Stable PS1 complexes are increased in AD ante-mortem CSF. (A) Representative blot and densitometric quantification of the accumulative immunoreactivity from the sum of higher molecular mass PS1 complex (100 + 150 kDa) in lumbar CSF samples from 12 AD (open circles) and 12 NDC controls (closed circles). (B) Eight of the 12 cases available from both the AD and NDC groups were also fractioned into 5-20% sucrose density gradients, and blotted with the NTF-PS1 antibody under denaturing conditions. Internal markers were β-galactosidase (G), catalase (C) and alkaline phosphatase (P), as in Figure 5. In the right panel the individual values for the quotient between highly stable complexes (100 + 150 kDa immunoreactive bands sediment at fractions 2-7) and unstable complexes (50 kDa immunoreactive bands sediment at fractions 8-12) are shown. *Significantly different (p < 0.05) from the NDC group, as assessed by Mann-Whitney U test.