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

Order parameter and current-phase relation in Josephson junctions composed of g+s-wave superconductors

Based on the analyses of bulk sensitive experimental data on penetration depths, Raman spectra, electron photoemission spectra, etc., G. M. Zhao concluded in a recent paper [Phys. Rev. B 64, 024503 (2001)] that the symmetry of high-Tc superconductors belongs to the g+s-wave type. To explore the common and uncommon features of the g+s-wave pairing state with respect to the d-wave pairing state, both superconductor-insulator-superconductor junction and superconductor-normal metal-superconductor junction have been studied self-consistently in this paper using the quasiclassical theory. The current phase relation for g+s-wave superconductors Δ(s,θ)=Δ0(s+cos 4θ) is investigated systematically as functions of s-wave component, crystal orientation angle β, as well as roughness ρ of the interface layer. Our results show that there exists a critical βC for a given s and ρ so that the current phase relation approaches asymptotically to I(φ)=ICsin(2φ) from I(φ)=ICsin(φ) as β→βC. The order parameter and βC-s relation are calculated self-consistently as interface roughness varies. Our results are compared with their counterparts in Josephson junctions with the d-wave pairing state obtained using a similar method.published_or_final_versio

A new Kalman filter-based power spectral density estimation for nonstationary pressure signals

IEEE International Symposium on Circuits and Systems, Island of Kos, Greece, 21-24 May 2006This paper presents a new Kalman filter-based power spectral density estimation (PSD) algorithm for nonstationary pressure signals. The pressure signal is assumed to be an autoregressive (AR) process, and a stochastically perturbed difference equation constraint model is used to describe the dynamics of the AR coefficients. The proposed Kalman filter frame uses variable number of measurements to estimate the time-varying AR coefficients and yield the PSD estimation with better time-frequency resolution. Simulation results show that the proposed algorithm achieves a better time-frequency resolution than conventional algorithms for nonstationary pressure signals. © 2006 IEEE.published_or_final_versio

Fabrication of Three-Dimensional Concave or Convex Shell Structures with Shell Elements at Micrometer Resolution in SU-8

This chapter presents a photo-lithographically-based technology for mass production of three-dimensional (3D) micro-structures with shell elements. In this technology, shell elements are photo-lithographically fabricated at micron or sub-micron resolution by illuminating with ultraviolet light radiating an ultraviolet light beam onto UV-opaque SU-8 monomer. The technology does not require any steps involving micro-injection molding or micro-stereolithography. Several prototypes have been fabricated to demonstrate the feasibility of this technology

A turning restriction design problem in urban road networks

Turning restriction is one of the commonest traffic management techniques and an effective low cost traffic improvement strategy in urban road networks. However, the literature has not paid much attention to the turning restriction design problem (TRDP), which aims to determine a set of intersections where turning restrictions should be implemented. In this paper, a bi-level programming model is proposed to formulate the TRDP. The upper level problem is to minimize the total travel cost from the viewpoint of traffic managers, and the lower level problem is to depict travelers' route choice behavior based on stochastic user equilibrium (SUE) theory. We propose a branch and bound method (BBM), based on the sensitivity analysis algorithm (SAA), to find the optimal turning restriction strategy. A branch strategy and a bound strategy are applied to accelerate the solution process of the TRDP. The computational experiments give promising results, showing that the optimal turning restriction strategy can obviously reduce system congestion and are robust to the variations of both the dispersion parameter of the SUE problem and the level of demand. © 2010 Elsevier B.V. All rights reserved.postprin

Investigating freeway traffic hypercongestion between an on-ramp and its immediate upstream off-ramp

This paper applies the freeway traffic congestion dynamics proposed in Laval and Leclercq [2010. “Continuum Approximation for Congestion Dynamics Along Freeway Corridors.” Transportation Science 44 (1): 87–97] but with a modified distribution scheme of freeway merging flows to investigation of traffic hypercongestion on a freeway between an on-ramp and its immediate upstream off-ramp. The reason to make this modification is that the original merging scheme of this dynamics is found to possibly give undesired full priority to the traffic from the on-ramp and also occasionally make the resulting flow going through the merge greater than the available capacity. Traffic hypercongestion in this paper refers to a state where speed and flow change in the same direction as density varies. A homogeneous freeway segment chosen for this investigation includes an on-ramp and an off-ramp, which may correspond to a freeway passing by a city or town, with an off-ramp lying upstream towards the city and an on-ramp downstream. The entry flow from the upstream approach of the freeway was fixed and constant within the time horizon while both deterministic and random on-ramp inflow rates were used in this investigation. Then the formation and dissipation of traffic hypercongestion is investigated as on-ramp demand and off-ramp departure profiles vary. The first finding of this investigation is that the density in the hypercongestion area behind the merge never reached the jam density. Second, the hypercongested area continued to grow as long as the sum of the demand from the upstream of the freeway and that from the on-ramp was greater than the available capacity at the merge. Third, as long as the rate of flow leaving from the freeway via the off-ramp was not smaller than the entry flow rates from the on-ramp, no hypercongestion had been observed. In addition, in analysing the numerical results, a series of discussions was carried out to build the linkage between the on- and off-ramp flow profiles and the generated and attracted demand of the city plus its adjacent area the two ramps served for; these discussions suggest that the balanced generated and attracted demand of the city plus its adjacent area can reduce or even remove traffic hypercongestion behind the merge on the chosen freeway segment.postprin