bluuebunny/crossref_metadata_2025 huggingface dataset:
The crystal structure of a 26-nucleotide RNA containing a hook-turn
Authors: SZÉP SZILVIA , WANG JIMIN , MOORE PETER B.
Published: January 2003

A crystal structure has been obtained for a 26-nucleotide RNA that contains the loop E sequence from Chromatium minutissimum. Rather than having a loop E-like conformation, it consists of an A-form helix that splits into two separate strands following a sheared A–G base pair. The backbone of the strand containing the G of the A–G pair makes a turn of almost 180° in the space of two nucleotides, and then interacts with the minor groove of the helix from which it originates. Similar structures, which we call hook-turns, occur in 16S and 23S rRNAs. They are found at places where the two strands of a helix separate at an A/G juxtaposition to interact with other sequences.
A possible tertiary rRNA interaction between expansion segments ES3 and ES6 in eukaryotic 40S ribosomal subunits
Authors: ALKEMAR GUNNAR , NYGÅRD ODD
Published: January 2003

Eukaryotic 16S-like ribosomal RNAs contain 12 so-called expansion segments, i.e., sequences not included in the RNA secondary structure core common to eubacteria, archaea, and eukarya. Two of these expansion segments, ES3 and ES6, are juxtaposed in the recent three-dimensional model of the eukaryotic 40S ribosomal subunit. We have analyzed ES3 and ES6 sequences from more than 2900 discrete eukaryotic species, for possible sequence complementarity between the two expansion segments. The data show that ES3 and ES6 could interact by forming a helix consisting of seven to nine contiguous base pairs in almost all analyzed species. We, therefore, suggest that ES3 and ES6 form a direct RNA–RNA contact in the ribosome.
Identification and characterization of Prp45p and Prp46p, essential pre-mRNA splicing factors
Authors: ALBERS MICHAEL , DIMENT ANN , MURARU MARIELA , RUSSELL CAROLINE S. , BEGGS JEAN D.
Published: January 2003

Through exhaustive two-hybrid screens using a budding yeast genomic library, and starting with the splicing factor and DEAH-box RNA helicase Prp22p as bait, we identified yeast Prp45p and Prp46p. We show that as well as interacting in two-hybrid screens, Prp45p and Prp46p interact with each other in vitro. We demonstrate that Prp45p and Prp46p are spliceosome associated throughout the splicing process and both are essential for pre-mRNA splicing. Under nonsplicing conditions they also associate in coprecipitation assays with low levels of the U2, U5, and U6 snRNAs that may indicate their presence in endogenous activated spliceosomes or in a postsplicing snRNP complex.
Nuclear translation: What is the evidence?
Authors: DAHLBERG JAMES E. , LUND ELSEBET , GOODWIN ELIZABETH B.
Published: January 2003

Recently, several reports have been published in support of the idea that protein synthesis occurs in both the nucleus and the cytoplasm. This proposal has generated a great deal of excitement because, if true, it would mean that our thinking about the compartmentalization of cell functions would have to be re-evaluated. The significance and broad implications of this phenomenon require that the experimental evidence used to support it be carefully evaluated. Here, we critique the published evidence in support of, or in opposition to, the question of whether translation occurs in the nucleus. Arguments in support of nuclear translation focus on three issues: (1) the presence of translation factors and ribosomal components in the nucleus, and their recruitment to sites of transcription; (2) amino acid incorporation in isolated nuclei and in nuclei under conditions that should not permit protein import; and (3) the fact that nuclear translation would account for observations that are otherwise difficult to explain. Arguments against nuclear translation emphasize the absence (or low abundance) from nuclei of many translation factors; the likely inactivity of nascent ribosomes; and the loss of translation activity as nuclei are purified from contaminating cytoplasm. In our opinion, all of the experiments on nuclear translation published to date lack critical controls and, therefore, are not compelling; also, traditional mechanisms can explain the observations for which nuclear translation has been invoked. Thus, while we cannot rule out nuclear translation, in the absence of better supporting data we are reluctant to believe it occurs.
ORF-less and reverse-transcriptase-encoding group II introns in archaebacteria, with a pattern of homing into related group II intron ORFs
Authors: DAI LIXIN , ZIMMERLY STEVEN
Published: January 2003

Although group II intron retroelements are prevalent in eubacteria, they have not been identified in archaebacteria in the first 10 genomes sequenced. However, the recently sequenced archael genome of Methanosarcina acetivorans contains 21 group II introns, including 7 introns that do not encode reverse transcriptase ORFs. To our knowledge, these are the first retroelements identified in archaebacteria, and the first ORF-less group II introns in bacteria. Furthermore, the insertion pattern of the introns is highly unusual. The introns appear to insert site-specifically into ORFs of other group II introns, forming nested clusters of up to four introns, but there are no flanking exons that could encode a functional protein after the introns have been spliced out.
Sex lethal and U2 small nuclear ribonucleoprotein auxiliary factor (U2AF65) recognize polypyrimidine tracts using multiple modes of binding
Authors: BANERJEE HIREN , RAHN ANDREW , DAVIS WILLIAM , SINGH RAVINDER
Published: January 2003

The molecular basis for specific recognition of simple homopolymeric sequences like the polypyrimidine tract (Py tract) by multiple RNA recognition motifs (RRMs) is not well understood. The Drosophila splicing repressor Sex lethal (SXL), which has two RRMs, can directly compete with the essential splicing factor U2AF65, which has three RRMs, for binding to specific Py tracts. We have combined site-specific photocross-linking and chemical cleavage of the proteins to biochemically map cross-linking of each of the uracils within the Py tract to specific RRMs. For both proteins, RRM1 and RRM2 together constitute the minimal Py-tract recognition domain. The RRM3 of U2AF65 shows no cross-linking to the Py tract. Both RRM1 and RRM2 of U2AF65 and SXL can be cross-linked to certain residues, with RRM2 showing a surprisingly high number of residues cross-linked. The cross-linking data eliminate the possibility that shorter Py tracts are bound by fewer RRMs. We present a model to explain how the binding affinity can nonetheless change as a function of the length of the Py tract. The results indicate that multiple modes of binding result in an ensemble of RNA–protein complexes, which could allow tuning of the binding affinity without changing sequence specificity.
A 100-kD complex of two RNA-binding proteins from mitochondria of Leishmania tarentolae catalyzes RNA annealing and interacts with several RNA editing components
Authors: APHASIZHEV RUSLAN , APHASIZHEVA INNA , NELSON ROBERT E. , SIMPSON LARRY
Published: January 2003

A stable 100-kD complex from mitochondria of Leishmania tarentolae containing two RNA-binding proteins, Ltp26 and Ltp28, was identified by cross-linking to unpaired 4-thiouridine nucleotides in a partially duplex RNA substrate. The genes were cloned and expressed and the complex was reconstituted from recombinant proteins in the absence of RNA or additional factors. The Ltp26 and Ltp28 proteins are homologs of gBP27 and gBP29 from Crithidia fasciculata and gBP25 and gBP21 from Trypanosoma brucei, respectively. The purified Ltp26/Ltp28 complex, the individual recombinant proteins, and the reconstituted complex are each capable of catalyzing the annealing of complementary RNAs, as was previously shown for gBP21 from T. brucei. A high-molecular-weight RNP complex consisting of the Ltp26/Ltp28 complex and several 55–60-kD proteins together with guide RNA could be purified from mitochondrial extract of L. tarentolae transfected with Ltp28-TAP. This complex also interacted in a less stable manner with the RNA ligase-containing L-complex and with the 3′ TUTase. The Ltp26/Ltp28 RNP complex is a candidate for catalyzing the annealing of guide RNA and pre-edited mRNA in the initial step of RNA editing.
Characterization of human Smg5/7a: A protein with similarities to Caenorhabditis elegans SMG5 and SMG7 that functions in the dephosphorylation of Upf1
Authors: CHIU SHANG-YI , SERIN GUILLAUME , OHARA OSAMU , MAQUAT LYNNE E.
Published: January 2003

Nonsense-mediated mRNA decay (NMD) in mammalian cells depends on phosphorylation of Upf1, an RNA-dependent ATPase and 5′-to-3′ helicase. Upf1 phosphorylation is mediated by Smg1, a phosphoinositol 3-kinase–related protein kinase. Here, we describe a human protein, which we call hSmg5/7a, that manifests similarity to Caenorhabditis elegans NMD factors CeSMG5 and CeSMG7, as well as two Drosophila melanogaster proteins that are also similar to the C. elegans NMD factors. Results indicate that hSmg5/7a functions in the dephosphorylation of Upf1. Furthermore, hSmg5/7a copurifies with Upf1, Upf2, Upf3X, Smg1, and the catalytic subunit of protein phosphatase 2A. We also demonstrate that Upf2, another factor involved in NMD, is a phosphoprotein. However, hSmg5/7a plays no role in the dephosphorylation of Upf2. These data indicate that hSmg5/7a targets protein phosphatase 2A to Upf1 but not Upf2. Results of Western blotting reveal that hSmg5/7a is mostly cytoplasmic in HEK293T cells.
Identification of the Hfq-binding site on DsrA RNA: Hfq binds without altering DsrA secondary structure
Authors: BRESCIA CRISTIN C. , MIKULECKY PETER J. , FEIG ANDREW L. , SLEDJESKI DARREN D.
Published: January 2003

DsrA RNA regulates the translation of two global regulatory proteins in Escherichia coli. DsrA activates the translation of RpoS while repressing the translation of H-NS. The RNA-binding protein Hfq is necessary for DsrA to function in vivo. Although Hfq binds to DsrA in vitro, the role of Hfq in DsrA-mediated regulation is not known. One hypothesis was that Hfq acts as an RNA chaperone by unfolding DsrA, thereby facilitating interactions with target RNAs. To test this hypothesis, we have examined the structure of DsrA bound to Hfq in vitro. Comparison of free DsrA to DsrA bound to Hfq by RNase footprinting, circular dichroism, and thermal melt profiles shows that Hfq does not alter DsrA secondary structures, but might affect its tertiary conformation. We identify the site on DsrA where Hfq binds, which is a structural element in the middle of DsrA. In addition, we show that although long poly(U) RNAs compete with DsrA for binding to Hfq, a short poly(U) stretch present in DsrA is not necessary for Hfq binding. Finally, unlike other RNAs, DsrA binding to Hfq is not competed with by poly(A) RNA. In fact, DsrA:poly(A):Hfq may form a stable ternary complex, raising the possibility that Hfq has multiple RNA-binding sites.
Gene silencing in Caenorhabditis elegans by transitive RNA interference
Authors: ALDER MATTHEW N. , DAMES SHALE , GAUDET JEFFREY , MANGO SUSAN E.
Published: January 2003

When a cell is exposed to double-stranded RNA (dsRNA), mRNA from the homologous gene is selectively degraded by a process called RNA interference (RNAi). Here, we provide evidence that dsRNA is amplified in Caenorhabditis elegans to ensure a robust RNAi response. Our data suggest a model in which mRNA targeted by RNAi functions as a template for 5′ to 3′ synthesis of new dsRNA (termed transitive RNAi). Strikingly, the effect is nonautonomous: dsRNA targeted to a gene expressed in one cell type can lead to transitive RNAi-mediated silencing of a second gene expressed in a distinct cell type. These data suggest dsRNA synthesized in vivo can mediate systemic RNAi.
Sequence requirements for micro RNA processing and function in human cells
Authors: ZENG YAN , CULLEN BRYAN R.
Published: January 2003

Most eukaryotes encode a substantial number of small noncoding RNAs termed micro RNAs (miRNAs). Previously, we have demonstrated that miR-30, a 22-nucleotide human miRNA, can be processed from a longer transcript bearing the proposed miR-30 stem-loop precursor and can translationally inhibit an mRNA-bearing artificial target sites. We also demonstrated that the miR-30 precursor stem can be substituted with a heterologous stem, which can be processed to yield novel miRNAs and can block the expression of endogenous mRNAs. Here, we show that a second human miRNA, termed miR-21, can also be effectively expressed when its precursor forms part of a longer mRNA. For both miR-30 and miR-21, mature miRNA production was highly dependent on the integrity of the precursor RNA stem, although the underlying sequence had little effect. In contrast, the sequence of the terminal loop affected miRNA production only moderately. Processing of the initial, miR-30-containing transcript led to the production of not only mature miR-30 but also to the largely nuclear excision of an ∼65-nucleotide RNA that is likely to represent an important intermediate in miR-30 processing. Consistent with this hypothesis, mutations that affected mature miR-30 production inhibited expression of this miR-30 pre-miRNA to an equivalent degree. Although point mutations could block the ability of both miR-30 and miR-21 to inhibit the translation of mRNAs bearing multiple artificial miRNA target sites, single point mutations only attenuated the miRNA-mediated inhibition of genes bearing single, fully complementary targets. These results suggest that miRNAs, and the closely similar small interfering RNAs, cannot totally discriminate between RNA targets differing by a single nucleotide.
Structure and function analysis of the poliovirus cis-acting replication element (CRE)
Authors: GOODFELLOW IAN G. , KERRIGAN DAVID , EVANS DAVID J.
Published: January 2003

The poliovirus cis-acting replication element (CRE) templates the uridylylation of VPg, the protein primer for genome replication. The CRE is a highly conserved structural RNA element in the enteroviruses and located within the polyprotein-coding region of the genome. We have determined the native structure of the CRE, defined the regions of the structure critical for activity, and investigated the influence of genomic location on function. Our results demonstrate that a 14-nucleotide unpaired terminal loop, presented on a suitably stable stem, is all that is required for function. These conclusions complement the recent analysis of the 14-nucleotide terminal loop in the CRE of human rhinovirus type 14. The CRE can be translocated to the 5′ noncoding region of the genome, at least 3.7-kb distant from the native location, without adversely influencing activity, and CRE duplications do not adversely influence replication. We do not have evidence for a specific interaction between the CRE and the RNA-binding 3CDpro complex, an essential component of the uridylylation reaction, and the mechanism by which the CRE is coordinated and orientated during the reaction remains unclear. These studies provide a detailed overview of the structural determinants required for CRE function, and will facilitate a better understanding of the requirements for picornavirus replication.
Degradation kinetics of meta‐ and para‐aromatic polyamides
Authors: Horta Arturo , Coca José , Díez Fernando V.
Published: January 2003

Poly(m‐phenylenediamineisophthal)amide (MPD‐I) and poly(p‐phenylenediamineterephthal)amide (PPD‐T) are among the most important high‐tech polymers. The degradation of three MPD‐I fibers with different molecular weight distributions and a PPD‐T fiber was studied in a proprietary laboratory degradation chamber. The results were fitted satisfactorily to a kinetic model describing the degradation as a combination of thermal scission, oxidation, and hydrolysis. PPD‐T degradation is slower than that of MPD‐I, and MPD‐I resistance to degradation increases as polydispersity decreases. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 15–21, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10031
2‐D numerical simulation of differential viscoelastic fluids in a single‐screw continuous mixer: Application of viscoelastic finite element methods
Authors: Connelly Robin K. , Kokini Jozef L.
Published: January 2003

Viscoelastic effects on mixing flows obtained with kneading paddles in a single‐screw, continuous mixer were explored using 2‐D finite element method numerical simulations. The single‐mode Phan–Thien Tanner nonlinear, viscoelastic fluid model was used with parameters for a dough‐like material. The viscoelastic limits of the simulations were found using elastic viscous stress splitting, 4 × 4 sub‐elements for stress, streamline upwind, and streamline upwind Petrov–Galerkin (SUPG). Mesh refinement and comparison between methods was also done. The single‐screw mixer was modeled by taking the kneading paddle as the point of reference, fixing the mesh in time. Rigid rotation and no slip boundary conditions at the walls were used with inertia taken into account. Results include velocity, pressure, and stress profiles. The addition of viscoelasticity caused the shear and normal stresses to vary greatly from the viscous results, with a resulting loss of symmetry in the velocity and pressure profiles in the flow region. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 22–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10038
Census and distribution of the golden lion tamarin (Leontopithecus rosalia)
Authors: Kierulff M. Cecília M. , Rylands Anthony B.
Published: January 2003

During 1990–1992, a survey of the golden lion tamarin,Leontopithecus rosalia, was carried out throughout its known distribution area. Forest remnants were identified by visual interpretation of Landsat‐TM satellite images. Localities occupied byL. rosaliawere first identified by interviews with local people. All forests more than 20 ha in size, and for which two or more interviews suggested the presence of the species, were surveyed using “play‐back” recordings of lion tamarin long calls. The total wild population ofL. rosalia, including that of the Poço das Antas Biological Reserve, was estimated to be 562 individuals in 109 groups. The lion tamarins were generally found in four major areas of forest (six or more groups per forest, not including Poço das Antas), with a further 12 groups isolated in small forest patches. Currently the species' distribution is restricted to just four municipalities in the state of Rio de Janeiro: Silva Jardim, Cabo Frio, Saquarema, and Araruama. Although they are typically confined to lowland forest of <300 m altitude,L. rosaliawas recorded at an altitude of 550 m in one locality. Average group size varied from 3.6 to 5.7 individuals, and densities from 0.39 groups/km2to 2.35 groups/km2(2.17 individuals/ km2to 8.53 individuals/km2). Six of the isolated groups found during the survey were successfully translocated to a forest of 2,400 ha. There is now also a significant population of reintroduced lion tamarins. Overall, however, the possibilities for further expansion of the wild population are severely limited. Am. J. Primatol. 59:29–44, 2003. © 2003 Wiley‐Liss, Inc.
Effect of dynamic vulcanization on properties and morphology of nylon/SAN/NBR blends: A new compatibilization method of nylon/ABS blends
Authors: Wang Zhongjian , Zhang Xiangfu , Zhang Yong , Zhang Yinxi , Zhou Wen
Published: January 2003

Dynamically vulcanized blends of nylon, styrene–acrylonitrile copolymer (SAN), and nitrile–butadiene rubber (NBR) were examined for mechanical properties, Shore D hardness, Vicat softening temperature, impact process, and phase morphology. The effect of a curing system such as phenolic formaldehyde resins (PF), dicumylperoxide (DCP), and a sulfur system on the mechanical properties of the nylon/SAN/NBR blends was studied, and dynamic vulcanization with a PF system was found to lead to outstanding toughness of the blends. The effect of PF content on the mechanical properties, Shore D hardness, and heat resistance of the nylon/SAN/NBR blends was also investigated. With increasing PF content the notched‐impact strength and Vicat softening temperature (VST) of the nylon/SAN/NBR (50/25/25) blends evidently improved, but tensile strength and Shore D hardness of the blends changed slightly. It can be concluded that the nylon/SAN/NBR (50/25/25) blends dynamically vulcanized by high‐content PF can attain excellent comprehensive mechanical properties, especially supertoughness, at room temperature. SEM was used to investigate the effect of dynamic vulcanization on disperse‐phase particle size, particle size distribution, and phase morphology. It was obvious that disperse‐phase particle size decreased with an increasing PF content. Thermal behavior and miscibility of dynamically vulcanized nylon/SAN/NBR with PF were investigated by DMTA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2057–2062, 2003
Functionalization of styrene–butadiene–styrene (SBS) triblock copolymer with glycidyl methacrylate (GMA)
Authors: Cordella Cristina D. , Cardozo Nilo S. M. , Neto Ricardo Baumhardt , Mauler Raquel S.
Published: January 2003

A styrene–butadiene–styrene triblock copolymer (SBS) was functionalized with glycidyl methacrylate (GMA). Grafting reactions were carried out in an internal mixer at 170°C, using dicumyl peroxide (DCP) as an initiator. The effect of three variables, % GMA, % DCP, and reaction time, on grafting were studied using a factorial design to analyze the experimental data. GMA was grafted onto SBS and its incorporation increased with the % GMA added. The factors levels studied indicated that was an optimum % DCP point about 0.1% w/w to achieve the best incorporation and conversion values. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2074–2079, 2003
Dynamic mechanical behavior of high‐density polyethylene/ethylene vinyl acetate copolymer blends: The effects of the blend ratio, reactive compatibilization, and dynamic vulcanization
Authors: John Biju , Varughese K. T. , Oommen Zachariah , Pötschke Petra , Thomas Sabu
Published: January 2003

The effects of the blend ratio, reactive compatibilization, and dynamic vulcanization on the dynamic mechanical properties of high‐density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blends have been analyzed at different temperatures. The storage modulus of the blend decreases with an increase in the EVA content. The loss factor curve shows two peaks, corresponding to the transitions of HDPE and EVA, indicating the incompatibility of the blend system. Attempts have been made to correlate the observed viscoelastic properties of the blends with the blend morphology. Various composite models have been used to predict the dynamic mechanical data. The experimental values are close to those of the Halpin–Tsai model above 50 wt % EVA and close to those of the Coran model up to 50 wt % EVA in the blend. For the Takayanagi model, the theoretical value is in good agreement with the experimental value for a 70/30 HDPE/EVA blend. The area under the loss modulus/temperature curve (LA) has been analyzed with the integration method from the experimental curve and has been compared with that obtained from group contribution analysis. The LA values calculated with group contribution analysis are lower than those calculated with the integration method. The addition of a maleic‐modified polyethylene compatibilizer increases the storage modulus, loss modulus, and loss factor values of the system, and this is due to the finer dispersion of the EVA domains in the HDPE matrix upon compatibilization. For 70/30 and 50/50 blends, the addition of a maleic‐modified polyethylene compatibilizer shifts the relaxation temperature of both HDPE and EVA to a lower temperature, and this indicates increased interdiffusion of the two phases at the interface upon compatibilization. However, for a 30/70 HDPE/EVA blend, the addition of a compatibilizer does not change the relaxation temperature, and this may be due to the cocontinuous morphology of the blends. The dynamic vulcanization of the EVA phase with dicumyl peroxide results in an increase in both the storage and loss moduli of the blends. A significant increase in the relaxation temperature of EVA and a broadening of the relaxation peaks occur during dynamic vulcanization, and this indicates the increased interaction between the two phases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2083–2099, 2003
New method for synthesizing polyorganozircosilazane as a Si/Zr/C/N‐based ceramic precursor
Authors: Liu Chunjuan , Yang Shiyan , Xu Caihong , Zhang Zhijie , Gao Wei , Xie Zemin
Published: January 2003

A new kind of polyorganozircosilazane as a Si/Zr/C/N‐based ceramic precursor was synthesized from the condensation reaction of hexamethylcyclotrisilazane lithium salts and zirconium tetrachloride. The pyrolysis of the precursor was carried out at 800°C under nitrogen. The results indicated that the precursor preparation temperature could affect the pyrolytic yields. The precursor, which was synthesized at 80°C, gave the highest pyrolytic yield. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2080–2082, 2003
Effect of interfacial stress on the crystalline structure of the matrix and the mechanical properties of high‐density polyethylene/CaCO3 blends
Authors: Zhang Yuncan , Pan Enli
Published: January 2003

A series of high‐density polyethylene (HDPE)/CaCO3 blends were prepared with different kinds of coupling agents, with CaCO3 particles of different sizes, and with matrixes of different molecular weights during the melt‐mixing of HDPE and CaCO3 particles. The mechanical properties of these blends and their dependence on the interfacial adhesion and matrix crystalline structure were studied. The results showed that the Charpy notched impact strength of these blends could be significantly improved with an increase in the interfacial adhesion or matrix molecular weight or a decrease in the CaCO3 particle size. When a CaCO3 surface was treated with a compounded coupling agent, the impact strength of the HDPE/CaCO3(60/40) blend was 62.0 kJ/m2, 2.3 times higher than that of unimproved HDPE; its Young's modulus was 2070 MPa, 1.07 times higher than that of unimproved HDPE. The heat distortion temperature of this blend was also obviously improved. The improvement of the mechanical properties and the occurrence of the brittle–tough transition of these blends were the results of a crystallization effect induced by the interfacial stress. When the interfacial adhesion was higher and the CaCO3 content was greater than 30%, the interfacial stress produced from matrix shrinkage in the blend molding process could strain‐induce crystallization of the matrix, leading to an increase in the matrix crystallinity and the formation of an extended‐chain (or microfibrillar) crystal network. The increase in the critical ligament thickness with an increasing matrix molecular weight was attributed to the strain‐induced areas becoming wider, the extended‐chain crystal layers becoming thicker, and the interparticle distance that formed the extended‐chain crystal network structure becoming larger with a higher matrix molecular weight. The formation of the extended‐chain crystal network and the increase in the matrix crystallinity were also the main reasons that Young's modulus and the heat distortion temperature of this blend were improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2120–2129, 2003
Thermal decomposition kinetics of photooxidized nylon 66
Authors: Singh R. P. , Desai Shrojal M. , Pathak G.
Published: January 2003

The thermoanalytical method offers a convenient means for testing a starting material before the end application. Differences in the kinetic parameters between neat and irradiated nylon 66 samples were estimated in the temperature range of 25°C–800°C by thermogravimetric analysis (TGA) and in the range of 25°C–300°C by differential scanning calorimetry (DSC). Under nitrogen flux the average activation energy for decomposition was in the range of 12.2–26.9 kcal/mol for the neat sample and 15.7–33.1 kcal/mol for the irradiated sample (250 h). Activation energy is affected by the process of bond breaking at the CN bonds, which is the rate‐determining step of the decomposition in nylon 66. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2146–2150, 2003
Preparation of porous hollow fiber membranes with a triple‐orifice spinneret
Authors: He T. , Mulder M. H. V. , Wessling M.
Published: January 2003

A triple‐orifice spinneret has been applied for the preparation of hollow fiber microfiltration membranes with a high surface porosity. Considering the general rules of diffusion induced phase separation, a low polymer concentration is required at the outer layer to obtain a highly interconnected open‐porous structure. Therefore, by using N‐methylpyrrolidone (NMP) as the external liquid at the outside orifice of the spinneret, a highly porous surface can be obtained. For a polymer solution containing a low molecular weight additive and with an initial concentration close to the cloud point, this technique shows slightly improvement on the pure water and gas fluxes since the major resistance of the membrane is located at the substructure and the inner skin. However, for a solution containing a high molecular weight additive and with an initial concentration far from the cloud point, a porous shell surface is obtained, resulting in a significant improvement in water flux. The effect of various external liquids on the morphology has been investigated as well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2151–2157, 2003
Pervaporation separation of a water–ethanol mixture by PSF–PEG membrane
Authors: Hsu Ching‐Shan , Liou Rey May , Chen Shih‐Hsiung , Hung Mu‐Ya , Tsia Hui‐An , Lai Juin‐Yih
Published: January 2003

For dehydrating a water–ethanol mixture by pervaporation, a polysulfone–And poly(ethylene glycol)(PSF–PEG) membrane was prepared. The separation performance of water and ethanol was found to strongly depend on the diffusion selectivity of permeates. On the other hand, the solubility selectivity of water to ethanol showed only minor change with an increasing PEG composition of the PSF–PEG membrane. This study found that the PEG content in a PSF–PEG membrane showed mobility enhancement of pervaporation properties and that the diffusion difference of permeates increased with increasing PEG content. The effect of PEG content on separation performance was a result of the improvement of the permeate diffusion properties of the PSF/PEG membrane. The diffusion difference in the membrane, not the solubility of water–ethanol in the membrane, was the dominant factor for the separation. Suitable PEG content in PSF/PEG membranes can prepare a high‐performance pervaporation membrane. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2158–2164, 2003
Pervaporation properties of aromatic/nonaromatic hydrocarbons of crosslinked membranes of copolymers based on diethyl vinylbenzylphosphonate
Authors: Wang Yong , Hirakawa Satoshi , Tanaka Kazuhiro , Kita Hidetoshi , Okamoto Ken‐ichi
Published: January 2003

Copoly(diethyl vinylbenzylphosphonate/hydroxyethyl methacrylate) [copoly(VBP–HEMA)] and copoly(diethyl vinylbenzylphosphonate/vinylbenzyl chloride) [copoly(VBP–VBC)] were prepared and their membranes crosslinked by a reaction of ethylene glycol diglycidyl ether and ethylene diamine with, respectively, hydroxyl and methylene chloride groups in their side chains. Pervaporation (PV) and sorption of benzene–n‐hexane (Bz–Hx), benzene–cyclohexane (Bz–Cx), and toluene–n‐octane (Tol–n‐Ot) mixtures were investigated. The membranes were in a rubbery state and preferentially permeable to aromatics. They had higher specific permeation flux and a lower PV separation factor compared with the crosslinked membranes of methacrylate copolymers with analogous pendant groups. They displayed better PV performance for Tol–n‐Ot. Sorption isotherms of Bz–Hx mixtures were represented by the Flory–Rehner model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2177–2185, 2003
Adalimumab, a fully human anti–tumor necrosis factor α monoclonal antibody, for the treatment of rheumatoid arthritis in patients taking concomitant methotrexate: The ARMADA trial
Authors: Weinblatt Michael E. , Keystone Edward C. , Furst Daniel E. , Moreland Larry W. , Weisman Michael H. , Birbara Charles A. , Teoh Leah A. , Fischkoff Steven A. , Chartash Elliot K.
Published: January 2003

Objective

To evaluate the efficacy and safety of adalimumab (D2E7), a fully human monoclonal tumor necrosis factor α antibody, in combination with methotrexate (MTX) in patients with active rheumatoid arthritis (RA) despite treatment with MTX.

Methods

In a 24‐week, randomized, double‐blind, placebo‐controlled study, 271 patients with active RA were randomly assigned to receive injections of adalimumab (20 mg, 40 mg, or 80 mg subcutaneously) or placebo every other week while continuing to take their long‐term stable dosage of MTX. The primary efficacy end point was the American College of Rheumatology criteria for 20% improvement (ACR20) at 24 weeks.

Results

An ACR20 response at week 24 was achieved by a significantly greater proportion of patients in the 20‐mg, 40‐mg, and 80‐mg adalimumab plus MTX groups (47.8%, 67.2%, and 65.8%, respectively) than in the placebo plus MTX group (14.5%) (P < 0.001). ACR50 response rates with the 20‐mg, 40‐mg, and 80‐mg adalimumab dosages (31.9%, 55.2%, and 42.5%, respectively) were significantly greater than that with placebo (8.1%) (P = 0.003, P < 0.001, and P < 0.001, respectively). The 40‐mg and 80‐mg doses of adalimumab were associated with an ACR70 response (26.9% and 19.2%, respectively) that was statistically significantly greater than that with placebo (4.8%) (P < 0.001 and P = 0.020). Responses were rapid, with the greatest proportion of adalimumab‐treated patients achieving an ACR20 response at the first scheduled visit (week 1). Adalimumab was safe and well tolerated; comparable numbers of adalimumab‐treated patients and placebo‐treated patients reported adverse events.

Conclusion

The addition of adalimumab at a dosage of 20 mg, 40 mg, or 80 mg administered subcutaneously every other week to long‐term MTX therapy in patients with active RA provided significant, rapid, and sustained improvement in disease activity over 24 weeks compared with MTX plus placebo.
Integrin‐mediated adhesion of human articular chondrocytes to cartilage
Authors: Kurtis Melissa S. , Schmidt Tannin A. , Bugbee William D. , Loeser Richard F. , Sah Robert L.
Published: January 2003

Objective

To determine 1) the kinetics and strength of adhesion of human articular chondrocytes to a cut cartilage surface, and 2) the role of specific integrins in mediating such adhesion, using an in vitro model.

Methods

Human articular chondrocytes isolated from cadaveric donors (mean ± SD age 38 ± 13 years) were cultured in high‐density or low‐density monolayer. Following release from culture with trypsin and a 2–2.5‐hour recovery period, chondrocytes were analyzed either for adhesion to cartilage or for integrin expression by flow cytometry.

Results

Following culture in monolayer, adhesion of chondrocytes to cartilage increased with time, from 6–16% at 10 minutes to a maximum of 59–82% at 80–320 minutes. After 80 minutes of adhesion, the resistance of cells to flow‐induced shear stress (50% detachment) was ∼21 Pa. Chondrocyte adhesion to cartilage decreased with pretreatment of cells with monoclonal antibodies that bound to and blocked certain integrins. After an 80‐minute incubation time, adhesion of chondrocytes cultured in high‐density monolayer decreased from the value of IgG1‐treated controls (55%) with blocking of the β1 integrin subunit (to 23%) or with blocking of α5β1 (to 36%). Following expansion of chondrocytes in low‐density monolayer, the mechanisms of adhesion to cartilage were generally similar. After an 80‐minute incubation time, adhesion of chondrocytes cultured in low‐density monolayer decreased from the value of IgG1‐treated controls (62%) with blocking of the β1 integrin subunit (to 30%) or with blocking of α5β1 (to 44%). Additionally, adhesion of these cells decreased to 46% by blocking of αvβ5, with a similar trend in effect for chondrocytes cultured in high‐density monolayer. Blocking of the α1 or α3 integrin subunits or αvβ3 had no detectable effect on adhesion, even though these receptors were detected by flow cytometry.

Conclusion

Under the culture and seeding conditions studied, β1, α5β1, and αvβ5 integrins mediate human chondrocyte adhesion to cartilage. These chondrocyte integrins have a potential role in the initial adhesion and retention of chondrocytes at a cartilage defect site following clinical procedures of chondrocyte transplantation.
Survival in rheumatoid arthritis: A population‐based analysis of trends over 40 years
Authors: Gabriel Sherine E. , Crowson Cynthia S. , Kremers Hilal Maradit , Doran Michele F. , Turesson Carl , O'Fallon W. Michael , Matteson Eric L.
Published: January 2003

Objective

To evaluate trends in and risk factors for mortality among patients with rheumatoid arthritis (RA) over a 40‐year period.

Methods

A population‐based inception cohort was assembled from among all Rochester, Minnesota residents ages ≥18 years who were first diagnosed with RA (fulfilling the 1987 American College of Rheumatology criteria for RA) between January 1, 1955 and December 31, 1994. Patients were followed up longitudinally through their entire medical records (including all inpatient and outpatient care by any provider) until death or migration from the county. Survival was described using the Kaplan‐Meier method. Observed and expected survival were compared using the log‐rank test, and standardized mortality ratios (SMRs) with expected survival were based on the sex and age of the study population and death rates from the Minnesota life tables. Cox proportional hazards models were used to estimate the influence of extraarticular manifestations and comorbidities, controlling for age, sex, body mass index (BMI), smoking, and rheumatoid factor positivity.

Results

Survival in this RA cohort was significantly lower than that expected in the population (P < 0.001) over the entire time period. Patients with RA were at significantly higher risk of death, with an SMR of 1.27 (95% confidence interval 1.13–1.41). Excess mortality among women was more pronounced than among men, with SMRs of 1.41 and 1.08, respectively. Presence of ≥1 extraarticular manifestation was the strongest predictor of mortality after adjusting for age, sex, BMI, smoking, and rheumatoid factor positivity.

Conclusion

Survival in RA patients is significantly lower than expected. The strongest predictors of survival appear to be those related to RA disease complications, specifically, extraarticular manifestations of the disease and comorbidities. More attention should be paid to mortality as an outcome measure in RA.
Induction of matrix metalloproteinase 1 gene expression is regulated by inflammation‐responsive transcription factor SAF‐1 in osteoarthritis
Authors: Ray Alpana , Kuroki Keiichi , Cook James L. , Bal B. Sonny , Kenter Keith , Aust Gabriela , Ray Bimal K.
Published: January 2003

Objective

To identify specific transcription factors that are activated in the cartilage tissue of osteoarthritis (OA) patients and are involved in the expression of matrix metalloproteinase 1 (MMP‐1).

Methods

DNase I footprint and electrophoretic mobility shift assays were performed to identify active elements of the MMP1 promoter and the transcription factors that interact with it. The relative abundance of the involved transcription factor in the cartilage was determined by immunohistochemical analysis. The role of serum amyloid A–activating factor 1 (SAF‐1) in MMP‐1 expression was assessed by transient transfection assay with plasmids containing either a functional or an antisense SAF‐1 complementary DNA.

Results

A novel promoter element was detected in the human MMP1 gene, and the inflammation‐responsive transcription factor SAF‐1 was found to interact with it. SAF‐1 activity was detected in the chondrocytes of OA cartilage, where most of the cells stained positive for SAF‐1. Overexpression of SAF‐1 in OA chondrocytes increased the expression of the MMP1 promoter, and interference of endogenous SAF‐1 activity by antisense SAF‐1 messenger RNA inhibited interleukin‐1–mediated MMP1 promoter activity.

Conclusion

The results indicate that SAF‐1 is involved in the regulation of MMP1 gene expression and it is highly abundant in the articular cartilage chondrocytes of OA patients. The data also demonstrate that control of SAF‐1 activity can suppress induced expression of MMP‐1. Conceivably, SAF‐1 could be a potential therapeutic target to control the overexpression of MMP‐1 associated with the pathogenesis of OA.
Rapid induction of peroxisome proliferator–activated receptor γ expression in human monocytes by monosodium urate monohydrate crystals
Authors: Akahoshi Tohru , Namai Rie , Murakami Yousuke , Watanabe Megumi , Matsui Toshimichi , Nishimura Akito , Kitasato Hidero , Kameya Toru , Kondo Hirobumi
Published: January 2003

Objective

Peroxisome proliferator–activated receptor γ (PPARγ) is a member of the nuclear hormone receptor superfamily and functions as a key regulator of lipid and glucose metabolism, atherosclerosis, and inflammatory responses. This study was undertaken to evaluate the biologic role of PPARγ in self‐limiting episodes of acute gouty arthritis. To do this, we investigated PPARγ expression by monosodium urate monohydrate (MSU) crystal–stimulated monocytes, and we studied the effects of PPARγ ligands on crystal‐induced acute inflammation.

Methods

PPARγ expression by MSU crystal–stimulated human peripheral blood mononuclear cells was determined by reverse transcription–polymerase chain reaction and immunostaining. Expression of CD36 on monocytes was detected by flow cytometric analysis. The effects of PPARγ ligands on in vitro crystal‐induced cytokine production and on in vivo cellular infiltration during crystal‐induced acute inflammation were also investigated.

Results

MSU crystals rapidly and selectively induced PPARγ expression by monocytes. Gene expression was detected as early as 2 hours, and maximum expression was observed at 4 hours after stimulation. The induced PPARγ was functional, since a PPARγ ligand was able to up‐regulate CD36 expression on monocytes. A natural ligand of PPARγ, 15‐deoxy‐Δ12,14‐prostaglandin J2 (15deoxy‐PGJ2), significantly reduced the crystal‐induced production of cytokines by monocytes. Indomethacin inhibited cytokine production only at high concentrations, and an antidiabetic thiazolidinedione (troglitazone) failed to exert significant effects. Administration of troglitazone and 15deoxy‐PGJ2 significantly prevented cellular accumulation in a mouse air‐pouch model of MSU crystal–induced acute inflammation.

Conclusion

Rapid induction of PPARγ expression on monocytes by MSU crystals may contribute, at least in part, to the spontaneous resolution of acute attacks of gout.
Long‐term efficacy and safety of etanercept in children with polyarticular‐course juvenile rheumatoid arthritis: Interim results from an ongoing multicenter, open‐label, extended‐treatment trial
Authors: Lovell Daniel J. , Giannini Edward H. , Reiff Andreas , Jones Olcay Y. , Schneider Rayfel , Olson Judyann C. , Stein Leonard D. , Gedalia Abraham , Ilowite Norman T. , Wallace Carol A. , Lange Mary , Finck Barbara K. , Burge Daniel J. ,   for the Pediatric Rheumatology Collaborative Study Group
Published: January 2003

Objective

To evaluate the long‐term efficacy and safety of etanercept in children with juvenile rheumatoid arthritis (JRA) participating in an ongoing multicenter, open‐label, extended‐treatment trial. All patients had been participants in an initial randomized efficacy and safety trial of etanercept.

Methods

Etanercept was administered at a dosage of 0.4 mg/kg (maximum 25 mg) subcutaneously twice each week. Safety and efficacy evaluations were performed every 3–4 months. The JRA 30% definition of improvement (DOI) was defined as improvement of ≥30% in at least 3 of 6 response variables used to assess disease activity, with no more than 1 variable worsening by more than 30%.

Results

At the time of analysis, 48 of the 58 patients (83%) were still enrolled in the study; 43 of them (74%) had completed 2 years of treatment. Of these 43 patients, 81% met the JRA 30% DOI, 79% met the JRA 50% DOI, and 67% met the JRA 70% DOI. Ten children started low‐dose methotrexate after year 1. Of the 32 children taking prednisone, the dosage was decreased to <5 mg/day in 26 (81%). Two children had serious infections (varicella with aseptic meningitis in one and complicated sepsis in the other). In general, adverse events were of the types seen in a general pediatric patient population.

Conclusion

Children with severe, longstanding, methotrexate‐resistant polyarticular JRA demonstrated sustained clinical improvement with >2 years of continuous etanercept treatment. Etanercept was generally well‐tolerated. There were no increases in the rates of adverse events over time. However, children taking etanercept should be monitored closely for infections.
Tachykinin expression in cartilage and function in human articular chondrocyte mechanotransduction
Authors: Millward‐Sadler S. J. , Mackenzie A. , Wright M. O. , Lee H.‐S. , Elliot K. , Gerrard L. , Fiskerstrand C. E. , Salter D. M. , Quinn J. P.
Published: January 2003

Objective

To assess whether substance P and the corresponding neurokinin 1 (NK1) receptor are expressed in human articular cartilage, and whether these molecules have a role in chondrocyte mechanotransduction.

Methods

Transgenic studies, immunohistochemistry, Western blotting, and reverse transcriptase–polymerase chain reaction were used to assess the expression of the preprotachykinin (PPT) gene, substance P, and NK1 in developing mice, in adult human articular cartilage, and in human chondrocytes in culture. Chondrocytes obtained from PPT knockout mice and human articular chondrocytes were mechanically stimulated in the presence or absence of inhibitors of substance P signaling, and cell membrane potentials or relative levels of aggrecan messenger RNA (mRNA) were measured.

Results

Replacing a region of the PPT gene transcriptional site that contains a dominant repressor of the proximal promoter activity with the constitutive minimal promoter of the human β‐globin promoter allowed expression of a marker gene in areas of chondrogenesis during mouse development and in adult chondrocytes grown in culture. Adult human articular chondrocytes expressed endogenous PPT mRNA, substance P, and the corresponding NK1 receptor in vivo and in vitro. Blockade of substance P signaling by a chemical antagonist to the NK1 receptor inhibited chondrocyte responses to mechanical stimulation.

Conclusion

Substance P is expressed in human articular cartilage and is involved in chondrocyte mechanotransduction via the NK1 receptor in an autocrine and paracrine manner. This suggests that substance P and the NK1 receptor have roles in the maintenance of articular cartilage structure and function that were previously unrecognized.