Do these studies contribute to our understanding of OPIDP? Unfortunately, so far only to a very limited extent. Clearly, NTE seems to play a role in membrane lipid metabolism, and may be involved in intra-neuronal membrane trafficking and lipid homeostasis. Whether its lysoPLA activity may be involved in OPIDP remains to be clarified, as this enzymatic activity is also affected by chemicals that do not cause OPIDP. Accumulated lysolecithin causes demyelination of neuronal sheaths, often accompanied by neuronal lesions [100], while changes in axonal morphology seem to be the early morphological events in OPDIP, with secondary attenuation of the myelin sheath [12]. Studies in genetically modified mice have provided some interesting insights in the physiological role of NTE. NTE appears to be required for normal blood vessel and placental development [103] and [104], and absence of brain NTE results in neuronal degeneration and loss of endoplasmic reticulum in various brain areas [105], two effects not directly related to OPIDP. Furthermore, mice, though an excellent tool for transgenic research, are resistant to OPIDP [18]. Thus, the most crucial issues in the mechanisms of OPIDP development and progression still remain obscure [13].