Experimental determination of in-medium cluster binding energies and Mott points in nuclear matter

In-medium binding energies and Mott points for d, t, 3He and α clusters in low-density nuclear matter have been determined at specific combinations of temperature and density in low-density nuclear matter produced in collisions of 47A MeV 40Ar and 64Zn projectiles with 112Sn and 124Sn target nuclei. The experimentally derived values of the in-medium modified binding energies are in good agreement with recent theoretical predictions based upon the implementation of Pauli blocking effects in a quantum statistical approach.

Magneto-optical stokes polarimetry and nanostructured magnetic materials

Stokes parameters fully characterize the polarization state of light in an experimentally accessible manner. Photoelastic modulator (PEM) based Stokes polarimetry offers a very high sensitivity which is particularly suitable for the investigation of the magneto-optical properties of nanostructured magnetic materials. In this paper, we shall describe a robust methodology recently developed by us that utilizes a dual PEM setup. As an example of its application, we report on the magneto-optical characteristics of focused Ga ion beam patterned Fe films. We have investigated Ga ion irradiation of single-layer polycrystalline Fe films deposited on Si3N4 substrates, which allows us to study the effects of ion implantation with minimum added complications. Complemented by structural and other characterization techniques, the absolute measurement of magneto-optical effects through the determination of Stokes parameters has enabled us to effectively separate the various contributions from film thinning due to sputtering, structural modifications and compositional changes caused by Ga incorporation. A comparison is also made between the magneto-optical behavior of patterned thin films and that of anodic aluminum oxide embedded magnetic nanowire arrays.

Chronic microstimulation of cat auditory cortex effective to evoke detection behaviors

The purpose of this study was to clarify stimulus pulse parameters effective to elicit behaviors of cats trained to detect electric pulse stimuli through chronically implanted electrodes in the primary auditory cortex. One or two pulse parameters were systematically shifted from the standard stimulus consisting of constant-current pulses of amplitude 80 μA, duration 0.2 ms, number of pulses 33, and rate 200 Hz (compatible with interpulse interval 5 ms). Interaction between the pulse amplitude and pulse duration was investigated: although the proportion of stimulus detection responses increased with increasing phase charge (pulse amplitude×pulse duration), a combination of relatively high amplitude during short pulse duration elicited a higher proportion of detection responses when phase charge was constant. Interaction between the number of pulses and interpulse intervals was investigated. We found that the proportion of detection responses is explained by the linear function of two factors, overall charge (phase charge×the number of pulses) and train duration: the proportion of detection responses increased with increasing overall charge and decreasing train duration. Interaction between pulse amplitude and the number of pulses was investigated. We again found that the proportion of detection responses is explained by the linear function of overall charge and train duration in the amplitude-number shift paradigm. Thus, the behavior performance (proportion of detection responses) is a linear time function of overall charge and train duration regardless of the stimulus paradigm. We believe that the findings will contribute to the development of auditory cortex implants for transfer of auditory information directly to the brain.

Deletion of estrogen receptor beta accelerates early stage of bone healing in a mouse osteotomy model

This study examined the role of estrogen receptor (ER) beta during mouse femoral fracture healing by employing ER knockout (KO) mice. The fracture healing in KO mice was enhanced in the early stage of neovascularization and the middle stage of endochondral ossification.

INTRODUCTION

This study was conducted to examine the role of ER beta during fracture healing.

METHODS

Female ERbeta knockout (KO) mice (18 weeks old) and age-matched female wild-type (WT) mice underwent open osteotomy on the right femur. They were sacrificed at 1, 2, 4 and 6 weeks post-fracture. The sera and callus samples were subjected to the following analyses: micro-computed tomography (CT)-based angiography, micro-CT evaluation, histological examination, histomorphometry examination, real-time polymerase chain reaction (PCR) analysis, biochemical marker, and mechanical testing.

RESULTS

Micro-CT-based angiography showed that the total vessel volume at the fracture site was larger in the KO group than the WT group at 1 and 2 weeks post-fracture. Micro-CT analysis revealed that the callus volume was significantly higher in the KO group from week 2 to week 4 post-fracture when compared with the WT group consistent with the histological data. Analysis of biochemical markers indicated that circulating P1NP levels in the KO mice were significantly higher than in the WT mice from week 2 to week 4 and that temporal expression of circulating C-terminal telopeptide of type I collagen (CTX) levels was also higher in the KO mice than in the WT mice. These results were consistent with quantitative real-time PCR analysis. The ultimate load, stiffness, and energy to failure were significantly higher in the KO mice than in the WT mice at week 4.

CONCLUSIONS

The fracture healing in KO mice was enhanced in the early stage of neovascularization and the middle stage of endochondral ossification, but not by the end of healing. Blockade of ERbeta can be considered as another therapeutic strategy for osteoporotic fracture and non-union fracture.

Emu model of full-range femoral head osteonecrosis induced focally by an alternating freezing and heating insult

The emu, a large bipedal bird with hip joint biomechanics similar to humans, was used to establish an experimental model of femoral head osteonecrosis and subsequent femoral head collapse. Focal lesions were induced in 20 adult male emus using an alternating liquid nitrogen freezing and radiofrequency heating insult. At 2, 4, 8, 12 and 16 weeks post-surgery, hip magnetic resonance imaging (MRI) was performed. Before the emus were sacrificed, barium sulphate was infused to the lower extremity to study blood vessel distribution patterns. Femoral samples were scanned by micro-computed tomography (micro-CT) and evaluated histologically. Hip MRI showed changes from broad oedema to femoral head collapse. Emus developed a crippled gait from post-operative week 6. Micro-CT scans and histology showed human-like osteonecrotic changes with an impaired local blood supply. The protocol resulted in consistent full-range osteonecrosis of the femoral head that may serve as a model for testing potential treatments.

Biodegradable CaMgZn bulk metallic glass for potential skeletal application

A low density and high strength alloy, Ca65Mg15Zn20 bulk metallic glass (CaMgZn BMG), was evaluated by both in vitro tests on ion release and cytotoxicity and in vivo implantation, aimed at exploring the feasibility of this new biodegradable metallic material for potential skeletal applications. MTT assay results showed that the experimental CaMgZn BMG extracts had no detectable cytotoxic effects on L929, VSMC and ECV304 cells over a wide range of concentrations (0-50%), whereas for MG63 cells concentrations in the range ~5-20% promoted cell viability. Meanwhile, alkaline phosphatase (ALP) activity results showed that CaMgZn BMG extracts increased alkaline phosphatase (ALP) production by MG63 cells. However, Annexin V-fluorescein isothiocyanate and propidium iodide staining indicated that higher concentrations (50%) might induce cell apoptosis. The fluorescence observation of F-actin and nuclei in MG63 cells showed that cells incubated with lower concentrations (0-50%) displayed no significant change in morphology compared with a negative control. Tumor necrosis factor-α expression by Raw264.7 cells in the presence of CaMgZn BMG extract was significantly lower than that of the positive and negative controls. Animal tests proved that there was no obvious inflammation reaction at the implantation site and CaMgZn BMG implants did not result in animal death. The cortical thickness around the CaMgZn BMG implant increased gradually from 1 to 4 weeks, as measured by in vivo micro-computer tomography.

Impaired bone healing in rabbits with steroid-induced osteonecrosis

Corticosteroids are prescribed for the treatment of many medical conditions and their adverse effects on bone, including steroid-associated osteoporosis and osteonecrosis, are well documented. Core decompression is performed to treat osteonecrosis, but the results are variable. As steroids may affect bone turnover, this study was designed to investigate bone healing within a bone tunnel after core decompression in an experimental model of steroid-associated osteonecrosis. A total of five 28-week-old New Zealand rabbits were used to establish a model of steroid-induced osteonecrosis and another five rabbits served as controls. Two weeks after the induction of osteonecrosis, core decompression was performed by creating a bone tunnel 3 mm in diameter in both distal femora of each rabbit in both the experimental osteonecrosis and control groups. An in vivo micro-CT scanner was used to monitor healing within the bone tunnel at four, eight and 12 weeks postoperatively. At week 12, the animals were killed for histological and biomechanical analysis.

In the osteonecrosis group all measurements of bone healing and maturation were lower compared with the control group. Impaired osteogenesis and remodelling within the bone tunnel was demonstrated in the steroid-induced osteonecrosis, accompanied by inferior mechanical properties of the bone.

We have confirmed impaired bone healing in a model of bone defects in rabbits with pulsed administration of corticosteroids. This finding may be important in the development of strategies for treatment to improve the prognosis of fracture healing or the repair of bone defects in patients receiving steroid treatment.

Effect of water-soluble P-chitosan and S-chitosan on human primary osteoblasts and giant cell tumor of bone stromal cells

Water-soluble phosphorylated chitosan (P-chitosan) and disodium (1 → 4)-2-deoxy-2-sulfoamino-β-D-glucopyranuronan (S-chitosan) are two chemically modified chitosans. In this study, we found that P-chitosan significantly promotes cell proliferation of both human primary osteoblasts (OBs) and the OB like stromal cell component of the giant cell tumor of bone (GCTB) cells at the concentration from 125 to 1000 µg ml⁻¹ at all time points of 1, 3, 5 and 7 days after treatment. Further investigation of the osteogenic effect of the P-chitosan suggested that it regulates the levels of osteoclastogenic factors, receptor activator of nuclear factor kappa B ligand and osteoprotegerin expression. An interesting finding is that S-chitosan at lower concentration (100 µg ml⁻¹) stimulates cell proliferation while a higher dose (1000 µg ml⁻¹) of S-chitosan inhibits it. The inhibitory effect of S-chitosan on human primary GCT stromal cells was greater than that of OBs (p < 0.05). Taken together, our findings elucidated the osteogenic effect of P-chitosan and the varying effects of S-chitosan on the proliferation of human primary OBs and GCT stromal cells and provided us the rationale for the construction of novel bone repair biomaterials with the dual properties of bone induction and bone tumor inhibition.