bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of antigen‐specific T cells by cytokine flow cytometry: the use of whole blood may underestimate frequencies
Authors: Hoffmeister Bodo , Bunde Torsten , Rudawsky Ina Maria , Volk Hans‐Dieter , Kern Florian 
Published: November 2003

AbstractAntigen‐specific T cells may be detected and enumerated by short‐term ex vivo antigen‐specific stimulation followed by cytokine flow cytometry. Most frequently, intracellular IFN‐γ is used to identify T cells specific for cytomegalovirus (CMV), Epstein‐Barr virus or HIV. Some researchers use whole blood, others peripheral blood mononuclear cells (PBMC) in this assay; however, the performance of the two systems has never been directly compared. Blood was drawn from previously characterized healthy CMV‐positive donors, and CMV‐derived peptides or CMV lysate were used as stimulants. In an initial series of experiments, lithium‐heparin was identified as the best coagulant to be used. Dose‐response curves were established using concentrations between 0.1 and 40 μg/ml of peptides and between 0.1 and 20 μg/ml of virus lysate, respectively. IFN‐γ‐positive T cells were expressed as percent of the reference population, and frequencies measured in whole blood and PBMC were compared. Maximum responses were consistently higher in PBMC than in whole blood and were reached at lower concentrations of stimulant. In several instances, responses identified with PBMCwere not at all detected with whole blood. In summary, studies using whole blood in this type of assay are likely to underestimate the frequencies of antigen‐specific T cells.
Hepatitis C virus non‐structural protein 4 suppresses Th1 responses by stimulating IL‐10 production from monocytes
Authors: Brady Miriam T. , MacDonald Angus J. , Rowan Aileen G. , Mills Kingston H. G. 
Published: November 2003

AbstractThe majority of hepatitis C virus (HCV) infections become chronic, despite the presence of HCV‐specific cellular and humoral immune responses. We have previously suggested that IL‐10‐secretingantigen‐specific regulatory T cells may contribute to viral persistence, and demonstrate here that peripheral blood mononuclear cells (PBMC) from chronically HCV‐infected patients secrete IL‐10, but not IFN‐γ, in response to HCV nonstructural protein 4 (NS4). A neutralizing anti‐IL‐10 antibody restored this defective antigen‐specific IFN‐γ production in vitro. Furthermore, PBMC from normal individuals secreted IL‐10 in response to NS4, suggesting that cells of the innate immune system, in addition to T cells, produced IL‐10 in the HCV‐infected patients. Cell separation experiments revealed that the innate IL‐10 was produced by blood monocytes, but not dendritic cells (DC). In addition, NS4 inhibited IL‐12 production by PBMC in response to LPS and IFN‐γ, and Th1 responses to recall antigens in normal individuals. Furthermore, supernatants from NS4‐stimulated monocytes inhibited LPS‐induced maturation of DC and suppressed their capacity to stimulate proliferation and IFN‐γ production by allospecific T cells. Our data suggest that HCV subverts cellular immunity by inducing IL‐10 and inhibiting IL‐12 production by monocytes, which in turn inhibits the activation of DC that drive the differentiation of Th1 cells.
Age‐related defects in CD4+ T cell activation reversed by glycoprotein endopeptidase
Authors: Garcia Gonzalo G. , Miller Richard A. 
Published: November 2003

AbstractCD4+ T cells from old mice show defects in the activation process including deficiency in the formation of immunosynapses with antigen‐presenting cells. We show that CD4+ T cells from old mice express unusually high levels of glycosylated forms of the bulky T cell glycoprotein CD43, particularly on a subset of functionally anergic cells expressing P‐glycoprotein. T cells from old donors also show a decline in the association of CD43 with cytoskeletal matrix and in the proportion of T cells that can exclude CD43 from the synapse. O‐sialoglycoprotein endopeptidase, which removes the external domain of CD43 and other O‐sialoglycoproteins from the aged naive CD4+ T cells of TCR‐transgenic mice, restores early agonist‐independent stages and later agonist‐dependent stages of synapse formation as well as expression of the activation markers CD69 and CD25 to the levels found in the young mice. These data support a model in which O‐glycosylated forms of T cell surface molecules, including CD43, are largely responsible for age‐related defects in TCR signaling and function.
Lithium Perchlorate‐Catalyzed Three‐Component Coupling: A Facile and General Method for the Synthesis of α‐Aminophosphonates under Solvent‐Free Conditions
Authors: Azizi Najmedin , Saidi Mohammad R. 
Published: November 2003

AbstractA simple, efficient, and general method has been developed for the synthesis of α‐aminophosphonates in the presence of solid lithium perchlorate under solvent‐free conditions. Thus secondary and tertiary α‐aminophosphonates were synthesized relatively quickly in good yields at room temperature. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Molecular mechanisms underlying IGF‐I‐induced attenuation of the growth‐inhibitory activity of trastuzumab (Herceptin) on SKBR3 breast cancer cells
Authors: Lu Yuhong , Zi Xiaolin , Pollak Michael 
Published: November 2003

AbstractThe clinical usefulness of trastuzumab (Herceptin; Genentech, San Francisco, CA) in breast cancer treatment is limited by the rapid development of resistance. We previously reported that IGF‐I signaling confers resistance to the growth‐inhibitory actions of trastuzumab in a model system, but the underlying molecular mechanism remains unknown. We used SKBR3/neo cells (expressing few IGF‐I receptors) and SKBR3/IGF‐IR cells (overexpressing IGF‐I receptor) as our experimental model. IGF‐I antagonized the trastuzumab‐induced increase in the level of the Cdk inhibitor p27Kip1. This resulted in decreased association of p27Kip1 with Cdk2, restoration of Cdk2 activity and attenuation of cell‐cycle arrest in G1 phase, all of which had been induced by trastuzumab treatment in SKBR3/IGF‐IR cells. We also found that the decrease in p27Kip1 induced by IGF‐I was accompanied by an increase in expression of Skp2, which is a ubiquitin ligase for p27Kip1, and by increased Skp2 association with p27Kip1. A specific proteasome inhibitor (LLnL) completely blocked the ability of IGF‐I to reduce the p27Kip1 protein level, while IGF‐I increased p27Kip1 ubiquitination. This suggests that the action of IGF‐I in conferring resistance to trastuzumab involves targeting of p27Kip1 to the ubiquitin/proteasome degradation machinery. Finally, specific inhibitors of MAPK and PI3K suggest that the IGF‐I‐mediated reduction in p27Kip1 protein level by increased degradation predominantly involves the PI3K pathway. Our results provide an example of resistance to an antineoplastic therapy that targets one tyrosine kinase receptor by increased signal transduction through an alternative pathway in a complex regulatory network. © 2003 Wiley‐Liss, Inc.
Role of 24‐hydroxylase in vitamin D3 growth response of OVCAR‐3 ovarian cancer cells
Authors: Miettinen Susanna , Ahonen Merja H. , Lou Yan‐Ru , Manninen Tommi , Tuohimaa Pentti , Syvälä Heimo , Ylikomi Timo 
Published: November 2003

AbstractVitamin D and its analogues are potent regulators of cell growth and differentiation both in vivo and in vitro. We studied the effects of 25‐hydroxyvitamin D3 [25(OH)D3], 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3] and vitamin D analogue, EB 1089, on the growth of a human ovarian cancer cell line, OVCAR‐3. We also studied the expression of vitamin D metabolising enzymes 24‐hydroxylase (24OHase) and 1α‐hydroxylase (1αOHase). Our results showed that high concentrations (10 and 100 nM) of 1,25(OH)2D3 inhibited a cell proliferation, whereas low concentration (0.1 nM) stimulated growth of the OVCAR‐3 cells. In the concentration range of 10–500 nM a prohormone, 25(OH)D3, stimulated growth. An amount of 1 nM EB 1089 and 100 nM 1,25(OH)2D3 inhibited growth with an equal magnitude. The expression of 24OHase was strongly induced by 1,25(OH)2D3 and EB 1089 in OVCAR‐3 cells, and analysis of vitamin D metabolites showed the functionality of 24OHase. An inhibition of 24OHase activity with a novel 24OHase inhibitor enhanced growth‐inhibiting effects of 1,25(OH)2D3 and suppressed the growth stimulation of 100 nM 25(OH)D3. We also report the expression of a vitamin D activating enzyme, 1αOHase, in 7 ovarian cancer cell lines. The production of 1,25(OH)2D3 in OVCAR‐3 cells was low, possibly due to an extensive activity of 24OHase or a low 1αOHase activity. These results suggest that in ovarian cancer cells vitamin D metabolizing enzymes might play a key role in modulating the growth response to vitamin D. The possible mitogenic effects of vitamin D should be considered when evaluating treatment of ovarian cancer with vitamin D. © 2003 Wiley‐Liss, Inc.
Polyglutamine repeat length in the AIB1 gene modifies breast cancer susceptibility in BRCA1 carriers
Authors: Kadouri Luna , Kote‐Jarai Zsofia , Easton Douglas F. , Hubert Ayala , Hamoudi Rifat , Glaser Benjamin , Abeliovich Dvorah , Peretz Tamar , Eeles Rosalind A. 
Published: November 2003

AbstractVariation in the penetrance estimates for BRCA1 and BRCA2 mutation carriers suggests that other factors may modify cancer risk from specific mutations. One possible mechanism is an epigenetic effect of polymorphisms in other genes. Genes involved in hormonal signal transduction are possible candidates. The AIB1 gene, an estrogen receptor (ER) coactivator, is frequently amplified in breast and ovarian tumors. Variation of a CAG repeat length has been reported within this gene that encodes a polyglutamine repeat in the C‐terminus of the protein. Three hundred eleven BRCA1/2 mutation carriers (257 were of Ashkenazi origin) were genotyped for the AIB1 polyglutamine repeat. Relative risks (RR) were estimated using a maximum likelihood approach. The estimated breast cancer (BC) RR per average repeat length adjusted for population type (Ashkenazi vs. non‐Ashkenazi) was 1.15 (95% CI = 1.02–1.30; p = 0.01) for BRCA1/2 carriers, and 1.25 (95% CI = 1.09–1.42; p = 0.001) when analysis was restricted to BRCA1 carriers. RR of BC was 1.17 (95% CI = 0.91–1.74), for individuals with 2 alleles ≥29 polyglutamine repeats and 0.78 (95% CI = 0.50–1.16) for those with at least 1 allele of ≤26 repeats, compared to individuals with the common genotypes 28;28, 28;29 or 28;30. The corresponding BC RR in BRCA1 mutation carriers was 0.55 (95% CI = 0.34–0.90) and 1.29 (95% CI = 0.85–1.96) in those with ≤26 and ≥29 repeats respectively (p = 0.025). These results indicate significant association of the risk for BC in carriers of BRCA1 mutations with the polyglutamine chain of the AIB1 gene. Longer repeat length correlates with elevated risk, whereas in carriers of a shorter AIB1 allele BC risk was reduced. The AIB1 polyglutamine length did not affect BC risk among BRCA2 mutation carriers. © 2003 Wiley‐Liss, Inc.
Comparison of risk factors for colon and rectal cancer
Authors: Wei Esther K. , Giovannucci Edward , Wu Kana , Rosner Bernard , Fuchs Charles S. , Willett Walter C. , Colditz Graham A. 
Published: November 2003

AbstractPredictors of colorectal cancer have been extensively studied with some evidence suggesting that risk factors vary by subsite. Using data from 2 prospective cohort studies, we examined established risk factors to determine whether they were differentially associated with colon and rectal cancer. Our study population included 87,733 women from the Nurses' Health Study (NHS) and 46,632 men from the Health Professionals Follow Up Study (HPFS). Exposure information was collected via biennial questionnaires (dietary variables were collected every 4 years). During the follow‐up period (NHS: 1980 to May 31, 2000; HPFS: 1986 to January 31, 2000), we identified 1,139 cases of colon cancer and 339 cases of rectal cancer. We used pooled logistic regression to estimate multivariate relative risks for the 2 outcomes separately and then used polytomous logistic regression to compare these estimates. In the combined cohort, age, gender, family history of colon or rectal cancer, height, body mass index, physical activity, folate, intake of beef, pork or lamb as a main dish, intake of processed meat and alcohol were significantly associated with colon cancer risk. However, only age and sex were associated with rectal cancer. In a stepwise polytomous logistic regression procedure, family history and physical activity were associated with statistically significant different relative risks of colon and rectal cancer. Our findings support previous suggestions that family history and physical activity are not strong contributors to the etiology of rectal cancer. Future investigations of colon or rectal cancer should take into consideration risk factor differences by subsite. © 2003 Wiley‐Liss, Inc.
A dual‐level ab initio and hybrid density functional theory dynamics study on the unimolecular decomposition reaction C2H5O → CH2O + CH3
Authors: Zhang Yue , Zhang Shaowen , Li Qian Shu 
Published: November 2003

AbstractWe present a direct ab initio and hybrid density functional theory dynamics study of the thermal rate constants of the unimolecular decomposition reaction of C2H5O → CH2O + CH3 at a high‐pressure limit. MPW1K/6‐31+G(d,p), MP2/6‐31+G(d,p), and MP2(full)/6‐31G(d) methods were employed to optimize the geometries of all stationary points and to calculate the minimum energy path (MEP). The energies of all the stationary points were refined at a series of multicoefficient and multilevel methods. Among all methods, the QCISD(T)/aug‐cc‐pVTZ energies are in good agreement with the available experimental data. The rate constants were evaluated based on the energetics from the QCISD(T)/aug‐cc‐pVTZ//MPW1K/6‐31+G(d,p) level of theory using both microcanonical variational transition state theory (μVT) and RRKM theory with the Eckart tunneling correction in the temperature range of 300–2500 K. The calculated rate constants at the QCISD(T)/aug‐cc‐pVTZ/MPW1K/6‐31+G(d,p) level of theory are in good consistent with experimental data. The fitted three‐parameter Arrhenius expression from the μVT/Eckart rate constants in the temperature range 200–2500 K is k = 2.52 × 1012T0.41e(−8894.0/T) s−1. The falloff curves of pressure‐dependent rate constants are performed using master‐equation method within the temperature range of 391–471 K. The calculated results are in good agreement with the available experimental data. © 2004 Wiley Periodicals, Inc. J Comput Chem 2: 218–226, 2003
Converging free energy estimates: MM‐PB(GB)SA studies on the protein–protein complex Ras–Raf
Authors: Gohlke Holger , Case David A. 
Published: November 2003

AbstractEstimating protein–protein interaction energies is a very challenging task for current simulation protocols. Here, absolute binding free energies are reported for the complex H‐Ras/C‐Raf1 using the MM‐PB(GB)SA approach, testing the internal consistency and model dependence of the results. Averaging gas‐phase energies (MM), solvation free energies as determined by Generalized Born models (GB/SA), and entropic contributions calculated by normal mode analysis for snapshots obtained from 10 ns explicit‐solvent molecular dynamics in general results in an overestimation of the binding affinity when a solvent‐accessible surface area‐dependent model is used to estimate the nonpolar solvation contribution. Applying the sum of a cavity solvation free energy and explicitly modeled solute–solvent van der Waals interaction energies instead provides less negative estimates for the nonpolar solvation contribution. When the polar contribution to the solvation free energy is determined by solving the Poisson–Boltzmann equation (PB) instead, the calculated binding affinity strongly depends on the atomic radii set chosen. For three GB models investigated, different absolute deviations from PB energies were found for the unbound proteins and the complex. As an alternative to normal‐mode calculations, quasiharmonic analyses have been performed to estimate entropic contributions due to changes of solute flexibility upon binding. However, such entropy estimates do not converge after 10 ns of simulation time, indicating that sampling issues may limit the applicability of this approach. Finally, binding free energies estimated from snapshots of the unbound proteins extracted from the complex trajectory result in an underestimate of binding affinity. This points to the need to exercise caution in applying the computationally cheaper “one‐trajectory‐alternative” to systems where there may be significant changes in flexibility and structure due to binding. The best estimate for the binding free energy of Ras–Raf obtained in this study of −8.3 kcal mol−1 is in good agreement with the experimental result of −9.6 kcal mol−1, however, further probing the transferability of the applied protocol that led to this result is necessary. © 2003 Wiley Periodicals, Inc. J Comput Chem 2: 238–250, 2003
Real‐time imaging of skeletal muscle velocity
Authors: Asakawa Deanna S. , Nayak Krishna S. , Blemker Silvia S. , Delp Scott L. , Pauly John M. , Nishimura Dwight G. , Gold Garry E. 
Published: November 2003

AbstractPurposeTo test the feasibility of using real‐time phase contrast (PC) magnetic resonance imaging (MRI) to track velocities (1–20 cm/second) of skeletal muscle motion.Materials and MethodsTo do this we modified a fast real‐time spiral PC pulse sequence to accommodate through‐plane velocity encoding in the range of −20 to +20 cm/second. We successfully imaged motion of the biceps brachii and triceps brachii muscles during elbow flexion and extension in seven unimpaired adult subjects using real‐time PC MRI.ResultsThe velocity data demonstrate that the biceps brachii and the triceps brachii, antagonistic muscles, move in opposite directions during elbow flexion and extension with velocity values in the muscle tissue ranging from –10 to +10 cm/second.ConclusionWith further development, real‐time PC MRI may provide a means to analyze muscle function in individuals with neurologic or movement disorders who cannot actively complete the repeated motions required for dynamic MRI techniques, such as cine PC MRI, that are more commonly used in musculoskeletal biomechanics applications. J. Magn. Reson. Imaging 2003;18:734–739. © 2003 Wiley‐Liss, Inc.
Bioresorbable Hydrogels Prepared Through Stereocomplexation between Poly(L‐lactide) and Poly(D‐lactide) Blocks Attached to Poly(ethylene glycol)
Authors: Li Suming 
Published: November 2003

AbstractBlock copolymers were synthesized by ring‐opening polymerization of L‐lactide or D‐lactide in the presence of mono‐ or dihydroxyl poly(ethylene glycol), using zinc metal as catalyst. The resulting copolymers were characterized by various techniques, namely 1H NMR spectroscopy, differential scanning calorimetry (DSC), X‐ray diffractometry, and Raman spectrometry. The composition of the copolymers was designed such that they were water soluble. Bioresorbable hydrogels were prepared from aqueous solutions containing both poly(L‐lactide)/poly(ethylene glycol) and poly(D‐lactide)/poly(ethylene glycol) block copolymers. Rheological studies confirmed the formation of hydrogels resulting from stereocomplexation between poly(L‐lactide) and poly(D‐lactide) blocks.Ring‐opening polymerization of L(D)‐lactide in the presence of dihydroxyl PEG using zinc powder as catalyst.magnified imageRing‐opening polymerization of L(D)‐lactide in the presence of dihydroxyl PEG using zinc powder as catalyst.
Functional polymeric materials: complexing amphiphiles as structure‐inducing elements
Authors: ten Brinke Gerrit , Ikkala Olli 
Published: November 2003

AbstractSelf‐assembly of polymeric comb‐shaped supramolecules is a powerful tool to prepare functional materials. Enhanced conductivity due to hexagonal self‐organization of conducting polyaniline and polarized photoluminance in solid‐state films of rodlike poly(2,5‐pyridinediyl) obtained by removing hydrogen‐bonded side chains from the aligned thermotropic smectic phase are two examples. Hierarchically structured materials are formed when the self‐organization of block copolymers is combined with that of comb‐shaped supramolecules. These form the basis for tunable nanoporous membranes, nano‐objects and materials with anisotropic properties such as tridirectional proton conductivity.
On the clathrate structures of syndiotactic poly(m‐methylstyrene)
Authors: Tarallo Oreste , Buono Annamaria , Califano Valeria , Petraccone Vittorio 
Published: November 2003

AbstractThe crystal structures of clathrate forms of syndiotactic poly(m‐methylstyrene) containing guest molecules having different steric hindrance (CS2, benzene and orto‐dichlorobenzene) are presented. The structures are all characterized by polymer chains in s(2/1)2 helical conformation and guest molecules packed in an orthorhombic unit cell according to the space group Pcaa. All the presented clathrates belongs to β class indipendently from the dimensions of the guest molecule. In this aspect they differ both from clathrate forms of syndiotactic polystyrene, all belonging to α class, and from clathrate forms of syndiotactic poly(p‐methylstyrene) that belong to α or β class according to the steric hindrance of the guest molecule.
Rationalizing the meaning of coefficients in Flory‐Huggins approach to polymer‐solvent interactions
Authors: Lucchelli Emilio , Caccianotti Luciano 
Published: November 2003

AbstractThe Flory‐Huggins interaction parameter for a polymer solution can be represented as the product of two functions, which separately take into account the effects of the polymer volume fraction and temperature. The latter factor contains three constants, usually viewed as best‐fit coefficients. They are expressed in terms of two thermodynamic quantities, namely, the excess partial molar heat capacity of the solution and a reference temperature, thus allowing to guess their physical meaning. The formulae so obtained were tested with satisfactory results for two solutions of polystyrene in acetone and for two polymer blends (PC/PMMA and PS/PVME.) Furthermore, an attempt was made to calculate the above‐mentioned reference temperature from data referring to the phases in solution.
Starch swelling and its role in modern ceramic shaping technology
Authors: Týnová Eva , Pabst Willi , Mikač Jan 
Published: November 2003

AbstractA microscopic real‐time visualisation of potato starch swelling in aqueous media at 56°C is performed. The viscosity increase of a starch‐water mixture during the swelling step is documented by viscometric measurements. The mechanism of ceramic green‐body formation in a new ceramic shaping process, called “starch consolidation”, is discussed. In particular, the rheological changes during swelling and their concomitant structural background can explain certain discrepancies between model predictions and experimental findings observed in previous work.
Dynamic properties of protein‐like heteropolymers: a computer simulation study
Authors: Romiszowski Piotr , Sikorski Andrzej 
Published: November 2003

AbstractA simple model of a single polypeptide chain was used in the computer simulation. The units in a model polypeptide were located at α‐carbons and embedded in a very flexible [310] lattice. The force field that mimics polymer‐polymer and polymer‐solvent interactions contained a long‐range contact potential between the residues as well as local preferences in forming helical structures. The chain consisted of two types of residues: hydrophilic and hydrophobic. The classic Metropolis simulation algorithm was used. Monte Carlo simulations were carried out for helical sequences of residues and for various temperature conditions. It was shown that the formation of secondary structures in the chain under consideration had an influence on local short‐time dynamic properties. The analysis of the autocorrelation functions enables one to identify the presence of secondary structures. The analysis of the formation of polymer‐polymer and polymer‐solvent contacts in ordered structures was also made.