Ethanol exposure induces a delay in the reacquisition of function during head regeneration in Schmidtea mediterranea.

Prenatal exposure to ethanol affects neurodevelopmental processes, leading to a variety of physical and cognitive impairments collectively termed Fetal Alcohol Spectrum Disorders (FASD). The molecular level ethanol-induced alterations that underlie FASD are poorly understood and are difficult to study in mammals. Ethanol exposure has been shown to affect regulation and differentiation of embryonic stem cells in vitro, suggesting that in vivo effects such as FASD could arise from similar alterations of stem cells. In this study, we hypothesize that ethanol exposure affects head regeneration and neuroregeneration in the Schmidtea mediterranea planarian. S. mediterranea freshwater flatworms have remarkable regenerative abilities arising from an abundant population of pluripotent adult somatic stem cells known as neoblasts. Here, we evaluated the mobility-normalized photophobic behavior of ethanol-exposed planaria as an indicator of cognitive function in intact and head-regenerating worms. Our studies show that exposure to 1% ethanol induces a delay in the reacquisition of behavior during head regeneration that cannot be attributed to the effect of ethanol on intact worms. This suggests that the S. mediterranea planarian could provide insight into conserved neurodevelopmental processes that are affected by ethanol and that lead to FASD in humans.

Temporomandibular joint fibrocartilage degeneration from unilateral dental splints.

OBJECTIVE: The objective of this study was to determine the extent to which altered loading in the temporomandibular joint (TMJ), as might be associated with a malocclusion, drives degeneration of articulating surfaces in the TMJ. We therefore sought to quantify the effects of altered joint loading on the mechanical properties and biochemical content and distribution of TMJ fibrocartilage in the rabbit. DESIGN: Altered TMJ loading was induced with a 1mm splint placed unilaterally over the maxillary and mandibular molars for 6 weeks. At that time, TMJ fibrocartilage was assessed by compression testing, biochemical content (collagen, glycosaminoglycan (GAG), DNA) and distribution (histology), for both the TMJ disc and the condylar fibrocartilage. RESULTS: There were no changes in the TMJ disc for any of the parameters tested. The condylar fibrocartilage from the splinted animals was significantly stiffer and the DNA content was significantly lower than that in control animals. There was significant remodeling in the condylar fibrocartilage layers as manifested by a change in GAG and collagen II distribution and a loss of defined cell layers. CONCLUSIONS: A connection between the compressive properties of TMJ condylar fibrocartilage after 6 weeks of splinting and the changes in histology was observed. These results suggest a change in joint loading leads to condylar damage, which may contribute to pain associated with at least some forms of TMJ disease.