bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and characterization of aromatic polyesters and copolyesters from 4,4′‐(1‐hydroxyphenylidene)diphenol and 4,4′‐(9‐fluorenylidene)diphenol
Authors: Loría‐Bastarrachea María I. , Vázquez‐Torres Humberto , Aguilar‐Vega Manuel de J.
Published: October 2002

Two isophthalic polyesters from 4,4′‐(1‐hydroxyphenylidene)diphenol (BAP/ISO) and 4,4′‐(9‐fluorenylidene)diphenol (BF/ISO), and three different copolyesters containing 75, 50, and 25 mol % of BAP/ISO were synthesized by interfacial polycondensation. This preparation method yielded polymers and copolymers that produced flexible and transparent films when they were cast from solution. Proton NMR spectrometry studies showed that the isophthalic copolyesters were obtained as random copolymers with differences in comonomer composition no larger than 2.5 mol % with respect to the expected compositions. Wide‐angle X‐ray diffraction measurements indicated that all the polyesters and copolyesters were amorphous. The copolyesters showed amorphous patterns with maxima that fell between those of the polyesters. It was also found that thermal properties such as glass‐transition temperature, onset of decomposition temperature, thermal stability, dynamic mechanical storage modulus, and maximum on the α‐transition of the damping factor tan δ of BF/ISO were higher than those of BAP/ISO. The values of these thermal properties in the copolyesters fell between those of the polyesters and were dependent on the amounts of BF/ISO and BAP/ISO present in the copolyester in a linear fashion. Therefore, the thermal properties of a given copolyester can be predicted directly from the comonomers' composition. Overall, it shows that the interfacial polycondensation method is suitable to obtain these copolyesters in a controlled manner and that their properties can be tailored to be between those of the homopolyesters. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2515–2522, 2002
Preparation and characterization of bismaleimide (N,N′‐bismaleimido‐4,4′‐diphenyl methane)–vinyl ester oligomer–modified unsaturated polyester interpenetrating matrices for advanced composites
Authors: Dinakaran K. , Alagar M.
Published: October 2002

Interpenetrating networks of varying percentages of bismaleimide (BMI) in vinyl ester oligomer (VEO) modified unsaturated polyester (UP) matrices have been developed. Vinyl ester oligomer was prepared by reacting commercially available epoxy resin GY 250 (Ciba‐Geigy) and acrylic acid, and used as a toughening agent for unsaturated polyester resin. Unsaturated polyesters modified with 10, 20, and 30 wt % vinyl ester oligomer were made. The VEO toughened unsaturated polyester matrix systems, further modified with 5, 10, and 15 wt % bismaleimide (BMI). BMI–VEO–UP matrices were characterized using differential scanning calorimetry, thermogravimetric analysis, and heat deflection temperature analysis. The matrices, in the form of castings, were characterized for their mechanical properties according to ASTM methods: tensile strength, flexural strength, and unnotched Izod impact test. Data obtained from mechanical studies and thermal characterization indicate that the introduction of VEO and BMI into unsaturated polyester resin improves thermomechanical properties according to their percentage concentration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2502–2508, 2002
Cellulose/chitin films blended in NaOH/urea aqueous solution
Authors: Zheng Hua , Zhou Jinping , Du Yumin , Zhang Lina
Published: October 2002

Regenerated cellulose/chitin blend films (RCCH) were satisfactorily prepared in 6 wt % NaOH/4 wt % urea aqueous solution by coagulating with 5 wt % CaCl2 aqueous solution then treating with 1 wt % HCl. The structure, miscibility, and mechanical properties of the RCCH films were investigated by infrared, scanning electron microscopy, ultraviolet spectroscopies, X‐ray diffraction, tensile test, and differential scanning analysis. The results indicated that the blends were miscible when the content of chitin was lower than 40 wt %. Moreover, the RCCH blend film achieved the maximum tensile strength in both dry and wet states of 89.1 and 43.7 MPa, respectively, indicating that the tensile strength and water resistivity of the RCCH film containing 10–20 wt % chitin was slightly higher than that of the RC film unblended with chitin. Structural analysis indicated that strong interaction occurred between cellulose and chitin molecules caused by intermolecular hydrogen bonding. Compared to the mechanical properties of chitin film, those of the blend films containing 10–50 wt % chitin were significantly improved. This work provided a novel way to obtain directly chitin material blended in the aqueous solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1679–1683, 2002
Radiation synthesis and application of a hydrogel based on acrylic acid and 2‐mercaptobenzimidazole
Authors: Nizam El‐Din Horia M. M.
Published: October 2002

A hydrogel based on gamma‐radiation polymerization of acrylic acid (AAc) in the presence of 2‐mercaptobenzimidazole (MBI) and a crosslinking agent was prepared. The properties of this AAc/MBI hydrogel were characterized in terms of gel content, swelling in different solvents, structure morphology, and IR spectroscopy. Moreover, the thermal decomposition behavior of the prepared hydrogel was investigated by thermogravimetric analysis (TGA). The TGA thermograms were also used to determine the different kinetic parameters such as order of reaction and activation energy. The sorption of some divalent metal ions such as Cu2+, Pb2+, Cd2+, and Hg2+ by the AAc/MBI hydrogel also was studied. The results showed that the AAc/MBI hydrogel has a higher tendency to swell in water and polar solvents than in nonpolar solvents. The highest metal uptake by the hydrogel was found for Hg2+ and Cd2+, whereas the lowest was for Cu2+ and Pb2+ ions. The ratios between the distribution coefficients of the different metals [separation factors (SF)] indicate that the hydrogel has a high selectivity for Hg2+ over Cu2+ (SF = 10.923) and Pb2+ (SF = 19.110). However, the hydrogel prefers Hg2+ over Cd2+ (SF = 1.356) and showed a high selectivity for Cd2+ over Cu2+ (SF = 7.822) and Pb2+ (SF = 7.240). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1607–1614, 2002
Effects of surface chemistry of silica particles on secondary structure and tensile properties of silica‐filled rubber systems
Authors: Suzuki Nozomu , Yatsuyanagi Fumito , Ito Masayoshi , Kaidou Hiroyuki
Published: October 2002

Silica particles were treated by silane coupling agents to study the effects of surface chemistry of silica particles on the secondary structure formed by silica particles in styrene–butadiene rubber (SBR). The relation between the size of secondary structure and tensile properties of silica‐filled SBR vulcanizates was also investigated. The water molecules adsorbed on the silica surface enhanced both the reactivity of the coupling agents with silanol groups on the silica surface and the condensation reaction between coupling agents. The averaged size of one agglomerate in the filled vulcanizate (Sagg) decreased with the increase of the hydrophobic character of silica particles, which were obtained by the introduction of coupling agents with alkyl groups. The initial slope of stress–strain curves for silica‐filled vulcanizates decreased with the decrease of Sagg. Further, a clear Payne effect was observed in all silica‐filled vulcanizates, with this tendency more prominent in the larger Sagg. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1622–1629, 2002
Bulk polymerization of methyl methacrylate initiated by high intensity ultrasonic irradiation and ESR study
Authors: Gu Chen‐bin , Wang Dong‐jun , Wang Xin‐qiu , Huang Yong‐ , Zhen Zhen , Liu Xin‐hou
Published: October 2002

High‐intensity ultrasound was used to initiate the bulk polymerization of methyl methacrylate. The polymerization rate varied with the sonication time, the intensity of the ultrasound, and the initiator concentration of poly (methyl methacrylate) in the monomer. Electron spin resonance (ESR) spectra, obtained by the spin trapping technique, testified that free radicals were produced during the sonication process, and the concentration of radicals also changed with the sonication condition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1731–1735, 2002
The effect of nano‐sized silicate layers from montmorillonite on glass transition, dynamic mechanical, and thermal degradation properties of segmented polyurethane
Authors: Tien Yun. I. , Wei Kung Hwa
Published: October 2002

The glass transition temperature of the hard‐segment phase and the storage modulus of segmented polyurethane increased substantially in the presence of a small amount of tethered nano‐sized layered silicates from montmorillonite compared with their pristine state (by 44°C and by 2.8‐fold, respectively). Furthermore, the heat resistance and degradation kinetics of these montmorillonite/polyurethane nanocomposites were enhanced, as shown by thermogravimetric analysis. In particular, a 40°C increase in the degradation temperature and a 14% increase in the degradation activation energy occurred in polyurethane containing 1 wt % trihydroxyl swelling agent‐modified montmorillonite compared to that of the pristine polyurethane. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1741–1748, 2002
Comprehensive experimental study of a starch/polyesteramide coextrusion
Authors: Martin O. , Avérous L.
Published: October 2002

A comprehensive study of the three‐layer film coextrusion was performed. Plasticized wheat starch (PWS) was chosen as the film central layer, and poly(ester amide) (PEA) was used as the surface outer layers. Single‐screw extruders and a standard feedblock attached to a flat coat‐hanger die were used to prepare the three‐layer films. The layer deformation and interfacial instability phenomena, inherent to multilayer flows, were thoroughly investigated. The effect of process variables, such as viscosity ratio, extrusion rate, layer thickness, and die geometry, were studied. Encapsulation of the central layer by the skin layers readily occurred at the edges of coextruded films. The stability of PEA/PWS/PEA coextrusion flows was closely related to the shear stress at the interface. Increasing global volumetric flow rates and the die gap geometry seemed to promote instabilities. Finally, the existence of instabilities at the interface increased the adhesion strength of multilayered products, due to mechanical interlocking between adjacent layers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2586–2600, 2002
Cationic cyclization of neoprene with a diethylaluminum chloride and organic chloride catalyst system
Authors: Wang Chaoyang , Huang Xuepin , Yang Jihua
Published: October 2002

The cyclization of neoprene was achieved with the aid of a cationic catalyst system based on diethylaluminum chloride (Et2AlCl) and an organic chloride, allyl chloride (CH2CHCH2Cl) or benzyl chloride (C6H5CH2Cl). The main parameters of the cyclization process were investigated. Elastomers with low intrinsic viscosity, ready solubility and some gelling were obtained. Xylene was a good solvent for the cyclization process, which took place in a very short time (≤5 min). The products were characterized with IR,1H‐NMR, differential scanning calorimetry, and gel permeation chromatography. The polycyclic structure was determined. The degree of cyclization and the incorporated solvent content were estimated with a1H‐NMR method. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2227–2231, 2002
Influence of a compatibilizer on the properties of polyethylene–octene elastomer/starch blends
Authors: Wu Chin‐San , Liao Hsin‐Tzu
Published: October 2002

The effect of a compatibilizer on the properties of corn starch‐reinforced metallocene polyethylene–octene elastomer (POE) blends was studied. The compatibility between POE and starch was improved markedly with an acrylic acid‐grafted POE (POE‐g‐AA) copolymer as a compatibilizer. Fourier transform infrared spectroscopy, X‐ray diffraction spectroscopy, differential scanning calorimetry, and scanning electron microscopy were used to examine the blends produced. The size of the starch phase increased with an increasing content of starch for noncompatibilized and compatibilized blends. The POE/starch blends compatibilized with the POE‐g‐AA copolymer lowered the size of the starch phase and had a fine dispersion and homogeneity of starch in the POE matrix. This better dispersion was due to the formation of branched and crosslinked macromolecules because the POE‐g‐AA copolymer had anhydride groups to react with the hydroxyls. This was reflected in the mechanical properties of the blends, especially the tensile strength at break. In a comparison with pure POE, the decrease in the tensile strength was slight for compatibilized blends containing up to 40 wt % starch. The POE‐g‐AA copolymer was an effective compatibilizer because only a small amount was required to improve the mechanical properties of POE/starch blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1792–1798, 2002
Fracture toughness of silica particulate‐filled epoxy composite
Authors: Adachi Tadaharu , Araki Wakako , Nakahara Takuya , Yamaji Akihiko , Gamou Masahiro
Published: October 2002

The relationship between the postcuring conditions and fracture toughness on three silica particulate‐filled epoxy composites was investigated. The glass transition temperature, Tg, and the fragility parameter, m, derived from the thermo‐viscoelasticity, were used to characterize the composites, which were postcured under various conditions. The glass transition temperature and fragility both depended on both of the curing conditions and the volume fraction of silica particles. The glass transition temperature increased with the postcuring time and temperature, while the fragility generally decreased as the volume fraction increased. There was no direct correlation between the glass transition temperature and fragility. The fracture toughness depended on both the glass transition temperature and fragility. The composites with a high glass transition temperature and low fragility had high fracture toughness. These results indicate that the glass transition temperature and fragility are useful parameters for estimating the fracture toughness of the silica particulate‐filled epoxy composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2261–2265, 2002
Characteristics of electrical responsive chitosan/polyallylamine interpenetrating polymer network hydrogel
Authors: Jeong Seon , Jun Park Sang , Shin Mi‐Seon , Kim Sun I.
Published: October 2002

An interpenetrating polymer network (IPN) hydrogel composed of chitosan and polyallylamine exhibited electric‐sensitive behavior. The chitosan/polyallylamine IPN hydrogel was synthesized by radical polymerization using 2,2‐dimethoxy‐2‐phenylacetophenone (DMPAP) and methylene bisacrylicamide (MBAAm) as initiator and crosslinker, respectively. The swelling behavior of the IPN was studied by immersion of the gel samples in aqueous NaCl solutions at various concentrations and pHs. The swelling ratio decreased with increasing concentration and pH of electrolyte solution. The stimuli response of the IPN hydrogel in electric fields was also investigated. When a swollen the IPN was placed between a pair of electrodes, the IPN exhibited bending behavior in response to the applied electric field. The IPN also showed stepwise bending behavior depending on the electric stimulus. In addition, thermal properties of the IPN were investigated by differential scanning calorimetry (DSC) and dielectric analysis (DEA). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2290–2295, 2002
Nitroxide‐mediated radical polymerization of 4‐vinylpyridine and its application on modification of silicon substrate
Authors: Chen Zhijun , Cai Jie , Jiang Xiqun , Yang Changzheng
Published: October 2002

The poly(4‐vinylpyridine) with hydroxyl end group and narrow polydispersity was synthesized by polymerization of 4‐vinylpyridine by the use of nitroxide initiator based on 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl and azobisisobutyronitrile. The effects of different initiator amounts and reaction time on polymerization rate, molecular weight, and molecular weight distribution of the poly(4‐vinylpyridine) were investigated at bulk polymerization. The experimental results have shown that the polymerization of 4‐vinylpyridine is a controlled living free‐radical polymerization; the molecular weight is proportional to reaction time; and the molecular weight and molecular weight distribution are affected by molar ratios of [4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl]/[azobisisobutyronitrile]. By varying the ratio of 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl to azobisisobutyronitrile, the poly(4‐vinylpyridine) with narrow polydispersity can be obtained. X‐ray photoelectron spectroscopy results show that the synthesized poly(4‐vinylpyridine) can be tethered on the surface of silicon wafer through the reaction between hydroxyl end of poly(4‐vinylpyridine) and native silicon oxide layer on the wafer surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2687–2692, 2002
Preparation and properties of water‐soluble polyester surfactants. I. Preparation and surface activity of poly(ethylene glycol)‐dimethyl 5‐sulfo‐isophthalate sodium salt polyester surfactants
Authors: Lin Li‐Huei , Chiang Chung‐Yu , Liu Hsin‐Jiant , Chen Keng‐Ming
Published: October 2002

The reaction of poly(ethylene glycol) (PEG, number‐average molecular weight Mn = 400‐2000) and dimethyl 5‐sulfoisophthalate sodium salt (SIPM) synthesized a series of anionic polymeric surfactants having a range of molecular weights. 1H‐NMR, FTIR, and elemental analysis were employed to characterize the structures of these compounds. Also, the influences of the PEG segment lengths of PEG/SIPM copolymers on the surface tension, foaming properties, wetting power, and dispersant properties were investigated. The experimental results indicated that the solution that contained the PEG/SIPM copolymer surfactants exhibited excellent surface‐active properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2727–2731, 2002
Supramolecular morphology of two‐step, melt‐spun poly(lactic acid) fibers
Authors: Cicero John A. , Dorgan John R. , Janzen Jay , Garrett James , Runt James , Lin J. S.
Published: October 2002

Fibers of poly(lactic acid) produced by two‐step melt spinning have been studied. The morphology is elucidated with respect to the thermal and mechanical properties of fibers produced at cold‐draw ratios of 1–8. With atomic force microscopy and small‐angle X‐ray scattering, a fibrillar morphology is found, with microfibril diameters ranging from 30 to 60 nm. Shrinkage properties indicate that, with increasing draw ratio, the fibers undergo a transition from class 2 to class 1 within the classification proposed by Keller. A supramolecular model for the morphology of the fibers is presented that entails a highly oriented skin with a core consisting of microfibrils. The orientation of the crystalline blocks within the microfibrils is similar to what has been reported for nylon fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2828–2838, 2002
Evolution of interactions between water and native corn starch as a function of moisture content
Authors: Brouillet‐Fourmann S. , Carrot C. , Lacabanne C. , Mignard N. , Samouillan V.
Published: October 2002

Thermostimulated current spectroscopy, thermogravimetric analysis, and differential scanning calorimetry (DSC) were used to study starch–water systems with moisture contents of 0–50% (on a total weight basis). DSC enabled the calculation of the amounts of bound and free water. The maximum quantity of bound water was detected for a 30% humidity sample. The existence of interactions between water and starch was proved and found to be weakened for samples containing more than 30% water. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2860–2865, 2002
Rheological properties of ionically crosslinked poly(propylene)‐type thermoplastic elastomers
Authors: Fujiyama Mitsuyoshi , Yamane Kazuhiro , Ayama Kazuhiko , Inata Hitoshi
Published: October 2002

Maleic anhydride was grafted onto poly(propylene) (PP)‐type thermoplastic elastomer PER by reactive processing with a screw extruder and a maleated PER (MPER) was prepared. With the intent of ionic crosslinking, metal compounds such as aluminum stearate (AlSt), magnesium stearate (MgSt), calcium stearate (CaSt), zinc stearate (ZnSt), potassium stearate (KSt), sodium stearate (NaSt), magnesium hydroxide (MH), zinc oxide (ZnO), and zinc sulfide (ZnS) were added to the MPER and melt‐mixed with the screw extruder, and crosslinked compounds were obtained. The degree of crosslinking estimated from the gel fraction was in the order AlSt, MgSt, CaSt, ZnSt > NaSt, KSt > MH > ZnO, ZnS > MPER. The rheological properties, such as capillary flow properties and dynamic viscoelasticities, of the compounds were measured and their melt processabilities were evaluated. The viscosity increased with increasing the content of the metal compounds and the increase was higher at the lower shear rate. The increasing effect of the viscosity at low shear rates was AlSt > MgSt > ZnSt > NaSt > KSt > MH > ZnO > ZnS > MPER. Namely, the viscosity increasing effect of the metal salt of stearic acid is the higher for the larger ionic charge and the viscosity increasing effects of other compounds are lower than those of the metal salts of stearic acid. Accordingly, by changing the kind and content of the metal compounds, the viscosity can be freely controlled. Considering also other rheological characteristics, these ionically crosslinked compounds are assumed to show ideal flow processabilities except for the extrudate appearance. To improve the appearance, it is necessary to dilute the compound with unmodified PER, PP, or fillers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2887–2897, 2002
Increased transcriptional activities of transforming growth factor β receptors in scleroderma fibroblasts
Authors: Yamane Kenichi , Ihn Hironobu , Kubo Masahide , Tamaki Kunihiko
Published: October 2002

Objective

To investigate the molecular mechanism of the overexpression of transforming growth factor β receptors (TGFβRs) in dermal fibroblasts from patients with systemic sclerosis (SSc).

Methods

Dermal fibroblasts from 7 patients with diffuse SSc of recent onset and from 7 healthy individuals were studied. The expression of TGFβR type I (TGFβRI), TGFβRII, and type I collagen proteins in dermal fibroblasts was determined by immunoblotting. TGFβRI, TGFβRII, and α2(I) collagen messenger RNA (mRNA) were evaluated by Northern blot analysis. The transcriptional activities of the TGFβRI and TGFβRII genes were examined by luciferase assay.

Results

SSc fibroblasts expressed increased levels of TGFβRI and TGFβRII protein and mRNA, as well as increased levels of type I collagen protein and α2(I) collagen mRNA. Moreover, the half‐lives of TGFβRI and TGFβRII mRNA in SSc fibroblasts did not change compared with those in control dermal fibroblasts. The promoter activities of the TGFβRI and TGFβRII genes were both significantly increased in SSc fibroblasts compared with those in control fibroblasts. Calphostin C, a specific inhibitor of protein kinase C (PKC), inhibited TGFβRI promoter activity in SSc fibroblasts, and LY294002, an inhibitor of phosphoinositide 3‐kinase (PI 3‐kinase), inhibited TGFβRII promoter activity in SSc fibroblasts. Moreover, calphostin C and LY294002 inhibited the up‐regulation of TGFβRI and TGFβRII mRNA, respectively, in SSc fibroblasts.

Conclusion

These results suggest that increased levels of TGFβRs in SSc fibroblasts play a role in excessive collagen production, and that up‐regulation of TGFβR expression might occur at the transcriptional levels. PKC and/or PI 3‐kinase might contribute to the up‐regulation of TGFβR expression in SSc fibroblasts.
Detection of nitrotyrosine in aging and osteoarthritic cartilage: Correlation of oxidative damage with the presence of interleukin‐1β and with chondrocyte resistance to insulin‐like growth factor 1
Authors: Loeser Richard F. , Carlson Cathy S. , Carlo Marcello Del , Cole Ada
Published: October 2002

Objective

To determine whether oxidative damage to cartilage proteins can be detected in aging and osteoarthritic (OA) cartilage, and to correlate the results with the local production of interleukin‐1β (IL‐1β) and the responsiveness of isolated chondrocytes to stimulation with insulin‐like growth factor 1 (IGF‐1).

Methods

The presence of nitrotyrosine was used as a measure of oxidative damage. Histologic sections of knee articular cartilage, obtained from young adult and old adult cynomolgus monkeys, which develop age‐related, naturally occurring OA, were evaluated. Each cartilage section was graded histologically on a scale of 0–7 for the presence of OA‐like changes, and serial sections were immunostained using antibodies to nitrotyrosine and IL‐1β. Chondrocytes isolated and cultured from cartilage adjacent to the sections used for immunostaining were tested for their response to IGF‐1 stimulation by measuring sulfate incorporation in alginate cultures. For comparison with the monkey tissues, cartilage sections from human tissue donors and from tissue removed at the time of OA‐related joint replacement surgery were also immunostained for nitrotyrosine and IL‐1β.

Results

The presence of nitrotyrosine was associated with aging and with the development of OA in cartilage samples from both monkeys and humans. All sections that were highly positive for IL‐1β also showed staining for nitrotyrosine. However, in a few sections from older adult monkeys and humans, nitrotyrosine was present but IL‐1β was absent, suggesting that some age‐related oxidative damage is independent of IL‐1β. In chondrocytes that were isolated from monkey cartilage positive for nitrotyrosine or IL‐1β, the response to stimulation with IGF‐1 was significantly reduced. In some samples from older adult monkeys, IGF‐1 resistance was seen in cells isolated from tissue that did not stain for nitrotyrosine or IL‐1β.

Conclusion

Oxidative damage due to the concomitant overproduction of nitric oxide and other reactive oxygen species is present in both aging and OA cartilage. This damage can contribute to the resistance of chondrocytes to IGF‐1 stimulation, but it is unlikely to be the sole cause of IGF‐1 resistance in these chondrocytes.
Fibronectin fragments and blocking antibodies to α2β1 and α5β1 integrins stimulate mitogen‐activated protein kinase signaling and increase collagenase 3 (matrix metalloproteinase 13) production by human articular chondrocytes
Authors: Forsyth Christopher B. , Pulai Judit , Loeser Richard F.
Published: October 2002

Objective

To determine if integrin‐mediated signaling results in activation of chondrocyte mitogen‐activated protein (MAP) kinases that lead to increased expression of matrix metalloproteinase 13 (MMP‐13; collagenase 3), a potent mediator of cartilage matrix degradation.

Methods

Human articular chondrocytes isolated from normal ankle and knee cartilage obtained from tissue donors were cultured in monolayers. The cells were treated with a 120‐kd fibronectin fragment (FN‐f) that binds the α5β1 integrin or with antibodies to specific integrin receptors. Activation of MAP kinases was determined by immunoblotting with phosphospecific antibodies. MMP production was measured by gelatin zymography, and MMP‐13 production and activation were determined by immunoblotting and by a fluorogenic peptide assay.

Results

Human articular chondrocytes were found to respond to the 120‐kd FN‐f and to adhesion‐blocking antibodies to the α2β1 and α5β1 integrins with increased phosphorylation of the extracellular signal–regulated kinase 1 (ERK1)/ERK2, c‐Jun N‐terminal kinase (JNK), and p38 MAP kinases. Intact FN and integrin‐blocking antibodies to α1, α3, and αVβ3 and a nonblocking α5 antibody had no effect. After MAP kinase activation, increased phosphorylation of c‐Jun and the nuclear factor κB inhibitor was noted, followed by increased pro‐ and activated MMP‐13 in the conditioned media. Inhibitors of mitogen‐activated protein kinase kinase, p38, and JNK were each able to inhibit increased MMP‐13 production, while the interleukin‐1 receptor antagonist (IL‐1Ra) protein did not. However, the IL‐1Ra partially inhibited FN‐f–induced activation of MMP‐13.

Conclusion

Integrin‐mediated MAP kinase signaling stimulated by FN‐f is associated with increased production and release of pro‐ and active MMP‐13. Autocrine production of IL‐1 appears to result in additional MMP‐13 activation. These processes may play a key role in feedback loops responsible for progressive cartilage degradation in arthritis.
Predictors of infection in rheumatoid arthritis
Authors: Doran Michele F. , Crowson Cynthia S. , Pond Gregory R. , O'Fallon W. Michael , Gabriel Sherine E.
Published: October 2002

Objective

Patients with rheumatoid arthritis (RA) have been shown to have an increased susceptibility to the development of infections. The exact causes of this increased risk are unknown, but may relate to immunologic disturbances associated with the disease or to the immunosuppressive effects of agents used in its treatment. This study was undertaken to identify predictors of serious infections among patients with RA. Identification of such factors is the necessary first step in reducing the excess risk of infection in RA.

Methods

Members of a population‐based incidence cohort of Rochester, Minnesota residents ages ≥18 years, who had been diagnosed with RA between 1955 and 1994, were followed up longitudinally through their complete medical records until January 1, 2000. We examined potential risk factors for the development of all objectively confirmed (by microbiology or radiology) infections and for infections requiring hospitalization. Potential risk factors included RA severity measures (rheumatoid factor positivity, elevated erythrocyte sedimentation rate, extraarticular manifestations of RA, and functional status), comorbidities (diabetes mellitus, alcoholism, and chronic lung disease), and other risk factors for infection (presence of leukopenia, smoking). Predictors were identified using multivariate time‐dependent Cox proportional hazards modeling.

Results

The 609 RA patients in the cohort had a total followup time of 7,729.7 person‐years (mean 12.7 years per patient). A total of 389 patients (64%) had at least 1 infection with objective confirmation, and 290 (48%) had at least 1 infection requiring hospitalization. Increasing age, presence of extraarticular manifestations of RA, leukopenia, and comorbidities (chronic lung disease, alcoholism, organic brain disease, and diabetes mellitus), as well as use of corticosteroids, were strong predictors of infection (P < 0.004) in both univariate and multivariate analyses. Notably, use of disease‐modifying antirheumatic drugs was not associated with increased risk of infection in multivariate analyses, after adjustment for demographic characteristics, comorbidities, and disease‐related variables.

Conclusion

We identified a number of strong predictors of infections in a population‐based cohort of patients with RA. These results can be used to prospectively identify high‐risk patients, who may benefit from closer followup and implementation of preventive strategies.
Mice lacking endogenous major histocompatibility complex class II develop arthritis resembling psoriatic arthritis at an advanced age
Authors: Bárdos Tamás , Zhang Jian , Mikecz Katalin , David Chella S. , Glant Tibor T.
Published: October 2002

Objective

To describe and characterize a novel inflammatory toe disease with severe bone destruction that developed spontaneously in “humanized” (HLA transgenic) mice lacking their own major histocompatibility complex (MHC).

Methods

We studied 5 different HLA transgenic mouse lines (HLA–DR2.Ab0, DR3.Ab0, DR4.Ab0, DQ6.Ab0, and DQ8.Ab0) in similar genetic background for an extended period of time (>14 months). Clinical, radiologic, and histologic abnormalities were monitored, and the MHC‐related major immunologic parameters in affected and resistant mice were compared.

Results

Animals of 4 transgenic lines (HLA–DR2.Ab0, DR4.Ab0, DQ6.Ab0, and DQ8.Ab0) developed severe toe inflammation accompanied by progressive bone resorption, hyperkeratosis, alopecia, loss of nails, and shortening and thickening of the distal phalanges. HLA–DR3.Ab0 transgenic mice were resistant to inflammation. The disease manifested only at advanced ages (6 months or older) and affected 70–100% of the mice, with a female preponderance. The clinical signs and the radiographic and histopathologic features of the affected toes were not similar to those of any disease previously described in mice but did resemble those described for human psoriatic arthritis (PsA). Mice from the 4 susceptible lines expressed lower levels of the HLA transgene and exhibited significantly fewer CD4+ cells in the peripheral blood and reduced natural killer cell activity compared with mice from the resistant HLA–DR3.Ab0 line.

Conclusion

This novel, spontaneously developing PsA‐like toe disease in MHC‐manipulated mice seems to be related to the absence of endogenous MHC class II. Replacement with HLA transgene expression that is insufficient (or no replacement at all) may result in imbalanced MHC class I and class II functions and lead to development of the disease.
Long‐term followup of children with neonatal lupus and their unaffected siblings
Authors: Martin Victor , Lee Lela A. , Askanase Anca D. , Katholi Margaret , Buyon Jill P.
Published: October 2002

Objective

To determine in a longitudinal cohort study whether children with varied manifestations of neonatal lupus or their unaffected siblings later develop autoantibodies and/or rheumatic diseases.

Methods

To obtain information on the health of children ages ≥8 years who had manifestations of neonatal lupus (affected group) and their unaffected siblings (unaffected group), questionnaires were sent to mothers (with anti‐SSA/Ro and/or anti‐SSB/La antibodies) who were enrolled in the National Institute of Arthritis and Musculoskeletal and Skin Diseases/Hospital for Joint Diseases Research Registry for Neonatal Lupus. Children of healthy mothers referred by the Registry enrollees comprised the control group. Further data were provided by review of medical records.

Results

Fifty‐five mothers enrolled in the Registry returned questionnaires on 49 children with neonatal lupus and their 45 unaffected siblings. Six children with definite rheumatic/autoimmune diseases were identified: 2 with juvenile rheumatoid arthritis, 1 with Hashimoto thyroiditis, 1 with psoriasis and iritis, 1 with diabetes mellitus and psoriasis, and 1 with congenital hypothyroidism and nephrotic syndrome. All had neonatal lupus, and their mothers had manifestations of autoimmune diseases (Sjögren's syndrome in 4, systemic lupus erythematosus/Sjögren's syndrome in 1, and undifferentiated autoimmune disease in 1). Antinuclear antibodies were present in 4 of 55 sera tested (2 of 33 affected children and 2 of 22 unaffected children). No serum contained antibodies reactive with SSA/Ro or SSB/La antigens.

Conclusion

These data suggest that children with neonatal lupus require continued followup, especially prior to adolescence and if the mother herself has an autoimmune disease. While there was no apparent increased risk of systemic lupus erythematosus, the development of some form of autoimmune disease (systemic or organ‐specific) in early childhood may be of concern. During adolescence and young adulthood, individuals with neonatal lupus and their unaffected siblings do not appear to have an increased risk of developing systemic rheumatic diseases.
Prospect theory analysis of guessing in multiple choice tests
Authors: Bereby‐Meyer Yoella , Meyer Joachim , Flascher Oded M.
Published: October 2002

The guessing of answers in multiple choice tests adds random error to the variance of the test scores, lowering their reliability. Formula scoring rules that penalize for wrong guesses are frequently used to solve this problem. This paper uses prospect theory to analyze scoring rules from a decision‐making perspective and focuses on the effects of framing on the tendency to guess. In three experiments participants were presented with hypothetical test situations and were asked to indicate the degree of certainty that they thought was required for them to answer a question. In accordance with the framing hypothesis, participants tended to guess more when they anticipated a low grade and therefore considered themselves to be in the loss domain, or when the scoring rule caused the situation to be framed as entailing potential losses. The last experiment replicated these results with a task that resembles an actual test. Copyright © 2002 John Wiley & Sons, Ltd.
Family of the green fluorescent protein: Journey to the end of the rainbow
Authors: Matz Mikhail V. , Lukyanov Konstantin A. , Lukyanov Sergey A.
Published: October 2002

Members of the family of the Green Fluorescent Protein (GFP) are the only known type of natural pigments that are essentially encoded by a single gene, since both the substrate for pigment biosynthesis and the necessary catalytic moieties are provided within a single polypeptide chain. In sharp contrast to the state of knowledge just three years ago when GFP was the only known protein of its kind, a whole family of related proteins, exhibiting striking diversity of features have now been identified. This provides new possibilities for a variety of studies ranging from applied biotechnology to evolutionary ecology. BioEssays 24:953–959, 2002. © 2002 Wiley Periodicals, Inc.
Lighting up gap junction channels in a flash
Authors: Evans W. Howard , Martin Patricia E.M.
Published: October 2002

Gap junction intercellular communication channels permit the exchange of small regulatory molecules and ions between neighbouring cells and coordinate cellular activity in diverse tissue and organ systems. These channels have short half‐lives and complex assembly and degradation pathways. Much of the recent work elucidating gap junction biogenesis has featured the use of connexins (Cx), the constituent proteins of gap junctions, tagged with reporter proteins such as Green Fluorescent Protein (GFP) and has illuminated the dynamics of channel assembly in live cells by high‐resolution time‐lapse microscopy. With some studies, however, there are potential short‐comings associated with the GFP chimeric protein technologies. A recent report by Gaietta et al., has highlighted the use of recombinant proteins with tetracysteine tags attached to the carboxyl terminus of Cx43, which differentially labels ‘old’ and ‘new’ connexins thus opening up new avenues for studying temporal and spatial localisation of proteins and in situ trafficking events.1 BioEssays 24:876–880, 2002. © 2002 Wiley Periodicals, Inc.
Do different branching epithelia use a conserved developmental mechanism?
Authors: Davies Jamie A.
Published: October 2002

Formation of branching epithelial trees from unbranched precursors is a common process in animal organogenesis. In humans, for example, this process gives rise to the airways of the lungs, the urine‐collecting ducts of the kidneys and the excretory epithelia of the mammary, prostate and salivary glands. Branching in these different organs, and in different animal classes and phyla, is morphologically similar enough to suggest that they might use a conserved developmental programme, while being dissimilar enough not to make it obviously certain that they do. In this article, I review recent discoveries about the molecular regulation of branching morphogenesis in the best‐studied systems, and present evidence for and against the idea of there being a highly conserved mechanism. Overall, I come to the tentative conclusion that key mechanisms are highly conserved, at least within vertebrates, but acknowledge that more work needs to be done before the case is proved beyond reasonable doubt. BioEssays 24:937–948, 2002. © 2002 Wiley Periodicals, Inc.
Centrosomal TACCtics
Authors: Gergely Fanni
Published: October 2002

Although the centrosome was first described over 100 years ago, we still know relatively little of the molecular mechanisms responsible for its functions. Recently, members of a novel family of centrosomal proteins have been identified in a wide variety of organisms. The transforming acidic coiled‐coil‐containing (TACC) proteins all appear to play important roles in cell division and cellular organisation in both embryonic and somatic systems. These closely related molecules have been implicated in microtubule stabilisation, acentrosomal spindle assembly, translational regulation, haematopoietic development and cancer progression. In this review, I summarise what we already know of this protein family and will use the TACC proteins to illustrate the many facets that centrosomes have developed during the course of evolution. BioEssays 24:915–925, 2002. © 2002 Wiley Periodicals, Inc.
RWPV bioreactor mass transport: Earth‐based and in microgravity
Authors: Begley Cynthia M. , Kleis Stanley J.
Published: October 2002

Mass transport and mixing of perfused scalar quantities in the NASA Rotating Wall Perfused Vessel bioreactor are studied using numerical models of the flow field and scalar concentration field. Operating conditions typical of both microgravity and ground‐based cell cultures are studied to determine the expected vessel performance for both flight and ground‐based control experiments. Results are presented for the transport of oxygen with cell densities and consumption rates typical of colon cancer cells cultured in the RWPV. The transport and mixing characteristics are first investigated with a step change in the perfusion inlet concentration by computing the time histories of the time to exceed 10% inlet concentration. The effects of a uniform cell utilization rate are then investigated with time histories of the outlet concentration, volume average concentration, and volume fraction starved. It is found that the operating conditions used in microgravity produce results that are quite different then those for ground‐based conditions. Mixing times for microgravity conditions are significantly shorter than those for ground‐based operation. Increasing the differential rotation rates (microgravity) increases the mixing and transport, while increasing the mean rotation rate (ground‐based) suppresses both. Increasing perfusion rates enhances mass transport for both microgravity and ground‐based cases, however, for the present range of operating conditions, above 5–10 cc/min there are diminishing returns as much of the inlet fluid is transported directly to the perfusion exit. The results show that exit concentration is not a good indicator of the concentration distributions in the vessel. In microgravity conditions, the NASA RWPV bioreactor with the viscous pump has been shown to provide an environment that is well mixed. Even when operated near the theoretical minimum perfusion rates, only a small fraction of the volume provides less than the required oxygen levels. @ 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 465–476, 2002.
Kinetic and inhibition studies for the aerobic cometabolism of 1,1,1‐trichloroethane, 1,1‐dichloroethylene, and 1,1‐dichloroethane by a butane‐grown mixed culture
Authors: Kim Young , Arp Daniel J. , Semprini Lewis
Published: October 2002

Batch kinetic and inhibition studies were performed for the aerobic cometabolism of 1,1,1‐trichloroethane (1,1,1‐TCA), 1,1‐dichloroethylene (1,1‐DCE), and 1,1‐dichloroethane (1,1‐DCA) by a butane‐grown mixed culture. These chlorinated aliphatic hydrocarbons (CAHs) are often found together as cocontaminants in groundwater. The maximum degradation rates (kmax) and half‐saturation coefficients (Ks) were determined in single compound kinetic tests. The highest kmax was obtained for butane (2.6 μmol/mg TSS/h) followed by 1,1‐DCE (1.3 μmol/mg TSS/h), 1,1‐DCA (0.49 μmol/mg TSS/h), and 1,1,1‐TCA (0.19 μmol/mg TSS/h), while the order of Ks from the highest to lowest was 1,1‐DCA (19 μM), butane (19 μM), 1,1,1‐TCA (12 μM) and 1,1‐DCE (1.5 μM). The inhibition types were determined using direct linear plots, while inhibition coefficients (Kic and Kiu) were estimated by nonlinear least squares regression (NLSR) fits to the kinetic model of the identified inhibition type. Two different inhibition types were observed among the compounds. Competitive inhibition among CAHs was indicated from direct linear plots, and the CAHs also competitively inhibited butane utilization. 1,1‐DCE was a stronger inhibitor than the other CAHs. Mixed inhibition of 1,1,1‐TCA, 1,1‐DCA, and 1,1‐DCE transformations by butane was observed. Thus, both competitive and mixed inhibitions are important in cometabolism of CAHs by this butane culture. For competitive inhibition between CAHs, the ratio of the Ks values was a reasonable indicator of competitive inhibition observed. Butane was a strong inhibitor of CAH transformation, having a much lower inhibition coefficient than the Ks value of butane, while the CAHs were weak inhibitors of butane utilization. Model simulations of reactor systems where both the growth substrate and the CAHs are present indicate that reactor performance is significantly affected by inhibition type and inhibition coefficients. Thus, determining inhibition type and measuring inhibition coefficients is important in designing CAH treatment systems. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 498–508, 2002.
Common and distinct features of cytokine effects on hematopoietic stem and progenitor cells revealed by dose–response surface analysis
Authors: Audet Julie , Miller Cindy L. , Eaves Connie J. , Piret James M.
Published: October 2002

Recent studies have identified thrombopoietin (TPO), flt‐3 ligand (FL), Steel factor (SF), and interleukin‐11 (IL‐11) as cytokines able to stimulate amplification of the most primitive murine hematopoietic cells in vitro. However, dose–response and interaction parameters that predict how to optimize mixtures of these cytokines have not been previously defined. To obtain this information, Sca‐1+lin− and c‐kit+Sca‐1+lin− adult mouse bone marrow cells were cultured for 10 and 14 days, respectively, in serum‐free medium with varying concentrations of these cytokines. Quantitative assays were performed to determine the influences of the cytokine combinations tested on changes in long‐term repopulating hematopoietic stem cells (HSCs), in vitro colony‐forming cells (CFCs), and total cell numbers. A two‐level factorial design was first used to screen the effects of TPO, SF, FL, and IL‐11 as well as two different incubation temperatures. IL‐11 and SF were found to be the most significant stimulators of murine HSC expansion. More detailed analyses of the effects on c‐kit+Sca‐1+lin− cells of IL‐11, SF, and FL concentrations and their interactions using response surface methodology showed IL‐11 to have a maximal stimulatory effect on HSC expansion at 20 ng/mL with higher concentrations being inhibitory. In contrast, not even high concentration saturation of the effects of either SF or FL was observed as the stimulatory effect of both SF and FL increased beyond 300 ng/mL. A negative interaction between SF and FL on HSCs was discovered. Interestingly, a generally similar pattern of cytokine effects was found to influence the 14‐day output of CFCs and total cells from the same c‐kit+Sca‐1+lin− starting cell population. However, compared with HSCs, the cytokine requirements for maximizing the generation of CFCs and total cells were at much lower cytokine doses. From the information provided by the factorial analysis, mathematical models based on Monod kinetics for inhibitory substrates were developed that allow total cell, CFC, and HSC expansion to be predicted as a function of the IL‐11, SF, and FL concentrations in terms of more widely recognized parameters. Overall, these methods should also serve as a guide for the future design and testing of other ex vivo stem cell expansion systems. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 393–404, 2002.