1. Volume 13, Issue 10, Pages 517-525 (October 2003)
Oldies but goldies: searching for Christmas trees within the nucleolar architecture 
Ivan Raška 
Trends in Cell Biology 
Volume 13, Issue 10, Pages (October 2003)
DOI: /j.tcb

2. Figure 1
Schematic representation of human ribosomal genes and transcripts, and the structure of their host organelle, the nucleolus. (a) A schematic representation of human ribosomal RNA (rRNA) gene-array, rRNA gene and rRNA gene transcript. The sizes of both coding and non-coding sequences vary among species. (b) The ultrastructure of human-cell nucleoli. Arrows indicate perinucleolar condensed chromatin. f, d and g correspond to fibrillar centers (FCs), dense fibrillar components (DFCs), and granular components (GCs), respectively. The (recently) nascent RNAs, labeled in vivo by incorporation of bromouridine and detected by gold particles (black dots), are within nucleoli, confined to DFCs. Reprinted from [55] by copyright permission of the Rockefeller University Press. Bar represents 0.2 μm.
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3. Figure 2
Electron micrograph of a nucleolus fixed in situ and spread nucleolar chromatin from mouse cells. (a) Thin-sectioned nucleolus from a mouse cell. Black arrows indicate perinucleolar condensed chromatin, and the asterisk shows dense fibrillar components (DFCs) clump in fibrillar centers (FCs). f, d and g correspond to FC, DFC and granular components (GCs), respectively. This image was provided by Ulrich Scheer, University of Würzburg. (b) Spread CT (Christmas tree structure) (∼4 μm long) from a mouse cell is shown at the same magnification as (a). (b) is reprinted from [11] by copyright permission of Wiley–Liss, Inc, a subsidiary of John Wiley & Sons, Inc. Bar represents 0.5 μm.
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4. Figure 3
Manually isolated, resin-embedded and thin-sectioned grasshopper oocyte nucleus. (a) Detailed view of an electron-lucent ‘nucleolar pocket’ with many Christmas trees (CT) structures (black arrows) together with an image of a nucleolus (inset). Note the presence of numerous highly electron-dense structures (white arrows), reminiscent of CTs in ‘dense fibrillar components’ (DFCs). Arrowheads show CTs that line up at the border between ‘DFCs’ and the ‘nucleolar pocket’. (b–e) Detailed views of individual CTs. The arrow in (b) designates a cross-sectioned CT; arrows in (c) designate the ‘trunk’ of CT. Reproduced from [24] by copyright permission of Springer-Verlag, GmbH & Co. Bars represent 0.5 μm (a) and 0.2 μm (b–e).
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5. Figure 4
Microscopical mapping of nucleolar transcription signal in resin-embedded and thin-sectioned permeable human cells. (a) Electron microscope (EM) image showing nucleolar transcription signal, which consists of numerous clusters of gold particles in dense fibrillar components (DFCs). The colored inset shows the corresponding light microscope (LM) image, where newly synthesized RNA is shown in red and nucleic acids are counterstained with YOYO-1 dye (green). (b) Magnified image of boxed area in (a). f, d and g correspond to fibrillar centers (FCs), dense fibrillar components (DFCs), and granular components (GCs), respectively. (c) Superimposed images of inverse EM (cyan) from (a) and a LM transcription signal (red) from the inset in (a). Note that the LM signal is present not only in DFCs but also in fibrillar centers (FCs) and the proximal part of the granular components (GCs). (d) After its deconvolution, the LM signal, shown in (c), is primarily seen in FCs but not in DFCs. Reproduced from [32,55] by copyright permission of the Rockefeller University Press and Elsevier. Bars represent 0.2 μm (a,c,d), 0.5 μm (b).
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6. Figure 5
Proposed model of the arrangement of Christmas tree (CT) structures in animal cells, where dense fibrillar components (DFC) encompass CTs. In this model, the schematic patterns of CTs as they appear in figure 2b–e are used. FC, fibrillar centers and GC, granular components.
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7. Fig. I
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8. Fig. I
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9. Fig. I
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