Effect of Spinal Fixation in Rabbits With Metastatic Tumor Using a Novel Spinal Fusion Model

STUDY DESIGN

An experimental assessment of the impact of spinal stabilization on metastasis growth using a rabbit model.

OBJECTIVE

To investigate the influence of spinal stabilization on the growth of metastatic spinal tumors in rabbits using a novel method of spinal fusion.

SUMMARY OF BACKGROUND DATA

For spinal metastasis patients, gait disturbances caused by back pain or paraplegia correlates with their prognosis. Palliative surgeries are good options for some patients; however, the appropriate timing and method of spinal surgery remains controversial.

METHODS

The biomechanical properties of a novel spinal fixation model with a locking plating system were first examined on the L2-L4 fixed vertebrae of 18 Japanese white rabbits. Biomechanical and radiographic examinations were performed at 0, 4, and 8 weeks as compared with controls. After this, another 31 rabbits were then inoculated with VX2 carcinoma cells into the L3 vertebral body and divided into fixation (N=16) and sham (N=15) groups to assess the impact of spinal stabilization on tumor growth. The time to paraplegia, and tumor cell growth and proliferation were evaluated by rabbit behavior, computed tomography, myelogram, and cell proliferation marker (MIB-1 index).

RESULTS

In the biomechanical loading test, fixed segments showed one eighth of the range of motion and 15 times bending stiffness as compared with controls at each timepoint. No pathologic fractures were observed in the rabbits inoculated with VX2 carcinoma cells before paraplegia, and there was no difference in the time to paraplegia between the fixation and sham groups (26.7 and 28 d, respectively). Similarly, no differences were observed in osteolytic area expansion or tumor cell proliferation (MIB-1 index; 38.1% and 38.0%, respectively).

CONCLUSIONS

Our locking plate fixation of rabbit spines exhibited sufficient biomechanical properties. Spinal fixation had little influence on the growth of the aggressive carcinoma and the time to paraplegia. However, further investigation is needed to determine the influence of spinal stabilization on slow-growing tumors.

Separating Reflective and Fluorescent Components Using High Frequency Illumination in the Spectral Domain

Hyperspectral imaging is beneficial to many applications but most traditional methods do not consider fluorescent effects which are present in everyday items ranging from paper to even our food. Furthermore, everyday fluorescent items exhibit a mix of reflection and fluorescence so proper separation of these components is necessary for analyzing them. In recent years, effective imaging methods have been proposed but most require capturing the scene under multiple illuminants. In this paper, we demonstrate efficient separation and recovery of reflectance and fluorescence emission spectra through the use of two high frequency illuminations in the spectral domain. With the obtained fluorescence emission spectra from our high frequency illuminants, we then describe how to estimate the fluorescence absorption spectrum of a material given its emission spectrum. In addition, we provide an in depth analysis of our method and also show that filters can be used in conjunction with standard light sources to generate the required high frequency illuminants. We also test our method under ambient light and demonstrate an application of our method to synthetic relighting of real scenes.

Radiation-induced colour changes in a spiropyran/BaFCl:Eu2+/polystyrene composite film and nonwoven fabric

A spiropyran dye and BaFCl:Eu²⁺ containing polystyrene (PS) film and nonwoven fabric successfully detects X-ray exposure doses in the order of milligray (mGy).

Gaze Estimation From Eye Appearance: A Head Pose-Free Method via Eye Image Synthesis

In this paper, we address the problem of free head motion in appearance-based gaze estimation. This problem remains challenging because head motion changes eye appearance significantly, and thus, training images captured for an original head pose cannot handle test images captured for other head poses. To overcome this difficulty, we propose a novel gaze estimation method that handles free head motion via eye image synthesis based on a single camera. Compared with conventional fixed head pose methods with original training images, our method only captures four additional eye images under four reference head poses, and then, precisely synthesizes new training images for other unseen head poses in estimation. To this end, we propose a single-directional (SD) flow model to efficiently handle eye image variations due to head motion. We show how to estimate SD flows for reference head poses first, and then use them to produce new SD flows for training image synthesis. Finally, with synthetic training images, joint optimization is applied that simultaneously solves an eye image alignment and a gaze estimation. Evaluation of the method was conducted through experiments to assess its performance and demonstrate its effectiveness.

From Intensity Profile to Surface Normal: Photometric Stereo for Unknown Light Sources and Isotropic Reflectances

We propose an uncalibrated photometric stereo method that works with general and unknown isotropic reflectances. Our method uses a pixel intensity profile, which is a sequence of radiance intensities recorded at a pixel under unknown varying directional illumination. We show that for general isotropic materials and uniformly distributed light directions, the geodesic distance between intensity profiles is linearly related to the angular difference of their corresponding surface normals, and that the intensity distribution of the intensity profile reveals reflectance properties. Based on these observations, we develop two methods for surface normal estimation; one for a general setting that uses only the recorded intensity profiles, the other for the case where a BRDF database is available while the exact BRDF of the target scene is still unknown. Quantitative and qualitative evaluations are conducted using both synthetic and real-world scenes, which show the state-of-the-art accuracy of smaller than 10 degree without using reference data and 5 degree with reference data for all 100 materials in MERL database.

Articular cartilage endurance and resistance to osteoarthritic changes require transcription factor Erg

OBJECTIVE

To determine whether and how the transcription factor Erg participates in the genesis, establishment, and maintenance of articular cartilage.

METHODS

Floxed Erg mice were mated with Gdf5-Cre mice to generate conditional mutants lacking Erg in their joints. Joints of mutant and control mice were subjected to morphologic and molecular characterization and also to experimental surgically induced osteoarthritis (OA). Gene expression, promoter reporter assays, and gain- and loss-of-function in vitro tests were used to characterize molecular mechanisms of Erg action.

RESULTS

Conditional Erg ablation did not elicit obvious changes in limb joint development and overall phenotype in juvenile mice. However, as mice aged, joints of mutant mice degenerated spontaneously and exhibited clear OA-like phenotypic defects. Joints in juvenile mutant mice were more sensitive to surgically induced OA and became defective sooner than operated joints in control mice. Global gene expression data and other studies identified parathyroid hormone-related protein (PTHrP) and lubricin as possible downstream effectors and mediators of Erg action in articular chondrocytes. Reporter assays using control and mutated promoter-enhancer constructs indicated that Erg acted on Ets DNA binding sites to stimulate PTHrP expression. Erg was up-regulated in severely affected areas in human OA articular cartilage but remained barely appreciable in areas of less affected cartilage.

CONCLUSION

The study shows for the first time that Erg is a critical molecular regulator of the endurance of articular cartilage during postnatal life and that Erg can mitigate spontaneous and experimental OA. Erg appears to do this through regulating expression of PTHrP and lubricin, factors known for their protective roles in joints.

A spiropyran-based X-ray sensitive fiber

This study attempted to visualize reversible X-ray radiation by using a poly-(l-lactic acid) (PLLA) composite fiber with an average diameter of 150 μm. The fiber contains photostimulable phosphor (PSP) BaFCl:Eu(2+) particles that are subsequently dyed with the photochromic spiropyran dye (1,3,3-trimethylindolino-6'-nitrobenzopyrylospiran) (6-nitro BIPS).

Adaptive Linear Regression for Appearance-Based Gaze Estimation

We investigate the appearance-based gaze estimation problem, with respect to its essential difficulty in reducing the number of required training samples, and other practical issues such as slight head motion, image resolution variation, and eye blinking. We cast the problem as mapping high-dimensional eye image features to low-dimensional gaze positions, and propose an adaptive linear regression (ALR) method as the key to our solution. The ALR method adaptively selects an optimal set of sparsest training samples for the gaze estimation via ℓ(1)-optimization. In this sense, the number of required training samples is significantly reduced for high accuracy estimation. In addition, by adopting the basic ALR objective function, we integrate the gaze estimation, subpixel alignment and blink detection into a unified optimization framework. By solving these problems simultaneously, we successfully handle slight head motion, image resolution variation and eye blinking in appearance-based gaze estimation. We evaluated the proposed method by conducting experiments with multiple users and variant conditions to verify its effectiveness.

Delineation of solution burst-phase protein folding events by encapsulating the proteins in silica gels

Many studies have shown that during the early stages of the folding of a protein, chain collapse and secondary structure formation lead to a partially folded intermediate. Thus, direct observation of these early folding events is crucial if we are to understand protein-folding mechanisms. Notably, these events usually manifest as the initial unresolvable signals, denoted the burst phase, when monitored during conventional mixing experiments. However, folding events can be substantially slowed by first trapping a protein within a silica gel with a large water content, in which the trapped native state retains its solution conformation. In this study, we monitored the early folding events involving secondary structure formation of five globular proteins, horse heart cytochrome c, equine β-lactoglobulin, human tear lipocalin, bovine α-lactalbumin, and hen egg lysozyme, in silica gels containing 80% (w/w) water by CD spectroscopy. The folding rates decreased for each of the proteins, which allowed for direct observation of the initial folding transitions, equivalent to the solution burst phase. The formation of each initial intermediate state exhibited single exponential kinetics and Arrhenius activation energies of 14-31 kJ/mol.

Systemic Administration of Granulocyte Colony-Stimulating Factor for Osteochondral Defect Repair in a Rat Experimental Model

OBJECTIVE

The objective of this study was to assess the effect of granulocyte colony-stimulating factor (G-CSF) on osteochondral defect repair in the rat knee.

DESIGN

Twenty-six 12-week-old male Lewis rats were randomly divided into 2 groups. From day 0 to day 4, the G-CSF group received glycosylated G-CSF, and the control group received phosphate-buffered saline. A 1.5-mm diameter and 1.0-mm deep osteochondral defect was introduced in the patellar groove of the bilateral femur in all rats on day 4. The peripheral blood nucleated cells were counted for 14 days from the first day of injection, the appearance of the cartilage repair was observed histologically and macroscopically for 2, 4, 8, 12, and 24 weeks after surgery.

RESULTS

The number of peripheral blood leukocytes increased 3 days and returned to normal levels 7 days after the first injection. Compared with the control group, the G-CSF group had more fibrous and/or bony tissue at earlier points in time. The tissue repair rate, which is defined as the percentage of repaired osteochondral defects, was significantly higher in the G-CSF group 4 weeks after surgery. However, there were no significant differences in the cartilage repair rate and the modified Wakitani score between the 2 groups at each time point.

CONCLUSIONS

The defect filling was significantly better in the G-CSF group in the early phases. Our findings suggest that G-CSF may promote the repair of osteochondral defects by mediating an increase in the number of peripheral blood nucleated cells.