Preservation of Tissue Cells
Figure 6 : A single soft osteocyte from Triceratops horn. Delicate fi lipodia extend out to connect with other cells (white arrows). Scale bar = 4 µm.
temporal limits on molecular preservation over millions of years [ 13 ]. In the case of soſt vessels recovered from dinosaur femur specimens, it seems reasonable that these tissues were seques- tered from the elements and from biological scavenging activity because of deep encapsulation within compact bone. Within the Triceratops horn, however, which was highly vascular, no seques- tration was likely because all of the vessels were openly exposed to air, soil, water, scavengers, dissolved salts and minerals, and the freeze-thaw cycle and heat of Montana seasonal weather; yet a high degree of preservation persists. While plant roots, fungal hyphae, and insect remains were all found traversing the horn, soſt fi brillar sheets of bone and well-preserved osteocytes remain. Discoveries of soſt blood vessels, RBC-like microstruc-
tures, and soſt bone osteocytes have been controversial [ 8 – 10 ]. One criticism maintained that these soſt tissue discoveries are not endogenous tissues but rather the remains of bacterial biofi lms, which “retain much of the original morphology” of dinosaur bone osteocytes and fi lipodia [ 8 ]. However osteocytes from other dinosaur specimens were later demonstrated to contain actin, tubulin, and histone H4 proteins, which are not found in bacteria or bacterial biofi lms. T ese osteocyte proteins are consistent with other dinosaur protein fi nds [ 7 ].
Figure 8 : White box surrounding delicate bifurcated termination of fi lipodia. Smooth edges of dendrite indicates the high degree of preservation. Scale bar = 7 µm.
Uncoated specimens of decalcifi ed bone in this study yielded osteocytes with a higher degree of ultrastructural preser- vation than previously reported [ 3 , 6 , 9 , 12 ]. Uncoated bone surfaces show lacunae depressions ( Figures 5 – 7 ), extensive fi lopodia ( Figures 6 – 10 ), collagen aggregates ( Figure 7 ), and cell surfaces displaying the indented impressions of overlying and compressing bone ( Figures 6 and 8 ). Figures 9 and 10 show cells that were successfully isolated
from fi brillar bone. In future work, it is hoped that individual cells such as these can be examined using immunohistochem- istry for the presence of endogenous proteins.
Conclusion Claims of contamination and biofi lm replication have
been dismissed [ 7 , 12 ], and identifi cation of intra-cellular and intra-nuclear proteins have been verifi ed showing that these are endogenous dinosaur tissues [ 12 ]. T erefore claims that these are not original dinosaur tissues appear to be questionable.
Figure 7 : Fine structure fi lipodia extend as dendrites from two soft osteocytes in Triceratops horn (white arrows). Black arrow is pointing to a band of collagen. Scale bar = 10 µm.
2016 January •
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Figure 9 : Isolated and washed Triceratops soft bone osteocyte under light microscopy. Cells often contained nucleus-like microstructures (black arrow). Scale bar = 5 µm.
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