Morphology recovery test

Mice exposed to 2,000 ppm of trichloroethylene, 4 hours/day for a 5-day period, had a significant increase in abnormal sperm morphology of 1% 28 days after the exposure (Land et al. 1981). No effect was seen at 200 ppm. A 6% increase in abnormal sperm was observed 4 weeks, but not 4 days or 10 weeks, after mice were exposed to 100 ppm trichloroethylene 7 hours per day for 5 days (Beliles et al. 1980). Based on the time after exposure at which sperm were affected, the study authors indicated that trichloroethylene damages sperm precursor cells but that spermatogonia were either unaffected or were capable of recovery. Reproductive performance was not tested in these studies. Another mouse study tested the effects of a 5-day exposure (6 hours/day) on spermatid micronuclei frequency no effects were observed at exposure levels of up to 500 ppm, the highest concentration tested (Allen et al. 1994). These results were interpreted as evidence that trichloroethylene did not cause meiotic chromosome breakage or loss. No treatment-related reproductive effects were seen in female rats exposed to 1,800 ppm trichloroethylene for 2 weeks (6 hours/day, 7 days/week) before mating (Dorfmueller et al. 1979). 

As summarized in Table 4, there are six major categories of approaches to alternative eye irritation tests. The first five of these aim at assessing portions of the irritation response (alterations in tissue morphology, toxicity to individual component cells, alterations in cell or tissue physiology, inflammation or immune modulation, and alterations in repair and recovery processes). These methods have the limitation that they assume that one of these component parts can or will predict effects in the complete organ system. A more likely case is that, while each may serve well to predict the effects of a set of chemical structures which have that component as a determining part of the ocular irritation response, a valid assessment across a broad range of structures will require the use of a collection or battery of such tests. 

Morphological characterization can be conducted by light and electron microscope techniques and by X-ray diffraction and thermal analysis, often used to determine crystallinity. Standard mechanical tests can be used to determine strength, extension to break in tension, and toughness. Normally, a selection of characterization methods is used with samples exposed for selected periods. When mechanical tests are used, the exposure period increment must be fairly short, in case a recovery phenomenon is present (see the section Engineering Properties—Consequences of Photodegradation ). Other tests related to appearance. 

Regarding the morphological stability along the time life of the space materials, NASA and ESA specified standardized degassing tests with the same acceptance limits (see ESA ECSS Q70 02A). The adhesive on space qualification does have an amount of a recovery mass loss (RML) and total mass loss (TML) less than 1% and of a collected volatile condensable material (GVGM) less than 0.1%. These acceptance limits are submitted for derogation depending on the absolute quantity of adhesive implemented. 

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