Persistence of micronuclei in peripheral blood normochromatic erythrocytes of subchronically benzene‐treated male mice

Abstract

The kinetics of micronucleus (MN) induction and decline in blood normochromatic erythrocytes (NCE) of mice subchronically exposed to benzene was investigated during and after exposure. Swiss (ICR) male mice (lO/group) were given 0.0,36.6,73.2, and 146.4 mglkg body weight benzene by gavage daily for 14 days, except for days 5 and 10. The frequency of MN increased significantly (P < .001) during benzene treatment as a function of both concentration and time. Eleven days after exposure the levels of MN were higher than those observed at the end of exposure. After an initial rapid decline in the frequency of MN from 11 to 18 days postexposure, the decline became linear with time through 60 days postexposure. Using linear regression analysis, the MN level in each treatment group was predicted to reach control levels by approximately 85 days post-treatment. Dose-dependent suppression and recovery of erythropoiesis, estimated by polychromatic erythrocyte frequency, were observed in the 1st and 2nd weeks of exposure, respectively. Red blood cell (RBC) production was markedly increased in the first 3 weeks after benzene treatment. At later times the rate of production of the RBC returned to normal and may account for the linear decline observed in MN frequency. This research indicates that the frequency of MN is dose and duration dependent, while the decline in MN frequency after the end of benzene exposure can be related to changes in the kinetics of erythropoiesis.

Effects of 100 MeV protons delivered at 0.5 or 1 cGy/min on the in vivo induction of early and delayed chromosomal damage

“…We recognize that these factors may interfere with statistical analyses. Had the number of cells evaluated per animal been large and similar in every instance, the preferred average square root transformation (ASQRT) [57,58], a routine method used in our laboratory [31,36,37,59,60], would be applied to each animal's aberration number and the analysis of variance would have been used. However, as the number of cells varied significantly and the total number of cells scored was small in some animals of some treatment groups, the preferred ASQRT was not applicable.…”

Analysis of chromosomal damage after in vivo exposure to 56Fe ions by means of mFISH and micronucleus methods

“…Therefore, the observation of the lowest frequency of MN-PCEs in mice exposed to the highest dose (3.0 Gy) of 137 Cs c rays indicates that the MN-PCE cells were markedly diluted by those newly formed PCEs. Such a phenomenon has previously been reported in mice exposed to benzene, a leukemogen (Rithidech et al, 1988). The life span of micronucleated red cells of the mouse is approximately 30 days (Schlegel and MacGregor, 1984).…”

Toxicological Evaluation of a Potential Immunosensitizer for Use as a Mucosal Adjuvant—Bacillus thuringiensis Cry1Ac Spore-Crystals: A Possible Inverse Agonist that Deserves Further Investigation

“…Because the life span of mouse red blood cells is much shorter than in larger animals, the effect of hemolysis on red cell mass occurs more quickly [ 22 ]. It has been suggested that the frequency of MN in peripheral blood normochromatic erythrocytes is dose and duration dependent, while the decline in MN frequency after the end of exposure can be related to changes in the kinetics of erythropoiesis [ 31 ]. Although our work was not also carried out with MN test in peripheral blood leukocytes, results reinforce the need for more research to avoid the potential risks of the increased bioavailability of these microbiological control agents (MCA), especially given that little is known about spore crystals’ adverse effects on non-target species [ 19 , 20 , 26 , 32 ].…”