Differences in the Microarchitectural and Histomorphologic Characteristics Between Glucocorticoid-induced Osteonecrosis of Femoral Head and Alcohol-induced Osteonecrosis of Femoral Head

AimsTo analyze microarchitecture and histomorphology characteristics of different regions in femoral heads from patients with glucocorticoid-induced osteonecrosis of femoral head (GIONFH) and alcohol-induced osteonecrosis of femoral head (AIONFH). MethodsPatients diagnosed with GIONFH and AIONFH were recruited. Femoral heads were obtained after total hip replacement. Micro-CT was applied to evaluate the microstructure of 9 regions of interest (ROIs) in the femoral head. Along the supero-inferior orientation, the femoral head was divided into necrotic region, reactive interface, and normal region; along the medio-lateral orientation, the femoral head was divided into medial region, central region and lateral region. Decalcified and undecalcified bone histology were then performed to assess histopathological alterations and bone remodeling levels. Results42 GIONFH patients (50 hips) and 43 AIONFH patients (50 hips) anticipated in the study. In the necrotic region, most of the microarchitectural parameters did not differ significantly between GIONFH and AIONFH, whereas both the reactive interface and normal region illustrated significant differences in the microstructure and histomorphometry. The reactive interface and normal region exhibited a less sclerotic microarchitecture, but a higher bone remodeling level in GIONFH as compared with AIONFH. Despite similar necrotic pathological manifestations, subchondral trabecular microfracture in the necrotic region was more severe and vasculature of the reactive interface was more abundant in GIONFH. ConclusionsAlthough these two subtypes of ONFH shared similar microarchitecture and pathological features in the necrotic region, GIONFH exhibited a less sclerotic microarchitecture and a more active bone metabolic status in both the reactive interface and normal region.

Abstract 16758: Presence of Left Atrial Fibrosis Contributes to Aberrant Hemodynamics and Increased Risk of Stroke in Atrial Fibrillation Patients

Introduction: Atrial fibrillation (AF) patients are at high risk of stroke, with the left atrial appendage (LAA) found to be the most common site of clot formation. Left atrial (LA) fibrosis is also associated with higher stroke risk. However, the mechanisms for increased stroke risk in patients with atrial fibrotic remodeling are poorly understood. We sought to explore these specific mechanisms using fluid dynamics analysis. Hypothesis: The presence of LA fibrosis leads to aberrant hemodynamics in the atria, contributing to increased stroke risk in AF patients. Methods: We retrospectively collected LGE-MRI images of 3 AF patients and reconstructed their 3D LA endocardial surfaces. Fibrotic regions were identified as those with intensity 3 standard deviations greater than the mean LA blood-pool intensity. Personalized computational fluid dynamic simulations were performed, and hemodynamics at the LA wall were quantified by wall shear stress (WSS, friction of blood) and oscillatory shear index (OSI, temporal directional change of WSS). For each case, WSS and OSI were compared between fibrotic and normal regions. Results: WSS was significantly lower in the fibrotic region as compared to normal region for all 3 cases. Additionally, OSI was higher in the fibrotic region as compared to normal region for all 3 cases. However, this different was statistically significant for cases 1 and 3; case 2 was not statistically significantly different. Low WSS and high OSI in the vicinity of the fibrotic wall suggest that local blood-flow was slow and oscillating, enabling pro-thrombotic conditions for circulating blood. Conclusion: LA fibrosis correlates with regions of aberrant hemodynamics, which renders it susceptible to blood thrombosis. AF patients with high LA fibrosis burden will have more pro-thrombotic regions, in addition to low flow in the LAA, providing more sites for a potential clot formation. These conditions might get exacerbated during an AF event and cause stroke.

Evaluation of regenerated tracheal cilia function on a collagen-conjugated scaffold in a canine model

OBJECTIVES It is unclear whether the movement and function of the regenerated cilia on collagen-conjugated artificial trachea are the same as those of normal cilia. This study assessed the ciliary beat frequency (CBF) and ciliary transport functions (CTFs) of regenerated cilia in a canine model. METHODS A tracheal defect introduced into the anterior portion of the cervical trachea of an adult beagle dog was covered with a collagen-conjugated prosthesis. Two months later, the trachea was harvested along the long axis, both from normal and regenerated regions. The cilia were stained with isothiocyanate-conjugated wheat germ agglutinin, and their movement was monitored with a high-speed camera to analyse CBF and CTF. Four samples each were obtained from the regenerated and normal regions for CBF analysis and 7 samples each were obtained for CTF analysis. RESULTS The wheat germ agglutinin-stained cells showed well-regulated beats in both the regenerated and normal regions of the trachea. Mean CBF in the regenerated and normal regions did not differ significantly (7.11 ± 0.41 vs 7.14 ± 1.09 Hz; P = 981). By contrast, CTF was significantly lower in the regenerated region than in the normal region (30.0 ± 6.62 vs 7.43 ± 0.58 μm/s; P = 0.005). CONCLUSIONS Mean CBF in the regenerated and normal regions did not differ significantly at 2 months. The CTF in the regenerated region recovered partially but remained lower than those in the normal region. Methods are needed to improve the CTF of regenerated cilia.

Bi-abundance photoionization models of planetary nebulae: determining the amount of oxygen in the metal-rich component

ABSTRACT We study the hypothesis of high-metallicity clumps being responsible for the abundance discrepancy found in planetary nebulae between the values obtained from recombination and collisionally excited lines. We generate grids of photoionization models combining cold metal-rich clumps emitting the heavy element recombination lines, embedded in a normal metallicity region responsible for the forbidden lines. The two running parameters of the grid are the metallicity of the clumps and its volume fraction relative to the whole nebula. We determine the density and temperatures (from the Balmer jump and the [O iii] 5007/4363 Å line ratio) and the ionic abundances from the collisional and recombination lines, as an observer would do. The metallicity of the near-to-solar region is recovered, while the metallicity of the clumps is systematically underestimated by up to two orders of magnitude. This is mainly because most of the Hβ emission is coming from the ‘normal’ region, and only the small contribution emitted by the metal-rich clumps should be used. We find that a given ADF(O++) can be reproduced by a small amount of rich clumps, or a bigger amount of less rich clumps. Finally, comparing with the observations of NGC 6153, we find two models that reproduce its ADF(O++) and the observed electron temperatures. We determine the fraction of oxygen embedded in the metal-rich region (with a fraction of volume less than 1 per cent) to be roughly between 25 per cent and 60 per cent of the total amount of oxygen in the nebula (a few 10−3M⊙).

Effect of Melting Interruption on Composition and Microstructure of BT22 Ingot in VAR

BT22 ingot was remelted by vacuum arc remelting (VAR) furnace with a melting rate of 20kg/min. The power of VA R was interrupted for five minutes when the weight of the remelted ingot is approximately 4000 kg. The melting process was then resumed at the same melting rate after the five minutes interruption. Optical microscopy (OM), inductively coupled plasma-mass spectrometry (ICP-MS) and electron probe micro analyzer (EPMA) were utilized to analyze the microstructure, composition and distribution of elements. No significant microstructural difference was oberved at the remelting interrupted region. The variation of Al, Mo, V, Cr, Fe contents between the melting interruption region and normal region is within 0.23 wt%. The distribution of elements in equiaxed grains of the melting interruption region and the normal regions were compared by EPMA analysis. The contents of Al, V, Fe and Cr increase from the center of equiaxed grains to their grain boundaries. The content of Mo decreases from the center of equiaxed grains to their grain boundaries. The trend of element content in the normal region is similar to that of the melting interrupted region. Key words: BT22; ingot; composition; microstructure