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Dense
Terms modified by Dense Selected AbstractsCircumferential strain in the wall of the common carotid artery: Comparing displacement-encoded and cine MRI in volunteersMAGNETIC RESONANCE IN MEDICINE, Issue 1 2008Alexander P. Lin The walls of conduit arteries undergo cyclic stretching from the periodic fluctuation of arterial pressure. Atherosclerotic lesions have been shown to localize to regions of excessive stretching of the arterial wall. We employed a displacement encoding with stimulated echoes (DENSE) sequence to image the motion of the common carotid artery wall and map the two-dimensional (2D) circumferential strain. The sequence utilizes a fully-balanced steady-state free-precession (SSFP) readout with 0.60 mm in-plane resolution. Preliminary results in volunteers at 1.5T (N = 4) and 3.0T (N = 17) are compared to measurements of the lumen circumference from cine images. The agreement between the two independent measurements at both field strengths (P , 0.001) supports the use of DENSE as a means to map the pulsatile strain in the carotid artery wall. Magn Reson Med 60:8,13, 2008. © 2008 Wiley-Liss, Inc. [source] Complementary displacement-encoded MRI for contrast-enhanced infarct detection and quantification of myocardial function in miceMAGNETIC RESONANCE IN MEDICINE, Issue 4 2004Wesley D. Gilson Abstract MRI is emerging as an important modality for assessing myocardial function in transgenic and knockout mouse models of cardiovascular disease, including myocardial infarction (MI). Displacement encoding with stimulated echoes (DENSE) measures myocardial motion at high spatial resolution using phase-reconstructed images. The current DENSE technique uses inversion recovery (IR) to suppress T1 -relaxation artifacts; however, IR is ill-suited for contrast-enhanced infarct imaging in the heart, where multiple T1 values are observed. We have developed a modified DENSE method employing complementary acquisitions for T1 -independent artifact suppression. With this technique, displacement and strain are measured in phase-reconstructed images, and contrast-enhanced regions of infarction are depicted in perfectly coregistered magnitude-reconstructed images. The displacement measurements and T1 -weighted image contrast were validated with the use of a rotating phantom. Modified DENSE was performed in mice (N = 9) before and after MI. Circumferential (Ecc) and radial (Err) strain were measured, and contrast-enhanced infarcted myocardium was detected by DENSE. At baseline, Ecc was ,0.16 ± 0.01 and Err was 0.39 ± 0.07. After MI, Ecc was 0.04 ± 0.02 and Err was 0.03 ± 0.04 in infarcted regions, whereas Ecc was ,0.12 ± 0.02 and Err was 0.38 ± 0.09 in noninfarcted regions. In vivo Ecc as determined by DENSE correlated well with Ecc obtained by conventional tag analysis (R = 0.90). Magn Reson Med 51:744,752, 2004. © 2004 Wiley-Liss, Inc. [source] Low Temperature Fabrication of ,-TCP,PCL Nanocomposites for Bone Implants,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Michael Bernstein Abstract A method to fabricate strong bioresorbable calcium phosphate,polymer nanocomposites with low polymer content without exposing the material to excessively high-processing temperatures is reported. Dense ,-TCP-based nanocomposites containing 5 or 15,vol% of uniformly distributed polycaprolactone (PCL) polymer were obtained by mixing ,-TCP nanopowder with PCL dissolved in chloroform followed by room temperature consolidation at the high pressure of 2.5,GPa (cold sintering). The composites had an attractive combination of compressive strength and ductility, and their dissolution behavior was similar to that of pure cold sintered ,-TCP. The immersion of ,-TCP,PCL composites in simulated body fluid (SBF) yielded in vitro deposition of a bone-like apatite layer suggesting the ability of these materials to bind to native bone tissue upon implantation. [source] Template-Directed Liquid ALD Growth of TiO2 Nanotube Arrays: Properties and Potential in Photovoltaic DevicesADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Thelese R. B. Foong Abstract Dense and well-aligned arrays of TiO2 nanotubes extending from various substrates are successfully fabricated via a new liquid-phase atomic layer deposition (LALD) in nanoporous anodic alumina (AAO) templates followed by alumina dissolution. The facile and versatile process circumvents the need for vacuum conditions critical in traditional gas-phase ALD and yet confers ALD-like deposition rates of 1.6,2.2,Å cycle,1, rendering smooth conformal nanotube walls that surpass those achievable by sol,gel and Ti-anodizing techniques. The nanotube dimensions can be tuned, with most robust structures being 150,400,nm tall, 60,70,nm in diameter with 5,20,nm thick walls. The viability of TiO2 nanotube arrays deposited on indium tin oxide (ITO),glass electrodes for application in model hybrid poly(3-hexylthiophene) (P3HT):TiO2 solar cells is studied. The results achieved provide platforms and research directions for further advancements. [source] Ultra Low- k Films Derived from Hyperbranched Polycarbosilanes (HBPCS),ADVANCED FUNCTIONAL MATERIALS, Issue 24 2008Jitendra S. Rathore Abstract Dense and porous hyperbranched carbosiloxane thin films (HBCSO) are obtained by sol,gel processing using methylene-bridged hyperbranched polycarbosilanes (HBPCSs) with the general compositional formula {(OMe)2Si(CH2)}. Introduction of porosity is achieved using a porogen templating approach, allowing the control of the films' dielectric constant from 2.9 to as low as 1.8. Over the entire dielectric range, the HBCSO films exhibit exceptional mechanical properties, 2,3 times superior to those obtained for non-alkylene bridged organosiloxanes such as methylsilsesquioxanes (MSSQs) of similar densities and k -values. [source] Strain Rate Effects in the Mechanical Response of Polymer-Anchored Carbon Nanotube Foams,ADVANCED MATERIALS, Issue 3 2009Abha Misra Strain rate effects on the mechanical properties of carbon nanotube forests are studied, and several related interesting new phenomena are reported. Dense vertically aligned foam-like forests of carbon nanotubes are anchored on a thin, flexible polymer layer to provide structural stability, particularly at the higher strain rates. Permanent deformation and for the first time the delamination and crumbling of carbon nanotube walls is observed. [source] Cover Picture: Surfactant-Mediated Generation of Iso-Oriented Dense and Mesoporous Crystalline Metal-Oxide Layers (Adv. Mater.ADVANCED MATERIALS, Issue 14 200614/2006) Abstract For certain metal oxides (e.g., MoO3) ordered mesoporous films can be obtained with the nanocrystals in the pore walls being uniformly oriented with respect to the substrate by applying evaporation-induced self-assembly followed by heating. This surprisingly facile process, described by Smarsly and co-workers on p.,1827, works on different polar substrates (glass, metals, etc.) for oxides with anisotropic unit cells, based on the interaction with surfactants during nucleation ("soft-epitaxy"). [source] Template-Assisted Fabrication of Dense, Aligned Arrays of Titania Nanotubes with Well-Controlled Dimensions on Substrates,ADVANCED MATERIALS, Issue 22 2004S. Sander Dense arrays of vertically aligned titania nanotubes (see Figure) are created directly on silicon substrates by combining atomic layer deposition with an alumina template-based fabrication approach. This method enables excellent control over the nanotube dimensions, including their wall thickness, diameter, and height. Nanotubes were fabricated with tube walls thin enough (<,3,nm) to exhibit a wall-thickness- dependent blue-shift in the optical absorption spectra of the arrays. [source] A promising method for electrodeposition of aluminium on stainless steel in ionic liquidAICHE JOURNAL, Issue 3 2009Guikuan Yue Abstract A promising method for aluminium deposition was proposed by using AlCl3/[bmim]Cl (1-butyl-3-methylimidazolium chloride) ionic liquid as electrolyte. By using this novel method, the volatile and flammable organic solvent systems and the high corrosive inorganic molten salts with high temperature can be substituted, and the deposit microstructure can be easily adjusted by changing the current density, temperature and electrolyte composition. The study was performed by means of galvano-static electrolysis and the optimum operating conditions were determined based on the systematic studies of the effects of current density, temperature, molar ratio of AlCl3 to [bmim]Cl, stirring speed and deposition time on the quality of deposited coatings. The electrical conductivities of electrolytes were also investigated as a function of temperature (298,358 K) and molar ratio of AlCl3 to [bmim]Cl (from 0.1:1 to 2.0:1). Dense, bright and adherent aluminium coatings were obtained over a wide range of temperature (298,348 K), current densities (8,44 mA/cm2) and molar ratio (1.6:1,2.0:1). Results from the analysis of crystal structure show that all of the electrodeposits exhibit a preferred (200) crystallographic orientation. Temperature has significant influence on the crystallographic orientation and there does not appear to be an apparent impact of current density on it. Analyses of the chronoamperograms indicate that the deposition process of aluminium on stainless steel was controlled by three-dimension nucleation with diffusion-controlled growth and there is a conversion from progressive nucleation to instantaneous nucleation. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Ionic Conductivity Enhancement of La2Mo2,xWxO9 Nanocrystalline Films Deposited on Alumina Substrates by the Sol,Gel MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2009Zhong Zhuang Dense, crack-free, and uniform La2Mo2,xWxO9 (x=0, 0.1, and 0.2) nanocrystalline films were successfully synthesized on poly-alumina substrates via a modified sol,gel method, with inorganic salt of La(NO3)3·6H2O, (NH4)6Mo7O24·4H2O, and (NH4)6H2W12O24 as precursors. Pure La2Mo2O9 phase was confirmed by X-ray diffractometer when the annealing temperature was >500°C. The average grain size of the La2Mo2,xWxO9 films is in the range of 90,400 nm, depending upon the conditions of thermal treatment, and the thickness of films can reach 1 ,m by repetitive spin-coating. The electrical conductivity increases with decreasing grain size and reaches 0.074 S/cm at 600°C in the film with a grain size of 90 nm, which is one order of magnitude higher than that in the corresponding bulk materials. W-doping can suppress the phase transition that occurs at 580°C in pure La2Mo2O9 and enhance the low-temperature ionic conductivity. Furthermore, the activation energy of conductivity in the nanocrystalline La2Mo2O9 films decreases to about 0.6 eV in comparison with 1.0 eV in the bulk ones, which implies that the grain resistance prevails in the total resistance, when grain size reduces to nanometer domain. [source] Novel Fabrication Route to Al2O3,TiN Nanocomposites Via Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2006Lianjun Wang A novel method for the preparation of Al2O3,TiN nanocomposites was developed. A mixture of TiO2, AlN, and Ti powder was used as the starting material to synthesize the Al2O3,TiN nanocomposite under 60 MPa at 1400°C for 6 min using spark plasma sintering. X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy were used for detailed microstructural analysis. Dense (up to 99%) nanostructured Al2O3,TiN composites were successfully fabricated, the average grain size being less than 400 nm. The fracture toughness (KIC) and bending strength (,b) of the nanostructured Al2O3,TiN composites reached 4.22±0.20 MPa·m1/2 and 746±28 MPa, respectively. [source] Synthesis of Dense, High-Defect-Concentration B4C through Mechanical Activation and Field-Assisted CombustionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2004E. M. Heian Dense fine-grained B4C was synthesized by the spark plasma sintering (SPS) method using mechanically activated elemental powders. Relative densities of up to 95% were achieved. When characterized by X-ray line broadening methods, the grains of the resulting product were determined to be nanometric in scale. However, transmission electron microscopy (TEM) observations showed the product to be composed of a mixture of fine (nanometric) crystallites and grains in the micrometer range. The TEM images showed a highly defective structure containing a high density of twins. Their presence is the reason for the discrepancy between the X-ray and TEM results. [source] Sintering Behavior of Nanocrystalline Zirconia Doped with Alumina Prepared by Chemical Vapor SynthesisJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2000Vladimir V. Srdi Powders of nanocrystalline zirconia doped with 3,30 mol% alumina have been synthesized using chemical vapor synthesis (CVS). Dense or mesoporous ceramics of small and narrowly distributed grain and pore sizes in the nanometer range are obtained via pressureless vacuum sintering. The microstructural development of the doped samples is strongly dependent on the alumina content. Sintering of zirconia samples with 3 and 5 mol% alumina at temperatures of 1000°C for 1 h results in fully dense, transparent ceramics with grain sizes of 40,45 nm and homogeneous microstructures. [source] Physical-mechanical properties of glass ionomer cements indicated for atraumatic restorative treatmentAUSTRALIAN DENTAL JOURNAL, Issue 3 2009CC Bonifácio Abstract Background:, This study evaluated mechanical properties of glass ionomer cements (GICs) used for atraumatic restorative treatment. Wear resistance, Knoop hardness (Kh), flexural (Fs) and compressive strength (Cs) were evaluated. The GICs used were Riva Self Cure (RVA), Fuji IX (FIX), Hi Dense (HD), Vitro Molar (VM), Maxxion R (MXR) and Ketac Molar Easymix (KME). Methods:, Wear was evaluated after 1, 4, 63 and 365 days. Two-way ANOVA and Tukey post hoc tests (P = 0.05) analysed differences in wear of the GICs and the time effect. Fs, Cs, and Kh were analysed with one-way ANOVA. Results:, The type of cement (p < 0.001) and the time (p < 0.001) had a significant effect on wear. In early-term wear and Kh, KME and FIX presented the best performance. In long-term wear, Fs and Cs, KME, FIX and HD had the best performance. Strong explanatory power between Fs and the Kh (r2 = 0.85), Cs and the Kh (r2 = 0.82), long-term wear and Fs of 24 h (r2 = 0.79) were observed. Conclusions:, The data suggested that KME and FIX presented the best in vitro performance. HD showed good results except for early-term wear. [source] Manifold Homotopy via the Flow ComplexCOMPUTER GRAPHICS FORUM, Issue 5 2009Bardia Sadri Abstract It is known that the critical points of the distance function induced by a dense sample P of a submanifold , of ,n are distributed into two groups, one lying close to , itself, called the shallow, and the other close to medial axis of ,, called deep critical points. We prove that under (uniform) sampling assumption, the union of stable manifolds of the shallow critical points have the same homotopy type as , itself and the union of the stable manifolds of the deep critical points have the homotopy type of the complement of ,. The separation of critical points under uniform sampling entails a separation in terms of distance of critical points to the sample. This means that if a given sample is dense enough with respect to two or more submanifolds of ,n, the homotopy types of all such submanifolds together with those of their complements are captured as unions of stable manifolds of shallow versus those of deep critical points, in a filtration of the flow complex based on the distance of critical points to the sample. This results in an algorithm for homotopic manifold reconstruction when the target dimension is unknown. [source] Mineralocorticoid Receptor Is Overexpressed in Cardiomyocytes of Patients With Congestive Heart FailureCONGESTIVE HEART FAILURE, Issue 1 2005Masahiro Yoshida MD Mineralocorticoid receptors (MRs) have been identified in the human cardiovascular tissues. We determined MR expression in the failing heart to clarify the mechanism of action of aldosterone antagonist in the treatment of congestive heart failure. MR protein and MR mRNA content were detected by immunohistochemical staining and in situ hybridization in the cardiac tissues. Immunohistochemical staining of the receptor, as well as in situ hybridization of MR mRNA, was dense in cardiomyocytes of the failing left ventricle as compared with the controls. The staining ratio of the cytoplasm to the interstitium showed that MRs were located mainly in the cytoplasm. The cytoplasm to the interstitium in the failing left ventricle was 1.53±0.13, which was significantly higher than that of the controls 1.25±0.19 (p<0.05). These findings suggest that the efficacy of aldosterone antagonists in treating congestive heart failure may be in part through blocking the MRs, which are upregulated in the failing heart. [source] Threatened Peripheral Populations in Context: Geographical Variation in Population Frequency and Size and Sexual Reproduction in a Clonal Woody ShrubCONSERVATION BIOLOGY, Issue 3 2007SARAH B. YAKIMOWSKI especies en riesgo; límites de distribución; poblaciones periféricas; reproducción sexual; Vaccinium stamineum Abstract:,Geographically peripheral populations of widespread species are often the focus of conservation because they are locally rare within political jurisdictions. Yet the ecology and genetics of these populations are rarely evaluated in a broader geographic context. Most expectations concerning the ecology and evolution of peripheral populations derive from the abundant-center model, which predicts that peripheral populations should be less frequent, smaller, less dense, and have a lower reproductive rate than central populations. We tested these predictions and in doing so evaluated the conservation value of peripheral populations for the clonal shrub Vaccinium stamineum L. (Ericaceae, deerberry), which is listed as threatened in Canada. Based on 51 populations sampled from the center to the northern range limits over 2 years, population frequency and size declined toward the range limit, but ramet density increased. Sexual reproductive output varied widely among populations and between years, with many populations producing very few seeds, but did not decline toward range margins. In fact seed mass increased steadily toward range limit, and this was associated with faster germination and seedling growth, which may be adaptive in seasonal northern environments. Our results did not support the prediction that clonal reproduction is more prevalent in peripheral populations or that it contributed antagonistically to the wide variation in seed production. Peripheral populations of V. stamineum are as productive as central populations and may be locally adapted to northern environments. This emphasizes the importance of a broad geographical perspective for evaluating the ecology, evolution, and conservation of peripheral populations. Resumen:,Las poblaciones geográficamente periféricas de una especie de amplia distribución a menudo son el foco de conservación porque son raras localmente dentro de jurisdicciones políticas. Sin embargo, la ecología y genética de estas poblaciones son evaluadas poco frecuentemente en un contexto geográfico más amplio. La mayoría de las expectaciones relacionadas con la ecología y evolución de las poblaciones periféricas se derivan del modelo centro-abundante, que predice que las poblaciones periféricas son menos frecuentes, más pequeñas, menos densas y menor tasa reproductiva que poblaciones centrales. Probamos estas predicciones y al hacerlo evaluamos el valor de conservación de poblaciones periféricas de una especie de arbusto clonal (Vaccinium stamineum L., Ericaceae), que está enlistada como amenazada en Canadá. Con base en 51 poblaciones muestreadas del centro hacia los límites norteños de su distribución durante 2 años, la frecuencia y tamaño poblacional declinó hacia los límites de su distribución, pero la densidad de rametos aumentó. La reproducción sexual varió ampliamente entre las poblaciones y entre años, con muchas poblaciones produciendo muy pocas semillas, pero no declinó hacia los límites de su distribución. De hecho, la masa de semillas incrementó sostenidamente hacia los límites, y esto se asoció a una acelerada germinación y crecimiento de plántulas, lo cual puede ser adaptativo en ambientes norteños estacionales. Nuestros resultados no sustentaron la predicción de que la reproducción clonal es más prevaleciente en poblaciones periféricas o que contribuye antagónicamente a la amplia variación en la producción de semillas. Las poblaciones periféricas de V. stamineum son tan productivas como las poblaciones centrales y pueden estar adaptadas localmente a ambientes norteños. Esto enfatiza la importancia de una perspectiva geográfica amplia cuando se evalúa la ecología, evolución y conservación de poblaciones periféricas. [source] Mesothelioma Symposium 11.30,12.30 Tuesday 16 September 2003CYTOPATHOLOGY, Issue 2003Darrel Whitaker Dr The diagnosis of malignant mesothelioma on the cytology of serous effusions is a two-phase process. First is to determine that the effusion is malignant based on morphological features such as a highly cellular fluid with many large three dimensional cell aggregates, and/or the recognition of minor malignant criteria including prominent cell engulfment, uniformly present very prominent nucleoli, or the finding of very large (giant) cells. In cell block sections, strong positive staining with EMA often with cell membrane accentuation provides compelling support for a cytological diagnosis of malignancy. Second is to recognize that the malignant cells have a mesothelial phenotype and do not represent metastatic malignancy (usually adenocarcinoma). Criteria in support of mesothelioma include the lack of a ,two cell' population, that is one native (mesothelial) and one foreign (metastatic), cells with abundant dense staining cytoplasm, the presence of ,windows' where mesothelioma cells lie in close apposition and intracytoplasmic glycogen presenting either as small peripheral vacuoles on MGG stained smears or large yellow refractile crescents on Papanicolaou stained smears. In addition, mesothliomas often possess connective tissue stromal cores occurring as either well-formed collagen within papillary aggregates or lying free as pink (MGG) or light green (Pap) amorphous material in the background of the smear or in loose association with mesothelioma cells. Finally small orange staining squamous-like cells can occasionally be identified and sometimes this may be a very prominent finding and has resulted in the false impression of a squamous cell carcinoma. Almost certainly these cells represent apoptotic tumour cells. The connective tissue mucin hyaluronic acid may be found as a net-like pattern in the smear background or as large hard-edged magenta-stained vacuoles on MGG-stained smears. Cell block sections provide architectural information and it is usually possible to separate mesothelioma aggregates with their cuboidal cells, central nuclei and abundant dense cytoplasm arranged in solid, papillary or hollow clusters from those of adenocarcinoma with less dense, often foamy cytoplasm, often composed of columnar cells with elongated nuclei. Aggregate form in adenocarcinoma can be variable but true acini are a rare finding. These cell block sections provide an ideal medium for histochemistry (PAS with and without diastase digestion) and immunocytochemistry. By using a panel of antibodies (Calretinin and CK 5/6, BerEp4, CEA, B72.3) it is almost always possible to distinguish mesothelioma from metastatic adenocarcinoma. Calretinin and CK 5/6 positive staining and absent staining with BerEp4, CEA and B72.3 is considered diagnostic of mesothelioma. [source] The heel and toe of the cell's foot: A multifaceted approach for understanding the structure and dynamics of focal adhesionsCYTOSKELETON, Issue 11 2009Haguy Wolfenson Abstract Focal adhesions (FAs) are large clusters of transmembrane receptors of the integrin family and a multitude of associated cytoplasmic "plaque" proteins, which connect the extracellular matrix-bound receptors with the actin cytoskeleton. The formation of nearly stationary FAs defines a boundary between the dense and highly dynamic actin network in lamellipodium and the sparser and more diverse cytoskeletal organization in the lamella proper, creating a template for the organization of the entire actin network. The major "mechanical" and "sensory" functions of FAs; namely, the nucleation and regulation of the contractile, myosin-II-containing stress fibers and the mechanosensing of external surfaces depend, to a major extent, on the dynamics of molecular components within FAs. A central element in FA regulation concerns the positive feedback loop, based on the most intriguing feature of FAs; that is, their dependence on mechanical tension developing by the growing stress fibers. FAs grow in response to such tension, and rapidly disassemble upon its relaxation. In this article, we address the mechanistic relationships between the process of FA development, maturation and dissociation and the dynamic molecular events, which take place in different regions of the FA, primarily in the distal end of this structure (the "toe") and the proximal "heel," and discuss the central role of local mechanical forces in orchestrating the complex interplay between FAs and the actin system. Cell Motil. Cytoskeleton 66: 1017,1029, 2009. © 2009 Wiley-Liss, Inc. [source] Mechanical computation in neuronsDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2009Jummi Laishram Abstract Growth cones are the main motile structures located at the tip of neurites and are composed of a lamellipodium from which thin filopodia emerge. In this article, we analyzed the kinetics and dynamics of growth cones with the aim to understand two major issues: first, the strategy used by filopodia and lamellipodia during their exploration and navigation; second, what kind of mechanical problems neurons need to solve during their operation. In the developing nervous system and in the adult brain, neurons constantly need to solve mechanical problems. Growth cones must decide how to explore the environment and in which direction to grow; they also need to establish the appropriate contacts, to avoid obstacles and to determine how much force to exert. Here, we show that in sparse cultures, filopodia grow and retract following statistical patterns, nearly optimal for an efficient exploration of the environment. In a dense culture, filopodia exploration is still present although significantly reduced. Analysis on 1271, 6432, and 185 pairs of filopodia of DRG, PC12 and Hippocampal neurons respectively showed that the correlation coefficient |,| of the growth of more than 50% of filopodia pairs was >0.15. From a computational point of view, filopodia and lamellipodia motion can be described by a random process in which errors are corrected by efficient feedback loops. This article argues that neurons not only process sensory signals, but also solve mechanical problems throughout their entire lifespan, from the early stages of embryogenesis to adulthood. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] GABAergic modulation of primary gustatory afferent synaptic efficacyDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2002Andrew A. Sharp Abstract Modulation of synaptic transmission at the primary sensory afferent synapse is well documented for the somatosensory and olfactory systems. The present study was undertaken to test whether GABA impacts on transmission of gustatory information at the primary afferent synapse. In goldfish, the vagal gustatory input terminates in a laminated structure, the vagal lobes, whose sensory layers are homologous to the mammalian nucleus of the solitary tract. We relied on immunoreactivity for the GABA-transporter, GAT-1, to determine the distribution of GABAergic synapses in the vagal lobe. Immunocytochemistry showed dense, punctate GAT-1 immunoreactivity coincident with the layers of termination of primary afferent fibers. The laminar nature and polarized dendritic structure of the vagal lobe make it amenable to an in vitro slice preparation to study early synaptic events in the transmission of gustatory input. Electrical stimulation of the gustatory nerves in vitro produces synaptic field potentials (fEPSPs) predominantly mediated by ionotropic glutamate receptors. Bath application of either the GABAA receptor agonist muscimol or the GABAB receptor agonist baclofen caused a nearly complete suppression of the primary fEPSP. Coapplication of the appropriate GABAA or GABAB receptor antagonist bicuculline or CGP-55845 significantly reversed the effects of the agonists. These data indicate that GABAergic terminals situated in proximity to primary gustatory afferent terminals can modulate primary afferent input via both GABAA and GABAB receptors. The mechanism of action of GABAB receptors suggests a presynaptic locus of action for that receptor. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 133,143, 2002 [source] Fine-needle aspiration diagnosis of a metastatic adult sclerosing rhabdomyosarcoma in a lymph nodeDIAGNOSTIC CYTOPATHOLOGY, Issue 10 2010Richard L. Cantley M.D. Abstract Adult sclerosing rhabdomyosarcoma (ASRMS) is a rare variant of rhabdomyosarcoma with a characteristic histological appearance of small, round cells in a dense, hyalinized stroma. Although nodal metastases of soft-tissue sarcomas are considered uncommon, up to 5% overall are associated with lymph node metastases. Nonetheless, there is little literature on the cytologic characteristics of metastatic soft-tissue sarcomas in lymph nodes, and to our knowledge, there are no reports of nodal metastasis of ASRMS diagnosed by fine-needle aspiration (FNA) cytology. We report here a 55-year-old woman who presented with a right thigh mass and associated ipsilateral inguinal lymphadenopathy. Biopsy of the mass revealed a uniform population of small, round cells in a dense, sclerotic background. A diagnosis of ASRMS was rendered. Subsequently, the patient underwent FNA of an enlarged inguinal lymph node, which revealed an identical population of small, round cells in a dense, myxoid background. This case highlights the cytologic features of a rare form of rhabdomyosarcoma, and emphasizes the utility of FNA in the assessment of lymphadenopathy in the setting of a soft-tissue sarcoma. Diagn. Cytopathol. 2010;38:761,764. © 2010 Wiley-Liss, Inc. [source] Follicular variant of papillary carcinoma: Cytologic findings on FNAB samples,experience with 16 casesDIAGNOSTIC CYTOPATHOLOGY, Issue 2 2001Franco Fulciniti M.D. Abstract Between January 1, 1992 and December 31, 1997, a cytopathological diagnosis of follicular variant of papillary thyroid carcinoma (FVPC) was made on a series of 16 out of 18 patients with palpable nodules who underwent fine-needle aspiration biopsy (FNAB) in our Department. The results of aspiration biopsy were followed by histopathological examination of the surgically excised tissues. There were three false-negative aspirations (16.6%), of which two were probably bound to fine-needle sampling and one due to a mixture of benign and malignant cells which had originally gone unrecognized. The accuracy of the cytopathologic diagnosis in this variant was 88.8%. An analysis of the diagnostic cytopathological criteria was performed, which demonstrated the importance of both architectural features (monolayered and branching sheets, microacinar structures, and their combinations) and nuclear features (presence of nuclear grooves). Background -bound features were mainly represented by dense, nonfilamentous colloid. The cytopathologic findings in FVPC were compared to those found in a series of 10 usual papillary carcinomas (UPC) and 10 follicular neoplasms (FN). These latter had originally been diagnosed by FNAB and were subsequently classified histologically as follicular adenoma (n = 6), follicular carcinoma (n = 3), or adenomatoid colloid nodule (n = 1). Statistical evaluation was performed on the cytopathological findings in the three classes of lesions (FVPC, UPC, and FN) as to their presence and relative frequency or absence by using a nonparametric one-way ANOVA (Kruskall-Wallis) and, where necessary, a Mann-Whitney U test. Papillary cellular fragments and multinucleated giant cells (P < 0.005), nonfilamentous dense colloid, squamoid cells, and syncytia were significantly more represented in UPC than in FVPC (P < 0.05), while histiocytes were significantly more frequent in FVPC (P < 0.005). Other nuclear and/or background features were significant only in the distinction between papillary carcinomas as a group and FN. The cytological differential diagnosis of the FVPC is briefly discussed with relevance to the possible pitfalls caused by its peculiar cyto- and histomorphology. Diagn. Cytopathol. 2001;25:86,93. © 2001 Wiley-Liss, Inc. [source] Ramsey on Judgment: The Theory of "Facts and Propositions"DIALECTICA, Issue 4 2004John M. Vickers Ramsey's "Facts and Propositions" is terse, allusive, and dense. The paper is far from easy to understand. The present essay is an effort, largely following Brian Loar's account,1 to say what Ramsey's goal is, to spell out what he took to be the means to accomplish it, and to show how those means, at least in the terms of F&P, cannot accomplish that end. I also contrast Loar's own account of judgment, explicitly modeled on Ramsey's view, with the latter. The exercise is not at all academic. Loar makes clear the striking depth and originality of Ramsey's insights. [source] On the morphology of Acanthostomum spiniceps (Looss, 1896) and A. absconditum (Looss, 1901) (Digenea: Cryptogonimidae: Acanthostominae) with particular reference to the juvenile stageACTA ZOOLOGICA, Issue 3 2006Mohammed Hasan Ibraheem Abstract The morphology of juvenile and adult stages of Acanthostomum spiniceps and A. absconditum, from bagrid fish of the river Nile in Egypt, was studied with both light and scanning electron microscopy. In early juveniles, circumoral spines are absent and the entire body surface is covered with tegumental spines. Late juveniles show gradual differentiation of the circumoral tegument into a collar of spines associated with a reduction in density of tegumental spines at the posterior extremity of the body. Genital primordia appear when juveniles are about 1.75 mm long. The distributions of tegumental spines on adult A. spiniceps and A. absconditum are similar. Spines are denser on the dorsal and ventral surfaces of the anterior and middle parts of the body and less dense towards the posterior end. The tegumental fold surrounding the ventral sucker of A. absconditum has spines while the fold of A. spiniceps lacks them. The most important morphological features differentiating both species are the number of circumoral spines, body shape, ratio of body length to width, sucker sizes, and the presence or absence of spines on the ventral sucker. [source] Correlation of fluorescence and electron microscopy of F-actin-containing sensory cells in the epidermis of Convoluta pulchra (Platyhelminthes: Acoela)ACTA ZOOLOGICA, Issue 1 2002R Pfistermüller Abstract Phalloidin-stained whole mounts of acoel turbellarians show brightly fluorescing club-shaped structures distributed over the epidermis and concentrated especially at the anterior and posterior tips of the body. By correlating electron micrographic images and fluorescence images of Convoluta pulchra, these structures can be seen to be sensory receptors with a central cilium surrounded by a collar of microvilli. The other candidate for showing fluorescence in the epidermis, namely gland necks, can be ruled out since their distribution is too dense to resemble the distribution of the fluorescent structures seen here. The collared sensory receptors were inserted between epidermal cells, and each bore a central cilium surrounded by a collar of 6,18 microvilli and an additional centrally positioned 2,7 microvilli of which 2 or 3 were associated with a modified rootlet called the swallow's nest. Confocal scanning laser microscopy resolved the core of actin filaments within the microvilli of the collar and their rootlet-like connections to the base of the sensory cell. Such receptors could also be identified by fluorescence microscopy in several other species of acoel turbellarians. [source] Variation in mistletoe seed deposition: effects of intra- and interspecific host characteristicsECOGRAPHY, Issue 2 2002Juliann Eve Aukema We investigated differences in host infection by a desert mistletoe, Phoradendron californicum, and examined one of the processes that contributes to these differences: variation in seed deposition among host individuals and species. In the Sonoran Desert, P. californicum parasitizes the sympatric leguminous trees Olneya tesota, Cercidium microphyllum, Prosopis velutina, Acacia constricta, and Acacia greggii. We hypothesized that seed deposition depends on host height and crown architecture. At a site in Arizona, frequency of infection did not reflect host relative abundance. Olneya tesota was parasitized at a higher frequency than expected from its abundance and maintained the highest mistletoe loads per individual host. In contrast, P. velutina was infected less frequently than expected. Infection frequency increased with host tree height for all hosts. Mistletoe seed deposition by avian dispersers differed among host species and was disproportionately high in O. tesota and P. velutina. Seed deposition was higher in infected than in non-infected host trees, and increased with tree height in O. tesota but not in C. microphyllum. We suspect that increased seed deposition with height in O. tesota may be due to the preference of seed-dispersing birds for higher perches. Some host tree species, such as C. microphyllum and A. constricta, probably received fewer mistletoe seeds because birds avoid hosts with dense and spiny crowns. Mistletoe populations are plant metapopulations in which host trees are patches and the frequency of infection in each host species/patch type is the result of interspecific differences in the balance between mistletoe colonization and extinction. From this perspective, our study of host use and seed dispersal is a metapopulation study of patch occupancy and propagule distribution among available patch types. Our seed-dispersal study demonstrates that the mechanisms that create pattern in patchy plant populations can be investigated in mistletoe systems. [source] Spatial correlations of Diceroprocta apache and its host plants: evidence for a negative impact from Tamarix invasionECOLOGICAL ENTOMOLOGY, Issue 1 2002Aaron R. Ellingson Abstract 1. The hypothesis that the habitat-scale spatial distribution of the Apache cicada Diceroprocta apache Davis is unaffected by the presence of the invasive exotic saltcedar Tamarix ramosissima was tested using data from 205 1-m2 quadrats placed within the flood-plain of the Bill Williams River, Arizona, U.S.A. Spatial dependencies within and between cicada density and habitat variables were estimated using Moran's I and its bivariate analogue to discern patterns and associations at spatial scales from 1 to 30 m. 2. Apache cicadas were spatially aggregated in high-density clusters averaging 3 m in diameter. A positive association between cicada density, estimated by exuvial density, and the per cent canopy cover of a native tree, Goodding's willow Salix gooddingii, was detected in a non-spatial correlation analysis. No non-spatial association between cicada density and saltcedar canopy cover was detected. 3. Tests for spatial cross-correlation using the bivariate IYZ indicated the presence of a broad-scale negative association between cicada density and saltcedar canopy cover. This result suggests that large continuous stands of saltcedar are associated with reduced cicada density. In contrast, positive associations detected at spatial scales larger than individual quadrats suggested a spill-over of high cicada density from areas featuring Goodding's willow canopy into surrounding saltcedar monoculture. 4. Taken together and considered in light of the Apache cicada's polyphagous habits, the observed spatial patterns suggest that broad-scale factors such as canopy heterogeneity affect cicada habitat use more than host plant selection. This has implications for management of lower Colorado River riparian woodlands to promote cicada presence and density through maintenance or creation of stands of native trees as well as manipulation of the characteristically dense and homogeneous saltcedar canopies. [source] Ultrastructural and electron energy-loss spectroscopic analysis of an extracellular filamentous matrix of an environmental bacterial isolateENVIRONMENTAL MICROBIOLOGY, Issue 9 2007Uta Böckelmann Summary Strain F8, a bacterial isolate from ,river snow', was found to produce extracellular fibres in the form of a filamentous network. These extracellular filaments, which were previously shown to be composed of DNA, have been studied for the first time by ultrastructural and electron energy-loss spectroscopy in the present work. ,Whole mount' preparations of strain F8 indicate these polymers are ultrastructurally homogeneous and form a network of elemental filaments, which have a width of 1.8,2.0 nm. When incubated at pH 3.5 with colloidal cationic ThO2 tracers they become intensely stained (electron dense), affording direct evidence that the fibres are negatively charged and thus acidic chemically. Elemental analysis of the extracellular filaments by Energy-filtered Transmission Electron Microscopy revealed phosphorus to be the main element present and, because pretreatment of F8 cells with DNase prevented thorium labelling, the fibres must be composed of extracellular DNA (eDNA). Neither ultrathin sections nor ,whole mount negative stain' caused DNA release by general cell lysis. Additionally, cells infected with phages were never observed in ultrathin sections and phage particles were never detected in whole mount samples, which rules out the possibility of phages being directly involved in eDNA release. [source] Socio-Spatial Relationships in Dairy CowsETHOLOGY, Issue 1 2010Lorenz Gygax Farm animals may serve as models for evaluating social networks in a controlled environment. We used an automated system to track, at fine temporal and spatial resolution (once per minute, ±50 cm) every individual in six herds of dairy cows (Bos taurus). We then analysed the data using social network analyses. Relationships were based on non-random attachment and avoidance relationships in respect to synchronous use and distances observed in three different functional areas (activity, feeding and lying). We found that neither synchrony nor distance between cows was strongly predictable among the three functional areas. The emerging social networks were tightly knit for attachment relationships and less dense for avoidance relationships. These networks loosened up from the feeding and lying area to the activity area, and were less dense for relationships based on synchronicity than on median distance with respect to node degree, relative size of the largest cluster, density and diameter of the network. In addition, synchronicity was higher in dyads of dairy cows that had grown up together and shared their last dry period. This last effect disappeared with increasing herd size. Dairy herds can be characterized by one strongly clustered network including most of the herd members with many non-random attachment and avoidance relationships. Closely synchronous dyads were composed of cows with more intense previous contact. The automatic tracking of a large number of individuals proved promising in acquiring the data necessary for tackling social network analyses. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||