bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Macroporous Poly(divinylbenzene) Gels via Living Radical Polymerization
Authors: Hasegawa Joji , Kanamori Kazuyoshi , Nakanishi Kazuki , Hanada Teiichi , Yamago Shigeru
Published: February 2009

Macroporous cross-linked polymeric dried gels have been obtained by inducing phase separation in a homogeneous poly(divinylbenzene) (PDVB) network formed by organotellurium-mediated living radical polymerization (TERP). The living polymerization reaction of DVB with the coexistence of a non-reactive polymeric agent, poly(dimethylsiloxane) (PDMS), in solvent 1,3,5-trimethylbenzene (TMB) resulted in polymerization-induced phase separation (spinodal decomposition), and the transient structure of spinodal decomposition has been frozen by gelation. Well-defined macroporous monolithic dried gels with bicontinuous structure in the micrometer scale are obtained after removing PDMS and TMB by simple washing and drying. The properties of the macropores have been controlled by changing starting composition.
Multi-Scale Grafted Polymeric Nanostructures Patterned Bottom-Up by Colloidal Lithography and Initiated Chemical Vapor Deposition (iCVD)
Authors: Trujillo Nathan J. , Baxamusa Salmaan H. , Gleason Karen K.
Published: February 2009

Colloidal lithography is a popular, non-conventional process that uses two–dimensional self-assembled monolayer arrays of colloidal nanoparticles as masks for techniques such as etching or sputtering. Initiated Chemical Vapor Deposition (iCVD) is a surface controlled process which offers unprecedented opportunity for producing polymeric layers grafted to substrates with dangling vinyl bonds and patterned through a colloidal template. We demonstrate a generic “bottom-up” process as an inexpensive and simple technique for creating well-ordered arrays of functional patterned polymeric nanostructures. These patterns were produced from thin polymer films of p(butyl acrylate) and p(hydroxyethyl methacrylate), and are robustly tethered to the underlying substrate, as demonstrated by their ability to withstand aggressive solvents. Furthermore, using capillary force lithography, we created topographical templates for large-scale orientation of the nanoparticle assembly. Through this “top-down” approach, for assisting the bottom-up assembly, we present a process for multi-scale patterning of functional polymeric materials, without the need for expensive lithography tools.
Synthesis of Thermoresponsive Copolymers Composed of Poly(ethylene oxide) and Poly(N-isopropylacrylamide) for Cell Encapsulation
Authors: Trongsatitkul Tatiya , Budhlall Bridgette
Published: February 2009

Thermoresponsive copolymers of poly(N- isopropyl acrylamide) (PNIPAm) and poly(acrylamide) microgels grafted with poly(ethylene glycol)(PEG) chains were synthesized by free-radical photopolymerization. Poly(ethylene glycol) methyl ether methacrylate (PEGMA) macromonomers with varying number-average molecular weights were used (Mn = 300 and 1,000 g/mol). A simple microarray technique coupled with a laser scanning confocal microscope (LSCM) was used to visualize the effect of temperature on the volume phase transition temperatures of the microgels. In general, increasing the concentration of PEGMA in the PNIPAm-co-Am-co-PEGMA copolymers resulted in a broader and higher lower critical solution temperature (LCST) compared to the PNIPAm microgels. We demonstrated that the PEGMA molecular weight and concentration influenced whether it was incorporated as a grafted copolymer or random copolymer in the PNIPAm microgel. The evidence for this is the shift in the LCST as determined by temperature and differential scanning calorimetry (DSC) measurements. This behavior suggests that incorporation of PEGMA in the copolymer depends on its hydrophilicity or water-solubility which in turn influenced the degree at which the copolymer chains collapsed from a coil-to-globule (volume phase transition) with increasing temperature.
A Novel Gap Narrowing Process for Creating High Aspect Ratio Transduction Gaps for MEM HF Resonators
Authors: Stoffels Steve , Bryce George , Van Hoof Rita , Du Bois Bert , Mertens Robert , Puers Robert , Tilmans Harrie A.C. , Witvrouw Ann
Published: February 2009

In this work a novel technique to create nanometer sized air gaps for high frequency (HF) mechanical resonators will be presented. The technique is based on the narrowing of initially wide gaps with a conformal “narrowing” layer. The novelty of this technique is that it enables the creation of narrow high-aspect ratio gaps (e.g. 100nm gaps in 10μm thick layers) without the need for complex lithography or high aspect ratio etching. Furthermore, the electrodes and the resonator itself can be patterned in a single processing step. The process methodology will be explained and validation experiments in a silicon-germanium (SiGe) based technology will be shown. This technology uses low temperature (∼450°C) poly silicon-germanium (SiGe) as the structural layer, which can be processed above CMOS, and therefore allows the fabrication of MEM devices above CMOS.
Dicing of Fragile MEMS Structures
Authors: Lange Peter , Marenco Norman , Gruenzig Sven , Warnat Stephan , Semperowitsch Thilo
Published: February 2009

Stealth dicing appears to be the appropriate methode to singulate surface sensitive microelectromechanical devices, without producing dicing debris or using water jet. The operating mode of the stealth dicing will be explained. A three dimensional integration project with open micromachined structures is taken as a reference to evaluate the advantages and limitations of this new dicing method. The preconditions for successful singulations will be discussed. Optical and SEM inspection results after successful separation will be discussed.
Active Field Effect Capacitive Sensors for High-throughput, Label-free Nucleic Acid Analysis
Authors: Sebastian Mannoor Manu , James Teena , Ivanov Dentcho V. , Braunlin Bill , Beadling Les
Published: February 2009

We report a highly selective technique for the rapid and label-free analysis of nucleic acid sample using Metal Oxide Semiconductor (MOS) capacitive sensors. The binding of charged macromolecules such as DNA on the surface of these Field Effect Devices modifies the charge distribution in the Semiconductor (Si) region of the sensor. These changes are manifested as a significant shift in the Capacitance-Voltage (C-V) characteristics measured across the device. The speed and selectivity of the detection process is enhanced by the use of external electric field of controlled intensity. This simple and high-throughput sensing technique holds promises for the future electronic DNA arrays and Lab-on-a chip devices
Nanorods as a precursor for high quality GaN layers
Authors: Cherns David , Griffiths Ian , Khongphetsak Somboon , Novikov Sergei , Farley Nicola , Campion Richard , Foxon Tom
Published: February 2009

The density of threading dislocations in GaN/(0001)sapphire films grown by molecular beam epitaxy can be reduced to about 108 cm−2 by growing an intermediate nanorod layer. This paper examines the growth of the nanorods and proposes that threading defects in the overlayer arise either through grain boundaries formed when nanorods coalesce, or through the propagation of dislocation dipoles seen during nanorod growth. Results showing that the latter often terminate or develop into voids during growth are discussed.
Effects of an Applied Electric Field on Silicon Nanocrystals Photoluminescence
Authors: Lacombe Alexandre , Barba David , Beaudoin Félix , Martin François , Ross Guy G.
Published: February 2009

The photoluminescence (PL) of silicon nanocrystals (Si-nc) obtained by ion implantation in the oxide layer of a MOS structure was measured during the application of a slowly varying electric field generated by biasing the gate electrode. As a result, both PL intensity enhancement and quenching have been observed. These reproducible intensity modulations exhibit a hysteresis effect when the applied electric field is varied and persist even after it is removed. The behavior of the current density and the absence of wavelength shift in the PL spectra during gate voltage sweeps suggest that these modulations are related to the motion of charge carriers rather than to field-induced mechanisms such as quantum-confined Stark effect (QCSE).
Light Emission from Three-Dimensional Silicon-Germanium Nanostructures
Authors: Lockwood David J. , Baribeau J.-M. , Lee E.-K. , Chang H.-Y. , Tsybeskov Leonid
Published: February 2009

Three-dimensional SiGe nanostructures grown on Si using molecular beam epitaxy exhibit photoluminescence (PL) in the important spectral range of 1.3–1.6 μm. At a higher level of photo-excitation, thermal quenching of the PL intensity is suppressed and the previously accepted type II energy band alignment at Si/SiGe cluster hetero-interfaces no longer controls radiative carrier recombination. Instead, a dynamic type I energy band alignment governs the strong decrease in carrier radiative lifetime and further increase in the luminescence quantum efficiency. In contrast to the strongly temperature dependent and slow radiative carrier recombination found in bulk Si, Auger mediated PL emanating from the nanometer-thick Si layers is found to be nearly temperature independent with a radiative lifetime approaching 10−8 s, which is comparable to that found in direct band gap III-V semiconductors. Such nanostructures are thus potentially useful as CMOS compatible light emitters and in optical interconnects.
Toxicity Effect of Cancer Cell Labeled with Visible Luminescent Nanocrystalline Silicon Particles and Visualization Observationin Vivo
Authors: Sato Keisuke , Hiruoka Masaki , Fujioka Kohki , Fukata Naoki , Hirakuri Kenji , Yamamoto Kenji
Published: February 2009

Cytotoxicity of human cervical carcinoma cell line (HeLa cells) labeled with the nanocrystalline silicon (nc-Si) particles before and after ultraviolet (UV) light exposure has studied on the viability and cellular membrane damages. The viability and cellular membrane damages of HeLa cells changed at high particle concentration of 1.12 mg/ml. The viability of HeLa cells labeled with the UV-exposed nc-Si particles was higher than that of unexposed nc-Si particles. However, the variation of cellular membrane damages was almost same for the nc-Si particles before and after UV exposure. These results substantiated the low toxicity of nc-Si particles. Moreover, the HeLa cells labeled with the nc-Si particles exhibited green fluorescence. On the other hand,in vivotest of nc-Si particles estimated by the visualization observation of the circulation from the lymphatic vessel to the lymph node of a mouse. The transfer pathway of nc-Si particles could be clearly monitored by the strong emission of red light.
Nanofabrication of High-resolution and Nanofocusing X-ray Optics Based on Silicon and Diamond: Obstacles and Progress
Authors: Isakovic Abdel F. , Evans-Lutterodt K. , Stein A. , Warren J. B. , Narayanan S. , Sandy A. R.
Published: February 2009

Nanofocusing, high-resolution X-ray optics demand good surface quality, the absence of tapered sidewalls, and a depth reaching into tens, sometimes hundreds of microns, all requirements that must be satisfied over large areas. In this report, we discuss our motivation for choosing group IV materials (predominantly Si, and C in its diamond form) for nanofocusing and high resolution in the hard X-ray portion of the spectrum. We elaborate on the design and nanofabrication procedures, and detail the etching parameters that offer a path for overcoming obstacles in making better optics. We briefly review tests for the assessing the quality of the optics.
ZnS, CdS and ZnxCd1-xS Thin Films from Zn(II) and Cd(II) Complexes of 1, 1, 5, 5-Tetramethyl-2-4-dithiobiuret As Single Molecular Precursors
Authors: Ramasamy Karthik , Malik Mohammad A. , O'Brien Paul , Raftery James
Published: February 2009

Synthesis of zinc and cadmium complexes of 1, 1, 5, 5-tetramethyl-2-4-dithiobiuret (M{N(SCNMe2)2}2) (M = Zn, Cd) is described together with X-ray single crystal of cadmium complex. These complexes have been used as a single molecular precursor for the deposition of ZnS, CdS and ZnxCd1-xS thin films by aerosol assisted chemical vapour deposition (AACVD) method. Adherent specular films of ZnS and CdS were obtained in the temperature range 300 – 500 °C. Hexagonal ZnxCd1-xS films were obtained at 400 °C by varying the precursor concentration. XRD of ZnS films showed cubic to hexagonal phase conversion above 350 °C. SEM showed that the morphology of the films varied depending on the deposition temperature. Films were also characterized by atomic force microscopy (AFM). To the best of our knowledge these complexes are the first in its class to be used as a single molecular precursor to deposit ZnS, CdS, and ZnxCd1-xS thin films.
New Aspects of Borate Chemistry under High-Pressure
Authors: Huppertz Hubert
Published: February 2009

At the moment, over 1100 borate crystal structures are listed in the Inorganic Crystal Structure Database ICSD. High-pressure investigations in this field are rare and were mainly performed from a geological point of view. Starting in 1999, systematic high-pressure / high-temperature experiments up to maximum pressures of 16 GPa have been carried out, using the multianvil technique to explore the synthetic possibilities in the field of borates under extreme conditions. This approach led to a variety of interesting new materials, which are unattainableviaconventional solid state syntheses. The communication will give a short survey of the most important results in the last years.
Driving Electrons to Anti-Bonding States: On the Synthesis of New Niobium Cluster Chlorides by Electrochemical Lithium Intercalation
Authors: Garcia-Alvarado Flaviano , Kuhn Alois , Gonzalo Elena , Meyer H. Juergen
Published: February 2009

The lithium intercalation chemistry of LiNb6Cl15, a 16 e− Nb-cluster, has been explored in order to obtain new Nb-cluster compounds. As a result, three different phases have been detected. Full de-intercalation of lithium produces Nb6Cl15, a new 15 e− Nb-cluster. The oxidation reaction is reversible since lithium can be intercalated again to produce the parent LiNb6Cl15. On the other hand, intercalation of lithium into LiNb6Cl15 seems to proceed through two single phases with the following stoichiometries: Li1.5Nb6Cl15 and Li3Nb6Cl15. For these two compositions the extra electrons (0.5 and 2 respectively/formula) should enter the eg* molecular orbitals arising from Nb-Nb interactions inside the cluster. The reductions of LiNb6Cl15 leading to these two new electron-rich Nb-cluster are reversible as detected by chronopotentiometry.
Electronic Structure, Magnetism and Spin-Fluctuations in Fe-As Based Superconductors
Authors: Singh David Joseph , Du Mao-Hua , Zhang Lijun , Subedi Alaska , An Jiming
Published: February 2009

The physical properties of the layered iron superconductors and related phases are discussed starting from first principles calculations. The electronic structure is described as that of metallic Fe2+ square lattice sheets with substantial direct Fe-Fe hopping and interactions with the neighboring anionic pnictogens or chalcogens. The materials have a semi-metallic band structure, and in particular the Fermi surface consists of small cylindrical electron sections centered at the zone corner, and compensating hole sections at the zone boundary. The density of states N(EF) is high placing the materials near itinerant magnetism in general, and furthermore the small Fermi surface sections are well nested leading to a tendency towards a spin density wave. Comparison of experimental and density functional results imply the presence of exceptionally strong spin fluctuations in these materials. Superconductivity is discussed within this context.
A Study of [Cr-O6]-based rutile analogues by means of EELS
Authors: Arevalo-Lopez Angel M. , Castillo-Martinez Elizabeth , Alario-Franco Miguel Ángel
Published: February 2009

We present in here the study by means of electron energy loss spectroscopy (EELS) of several rutile based oxides, having in common the presence of octahedrally oxygen coordinated chromium, [Cr-O6], in three different formal oxidation states: Cr4+ in CrO2, a regular rutile; Cr3+ in CrOOH, a H bonded orthorrombic distorted rutile and in CrTaO4, a metal disordered rutile and Cr2+ in CrTa2O6 an ordered trirutile structure. A linear relationship is observed between the formal oxidation state of chromium in all these rutile oxides and the separation between the Cr-L2,3 and O-K energy loss peaks.
Single-Crystal Thin Films of SrFeO2 and LaNiO2 with Infinite-Layer Structures
Authors: Shimakawa Yuichi , Inoue Satoru , Kawai Masanori , Ichikawa Noriya , Mizumaki Masaichiro , Kawamura Naomi
Published: February 2009

Infinite-layer-structure epitaxial thin films of SrFeO2 and LaNiO2 respectively were prepared by low-temperature reduction with CaH2 from brownmillerite SrFeO2.5 and perovskite LaNiO3 epitaxial thin films grown on single-crystal substrates. The reduction process, removing oxygen ions from the perovskite-structure framework and causing rearrangements of oxygen ions, topotactically transforms the initial compounds to the c-axis oriented infinite-layer-structure epitaxial thin films. Consequently, the oxidation state of transition-metal ions in the film changed in wide ranges.
Single Step Synthesis of Y2O3:Eu3+ Nanophosphor Prepared by Flame Spray Pyrolysis
Authors: Lee Jae Seok , Kim Sejin , Oh Myoung Hwan , Ranade Madhav B , Singh Rajiv K
Published: February 2009

A novel ceramic synthesis technique, flame spray pyrolysis (FSP) was investigated for the production of nanophosphor particles. Among the various types of synthesis technique for phosphors, FSP is a powerful method which is capable of producing particles with good crystallinity and high luminescence efficiency. Red light emitting Eu3+ doped Y2O3 nanophosphor was prepared by FSP from nitrate based liquid precursors with high flame temperature. Flame temperature is an important factor to obtain phosphor particles with dense and spherical shape. Different molar percentage of urea was added into the precursor, addition of urea increases the temperature in the flame zone and promotes the formation of nano-size and spherical shaped particles. The importance of urea in the precursor to obtain well dispersed Y2O3:Eu3+ nanophosphor has been studied. The characteristics of nanophosphor such as crystallinity, morphology and photoluminescence in the presence of different moles of urea in nitrate based aqueous solution were investigated. On varying the overall concentration of the precursor, both the optical properties and crystallinity were investigated. XRD spectra showed as-prepared phosphors were obtained directly as cubic phase Y2O3:Eu3+ nanophosphor with high crystallinity and without any post-heat treatments. Luminescence intensity of nanophosphor increased with the amount of urea till 2 M percentages, further increase in urea concentration was found to reduce the PL intensity. We have developed a continuous single-step fabrication method for nanocrystalline Y2O3:Eu3+ nanophosphor without any post-heat treatments procedure.
Organically-functionalised supertetrahedra as building blocks for hybrid materials
Authors: Vaqueiro Paz , Romero M Lucia
Published: February 2009

The crystal structures of gallium sulfides prepared under solvothermal conditions, using 4-picoline as a solvent, are described. These materials contain [Ga10S16(NC6H7)4]2− clusters, in which the terminal S2− anions have been replaced by covalently bonded 4-picoline molecules. Whilst these phases contain isolated supertetrahedral clusters separated by organic moieties, linkage of such clusters via organic ligands is possible under suitable reaction conditions. These organically-functionalised supertetrahedra could therefore be used to design novel Metal-Organic frameworks (MOFs) in which the normally-encountered metal centers are replaced by supertetrahedral clusters.
Mixed Valent Rhodates
Authors: Mizoguch Hiroshi , Sleight Arthur William , Subramanian Mas
Published: February 2009

Exploratory synthesis of mixed oxides of rhodium has produced many new rhodates containing both Rh3+ and Rh4+. The structures of all the compounds are based on networks formed from RhO6 octahedra sharing both corners and edges. All compounds exhibit good electrical conductivity, and some also show a high thermopower.
Crystallization Processes of Amorphous Si During Excimer Laser Annealing in Complete-melting and Near-complete-Melting Conditions: A Molecular Dynamics Study
Authors: Ogata Tomohiko , Mitani Takanori , Munetoh Shinji , Motooka Teruaki
Published: February 2009

We investigated crystallization processes of amorphous Si (a-Si) during the excimer laser annealing in the complete-melting and near-complete-melting conditions by using molecular dynamics simulations. The initial a-Si configuration was prepared by quenching liquid Si (l-Si) in a MD cell with a size of 50×50×150Å3 composed of 18666 atoms. KrF excimer laser (wavelength: 248nm) annealing processes of a-Si were calculated by taking account of the change in the optical constant upon melting during a laser pulse shot with the intensity Ioexp[−(t–t0)2/ς2] (Io: laser fluence, t: irradiation time). The refractive indices of a-Si and l-Si were set at n+ik=1.0+3.0i and n+ik=1.8+3.0i, respectively. The simulated results well reproduced the observed melting rate and the near-complete-melting and complete-melting conditions were obtained for Io = 160mJ/cm2 and 180mJ/cm2, respectively. It was found that larger grains were obtained in the near-complete-melting condition. Our MD simulations also suggest that nucleation occurs first in a-Si and subsequent crystallization proceeds toward l-Si in the near-complete-melting case.
Pre-edge peak of Ti K XANES: Determined by Short- or Medium-Range Structure?
Authors: Jiang Nan
Published: February 2009

The calculations of Ti K-edge X-ray absorption near-edge structures (XANES) in fresnoite Sr2TiSi2O8 are carried out using multiple-scattering method. The origins of the pre-edge peak along with the fine structures in the main peak of Ti K-edge XANES are interpreted by comparing the calculations in various modified structure models. It concludes that the pre-edge peak is dominantly determined by the structure (including both coordination and bond lengths) within the nearest-neighbor distance, while the fine structures beyond the pre-edge peak region are sensitively determined by the structure extending to the medium-range distance
Loss of neuronatin expression is associated with promoter hypermethylation in pituitary adenoma
Authors: Revill K , Dudley K J , Clayton R N , McNicol A M , Farrell W E
Published: February 2009

The imprinted gene, neuronatin (NNAT), is one of the most abundant transcripts in the pituitary and is thought to be involved in the development and maturation of this gland. In a recent whole-genome approach, exploiting a pituitary tumour cell line, we identified hypermethylation associated loss of NNAT. In this report, we determined the expression pattern of NNAT in individual cell types of the normal gland and within each of the different pituitary adenoma subtypes. In addition, we determined associations between expression and CpG island methylation and used colony forming efficiency assays (CFE) to gain further insight into the tumour-suppressor function of this gene. Immunohistochemical (IHC) co-localization studies of normal pituitaries showed that each of the hormone secreting cells (GH, PRL, ACTH, FSH and TSH) expressed NNAT. However, 33 out of 47 adenomas comprising, 11 somatotrophinomas, 10 prolactinomas, 12 corticotrophinomas and 14 non-functioning tumours, irrespective of subtype failed to express either NNAT transcript or protein as determined by quantitative real-time RT-PCR and IHC respectively. In normal pituitaries and adenomas that expressed NNAT the promoter-associated CpG island showed characteristics of an imprinted gene where ∼50% of molecules were densely methylated. However, in the majority of adenomas that showed loss or significantly reduced expression of NNAT, relative to normal pituitaries, the gene-associated CpG island showed significantly increased methylation. Induced expression of NNAT in transfected AtT-20 cells significantly reduced CFE. Collectively, these findings point to an important role for NNAT in the pituitary and perhaps tumour development in this gland.
Endocrine disruptive chemicals: mechanisms of action and involvement in metabolic disorders
Authors: Swedenborg Elin , Rüegg Joëlle , Mäkelä Sari , Pongratz Ingemar
Published: February 2009

Endocrine disruption refers to the ability of chemicals to interfere with hormonal systems, and has raised considerable concern in recent years. Endocrine disruptive chemicals (EDCs) pose a documented risk to wildlife and have the potential to negatively influence human health. This review focuses on the molecular mechanisms of endocrine disruption and the possible involvement of EDCs in metabolic disorders. The first part describes the role of aryl hydrocarbon receptor (AhR) and nuclear receptors (NRs) in mediating effects of EDCs, in particular, how cross-talk between AhR and NR pathways can lead to endocrine disruption. The second part deals with how these receptors are involved in metabolic functions and how their targeting by EDCs can lead to disturbances in glucose and fat metabolism. The article illustrates that, although there is accumulating data on molecular mechanisms of EDC action as well as on EDC involvement in metabolic disorders, there is still a great demand for data that can unite the mechanistic and the toxicological/epidemiological observations.
The retinoid X receptor binding to the thyroid hormone receptor: relationship with cofactor binding and transcriptional activity
Authors: Tagami Tetsuya , Yamamoto Hiroyuki , Moriyama Kenji , Sawai Kuniko , Usui Takeshi , Shimatsu Akira , Naruse Mitsuhide
Published: February 2009

Transcriptional regulation is mediated by thyroid hormone (tri-iodothyronine, T3) receptors (TR), which bind to T3 response elements as heterodimers with retinoid X receptors (RXR). TR binds to corepressor proteins (CoR) in the absence of T3, which mediate transcriptional repression and to coactivator proteins (CoA) in the presence of T3, which mediate transcriptional stimulation, by recruiting additional proteins to the promoter. To determine the relationship between TR functions and cofactor bindings, we selected 13 single-point mutants on the ligand binding domain of TR, of which T3 bindings were well preserved and created VP16 chimeric receptors. Using mammalian two-hybrid assays, RXR binding in the absence of T3 was almost abolished for Y406K (helix; H10) and L422R (H11), while it was preserved for most other TR mutants. RXR binding was increased for I280K, V284R (H3), and C309K (H6). Addition of T3 enhanced RXR binding and T3 restored the RXR binding to Y406K but not to L422R. CoR binding was reduced for P214R, W219K (H1), R316H (H6), D366R (H9), and M423A (H11) in addition to the mutants of which RXR binding was affected, and CoA binding was impaired for I280K, V284R (H3), C309K (H6), and E457K (H12), indicating that sites for CoR, CoA, and RXR binding partially overlap. CoR binding was well correlated with T3-independent transcriptional regulation and CoA binding was well correlated with T3-dependent regulation, while RXR binding was not correlated with any of these functions among TR mutants, suggesting that transcriptional regulation by TR is mainly mediated by an exchange of CoRs and CoAs.
Misexpression of CCAAT/enhancer binding protein beta causes osteopenia
Authors: Zanotti Stefano , Stadmeyer Lisa , Smerdel-Ramoya Anna , Durant Deena , Canalis Ernesto
Published: February 2009

CCAAT/enhancer binding proteins (C/EBPs) are expressed by osteoblasts and adipocytes during differentiation. C/EBPβ is critical for adipogenesis; however, its role in osteoblastogenesis is unclear, and its function in the postnatal skeleton is not known. To study C/EBPβ in osteoblasts in vivo, we created transgenic mice expressing full length C/EBPβ under the control of a 3.8 kb fragment of the human osteocalcin promoter. Two transgenic lines were established in a friend leukemia virus strain B genetic background, and compared with wild type littermate controls. Both C/EBPβ transgenic lines exhibited osteopenia, with a 30% decrease in bone volume, due to a decrease in trabecular number. The number of osteoblasts and osteoclasts per bone perimeter was not changed. Bone marrow stromal cells from C/EBPβ transgenics showed reduced mineralization, and reduced alkaline phosphatase mRNA levels. Calvarial osteoblasts from C/EBPβ transgenics displayed reduced alkaline phosphatase activity. To determine the consequences of the Cebpb deletion in vivo, the phenotype of Cebpb null mice was compared with that of wild type controls of identical genetic composition. Cebpb null mice exhibited reduced weight, body fat, and bone mineral density, and decreased bone volume, due to a decrease in trabecular number. The number of osteoblasts and osteoclasts per bone perimeter was not changed. C/EBPβ downregulation by RNA interference in calvarial osteoblasts had no effect on osteoblast differentiation/function. The phenotype of the Cebpb inactivation may be secondary to systemic indirect effects, and to direct effects of C/EBPβ in osteoblasts. In conclusion, C/EBPβ plays a role in mesenchymal cell differentiation and its misexpression in vivo causes osteopenia.
No increase in colonization rate of boreal bryophytes close to propagule sources
Authors: Hylander Kristoffer
Published: February 2009

Knowledge of the process of recolonization, and which temporal and spatial scale it operates on, is central to our understanding of species distributions, metapopulation dynamics, regional extinction risks, and ecosystem resilience. In this study the recolonization pattern of boreal forest bryophytes was investigated in stands that had been clear‐cut ∼50 years ago. Species known to be sensitive to clear‐cutting were inventoried in 23 mature forest stands and in adjacent young stands at 10, 20, 40, and 80 m from the former forest–clear‐cut edge. Based on previous studies showing that bryophytes tend to be dispersal limited at local population levels, it was hypothesized that the recolonizaton of many bryophyte species should be higher closer to the mature forest edge. It was also hypothesized that some species would show full recovery, while for others the young stands would still be inhospitable. All these patterns were found for individual species, but the main pattern was, however, quite different. Most species had started to recolonize the young stands (i.e., little or much, depending on species), but without any tendency of a higher colonization rate close to the mature stands. Possible explanations for the limited signs of positive influence of local propagule sources might be microsite limitation or that the local propagule availability displays a rapid decline from its sources and is masked by a higher regional propagule rain. For organisms with light propagules able to build up a regional background level, the role of mature forest stands in the recolonization process of the matrix may rather be to contribute to the regional background level of spores in the landscape than to affect the adjacent stands directly.
Habitat edges, within‐patch dispersion of hosts, and parasitoid oviposition behavior
Authors: Cronin James T.
Published: February 2009

Although density–edge effects are commonly reported, we have only scratched the surface in understanding the mechanisms underlying how habitat edges mediate species interactions. Here, I use a combination of field surveys and experiments to explore the linkages between the presence of host‐plant edges (Scolochloa festucacea), the within‐patch distribution of planthopper eggs (Delphacodes scolochloa), and the oviposition behavior of their egg parasitoids (Anagrus spp.). The field surveys revealed that densities of hosts and parasitoids at the edge were ≥2.5 times lower than densities in the patch interior and that the effect was independent of patch size. As a consequence of its edge‐avoidance behavior, host within‐patch dispersion was significantly more aggregated in the presence, as compared to the absence, of an edge. Also, as patch size decreased, the proportion of the patch that was core (i.e., beyond the influence of the edge) decreased, and the degree of host aggregation increased. In a subsequent field experiment, I found that the dispersion of hosts affected Anagrus oviposition behavior only when hosts were present on islands with discrete edges. Under these circumstances, the proportion parasitized and per capita parasitized were 2.3 and 3.4 times higher, respectively, when hosts were clumped as compared to when hosts were uniformly or randomly distributed. Based on a laboratory experiment using small S. festucacea patches, I found that Anagrus had 40% shorter step lengths, spent 52% more time in the patch, and parasitized 84% more hosts when hosts were clumped as compared to uniformly distributed. These results were indicative of area‐restricted search by Anagrus, which is an effective foraging strategy when hosts are clumped. This is the first study to demonstrate that predator foraging behavior in response to prey dispersion can be mediated by the presence of a patch edge. Also, because edge‐averse behavior is commonly reported in the literature, an underappreciated effect of fragmentation on predator–prey interactions and stability could arise from edge‐mediated effects on prey within‐patch aggregation.
Perturbation analysis for patch occupancy dynamics
Authors: Martin Julien , Nichols James D. , McIntyre Carol L. , Ferraz Gonçalo , Hines James E.
Published: February 2009

Perturbation analysis is a powerful tool to study population and community dynamics. This article describes expressions for sensitivity metrics reflecting changes in equilibrium occupancy resulting from small changes in the vital rates of patch occupancy dynamics (i.e., probabilities of local patch colonization and extinction). We illustrate our approach with a case study of occupancy dynamics of Golden Eagle (Aquila chrysaetos) nesting territories. Examination of the hypothesis of system equilibrium suggests that the system satisfies equilibrium conditions. Estimates of vital rates obtained using patch occupancy models are used to estimate equilibrium patch occupancy of eagles. We then compute estimates of sensitivity metrics and discuss their implications for eagle population ecology and management. Finally, we discuss the intuition underlying our sensitivity metrics and then provide examples of ecological questions that can be addressed using perturbation analyses. For instance, the sensitivity metrics lead to predictions about the relative importance of local colonization and local extinction probabilities in influencing equilibrium occupancy for rare and common species.
Sexual Autophagic Differences in the Androgen‐Dependent Flank Organ of Syrian Hamsters
Authors: Coto‐Montes Ana , Tomás‐Zapico Cristina , Martínez‐Fraga Jorge , Vega‐Naredo Ignacio , Sierra Verónica , Caballero Beatriz , Huidobro‐Fernández Covadonga , Soria‐Valles Clara , Tolivia Delio , Rodríguez‐Colunga Maria Josefa
Published: February 2009

ABSTRACT: The flank organ of the Syrian hamster shows a biodynamic response to androgenic stimulation and is, therefore, a suitable model for the study of androgenic effects on hair and sebaceous glands. This organ is susceptible to programmed cell death (PCD), a prominent feature associated with sexual organ adjustment. In the present report, the type of PCD (apoptosis or autophagy) exhibited by this organ was evaluated. Caspase‐3 activity, indicative of apoptosis, was not detectable in flank organ homogenates. Furthermore, cytokeratins, which are normally degraded during apoptosis, remained intact. On the other hand, Western blotting of Beclin 1 and light chain 3‐II, both important autophagy markers, revealed autophagic processes in the flank organ in both sexes, especially in females. Cathepsin D activity, higher in males than in females, and procathepsin D expression were also consistent with autophagy and not apoptosis. Taken together, these data indicate that macroautophagy, and not apoptosis, is the main mechanism by which the flank organ responds to androgen. This is the first direct evidence establishing the relationship between autophagy and morphological changes in androgen‐dependent organs.
Expression of Nitric Oxide Synthase During Germ Cell Apoptosis in Testis of Cynomolgus Monkey After Testosterone and Heat Treatment
Authors: Guo Jian , Jia Yue , Tao Shi‐Xin , Li Yin‐Chuan , Zhang Xue‐Sen , Hu Zhao‐Yuan , Chiang Naomi , Lue Yan‐He , Hikim Amiya P. Sinha , Swerdloff Ronald S. , Wang Christina , Liu Yi‐Xun
Published: February 2009

ABSTRACT:This study investigates the possible involvement of nitric oxide synthase (NOS) in activating germ cell death in monkeys after mild testicular hyperthermia and/or hormonal deprivation. Groups of 8 adult male monkeys received 1 of the following treatments for 12 weeks: 1) 2 empty Silastic implants, 2) 2 testosterone (T) implants, 3) daily exposure of testes to heat (43°C for 30 minutes) for 2 consecutive days, or 4) 2 T implants plus testicular heat exposure. Testicular biopsies were performed before and on days 3, 8, 28, and 84 of the treatment. In control monkey testes, endothelial NOS (eNOS) was observed mainly in Sertoli cells and spermatogonia. No obvious alteration in eNOS levels was detected in any of the treatment group as assessed by Western blotting. Induction of inducible NOS (iNOS) in testes of the 3 treated groups was detected by immunoblotting as early as day 3 after treatment compared with that of controls. Immunocytochemistry further revealed a small increase in iNOS expression in both germ cells and Sertoli cells after T treatment. However, treatment of heat or heat in combination with T markedly induced iNOS expression in germ cells. These data suggest that iNOS, but not eNOS, may be involved in monkey testicular germ cell death after heat and/or T treatment.
Nitric Oxide—Dependent Human Acrosomal Loss Induced by PPCM (SAMMA) and by Nitric Oxide Donors Occurs by Independent Pathways: Basis for Synthesis of an Improved Contraceptive Microbicide
Authors: Anderson Robert A. , Feathergill Kenneth A. , Chany Calvin J. , Jain Sanjay , Krunic Aleksej
Published: February 2009

ABSTRACT:PPCM (previously designated sulfuric acid—modified mandelic acid [SAMMA]) is a contraceptive microbicide in preclinical development. Its contraceptive activity is attributable in part to its ability to promote premature acrosomal loss. Prior studies showed that PPCM‐induced human acrosomal loss (PAL) is Ca2+‐dependent. This study was carried out to determine transduction elements downstream from Ca2+entry. PAL is inhibited by inhibitors selective for endothelial‐type nitric oxide synthase. PAL is completely inhibited by 0.1 μM ODQ (soluble guanylate cyclase inhibitor). PAL is inhibited by protein kinase G inhibitors with selectivity for the type II isotype. Several inhibitors of the nitric oxide/cyclic guanosine monophosphate (cGMP)/protein kinase G pathway induce Ca2+‐dependent acrosomal loss when added alone. These responses are inhibited by nifedipine, a blocker of Cav1.xvoltage‐dependent channels. Acrosomal loss induced by the nitric oxide donor SNAP (SNAL) does not require added Ca2+. Sperm production of nitric oxide is increased by PPCM, an effect inhibited by nitro‐l‐arginine (nitric oxide synthase inhibitor). Although inhibited by ODQ, SNAL and acrosomal loss induced by other nitric oxide donors are unaffected by KT5823 (protein kinase G inhibitor). Unlike PAL, SNAL is partially inhibited by KT5720 (protein kinase A inhibitor) and genistein (protein tyrosine kinase inhibitor). Acrosomal loss response to PPCM and SNAP added in combination suggests that these agents act by independent mechanisms. A PPCM derivative was synthesized, in which a nitric oxide donor was esterified to PPCM (NOSPPA‐23). NOSPPA‐23 induces acrosomal loss with or without added Ca2+. The ED50of NOSPPA‐23 (4.8 nM) in the presence of Ca2+is 35‐fold less than that of PPCM. These findings suggest the following: 1) elements responsible for PAL include endothelial nitric oxide synthase, soluble guanylate cyclase, and type II protein kinase G; 2) the resting state of the nitric oxide/cGMP/protein kinase G pathway is a determinant of acrosomal status; 3) PPCM and nitric oxide donors induce acrosomal loss via nitric oxide, but through independent pathways; and 4) covalent attachment of a nitric oxide donor to PPCM provides synergistic efficacy as a stimulus of acrosomal loss. Further studies with this novel prototype as an improved contraceptive microbicide are warranted.
Procyanidin Induces Apoptosis and Necrosis of Prostate Cancer Cell Line PC‐3 in a Mitochondrion‐Dependent Manner
Authors: Shang X. J. , Yao G. , Ge J. P. , Sun Y. , Teng W. H. , Huang Y. F.
Published: February 2009

ABSTRACT: Our objective was to study the effects of procyanidin on the cell death of human hormone‐resistant prostate carcinoma cell line PC‐3 and its mechanism. PC‐3 cells were treated with procyanidin of different concentrations. The cell apoptosis rates were detected by annexin V‐FITC and propidium iodide double staining followed by flow cytometry (FCM) analysis. Mitochondrial membrane potential (Δψm) was analyzed by FCM with rhodamine 123 staining. After 24 hours of treatment with 300 μg/mL procyanidin, the apoptosis rate of PC‐3 cells was 44.86%, and Δψm was significantly decreased by 87.30%. With the extending of procyanidin treatment, the apoptosis rate decreased whereas the necrosis rate increased. Procyanidin could induce apoptosis and necrosis in PC‐3 cells, which might be related to down‐regulation of Δψm.
Hormonal Treatment of Male Infertility: Promises and Pitfalls
Authors: Madhukar Dama , Rajender Singh
Published: February 2009

ABSTRACT: Approximately 50% of infertility issues are attributable to male factors. A number of different factors may result in similar reductions of sperm count or motility and affect sperm morphology. Not only is the etiology of male infertility difficult to understand, but it is equally challenging to treat male infertility because of its etiological heterogeneity. Because of complex and incomplete knowledge of the underlying causes, most infertile men are described as idiopathically oligozoospermic and/or asthenozoospermic. Different hormonal treatments have been attempted, aiming to improve mainly endogenous follicle‐stimulating hormone and/or androgen levels and subsequent spermatogenesis. Various studies have tried to treat infertility through natural pregnancies or increased sperm retrieval for in vitro fertilization techniques, or by treating spermatozoa in vitro to improve its fertilizing potential. The present review focuses on all of the aspects of male infertility treatment by hormone supplementation.
Homo sapiens Lactate Dehydrogenase c (Ldhc) Gene Expression in Cancer Cells Is Regulated by Transcription Factor Sp1, CREB, and CpG Island Methylation
Authors: Tang Huanghui , Goldberg Erwin
Published: February 2009

ABSTRACT: The human testis‐specific lactate dehydrogenase c gene (hLdhc) is transcribed only in cells of the germinal epithelium. Recently hLdhc was reported to express in a broad spectrum of tumors with relatively high frequency in lung cancer, melanoma, and breast cancer, and in some prostate cancers. Two melanoma cell lines that express the hLdhc gene, A375M and C81–61, were identified and were used to characterize the hLdhc promoter and explore transcriptional regulation of this gene. A 110‐bp core promoter, including a conserved GC box and cyclic adenosine monophosphate—responsive element (CRE), were identified as essential for basal promoter activity. The methylation status of the CpG island (CGI) in the hLdhc core promoter sequence was analyzed in hLdhc‐expressing and nonexpressing cells and human prostate tumor tissues. The CGI in 2 cell lines expressing the gene was hypomethylated whereas the DNA from cells that did not express hLdhc was hypermethylated. The role of methylation in regulating this promoter was confirmed by experimental induction of hLdhc transcription with the methylation inhibitor 5′aza‐deoxycytidine. Quantitative analyses of the methylation level in the CGI were performed in prostate tumor tissues by pyrosequencing. Overall, these experiments demonstrated that hLdhc expression in cancer cells was regulated by transcription factor Sp1 and CREB and promoter CGI methylation. In addition, these findings suggest the possibility of developing a biomarker for cancer diagnosis/prognosis based on DNA methylation of the Ldhc gene.
Effect of Testosterone on Epithelial Cell Proliferation in the Regressed Rat Epididymis
Authors: Hamzeh Mahsa , Robaire Bernard
Published: February 2009

ABSTRACT: It is well established that testosterone plays a crucial role in maintaining the integrity of epididymal structure and function. However, the role of testosterone in restoring the cellular architecture of the regressed epididymis is not well known. The present study was undertaken to test the hypothesis that testosterone triggers the regressed epididymis by re‐expanding existing cells and inducing cell proliferation. Testosterone‐dependent epididymal morphology was evaluated in orchidectomized, regressed rats after initiation of treatment with testosterone. Besides that, the proliferative activity of epithelial cells in all regions of the epididymis of the orchidectomized, regressed rats was assessed at 1, 3, 7, and 28 days after testosterone replacement. Epithelial cell proliferation decreased after testosterone withdrawal and increased following testosterone administration. We found that bromodeoxyuridine incorporation and proliferating nuclear antigen expression increased significantly 3 days after testosterone replacement in all regions of the regressed epididymis except in the initial segment. The highest mitotic activity was seen in the corpus epididymidis at 3 days postimplantation. Using specific markers for each cell type, we found no significant changes in the proportion of each cell type compared with the control. We observed labeled nuclei in all epithelial cell types in the control; however, principal cells were the major cell types that responded to testosterone after regression. These observations demonstrate that the mammalian epididymis is not a static tissue without any significant cell renewal, either under control conditions or when androgen exposure is altered, thus providing new insight in the role of androgen in restoration and maintenance of the architecture of the epididymis.