Regulation of Nectin-2 by Cadmium Chloride (CdCl2)

Poster presentationSession: Cell-Cell Junctions INectin-2 is a major component of the adherens junctions (AJs) between Sertoli cells and germ cells in the testis. Recent studies have shown that male knockout mice of nectin-2 are sterile. Cadmium (Cd), an environmental toxicant, is known to be also an endocrine disruptor that affects spermatogenesis. In this study, we investigate whether cadmium chloride (CdCl2) plays a role in nectin-2 expression. CdCl2 negatively regulates mRNA and protein levels of nectin-2 in mouse Sertoli cell line, TM4 cells. Luciferase reporter assays indicated that CdCl2 reduces nectin-2 promoter activity within the region of nucleotides (nt) -246 and -211 (relative to the translation start site) where putative transcription factors (TFs) binding motifs are identified. However, site-directed mutational studies have shown that no specific motif is found to involve in CdCl2-mediated nectin-2 gene repression. Hence, six consecutive cis-acting regions (each contains 6 nucleotides) between nt -246 and -211 are mutated respectively to identify the cisacting region involved in the CdCl2 effect. Results showed that the second 6-bp region (between nt -240 and -235) is involved in CdCl2-mediated reduction of nectin-2 promoter activity. In addition, putative TFs binding to this region are identified. By EMSAs, we found that DNA (nt - 240 to -235)-protein complexes are formed in a dose-dependent manner and CdCl2 treatment could diminish the formation of the complexes. Antibody supershift assays have shown that TFs, E2F1, Sp1 and KLF4, are present in the complexes. We also found that CdCl2 downregulates the expression level of these TFs including E2F1, Sp1 and KLF4 in the nucleus. Apart from transcriptional regulation, cycloheximide assay indicated that CdCl2 negatively modulates nectin-2 protein level via post-translational modification and we are now investigating the underlying mechanism. Taken together, CdCl2-mediated down-regulation of nectin-2 is mediated through transcriptional modification by negatively affecting its basal gene transcription and post-translational modification. [This work was supported by Hong Kong Research Grants Council (HKU772009 and HKU773710) and CRCG Seed Funding for Basic Research.]published_or_final_versio

Transforming Growth Factor-β3-Mediated Regulation of Junctional Adhesion Molecule-B (JAM-B) in Testicular Cells

Session: Cell-Cell Junctions IIPoster presentationJunctional adhesion molecule-B (JAM-B) is found between Sertoli cells as well as between Sertoli and germ cells in the testis. The expression of JAM-B is highly regulated to facilitate the passage of developing germ cells across the blood-testis barrier as well as the release of mature spermatids. Transforming growth factor beta (TGF-β) family is implicated in the regulation of testicular cell junction dynamics during spermatogenesis. This study aims to investigate the influence of TGF-β3 on the expression of JAM-B as well as the underlying mechanisms. TGF-β3 (5 ng/ml) treatment coupled with RT-PCR and immunoblot analyses have shown that TGF-β3 down-regulates JAM-B expression on mRNA and protein levels in a timedependent manner in mouse Sertoli cell line, MSC-1 cells. Cycloheximide assay further indicates that the reduction of JAM-B protein by TGF-β3 is mediated via post-translational modification. Moreover, the involvement of ubiquitin-proteasome pathway in TGF-β3-mediated JAM-B protein destabilization was demonstrated by proteasome inhibitor, MG-132, treatment and ubiquitin siRNA knockdown assays. Furthermore, co-immunoprecipitation (Co-IP) assay has further confirmed that JAM-B protein is conjugated by a chain of ubiquitin upon TGF-β3 stimulation in the presence of MG-132. TGF-β3 also speeds up the degradation of JAM-B through Smad-dependent pathway. As knockdown of Smad3 and/or Smad4 effectively abolish TGF-β3-mediated JAM-B degradation. Taken together, the involvement of both ubiquitinproteasome pathway and Smad-dependent signalling are essential for TGF-β3-mediated JAM-B regulation in mouse Sertoli cells. [This work was supported by Hong Kong Research Grants Council (HKU772009 and HKU773710) and CRCG Seed Funding for Basic Research.]published_or_final_versio

Novel bandwidth strategy for wireless P2P file sharing

With the rapid development of the mobile device technology and wireless network technology, the need of an efficient file sharing method on wireless network becomes more and more significant. Peer-to-Peer(P2P) file distribution, as a quite popular method being used now, is a promising choice. However, the limitation of bandwidth of wireless networks greatly restricts the performance of wireless P2P. In this paper, we propose a new idea of better utilizing the limited bandwidth to improve the file distribution performance. The criteria of an optimal splitting of the half-duplex bandwidth is deduced with mathematical analysis. To achieve a further improvement on the average distribution time, we also propose a grouping strategy which works with the bandwidth strategy. Simulation results show that our mechanism can efficiently reduce the file distribution time among wireless peers. © 2011 IEEE.published_or_final_versionThe 2011 IEEE Wireless Communications and Networking Conference (WCNC), Cancun, Mexico, 28-31 March 2011. In IEEE Wireless Communications and Networking Conference Proceedings, 2011, p. 2161-216

A novel grouping strategy for reducing average distribution time in P2P file sharing

Peer-to-Peer(P2P) file distribution has been widely used for file sharing in recent years. When compared with the traditional client-server model, the P2P model is a lot more efficient as each user can act as both a client and a server. This enables the P2P file distribution to scale well with increasing number of users. Grouping strategy has been introduced to reduce the average distribution time among peers without prolonging the total time needed to obtain a file. In this paper, a novel grouping strategy which groups peers of similar bandwidth together is introduced. We mathematically illustrate that under certain circumstances, this new grouping strategy performs better than the Greedy Grouping mechanism. To understand the performance of our grouping mechanism more comprehensively, we conduct extensive simulations. The results show that our mechanism can enhance the performance significantly in different network settings. ©2010 IEEE.published_or_final_versionThe 2010 IEEE International Conference on Communications (ICC), Cape Town, South Africa, 1-5 May 2010. In IEEE International Conference on Communications, 201

A power-efficient ultra-wideband pulse generator based on multiple PM-IM conversions

A novel photonic generation of power-efficient ultra-wideband (UWB) pulse by incoherent summation of two asymmetric monocycle pulses with inverted polarities is experimentally demonstrated. The principles of multiple cross-phase modulations in a highly nonlinear fiber and multiple phase modulation to intensity modulation conversions in a commercially available arrayed-waveguide grating are used. The combined UWB pulse exploiting spectral efficiency of 50.59% in experiment is fully compliant with the Federal Communications Commission (FCC) spectral mask without power attenuation. The FCC-compliant UWB pulse gains larger than 11.5- and 6-dB improvement against monocycle and doublet pulses after power attenuation to respect the FCC spectral mask, respectively. Such a power-efficient UWB pulse with pulse duration of approximately 320 ps has potential to achieve high-speed transmission without pulse overlapping and obvious distortion. © 2010 IEEE.published_or_final_versio

Photonic ultrawideband pulse generation with HNL-DSF-based phase and intensity modulator

We propose and experimentally demonstrate a photonic ultrawideband (UWB) pulse (monocycle and doublet) generator based on a highly nonlinear dispersion-shifted fiber (HNL-DSF). The pulsed pump, located in the anomalous group-velocity dispersion regime of the HNL-DSF, performs as both an intensity and a phase modulator in our scheme. We experimentally prove, for the first time to the best of our knowledge, that the UWB doublet pulse can be generated when the optical carrier is located at the center of a narrow tunable filter's passband. Furthermore, the encoded doublet signal, fully compliant with the Federal Communications Commission (FCC) regulations, is transmitted at 950 Mb/s through a 25-km single-mode fiber without introducing any obvious pulse distortion. © 2006 IEEE.published_or_final_versio

A power-efficient ultra-wideband pulse generator based on multiple PM-IM conversions

A novel photonic generation of power-efficient ultra-wideband (UWB) pulse by incoherent summation of two asymmetric monocycle pulses with inverted polarities is experimentally demonstrated. The principles of multiple cross-phase modulations in a highly nonlinear fiber and multiple phase modulation to intensity modulation conversions in a commercially available arrayed-waveguide grating are used. The combined UWB pulse exploiting spectral efficiency of 50.59% in experiment is fully compliant with the Federal Communications Commission (FCC) spectral mask without power attenuation. The FCC-compliant UWB pulse gains larger than 11.5- and 6-dB improvement against monocycle and doublet pulses after power attenuation to respect the FCC spectral mask, respectively. Such a power-efficient UWB pulse with pulse duration of approximately 320 ps has potential to achieve high-speed transmission without pulse overlapping and obvious distortion. © 2010 IEEE.published_or_final_versio

High-speed photonic power-efficient ultra-wideband transceiver based on multiple PM-IM conversions

We experimentally demonstrate a novel photonic ultra-wideband (UWB) transceiver with pulse spectral efficiency of 50.97% and transmission speed up to 3.125 Gb/s. The UWB generator only consists of a highly nonlinear fiber (HNLF) and a commercial arrayed-waveguide grating (AWG). By using the concept of multiple cross-phase modulation in the HNLF and multiple phase modulation to intensity modulation conversions in the AWG, a power-efficient UWB pulse is combined with incoherent summation of two asymmetric monocycle pulses with inverted polarities. Benefiting from the ultra-fast response of fiber nonlinearities in the HNLF, onoff keying encoded UWB signals generated at 781.25 Mb/s, 1.5625 Gb/s, and 3.125 Gb/s are all error-free transmitted through a 22.5-km single-mode fiber (SMF) with power penalties lower than 1 dB. The bit-error rate is directly measured on down-converted baseband signals by using optical full rectification and electrical low-pass filtering technologies. The measured electrical spectra before and after 22.5-km SMF link transmission both fully comply with the spectral mask specified by the U.S. Federal Communications Commission (FCC) without power attenuation. © 2006 IEEE.published_or_final_versio

A Neuroanatomical Signature for Schizophrenia Across Different Ethnic Groups

Schizophrenia is a disabling clinical syndrome found across the world. While the incidence and clinical expression of this illness are strongly influenced by ethnic factors, it is unclear whether patients from different ethnicities show distinct brain deficits. In this multicentre study, we used structural Magnetic Resonance Imaging to investigate neuroanatomy in 126 patients with first episode schizophrenia who came from 4 ethnically distinct cohorts (White Caucasians, African-Caribbeans, Japanese, and Chinese). Each patient was individually matched with a healthy control of the same ethnicity, gender, and age (±1 year). We report a reduction in the gray matter volume of the right anterior insula in patients relative to controls (P < .05 corrected); this reduction was detected in all 4 ethnic groups despite differences in psychopathology, exposure to antipsychotic medication and image acquisition sequence. This finding provides evidence for a neuroanatomical signature of schizophrenia expressed above and beyond ethnic variations in incidence and clinical expression. In light of the existing literature, implicating the right anterior insula in bipolar disorder, depression, addiction, obsessive-compulsive disorder, and anxiety, we speculate that the neuroanatomical deficit reported here may represent a transdiagnostic feature of Axis I disorders