bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exploring polyethylenimine‐mediated DNA transfection and the proton sponge hypothesis
Authors: Akinc Akin , Thomas Mini , Klibanov Alexander M. , Langer Robert 
Published: November 2004

AbstractBackgroundThe relatively high transfection efficiency of polyethylenimine (PEI) vectors has been hypothesized to be due to their ability to avoid trafficking to degradative lysosomes. According to the proton sponge hypothesis, the buffering capacity of PEI leads to osmotic swelling and rupture of endosomes, resulting in the release of the vector into the cytoplasm.MethodsThe mechanism of PEI‐mediated DNA transfer was investigated using quantitative methods to study individual steps in the overall transfection process. In addition to transfection efficiency, the cellular uptake, local pH environment, and stability of vectors were analyzed. N‐Quaternized (and therefore non‐proton sponge) versions of PEI and specific cell function inhibitors were used to further probe the proton sponge hypothesis.ResultsBoth N‐quaternization and the use of bafilomycin A1 (a vacuolar proton pump inhibitor) reduced the transfection efficiency of PEI by approximately two orders of magnitude. Chloroquine, which buffers lysosomes, enhanced the transfection efficiency of N‐quaternized PEIs and polylysine by 2–3‐fold. In contrast, chloroquine did not improve the transfection efficiency of PEI. The measured average pH environment of PEI vectors was 6.1, indicating that they successfully avoid trafficking to acidic lysosomes. Significantly lower average pH environments were observed for permethyl‐PEI (pH 5.4), perethyl‐PEI (pH 5.1), and polylysine (pH 4.6) vectors. Cellular uptake levels of permethyl‐PEI and perethyl‐PEI vectors were found to be 20 and 90% higher, respectively, than that of parent PEI vectors, indicating that the reduction in transfection activity of the N‐quaternized PEIs is due to a barrier downstream of cellular uptake. A polycation/DNA‐binding affinity assessment showed that the more charge dense N‐quaternized PEIs bind DNA less tightly than PEI, demonstrating that poor vector unpackaging was not responsible for the reduced transfection activity of the N‐quaternized PEIs.ConclusionsThe results obtained are consistent with the proton sponge hypothesis and strongly suggest that the transfection activity of PEI vectors is due to their unique ability to avoid acidic lysosomes. Copyright © 2004 John Wiley & Sons, Ltd.
Raman spectroscopic study of non‐catalytic hydrogenation of unsaturated rubbers
Authors: Samran Jareerat , Phinyocheep Pranee , Daniel Philippe , Derouet Daniel , Buzaré Jean‐Yves 
Published: November 2004

AbstractThe non‐catalytic hydrogenation of natural rubber (NR) and two epoxidized NRs (ENRs) i.e. ENR‐22 and ENR‐40 containing 22 and 40 mol% of epoxide, respectively, was carried out using p‐toluenesulfonylhydrazide (TSH) as a hydrogenating agent. A two‐fold molar excess of TSH compared with unsaturated units of the rubber was used. The evidence of hydrogenation is a decrease in the intensity of the characteristic signal of the carbon–carbon double bond stretching vibration of the rubber in both the Raman and FT‐IR spectra. The percentage hydrogenation was successfully determined by Raman spectroscopy since the vibrational mode of the carbon–carbon unsaturation is strongly Raman active. The progress of the hydrogenation could be monitored by means of the techniques mentioned above as a function of reaction time. The maximum degree of hydrogenation of NR is ∼89% whereas in the case of ENR‐22 and ENR‐40 it reaches 94 and 96%, respectively. Solid‐state 13C NMR spectroscopy was also used to confirm the microstructure characteristics of the hydrogenated rubbers. 13C NMR analysis showed that cis–trans isomerization of carbon–carbon unsaturations occur during hydrogenation. Copyright © 2004 John Wiley & Sons, Ltd.
Physical Characterization of Coupled Poly(lactic acid)/Starch/Maleic Anhydride Blends Plasticized by Acetyl Triethyl Citrate
Authors: Zhang Jian‐Feng , Sun Xiuzhi 
Published: November 2004

AbstractSummary: Acetyl triethyl citrate (ATC) was used as a plasticizer for poly(lactic acid) (PLA)/starch blends coupled with maleic anhydride and an initiator of 2,5‐bis(tert‐butylperoxy)‐2,5‐dimethylhexane (L101). Elongation of the blend at break was markedly increased when the ATC content was above the 8% loading level, which is referred to as the percolation threshold. The extended elongation was achieved at the expense of tensile strength and elastic modulus. Thermal transitions of the blend, including the glass transition temperature (Tg), cold crystallization temperature (Tc) and melting temperature (Tm), decreased with ATC content. Thermally induced ATC migration affected the thermal behavior of the plasticized blends and reduced elongation and tensile strength, whereas the elasticity modulus increased. ATC migration increased with ambient temperature, which was controlled by the activation energy of the blend system. Leaching of ATC was slow at room temperature in distilled water, but significant in boiling water. Additionally, the leaching rate was also directly proportional to the ATC content of the blend.Glass transition temperatures of PLA/starch/MA/L101 blends with various acetryl triethyl citrate contents.magnified imageGlass transition temperatures of PLA/starch/MA/L101 blends with various acetryl triethyl citrate contents.
High‐Molecular‐Weight Polyketones from Higher α‐Olefins: A General Method
Authors: Pérez‐Foullerat David , Meier Uwe W. , Hild Sabine , Rieger Bernhard 
Published: November 2004

AbstractSummary: A method to optimize the polymerization conditions in order to favor chain propagation is described for the synthesis of polymers containing low reactive, long, linear 1‐olefins and carbon monoxide (CO). It consists of the use of the olefin monomer as the polymerization solvent, together with the emulsification of a carefully chosen immiscible activator. This is given as a general method applicable to different families of catalyst able to produce 1,4‐polyketones. When the catalyst precursor is [dpppPd(NCCH3)2](BF4)2, which has been extensively studied, the polymerization degrees are the highest published (up to 2.4 × 105 g · mol−1). The influence of parameters like temperature, CO pressure, volume of activator, and catalyst counter ion or ligand substitutions are reported. Some chemical and physical properties of the polymers, such as glass transition temperature, melting processes, and mechanical behavior, are examined and compared with the linear 1‐olefin homologues from C3 to C10. These properties are shown in some cases to be unprecedented.DSC profiles from the 1st scan for α‐olefin/CO copolymers.magnified imageDSC profiles from the 1st scan for α‐olefin/CO copolymers.
Hybrid particle methods in frictionless impact‐contact problems
Authors: Huang H. , Dyka C. T. , Saigal S. 
Published: November 2004

AbstractThe dual particle dynamic (DPD) methods which employ two sets of particles have been demonstrated to have better accuracy and stability than the co‐locational particle methods, such as the smooth particle hydrodynamics (SPH). The hybrid particle method (HPM) is an extension of the DPD method. Besides the advantages of the DPD method, the HPM possesses features which better facilitate the simulation of large deformations. This paper presents the continued development of the HPM for the numerical solution of two‐dimensional frictionless contact problems. The interface contact force algorithm which employs a modified kinematic constraints method is used to determine the contact tractions. In this method, both the impenetrability condition and the traction condition are simultaneously enforced. In the original kinematic constraints method, only the former condition is satisfied. A new formulation to find stress derivatives at stress‐free corners by imposing stress‐free boundary conditions is also developed. The results for 1‐D and 2‐D contact problems indicate good accuracy for the contact formulation as well as the corner treatment when compared to analytical solutions and explicit finite element results using the commercial code LS‐DYNA. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and polymerization of new self‐polymerizable quinoxaline monomers
Authors: Baek Jong‐Beom , Harris Frank W. 
Published: November 2004

AbstractExtended self‐polymerizable poly(phenylquinoxaline) monomer mixtures {i.e.,2‐[4‐(4‐hydroxyphenoxy)phenyl]‐3‐phenyl‐6‐chloroquinoxaline and 3‐[4‐(4‐hydroxy phenoxy)phenyl]‐2‐phenyl‐6‐chloroquinoxaline, 2‐[4‐(4‐hydroxyphenoxy)phenyl]‐3‐phenyl‐6‐fluoroquinoxaline and 3‐[4‐(4‐hydroxyphenoxy)phenyl]‐2‐phenyl‐6‐fluoroquinoxaline, and 2‐(4‐fluorophenyl)‐3‐phenyl‐6‐(4‐hydroxyphenoxy)quinoxaline and 3‐(4‐fluorophenyl)‐2‐phenyl‐6‐(4‐hydroxyphenoxy)quinoxaline} more flexible and nucleophilic than a previously reported monomer mixture [i.e., 3‐(4‐hydroxyphenyl)‐2‐phenyl‐6‐fluoroquinoxaline and 2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline] were synthesized. The monomer mixtures were then polymerized into high‐molecular‐weight polymers. A sample was obtained, through a chlorine displacement reaction, that was a semicrystalline polymer with an intrinsic viscosity of 1.11 dL/g in m‐cresol at 30 ± 0.1 °C and two melting temperatures at 339 and 377 °C in the first differential scanning calorimetry scan. There was a melting temperature at 328 °C without a detectable glass‐transition temperature (Tg) when the sample was subjected to a second differential scanning calorimetry scan. The samples from fluorine displacement reactions were completely amorphous polymers. They had intrinsic viscosities of 0.53–0.90 dL/g in m‐cresol at 30 ± 0.1 °C and Tg's of 220–224 °C. The polymer samples from fluorine displacement reactions were evaluated with gel permeation chromatography and matrix‐assisted laser desorption/ionization time‐of‐flight analyses, which monitored the existence of certain amounts of cyclic oligomers. The thin films of the polymers had room‐temperature tensile strengths of 97–113 MPa, room‐temperature Young's moduli of 2.30–2.35 GPa, and room‐temperature elongations at break of 40–150%. The melt viscosity decreased from 107 to less than 104 Pa s at 310 °C as the frequency was increased from 10−2 to 102 rad/s. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 78–91, 2005
An Empirical Bayes Process Monitoring Technique for Polytomous Data
Authors: Shiau Jyh‐Jen H. , Chen Chih‐Rung , Feltz Carol J. 
Published: November 2004

AbstractWhen a product item is tested, usually one has more information than just pass or fail. Often there are categories of failure modes. The purpose of this paper is to develop a method to monitor the fractions of the tested items falling into different categories of pass/fail modes. Using the multinomial model with Dirichlet prior, we describe the theory underlying an empirical Bayes approach to monitoring polytomous data generated in manufacturing processes. A pseudo maximum likelihood estimator (PMLE) and the method‐of‐moments estimator (MME) of the hyperparameters of the prior distribution are considered and compared by a simulation study. It is found that the PMLE performs slightly better than the MME. A monitoring scheme based on the marginal distributions of the observed pass/fail fractions is proposed. The average run length behavior of the proposed monitoring scheme is investigated. Finally, an example to illustrate the use of the technique is given. Copyright © 2004 John Wiley & Sons, Ltd.
Ultrasound detection of nuchal cord prior to labor induction and the risk of Cesarean section
Authors: Peregrine E. , O'Brien P. , Jauniaux E. 
Published: November 2004

AbstractObjectivesTo investigate the ability of ultrasound to detect the presence of a nuchal cord immediately prior to induction of labor and the association of its presence with delivery by Cesarean section.MethodsA transabdominal ultrasound scan using gray‐scale and color Doppler imaging was performed immediately prior to induction of labor in 289 women in a prospective study to assess the presence of a nuchal cord. The presence of a nuchal cord was classified as present, absent or uncertain. The outcomes of labor, delivery and the neonates were obtained from the patient notes after delivery.ResultsA nuchal cord was present at 18% of deliveries. The incidence was not affected by parity, fetal position or reduced amniotic fluid volume. The sensitivity of ultrasound in diagnosing a nuchal cord was 37.5%, with specificity, positive and negative predictive values of 80%, 29% and 85%, respectively. The presence of a nuchal cord did not significantly increase the risk of delivery by Cesarean section (35% vs. 28%; relative risk = 1.22; 95% CI, 0.80–1.87), instrumental delivery for fetal distress, an abnormal cardiotocograph in labor or at delivery, an Apgar score < 7 at 1 min, arterial cord pH < 7.1 or neonatal unit admission.ConclusionsThe sensitivity of the ultrasound diagnosis of a nuchal cord is low prior to induction of labor at term. A nuchal cord does not appear to increase the risk of Cesarean section or of poor neonatal outcome. The low ultrasound detection rate of a nuchal cord limits its use in decision making prior to induction of labor in high‐risk pregnancies. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Posttranslational activation, site‐directed mutation and phylogenetic analyses of the lysine biosynthesis enzymes α‐aminoadipate reductase Lys1p (AAR) and the phosphopantetheinyl transferase Lys7p (PPTase) from Schizosaccharomyces pombe
Authors: Guo Shujuan , Bhattacharjee J. K. 
Published: November 2004

Abstractα‐Aminoadipate reductase (AAR), the signature enzyme for lysine biosynthesis in fungi, catalyses the conversion of α‐aminoadipate to α‐aminoadipate‐semiadehyde in the presence of ATP and NADPH. In Saccharomyces cerevisiae and Candida albicans, the LYS2‐encoded AAR is posttranslationally activated by CoA and the LYS5‐encoded PPTase. The fission yeast Schizosaccharomyces pombe is evolutionarily highly diverged from S. cerevisiae and C. albicans. We report here several unusual activation characteristics of Sz. pombe Lys1p and Lys7p, isofunctional to Lys2p (AAR) and Lys5p (PPTase), respectively. Unlike the Lys2p from S. cerevisiae and C. albicans, the Sz. pombe Lys1p was active when expressed in E. coli and exhibited significant AAR activity without the addition of CoA or the Sz. pombe Lys7p intron free PPTase. Somewhat higher AAR activity was obtained with the addition of CoA and the Sz. pombe Lys7p PPTase. Substitution of G910A, S913T or S913A in the Sz. pombe Lys1p activation domain (IGGHSI) resulted in no AAR activity. Similarly, substitutions of several amino acid residues in the Sz. pombe Lys7p PPTase domain (G79A, R80K and P81A in Core 1; F93W, D94E, F95W and N96D in Core 1a; G124A, V125I and D126E in Core 2; K172R, E173D and K177R in Core 3) also resulted in no activation of Lys1p and no AAR activity. The Sz. pombe Lys1p amino acid sequence showed a high degree of similarity to other fungal Lys2p proteins; however, the Lys7p amino acid sequence showed much less similarity to other bacterial, fungal and animal PPTases representing several phylogenetic groups. Copyright © 2004 John Wiley & Sons, Ltd.
Segmental glomerulosclerosis in IgA nephropathy after renal transplantation: relationship with proteinuria and therapeutic response to enalapril
Authors: Jeong Hyeon Joo , Kim Yu Seun , Kwon Kye Won , Kim Myoung Soo , Kim Soon , Choi Kyu Hun , Lee Ho Yung , Han Dae Suk , Park Kiil 
Published: November 2004

Abstract: Introduction:Although graft dysfunction has been increasingly reported in post‐transplant IgA nephropathy (Tx‐IgAN), intragraft morphological changes have been largely overlooked. We evaluated glomerular changes in Tx‐IgAN to identify the histological features pertaining to significant proteinuria and therapeutic response to enalapril.Materials and methods:Fifty‐four renal allograft biopsies, diagnosed as Tx‐IgAN at a median of 46 months after transplantation, were the subject of the study. In 10 patients, glomerular morphometry was performed. In 14 patients who have been treated with enalapril for more than 12 months, we correlated the therapeutic response to enalapril with allograft histology.Results:No uniform pattern was found in the glomeruli of Tx‐IgAN. The glomerular mesangium was mostly indistinct. Interstitial fibrosis was negative or mild in 88.9%. By morphometry, the glomerular tuft areas and mesangial areas were significantly larger in Tx‐IgAN than those of the normal native kidney (p < 0.05), but were not different from transplant cases without glomerulonephritis. Proteinuria of ≥1 g/24 h was correlated with glomerulosclerosis, interstitial fibrosis and interstitial inflammation at time of biopsy (p < 0.005). The presence of segmental sclerosis (SS) correlated well with the amount of 24‐h proteinuria (p < 0.001). After treatment with enalapril, the amount of proteinuria reduced in 64.3%. Therapeutic response to enalapril tended to be less effective in patients having SS (28.6 versus 71.4%), but this finding did not reach a statistical significance.Conclusions:Significant proteinuria was associated with advanced chronic injury, especially with the presence of SS in Tx‐IgAN, but anti‐proteinuric effect of enalapril was not affected by graft histology. It remains to be clarified whether glomerular mesangial expansion plays a role in graft dysfunction in a subset of Tx‐IgAN showing prominent mesangial changes.
Macrophage depletion improves survival of porcine neonatal pancreatic cell clusters contained in alginate macrocapsules transplanted into rats
Authors: Omer Abdulkadir , Keegan Mitchell , Czismadia Eva , De Vos Paul , Van Rooijen Nico , Bonner‐Weir Susan , Weir Gordon C. 
Published: November 2004

Omer A, Keegan M, Czismadia E, De Vos P, Van Rooijen N, Bonner‐Weir S and Weir GC. Macrophage depletion improves survival of porcine neonatal pancreatic cell clusters contained in alginate macrocapsules transplanted into rats. Xenotransplantation 2003; 10: 240–251. © Blackwell Munksgaard 2003Background: Macrophages can accumulate on the surface of empty and islet‐containing alginate capsules, leading to loss of functional tissue. In this study, the effect of peritoneal macrophage depletion on the biocompatibility of alginate macrocapsules and function of macroencapsulated porcine neonatal pancreatic cell clusters (NPCCs) was investigated. Methods: Clodronate liposomes were injected into the peritoneal cavities of normoglycemic Lewis rats 5 and 2 days before the transplantation. Empty or NPCC‐containing Ca‐alginate poly L‐lysine (PLL)‐coated macrocapsules were transplanted into the peritoneal cavities of rats injected with either clodronate liposomes or saline. On days 7, 14 and 21, samples were evaluated by immunohistochemistry for cellular immune responses on the surface of the macrocapsules and for macrophage populations in omental tissue. To assess the function of macroencapsulated NPCCs, insulin secretory responses to glucose and theophylline were measured after capsule retrieval. Results: In saline‐injected control groups, all of the empty and NPCC‐containing macrocapsules were overgrown with macrophages, this being especially severe on NPCC‐containing macrocapsules. In the clodronate liposomes‐injected group, the majority of the empty macrocapsules were free of macrophage accumulation and the NPCC‐containing macrocapsules were less overgrown than in control animals. Higher insulin responses to glucose and theophylline were observed in NPCCs retrieved from rats injected with clodronate liposomes. Conclusion: We conclude that depletion of peritoneal macrophages with clodronate liposomes improve the survival of macroencapsulated NPCCs.
Advances in imaging: impact on studying craniofacial bone structure
Authors: Majumdar S 
Published: November 2004

Abstract
Author– Majumdar SMethods for measuring the structure of craniofacial bones are discussed in this paper. In addition to the three‐dimensional macro‐structure of the craniofacial skeleton, there is considerable interest in imaging the bone at a microscopic resolution in order to depict the micro‐architecture of the trabecular bone itself. In addition to the density of the bone, the micro‐ architecture reflects bone quality. An understanding of bone quality and density changes has implications for a number of craniofacial pathologies, as well as for implant design and understanding the biomechanical function and loading of the jaw. Trabecular bone micro‐architecture has been recently imaged using imaging methods such as micro‐computed tomography, magnetic resonance imaging, and the images have been used in finite element models to assess bone mechanical properties. In this paper, some of the recent advances in micro‐computed tomography and magnetic resonance imaging are reviewed, and their potential for imaging the trabecular bone in mandibular bones is presented. Examples of in vitro and in vivo images are presented.
Using three‐dimensional imaging to assess treatment outcomes in orthodontics: a progress report from the University of the Pacific
Authors: Baumrind S , Carlson S , Beers A , Curry S , Norris K , Boyd RL 
Published: November 2004

Abstract
Authors– Baumrind S, Carlson S, Beers A, Curry S, Norris K, Boyd RLPast research in integrated three‐dimensional (3D) craniofacial mapping at the Craniofacial Research Instrumentation Laboratory (CRIL) of the University of the Pacific is summarized in narrative form. The advantages and limitations of recent commercial developments in the application of cone beam geometry volumetric X‐ray scanners in dentistry and surface digital mapping of study casts are discussed. The rationale for methods currently in development at CRIL for merging longitudinal information from existing 3D study casts and two‐dimensional lateral X‐ray cephalograms in studies of orthodontic treatment outcome is presented.
Measurement of mechanical strain on mandibular surface with mastication robot: influence of muscle loading direction and magnitude
Authors: Usui T , Maki K , Toki Y , Shibasaki Y , Takanobu H , Takanishi A , Hatcher D , Miller A 
Published: November 2004

Structured Abstract
Authors– Usui T, Maki K, Toki Y, Shibasaki Y, Takanobu H, Takanishi A, Hatcher D, Miller A
Objectives –
To investigate the mechanical effects of mastication on the mandible, we developed computational controlled mastication robot system with human dry skull and analyzed the strain distribution on the mandibular bone surface.
Design –
In the mastication robot, the mandible was suspended by eight wires, which simulated masticatory muscles. A non‐linear spring damper generated viscoelastic properties, and tension sensors for simulation of jaw reflection to avoid unusual biting force were applied as a biological feedback mechanism. By using this robot system, various patterns of muscle loading (change of wire direction and magnitude) were performed.
Results –
From the results, significant differences in the amount of principal strain and its distribution were demonstrated in each condition (ANOVA, post hoc test, and p < 0.05). The value of maximum principal strain ranged from 79.66 × 10−6 [at anterior border of ramus (Buccal side), 128 N] to −1.42 × 10−6 [at foramen mentale (Buccal side), 32 N].
Conclusion –
These results suggested that the muscle loading generated the mechanical strain on the mandibular bone surface and it was affected by the changes in loading direction and magnitude.