Tests with Higher Animals

Toxicity test procedure in higher animals (e.g., rats, mice, rabbits, dogs, and monkeys) is different from that in lower animals because the number of available animals usually is limited. As mentioned earlier, it is not economical or practical to use a few hundred mammals for the evaluation of a single toxicity test. The limitation in number has necessitated several adjustments to assure the validity of toxicity determinations in higher animals. Typically, in the pesticide industry, three types of tests are required acute, subacute, and chronic. 

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The AEGL-1 concentration was based on a 1-hour (h) no-effect concentration of 8,000 parts per million (ppm) in healthy human subjects (Emmen et al. 2000). This concentration was without effects on pulmonary function, respiratory parameters, the eyes (irritation), or the cardiovascular system. Because this concentration is considerably below that causing any adverse effect in animal studies, an intraspecies uncertainty factor (UF) of 1 was applied. The intraspecies UF of 1 is supported by the absence of adverse effects in therapy tests with patients with severe chronic obstructive pulmonary disease and adult and pediatric asthmatics who were tested with metered-dose inhalers containing HFC-134a as the propellant. Because blood concentrations in this study approached equilibrium following 55 minutes (min) of exposure and effects are determined by blood concentrations, the value of 8,000 ppm was made equivalent across all time periods. The AEGL-1 of 8,000 ppm is supported by the absence of adverse effects in experimental animals that inhaled considerably higher concentrations. No adverse effects were observed in rats exposed at 81,000 ppm for 4 h (Silber and Kennedy 1979) or in rats exposed... 

Data adequacy The key study was well conducted and documented. Supporting data include both human and animal studies. Animal studies covered acute, subchronic, and chronic exposure durations and addressed systemic toxicity as well as neurotoxicity, reproductive and developmental effects, cardiac sensitization, genotoxicity, and carcinogenicity. Other effects in animal studies occurred at much higher concentrations or with repeated exposures the latter are not relevant for setting short-term exposures. No effects other than narcosis occurred in rats and mice exposed at 200,000 ppm for various periods of time. Adjustment by a total UF of 10 results in a higher value (20,000 ppm) than from the cardiac sensitization test with dogs. ... 

The AEGL-1 value was based on the observation that exercising healthy human subjects could tolerate exposure to concentrations of 500 or 1,000 ppm for 4 h with no adverse effects on lung function, respiratory symptoms, sensory irritation, or cardiac symptoms (Utell et al. 1997). The exercise, which tripled the subjects minute ventilation, simulates an emergency situation and accelerates pulmonary uptake. Results of the exposure of two subjects for an additional 2 h to the 500-ppm concentration and the exposure of one subject to the 1,000-ppm concentration for an additional 2 h failed to elicit any clear alterations in neurobehavioral parameters. The 4- or 6-h 1,000-ppm concentration is a NOAEL in exercising individuals, there were no indications of response differences among tested subjects, and animal studies indicate that adverse effects occur only at considerably higher concentrations, so the 1,000-ppm value was adjusted by an uncertainty factor (UF) of 1. The intraspecies UF of 1 is supported by the lack of adverse effects in patients with severe... 

The incidence of neoplasms is compared between the test and control groups for statistical significance and to detect whether there is a trend, that is, increasing incidence with higher doses. Such a comparison is made by tissue, so that all the neoplasms in the liver, for example, are compared between groups. Also, the total number of animals with single and multiple tumours is compared to see if there is a non-specific increase in tumour burden. 

Groups of 25 male and 25 female Swiss CD-I mice, four to six weeks of age, were fed 4-chloro-ort/2o-toluidine hydrochloride (97-99% pure) in the diet at dose levels of 0, 750 or 1500 mg/kg diet (ppm) (males) or 0, 2000 or 4000 ppm (females) for 18 months. Animals were kept without treatment for three further months and then killed. The doses were chosen on the basis of preliminary tests, the higher being the maximum tolerated dose. Additional control groups were prepared for the other compounds tested in the study, and tumour incidences of concurrent and pooled controls were compared statistically (both separately and together) with those of treated groups. Animals that... 

Several terpenoids have been evaluated for their inhibitory effects on EBV-EA activation induced by TPA. Table 6 shows the inhibitory effects of monoterpenoids [70,71], sesquiterpenoids [20,119-123], diterpenoids [21,123-131], and meroterpenoids [117] against TPA (32 pmol, 20 ng)-induced EBV-EA activation in Raji cells. The inhibitory effects were compared with that of [3-carotene, a vitamin A precursor that has been studied intensively in cancer chemoprevention using animal models [2,4]. All of the terpenoids tested caused higher viability (60-80%) of Raji cells even at mol ratio of compound to TPA = 1000 1 indicating their very low cytotoxicity at that high concentration (refer to Table 6). 

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