) was also associated with reversible inflammation within the nasal respiratory epithelium, while the olfactory epithelium was unaffected by manganese inhalation. These results confirm that high-dose manganese inhalation can result in nasal toxicity (irritation) and increased delivery of manganese to the brain; however, we could not confirm that manganese inhalation would result in altered brain GFAP concentrations.     

90-Day Subchronic Toxicity Study in Rats and Mice Fed N-Methylpyrrolidone (NMP) Including Neurotoxicity Evaluation in Rats

ABSTRACT

Ninety-day feeding studies were conducted to evaluate the repeated dose toxicity of NMP, a widely used industrial solvent, in Crl:CD®BR rats and B6C3F1 mice. Groups of 20 to 26 male and female rats each were fed either 0, 3,000, 7,500, or 18,000 ppm NMP for 90 days. Groups of 10 male and female mice were fed either 0, 1,000, 2,500, or 7,500 ppm NMP for 28 or 90 days. In vivo parameters, hematology and clinical chemistry parameters, ophthalmologic examinations, functional and histopathologic neurologic parameters (rats only), and complete pathology evaluations were conducted after 90 days.

Decreases in mean body weights, reflecting decreases in food consumption and efficiency were observed in male and female rats fed either 7,500 or 18,000 ppm NMP. A change in urine coloration was observed at 3,000 ppm and above in both males and females. This was considered to be evidence of systemic availability since it was not associated with any functional or pathological changes. Of 36 neurobehavioral parameters investigated, male rats in the 7,500 and 18,000 ppm groups showed an increase in foot splay, and 18,000 ppm males had a higher incidence of low arousal and slight palpebral closure suggestive of a sedative effect. Absolute and relative liver weights were increased in 18,000 ppm females which were associated with an increased incidence of centrilobular hepatocellular hypertrophy and were considered to be an adaptive/physiological response. Absolute and relative kidney weights were increased in 18,000 ppm males and females, however, there were no pathological or functional changes associated with the increases.

In mice, there were no effects on body weight or food consumption. As observed in rats, mice fed 2,500 or 7,500 ppm exhibited a change in urine coloration which was not associated with morphological changes in the kidney. In 2,500 and/or 7,500 ppm mice, changes in cholesterol, triglycerides, calcium, and alkaline phosphatase occurred at 28 days but not 90 days. These changes are thus assessed as being of minor toxicological relevance. Liver weights were elevated in males fed 2,500 or 7,500 ppm and centrilobular hypertrophy was seen in both sexes fed 7,500 ppm. These changes may be regarded as an adaptation process but are clearly related to NMP exposure. Other toxicological endpoints examined were unaffected by NMP.

The NOAEL was 3,000 ppm for both sexes of rats based on body weight effects and changes in 3 neurobehavioral parameters (males only) at higher feeding levels. In mice, the NOAEL was 1,000 ppm based on liver responses to higher concentrations.     

Acute, Subchronic, and Developmental Toxicity and Genotoxicity of 1,1,1-Trifluoroethane (HFC-143a)

The toxicity potential of 1,1,1-trifluoroethane (HFC-143a),a CFC alternative, was evaluated in several acute, subchronic,and developmental toxicity studies by the inhalation route andin genotoxicity studies. HFC-143a has a very low acute inhalationtoxicity potential as shown by a 4-hr LC50 of >540,000 ppmin rats. HFC-143a has a low potential to induce cardiac sensitizationin experimental screening studies in dogs; only the highestconcentration tested—300,000 ppm—elicited a cardiacsensitization response. In an initial 4-week nose-only inhalationstudy, male and female rats were exposed 6 hr/day, 5 days/weekat concentrations of 0, 2000, 10,000, or 40,000 ppm. Femalesshowed no evidence of toxicity at any exposure level; male ratsdid exhibit degenerative changes only in the testes at all exposurelevels. However, because of exposure system irregularities,which resulted in excessive temperature conditions and stressin the HFC-143a-exposed groups, the study was repeated in malerats exposed by whole-body inhalation. In this repeat studyno toxicity was observed at 40,000 ppm. Moreover, a subsequent90-day whole-body inhalation study in rats exposed 6 hr/day,5 days/week at 0, 2000, 10,000, or 40,000 ppm resulted in noevidence of toxicity at any exposure concentration. The resultsof the second 4-week and the 90-day studies using whole-bodyexposures indicate that the findings from the first 4-week studywere related to the stress induced by excessive temperaturesand nose-only restraint. Therefore, the no-observed-effect level(NOEL) for rats repeatedly exposed up to 90 days was consideredto be 40,000 ppm. In developmental toxicity studies with ratsand rabbits, an increase in visceral variations or skeletalmalformations was observed, respectively, at HFC-143a concentrationsof 2000, 10,000, or 40,000 ppm (rat) or at the low and highconcentrations (rabbit). Because of the unusually low controlincidence of variations (1.6% per litter in the control versus6.8–16.8% for historical control values), the lack ofa clear dose-response relationship, and the lack of other developmentaleffects, these findings were not considered related to HFC-143aexposure. In adition, results from genotoxicity studies (Ames,chromosomal aberration with human lymphocytes, mouse micronucleus)demonstrated that HFC-143a Was not mutagenic.     

Subchronic Toxicity, Metabolism, and Pharmacokinetics of the Aminobenzamide Anticonvulsant Ameltolide (LY2O1 116) in Rhesus Monkeys

Studies were undertaken to define the subchronic toxicologicprofile of ameltolide, an aminobenzamide anticonvulsant, inyoung adult rhesus monkeys. Daily doses of ameltolide, dissolvedin 10% aqueous acacia, were administered orally via nasogastricintubation at dosages of 5, 10, 20, 45, and 100 mg/kg. Deathsoccurred in two monkeys, one each at 45 and 100 mg/kg, whichwere directly attributable to the effects of the compound. Theexact cause of death in these monkeys was not readily apparent.A third monkey (100 mg/kg) was killed moribund on Day 82 ofthe study due to conditions not directly related to treatment.Clinical signs in monkeys treated with 100 mg/kg included convulsions, diarrhea, weakness, inappetance, vomition, and ataxia.Plasma concentrations of the N-acetyl metabolite of ameltolidewere greater than parent drug concentrations by one to two ordersof magnitude. Mean area under the plasma-time curve (AUC) valuesfor ameltolide were larger than expected at doses of 20 mg/kgor greater, while AUC values for the metabolite were less thanexpected at 45 and 100 mg/kg. These findings suggest a saturationof metabolism and/or excretion at the two higher doses. Similarnonlinearity was seen with mean peak concentrations for bothparent and metabolite. No specific target organ toxicity wasfound on histological evaluation of tissue sections. Methemoglobinconcentration was increased in monkeys given 45 or 100 mg ameltolide/kg.This change was not considered to be toxicologically importantas there were no corroborative clinical, gross, or histopathologicalfindings. A meltolide administered by nasogastric intubationat doses up to 20 mg/kg/day for 3 months did not cause any toxicologicallyimportant alterations in rhesus monkeys.     

In Vitro and In Vivo Toxicity Evaluation of Natural Products with Potential Applications as Biopesticides

The use of natural products in agriculture as pesticides has been strongly advocated. However, it is necessary to assess their toxicity to ensure their safe use. In the present study, mammalian cell lines and fish models of the zebrafish (Danio rerio) and medaka (Oryzias latipes) have been used to investigate the toxic effects of ten natural products which have potential applications as biopesticides. The fungal metabolites cavoxin, epi-epoformin, papyracillic acid, seiridin and sphaeropsidone, together with the plant compounds inuloxins A and C and ungeremine, showed no toxic effects in mammalian cells and zebrafish embryos. Conversely, cyclopaldic and α-costic acids, produced by Seiridium cupressi and Dittrichia viscosa, respectively, caused significant mortality in zebrafish and medaka embryos as a result of yolk coagulation. However, both compounds showed little effect in zebrafish or mammalian cell lines in culture, thus highlighting the importance of the fish embryotoxicity test in the assessment of environmental impact. Given the embryotoxicity of α-costic acid and cyclopaldic acid, their use as biopesticides is not recommended. Further ecotoxicological studies are needed to evaluate the potential applications of the other compounds.     

Subchronic (13-Week) Toxicity Studies of Oral Phenolphthalein in Fischer 344 Rats and B6C3F1 Mice

Phenolphthalein is a cathartic agent that is widely used inover-the-counter laxatives. Thirteen-week toxicity studies ofphenolphthalein were performed using F344/N rats and B₆C₃F₁mice. Rats and mice were fed ad libitum with a NIH 07 diet containing0; 3000; 6000; 12,000; 25,000; or 50,000 ppm phenolphthalein.On a milligram per kilogram body weight basis, rats and micefed 50,000 ppm phenolphthalein ingested more drug than wouldbe expected during human laxative abuse. Phenolphthalein producedlittle evidence of toxicity in rats. There was slightly lowerweight gain among the 25,000 and 50,000 ppm groups. Treatedrats showed elevated relative kidney weights (males only) andelevated absolute and relative liver weights at 12,000–50,000ppm phenolphthalein. Rat serum bile acids were depressed early(Days 5 and 6) by phenolphthalein treatment. Several treatment-relatedtoxic effects, however, were identified in mice who receivedmore phenolphthalein per unit body weight than rats. Althoughthere were no effects on body weight gain, elevated liver weightswere noted in female mice receiving 6000–50,000 ppm phenolphthalein.The primary treatment-related findings that occurred duringthe mouse studies involved the reproductive and hematopoieticsystems. Reproductive changes including depressed testis andright epididymal weights and sperm density, an elevated productionof abnormal sperm, and morphologic alterations in seminiferoustubules occurred at all levels of exposure (3000–50,000ppm). Hematopoietic changes included bone marrow hypoplasia(12,000–50,000 ppm), increased splenic hematopoiesis (malesonly, 25,000 and 50,000 ppm), and an elevated incidence of micronucleatederythrocytes (6000–50,000 ppm).     

Subchronic (13-week) oral toxicity study of alpha-cyclodextrin in dogs

The oral toxicity of alpha-cyclodextrin (alpha-CD) was examined in a 13-week feeding study in which groups of Beagle dogs received alpha-CD in the diet at concentrations of 0 (control), 5, 10, or 20% (4 dogs/sex/group). No treatment-related changes were noted in behavior or appearance of the dogs and no mortalities occurred. Diarrhea occurred in all alpha-CD groups. The incidence and severity of diarrhea increased with increasing dietary levels of alpha-CD and was more pronounced in males than females. Nonetheless, all dogs remained in good health and gained weight. Food intake was slightly increased and food efficiency was slightly decreased in the 20% alpha-CD group. However, these changes did not reach statistical significance. No treatment-related differences were observed with respect to ophthalmoscopic examinations, hematological parameters, clinicochemical analyses of the plasma, and semiquantitative urine analyses. Only the urinary pH was slightly below control levels in males (p > 0.05) and females (p < 0.05) of the 20% alpha-CD group. No abnormalities were seen at necropsy that could be attributed to the treatment. The organ weight data revealed cecal enlargement in the 10 and 20% alpha-CD groups (significant only in males). The relative weight of the colon was also slightly increased in the 10 and 20% alpha-CD groups (significant only in females of the 10% alpha-CD group). On microscopic examination, no treatment-related alterations were observed in any of the various organs and tissues. In conclusion, transient diarrhoea, enlargement of the cecum and colon and a slightly increased acidity of the urine were the only treatment-related effects. These changes are well-known physiological responses to the presence of high amounts of not digested, fermentable carbohydrates in the lower gut. They are known to be reversible on cessation of the treatment and are not associated with histological alterations of the intestinal tissues. It is concluded, therefore, that the high dose level, at which the male and female dogs consumed about 9.8 and 10.4 g alpha-CD/kg bw/d, respectively, is the NOAEL of this 13-week toxicity study.     

Subchronic (13-week) oral toxicity of neohesperidin dihydrochalcone in rats

Neohesperidin dihydrochalcone was administered to groups of 20 male and 20 female Wistar rats at dietary levels of 0, 0.2, 1.0 and 5.0% for 91 days. No treatment-related ophthalmoscopical, haematological or histopathological effects were observed. In the high-dose group, a marked caecal enlargement occurred in both sexes, accompanied by soft stools in the early stages of the study, somewhat lower plasma urea concentrations and increased plasma alkaline phosphatase activity and a decreased urinary pH. This group also showed slight growth depression accompanied by transient reduction in food intake; in males the body weights remained relatively low throughout the experimental period. Furthermore, bilirubin level was increased in females and total protein level was decreased in males of the high-dose group. The above changes were considered adaptive responses or chance effects rather than manifestations of clear toxicity. The low-and intermediate- dose groups did not show any compound-related untoward effect. It was concluded that the intermediate dose, providing an overall intake of about 750 mg neohesperidin dihydrochalcone per kg body weight per day, was the no-effect level.     

Subchronic (13-week) inhalation toxicity study of formaldehyde in rats

Male and female albino Wistar rats were exposed to concentrations of 0, 1, 10 or 20 ppm formaldehyde vapour during 6 h/day, 5 days/wk for 13 weeks. Treatment-related changes observed at 20 ppm included in both sexes: stared coats, uncoordinated locomotion and excitation during the first 30 minutes of each exposure, yellowing of the fur, growth retardation, a decreased level of plasma protein, severe and extensive karatinized stratified squamous metaplasia of the nasal respiratory epithelium, and focal degeneration and squamous metaplasia occasionally accompanied by keratinization of the olfactory epithelium; in males only; increased activities of plasma aspartate amino transferase (ASAT), alanine amino transferase (ALAT) and alkaline phosphatase (ALP) and squamous metaplasia of the laryngeal epithelium. Lesions seen at 10 ppm included yellowing of the fur and moderate squamous metaplasia of the nasal respiratory epithelium. The only change observed in three out of twenty 1 ppm exposed animals that might or might not be treatment-related was minimal focal epithelial hyperplasia and squamous metaplasia of the respiratory epithelium lining the nasal septum and maxillary turbinates. No histopathological evidence of hepatotoxicity was detected in any of the formaldehyde-treated groups. An in vivo/in vitro cell proliferation study showed an increase in [3H]-thymidine labeling index of the respiratory epithelium lining the nasoturbinates of rats exposed to 10 or 20 ppm formaldehyde on three successive days, whereas at the 1 ppm level the labeling index was similar to that of controls. It was concluded that under the conditions of the present 13-week inhalation study, formaldehyde at concentrations up to 10 ppm was not hepatotoxic to rats. At the 20 ppm formaldehyde level, a slight effect on the liver of male rats cannot be completely excluded. The study was inconclusive with respect to 1 ppm formaldehyde being a cytotoxic or a no-cytotoxic effect level for the nasal epithelium.     

Subchronic Toxicity of 3,3',4,4',5-Pentachlorobiphenyl in the Rat: I. Clinical, Biochemical, Hematological, and Histopathological Changes

The systemic, toxicity of 3,3',4,4',5-pentachlorobiphenyl (PCB126) following subchronic dietary exposure was investigatedin Sprague-Dawley rats. PCB 126 was administered to rats ofboth sexes at concentrations of 0.1, 1.0, 10, or 100 ppb intheir diet for 13 weeks. Another group of rats received a loadingdose of 5 µg PCB/kg body wt at the start of the feedingperiod followed by exposure to 10 ppb PCB diet for the sameperiod of time as the other groups. Growth suppression and decreasedfood consumption were observed in the highest dose groups ofboth sexes. Increased organ/body weight ratios for the liveroccurred in the 10 and 100 ppb groups of both sexes. Rats ofboth sexes exposed to the highest dose of the PCB also exhibitedincreased relative kidney, spleen, and brain weights. Hematologicaland most serum biochemical changes were confined to the 100ppb groups. These included elevated alkaline phosphatase, bilirubin,cholesterol, and aspartate aminotransferase, and decreased serumglucose, hemoglobin, erythrocytes, hematocrit, and platelets.A dose-dependent increase in liver ethoxyre-sorufin-O-deethylaseactivity was observed in rats of both sexes starting at 0.1ppb. A dose-dependent increase in liver uroporphyrin levelswas observed in both sexes and significant changes occurredin the female rats at 1.0 ppb and higher dose groups. Decreasedliver vitamin A was observed in the 10 ppb group and higherin both sexes. Kidney vitamin A was elevated in the 100 ppbgroup. No statistically significant changes were noted in concentrationsof brain biogenic amines. PCB 126 residues were 10-fold higherin liver than in fat. Treatment-related histopathological changeswere observed in the thymus, thyroid, bone marrow, and liverof rats exposed to the 10 ppb diet, but increased frequencyof mild changes was observed in most of these tissues at the1.0 ppb level. Based on the above data, the no adverse effectlevel was judged to be 0.1 ppb in the diet or 0.01 µg/kgbody wt/day.