bluuebunny/crossref_metadata_2025_split huggingface dataset:
Semiparametric hedonic price models: assessing the effects of agricultural nonpoint source pollution
Authors: Bontemps Christophe , Simioni Michel , Surry Yves 
Published: September 2008

AbstractIn the area of environmental analysis using hedonic price models, we investigate the performance of various nonparametric and semiparametric specifications. The proposed model specifications are made up of two parts: a linear component for house characteristics and a non‐(semi)parametric component representing the nonlinear influence of environmental indicators on house prices. We adopt a general‐to‐specific search procedure, based on recent specification tests comparing the proposed specifications with a fully nonparametric benchmark model, to select the best model specification. An application of these semiparametric models to rural districts indicates that pollution resulting from intensive livestock farming has a significant nonlinear impact on house prices. Copyright © 2008 John Wiley & Sons, Ltd.
Efficiency externalities of trade and alternative forms of foreign investment in OECD countries
Authors: Iyer Krishna G. , Rambaldi Alicia N. , Tang Kam Ki 
Published: September 2008

AbstractThe literature on the spillover effects of trade and inflows of foreign direct investment (FDI) has concentrated on technological externalities. Little effort has been directed towards identifying their efficiency externalities. This paper measures the efficiency externalities of trade and various forms of foreign investment for a sample of 20 OECD countries between 1982 and 2000 using a stochastic frontier approach. Trade and all foreign investment inflows are found to enhance efficiency, whereas outflows of FDI are found to exacerbate inefficiency. The efficiency externalities from foreign investment are contingent on the absorptive capacity of the host economies. Copyright © 2008 John Wiley & Sons, Ltd.
Random Recursive Partitioning: a matching method for the estimation of the average treatment effect
Authors: Porro Giuseppe , Iacus Stefano Maria 
Published: September 2008

AbstractIn this paper we introduce the Random Recursive Partitioning (RRP) matching method. RRP generates a proximity matrix which might be useful in econometric applications like average treatment effect estimation. RRP is a Monte Carlo method that randomly generates non‐empty recursive partitions of the data and evaluates the proximity between two observations as the empirical frequency they fall in a same cell of these random partitions over all Monte Carlo replications. From the proximity matrix it is possible to derive both graphical and analytical tools to evaluate the extent of the common support between data sets. The RRP method is “honest” in that it does not match observations “at any cost”: if data sets are separated, the method clearly states it.The match obtained with RRP is invariant under monotonic transformation of the data. Average treatment effect estimators derived from the proximity matrix seem to be competitive compared to more commonly used estimators. RRP method does not require a particular structure of the data and for this reason it can be applied when distances like Mahalanobis or Euclidean are not suitable, in the presence of missing data or when the estimated propensity score is too sensitive to model specifications. Copyright © 2008 John Wiley & Sons, Ltd.
The wages of BMI: Bayesian analysis of a skewed treatment–response model with nonparametric endogeneity
Authors: Kline Brendan , Tobias Justin L. 
Published: September 2008

AbstractWe generalize the specifications used in previous studies of the effect of body mass index (BMI) on earnings by allowing the potentially endogenous BMI variable to enter the log wage equation nonparametrically. We introduce a Bayesian posterior simulator for fitting our model that permits a nonparametric treatment of the endogenous BMI variable, flexibly accommodates skew in the BMI distribution, and whose implementation requires only Gibbs steps. Using data from the 1970 British Cohort Study, our results indicate the presence of nonlinearities in the relationships between BMI and log wages that differ across men and women, and also suggest the importance of unobserved confounding for our sample of males. Copyright © 2008 John Wiley & Sons, Ltd.
Human umbilical cord mesenchymal stem cells: Osteogenesis in vivo as seed cells for bone tissue engineering
Authors: Diao Yinze , Ma Qingjun , Cui Fuzhai , Zhong Yanfeng 
Published: September 2008

AbstractMesenchymal stem cells (MSCs) are ideal seed cells for bone tissue engineering. However, intrinsic deficiencies exist for the autologous transplantation strategy of constructing artificial bone with MSCs derived from bone marrow of patients. In this study, MSCs‐like cells were isolated from human umbilical cords and were expanded in vitro. Flow cytometric analysis revealed that cells from the fourth passage were positive for CD29, CD44, CD71, CD73, CD90, and CD105 whereas they were negative for CD14, CD34, CD45, and CD117. Furthermore, these cells expressed HLA‐A, B, C (MHC‐I), but not HLA‐DP, DQ, DR (MHC‐II), or costimulatory molecules such as CD80 and CD86. Following incubation in specific inductive media for 3 weeks, cultured cells were shown to possess potential to differentiate into adipogenic, osteogenic or chondrogenic lineages in vitro. The umbilical cord‐derived MSCs (UC‐MSCs) were loaded with a biomimetic artificial bone scaffold material before being implanted subcutaneously in the back of Balb/c nude mice for four to twelve weeks. Our results revealed that UC‐MSCs loaded with the scaffold displayed capacity of osteogenic differentiation leading to osteogenesis with human origin in vivo. As a readily available source of seed cells for bone tissue engineering, UC‐MSCs should have broad application prospects. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Enhanced biological stability of collagen with incorporation of PAMAM dendrimer
Authors: Zhong Shaoping , Yung Lin Yue Lanry 
Published: September 2008

AbstractThe crosslinking methods of collagen using glutaraldehyde (GTA) and 1‐ethyl‐3‐(3‐dimethyl aminopropyl) carbodiimide (EDC)/N‐hydroxysuccinimide (NHS) are frequently performed in biomedical applications, but both methods still have their own disadvantages, including the GTA cytotoxicity and low degree of EDC/NHS crosslinking. In this study, we incorporated polyamidoamine (PAMAM) dendrimer with surface amine groups into the two aforementioned crosslinking methods to improve the biostability and structural integrity of collagen. Fifty micromolar of dendrimer concentration was found to have negligible in vitro cytotoxicity and was used for EDC and GTA crosslinking of collagen. The collagenase digestion assay showed that the collagen scaffolds crosslinked in the presence of PAMAM exhibited a higher denature temperature and higher resistance against collagenase digestion compared with their counterparts without dendrimer. Cell proliferation with human conjunctival fibroblasts showed that the incorporation of PAMAM in EDC crosslinking significantly increased the proliferation. All the crosslinked scaffolds also exhibited higher structural stability than the noncrosslinked scaffold. Crosslinking with EDC and PAMAM together yielded substantially higher proliferation and may be a suitable collagen scaffold for biomedical applications. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2009
Flow perfusion culture of human fetal bone cells in large β‐tricalcium phosphate scaffold with controlled architecture
Authors: Wang Lin , Hu Yun‐Yu , Wang Zhen , Li Xiang , Li Di‐Chen , Lu Bing‐Heng , Xu Song‐Feng 
Published: September 2008

AbstractOne unsolved problem in bone tissue engineering is how to enable the survival and proliferation of osteoblastic cells in large scaffolds. In this work, large β‐tricalcium phosphate scaffolds with tightly controlled channel architectures were fabricated and a custom‐designed perfusion bioreactor was developed. Human fetal bone cells in third passage were seeded onto the scaffolds and cultured in static or flow perfusion conditions for up to 16 days. Compared with nonperfused constructs, flow perfused constructs demonstrated improved cells proliferation and differentiation according to cell viability, glucose consumption, alkaline phosphatase activity, and osteopontin. Moreover, after 16 days of perfusion culture, a homogenous layer composed of cells and mineralized matrix throughout the whole scaffold was observed by scanning electron microscopy and histological study. In contrast, cells were located only along the scaffold perimeter in static culture. These results demonstrated the feasibility and benefit of perfusion culture in conjunction with well‐defined three‐dimensional environment for large bone graft construction. Porous scaffold with controlled architecture can be a potential tool to evaluate the effects of scaffold specific geometry on fluid flow configuration and cell behavior under perfusion culture. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Antibiotic delivery system using nano‐hydroxyapatite/chitosan bone cement consisting of berberine
Authors: Zou Qin , Li Yubao , Zhang Li , Zuo Yi , Li Junfeng , Li Jidong 
Published: September 2008

AbstractDifferent concentrations of berberine were mixed with nano‐hydroxyapatite/chitosan (n‐HA/CS) bone cement to generate an antibiotic drug delivery system for treatment of bone defects. Properties of the system such as setting time, compressive strength, surface morphology, phase compositions, drug release profiles and antimicrobial activity were also characterized. It was shown that the setting time of the cement ranged from 17.03 ± 0.50 min to 28.47 ± 0.96 min and the compressive strength changed from 184.00 ± 7.94 MPa to 120.33 ± 9.02 MPa with the increase of berberine. The XRD, IR, and SEM analyses suggested that berberine powders were stable in the bone cement in simulated body fluid (SBF). In vitro release of berberine from the bioactive bone cement pellets in SBF could last more than 4 weeks. The release profiles of 1.0 wt % berberine loaded bone cement followed the Higuchi equation at the infusion stage. The drug loaded pellets can inhibit bacterial growth (Staphylococcus aureus) at the standardized berberine minimum inhibitory concentration of 0.02 mg/mL during berberine release from 1 to 28 days. The n‐HA/CS bone cement only with 1.0 wt % berberine proved to be an efficient antibiotic drug delivery system. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Mixing conditions for cell scaffolds affect the bone formation induced by bone engineering with human bone marrow stromal cells, β‐tricalcium phosphate granules, and rhBMP‐2
Authors: Uchida Moritoshi , Agata Hideki , Sagara Hiroshi , Shinohara Yoshinori , Kagami Hideaki , Asahina Izumi 
Published: September 2008

AbstractBone regenerative medicine via tissue engineering is expected to be an alternative treatment for conventional autogenous bone graft, as it is less invasive. One of the best triads for bone engineering is bone marrow stromal cells, calcium phosphate ceramics, and bone morphogenetic protein (BMP). However, the optimal mixing conditions for BMP‐induced osteoblasts and ceramic granules remain unclear. Therefore, we investigated the effect of the mixing conditions for cell scaffolds on the bone‐forming potential. The cells were mixed with beta‐tricalcium phosphate (β‐TCP) granules followed by osteoblast induction with recombinant human BMP‐2 (rhBMP‐2) (first mixture), or were first induced with rhBMP‐2 on plastic dishes and then mixed with the β‐TCP granules (last mixture) just prior to the operation. Both the first and last mixtures were transplanted into nude mice subcutaneously, with the amount of bone formation analyzed histomorphometrically. In addition, cell numbers and alkaline phosphatase (ALP) activity before transplantation was determined in both the mixtures. In vitro analyses revealed that cell numbers were greater in the last mixture, whereas ALP activity was greater in the first mixture. In vivo analyses revealed that the first mixture was much more osteogenic than the last mixture with respect to new bone formation and osteocalcin synthesis. These data suggest that cell‐scaffold mixing conditions have a significant influence on the bone‐forming capacity via bone engineering and that first mixture might be the optimal condition for rhBMP‐2‐induction of human osteoblasts. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Behavior of rat periodontal ligament cells on fibroblast growth factor‐2‐immobilized titanium surfaces treated by plasma modification
Authors: Kokubu Eitoyo , Yoshinari Masao , Matsuzaka Kenichi , Inoue Takashi 
Published: September 2008

AbstractThe aim of this study was to investigate the behavior of rat periodontal ligament (PDL) cells cultured on fibroblast growth factor‐2 (FGF‐2)‐immobilized titanium surfaces treated by oxygen (O2) plasma. We used cell disks (15 mm in diameter), and 35‐mm culture dishes sputter‐coated with titanium. These were treated with oxygen plasma and dipped in FGF‐2 solution. Immobilized FGF‐2 was visualized with a confocal laser‐scanning microscope, and its weight was calculated to be ˜22.6 ng/cm2 using a quartz crystal microbalance‐dissipation apparatus. The PDL cells were obtained from rat incisors. Cells from fourth subculture were seeded onto the FGF‐2‐immobilized titanium surface. Proliferation ratio, alkaline phosphatase (ALP) activity, and expressions of type I collagen and vascular endothelial growth factor (VEGF) mRNAs were evaluated. Proliferation ratio and expressions of type I collagen and VEGF mRNAs were significantly higher, whereas ALP activity was significantly lower in FGF‐2‐immobilized cells than in control group (p < 0.05). These findings suggest that oxygen plasma modification can immobilize FGF‐2 onto a titanium surface. Immobilized FGF‐2, although inferior to culture medium with FGF‐2, influenced the proliferation of PDL cells and might have promoted collagen and vascular synthesis. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2009
Effect of carbon nanotubes on cellular functions in vitro
Authors: Li Xiaoming , Gao Hong , Uo Motohiro , Sato Yoshinori , Akasaka Tsukasa , Feng Qingling , Cui Fuzhai , Liu Xinhui , Watari Fumio 
Published: September 2008

AbstractCarbon nanotubes (CNTs) have been shown to affect cell behavior. But how and why the CNTs affect potential differentiation of the attached cells has not been largely known. In this study, multiwalled carbon nanotubes (MWNTs) and graphite (GP) were pressed as compacts. Higher ability of CNTs to adsorb proteins, compared with GP, was shown. Myoblastic mouse cells (C2C12) were cultured and the cell responses to the two kinds of compacts were compared in vitro. Meanwhile, we used cell culture on the culture plate as a control. During the conventional culture, significantly better cell attachment, proliferation, and differentiation of cells on the MWNTs were found. To confirm the hypothesis that the larger amount of protein adsorbed on the CNTs was crucial for this, we made the compacts adsorb more proteins in culture medium with 50% fetal bovine serum (FBS) before cell culture. With the adsorption of the proteins in advance, the increments of the total‐protein/DNA and alkaline phosphatase (ALP)/DNA for the MWNTs was respectively as about 11 times and 18 times as the increments of those for GP and the control at both day 4 and day 7. Therefore, the CNTs might induce cellular functions by adsorbing more proteins, which indicated that the CNTs might be a candidate for scaffold material for tissue engineering. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2009
Bioactive glass sol‐gel foam scaffolds: Evolution of nanoporosity during processing and in situ monitoring of apatite layer formation using small‐ and wide‐angle X‐ray scattering
Authors: FitzGerald V. , Martin R. A. , Jones J. R. , Qiu D. , Wetherall K. M. , Moss R. M. , Newport R. J. 
Published: September 2008

AbstractRecent work has highlighted the potential of sol‐gel–derived calcium silicate glasses for the regeneration or replacement of damaged bone tissue. The work presented herein provides new insight into the processing of bioactive calcia‐silica sol‐gel foams, and the reaction mechanisms associated with them when immersed in vitro in a simulated body fluid (SBF). Small‐angle X‐ray scattering and wide‐angle X‐ray scattering (diffraction) have been used to study the stabilization of these foams via heat treatment, with analogous in situ time‐resolved data being gathered for a foam immersed in SBF. During thermal processing, pore sizes have been identified in the range of 16.5–62.0 nm and are only present once foams have been heated to 400°C and above. Calcium nitrate crystallites were present until foams were heated to 600°C; the crystallite size varied from 75 to 145 nm and increased in size with heat treatment up to 300°C, then decreased in size down to 95nm at 400°C. The in situ time‐resolved data show that the average pore diameter decreases as a function of immersion time in SBF, as calcium phosphates grow on the glass surfaces. Over the same time, Bragg peaks indicative of tricalcium phosphate were evident after only 1‐h immersion time, and later, hydroxycarbonate apatite was also seen. The hydroxycarbonate apatite appears to have preferred orientation in the (h,k,0) direction. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Osteoblast activity on collagen‐GAG scaffolds is affected by collagen and GAG concentrations
Authors: Tierney Claire M. , Jaasma Michael J. , O'Brien Fergal J. 
Published: September 2008

AbstractOptimization of a tissue engineering scaffold for use in bone tissue engineering requires control of many factors such as pore size, porosity, permeability and, as this study shows, the composition of the matrix. The collagen‐glycosaminoglycan (GAG) scaffold variants were fabricated by varying the collagen and GAG content of the scaffold. Scaffolds were seeded with MC3T3 osteoblasts and cultured for up to 7 days. During the culture period, osteoblastic activity was evaluated by measuring metabolic activity, cell number, and spatial distribution. Collagen and GAG concentrations both affected osteoblast viability, proliferation, and spatial distribution within the scaffold. Scaffolds containing 1% collagen (w/v) and 0.088% GAG (w/v) were found to have a porosity of ∼99%, high cell metabolic activity and cell number, and good cell infiltration over the 7 days in culture. Taken together, these results indicate the need to tailor the parameters of a biological substrate for use in a specific tissue application, in this case bone tissue engineering. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Mammary epithelial cell transformation is associated with deregulation of the vitamin D pathway
Authors: Kemmis Carly M. , Welsh JoEllen 
Published: September 2008

AbstractThe vitamin D endocrine system mediates anti‐proliferative and pro‐differentiating signaling in multiple epithelial tissues, including mammary gland and breast tumors. The vitamin D metabolite 1α,25(OH)2D3 mediates growth inhibitory signaling via activation of the vitamin D receptor (VDR), a ligand dependent transcription factor. 1α,25(OH)2D3 is synthesized from 25(OH)D3 (the major circulating form of the vitamin) by the mitochondrial enzyme CYP27b1 in renal and other tissues. Human mammary epithelial (HME) cells express VDR and CYP27b1 and undergo growth inhibition when exposed to physiological concentrations of 25(OH)D3, suggesting that autocrine or paracrine vitamin D signaling contributes to maintenance of differentiation and quiescence in the mammary epithelium. In the current studies we tested the hypothesis that cancer cells would exhibit reduced sensitivity to vitamin D mediated negative growth regulation. We used a series of progressively transformed HME cell lines expressing known oncogenic manipulations to study the effects of transformation per se on the vitamin D pathway. We report that mRNA and protein levels of VDR and CYP27b1 were reduced greater than 70% upon stable introduction of known oncogenes (SV40 T antigens and H‐rasV12) into HME cells. Oncogenic transformation was also associated with reduced 1α,25(OH)2D3 synthesis, and cellular sensitivity to growth inhibition by 1α,25(OH)2D3 and 25(OH)D3 was decreased approximately 100‐fold in transformed cells. These studies provide evidence that disruption of the vitamin D signaling pathway occurs early in the cancer development process. J. Cell. Biochem. 105: 980–988, 2008. © 2008 Wiley‐Liss, Inc.
E‐cadherin dis‐engagement activates the Rap1 GTPase
Authors: Asuri Sirisha , Yan Jingliang , Paranavitana Nivanka C. , Quilliam Lawrence A. 
Published: September 2008

AbstractE‐cadherin based adherens junctions are finely regulated by multiple cellular signaling events. Here we show that the Ras‐related Rap1 GTPase is enriched in regions of nascent cell–cell contacts and strengthens E‐cadherin junctions: constitutively active Rap1 expressing MDCK cells exhibit increased junctional contact and resisted calcium depletion‐induced cell–cell junction disruption. E‐cadherin disengagement activated Rap1 and this correlated with E‐cadherin association with the Rap GEFs, C3G and PDZ‐GEF I. PDZ‐GEF I associated with E‐cadherin and β‐catenin whereas C3G interaction with E‐cadherin did not involve β‐catenin. Knockdown of PDZ‐GEF I in MDCK cells decreased Rap1 activity following E‐cadherin junction disruption. We hereby show that Rap1 plays a role in the maintenance and repair of E‐cadherin junctions and is activated via an “outside‐in” signaling pathway initiated by E‐cadherin and mediated at least in part by PDZ‐GEF I. J. Cell. Biochem. 105: 1027–1037, 2008. © 2008 Wiley‐Liss, Inc.
Negative effects of the amino acids Lys, His, and Thr on S6K1 phosphorylation in mammary epithelial cells
Authors: Prizant Rotem Ladovsky , Barash Itamar 
Published: September 2008

AbstractThe role of essential amino acids (AA) on protein synthesis via the mTOR pathway was studied in murine mammary epithelial cells cultured under lactogenic conditions. Leu, Ile, and Val increased S6K1 phosphorylation compared to that measured in AA‐deprived cells. Trp, Phe, and Met had no effect. Surprisingly, Lys, His, and Thr inhibited S6K1 phosphorylation in both murine and bovine mammary cells. Thr exhibited the most potent inhibition, being the only amino acid that competed with Leu's positive role. In non‐deprived cells, there was no observable effect of Lys, His, or Thr on S6K1 phosphorylation at concentrations up to five times those in the medium. However, their addition as a mix revealed a synergistic negative effect. Supplementation of Lys, His, and Thr abrogated mTOR Ser 2448 phosphorylation, with no effect on Akt Ser 473—an mTORC2 target. This confirms specific mTORC1 regulation of S6K1 phosphorylation. The individual supplementation of Lys, His, and Thr maintained a low level of IRS‐1 phosphorylation, which was dose‐dependently increased by their combined addition. Thus, in parallel to inhibiting S6K1 activity, these AA may act synergistically to activate an additional kinase, phosphorylating IRS‐1 via an S6K1‐independent pathway. In cultures supplemented by Lys, His, and Thr, cellular protein synthesis decreased by up to 65%. A more pronounced effect was observed on β‐casein synthesis. These findings indicate that positive and negative signaling from AA to the mTOR pathway, combined with modulation of insulin sensitization, mediate the synthesis rates of total and specific milk proteins in mammary epithelial cells. J. Cell. Biochem. 105: 1038–1047, 2008. © 2008 Wiley‐Liss, Inc.