bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave‐Assisted Synthesis under Continuous‐Flow Conditions
Authors: Glasnov Toma N. , Kappe C. Oliver
Published: February 2007

Microwave‐assisted chemistry is about to change the art and practice of synthesis performed in many academic and industrial laboratories. One of the major drawbacks of this enabling technology is the difficulty associated with scale‐up. Because of the limited penetration depth of microwaves into absorbing media, the solution to scale‐up lies in continuous‐flow processing. In this review we summarize the current state of the art in this field and present an overview on published examples of microwave‐assisted synthesis using continuous‐flow and stop‐flow processing in custom‐built or commercially available microwave reactors.

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Microwave Irradiation: A Novel Method for Rapid Synthesis of D,L‐Lactide
Authors: Zhang Ying Min , Wang Peng , Han Ning , Lei Hai Fen
Published: February 2007

D,L‐Lactide with a yield of about 36% was synthesized from D,L‐lactic acid by the addition of SnCl2 and Cat‐A as catalyst under continuous microwave irradiation in less than 1 h. In order to gain a higher yield, the viscosity‐average molecular weight of the oligomer was preferably over 3 000 g · mol−1, and the microwave power in the depolymerization process was chosen for 200 W with 100 g of D,L‐lactic acid. On comparison with conventional heating in the same experimental conditions, no non‐thermal effect of microwave irradiation was revealed.

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Microwave‐Assisted Synthesis of PLLA‐PEG‐PLLA Triblock Copolymers
Authors: Zhang Chao , Liao Liqiong , Gong Shaoqin (Sarah)
Published: February 2007

Poly(L‐lactide)‐block‐poly(ethylene glycol)‐block‐poly(L‐lactide) (PLLA‐PEG‐PLLA) triblock copolymers were synthesized effectively by poly(ethylene glycol) initiated ring‐opening polymerization (ROP) of L‐lactide under microwave irradiation. The products were characterized by 1H NMR, GPC, and DSC. The experimental results have demonstrated that PLLA‐PEG‐PLLA triblock copolymer with a number‐average molar mass of 28 230 g · mol−1 and an L‐lactide conversion of 92.4% could be synthesized after the L‐lactide/PEG2000 reaction mixture was irradiated for 3 min at 100 °C. The L‐lactide/PEG feed ratio had a strong influence on the microwave‐assisted ring‐opening polymerization, in which higher L‐lactide/PEG feed ratios led to copolymers with higher molar masses and lower L‐lactide conversions. Prolonged microwave irradiation at 100 °C did not change the molar mass of the copolymers significantly. The DSC study indicated that higher glass transition and melting temperatures were obtained for PLLA‐PEG‐PLLA triblock copolymers with longer PLLA segment length. The synthesis of the triblock copolymers via microwave heating was much faster than via conventional heating.

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Microwave‐Accelerated RAFT Polymerization of Polar Monomers
Authors: Brown Steven L. , Rayner Christopher M. , Perrier Sébastien
Published: February 2007

A monomodal microwave reactor has been employed, for the first time, for the RAFT‐mediated polymerization of methyl acrylate (MA), methyl methacrylate (MMA) and styrene. At comparable temperatures, and a uniform power output of between 1 and 3 Watts, the microwave outperformed the oil bath in terms of polymerization rate for both MA and MMA, showing rate enhancements of up to 152% and 254% for the two monomers respectively, when compared to conventional heating. Furthermore, the control appears unaffected by the rate increase, yielding low polydispersities (PDIs) (as low as 1.05) and molecular‐weight values close to predicted values. Interestingly, however, the polymerization rate of styrene ‐ a nonpolar monomer ‐ does not seem to be enhanced by the use of microwave heating.

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Comprehensive Modelling of the Experimental Temperature and Stress Response of Time‐Dependent Materials
Authors: André José R. S. , Pinto José J. Cruz
Published: February 2007

The stress‐ and temperature‐dependent non‐linear creep behaviour of polymers and other materials is quantitatively modelled as a superposition of a wide range of activated motions at the molecular scale, covering wide but well‐defined space and time scales. The resulting time, temperature and stress dependences are coupled (not fully separable) except at low stress values, where linear viscoelastic behaviour is directly obtained, improving on previous (approximate or questionable) time‐temperature and time‐stress superposition or equivalence relationships. The behaviour has been shown to have a strong cooperative nature, which may be interpreted in terms of varying clusters of identifiable structural elements within the material. Reasonably good descriptions of the experimental creep behaviour of both amorphous and semicrystalline polymers have already been achieved, but this work concentrates on the behaviour of an amorphous polycarbonate (PC), including the physical characterization and modelling of its retardation time spectrum.
An Electric Criterion to Evaluate Glass Transition Temperature: Dielectric Relaxation Measurements
Authors: D'Angelo P. , Barra M. , Cassinese A. , Guido S. , Tomaiuolo G.
Published: February 2007

In this contribution, a dielectric measurement technique for the evaluation of phase transition temperature and the study of physical aging on polymeric thin films is considered. This kind of measurement provides the possibility of displaying phase transitions with a high degree of precision. Furthermore, it can be considered alternatively to techniques not applicable in the case of thin films, such as Differential Scanning Calorimetry (DSC). In this work, owing to the high sensitivity of the utilized experimental set‐up, a glass transition TG of 156 K, with a precision equal to 0.3%, and a melting TM = 220 K have been assessed for 4 µm thick Polydimethylsiloxane (PDMS) films. Performing measurement as a function of time, it was possible to monitor physical aging phenomena, mainly consisting in a change of dielectric properties. As expected, the time evolution of the aging phenomena can be described by a simple logarithmic law.
Rheological Aspects of PP‐TiO2 Micro and Nanocomposites: A Preliminary Investigation
Authors: Acierno D. , Filippone G. , Romeo G. , Russo P.
Published: February 2007

The linear rheology of PP‐TiO2 composites was investigated as a function of the filler particle size. Small amounts (ϕ = 4.5%) of micron and nano‐sized TiO2 spherical particles were added to the polymer by melt compounding. In spite of the low particle volume fractions and the weak polymer‐filler interactions, relevant changes have been observed in the linear viscoelastic behaviour of the nanostructured formulations. Microstructural analyses performed through electron microscopy have shown a good degree of dispersion of micron‐sized particles. Conversely, the presence of a relevant number of TiO2 nanoparticle clusters has been detected for the nanocomposite. The structure of these aggregates seems to be strongly responsible for the rheological behaviour of these last materials in comparison with microstructured ones. Relevant similarities between the viscoelastic properties of nanocomposite and the flow feature of many soft glassy materials have been noticed, and a simple physical picture has been proposed in order to interpret the rheological response of studied nanocomposites.
Organic‐Inorganic Hybrid Fillers for The Controlled Release of Antioxidants
Authors: Mascia Leno , Capra Carlo , Lavorgna Marino
Published: February 2007

the barrier provided by the inorganic domains of organic‐inorganic hybrids towards the absorption of low molecular weight penetrants was used in this study as a basis for the development of systems capable of desorbing antioxidants at a slow rate. Polyethyleneoxide‐silica hybrids, compatibilized with glycidoxylpropyltrimethoxysilane, were used as carriers of conventional stabilizers for polymers, respectively two phenolic antioxidants and one hindered aromatic diamine system. Ternary phase diagrams were produced in order to determine the “compatibile compositions” using DSC to measure changes in melting point and enthalpy of the antioxidant and polyethylene oxide (PEO). A compatible composition of PEO‐silica‐BHT (tert. butyl hydroxyl toluene) was used to produce a filler, which was pressed on the form of a fine powder between two polyamide‐6 films and subsequently sandwiched with further seven layers of fresh films. The multiple‐film stack was aged first in an air circulated oven at 60 °C for 360 days and then for further 475 days at ambient atmospheric conditions. The concentration of carbonyl groups in the aged films was monitored by ATR‐IR spectroscopy. A sigmoidal increase was found for the amount of new carbonyl groups formed, starting from the inside layer nearest to the source of antioxidant. This confirms that the antioxidant has diffused from the filler into the surrounding polymer matrix and has reduced the rate of evolution of carbonyl groups resulting from oxidative degradation reactions.
Dynamic‐mechanical Investigation of Melt Compounded Poly(butylenterephtalate)/organoclay Nanocomposites
Authors: Acierno Domenico , Amendola Eugenio , Russo Pietro
Published: February 2007

Nanocomposites constituted by neat or opportunely toughened polybuthylene terephtalate filled with a commercial organoclay (Somasif™MEE) were analysed to asses their potential use in the automotive field. In particular, hybrid systems including 3–6% by weight of MEE, in presence or not of a toughening agent such as an engineering thermoplastic elastomer (Pibiflex), and obtained by melt intercalation were considered. All materials were characterised in terms of dynamic‐ mechanical properties. Results clearly proved that the optimization of the formulation composition allows to achieve a considerable improvement of the ultimate damping performances.
In Situ Formation of a Uniform Distribution of Silver Nanoparticles in PVDF: Kinetics of Formation and Resulting Properties
Authors: Compton J. , Kranbuehl D. , Martin G. , Espuche E. , David L.
Published: February 2007

Hybrid organic/silver nanoparticle thermoplastic films have been prepared using a single step process where the silver nanoparticles were formed during a cure cycle applied to the film. Figure 1 is a TEM demonstrating the ability of our technique to produce silver nanoparticles in the semi‐crystalline polymer Poly(vinylidene fluoride) (PVDF). The current laboratory focus is on characterizing kinetics and particularly the diameter growth and inter‐particle distance as a function of time and temperature using the techniques of small‐angle X‐ray scattering (SAXS), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD). Using the Beaucage model, the SAXS data demonstrates that the particle size reaches equilibrium after approximately 70 minutes of curing at 240 °C. This result is also observed in the XRD results where the half width of the diffraction peaks becomes smaller quickly during the initial hour. In a parallel experiment using DSC, the exothermic heat flow increases rapidly during the first hour but does not reach completion until almost 150 minutes.
The Twist‐Bending Behavior of Forward Swept Wings: A Case Study of a Glass/Carbon Hybrid Composite Structure
Authors: Blasi L. , Caputo F. , D'Amore A. , Golia C. , Grassia L. , Iuspa L. , Scaramuzzino F. , Soprano A.
Published: February 2007

The behavior of the wing of an aircraft is characterized by the complex interaction among dynamic (distribution of the masses), elastic (ownership of the materials) and aerodynamic (shapes, forces and moments) phenomena. As a rule it is expected from us that the aerodynamic actions damp the oscillations (natural or forced) of the wing. However, above given speeds a lot of undesired aero‐elastic phenomena, among which the divergence of the wings, occur and became of considerable importance in view of safety. To potentially prevent dangerous situations, generally the speed of the aircraft is limited; a possible alternative is to endow the “system wing” of proper devices (passive or active, i.e. controls) in order to prevent that the energy transfer of aerodynamic actions amplifies its instability. The forward swept wings are extremely efficient in terms of aerodynamics performance (stall and supersonic behavior) and therefore of maneuverability of the aircraft, even if, unfortunately, they are extremely critic under the profile of the aero‐elastic stability. The solution of the technical‐scientific and technological problems associated with the use of innovative configurations of wings prefigures a meaningful breakthrough in the international aerospace sector. Within this work the authors aim to determine a particular configuration of composite material for the realization of a forward swept wing in such a way that, under the action of the effective aerodynamic loads, the wings structural response provides a coupled bending‐torsion deformations with stability effects. It will be shown that by using a recursive analysis of the composite lay‐up one can tailor the overall bending/torsion deformation ratio value.
Numerical Investigation of the Optimum Placement Locations of Optical Fiber Bragg Grating Sensors for the Health Monitoring of Bonded Composite Repairs
Authors: Tsamasphyros G. , Kanderakis G. N. , Vrettos C. , Kalkanis K.
Published: February 2007

the use of optical Fiber Bragg Grating sensors (FBG) embedded into composite laminates has proven to be an efficient way for the monitoring of the strain field inside composite laminates. The current work focuses on the use of such sensors for structural health monitoring of bonded composite repairs, often used in the aerospace as well as in the maritime industry. In such applications, the embedding location of the FBG sensors is of great importance, since apart from general strain measurements of the composite, they provide the ability of detecting whether a crack has propagated in the metal or a debonding has occurred between the metal and the composite. Within the current work, a representative case of bonded composite repair of a cracked metallic structure is examined and a series of 3D elasticity linear static finite element models are developed. Various crack lengths and patch disbond sizes have been studied while varying strain distributions were recorded along numerous paths inside the structure. Having recorded and analyzed these strain distributions, certain guidelines have been derived concerning the optimum FBG placement inside the patch, in order to ensure efficient structural health monitoring.
Morphology of Compatibilized Ternary Blends
Authors: de Freitas Cássia Alves , Valera Ticiane Sanches , Catelli de Souza Adriana Martinelli , Demarquette Nicole Raymonde
Published: February 2007

In this work, the evolution of the morphology of polypropylene/polystyrene/poly(methyl metacrylate) (PP/PS/PMMA) blends to which graft copolymers polypropylene‐graft‐polystyrene (PP‐g‐PS) of 2 compositions (55/45 and 70/30), polypropylene‐graft‐poly(methyl metacrylate) (PP‐g‐PMMA), or styrene‐block‐(ethylene‐ co‐butadiene)‐block‐styrene (SEBS) was added has been studied. The ternary blends morphologies were predicted using phenomenological models that predict the morphology of ternary blends as a function of the interfacial tension between the blend components (spreading coefficient and free energy minimization). All blends studied presented a core‐shell morphology with PS as shell and PMMA as core. The addition of PP‐g‐PS or SEBS resulted in a reduction of the size of the PS shell phase and, the addition of PP‐g‐PMMA did not seem to have any effect on the diameter of PMMA. The difference observed between the different morphologies relied on the number of droplets of core within the shell. All the phenomenological models predictions corroborated the experimental results, except when PP‐g‐PMMA was added to the blend.
Essential Work of Fracture of photo‐oxidized LDPE/EVA Films
Authors: Fasce L. , Chiaverano G. , Lach R. , Frontini P.
Published: February 2007

The Essential Work of Fracture approach (EWF) was used to determine how UV‐C irradiation alters the fracture behaviour of LDPE/EVA films. Complementary characterization was performed by FTIR, DSC, TOM, and uniaxial tensile testing. The crosslinking reactions that govern photo‐oxidation process at initial stage of exposure stiffened the amorphous phase of the polymer, leading to films with enhanced elastic modulus, yield stress and ultimate strength, but impaired strain at break. In the fracture experiments carried out on films irradiated within 0 and 5 days, EWF methodology requirements were met and the corresponding fracture toughness parameters (we and βwp ) turned out to be sensitive to UV‐C irradiation. Longer irradiation time triggered the development of microcracks, which not allowed further stable crack growth and invalidated the application of EWF approach.
Spectromechanical Properties of Polymeric Gel Electrolytes and Blends
Authors: Nicotera I. , Coppola L. , Oliviero C. , Ranieri G. A.
Published: February 2007

In this paper we studied the spectro‐mechanical properties of polymer gel electrolytes and blends by means of shear rheology. These electrolytes were obtained by immobilizing EC/PC/LiClO4 solutions in a polymeric matrix of PEO, PAN and PMMA, respectively. Two structural and thermoreversible transitions, a strong‐to‐weak gel and a gel‐to‐sol, were revealed and discussed. Moreover, PMMA‐PVdF blends have been studied as a function of the different polymeric ratios in order to obtain the best compromise between ionic conduction and mechanical properties. Interesting mechanical properties were observed at some intermediate blend compositions.
Smart hydrogels for Novel Optical Functions
Authors: Dispenza Clelia , Leone Maurizio , Lo Presti Caterina , Librizzi Fabio , Vetri Valeria , Spadaro Giuseppe
Published: February 2007

Nanocomposites of inherently conductive polyaniline (PANI) within a highly hydrophilic polyvinyl alcohol (PVA) based hydrogel have been produced by coupling a conventional dispersion chemical oxidative polymerization to a subsequent high energy irradiation step, in order to convert the polymer stabilizing the aqueous dispersion, namely the PVA, into a highly water swollen hydrogel incorporating the PANI particles. The incorporation of the electroactive and “pH‐sensitive” polymer into a transparent and highly permeable hydrogel matrix has been pursued as a route to the development of a novel class of potentially biocompatible, smart hydrogels that can respond to changes of the surrounding environment with measurable changes in their optical properties. Absorption spectra show that the optical absorption bands typical of PANI, known to be reversibly affected by changes of the polymer oxidation state or pH or both, are well preserved in the PVA hydrogels. Even more interestingly, fluorescence is observed from the nanoparticles of PANI in its inherently conductive form, whose intensity is strongly affected by changes of pH. This has enhanced the importance of this material to a large extent from both a scientific and a practical point of view.
Synthesis of Biodegradable Polycaprolactone/Montmorillonite Nanocomposites by Direct In‐situ Polymerization Catalysed by Exchanged Clay
Authors: Harrane A. , Belbachir M.
Published: February 2007

Poly (e‐caprolactone) (PCL) layered silicate nanocomposites have the advantage adding biocompatibility and biodegradability to the traditional properties of nanocomposites. They can be prepared by in situ ring‐opening polymerization of e‐caprolactone using conventional initiator to induce polymerization in the presence of an organophilic clay, such as organomodified montmorillonite. In this work, we have used an alternative method to prepare poly(e‐caproilactone)/montmorillonite nanocomposites. The cationic polymerization of e ‐caprolactone was initiated directly by Maghnite‐TOA, organomodified montmorillonite clay, to produce nanocomposites. Resulted nanocomposites were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), force atomic microscopy (AFM) and thermogravimetry. The evolution of mechanical properties was also studied.

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Correction: Synthesis of Biodegradable Polycaprolactone/Montmorillonite Nanocomposites by Direct In‐situ Polymerization Catalysed by Exchanged Clay

Vol. 247, Issue 1, page n/a, Article first publshed online: 1 AUG 20111; DOI 10.1002/masy.200750150
Synthesis of New Methylsiloxane Oligomers with Pendant Trialkoxysilylethyl Groups for Preparation of Silicon hard Coatings
Authors: Mukbaniani O. , Zaikov G. E. , Tatrishvili T. , Titvinidze G. , Phatsatsia S.
Published: February 2007

For the purpose to prepare precursor materials for the silicon hard coatings, the hydrosilylation reactions of α, ω–bis(trimethylsiloxy)methylhydridesiloxane to trialkoxyvinylsilanes in the presence of platinum hydrochloric acid (0.1 M solution in THF), Karstedt's catalyst (Pt2[(VinSiMe2)2O]3) and platinum on the carbon (5%) were investigated. Hydrosilylation reactions at different ratios of initial compounds and at various temperatures (40–60 °C) were investigated and methylsiloxane oligomers with pendant trialkoxy fragments have been obtained. It was shown that completely hydrosilylation of all active SiH groups do not take place. The hydrosilylation reaction order, activation energy and rate constants were determined. The synthesized oligomers were characterized by 1H, 13C NMR and FTIR spectra data. Gel‐permeation chromatography, differential scanning calorimetric, thermogravimetric and wide‐angle X‐ray investigations of synthesized oligomers were carried out. Synthesized oligomers together with tetraethoxysilane were used for preparation of silicon hard coatings via sol‐gel processes.
Detection of novel non‐ras oncogenes in rat nasal squamous cell carcinomas
Authors: Hochwalt Anne E. , Wirgin Isaac , Felber Mary , Currie Diane D. , Garte Seymour J.
Published: February 2007

Rat nasal squamous cell carcinomas induced by inhalation of three direct‐acting alkylating agents yielded DNA containing activated oncogenes with no homology to any member of the ras family. The novel NIH 3T3 transforming oncogenes from tumors induced by β‐propiolactone and methylmethane sulfonate are distinct from each other based on restriction analysis. The gene isolated from β‐propiolactone—induced tumors is between 6 and 9 kb in size. None of the tumors induced by dimethylcarbamyl chloride contained positive DNA in the NIH 3T3 focus assay or in the nude mouse cotransfection assay. The rat nasal tumor model is apparently ideally suited for analysis of the roles of carcinogen and tissue specificity in oncogene activation, especially related to novel (non‐ras) transforming oncogenes.
Comparison of three recombinant murine leukemia viruses carrying the v‐src oncogene of avian sarcoma virus: Differences in in vitro transformation and in vivo pathogenicity
Authors: Feuerman Miriam H. , Lee William T.‐L. , Pattengale Paul K. , Fan Hung
Published: February 2007

We previously described a recombinant Moloney murine leukemia virus (Mo‐MuLV) carrying the v‐src oncogene, Mo‐MuLV(src). Mo‐MuLV(src) encodes a gag‐src fusion protein, transforms cells in culture, and induces fibrosarcomas in vivo. To compare transforming properties of the gag‐src fusion protein to pp60src encoded by Rous sarcoma virus, we constructed a new recombinant virus, Mo‐MuLV(+src). Mo‐MuLV(+src) encodes pp60src in the context of Mo‐MuLV. Cells transformed by Mo‐MuLV(+src) were round and formed colonies in soft agar, whereas Mo‐MuLV(src)‐infected cells were fusiform and did not grow in suspension. Thus, the extent of transformation induced by Mo‐MuLV(+src) was greater than that induced by Mo‐MuLV(src). Subcutaneous inoculation of either virus into neonatal NIH Swiss mice resulted in fibrosarcomas at the site of injection. Further studies indicated that tumors induced by Mo‐MuLV(+src) grew rapidly but rarely metastasized. In contrast, tumors induced by Mo‐MuLV(src) grew somewhat more slowly but metastasized with a high frequency (60%). These viruses may provide a useful model system for tumor metastasis. Another src‐containing virus was also studied, MRSV (constructed by Anderson and Scolnick). MRSV also encodes pp60src but in the context of amphotropic MuLV. When injected intravenously into six‐week‐old mice, MRSV induced splenomegaly and spleen foci but no solid tumors, as reported previously. In contrast, Mo‐MuLV(src)‐induced fibrosarcomas mostly in the spleen under the same inoculation protocol. These results suggest that the v‐src oncogene was the major pathogenic determinant in neonatal mice for all three src‐containing viruses; however, variations in the nature of the transforming protein modulated the behavior of the induced tumors. In adult mice, greater differences in pathogenicity were observed.
Aberrant expression during two‐stage mouse skin carcinogenesis of a type 147‐kDa keratin, k13, normally associated with terminal differentiation of internal stratified epithelia
Authors: Nischt Roswitha , Roop Dennis R. , Mehrel Thomas , Yuspa Stuart H. , Rentrop Martin , Winter Hermelita , Schweizer Jürgen
Published: February 2007

Specific keratin cDNA probes and monospecific antikeratin antisera were used to analyze mouse epidermis and epidermal tumors for the expression of a type I 47‐kDa keratin, K13, normally associated with terminal differentiation of internal stratified epithelia. We demonstrated that this keratin was virtually absent from the entire body epidermis at various stages of development. Also, it was not detected in various forms of acute and chronic epidermal hyperproliferation or in epidermal cells cultured under conditions that favored either cell proliferation or in vitro differentiation. In contrast, K13 was consistently expressed in squamous cell carcinomas of the skin induced by 7,12‐dimethylbenz[a]anthracene and 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), whereas papillomas obtained by the same two‐stage protocol were distinctly heterogeneous with regard to the expression of this keratin. These findings were true for two different strains of mice (NMRI and Sencar). Papillomas collected from Sencar mice after 12 wk or from NMRI mice after 15 wk of promotion with TPA were either negative for K13 or elicited variable amounts of this keratin. In all cases of positive expression of K13 in tumors, as in normal stratified internal epithelia, both the keratin protein and its mRNA invariably occurred in the differentiating cell compartments. In contrast to what we found in internal stratified epithelia, however, K13 was expressed without its commonly encountered type II 57‐kDa partner, K4. Papillomas negative for the K13 protein were also devoid of K13 transcripts. This indicates that the aberrant K13 expression in tumors is regulated at the level of transcription. Our results suggest that K13 may provide a marker for malignant conversion in the mouse two‐stage skin carcinogenesis model and may be especially suited for studies of gene expression regulation.
Altered expression of acute‐phase reactants in mouse liver tumors
Authors: Liao Warren S. L. , Ma Kang‐Tao , Becker Frederick F.
Published: February 2007

We studied the expression of eight liver acute‐phase genes in spontaneous and diethylnitrosamine‐induced mouse liver tumors (MLTs) under basal and induced conditions. Primary spontaneous and chemically induced MLTs were used for RNA isolation and histopathologic analysis. In the noninduced state, all MLTs showed similar levels of mRNA for albumin, serum amyloid A, α1‐acid glycoprotein, haptoglobin, and α‐, β‐, and γ‐fibrinogens compared with control or background livers. The mRNA for the α‐major acute‐phase protein, however, was consistently elevated in both spontaneous and diethylnitrosamine‐induced MLTs.

The expression of these acute‐phase reactants in 11 MLTs was examined following exposure of the mice to turpentine. The relative expression of these mRNAs in these MLTs varied widely compared with mRNA expression in controls. Though all MLTs expressed the same three species of fibrinogen mRNAs as did the controls, no MLT demonstrated downregulation of albumin mRNA levels, and only 1 of 11 MLTs showed a marginal increase in serum amyloid A mRNA levels. Synthesis of mRNA for α‐acid glycoprotein and haptoglobin was intermediate.

The study of the response of MLTs to specific acute‐phase stimuli may make possible a better understanding of the basis for coordinated expression of acute‐phase reactants and of the variable phenotypes associated with cancers.
Malignant transformation of human bladder epithelial cells by DNA transfection with the v‐raf oncogene
Authors: Skouv Jan , Ottesen Svend , Mark George , Autrup Herman
Published: February 2007

Transfection of the v‐raf oncogene into immortalized, nontumorigenic human bladder epithelial cells resulted in the isolation of two tumorigenic transformants. Both were identified as human and of the same origin as the parent cell line by human leukocyte antigen typing and Southern blot analysis. Both the primary tumorigenic transfectants and the cell lines established from the induced tumors expressed v‐raf mRNA and v‐raf protein. In both tumorigenic transformants the level of c‐myc mRNA was enhanced compared with that of the parent cell line.
Increased expression of glycolysis‐associated genes in oncogene‐transformed and growth‐accelerated states
Authors: Persons Derek A. , Schek Nancy , Hall Bruce Lee , Finn Olivera J.
Published: February 2007

An accelerated rate of glucose transport and catabolism is a common characteristic of cellular transformation. We have previously found elevated expression of the glycolytic enzyme glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) in human pancreatic and colonic adenocarcinomas (Schek et al.: Cancer Res 48:6354–6359, 1988). To investigate further the expression of this enzyme in the process of tumorigenesis, we examined GAPDH expression in a panel of oncogene‐transformed fibroblasts. Significant elevations of GAPDH mRNA and glucose transporter protein mRNA levels were observed in ras‐ and mos‐transformed NIH 3T3 cells, whereas little or no change was found in c‐src‐, v‐src‐, c‐myc‐, E1A‐, v‐fos‐, and PKC‐γ‐transfected cells. Furthermore, the level of GAPDH mRNA correlated with the transformed state in a series of ras‐transformed and revertant cell lines. Immunoblot analysis confirmed that GAPDH polypeptide was significantly elevated in the cell lines with elevated mRNA levels. Cell cycle analysis data suggested that the effect on GAPDH expression correlated with oncogene expression rather than cell growth fraction. These results suggest that altered GAPDH gene expression occurs during some growth deregulated states, and this, along with increased glucose transporter (and possibly other glycolytic enzyme) expression, is likely to contribute to the increased metabolic capacity of cells in these states.
Codon 61 Mutations in the c‐Harvey‐ras Gene in Mouse Skin Tumors Induced by 7,12‐Dimethylbenz[a]anthracene Plus Okadaic Acid Class Tumor Promoters
Authors: Fujiki Hirota , Suganuma Masami , Yoshizawa Shigeru , Kanazawa Hiroshi , Sugimura Takashi , Manam Sujata , Kahn Scott M. , Jiang Wei , Hoshina Sadayori , Weinstein I. Bernard
Published: February 2007

Three okadaic acid class tumor promoters, okadaic acid, dinophysistoxin‐1, and calyculin A, have potent tumor‐promoting activity in two‐stage carcinogenesis experiments on mouse skin. DNA isolated from tumors induced by 7,12‐dimethylbenz[a]anthracene (DMBA) and each of these tumor promoters revealed the same mutation at the second nucleotide of codon 61 (CAA → CTA) in the c‐Ha‐ras gene, determined by the polymerase chain reaction procedure and DNA sequencing. Three potent 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA)‐type tumor promoters, TPA, teleocidin, and aplysiatoxin, showed the same effects. These results provide strong evidence that this mutation in the c‐Ha‐ras gene is due to a direct effect of DMBA rather than a selective effect of specific tumor promoters.
Human cDNA‐Expressed Cytochrome P450 IA2: Mutagen Activation and Substrate Specificity
Authors: Aoyama Toshifumi , Gonzalez Frank J. , Gelboin Harry V.
Published: February 2007

The vaccinia virus cDNA expression system was used to produce human cytochrome P450 IA2 in a hepatoma cell line that is devoid of significant basal levels of P450. The expressed enzyme yielded a reduced carbon monoxide‐bound difference spectrum with a λmax of 449 nm. Catalytic activities and mutagen activation ability of the human enzyme were assessed and directly compared with results obtained with the orthologous mouse IA2, which was also expressed using vaccinia virus. Both the human and mouse enzymes were able to catalyze efficiently the p‐hydroxylation of aniline. Mouse IA2 also catalyzed ethoxyresorufin O‐deethylation, and its activity was sevenfold greater than expressed human IA2. The mouse and human enzymes also activated several promutagens and procarcinogens. Mouse IA2 was five‐ to sevenfold more active than the human enzyme for activation of the procarcinogens 2‐acetylaminofluorene and benzo[a]pyrene‐trans‐7,8‐dihydrodiol and the promutagens Glu‐P‐2 and Trp‐P‐1. Comparable activities were observed with 2‐aminoanthracene, 2‐aminofluorene, and Glu‐P‐1. These data demonstrate the utility of cDNA expression for examining the activities of human P450s and further suggest potentially important differences in catalytic activities of orthologous P450s found in different species.
Abolishment of c‐fos Inducibility in ras‐Transformed Mouse Osteoblast Cell Lines
Authors: Nose Kiyoshi , Itami Makiko , Satake Masanobu , Ito Yoshiaki , Kuroki Toshio
Published: February 2007

Proto‐oncogene c‐fos is induced by many types of cellular stimuli, such as 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), epidermal growth factor (EGF), serum (fetal bovine), calcium ionophore A23187, and dibutyryl cAMP (But2cAMP). In this study, c‐fos induction was abolished in ras‐transformed mouse osteoblast cells (MC3T3). Transformants of MC3T3 were isolated after transfection with Ki or Ha murine sarcoma virus DNA. All Ki‐ or Ha‐ras transformed MC3T3 clones examined showed exceedingly low levels of c‐fos induction by all inducers, as determined by the change in amounts of c‐fos mRNA or its product. Induction of other TPA‐responsive genes, such as metallothionein, was not altered in some ras‐transformed cells; c‐myc and c‐jun expression was constitutively high in all the ras‐transformed clones. Nuclear extracts and gel shift assay showed that the binding activity to c‐fos enhancer element (serum response element) was altered in ras‐transformed cells. These results indicate that transformation with ras oncogene induces modification of c‐fos enhancer binding factors and that this modification is one cause for the decrease in c‐fos induction.
Deletion of the c‐Ha‐ras‐1 Allele in Human Skin Cancers
Authors: Ananthaswamy Honnavara N. , Applegate Lee A. , Goldberg Leonard H. , Bales Elise S.
Published: February 2007

Previous studies have shown that c‐Ha‐ras‐1 and other genes located on the short arm of chromosome 11 are frequently lost in a number of human tumors. We investigated whether similar losses of the c‐Ha‐ras‐1 allele occurred in human squamous cell carcinomas (SCCs) and basal cell carcinomas (BCCs). DNAs were isolated from 35 pairs of skin tumors (25 BCCs and 10 SCCs) and matching normal skin from the same patients and analyzed for c‐Ha‐ras gene polymorphism by Southern blot hybridization. Sixteen BCC patients and 1 SCC patient were constitutionally heterozygous for the c‐Ha‐ras gene in their normal skin DNA. Of these 17 patients, five patients (four with BCC and one with SCC) (29%) showed loss of one of the c‐Ha‐ras alleles in their tumor DNA. One of the constitutionally heterozygous BCC patients exhibited deletion of the 6.6‐kb c‐Ha‐ras allele and an extra copy of the 7.8‐kb allele. In summary, loss of heterozygosity at the c‐Ha‐ras locus occurred frequently (29%) in the 17 human skin cancers studied. However, our finding that 90% of the patients with SCC, as opposed to 36% of the patients with BCC, had only one of the c‐Ha‐ras alleles in their normal skin tissue requires further study. Whether c‐Ha‐ras homozygosity has any bearing on genetic susceptibility to SCC remains to be established.
Amplification and Overexpression of c‐myc Proto‐Oncogene Correlate With the Loss of Glucocorticoid Dependence in Rodent Cells Transformed by Human Papillomavirus Type 16
Authors: Crook Tim , Banks Lawrence , Smith Katy , Crawford Lionel
Published: February 2007

Transformation of baby mouse kidney epithelial cells by human papillomavirus (HPV) type 16 is dependent both upon the cooperating oncogene and on the hormonal conditions after transfection. With v‐fos as the oncogene, the transformed cells require glucocorticoid hormone, such as dexamethasone, for proliferation. This requirement is lost on continued passage of cell lines, and the cells become dexamethasone independent. Steroid‐independent cell lines are also produced by growth of the HPV16/v‐fos cells in 17 β‐estradiol following transfection, but cell lines produced in this manner showed no subsequent requirement for estradiol or dexamethasone. Expression of the c‐myc proto‐oncogene was measured in dexamethasone‐dependent and independent cell lines. Dexamethasone‐dependent cell lines all exhibited low level c‐myc expression, but this markedly increased in the cell lines that had become dexamethasone independent as a result of continued in vitro growth. The low level of c‐myc expression in some early passage dexamethasone‐dependent cell lines appears to be associated with rearrangement of the c‐myc locus, whereas late passage dexamethasone‐independent cell lines contain amplified c‐myc sequences. Dexamethasone‐independent cell lines derived by growth in 17 β‐estradiol showed higher levels of c‐myc expression, together with higher c‐myc copy number, than dexamethasone‐dependent lines. Taken together, these studies indicate that the steady‐state level of c‐myc expression affects the continued requirement of HPV 16‐transformed cells for dexamethasone.
Altered Growth Factor Dependence and Transforming Growth Factor Gene Expression in Transformed Rat Tracheal Epithelial Cells
Authors: Ferriola Patrice C. , Walker Cheryl , Robertson Alice T. , Earp H. Shelton , Rusnak David W. , Nettesheim Paul
Published: February 2007

The role of peptide growth factors in neoplastic progression of transformed rat tracheal epithelial (RTE) cells was assessed by examining growth factor requirements and expression of growth factor and growth factor receptor genes in normal and transformed RTE cells. Neoplastically transformed cell lines showed decreased requirements for bovine pituitary extract, insulin, and epidermal growth factor compared to normal primary RTE cells. Neoplastic RTE cell lines expressed significantly increased levels of transforming growth factor α (TGFα) RNA and secreted TGFα into the media, suggesting an autocrine role for this growth factor. Increased levels of TGFα RNA were also observed in the preneoplastic stages of the same cell lines, indicating that increased TGFα expression is an early event in the multistage process of neoplastic transformation of RTE cells. TGFβ transcripts were also overexpressed in neoplastically transformed cell lines. Our studies suggest that aberrant expression of growth factors may play an important role in the development and/or maintenance of the transformed phenotype in RTE cells.
Stable expression of human cytochrome P450IA2 cDNA in a human lymphoblastoid cell line: Role of the enzyme in the metabolic activation of aflatoxin B1
Authors: Crespi Charles L. , Steimel Dorothy T. , Aoyama Toshifumi , Gelboin Harry V. , Gonzalez Frank J.
Published: February 2007

A human lymphoblastoid cell line stably expressing a human cytochrome P4501A2 cDNA was developed. This
recombinant cell line displayed P4501A2 protein and estradiol2‐hydroxylase activity, neither of which was detected
in the parental cell line. The recombinant cell line was also approximately 1000‐fold more sensitive t o the cyto‐
toxicity and mutagenicity of the carcinogenic mycotoxin aflatoxin B1 than was the parent cell line. The increase
in mutagenicity was supported by a corresponding increase in the level of aflatoxin B1 binding t o DNA in cells
expressing P4501A2 relative to control cells.
A common cellular pathway for v‐mos and v‐Ki‐ras is not required for v‐Ki‐ras‐induced tumorigenicity in a nonmalignant, v‐mos‐expressing revertant cell
Authors: Gerfaux Jacqueline , Sergiescu Dina , Hamelin Richard , Joret Anne‐Marie , Lallemand Christophe
Published: February 2007

A revertant cell line was selected from Moloney sarcoma virus‐transformed BALB/c cells after long‐term treatment with type I interferon. Despite an actively transcribed and transferable v‐mos gene, these revertant cells were nontumorigenic in nude mice. The functionality of the mos protein was investigated, focusing on the α2(1) collagen promoter regulation, which is known to be affected by mos‐induced trans‐acting factors. Both in transient expression assays and after stable integration into the cellular genome, the transfected α2(1) collagen promoter fused to the cat reporter gene was activated in the revertant while being downregulated in the original transformed cells. In retransformation assays of the revertant by Moloney sarcoma virus strains homologous to the original transforming virus, no detectable change was noted in the in vitro phenotype or in tumorigenicity. These results reveal that the mos‐directed factors were no longer effective on their specific targets. Thus, the R.MSVIF cell could be either an oncoprotein‐deficient or a target‐related revertant. Attempts at retransformation with unrelated sarcoma viruses bearing v‐sis, v‐fms, or v‐fos oncogenes were also negative. In contrast, tumorigenicity was obtained with the unrelated Kirsten sarcoma virus without any change in the revertant morphology or collagen expression. These findings showed that the common pathway blocked by the reversion and shared by v‐mos and v‐ras was not required for ras‐induced tumorigenicity.
Decreased expression of the growth hormone receptor and growth hormone binding protein in rat liver nodules
Authors: Levinovitz Agneta , Husman Bolette , Eriksson Lennart C. , Norstedt Gunnar , Andersson Göran
Published: February 2007

The growth hormone receptor (GHR) and growth hormone‐binding protein (GH‐BP) expression were characterized in liver nodules and hepatomas from male Wistar rats. The mRNA levels of GHR and GH‐BP, studied by northern blot analysis and solution hybridization, were 35–50% (in nodules) and 2–6% (in hepatomas) of the level found in liver from untreated, age‐matched rats. The binding of 125I‐labeled human growth hormone to a low‐density membrane fraction (LDMF) containing Golgi and endosome membranes in the presence of excess ovine prolactin was 75–80% lower in nodules than in liver. When endogenous ligand was removed, the binding increased in nodules but not in liver. Affinity cross‐linking experiments revealed identical specific receptor‐binding protein complexes at Mr of 95,000, 55,000, and 43,000 in both nodules and liver, assuming stochiometric binding of ligand. The in vivo endocytosis of 125I‐labeled bovine growth hormone correlated with the level of GH binding and was thus reduced 75–80% in nodules, compared with liver. The level of insulin‐like growth factor‐I (IGF‐I) mRNA was reduced by 50% in nodules; however, GH administration resulted in a twofold induction of IGF‐I mRNA in both nodules and liver. It is concluded that the greater proportion of occupied GHR in nodules could result from an impaired dissociation of endogenous GH, which might explain the reduced GHR mRNA expression. Furthermore the low GHR mRNA expression may reflect a de‐differentiated phenotype in nodules.
Effects of protease inhibitors on c‐myc expression in normal and transformed C3H 10T1/2 cell lines
Authors: Chang Janice D. , Li Jih‐Heng , Billings Paul C. , Kennedy Ann R.
Published: February 2007

In the present study, the effect of protease inhibitors on c‐myc expression in normal and transformed C3H 10T1/2 cells was examined. Steady‐state c‐myc RNA levels were reduced in normal proliferating C3H 10T1/2 cells grown in medium containing antipain, leupeptin, and Bowman Birk inhibitor (BBI). These protease inhibitors have been shown previously to suppress transformation yields in carcinogen‐exposed cells. A lesser reduction in c‐myc RNA levels was observed when cells were grown in the presence of protease inhibitors that do not suppress carcinogenesis and when transformed C3H 10T1/2 cell populations were grown in the presence of the anticarcinogenic protease inhibitors. Studies to determine the effects of antipain on the stability of the c‐myc message and on c‐myc transcription rates were also performed. The half‐life of the c‐myc message increased from 10 to 40 min when cells were grown in antipain; cycloheximide further stabilized the c‐myc message. Interestingly, nuclear run‐off experiments showed that antipain had no effect on c‐myc transcription rates. These data suggest that proteases may be involved in the regulation of c‐myc RNA expression in normal C3H 10T1/2 cells, possibly by a posttranscriptional mechanism.
Specific Ki‐ras codon 61 mutations may determine the development of urethan‐induced mouse lung adenomas or adenocarcinomas
Authors: Nuzum Edwin O. , Malkinson Alvin M. , Beer David G.
Published: February 2007

In A/J strain mice, the carcinogen urethan induces lung adenomas and adenocarcinomas that contain Ki‐ras‐activating mutations primarily in codon 61. These mutations affect the middle adenine in codon 61 resulting in the substitution of either arginine (AT→GC transition) or leucine (AT→TA transversion) for the wild‐type gluta‐mine. To analyze the expression of the wild‐type and mutant Ki‐ras mRNAs in primary mouse lung tumors and transformed mouse lung cell lines, we utilized reverse transcription of total mRNA and DNA amplification by the polymerase chain reaction. The wild‐type allele of coden 61 was expressed in all normal lung and primary tumor samples and in all transformed cell lines, except one. Significantly, the leucine‐substituted allele was expressed primarily in very small lung adenomas, whereas the arginine‐substituted allele was expressed in large lung adenocarcinomas and transformed lung cell lines. The relative amounts of expression of the mutant versus wild‐type Ki‐ras alleles and the total Ki‐ras mRNA expression was similar in both lung adenomas and adenocarcinomas. Further, the arginine mutant allele was present in adenocarcinomas having either alveolar or papillary tumor morphologies. These results suggest that the specific activating Ki‐ras mutation is more critical to either lung adenoma or adenocarcinoma development than is the tumor's cell of origin or the extent to which the mutant alleles are expressed. A distinct role of the specific activating Ki‐ras mutations in affecting lung tumor growth or malignant potential is indicated.