Spin-valley locking and bulk quantum Hall effect in a noncentrosymmetric Dirac semimetal BaMnSb2

Spin-valley locking in monolayer transition metal dichalcogenides has attracted enormous interest, since it offers potential for valleytronic and optoelectronic applications. Such an exotic electronic state has sparsely been seen in bulk materials. Here, we report spin-valley locking in a Dirac semimetal BaMnSb2. This is revealed by comprehensive studies using first principles calculations, tight-binding and effective model analyses, angle-resolved photoemission spectroscopy measurements. Moreover, this material also exhibits a stacked quantum Hall effect (QHE). The spin-valley degeneracy extracted from the QHE is close to 2. This result, together with the Landau level spin splitting, further confirms the spin-valley locking picture. In the extreme quantum limit, we also observed a plateau in the z-axis resistance, suggestive of a two-dimensional chiral surface state present in the quantum Hall state. These findings establish BaMnSb2 as a rare platform for exploring coupled spin and valley physics in bulk single crystals and accessing 3D interacting topological states.

Effect of Crystal Symmetry on the Spin States of Fe3+ and Vibration Modes in Lead-free Double-Perovskite Cs2AgBi(Fe)Br6

We show by electron spin resonance (ESR) and Raman spectroscopies that the crystal phase transition of the lead-free double-perovskite Cs₂AgBiBr₆ has a profound symmetry-breaking effect on the high spin states of, for example, a transition-metal ion Fe³⁺ and the vibrational modes. It lifts their degeneracy when the crystal undergoes the cubic-tetragonal phase transition, splitting the six-fold degenerate S = 5/2 state of Fe³⁺ to three Kramer doublets and the enharmonic breathing mode T_g of the MBr₆ octahedra (M = Ag, Bi, Fe) into E_g + A_g. The magnitudes of both spin and Raman line splitting are shown to directly correlate with the strength of the tetragonal strain field. This work, in turn, demonstrates the power of the ESR and Raman spectroscopies in probing structural phase transitions and in providing in-depth information on the interplay between the structural, spin, and vibrational properties of lead-free double perovskites, a newly emerging and promising class of materials for low-cost and high-efficiency photovoltaics and optoelectronics.

[Application of preventive flap-placement of terminal ileostomy in laparoscopic radical resection of low rectal cancer]

Objective: To evaluate the value of preventive flap placement of terminal ileostomy in laparoscopic radical resection of low rectal cancer. Methods: A retrospective analysis was conducted in the patients (n=63) who received preventive terminal ileostomy in laparoscopic radical resection of low rectal cancer in our institution from April 2016 to March 2018, including 33 patients who underwent ileostomy with flap-placement (flap group), and 30 patients who underwent ileostomy with stent (stent group). Clinical data were collected from both groups and statistically analyzed. Results: All patients were successfully completed laparoscopic radical resection with preventive ileostomy. All patients of stent group received stoma-closure surgery one month later after rectal resection. There were significantly statistical differences in operating time of ileostomy (28.9±4.3 vs 36.3±2.3, t=11.73, P<0.001) and overall stoma-related complications (1 vs 7, χ(2)=4.155, P=0.042), but no difference in anastomosis leakage, operating time of stoma-reversal, parastomal infection, parastomal hernia and parastomal prolapse. Conclusions: Preventive flap placement of terminal ileostomy represents a secure and feasible approach to laparoscopic low rectal cancer resection. Patients can be released from the discomfort of removing the stent and may suffer fewer stoma-related complications.

[Clinical effect of preservation of the left colonic artery in laparoscopic anterior resection for rectal cancer]

Objective: To evaluate the value and feasibility of preservation of the left colonic artery (LCA) in laparoscopic anterior resection for rectal cancer. Methods: The clinical data of 97 patiens who received laparoscopic anterior resection of rectal cancer from 2009.3 to 2015.3 were randomly divided into two groups, including 52 cases with preservation of LCA and 45 cases without preservation of LCA. The operation time, quantity of bleeding, number of lymph nodes removed around the root of inferior mesenteric artery (IMA), the rate of lymph node metastasis around the root of IMA, the incidence of transverse colostomy and anastomotic leak were compared between the two groups. Results: All 97 operations were successfully completed by laparoscopic operation. There were significantly statistical differences in operation time, quantity of bleeding and transverse colon stoma between two groups(P<0.05), but no difference in the number of lymph nodes removed and the rate of lymph node metastasis. Conclusions: The preservation of the left colonic artery in laparoscopic anterior resection of rectal cancer can preserve more supplying vessels for anastomosis and prevent anastomotic leak.

Potent effects of peracetylated (-)-epigallocatechin-3-gallate against hydrogen peroxide-induced damage in human epidermal melanocytes via attenuation of oxidative stress and apoptosis

BACKGROUND

Damage to melanocytes induced by oxidative stress plays an important role in the pathogenesis of vitiligo. A polyphenol found in green tea, (-)-epigallocatechin-3-gallate (EGCG), exhibits certain antioxidative effects in the treatment of various diseases. The major problem that limits the clinical application of this polyphenol is its low bioavailability and stability. Peracetylated EGCG (AcEGCG), a fully acetylated derivative of EGCG, is more stable and bioavailable than EGCG, but the effects of its action on human epidermal melanocytes have not been elucidated.

AIM

To compare the protective effects of AcEGCG and EGCG on hydrogen peroxide (H2 O2 )-induced damage to human melanocytes.

METHODS

Effects of AcEGCG and EGCG on human melanocytes were examined by measuring cell viability, levels of reactive oxygen species (ROS), the mitochondrial membrane potential (ΔΨm)and protein levels of caspase-9, caspase-3 and p38 mitogen-activated protein kinase.

RESULTS

Both AcEGCG and EGCG decreased ROS generation, restored lost mitochondrial membrane potential and reduced H2 O2 -induced apoptosis in melanocytes. All of these effects were more pronounced with AcEGCG than with EGCG. Furthermore, AcEGCG effectively suppressed H2 O2 -induced p38 mitogen-activated protein kinase phosphorylation, which has been suggested to contribute to melanocyte damage.

CONCLUSIONS

AcEGCG is a more potent agent than EGCG for protection of melanocytes from oxidative damage.

[Effect of radiation dose and dose rate on pulmonary fibrosis in mice]

OBJECTIVE

To study the effect of radiation dose and dose rate on radiation-induced pulmonary fibrosis in mice.

METHODS

Twenty-four C57BL/6 mice were randomly divided into a control group (n=6) and an irradiation group(n=18). The irradiation group was further assigned to 3 subgroups according to the whole lung radiation with 15 Gy at 400 cGy/min, 20 Gy at 400 cGy/min and 20 Gy at 100 cGy/min, while the control group received sham-irradiation. All mice were scanned with computed tomograph (CT) 20 weeks post-irradiation, and then they were sacrificed and lung tissues were collected. H&E staining, sirius red staining, lung fibrosis scored and hydroxyproline content analysis were used to assess lung fibrosis and collagen deposition. Real time PCR was used to measure the mRNA expression of type Ⅰ collagen. Immunohistochemical staining was used to detect the activatin and distribution of a-SMA(+) -myofibroblasts.

RESULTS

Compared to the control group, mice from irradiation groups exhibited significant pulmonary consolidation and collagen deposition.At the same dose rate, the higher irradiated dose used, the more severe pulmonary fibrosis was.On the other hand, with the same dose, the dose rate had less effect on pulmonary fibrosis.

CONCLUSION

The effect of radiation dose on the degree of pulmonary fibrosis in mice is more than effect of the dose rate.

Comparative SAGE analysis of the response to hypoxia in human pulmonary and aortic endothelial cells

We utilized serial analysis of gene expression (SAGE) to analyze the temporal response of human pulmonary artery endothelial cells (HPAECs) to short-term chronic hypoxia at the level of transcription. Primary cultures of HPAECs were exposed to 1% O2hypoxia for 8 and 24 h and compared with identical same-passage cells cultured under standard (5% CO2-95% air) conditions. Hierarchical clustering of significant hypoxia-responsive genes identified temporal changes in the expressions of a number of well-described gene families including those encoding proteins involved in thrombosis, stress response, apoptosis, angiogenesis, and cell proliferation. These experiments build on previously published data describing the transcriptomic response of human aortic endothelial cells (HAECs) obtained from the same donor and cultured under identical conditions, and we have thus taken advantage of the immortality of SAGE data to make direct comparisons between these two data sets. This approach revealed comprehensive information relating to the similarities and differences at the level of mRNA expression between HAECs and HPAECs. For example, we found differences in the cell type-specific response to hypoxia among genes encoding cytoskeletal factors, including paxillin, and proteins involved in metabolic energy production, the response to oxidative stress, and vasoreactivity (e.g., endothelin-1). These efforts contribute to the expanding collection of publicly available SAGE data and provide a foundation on which to base further efforts to understand the characteristics of the vascular response to hypoxia in the pulmonary circulation relative to systemic vasculature.

Phosphatidylinositol 3-kinase/Akt pathway mediates heme oxygenase-1 regulation by lipopolysaccharide

The stress-inducible protein heme oxygenase-1 exerts potent antiinflammatory, antiapoptotic and cytoprotective effects in vitro and in vivo. Another important mediator of cytoprotection, the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway activates many proteins involved in the maintenance of cellular homeostasis. Since activation of heme oxygenase-1 and PI3K/Akt both protect the cellular environment, we postulated that PI3K/Akt can regulate the induction of heme oxygenase-1 by proinflammatory stress. The treatment of primary murine macrophage cells (RAW 264.7) with lipopolysaccharide induced heme oxygenase-1 protein and mRNA expression, and increased the phosphorylation of Akt and p38 mitogen activated protein kinase (p38 MAPK). These cellular effects of lipopolysaccharide were markedly diminished by pre-treatment with wortmannin, a specific inhibitor of PI3K. Furthermore, lipopolysaccharide-inducible heme oxygenase expression was blocked by SB203580, a specific inhibitor of p38 MAPK. Both wortmannin and SB203580 decreased lipopolysaccharide-inducible NF-E2-related factor (Nrf2) DNA binding activity. Transfection of macrophages with dominant negative mutants of PI3K, Akt and Nrf2, as well as wortmannin treatment, significantly reduced the transcriptional activity of a minimal heme oxygenase-1 promoter luciferase construct (D33HO-1luc). We demonstrate, to our knowledge for the first time, that upon proinflammatory stimulation heme oxygenase-1 gene expression in macrophages depends on PI3K/Akt and p38 MAPK acting upstream of Nrf2-dependent promoter activation.

Genome-wide analysis of the endothelial transcriptome under short-term chronic hypoxia

We have utilized serial analysis of gene expression (SAGE) to analyze the temporal response of human aortic endothelial cells (HAECs) to short-term chronic hypoxia at the level of transcription. Primary cultures of HAECs were exposed to 1% O2hypoxia for 8 and 24 h and compared with identical same passage cells cultured under standard (5% CO2-95% air) conditions. A total of 121,446 tags representing 37,096 unique tags were sequenced and genes whose expression levels were modulated by hypoxia identified by novel statistical analyses. Hierarchical clustering of genes displaying statistically significant hypoxia-responsive alterations in expression revealed temporal modulation of a number of major functional gene families including those encoding heat shock factors, glycolytic enzymes, extracellular matrix factors, cytoskeletal factors, apoptotic factors, cell cycle regulators and angiogenic factors. Within these families we documented the coordinated modulation of both previously known hypoxia-responsive genes, numerous genes whose expressions have not been previously shown to be altered by hypoxia, tags matching uncharacterized UniGene entries and entirely novel tags with no UniGene match. These preliminary data, which indicate a reduction in cell cycle progression, elevated metabolic stress and increased cytoskeletal remodeling under acute hypoxic stress, provide a foundation for further analyses of the molecular mechanisms underlying the endothelial response to short-term chronic hypoxia.

C-Terminus of desmoyokin/AHNAK protein is responsible for its translocation between the nucleus and cytoplasm

We previously demonstrated that desmoyokin gene is identical to AHNAK gene, which is downregulated in neuroblastomas. Whereas desmoyokin/AHNAK protein is distributed in the nucleus and cytoplasm in nonepithelial tissues, it is distributed in the cell membrane in epithelial tissues. It is present diffusely in the cytoplasm and nucleus of epithelial cell lines cultured in low calcium condition. Low to normal calcium shift translocates it to the cell boundary. In this study, we investigated which domain(s) of desmoyokin/AHNAK protein are responsible for its different distribution. We constructed three different eukaryotic expression plasmids, pN-DY, pM-DY, and pC-DY, which expressed N-terminus, central domain, and C-terminus of this molecule, respectively, when transfected into COS-7 cells, normal human keratinocytes, and HeLa cells. In normal calcium medium, whereas N-terminus and central domain of desmoyokin/AHNAK protein were present mainly in the cytoplasm, C-terminus was present in the nucleus, cytoplasm, and weakly in the cell membrane. In low calcium medium, C-terminus was present exclusively in the nucleus, and a part of the molecules translocated from the nucleus to the cytoplasm, 3 h after the shift to normal calcium medium or 3 h after addition of protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate in low calcium medium. Calcium shift showed no effects on the distribution of N-terminus and central domain. These results suggested that C-terminus, but neither N-terminus nor central domain, is responsible for the translocation of this protein into the nucleus. This study may also suggest that C-terminus play a role in the translocation to the cell membrane, although further evidence is necessary.

Identification of two chilling-regulated 1-aminocyclopropane-1-carboxylate synthase genes from citrus (Citrus sinensis Osbeck) fruit

Diurnal change in the temperature below or above 12.5 degrees C hastens the degreening of citrus peel and elicits the phytohormone ethylene production in citrus fruit. Ethylene triggers the degradation of chlorophyll and synthesis of carotenoids in citrus peel. To investigate if ethylene is required for the degreening of citrus peel elicited by low temperatures, we studied the chilling-regulated gene expression of ACC synthase, one of the key enzymes catalyzing ethylene biosynthesis. We isolated and characterized a chilling-inducible 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) gene, CS-ACS1, and a chilling-repressible gene, CS-ACS2, from citrus peel. The CS-ACS1 transcript 1.7 kb in length encodes a polypeptide of 483 amino acids (Mr 54,115, pI 6.63), whereas the CS-ACS2 transcript of 1.8 kb encodes a polypeptide of 477 amino acids (Mr 53,291, pI 6.72). Both genes showed a rapid but transient induction (within 2.4 h) of transcripts upon rewarming after the chilling (4 degrees C) treatment. After 24 h of incubation at room temperature, CS-ACS1 mRNA diminished to an undetectable level, whereas the CS-ACS2 mRNA regained its basal level of expression attained prior to the chilling treatment. Chilling-induced ethylene production and ACC accumulation were also observed upon rewarming. Both genes were also induced by the wound stress (excision). The protein synthesis inhibitor cycloheximide super-enhances the accumulation of both ACS transcripts at room temperature. Molecular analysis of the 3.3 kb genomic DNA of CS-ACS1 revealed that this gene consists of three introns and four exons. The intron 3 is exceptionally large ( 1.2 kb) and shares significant homology with mitochondrial DNA, supporting the intron-late theory.

[Phacoemulsification through a small pupil]

OBJECTIVE

To discuss the surgical techniques and attention points in phacoemulsification through a small pupil.

METHOD

Eighty three cataracts of 77 patients were emulsified by using non-cut pupil dilation, cystotome or diathermic high-frequency capsulorrhexis.

RESULTS

The 66 cataracts of 83 eyes were emulsified by means of the above method. After the surgery, all the pupils were recovered to normal size (2 to 3 mm), and none of them were damaged. In 17 eyes, the procedure was performed after separation of synechia and excision of the organized membranes; after the surgery, a round pupil was obtained in 15 cases and an irregular pupil in 2 cases. The visual acuity at postoperative 1 month was >or= 0.5 in 46 eyes (55.4%) and corrected >or= 0.5 in 71 eyes (85.5%).

CONCLUSION

After phacoemulsification through a small pupil by non-cut pupil dilation method, the pupil can be recovered to normal and no unfavorable reaction is seen.

[Spectra analysis of ignition flame in two-stroke gasoline engine burning blended fuel]

In a two-stroke gasoline engine, exhaust gas pollution is especially severe when it burns rich mixture of blended fuel. The results of spectra analysis of ignition combustion flame show that the peak luminous intensities of three characteristic spectra CH(431.5nm), C2(516.5nm) and CN(387nm) are strong, of which the peak luminous intensity of CN(387nm) is the most outstanding. The mechanism of NO(x) formation in exhaust gas can be illustrated by Fenimore theorem. The mechanism was also verified by experiments conducted by Japanese researcher K. Nagase.

Novel non-radioisotope immunoprecipitation studies indicate involvement of pemphigus vulgaris antigen in paraneoplastic pemphigus

We have developed two different novel immunoprecipitation assays in which radioisotopes are not used, and have examined antigens for four cases of paraneoplastic pemphigus (PNP) including three new patients. The PNP sera showed a clear reactivity with transitional epithelia of rat urinary bladder by immunofluorescence, and reacted with a characteristic doublet of the 210 and 190 kD proteins by immunoblotting of normal human epidermal extract, confirming the diagnosis of PNP. In addition, by immunoprecipitation using silver-stain to detect immunoprecipitated proteins, the PNP sera detected the 250, 210 and 190 kD proteins, while control bullous pemphigoid sera detected only the 230 kD bullous pemphigoid antigen. Furthermore, with another immunoprecipitation using cell surface biotinylation, three of the four PNP sera specifically reacted with the 130 kD pemphigus vulgaris antigen (Dsg3), indicating that pemphigus vulgaris antigen may be involved in PNP. This reactivity was further suggested by the immunoblot analysis using recombinant pemphigus vulgaris antigen. In future, these non-radioisotope immunoprecipitation assays should become a useful tool not only to unravel the complex situation for the PNP antigens, but also to study antigens in other autoimmune bullous skin diseases.

Activation of protein kinase C-zeta and phosphatidylinositol 3'-kinase and promotion of macrophage differentiation by insulin-like growth factor-I

Phosphoinositides that are phosphorylated at the D3 position have been reported to activate an atypical, Ca2-independent protein kinase C (PKC) isoform designated PKC-zeta, and overexpression of this enzyme leads to monocytic differentiation. In this study, we cultured human HL-60 promyeloid cells with vitamin D3 and insulin-like growth factor-I (IGF-I), a 70-amino-acid peptide that activates phosphatidylinositol 3'-kinase (PI 3-kinase) in murine promyeloid cells. Two days later, the proportion of cells differentiating into macrophages in serum-free medium, as assessed by expression of the alpha-subunit of the beta2 integrin CD11b, increased from 5 +/- 1% to 25 +/- 3%. Addition of IGF-I increased the proportion of cells differentiating into CD11b-positive macrophages to 78 +/- 5%. In the absence of vitamin D3, IGF-I did not induce expression of CD11b (6 +/- 1%). The IGF-I-promoted macrophage differentiation was blocked specifically by preincubation of HL-60 cells with a mAb (alphaIR3) directed against the IGF type I receptor. Similarly, pretreatment of cells with either alphaIR3 or an IGF-binding protein, IGFBP-3, led to a 75% inhibition of CD11b expression when cells were cultured with vitamin D3 in serum-containing medium. IGF-I, but not vitamin D3, caused a sevenfold increase in the enzymatic activity of both PI 3-kinase and atypical PKC-zeta. Inhibition of IGF-I-inducible PI 3-kinase with either wortmannin or LY294002 abrogated the IGF-I-induced activation of PKC-zeta and totally blocked the enhancement in macrophage differentiation caused by IGF-I. These data establish that PKC-zeta is a putative downstream target of PI 3-kinase that is activated during IGF-I-promoted macrophage differentiation.

Comparison of the direct effects of nifedipine and verapamil on the electrical activity of the sinoatrial and atrioventricular nodes of the rabbit heart

We compared the effects of nifedipine and verapamil on the rabbit sinus and atrioventricular nodes. Both drugs slowed the rate of impulse initiation by sinus node cells. Verapamil exerted a greater negative chronotropic effect at low concentrations, but at higher concentrations verapamil and nifedipine were equipotent. Nifedipine also reduced the amplitude of sinus node action potentials and the Vmax of phase O, effects which are identical to those previously described for verapamil. Both drugs slowed AV nodal conduction and prolonged refractory periods, but verapamil was more potent than nifedipine. Nifedipine reduced the amplitude of AV nodal action potentials and Vmax of phase O the same as verapamil. Nifedipine and verapamil, therefore, have nearly identical direct effects on the nodes. The failure of nifedipine to depress AV nodal conduction in situ and abolish reentrant AV nodal tachycardia is probably a result of the decreased sensitivity of the AV node to nifedipine compared to verapamil.