bluuebunny/crossref_metadata_2025 huggingface dataset:
Alterations in the Fhit gene in pancreatic duct adenocarcinomas induced by N‐nitrosobis(2‐oxopropyl)amine in hamsters
Authors: Tsujiuchi Toshifumi , Sasaki Yasutaka , Kubozoe Tadahiko , Konishi Yoichi , Tsutsumi Masahiro
Published: January 2003

Alteration of the Fhit gene was investigated in pancreatic duct adenocarcinomas induced by N‐nitrosobis(2‐oxopropyl)amine (BOP) in Syrian golden hamsters. The animals received 70 mg/kg BOP, followed by repeated exposure to an augmentation pressure regimen consisting of a choline‐deficient diet combined with DL‐ethionine and then L‐methionine and administration of 20 mg/kg BOP. A total of 15 pancreatic duct adenocarcinomas were obtained 10 wk after the beginning of the experiment, and total RNAs were extracted from each for assessment of aberrant transcription of the Fhit gene by reverse transcription–polymerase chain reaction analysis. Aberrant transcripts lacking nucleotides in the regions of nt −75 to 348, nt −15 to 348, or nt −75 to 178 were detected in 11 adenocarcinomas (73.3%). Southern blot analysis of eight tumors did not show any evidence of gross rearrangement or deletion. These results indicated that changes in the Fhit gene occurred frequently and thus may have played a role in the development of pancreatic duct adenocarcinomas induced by BOP in hamsters. © 2003 Wiley‐Liss, Inc.
On the nature of genetic changes required for the development of esophageal cancer
Authors: Uys Pieter , van Helden Paul D.
Published: January 2003

It is clear that genetic mutations are necessary for the development of cancer, but the exact number required is not clear, with estimates ranging from one critical hit (e.g., p53) to dozens or perhaps even hundreds of expression changes (by microarray analysis) or chromosomal aberrations. We have used a mathematical model to estimate the critical number of mutations required for the development of esophageal cancer (EC) and to test for the likelihood of an EC major susceptibility gene. Our results suggest that six or seven mutations are required for the development of EC and that there is no evidence of a major susceptibility gene. This does not exclude the possibility that gene‐environment interactions may not confer susceptibility or risk. The gradual accumulation of aberrant gene function also can explain the progression of pathologic states seen in the esophagus, from early dysplasia through mild to severe dysplasia and, finally, to cancer, as illustrated in our model. © 2003 Wiley‐Liss, Inc.
The expression of the tumor suppressor gene connexin 26 is not mediated by methylation in human esophageal cancer cells
Authors: Loncarek Jadranka , Yamasaki Hiroshi , Levillain Pierre , Milinkevitch Serge , Mesnil Marc
Published: January 2003

Gap junctional intercellular communication is thought to play an important role in cell differentiation and tissue homeostasis. Gap junctional intercellular communication is mediated by intercellular channels connecting adjacent cells and composed of connexin (Cx) proteins. Until now, approximately 20 different Cx have been characterized in mammals, and they are expressed in a tissue‐specific manner. The downregulation of Cx expression is often observed in tumors and transformed cell lines and is believed to contribute to the loss of proliferating control. Connexin 26 (Cx26) is a Cx constitutively expressed in the normal epithelial esophageal tissue. In the majority of esophageal tumors, Cx26 expression is low or totally absent. CpG island hypermethylation is known to be associated with gene silencing in cancer. Because the promoter and exon 1 region of Cx26 are rich in CpG dinucleotides, we examined whether the loss of Cx26 expression in human esophageal TE cell lines was related to the hypermethylation of this region. We analyzed several TE cell lines derived from different human esophageal carcinomas and exhibiting different levels of Cx26 expression by using methylation‐sensitive restriction digestion and Southern blot analysis. We did not find any correlation between the Cx26 expression and the methylation level of the promoter region of the Cx26 gene. Our results suggest that methylation was probably not involved as a primary mechanism of Cx26 regulation in human esophageal cancer cell lines. © 2003 Wiley‐Liss, Inc.
Design of “Smart” polymers that can ­direct intracellular drug delivery
Authors: Hoffman Allan S. , Stayton Patrick S. , Press Oliver , Murthy Niren , Lackey Chantal A. , Cheung Charles , Black Fiona , Campbell Jean , Fausto Nelson , Kyriakides Themis R. , Bornstein Paul
Published: January 2003

One of the important characteristics of biological systems is their ability to change important properties in response to small environmental signals. The molecular mechanisms that biological molecules utilize to sense and respond provide interesting models for the development of “smart” polymeric biomaterials with biomimetic properties. An important example of this is the protein coat of viruses, which contains peptide units that facilitate the trafficking of the virus into the cell via endocytosis, followed by delivery of the genetic material out of the endosome into the cytoplasm, and from there into the nucleus. We have designed several new types of synthetic polymers to facilitate intracellular trafficking of drugs. One of these has been designed to mimic the specific peptides on viral coats that facilitate endosomal escape. Another has been designed to contain pH‐degradable bonds, facilitating endosomal escape of the drug only after the bonds are degraded at the acidic pHs of the endosomes. Both types of polymer are responsive to the lowered pH within endosomes, leading to disruption of the endosomal membrane and release of important biomolecular drugs such as DNA, RNA, peptides and proteins to the cytoplasm before they are trafficked to lysosomes and degraded by lysosomal enzymes. In this article, we review our work on the design, synthesis and action of such smart, pH‐sensitive polymers. Copyright © 2003 John Wiley & Sons, Ltd.
Biodegradable comb polyesters containing polyelectrolyte backbones facilitate the preparation of nanoparticles with defined surface structure and bioadhesive properties
Authors: Breitenbach A. , Jung T. , Kamm W. , Kissel T.
Published: January 2003

A major challenge in oral peptide and protein delivery remains the search for suitable carrier systems. Therefore, a new concept was investigated combining a modified three‐dimensional architecture, increased hydrophilicity of poly(lactic‐co‐glycolic acid) (PLGA) and charged groups in a single polymer. Biodegradable comb PLGA were synthesized by grafting short PLGA chains onto different poly(vinyl alcohol) (PVA) based backbone polyols, poly(2‐sulfobutyl‐vinyl alcohol) and poly(diethylaminoethyl‐vinyl alcohol). The polyelectrolyte backbones were obtained by etherification of PVA with charge‐containing pendent groups. The comb polymer structure could be confirmed by nuclear magnetic resonance, infrared spectroscopy, differential scanning calorimetry, elemental analysis and measurement of intrinsic viscosity. Nanoparticles (NP), as potential mucosal carriers systems, were prepared by controlled precipitation and investigated as a function of polymer composition. The amphiphilic character and the three‐dimensional architecture of the novel polyesters allowed the preparation of small nanoparticles even without the use of surfactants. Surface NMR, surface charge and hydrophobicity determination indicate a core–corona‐like NP structure, especially in the case of negatively charged polyesters. A structural model is proposed for the NP with an inner polyester core and an outer charged‐groups‐containing surface, depending on polymer composition and backbone charge density. The higher the polymer backbone charge density, the more pronounced its influence on the nanoparticle surface properties. The possibility of preparing NP without the use of a surfactant, as well as of designing the NP surface characteristics by polymer backbone charge density and polymer hydrophilic–hydrophobic balance, will be a major advantage in protein adsorption, bioadhesion and organ distribution. This makes these biodegradable polymers promising candidates for colloidal protein and peptide delivery. Copyright © 2003 John Wiley & Sons, Ltd.
A polymer as an active ingredient in a drug – the development of Copolymer 1 as a drug against multiple sclerosis
Authors: Sela Michael
Published: January 2003

A polymer of four amino acids, L‐lysine, L‐glutamic acid, L‐tyrosine and L‐alanine, prepared from their respective N‐carboxy‐amino acid anhydrides, has been approved by the regulatory agencies in the United States and forty other countries as a drug/vaccine against the exacerbating‐remitting type of multiple sclerosis. The drug, Copolymer 1 (Cop1), is called Copaxone by the industry. It is a specific drug for multiple sclerosis and is not active against other autoimmune diseases. Thus, it serves as a prototype of specific drugs/vaccines against autoimmune diseases. In the case of Cop1, this is due to its immunological cross‐reaction with the myelin basic protein, a substance in the myelin sheath of the brain that seems to be the main cause of the autoimmune phenomenon in multiple sclerosis. From the point of view of polymer chemistry, it is of interest that Copaxone is the first drug of a polymeric nature approved for treatment of a disease. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and preliminary in vitro evaluation of polymeric dicarboxylato‐ and dihydroxylatoplatinum(II) chelates as antiproliferative agents
Authors: Neuse Eberhard W. , Mphephu Ntshengedzeni , Netshifhefhe Humphrey M. , Johnson Mark T.
Published: January 2003

Despite much progress in the chemotherapy of cancerous diseases, antitumor drugs in current clinical use suffer from major pharmacological deficiencies. The platinum drug family, represented by the parent drug cisplatin, falls directly into this category of medicinal agents, with toxicity and resistance problems implicated as key factors leading to suboptimal therapeutic effectiveness. Polymer–drug conjugation, a technique involving the bioreversible drug binding to suitably designed, water‐soluble carrier polymers, ranks as one of the most promising tools in advanced drug research for the enhancement of a drug's therapeutic index through modification of its pharmacokinetic pathway. The conjugate acts as a prodrug, transporting the bioactive constituent from central circulation to, and into, the transformed target cell, where it is released from the carrier for biological action. This technique is utilized here as a means to enhance the therapeutic effectiveness of selected platinum drug species. Platinum is polymer‐bound (conjugated) through chelation with carrier‐attached pairs of carboxyl or hydroxyl functionalities carrier‐attached in 1,1‐ or 1,2‐geometry, acting as leaving group ligands upon metal coordination. Within the carrier's structural framework, the ligand pairs are arranged either as main‐chain constituents or else as side‐chain functionalities. Platinum chelation with these functionalities is accomplished by treatment of the carrier in aqueous solution with trans‐diaminocyclohexanediaquaplatinum(II) dinitrate (DACH‐Pt), used here as the platination agent. Molar reactant ratios are chosen so as to achieve platinum incorporation in the range from about 4% to 7% by mass. Under these conditions the conjugates, purified by dialysis and isolated by freeze‐drying, are found to retain solubility in water. Selected conjugates submitted to a preliminary in vitro screen show antiproliferative activities on a par with cisplatin against the (sensitive) HeLa cancer line, and up to ten times higher than cisplatin against the (multidrug‐resistant) Colo 320 DM Line. Copyright © 2003 John Wiley & Sons, Ltd.
Integrated device based on conjugated oligoaniline
Authors: Kuo Chin‐Tsou , Weng Shou‐Zheng
Published: January 2003

An integrated optoelectronic device is demonstrated with a high–mobility conjugated oligoaniline field‐effect transistor (FET) driving a poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylene)vinylene (MEH‐PPV) light‐emitting diode (LED). The FET fabricated with oligoaniline (16‐mer) thin film as the semiconductor layer exhibits ideal source current–drain‐source voltage characteristics. Its performance is close to those of inorganic amorphous silicon FETs, with field‐effect mobilities of 0.1–1.0 cm2/V s and on–off current ratio of 106. The FET‐LED integrated device exhibits a current of 8 × 10−4 A with the maximum brightness on the order of 10 cd/m2 at gate voltage of −100 V and drain‐source voltage of 60 V. Copyright © 2003 John Wiley & Sons, Ltd.
Water‐soluble acidic polyelectrolytes with metal‐removing ability
Authors: Rivas Bernabé L. , Pereira Eduardo D. , Gallegos Paola , Geckeler Kurt E.
Published: January 2003

Water‐soluble polymers containing carboxylic acid, phosphonic acid, and sulfonic acid groups were investigated as polychelatogens under different experimental conditions. The maximum retention capacity (MRC) of these polymers was determined at different pH and polymer–metal ion ratios. The metal ions investigated were: Ag(I), Cu(II), Co(II), Ni(II), and Cr(III). The MRC values of the divalent metal ions were found to be very similar and higher than those of the trivalent cations, and there was an important effect of the pH on the MRC. This indicates that the polymer–metal ion interactions were dominated by electrostatic forces. Copyright © 2003 John Wiley & Sons, Ltd.
Degradation of polyamide‐6 by using metal salts as catalyst
Authors: Klun Urša , Kržan Andrej
Published: January 2003

Polyamide‐6 (PA‐6) is a widely used polycondensation polymer that can be recycled by hydrolysis to its monomer ϵ‐caprolactam. The reaction is normally catalyzed by mineral acids. Using microwaves as the source of heating, zinc chloride, acetate and triflate were evaluated as non‐acid catalysts for the reaction. Gravimetric and electron spray ionization mass spectrometry analysis of reaction products showed ZnCl2 as the most effective salt catalyst. A 50wt% (versus PA‐6) addition gave 75% water‐soluble, low‐molecular‐weight oligomers, which is approximately 25% lower than when using phosphoric acid. The triflate salt was effective only when used as an addition to a mineral acid, whereas the acetate was ineffective. FTIR and NMR spectroscopy of degradation products showed that dissociated ions from ZnCl2 bind to the amide group of the polymer. Using the triflate salt no such interaction could be observed, indicating that the degradation and catalysis mechanisms differ with the chloride and triflate salt. Five water‐stable lanthanide triflates showed no catalytic effect on the reaction. Copyright © 2003 John Wiley & Sons, Ltd.
Composite membranes with conducting polymer microtubules as new electroactive and transport systems
Authors: Elyashevich G. K. , Kuryndin I. S. , Rosova E. Yu.
Published: January 2003

Composite membranes consisting of microporous polyethylene films and the layers of electroconducting polymers have been elaborated. Polyethylene films were prepared in the process based on melt extrusion with subsequent annealing, uniaxial extension, and thermofixation. Permeability, the size distribution of the through flow channels, and mechanical characteristics of porous films have been determined. Polypyrrole and polyaniline were used as conducting polymers which were deposited onto porous films by oxidative polymerization from a gas (polypyrrole) or liquid (polyaniline) phase of a monomer. It has been shown that the relief‐like character of the surface and the porous structure of polyethylene films provide very high adhesion of conducting layer to porous support. Conducting layers were deposited onto the surface of the porous support and also on the pore walls of pores. The layers inside through flow channels in the porous support form microtubules connecting two membrane surfaces. Surface and volume electrical conductivity, resistance of composite membranes in electrolytes, and their mechanical characteristics have been measured. Shrinkage and thermodeformational behavior of the polyethylene support and composites have been compared and analyzed. Atomic force microscopy, IR spectroscopy, electrochemical measurements, and mechanical and thermomechanical tests have been used for investigation of the structure and properties of porous films and composite membranes. Copyright © 2003 John Wiley & Sons, Ltd.
An X‐ray method for determination of crystallinity as a function of depth from a polymer surface
Authors: Khalfin Rafail L. , Cohen Yachin
Published: January 2003

Manufactured articles of semicrystalline polymers usually have a variation in texture (degree of crystallinity and crystal orientation) as a function of the depth from the external surface. This is often due to the fact that the crystallization process near the surfaces occurs at different conditions and rates relative to the bulk of the material. In this report we present an X‐ray diffraction technique to elucidate the changes in the degree of crystallinity as a function of depth from the surface. Changes in the scheme of X‐ray diffractometer (reflection or transmission, slit width, etc.), the linear material absorption coefficient (using different wavelengths) and the diffraction angle have different effects on the scattering from layers at different depths. It is thus possible to define the material heterogeneity as a function of depth. This method is demonstrated using a film of vinylidene fluoride–tetrafluoroethylene (5 mol%) copolymer that has been crystallized asymmetrically by quenching on one side. The increase in crystallinity from a negligible value on the quenched side to the bulk value is presented. Copyright © 2003 John Wiley & Sons, Ltd.
Oligophenylazomethines: synthesis, structure, electrochemical property and photocyclization
Authors: Higuchi Masayoshi , Yamamoto Kimihisa
Published: January 2003

Oligophenylazomethines (OPAs) and the aniline‐capped OPAs (OPA's) as soluble model compounds of polyphenylazomethine (PPA) were synthesized via dehydration of 4‐aminobenzophenone in the presence of TiCl4 or PTS as a Lewis acid. The 1H‐NMR spectra of OPAs revealed that OPAs have some isomers, which are based on the E/Z conformation of the azomethine moieties, and the formation ratio of the E/Z isomers changes due to the intramolecular steric hindrance of the oligomers. The cyclic voltammograms of OPA's showed irreversible redox waves in the presence of trifluoroacetic acid. Photocyclization of OPA's proceeded in concentrated sulfuric acid. Copyright © 2003 John Wiley & Sons, Ltd.
Design your own elastomeric or stereoregular polymer
Authors: Shmulinson Michal , Volkis Victoria , Lisovskii Anatoli , Nelkenbaum Elza , Eisen Moris S.
Published: January 2003

This study reports the synthesis and activity as precatalysts for the polymerization of propylene of five racemic group 4 complexes, cis‐[p‐R′C6H4C(NR)2]2MX2 (R′ = CH3, R = SiMe3, M = Ti, X = Cl (1); R′ = CH3, R = SiMe3, M = Zr, X = Cl (2); R′ = H, R = i‐pr, M = Zr, X = Cl (3); R′ = CH3, R = SiMe3, M = Zr, X = CH3 (4)) and (acac)2MCl2 (M = Ti (5), M = Zr (6)) (acac = acetylacetone). The hydrocarbyl complex 4 was prepared by the alkylation of the corresponding complex 2 with MeLi·LiBr. Reaction of complex 4 with B(C6F5)3 or all complexes with MAO (MAO = methylalumoxane) results in the formation of a “cationic” intermediate complex which rapidly reacts with the incoming monomer. Some of the complexes catalyze the stereoregular polymerization of propylene only under pressure in either toluene or CH2Cl2, producing polypropylene with very large isotacticities (mmmm % = ∼95–98), high melting points (140–154 °C) and similar molecular weights as compared with cyclopentadienyl complexes, whereas complex 5 is active for the polymerization of elastomeric polypropylene. Copyright ­© 2003 John Wiley & Sons, Ltd.
Synthesis of high‐molecular‐weight cyclic and multicyclic polystyrenes
Authors: Lepoittevin Bénédicte , Hémery Patrick
Published: January 2003

Different cyclic architectures were prepared by combination of living anionic polymerization and coupling reactions. Well‐defined macrocyclic polystyrenes were obtained by reaction of a two‐ended living precursor dianion with an electrophile compound. Two types of coupling agent (diethylenic and dihalogeno compounds) were used and their influence on the cyclization yield was studied. Cyclization with a diethylenic product is preferred as it generates a macrocycle with two living centers and is able to react with a (multifunctional) nucleophile leading to more complex architecture. Cyclic polystyrenes with two attached linear branches were obtained by consecutive coupling of monofunctional and difunctional living chains with DDPE (1,3‐bis(phenyl‐ethylenyl)benzene). High molar mass multicyclic polystyrene was prepared by reaction of living macrocycles with poly(chloromethylstyrene). Size exclusion chromatography and matrix‐assisted laser desorption ionization time of flight (MALDI‐TOF) mass spectrometry analyses have confirmed the high efficiency of these coupling reactions. Copyright © 2003 John Wiley & Sons, Ltd.
Highly conductive, oriented polymer electrolytes for lithium batteries
Authors: Golodnitsky D. , Livshits E. , Ulus A. , Peled E.
Published: January 2003

In semicrystalline complexes of poly(ethylene oxide) (PEO) with different salts, such as lithium iodide, lithium trifluoromethanesulfonate (LiTF) and lithium trifluoromethanesulfonimide (LiTFSI), stretching induced longitudinal DC conductivity enhancement was observed, in spite of the formation of more ordered polymer electrolyte (PE) structure. It was found that the more amorphous the PE, the less its lengthwise conductivity is influenced by stretching. The results of our investigation suggest that ionic transport occurs preferentially along the PEO helical axis, at least in the crystalline phase, and that the rate‐determining step of the lithium ion conduction in LiI:P(EO)20, LiTF:­P(EO)20 polymer electrolytes below Tm is “interchain” hopping. Understanding ion transport processes is clearly a fertile field for research and development in the synthesis of new rigid polymers with ordered channels and composition appropriate for enhanced ionic conductivity. Copyright © 2003 John Wiley & Sons, Ltd.
Controlling the properties of single‐polymer composites by surface melting of the reinforcing fibers
Authors: Rein D. M. , Vaykhansky L. , Khalfin R. L. , Cohen Y.
Published: January 2003

All‐thermoplastic single‐polymer composites are materials in which both the reinforcing fibrous phase and the matrix between them are made of the same thermoplastic polymer. Excellent bonding is achieved by mutual entanglement macromolecules due to controlled surface melting of the fibers. This results in a uniform structure of a single chemical entity. The physical properties of the consolidated material, such as modulus and coefficient of thermal expansion (CTE), can be controlled by the extent of melting effected in the process, which determines the fiber/matrix ratio. The fabrication technology utilizes oriented polymer fibers in various forms: unidirectional lay‐up, woven fabric or chopped fibers/non‐woven felt. The key element in the processing scheme is the control of the fibers' melting temperature by hydrostatic pressure. The fibers are heated under high pressure to a temperature that is below their melting point at the high pressure but above the melting temperature at some lower pressure. Reduction of pressure for controlled time results in melting of the fibers, which starts at the fiber surface. This surface melting under controlled pressure followed by crystallization produces the consolidated structure. We illustrate and describe this process using fibers of ultra‐high‐molecular‐weight polyethylene (UHMWPE), showing the effect of the processing conditions on the flexural modulus, fiber/matrix ratio, and CTE in plane and in the thickness direction. These properties are relevant to the use of such composites as substrates for microwave antennae. Copyright © 2003 John Wiley & Sons, Ltd.
Gel point prediction of metal‐filled castor oil‐based polyurethanes system
Authors: Srivastava Anil , Singh P.
Published: January 2003

Prediction of gel point conversion and network formation is of great importance in polycondensation during synthesis as well as processing. It enables one to estimate the safe conversions for reactor operation without gelation and the cycle time during processing, and plays an important role in controlling the molding parameters used for reinforced reaction injection molding (RRIM), reaction injection molding (RIM) and compression molding. Theories of gelation have been extensively published in the literature and supported by experimental data for various polycondensation systems. However, most such studies relate to unfilled systems. In this work, metal‐filled polyurethanes have been synthesized in bulk by reacting toluene di‐isocyanate with castor oil and its polyols possessing different hydroxyl values. Metallic aluminum powder (10–40% by weight) was dispersed thoroughly in castor oil and its polyols before reacting at different temperatures (30–60 °C) in a moisture‐free, inert environment. The gel point conversions were measured experimentally and an empirical model from the experimental data has been developed to predict the gelation behavior. The proposed model could be of immense importance in the paints, adhesives and lacquers industries, which use castor oil in bulk. From these experiments it was concluded that: (i) fine metal powder gives a rise in viscosity; (ii) metal fillers not only restrict the molecular motion due to the increase in viscosity, but also lower the conversion; (iii) the vegetable oil and its polyols have a number of bulky groups, which also impart the delay tendency in gel time; (iv) there is a change in gelation dynamics at 50 °C – this is due to the change in reactivity of di‐isocyanates; (v) the presence of metal filler does not initiate the intermolecular condensation; (vi) there is a gap between theoretical and experimental gel point owing to the unequal reactivity of the secondary alcohol position; (vii) there is an inverse relationship of gel time with the reaction temperature and hydroxyl value of polyols. An empirical model based on process parameters, i.e., hydroxyl value, temperature, shape factor and filler concentration, has been derived and found to be adequate for the metal‐filled system. The correlation coefficient on the data is on the lower side in some cases because the following were not taken into account: (i) the first‐order kinetics followed by the reaction in the second half while it is tending towards gelation; (ii) the error in observing the gel point viscosity; (iii) errors in assuming the spherical shape of aluminum metal powder; (iv) errors due to failure to maintain the constant speed in agitation. Copyright © 2003 John Wiley & Sons, Ltd.
The use of polymers for coating of cells
Authors: Kampf Nir
Published: January 2003

Bare cells or tissues are sometimes exposed to external hazardous conditions, physical (thermal changes), chemical or biological (such as enzymes, bacteria and viruses). Liquids, semi‐liquids (e.g. gels) or solid films are often used to surround individual cells or tissues in order to protect them and to achieve greater stability in laboratory and industrial uses. On the one hand there is a need for isolation and creating a barrier between the cell and its surroundings, and on the other hand this should not affect the metabolism and viability of the cell used. Polymers are major substances for cell encapsulation and entrapment. These preparations are often used for the manufacture of drugs and other cell metabolites. There are only a few publications describing single‐cell coating. We can consider a definition of coating as a process of surrounding an object with a thin film, having a thickness of only a small fraction of the object's dimensions. Taking this definition into account, in fact, most coating experiments actually deal with entrapment or immobilization rather than coating. The latest research shows for the first time the ability to coat a single cell by producing a thin gel layer around it. Xenopus laevis eggs and embryos were used as a model system for coating with thin films composed of low‐methoxy pectin (LMP), alginate, and ι‐ and κ‐carrageenans. These gums have different compositions and structures and accordingly created different coatings around the cells. The first goal was to achieve a thin film (∼50 µm) around an individual non‐fertilized egg (one cell). Next, the influence of coating an early‐stage toad embryo was tested. All coated embryos appeared to develop normally, similar to non‐coated embryos. The survival percentages after hatching of coated embryos were significantly higher than of the non‐coated control. In addition, the coating served as a barrier to microbial contamination and thus improved survival prospects. The coatings delayed hatching by 18 to 24 hr. At hatch, the embryos were at a more developed stage than their non‐coated counterparts. Thus, coating cells by polymeric thin film appears to be a suitable tool for laboratories interested in performing longer‐term experiments with cells or embryos. Copyright © 2003 John Wiley & Sons, Ltd.
Process–structure–property relationships of erodable polymeric biomaterials, I: Poly(desaminotyrosyl arylates)
Authors: Jaffe Michael , Pai Vaishali , Ophir Zohar , Wu Jing , Kohn Joachim
Published: January 2003

Polymeric biomaterials, especially new compositions, are often tested for biocompatibility, bioerosion rate or cell growth specificity without regard to the morphological structures introduced during materials processing. It will be shown that in addition to the potential influence on biological response, processing induced structure profoundly influences materials properties under bio‐relevant conditions. Using a combinatorial library of erodable Polyarylates, these issues will be explored with emphasis on in‐vivo dimensional stability and mechanical property retention. Copyright © 2003 John Wiley & Sons, Ltd.
ATR‐FTIR studies on the effect of strong salting‐out salts on the phase separation scenario in aqueous solutions of poly(N‐isopropylacrylamide) [PNIPA]
Authors: Kesselman Ellina , Ramon Ory , Berkovici Ronen , Paz Yaron
Published: January 2003

Attenuated total reflectance (ATR) FTIR spectroscopy was used to investigate the effect of two strong salting‐out salts (Na2SO4 and K2SO4) on the temperature‐induced phase separation process in aqueous solutions of poly(N‐isopropylacrylamide) [PNIPA]. It was found that the addition of these salts not only depresses the phase transition temperature (as was pointed out by other groups in the past) but, in fact, changes the whole scenario below, at, and above the aggregation temperature. Deconvolution of the amide II peak into three sub‐bands reflecting three types of populations that differ by their hydrogen bonding types revealed that the sulfate ions decreased the amount of amide–water hydrogen bonds, while increasing the amount of amide–amide intramolecular H‐bond population. This led to a relatively compact structure even at low temperatures. Based on the behavior of the hydrophobic IR peaks it is suggested that addition of sulfate ions increases the importance of hydrophobic interactions below the phase separation temperature. This study demonstrates the potential of ATR‐FTIR in providing information at a molecular level on phase separation phenomena in aqueous solutions of hydrophobic polymers and, in particular, on the effects of co‐solutes in such systems. Copyright © 2003 John Wiley & Sons, Ltd.
Studies on hydrolytic degradation of epoxy‐polyester resins cured with glutaric anhydride
Authors: łukaszczyk Jan , Jaszcz Katarzyna
Published: January 2003

Biodegradable epoxy‐polyester resins were synthesized in two steps: (1) synthesis of the polyesters with allyl pendent groups; (2) epoxidation of allyl groups in the polyesters. Polyesters with allyl pendent groups were synthesized by melt copolymerization of succinic anhydride (SA) and allyl glycidyl ether (AGE) in the presence of benzyltrimethylammonium chloride (BTMAC) as a catalyst. Functionality of some polyesters was reduced by replacing a part of AGE with butyl glycidyl ether (BGE). The epoxidation of the polyesters obtained was carried out using m‐chloroperbenzoic acid (MCPBA). The multifunctional epoxy‐polyester resins were cured using different amounts of glutaric anhydride (GA) and without use of it. The cured resins were degraded in aqueous buffer of pH = 7.4 at 70 and 37 °C. The hydrolytic degradation was monitored by determination of mass loss. Fracture surfaces of the samples were examined by scanning electron microscopy. Influence of the composition of initial resins and amount of GA used on the hydrolytic degradation was studied. The products of degradation were identified by HPLC and 1H‐NMR. Copyright © 2003 John Wiley & Sons, Ltd.
Advanced environment‐friendly polymer materials
Authors: Ioelovich M. , Figovsky O.
Published: January 2003

Novel environment‐friendly hydrophobic polymer materials–layer composites–were developed. These composites consist of a thick layer of cellulose substrate and a thin protective layer of a biodegradable polymer. Various types of the layer composites and their applications were described. Correlation between a porous structure of the protective polymer layer and composite properties was found. Wastes of the novel polymer materials can be utilized in two ways: by repulping and by biodegradation. Widespread usage of the proposed polymer composite materials will bring about an improvement in the ecological state of the environment. Copyright © 2003 John Wiley & Sons, Ltd.
Sociocultural and individual influences on muscle gain and weight loss strategies among adolescent boys and girls
Authors: RICCIARDELLI LINA A. , McCABE MARITA P.
Published: January 2003

The study examined the role of body dissatisfaction, body image importance, sociocultural influences (media and parent and peer encouragement), self‐esteem and negative affect on body change strategies to decrease weight and increase muscles in adolescent boys and girls. Surveys were administered to 587 boys and 598 girls aged between 11 and 15 years. For both genders, parent and peer encouragement and negative affect were the primary predictors of body dissatisfaction, body image importance and strategies to decrease weight and increase muscles. In addition, body image importance was a significant factor in the development of both types of body change strategies, while the media only predicted strategies to decrease weight. Lastly, the effects of self‐esteem were mediated by body dissatisfaction. For boys, a stronger focus on body importance occurred among the boys who were generally satisfied with their bodies while the reverse was the case for girls. © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 209–224, 2003.
Written emotional expression as an intervention for asthma
Authors: BRAY MELISSA A. , THEODORE LEA A. , PATWA SHAMIM S. , MARGIANO SUZANNE G. , ALRIC JOLIE M. , PECK HEATHER L.
Published: January 2003

This investigation employed a multiple baseline design across five participants to examine written emotional expression as an intervention to improve lung function in high school‐aged students, college students, and adults with asthma. The predicted forced expiratory volume in 1 second (FEV1 measure of large airway functioning) and forced expiratory flow (FEF25–75 measure of small airway functioning) were evaluated using spirometry. In addition, anxiety was measured using state and trait anxiety self‐report scales. Generally, results were effective. Individuals with asthma are at higher risk for increased hospitalization and death. For the school‐aged population, asthma is associated with increased absenteeism, restriction of various class activities such as physical education, and poor relationships with peers. Therefore, adults and children with asthma are in need of services and school psychologists appear uniquely qualified to intervene. More recently, the role of the school psychologist is diversifying with corresponding training (e.g., wellness, consultation, prevention, assessment and treatment of health issues) in the areas of health‐related disorders that involve a psychological component. © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 193–207, 2003.
Student sexual orientation, promiscuity and urban acculturation as factors that influence teacher judgments about HIV+ students
Authors: CRUCE MICHAEL K. , STINNETT TERRY A. , CHOATE KURT T.
Published: January 2003

Attributions toward HIV+ adolescents made by teacher education students who graduated from rural or urban high schools were examined. Participants read vignettes in which level of promiscuity and sexual orientation were varied, then completed a rating scale that reflected various attitudes toward HIV+ students. The vignette student labeled promiscuous was blamed and judged more personally responsible for contracting the disease than the non‐promiscuous student. Participants who reported graduating from urban high schools indicated more positive affect and positive attitude toward integration, but also higher levels of fearfulness, than did those from rural high schools. Sexual orientation and the participant's high school location interacted on the need for reporting/precautions variable. Those from urban high schools indicated a higher need for reporting and safety precautions than did those from rural high schools when the HIV+ student was labeled heterosexual. School Psychologists should be aware of the varied factors that are involved in teacher judgments concerning HIV+ students. © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 173–182, 2003.
Comparison of a QM/MM force field and molecular mechanics force fields in simulations of alanine and glycine “dipeptides” (Ace‐Ala‐Nme and Ace‐Gly‐Nme) in water in relation to the problem of modeling the unfolded peptide backbone in solution
Authors: Hu Hao , Elstner Marcus , Hermans Jan
Published: January 2003

We compare the conformational distributions of Ace‐Ala‐Nme and Ace‐Gly‐Nme sampled in long simulations with several molecular mechanics (MM) force fields and with a fast combined quantum mechanics/molecular mechanics (QM/MM) force field, in which the solute's intramolecular energy and forces are calculated with the self‐consistent charge density functional tight binding method (SCCDFTB), and the solvent is represented by either one of the well‐known SPC and TIP3P models. All MM force fields give two main states for Ace‐Ala‐Nme, β and α separated by free energy barriers, but the ratio in which these are sampled varies by a factor of 30, from a high in favor of β of 6 to a low of 1/5. The frequency of transitions between states is particularly low with the amber and charmm force fields, for which the distributions are noticeably narrower, and the energy barriers between states higher. The lower of the two barriers lies between α and β at values of ψ near 0 for all MM simulations except for charmm22. The results of the QM/MM simulations vary less with the choice of MM force field; the ratio β/α varies between 1.5 and 2.2, the easy pass lies at ψ near 0, and transitions between states are more frequent than for amber and charmm, but less frequent than for cedar. For Ace‐Gly‐Nme, all force fields locate a diffuse stable region around ϕ = π and ψ = π, whereas the amber force field gives two additional densely sampled states near ϕ = ±100° and ψ = 0, which are also found with the QM/MM force field. For both solutes, the distribution from the QM/MM simulation shows greater similarity with the distribution in high‐resolution protein structures than is the case for any of the MM simulations. Proteins 2003;50:451–463. © 2003 Wiley‐Liss, Inc.
Basic interdomain boundary residues in calmodulin decrease calcium affinity of sites I and II by stabilizing helix–helix interactions
Authors: Faga Laurel A. , Sorensen Brenda R. , VanScyoc Wendy S. , Shea Madeline A.
Published: January 2003

Calmodulin is an EF‐hand calcium‐binding protein (148 a.a.) essential in intracellular signal transduction. Its homologous N‐ and C‐terminal domains are separated by a linker that appears disordered in NMR studies. In a study of an N‐domain fragment of Paramecium CaM (PCaM1–75), the addition of linker residues 76 to 80 (MKEQD) raised the Tm by 9°C and lowered calcium binding by 0.54 kcal/mol (Sorensen et al., Biochemistry 2002;41:15–20), showing that these tether residues affect energetics as well as being a barrier to diffusion. To determine the individual contributions of residues 74 through 80 (RKMKEQD) to stability and calcium affinity, we compared a nested series of 7 fragments (PCaM1–74 to PCaM1–80). For the first 4, PCaM1–74 through PCaM1–77, single amino acid additions at the C‐terminus corresponded to stepwise increases in thermostability and decreases in calcium affinity with a net change of 13.5°C in Tm and 0.55 kcal/mol in free energy. The thermodynamic properties of fragments PCaM1–77 through PCaM1–80 were nearly identical. We concluded that the 3 basic residues in the sequence from 74 to 77 (RKMK) are critical to the increased stability and decreased calcium affinity of the longer N‐domain fragments. Comparisons of NMR (HSQC) spectra of 15N‐PCaM1–74 and 15N‐PCaM1–80 and analysis of high‐resolution structural models suggest these residues are “latched” to amino acids in helix A of CaM. The addition of residues E78, Q79, and D80 had a minimal effect on sites I and II, but they may contribute to the mechanism of energetic communication between the domains. Proteins 2003;50:381–391. © 2003 Wiley‐Liss, Inc.
Seasonal variation of the lipoidal matters and hypolipidaemic activity of the red alga Corallina officinalis L.
Authors: Awad N. E. , Selim M. A. , Saleh M. M. , Matloub A. A.
Published: January 2003

The lipoidal matters of Corallina officinalis L. showed a seasonal nonsignificant quantitative variation. However, the fatty acids revealed a relative increase in the summer and winter, while unsaponifiable matter exhibited a slight increase in the spring. The GC/MS analysis of saponifiable and unsaponifiable matter of the algal samples collected in different seasons revealed that samples collected in the spring contained a low cholesterol content and high steroidal compounds as well as high polyunsaturated fatty acids. The alcohol extract, hexane extract and fatty acid fraction of this algal sample exhibited a significant hypolipidaemic activity. Also, two biologically active fractions of hydrocarbons were isolated by CC technique from the hexane fraction of C. officinalis L. and identified by GC/MS. Copyright © 2003 John Wiley & Sons, Ltd.
Hepatoprotective and antihyperliposis activities of in vitro cultured Anoectochilus formosanus
Authors: Du Xiao‐Ming , Sun Ning‐Yi , Hayashi Jun , Chen Yang , Sugiura Minoru , Shoyama Yukihiro
Published: January 2003

The pharmacological effects of an aqueous extract of the whole plants of in vitro cultured Anoectochilus formosanus were investigated experimentally for hepatoprotective and antihyperliposis activities. The extract showed significant antihepatotoxic activity against carbon tetrachloride induced cytotoxicity in primary cultured rat hepatocytes. In an assay for antihyperliposis using aurothioglucose‐induced obese mice, the extract suppressed significantly the increase in the weights of body and liver, ameliorated triglyceride levels in the liver and serum, and also significantly reduced the deposition of adipose tissue. Copyright © 2003 John Wiley & Sons, Ltd.
In vitro immunomodulatory activity of flavonoid glycosides from Urtica dioica L.
Authors: Akbay Pinar , Basaran A. Ahmet , Undeger Ulkü , Basaran Nursen
Published: January 2003

The major compounds isolated from the methanolic extract of the aerial parts of Urtica dioica L. were determined as quercetin‐3‐O‐rutinoside (1), kaempherol‐3‐O‐rutinoside (2) and isorhamnetin‐3‐O‐glucoside (3) by chromatographic, chemical (acidic hydrolysis) and spectral (UV, IR, 1H‐NMR, 13C‐NMR) methods. Their immunomodulatory activities were studied in vitro by chemotaxis (Boyden Migration Chamber) and intracellular killing activity (NBT reduction) tests. Compounds 1, 2, 3 and the total flavonoid fraction were determined to have significant chemotactic effects in 4, 8, 16 μg doses. According to the results of the NBT reduction test, all flavonoid glycosides showed high intracellular killing activity. The results of both assays confirmed the immunostimulatory activity of the flavonoid fraction and the isolated flavonoid glycosides on neutrophils suggesting that they could possibly be useful for treating patients suffering from neutrophil function deficiency and chronic granulomatous diseases. Copyright ­© 2003 John Wiley & Sons, Ltd.
Anticonvulsant effect of FS‐1 subfraction isolated from roots of Delphinim denudatum on hippocampal pyramidal neurons
Authors: Raza Mohsin , Shaheen Farzana , Choudhary M. I. , Rahman Atta‐ur‐ , Sombati Sompong , Suria Amin , Rafiq Azhar , DeLorenzo R. J.
Published: January 2003

The effects were investigated of a partially purified subfraction (FS‐1) isolated from Delphinium denudatum on sustained repetitive firing (SRF) of cultured neonatal rat hippocampal pyramidal neurons. The blockade of sustained repetitive firing is one of the basic mechanisms of antiepileptic drugs at the cellular level. Using the whole cell current‐clamp technique, sustained repetitive firing was elicited in pyramidal neurons under study by a depolarizing pulse of 500 ms duration, 0.3 Hz and 0.1–0.6 nA current strength. FS‐1 (0.01–0.06 mg/mL) reduced the number of action potentials per pulse in a dose‐dependent manner until no action potentials were elicited for the remainder of the pulse. There was a corresponding use‐dependent reduction in amplitude and V
max of action potentials. The V
max of action potential 1 exhibited a dose‐dependent reduction. At a dose of 0.06 mg/mL FS‐1 reduced V
max to 29%–38% and amplitude to 16%–20 % of the control values. The blockade of sustained repetitive firing by FS‐1 was reversed by hyperpolarization of the membrane potential (−65 to −75 mV) while depolarization of the membrane potential (−53mV to −48 mV) potentiated the block. The results suggest that FS‐1 blocks sustained repetitive firing in hippocampal neurons in a use‐dependent and voltage‐dependent manner similar to the prototype anticonvulsant drug, phenytoin. However, unlike phenytoin, which binds preferably to the inactive state, the compounds present in FS‐1 also interacted with the resting state of the Na+ channels by reducing V
max of action potential 1. The results indicate that the partially purified FS‐1 subfraction of Delphinium denudatum contains a potent anticonvulsant compound. Copyright © 2003 John Wiley & Sons, Ltd.
Correction of haemorheological disturbances in myocardial infarction by diquertin and ascorbic acid
Authors: Plotnikov M. B. , Aliev O. I. , Maslov M. Ju , Vasiliev A. S. , Tjukavkina N. A.
Published: January 2003

In a model of the high blood viscosity syndrome, developed after myocardial infarction in rats, it was observed that a therapy of a combination of diquertin (20 mg/kg) and ascorbic acid (50 mg/kg) for a ­period of 6 days, resulted in an improvement of haemorheological indices. The decrease in blood ­viscosity was primarily due to an improved deformability of erythrocytes, and to some extent, due to a decrease in the content of plasma fibrinogen and erythrocyte aggregation. Copyright © 2003 John Wiley & Sons, Ltd.