Focal traumatic brain injury (TBI) induces astrogliosis, a process essential to protecting uninjured brain areas from secondary damage. However, astrogliosis can cause loss of astrocyte homeostatic functions and possibly contributes to comorbidities such as posttraumatic epilepsy (PTE). Scar-forming astrocytes seal focal injuries off from healthy brain tissue. It is these glial scars that are associated with epilepsy originating in the cerebral cortex and hippocampus. However, the vast majority of human TBIs also present with diffuse brain injury caused by acceleration-deceleration forces leading to tissue shearing. The resulting diffuse tissue damage may be intrinsically different from focal lesions that would trigger glial scar formation. Here, we used mice of both sexes in a model of repetitive mild/ concussive closed-head TBI, which only induced diffuse injury, to test the hypothesis that astrocytes respond uniquely to diffuse TBI and that diffuse TBI is sufficient to cause PTE. Astrocytes did not form scars and classic astrogliosis characterized by upregulation of glial fibrillary acidic protein was limited. Surprisingly, an unrelated population of atypical reactive astrocytes was characterized by the lack of glial fibrillary acidic protein expression, rapid and sustained downregulation of homeostatic proteins and impaired astrocyte coupling. After a latency period, a subset of mice developed spontaneous recurrent seizures reminiscent of PTE in human TBI patients. Seizing mice had larger areas of atypical astrocytes compared with nonseizing mice, suggesting that these atypical astrocytes might contribute to epileptogenesis after diffuse TBI.

Mining, whether current or inactive, generally increases salt concentrations in catchment watersheds due to precipitation on and through exposed rock surfaces. Practices like mountaintop removal mining have exacerbated this issue, with measurements of salt concentrations in nearby catchment systems well above normal levels. Nevertheless, the impact of the ionic composition of mining effluent on aquatic animal health is not well understood. This is a particularly important issue in Appalachia because it is home to an enormous diversity of organisms, including a huge array of amphibians that live in streams that receive mining effluent from operating and abandoned mines. To investigate this issue, we examined the effects of reconstituted mining effluent on the development of wild-caught wood frog (Lithobates sylvaticus) tadpoles. We collected day-old fertilized eggs from a creek near Blacksburg, VA in early March, 2018 and raised them to hatch. Tadpoles were then assigned to either sulfate or chloride-based reconstituted mining effluent diluted to six different conductivities (100 µS/cm -2,400 µS/cm). After 7 or 14 days of treatment, tadpoles were euthanized and fixed in paraformaldehyde. We imaged the heads and bodies of tadpoles for morphometric analysis before dissecting out brains and immunostaining them for phospho-histone H3, which labels dividing progenitor cells in the brain. We found that sulfate-based reconstituted mining effluent significantly lowered progenitor cell division at 1200 µS/cm at Day 7 and at 600 µS/cm at Day 14 relative to control. Chloride-based reconstituted mining effluent was less impactful, with no significant differences observed at Day 7 and significantly lowered progenitor cell division at 2400 µS/cm at Day 14. In addition, both treatments slowed growth of some head morphological features, including head size and interocular distance. Chloride treatment slowed growth of body length at Day 14 at 600 µS/cm, whereas sulfate-based reconstituted mining effluent had no effect on body length. These data show that sulfate-based mining effluent has a substantial