Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 2 (1996) / Chapter Skim
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B6 Indole
B6 Indole
Pages 235-250
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Johnson Space Center Toxicology Group Biomedical Operations and Research Branch Houston, Texas PHYSICAL AND CHEMICAL PROPERTIES Indole is a colorless crystalline solid. It has an intense fecal odor at moderate concentrations; however, the oclor at very low concentrations is pleasant (Merck Index, 19891.
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When 10 mg of indole was injected intravenously into each of the five rabbits, an average plasma indole concentration of 0.3 ma% was detected only in the blood samples taken 15 min after the injection. Because of the inability to detect indole in the blood thereafter, Sgibnew and Oriova concluded that indole was quickly removed and rendered harmIess.
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posing 20 mice and 15 rats to indole at a concentration of 9-10 mg/m3 for 2 h produced no toxic signs except some unrest during the first 15 mini no deaths occurred during the 14-day post-exposure observation period (Sgibnew and Orlova, 19711. The hematological effects and subsequent renal lesions induced by indole were observed in four cows given the compound at a single oral dose of 100 mg/kg and then 200 mg/kg 2 w later (Hammond et al., 1980~.
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Instead of the fine thread-like reticulum of normal reticulocytes, there was a profuse, densely staining nuclear material that filled the cell, which appeared to consist of coarse granules. Pathological studies on 25 % of the exposed mice revealed 95 % of the animals had pigment in the renal tubular cells.
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, who injected indole subcutaneously in mice at a weekly dose of 1 mg for 9 mot The author reported that of 60 surviving mice, 13 showed leukosis and 21 had pulmonary adenomas. Exposure to tryptophan (presumably serving as controls)
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240 Cry ._ C)
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241 Ct i_ Cal _ o .
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Inhaled indole is not known to induce effects on the respiratory system; therefore, systemically mediated effects, produced by an absorbed dose from inhalation or other route of administration, might be considered equivalent. Moderate amounts of indole are normally absorbed from the gastrointestinal tract, so there is a significant systemic body burden.
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Slight nausea is tolerable for brief periods as long as crew-member performance is not affected; however, interpretation of the duration of exposure is difficult from the original study. It was estimated that reducing the exposure concentration by a factor of 2 would have caused no more than slight nausea in a few people even if the exposure were for 1 h.
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However, the mechanism of the red-cell-mass changes has not been clearly elucidated at this time. The hematology factor should be smaller than the factor of 5 used for cardiac effects because cardiac effects have actually caused a cosmonaut to be returned early from a mission (Gazenko et al., 1990~.
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as equivocal, and the remaining study (Eckhart and Stich, 1957) appears positive for leukemogenic effects.
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Nonnal Indole Uptake Daily urinary excretion of indican averages 200 mg in normal adults, and this is equivalent to 110 mg of indole absorbed from the gastrointestinal tract. It is reasonable to assume that a 5 % increase in this indole input from an inhalation source would be toxicologically insignificant.
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247 Cat o c o V U)
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Kosmicheskaya Biologiya i Aviakosmicheskaya Meditsina 23~4~:3-11; translated and abstracted in USSR Space Life Sciences Digest, L.R. Stone and R
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1961. Tolerance Criteria for Continuous Inhalation Exposure to Toxic Material.
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