Daily Archives: July 24, 2017

Love in any language

Environment and contaminants, Nuclear pores and nuclear architecture, Science and art cover illustrations, The cell: images, Ultimate order, the cell

Totally unnecessary post of bone marrow nuclei: but what it says very clearly is that symmetry prevails, may not be the symmetry we expect from a set of identical chromosomes all lined up in on-off status, both sides the same (X chromosome or barr body excepted).  I see here a great symmetry, right to left mirror, top to bottom asymmetry, pointy at the bottom because this is an area where the nuclear membrane might just get segmented into a thin band between two bottom areas of chromatin…. going from what might appear to be a point, to two cheeks.

I am thinking about writing up an editorial on this symmetry…. make the cover submission first, always my motto.  Each of the hearts below is from bone marrow from an hypoplastic animal (CyP1a1null) either given benzo(a)pyrene or control diet.  These particular nuclei are not yet hypersegmented…  just fun examples of symmetry, which i have outlined in an identical micrograph below this.

four bone marrow nuclei polys chromatin condensation symmetryfour bone marrow nuclei polys chromatin condensationSo there is symmetry, it is bilateral in one dimension, but will take some thinking to see how to describe a third dimension in symmetry.

Because the chromosome territories likely (per published data) kind of interdigitate, most assuredly, at many sites along each chromosome for functional reasons) the symmetry will be highly simplified in light micrographs at best.

All this discussion could lead to a place to examine the chromatin patterns in the X (barr body) in neutrophils where they are hanging on by a nuclear membrane thread – so to speak) and other parts of the neutrophil nucleus where transcriptional activites are going on.

I found a match for what I see in bone marrow… yippie

Ultimate order, the cell

For at least one decade I have thought about some nuclear morphology, typically found in bone marrow in progenitor cells (mouse) particularly in mice who have been dosed with 125mg/kg/day benzo(a)pyrene (BaP) for 18 days, underpinned by the presence or lack of Cyp1a1 (Fig. 3. Histology of bone marrow) which showed severe hypolasia of the bone marrow and a significant increase in the hypersegmentation of the bone marrow cells (all kinds). Lymphocytes were increased regardless of BaP in the Cyp1a1(-/-) mice regardless of BaP treatment as was hypersegmentation. So this was interesting, but never pursued as a separate topic. I have micrographs which show this same bilateral segmentation, which may turn out to be portions of (or whole) chromosome territories. I searched the literature (the relatively current literature and current literature during the study and didn’t find anyone who had any images which would suggest the cause.

Then as chromosome territories became a target of interest, two very old (I mean really old) documents were cited in Cold spring Harbor Perspectives in Biology in 2010: (Cold Spring Harb Perspect Biol. 2010 Mar;2(3):a003889. doi: 10.1101/cshperspect.a003889. Chromosome territories. Cremer T, Cremer M.) listed as Rabl 1885, and Boveri 1909 (In the drawings of two cells in prophase from Ascaris megalocephala univalens embryos. He mentioned that these protrusions were germ line chromosomes.  This renewed my interest in trying to figure out which chromosomes were blipped out (or cued for hypersegmentation) in the null mice, and whether this indirectly relates simply to high levels of cell renewal in their hypodcellular bone marrow or whether it relates directly to the loss of CyP1a1 in mice somehow.

I have redrawn the figure of Boveri (1909) and added some images from bone marrow of hypersegmented cells (which I now assume to be specific chromosome territories of specific chromosomes, but which chromosomes is not known. Another interesting point is that Boveri thought that the two top cells were initially responsible for the two bottom cells (which he called daughter cells) and the difference in two vs four areas of chromosome blipping are evident (this would be high condensation and sort of a promise later of becoming an area tethered by a thin strand of nuclear membrane, or budded off as a microbody).  Certainly this man spent a lot of time at the microscope.  These types of symmetries, and associations are randomly seen usually and lots and lots of view-time are required before patterns emerge.

(Adding one more coincidence? comment! is that Boveri drew his cells with about a 64 degrees  of “arc” from approximate (obviously not know for sure –i dont even know if anyone has decided where the “center” of the nucleus actually is.. ha ha–i will have to google that). When i calculated the angular dimensions of the two similarly painted chromosomes in FISH and other fluorescent tags for chromosome territories, i could almost always envision and measure a distance of about 70 degrees between chromosomes.  This is kind of exciting, as it give bilateral symmetry to the nucleus which is NOT an exact mirror,  but something different.  The Arc of Separation between chromosomes I will have to research.