Changes in Phospho-MAP/Tau during Neuronal Stress Figure 5. Rod-like accumulations in neurites of primary chick neurons contain densely packed filaments. Transmission electron micrographs of primary chick neurons treated with 1 mM AM for 15 min, fixed and processed for TEM as described in Methods. (A) Densely packed linear arrays of filaments occur in the neurite (white arrows). The lower panel shows a higher magnification view of the boxed region above. (B) Another example of densely packed filaments within a neurite (white arrow). Here the filament bundle spans a large proportion of the width of the neurite. (C) In contrast, unaffected neurites contain individual separated microtubules approximately 24 nm in diameter (black arrows). Scale bars = 0.2 mm. doi:10.1371/journal.pone.0020878.g005 cellular response to ischemia (mimicked by transient ATP depletion) [50]. An interesting exception to this, consistent in both cell culture and in an animal model, is the enduring phosphorylation of the 12E8 epitope that has been reported in a gerbil-model of brain ischemia [51]. However after reperfusion, tau proteins are slowly phosphorylated and accumulate, resulting in hyperphosphorylation days after the initial ischemic event in the animal potentially due to the down-regulation of phosphatases or induction of specific kinases, although the mechanism remains to be determined [50]. Importantly, our cell culture model is consistent with the animal models and mimics early signaling events directed to tau during transient brain ischemia. While we are not saying that such a large scale global ischemic event is directly relevant to AD, it is interesting that stroke is a significant risk factor for the later development of dementia and AD [50]. More commonly in AD, smaller less severe microischemic events PLoS ONE | www.plosone.org 8 June 2011 | Volume 6 | Issue 6 | e20878