bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signal transduction of the melatonin receptor MT1 is disrupted in breast cancer cells by electromagnetic fields
Authors: Girgert Rainer , Hanf Volker , Emons Günter , Gründker Carsten 
Published: October 2009

AbstractThe growth of estrogen‐receptor positive breast cancer cells is inhibited by the pineal gland hormone, melatonin. Concern has been raised that power‐line frequency and microwave electromagnetic fields (EMFs) could reduce the efficiency of melatonin on breast cancer cells. In this study we investigated the impact of EMFs on the signal transduction of the high‐affinity receptor MT1 in parental MCF‐7 cells and MCF‐7 cells transfected with the MT1 gene. The binding of the cAMP‐responsive element binding (CREB) protein to a promoter sequence of BRCA‐1 after stimulation with melatonin was analyzed by a gel‐shift assay and the expression of four estrogen‐responsive genes was measured in sham‐exposed breast cancer cells and cells exposed to a sinusoidal 50 Hz EMF of 1.2 µT for 48 h. In sham‐exposed cells, binding of CREB to the promoter of BRCA‐1 was increased by estradiol and subsequently diminished by treatment with melatonin. In cells exposed to 1.2 µT, 50 Hz EMF, binding of CREB was almost completely omitted. Expression of BRCA‐1, p53, p21WAF, and c‐myc was increased by estradiol stimulation and subsequently decreased by melatonin treatment in both cell lines, except for p53 expression in the transfected cell line, thereby proving the antiestrogenic effect of melatonin at molecular level. In contrast, in breast cancer cells transfected with MT1 exposed to 1.2 µT of the 50 Hz EMF, the expression of p53 and c‐myc increased significantly after melatonin treatment but for p21WAF the increase was not significant. These results convincingly prove the negative effect of EMF on the antiestrogenic effect of melatonin in breast cancer cells. Bioelectromagnetics 31:237–245, 2010. © 2009 Wiley‐Liss, Inc.
Protein disulfide isomerase does not control recombinant IgG4 productivity in mammalian cell lines
Authors: Hayes N.V.L. , Smales C.M. , Klappa P. 
Published: October 2009

AbstractPost‐translational limitations in the endoplasmic reticulum during recombinant monoclonal antibody production are an important factor in lowering the capacity for synthesis and secretion of correctly folded proteins. Mammalian protein disulfide isomerase (PDI) has previously been shown to have a role in the formation of disulfide bonds in immunoglobulins. Several attempts have been made to improve the rate of recombinant protein production by overexpressing PDI but the results from these studies have been inconclusive. Here we examine the effect of (a) transiently silencing PDI mRNA and (b) increasing the intracellular levels of members of the PDI family (PDI, ERp72, and PDIp) on the mRNA levels, assembly and secretion of an IgG4 isotype. Although transiently silencing PDI in NS0/2N2 cells suggests that PDI is involved in disulfide bond formation of this subclass of antibody, our results show that PDI does not control the overall IgG4 productivity. Furthermore, overexpression of members of the PDI family in a Chinese hamster ovary (CHO) cell line does not improve productivity and hence we conclude that the catalysis of disulfide bond formation is not rate limiting for IgG4 production. Biotechnol. Bioeng. 2010. 105: 770–779. © 2009 Wiley Periodicals, Inc.
Model‐based high cell density cultivation of Rhodospirillum rubrum under respiratory dark conditions
Authors: Zeiger Lisa , Grammel Hartmut 
Published: October 2009

AbstractThe potential of facultative photosynthetic bacteria as producers of photosynthetic pigments, vitamins, coenzymes and other valuable products has been recognized for decades. However, mass cultivation under photosynthetic conditions is generally inefficient due to the inevitable limitation of light supply when cell densities become very high. The previous development of a new cultivation process for maximal expression of photosynthetic genes under semi‐aerobic dark conditions in common bioreactors offers a new perspective for utilizing the facultative photosynthetic bacterium Rhodospirillum rubrum for large‐scale applications. Based on this cultivation system, the present study aimed in determining the maximal achievable cell density of R. rubrum in a bioreactor, thereby providing a major milestone on the way to industrial bioprocesses. As a starting point, we focus on aerobic growth due to higher growth rates and more facile process control under this condition, with the option to extend the process by an anaerobic production phase. Process design and optimization were supported by an unstructured computational process model, based on mixed‐substrate kinetics. Key parameters for growth and process control were determined in shake‐flask experiments or estimated by simulation studies. For fed‐batch cultivation, a computer‐controlled exponential feed algorithm in combination with a pH‐stat element was implemented. As a result, a maximal cell density of 59 g cell dry weight (CDW) L−1 was obtained, representing so far not attainable cell densities for photosynthetic bacteria. The applied exponential fed‐batch methodology therefore enters a range which is commonly employed for industrial applications with microbial cells. The biochemical analysis of high cell density cultures revealed metabolic imbalances, such as the accumulation and excretion of tetrapyrrole intermediates of the bacteriochlorophyll biosynthetic pathway. Biotechnol. Bioeng. 2010. 105: 729–739. © 2009 Wiley Periodicals, Inc.
Bioreactor expansion of human neural precursor cells in serum‐free media retains neurogenic potential
Authors: Baghbaderani Behnam A. , Mukhida Karim , Sen Arindom , Kallos Michael S. , Hong Murray , Mendez Ivar , Behie Leo A. 
Published: October 2009

AbstractHuman neural precursor cells (hNPCs), harvested from somatic tissue and grown in vitro, may serve as a source of cells for cell replacement strategies aimed at treating neurodegenerative disorders such as Parkinson's disease (PD), Huntington's disease (HD), and intractable spinal cord pain. A crucial element in a robust clinical production method for hNPCs is a serum‐free growth medium that can support the rapid expansion of cells while retaining their multipotency. Here, we report the development of a cell growth medium (PPRF‐h2) for the expansion of hNPCs, achieving an overall cell‐fold expansion of 1013 over a period of 140 days in stationary culture which is significantly greater than other literature results. More importantly, hNPC expansion could be scaled‐up from stationary culture to suspension bioreactors using this medium. Serial subculturing of the cells in suspension bioreactors resulted in an overall cell‐fold expansion of 7.8 × 1013 after 140 days. These expanded cells maintained their multipotency including the capacity to generate large numbers of neurons (about 60%). In view of our previous studies regarding successful transplantation of the bioreactor‐expanded hNPCs in animal models of neurological disorders, these results have demonstrated that PPRF‐h2 (containing dehydroepiandrosterone, basic fibroblast growth factor and human leukemia inhibitory factor) can successfully facilitate the production of large quantities of hNPCs with potential to be used in the treatment of neurodegenerative disorders. Biotechnol. Bioeng. 2010. 105: 823–833. © 2009 Wiley Periodicals, Inc.
Dynamic flux responses in riboflavin overproducing Bacillus subtilis to increasing glucose limitation in fed‐batch culture
Authors: Rühl Martin , Zamboni Nicola , Sauer Uwe 
Published: October 2009

AbstractHow do intracellular fluxes respond to dynamically increasing glucose limitation when the physiology changes from strong overflow metabolism near to exclusively maintenance metabolism? Here we investigate this question in a typical industrial, glucose‐limited fed‐batch cultivation with a riboflavin overproducing Bacillus subtilis strain. To resolve dynamic flux changes, a novel approach to 13C flux analysis was developed that is based on recording 13C labeling patterns in free intracellular amino acids. Fluxes are then estimated with stationary flux ratio and iterative isotopomer balancing methods, for which a decomposition of the process into quasi‐steady states and estimation of isotopic steady state 13C labeling patterns was necessary. By this approach, we achieve a temporal resolution of 30–60 min that allows us to resolve the slow metabolic transients that typically occur in such cultivations. In the late process phase we found, most prominently, almost exclusive respiratory metabolism, significantly increased pentose phosphate pathway contribution and a strongly decreased futile cycle through the PEP carboxykinase. As a consequence, higher catabolic NADPH formation occurred than was necessary to satisfy the anabolic demands, suggesting a transhydrogenase‐like mechanism to close the balance of reducing equivalents. Biotechnol. Bioeng. 2010. 105: 795–804. © 2009 Wiley Periodicals, Inc.
Drug release and its relationship with kinetic and thermodynamic parameters of drug sorption onto starch acetate fibers
Authors: Xu Weijie , Yang Yiqi 
Published: October 2009

AbstractDrug release and its relationship with kinetic and thermodynamic parameters of drug sorption onto starch acetate (SA) fibers have been studied using Diclofenac, 5‐Fluorouracil (5‐Fu), and Metformin as model drugs. The sorption method is more flexible and can avoid limitations or problems which occur with molten or dissolution methods. To understand drug release of sorption loading, kinetic and apparent thermodynamic parameters, such as diffusion coefficient, activation energy for diffusion, affinity, and sorption enthalpy and entropy, have been investigated. The quantitative relationship between drug release and drug‐loading concentration, affinity, and activation energy for diffusion has been established to predict the initial burst and subsequent release of the drugs. Up to 12% of Diclofenac, based on the weight of SA, can be loaded onto fibers using the sorption method. Drugs with higher activation energy for diffusion, lower diffusion coefficients, and higher affinity for SA fiber, such as Diclofenac, are more suitable for sorption loading. It has also been found that elevated temperatures will achieve higher loading capacity and a more constant release rate. Biotechnol. Bioeng. 2010. 105: 814–822. © 2009 Wiley Periodicals, Inc.
Comprehending Canadian police cautions: are the rights to silence and legal counsel understandable?
Authors: Eastwood Joseph , Snook Brent 
Published: October 2009

AbstractComprehension of a Canadian police right to silence caution and a right to legal counsel caution was examined. Each caution was first presented verbally in its entirety, followed by its sentence‐by‐sentence presentation in written format. Participants (N = 56) were asked to indicate, after each presentation, their understanding of the caution. When delivered in verbal format, 4 and 7% of participants fully understood the right to silence and legal counsel cautions, respectively. However, 48 and 32% of participants fully understood the right to silence and legal counsel cautions, respectively, when delivered in written format. Comprehension of the cautions was not influenced by gender, experience with the caution, or whether the caution was interpreted by a police recruit or regular student. The implications of the results for statement admissibility and protection of suspects' rights are discussed. Copyright © 2009 John Wiley & Sons, Ltd.
Dynamic culture of droplet‐confined cell arrays
Authors: Cimetta Elisa , Cagnin Stefano , Volpatti Annamaria , Lanfranchi Gerolamo , Elvassore Nicola 
Published: October 2009

AbstractResponding to the need of creating an accurate and controlled microenvironment surrounding the cell while meeting the requirements for biological processes or pharmacological screening tests, we aimed at designing and developing a microscaled culture system suitable for analyzing the synergic effects of extracellular matrix proteins and soluble environments on cell phenotype in a high‐throughput fashion. We produced cell arrays deposing micrometer‐scale protein islands on hydrogels using a robotic DNA microarrayer, constrained the culture media in a droplet‐like volume and developed a suitable perfusion system. The droplet‐confined cell arrays were used either with conventional culture methods (batch operating system) or with automated stable and constant perfusion (steady‐state operating system). Mathematical modeling assisted the experimental design and assessed efficient mass transport and proper fluidodynamic regimes. Cells cultured on arrayed islands (500 μm diameter) maintained the correct phenotype both after static and perfused conditions, confirmed by immunostaining and gene expression analyses through total RNA extraction. The mathematical model, validated using a particle tracking experiment, predicted the constant value of velocities over the cell arrays (less than 10% variation) ensuring the same mass transport regime. BrdU analysis on an average of 96 cell spots for each experimental condition showed uniform expression inside each cell island and low variability in the data (average of 13%). Perfused arrays showed longer doubling times when compared with static cultures. In addition, perfused cultures showed a reduced variability in the collected data, allowing to detect statistically significant differences in cell behavior depending on the spotted ECM protein. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010
A Conserved Lysine in β‐Lactam Synthetase Assists Ring Cyclization: Implications for Clavam and Carbapenem Biosynthesis
Authors: Raber Mary L. , Castillo Alvaro , Greer Alexander , Townsend Craig A. 
Published: October 2009

Abstractβ‐Lactam synthetase (β‐LS) is the paradigm of a growing class of enzymes that form the critical β‐lactam ring in the clavam and carbapenem antibiotics. β‐LS catalyzes a two‐stage reaction in which N2‐(2‐carboxyethyl)‐L‐arginine is first adenylated, and then undergoes intramolecular ring closure. It was previously shown that the forward kinetic commitment to β‐lactam formation is high, and that the overall rate of reaction is partially limited to a protein conformational change rather than to the chemical step alone of closing the strained ring. β‐Lactam formation was evaluated on the basis of X‐ray crystal structures, site‐specific mutation, and kinetic and computational studies. The combined evidence clearly points to a reaction coordinate involving the formation of a tetrahedral transition state/intermediate stabilized by a conserved Lys. The combination of substrate preorganization, a well‐stabilized transition state and an excellent leaving group facilitates this acyl substitution to account for the strong forward commitment to catalysis and to lower the barrier of four‐membered ring formation to the magnitude of a protein conformational change.
Plasticity changes in the brain in hypnosis and meditation
Authors: Halsband Ulrike , Mueller Susanne , Hinterberger Thilo , Strickner Simon 
Published: October 2009

AbstractNeuroscientific evidence interprets both hypnotic trance induction and different meditation traditions as modified states of consciousness that emphasize attention, concentration and the letting go of thoughts, but they differ in terms of sensory input, processing, memory, and the sense of time. Furthermore, hypnosis is based on the suggestibility of a person and meditation on mindfulness; therefore it is not surprising to find differential brain plasticity changes. We analysed shared and non‐shared neural substrates using electroencephalography (EEG), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI). Most pronounced EEG changes were in deep as compared to light hypnosis (step‐by‐step induction) and in arm levitation where suggested movement was perceived as external. In a within‐subject‐design changes in brain activity during hypnosis and Tibetan Buddhist meditation were compared. High amplitudes in alpha frequency bands were most pronounced with meditation at frontal positions and with hypnosis in central and temporal locations. Significantly greater activity in theta 2 band was observed only with hypnosis in both hemispheres. PET cerebral activation patterns of imagery‐mediated learning were analysed in hypnosis in a within‐subject‐design. Compared with baseline the learning of high‐imagery words was associated with (i) more pronounced bilateral activation in the occipital cortex and prefrontal areas and (ii) improved memory performance. Visual illusion in hypnosis was studied with fMRI, analysed with Granger Causality Mapping, showing changes in the effective connectivity relations of fusiform gyrus, anterior cingulate cortex and intraparietal sulcus. Little is known about the neurobiological basis of theprocessof enhancing cognitive and emotional traits in meditation. In a longitudinal fMRI study attention abilities through intensive Soto‐Zen meditation were investigated before (baseline), after training (6 months) and at follow‐up (9 months). After six months differences were observed in the left inferior and left superior frontal gyrus; after 9 months activations in the left precuneus. Taken together, the findings advance understanding of the neural mechanisms that underlie hypnosis and meditation. Further studies with a greater sample size are needed to explore the differences and commonalities of hypnosis and different meditation techniques. Copyright © 2009 British Society of Experimental & Clinical Hypnosis. Published by John Wiley & Sons, Ltd.
Total Synthesis and Biological Evaluation of (+)‐Neopeltolide and Its Analogues
Authors: Fuwa Haruhiko , Saito Asami , Naito Shinya , Konoki Keiichi , Yotsu‐Yamashita Mari , Sasaki Makoto 
Published: October 2009

AbstractThe stereocontrolled total synthesis of the originally proposed (1) and correct (2) structures of (+)‐neopeltolide, a novel marine macrolide natural product with highly potent antiproliferative activity against several cancer cell lines as well as potent antifungal activity, has been achieved by exploiting a newly developed Suzuki–Miyaura coupling/ring‐closing metathesis strategy. Alkylborate 44, which was generated in situ from iodide 34, was coupled with enol phosphate 8 by a Suzuki–Miyaura coupling. Ring‐closing metathesis of the derived diene 45 followed by stereoselective hydrogenation afforded tetrahydropyran 47 as a single stereoisomer in high overall yield from 34. Our convergent strategy enabled us to construct the 14‐membered macrolactone core structure of 2 in a rapid and efficient manner. Total synthesis and biological evaluation of synthetic intermediates and designed synthetic analogues, performed to establish the structure–activity relationships of 2, led to the discovery of a structurally simple yet potent cytotoxic analogue, 9‐demethylneopeltolide (54).
A Unidirectional Open–Close Mechanism of Metal‐Ion‐Driven Molecular Hinges with Adjustable Amplitude
Authors: Ernst Silvia , Haberhauer Gebhard 
Published: October 2009

AbstractA basic requirement for each molecular system that is supposed to perform work is a synchronized and unidirectional movement. Unidirectionality can be achieved by a change of configuration or conformation that is controllable by external stimulation. Molecular hinges based on a bipyridine unit work unidirectionally and are able to reach an amplitude of motion that amounts to about 180°. To analyze if it is possible to adjust the height of the unidirectional amplitude of motion, three planar chiral molecular hinge systems with a 2,2′‐bipyridine unit as functional element were designed and stimulated with various divalent metal ions in different solvents. The configurations of the hinges were determined by DFT calculations using B3LYP and the 6‐31G* basis set and experimentally verified by 2D NMR NOESY spectra. Circular dichroism (CD) and UV spectroscopy were used to study the properties of the hinges by the addition of metal ions (primarily Zn2+ and Hg2+) in dichloromethane and methanol. The choice of metal ions and solvents determines whether or not and how far the hinges are closed. Furthermore, a drastic change in the height of the amplitude of motion can be reached by modifying the position of the bipyridine unit in the hinge. Amplitude values from 45 up to 190° were obtained from quantum mechanical calculations. This control of the amplitude of motion can in the future be used for more complex switching processes of molecular machines.
Preparation of Ni/TiO2 Nanoparticles and Their Catalytic Performance on the Thermal Decomposition of Ammonium Perchlorate
Authors: Li Cheng , Ma Zhenye , Zhang Lixiong , Qian Renyuan 
Published: October 2009

AbstractMetal/oxide nanoparticles are attractive because of their special structure and better properties. The Ni/TiO2 nanoparticles were prepared by a liquid phase chemical reduction method in this paper. The obtained‐products were characterized by inductively coupled plasma (ICP), X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The results show that Ni particles in Ni/TiO2 nanoparticles exhibit better dispersion and the size of most Ni particles is 10 nm or so. The catalytic activity of Ni/TiO2 nanoparticles on the thermal decomposition of ammonium perchlorate (AP) was investigated by simultaneous thermogravimetry and differential thermal analysis (TG‐DTA). Results show that composite process of Ni and TiO2 can improve the catalytic activity of Ni nanoparticles on the thermal decomposition of AP, which is mainly attributed to the improvement of Ni dispersion in Ni/TiO2 nanoparticles. The catalytic activity of Ni/TiO2 nanoparticles increases with increasing the weight ratio of Ni to AP.
Synthesis and Characterization of Imidacloprid/Hydrotalcite‐like Compound Nanohybrids
Authors: Qiu Depeng , Hou Wanguo , Xu Jie , Liu Jianqiang , Liu Shaojie 
Published: October 2009

AbstractHydrotalcite‐like compounds (HTlc) were first modified by sodium dodecyl sulfate (SDS), then the intercalation of imidacloprid (IM) into modified HTlc was carried out in mixed solvent of toluene/ethanol by an evaporating solvent enhanced intercalation method, obtaining IM‐SDS‐HTlc nanohybrids. It was found that the nanohybrids could well control the release of imidacloprid, demonstrating that the nanohybrids are a potential pesticide controlled‐release formulation. The release of imidacloprid from IM‐SDS‐HTlc nanohybrids is dependent on the pH and the presence of electrolyte in release medium. Acidic medium and the presence of electrolytes induce the higher release rate of imidacloprid. The release process of imidacloprid from IM‐SDS‐HTlc nanohybrids can be described by pseudo‐second‐order release kinetics.