sentence: Electron microscopic studies and evidence from immunolabeling of presynaptic and neurotransmitter markers ( e.g ., synaptophysin ( SYN ) , choline acetyltransferase , tyrosine hydroxylase , glutamate decarboxylase and vesicular glutamate transporters ) in plaque-associated DNs suggest that they appear to be largely abnormal axons including presynaptic terminals ( Luse and Smith , 1964 ; Gonatas et al ., 1967 ; Struble et al ., 1982 , 1987 ; Walker et al ., 1985 ; Masliah et al ., 1991 ; Ferrer et al ., 1998 ; Cai et al ., 2010 ; Yan et al ., 2014 ; Sadleir et al ., 2016 ) .