Table 2.
Distribution of assembled β-tubulin and assembled tau along the axon
| Profile parameters | Average ± SD (minimum/maximum) | |
|---|---|---|
| β-Tubulin | Tau | |
| Proportion of axons showing a distal rise in staining intensity | 69% | 94% |
| Length of distal region (μm)2_a | 189 ± 80 | 198 ± 71 |
| (55/358) | (90/345) | |
| Distance from axon tip of distal segment containing peak ADU (μm) | 51 ± 65 | 29 ± 19 |
| (13/251) | (8/74) | |
| (Peak ADU distal axon)/(mean ADU proximal axon) | 4.0 ± 2.6 | 13.4 ± 9.7 |
| (1.4/10.2) | (2.7/32.4) | |
| (Peak ADU distal axon)/(median ADU entire axon) | 3.5 ± 2.2 | 10.1 ± 8.8 |
| (1.2/8.3) | (1.8/29.0) | |
| (Amount in distal axon)/(total amount in axon) | 0.48 ± 0.2 | 0.66 ± 0.15 |
| (0.1/0.75) | (0.32/0.85) | |
The data were obtained from 16 axons processed by combined extraction and fixation (according to procedure 3), double-stained with the mouse monoclonal antibody against β-tubulin and a rabbit polyclonal antibody against tau (tau-5′, according to staining condition 2). As described in the text, the tubulin and tau staining in axons processed in this manner reflects specifically tubulin and tau assembled into MTs. The table shows several parameters of these distributions obtained with the segmented mask procedure. The average length of the axons analyzed was 504 ± 104 μm (range = 306–635 μm). The measurements regarding the distal region are based only on those axons that showed a distal rise in staining intensity.
To facilitate the comparison of the distribution of total tubulin and total tau along the axon (Table 1) with that of assembled tubulin and assembled tau (Table 2), the quantitative data shown in both tables were obtained from a single experiment using sister cultures. The staining procedures used on all cells were identical and were performed in parallel using the same reagents. Also, the images of the cells on which the quantitative analyses were based were obtained using the same exposure times. Thus, we have controlled for as many variables as possible so that the specific quantitative results obtained with the two fixation procedures can be reliably compared with each other.
This refers to the length of the distal axon over which the staining intensity for tubulin and tau increased from the proximal plateau region.