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Blood Clots in Dinosaur Bones


attacking nature of the radicals; “Some of these reactions are chain processes, with a greater concentration of amino acids dam- aged than initial attacking radicals gener- ated,” and “15 amino acids [are] consumed per HO generated which is modest by com- parison with lipid peroxidation.” Balla et al. [28] found that iron-derived reactive oxy- gen species are responsible for “numerous vascular disorders,” and are highly toxic to cells because of “the ease with which this highly hydrophobic compound can enter and cross cell membranes,” leaving oxi- dized, damaged, and dead cells. Other workers add, “DNA, proteins,


Figure 6: Higher magnification from Figure 5 showing undulating white Bands of Fontana (arrows). Scale bar, 20 µm.


must be lysed, hemoglobin must be released (and degraded), and oxygen and water must be present to generate hydroxyls. Te highly reactive hydroxyl (HO) and peroxyl (HOO) spe-


cies generated during Fenton chemistry are known to be highly destructive to biomolecules [27,28,32–36]. McCord [34] has stated, “Tis hydroxyl radical can attack all classes of biologi- cal macromolecules. It can depolymerize polysaccharides, cause DNA strand breaks, inactivate enzymes and initiate lipid peroxi- dation … lipid peroxidation is a chain reaction … ”. Hawkins and Davies [32] note that it can be frustrating to determine the sites of radical attack on large proteins because of the chain-reaction


lipids and other organics are damaged and destroyed by oxidative radicals” [35]. Schaer et al. [37] have remarked, “When hemo- globin (Hb) bursts from RBCs because of hemolysis, the naked Hb, devoid of its anti- oxidant sentries that are normally available


within the RBC, can wreak oxidative havoc in the vasculature and in exposed tissues.” Tey add, “ … Hb and hemin (oxidized heme) trigger vascular and organ dysfunction that


leads to adverse


clinical effects.” Loures et al. [33] list the reduction potential of hydroxyl radicals as second only to fluorine and show they are 30% more reactive than peroxyl radicals. Tus, it is well established that Fenton reactions can be


highly destructive to cells, tissues, and proteins. Tis high reac- tivity, and in theory ability of free iron to destroy cell mem- branes, should destroy more tissues than it helps. However, in the case of the Triceratops horn collected from the Hell Creek Formation, filipodia from bone osteocytes imaged just outside of


the vessel canals


are long and unfragmented (Figure 7, see arrows), suggesting that Fenton reactions never occurred within the lacuno-cana- licular network of the horn and thus never acted on cell membranes or filipodial extensions.


What of Clotting? Schweitzer et al. took extraordinary


measures to inhibit thrombosis during experiments conducted on ostrich vessels soaked in hemoglobin [11]. Chicken and ostrich blood collected for the harvesting of heme was infused with anticoagulant (EDTA) upon collection. It was subse- quently centrifuged at high rpm and later filtered to separate plasma, serum, cells (white cells and platelets), cell debris (aſter red blood cells were mechanically lysed), and all associated tissue factors and co- clotting factors that


initiate and regu-


Figure 7: SEM of uncoated Triceratops horn (HCTH-03) osteocyte with 24 µm long filipodia (arrows, left side). Scale bar, 1 µm.


34


late the normal thrombotic reaction. A more rigorous experimental investigation would benefit by real-world conditions of buried animal remains.


www.microscopy-today.com • 2020 September


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