bluuebunny/crossref_metadata_2025 huggingface dataset:
Subpopulations of proliferating cells of the adult hippocampus respond differently to physiologic neurogenic stimuli
Authors: Kronenberg Golo , Reuter Katja , Steiner Barbara , Brandt Moritz D. , Jessberger Sebastian , Yamaguchi Masahiro , Kempermann Gerd
Published: November 2003

To study how adult hippocampal neurogenesis might originate from the proliferation of stem or progenitor cells in vivo, we have used transgenic mice expressing green fluorescent protein (GFP) under the nestin promoter to identify these cells. Having described an astrocyte‐like type 1 cell with low proliferative activity, a characteristic morphology, vascular end feet, and passive electrophysiological properties, we focused here on the large population of nestin‐GFP‐expressing type 2 cells, which lack all these features. Type 2 cells were highly proliferative and showed signs suggestive of their involvement in the neuronal lineage. They could be subclassified by the absence (type 2a) or presence (type 2b) of a coexpression of the early neuronal marker doublecortin. A third type of proliferating cells was doublecortin positive but nestin‐GFP negative (type 3). We believe that type 2a, 2b, and 3 cells mirror a marker progression during earliest neuronal development. This view is supported by the increasing coexpression of the early granule cell‐specific marker Prox‐1. The low proliferative activity of type 1 cells showed little change over time or under “neurogenic interventions,” such as a challenge by environmental complexity (ENR) or voluntary physical activity (RUN). However, RUN led to a significant increase of type 2 cells labeled with the proliferation marker bromodeoxyuridine (BrdU). ENR did not cause increased cell proliferation or an increased number of BrdU‐labeled type 2 cells, but both ENR and RUN resulted in more newly generated cells lacking nestin‐GFP immunoreactivity and expressing Prox‐1. These findings allow us to break down what was broadly perceived as “proliferation” in earlier experiments into the relative contribution of several cell types, representing the earliest steps of neuronal development. J. Comp. Neurol. 467:455–463, 2003. © 2003 Wiley‐Liss, Inc.
Internal structure of the nucleus rotundus revealed by mapping cadherin expression in the embryonic chicken visual system
Authors: Becker Tanja , Redies Christoph
Published: November 2003

The nucleus rotundus is the largest nucleus of the avian thalamus. It is an important center of visual information processing and conveys information from the optic tectum to the ectostriatum in the telencephalon. The nucleus rotundus is generally believed to contain internal divisions processing information on color, form, motion, and looming of visual objects. The detailed arrangement of these internal divisions is unclear. Here, we map the expression of four classic cadherins (N‐cadherin, R‐cadherin, cadherin‐6B, and cadherin‐7), which are markers for specific functional gray matter divisions and their fiber connections in the vertebrate brain. Results show that each cadherin is expressed by one coherent part of the nucleus rotundus that is connected to other brain structures by fiber tracts expressing the same subtype of cadherin. Overall, the expression of the four cadherins encompasses almost the entire nucleus rotundus. The four cadherin‐expressing parts show different degrees of overlap. For example, the cadherin‐6B part and the cadherin‐7 part overlap extensively, whereas the R‐cadherin part and the cadherin‐6B part show little overlap and are partially complementary. Regions with shallow gradients of cadherin expression alternate with regions that show relatively abrupt changes in cadherin expression. At some points, changes of cadherin expression are also arranged in a pinwheel‐like fashion, alternating between clockwise and counterclockwise orientations. In general, these results are reminiscent of the organization of functional modules in the mammalian visual cortex. It is speculated that each domain of cadherin expression corresponds to a functional domain, which processes a specific stimulus feature. J. Comp. Neurol. 467:536–548, 2003. © 2003 Wiley‐Liss, Inc.
A twin‐star hyperchaotic attractor and its circuit implementation
Authors: Yang Xiao‐Song , Li Qingdu , Chen Guanrong
Published: November 2003

A very simple 4D system with a twin‐star hyperchaotic attractor is presented in this letter. Computer simulation is given to visualize the attractor, and a simple circuitry is designed for system implementation. Copyright © 2003 John Wiley & Sons, Ltd.
Molecular analysis of antilipemic effects of FR218944, a novel vasopressin V1a receptor antagonist, in genetically diabetic db/db mice in comparison with pioglitazone and fenofibrate
Authors: Morita Masahiko , Ohkubo‐Suzuki Akiko , Takahashi Tokiko , Nagashima Akira , Sawada Yuki , Ohkawa Takehiko , Nishimura Shintaro , Kita Yasuhiro
Published: November 2003

Arginine vasopressin V1a receptor is highly expressed in liver. The aim of this article is to perform a molecular analysis of the effects of a novel nonpeptide V1a receptor (V1aR) antagonist, FR218944 (2‐methoxy‐N‐(2‐methyl‐1H‐benzimidazol‐4‐yl)‐4‐(2,3,4,5‐tetrahydro‐1H‐1‐benzazepin‐1‐yl‐carbonyl)benzamide methanesulfonate), on plasma glucose (Glu) and triglyceride (TG) levels in diabetic db/db mice in comparison with those of a peroxisome proliferator‐activated receptor γ (PPARγ) agonist, pioglitazone, and a PPARα agonist, fenofibrate. FR218944 significantly lowered the plasma TG level but not plasma Glu level after oral administration at 32 mg/kg twice a day for 2 weeks. On the other hand, 10 mg/kg pioglitazone significantly lowered both TG and Glu levels, and 10 mg/kg fenofibrate significantly lowered only the TG level. Significant weight gain was observed only with pioglitazone treatment. db/db mice had lower levels of hepatic V1aR mRNA than normal +/+ mice. The three compounds lowered the mRNA level further. FR218944 significantly raised mRNA levels of β‐oxidation enzymes, Acyl‐CoA oxidase and bifunctional enzymes (BFE). Pioglitazone significantly increased mRNA levels of all the tested enzymes for β‐oxidation and fatty acid synthesis. Fenofibrate significantly increased mRNA levels of Acyl‐CoA synthase and BFE for β‐oxidation and decreased the mRNA level of sterol regulatory element‐binding protein 1, which transactivates many enzymes for fatty acid synthesis. In conclusion, chronic administration of FR218944, a V1aR antagonist, would lower the plasma TG level by increasing energy consumption via upregulation of β‐oxidation enzymes. Furthermore, the compound expresses its antilipemic effect via a different gene‐regulatory pathway from pioglitazone and fenofibrate. FR218944 has the potential to become a new drug for hyperlipemia. Drug. Dev. Res. 60:241–251, 2003. © 2003 Wiley‐Liss, Inc.
Antileishmanial action of Tephrosia purpurea linn, extract and its fractions against experimental visceral leishmaniasis
Authors: Sharma Preeti , Rastogi Subha , Bhatnagar Sunita , Srivastava Janmejya K. , Dube Anuradha , Guru Purushottam Y. , Kulshrestha Dinesh K. , Mehrotra Bishan N. , Dhawan Bhola N.
Published: November 2003

Tephrosia purpurea (family: Fabaceae), which is used in traditional remedies for the treatment of febrile attacks, enlargement and obstruction of liver, spleen, and kidney, was found to have significant antileishmanial activity, and has been extensively fractionated to locate the abode of activity. A fraction (F062) obtained from N‐butanol extract of T. purpurea showed consistent antileishmanial activity at 50 mg/ kg × 5 days by oral route against Leishmania donovani infection in hamsters. Activity was further confirmed in a secondary model, i.e., Indian langur monkeys (Presbytis entellus). Thus, the fraction F062 from this plant possesses potential to produce significant antileishmanial activity by oral route without producing any toxic side effects. Drug. Dev. Res. 60:285–293, 2003. © 2003 Wiley‐Liss, Inc.
Modelling the effect of form and profile adjustments on channel equilibrium timescales
Authors: Doyle Martin W. , Harbor Jon M.
Published: November 2003

A model for describing river channel proﬁle adjustments through time is developed and applied to a river responding to base‐level lowering in order to examine the effect of channel widening and downstream aggradation on equilibrium timescales. Across a range of boundary conditions, downstream aggradation controlled how quickly a channel reached equilibrium. Channel widening either increased or decreased the equilibrium timescale, depending on whether or not sediment derived from widening was deposited downstream. Results suggest that proﬁle adjustments are more important than channel width adjustments in controlling equilibrium timescales for a channel responding to base‐level lowering. Copyright © 2003 John Wiley & Sons, Ltd.
Gelifluction: viscous flow or plastic creep?
Authors: Harris Charles , Davies Michael C. R. , Rea Brice R.
Published: November 2003

This paper reports results from two scaled centrifuge modelling experiments, designed to simulate thaw‐related geliﬂuction. A planar 12° prototype slope was modelled in each experiment, using the same natural ﬁne sandy silt soil. However two different scales were used. In Experiment 1, the model scale was 1/10, tested in the centrifuge at 10 gravities (g) and in Experiment 2, the scale was 1/30, tested at 30 g. Centrifuge scaling laws indicate that the time scaling factor for thaw consolidation between model and prototype is N2, where N is the number of gravities under which the model was tested. However, the equivalent time scaling for viscous ﬂow is 1/1. If geliﬂuction is a viscosity‐controlled ﬂow process, scaling conﬂicts will therefore arise during centrifuge modelling of thawing slopes, and rates of displacement will not scale accurately to the prototype. If, however, no such scaling conﬂicts are observed, we may conclude that geliﬂuction is not controlled by viscosity, but rather by elasto‐plastic soil deformation in which frictional shear strength depends on effective stress, itself a function of the thaw consolidation process.

Models were saturated, consolidated and frozen from the surface downwards on the laboratory ﬂoor. The frozen models were then placed in the geotechnical centrifuge and thawed from the surface down. Each model was subjected to four freeze–thaw cycles. Soil temperatures and pore water pressures were monitored, and frost heave, thaw settlement and downslope displacements measured. Pore water pressures, displacement rates and displacement proﬁles reﬂecting accumulated shear strain, were all similar at the two model scales and volumetric soil transport per freeze–thaw cycle, when scaled to prototype, were virtually identical. Displacement rates and proﬁles were also similar to those observed in earlier full‐scale laboratory ﬂoor experiments. It is concluded therefore that the modelled geliﬂuction was not a time‐dependent viscosity‐controlled ﬂow phenomenon, but rather elasto‐plastic in nature. A ﬁrst approximation ‘ﬂow’ law is proposed, based on the ‘Cam Clay’ constitutive model for soils. Copyright © 2003 John Wiley & Sons, Ltd.
Mechanisms of riverbank failure along the Arno River, central Italy
Authors: Dapporto Stefano , Rinaldi Massimo , Casagli Nicola , Vannocci Pietro
Published: November 2003

Riverbanks along the Arno River have been investigated with the aims of deﬁning the main mechanisms of failure and retreat, their spatial distribution, and their causes. Geomorphological aspects were investigated by a reconnaissance of riverbank processes, for a number (26) of representative sites. Laboratory and in situ tests were then performed on a selected number of riverbanks (15). Based on the material characteristics, six main typologies of riverbanks have been deﬁned, with homogeneous ﬁne‐grained and composite banks representing the most frequent types. Slab‐type failures are the most frequent mechanism observed on ﬁne‐grained banks, while cantilever failures prevail on composite banks.

The role of river stage and related pore water pressure distributions in triggering the main observed mechanisms of failure has been investigated using two different types of stability analysis. The ﬁrst was conducted for 15 riverbanks, using the limit equilibrium method and considering simpliﬁed hypotheses for pore water pressure distribution (annulment of negative pore pressures in the portion of the bank between low water stage and peak stage). Stability conditions and predicted mechanisms of failure are shown to be in reasonably good agreement with ﬁeld observations. Three riverbanks, representative of the main alluvial reaches of the river, were then selected for a more detailed bank stability analysis, consisting of: (a) deﬁnition of characteristic hydrographs of the reach with different return periods; (b) modelling of saturated and unsaturated ﬂow using ﬁnite element seepage analysis; and (c) stability analysis with the limit equilibrium method, by adopting pore water pressure values derived from the seepage analysis. The results are compared to those obtained from the previous simpliﬁed analysis, and are used to investigate the different responses, in terms of stability, to different hydrological and riverbank conditions. Copyright © 2003 John Wiley & Sons, Ltd.
Nanofabrication for micropatterned cell arrays by combining electron beam‐irradiated polymer grafting and localized laser ablation
Authors: Yamato Masayuki , Konno Chie , Koike Shunsuke , Isoi Yuki , Shimizu Tatsuya , Kikuchi Akihiko , Makino Kimiko , Okano Teruo
Published: November 2003

Most methods reported for cell‐surface patterning are generally based on photolithography and use of silicon or glass substrates with processing analogous to semiconductor manufacturing. Herein, we report a novel method to prepare patterned plastic surfaces to achieve cell arrays by combining homogeneous polymer grafting by electron beam irradiation and localized laser ablation of the grafted polymer. Poly(N‐isopropylacrylamide) (PIPAAm) was covalently grafted to surfaces of tissue culture‐grade polystyrene dishes. Subsequent ultraviolet ArF excimer laser exposure to limited square areas (sides of 30 or 50 μm) produced patterned ablative photodecomposition of only the surface region (∼100‐nm depth). Three‐dimensional surface profiles showed that these ablated surfaces were as smooth and flat as the original tissue culture‐grade polystyrene surfaces. Time‐of‐flight secondary ion mass spectrometry analysis revealed that the ablated domains exposed basal polystyrene and were surrounded with PIPAAm‐grafted chemistry. Before cell seeding, fibronectin was adsorbed selectively onto ablated domains at 20°C, a condition in which the non‐ablated grafted PIPAAm matrix remains highly hydrated. Hepatocytes seeded specifically adhered onto the ablated domains adsorbed with fibronectin. Because PIPAAm inhibits cell adhesion and migration even at 37°C when the grafted density is >3 μg/cm2, all the cells were confined within the ablated domains. A 100‐cell domain array was achieved by this method. This surface modification technique can be utilized for fabrication of cell‐based biosensors as well as tissue‐engineered constructs. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1065–1071, 2003
Biological response of chondrocytes cultured in three‐dimensional nanofibrous poly(ϵ‐caprolactone) scaffolds
Authors: Li Wan‐Ju , Danielson Keith G. , Alexander Peter G. , Tuan Rocky S.
Published: November 2003

Nanofibrous materials, by virtue of their morphological similarities to natural extracellular matrix, have been considered as candidate scaffolds for cell delivery in tissue‐engineering applications. In this study, we have evaluated a novel, three‐dimensional, nanofibrous poly(ϵ‐caprolactone) (PCL) scaffold composed of electrospun nanofibers for its ability to maintain chondrocytes in a mature functional state. Fetal bovine chondrocytes (FBCs), maintained in vitro between passages 2 to 6, were seeded onto three‐dimensional biodegradable PCL nanofibrous scaffolds or as monolayers on standard tissue culture polystyrene (TCPS) as a control substrate. Gene expression analysis by reverse transcription–polymerase chain reaction showed that chondrocytes seeded on the nanofibrous scaffold and maintained in serum‐free medium supplemented with ITS+, ascorbate, and dexamethasone continuously maintained their chondrocytic phenotype by expressing cartilage‐specific extracellular matrix genes, including collagen types II and IX, aggrecan, and cartilage oligomeric matrix protein. Specifically, expression of the collagen type IIB splice variant transcript, which is indicative of the mature chondrocyte phenotype, was up‐regulated. FBCs exhibited either a spindle or round shape on the nanofibrous scaffolds, in contrast to a flat, well‐spread morphology seen in monolayer cultures on TCPS. Organized actin stress fibers were only observed in the cytoplasm of cells cultured on TCPS. Histologically, nanofibrous cultures maintained in the supplemented serum‐free medium produced more sulfated proteoglycan‐rich, cartilaginous matrix than monolayer cultures. In addition to promoting phenotypic differentiation, the nanofibrous scaffold also supported cellular proliferation as evidenced by a 21‐fold increase in cell growth over 21 days when the cultures were maintained in serum‐containing medium. These results indicate that the biological activities of FBCs are crucially dependent on the architecture of the extracellular scaffolds as well as the composition of the culture medium, and that nanofibrous PCL acts as a biologically preferred scaffold/substrate for proliferation and maintenance of the chondrocytic phenotype. We propose that the PCL nanofibrous structure may be a suitable candidate scaffold for cartilage tissue engineering. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1105–1114, 2003
Manipulations in hydrogel chemistry control photoencapsulated chondrocyte behavior and their extracellular matrix production
Authors: Bryant Stephanie J. , Durand Kevin L. , Anseth Kristi S.
Published: November 2003

In engineering a cell‐carrier to support cartilage growth, hydrogels provide a unique, largely aqueous environment for 3‐dimensional chondrocyte culture that facilitates nutrient transport yet provides an elastic framework dictating tissue shape and supporting external loads. Although the gel environment is often >90% water, we demonstrate that slight variations in hydrogel chemistry control gel degradation, evolving macroscopic properties, and ultimately the secretion and distribution of extracellular matrix molecules. Specifically, biodegradable poly(ethylene glycol)‐co‐poly(lactic acid) hydrogels were fabricated via photopolymerization. When chondrocytes were photoencapsulated in these gels, changes in the poly(ethylene glycol)‐co‐poly(lactic acid) repeat unit ratio from 19 to 7 increased total collagen synthesis 2.5‐fold after 6 weeks in vitro. Furthermore, the ratio of collagen to glycosaminoglycans varied from glycosaminoglycan‐rich, 0.33 ± 0.13, to collagen‐rich, 4.58 ± 1.21, depending on gel chemistry and in vitro versus in vivo culture environment. By tuning scaffold chemistry, and subsequently, gel structure and degradation behavior, we can better guide tissue evolution and development. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1430–1436, 2003
Gradient micropattern immobilization of a thermo‐responsive polymer to investigate its effect on cell behavior
Authors: Liu Hongchun , Ito Yoshihiro
Published: November 2003

A gradient micropattern immobilization technique using a photomask was developed to investigate by microscopic observation the effect of the surface concentration of an immobilized thermo‐responsive polymer. Poly(N‐isopropylacrylamide‐co‐acrylic acid) was chosen as the thermo‐responsive polymer, and was conjugated with 4‐azidoaniline to form a photo‐reactive thermo‐responsive polymer (PIA‐Az). The PIA‐Az was coated onto a polystyrene plate, and immobilized using UV irradiation in the presence of a gradient micropattern photomask. The immobilization was performed with and without gelatin. Mouse fibroblast STO cells cultured on the plate did not adhere to the surface when PIA‐Az had a high surface density, and no cell detachment was observed in any region when the temperature was lowered. However, on the gelatin coimmobilized surfaces, the cells adhered to all surfaces independent of the PIA‐Az density, and detached from the high PIA‐Az surface density areas when the temperature was lowered. The present technique demonstrates the effect of the surface concentration‐dependent immobilization of the molecules. We show that cell detachment can be regulated by perturbating a small part of the cell‐immobilized polymer interface. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1424–1429, 2003
Variations in the ability of adsorbed fibrinogen to mediate platelet adhesion to polystyrene‐based materials: A multivariate statistical analysis of antibody binding to the platelet binding sites of fibrinogen
Authors: Tsai Wei‐Bor , Grunkemeier John M. , Horbett Thomas A.
Published: November 2003

Platelet adhesion to the surfaces of biomaterials preadsorbed with plasma previously has been shown to be mediated exclusively by surface‐bound fibrinogen and does not seem to involve the other adhesion proteins in plasma (Tsai et al., J Biomed Mater Res 2002;60:348–359). In this study, the influence of surface‐bound fibrinogen on platelet adhesion to five different types of polystyrene‐based microtiter plates preadsorbed with plasma was analyzed relative to the amount of adsorbed fibrinogen and monoclonal antibody binding to the adsorbed fibrinogen. There was no significant correlation between platelet adhesion and the absolute amount of adsorbed fibrinogen. However, platelet adhesion was positively correlated to the ability of the adsorbed fibrinogen to bind three types of monoclonal antibodies. The antibodies used bound to the sites on fibrinogen thought to be involved in platelet binding (the two γ chain C‐terminal dodecapeptides and the RGDF and RGDS sequences in each of the Aα chains). A partial least‐squares calibration model was used to analyze the relative importance of these binding sites in fibrinogen to platelet adhesion. The γ chain C‐terminal dodecapeptide was shown to be the most important site in adsorbed fibrinogen in mediating platelet adhesion. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1255–1268, 2003
Isolation of intact aortic valve scaffolds for heart‐valve bioprostheses: Extracellular matrix structure, prevention from calcification, and cell repopulation features
Authors: Spina M. , Ortolani F. , Messlemani A. El , Gandaglia A. , Bujan J. , Garcia‐Honduvilla N. , Vesely I. , Gerosa G. , Casarotto D. , Petrelli L. , Marchini M.
Published: November 2003

Extracellular matrix (ECM) scaffolds isolated from valvulated conduits can be useful in developing durable bioprostheses by tissue engineering provided that anatomical shape, architecture, and mechanical properties are preserved. As evidenced by SEM, intact scaffolds were derived from porcine aortic valves by the combined use of Triton X‐100 and cholate (TRI‐COL) or N‐cetylpyridinium (CPC) and subsequent nucleic acid removal by nuclease. Both treatments were effective in removing most cells and all the cytomembranes, with preservation of (1) endothelium basal membranes, (2) ECM texture, including the D‐periodical interaction of small proteoglycans with normally D‐banded collagen fibrils, and (3) mechanical properties of the treated valves. Ultrastructural features agreed with DNA, hexosamine, and uronic acid biochemical estimations. Calcification potential, assessed by a 6‐week rat subdermal model, was significantly reduced by TRI‐COL/nuclease treatment. This was not true for CPC only, despite better proteoglycan preservation, suggesting that nucleic acids also are involved in calcification onset. Human fibroblasts, used to repopulate TRI‐COL samples, formed mono‐ or multilayers on surfaces, and groups of cells also were scattered within the valve leaflet framework. A biocompatible scaffolds of this kind holds promise for production of durable valve bioprostheses that will be able to undergo probable turnover and/or remodeling by repopulating recipient cells. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1338–1350, 2003
Performance of hydroxyapatite bone repair scaffolds created via three‐dimensional fabrication techniques
Authors: Dutta Roy Tithi , Simon Joshua L. , Ricci John L. , Rekow E. Dianne , Thompson Van P. , Parsons J. Russell
Published: November 2003

The current study analyzes the in vivo performance of porous sintered hydroxyapatite (HA) bone repair scaffolds fabricated using the TheriForm™ solid freeform fabrication process. Porous HA scaffolds with engineered macroscopic channels had a significantly higher percentage of new bone area compared with porous HA scaffolds without channels in a rabbit calvarial defect model at an 8‐week time point. An unexpected finding was the unusually large amount of new bone within the base material structure, which contained pores less than 20 μm in size. Compared with composite scaffolds of 80% polylactic‐co‐glycolic acid and 20% β‐tricalcium phosphate with the same macroscopic architecture as evaluated in a previous study, the porous HA scaffolds with channels had a significantly higher percentage of new bone area. Therefore, the current study indicates that scaffold geometry, as determined by the fabrication process, can enhance the ability of a ceramic material to accelerate healing of calvarial defects. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1228–1237, 2003
Polymers with nano‐dimensional surface features enhance bladder smooth muscle cell adhesion
Authors: Thapa Anil , Webster Thomas J. , Haberstroh Karen M.
Published: November 2003

Previous studies investigating the design of synthetic bladder wall substitutes have involved polymers with micro dimensional structures. Since the body is made up of nano‐structured components (e.g., extracellular matrix proteins), the focus of the present in vitro study was to design nano‐structured polymers for use as synthetic bladder constructs that mimic the topography of natural bladder tissue. In order to complete this task, novel nano‐structured biodegradable polymeric films of poly‐lactic‐co‐glycolic‐acid (PLGA), poly‐ether‐urethane (PU), and poly‐caprolactone (PCL) were fabricated and separately treated with various concentrations of NaOH (for PLGA and PCL) and HNO3 (for PU) for select time periods. These treatments reduced the polymer surface feature dimensions from conventional micron dimensions to biologically inspired nanometer dimensions. Select cytocompatibility properties of these biomaterials were tested in vitro. Results provide the first evidence that adhesion of bladder smooth muscle cells is enhanced as polymer surface feature dimensions are reduced into the nanometer range. In addition, surface analysis results reveal that the polymer nanometer surface roughness is the primary design parameter that increases bladder smooth muscle cell adhesion. For this reason, the “next generation” of tissue‐engineered bladder constructs with increased efficacy should contain surfaces with nanometer (as opposed to micron) surface features. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1374–1383, 2003
Effects of matrix stabilization when using glutaraldehyde on the material properties of porcine meniscus
Authors: Hunter Shawn A. , Noyes Frank R. , Haridas Balakrishna , Levy Martin S. , Butler David L.
Published: November 2003

Meniscus transplantation frequently is one of the only options available for treating symptomatic younger patients with tibiofemoral pain and early arthrosis after a prior meniscectomy. However, clinical results indicate that current meniscal allografts may undergo degenerative changes due to enzymatic degradation during the remodeling phase. The objective of this study was to evaluate the effects of glutaraldehyde‐induced matrix stabilization on the material properties of porcine meniscus prior to surgical implantation. Protocols for fabricating heart‐valve replacements were examined, followed by an exploration of the effects of reducing glutaraldehyde concentration and exposure time. Cylindrical meniscus specimens were tested in uniaxial confined compression under a 0.196 MPa compressive stress, and aggregate modulus (HA), permeability (k), and compressive strains at equilibrium (ϵeq) were calculated from the creep response. Compared to controls, the mean values for HA and k increased, on average, by 213 and 709%, respectively, and ϵeq decreased by 57% for all “heart‐valve” treatments. Reducing tissue exposure time to glutaraldehyde had little effect, but decreasing glutaraldehyde concentration to 0.02% resulted in tissues with material properties no different from the untreated controls. We conclude that minimal concentrations of glutaraldehyde (less than 0.2%) should be used in future studies to preserve normal meniscus properties. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1245–1254, 2003
Competitive plasma protein adsorption onto fluorinated polyimide surfaces
Authors: Kawakami H. , Kanno M. , Nagaoka S. , Kubota S.
Published: November 2003

A series of fluorinated polyimides cured at different temperatures was prepared, and plasma protein adsorption and platelet adhesion onto the polyimide films were evaluated in vitro using scanning electron microscopy, a micro‐bicinchoninic acid protein assay, and a gold–colloid‐labeled immunoassay. In particular, we focused on competitive plasma protein adsorption onto polyimide film because elucidation of the competitive adsorption mechanism is needed for a good understanding of in vivo biocompatibility of polyimide. Interestingly, the trend of IgG adsorption onto the polyimide surface measured in human plasma was completely contrary to that observed with IgG dissolved in PBS, and the adsorption increased with an increase in the curing temperature. We propose that the human plasma Fc region in IgG might selectively adsorb onto polyimide film cured at high temperatures because of competitive plasma protein adsorption to the surface. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1393–1400, 2003
Bioinspired organic‐inorganic composite materials prepared by an alternate soaking process as a tissue reconstitution matrix
Authors: Ogomi Daisuke , Serizawa Takeshi , Akashi Mitsuru
Published: November 2003

Poly(acrylic acid) (PAAc) grafted poly(ethylene) (PE) (PAAc‐g‐PE) film‐apatite or calcium carbonate (CaCO3) composite materials were prepared by an alternate soaking process, which simply forms apatite or CaCO3 on the polymer materials by alternate soaking in Ca2+‐ and PO‐ or CO32−‐containing solutions. X‐ray diffraction analysis of the composite films indicated the presence of hydroxyapatite or CaCO3 on the film. Scanning electron microscopic observation revealed that the whole surface of the film was covered by the apatite or CaCO3. Cell compatibility tests of the apatite‐ or CaCO3‐coated film suggested that the greater number of cells adhered on the films and that the cell proliferation properties were extremely greater on the films. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1360–1366, 2003
In vitroevaluation of novel bioactive composites based on Bioglass®‐filled polylactide foams for bone tissue engineering scaffolds
Authors: Blaker J. J. , Gough J. E. , Maquet V. , Notingher I. , Boccaccini A. R.
Published: November 2003

Highly porous poly(DL‐lactic acid) (PDLLA) foams and Bioglass®‐filled PDLLA composite foams were characterized and evaluatedin vitroas bone tissue engineering scaffolds. The hypothesis was that the combination of PDLLA with Bioglass® in a porous structure would result in a bioresorbable and bioactive composite, capable of supporting osteoblast adhesion, spreading and viability. Composite and unfilled foams were incubated in simulated body fluid (SBF) at 37°C to study thein vitrodegradation of the polymer and to detect hydroxyapatite (HA) formation, which is a measure of the materials'in vitrobioactivity. HA was detected on all the composite samples after incubation in SBF for just 3 days. After 28 days immersion the foams filled with 40 wt % Bioglass® developed a continuous layer of HA. The formation of HA for the 5 wt % Bioglass®‐filled foams was localized to the Bioglass® particles. Cell culture studies using a commercially available (ECACC) human osteosarcoma cell line (MG‐63) were conducted to assess the biocompatibility of the foams and cell attachment to the porous substrates. The osteoblast cell infiltration study showed that the cells were able to migrate through the porous network and colonize the deeper regions within the foam, indicating that the composition of the foams and the pore structures are able to support osteoblast attachment, spreading, and viability. Rapid formation of HA on the composites and the attachment of MG‐63 cells within the porous network of the composite foams confirms the highin vitrobioactivity and biocompatibility of these materials and their potential to be used as scaffolds in bone tissue engineering and repair. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1401–1411, 2003
Epigenetic regulation of Igf2/H19 imprinting at CTCF insulator binding sites
Authors: Yang Youwen , Hu Ji‐Fan , Ulaner Gary A. , Li Tao , Yao Xiaoming , Vu Thanh H. , Hoffman Andrew R.
Published: November 2003

The mouse insulin‐like growth factor II (Igf2) and H19 genes are located adjacent to each other on chromosome 7q11‐13 and are reciprocally imprinted. It is believed that the allelic expression of these two genes is regulated by the binding of CTCF insulators to four parent‐specific DNA methylation sites in an imprinting control center (ICR) located between these two genes. Although monoallelically expressed in peripheral tissues, Igf2 is biallelically transcribed in the CNS. In this study, we examined the allelic DNA methylation and CTCF binding in the Igf2/H19 imprinting center in CNS, hypothesizing that the aberrant CTCF binding as one of the mechanisms leads to biallelic expression of Igf2 in CNS. Using hybrid F1 mice (M. spretus males × C57BL/6 females), we showed that in CNS, CTCF binding sites in the ICR were methylated exclusively on the paternal allele, and CTCF bound only to the unmethylated maternal allele, showing no differences from the imprinted peripheral tissues. Among three other epigenetic modifications examined, histone H3 lysine 9 methylation correlated well with Igf2 allelic expression in CNS. These results suggest that CTCF binding to the ICR alone is not sufficient to insulate the Igf2 maternal promoter and to regulate the allelic expression of the gene in the CNS, thus challenging the aberrant CTCF binding as a common mechanism for lack of Igf2 imprinting in CNS. Further studies should be focused on the identification of factors that are involved in histone methylation and CTCF‐associated factors that may be needed to coordinate Igf2 imprinting. © 2003 Wiley‐Liss, Inc.
High dose M‐CSF partially rescues the Dap12−/− osteoclast phenotype
Authors: Faccio Roberta , Zou Wei , Colaianni Graziana , Teitelbaum Steven L. , Patrick Ross F.
Published: November 2003

Osteoclasts are macrophage derived cells and as such are subject to regulation by molecules impacting other members of the immune system. Dap12 is an adaptor protein expressed by NK cells and B and T lymphocytes. Dap12 also mediates maturation of myeloid cells and is expressed by osteoclasts which are dysfunctional in its absence. We find Dap12−/− osteoclast precursors fail to differentiate, in vitro, and the abnormality is partially rescued by high dose M‐CSF. The relative paucity of osteoclast number, even in presence of high dose cytokine, is attended by dampened proliferation of precursor cells and their failure to normally migrate towards the osteoclast‐recognized matrix protein, osteopontin. Furthermore, Dap12−/− osteoclasts generated in high dose M‐CSF fail to normally organize their cytoskeleton. The incapacity of Dap12 null cells to undergo normal osteoclast differentiation is not due to blunted stimulation of major RANK ligand (RANKL) or M‐CSF induced signaling pathways. On the other hand, when plated on osteopontin, Dap12−/− pre‐osteoclasts do not activate the tyrosine kinase, Syk, which normally binds to the adaptor protein and transmits downstream signals. Attesting to the importance of the Dap12/Syk complex, Syk deficient macrophages do not undergo normal osteoclastogenesis. Furthermore, the same cells plated onto osteopontin, adhere poorly and fail to phosphorylate c‐Src or Pyk2, two kinases central to organization of the osteoclast cytoskeleton. © 2003 Wiley‐Liss, Inc.
New micromachined microstrip transmission lines for application in millimeter‐wave circuits
Authors: Lee Han‐Shin , Kim Sung‐Chan , Lim Byoung‐Ok , Kim Kyoung‐Man , Uhm Won‐Young , Chun Young‐Hoon , Shin Dong‐Hoon , Kim Soon‐Koo , Park Hyun‐Chang , Rhee Jin‐Koo
Published: November 2003

In this paper, we describe a new GaAs‐based micromachined microstrip line, supported by an electrically supported air‐gapped microstrip line (DAML) structure and developed using RF MEMS techniques to achieve low losses at millimeter‐wave frequency bands with wide impedance ranges. The measured DAML with a 10‐μm post height shows less than 1.5‐dB/cm attenuation at 50 GHz with 20–100Ω, which agrees well with the simulated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 6–9, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11270
Consistency of the numerical dispersion relation expressed in different forms for the ADI‐FDTD method
Authors: Zhao An Ping
Published: November 2003

The relationship of the numerical dispersion relation presented in different mathematical expressions (that are independently derived in 1, 2) for the three‐dimensional alternating direction implicit finite‐difference time‐domain (3D ADI‐FDTD) method is investigated. It is found that, unlike the statement made in 2, the formulae of the numerical dispersion relation proposed in 1, 2 are unconditionally equivalent to each other, as they can be transformed from one to another, which in turn demonstrates the consistency of these formulae. The consistency of the formulae expressed in different forms derived for the one‐dimensional and two‐dimensional cases is also demonstrated, as a by‐product of this paper. Furthermore, it is found that the formulae expressed in the form of tan(ωΔt/2) have the simplest and most convenient forms for the ADI‐FDTD method. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 12–13, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11272
Experimental study of the SAR characteristics of mobile phones
Authors: Chan K. H. , Leung S. W. , Fung L. C. , Siu Y. M.
Published: November 2003

The specific absorption rate (SAR) on a human head due to the radiation of mobile phones can be influenced by many parameters, including the phones' antenna design and profile. In this paper, an experimental study of the characteristics of the SAR of mobile phones is presented. Statistical results illustrate that mobile phones, in general, satisfy the ICNIRP safety limit, and that the SAR values are affected by the transmission frequency of mobile phones. In most cases, the maximum SAR is at the cheek position and is twice that at the ear position. We conclude that there is no significant difference in the SAR value between phones with internal and external antennas and that, at the ear position, the SAR value of the flip phones is about 22% lower than that of nonflip phones. We also conclude that the SAR hot spot is generally located near the antenna position. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 22–26, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11275
A compact dual‐band dual‐polarized antenna element for GSM/DCS/UMTS base stations
Authors: Deillon V. , Zürcher J‐F. , Skrivervik A. K.
Published: November 2003

A dual‐band dual‐polarized antenna suitable for operation in telecommunication base stations is presented. One of the bands covers the GSM band, while the other covers both the DCS and UMTS bands. The design is compact and yields good radiation characteristics, with excellent isolation between polarizations and bands. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 29–33, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11277
Experimental investigation of the field conditions in a vibrating intrinsic reverberation chamber
Authors: Kouveliotis N. K. , Trakadas P. T. , Hairetakis I. I. , Capsalis C. N.
Published: November 2003

The field uniformity and field distribution of a vibrating reverberation chamber is examined using measurements performed in a reverberating screened room. The field conditions in this kind of chamber are investigated, assuming that the direct path signal between the transmitter and the observation point exists. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 35–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11279
Broadband aperture‐coupled circularly polarized microstrip antenna fed by a three‐stub hybrid coupler
Authors: Qing X. M.
Published: November 2003

A novel aperture‐coupled circularly polarized microstrip antenna with a three‐stub hybrid coupler feed circuit in order to generate broadband circular polarization radiation is proposed. The bandwidth is 32.3% for 2:1 VSWR and 42.6% for 3‐dB axial ratio. The achievable maximum gain is 8.8 dBic. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 38–41, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11280
Multiwavelet based moment method under discrete Sobolev‐type norm
Authors: Pan George , Tong Meisong , Gilbert Barry
Published: November 2003

Multiwavelets are successfully applied to Galerkin's method for solving integral equations. High precision and fast convergence are demonstrated because of the desirable properties of multiwavelets, including compact support, symmetry and antisymmetry, regularity (continuity and smoothness), explicit expressions, and more importantly, the orthogonality under a Sobolev‐type inner product. As a result, numerical integrations in the testing procedure are carried out explicitly. Numerical examples are conducted for electromagnetic waves scattering from smooth surfaces and surfaces with sharp edges, and propagating along microstrips with finite thickness. The new algorithm demonstrates significant improvement over the traditional MoM in terms of momery and CPU time up to two orders of magnitude. The new algorithm is easy to implement and program. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 47–50, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11282
A generalized ZY Smith chart for solving nonreciprocal uniform transmission‐line problems
Authors: Torungrueng D. , Thimaporn C.
Published: November 2003

Nonreciprocal transmission lines have found various applications in microwave technology. Because the governing equations of nonreciprocal transmission lines are quite complicated, the need for a graphical tool to assist in the analysis and design of nonreciprocal devices is obvious. The Smith chart has shown to be a very useful graphical tool when solving reciprocal uniform transmission‐line problems. However, the Smith chart needs to be modified for nonreciprocal transmission lines; this is called a generalized Smith chart. This novel chart can be easily generated using Matlab. It is found that the ZY Smith chart is a special case of a generalized ZY Smith chart. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 57–61, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11284
A novel broadband triple‐layer triangular patch antenna
Authors: Haridim M. , Shukrun D. , Matzner H.
Published: November 2003

A novel broadband L‐band patch antenna is presented. The proposed antenna consists of three layers, each containing a triangular patch of a different size. The layers are separated by substrates of equal thickness and permittivity. The antenna is fed through the lowest patch, with the upper patches fed parasitically. Both simulation and experimental results show relatively broadband characteristics. The antenna has a fair gain, comparable to that of single‐layer patch antennas. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 66–70, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11286
Coplanar‐waveguide‐fed uniplanar antenna using a broadband balun
Authors: Chiu C. W.
Published: November 2003

In this paper, we present a uniplanar strip‐dipole antenna and a bow‐tie antenna fed by a coplanar waveguide (CPW) that both use a wideband and compact balun. The balun, which consists of planar lumped‐LC circuits, affects the transition from an unbalanced CPW to a balanced coplanar strip. The antennas are designed to operate at the 2.44‐GHz ISM‐band. The measured data show that such broadband balun‐based antennas enjoy the advantages of broad bandwidth and extra compactness. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 70–73, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11287
Feed effects on the dimensions of wideband slot antennas
Authors: Rao Patnam H.
Published: November 2003

The feed interaction of wideband slot antennas is analyzed using finite‐element method optimizations. The achievable bandwidth with bow‐tie feed is around 115% (more than 2:1) for VSWR ≤ 2 and a similar configuration could achieve a bandwidth of 45% for VSWR ≤ 2 with radial stub feed. The effect of feeding mechanisms on the dimensions of the slots is discussed. A comparison of measured results for various feed configurations is presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 77–79, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11289
Simple derivation and proof of geometrical stability criteria for linear two‐ports
Authors: Tan Eng Leong
Published: November 2003

This paper presents a simple derivation of the single‐parameter geometrical stability criteria for linear two‐ports. The derivation is directly based on the classical constraints familiar to most circuit designers with regard to stability circles and stable regions. A straightforward proof of the mutual implications of various geometrical stability criteria involving dual or single parameters is also provided in a concise manner. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 81–83, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11291
RF curve‐fitting predistorter for extending the dynamic range of a linearized power amplifier
Authors: Cho Kyung‐Joon , Jang Dong‐Hee , Kim Sang‐Hee , Kim Jong‐Heon , Stapleton Shawn P.
Published: November 2003

In this paper, an RF curve‐fitting predistorter is proposed to extend the linearized dynamic range of a power amplifier. AM‐AM and AM‐PM distortion of the power amplifier can be compensated by accurately adjusting the gain and phase gradients of the three‐reflection‐type diode predistorter. The proposed predistorter extends the linearized dynamic range by more than six times that of a conventional predistorter. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 83–87, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11292