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Effects of developmental and longitudinal exposure to the PCB Aroclor® 1254 on balance in black Swiss-Webster mice.

*M. WRIGHT1, T. PROVOST2, A. K. PACK2,3;

2Biol., 1Utica Col., Utica, NY; 3Biomed. and Chem. Engin., Inst. for Sensory Res., Syracuse, NY

 

Abstract: Polychlorinated biphenyls (PCBs) have been previously shown to create hearing deficits in mice that were exposed during early development, presumably by acting on thyroid hormone receptors, which are critical for normal development of both cochlear and vestibular epithelia. In the current study, mice (n=43) were exposed to high (12.5 ppm, n=16) or low (1.25 ppm, n=15) levels of a specific mixture of PCB congeners, Aroclor® 1254 in the diet during development and/or throughout their lifespan. PCBs have their greatest impact when the organism is in gestation and nursing, because the lipophilic nature of PCBs causes them to be stored in tissues such as the placenta and breast milk. The balancing abilities of the pups, as indicated by foot faults while traversing varying beam widths and shapes, were tested using a balance beam test. At either post-natal day 29 or post-natal day 184 mice were euthanized and both cochleae and posterior ampullae were retrieved and prepared for histological analysis. Mice that were exposed to the PCB over their lifetime had a greater number of foot faults on the most difficult beam than mice that were exposed to the same level of PCB only during development at post-natal day 29. This trend was seen for both the high level and low level dosage of PCB. Higher number of foot faults corresponded, albeit weakly, to number of hair cells present in the sensory epithelium of the posterior ampullae. Our date are consistent with a longer exposure time impacting balance by preventing vestibular hair cell regeneration. It also provides tentative support for the hypothesis that vestibular hair cells have the potential to regenerate after PCB exposure.

Effects of developmental and longitudinal exposure to the PCB Aroclor® 1254 on balance in black
Swiss-Webster mice
AUTHOR BLOCK: *M. WRIGHT1, T. PROVOST2, A. K. PACK2,3;
2Biol., 1Utica Col., Utica, NY; 3Biomed. and Chem. Engin., Inst. for Sensory Res., Syracuse, NY
Abstract: Polychlorinated biphenyls (PCBs) have been previously shown to create hearing deficits in
mice that were exposed during early development, presumably by acting on thyroid hormone receptors,
which are critical for normal development of both cochlear and vestibular epithelia.
In the current study, mice (n=43) were exposed to high (12.5 ppm, n=16) or low (1.25 ppm, n=15) levels
of a specific mixture of PCB congeners, Aroclor® 1254 in the diet during development and/or
throughout their lifespan. PCBs have their greatest impact when the organism is in gestation and
nursing, because the lipophilic nature of PCBs causes them to be stored in tissues such as the placenta
and breast milk. The balancing abilities of the pups, as indicated by foot faults while traversing varying
beam widths and shapes, were tested using a balance beam test. At either post-natal day 29 or post-natal
day 184 mice were euthanized and both cochleae and posterior ampullae were retrieved and prepared for
histological analysis.
Mice that were exposed to the PCB over their lifetime had a greater number of foot faults on the most
difficult beam than mice that were exposed to the same level of PCB only during development at
post-natal day 29. This trend was seen for both the high level and low level dosage of PCB. Higher
number of foot faults corresponded, albeit weakly, to number of hair cells present in the sensory
epithelium of the posterior ampullae. Our date are consistent with a longer exposure time impacting
balance by preventing vestibular hair cell regeneration. It also provides tentative support for the
hypothesis that vestibular hair cells have the potential to regenerate after PCB exposure.