Polarization-driven topological insulator transition in a GaN/InN/GaN quantum well

Topological insulator (TI) states have been demonstrated in materials with a narrow gap and large spin-orbit interactions (SOI). Here we demonstrate that nanoscale engineering can also give rise to a TI state, even in conventional semiconductors with a sizable gap and small SOI. Based on advanced first-principles calculations combined with an effective low-energy k · p Hamiltonian, we show that the intrinsic polarization of materials can be utilized to simultaneously reduce the energy gap and enhance the SOI, driving the system to a TI state. The proposed system consists of ultrathin InN layers embedded into GaN, a layer structure that is experimentally achievable.

αA- and αB-crystallins interact with caspase-3 and Bax to guard mouse lens development

The small heat shock protein, α-crystallin, exists in two isoforms, αA and αB, and displays strong ability against stress-induced apoptosis. Regarding their functional mechanisms, we and others have demonstrated that they are able to regulate members in both caspase and Bcl-2 families. In addition, we have also shown that αA and αB may display differential anti-apoptotic mechanisms under certain stress conditions. While αA-crystallin regulates activation of the AKT signaling pathway, αB negatively regulates the MAPK pathway to suppress apoptosis induced by UV and oxidative stress. Although previous studies revealed that αA and αB could regulate members in both caspase and Bcl-2 families, the molecular mechanism, especially the in vivo regulation still waits to be elucidated. In the present communication, we present both in vitro and in vivo evidence to further demonstrate the regulation of caspase-3 and Bax by αA and αB. First, Surface Plasmon Resonance (SPR) and yeast two-hybrid selection analysis demonstrate that αA and αB directly bind to caspase-3 and Bax with differential affinities. Second, immunohistochemistry reveals that αA and αB regulate caspase-3 and Bax at different developmental stages of mouse embryo. Third, coimmunoprecipitation shows that αA and αB form in vivo interacting complexes with caspase-3 and Bax. Together, our results further confirm that αA and αB regulate caspase-3 and Bax in vitro and in vivo to regulate lens differentiation.

Reduced chondrocyte proliferation, earlier cell cycle exit and increased apoptosis in neuronal nitric oxide synthase-deficient mice

OBJECTIVE

Nitric oxide (NO) has been implicated in the local regulation of bone metabolism. However, the contribution made by specific nitric oxide synthase (NOS) enzymes to skeletal development is unclear. The objective of this study was to examine the effects of inactivation of neuronal nitric oxide synthase (nNOS) on cartilage development in mice.

DESIGN

Mice carrying a null mutation in the nNOS gene were used to address our objectives. Histological staining, immunohistochemistry and in situ analyses were employed along with real-time reverse transcriptase - polymerase chain reaction (RT-PCR).

RESULTS

nNOS-null mice show transient growth retardation and shorter long bones. nNOS-deficient growth plates show a reduction in replicating cells. Reduced chondrocyte numbers may in part be due to slower cell cycle progression and premature cell cycle exit caused by decreased cyclin D1 and increased p57 expression in mutants. In addition, apoptosis was increased as shown by increased cleaved-caspase 3 staining in hypertrophic chondrocytes in mutants. Real-time PCR demonstrated that expression of early chondrocyte markers such as Sox genes was reduced in mutant mice, while expression of prehypertrophic markers such as RORα was increased. Histological sections also demonstrated thinner cortical bone, fewer trabeculae and reduced mineralization in mutant mice.

CONCLUSIONS

These data identify an important role of nNOS in chondrocyte proliferation and endochondral bone growth and demonstrate that nNOS coordinates cell cycle exit and chondrocyte differentiation in cartilage development.

Successful organ donation from brain dead donors in a Chinese organ transplantation center

Solid organ transplantation is an effective treatment for patients with end-stage organ failure. Donation after brain death (DBD) is a means of addressing the inadequate supply of acceptable donor organs but has only gradually begun to be accepted in mainland China. A major barrier has been the absence of brain death and organ transplant legislation. This paper describes our initial experience with organ transplantation using organs from brain dead donors and discusses strategies for encouraging organ transplantation and brain death legislation in China. Six patients underwent renal transplantation and two patients underwent liver transplantation with organs procured from three brain dead donors at the Organ Transplantation Center, the 181st Hospital. All patients are alive with excellent graft function. DBD is an important means of increasing the number of organs available for transplantation and its widespread implementation in China should be encouraged. Brain death and organ transplantation legislation is necessary to ensure the rights and obligations of donors, recipients and medical institutions.

The von Hippel-Lindau tumor suppressor protein regulates gene expression and tumor growth through histone demethylase JARID1C

In clear-cell renal cell carcinoma (ccRCC), inactivation of the tumor suppressor von Hippel-Lindau (VHL) occurs in the majority of the tumors and is causal for the pathogenesis of ccRCC. Recently, a large-scale genomic sequencing study of ccRCC tumors revealed that enzymes that regulate histone H3 lysine 4 trimethylation (H3K4Me3), such as JARID1C/KDM5C/SMCX and MLL2, were mutated in ccRCC tumors, suggesting that H3K4Me3 might have an important role in regulating gene expression and tumorigenesis. In this study we report that in VHL-deficient ccRCC cells, the overall H3K4Me3 levels were significantly lower than that of VHL+/+ counterparts. Furthermore, this was hypoxia-inducible factor (HIF) dependent, as depletion of HIF subunits by small hairpin RNA in VHL-deficient ccRCC cells restored H3K4Me3 levels. In addition, we demonstrated that only loss of JARID1C, not JARID1A or JARID1B, abolished the difference of H3K4Me3 levels between VHL-/- and VHL+/+ cells, and JARID1C displayed HIF-dependent expression pattern. JARID1C in VHL-/- cells was responsible for the suppression of HIF-responsive genes insulin-like growth factor-binding protein 3 (IGFBP3), DNAJC12, COL6A1, growth and differentiation factor 15 (GDF15) and density-enhanced phosphatase 1. Consistent with these findings, the H3K4Me3 levels at the promoters of IGFBP3, DNAJC12, COL6A1 and GDF15 were lower in VHL-/- cells than in VHL+/+ cells, and the differences disappeared after JARID1C depletion. Although HIF2α is an oncogene in ccRCC, some of its targets might have tumor suppressive activity. Consistent with this, knockdown of JARID1C in 786-O VHL-/- ccRCC cells significantly enhanced tumor growth in a xenograft model, suggesting that JARID1C is tumor suppressive and its mutations are tumor promoting in ccRCC. Thus, VHL inactivation decreases H3K4Me3 levels through JARID1C, which alters gene expression and suppresses tumor growth.

New phylogenetically distinct cyanophages found in the coastal Yellow Sea by Qingdao

Genetic composition of natural cyanophage population in the coastal Yellow Sea area near Qingdao was investigated using the g20 gene as a genetic marker. Amplification of this gene by PCR yielded sequences, which were cloned and subjected to the restriction fragment length polymorphism (RFLP) analysis. Sixteen clones exhibiting different RFLP patterns were sequenced and analyzed. The sequence analysis indicated a diversity of cyanophages covering sixteen g20 genotypes. Their phylogenetic analysis revealed two distinct phylogenetic groups. One group (7clones) localized with the cyanophage P77 in the cluster III described before. Second group (9 clones) did not localize with any of the cyanophage described so far and was designated as a novel W cluster. The study revealed a genetic diversity of cyanophages in the coastal Yellow Sea and confirmed the genetic differences between cyanophage populations in Western and Eastern Pacific.

Developmental expression of ACRV1 in humans and mice

To identify the developmental expression of the ACRV1 gene in humans and mice, testes cDNA samples were collected at different post-natal days (days 4, 9, 18, 35, 54, and 6 months) from Balb/c mice and were hybridised to the mouse whole genome 430 2.0 Array (Affymetrix Inc.) chip. The characteristics of ACRV1 were analysed using various cellular and molecular biotechnologies. The results showed that the expression of mouse ACRV1 was not detected in mouse testes on days 4, 9, and 18 but was present on days 35, 54, and 6 months. Using RT-PCR analysis of mouse ACRV1, we determined that mouse ACRV1 was expressed specifically in the mouse testis, and its expression began at days 35. Western blot analysis demonstrated that human ACRV1 was primarily expressed in human testes, and immunofluorescent and immunohistochemistry staining showed that human ACRV1 protein was predominantly located in round and elongated spermatids in human testes, indicating that ACRV1 may play an important role in mammalian spermatogenesis and may be a target of a contraceptive vaccine.

Apoptosis: its functions and control in the ocular lens

The ocular lens is a non-vascular and non-innervated transparent organ that plays an important role in vision processing. This unique organ is derived from the embryonic ectoderm of the brain region through a complicated differentiation process in which apoptosis plays a key role. First, when the committed ectoderm becomes thickened and invaginated, the defined number of cells required to form the lens vesicle is partially determined by apoptosis. Second, separation of lens vesicle from the above corneal ectoderm is executed through apoptosis of the lens stalk cells. Finally, differentiation of the lens epithelial cells is controlled by the regulators, most of which are involved in control of apoptosis at multiple signaling steps. The lens is also characterized by continuous growth and differentiation in the adulthood. Through the different stages of growth and differentiation in the adult lens, various stress conditions can induce apoptosis of the lens epithelial cells, leading to eventual non-congenital cataractogenesis. The present review summarizes the current knowledge on the functions and regulators of apoptosis in the ocular lens.

Increased serum retinol-binding protein-4 levels in pregnant women with and without gestational diabetes mellitus

OBJECTIVE

Retinol-binding protein 4 (RBP4) is thought to be associated with insulin resistance in humans, while pregnancy is normally characterized by progressive insulin resistance. Gestational diabetes (GDM) occurs when pancreatic beta-cell function is unable to compensate for insulin resistance. This study aimed to determine whether or not serum RBP4 levels are elevated in pregnancy, and to explore the relationship between RBP4 levels and insulin resistance during pregnancy.

METHODS

Serum RBP4 was measured at median gestational week 26 in 121 pregnant women, including 63 with GDM (GDM group) and 58 normal, glucose-tolerant pregnant women (P-NGT group), as well as 65 non-pregnant normal, glucose-tolerant women (NP-NGT group). Multiple stepwise regression analysis was used to explore the independent factors of RBP4.

RESULTS

Serum RBP4 levels in the P-NGT and GDM groups were significantly higher than in the NP-NGT group (34.50±9.80 mg/L and 41.64±12.21 mg/L vs 30.64±9.46 mg/L, respectively; P<0.05) after adjusting for age, body mass index (BMI) and blood pressure. Furthermore, RBP4 levels were much higher in the GDM vs P-NGT group. Spearman's correlation analysis showed that serum RBP4 levels were positively correlated with triglycerides (TG), fasting plasma glucose, postprandial 2h plasma glucose and HOMA-IR in pregnancy. Of these, TG and HOMA-IR (r(2)=0.312) were independent factors of serum RBP4.

CONCLUSION

Serum RBP4 levels are significantly increased in pregnancy, independent of age and BMI, and are also considerably higher in pregnant women with GDM than in those with normal glucose tolerance. In addition, serum RBP4 levels appear to be a valuable marker of insulin resistance and dysfunctional lipid metabolism in pregnancy.

Lymphatic drainage of the skull base: comparative anatomic and advanced imaging studies in the rabbit and human with implications for spread of nasopharyngeal carcinoma

This preliminary study investigated the lymphatic drainage and distribution of lymphatic structures in the skull base. Characteristics of the rabbit skull base were analyzed and compared correspondingly with those of the human skull. The lymphatic circulation in the rabbit cranial base was detected by digital subtraction angiography (DSA), and lymph drainage in the human skull base was illustrated by interstitial magnetic resonance lymphography (MRL). Lymphatic structures and their distribution in MRL were identified by comparing with contrast-enhanced MRI and clinical data on basilar metastasis of nasopharyngeal carcinoma (NPC) in the human skull base. Anatomic similarity was found between the rabbit and human basilar regions. Well-visualized lymphatic pathways were found in the rabbit cranial base, and human lymphatic structures showed high signal intensity in enhanced T1-weighted MRL images. Lymphatic tissues in the human basilar region were found mainly distributed in the areas of the jugular foramen, foramen lacerum, and petrosal section of the internal carotid artery (ICA). Their distribution in the human basilar region was similar to the distribution in the rabbit basilar region and consistent with our clinical findings of the predilection sites of NPC metastasis in the skull base. Our studies show that bilateral symmetrical lymphatic structures were distributed along the ICA, internal jugular vein, and dura of cranial base in the central part of the middle and posterior skull base.

Phospho-Olivine as Advanced Cathode Material for Lithium Batteries

<p>Nano-sized and micron-sized LiFePO₄ electrode materials were prepared by a sol gel and coprecipitation reactions. An improvement of the cycling and rate performances in lithium cells was observed for the carbon coated LiFePO₄ materials. The coating process uses a solid/gas-phase reaction which consists of decomposing propylene gas, as carbon source, inside a reactor containing olivine LiFePO₄ materials. Optimized LiFePO₄ electrode cells, cycled at RT between 3.0 and 4.3 V at a C/10 rate, do not show any sign of capacity fade during the first 50 cycles. Combination of the high volumetric energy density and low cost preparation method makes the micron-sized LiFePO₄ olivine an attractive safe cathode for lithium-ion batteries.</p>

Occurrence of ammonia-oxidizing Archaea in activated sludges of a laboratory scale reactor and two wastewater treatment plants

AIMS

Characterization of the ammonia-oxidizing archaea (AOA) community in activated sludge from a nitrogen removal bioreactor and wastewater treatment plants (WWTPs).

METHODS AND RESULTS

Three primer sets specific for ammonia mono-oxygenase alpha-subunit (amoA) were used to construct clone libraries for activated sludge sample from a nitrogen removal bioreactor. One primer set resulted in strong nonspecific PCR products. The other two clone libraries retrieved both shared and unique AOA amoA sequences. One primer set was chosen to study the AOA communities of activated sludge samples from Shatin and Stanley WWTPs. In total, 18 AOA amoA sequences were recovered and compared to the previous reported sequences. A phylogenetic analysis indicated that sequences found in this study fell into three clusters.

CONCLUSIONS

Different primers resulted in varied AOA communities from the same sample. The AOA found from Hong Kong WWTPs were closely similar to those from sediment and soil, but distinct from those from activated sludge in other places. A comparison of clone libraries between Shatin WWTP and bioreactor indicated the AOA community significantly shifted only after 30-day enrichment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study confirmed the occurrence of AOA in a laboratory scale nitrogen removal bioreactor and Hong Kong WWTPs treating saline or freshwater wastewater. AOA communities found in this study were significantly different from those found in other places. To retrieve diverse AOA communities from environmental samples, a combination of different primers for the amoA gene is needed.

High-coercivity FePt nanoparticle assemblies embedded in silica thin films

The ability to process assemblies using thin film techniques in a scalable fashion would be a key to transmuting the assemblies into manufacturable devices. Here, we embed FePt nanoparticle assemblies into a silica thin film by sol-gel processing. Annealing the thin film composite at 650 degrees C transforms the chemically disordered fcc FePt phase into the fct phase, yielding magnetic coercivity values H(c)>630 mT. The positional order of the particles is retained due to the protection offered by the silica host. Such films with assemblies of high-coercivity magnetic particles are attractive for realizing new types of ultra-high-density data storage devices and magneto-composites.