ABSTRACT:The in vivo effects of coating titanium implants with organic extracellular matrix molecules were examined in the sheep tibia.Titanium screws (5.0 mm) were coated with type I collagen (Ti/Coll) or type I collagen and chondroitin sulfate (Ti/Coll/CS) by biomimetic fibrillogenesis. Uncoated screws (Ti) and screws coated with hydroxyapatite (Ti/HA) served as control. Six adult female sheep received one screw of each type to stabilize a midshaft tibial fracture with external fixation. Four cylindrical implants of 4-mm outer diameter and 3.3-mm inner diameter with the same coatings were inserted into the tibial head. No pin track infections were seen at the time of implant retrieval 6 weeks after implantation. Extraction torque was greater for Ti/HA (1181 Nmm) and Ti/ Coll/CS (1088 Nmm) compared to Ti/Coll (900 Nmm) and Ti (904 Nmm) [N.S.]. Newly formed bone was noted around all coated screws within the medullary cavity. Macrophage and osteoclast activity was significantly reduced around Ti/Coll/CS in both types of implants compared to uncoated controls (p < 0.05). Osteoblast activity was significantly increased around loaded Ti/Coll and Ti/Coll/CS screws compared to uncoated Ti screws (p < 0.05). Microtomographic evaluation (SRmCT) revealed no significant differences in new bone formation around the unloaded tibial head implants.Coating of external fixation devices with of type I collagen and chondroitin sulfate appears to have similar effects with respect to stability and bone healing as HA but with less osteoclast activity. These findings were more pronounced under loaded than unloaded conditions in the sheep tibia. ß

Osteohistology, the study of bone microstructure, provides an important avenue for assessing extinct and extant vertebrate growth and life history. Cortical vascularity and collagen fibre organization are direct reflections of growth rate, while bone growth marks are indicative of absolute age. However, each skeletal element has its own ontogenetic trajectory and microstructure of certain bones may not be a true representation of whole body growth. Extensive comparative study of modern taxa

Analysis of ontogenetic changes in long bone microstructure aid in vertebrate life history reconstructions. Specifically, osteohistological examination of common fauna can be used to infer growth strategies of biologically uncommon, threatened, or extinct vertebrates. Although nine-banded armadillo biology has been studied extensively, work on growth history is limited. Here we describe long bone microstructure in tibiae and femora of a limited ontogenetic series of nine- banded armadillos ( Dasypus novemcinctus ) to elucidate patterns of bone growth. The cortex of the smallest individual is composed of compacted coarse cancellous bone (CCCB) and woven tissue. Extensive cortical drift is driven by periosteal erosion and further compaction of trabeculae resulting in an increase in the amount of CCCB. The cortex of the largest specimens is primarily CCCB with thickened endosteal bone and thin outer cortices of lamellar and parallel-fibered tissue. The outer cortices of the largest individuals are interpreted as an external fundamental system (EFS) indicating a cessation of appositional bone growth corresponding to skeletal maturity (i.e. asymptotic or adult size). The EFS forms in femora prior to tibiae, indicating femoral growth rates begin decreasing earlier than tibial in D . novemcinctus . Growth trends in common fauna like the nine-banded armadillo can be used as a foundation for understanding life histories of related, but uncommon or extinct, species of cingulates.

Histological examination of bone microstructure provides insight into extant and extinct vertebrate physiology. Fossil specimens sampled for histological examination are typically first embedded in an inexpensive polyester resin and then cut into thin sections, mounted on slides, and polished for viewing. Modern undecalcified bone is chemically processed prior to embedding in plastic resin, sectioning, mounting, and polishing. Conversely, small fossil material and modern undecalcified bone are typically embedded in higher priced epoxy resin because these specimen types require final sections near or below 100 µm thick. Anecdotal evidence suggests thin sections made of polyester resin embedded material polished thinner than 100 µm increases likelihood of sample peeling, material loss, and is unsuitable for modern tissue and small fossil material. To test this assertion, a sample of modern bones and fossil bones, teeth, and scales were embedded in either polyester resin or epoxy resin. Embedded specimens were sectioned and mounted following standard published protocol. Thin sections were ground on a lapidary wheel using decreasing grit sizes until tissue microstructure was completely discernible when viewed under a polarizing light microscope. Additionally, eight prepared thin sections (four from polyester resin embedded specimens and four from epoxy resin embedded specimens) were continuously ground on a lapidary wheel using 600 grit carbide paper until peeling occurred or material integrity was lost. Slide thickness when peeling occurred was measured for comparing slide thickness when specimen integrity was lost between the two resin types. Final slide thickness ranged from 38 µm to 247 µm when tissue was identifiable using a polarizing microscope. Finished slide thickness varied between resin types despite similar tissue visibility. However, finished slide thickness appears more dependent on hard tissue composition than resin type. Additionally, we did not find a difference of slide thickness when material was lost between resin types. The results of this preliminary study suggest that polyester resins can be used for embedding undecalcified modern hard tissues and fossilized hard tissues without loss of tissue visibility or material integrity, at least in the short term.

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BackgroundRisk stratification of patients with non-ischemic dilated cardiomyopathy remains a matter of debate in the era of device implantation.ObjectiveWe investigated associations between histopathological findings, contrast-enhanced cardiac MRI and the inducibility of ventricular tachycardia (VT) or fibrillation (VF) in programmed ventricular stimulation.Methods56 patients with impaired left ventricular ejection fraction (LVEF≤50%, mean 36.6±10.5%) due to non-ischemic dilated cardiomyopathy underwent cardiac MRI, programmed ventricular stimulation, and endomyocardial biopsy and were retrospectively investigated. Inducibility was defined as sustained mono- or polymorphic VT or unstable VT/VF requiring cardioversion/defibrillation. Primary study endpoint was defined as the occurrence of hemodynamically relevant VT/VF and/or adequate ICD-therapy during follow-up.ResultsEndomyocardial biopsy detected cardiac fibrosis in 18 (32.1%) patients. Cardiac MRI revealed 35 (62.5%) patients with positive late gadolinium enhancement. VT/VF was induced in ten (17.9%) patients during programmed ventricular stimulation. Monomorphic VT was inducible in 70%, while 20% of patients showed polymorphic VT. One patient (10%) presented with VF. Inducibility correlated significantly with the presence of positive late gadolinium enhancement in cardiac MRI (p<0.01). We could not find a significant association between inducibility and the degree of cardiac inflammation and fibrosis in non-site directed routine right ventricular endomyocardial biopsy. During a mean follow-up of 2.6 years, nine (16.1%) patients reached the primary endpoint. Monomorphic VTs were found in 66.7% patients and were terminated by antitachycardia pacing therapy. One patient with polymorphic VT and two patients with VF received adequate therapy by an ICD-shock. However, inducibility did not correlate with the occurrence of endpoints.ConclusionInducibilty during programmed ventricular stimulation is associated with positive late gadolinium enhancement in cardiac MRI of patients with non-ischemic dilated cardiomyopathy. The presence of myocardial fibrosis or inflammation in undirected endomyocardial biopsy does not seem to be sufficient to predict future ventricular arrhythmias.

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