Preservation of Tissue Cells
Figure 2 : Soft blood vessel wall extending from Haversian canal (black arrow), Triceratops rib. Scale bar = 20 µm.
gold for 90 seconds at 20 mA and were imaged at 30 kV under high vacuum in a Hitachi S2500 SEM. Bone specimens in Figures 5 – 6 were leſt uncoated and imaged at 10 kV in a Zeiss EVO SEM with a backscatter electron detector. Bones in Figures 7 and 8 were leſt uncoated by metal and imaged in a Zeiss EVO SEM at 3.1 10 -4 Pa with a secondary electron detector.
Results
Fibrillar Bone . Soſt , stretchy sheets of fi brillar bone tissue exhibited layers of bone cells (osteocytes). T ese would come into focus depending on the layer imaged in light microscopy ( Figure 1 ).
Blood vessels . Soſt blood vessels (arrow in Figure 2 ) extended from many Haversian canals in the fractured rib. It is clear that when the living vessel was fully extended by blood and serum, it tightly abutted against the undulations in the Haversian canal wall. Spherical microstructures, consistent with the size and shape of RBCs, were observed in the lumens of many vessels in non-decalcifi ed Triceratops rib specimens
Figure 4 : Blood vessels from decalcifi ed sample of Triceratops horn. Cross-linking Volkman’s canals are evident (white arrows). It was on the surfaces of these blood vessels where soft bone osteocytes were found (discrete dots on vessels). Scale bar = 1 mm.
( Figure 3 ). T e amount of rib material collected did not allow for decalcifi cation experiments, therefore it is unknown if large regions of soſt vessels within the rib were preserved. Horn blood vessels appeared to be permineralized aſt er
decalcifi cation removed the bone mineral ( Figure 4 ). Volkmann canals were present ( Figure 4 arrows), and the outside surfaces of vessels were wrapped in soſt fi brillar bone sheets. Figures 4 and 5 show many osteocytes on the surface of these sheets as well as within adjoining sheets of fi brillar bone (small white dots on the surfaces of vessels, in Figure 4 and arrows on Figure 5 ). Bone cells . Osteocytes imaged with SEM exhibited smoothly tapered fi lopodia, which extended to 20 µm in length in some instances (white arrows in Figures 6 and 7 ). A band of preserved collagen is labeled with a black arrow in Figure 7 .
Discussion T e remarkable preservation of delicate ultrastructures such
as fi lopodia and cell-to-cell junctions (white arrows, Figures 6 and 7 ) has resisted a simple explanation despite hypothesized
Figure 3 : Spherical microstructures, consistent with size of RBCs, within Haversian canal of Triceratops rib. Scale bar = 40 µm.
20
Figure 5 : Numerous soft bone osteocytes are seen on the surface of a blood vessel (white arrows). Scale bar = 35 µm.
www.microscopy-today.com • 2016 January
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68