Figure 1
The tubulohelical membrane array (TUHMA) visualized by transmission electron microscopy and light microscopy. A) Processing by microwave-accelerated fixation with 0.5% glutaraldehyde in buffer solution, followed by treatment with OsO4, and embedding in epoxy resin for thin sectioning [8]. The organelle displays darkly contrasted tubules of uniform diameter of 80 nm, numbered 1-4. The tubules are incorporated in a regular stack of membranes and confined by helical bands that contrast in black. Note also a twisting pattern of the tubules within the plane of section and the size relation of the TUHMA in comparison with a mitochondrion, m. (courtesy of Cell Biol Intern [4]). B) Processing by microwave-accelerated fixation with 0.5% paraformaldehyde buffer solution and extraction with 0.1% Triton X-100, followed by treatment with OsO4 prior to embedding and thin sectioning. While the lipid membranes are dissolved, the proteinaceous core tubules remain intact exposing their helix-like aspects with great clarity. The core tubule on the right seems to detangle into separate threads (black arrows) giving the impression of a double helix bridged by delicate filaments. Bars in A and B, 500 nm. C) Confocal image of a cell immunolabeled with mAb 414. In the cytoplasm a Texas Red-fluorescent tubular structure is apparent. D) A tubular pattern in the DIC-contrast (arrow) co-localizes with the fluorescent tubular structure in C. Note that the cell in C, D was fixed and extracted with Triton X-100 in the same way as the EM sample in B. E) Confocal section of a cell indirectly immunolabeled with human autoimmune Abs against Nup62 and Texas Red-conjugated Abs, and counterstained with Hoechst 33258. Note that both the mAb 414 and the autoimmune Abs label NPCs at the nuclear envelope. Bars in C-E, 5 μm.