Transparent glass-ceramics for thermal management application: achievement of optical transparency and high thermal conductivity

Oxide glass is an industrial material with advantages such as optical transparency and shaping ability of the melt, but at the same time, it is a bad conductor of heat due to its disordered structures. Therefore, heat dissipation in glass components often becomes a problem and its applications to the thermal management has been limited to use as a heat insulator. To break this mold and to apply it to fields, e.g., transparent sealing materials, for which low thermal conductive glasses and organic polymers have been conventionally used, we fabricated an MgO-dispersed glass-ceramics in our previous work. It comprises MgO crystal and glass matrix and their reflective indices are matched, leading to optical transparency and improvement in thermal conductivity. Here we investigate the atomic-scale structures in the MgO-dispersed glass-ceramics by nuclear magnetic resonance, etc. and attempt to further improve the thermal conductivity and the transparency. As a result, we show an MgO-dispersed glass-ceramic with a thermal conductivity of 3.3 W (m⁻¹ K⁻¹), corresponding to 300% of that of the glass matrix, high optical transparency, and glass transition. This report highlights that our strategies pave the way for development of novel transparent, functional glass-ceramics.

Oxide glass is an industrial material with advantages such as optical transparency and shaping ability of the melt, but at the same time, it is a bad conductor of heat due to its disordered structures.     

Effects of stress‐shielding on the dynamic viscoelasticity and ordering of the collagen fibers in rabbit Achilles tendon

We investigated the effects of stress‐shielding on both viscoelastic properties and microstructure of collagen fibers in the Achilles tendon by proton double‐quantum filtered (¹H‐DQF) NMR spectroscopy. The right hind‐limbs of 20 Japanese white rabbits were immobilized for 4 weeks in a cast with the ankle in plantarflexion. Dynamic viscoelasticity of the Achilles tendons was measured using a viscoelastic spectrometer. Proton DQF NMR signals were analyzed to determine the residual dipolar coupling of bound water molecules in the Achilles tendons. Both the dynamic storage modulus (E′) and dynamic loss modulus (E″) decreased significantly in the Achilles tendons of the stress‐shielding group. The results of the ¹H‐DQF NMR examination demonstrated significantly reduced residual dipolar coupling in the Achilles tendons of this same group. The disorientation of collagen fibers by stress‐shielding should contribute to degradation of the dynamic storage and loss moduli. The alterations of the collagen fiber orientation that contributed to the function of tendinous tissue can be evaluated by performing an analysis of ¹H DQF NMR spectroscopy. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1708–1712, 2013     

Clinical Effect of Switching from a Luteinizing Hormone-Releasing Hormone Agonist to an Antagonist in Patients with Castration-Resistant Prostate Cancer and Serum Testosterone Level ≥ 20 ng/dl

Introduction

The efficacy of conversion from a luteinizing hormone-releasing hormone agonist to an antagonist was evaluated prospectively in patients with castration-resistant prostate cancer.

Materials and Methods

From October 2012 to December 2014, 8 cases with a serum testosterone level ≥ 20 ng/dl during following androgen deprivation therapy were enrolled and received degarelix monthly. The primary end-pointgoal was to determine the effective prostate-specific antigen response rate. The secondary end-pointgoal was to assess the proportion of cases with a decrease in serum testosterone level to < 20 ng/ml.

Results

One patient achieved a complete response, with a prostate-specific antigen level of 0.02 ng/ml at the nadirend of the study. The effective response rate was 25.0% (2/8), and the proportion of cases with prostate-specific antigen decline was 62.5% (5/8). In 5/8 cases (5/8, 62.5%), serum testosterone levels declined to < 20 ng/dl.

Conclusion

Switching to a luteinizing hormone-releasing hormone antagonist in patients with testosterone levels ≥ 20 ng/dl may be an option in sequential androgen deprivation therapy for some patients.Key Words: Castration-resistant, Degarelix, Prostatic neoplasms, Luteinizing hormone-releasing hormone, Testosterone     

Arachidonic acid preserves hippocampal neuron membrane fluidity in senescent rats

Previous studies indicate that long-term dietary supplementation with arachidonic acid (AA) in 20-month-old rats (OA) effectively restores performance in a memory task and the induction of long-term potentiation in the hippocampus to the level of young control animals (YC). The present study examined protein mobility using the live cell imaging technique "Fluorescent Recovery After Photobleaching (FRAP)" in YC, old control (OC) and OA neurons in hippocampal slice preparations. Three measures; mobile fraction (M(f)), diffusion constant (D) and time constant (tau), were estimated among YC, OC and OA. Each of these parameters was significantly different between OC and YC, suggesting that membrane fluidity is lower in OC than in YC. In contrast, D and tau were comparable in OA and YC, indicating that hippocampal neuronal membranes supplemented with AA were more fluid than those in OC, whereas the fraction of diffusible protein in the bleached region remained smaller than in YC. Long-term administration of AA to senescent rats might help to preserve membrane fluidity and maintain hippocampal plasticity.     

Distribution and frequencies of CDH23 mutations in Japanese patients with non-syndromic hearing loss

Mutations in the CDH23 gene are known to be responsible for both Usher syndrome type ID (USH1D) and non-syndromic hearing loss (DFNB12), and the molecular confirmation of the CDH23 gene has become important in the diagnosis of these conditions. The present study was performed to find whether the CDH23 mutations are also responsible for non-syndromic hearing loss in patients in the Japanese population. A total of 51 sequence variants were found in 64 Japanese probands with non-syndromic sensorineural hearing impairment from autosomal recessive families. Among them, at least four missense mutations in six patients from five families were confirmed to be responsible for deafness by segregation study. All mutations detected were missense mutations, corroborating the previous reports regarding DFNB12. The present data confirmed that CDH23 mutations are frequently found and significantly responsible in Japanese. Interestingly, the CDH23 mutation spectrum in Japanese is very different from that found in Caucasians. This Japanese spectrum may be representative of those in Eastern Asian populations and its elucidation is expected to facilitate the molecular diagnosis of DFNB12 and USH1D.     

Thirteen week toxicity study of dietary l‐tryptophan in rats with a recovery period of 5 weeks

Although l ‐tryptophan is nutritionally important and widely used in medical applications, toxicity data for its oral administration are limited. The purpose of this study was to evaluate the potential toxicity of an experimental diet containing added l ‐tryptophan at doses of 0 (basal diet), 1.25%, 2.5% and 5.0% when administered to Sprague–Dawley rats for 13 weeks. There were no toxicological changes in clinical signs, ophthalmology, urinalysis, hematology, necropsy, organ weight and histopathology between control rats and those fed additional l ‐tryptophan. Body weight gain and food consumption significantly decreased throughout the administration period in males in the 2.5% group and in both sexes in the 5.0% group. At the end of the dosing period, decreases in water intake in males in the 5.0% group and in serum glucose in females in the 5.0% group were observed. The changes described above were considered toxicologically significant; however, they were not observed after a 5 week recovery period, suggesting reversibility. Consequently, the no‐observed‐adverse‐effect level of l ‐tryptophan in the present study was 1.25% for males and 2.5% for females (mean intake of l ‐tryptophan: 779 mg kg^–1 body weight day^–1 [males] and 1765 mg kg^–1 body weight day^–1 [females]). As the basal diet used in this study contained 0.27% of proteinaceous l ‐tryptophan, the no‐observed‐adverse‐effect level of overall l ‐tryptophan was 1.52% for males and 2.77% for females (mean intake of overall l ‐tryptophan: 948 mg kg^–1 body weight day^–1 (males) and 1956 mg kg^–1 body weight day^–1 (females)). We conclude that l ‐tryptophan has a low toxicity profile in terms of human use.