Direct observation of a two-dimensional hole gas at oxide interfaces

The discovery of a two-dimensional electron gas (2DEG) at the LaAlO₃/SrTiO₃ interface ¹ has resulted in the observation of many properties^2-5 not present in conventional semiconductor heterostructures, and so become a focal point for device applications^6-8. Its counterpart, the two-dimensional hole gas (2DHG), is expected to complement the 2DEG. However, although the 2DEG has been widely observed ⁹ , the 2DHG has proved elusive. Herein we demonstrate a highly mobile 2DHG in epitaxially grown SrTiO₃/LaAlO₃/SrTiO₃ heterostructures. Using electrical transport measurements and in-line electron holography, we provide direct evidence of a 2DHG that coexists with a 2DEG at complementary heterointerfaces in the same structure. First-principles calculations, coherent Bragg rod analysis and depth-resolved cathodoluminescence spectroscopy consistently support our finding that to eliminate ionic point defects is key to realizing a 2DHG. The coexistence of a 2DEG and a 2DHG in a single oxide heterostructure provides a platform for the exciting physics of confined electron-hole systems and for developing applications.

Strongly Coupled Magnetic and Electronic Transitions in Multivalent Strontium Cobaltites

The topotactic phase transition in SrCoO_x (x = 2.5–3.0) makes it possible to reversibly transit between the two distinct phases, i.e. the brownmillerite SrCoO_2.5 that is a room-temperature antiferromagnetic insulator (AFM-I) and the perovskite SrCoO₃ that is a ferromagnetic metal (FM-M), owing to their multiple valence states. For the intermediate x values, the two distinct phases are expected to strongly compete with each other. With oxidation of SrCoO_2.5, however, it has been conjectured that the magnetic transition is decoupled to the electronic phase transition, i.e., the AFM-to-FM transition occurs before the insulator-to-metal transition (IMT), which is still controversial. Here, we bridge the gap between the two-phase transitions by density-functional theory calculations combined with optical spectroscopy. We confirm that the IMT actually occurs concomitantly with the FM transition near the oxygen content x = 2.75. Strong charge-spin coupling drives the concurrent IMT and AFM-to-FM transition, which fosters the near room-T magnetic transition characteristic. Ultimately, our study demonstrates that SrCoO_x is an intriguingly rare candidate for inducing coupled magnetic and electronic transition via fast and reversible redox reactions.

Use of supplemental anti-HBc testing of donors showing non-discriminating reactive results in multiplex nucleic acid testing

BACKGROUND AND OBJECTIVES

The Korean Red Cross began nucleic acid amplification testing (NAT) for HIV and HCV in February 2005, and added HBV NAT beginning in June 2012. The current NAT system utilizes a multiplex assay for simultaneous detection of HBV DNA, HCV RNA and HIV-1 RNA. For samples that are reactive in the multiplex assay, we do specific tests for each virus. However, there have been cases of non-discriminated reactive (NDR) results which appear to be the result of non-specific reactions or cross-contamination, although some cases are considered to arise from the presence of low levels of HBV DNA due to occult hepatitis B infection.

MATERIALS AND METHODS

We examined the incidence of NDR results in previous donations of some NAT-reactive donors. Additionally, for those donors with NDR results, we performed an HBV core antibody (anti-HBc) assay.

RESULTS

From November 2015 to March 2016, there were 408 NAT-reactive donors. Of these, nineteen HBV NAT-reactive donors showed a history of NDR results in the past donations. Seven donors showed NDR results more than once. Of 771 NDR donors, 362 (47·0%) were anti-HBc reactive.

CONCLUSION

The NDR donors had a substantially higher rate of anti-HBc reactivity than other blood donors indicating that some with anti-HBc reactivity represent donors with occult HBV. Therefore, the incorporation of an anti-HBc testing for NDR donors could improve blood safety testing for the Korean Red Cross.

Impact of high-mobility group box 1 on melanocytic survival and its involvement in the pathogenesis of vitiligo

BACKGROUND

Vitiligo is attributable to loss of functional melanocytes and is the most common acquired depigmenting disorder. Oxidative stress and intense ultraviolet irradiation are known to aggravate this condition. The nonhistone high-mobility group box 1 (HMGB1) DNA-binding protein is a physiological activator of immune responses, cellular proliferation and cell death. Although it is implicated in the pathogenesis of autoimmune diseases and cutaneous disorders, the precise role of HMGB1 in melanocytes has yet to be studied.

OBJECTIVES

To elucidate the effect of HMGB1 on melanocytic survival and its involvement in the pathogenesis of vitiligo.

METHODS

Melanocytes were treated with recombinant HMGB1 (rHMGB1). Thereafter, apoptosis-, autophagy- and melanogenesis-related molecules were detected. Ex vivo skin organ culture was performed after rHMGB1 treatment. Also, levels of HMGB1 were examined in blood and skin specimens from patients with vitiligo.

RESULTS

In this study, rHMGB1 increased expression of cleaved caspase 3 and decreased melanin production and expression of melanogenesis-related molecules. rHMGB1-induced caspase 3 activation was confirmed through preincubation with a pan-caspase inhibitor. In ex vivo experiments for the confirmation of HMGB1-induced melanocyte apoptosis, melanocyte disappearance and increased caspase 3 activation were observed in rHMGB1-treated skin tissues. In Western blot analysis and enzyme-linked immunosorbent assay, patients with active vitiligo showed significantly higher blood levels of HMGB1 (vs. healthy controls). Also, greater expression of HMGB1 was observed in vitiliginous skin (vs. uninvolved skin).

CONCLUSIONS

External stimuli (e.g. oxidative stress and ultraviolet irradiation) may trigger HMGB1 release by keratinocytes, thereby perpetuating vitiligo through HMGB1-induced melanocytic apoptosis.

USP8 suppresses death receptor-mediated apoptosis by enhancing FLIPL stability

FLICE-like inhibitory protein (FLIP) is a critical regulator of death receptor-mediated apoptosis. Here, we found ubiquitin-specific peptidase 8 (USP8) to be a novel deubiquitylase of the long isoform of FLIP (FLIP_L). USP8 directly deubiquitylates and stabilizes FLIP_L, but not the short isoform. USP8 depletion induces FLIP_L destabilization, promoting anti-Fas-, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)- and tumor necrosis factor alpha-induced extrinsic apoptosis by facilitating death-inducing signaling complex or TNFR1 complex II formation, which results in the activation of caspase-8 and caspase-3. USP8 mRNA levels are elevated in melanoma and cervical cancers, and the protein levels of USP8 and FLIP_L are positively correlated in these cancer cell lines. Xenograft analyses using ME-180 cervical cancer cells showed that USP8 depletion attenuated tumor growth upon TRAIL injection. Taken together, our data indicate that USP8 functions as a novel deubiquitylase of FLIP_L and inhibits extrinsic apoptosis by stabilizing FLIP_L.

Clinical significance of serum YKL-40 in Behçet disease

BACKGROUND

Serum YKL-40 is an inflammatory biomarker of endothelial dysfunction and may play a role in the inflammatory process of Behçet disease (BD).

OBJECTIVES

Serum YKL-40 levels were evaluated in patients with BD in order to identify associations with other inflammatory cytokines and establish laboratory parameters. Serum YKL-40 levels were also compared with BD clinical features and disease activity.

METHODS

In total, 112 patients with BD and 45 age- and sex-matched healthy volunteers were included. Disease activity was assessed with BD Current Activity Form score and Electronic Medical Record-based Activity Index (EMRAI) score.

RESULTS

Serum YKL-40 levels were significantly higher in patients with BD (median 41·88, range 12·52-171·30 ng mL(-1) ) than in healthy volunteers (median 20·92, range 5·01-64·20 ng mL(-1) ; P < 0·01). The cut-off value for YKL-40 (30·005 ng mL(-1) ) was determined from the receiver operating characteristic curve. EMRAI scores and the proportion of patients in the active phase of BD presenting with two or more major criteria were significantly higher in patients with elevated YKL-40 levels (P = 0·04 and P = 0·04, respectively). A statistically significant elevation in YKL-40 levels was observed in patients with active BD compared with patients with inactive BD (P = 0·05). Serum YKL-40 values were positively correlated with interleukin-6 and EMRAI scores (both P = 0·04), indicating that serum YKL-40 levels are increased in patients with BD and positively correlate with disease activity.

CONCLUSIONS

YKL-40 may play a role in the pathophysiology of BD and provide a useful marker for monitoring patients with BD.

Relationship between tinnitus and suicidal behaviour in Korean men and women: a cross-sectional study

OBJECTIVES

This study investigated the prevalence of suicidal ideation and behaviour in a representative sample of South Koreans with or without tinnitus.

DESIGN

A cross-sectional study.

SETTING

Based on data from the 2010 to 2012 Korean National Health and Nutrition Examination Survey (KNHANES).

PARTICIPANTS

The study included 17 446 Korean individuals.

MAIN OUTCOME MEASURES

Participants provided demographic, socio-economic and behavioural information, as well as responses to questionnaires assessing the presence and severity of tinnitus, mental health status regarding stress, depression, and suicidal ideation and attempts. In the univariate analysis, the Rao-Scott chi-square test and logistic regression analysis were used to test the association between tinnitus and risk factors. Simple and multiple linear regression analyses were used to examine the association between tinnitus and mental status.

RESULTS

A total of 20.9% and 1.2% of participants with tinnitus, and 12.2% and 0.6% of those without, reported suicidal ideation and attempts, respectively (P < 0.0001 and P = 0.001). Participants reporting suicide attempts showed a higher proportion of severe annoying (6.0%) and irritating (11.8%) tinnitus than those with suicidal ideation (1.4% and 10.2%, respectively). Risks for experiencing tinnitus were significantly associated with suicidal ideation and attempts after adjusting for confounding variables.

CONCLUSION

This study has important implications for enhanced screening and evaluation of mental health status and suicidal ideation/behaviour among tinnitus patients.

Retinoic Acid as a Radiosensitizer on the Head and Neck Squamous Cell Carcinoma Cell Lines

PURPOSE

Retinoic acid is a substance that has previously been reported to increase radiosensitivity, but at concentrations likely to inhibit cell growth or to induce celluar differentiation. We choose head and neck cancer cell lines to investigate the role of retinoic acid as a radiosensitizer and to elucidate the mechanism through the changes in the expression of retinoid receptors and squamous cell differentiation marker.

MATERIALS AND METHODS

Three cell lines (PCI-50, SqCC/ Y1 and UMSCC-11B) were used. 7-AAD staining for apoptosis and Western blot analysis for RAR-alpha, beta, gamma, RXR-alpha, beta, gamma and involucrin were performed after various treatments (control, beta-all-trans-retinoic acid (t-RA) only (10 6 M), radiation only (3 Gy), radiation with t-RA).

RESULTS

The synergistic radiosensitivity effect of t-RA was seen only radioresistant UMSCC-11B cell line. Expression of RAR-beta was induced by t-RA in maily UMSCC- 11B cell line. RAR-alpha,gamma, and RXR-alpha, beta, gamma expression were not changed in all cell lines tested. Expression of involucrin was inhibited by t-RA in PCI-50 cell line but other two cell lines were not changed by t-RA treatment.

CONCLUSION

We found that only radioresistant cell line (UMSCC-11B) showed synergistic radiosensitivity effect by t-RA and this mechanism may be through RAR-beta expression induction.