- The Acetylation Method
Compared to the nucleus aspect shown with the usual routine methods for electron microscopy (Figure 11.1), acetylation carried out prior to embedding allows a striking identification of condensed chromatin masses within the nucleoplasm (Figure 11.2). The acetylation can be performed on tissue or cell sections, but better results were observed after en bloc treatment. In particular, in the nucleolus, it allows clear visualization of the clumps of condensed chromatin surrounding the nucleolus and their intranucleolar invaginations (Figure 11.3). The nucleolar components, the fibrillar centers, the dense fibrillar component, and the granular components are also easily distinguished (Figure 11.3). The interchromatin granule clusters and the perichromatin granules are particularly well visible (Figure 11.4). By contrast, the nuclear envelope as well as all the membrane rich cytoplasmic structures (i.e., Golgi apparatus, mitochondria, and endoplasmic reticulum) are unstained or very faintly stained. In the cytoplasm (Figure 11.2), only the ribosomes are clearly obvious.