bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative phylogeography of livebearing fishes in the genera Poeciliopsis and Poecilia (Poeciliidae: Cyprinodontiformes) in central Mexico
Authors: Mateos Mariana
Published: April 2005

Aim  To test the hypothesis that the vicariant event responsible for north–south divergences in two clades of the fish genus Poeciliopsis Regan was also responsible for north–south divergences in the fish Poecilia butleri Jordan.

Location  Central Mexico.

Methods  Parsimony, distance, maximum likelihood and Bayesian phylogenetic analyses of a mitochondrial gene. Molecular clock test and Bayesian analyses of divergence time.

Results  We report concordant phylogeographical patterns between two clades in the genus Poeciliopsis (i.e. the other formed by P. latidens Garman and P. fasciata Meek, and the other formed by P. presidionis Jordan and P. turneri Miller) and the clade of Poecilia butleri, with northern and southern individuals within each clade grouping into separate lineages. There is also evidence for slower substitution rates in Poecilia compared with Poeciliopsis. After taking into account these substitution rate discrepancies with Bayesian relaxed molecular clock analyses, north–south divergences in Poecilia butleri were equivalent to those reported for Poeciliopsis latidens‐fasciata and P. presidionis‐turneri.

Main conclusions  The same Plio‐Pleistocene vicariant event associated with geological activity of the Trans‐Mexican Volcanic Belt (TMVB) appears to have caused divergence in three different freshwater fish lineages. This study is an example of how comparative phylogeography can strengthen inferences about vicariant events in regions of high biological diversity and complex geological history such as the TMVB.
Directional asymmetry of long‐distance dispersal and colonization could mislead reconstructions of biogeography
Authors: Cook Lyn G. , Crisp Michael D.
Published: April 2005

Aim  Phylogenies are increasingly being used to attempt to answer biogeographical questions. However, a reliance on tree topology alone has emerged without consideration of earth processes or the biology of the organisms in question. Most ancestral‐state optimization methods have inherent problems, including failure to take account of asymmetry, such as unequal probabilities of losses and gains, and the lack of use of independent cost estimates. Here we discuss what we perceive as shortcomings in most current tree‐based biogeography interpretation methods and show that consideration of processes and their likelihoods can turn the conventional biogeographical interpretation on its head.

Location  Southern hemisphere focus but applicable world‐wide.

Methods  The logic of existing methods is reviewed with respect to their adequacy in modelling processes such as geographical mode of speciation and likelihood of dispersal, including directional bias. Published reconstructions of dispersal of three plant taxa between Australia and New Zealand were re‐analysed using standard parsimony and maximum likelihood (ML) methods with rate matrices to model expected asymmetry of dispersal.

Results  Few studies to date incorporate asymmetric dispersal rate matrices or question the simplistic assumption of equal costs. Even when they do, cost matrices typically are not derived independently of tree topology. Asymmetrical dispersal between Australia and New Zealand could be reconstructed using parsimony but not with ML.

Main conclusions  The inadequacy of current models has important consequences for our interpretation of southern hemisphere biogeography, particularly in relation to dispersal. For example, if repeated directional dispersals and colonization in the direction of prevailing winds have occurred, with intervening periods of speciation, then there is no need to infer dispersals against those winds. Failure to take account of directionality and other biases in reconstruction methods has implications beyond the simple misinterpretation of the biogeography of a taxonomic group, such as calibration of molecular clocks, the dating of vicariance events, and the prioritization of areas for conservation.
Assumption 2: opaque to intuition?
Authors: Ebach Malte C. , Humphries Christopher J. , Newman Rhys A. , Williams David M. , Walsh Stig A.
Published: April 2005

Aim The aim of this paper was to revise the historical biogeographical method for resolving complicated distribution patterns through a technique that has come to be called assumption 2. Assumption 2 was used to resolve multiple areas on a single terminal branch (masts) as well as paralogous and missing areas in two or more areagrams. Recent examples, however, have shown that assumption 2 may beusingrather thanresolvingparalogy. The paper attempts to resolve this problem by formulating a separate procedure to avoid using paralogous (redundant) area data in area cladistic analyses.

Method The revision results in a new derivative method, the transparent method, to replace assumptions 1 and 2. It separates the procedures for resolving paralogy and for solving distribution patterns that occur in more than one area (masts).

Results Several hypothetical examples show how the transparent method reduces paralogy and masts. The results show that paralogy can be reduced if the paralogy subtree method is applied after uncovering all possible relationships as single components on the terminals of areagrams.

Conclusion The transparent method is a significant step forward in cladistic biogeography as it utilizes area relationships rather than generating general areagrams based on paralogous data.
Biocompatibility of Fluor‐Hydroxyapatite Bioceramics
Authors: Lee Eun‐Jung , Kim Hae‐Won , Kim Hyoun‐Ee
Published: April 2005

Fluoridated hydroxyapatite (FHA) powders were fabricated by a solid‐state reaction, and their dense bodies were obtained by sintering at 1350°C. The biological performance of FHAs was evaluated and compared with that of pure hydroxyapatite (HA). The fluoridation of FHAs was confirmed by the changes in their lattice parameters. Human osteoblast‐like cells attached and proliferated well on all of the FHAs, including pure FA. The proliferation and differentiation levels of the cells on FHAs were similar to those on pure HA. This finding suggests that the FHAs possess cell viability and activity comparable to pure HA, and thus are potentially applicable as hard tissue substitutes.
Stability of Mullite Protective Coatings for Silicon‐Based Ceramics
Authors: Krishnamurthy Ramanathan , Sheldon Brian W. , Haynes J. Allen
Published: April 2005

Silicon‐based ceramics are prone to severe oxidation and volatilization problems in the presence of water vapor. To address these issues, mullite has been investigated in recent years as a possible protective coating material. To analyze the stability of such coatings, a multi‐species diffusion model for ionic species is developed. Onsager reciprocity is assumed for the mobility coefficients and the resulting moving boundary problem is solved numerically. The formulation also accounts for substantial Si volatilization away from the outer surface of the coating. This model is used to analyze an initial transient leading to the formation of an internal silica layer, a second transient period that follows this silica formation, and a steady‐state regime that can only be attained if Si diffusion is sufficiently fast.
Crack Bifurcation at the Surface of Laminar Ceramics That Exhibit a Threshold Strength
Authors: Pontin Michael G. , Lange Fred F.
Published: April 2005

Previous literature has shown that when a crack extends across a compressive layer within a two‐phase laminar ceramic, the crack can bifurcate under special conditions. These special conditions appeared to require that a second crack (known as an edge‐crack) had to preexist along the center line of the compressive layer. Here, it is shown that a crack can exhibit bifurcation without the formation of an edge‐crack. It was found that a critical combination of residual compressive stress and layer thickness exists in which edge‐cracking of the layer does not occur, yet the crack bifurcates when entering the compressive layer. Additionally, it was observed that crack bifurcation only occurs within the surface region of the compressive layer, while within the bulk, the crack extends straight across the compressive layer. These observations strongly suggest that the stresses on the surface of the compressive layer, which are known to be different from those within the bulk, will encourage crack bifurcation.
Effect of Liquid Phase Sintering on Microstructure and Mechanical Properties of Yb2O3‐AlN Containing SiC‐Based Ceramics
Authors: Izhevskyi V. A. , Bressiani A. H. A. , Bressiani J. C.
Published: April 2005

A series of silicon carbide‐based ceramics with different sintering additives were liquid‐phase sintered to high densities. Yb2O3 in combination with AlN was used as the additive, instead of the commonly used Y2O3–AlN, to improve the refractoriness of the secondary phase. Thermo‐chemical decomposition of AlN was sufficiently suppressed with the use of nitrogen overpressure and reasonable weight loss was achieved in the different additive containing SiC ceramics without a reactive powder bed. Use of the heavier rare‐earth element modified the liquid phase formed during sintering and reduced the phase transformation controlled grain growth rate, compared with Y2O3 doped materials. It also permitted microstructure tailoring through post‐sintering heat treatments in nitrogen. Materials with self‐reinforced microstructures, formed as a result of anisotropic grain growth, were obtained. Improved fracture toughness (4.5–5 MPa/m1/2) and good flexural strength retention up to 1400°C were also observed.
The Optical Properties and Band Gap Energy of Nanocrystalline La0.4Sr0.6TiO3 Thin Films
Authors: Suzuki Toshio , Jasinski Piotr , Petrovsky Vladimir , Anderson Harlan U.
Published: April 2005

The effects of microstructure on the optical properties of La0.4Sr0.6TiO3 thin films were investigated. Dense films with the thickness of ∼200 nm and grain size 14–30 nm were produced on monocrystalline sapphire substrates by using a polymeric precursor spin coating technique at annealing temperatures under 800°C. X‐ray data showed the formation of a single‐phase cubic perovskite‐type structure similar to undoped SrTiO3 for annealing temperatures >500°C. The results of optical measurements showed that the optical spectra varied with the change of the grain size. From these data, the absorption coefficients were calculated and the band gap energy determined. In agreement with the quantum confinement model, it was shown that the band gap energy increased as the grain size decreased.
Fixing Arsenic in Alkali‐Activated Cementitious Matrices
Authors: Fernández‐Jiménez A. , Palomo A. , Macphee D. E. , Lachowski E. E.
Published: April 2005

Portland cement‐based materials are frequently used for fixing heavy metals but are not very effective for arsenic. Alternatively, alkali activated metakaolin and fly ash systems were tested for arsenic retention by the toxic characteristic leaching procedure and American Nuclear Society 16.1 methods. The influence of Fe and Mn on As leaching rates was assessed. These materials perform well in aggressive environments (pH<3) but the activated metakaolin matrix is less able to retain As than the activated fly ash matrix. The leaching in fly ash matrices occurs in two steps: immediate initial leaching followed by a slow diffusion‐controlled process.
Aqueous Synthesis at 200°C of Sub‐10 Nanometer Yttria Tetragonally Stabilized Zirconia Using a Metal‐Ligand Approach
Authors: Kimel R. Allen , Adair James H.
Published: April 2005

The objective of this study was to produce well‐dispersed nanosized yttria tetragonally stabilized zirconia (Y‐TZP) powder in aqueous suspension. The Y‐TZP powder was produced by precipitation from homogeneous solution at 200°C under hydrothermal conditions. A homogeneous solution was created through the use of a complexing agent, which subsequently could be used in a dispersion scheme developed for the nanosized Y‐TZP powder. Characterization of the Y‐TZP powder was performed using X‐ray diffraction, Raman spectroscopy, X‐ray fluorescence, and high‐resolution transmission electron microscope. The overall goal of this study is the eventual production of bulk ceramics from well‐dispersed nanosized aqueous ceramic suspensions via wet processing techniques.
Influence of Planetary High‐Energy Ball Milling on Microstructure and Mechanical Properties of Silicon Nitride Ceramics
Authors: Liu Xue‐Jian , Huang Zhi‐Yong , Pu Xi‐Peng , Sun Xing‐Wei , Huang Li‐Ping
Published: April 2005

The influence of ball‐milling methods on microstructure and mechanical properties of silicon nitride (Si3N4) ceramics produced by pressureless sintering for a sintering additive from MgO–Al2O3–SiO2 system was investigated. For planetary high‐energy ball milling, the mechanical properties of Si3N4 ceramics were evidently improved and a homogeneous microstructure developed. In contrast, some exaggerated elongated grains were developed due to the local enrichment of sintering additives in the specimen prepared by general ball milling. For Si3N4 ceramics produced by planetary ball milling, flexure strength of 1.06 GPa, Vickers hardness of 14.2 GPa, and fracture toughness of 6.6 MPa·m0.5 were achieved. The differences in the mechanical properties of Si3N4 ceramics produced by different processing seem to arise mainly from the changes in microstructural homogenization and sinterability. The planetary high‐energy ball‐milling process provides a good route to mix starting powders for developing ceramics with uniform microstructure and promising mechanical properties.
Processing and Piezoelectric Properties of Lead‐Free (K,Na) (Nb,Ta) O3 Ceramics
Authors: Matsubara Masato , Yamaguchi Toshiaki , Sakamoto Wataru , Kikuta Koichi , Yogo Toshinobu , Hirano Shin‐ichi
Published: April 2005

The preparations of (K0.5Na0.5)NbO3 (KNN)‐based ceramics were studied as lead‐free piezoelectric materials. The authors found that the addition of CuO greatly enhanced the sinterability of the KNN‐based ceramics. The sinterability and piezoelectric properties of these ceramics were dependent upon the A/B ratio, CuO doping, and the formation of a solid solution with KTaO3. Perovskite (K0.5Na0.5)xNbO3 (x=A/B ratio) was synthesized with A/B ratios of 1.00 and 1.05 by CuO doping, while (K0.5Na0.5)NbO3 contained K4CuNb8O23 as a second phase with A/B ratios below 0.98. Although the A site‐rich (K0.5Na0.5)NbO3 (x=1.00 and 1.05) ceramics exhibited deliquescence, the A site‐poor (K0.5Na0.5)NbO3 (x≤0.98) ceramics with K4CuNb8O23 had higher densities without deliquescence. K4CuNb8O23 also improved Qm, which reached 1400 for the (K0.5Na0.5)1.0NbO3 doped with 0.5 mol% K4CuNb8O23. The formation of a solid solution with KTaO3 raised the melting point of the system and also improved its sinterability. The kp and Qm of (K0.5Na0.5)0.97(Nb0.95Ta0.05)O3 with CuO were 0.41 and 1400, respectively.
Influence of Surface Cleaning and Calcination on Rheological Properties of Silicon Carbide Aqueous Suspensions
Authors: Li Wei , Cheng Ping , Gu Mingyuan
Published: April 2005

The influence of surface cleaning, including deionized water, acid, and base cleaning, on the rheological properties of silicon carbide (SiC) aqueous suspensions was investigated. The SiC powders were well dispersed irrespective of the surface treatment. However, the viscosity was affected by the surface cleaning. The experimental results indicated that base cleaning caused a lower viscosity. The reason of the cleaning influence on viscosity was discussed. The influence of SiC oxidative thermal treatment was determined for SiC suspensions. Calcination of SiC powders at 550°C is observed to evidently reduce the viscosity of the SiC slurry. But further increase of the calcination temperature will be deleterious to the rheologic properties. The hydration of amorphous SiO2 on the SiC surface is used to clarify the phenomenon.
Cyclic Fatigue Crack Growth in PZT Under Mechanical Loading
Authors: Salz Christopher R. J. , Hoffman Mark , Westram Ilona , Rödel Jürgen
Published: April 2005

Crack growth under static and cyclic mechanical loading in lead zirconate titanate was studied using four point bend specimens in poled and unpoled states. Fatigue crack growth occurred at lower stress intensity factors than crack growth observed under static loading. The relation between crack velocity and applied stress intensity factor under static loading was affected by poling and followed a power‐law relationship. Crack velocity vs. stress intensity amplitude under cyclic loading followed a Paris power‐law relationship and was found to be unaffected by poling. A controlled unloading experiment revealed that the apparent stress intensity factor for crack extension decreased with increased unloading time but was essentially unaffected when the unloading cycle was less than five seconds, hence indicating the absence of an extrinsic fatigue mechanism.
The 1300°C Isothermal Section in the Ti–In–C Ternary Phase Diagram
Authors: Ganguly A. , Barsoum M. W. , Schuster J.
Published: April 2005

In this paper we map out the 1300°C isothermal section in the Ti–In–C ternary system. Two ternary compounds exist: Ti2InCα and Ti3InCδ. At 1300°C TiCx is in equilibrium with all phases, Ti3InCδ is in equilibrium with all the phases except C, and Ti2InC is in equilibrium with all phases except Ti and C. The range of δ in Ti3InCδ varies from 0.95 to 0.8. A correlation was found between δ and the lattice parameters of this phase. The maximum solubilities of In and C in Ti are 14 and 4 at.%, respectively. Similarly, α in Ti2InCα varies from ≈0.85 to 1. The dissolution of ∼4±0.3 at.% In in TiCx reduces the C concentration to ≈24 at.%. In the In‐rich corner, a liquid region exists.
Temperature–Time–Mechanical Properties of Glass–Ceramics Produced from Coal Fly Ash
Authors: Kim Jae Myung , Kim Hyung Sun
Published: April 2005

Physical and mechanical properties of glass–ceramics fabricated from thermal power plant fly ash were analyzed and compared with suggest a temperature–time–mechanical (T–T–M) diagram. Coal fly ash with SiO2–Al2O3–MgO–CaO as major components and TiO2 as a nuclear agent were used to develop glass–ceramic materials which were heat treated at 900°–1050°C for 0.5–4 h for crystallization. It was verified that the high aspect ratio of unknown crystallines in the microstructure contributed high hardness, strength, fracture toughness, and wear resistance. These results are correlated with heat treatment conditions and microstructure and a T–T–M properties (hardness, strength, elastic constant, toughness, and wear rate) diagram on glass–ceramics produced from coal fly ash is proposed.
The Mechanics of Indentation Induced Lateral Cracking
Authors: Chen Xi , Hutchinson John W. , Evans Anthony G.
Published: April 2005

The mechanics governing the lateral cracks that form when a hard object plastically penetrates a ceramic is presented. The roles of indentation load, penetration depth, and work of indentation are all highlighted, as are the influences of the mechanical properties of the material. A closed form solution for cracking induced by expansion of a two‐dimensional cavity is used to bring out essential features related to parametric dependence and scaling. The three‐dimensional axisymmetric problem for an annular crack driven by a rigid spherical or conical indenter is solved using numerical methods. The region of highest tensile stress is identified corresponding to the location where a crack is most likely to nucleate. This location coincides with the depth below the surface where the crack will expand parallel to the surface under mode I conditions. The solutions have been substantiated by comparison with measurements of the cracks that form upon Vickers indentation. The basic formula for the crack radius has been used to predict trends in cracking upon static penetration and impact by a projectile. In both cases, the extent of the cracking is substantially diminished by increasing the toughness of the material. The yield strength has a much smaller effect. The cracks caused by penetration and the volume removed per impact both decrease marginally at higher yield strength.
Preparation of Single‐Phase High Tc Superconductor (Bi,Pb)2Sr2Ca2Cu3Ox (2223) with Hg Substitution
Authors: Mackinnon Christopher W. , Li Deyu , Low It‐Meng
Published: April 2005

The successful preparation of single‐phase Hg‐doped (2223) using a nitrate decomposition/solid state reaction method is described in this paper. The effects of Hg doping on the formation of single‐phase (2223) have been investigated by X‐ray and synchrotron radiation diffraction. When compared with Pb‐doped system, the use of Hg as a dopant has resulted in the reduction of both the final sintering temperature and the annealing time of the single‐pure (2223) material, without any obvious deterioration of the superconducting properties.
Compressibility and Phase Transition Kinetics of Lanthanide‐Doped Zircon
Authors: Van Westrenen Wim , Frank Mark R. , Fei Yingwei , Hanchar John M. , Finch Robert J. , Zha Chang‐Sheng
Published: April 2005

The structure and compressibility of synthetic lanthanide‐doped zircon (ZrSiO4 with a total of 2.0 mol% trivalent Gd, Dy, Er, Yb, and Y, charge‐balanced by addition of P5+) were determined from static compression experiments to 25.9 GPa. The sample bulk modulus, KT0=189±1 GPa is 5% lower than KT0 for undoped zircon, and the sample transforms from the zircon to the scheelite structure above 22.6 GPa, 3 GPa greater than the transformation pressure in pure ZrSiO4. A simple model is presented linking compressibility with unit‐cell volume for zircon‐structured and scheelite‐structured ABO4 compounds, allowing prediction of the compressibility of zircon‐structured vanadates and phosphates.
Microstructural Evolution on Firing Soda–Lime–Silica Glass Fluxed Whitewares
Authors: Tarvornpanich T. , Souza G. P. , Lee W. E.
Published: April 2005

Density and microstructural evolution of porcelains containing 0–25 wt% soda–lime–silica (SLS) waste glass fired over a range of temperatures from 600° to 1400°C have been investigated. After firing 3 h at 1100°C, batches containing 6.25 wt% SLS glass and 18.75 wt% nepheline syenite flux system attained open‐pore closure and a bulk density of 2.40 g/cm3, comparable to results from commercial porcelain after firing at 1200°C. SLS glass softens and melts, conferring early densification and overfiring on porcelains fired at normal commercial firing temperatures. The microstructural evolution examined using XRD, SEM/energy dispersive spectroscopy (EDS), and TEM/EDS revealed formation of a variable composition plagioclase, rounded wollastonite particles, sodium silicates, and tridymite in batches containing SLS glass, in addition to primary and secondary mullites, partially dissolved quartz, and a glassy matrix as found in the waste‐free batch. Ca2+ and Na+ from the SLS glass migrate to regions containing the products of clay decomposition to form plagioclase, limiting the extent of mullite crystallization. The presence of a solution rim surrounding quartz and different glass compositions around wollastonite crystals indicate that the system is not in equilibrium, although phases predicted by the Na2O–CaO–SiO2 equilibrium diagram were formed.
Thermal Expansion Properties of Lanthanum‐Substituted Lead Titanate Ceramics
Authors: Chen Jun , Xing Xianran , Yu Ranbo , Liu Guirong
Published: April 2005

The Pb1−xLaxTiO3 powders were prepared by a sol–gel route in the composition range from x=0.0 to 0.3 in 0.05 increments. The lattice parameters of Pb1−xLaxTiO3 (x=0.0, 0.05, 0.10, 0.15, 0.20, 0.30) were determined by a high temperature X‐ray diffraction, and the intrinsic thermal expansion coefficients were obtained in the temperature range from room temperature to 900°C. The Pb1−xLaxTiO3 compounds (x=0.10, 0.15, 0.20) in the tetragonal system exhibit low thermal expansion behaviors. As the La content is increased, the phase transition in the Pb1−xLaxTiO3 changes continuously from conventional to diffuse phase transition.
Effect of Oxidation on Crack Deflection in SiC/Al2O3 Laminated Ceramic Composites
Authors: Krishnamurthy R. , Rankin J. , Sheldon B.W.
Published: April 2005

Laminated composites consisting of SiC and a thin porous alumina interphase were exposed to air at 500°C to produce a persistent, nearly uniform oxidation product layer. Crack deflection at the interface was then studied using a four‐point bend testing procedure and interfacial fracture resistances were found to decrease with increasing oxidation times. Electron microscopy observations of the fractured interface show a complex multi‐phase microstructure. These results show that oxidation can produce a sufficiently weak interface in a SiC‐porous alumina interphase composite, in contrast to most other SiC composites where interface oxidation produces a strongly bonded interface which inhibits crack deflection.
Vacuum‐Assisted Microfluidic Lithography of Ceramic Microstructures
Authors: Ahn Sung‐Jin , Moon Jooho
Published: April 2005

The method to fabricate complex shaped micro‐patterned ceramic structures has been developed. Vacuum‐assisted infiltrating the suspensions to the micro channels generated by the contact of polydimethylsiloxane mold to the substrate enables simple micro patterning of ceramics with complex structures in a relatively large area in short time. The use of well‐dispersed ethanol‐based suspensions of solid loading ∼20 vol% plays an important role in a successful pattern formation without defects. The current process, called microfluidic lithography, is applicable to the entire range of ceramic materials which can be processed to colloidal suspension with relatively low viscosity. It is demonstrated that the interdigitated ceramic structures with 50 μm in the width composed of Al2O3 and NiO on a Si substrate were fabricated in an area of 5 mm × 5 mm.
Bacterial vaginosis Transmission, role in genital tract infection and pregnancy outcome: an enigma
Authors: LARSSON P. G. , BERGSTRÖM M. , FORSUM U. , JACOBSSON B. , STRAND A. , WÖLNER‐HANSSEN P.
Published: April 2005

Whether bacterial vaginosis (BV) is acquired from an endogenous or an exogenous source is subject to controversy. Despite findings of an association between sexual behaviour and BV, some data indicate that BV is not a sexually transmitted infection in the traditional sense, while other data indicate that BV is an exogenous infection. A third aspect of BV is its tendency to go unnoticed by affected women. All of this will have a strong impact on how physicians view the risks of asymptomatic BV. This review focuses on whether or not BV should be regarded as a sexually transmitted infection (STI), its role in postoperative infections and pelvic inflammatory disease (PID), and on whether or not treatment of BV during pregnancy to reduce preterm delivery should be recommended. The reviewed studies do not lend unequivocal support to an endogenous or exogenous transmission of the bacteria present in BV. For women undergoing gynaecological surgery such as therapeutic abortion, the relative risk of postoperative infection is clearly elevated (approx. 2.3–2.8). A weaker association exists between BV and pelvic inflammatory disease. Data on treatment of BV as a way of reducing preterm delivery are inconclusive and do not support recommendations for general treatment of BV during pregnancy. The discrepant associations between BV and preterm birth found in recent studies may be explained by variations in immunological response to BV. Genetic polymorphism in the cytokine response – both regarding the TNF alleles and in interleukin production – could make women more or less susceptible to BV, causing different risks of preterm birth. Thus, studies on the vaginal inflammatory response to microbial colonization should be given priority.
The multifunctional role of the immunohistochemical expression of MMP‐7 in invasive breast cancer
Authors: MYLONA E. , KAPRANOU A. , MAVROMMATIS J. , MARKAKI S. , KERAMOPOULOS A. , NAKOPOULOU L.
Published: April 2005

The secretion of matrix metalloproteinases (MMPs) is crucial in the metastasis of cancer cells, since MMPs are responsible for the degradation of extracellular matrix (ECM). Among them, matrix metalloproteinase‐7 (MMP‐7) or matrilysin 1 is a stromelysin which degrades type‐IV collagen, fibronectin and laminin. Immunohistochemistry was performed to detect MMP‐7 protein in infiltrative breast carcinomas. MMP‐7 was studied along with clinicopathological parameters, disease‐free and overall survival, and p53, c‐erbB‐2, topoIIa, MMP‐2, uPAR and β‐catenin. MMP‐7 immunoreactivity was detected in the cytoplasm of cancer cells in 54.2% (96/177) and tumor stromal cells in 47.5% (84/177), as well as in normal epithelium adjacent to malignant epithelium. MMP‐7 reactivity in cancer cells displayed an inverse association with nuclear grade (p=0.049) and topoIIa (p=0.03). A parallel association was observed between the expression of MMP‐7 in both malignant and stromal cells with uPAR in cancer cells (p=0.033 and p=0.027, respectively). MMP‐7 of tumor stromal cells depicted a parallel correlation with MMP‐2 of the same cell type (p=0.044), while abnormal β‐catenin expression was inversely associated with MMP‐7 of cancer cells (p=0.047). Our results show the multifunctional role of MMP‐7 in the mammary gland, since it seems to be associated with a less aggressive phenotype, while, at the same time, being involved in invasion, through its collaboration with indicators of invasion.
Effect of monophosphoryl lipid A on antibody response to diphtheria toxin and its subunits
Authors: CAGLAR KAYHAN , AYBAY CEMALETTIN , ATAOGLU HALUK
Published: April 2005

Monophosphoryl lipid A (MPL) was evaluated for its ability to enhance the antibody response to diphtheria toxin and its fragment A and fragment B subunits. BALB/c mice were immunized subcutaneously with 1 Lf of diphtheria toxoid in the presence of 25 μg of MPL on days 0 and 14. Two weeks after the second immunization, sera were obtained from the mice and analysed for antibody response to diphtheria toxin and its subunits. A new ELISA method, developed in our laboratory, was used to measure antibody levels against the toxin, fragment A, and fragment B. It was observed that MPL significantly enhanced antibody responses to diphtheria toxin and its subunits. However, there was no statistical difference between anti‐A and anti‐B responses. The results indicated that MPL seems to be a potential candidate as an adjuvant for future diphtheria vaccine formulation.
Intravenous immunoglobulin preparations promote apoptosis in lipopolysaccharide‐stimulated neutrophils via an oxygen‐dependent pathway in vitro
Authors: TAKESHITA SEIICHIRO , TSUJIMOTO HIROSHI , NAKATANI KEIGO
Published: April 2005

Since prolonged survival of activated neutrophils has an autotoxic potential, neutrophil apoptosis plays an important role in the rapid resolution of inflammation. Intravenous immunoglobulin (IVIG) preparations, which are beneficial therapeutic agents for the treatment of autoimmune diseases and systemic inflammatory diseases, have been reported to induce apoptosis of lymphocytes and endothelial cells in vitro. In the present study, we investigated whether IVIG may induce apoptosis of neutrophils cultured in vitro. After neutrophils prestimulated with or without lipopolysaccharide (LPS) were cultured in the presence or absence of IVIG, the number of apoptotic cells, intracellular H2O2 and GSH were measured by a flow cytometer. IVIG induced apoptosis of LPS‐stimulated neutrophils dose dependently, but not in unstimulated neutrophils. Although anti‐Fas monoclonal antibodies (mAbs) had no effect on the IVIG‐induced apoptosis in the LPS‐stimulated neutrophils, anti‐Fcγ receptor (FcγR) II‐ and III‐blocking mAbs significantly inhibited the IVIG‐induced apoptosis. IVIG increased the production of intracellular H2O2, while it decreased the production of GSH, in the LPS‐stimulated neutrophils. Furthermore, a specific NADPH oxidase inhibitor and anti‐oxidants inhibited the IVIG‐induced neutrophil apoptosis. Therefore, these findings indicate that IVIG preparations induce apoptosis of LPS‐stimulated neutrophils and suggest that the IVIG‐induced apoptosis may be mediated by an oxygen‐dependent pathway via FcγRII and III.
Ovarian ependymoma
Authors: ERDOǦAN GÜLGÜN , ÖZEL ESIN , PEŞTERELI HADICE ELIF , SALAR ZEKI , TIRAK BILAL , KARAVELI ŞEYDA
Published: April 2005

A 76‐year‐old woman presented with a large calcifying mass behind the bladder. The tumor contained solid areas of a yellowish white color. Microscopic examination revealed highly cellular solid areas with many typical ependymal perivascular pseudorosettes. The cells contained uniform round‐to‐oval nuclei, some of which had irregular contours, clumped chromatin and occasional prominent nucleoli. There was widespread geographic necrosis and there were 5 atypical mitotic figures per 10 high power fields. Glial fibrillary acidic protein (GFAP) immunopositivity was observed in the cytoplasm of the tumor cells. Based on the histopathologic and immunohistochemical features, the tumor was diagnosed as an anaplastic ependymoma. This is to the best of our knowledge only the second case of anaplastic ependymoma in the medical literature.
Spectrally opponent inputs to the human luminance pathway: slow +M and −L cone inputs revealed by intense long‐wavelength adaptation
Authors: Stockman Andrew , Plummer Daniel J. , Montag Ethan D.
Published: April 2005

The nature of the inputs to achromatic luminance flicker perception was explored psychophysically by measuring middle‐ (M‐) and long‐wavelength‐sensitive (L‐) cone modulation sensitivities, M‐ and L‐cone phase delays, and spectral sensitivities as a function of temporal frequency. Under intense long‐wavelength adaptation, the existence of multiple luminance inputs was revealed by substantial frequency‐dependent changes in all three types of measure. Fast (f) and slow (s) M‐cone input signals of the same polarity (+sM and +fM) sum at low frequencies, but then destructively interfere near 16 Hz because of the delay between them. In contrast, fast and slow L‐cone input signals of opposite polarity (−sL and +fL) cancel at low frequencies, but then constructively interfere near 16 Hz. Although these slow, spectrally opponent luminance inputs (+sM and −sL) would usually be characterized as chromatic, and the fast, non‐opponent inputs (+fM and +fL) as achromatic, both contribute to flicker photometric nulls without producing visible colour variation. Although its output produces an achromatic percept, the luminance channel has slow, spectrally opponent inputs in addition to the expected non‐opponent ones. Consequently, it is not possible in general to silence this channel with pairs of ‘equiluminant’ alternating stimuli, since stimuli equated for the non‐opponent luminance mechanism (+fM and +fL) may still generate spectrally opponent signals (+sM and +sL).
Spectrally opponent inputs to the human luminance pathway: slow +L and −M cone inputs revealed by low to moderate long‐wavelength adaptation
Authors: Stockman Andrew , Plummer Daniel J.
Published: April 2005

The luminance pathway has slow (s), spectrally opponent cone inputs in addition to the expected fast (f), non‐opponent inputs. The nature of these inputs to luminance flicker perception was further explored psychophysically by measuring middle‐ (M‐) and long‐wavelength‐sensitive (L‐) cone modulation sensitivities, M‐ and L‐cone phase delays, and flicker spectral sensitivities under three conditions of low to moderate long‐wavelength adaptation. Under these conditions we find that the luminance channel has fast M‐ and L‐cone input signals (+fM and +fL), and slow, spectrally opponent cone input signals (+sL and −sM). The slow signals found under these conditions are therefore of the opposite polarity to those (+sM and −sL) found under more intense long‐wavelength adaptation. At these less intense levels, fast and slow M‐cone signals of opposite polarity (−sM and +fM) cancel at low frequencies, but then constructively interfere at intermediate frequencies (ca 12.5–22.5 Hz, depending on adapting level) because of the delay between them. In contrast, fast and slow L‐cone signals of the same polarity (+sL and +fL) sum at low frequencies, but then destructively interfere at intermediate frequencies. Importantly, the spectrally opponent signals (+sL and −sM) contribute to flicker nulls without producing visible colour variation. Although its output generates an achromatic percept, the luminance channel has slow spectrally opponent as well as fast non‐opponent inputs.
Cerebrovascular responses to hypoxia and hypocapnia in high‐altitude dwellers
Authors: Norcliffe L. J. , Rivera‐Ch M. , Claydon V. E. , Moore J. P. , Leon‐Velarde F. , Appenzeller O. , Hainsworth R.
Published: April 2005

Cerebral blood flow is known to increase in response to hypoxia and to decrease with hypocapnia. It is not known, however, whether these responses are altered in high‐altitude dwellers who are not only chronically hypoxic and hypocapnic, but also polycythaemic. Here we examined cerebral blood flow responses to hypoxia and hypocapnia, separately and together, in Andean high‐altitude dwellers, including some with chronic mountain sickness (CMS), which is characterized by excessive polycythaemia. Studies were carried out at high altitude (Cerro de Pasco (CP), Peru; barometric pressure (PB) 450 mmHg) and repeated, following relief of the hypoxia, on the day following arrival at sea level (Lima, Peru; PB 755 mmHg). We compared these results with those from eight sea‐level residents studied at sea level. In nine high‐altitude normal subjects (HA) and nine CMS patients, we recorded middle cerebral artery mean blood flow velocity (MCAVm) using transcranial Doppler ultrasonography, and expressed responses as changes from baseline. MCAVm responses to hypoxia were determined by changing end‐tidal partial pressure of oxygen (PET,O2) from 100 to 50 mmHg, with end‐tidal partial pressure of carbon dioxide clamped. MCAVm responses to hypocapnia were studied by voluntary hyperventilation with (PET,O2) clamped at 100 and 50 mmHg. There were no significant differences between the cerebrovascular responses of the two groups to any of the interventions at either location. In both groups, the MCAVm responses to hypoxia were significantly greater at Lima than at CP (HA, 12.1 ± 1.3 and 6.1 ± 1.0%; CMS, 12.5 ± 0.8 and 5.6 ± 1.2%; P < 0.01 both groups). The responses at Lima were similar to those in the sea‐level subjects (13.6 ± 2.3%). The responses to normoxic hypocapnia in the altitude subjects were also similar at both locations and greater than those in sea‐level residents. During hypoxia, both high‐altitude groups showed responses to hypocapnia that were significantly smaller at Lima than at CP (HA, 2.17 ± 0.23 and 3.29 ± 0.34% mmHg−1, P < 0.05; CMS, 1.87 ± 0.16 and 3.23 ± 0.24% mmHg−1; P < 0.01). The similarity of the results from the two groups of altitude dwellers suggests that haematocrit is unlikely to greatly affect cerebrovascular reactivity to hypoxia and hypocapnia. The smaller vasodilatation to hypoxia and larger vasoconstriction to hypoxic hypocapnia at high altitude suggest that cerebrovascular responses may be impaired at the high altitude, i.e. a maladaptation. The changes in the responses within less than 24 h at sea level indicate that this impairment is rapidly reversible.
Reduced α‐adrenoceptor responsiveness and enhanced baroreflex sensitivity in Cry‐deficient mice lacking a biological clock
Authors: Masuki Shizue , Todo Takeshi , Nakano Yasushi , Okamura Hitoshi , Nose Hiroshi
Published: April 2005

To reveal the role of clock genes in generating the circadian rhythm of baroreflexes, we continuously measured mean arterial pressure and baroreflex sensitivity in free‐moving normal wild‐type mice, and in Cry‐deficient mice which lack a circadian rhythm, in constant darkness for 24 h. In wild‐type mice the mean arterial pressure was higher at night than during the day, and was accompanied by a significantly enhanced baroreflex sensitivity of −13.6 ± 0.8 at night compared with −9.7 ± 0.7 beats min−1 mmHg−1 during the day (P < 0.001). On the other hand, diurnal changes in arterial pressure disappeared in Cry‐deficient mice with remarkably enhanced baroreflex sensitivity compared with wild‐type mice (P < 0.001): −21.9 ± 1.6 at night and −23.1 ± 2.1 beats min−1 mmHg−1 during the day. Moreover, the mean arterial pressure response to 10 μg kg−1 of phenylephrine, an α1‐adrenoceptor agonist, was severely suppressed in Cry‐deficient mice regardless of time, while that for the wild‐type mice was 10.1 ± 1.9 mmHg in the night, significantly lower than 22.0 ± 3.5 mmHg in the day (P < 0.01). These results suggest that CRY genes are involved in generating the circadian rhythm of baroreflex sensitivity, partially by regulating α1‐adrenoceptor‐mediated vasoconstriction in peripheral vessels.
Biophysical and pharmacological characterization of nicotinic cholinergic receptors in rat cochlear inner hair cells
Authors: Gómez‐Casati María Eugenia , Fuchs Paul A. , Elgoyhen Ana Belén , Katz Eleonora
Published: April 2005

Before the onset of hearing, a transient efferent innervation is found on inner hair cells (IHCs). This synapse is inhibitory and mediated by a nicotinic cholinergic receptor (nAChR) probably formed by the α9 and α10 subunits. We analysed the pharmacological and biophysical characteristics of the native nAChR using whole‐cell recordings from IHCs in acutely excised apical turns of the rat organ of Corti. Nicotine did not activate but rather blocked the acetylcholine (ACh)‐evoked currents with an IC50 of 1 ± 0.1 μm. Antagonists of non‐cholinergic receptors such as strychnine, bicuculline and ICS‐205930 blocked ACh‐evoked responses with an IC50 of 8.6 ± 0.8 nm, 59 ± 4 nm and 0.30 ± 0.02 μm, respectively. The IHC nAChR was both permeable to (PCa/PNa= 8 ± 0.9) and modulated by external Ca2+. ACh‐evoked currents were potentiated by Ca2+ up to 500 μm but were reduced by higher concentrations of this cation. Ba2+ mimicked the effects of Ca2+ whereas Mg2+ only blocked these currents. In addition, elevation of extracellular Ca2+ reduced the amplitude of spontaneous synaptic currents without affecting their time course. The receptor had an EC50 for ACh of 60.7 ± 2.8 μm in 0.5 mm Ca2+. In the absence of Ca2+, the EC50 for ACh increased, suggesting that potentiation by Ca2+ involves changes in the apparent affinity for the agonist. These pharmacological and biophysical characteristics of the IHC nAChR closely resemble those of the recombinant α9α10 nAChR, reinforcing the hypothesis that the functional nAChR at the olivocochlear efferent–IHC synapse is composed of both the α9 and α10 subunits.
Inositide evolution – towards turtle domination?
Authors: Irvine Robin F.
Published: April 2005

When viewing the changes in our understanding of inositides over the last 20 years, it is difficult to know whether to be more impressed by the proliferation in the number of inositides themselves (e.g. seven polyphosphoinositol lipids, more than 30 inositol phosphates), or by the number of functions for each. This review will focus on two specific aspects of this diversity: the evolution of the polyphosphoinositides, and the synthesis and functions of the higher inositol phosphates.
A cAMP and Ca2+ coincidence detector in support of Ca2+‐induced Ca2+ release in mouse pancreatic β cells
Authors: Kang Guoxin , Chepurny Oleg G. , Rindler Michael J. , Collis Leon , Chepurny Zina , Li Wen‐hong , Harbeck Mark , Roe Michael W. , Holz George G.
Published: April 2005

The blood glucose‐lowering hormone glucagon‐like peptide‐1 (GLP‐1) stimulates cAMP production, promotes Ca2+ influx, and mobilizes an intracellular source of Ca2+ in pancreatic β cells. Here we provide evidence that these actions of GLP‐1 are functionally related: they reflect a process of Ca2+‐induced Ca2+ release (CICR) that requires activation of protein kinase A (PKA) and the Epac family of cAMP‐regulated guanine nucleotide exchange factors (cAMPGEFs). In rat insulin‐secreting INS‐1 cells or mouse β cells loaded with caged Ca2+ (NP‐EGTA), a GLP‐1 receptor agonist (exendin‐4) is demonstrated to sensitize intracellular Ca2+ release channels to stimulatory effects of cytosolic Ca2+, thereby allowing CICR to be generated by the uncaging of Ca2+ (UV flash photolysis). This sensitizing action of exendin‐4 is diminished by an inhibitor of PKA (H‐89) or by overexpression of dominant negative Epac. It is reproduced by cell‐permeant cAMP analogues that activate PKA (6‐Bnz‐cAMP) or Epac (8‐pCPT‐2′‐O‐Me‐cAMP) selectively. Depletion of Ca2+ stores with thapsigargin abolishes CICR, while inhibitors of Ca2+ release channels (ryanodine and heparin) attenuate CICR in an additive manner. Because the uncaging of Ca2+ fails to stimulate CICR in the absence of cAMP‐elevating agents, it is concluded that there exists in β cells a process of second messenger coincidence detection, whereby intracellular Ca2+ release channels (ryanodine receptors, inositol 1,4,5‐trisphosphate (IP3) receptors) monitor a simultaneous increase of cAMP and Ca2+ concentrations. We propose that second messenger coincidence detection of this type may explain how GLP‐1 interacts with β cell glucose metabolism to stimulate insulin secretion.
Facilitatory effect of Ins(1,4,5)P3 on store‐operated Ca2+‐permeable cation channels in rabbit portal vein myocytes
Authors: Liu M. , Albert A. P. , Large W. A.
Published: April 2005

In rabbit portal vein smooth muscle cells, store‐operated Ca2+‐permeable cation channels (SOCs) display multi‐modal gating mechanisms. SOCs are activated by depletion of intracellular Ca2+ stores but also may be stimulated in a store‐independent manner by noradrenaline acting on α‐adrenoceptors and by diacylglycerol (DAG) via protein kinase C (PKC). In the present study we have investigated whether inositol 1,4,5‐trisphosphate (Ins(1,4,5)P3) modulates SOC activity in freshly dispersed rabbit portal vein myocytes with patch pipette recording techniques. Inclusion of 1 μm Ins(1,4,5)P3 in the patch pipette solution increased whole‐cell currents evoked by the Ca2+‐ATPase inhibitor cyclopiazonic acid (CPA) by about 3‐fold at −80 mV. In the cell‐attached configuration the cell‐permeable Ca2+ chelator BAPTA‐AM stimulated SOC activity and after excision of an isolated inside‐out patch bath application of 1 μm Ins(1,4,5)P3 increased open channel probability (NPo) by approximately 3‐fold. Ins(1,4,5)P3 also produced a similar increase in NPo of SOCs stimulated by the phorbol ester, phorbol 12,13‐dibutyrate (PDBu) in inside‐out patches and these channel currents had a unitary conductance of about 2 pS. The equilibrium constant of Ins(1,4,5)P3 on increasing PDBu‐evoked SOC activity was about 0.4 μm. The facilitatory effect of Ins(1,4,5)P3 was also manifest as markedly increasing the rate of activation of SOCs. The synergistic effect of Ins(1,4,5)P3 was mimicked by the metabolically stable analogue 3‐fluoro‐Ins(1,4,5)P3 and Ins(1,4)P2, a metabolite of Ins(1,4,5)P3, but was not inhibited by the classical Ins(1,4,5)P3 receptor antagonist heparin. Finally Ins(1,4,5)P3 also increased NPo of SOCs activated by a PKC catalytic subunit. It is concluded that Ins(1,4,5)P3 facilitates SOC opening via a heparin‐insensitive mechanism at, or close to, the channel protein.