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The temperature-dependent polarized photoluminescence spectra of nonpolar ZnO samples were investigated by 263 nm laser. The degree of polarization (DOP) of m-plane quantum wells changes from 76% at 10 K to 40% at 300 K, which is much higher than that of epilayer. The strong anisotropy was presumably attributed to the enhanced confinement effect of a one-dimension confinement structure formed by the intersection of quantum well and basal stacking fault. The polarization of laser beam also has an influence on the DOP. It is assumed that the luminescence polarization should be affected not only by the in-plane strains but also the microstructural defects, which do modify the electronic band structure.

Background: Visfatin is an adipokine that is highly expressed in visceral fat. Plasma levels of visfatin have been reported to be higher in subjects with obesity and/or type 2 diabetes mellitus. However, the role of visfatin in endothelial dysfunction has been largely unexplored., Objectives: We investigated the possible pathogenic role of visfatin in endothelial dysfunction, particularly focusing on its effect on inflammatory mediators., Design: Primary human umbilical vein endothelial cells (HUVECs) pretreated with visfatin (1, 10 and 50 ng ml(-1)) were used to study the relationship between visfatin and endothelium dysfunction. Expressions of adhesion molecules (ICAM-1, VCAM-1 and E-selectin) and cytokines (interleukin (IL)-6 and IL-8) affected by visfatin were investigated by enzyme-linked immunosorbent assay, flow cytometry and real-time PCR. Activity of nuclear factor (NF)-kappaB was examined by electrophoretic mobility shift assay., Results: At a visfatin concentration of 50 ng ml(-1), significant increases in IL-6, IL-8, ICAM-1, VCAM-1 and E-selectin gene expression along with increased IL-6, IL-8 and sE-selectin protein levels in the conditioned medium were detected. Flow cytometry showed that the addition of visfatin significantly increased ICAM-1 expression and VCAM-1 expression (10 and 50 ng ml(-1), respectively). Electrophoretic mobility shift assay confirmed that visfatin increased the DNA-binding activity of NF-kappaB. In addition, pretreatment with visfatin (10 and 50 ng ml(-1)) increased human monocyte cell line THP-1 adhesion to HUVECs., Conclusions: Our findings suggest that visfatin causes endothelial dysfunction by increasing inflammatory and adhesion molecule expression at least partly through the upregulation of NF-kappaB activity.

Objective: The aim of this study was to evaluate the efficacy of transabdominal color Doppler ultrasound in diagnosing placenta previa accreta., Design: Eighty patients with persistent placenta previa underwent transabdominal B-mode and color Doppler ultrasound evaluation in the second and third trimesters because they had a high risk of placenta accreta. Color Doppler imaging criteria used included diffuse intraparenchymal placental lacunar flow; focal intraparenchymal placental lacunar flow; bladder-uterine serosa interphase hypervascularity; prominent subplacental venous complex; and loss of subplacental Doppler vascular signals. The color Doppler images were interpreted prospectively for signs of placenta previa accreta according to the exhibited color Doppler sonographic features., Results: Sixteen of the 80 patients exhibited characteristic color Doppler imaging patterns highly specific for placenta accreta according to the preceding criteria, and 14 of these had histopathological proof of placenta accreta. Two patients had false-positive color Doppler imaging evidence mistaken for interphase hypervascularity caused by bladder varices. Thirteen patients underwent hysterectomy in the group suspicious for accreta. Of the 64 patients with negative color Doppler imaging results, three had placenta accreta, while two required cesarean hysterectomy; the remaining patient underwent uterine artery ligation for bleeding from the lower uterine segment. The sensitivity of color Doppler imaging in the diagnosis of placenta previa accreta was 82.4% (14/17) and the specificity was 96.8% (61/63). The positive and negative predictive values were 87.5% (14/16) and 95.3% (61/64), respectively., Conclusions: Variable vascular morphological patterns of placenta previa accreta were exhibited and categorized by transabdominal color Doppler sonography in the antenatal period. The identification of these specific vascular patterns had a positive impact on the peripartum clinical management of the affected patients.

Background: Protein kinase C zeta (PKC zeta) is a member of the PKC family of enzymes and is involved in a wide range of physiological processes including mitogenesis, protein synthesis, cell survival and transcriptional regulation. PKC zeta has received considerable attention recently as a target of phosphoinositide 3-kinase (PI 3-kinase), although the mechanism of PKC zeta activation is, as yet, unknown. Recent reports have also shown that the phosphoinositide-dependent protein kinase-1 (PDK-1), which binds with high affinity to the PI 3-kinase lipid product phosphatidylinositol-3,4,5-trisphosphate (Ptdins-3,4,5-P3), phosphorylates and potently activates two other PI 3-kinase targets, the protein kinases Akt/PKB and p70S6K. We therefore investigated whether PDK-1 is the kinase that activates PKC zeta., Results: In vivo, PI 3-kinase is both necessary and sufficient to activate PKC zeta. PDK-1 phosphorylates and activates PKC zeta in vivo, and we have shown that this is due to phosphorylation of threonine 410 in the PKC zeta activation loop. In vitro, PDK-1 phosphorylates and activates PKC zeta in a Ptdins-3,4,5-P3-enhanced manner. PKC zeta and PDK-1 are associated in vivo, and membrane targeting of PKC zeta renders it constitutively active in cells., Conclusions: Our results have identified PDK-1 as the kinase that phosphorylates and activates PKC zeta in the PI 3-kinase signaling pathway. This phosphorylation and activation of PKC zeta by PDK-1 is enhanced in the presence of Ptdins-3,4-5-P3. Consistent with the notion that PKCs are enzymes that are regulated at the plasma membrane, a membrane-targeted PKC zeta is constitutively active in the absence of agonist stimulation. The association between PKC zeta and PDK-1 reveals extensive cross-talk between enzymes in the PI 3-kinase signaling pathway.

Cyclin-dependent kinase 5 (Cdk5) and its neuron-specific regulator p35 are essential for neuronal migration and for the laminar configuration of the cerebral cortex. In addition, p35/Cdk5 kinase concentrates at the leading edges of axonal growth cones and regulates neurite outgrowth in cortical neurons in culture. The Rho family of small GTPases is implicated in a range of cellular functions, including cell migration and neurite outgrowth. Here we show that the p35/Cdk5 kinase co-localizes with Rac in neuronal growth cones. Furthermore, p35 associates directly with Rac in a GTP-dependent manner. Another Rac effector, Pak1 kinase, is also present in the Rac-p35/Cdk5 complexes and co-localizes with p35/Cdk5 and Rac at neuronal peripheries. The active p35/Cdk5 kinase causes Pak1 hyperphosphorylation in a Rac-dependent manner, which results in down-regulation of Pak1 kinase activity. Because the Rho family of GTPases and the Pak kinases are implicated in actin polymerization, the modification of Pak1, imposed by the p35/Cdk5 kinase, is likely to have an impact on the dynamics of the reorganization of the actin cytoskeleton in neurons, thus promoting neuronal migration and neurite outgrowth.

cDNAs encoding the Drosophila 70-kDa S6 kinase (S6K) were isolated by low-stringency hybridization with mammalian p70S6k probes. Conceptual translation of S6k cDNA sequences yields a product containing all of the canonical features typical of serine/threonine kinases and has 78% amino acid identity in the catalytic domain with the human p70S6k homologue. The S6k gene, located at polytene chromosome site 65D, gives rise to two predominant transcripts of 3.0 and 5.0 kb and at least two smaller transcripts (< 3.0 kb) that are found in whole-animal RNAs at all stages of development. Blood cells derived from the hematopoietic organs of ribosomal protein S6 (RpS6air8) mutant animals express higher levels of the smaller S6k transcripts, suggesting tissue- or genotype-specific differences in the regulation of the S6k gene. Drosophila S6K expressed in COS or NIH 3T3 cells phosphorylates mammalian RPS6 in a mitogen-dependent wortmannin- and rapamycin-sensitive manner, suggesting that its regulation is similiar to mammalian p70S6k.

The 70 kDa ribosomol S6 kinase (pp70S6k) plays an important role in the progression of cells through G1 phase of the cell cycle. However, little is known of the signaling molecules that mediate its activation. We demonstrate that Rho family G proteins regulate pp70S6k activity in vivo. Activated alleles of Cdc42 and Rac1, but not RhoA, stimulate pp70S6k activity in multiple cell types. Activation requires an intact effector domain and isoprenylation of Cdc42 and Rac1. Coexpression of Dbl, an exchange factor for Cdc42, also activates pp70S6k. Growth factor-induced activation of pp70S6k is abrogated by dominant negative alleles of Cdc42 and Rac1. In addition, Cdc42 and Rac1 form GTP-dependent complex with the catalytically inactive form of pp70S6k in vitro and in vivo, suggesting a mechanism by which these G proteins activate pp70S6k.