bluuebunny/crossref_metadata_2025 huggingface dataset:
Ectopic Expression of a Phytase Gene from Medicago truncatula Barrel Medic Enhances Phosphorus Absorption in Plants
Authors: Xiao Kai , Zhang Jian‐Heng , Harrison Maria , Wang Zeng‐Yu
Published: January 2006

In the present study, the phosphorus‐absorption capacity of transgenic Arabidopsis plants ectopically expressing a novel phytase gene from Medicago truncatula Barrel Medic was evaluated. A full‐length cDNA encoding an extracellular form of phytase was isolated from the model legume M. truncatula. The phytase gene (MtPHY1) has an open reading frame of 1 632 bp predicted to encode 543 amino acids, including an N‐terminal signal peptide of 27 amino acids. The genomic sequence of the MtPHY1 gene is 5 151 bp, containing seven exons interrupted by six introns. Under high‐Pi (2 mmol/L) growth conditions, higher levels of MtPHY1 transcripts accumulated in the leaf and stem than in the root. The transcript level was reduced in the stem and increased in the root, with no obvious changes in the hybridization signal detected in the leaf under low‐Pi (10 μmol/L) conditions. Chimeric transgenes were constructed by placing MtPHY1 under the control of the constitutive CaMV35S promoter and the root‐specific MtPT1 promoter. Phytase activities in root apoplast of transgenic Arabidopsis were 12.3‐to 16.2‐fold of that in control plants. The phytase expressed was secreted into the rhizosphere, as demonstrated by HPLC analysis of phytate degradation by root exudates. Ectopic expression of MtPHY1 in Arabidopsis, leading to significant improvement in organic phosphorus absorption and plant growth, indicated that MtPHY1 has great potential for improving plant phosphorus absorption and phytoremediation.

(Managing editor: Li‐Hui Zhao)
An Integrative Analysis of the Effects of Auxin on Jasmonic Acid Biosynthesis in Arabidopsis thaliana
Authors: Liu Jun , Wang Xiu‐Jie
Published: January 2006

Auxin and jasmonic acid (JA) are two plant phytohormones that both participate in the regulation of many developmental processes. Jasmonic acid also plays important roles in plant stress response reactions. Although extensive investigations have been undertaken to study the biological functions of auxin and JA, little attention has been paid to the cross‐talk between their regulated pathways. In the few available reports examining the effects of auxin on the expression of JA or JA‐responsive genes, both synergetic and antagonistic results have been found. To further investigate the relationship between auxin and JA, we adopted an integrative method that combines microarray expression data with pathway information to study the behavior of the JA biosynthesis pathway under auxin treatment. Our results showed an overall down regulation of genes involved in JA biosynthesis, providing the first report of a relationship between auxin and the JA synthesis pathway in Arabidopsis seedlings.

(Managing editor: Ya‐Qin Han)
Further Analysis of the Function of AtBHLH29 in Regulating the Iron Uptake Process in Arabidopsis thaliana
Authors: Zhang Juan , Zhu Hui‐Fen , Liang Hui , Liu Kun‐Fan , Zhang Ai‐Min , Ling Hong‐Qing , Wang Dao‐Wen
Published: January 2006

Using T‐DNA insertion and chemical mutants, two recent studies have shown that AtBHLH29, encoding a putative basic helix‐loop‐helix (BHLH) protein, is involved in regulating the iron uptake process in Arabidopsis thaliana. Herein, we report that RNA interference (RNAi) mutants can be used to reveal more accurately the genetic function of AtBHLH29. We compared the iron deficiency responses of seven RNAi strains that contained decreasing amounts of AtBHLH29 transcripts. Under high iron conditions (50 μmol/L iron), only in the most severe RNAi strains (R101, R111, and R119) was plant growth significantly retarded. However, these mutants could still survive and produce seeds. This suggests that the function of AtBHLH29 is beneficial, but not absolutely essential, to plant growth when iron supply is not limiting. Under low iron conditions (less than 10 μmol/L iron), the R111 and R119 strains died prematurely, demonstrating that AtBHLH29 is absolutely necessary for plant survival when iron supply is restricted. The transcription of AtBHLH29 was essential for the expression of AtFRO2 (encoding the ferric chelate reductase). In contrast, the expression of AtIRT1 (encoding the high‐affinity iron transporter) was not so strongly dependent upon the transcription of AtBHLH29. By transient expression, we found that the AtBHLH29‐GUS fusion protein was targeted specifically to the nucleus in plant cells. Interestingly, the nuclear localization of AtBHLH29‐GUS was abolished when the four consecutive arginine residues located in the basic region of the putative AtBHLH29 protein were replaced by alanine residues by mutagenesis. The implications of our findings on further studies of the mechanism underlying the function of AtBHLH29 are discussed.

(Managing editor: Wei Wang)
Parental RNA is Significantly Degraded During Arabidopsis Seed Germination
Authors: Li Qing , Feng Jian‐Xun , Han Pei , Zhu Yu‐Xian
Published: January 2006

Germination is the first and maybe the foremost growth stage in the life cycle of a plant. Herein, we report that initiation of germination in the Arabidopsis Columbia ecotype was accompanied by a sharp decrease in the amount of extractable total RNA. At the beginning of our germination experiment, we were usually able to obtain 35–40 μg total RNA from 100 mg dry seeds. However, after 3 d of cold stratification, we could only obtain less than 5 μg total RNA from the same amount of starting material. Young seedlings contained approximately 100 μg total RNA per 100 mg fresh tissue. Further studies showed that inhibition of de novo RNA synthesis by actinomycin D prevented the degradation of parental RNA and, in the meantime, significantly delayed the germination process. Several ribonuclease‐like genes that were highly expressed in dry seeds, and especially during the cold stratification period, were discovered. We propose that these enzymes are involved in the regulation of parental RNA degradation. These results indicate that parental RNA metabolism may be an important process for Arabidopsis seed germination.

(Managing editor: Ya‐Qin Han)
Supply Chain Coordination and Cooperation Mechanisms: An Attribute‐Based Approach
Authors: Xu Lei , Beamon Benita M.
Published: January 2006

Coordination within a supply chain is a strategic response to the problems that arise from inter‐organizational dependencies within the chain. A coordination mechanism is a set of methods used to manage interdependence between organizations. Given the increasing importance of high‐performance supply, and the advantages to be gained through supply chain coordination, the challenge to an organization is how to select the appropriate coordination mechanism to manage organizational interdependencies. This paper develops and illustrates an attribute‐based, systematic process for selecting coordination mechanisms in a supply chain.
The Implementation of Target Costing in the United States: Theory Versus Practice
Authors: Ellram Lisa M.
Published: January 2006

Target costing has been touted as a process that can significantly improve new product development results in the accounting, engineering, operations management, and purchasing literature. The target costing process considers the voice of the customer, incorporates earlier supplier involvement and concurrent engineering, utilizes cross‐functional teams, and focuses on creating a good or service that is both desirable and affordable to the customer and profitable to the producing organization. Unlike previous studies, which have focused on Japanese firms, or used single case studies, this paper uses the findings from case studies of 11 organizations actively engaged in the target costing process. This paper explores how the target costing process is used in practice in the United States, comparing it with the popular theoretical model of target costing. It helps shed light on to target costing practices of U.S. and other Western firms, and highlights the often overlooked role of the purchasing function in successful target costing efforts.
Total Cost of Ownership in the Services Sector: A Case Study
Authors: Hurkens Krisje , van der Valk Wendy , Wynstra Finn
Published: January 2006

Few detailed studies exist of the trade‐offs to be made when developing a comprehensive, strategically focused total cost of ownership (TCO) model. Moreover, most studies of TCO have been conducted in manufacturing firms, with little or no TCO research directed toward service organizations. This research presents the results of a study conducted at a leading vehicle glass repair and replacement organization. The results show how TCO information can be used for strategic decision making regarding the allocation of volumes. This information can also be used in the identification of improvement areas for preferred suppliers by introducing a limited number of key performance indicators that have a significant impact on the TCO of supplier offerings. The paper highlights some of the trade‐offs required in designing such a model. It fills an existing literature gap that allows service organizations to better understand the development and implementation of total cost measurement systems.
Review of Thermal Joint Resistance Models for Nonconforming Rough Surfaces
Authors: Bahrami M. , Culham J. R. , Yananovich M. M. , Schneider G. E.
Published: January 2006

The thermal contact resistance (TCR) in a vacuum is studied. The TCR problem is divided into three different parts: geometrical, mechanical, and thermal. Each problem includes a macro- and microscale subproblem; existing theories and models for each part are reviewed. Empirical correlations for microhardness, and the equivalent (sum) rough surface approximation, are discussed. Suggested correlations for estimating the mean absolute surface slope are summarized and compared with experimental data. The most common assumptions of existing thermal analyses are summarized. As basic elements of thermal analyses, spreading resistance of a circular heat source on a half-space and flux tube are reviewed; also existing flux tube correlations are compared. More than 400 TCR data points collected by different researchers during the last 40years are grouped into two limiting cases: conforming rough and elastoconstriction. Existing TCR models are reviewed and compared with the experimental data at these two limits. It is shown that the existing theoretical models do not cover both of the above-mentioned limiting cases. This review article cites 58 references.
Phospholipid Nonwoven Electrospun Membranes
Authors: McKee Matthew G. , Layman John M. , Cashion Matthew P. , Long Timothy E.
Published: January 2006

Nonwoven fibrous membranes were formed from electrospinning lecithin solutions in a single processing step. As the concentration of lecithin increased, the micellar morphology evolved from spherical to cylindrical, and at higher concentrations the cylindrical micelles overlapped and entangled in a fashion similar to polymers in semi-dilute or concentrated solutions. At concentrations above the onset of entanglements of the wormlike micelles, electrospun fibers were fabricated with diameters on the order of 1 to 5 micrometers. The electrospun phospholipid fibers offer the potential for direct fabrication of biologically based, high-surface-area membranes without the use of multiple synthetic steps, complicated electrospinning designs, or postprocessing surface treatments.
Internal Rotation and Spin Conversion of CH
3
OH in Solid para-Hydrogen
Authors: Lee Yuan-Pern , Wu Yu-Jong , Lees R. M. , Xu Li-Hong , Hougen Jon T.
Published: January 2006

The quantum solid para-hydrogen (
p
-H
2
) has recently proven useful in matrix isolation spectroscopy. Spectral lines of compounds embedded in this host are unusually narrow, and several species have been reported to rotate in
p
-H
2
. We found that a
p
-H
2
matrix inhibits rotation of isolated methanol (CH
3
OH) but still allows internal rotation about the C–O bond, with splittings of the E/A torsional doublet in internal rotation–coupled vibrational modes that are qualitatively consistent with those for CH
3
OH in the gaseous phase. This simplified high-resolution spectrum further revealed the slow conversion of nuclear spin symmetry from species E to species A in the host matrix, offering potential insight into nuclear spin conversion in astrophysical sources.
Vaccinia Virus-Induced Cell Motility Requires F11L-Mediated Inhibition of RhoA Signaling
Authors: Valderrama Ferran , Cordeiro João V. , Schleich Sibylle , Frischknecht Friedrich , Way Michael
Published: January 2006

RhoA signaling plays a critical role in many cellular processes, including cell migration. Here we show that the vaccinia F11L protein interacts directly with RhoA, inhibiting its signaling by blocking the interaction with its downstream effectors Rho-associated kinase (ROCK) and mDia. RNA interference–mediated depletion of F11L during infection resulted in an absence of vaccinia-induced cell motility and inhibition of viral morphogenesis. Disruption of the RhoA binding site in F11L, which resembles that of ROCK, led to an identical phenotype. Thus, inhibition of RhoA signaling is required for both vaccinia morphogenesis and virus-induced cell motility.
Solvent-Induced Association of Polymers: Phase Stability
Authors: Pouchlý Julius , Živný Antonín , Sikora Antonín
Published: January 2006

In the preceding paper, basic thermodynamic functions have been derived for a solution of macromolecules associating by means of functional groups (stickers), thus forming junctions, each of which consists of m stickers and bm molecules of solvent. In the present communication, phase stability of the systems under consideration is analyzed. For several values of parameters m and b, spinodal curves are calculated and their minima (i.e. critical solution points) are localized. At higher junction multiplicity values (e.g. at m = 10), a local maximum appears on the spinodal, dividing it into two lobes, each displaying a different critical point. The effect of the stoichiometric parameter b on splitting the spinodal and on positions of the critical solution points is described.
Low-Polarity Phytoecdysteroids from the Juice of Serratula coronata L. (Asteraceae)
Authors: Odinokov Victor N. , Kumpun Saowanee , Galyautdinov Ilgiz V. , Evrard-Todeschi Nathalie , Veskina Natalya A. , Khalilov Leonard M. , Girault Jean-Pierre , Dinan Laurence , Maria Annick , Lafont René
Published: January 2006

Eleven phytoecdysteroids have been isolated and identified from the low polarity fractions of Serratula coronata juice by a combination of column chromatography and HLPC. Four of them are new, i.e. ecdysone 22-acetate 7, (25S)-inokosterone 26-acetate 9, 20,22-O-(R-ethylidene)-20-hydroxyecdysone 10 and 20,22-O-(R-ethylidene)-ajugasterone C 11. The biological activity of these new ecdysteroids in the Drosophila melanogaster BII cell bioassay is reported.
Reactions of Substituted Furo[3,2-b]pyrrole-5-carbohydrazides Under Classical and Microwave Conditions
Authors: Gašparová Renata , Lácová Margita , Krutošíková Alžbeta
Published: January 2006

Substituted hydrazones 5 and 6 were synthesized by the reaction of the corresponding furo[3,2-b]pyrrole-5-carboxyhydrazides 1 with 6-substituted 4-oxochromene-3-carbaldehydes 2 and methyl 2-formylfuro[3,2-b]pyrrole-5-carboxylates 3 under microwave irradiation as well as by the classical method. The beneficial effect of the microwave irradiation on these reactions was a shortening of the reaction time and an increase in the yields. The reactions of 1 with 4-[(4-oxochromen-3-yl)methylidene]-2-phenyloxazol-5(4H)-one (4) were also studied. Compounds 7 or 8 were obtained, depending on the reaction temperature.
SLOWLY ROTATING PROTO STRANGE STARS IN QUARK MASS DENSITY- AND TEMPERATURE-DEPENDENT MODEL
Authors: SHEN JIANYONG , ZHANG YUN , WANG BIN , SU RU-KENG
Published: January 2006

Employing the Quark Mass Density- and temperature-dependent model and the Hartle's method, we have studied the slowly rotating strange star with uniform angular velocity. The mass–radius relation, the moment of inertia and the frame dragging for different frequencies are given. We found that we cannot use the strange star to solve the challenges of Stella and Vietri for the horizontal branch oscillations and the moment of inertia I45/(M/Ms)>2.3. Furthermore, we extended the Hartle's method to study the differential rotating strange star and found that the differential rotation is an effective way to get massive strange star.
CLASSICAL LIMIT PROBLEM OF QUANTUM MECHANICAL ENERGY EIGENFUNCTIONS — EXTENSION TO TWO- AND THREE-DIMENSIONAL CASES
Authors: SEN D. , SENGUPTA S.
Published: January 2006

In an earlier paper appropriate limiting procedure is discussed in a general way for quantum mechanical energy eigenfunctions (one-dimensional bound states) — a single interpretational postulate leading smoothly to entire compatible classical objective description without facing any contradiction. The method is consistently extended to two- and three-dimensional cases and it is interesting to note that results of earlier study on the classical limit of the radial distribution function of hydrogen atom are easily obtained as special cases of our analysis.
A DYNAMICAL GLUON MASS SOLUTION IN MANDELSTAM'S APPROXIMATION
Authors: AGUILAR A. C. , NATALE A. A.
Published: January 2006

We discuss the pure gauge Schwinger–Dyson equation for the gluon propagator in the Landau gauge within an approximation proposed by Mandelstam many years ago. We show that a dynamical gluon mass arises as a solution. This solution is obtained numerically in the full range of momenta that we have considered without the introduction of any ansatz or asymptotic expression in the infrared region. The vertex function that we use follows a prescription formulated by Cornwall to determine the existence of a dynamical gluon mass in the light cone gauge. The renormalization procedure differs from the one proposed by Mandelstam and allows for the possibility of a dynamical gluon mass. Some of the properties of this solution, such as its dependence on Λ QCD and its perturbative scaling behavior are also discussed.
NONROTATING COSMIC STRINGS INTERACTING WITH GRAVITATIONAL AND ELECTROMAGNETIC WAVES
Authors: YAZADJIEV STOYTCHO S.
Published: January 2006

Exact cylindrically symmetric solutions of Einstein–Maxwell equations are presented. They are regular on the axis of symmetry, asymptotically flat and free from curvature singularities. The solutions can be interpreted as nonrotating cosmic strings interacting with gravitational and electromagnetic waves.
STRUCTURAL ORDER IN LIQUIDS INDUCED BY INTERFACES WITH CRYSTALS
Authors: Kaplan Wayne D. , Kauffmann Yaron
Published: January 2006

▪ Abstract  Interfaces between solids and liquids are important for a range of materials processes, including soldering and brazing, liquid-phase sintering, crystal growth, and lubrication. There is a wealth of fundamental studies on solid-liquid interfaces in materials, primarily focused on thermodynamics (relative interface energies and segregation effects) from high-temperature wetting experiments, which is often applied to processing design. Less is known about the atomistic structure at solid-liquid interfaces, mainly because of the difficulty involved in obtaining such information experimentally. This work reviews both theoretical and experimental studies of atomistic configurations at solid-liquid interfaces, focusing on the issue of ordering in the liquid adjacent to crystalline solids.
Convergence of Ca2+-desensitizing mechanisms activated by forskolin and phenylephrine pretreatment, but not 8-bromo-cGMP
Authors: Porter Melissa , Evans Melissa C. , Miner Amy S. , Berg Krystina M. , Ward Kevin R. , Ratz Paul H.
Published: January 2006

Contractile stimuli can sensitize myosin to Ca2+ by activating RhoA kinase (ROK) and PKC that inhibit myosin light chain phosphatase (MLCP) activity. Relaxant stimuli, acting through PKA and PKG (cyclic nucleotide-dependent protein kinases), and pretreatment with contractile agents such as phenylephrine (PE), can desensitize myosin to Ca2+. It is unknown precisely how these stimuli cause Ca2+ desensitization. To test the hypothesis that PKA, PKG, and PE pretreatment signaling systems converge to cause relaxation by inhibition of ROK in intact, isolated tissues, we examined the effects of forskolin (FSK; PKA activation), 8-bromo-cGMP (8br-cGMP; PKG activation), and PE pretreatment on KCl-induced force maintenance in rabbit arteries, a response nearly completely dependent on ROK activation. PE pretreatment and agents activating PKA and PKG caused Ca2+ desensitization by inhibiting KCl-induced tonic force and MLC phosphorylation without inhibiting intracellular [Ca2+]. At pCa 5 in β-escin-permeabilized muscle, FSK and 8b-cGMP accelerated the relaxation rate when tissues were returned to pCa 9, suggesting that both agents can elevate MLCP activity. However, a component of the Ca2+ desensitization attributed to PKG activation in intact tissues appeared to involve a MLC phosphorylation-independent component. Inhibition of KCl-induced tonic force by the ROK inhibitor, Y-27632, and by PE pretreatment, were synergistically potentiated by 8b-cGMP, but not FSK. FSK and PE pretreatment, but not 8b-cGMP, inhibited the KCl-induced increase in site-specific myosin phosphatase target protein-1 phosphorylation at Thr853. These data support the hypothesis that PKA and PE pretreatment converge on a common Ca2+-desensitization pathway, but that PKG can act by a mechanism different from that activated by PKA and PE pretreatment.
Enteric glia inhibit intestinal epithelial cell proliferation partly through a TGF-β1-dependent pathway
Authors: Neunlist M. , Aubert P. , Bonnaud S. , Van Landeghem L. , Coron E. , Wedel T. , Naveilhan P. , Ruhl A. , Lardeux B. , Savidge T. , Paris F. , Galmiche J. P.
Published: January 2006

Although recent studies have shown that enteric neurons control intestinal barrier function, the role of enteric glial cells (EGCs) in this control remains unknown. Therefore, our goal was to characterize the role of EGCs in the control of intestinal epithelial cell proliferation using an in vivo transgenic and an in vitro coculture model. Assessment of intestinal epithelial cell proliferation after ablation of EGCs in transgenic mice demonstrated a significant increase in crypt cell hyperplasia. Furthermore, mucosal glial network (assessed by immunohistochemical detection of S-100β) is altered in colon adenocarcinoma compared with control tissue. In an in vitro coculture model of subconfluent Caco-2 cells seeded onto Transwell filters with EGCs, Caco-2 cell density and [3H]thymidine incorporation were significantly lower than in control (Caco-2 cultured alone). Flow cytometry analysis showed that EGCs had no effect on Caco-2 cell viability. EGCs induced a significant increase in Caco-2 cell surface area without any sign of cellular hypertrophy. These effects by EGCs were also seen in various transformed or nontransformed intestinal epithelial cell lines. Furthermore, TGF-β1 mRNA was expressed, and TGF-β1 was secreted by EGCs. Exogenously added TGF-β1 reproduced partly the EGC-mediated effects on cell density and surface area. In addition, EGC effects on Caco-2 cell density were significantly reduced by a neutralizing TGF-β antibody. In conclusion, EGCs have profound antiproliferative effects on intestinal epithelial cells. Functional alterations in EGCs may therefore modify intestinal barrier functions and be involved in pathologies such as cancer or inflammatory bowel diseases.
Ghrelin receptors in rat and human nodose ganglia: putative role in regulating CB-1 and MCH receptor abundance
Authors: Burdyga Galina , Varro Andrea , Dimaline Rod , Thompson David G. , Dockray Graham J.
Published: January 2006

Intact vagal afferent neurons are required for the satiety effects of the intestinal hormone cholecystokinin (CCK) and the orexigenic effects of the gastric regulatory peptide ghrelin. In this study, we examined the localization of ghrelin receptors in nodose ganglia and their function in regulating the expression of other orexigenic receptors, notably cannabinoid (CB)-1 and melanin-concentrating hormone (MCH)-1 receptors. With the use of RT-PCR, transcripts corresponding to both functional [growth hormone secretagogue receptor (GHS-R)1a] and truncated forms (GHS-R1b) of the ghrelin receptor were detected in rat nodose ganglia. There was no difference in expression between rats fed ad libitum or fasted for up to 48 h. Immunohistochemical studies using antibodies directed at GHS-R1a revealed expression in over 75% of neurons also expressing CCK-1 receptors in the mid- and caudal regions of the ganglion. There was also expression in human nodose ganglia. In fasted rats in which CB-1 and MCH-1 receptor expression was increased, administration of ghrelin prevented the downregulation by refeeding. We conclude that the actions of CCK and ghrelin are mediated by a common population of vagal afferent neurons. Ghrelin may act to limit the action of CCK in depressing expression of CB-1 and MCH-1 receptors and other receptors.
Synaptic Interactions Underlying Song-Selectivity in the Avian Nucleus HVC Revealed by Dual Intracellular Recordings
Authors: Rosen Merri J. , Mooney Richard
Published: January 2006

Stimulus-dependent synaptic interactions underlying selective sensory representations in neural circuits specialized for sensory processing and sensorimotor integration remain poorly understood. The songbird telencephalic nucleus HVC is a sensorimotor area essential to learned vocal control with one projection neuron (PN) type (HVCRA) innervating a song premotor pathway, another PN (HVCX) innervating a basal ganglia pathway essential to vocal plasticity, and interneurons (HVCInt). Playback of the bird's own song (BOS), but not other songs, evokes action potential bursts from both PNs, but HVCRA and HVCX display distinct BOS-evoked subthreshold responses. To characterize synaptic interactions underlying HVC's BOS-selective responses and assess stimulus-evoked changes in functional interactions between HVC neurons, we made simultaneous in vivo intracellular recordings from various HVC neuron pairs in urethan-anesthetized zebra finches. Spike-triggered averaging revealed that all HVC neuron types receive common excitation and that the onset of this excitation occurs during a narrower time window in projection neurons during BOS playback. To distinguish local from extrinsic contributions to HVC subthreshold response patterns, we inactivated the HVC local circuit with GABA or occluded inhibition in single HVCX cells. After either treatment, BOS-evoked responses in HVCX neurons became purely depolarizing and subthreshold responses of HVCX and HVCRA cells became remarkably similar to one another while retaining BOS selectivity. Therefore both PN types receive a common extrinsic source of BOS-selective excitation, and local inhibition specifically alters processing of auditory information in HVCX cells. In HVC, excitatory and inhibitory synaptic interactions are recruited in a stimulus-dependent fashion, affecting auditory representations of the BOS locally and in other song nuclei important to song learning and production.
Differential Roles for Group 1 mGluR Subtypes in Induction and Expression of Chemically Induced Hippocampal Long-Term Depression
Authors: Volk Lenora J. , Daly Christine A. , Huber Kimberly M.
Published: January 2006

Although metabotropic glutamate receptors (mGluRs) mGluR1 and mGluR5 are often found to have similar functions, there is considerable evidence that the two receptors also serve distinct functions in neurons. In hippocampal area CA1, mGluR5 has been most strongly implicated in long-term synaptic depression (LTD), whereas mGluR1 has been thought to have little or no role. Here we show that simultaneous pharmacological blockade of mGluR1 and mGluR5 is required to block induction of LTD by the group 1 mGluR agonist, ( RS)-3,5-dihydroxyphenylglycine (DHPG). Blockade of mGluR1 or mGluR5 alone has no effect on LTD induction, suggesting that activation of either receptor can fully induce LTD. Consistent with this conclusion, mGluR1 and mGluR5 both contribute to activation of extracellular signal-regulated kinase (ERK), which has previously been shown to be required for LTD induction. In contrast, selective blockade of mGluR1, but not mGluR5, reduces the expression of LTD and the associated decreases in AMPA surface expression. LTD is also reduced in mGluR1 knockout mice confirming the involvement of mGluR1. This shows a novel role for mGluR1 in long-term synaptic plasticity in CA1 pyramidal neurons. In contrast to DHPG-induced LTD, synaptically induced LTD with paired-pulse low-frequency stimulation persists in the pharmacological blockade of group 1 mGluRs and in mGluR1 or mGluR5 knockout mice. This suggests different receptors and/or upstream mechanisms for chemically and synaptically induced LTD.
Contribution of Feedback and Feedforward Strategies to Locomotor Adaptations
Authors: Lam Tania , Anderschitz Martin , Dietz Volker
Published: January 2006

The aim of this study was to examine the strategies used by human subjects to adapt their walking pattern to a velocity-dependent resistance applied against hip and knee movements. Subjects first walked on a treadmill with their lower limbs strapped to an exoskeletal robotic gait orthosis with no resistance against leg motions (null condition). Afterward, a velocity-dependent resistance was applied against left hip and knee movements (force condition). Catch trials were interspersed throughout the experiment to track the development of adaptive changes in the walking pattern. After 188 steps in the force condition, subjects continued to step in the null condition for another 100 steps (washout period). Leg muscle activity and joint kinematics were recorded and analyzed. The adaptive modifications in the locomotor pattern suggest the involvement of both feedback and feedforward control strategies. Feedback-driven adaptations were reflected in increases in rectus femoris and tibialis anterior activity during swing, which occurred immediately, only in the presence of resistance, and not during the catch trials. Locomotor adaptations involving feedforward strategies were reflected in enhanced pre-swing activity in the biceps femoris and medial hamstrings muscles, which required experience and persisted in the catch trials. During washout subjects showed a gradual deadaptation of locomotor activity to control levels. In summary, adaptive changes in the walking pattern were driven by both feedback and feedforward adjustments in the walking pattern appropriate for overcoming the effects of resistance.
Expression of a Functional Hyperpolarization-Activated Current (Ih) in the Mouse Nucleus Reticularis Thalami
Authors: Rateau Y. , Ropert N.
Published: January 2006

The GABAergic neurons of the nucleus reticularis thalami (nRT) express the type 2 hyperpolarization-activated cAMP-sensitive (HCN2) subunit mRNA, but surprisingly, they were reported to lack the hyperpolarization-activated ( Ih) current carried by this subunit. Using the voltage-clamp recordings in the thalamocortical slice preparation of the newborn and juvenile mice (P6–P23), we demonstrate that, in the presence of 1 mM barium (Ba2+), the nRT neurons express a slow hyperpolarization-activated inward current, suggesting that the Ih is present but masked in control conditions by K+ leak currents. We investigate the identity of the hyperpolarization-activated current in the nRT by studying its physiological and pharmacological profile in presence of Ba2+. We show that it has voltage- and time-dependent properties typical of the Ih, that it is blocked by cesium and ZD7288, two blockers of the Ih, and that it is carried both by the K+ and Na+ ions. We could also alter the gating characteristics of the hyperpolarization-activated current in the nRT by adding a nonhydrolysable analogue of cAMP to the pipette solution. Finally, using the current-clamp recording, we showed that blocking the hyperpolarization-activated current induced an hyperpolarization correlated with an increase of the Rin of the nRT neurons. In conclusion, our results demonstrate that the nRT neurons express the Ih with slow kinetics similar to those described for the homomeric HCN2 channels, and we show that the Ih of the nRT contributes to the excitability of the nRT neurons in normal conditions.
Neuronal Activity Related to Elapsed Time in Prefrontal Cortex
Authors: Genovesio Aldo , Tsujimoto Satoshi , Wise Steven P.
Published: January 2006

We studied prefrontal cortex activity during a saccade task. On each trial, one of three delay periods elapsed between the onset of a visual stimulus and its offset, which triggered a saccade. After stimulus offset, many neurons showed phasic increases in activity that depended on the duration of the preceding delay period. This delay-dependent activity varied only weakly with reaction time and instead appeared to reflect a more general aspect of elapsed time.
Differential Mechanisms Underlying the Modulation of Delayed-Rectifier K+Channel in Mouse Neocortical Neurons by Nitric Oxide
Authors: Han Nian-Lin R. , Ye Jian-Shan , Yu Albert Cheung Hoi , Sheu Fwu-Shan
Published: January 2006

The modulatory effects of nitric oxide (NO) on voltage-dependent K+channels are intricate. In our present study, the augmentation and reduction of K+currents by NO donor S-nitro- N-acetylpenicillamine (SNAP) and pure dissolved NO was observed in dissociated neurons from mice neocortex with both whole cell and cell-attached patch clamp. By using a specific electrochemical sensor, the critical concentrations of NO that increased or reduced the channel activities were accurately quantified. Low concentrations of SNAP (20 μM) or NO solution (0.1 μM) enhanced whole cell delayed rectifier K+-current ( IK) and left the fast inactivating A current ( IA) unchanged. However, high concentrations of SNAP (100 μM) and NO (0.5 μM) reduced both IKand IAcurrents. In cell-attached experiments, a significant increase in channel open probability (NP0) was observed when using low concentrations of SNAP or NO. High concentrations of SNAP or NO dramatically decreased NP0. The increase in channel activities by low concentrations of SNAP was abolished in the presence of either inhibitors of soluble guaylate cyclase or inhibitors of cGMP-dependent protein kinase G, suggesting a link to the NO-cGMP signaling cascade. The reduction of channel activities by high concentrations of SNAP was reversed by the reducing agent dithiothreitol, implying a redox reaction mechanism. Thus both NO-cGMP signaling and a redox mechanism are involved in the modulation of IKchannel activity for neuron excitability.
Spatial Resolution for Feature Binding Is Impaired in Peripheral and Amblyopic Vision
Authors: Neri Peter , Levi Dennis M.
Published: January 2006

We measured spatial resolution for discriminating targets that differed from nearby distractors in either color or orientation or their conjunction. In the fovea of normal human observers, whenever both attributes are big enough to be individually visible, their conjunction is also visible. In the periphery, the two attributes may be visible, but their conjunction may be invisible. We found a similar impairment in resolving conjunctions for the fovea of deprived eyes of humans with abnormal visual development (amblyopia). These results are quantitatively explained by a model of primary visual cortex (V1) in which orientation and color maps are imperfectly co-registered topographically. Our results in persons with amblyopia indicate that the ability of the fovea to compensate for this poor co-registration is consolidated by visual experience during postnatal development.
Nitric Oxide Is a Factor in the Stabilization of Hypoxia-Inducible Factor-1α in Cancer: Role of Free Radical Formation
Authors: Quintero Marisol , Brennan Peter A. , Thomas Gareth J. , Moncada Salvador
Published: January 2006

Widespread expression of the α-subunit of hypoxia-inducible factor (HIF-1α) was observed in samples of human oral squamous cell carcinoma. In all the cases, this was accompanied by a widespread distribution of nitric oxide (NO) synthases (NOS). Furthermore, in three human cell lines derived from human oral squamous cell carcinoma, the accumulation of HIF-1α was prevented either by inhibition of NOS activity with the nonspecific NOS inhibitor NG-monomethyl-l-arginine or by the antioxidants N-acetyl-l-cysteine and ascorbic acid. We suggest that, in certain forms of cancer, NO might be responsible for the accumulation of HIF-1α by a mechanism dependent on free radicals. (Cancer Res 2006; 66(2): 770-4)
RNA Interference–Mediated Depletion of Phosphoinositide 3-Kinase Activates Forkhead Box Class O Transcription Factors and Induces Cell Cycle Arrest and Apoptosis in Breast Carcinoma Cells
Authors: Reagan-Shaw Shannon , Ahmad Nihal
Published: January 2006

Breast cancer is one of the most common malignancies affecting women in the Western world and one in seven women is predicted to develop invasive breast cancer in their lifetime. Breast cancer arises following the accumulation of a series of somatic changes often including deregulation of key signal transduction pathways. The phosphoinositide 3-kinase (PI3K) pathway has been shown to be activated in breast cancer and overexpression of PI3K is sufficient to confer a malignant phenotype. Activation of the PI3K pathway serves to repress forkhead box class O (FoxO) transcription factor–mediated growth arrest and apoptosis. In this study, we used small interfering RNA (siRNA) to knockdown PI3K in three breast cancer cell lines representing different stages of cancer development. Transfection of PI3K siRNA in breast cancer cells resulted in a significant decrease in cell viability and induction of apoptosis irrespective of their estrogen receptor α (ERα) or ErbB2 status. PI3K depletion also resulted in a significant G1 phase cell cycle arrest in ERα-positive breast cancer cells. Further, our data showed that PI3K knockdown resulted in a significant activation of FoxO; interestingly, a simultaneous knockdown of FoxO1a rescued the cells from apoptosis. Furthermore, the downstream effects of FoxO activation were found to be inhibition of cyclin-dependent kinase 4, cyclin-dependent kinase 6, and cyclin D1, and accumulation of p27/Kip1. Thus, we suggest that (a) PI3K plays a critical role in breast cancer development and (b) gene therapeutic approaches aimed at PI3K or the pharmacologic inhibitors of PI3K could be developed for the management of breast cancer. (Cancer Res 2006; 66(2): 1062-9)
Elevated Expression of ISG15 in Tumor Cells Interferes with the Ubiquitin/26S Proteasome Pathway
Authors: Desai Shyamal D. , Haas Arthur L. , Wood Laurence M. , Tsai Yu-Chen , Pestka Sidney , Rubin Eric H. , Saleem Ahamed , Nur-E-Kamal Alam , Liu Leroy F.
Published: January 2006

IFN-stimulatory gene factor 15 (ISG15) is a ubiquitin-like protein, which is conjugated to many cellular proteins. However, its role in protein degradation is unclear. Here, we show that ISG15 is highly elevated and extensively conjugated to cellular proteins in many tumors and tumor cell lines. The increased levels of ISG15 in tumor cells were found to be associated with decreased levels of polyubiquitinated proteins. Specific knockdown of ISG15 expression using ISG15-specific small interfering RNA (siRNA) was shown to increase the levels of polyubiquitinated proteins, suggesting an antagonistic role of ISG15 in regulating ubiquitin-mediated protein turnover. Moreover, siRNA-mediated down-regulation of the major E2 for ISG15 (UbcH8), which blocked the formation of ISG15 protein conjugates, also increased the levels of polyubiquitinated proteins. Together, our results suggest that the ISG15 pathway, which is deregulated during tumorigenesis, negatively regulates the ubiquitin/proteasome pathway by interfering with protein polyubiquitination/degradation. (Cancer Res 2006; 66(2): 921-8)
Gr-1+CD115+ Immature Myeloid Suppressor Cells Mediate the Development of Tumor-Induced T Regulatory Cells and T-Cell Anergy in Tumor-Bearing Host
Authors: Huang Bo , Pan Ping-Ying , Li Qingsheng , Sato Alice I. , Levy David E. , Bromberg Jonathan , Divino Celia M. , Chen Shu-Hsia
Published: January 2006

The accumulation of myeloid suppressor cells (MSCs) is associated with immune suppression in tumor-bearing mice and in cancer patients. The suppressive activity of MSC correlates with the expression of the myeloid markers Gr-1, CD115 (macrophage colony-stimulating factor receptor), and F4/80. Gr-1+CD115+ MSCs, in addition to being able to suppress T-cell proliferation in vitro, can induce the development of Foxp3+ T regulatory cells (Treg) in vivo, which are anergic and suppressive. Furthermore, the secretion of interleukin (IL)-10 and transforming growth factor-β by Gr-1+CD115+ MSCs was induced and enhanced, respectively, on IFN-γ stimulation. The development of Treg requires antigen-associated activation of tumor-specific T cells, depends on the presence of IFN-γ and IL-10, and is independent of the nitric oxide–mediated suppressive mechanism by MSC. Our data provide evidence that Gr-1+CD115+ MSC can mediate the development of Treg in tumor-bearing mice and show a novel immune suppressive mechanism by which MSCs can suppress antitumor responses. (Cancer Res 2006; 66(2): 1123-31)
Phospholipase D Prevents Etoposide-Induced Apoptosis by Inhibiting the Expression of Early Growth Response-1 and Phosphatase and Tensin Homologue Deleted on Chromosome 10
Authors: Kim Joommo , Lee Young Han , Kwon Taeg Kyu , Chang Jong-Soo , Chung Kwang Chul , Min Do Sik
Published: January 2006

Phospholipase D (PLD) has emerged as a critical regulator of cell proliferation and survival signaling. We show for the first time that elevated expression of PLD isozymes attenuates expression of the tumor suppressors early growth response-1 (Egr-1) and the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) tumor suppressor and apoptosis during etoposide treatment. When formation of phosphatidic acid was inhibited by overexpression of catalytically inactive PLD during etoposide treatment, expression of Egr-1 and PTEN and the apoptotic effect of etoposide were not inhibited. This suggests that PLD inhibits expression of these tumor suppressors and inhibits apoptosis. Deletion of a specific Egr-1-binding site present in the PTEN promoter blocked etoposide-induced PTEN activity and elevated expression of PLD decreased the sensitivity to apoptosis induced by ectopic expression of Egr-1. Etoposide-induced activation of Akt was potentiated by overexpression of PLD and PLD-stimulated suppression of Egr-1 was blocked by inhibition of phosphatidylinositol 3-kinase/Akt survival pathway at the both transcriptional and posttranscriptional levels. These results show that survival signals generated by PLD attenuate expression of Egr-1 by activation of phosphatidylinositol 3-kinase signaling pathway and induction of PTEN by Egr-1, which confers resistance to apoptosis. (Cancer Res 2006; 66(2): 784-93)
PEG10 Is a c-MYC Target Gene in Cancer Cells
Authors: Li Chi-Ming , Margolin Adam A. , Salas Martha , Memeo Lorenzo , Mansukhani Mahesh , Hibshoosh Hanina , Szabolcs Matthias , Klinakis Apostolos , Tycko Benjamin
Published: January 2006

The product of the imprinted gene paternally expressed gene-10 (PEG10) has been reported to support proliferation in hepatocellular carcinomas, but how this gene is regulated has been an open question. We find that MYC knockdown by RNA interference suppresses PEG10 expression in Panc1 pancreatic carcinoma and HepG2 hepatocellular carcinoma cells and that knockdown of PEG10 inhibits the proliferation of Panc1, HepG2, and Hep3B cells. Conversely, PEG10 was up-regulated by inducing c-MYC expression in a B-lymphocyte cell line. Chromatin immunoprecipitation from Panc1 cells showed c-MYC bound to an E-box-containing region in the PEG10 first intron and site-directed mutagenesis showed that the most proximal E-box is essential for promoter activity. In a mouse mammary tumor virus (MMTV)-MYC transgenic mouse model of breast cancer, most but not all of the mammary carcinomas had strongly increased Peg10 mRNA compared with normal mammary gland. By immunohistochemistry, normal human breast and prostate epithelium was negative for the major isoform [reading frame-1 (RF1)] of PEG10 protein, but this cytoplasmic protein was strongly expressed in a subset of breast carcinomas in situ and invasive ductal carcinomas (∼30%) and in a similar percentage of prostate cancers. As in the mouse model, we found positive, but not absolute, correlations between PEG10 and c-MYC in tissue arrays containing 161 human breast cancers (P < 0.002) and 30 prostate cancers (P = 0.014). Immunostaining of human placenta showed PEG10 and c-MYC proteins coexpressed in proliferating cytotrophoblast and coordinately lost in postmitotic syncytiotrophoblast. These findings link cancer genetics and epigenetics by showing that a classic proto-oncogene, MYC, acts directly upstream of a proliferation-positive imprinted gene, PEG10. (Cancer Res 2006; 66(2): 665-72)
Rapamycin Disrupts Cyclin/Cyclin-Dependent Kinase/p21/Proliferating Cell Nuclear Antigen Complexes and Cyclin D1 Reverses Rapamycin Action by Stabilizing These Complexes
Authors: Law Mary , Forrester Elizabeth , Chytil Anna , Corsino Patrick , Green Gail , Davis Bradley , Rowe Thomas , Law Brian
Published: January 2006

Rapamycin and its derivatives are promising anticancer agents, but the exact mechanisms by which these drugs induce cell cycle arrest and inhibit tumor growth are unknown. A biochemical analysis of human mammary tumor cell lines indicated that rapamycin-induced antiproliferative effects correlated with down-regulation of cellular p21 levels and the levels of p21 in cyclin-dependent kinase (Cdk) 2 and 4 complexes. Cyclin D1 overexpression reversed rapamycin action and this reversal correlated with increased levels of cellular p21, higher levels of p21 associated with Cdk2, and stabilization of cyclin D1/Cdk2/p21/proliferating cell nuclear antigen (PCNA) complexes. Experiments using a novel cyclin D1-Cdk2 fusion protein or a kinase-dead mutant of the fusion protein indicated that reversal of rapamycin action required not only the formation of complexes with p21 and PCNA but also complex-associated kinase activity. Similar results were observed in vivo. The rapamycin derivative RAD001 (everolimus) inhibited the growth of mouse mammary tumors, which correlated with the disruption of cyclin D1/Cdk2 complexes. The potential implications of these results with respect to the use of rapamycin derivatives in breast cancer therapy are discussed. (Cancer Res 2006; 66(2): 1070-80)