bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and characterization of aromatic cyclolinear phosphazene polyetherketones containing bis‐Spiro‐substituted cyclotriphosphazene unit
Authors: Tunca Umit , Erdogmus Ali , Hizal Gurkan
Published: August 2002

A novel monomer, 2,2‐bis‐(4′‐fluorobenzoylphenoxy)‐4,4,6,6‐bis[spiro‐(2′,2″‐dioxy‐1′, 1′‐biphenylyl)] cyclotriphosphazene, was synthesized and polymerized with 4,4′‐difluorobenzophenone as a comonomer and 4,4′‐isopropylidenediphenol or 4,4′‐(hexafluoroisopropylidene) diphenol in N,N‐dimethylacetamide at 162 °C for 4 h to give two series of aromatic cyclolinear phosphazene polyetherketones containing bis‐spiro‐substituted cyclotriphosphazene groups. The structure of the monomer was confirmed by 1H, 13C, and 31P NMR. The effect of the incorporation of the bis‐spiro‐substituted cyclotriphosphazene group on the thermal properties of these polymers was investigated by DSC and thermogravimetric analysis. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2993–2997, 2001
Analysis of ethylene oxide sequences of the acetal copolymer from trioxane and ethylene oxide
Authors: Yamasaki Naoaki , Kanaori Kenji , Masamoto Junzo
Published: August 2002

An NMR method for the analysis of the ethylene oxide sequence of the acetal copolymer from trioxane and ethylene oxide has not yet been established. We found three novel cyclic compounds composed of 1 mol of ethyelene oxide and 1 mol of trioxane, 2 mol of ethylene oxide and 1 mol of trioxane, and 3 mol of ethylene oxide and 1 mol of trioxane. These compounds gave only one consecutive oxyethylene unit, two consecutive oxyethylene units, and three consecutive oxyethylene units in three consecutive oxymethylene units, respectively, and gave different 1H NMR spectra for each oxyethylene unit. Considering these data, we synthesized three polymeric model compounds that have one consecutive oxyethylene sequence, two consecutive oxyethylene sequences, and three consecutive oxyethylene sequences in an oxymethylene main chain. By a linear combination of the 1H NMR spectrum of each oxyethylene unit of the three polymeric model compounds, we succeeded in determining the ethylene oxide sequence by the 1H NMR method for the copolymer from trioxane and ethylene oxide. Good agreement was observed between the 1H NMR method and the hydrolysis method for the analysis of the ethylene oxide sequences. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3239–3245, 2001
Lamellar‐level morphology induced by combined crystallization and liquid–liquid demixing in a poly(ethylene terephthalate)/poly(ethylene‐2,6‐naphthalate) blend
Authors: Lee Jong Kwan , Bang Hyo Jae , Lee Kwang Hee
Published: August 2002

The lamellar‐level morphology of an extruded poly(ethylene terephthalate) (PET)/poly(ethylene‐2,6‐naphthalate) (PEN) blend was investigated with small‐angle X‐ray scattering (SAXS). Measurements were made as a function of the annealing time in the melt and the crystallization temperature. The characteristic morphological parameters at the lamellar level were determined by correlation function analysis of the SAXS data. At a low crystallization temperature of 120 °C, the increased amorphous layer thickness was identified in the blend, indicating that some PEN was incorporated into the interlamellar regions of PET during crystallization. The blend also showed a larger lamellar thickness than pure PET. A reason for the increase in the lamellar thickness might be that the formation of thinner lamellar stacks by secondary crystallization was significantly restricted because of the increased glass‐transition temperature. At high crystallization temperatures above 200 °C, the diffusion rates of noncrystallizable components were faster than the growth rates of crystals, with most of the noncrystallizable components escaping from the lamellar stacks. As a result, the blend showed an interfibrillar or interspherulitic morphology. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 317–324, 2002
Structure and properties of the mesophase of syndiotactic polystyrene. I. Effect of casting conditions on the preparation of the mesophase
Authors: Rani D. Amutha , Yamamoto Y. , Saito A. , Sivakumar M. , Tsujita Y. , Yoshimizu H. , Kinoshita T.
Published: August 2002

A syndiotactic polystyrene–toluene solution was cast under two different casting conditions to obtain the δ form. A systematic study of its conformational transition, thermal behavior, and structural transformation as functions of the annealing temperature and time was performed. Spectroscopic studies revealed the content of its helical conformations and its retention up to 190 °C. Thermal analyses showed a significant difference in the transformation from the γ form to the α form. The retention of the intermediate emptied clathrate form (mesophase) of the conformational order for a longer duration (from 120 to 180 °C) in a syndiotactic polystyrene membrane cast at room temperature was confirmed by X‐ray diffraction analysis. On the basis of the experimental results in this work, the transition mechanism is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 530–536, 2002; DOI 10.1002/polb.10120
Binary versus ternary interactions in a completely miscible three‐polymer blend system: Poly(ϵ‐caprolactone) with two different methacrylic polymers
Authors: Lee Su‐Chiu , Woo E. M.
Published: August 2002

A truly miscible ternary miscible blend consisting of poly(ϵ‐caprolactone) (PCL), poly(phenyl methacrylate), and poly(benzyl methacrylate) (PBzMA) was discovered. The three‐polymer blend system was completely miscible within the entire composition range at ambient temperature up to about 150 °C, and ternary phase diagrams at increasing temperatures were characterized and interpreted. A ternary‐interaction model based on the modified Flory–Huggins expression was used to describe the phase diagrams with the individual binary interaction strengths. The model fitted well with the experimental‐phase diagram for the ternary blend system at T = 250 °C, where the binary PCL‐PBzMA blend system is on the critical points of phase separation. Interpretation of discrepancy between the model and experimental at other temperatures was handled with an empirical approach. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 747–754, 2002
Development of a methodology to predict material properties from environmental exposure. II. Structural features
Authors: Robertson J. E. , Ward T. C.
Published: August 2002

A general scheme is presented in the first part of this series in which degradation‐induced changes in a polymer that are produced by exposure to an aggressive environment are linked to measurable kinetic parameters and molecular weight distribution variations. Although general in nature for all polymers and environments, the data were collected on bisphenol A polycarbonate that was degraded by elevated temperatures. A parameter, τ, the product of a kinetic rate constant, k, and the environmental exposure time, provided a metric that was suitable for superposition methods to reduce the data. τ was directly related to the molecular weight distribution shifting during environmentally induced changes. This article extends the methodology to structure–property correlations such as the relationship of the glass‐transition temperature, rheology, and the tensile strength of polycarbonate after the environmental treatment. Again, in a universal fashion, the τ value (the degree of degradation) was sufficient to model the observed physical property changes with the amount of exposure to the hostile environment. As long as the kinetics of the process of change are amenable to a mathematical model and a quantitative measure of the change in a fundamental polymer parameter is available, this methodology should be applicable to any polymer in any environment. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 802–812, 2002
Excited‐state energy dynamics of conjugated polycarbogermane oligomers: Introduction effects of germanium atom into π‐conjugated molecular system
Authors: Choi Sang Ho , Hwang In‐Wook , Kim Sung Hee , Park Young Tae , Kim Yong‐Rok
Published: August 2002

Excited‐state energy dynamics of the conjugated polycarbogermane oligomers, poly{[1,4‐bis(thiophenyl)buta‐1,3‐diyne]‐alt‐(dimethylgermane)} (PBTBD‐DMG; n = 33), poly{[1,4‐bis‐(thiophenyl)buta‐1,3‐diyne]‐alt‐(diphethylgermane)} (PBTBD‐DPG; n = 12), poly{[1,4‐bis(phenyl)buta‐1,3‐diyne]‐alt‐(dimethylgermane)} (PBPBD‐DMG; n = 36), and poly{[1,4‐bis(phenyl)buta‐1,3‐diyne]‐alt‐(diphenylgermane)} (PBPBD‐DPG; n = 2), were investigated by steady‐state and picosecond time‐resolved fluorescence spectroscopies in liquid solution. The introduction effect of a germanium atom into π‐conjugated oligomer backbones and the substitution effect of a methyl or phenyl group on the germanium atom are discussed from solvent polarity‐dependent studies. Steady‐state and time‐resolved fluorescence studies on the thiophene‐containing polycarbogermane (PBTBD‐DMG and PBTBD‐DPG) oligomers revealed considerable solvent polarity‐dependent characteristics, whereas those of the phenylene‐containing polycarbogermane (PBPBD‐DMG and PBPBD‐DPG) oligomers do not significantly show such characteristics. As the solvent polarity increased from n‐hexane to tetrahydrofuran, the steady‐state fluorescence spectra of PBTBD‐DMG and PBTBD‐DPG oligomers were significantly redshifted, and their fluorescence lifetimes seemed to change from ∼624 to ∼46 ps. These results suggest that the excited‐state dynamics of PBTBD‐DMG and PBTBD‐DPG oligomers are related to an intramolecular charge transfer (ICT) emission process through (d‐p) π conjugation between the π‐conjugated system and unoccupied 4d orbitals of the germanium atom. These results are supported by quantum chemical (AM1 and CNDO/2) calculations. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1298–1306, 2002
Synthesis, structural characterization, and properties of polyurethane elastomers containing various degrees of unsaturation in the chain extenders
Authors: Auten Kenneth L. , Petrović Zoran S.
Published: August 2002

We prepared polyurethane block copolymers with both 50 and 70% soft segment concentrations, using 4,4′‐diphenylmethane diisocyanate–poly(propylene glycol) prepolymer and 1,4‐butanediol, cis‐2‐butene‐1,4‐diol, and 2‐butyne‐1,4‐diol as chain extenders. The effects of the different chain extenders were observed during synthesis and in the final products. A comparison of spectroscopic, mechanical, and thermal data reveals that polymer properties can be significantly altered by differences in chemical bonding within the chain extender backbone. Although all data support the expected differences in phase morphology between the two series of samples, they also suggest that increasing chain extender unsaturation reduced reactivity with isocyanate, adversely affected hydrogen bonding, lowered the degree of crystallinity of the hard segments, and decreased phase separation. The tensile strength, elongation, modulus, and elastic recovery decreased and the electrical conductivity of iodine‐doped samples increased with increasing chain extender unsaturation. The thermal stability of the urethane group was also lower in samples with increased unsaturation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1316–1333, 2002
Melting behavior, crystallization kinetics, and crystal structure of poly(2‐hydroxyethoxybenzoate)
Authors: Finelli L. , Siracusa V. , Lotti N. , Munari A. , Gazzano M.
Published: August 2002

The melting behavior and crystallization kinetics of poly(2‐hydroxyethoxybenzoate) (PHEBA) were investigated with differential scanning calorimetry and hot‐stage optical microscopy. The observed multiple endotherms, commonly displayed by polyesters, were influenced by the crystallization temperature. By the application of the Hoffman–Weeks method to the melting temperatures of isothermally crystallized samples, a value of 232 °C was obtained for the equilibrium melting temperature. Isothermal crystallization kinetics were analyzed according to Avrami's treatment. Values of Avrami's exponent n close to 3 were obtained, independently of the crystallization temperature, in agreement with a crystallization process originating from predetermined nuclei and characterized by three‐dimensional spherulitic growth. In fact, space‐filling banded spherulites were observed by hot‐stage optical microscopy at all crystallization temperatures explored, with the band spacing increasing with increasing crystallization temperature. The rate of crystallization became lower as the crystallization temperature increased as usual at low undercooling, with the crystallization process controlled by nucleation. The equilibrium heat of fusion was determined by differential scanning calorimetry and wide‐angle X‐ray scattering measurements. Finally, the crystal phase of PHEBA was investigated with wide‐angle X‐ray scattering, and a triclinic unit cell was hypothesized. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1354–1362, 2002
A model for structural relaxation in amorphous glassy polymers based on the aggregation–fragmentation theory
Authors: Drozdov Aleksey D.
Published: August 2002

Governing equations are derived for the kinetics of physical aging in polymeric glasses. An amorphous polymer is treated as an ensemble of cooperatively rearranged regions (CRRs). Any CRR is thought of as a string of elementary clusters (ECs). Fragmentation of the string occurs at random times at any border between ECs. Two strings aggregate at random instants to produce a new string. Aggregation and fragmentation are treated as thermally activated processes, and the rate of fragmentation is assumed to grow with temperature more rapidly than the rate of coalescence. A nonlinear differential equation is developed for the distribution of CRRs with various numbers of ECs. Adjustable parameters of the model are found by the fitting of experimental data for polycarbonate, poly(methyl methacrylate), polystyrene, and poly(vinyl acetate) (PVA). Fair agreement is established between observations and results of numerical simulation. For PVAc, the relaxation spectrum found by matching data in a calorimetric test is successfully employed to predict experimental data in a shear relaxation test. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1312–1325, 2001
Morphology development during isothermal crystallization. II. Isotactic and syndiotactic polypropylene blends
Authors: Wang Zhi‐Gang , Phillips Roger A. , Hsiao Benjamin S.
Published: August 2002

Morphology development during isothermal crystallization in equal molecular weight isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), and iPP/sPP blends was studied with time‐resolved simultaneous small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray diffraction (WAXD) with synchrotron radiation. The sPP melting point is 15–20 °C below that of the iPP component, and sPP multiple melting is not affected by blending for 50–100 wt % sPP compositions. SAXS and WAXD (at 115 and 137.5 °C) show that sPP crystallizes more slowly than iPP. The sPP long spacing is larger than that of iPP at both crystallization temperatures, exhibits a broader distribution, and changes to a greater extent during crystallization. Differential scanning calorimetry (DSC) cooling and SAXS/WAXD measurements show iPP crystallizing first and nearly to completion before sPP in a 50:50 iPP/sPP blend. At 115 °C, iPP crystals nucleate sPP in a 50:50 blend and modify the sPP lamellar spacing. The nucleation does not overcome the large difference in the iPP and sPP rates at 137.5 °C. Before sPP crystallization in a 50:50 blend (115 °C), the iPP long spacing is not affected by molten sPP. The iPP long spacing is slightly expanded by molten sPP, and the WAXD induction time is delayed at 137.5 °C. The observed iPP long spacing in the presence of molten sPP is consistent with previously reported results for iPP/atactic polypropylene (aPP) blends of similar molecular weight. Quantitative differences between the two types of blends are consistent with previously reported thermodynamic rankings. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1876–1888, 2001
Swelling behaviors of sub‐micron‐sized copolymer gel particles: The effect of physical crosslinking
Authors: Choi Hyun Seok , Kim In Ha , Bae Young Chan
Published: August 2002

The swelling equilibria model of copolymer gel particles is proposed. It accounts for physical crosslinking as a result of hydrogen bonding. The modified Flory–Erman model is used to describe the elastic contribution to swelling. The model considers hydrogen bonding as a physical crosslinker. A free‐energy‐of‐mixing term is represented using the extended Flory–Huggins theory. The interaction parameter χ in the model is a function of both composition and temperature. We then compare the proposed model with the swelling behaviors of copolymer gel particles. Our model offers fairly good agreement with the experimental data for given systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1928–1934, 2001
Orientation of cellulose triacetate films cast from solution in high magnetic field
Authors: Kimura T. , Yamato M. , Endo S. , Kimura F. , Sata H. , Kawasaki H. , Shinagawa Y.
Published: August 2002

Cellulose triacetate solutions with various solvents, including methylene chloride, methyl acetate, and their mixture with ethanol, were cast in high magnetic fields, and the obtained films were subjected to the optical and infrared measurements. The film cast from a solution with a methyl acetate/ethanol mixed solvent exhibited birefringence as well as infrared dichroism, whereas the films cast from the other solutions did not. The aligned structure was discussed by comparison with a mechanically stretched sample. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1942–1947, 2001
High‐throughput characterization of pattern formation in symmetric diblock copolymer films
Authors: Smith Archie P. , Douglas Jack F. , Meredith J. Carson , Amis Eric J. , Karim Alamgir
Published: August 2002

Surface‐pattern formation in thin block copolymer films was investigated by utilizing a high‐throughput methodology to validate the combinatorial measurement approach and to demonstrate the value of the combinatorial method for scientific investigation. We constructed measurement libraries from images of subregions of block copolymer films having gradients in film thickness and a range of molecular mass,M.A single gradient film covers a wide range of film morphologies and contains information equivalent to a large number of measurements of films having a fixed thickness,h.Notably, the scale of the surface patterns is generally much larger than the molecular dimensions so that the interpretation of the patterns is more subtle than ordering in bulk block copolymer materials, and there is no predictive theory of this type of surface‐pattern formation. We observed a succession of surface patterns that repeat across the film with increasingh[extended smooth regions, regions containing circular islands, labyrinthine (“spinodal”) patterns, holes, and smooth regions again]. The extended smooth regions and the labyrinthine patterns appear to be novel features revealed by our combinatorial study, and these patterns occurred as bands ofhthat were quantized by integral multiples of the bulk lamellar period,Lo.The magnitude of the height gradient influenced the width of the bands, and the smooth regions occupied an increasing fraction of the film‐surface area with an increasing film gradient. The average size of the spinodal patterns, λ, was found to scale asλ ∼ Lorλ ∼ M−1.65and reached a limiting size at long annealing times. The hole and island features had a size comparable to λ, and their size likewise decreased with increasingM.The smooth regions were attributed to an increase in the surface‐chain density in the outer brushlike block copolymer layer with increasingh,and the scaling of λ withMwas interpreted in terms of the increasing surface elasticity withM.© 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2141–2158, 2001
Molecular dimensions and melt rheology of an all‐aromatic liquid crystalline polymer
Authors: Seo K. S. , Caflisch G. B.
Published: August 2002

The molecular dimensions and melt rheology of a thermotropic all‐aromatic liquid crystalline polyester (TLCP) composed of p‐hydroxy benzoic acid, hydroquinone, terephthalic acid, and 2,4‐naphthalenedicarboxylic acid is examined. The Mark–Houwink exponent (α) of 0.95 is estimated for the TLCP. The persistence length estimated from molecular weight (M) and intrinsic viscosity ([η]) data using the Bohdanecky–Bushin equation is about 95 Å, whereas that estimated from light scattering data is 117 Å. These persistence lengths and the observed α value, both higher than those for flexible polymers, suggest that the present TLCP is a semirigid polymer. The zero shear melt viscosity (η0) varies with approximately M6 for molecular weight M > 3 × 104 g/mol; below this molecular weight, η0 varies almost linearly with M. Widely different entanglement molecular weights (Me) are predicted, depending on the method used; the plateau modulus estimates Me of about 8 × 105 g/mol, whereas the ratio of mean square end‐to‐end distance and molecular weight (〈R2〉0/M) predicts Me's either too small (0.33 g/mol) or too large (2.5 × 106 g/mol), depending on the theory used. Although the change in the molecular weight dependency of melt viscosity appears to be associated with the onset of entanglement coupling of the semirigid molecules, its origin needs further investigation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2378–2389, 2001
Slow ester side‐group flips in glassy poly(alkyl methacrylate)s characterized by centerband‐only detection of exchange nuclear magnetic resonance
Authors: Bonagamba T. J. , Becker‐Guedes F. , DeAzevedo E. R. , Schmidt‐Rohr K.
Published: August 2002

Slow side‐group dynamics in a series of five poly(alkyl methacrylate)s with various side‐group sizes [poly(methacrylic acid) (PMAA), poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), poly(isobutyl methacrylate) (PiBMA), and poly(cyclohexyl methacrylate), with H, CH3, CH2CH3, CH2CH(CH3)2, and cyclohexyl alkyl substituents (CODEX), respectively] were studied quantitatively by centerband‐only detection of exchange nuclear magnetic resonance (NMR). Flips and small‐angle motions of the ester groups associated with the β relaxation were observed distinctly in the CODEX NMR data, and the fraction of slowly flipping groups was measured with a precision of 3%. In PMMA, 34% of the side groups flipped on a 1‐s timescale, whereas the fraction was 31% in PEMA at 25 °C. Even the large isobutylether and cyclohexylester side groups flipped in the glassy state, although the flipping fraction was reduced to 22 and about 10%, respectively. In PMAA, no slow side‐group flips were detected on the 1‐s timescale. A striking difference in the temperature dependence of the flipping fraction in PMMA versus PEMA and PiBMA was observed. In PMMA, the flipping fraction was temperature‐independent between 25 and 80 °C, whereas in PEMA, it increased continuously from 31 to 60% between 25 and 60 °C. A similar doubling was also observed in PiBMA. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2444–2453, 2001
Internal Structure of a relict rock glacier, Ślęża Massif, Southwest Poland
Authors: Żurawek Roman
Published: August 2002

The sediments of a large accumulation landform, interpreted as one of six Pleistocene rock glaciers occurring in the Ślęża Massif, southwest Poland, are described. The sediments have been subject to strong compression and the main deformation mechanism is that of shearing. The similar angle of shear in sediments of extremely different lithology is inferred from the geometry of failure surfaces and indicates that ice was necessary for the debris transport. Because the geomorphological setting excludes a glacigenic origin, the sediments are interpreted to result from the creep of permafrost, i.e. the landform is a relict rock glacier. The movement of the rock glacier, at least in its terminal stage, is associated with a dense pattern of shear planes and would have occurred even in the presence of a small amount of interstitial ice. Copyright © 2002 John Wiley & Sons, Ltd.
Effects of exogenous surfactant on gas exchange and compliance in rabbits after meconium aspiration
Authors: Robinson Tonya W. , Roberts Andrew M.
Published: August 2002

Success in using adjunctive surfactant therapy for meconium aspiration has been inconsistent. We tested the hypothesis that the ability of exogenous surfactant to improve gas exchange and pulmonary compliance after meconium aspiration is related to the method of surfactant administration. In anesthetized rabbits (2.4 ± 0.16 kg body weight), an endotracheal tube (ETT) was placed in the lower trachea, and the lungs were ventilated mechanically. After a control period, filtered meconium (3–5 mL/kg) was instilled through the ETT. Group 1 (n = 5) was not given surfactant. Thirty minutes after meconium instillation, group 2 (n = 5) was given a bolus of bovine surfactant (Beractant, 4 mL/kg) through the ETT, and group 3 (n = 5) was given an infusion of Beractant (4 mL/kg for 1 hr) through the side‐port of the ETT.

Thirty minutes after meconium instillation, tracheal pressure increased by 8 ± 1 cm H2O (mean ± SEM), dynamic compliance decreased by 0.36 ± 0.07 mL/cm H2O/kg, arterial PO2 (PaO2) decreased by 49 ± 6.0 mmHg, arterial PCO2 (PaCO2) increased by 12 ± 2.4 mmHg, and arterial pH (pHa) decreased by 0.09 ± 0.02. After 3 hr of exposure to meconium, tracheal pressure was significantly (P < 0.001) lower in group 3 compared to groups 1 or 2. PaO2 remained below baseline in all groups. Group 3 had a significantly (P = 0.001) higher dynamic compliance than groups 1 or 2. Likewise, static compliance was higher for group 3 compared to groups 1 or 2, with the greatest difference at low lung volume. Mean arterial blood pressure, pulse rate, PaCO2, and pHa were not significantly different between groups.

These results suggest that continuous infusion of exogenous surfactant is more effective than bolus administration in improving pulmonary function after meconium aspiration. Pediatr Pulmonol. 2002; 33:117–123. © 2002 Wiley‐Liss, Inc.
Snoring and obstructive sleep apnea in Thai school‐age children: Prevalence and predisposing factors
Authors: Anuntaseree Wanaporn , Rookkapan Korpong , Kuasirikul Surachai , Thongsuksai Paramee
Published: August 2002

We studied the prevalence of habitual snoring and its associations with tonsillar size, allergic rhinitis, obesity, and parental smoking, as well as prevalence of obstructive sleep apnea (OSAS) in a sample of 1,142 children aged 6–13 years (mean, 7.25 ± 0.58) from seven randomly selected schools in Hat yai, Southern Thailand.

Eighty‐five (8.5%) of the children were habitual snorers; the prevalence was the same in boys and girls. Significant and independent association was present between snoring and allergic rhinitis with an odds ratio of 5.27 (95% CI, 1.57–17.77). The odds ratio was significantly increased to 2.65 (CI, 1.31–5.39), 5.72 (CI, 2.67–12.25), and 11.06 (CI, 1.91–63.84) in children with tonsillar size of 2+ , 3+ , and 4+ , respectively. Of the 85 habitual snorers, 69 could be contacted by telephone call or by hospital visit. Eight of these were reported to have at least one of the following symptoms: difficulty breathing during sleep, stop breathing at night, restless sleeping and frequent awakening, sleeping with the head tipped back, and a tendency to breathe through the mouth rather than the nose. Polysomnographic studies in these 8 children demonstrated an apnea/hypopnea index of 0.6–4.7 per hr. Seven children met the criteria for OSAS. Thus, our estimate of the prevalence of OSAS among Thai schoolchildren was 7/1,008 (0.69%).

We have shown that the prevalence of habitual snoring was 8.5%, and the prevalence of OSAS in a sample of Asian school‐age children in Southern Thailand was 0.69%, which was similar to that observed in Western populations. An association of snoring with tonsillar size or allergic rhinitis was demonstrated. All but one of the snoring children with sleep‐related symptoms had OSAS, but all were mild cases. Pediatr Pulmonol. 2001; 32:222–227. © 2001 Wiley‐Liss, Inc.
Elevated serum progastrin‐releasing peptide (31–98) in metastatic and androgen‐independent prostate cancer patients*
Authors: Yashi Masahiro , Muraishi Osamu , Kobayashi Yutaka , Tokue Akihiko , Nanjo Hiroshi
Published: August 2002

BACKGROUND

Increases in neuroendocrine phenotype and secretory products are closely correlated with tumor progression and androgen independence in prostate cancer. In this study, we explored this correlation using serum progastrin‐releasing peptide (ProGRP), a carboxy‐terminal region common to three subtypes of precursors for gastrin‐releasing peptide (GRP), which is released from the neuroendocrine phenotype to act as a growth factor.

METHODS

In 60 patients with benign prostatic hyperplasia (BPH) and 200 with prostate cancer, serum ProGRP levels were determined with an enzyme‐linked immunosorbent assay (ELISA) kit and evaluated in relation to clinical stage, hormonal treatment, and prostate‐specific antigen (PSA) values. Fourteen randomly selected patients were entered in the follow‐up study. Additionally, expression of ProGRP as determined by immunohistochemical analysis was compared to that of chromogranin‐A (CgA) in tissue samples from several subjects.

RESULTS

We found a positive correlation between PSA and ProGRP in patients with untreated prostate cancer; no correlation was found in the treated groups. The increases in the ProGRP value and in the percentage of patients with higher than normal values were significant (P < 0.0001), especially in the androgen‐independent group (P < 0.0001). A longitudinal study showed that, in a subset of patients, the ProGRP values tended to increase transiently when the cancer became androgen independent, but remained unchanged or decreased at the androgen‐dependent stage. Positive staining for ProGRP occurred in a different distribution in neuroendocrine tissues than that of staining for CgA.

CONCLUSIONS

The clinical results demonstrated the existence of a regulatory mechanism for GRP, which to date had only been observed in cell lines. These findings suggest that GRP is a growth factor potentially upregulated by androgen but that does not rely principally on androgen modulation. The large overlap in levels of ProGRP among the groups limits the use of this value as a monitoring tool. Measurement of ProGRP, however, does have potential as an independent parameter to evaluate androgen‐independent progression and to facilitate a new therapeutic strategy that may compensate for current limitations of diagnosis based on PSA alone. Prostate 51: 84–97, 2002. © 2002 Wiley‐Liss, Inc.
Silencing of π‐class glutathione S‐transferase in MDA PCa 2a and MDA PCa 2b cells
Authors: Vidanes Genevieve M. , Paton Vince , Wallen Eric , Peehl Donna M. , Navone Nora , Brooks James D.
Published: August 2002

BACKGROUND

Loss of expression of the glutathione S‐transferase‐π (GSTP1) is the most common genetic alteration described in human prostate cancer, occurring in virtually all tumors regardless of grade or stage. Of the available human prostate cancer cell lines, only LNCaP mirrors this phenotype. We investigated whether the prostate cancer cell lines MDA PCa 2a and MDA PCa 2b share this phenotype.

METHODS

GSTP1 protein and mRNA levels were assessed in the MDA PCa 2a and MDA PCa 2b cell lines by Western and Northern blot. DNA methylation was evaluated by Southern blot analysis of genomic DNA digested with the methylation‐sensitive restriction enzymes BssHII, NotI, and SacII. Re‐expression of GSTP1 was determined by RT‐PCR following treatment with 5‐azacytidine, a DNA methyltransferase inhibitor, and/or the histone deacetylase inhibitor trichostatin A (TSA).

RESULTS

Like all human prostatic carcinomas in vivo, both the MDA PCa 2a and 2b cell lines lack protein and mRNA expression of GSTP1. This lack of expression is associated with methylation in the GSTP1 gene promoter. Treatment with the methyltransferase inhibitor 5‐azacytidine resulted in re‐expression of GSTP1. By itself, TSA did not result in re‐expression of GSTP1, nor did it augment expression induced by 5‐azacytidine.

CONCLUSIONS

MDA PCa 2a and 2b appear to be useful models of human prostatic carcinoma in that they lack expression of GSTP1 due to gene silencing via promoter methylation. Inhibition of histone acetylation does not appear to affect GSTP1 expression. Prostate 51: 225–230, 2002. © 2002 Wiley‐Liss, Inc.
Mixed lineage kinase (MLK) family members are not involved in androgen regulation of prostatic proliferation or apoptosis*
Authors: Gao Jin , Isaacs John T.
Published: August 2002

BACKGROUND

Once paracrine growth factors are secreted by androgen receptor expressing prostatic stromal cells, they diffuse across the basement membrane of glandular acini, where they bind to epithelial cell surface receptors. This binding stimulates signaling pathways that regulate both the rate of proliferation and apoptosis of prostate epithelial cells. In the present studies, the role of mixed lineage kinases (MLKs) in these signaling processes were studied using a pharmacological approach.

METHODS

The indolocarbazole CEP‐1347 (KT 7515) is a potent inhibitor of kinase activity of MKLs. Male rats were treated with CEP‐1347 (1 mg/kg of body weight/day) to determine whether inhibition of the MLKs can prevent androgen ablation (i.e. castration) induced apoptosis of prostatic epithelial cells, using as indexes total ventral prostatic DNA content and the percentage of ventral prostatic epithelial cells whose DNA can be terminal transferase end‐labeled. In addition, animals previously castrated a week earlier were treated daily with either vehicle or CEP‐1347 and exogenous androgen replacement to induce the proliferative re‐growth of the prostatic epithelial cells. After 1 week of treatment, the total ventral prostatic DNA content in the vehicle vs. CEP‐1347 groups was compared.

RESULTS

Using the National Center for Bio‐Informatics data bank, MLK2, MLK3, and DLK members of the MLK family are expressed by the normal prostate. Inhibition of the MLKs with CEP‐1347 did not affect the kinetics of apoptosis of prostatic epithelial cells induced by androgen ablation. In addition, such MLK inhibition did not prevent androgen replacement induced proliferative regrowth of the prostate epithelium in castrated animals.

CONCLUSIONS

Signaling through the MLK family is not involved in either the androgen‐induced proliferation or the androgen ablation‐induced apoptosis of prostatic epithelial cell in the rat. Prostate 48:67–70, 2001. © 2001 Wiley‐Liss, Inc.
Activation of latent protease function of pro‐hk2, but not pro‐PSA, involves autoprocessing
Authors: Denmeade Samuel R. , Lövgren Janita , Khan Saeed R. , Lilja Hans , Isaacs John T.
Published: August 2002

BACKGROUND

Human glandular kallikrein 2 (hK2) and prostate‐specific antigen (PSA) are members of an extensive kallikrein family of proteases. Both proteases are secreted as zymogens or proenzymes containing a seven amino acid propeptide that must be proteolytically removed for enzymatic activation. The physiological proteases that activate pro‐hK2 and pro‐PSA are not known.

METHODS

The pro‐hK2 peptide sequence is Val‐Pro‐Leu‐Ile‐Gln‐Ser‐Arg (VPLIQSR). For PSA, the amino acid sequence of the propeptide is Ala‐Pro‐Leu‐Ile‐Leu‐Ser‐Arg (APLILSR). Fluorescent substrates were made by coupling these peptide sequences to 7‐amino‐4‐methylcoumarin (AMC). The hydrolysis of the VPLIQSR‐AMC and APLILSR‐AMC substrates by hK2, PSA, and a panel of purified proteases was determined.

RESULTS

HK2 readily cleaved the pro‐hK2 peptide substrate VPLIQSR‐AMC with a rate of hydrolysis that was ∼ 8‐fold higher than an equimolar amount of purified trypsin. HK2 also had the highest hydrolysis rate from among a group of other trypsin‐like proteases. In contrast, neither hK2 nor PSA was able to appreciably cleave the pro‐PSA substrate APLILSR‐AMC. The pro‐PSA substrate was most readily hydrolyzed by urokinase and trypsin.

CONCLUSIONS

HK2 can hydrolyze the pro‐hK2 substrate suggesting that maturation of pro‐hK2 to enzymatically active hK2 involves autoprocessing. As expected, PSA, a chymotrypsin‐like protease, was unable to hydrolyze either of the propeptide substrates. Therefore, it is unlikely that PSA can auto‐process its own enzymatic function. HK2 has trypsin‐like specificity but was unable to hydrolyze the pro‐PSA substrate. These results raise the possibility that an additional processing protease may be required to fully process PSA to an enzymatically active form. Prostate 48:122–126, 2001. © 2001 Wiley‐Liss, Inc.
Expression of a human cell adhesion molecule, MUC18, in prostate cancer cell lines and tissues
Authors: Wu Guang‐Jer , Varma Vijay A. , Wu Mei‐Whey H. , Wang Shur‐Wern , Qu Pengpeng , Yang Hsiuchin , Petros John A. , Lim So Dug , Amin Mahul B.
Published: August 2002

BACKGROUND

Over expression of huMUC18, a cell adhesion molecule in the immunoglobulin gene superfamily, causes a non‐metastatic human melanoma cell line to become metastatic in a nude mouse system. To determine if MUC18 expression correlates with the malignant progression of prostate cancer, we investigated differential expression of human MUC18 (huMUC18) in normal prostate epithelial cells, prostate cancer cell lines, and prostatic normal and cancer tissues.

METHODS

RT‐PCR and Western blot analyses were used to analyze the expression of MUC18 mRNA and protein in four human prostate cancer cell lines, cultured primary normal prostate epithelial cells, normal prostate and malignant prostate tissues. Immunohistochemistry was used to determine the expression of MUC18 antigen in prostatic tissues at different stages of malignancy.

RESULTS

Human MUC18 mRNA and protein was expressed in three different prostate cancer cell lines (TSU‐PR1, DU145, and PC‐3), but not in one prostate cancer cell line (LNCaP.FGC). HuMUC18 protein was also expressed at high levels in extracts prepared from tissue sample sections containing high grade prostatic intraepithelial neoplasia (PIN), but weakly expressed in extracts prepared from either cultured primary normal prostatic epithelial cells or the normal prostate gland. Immunohistochemical analysis showed that huMUC18 was expressed at higher levels in the epithelial cells of high‐grade PIN and prostatic carcinomas and in cells of a lymph node metastasis compared to that in normal or benign hyperplastic epithelium (BPH).

CONCLUSIONS

We therefore conclude that MUC18 is expressed at higher levels in pre‐malignant and malignant prostatic epithelium, including metastasis. We suggest that over‐expression of MUC18 may be a new marker of human prostate cancer and also implicates its possible role in development and progression of prostate cancer. Prostate 48:305–315, 2001. © 2001 Wiley‐Liss, Inc.
Structural determinants of binding and specificity in transforming growth factor–receptor interactions
Authors: Shah Parantu K. , Buslje Cristina Marino , Sowdhamini R.
Published: August 2002

Transforming growth factor (TGF‐β) protein families are cytokines that occur as a large number of homologous proteins. Three major subgroups of these proteins with marked specificities for their receptors have been found—TGF‐β, activin/inhibin, and bone morphogenic protein. Although structural information is available for some members of the TGF‐β family of ligands and receptors, very little is known about the way these growth factors interact with the extracellular domains of their cell surface receptors, especially the type II receptor. In addition, the elements that are the determinants of binding and specificity of the ligands are poorly understood. The structure of the extracellular domain of the receptor is a three‐finger fold similar to some toxin structures. Amino acid exchanges between multiply aligned homologous sequences of type II receptors point to a residue at the surface, specifically finger 1, as the determinant of ligand specificity and complex formation. The “knuckle” epitope of ligands was predicted to be the surface that interacts with the type II receptor. The residues on strands β2, β3, β7, β8 and the loop region joining β2 and β3 and joining β7 and β8 of the ligands were identified as determinants of binding and specificity. These results are supported by studies on the docking of the type II receptor to the ligand dimer–type I receptor complex. Proteins 2001;454:408–420. © 2001 Wiley‐Liss, Inc.
Protein sequence threading: Averaging over structures
Authors: Russell Anthony J. , Torda Andrew E.
Published: August 2002

Multiple sequence alignments are a routine tool in protein fold recognition, but multiple structure alignments are computationally less cooperative. This work describes a method for protein sequence threading and sequence‐to‐structure alignments that uses multiple aligned structures, the aim being to improve models from protein threading calculations. Sequences are aligned into a field due to corresponding sites in homologous proteins. On the basis of a test set of more than 570 protein pairs, the procedure does improve alignment quality, although no more than averaging over sequences. For the force field tested, the benefit of structure averaging is smaller than that of adding sequence similarity terms or a contribution from secondary structure predictions. Although there is a significant improvement in the quality of sequence‐to‐structure alignments, this does not directly translate to an immediate improvement in fold recognition capability. Proteins 2002;47:496–505. © 2002 Wiley‐Liss, Inc.
Ionic network at the C‐terminus of the β‐glycosidase from the hyperthermophilic archaeon Sulfolobus solfataricus: Functional role in the quaternary structure thermal stabilization
Authors: Cobucci‐Ponzano Beatrice , Moracci Marco , Di Lauro Barbara , Ciaramella Maria , D'Avino Rossana , Rossi Mosé
Published: August 2002

Biochemical, crystallographic, and computational data support the hypothesis that electrostatic interactions are among the dominant forces in stabilizing hyperthermophilic proteins. The thermostable β‐glycosidase from the hyperthermophile Sulfolobus solfataricus (Ssβ‐gly) is an interesting model system for the study of protein adaptation to high temperatures. The largest ion‐pair network of Ssβ‐gly is located at the tetrameric interface of the molecule; in this paper, key residues in this region were modified by site‐directed mutagenesis and the stability of the mutants was analyzed by kinetics of thermal denaturation. All mutations produced faster enzyme inactivation, suggesting that the C‐terminal ionic network prevents the dissociation into monomers, which is the limiting step in the mechanism of Ssβ‐gly inactivation. Moreover, the calculated reaction order showed that the mechanism of inactivation depends on the mutation introduced, suggesting that intermediates maintaining enzymatic activity are produced during the inactivation transition of some, but not all, mutants. Molecular models of each mutant allow us to rationalize the experimental evidence and give support to the current theories on the mechanism of ion pair stabilization in proteins from hyperthermophiles. Proteins 2002;48:98–106. © 2002 Wiley‐Liss, Inc.
Molecular engineering of a polymer of tetrameric hemoglobins
Authors: Fronticelli Clara , Arosio Daniele , Bobofchak Kevin M. , Vasquez Gregory B.
Published: August 2002

We have engineered a recombinant mutant human hemoglobin, Hb Prisca β(S9C+C93A+C112G), which assembles in a polymeric form. The polymerization is obtained through the formation of intermolecular SS bonds between cysteine residues introduced at position β9, on the model of Hb Porto Alegre (β9Ser → Cys) (Bonaventura and Riggs, Science 1967;155:800–802). Cβ93 and Cβ112 were replaced in order to prevent formation of spurious SS bonds during the expression, assembly, and polymerization events. Dynamic light scattering measurements indicate that the final polymerization product is mainly formed by 6 to 8 tetrameric hemoglobin molecules. The sample polydispersity Q = 0.07 ± 0.02, is similar to that of purified human hemoglobin (Q = 0.02 ± 0.02), consistent with a good degree of homogeneity. In the presence of strong reducing agents, the polymer reverts to its tetrameric form. During the depolymerization process, a direct correlation is observed between the hydrodynamic radius and the light scattering of the system, which, in turn, is proportional to the mass of the protein. We interpret this to indicate that the hemoglobin molecules are tightly packed in the polymer with no empty spaces. The tight packing of the hemoglobin molecules suggests that the polymer has a globular shape and, thus, allows estimation of its radius. An illustration of an arrangement of a finite number of tetrameric hemoglobin molecules is presented. The conformational and functional characteristics of this polymer, such as heme pocket conformation, stability to denaturation, autoxidation rate, oxygen affinity, and cooperativity, remain similar to those of tetrameric human hemoglobin. Proteins 2001;44:212–222. © 2001 Wiley‐Liss, Inc.
Dipeptide frequency/bias analysis identifies conserved sites of nonrandomness shared by cysteine‐rich motifs
Authors: Campion Stephen R. , Ameen Abdullah S. , Lai Longsheng , King Jeniffer M. , Munzenmaier Tracy N.
Published: August 2002

This report describes the application of a simple computational tool, AAPAIR.TAB, for the systematic analysis of the cysteine‐rich EGF, Sushi, and Laminin motif/sequence families at the two‐amino acid level. Automated dipeptide frequency/bias analysis detects preferences in the distribution of amino acids in established protein families, by determining which “ordered dipeptides” occur most frequently in comprehensive motif‐specific sequence data sets. Graphic display of the dipeptide frequency/bias data revealed family‐specific preferences for certain dipeptides, but more importantly detected a shared preference for employment of the ordered dipeptides Gly–Tyr (GY) and Gly–Phe (GF) in all three protein families. The dipeptide Asn–Gly (NG) also exhibited high‐frequency and bias in the EGF and Sushi motif families, whereas Asn–Thr (NT) was distinguished in the Laminin family. Evaluation of the distribution of dipeptides identified by frequency/bias analysis subsequently revealed the highly restricted localization of the G(F/Y) and N(G/T) sequence elements at two separate sites of extreme conservation in the consensus sequence of all three sequence families. The similar employment of the high‐frequency/bias dipeptides in three distinct protein sequence families was further correlated with the concurrence of these shared molecular determinants at similar positions within the distinctive scaffolds of three structurally divergent, but similarly employed, motif modules. Proteins 2001;44:321–328. © 2001 Wiley‐Liss, Inc.
Self‐repair of biological fibers catalyzed by the surface of a virus crystal
Authors: Kuznetsov Yu. G. , Malkin A. J. , McPherson A.
Published: August 2002

Helical fibers, presumably proteinaceous and of microbial origin, have been visualized by atomic force microscopy on the surfaces of crystals of satellite tobacco mosaic virus. If the crystals are growing, then the fibers are incorporated intact into the crystal lattice. If broken on the crystal surface, then within a few minutes, the fibers self‐reassemble to reestablish continuity. This, we believe, is the first observation of such a crystal surface–catalyzed repair of a biological structure. The surfaces of virus crystals provide ideal workbenches for the visualization and manipulation of nanoscale objects, particularly extended structures such as these fibers. Proteins 2001;44:392–396. © 2001 Wiley‐Liss, Inc.