bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of melting and characterization of the thermodynamic and kinetic properties of syndiotactic polystyrene
Authors: Sorrentino A. , Pantani R. , Titomanlio G.
Published: December 2006

A study of the crystallization process of syndiotactic polystyrene is carried out, with particular emphasis on the effect of previous melt annealing on the subsequent crystallization kinetics and polymorphism, with a combination of thermal analysis, infrared spectroscopy, and X‐ray diffraction. An effort is made to obtain quantitative results in terms of the relative crystallinity content of the α and β phases after a given thermal treatment. A kinetics of melting for the crystalline memory is proposed, which enables the determination of the time at a given temperature that ensures the complete fusion of the α crystals. This leads to a generalization of the effects of the time–temperature couple on the memory effect. A particular protocol is identified, which upon solidification from the melt induces the development of just one crystalline phase, either α or β. This allows the determination of the enthalpy of crystallization, the maximum attainable crystal volume fraction, the crystallization half‐time as a function of temperature, and the Avrami index for each of the two crystalline phases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 196–207, 2007
Does PSA play a role as a promoting agent during the initiation and/or progression of prostate cancer?
Authors: Williams Simon A. , Singh Pratap , Isaacs John T. , Denmeade Samuel R.
Published: December 2006

Prostate cancer cells, like normal prostate epithelial cells, produce high levels of the differentiation marker and serine protease prostate‐specific antigen (PSA). PSA is used extensively as a biomarker to screen for prostate cancer, to detect recurrence following local therapies, and to follow response to systemic therapies for metastatic disease. While much is known about PSA's role as a biomarker, only a relatively few studies address the role played by PSA in the pathobiology of prostate cancer. Autopsy studies have documented that not only do prostate cancer cells maintain production of high amounts of PSA but they also maintain the enzymatic machinery required to process PSA to an enzymatically active form. A variety studies performed over the last 10 years have hinted at a role for PSA in growth, progression, and metastases of prostate cancer. A fuller understanding of PSA's functional role in prostate cancer biology, however, has been hampered by the lack of appropriate models and tools. Therefore, the purpose of this review is not to address issues related to PSA as a biomarker. Instead, by reviewing what is known about the genetics, biochemistry, and biology of PSA in normal and malignant prostate tissue, insights may be gained into the role PSA may be playing in the pathobiology of prostate cancer that can connect measurement of this biomarker to an understanding of the underlying etiology and progression of the disease. Prostate 67:312–329, 2007. © 2006 Wiley‐Liss, Inc.
Trapping choline oxidase in a nonfunctional conformation by freezing at low pH
Authors: Hoang Jane V. , Gadda Giovanni
Published: December 2006

Choline oxidase is a flavin‐dependent enzyme that catalyzes the oxidation of choline to glycine–betaine, with oxygen as electron acceptor. Storage at pH 6 and −20°C resulted in a change in the conformation of choline oxidase, which was associated with complete loss of catalytic activity when the enzyme was assayed at pH 6. Incubation of the inactive enzyme at pH values ≥6.5 and 25°C resulted in a fast and partial reactivation of the enzyme, which occurred with slow onset of steady state during enzymatic turnover. The rate of approaching steady state was independent of the concentrations of choline and enzyme, but increased to a limiting value with increasing pH, defining a pKa value of ∼7.3 for an unprotonated group required for enzyme activation. Prolonged incubation of the inactive enzyme at pH 6 and temperatures ≥20°C, at which no hysteretic behavior was observed, resulted in the slow and full recovery of activity over 3 h, associated with a conformational change that reverted the enzyme to the native form. Activation of the enzyme at pH 6 was enthalpy‐driven with ΔH‡ and TΔS‡ values of ∼112 kJ mol−1 and ∼20 kJ mol−1 determined at 25°C. These data suggest that freezing the enzyme at low pH induces a localized and reversible conformational change that is associated with the complete and reversible loss of catalytic activity. Proteins 2007. © 2006 Wiley‐Liss, Inc.
Destabilization of transthyretin by pathogenic mutations in the DE loop
Authors: Takeuchi Makoto , Mizuguchi Mineyuki , Kouno Takahide , Shinohara Yoshinori , Aizawa Tomoyasu , Demura Makoto , Mori Yoshihiro , Shinoda Hiroyuki , Kawano Keiichi
Published: December 2006

Transthyretin single‐amino‐acid variants are responsible for familial amyloidotic polyneuropathy, in which transthyretin variants accumulate extracellularly in the form of fibrillar aggregates. We studied the structural stabilities of four transthyretin variants (L58H, L58R, T59K, and E61K), in which a positively charged amino acid is introduced in a loop region between the D‐ and E‐strands. In addition to being located in the DE‐loop, L58 and T59 are involved in the core of the transthyretin monomer. The L58H, L58R, and T59K substitutions destabilized transthyretin more than the E61K mutation did, indicating that transthyretin is substantially destabilized by the substitution of residues located in both the DE‐loop and the monomer core. By utilizing hydrogen‐deuterium exchange and nuclear magnetic resonance, we demonstrated that residues in the G‐strand and the loop between the A‐ and B‐strands were destabilized by these pathogenic mutations in the DE loop. At the quaternary structural level, the DE‐loop mutations destabilized the dimer–dimer contact area, which may lead to transient dissociation into a dimer. Our results suggest that the destabilization of the dimer–dimer interface and the monomer core is important for the amyloidogenesis of transthyretin. Proteins 2007. © 2006 Wiley‐Liss, Inc.
Assessment of QoI resistance in Plasmopara viticola oospores
Authors: Toffolatti Silvia L , Serrati Luca , Sierotzki Helge , Gisi Ulrich , Vercesi Annamaria
Published: December 2006

QoI fungicides, inhibitors of mitochondrial respiration at the Qo site of cytochrome b in the mitochondrial bc1 enzyme complex, are commonly applied in vineyards against Plasmopara viticola (Berk. & MA Curtis) Berl. & De Toni. Numerous treatments per year with QoI fungicides can lead to the selection of resistant strains in the pathogen population owing to the very specific and efficient mode of action. In order to evaluate the resistance risk and its development, two different methods, biological and molecular, were applied to measure the sensitivity of oospores differentiated in vineyards, both treated and untreated with azoxystrobin, from 2000 to 2004. Assays using oospores have the advantage of analysing the sensitivity of bulked samples randomly collected in vineyards, describing accurately the status of resistance at the end of the grapevine growing season. Both methods correlated well in describing the resistance situation in vineyards. QoI resistance was not observed in one vineyard never treated with QoI fungicides. In the vineyard where azoxystrobin had been used in mixture with folpet, the selection of QoI‐resistant strains was lower, compared with using solely QoI. In vineyards where QoI treatments have been stopped, a decrease in resistance was generally observed. Copyright © 2006 Society of Chemical Industry
Electronic structure of CuAlO2 and CuScO2 delafossites under pressure
Authors: Gilliland S. , Pellicer‐Porres J. , Segura A. , Muñoz A. , Rodríguez‐Hernández P. , Kim D. , Lee M. S. , Kim T. Y.
Published: December 2006

The electronic structure of CuAlO2 and CuScO2 delafossites is investigated by means of optical absorption measurements under pressure and ab initio band structure calculations. Measurements are carried out on CuAlO2 monocrystals and pulsed laser deposited CuAlO2 and CuScO2 thin films up to 20 GPa. CuAlO2 is an indirect semiconductor that is stable in the pressure range explored here. The pressure coefficients of the indirect and direct gaps are found to be 15 meV/GPa and 2 meV/GPa respectively. CuScO2 is a direct semiconductor and the pressure coefficient of the excitonic peak energy is –5.5 meV/GPa. Two reversible phase transitions are observed in CuScO2. At 13 GPa the delafossite structure becomes unstable and an unidentified intermediate high pressure phase is observed, which coexists with the delafossite phase up to 18 GPa. The intermediate phase is also a wide gap semiconductor, with an step‐like absorption edge at the energy of 3.42 ± 0.02 eV at 14.0 GPa and a positive pressure coefficient. Above 18 GPa, the absorption edge becomes structureless and its form seems to be that of an indirect gap. In the downstroke, the same sequence of changes is observed, with a hysteresis of about 4 GPa, confirming the structural nature of the transitions. These results are interpreted in the light of theoretical ab initio band structure calculations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrahigh‐pressure effects in metallo‐organics
Authors: Kagoshima Seiichi , Kondo Ryusuke , Matsushita Nobuyuki , Higa Momoka , Ovsyannikov Sergey V. , Shaydarova Nadezhda A. , Shchennikov Vladimir V. , Manakov Andrey Y. , Likhacheva Anna Y.
Published: December 2006

The results are reported of the pressure (P) dependence of the electrical resistance (R), the thermoelectric power (Seebeck effect) (S), and compressibility as well as the time dependence of R at fixed P up to 20 GPa for four metallo‐organics based on the BEDT‐TTF (bisethylenedithiolo‐tetrathiofulvalene) group, θ ‐(BEDT‐TTF)2CsZn(SCN)4, α ‐(BEDT‐TTF)2I3, β ′‐(BEDT‐TTF)2PF6, and (BEDT‐TTF)‐TCNQ. X‐ray powder and single‐crystal diffraction studies were also made on θ ‐(BEDT‐TTF)2CsZn(SCN)4 at high pressures up to P ∼ 10 GPa. The R values of all the crystals decreased with pressure up to P ∼ 3–5 GPa (low‐pressure regime), and then the sign of dR /dP inverted (high‐pressure regime). From the investigation of the mechanical and structural properties, these materials were found to have a large compressibility in the low‐pressure regime, and a small one in the high‐pressure region. In θ ‐(BEDT‐TTF)2CsZn(SCN)4 we observed pressure‐ induced reversible degradation (amorphization) in structure without a solid‐phase reaction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pressure related defect engineering in silicon‐on‐insulator‐like structures produced by either oxygen or nitrogen ion implantation
Authors: Antonova I. V.
Published: December 2006

Pressure‐related effects in silicon‐on‐insulator‐like structures fabricated in either nitrogen or oxygen implanted silicon during subsequent annealing are analyzed. Among them are the removal of radiation defects from the top silicon layer, some degradation of the buried insulator, pressure dependence of charges at the Si/SiO2 (or Si/SiNx ) interface, formation of the electrically active centers in the top silicon layer and the substrate. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of pressure on the structural properties and electronic band structure of GaSe
Authors: Schwarz U. , Olguin D. , Cantarero A. , Hanfland M. , Syassen K.
Published: December 2006

The structural properties of GaSe have been investigated up to 38 GPa by monochromatic X‐ray diffraction. The onset of the phase transition from the ε ‐GaSe to a disordered NaCl‐type structural motif is observed near 21 GPa. Using the experimentally determined lattice parameters of the layered ε ‐phase as input, constrained ab‐initio total energy calculations were performed in order to optimize the internal structural parameters at different pressures. The results obtained for the nearest‐neighbor Ga–Se distance agree with those derived from recent EXAFS measurements. In addition, information is obtained on the changes of Ga–Ga and Se–Se bond lengths which were not accessible to a direct experimental determination yet. Based on the optimized structural parameters, we report calculations of band gap changes of ε ‐GaSe under pressure. The optical response and electronic band structure of the metallic high‐pressure phase of GaSe are discussed briefly. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural changes in amorphous chalcogenide semiconductors under high pressure: a Raman study
Authors: Boulmetis Y. C. , Stavrou E. , Raptis C.
Published: December 2006

The Raman spectra of binary As–S and ternary Ge–As–S semiconducting chalcogenide glasses have been studied under variable hydrostatic pressure up to 7.0 GPa. Two As–S glasses were investigated, the first at the stoichiometric composition As2S3 (with critical mean coordination number value Z = 2.4) and the other S‐rich, non‐stoichiometric one belonging to the floppy network regime (AsS4, Z = 2.2), while the ternary Ge–As–S glass was on the rigid network side (Ge25As10S65, Z = 2.6). Reversible pressure‐induced effects have been observed in the floppy AsS4 glass manifested by the amorphization of its crystalline sulphur domains. In contrast, the pressure‐induced appearance of homopolar Ge–Ge bonds and the formation of “ethanol‐like” S3Ge–GeS3 units in the rigid ternary Ge25As10S65 glass are irreversible, after pressure relief. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pressure dependence of the optical properties of wurtzite and rock‐salt Zn1–xCoxO thin films
Authors: Sans J. A. , Segura A. , Sánchez‐Royo J. F. , Ferrer‐Roca Ch. , Guillotel E.
Published: December 2006

In this paper we investigate the electronic structure of Zn1–x Cox O by means of optical absorption measurements under pressure. Thin films of Zn1–x Cox O with different Co content (from 1 to 30%) were prepared by pulsed laser deposition on mica substrates. Absorption spectra exhibit three main features that are clearly correlated to the Co content in the films: (i) absorption peaks in the infrared associated to crystal‐field‐split internal transitions in the Co 3d shell, with very small pressure coefficients due to their atomic character; (ii) a broad absorption band below the fundamental edge associated to charge transfer transitions, that exhibit relatively large pressure coefficients, indicating that the Co 3d final states must be strongly hybridized to the conduction band; and (iii) a blue‐shifted fundamental absorption edge associated to band to band transitions with a pressure coefficient close to that of pure ZnO. In the up‐stroke the transition pressure from wurtzite to rock‐salt phase decrease almost linearly as the Co increases, from 9.5 GPa in pure ZnO to about 6.5 GPa for x = 30%. In the down‐stroke pressure we observe a similar behavior, yielding a metastable rock‐salt phase at room pressure, after a pressure cycle up to 15 GPa. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pressure‐induced transition of 2DEG in δ‐doped GaAs to insulating state
Authors: Dizhur Eugene , Voronovsky Anatoly , Kotel'nikov Igor , Dizhur Sergey
Published: December 2006

The tunnelling and lateral conductance of a two‐dimensional electron gas (2DEG) formed in GaAs with a δ‐doped layer were measured simultaneously at hydrostatic pressures at helium temperatures. The resistivity of the δ‐doped layer sharply increases by more than three orders of magnitude at about 2 GPa and its temperature coefficient changes from about –0.04 to about –4 K–1. The tunnelling resistance shows only a slight change of exponential behaviour at about 1.5 GPa while a drastic change of the zero bias anomaly (ZBA) takes place just at the metal–insulator transition (MIT). Such behaviour is interpreted in terms of the pressure dependence of the GaAs band structure and DX‐level position as well as Coulomb gap formation at the MIT. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fourier grid Hamiltonian‐based multidimensional Floquet propagator method for continuous, pulsed, and bichromatic laser field: Application to the multiphoton dissociation dynamics of HCN molecule
Authors: Saha Aparna , Sarkar Pranab , Adhikari S.
Published: December 2006

We present a Fourier grid Hamiltonian‐based multidimensional propagator method for multiphoton dissociation dynamics of triatomic molecule in continuous, pulsed, and bichromatic laser field. The method has been successfully applied to the photodissociation dynamics of HCN molecule, i.e., collinear geometry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Rainbow Hamilton cycles in random regular graphs
Authors: Janson Svante , Wormald Nicholas
Published: December 2006

A rainbow subgraph of an edge‐colored graph has all edges of distinct colors. A random d‐regular graph with d even, and having edges colored randomly with d/2 of each of n colors, has a rainbow Hamilton cycle with probability tending to 1 as n →∞, for fixed d ≥ 8. © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2007
A simple solution to the k‐core problem
Authors: Janson Svante , Luczak Malwina J.
Published: December 2006

We study the k‐core of a random (multi)graph on n vertices with a given degree sequence. We let n →∞. Then, under some regularity conditions on the degree sequences, we give conditions on the asymptotic shape of the degree sequence that imply that with high probability the k‐core is empty and other conditions that imply that with high probability the k‐core is non‐empty and the sizes of its vertex and edge sets satisfy a law of large numbers; under suitable assumptions these are the only two possibilities. In particular, we recover the result by Pittel, Spencer, and Wormald (J Combinator Theory 67 (1996), 111–151) on the existence and size of a k‐core in G(n,p) and G(n,m), see also Molloy (Random Struct Algor 27 (2005), 124–135) and Cooper (Random Struct Algor 25 (2004), 353–375). Our method is based on the properties of empirical distributions of independent random variables and leads to simple proofs. © 2006 Wiley Periodicals, Inc. Random Struct. Alg.,, 2007
Probabilistic strategies for the partition and plurality problems
Authors: Dvořák Zdeněk , Jelínek Vít , Král' Daniel , Kynčl Jan , Saks Michael
Published: December 2006

We consider a game played by two players, Paul and Carol. Carol fixes a coloring ofnballs with three colors. At each step, Paul chooses a pair of balls and asks Carol whether the balls have the same color. Carol truthfully answers yes or no. In the Plurality problem, Paul wants to find a ball with the most common color. In the Partition problem, Paul wants to partition the balls according to their colors. Paul's goal is to ask Carol the fewest number of questions to reach his goal. We find optimal probabilistic strategies for the Partition problem and the Plurality problem in the considered setting. © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2007
On the exact interval estimation for the difference in paired areas under the ROC curves
Authors: Li Chi‐Rong , Liao Chen‐Tuo , Liu Jen‐Pei
Published: December 2006

An important measure for comparison of accuracy between two diagnostic procedures is the difference in paired areas under the receiver operating characteristic (ROC) curves. Non‐parametric and maximum likelihood methods have been proposed for interval estimation for the difference in paired areas under ROC curves. However, these two methods are asymptotic procedures and their performance in finite sample sizes has not been thoroughly investigated. We propose to use the concept of generalized pivotal quantities (GPQs) to construct an exact confidence interval for the difference in paired areas under ROC curves. A simulation study is conducted to empirically investigate the probability coverage and expected length of the three methods for various combinations of sample sizes, values of the area under the ROC curve and correlations. Simulation results demonstrate that the exact confidence interval based on the concept of GPQs provides not only sufficient probability coverage but also reasonable expected length. Numerical examples using published data sets illustrate the proposed method. Copyright © 2006 John Wiley & Sons, Ltd.
A 25‐year review of sequential methodology in clinical studies
Authors: Todd Susan
Published: December 2006

This paper explores the theoretical developments and subsequent uptake of sequential methodology in clinical studies in the 25 years sinceStatistics in Medicinewas launched. The review examines the contributions which have been made to all four phases into which clinical trials are traditionally classified and highlights major statistical advancements, together with assessing application of the techniques. The vast majority of work has been in the setting of phase III clinical trials and so emphasis will be placed here. Finally, comments are given indicating how the subject area may develop in the future. Copyright © 2006 John Wiley & Sons, Ltd.
Cardiovascular correlates of disclosing homosexual orientation
Authors: Pérez‐Benítez Carlos I. , O'Brien William H. , Carels Robert A. , Gordon Anne K. , Chiros Christine E.
Published: December 2006

Many people conceal their homosexuality. Concealment of homosexual orientation can be experienced as chronic stress and be associated with increased levels of physical symptoms. Research suggests that disclosure may produce a reduction in perceived stress, physical symptoms, and physiological activation. The cardiovascular activations levels of 27 healthy adult gay males were measured during resting baseline, a disclosure task (i.e. participants were instructed to talk about the difficulties associated with concealing one's sexual orientation), and a recovery phase. Several 2 (high/low concealment) × 2 (high/low disclosure) ANOVAs were conducted to determine if there was an interaction between level of concealment and level of disclosure during the recovery period. Results indicated that participants with a high concealment and high disclosure during the study exhibited significantly greater cardiovascular recovery than participants who engaged in a lower level of disclosure. These findings are discussed in light of Pennebaker's research on inhibition and confession. Copyright © 2006 John Wiley & Sons, Ltd.
Daily hassles and depressive symptoms among first year psychology students in France: the role of coping and social support
Authors: Bouteyre Evelyne , Maurel Marion , Bernaud Jean‐Luc
Published: December 2006

The start of university life demands an adaptation period, which can sometimes have an impact on the mental health of students. A total of 233 first year psychology students answered a questionnaire based on a Beck Depression Inventory, Coping Inventory of Stressful Situations, Social Support Questionnaire and Hassles Scale. The results showed 41 per cent of those surveyed suffered of depressive symptoms and that daily hassles encountered during the first year of university could be considered a relevant risk factor for depression. This study makes it possible to observe that not all coping strategies work equally well. Only task‐centered, active coping strategies were effective. With many students having to cope with leaving home, social support also plays a fundamental role. In fact, 70 per cent of those interviewed had left their hometown in order to study. The results of this study suggest that depressive symptoms should be considered a significant problem particularly in first year students. Copyright © 2006 John Wiley & Sons, Ltd.
Obstacles to instructional innovation according to college science and mathematics faculty
Authors: Walczyk Jeffrey J. , Ramsey Linda L. , Zha Peijia
Published: December 2006

Numerous studies have documented the infrequent use of learner‐centered instruction in college science and mathematics classrooms and its negative effects on undergraduate learning and motivation. The present research deepened understanding of why. Specifically, an Internet survey was constructed that explored obstacles, supports, and incentives for instructional innovation in the classroom and was sent out to college science and mathematics faculty of Louisiana. Results revealed that colleges generally were perceived to assign little or an indeterminate weight to instruction in personnel decision making. Faculty members generally have little training in pedagogy; but when they do, they are more likely to consult sources of instructional innovation and consider teaching an important part of their professional identities. Data concerning the most common sources of instructional innovation information are presented. Several suggestions are made for institutional reform that if enacted might contribute to systemic improvement in the quality of instruction undergraduates receive. © 2006 Wiley Periodicals, Inc. J Res Sci Teach
Concept maps: Experiments on dynamic thinking
Authors: Derbentseva Natalia , Safayeni Frank , Cañas Alberto, J.
Published: December 2006

Three experiments were conducted to examine the effects of map structure, concept quantification, and focus question on dynamic thinking during a Concept Map (CMap) construction task. The first experiment compared cyclic and hierarchical structures. The second experiment examined the impact of the quantification of the header concept in the map. The third experiment explored the effect of the focus question on the map. For all three experiments, the content of the CMaps was assessed for the number of dynamic propositions and the number of quantified concepts. The results show that the cyclic structure, the quantification of the header concept, and the focus question “How” significantly increased dynamic thinking. The studies, the theoretical background, and the implications of the findings are discussed. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 44: 448–465, 2007
Enzymatic acylation of ether and ester lysophospholipids in rat liver microsomes
Authors: Neumüller W. , Fleer E. A. M. , Unger C. , Eibl H.
Published: December 2006

The acylation of lysophospholipids by rat liver acyltransferases was studied. A comparison between ester and ether lysophospholipids as substrates revealed large differences in substrate properties. For instance, oleic acid from oleoyl‐CoA and arachidonic acid from arachidonoyl‐CoA were not incorporated into 1‐O‐octadecyl‐sn‐glycero‐3‐phosphocholine under experimental conditions that allowed an optimal transfer of oleic acid and arachidonic acid to 1‐O‐palmitoyl‐sn‐glycero‐3‐phosphocholine. However, we observed an acyl‐CoA‐independent transfer of arachidonic acid from 1‐O‐stearoyl‐2‐O‐arachidonoyl‐sn‐glycero‐3‐phosphoinositol to 1‐O‐octadecyl‐sn‐glycero‐3‐phosphocholine.
A continuous assay forO‐alkylglycerol monooxygenase (E.C. 1.14.16.5)
Authors: Koetting Jochem , Unger Clemens , Eibl Hansjoerg
Published: December 2006

The antitumor activity of alkyl lysophospholipids has raised some questions concerning the degradation ofO‐alkyl bonds in naturally occurring ether lipids. In this report, we describe the first continuous assay forO‐alkylglycerol monooxygenase (AGMO), the only enzyme known to cleave theO‐alkyl bond in saturated ether lipids and ether phospholipids. AGMO activity was monitored at 340 nm by coupling the NADH redox reaction to the tetrahydropteridine cofactor of the rat liver microsomal enzyme. Turnover rates as low as 0.6 nmol/min could be measured. Using radiolabeled substrates, the products were identified with a TLC‐Linear‐Analyzer. The only interference with this assay can arise from other reducing agents, e.g. dithiothreitol. The assay was used to develop protocols for the solubilization of AGMO from membrane preparations in the presence of detergents.
Differential effects of ether lipids on the activity and secretion of interleukin‐1 and interleukin‐2
Authors: Andreesen Reinhard , Giese Veronika
Published: December 2006

Alkyl lysophospholipids (ALP) are synthetic analogues of lysophosphatidylcholine and represent a new generation of antitumor drugs currently being tested in phase‐I trials in patients with cancer. The present study reports the differential modulation of human immunocompetent cells in vitro by ALP. Serum‐bound ALP effectively blocked the response of growth factor‐dependent cells to interleukin‐2 (IL‐2), inhibited the cellular production and release of IL‐2 and suppressed the comitogenic effect of interleukin‐1 (IL‐1) on mouse thymocytes. In contrast, ALP‐primed, monocyte‐derived macrophages (MO) lost their ability to release IL‐1 in response to stimuli like lipopolysaccharides (LPS) during terminal maturation from monocytes. Supernatants from ALP‐primed, LPS‐induced MO possessed costimulatory as well as direct mitogenic activity. Neither ALP alone nor ALP‐conditioned MO supernatants stimulated mouse thymocytes. Priming of MO by ET‐18‐OH, an ALP molecule not substituted in thesn‐2 position, occurred at concentrations 4‐ to 16‐fold higher than the most active compounds ET‐18‐OCH, and the thioether analogue BM 41.440. ALP also primed MO for subsequent activation of tumor cytotoxicity by LPS and interferon‐gamma.

IL‐1 has multiple biological activities in common with ALP, and it may mediate antitumor activity and other ALP effects in vivo. The ability of ALP to induce differential immunomodulation, as demonstrated in this study, may make ALP worthy of study for the therapy of both autoimmune and neoplastic disease.
A metabolite of an antineoplastic ether phospholipid may inhibit transmembrane signalling via protein kinase C
Authors: van Blitterswijk Wim J. , van der Bend Rob L. , Kramer Ïjsbrand M. , Verhoeven Arthur J. , Hilkmann Henk , de Widt John
Published: December 2006

In our search for the mechanisms by which the drug 1‐O‐alkyl‐2‐O‐methylglycero‐3‐phosphocholine (AMG‐PC) inhibits tumor growth and metastasis, we have detected a metabolite, 1‐O‐alkyl‐2‐O‐methylglycerol (AMG), in membranes of MO4 mouse fibrosarcoma cells grown in the presence of the drug. Synthetic AMG inhibited the activation of highly purified human protein kinase C by diacylglycerol in the presence of phosphatidylserine. Furthermore, AMG also inhibited the receptor‐specific binding of3H‐phorbol‐12,13‐dibutyrate to human HL‐60 promyeloid leukemia cells in a dose‐dependent fashion. AMG‐PC was not effective or much less so in these assays. We suggest that interaction of the metabolite AMG with protein kinase C may inhibit stimulus‐response coupling in tumor cells and may thus potentially contribute to the mechanism by which AMG‐PC exerts its anticancer activities.
Effect of lipid derivatives on invasion in vitro and on surface glycoproteins of three rodent cell types
Authors: Storme Guy A. , Bruyneel Erik A. , Schallier Denis C. , Bolscher Jan G. , Berdel Wolfgang E. , Mareel Marc M.
Published: December 2006

The antiinvasive activity on MO4 mouse cells of the following lipid derivatives was tested in vitro: an alkyllysophospholipid derivative (BM 41.440), an alkyl‐linked lipoidal amine (CP‐46,665) and a naturally occurring ester‐linked phospholipid (2‐LPC). In this test, BM 41.440 had the same antiinvasive potency as ET‐18‐OCH3, whereas CP‐46,665 and 2‐LPC had no effect on invasion. Comparison of the antiinvasive effect of ET‐18‐OCH3 on three types of cells showed the following ranking: 12R1C‐RK rat kidney adenovirus type 12 transfected cells>MO4 mouse cells>LLC‐H61 Lewis lung carcinoma cells. This ranking was not reflected in ET‐18‐OCH3‐induced changes of cell surface exposed glycopeptides derived from the three types of cells metabolically labeled with radioactive fucose. The present and previous experiments suggested that changes in invasion caused by lipid derivatives depended upon relative cell surface fucosylglycopeptide alterations in both the invasive cells and the normal tissue.
Metabolism of ether phospholipids and analogs in neoplastic cells
Authors: Fleer E. A. M. , Unger C. , Kim D. ‐J. , Eibl H.
Published: December 2006

The ether phospholipid 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (OM‐GPC) is known to be a potent inhibitor of cell growth. Metabolic studies in both Raji and L1210 leukemic cells on OM‐GPC,3H‐labeled in the methyl groups of the choline moiety, showed a (diacyl)‐phosphatidylcholine as the only labeled metabolite. Since the formation of radiolabeled (diacyl)‐phosphatidylcholine showed a direct correlation with cell death, we tested other lipid analogs. One of these compounds, hexadecylphosphocholine (He‐PC), which was3H‐labeled in the methyl‐choline groups, showed a formation of labaled (diacyl)‐phosphatidylcholine similar to that found with OM‐GPC. Again, there was a direct linear correlation between the formation of the labeled product and cell death. He‐PC was found to be a potent cell toxin in in vitro experiments on cell cultures. However, analogs with an elongated phosphor to trimethylammonium distance showed no toxicity towards the cells in in vitro experiments. From the data, we conclude that the ether phospholipids are substrates for a phospholipase C or related enzyme. This substrate property may be responsible for the toxicity of the compounds in neoplastic cells.
Effect of synthetic phospholipids on platelet aggregation and serotonin release
Authors: Söling Ulrike , Eibl Hansjörg , Nagel Gerd A. , Unger Clemens
Published: December 2006

1‐O‐Hexadecyl‐2‐O‐acetyl‐sn‐glycerol‐3‐phosphocholine (platelet‐activating factor, PAF) is known to stimulate platelet aggregation and serotonin release in concentrations ranging from 10−10–10−5 M. Since a variety of synthetic PAF analogues are potent antineoplastic agents in vitro and in vivo, it was the aim of this study to examine the PAF‐like activity of 15 analogues, including 1‐O‐actadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (ET‐18‐OCH3) and a thioether analogue. In platelet‐rich plasma from human blood, platelet aggregation and serotonin release were studied to compare the effects on PAF and the analogues. Platelet function was controlled by testing their response to adenosine diphosphate, arachidonic acid, collagen and epinephrine. Our results show that only PAF was able to induce platelet aggregation and serotonin release in concentrations from 10−9 to 10−5 M, whereas all the tested analogues up to a concentration of 10−3 M failed to induce these effects.
Immunomodulatory and therapeutic properties of alkyl lysophospholipids in mice
Authors: Talmadge James E. , Schneider Mark , Lenz Barbara , Phillips Hamblin , Long Cedric
Published: December 2006

This paper describes the immunomodulatory and therapeutic properties of the alkyl lysophospholipids [ALP; 1‐O‐octadecyl‐2‐O‐rac‐glycero‐3‐phosphocholine (ET‐18‐OCH3)]. ALP was able to activate macrophages both in vitro and in vivo as well as to act as an immunoadjuvant for syngeneic tumor vaccines. However, ALP appeared to be transferred, at least in part, to the macrophage membrane, and some of the tumoricidal macrophage‐activating properties seem to be associated with the direct cytotoxic effect of membrane‐released ALP. ALP also had some therapeutic activity for experimental and spontaneous metastases, requiring administration three but not two times weekly at near‐toxic doses; this suggests that at least some of its therapeutic activity is due to direct cytotoxicity.
Antitumor activity of SRI 62‐834, a cyclic ether analog of ET‐18‐OCH3
Authors: Houlihan William J. , Lee Mark L. , Munder Paul G. , Nemecek Georgina M. , Handley Dean A. , Winslow Christine M. , Happy John , Jaeggi Christian
Published: December 2006

SRI 62‐834, an analog of the antitumor agent ET‐18‐OCH3 in which the oxygen atom at carbon atom 2 has been incorporated into a five‐membered heterocycle, has been prepared and evaluated as an antitumor agent. The compound exhibited good cytotoxicity in vitro against a variety of tumor cell lines and was as effective as ET‐18‐OCH3 given orally in the mouse Meth A sarcoma model. SRI 62‐834 was shown to be an inhibitor of platelet‐derived growth factor (PDGF), possibly at the receptor level, and platelet‐activating factor (PAF) at the receptor level.
Liposomes in chemo‐ and immunotherapy of cancer
Authors: Scherphof Gerrit L. , Daemen Toos , Spanjer Halbe H. , Roerdink Frits H.
Published: December 2006

In this paper, we report on the in vivo behavior of liposomes as a function of their size and composition. It is emphasized that by varying these parameters we can influence not only the rate of blood elimination but also the intrahepatic destination of the liposomes. Thus, we show that small liposomes with diameters well below 100 nm can reach and be internalized by the parenchymal cells of the liver, i.e. the hepatocytes. The rate and the extent at which this occurs depends on the liposomal composition. With respect to the application of liposomes as a drug carrier system in anticancer therapy, we put emphasis on the liver macrophage, i.e. the Kupffer cell, as a target cell. Large liposomes with diameters well over 100 nm exclusively are taken up by these cells as far as hepatic uptake is concerned. By encapsulation within liposomes, a drug may be delivered specifically to these macrophages; this will prevent its rapid excretion from the body and/or undesired accumulation in other cell types. Two examples of the way in which this condition may be exploited are presented. First, we demonstrate the formation of intracellular depots in the macrophages of the cytostatic drug 5‐fluorodeoxyuridine (FUdR), thus preventing the rapid metabolism of the drug by the hepatocytes and allowing its sustained release from the macrophages and subsequent uptake by adjacent metastatic tumor cells. Second, we show that the liposome‐encapsulated immunomodulator muramyl dipeptide is capable of activating liver macrophages both in vitro and in vivo to a tumor‐specific cytotoxic state, and this can result in substantial reduction of metastatic growth in the livers of mice inoculated in the spleen with colon adenocarcinoma cells.
Structure‐cytotoxicity studies on alkyl lysophospholipids and some analogs in leukemic blasts of human origin in vitro
Authors: Danhauser Susanne , Berdel Wolfgang E. , Schick Hans D. , Fromm Michael , Reichert Anneliese , Fink Ulrich , Busch Raymonde , Eibl Hansjörg , Rastetter Johann
Published: December 2006

Eleven lipids have been tested for cytotoxic (trypan blue dye exclusion) activity in cells from eight freshly explanted human leukemias in vitro. 4‐Aminomethyl‐1‐[2,3‐(di‐N‐decyloxy)N‐propyl]‐4‐phenylpiperidine (CP‐46,665), 1‐mercapto‐hexadecyl‐2‐methoxymethyl‐rac‐glycero‐3‐phosphocholine (BM 41.440), the 2‐acetamide analog of platelet‐activating factor (PAF) and 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (ET‐18‐OCH3) were found among the most active compounds. 2‐Lysophosphatidylcholine (2‐LPC) showed the lowest activity. However, in addition there was variation among the results regarding the activity of the 1‐octadecyl‐rac‐glycero‐3‐phosphocholine (ET‐18‐OH) and its D‐ and L‐forms, but a significantly higher cytotoxic activity of D‐ET‐18‐OH compared with L‐ET‐18‐OH on the basis of 2‐LPC as control after an incubation time of 48 hr. We conclude that with the limited number of structures available, this type of study is not sufficient to yield further information about the mode of the accumulation and toxicity of this type of lipids.
Experimental studies on the role of alkyl lysophospholipids in autologous bone marrow transplatation
Authors: Vogler William R. , Olson Anita C. , Okamoto Shinichiro , Somberg Lewis B. , Glasser Lewis
Published: December 2006

The selective cytocidal effect of alkyl lysophospholipids against neoplastic cells while sparing normal cells make these ideal candidates for purging leukemic cells from bone marrows obtained during remission. To test the feasibility of such an approach, a murine model and an in vitro human cell model were developed. In the murine system a mixture of normal bone marrow cells and WEHI IIIB myelomonocytic leukemic cells was incubated with varying doses of 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (ET‐Me) for 24 hr before being injected into tail veins of lethally irradiated Balb/c mice. At doses of 20 and 100 μg/ml, long‐term survivors were noted. The additional steps of freezing and thawing following incubation resulted in significantly longer survival with doses of 10 to 50 μg/ml, but were toxic to marrow stem cells at 100 μg/ml.

In the in vitro model, normal marrow progenitor cells and leukemic cells (the promyelocytic cell line HL60) were exposed to varying concentrations of ET‐Me for 1 and 4 hr alone or mixed, and clonogenicity was assayed by colony formation in semisolid medium during 7–14 days’ incubation. At doses up to 100 μg/ml exposed for 4 hr normal progenitor cells were spared and HL60 colonies eliminated. Other phospholipids analogues were less effective in eliminating leukemic cells, but spared normal progenitor cells.

A survey of fresh leukemic cells found varying degrees of sensitivity to ET‐Me, indicating the need for testing a variety of compounds.

These studies clearly indicated the potential usefulness of alkyl lysophospholipid compounds in selectively purging leukemic cells from remission marrows for autologous bone marrow transplantation.
Therapeutic activity of ET‐18‐OCH3 and hexadecylphosphocholine against mammary tumors in BD‐VI rats
Authors: Scherf H. R. , Schuler B. , Berger M. R. , Schmähl D.
Published: December 2006

The present therapy experiments with two different transplantable mammary tumors were performed to compare the therapeutic efficacy in BD‐VI rats of 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (ET‐18‐OCH3) and hexadecylphosphocholine (HPC). Both compounds were administered orally, subcutaneously or intracutaneously at equimolar doses ranging from 4.8 to 88 μmol/kg/day five times per week for two weeks. Under the experimental conditions, both transplanted mammary carcinomas were moderately sensitive to the therapy with either HPC or ET‐18‐OCH3. Comparing both tumors, TMA2 was more sensitive than TMA1. The activity and toxicity of both compounds were dose‐related in both tumor lines. Females seemed to be less sensitive with respect to antineoplastic activity and toxicity. Like ET‐18‐OCH3, HPC was active also at low, probably noncytotoxic doses associated with no detectable toxicity according to body weight development. This suggests that there are at least two different mechanisms of action that lead to tumor growth inhibition.
Antineoplastic activity of conjugates of lipids and 1‐β‐d‐arabinofuranosylcytosine
Authors: Berdel Wolfgang E. , Danhauser Susanne , Schick Hans D. , Hong Chung , West Charles R. , Fromm Michael , Fink Ulrich , Reichen Anneliese , Rastetter Johann
Published: December 2006

Five different lipid conjugates of 1‐β‐D‐arabinofuranosylcytosine (ARA‐C) were tested in comparison with ARA‐C, the ether lipid ET‐18‐OCH3 (1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine) and their equimolar mixtures. The compounds were tested in vitro for cytotoxicity in the trypan blue dye exclusion test with cells from six different leukemias, one glioblastoma and two bronchogenic carcinomas of human origin. The compounds were given in vivo to assess their therapeutic activity against 3‐Lewis lung carcinoma (3‐LL) of syngeneic C57Bl6 mice. Although some of the conjugates have shown cytotoxic activity in vitro against the cell samples tested, they have not revealed higher cytotoxicity than ET‐18‐OCH3, ARA‐C or their equimolar mixtures. In these experiments, ARA‐CDP‐D,L‐MBA was the conjugate with the highest cytotoxicity. Some of the conjugates significantly inhibited tumor growth and also increased survival of C57Bl6 mice with intraperitoneally (ip) implanted 3‐LL. In these experiments, ARA‐CDP‐D,L‐PTBA, ARA‐CDP‐D,L‐PBA, ARA‐CDP‐L‐dipalmitin and ARA‐CDP‐D,L‐PCA were more active than either the parent compounds ARA‐C and ET‐18‐OCH3 alone or their equimolar mixtures. Furthermore, when the conjugates were injected as adjuvant chemotherapy shortly after the surgical removal of the primary 3‐LL, they inhibited the metastasis of 3‐LL to the lungs of the animals, demonstrated by an increase of the survival time and the number of surviving animals. The mode of action of these new antineoplastic compounds still is speculative.
Cytotoxic activity of the thioether phospholipid analogue BM 41.440 in primary human tumor cultures
Authors: Herrmann Dieter B. J. , Neumann Herbert A.
Published: December 2006

The inhibitory effect of the new thioether alkyl lysophospholipid analogue 1‐hexadecylmercapto‐2‐methoxymethyl‐rac‐glycero‐3‐phosphocholine (BM 41.440, Ilmofosine) on colony formation of different spontaneous human tumors was studied in vitro using a methyl cellulose monolayer assay. The most sensitive tumors were lung (small cell, squamous cell and adenocarcinomas), gastrointestinal and ovarian cancers and hyernephromas. On the basis of the current difinition of sensitivity by the National Cancer Institute, Bethesda, MD, i.e. more than 70% inhibition of colony formation at an arbitrary concentration of 10 μg/ml, 34 out of 64 malignancies tested were susceptible to BM 41.440.
Phase I trial of the thioether phospholipid analogue BM 41.440 in cancer patients
Authors: Herrmann Dieter B. J. , Neumann Herbert A. , Berdel Wolfgang E. , Heim Manfred E. , Fromm Michael , Boerner Dietmar , Bicker Uwe
Published: December 2006

BM 41.440 (1‐hexadecylmercapto‐2‐methoxymethyl‐rac‐glycero‐3‐phosphocholine) is a new thioether phospholipid, which has been shown to possess antineoplastic, antimetastatic, anti‐invasive and immunomodulating properties in serveral tumor models. The mechanism whereby this compound exerts its direct antineoplastic effect is thought to be related to specific interference with the normal phospholipid metabolism, preferentially of neoplastic cells. BM 41.440 was evaluated in a multicenter phase I study in patients (pts) with refractory cancers. In phase I A, 34 pts were orally treated with doses ranging from 0.5 to 7.0 mg/kg body weight (bw). Three different formulations were tested. The maximum‐tolerated dose (MTD) was ca. 5 mg/kg bw. The limiting side effects were nausea and vomiting. There was no evidence for systemic toxicities like myelosuppression, nephro‐, neuro‐, hepatotoxicity or hematological side effects. The current phase I B is designed to determine the MTD of BM 41.440 administered orally on a daily schedule for at least eight weeks. So far, 19 pts have entered this trial at dose levels ranging from 1.0 to 5.0 mg/kg bw/day. Some pts receiving 1.0 and 2.5 mg/kg bw/day, respectively, have been treated, up to now, for more than nine months. Clinical progress was followed with at‐least‐weekly blood counts, chemistry profiles, urine analysis, liver function tests and recordings of side effects. Tumor parameters were evaluated at eight‐week intervals. In parallel, pharmacokinetic investigations were performed in some pts in phase I A and IB. First results on tolerability and therapeutic efficacy of the long‐term BM 41.440 treatment are reported in this intermediate evaluation.
Clinical phase I pilot study of the alkyl lysophospholipid derivative ET‐18‐OCH3
Authors: Berdel Wolfgang E. , Fink Ulrich , Rastetter Johann
Published: December 2006

Sixteen patients suffering from widespread malignant disease, the majority pretreated and found in poor general health, were treated in a phase I pilot study with the alkyl lysophospholipid derivative 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (E‐18‐OCH3). Eleven patients were treated intravenously, and five were given oral therapy. Prolonged IV administration of 15–20 mg/kg/day at a concentration of 5 mg ET‐18‐OCH3 per 1 ml 20% human serum albumin could be continued safely. The maximum‐tolerated dose was either 50 mg/kg as a single injection or 20 mg/kg during daily dispensions. Grade 2–4 toxicity, as pulmonary edema and impairment of hepatic function, then occurred during daily treatment. Toxicity was reversible. Mitogen stimulation and mixed lymphocyte culture studies revealed possible immunosuppressive effects of higher doses of ET‐18‐OCH3. There were no chromosomal changes in cytogenetic studies. Frequent post‐mortem examinations revealed no further toxicity. IV and oral treatment showed few encouraging response data since there were two partial remissions in non‐small cell lung cancers and a reduction of leukemic blasts to less than 10% in an acute myelomonocytic leukemia.