Cajal bodies (that have many other names as well, best one might be nucleolar accessory body) typically have a coiled architecture. I wonder if this is part of a necessary architecture, or whether is has been recognized as such because it was easy to identify, but Cajal bodies could possibly exist without such coiling, or better yet, maybe there are several different steps in the coiling in Cajal bodies, a a coarse coiling (50 nm thread width) and a fine coiling (5 nm thickness). I vote for the latter.  I think the rounded shape and polar position on the nucleolus, and the whole Cajal body size (it is a pretty large nuclear structure and was discovered first by light microscopy – the resolution of a structure there would be about 0.2 microns… so 200 nm).

My points: logs of transcriptional activity is found in neurons, in dividing cells, in cancer cells, but it has been my observation that there is also lots of activity in apoptosis.  It is something I hope to pursue, that is, whether the rounded structures, perinucleolar, the right size and shape for a Cajal body, but with out the coarse thread-look) might be a variation on a Cajal body, in anticipation of taking the cell down the route to apoptosis.

Really frustrating search for other images of Cajal bodies online, and one article published in a respectable journal talks about Cajal bodies WITHOUT an ultrastructural pix — who does that.

So this nucleolus is in an hepatocyte, the hepatocyte is highly active, there is little condensed chromatin the cytoplasm is full of vesicles, and mitochondria show oxidative stress, all in all a pretty taxes cell, and the reason is that it is a Gclc ko mouse, at 28 days, without any rescue antioxidant treatment and the hepatocytes are in the process of undergoing apoptosis. So this particular nucleolus, shows no dense fibrillar component around the fibrillar centers, and it has dense areas NOT the dense granular component, ut much more coiled and dense, and i think they look like Cajal bodies (but these would be bodies that do not have the 50 nm coiling, but seemingly the very much thinner filaments, those of 5 nm)  this is speculation at the moment, but I will add more info.

17740_73229_#203_mouse_wc/ii 28d, no NAC.   The dark round thing i think is the Cajal body is many hundred nm  in diameter,  bar = 300 nm, based on the size of several ribosomes (estimated at 27 nm diameter)(inset).

The nucleus is a terrific place to do electron microscopy. Aside from the non-membrane bound elements within which increase the difficulty for any attempts at reconstruction in 3D (at least in my mind) the micro-environmental pressures push this dynamic organelle to rapidly change and adapt. The nucleus here had one particular area that caught my eye, that is the fibrillar center – dense fibrillar component (within the black box) of the top figure. The electron micrograph is from liver and it shows a fibrillar center with a circular (perhaps more octagonal) shape (as do most fibrillar centers) but the arms of the dense fibrillar component extend in a rotational pattern. In this case there are four long spiral arms and four short spiral arms (think “galaxy” with spiral arms). This is not seen often and it may be chance but not likely, in my opinion, particularly when one views the old time lapse videos of cells in culture and sees the nucleus and nucleolus spinning like little worlds in the medium called space. Rotational forces are alive and well within the cell and it is not a big stretch to witness their effects.

That said, here is a little fantasy (all else preceding is for real) — would galaxy arms of the dense fibrillar component in all cells go the same direction?, would it be clockwise, would the dense fibrillar component drag off to the counter counter-clockwise south of the equator,  ha ha. For real, this is not a pattern I have seen described in the literature, nor recognized in the thousands of electron micrographs of my own, and thousands of others viewed, but I predict it will appear again and again.

Top figure is the original micrograph of a mouse hepatocyte,  exposure evened in photoshop, one tiny scratch is patched (dare you to find it) without affecting interpretation. Black box surrounds the nucleolar fibrillar center and spiral arms of the dense fibrillar components which were copied and enlarged from the original micrograph.  Inset lower left: burn tool in photoshop enhances direction of the galactic arms of the dense fibrillar component (which is visible in the original before emphasis), light central area is the fibrillar center.  Diagram in lower right – stick figure for orientation, FC, fibrillar center of the inset to left, DF dense fibrillar component (galactic arms), and GC granular component. 12531_73229_#203 wc/ii liver 28d.