1.3-µm identical active electro-absorption modulated laser with quantum well intermixed passive waveguide.

Quantum well intermixing (QWI) is an effective method for simple and well-defined monolithic integration of photonic devices. We introduce an identical-active electro-absorption modulated laser (IA-EML) with optimized QWI, which is applied to reduce the absorptive waveguide region. To determine the optimal intermixed IA-EML structure, we conduct a comparative analysis between the cases of an IA-EML with only an intermixed waveguide region and with both intermixed waveguide and electro-absorption modulator (EAM) regions, as well as the case without QWI. The results reveal that the intermixed region effectively inhibits the absorption in the waveguide. In particular, the IA-EML with only waveguide intermixing exhibits superior modulation characteristics with low driving voltages and a high extinction ratio. Our work provides an attractive approach for suppressing the absorptive waveguide region in the IA-EML to enhance modulation performance and to develop photonic integrated circuits with a simplified process.

Active control of polarization state of the light in InP waveguide.

We demonstrate an InP deep-ridge type multi-quantum-wells (MQWs) waveguide-based active polarization control scheme by using two positive-intrinsic-negative diode phase shifters. The polarization state of horizontal/vertical linearly polarized input light is rotated along the ± 45°-linear polarization axis on the Poincaré sphere by 45°-eigenmode-rotated first phase shifter 1 and subsequently rotated along the vertical/horizontal axis by second normal phase shifter 2. The rotation of the eigenmode axes is obtained by using the surface plasmonic effect. The effective index of the waveguide is changed via quantum-confined Stark effect in the MQW core. The length of each phase shifter is 240 µm. The applied reverse bias voltages are -2.7 V and -1.95 V for the phase shifter 1 and 2, respectively.

Integrated InP polarization rotator using the plasmonic effect.

we report on an integrated InP based polarization rotator scheme using the plasmonic effect. It operates as a half-wave retarder in ridge waveguide structure. The rotation angle of the eigenmode axes of the half-wave retarder waveguide is determined by the position off a bottom corner of a metal layer placed above the waveguide core in the upper cladding region. The simple rotator structure enables an easy and tolerant fabrication process. The length of the fabricated device is less than 50 µm, and a polarization extinction ratio (PER) of 20 dB has been achieved.

Design and performance of 10-Gb/s L-band REAM-SOA for OLT Transmitter in next generation access networks.

We present a 10-Gb/s L-band reflective electro-absorption modulator integrated with a semiconductor optical amplifier (REAM-SOA) having improved transmission performance at very low input power of seed light. To decrease the input power of seed light, the absorption characteristics of the REAM are adjusted to reduce the amplified spontaneous emission light returned into the SOA, suppressing the gain saturation effect of the SOA. At a considerably low input power of -16 dBm, the REAM-SOA exhibits a low transmission penalty of about 1.2 dB after 50-km SMF transmission. Over a wide input power range from -16 dBm to 5 dBm, a penalty of less than 1.6 dB is achieved at 50-km transmission.

B-cell translocation gene-2 increases hepatic gluconeogenesis via induction of CREB.

Hepatic gluconeogenesis is mediated by the network of transcriptional factors and cofactors. Here, we show that B-cell translocation gene-2 (BTG2) plays a crucial cofactor in hepatic gluconeogenesis via upregulation of the cyclic AMP (cAMP) response element binding (CREB) in hepatocytes. cAMP/dexamethasone (Dex) significantly increased BTG2 and other gluconeogenic genes such as Nur77, phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G6Pase) in hepatocytes. In contrast, insulin treatment completely blocks their expressions. Interestingly, overexpression of BTG2 using adenoviral system (Ad-BTG2) significantly elevated hepatic glucose production via the increase of transcriptional activity and gene expression of CREB, PEPCK, and G6Pase in hepatocytes, suggesting that BTG2 is the key player on hepatic glucose production. Physiological interaction studies demonstrated that BTG2 correlated CREB recruitment on the PEPCK gene promoter via a direct interaction. Finally, knockdown of endogenous BTG2 expression markedly inhibits the cAMP/Dex-induced transcriptional activity of gluconeogenic genes and glucose production in hepatocytes. Overall, the present study provides us with a novel molecular mechanism of BTG2-mediated induction of hepatic gluconeogenesis and suggests that BTG2 plays an important role in hepatic glucose metabolism.

Mitigation of Rayleigh crosstalk using noise suppression technique in 10-Gb/s REAM-SOA.

We demonstrate a mitigation of Rayleigh back-scattering (RBS) impact in 10-Gb/s reflective electroabsorption modulator monolithically integrated with semiconductor optical amplifier (REAM-SOA). The technique is based on the intensity-noise suppression of the centralized incoherent seed-light, which enables smooth evolution of deployed DWDM applications. We exhibit the power penalty of less than 1 dB at the large RBS crosstalk value of about 8 dB when the optical power of seed-light is lowered about -10 dBm.

10-Gb/s direct modulation of polymer-based tunable external cavity lasers.

We demonstrate a directly-modulated 10-Gb/s tunable external cavity laser (ECL) fabricated by using a polymer Bragg reflector and a high-speed superluminescent diode (SLD). The tuning range and output power of this ECL are measured to be >11 nm and 2.6 mW (@ 100 mA), respectively. We directly modulate this laser at 10 Gb/s and transmit the modulated signal over 20 km of standard single-mode fiber. The power penalty is measured to be <2.8 dB at the bit-error rate (BER) of 10(-10).

Citreorosein inhibits production of proinflammatory cytokines by blocking mitogen activated protein kinases, nuclear factor-κB and activator protein-1 activation in mouse bone marrow-derived mast cells.

Citreorosein (CIT), an anthraquinone component of Polygoni cuspidati (P. cuspidati) radix, suppressed gene expression of proinflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1ß in mouse bone marrow-derived mast cells (BMMCs) stimulated with phorbol 12-myristate 13-acetate (PMA) plus the calcium ionophore A23187. To investigate the molecular mechanisms underlying CIT inhibition of the pro-inflammatory cytokine production, its effects on the activation of both nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs) were assessed. CIT attenuated phosphorylation of the MAPKs including extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAP kinase and c-Jun NH(2)-terminal kinase (JNK). Furthermore, CIT strongly inhibited DNA binding activity of NF-κB through the inhibition of phosphorylation and degradation of inhibitor of kappaB (IκB) as well as activator protein-1 (AP)-1 through the reduction of phosphorylation of c-Jun. These results demonstrate that CIT inhibits proinflammatory cytokines production through the inhibition of both MAPKs and AKT-mediated IκB kinase (IKK) phosphorylation and subsequent inhibition of transcription factor NF-κB activation, thereby attenuating the production of proinflammatory cytokines.

Ring-resonator-integrated tunable external cavity laser employing EAM and SOA.

We propose and demonstrate a tunable external cavity laser (ECL) composed of a polymer Bragg reflector (PBR) and integrated gain chip with gain, a ring resonator, an electro-absorption modulator (EAM), and a semiconductor optical amplifier (SOA). The cavity of the laser is composed of the PBR, gain, and ring resonator. The ring resonator reflects the predetermined wavelengths into the gain region and transmits the output signal into integrated devices such as the EAM and SOA. The output wavelength of the tunable laser is discretely tuned in steps of about 0.8 nm through the thermal-optic effect of the PBR and predetermined mode spacing of the ring resonator.

Manassantin A isolated from Saururus chinensis inhibits 5-lipoxygenase-dependent leukotriene C4 generation by blocking mitogen-activated protein kinase activation in mast cells.

In this study, manassantin A (Man A), an herbal medicine isolated from Saururus chinensis (S. chinensis), markedly inhibited 5-lipoxygenase (5-LO)-dependent leukotriene C(4) (LTC(4)) generation in bone marrow-derived mast cells (BMMCs) in a concentration-dependent manner. To investigate the molecular mechanisms underlying the inhibition of LTC(4) generation by Man A, we assessed the effects of Man A on phosphorylation of cytosolic phospholipase A(2) (cPLA(2)) and mitogen-activated protein kinases (MAPKs). Inhibition of LTC(4) generation by Man A was accompanied by a decrease in cPLA(2) phosphorylation, which occurred via the MAPKs including extracellular signal-regulated protein kinase-1/2 (ERK1/2) as well as p38 and c-Jun N-terminal kinase (JNK) pathways. Taken together, the present study suggests the Man A represents a potential therapeutic approach for the treatment of airway allergic-inflammatory diseases.

10.7 Gb/s reflective electroabsorption modulator monolithically integrated with semiconductor optical amplifier for colorless WDM-PON.

We demonstrated 10.7 Gb/s reflective electroabsorption modulator monolithically integrated with semiconductor optical amplifier (REAM-SOA) using simplified fabrication process. Good performance at 10.7 Gb/s was obtained with an extinction ratio of > 10 dB and a power penalty of < 1 dB at a 10(-9) bit error rate (BER) up to 20 km transmission. The device operated over a 50 nm spectral range within 1 dB received power variation at a 10(-9) BER.

2.5-Gb/s hybridly-integrated tunable external cavity laser using a superluminescent diode and a polymer Bragg reflector.

We presented a hybridly-integrated tunable external cavity laser with 0.8 nm mode spacing 16 channels operating in the direct modulation of 2.5-Gbps for a low-cost source of a WDM-PON system. The tunable laser was fabricated by using a superluminescent diode (SLD) and a polymer Bragg reflector. The maximum output power and the power slope efficiency of the tunable laser were 10.3 mW and 0.132 mW/mA, respectively, at the SLD current of 100 mA and the temperature of 25 degrees C. The directly-modulated tunable laser successfully provided 2.5-Gbps transmissions through 20-km standard single mode fiber. The power penalty of the tunable laser was less than 0.8 dB for 16 channels after a 20-km transmission. The power penalty variation was less than 1.4 dB during the blue-shifted wavelength tuning.

L-band tunable external cavity laser based on 1.58 µm superluminescent diode integrated with spot-size converter.

We report a 1.58 µm superluminescent diode (SLD) with a spot-size converter (SSC) designed and fabricated as a light source for a tunable external cavity laser (T-ECL). The active section of the SLD is fabricated by using a planar buried heterostructure (PBH) for low-threshold current and high-output power operation at a low injection current. The SSC structure of the SLD is designed to possess a buried deep-ridge waveguide (BD-RWG) and show a beam of less divergence. The full-width at half maximum (FWHM) of the horizontal and vertical far-field patterns (FFPs), due to the beam of the less divergence, are 14° and 13°, respectively. We also confirm that an L-band T-ECL employing the SSC SLD operates well enough to prove the characteristics of high performance.

Improvement of modulation bandwidth in multisection RSOA for colorless WDM-PON.

We demonstrated two-section reflective semiconductor optical amplifier (RSOA) with dramatic improvement of small-signal modulation bandwidth above 10 GHz as colorless source for wavelength division multiplexed-passive optical network (WDM-PON). The device provides the fiber-to-fiber gain of 22.8 dB, 3-dB amplified spontaneous emission (ASE) bandwidth of 30 nm, and ripple of 1.5 dB. Good performance at 2.5 Gbps was obtained with an extinction ratio of 8 dB and a power penalty of 2 dB at a 10(-9) bit error rate (BER) up to 20 km transmission.

Controlling temperature dependence of silicon waveguide using slot structure.

We show that the temperature dependence of a silicon waveguide can be controlled well by using a slot waveguide structure filled with a polymer material. Without a slot, the amount of temperature-dependent wavelength shift for TE mode of a silicon waveguide ring resonator is very slightly reduced from 77 pm/ degrees C to 66 pm/ degrees C by using a polymer (WIR30-490) upper cladding instead of air upper cladding. With a slot filled with the same polymer, however, the reduction of the temperature dependence is improved by a pronounced amount and can be controlled down to -2 pm/ degrees C by adjusting several variables of the slot structure, such as the width of the slot between the pair of silicon wires, the width of the silicon wire pair, and the height of the silicon slab in our experiment. This measurement proves that a reduction in temperature dependence can be improved about 8 times more by using the slot structure.

Britanin Suppresses IgE/Ag-Induced Mast Cell Activation by Inhibiting the Syk Pathway.

The aim of this study was to determine whether britanin, isolated from the flowers of Inula japonica (Inulae Flos), modulates the generation of allergic inflammatory mediators in activated mast cells. To understand the biological activity of britanin, the authors investigated its effects on the generation of prostaglandin D2 (PGD2), leukotriene C4 (LTC4), and degranulation in IgE/Ag-induced bone marrow-derived mast cells (BMMCs). Britanin dose dependently inhibited degranulation and the generations of PGD2 and LTC4 in BMMCs. Biochemical analyses of IgE/Ag-mediated signaling pathways demonstrated that britanin suppressed the phosphorylation of Syk kinase and multiple downstream signaling processes, including phospholipase Cγ1 (PLCγ1)-mediated calcium influx, the activation of mitogen-activated protein kinases (MAPKs; extracellular signal-regulated kinase 1/2, c-Jun NH2-terminal kinase and p38), and the nuclear factor-κB (NF-κB) pathway. Taken together, the findings of this study suggest britanin suppresses degranulation and eicosanoid generation by inhibiting the Syk-dependent pathway and britanin might be useful for the treatment of allergic inflammatory diseases.

B-cell translocation gene 2 positively regulates GLP-1-stimulated insulin secretion via induction of PDX-1 in pancreatic ß-cells.

Glucagon-like peptide-1 (GLP-1) is a potent glucoincretin hormone and an important agent for the treatment of type 2 diabetes. Here we demonstrate that B-cell translocation gene 2 (BTG2) is a crucial regulator in GLP-1-induced insulin gene expression and insulin secretion via upregulation of pancreatic duodenal homeobox-1 (PDX-1) in pancreatic ß-cells. GLP-1 treatment significantly increased BTG2, PDX-1 and insulin gene expression in pancreatic ß-cells. Notably, adenovirus-mediated overexpression of BTG2 significantly elevated insulin secretion, as well as insulin and PDX-1 gene expression. Physical interaction studies showed that BTG2 is associated with increased PDX-1 occupancy on the insulin gene promoter via a direct interaction with PDX-1. Exendin-4 (Ex-4), a GLP-1 agonist, and GLP-1 in pancreatic ß-cells increased insulin secretion through the BTG2-PDX-1-insulin pathway, which was blocked by endogenous BTG2 knockdown using a BTG2 small interfering RNA knockdown system. Finally, we revealed that Ex-4 and GLP-1 significantly elevated insulin secretion via upregulation of the BTG2-PDX-1 axis in pancreatic islets, and this phenomenon was abolished by endogenous BTG2 knockdown. Collectively, our current study provides a novel molecular mechanism by which GLP-1 positively regulates insulin gene expression via BTG2, suggesting that BTG2 has a key function in insulin secretion in pancreatic ß-cells.

Saucerneol F, a new lignan, inhibits iNOS expression via MAPKs, NF-κB and AP-1 inactivation in LPS-induced RAW264.7 cells.

Saucerneol F (SF), a new tetrahydrofuran-type sesquilignan isolated from Saururus chinensis, dose-dependently inhibited nitric oxide (NO) production, with concomitant reduction of inducible nitric oxide synthase (iNOS) protein and mRNA expression in lipopolysaccharide (LPS)-stimulated murine macrophage RAW264.7 cells. To elucidate the molecular mechanism underlying the inhibition of iNOS expression by SF, we assessed the effects of SF on nuclear factor-κB (NF-κB) DNA-binding activity, NF-κB-dependent reporter gene activity, inhibitory factor-κB (IκB) phosphorylation and degradation, and p65 nuclear translocation. Treatment with SF decreased the luciferase activities of NF-κB reporter promoters in a dose-dependent manner and translocation of NF-κB p65. In addition, pretreatment of SF reduced LPS-stimulated activation of mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, and c-Jun NH(2)-terminal kinase (JNK). Furthermore, SF attenuated the luciferase activities of AP-1 reporter promoters and the DNA-binding capacity of AP-1. Taken together, the present results indicate that SF attenuates NO production and iNOS expression by blocking LPS-induced activation of NF-κB, MAPKs, and AP-1, suggesting that SF is potentially applicable as an anti-inflammatory drug.

Expression of cyclooxygenase-2 and pro-inflammatory cytokines induced by 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) in human mast cells requires NF-kappa B activation.

Mast cells are critical for initiating innate immune and inflammatory responses by releasing a number of pro-inflammatory mediators. The potential immunomodulatory properties of hydrogenated aromatic hydrocarbons have been the subject of extensive investigation, as the immune system is a sensitive target for hydrogenated aromatic hydrocarbon toxicity. In this report, the effects of polychlorinated biphenyl (PCB) on the expression of cyclooxygenase-2 and pro-inflammatory cytokines such as interleukin-1beta (IL-1beta), IL-6 and tumor necrosis factor (TNF)-alpha in the human leukemic mast cell line were investigated. TNF-alpha and IL-1beta expressed their respective mRNA in the presence or absence of PCB, while cyclooxygenase-2 (COX-2) and IL-6 mRNA expression were highly induced by PCB after 2 h. Moreover, pre-treatment with the nuclear factor (NF)-kappaB pathway inhibitor, pyrrolidine dithiocarbamate, suppressed COX-2, TNF-alpha and IL-1beta induction and reduced the IL-6 mRNA levels induced by PCB. The NF-kappaB activity was determined by electrophoretic mobility shift analysis (EMSA) using an oligonucleotide containing a consensus NF-kappaB binding sequence. Stimulating the cells with PCB activated NF-kappaB. However, pre-treating them with a NF-kappaB pathway inhibitor, pyrrolidine dithiocarbamate, suppressed PCB-induced NF-kappaB activation. This suggests that PCB induces cycloxoygenase-2 and pro-inflammatory cytokine expression, and that this induction occurs through NF-kappaB.