bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymethylmethacrylate particles inhibit osteoblastic differentiation of bone marrow osteoprogenitor cells
Authors: Chiu Richard , Ma Ting , Smith R. Lane , Goodman Stuart B. 
Published: April 2006

AbstractAseptic implant loosening of total joint replacements often results from particle‐mediated bone loss, which may be a combined effect of osteolysis and suppressed bone formation. Bone regeneration in the prosthetic bed depends on the activity of osteoblasts and their differentiation from osteoprogenitors in the bone marrow. This study investigated the effects of polymethylmethacrylate (PMMA) particles on the ability of bone marrow osteoprogenitors to differentiate into osteoblasts in vitro. Murine bone marrow cells challenged with PMMA particles on the first day of differentiation in osteogenic medium showed a dose‐dependent decrease in osteoprogenitor proliferation, alkaline phosphatase expression, and mineralization. Undifferentiated bone marrow cells pretreated with PMMA particles in nonosteogenic medium for 5 days also showed a dose‐dependent loss in osteogenic potential, which was sustained throughout subsequent growth in particle‐free, osteogenic medium. Bone marrow cells challenged with PMMA particles after the fifth day of differentiation in osteogenic medium showed significant reductions in cellular proliferation, but not alkaline phosphatase expression and mineralization, indicating that bone marrow cells were most sensitive to particle treatment during the first 5 days of differentiation. This study demonstrated that PMMA particles inhibit osteoblastic differentiation of bone marrow osteoprogenitor cells, which may contribute to periprosthetic bone loss and implant failure. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Intra‐ and intermolecular interactions between cyclic‐AMP receptor protein and DNA: Ab initio fragment molecular orbital study
Authors: Fukuzawa Kaori , Komeiji Yuto , Mochizuki Yuji , Kato Akifumi , Nakano Tatsuya , Tanaka Shigenori 
Published: April 2006

AbstractThe ab initio fragment molecular orbital (FMO) calculations were performed for the cAMP receptor protein (CRP) complexed with a cAMP and DNA duplex to elucidate their sequence‐specific binding and the stability of the DNA duplex, as determined by analysis of their inter‐ and intramolecular interactions. Calculations were performed with the AMBER94 force field and at the HF and MP2 levels with several basis sets. The interfragment interaction energies (IFIEs) were analyzed for interactions of CRP–cAMP with each base pair, DNA duplex with each amino acid residue, and each base pair with each residue. In addition, base–base interactions were analyzed including hydrogen bonding and stacking of DNA. In the interaction between DNA and CRP–cAMP, there was a significant charge transfer (CT) from the DNA to CRP, and this CT interaction played an important role as well as the electrostatic interactions. It is necessary to apply a quantum mechanical approach beyond the “classical” force‐field approach to describe the sequence specificity. In the DNA intramolecular interaction, the dispersion interactions dominated the stabilization of the base‐pair stacking interactions. Strong, attractive 1,2‐stacking interactions and weak, repulsive 1,3‐stacking interactions were observed. Comparison of the intramolecular interactions of free and complexed DNA revealed that the base‐pairing interactions were stronger, and the stacking interactions were weaker, in the complexed structure. Therefore, the DNA duplex stability appears to change due to both the electrostatic and the CT interactions that take place under conditions of DNA–CRP binding. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 948–960, 2006
Rapidly convergent procedure to solve the density profile equation in the classical density functional theory
Authors: Zhou Shiqi 
Published: April 2006

AbstractAn efficient recursive procedure to solve the density profile equation in the classical density functional theory (DFT) using an inverse Broyden method is described. The present iterative procedure is free of calculation of the Jacobian matrix, and its inversion unavoidable for the well‐known Newton–Raphson (NR) method and its variants. Numerical calculation indicates that only the approximate solution and iterative matrix of the lower bulk density case are employed as the corresponding initial guesses of the higher bulk density case, the present recursive procedure can converge quickly to the physical solution with an accuracy of ε = 10−14; thererfore, the procedure provides an efficient numerical algorithm for the theory in which acquirement of a density profile of high accuracy is a key step. Extensive numerical calculation shows the advantage of the present inverse Broyden method over Broyles' mixing procedure and a modified Powell hybrid algorithm (a variation of the NR method). © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 941–947, 2006
Determination of the ΔpKa between the active site cysteines of thioredoxin and DsbA
Authors: Carvalho Alexandra T. P. , Fernandes P. A. , Ramos Maria J. 
Published: April 2006

AbstractThioredoxin superfamily members share a considerable degree of structural similarity, with a conserved CXiXjC motif at the active site, where C stand for two cysteines that alternate between a reduced thiol and oxidized disulfide states, and Xiand Xj are two amino acids different in each family member. Despite these similarities, they display very different redox potentials and pKas for the active site dithiol, and fulfill different physiological roles. Thioredoxin, for example, promotes the reduction of disulfide bonds, while DsbA promotes their oxidation in prokaryotic cells. The factors that promote these differences are still not fully understood. However, it is generally accepted that the different stabilities of the redox active disulfide bond depends on the degree of stabilization, in the reduced state, of the thiolate of one of the active site cysteines (nucleophilic cysteine). In this work we have used QM/MM methods to compare and characterize the active site dithiols of both enzymes, and to shed some light on the structural features responsible for the large differences in pKa and redox potential between two homologous enzymes, thioredoxin and DsbA. We have also analyzed the main factors pointed out in the literature as responsible for their different properties. We obtained the value of 4.5 for pKa difference (ΔpKa) between the nucleophilic cysteines of both enzymes, which is in excellent agreement with most of the experimental values. Additionally, we found that the principal differentiating factor responsible for this observed ΔpKa are the α2‐alpha helices, which greatly contribute to the mentioned value, by stabilizing the DsbA thiolate in a much greater extend than the thioredoxin thiolate. A double mutation of the conserved residues Asp26 and Lys57, in thioredoxin, and Glu24 Lys58, in DsbA, by alanines did not change the ΔpKa value; this supports the hypothesis that these residues are not involved in the differentiation of the properties of the active centre dithiol. However, we found out that these residues are important for the stabilization of the nucleophilic thiolate. The Xi and Xj residues also do not seem to promote the stabilization of the thiolates. In fact, the corresponding double alanine mutants are more stable than the wild‐type enzymes. However, these residues are involved in the differentiation between thioredoxin and DsbA, stabilizing the DsbA thiolate by a larger extent than the thioredoxin thiolate. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 966–975, 2006
On the joint time‐frequency characteristics of chemical oscillations
Authors: Darowicki K. , Felisiak W. 
Published: April 2006

AbstractA method of time‐frequency transformations of nonstationary signals has been discussed and applied to the analysis of oscillatory Belousov—Zhabotinsky (BZ) reaction. Selected registers of BZ reactions, that represent regular and complex dynamic behavior, have been submitted to the detailed spectral analysis using the short time Fourier transform (STFT). It has been demonstrated that the STFT is an accurate and suitable method for decomposition of chemical oscillations in the joint time and frequency domain. The energy distribution via STFT, presented in this article, revealed some specific characteristics of transitions between different regimes in the closed system of BZ reaction. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 961–965, 2006
Phosphorylation regulates Myc expression via prolonged activation of the mitogen‐activated protein kinase pathway
Authors: Wang Ziqiu , Ge Lisheng , Wang Meifang , Carr Brian I. 
Published: April 2006

AbstractWe previously showed that prolonged and strong ERK phosphorylation induced by Compound 5 (Cpd 5), a Cdc25A protein phosphatase inhibitor, was involved in its mechanism of cell growth inhibition. To study the relationship between ERK phosphorylation and cell growth inhibition, we used Cpd 5 as a tool to investigate ERK‐regulated c‐Myc expression in Hep3B hepatoma cells. We found that ERK phosphorylation caused by Cpd 5 induced c‐Myc phosphorylation, but suppressed c‐Myc expression at the mRNA and protein levels. Furthermore, Cpd 5 inhibited c‐Myc transcriptional activity and DNA binding ability, and this inhibition was antagonized by ERK kinase (MEK) inhibitor U‐0126, implying that the ERK pathway was involved in regulating c‐Myc expression. Since the participation of c‐Myc protein in transcription requires its dimerization with Max protein, we examined the Myc‐Max association in Cpd 5‐treated cells and found that Cpd 5 suppressed Myc‐Max dimerization. Transfection of Hep3B cells with mutated ERK (T188A/Y190F), which has lost its dual‐phosphorylation sites, attenuated the actions of Cpd 5 on Myc‐Max association. To further demonstrate whether Myc phosphorylation by Cpd 5‐induced ERK activation was able to directly regulate c‐myc gene expression, a chromatin immunoprecipitation (ChIP) assay was used to examine the binding of phospho‐Myc to the c‐myc promoter region. We found that phospho‐Myc induced by Cpd 5 had lost its ability to bind to the c‐myc promoter, whereas MEK inhibitor U‐0126 antagonized this inhibitory effect. These data suggest that an increase in c‐Myc phosphorylation in response to prolonged ERK phosphorylation negatively auto‐regulates c‐Myc gene expression, leading to the suppression of its target gene expression and cell cycle block. J. Cell. Physiol. © 2006 Wiley‐Liss, Inc.
Impact of reliance on CT pulmonary angiography on diagnosis of pulmonary embolism: A Bayesian analysis
Authors: Ranji Sumant R. , Shojania Kaveh G. , Trowbridge Robert L. , Auerbach Andrew D. 
Published: April 2006

AbstractBACKGROUNDSpiral computed tomographic pulmonary angiography (CTPA) has become the primary test used to investigate suspected pulmonary embolism (PE) at many institutions, despite uncertainty regarding its sensitivity and specificity. Although CTPA‐based diagnostic algorithms focus on minimizing the false‐negative rate, we hypothesized that increasing use of CTPA also might lead to false‐positive diagnoses.OBJECTIVEDetermine the frequency of possible false‐positive diagnoses of PE when CTPA is the primary diagnostic test.DESIGNRetrospective cohort study.SETTINGTwo academic teaching hospitals.PARTICIPANTS322 patients with suspected PE evaluated with CTPA.MEASUREMENTSWe used a validated prediction rule to determine the pretest probability of PE in each patient. We combined these pretest probabilities with published estimates of CTPA test characteristics to generate expected posttest probabilities of PE. We compared these posttest probabilities to actual treatment decisions to determine the rate of false‐positive diagnoses of PE.RESULTSAmong 322 patients investigated for PE, 37 (12%) had high pretest probability, 101 (32%) moderate, and 184 (57%) low. CT scans were interpreted as positive for PE in 57 patients (17.8%). Regardless of the pretest probability of PE, 96.5% of patients with a positive CTPA were treated with anticoagulants. Even under an optimistic assumption of CTPA test characteristics, as many as 25.4% of these patients may have been treated unnecessarily as a result of a false‐positive diagnosis. Most of these patients had a low pretest probability of PE.CONCLUSIONSFailure to utilize Bayesian reasoning when interpreting CTPA may lead to false‐positive diagnoses of pulmonary embolism in a substantial proportion of patients. Journal of Hospital Medicine 2006;1:81–87. © 2006 Society of Hospital Medicine
Topography and recent winter rainfall regime change in temperate Western European areas: a case study in the Rhine‐Meuse basin
Authors: Gilles Drogue , Christian Wagner , Nicole Mahr , Lucien Hoffmann , Laurent Pfister 
Published: April 2006

AbstractEarlier trend analyses on rainfall series have clearly shown that the winter rainfall regime has changed since World War II over Northwestern Europe as a consequence of an enhanced westerly atmospheric circulation. However, few studies have been conducted on the potential link between the spatial variability of winter rainfall regime change and the topography. In the present study, a time series analysis of winter rainfall due to atmospheric westerly fluxes is performed and related to the topography of the middle Rhine‐Meuse area. The resulting geographical patterns show a zonal anisotropism of the winter rainfall regime change implying an intensification of horizontal rainfall gradients. More contrasted westerly winter rainfall amounts are observed in mountainous areas during the post‐1979 period following the changing‐point year of atmospheric circulation over Northwestern Europe. Copyright © 2006 Royal Meteorological Society.
Relevance of Osteoinductive Biomaterials in Critical‐Sized Orthotopic Defect
Authors: Habibovic Pamela , Yuan Huipin , van den Doel Mirella , Sees Tara M. , van Blitterswijk Clemens A. , de Groot Klaas 
Published: April 2006

AbstractSeveral publications have shown the phenomenon of osteoinduction by biomaterials to be real. However, whether the ability of a biomaterial to initiate bone formation in ectopic implantation sites improves the performance of such osteoinductive biomaterial in clinically relevant orthotopic sites remains unclear. No studies have been published in which osteoinductive potential of a biomaterial is directly related to its performance orthotopically. In this study, we compared osteoinductive and nonosteoinductive biphasic calcium–phosphate (BCP) ceramics ectopically and in a clinically relevant critical‐sized orthotopic defect in goats. The two materials, BCP1150 and BCP1300, had similar chemical compositions, crystallinities, and macrostructures, but their microstructures differed significantly. BCP1150, sintered at a lower temperature, had a large amount of micropores, small average crystal size, and hence a high specific surface area. In contrast, BCP1300, with few micropores, had a significantly lower specific surface area as compared to BCP1150. Twelve‐week intramuscular implantation in goats (n = 10) showed that bone was induced in all BCP1150 implants, while no signs of bone formation were found in any of the BCP1300 implants. After 12 weeks of implantation in a bilateral critical‐sized iliac wing defect in the same goats, BCP1150 showed significantly more bone than BCP1300. In addition, the analysis of fluorochrome markers, which were administered to the animals 4, 6, and 8 weeks after implantation to follow the bone growth dynamics, showed an earlier start of bone formation in BCP1150 as compared to BCP1300. Significantly better performance of an osteoinductive ceramic in a critical‐sized orthotopic defect in a large animal model in comparison to a nonosteoinductive ceramic suggests osteoinduction to be clinically relevant. Further improvement of material osteoinductive properties is thus a significant step forward in the search for alternatives for autologous bone graft. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
Joint capsule matrix turnover in a rabbit model of chronic joint contractures: Correlation with human contractures
Authors: Hildebrand Kevin A. , Zhang Mei , Hart David A. 
Published: April 2006

AbstractTo evaluate changes in matrix molecules of the joint capsule, the right knees of 24 skeletally mature female NZW rabbits were immobilized while the contralateral limb served as an unoperated control. The immobilization was discontinued at 8 weeks and the rabbits were divided among four groups (n = 6) based on the number of weeks the right knees were remobilized: 0, 8, 16, or 32. Three rabbits (six knees) that did not have operations provided normal control joint capsules. The mRNA levels for collagen types I, II, and III, and MMP‐1 and ‐13 were significantly increased in the joint capsules of the contracture knees in all groups when compared to normal and contralateral limb joint capsules. In contrast, the mRNA levels for TIMP‐1, ‐2, and ‐3 were decreased in the joint capsules of the contracture knees in all groups when compared to normal and contralateral limb joint capsules. The mRNA levels for lumican and decorin were increased in the joint capsules of the contracture knees in all groups when compared to normal capsules. Many of the changes observed in this animal model are similar to those observed in human joint capsules from posttraumatic elbow contractures, supporting the value of this rabbit model. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
Raman spectral study on the thermal stability of Ni/Zr/Ni/Si and Ni/Co/Ni/Si structures
Authors: Shao Jia , Lu Jianzheng , Huang Wei , Gao Yuzhi , Zhang Lichun , Zhang Shu‐Lin 
Published: April 2006

AbstractNickel silicide is becoming an important candidate material for the future generation of complementary metal‐oxide semiconductor (CMOS) devices and nanowire hetero‐structures. The Raman spectral measurement demonstrates quickly and nondestructively that instead of the more expensive Ni(Pt)Si sandwich structure, a new Ni/Zr/Ni/Si structure can raise the temperature of thermal stability from 650 °C to above 800 °C, thereby helping to improve device technology. Copyright © 2006 John Wiley & Sons, Ltd.
Distribution of co‐activators CBP and p300 during mouse oocyte and embryo development
Authors: Kwok Roland P.S. , Liu Xiao‐Tie , Smith Gary D. 
Published: April 2006

AbstractcAMP response element binding protein (CREB)‐binding protein (CBP) and p300 are two structurally related transcriptional co‐activators that activate expression of many eukaryotic genes. Current dogma would suggest that these transcriptional co‐activators have similar mechanisms of transcription regulation. Studies of CBP or p300 homozygotic mouse mutants indicate that normal embryogenesis requires the existence of both factors. However, whether this is indicative of a dosage effect of these two proteins, or whether these proteins play different roles in mouse embryo development is not clear. Here we demonstrated that both factors are first found in the cytoplasm of oocytes within primordial follicles, and that they enter into the oocyte nucleus at different stages of oocyte growth, suggesting that they may play different roles in gene expression during oocyte growth and development. Consistent with this model, in the pre‐implantation mouse embryos, from the two‐cell stage to the blastocyst stage, the localizations of CBP and p300 are different, at times opposite, indicating that CBP and p300 also have different functions in early mouse embryogenesis. Mol. Reprod. Dev. © 2006 Wiley‐Liss, Inc.
hCG‐dependent regulation of angiogenic factors in human granulosa lutein cells
Authors: Phan B. , Rakenius A. , Pietrowski D. , Bettendorf H. , Keck C. , Herr D. 
Published: April 2006

AbstractAs prerequisite for development and maintenance of many diseases angiogenesis is of particular interest in medicine. Pathologic angiogenesis takes place in chronic arthritis, collagen diseases, arteriosclerosis, retinopathy associated with diabetes, and particularly in cancers. However, angiogenesis as a physiological process regularly occurs in the ovary. After ovulation the corpus luteum is formed by rapid vascularization of initially avascular granulosa lutein cell tissue. This process is regulated by gonadotropic hormones. In order to gain further insights in the regulatory mechanisms of angiogenesis in the ovary, we investigated these mechanisms in cell culture of human granulosa lutein cells. In particular, we determined the expression and production of several angiogenic factors including tissue inhibitor of matrix metalloproteinases‐1 (TIMP‐1), Leptin, connective tissue growth factor (CTGF), meningioma‐associated complimentary DNA (Mac25), basic fibroblast growth factor (bFGF), and Midkine. In addition, we showed that human chorionic gonadotropin (hCG) has distinct effects on their expression and production. hCG enhances the expression and production of TIMP‐1, whereas it downregulates the expression of CTGF and Mac25. Furthermore it decreases the expression of Leptin. Our results provide evidence that hCG determines growth and development of the corpus luteum by mediating angiogenic pathways in human granulosa lutein cells. Hence we describe a further approach to understand the regulation of angiogenesis in the ovary. Mol. Reprod. Dev. © 2006 Wiley‐Liss, Inc.
Study of the polyol pathway in the porcine epididymis
Authors: Pruneda Anna , Pinart Elisabet , Bonet Sergi , Yeung Ching‐Hei , Cooper Trevor G. 
Published: April 2006

AbstractConcentrations of D‐glucose, D‐fructose and D‐sorbitol were quantified in porcine epididymal fluid by spectrofluorimetric assays and aldose reductase (AR) and sorbitol dehydrogenase (SDH) were located immunohistochemically in the epididymal epithelium. Glucose and fructose concentrations were low (<1 mM) and decreased in the cauda whereas sorbitol concentration (4–7 mM) was rather uniform along the duct. AR was luminally located on microvilli in the caput and corpus with less presence distally and was present in the lumen. SDH was present apically and basally in epithelial cells throughout the epididymis and in the lumen. The observations are consistent with diffusion of circulating glucose into the lumen, its conversion via AR to sorbitol which accumulates in the lumen and the action of SDH on sorbitol to produce fructose. Sperm metabolism of glucose and fructose may explain their lower concentrations in the cauda and sorbitol could be a metabolic substrate or osmolyte required for volume regulation. Mol. Reprod. Dev. © 2006 Wiley‐Liss, Inc.
Tektin 4 is located on outer dense fibers, not associated with axonemal tubulins of flagella in rodent spermatozoa
Authors: Iida Hiroshi , Honda Yoshiko , Matsuyama Takuya , Shibata Yosaburo , Inai Tetsuichiro 
Published: April 2006

AbstractTektins, which are thought to be the constitutive proteins of microtubules in cilia, flagella, basal bodies, and centrioles, have been reported to be involved in the stability and structural complexity of axonemal microtubules. Four types of mammalian Tektins have been reported, and at least two types of Tektins, Tektin 2 and Tektin 4, have been verified to be present in sperm flagella. To elucidate the molecular localization of Tektin 4 in flagella of rodent spermatozoa, we performed immunocytochemistry, fractionation study followed by immunoblot analysis, and immunogold electron microscopy. Confocal laser scanning microscopy and immunogold electron microscopy indicated that Tektin 4 was associated with outer dense fibers (ODFs) in both the middle and principal piece of flagella in rat and mouse spermatozoa. Tektin 4 in rat spermatozoa is completely released by 6 M urea treatment, but not extracted by 1% Triton X‐100 and 0.6 M potassium thiocyanate. Pre‐embedding immunoelectron microscopy demonstrated that Tektin 4 located on the abaxial (convex) surface of ODFs in flagella, not associate with axonemal microtubules. Our data strongly suggested that Tektin 4 is not associated with axonemal tubulins but an ODFs‐affiliated molecule in rodent spermatozoa. Mol. Reprod. Dev. © 2006 Wiley‐Liss, Inc.