bluuebunny/crossref_metadata_2025 huggingface dataset:
COMPLEXCITY: MODELING URBAN MOBILITY
Authors: BAZZANI ARMANDO , RAMBALDI SANDRO , GIORGINI BRUNO , TURCHETTI GIORGIO
Published: January 2008

We consider the problem of modeling urban mobility using the complex systems key of lecture. We discuss the properties of the Auto-mobilis model, a virtual simulator for private car mobility based on the individual citizen propensities and the existence of "chronotopoi", which are the primary causes of citizens' mobility requests. Auto-mobilis is a microscopic agent-based model that takes into account both the physical interactions and the cognitive dynamics. We present the current status of the project and discuss the applications to real situations. The model assumptions are justified by a comparison with GPS observational data on single vehicle trajectories.
PRELIMINARY RESULTS OF A MULTIAGENT TRAFFIC SIMULATION FOR BERLIN
Authors: BEUCK ULRIKE , NAGEL KAI , RIESER MARCEL , STRIPPGEN DAVID , BALMER MICHAEL
Published: January 2008

This paper provides an introduction to multiagent traffic simulation. It includes some description of where we are with respect to the implementation of a real-world Berlin scenario. It turns out that the difficulties there, because of data availability and because of the special situation of Berlin after the reunification, are considerably larger than in previous scenarios that we have treated.
SCANNING PROBE MICROSCOPY BASED NANOSCALE PATTERNING AND FABRICATION
Authors: XIE XIAN NING , CHUNG HONG JING , WEE ANDREW THYE SHEN
Published: January 2008

Nanotechnology is vital to the fabrication of integrated circuits, memory devices, display units, biochips and biosensors. Scanning probe microscope (SPM) has emerged to be a unique tool for materials structuring and patterning with atomic and molecular resolution. SPM includes scanning tunneling microscopy (STM) and atomic force microscopy (AFM). In this chapter, we selectively discuss the atomic and molecular manipulation capabilities of STM nanolithography. As for AFM nanolithography, we focus on those nanopatterning techniques involving water and/or air when operated in ambient. The typical methods, mechanisms and applications of selected SPM nanolithographic techniques in nanoscale structuring and fabrication are reviewed.
SYNCHROTRON-RADIATION-SUPPORTED HIGH-ASPECT-RATIO NANOFABRICATION
Authors: CHEN A. , LIU G. , JIAN L. K. , MOSER HERBERT O.
Published: January 2008

X-ray lithography with synchrotron radiation is an important nanolithographic tool which has unique advantages in the production of high aspect ratio nanostructures. The optimum synchrotron radiation spectrum for nanometer scale X-ray lithography is normally in the range of 500 eV to 2 keV. In this paper, we present the main methods, equipment, process parameters and preliminary results of nanofabrication by proximity X-ray lithography within the nanomanufacturing program pursued by Singapore Synchrotron Light Source (SSLS). Nanostructures with feature sizes down to 200 nm and an aspect ratio up to 10 have been successfully achieved by this approach.
Fast calcium wave propagation mediated by electrically conducted excitation and boosted by CICR
Authors: Kusters J. M. A. M. , van Meerwijk W. P. M. , Ypey D. L. , Theuvenet A. P. R. , Gielen C. C. A. M.
Published: January 2008

We have investigated synchronization and propagation of calcium oscillations, mediated by gap junctional excitation transmission. For that purpose we used an experimentally based model of normal rat kidney (NRK) cells, electrically coupled in a one-dimensional configuration (linear strand). Fibroblasts such as NRK cells can form an excitable syncytium and generate spontaneous inositol 1,4,5-trisphosphate (IP3)-mediated intracellular calcium waves, which may spread over a monolayer culture in a coordinated fashion. An intracellular calcium oscillation in a pacemaker cell causes a membrane depolarization from within that cell via calcium-activated chloride channels, leading to an L-type calcium channel-based action potential (AP) in that cell. This AP is then transmitted to the electrically connected neighbor cell, and the calcium inflow during that transmitted AP triggers a calcium wave in that neighbor cell by opening of IP3 receptor channels, causing calcium-induced calcium release (CICR). In this way the calcium wave of the pacemaker cell is rapidly propagated by the electrically transmitted AP. Propagation of APs in a strand of cells depends on the number of terminal pacemaker cells, the L-type calcium conductance of the cells, and the electrical coupling between the cells. Our results show that the coupling between IP3-mediated calcium oscillations and AP firing provides a robust mechanism for fast propagation of activity across a network of cells, which is representative for many other cell types such as gastrointestinal cells, urethral cells, and pacemaker cells in the heart.
Stimulation of calcineurin Aα activity attenuates muscle pathophysiology inmdxdystrophic mice
Authors: Stupka Nicole , Schertzer Jonathan D. , Bassel-Duby Rhonda , Olson Eric N. , Lynch Gordon S.
Published: January 2008

Calcineurin activation ameliorates the dystrophic pathology of hindlimb muscles in mdx mice and decreases their susceptibility to contraction damage. In mdx mice, the diaphragm is more severely affected than hindlimb muscles and more representative of Duchenne muscular dystrophy. The constitutively active calcineurin Aα transgene (CnAα) was overexpressed in skeletal muscles of mdx ( mdx CnAα*) mice to test whether muscle morphology and function would be improved. Contractile function of diaphragm strips and extensor digitorum longus and soleus muscles from adult mdx CnAα* and mdx mice was examined in vitro. Hindlimb muscles from mdx CnAα* mice had a prolonged twitch time course and were more resistant to fatigue. Because of a slower phenotype and a decrease in fiber cross-sectional area, normalized force was lower in fast- and slow-twitch muscles of mdx CnAα* than mdx mice. In the diaphragm, despite a slower phenotype and a ∼35% reduction in fiber size, normalized force was preserved. This was likely mediated by the reduction in the area of the diaphragm undergoing degeneration (i.e., mononuclear cell and connective and adipose tissue infiltration). The proportion of centrally nucleated fibers was reduced in mdx CnAα* compared with mdx mice, indicative of improved myofiber viability. In hindlimb muscles of mdx mice, calcineurin activation increased expression of markers of regeneration, particularly developmental myosin heavy chain isoform and myocyte enhancer factor 2A. Thus activation of the calcineurin signal transduction pathway has potential to ameliorate the mdx pathophysiology, especially in the diaphragm, through its effects on muscle degeneration and regeneration and endurance capacity.
Inhibition of glucokinase translocation by AMP-activated protein kinase is associated with phosphorylation of both GKRP and 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase
Authors: Mukhtar Mohammed H. , Payne Victoria A. , Arden Catherine , Harbottle Andrew , Khan Salmaan , Lange Alex J. , Agius Loranne
Published: January 2008

The rate of glucose phosphorylation in hepatocytes is determined by the subcellular location of glucokinase and by its association with its regulatory protein (GKRP) in the nucleus. Elevated glucose concentrations and precursors of fructose 1-phosphate (e.g., sorbitol) cause dissociation of glucokinase from GKRP and translocation to the cytoplasm. In this study, we investigated the counter-regulation of substrate-induced translocation by AICAR (5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside), which is metabolized by hepatocytes to an AMP analog, and causes activation of AMP-activated protein kinase (AMPK) and depletion of ATP. During incubation of hepatocytes with 25 mM glucose, AICAR concentrations below 200 μM activated AMPK without depleting ATP and inhibited glucose phosphorylation and glucokinase translocation with half-maximal effect at 100–140 μM. Glucose phosphorylation and glucokinase translocation correlated inversely with AMPK activity. AICAR also counteracted translocation induced by a glucokinase activator and partially counteracted translocation by sorbitol. However, AICAR did not block the reversal of translocation (from cytoplasm to nucleus) after substrate withdrawal. Inhibition of glucose-induced translocation by AICAR was greater than inhibition by glucagon and was associated with phosphorylation of both GKRP and the cytoplasmic glucokinase binding protein, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK2) on ser-32. Expression of a kinase-active PFK2 variant lacking ser-32 partially reversed the inhibition of translocation by AICAR. Phosphorylation of GKRP by AMPK partially counteracted its inhibitory effect on glucokinase activity, suggesting altered interaction of glucokinase and GKRP. In summary, mechanisms downstream of AMPK activation, involving phosphorylation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase and GKRP are involved in the ATP-independent inhibition of glucose-induced glucokinase translocation by AICAR in hepatocytes.
IGF-I alleviates diabetes-induced RhoA activation, eNOS uncoupling, and myocardial dysfunction
Authors: Ren Jun , Duan Jinhong , Thomas D. Paul , Yang Xiaoping , Sreejayan Nair , Sowers James R. , Leri Annarosa , Kajstura Jan , Gao Feng , Anversa Piero
Published: January 2008

IGF-I rescues diabetic heart defects and oxidative stress, although the underlying mechanism of action remains poorly understood. This study was designed to delineate the beneficial effects of IGF-I with a focus on RhoA, Akt, and eNOS coupling. Echocardiography was performed in normal or diabetic Friend Virus-B type (FVB) and IGF-I transgenic mice. Cardiomyocyte contractile properties were evaluated using peak shortening (PS), time-to-90% relengthening (TR90), and intracellular Ca2+ rise and decay. Diabetes reduced fraction shortening, PS, and intracellular Ca2+; it increased chamber size, prolonged TR90, and intracellular Ca2+ decay. Levels of RhoA mRNA, active RhoA, and O2− were elevated, whereas nitric oxide (NO) levels were reduced in diabetes. Diabetes-induced O2− accumulation was ablated by the NO synthase (NOS) inhibitor nitro-l-arginine methyl ester (l-NAME), indicating endothelial NOS (eNOS) uncoupling, all of which except heart size were negated by IGF-I. The IGF-I-elicited beneficial effects were mimicked by the Rho kinase inhibitor Y27632 and BH4. Diabetes depressed expression of Kv1.2 and dihydrofolate reductase (DHFR), increased β-myosin heavy-chain expression, stimulated p38 MAPK, and reduced levels of total Akt and phosphorylated Akt/eNOS, all of which with the exception of myosin heavy chain were attenuated by IGF-I. In addition, Y27632 and the eNOS coupler folate abrogated glucose toxicity-induced PS decline, TR90 prolongation, while it increased O2− and decreased NO and Kv1.2 levels. The DHFR inhibitor methotrexate impaired myocyte function, NO/O2− balance, and rescued Y27632-induced cardiac protection. These results revealed that IGF-I benefits diabetic hearts via Rho inhibition and antagonism of diabetes-induced decrease in pAkt, eNOS uncoupling, and K+ channel expression.
Intracellular calcium accumulation following eccentric contractions in rat skeletal muscle in vivo: role of stretch-activated channels
Authors: Sonobe Takashi , Inagaki Tadakatsu , Poole David C. , Kano Yutaka
Published: January 2008

Although the accumulation of intracellular calcium ions ([Ca2+]i) is associated with muscle damage, little is known regarding the temporal profile of muscle [Ca2+]iunder in vivo conditions, and, specifically, the effects of different contraction types [e.g., isometric (ISO); eccentric (ECC)] on [Ca2+]iremain to be determined. The following hypotheses were tested. 1) For 90 min at rest, an in vivo vs. in vitro preparation would better maintain initial [Ca2+]i. 2) Compared with ISO, ECC contractions (50 contractions, 10 sets, 5-min interval) would lead to a greater increase of [Ca2+]i. 3) Elevated [Ca2+]iduring ECC would be reduced or prevented by the stretch-activated ion channel blockers streptomycin and gadolinium (Gd3+). Spinotrapezius muscles of Wistar rats were exteriorized (in vivo) or excised (in vitro). [Ca2+]iwas evaluated by loading the muscle with fura 2-AM using fluorescence imaging. [Ca2+]irose progressively beyond 40 min at rest under in vitro but not in vivo conditions during the 90-min protocol. In vivo [Ca2+]iincreased more rapidly during ECC (first set) than ISO (fifth set) ( P < 0.05 vs. precontraction values). The peak level of [Ca2+]iwas increased by 21.5% (ISO) and 42.8% (ECC) after 10 sets (both P < 0.01). Streptomycin and Gd3+abolished the majority of [Ca2+]iincrease during ECC (69 and 86% reduction, respectively; P < 0.01 from peak [Ca2+]iof ECC). In conclusion, in vivo quantitative analyses demonstrated that ECC contractions elevate [Ca2+]isignificantly more than ISO contractions and that stretch-activated channels may play a permissive role in this response.
Impaired responsiveness of renal sensory nerves in streptozotocin-treated rats and obese Zucker diabetic fatty rats: role of angiotensin
Authors: Kopp Ulla C. , Cicha Michael Z. , Yorek Mark A.
Published: January 2008

Increasing afferent renal nerve activity decreases efferent renal nerve activity and increases urinary sodium excretion. Activation of renal pelvic mechanosensory nerves is impaired in streptozotocin (STZ)-treated rats (model of type 1 diabetes). Decreased activation of renal sensory nerves would lead to increased efferent renal nerve activity, sodium retention, and hypertension. We examined whether the reduced activation of renal sensory nerves in STZ rats was due to increased renal angiotensin activity and whether activation of the renal sensory nerves was impaired in obese Zucker diabetic fatty (ZDF) rats (model of type 2 diabetes). In an isolated renal pelvic wall preparation from rats treated with STZ for 2 wk, PGE2failed to increase the release of substance P, from 5 ± 1 to 6 ± 1 pg/min. In pelvises from sham STZ rats, PGE2increased substance P release from 6 ± 1 to 13 ± 2 pg/min. Adding losartan to the incubation bath increased PGE2-mediated release of substance P in STZ rats, from 5 ± 1 to 10 ± 2 pg/min, but had no effect in sham STZ rats. In pelvises from obese ZDF rats (22–46 wk old), PGE2increased substance P release from 12.0 ± 1.2 to 18.3 ± 1.2 pg/min, which was less than that from lean ZDF rats (10.3 ± 1.6 to 22.5 ± 2.4 pg/min). Losartan had no effect on the PGE2-mediated substance P release in obese or lean ZDF rats. We conclude that the mechanisms involved in the decreased responsiveness of the renal sensory nerves in STZ rats involve activation of the renin angiotensin system in STZ but not in obese ZDF rats.
Effects on kidney filtration rate by agmatine requires activation of ryanodine channels for nitric oxide generation
Authors: Satriano Joseph , Cunard Robyn , Peterson Orjan W. , Dousa Thomas , Gabbai Francis B. , Blantz Roland C.
Published: January 2008

Agmatine, decarboxylated arginine, is produced in the kidney and can increase nephron and kidney filtration rate via renal vasodilatation and increases in plasma flow. This increase in filtration rate after agmatine is prevented by administration of nitric oxide synthase (NOS) inhibitors. In endothelial cells, agmatine-stimulated nitrite production is accompanied by induction of cytosolic calcium. NOS activity requires calcium for activation; however, the source of this calcium remains unknown. Ryanodine receptor (RyR) calcium-activated calcium release channels are present in the kidney cortex, and we evaluated if RyR contributes to the agmatine response. Agmatine microperfused into Bowman's space reversibly increases nephron filtration rate (SNGFR) by ∼30%. cADP-ribose (cADPR) regulates RyR channel activity. Concurrent infusion of agmatine with the cADPR blocker 8-bromo-cADPR (2 μM) prevents the increase in filtration rate. Furthermore, direct activation of the RyR channel with ryanodine at agonist concentrations (5 μM) increases SNGFR, and, like agmatine, this increase is prevented by administration of NG-monomethyl-l-arginine, a nonselective NOS blocker. We demonstrate that agmatine does not elicit ADPR cyclase activity in vascular smooth muscle membranes and does not directly affect RyR calcium channel responses using sea urchin egg homogenates. These results imply interplay between endothelial cell cADPR/RyR/Ca2+/NO and the cADPR/RyR/Ca2+pathways in vascular smooth muscle cells in arterioles in the regulation of kidney filtration rate. In conclusion, we show that agmatine-induced effects require activation of cADPR and RyR calcium release channels for NO generation, vasodilation, and increased filtration rate.
Course of preeclamptic glomerular injury after delivery
Authors: Hladunewich M. A. , Myers B. D. , Derby G. C. , Blouch K. L. , Druzin M. L. , Deen W. M. , Naimark D. M. , Lafayette R. A.
Published: January 2008

We evaluated the early postpartum recovery of glomerular function over 4 wk in 57 women with preeclampsia. We used physiological techniques to measure glomerular filtration rate (GFR), renal plasma flow, and oncotic pressure (πA) and computed a value for the two-kidney ultrafiltration coefficient ( Kf). Compared with healthy, postpartum controls, GFR was depressed by 40% on postpartum day 1, but by only 19% and 8% in the second and fourth postpartum weeks, respectively. Hypofiltration was attributable solely to depression, at corresponding postpartum times, of Kf by 55%, 30%, and 18%, respectively. Improvement in glomerular filtration capacity was accompanied by recovery of hypertension to near-normal levels and significant improvement in albuminuria. We conclude that the functional manifestations of the glomerular endothelial injury of preeclampsia largely resolve within the first postpartum month.
Optimal Temporal Decoding of Neural Population Responses in a Reaction-Time Visual Detection Task
Authors: Chen Yuzhi , Geisler Wilson S. , Seidemann Eyal
Published: January 2008

Behavioral performance in detection and discrimination tasks is likely to be limited by the quality and nature of the signals carried by populations of neurons in early sensory cortical areas. Here we used voltage-sensitive dye imaging (VSDI) to directly measure neural population responses in the primary visual cortex (V1) of monkeys performing a reaction-time detection task. Focusing on the temporal properties of the population responses, we found that V1 responses are consistent with a stimulus-evoked response with amplitude and latency that depend on target contrast and a stimulus-independent additive noise with long-lasting temporal correlations. The noise had much lower amplitude than the ongoing activity reported previously in anesthetized animals. To understand the implications of these properties for subsequent processing stages that mediate behavior, we derived the Bayesian ideal observer that specifies how to optimally use neural responses in reaction time tasks. Using the ideal observer analysis, we show that 1) the observed temporal correlations limit the performance benefit that can be attained by accumulating V1 responses over time, 2) a simple temporal decorrelation operation with time-lagged excitation and inhibition minimizes the detrimental effect of these correlations, 3) the neural information relevant for target detection is concentrated in the initial response following stimulus onset, and 4) a decoder that optimally uses V1 responses far outperforms the monkey in both speed and accuracy. Finally, we demonstrate that for our particular detection task, temporal decorrelation followed by an appropriate running integrator can approach the speed and accuracy of the optimal decoder.
A Computational Model of Perceptual Fill-in Following Retinal Degeneration
Authors: McManus Justin N. J. , Ullman Shimon , Gilbert Charles D.
Published: January 2008

The ablation of afferent input results in the reorganization of sensory and motor cortices. In the primary visual cortex (V1), binocular retinal lesions deprive a corresponding cortical region [lesion projection zone (LPZ)] of visual input. Nevertheless, neurons in the LPZ regain responsiveness by shifting their receptive fields (RFs) outside the retinal lesions; this re-emergence of neural activity is paralleled by the perceptual completion of disrupted visual input in human subjects with retinal damage. To determine whether V1 reorganization can account for perceptual fill-in, we developed a neural network model that simulates the cortical remapping in V1. The model shows that RF shifts mediated by the plexus of spatial- and orientation-dependent horizontal connections in V1 can engender filling-in that is both robust and consistent with psychophysical reports of perceptual completion. Our model suggests that V1 reorganization may underlie perceptual fill-in, and it predicts spatial relationships between the original and remapped RFs that can be tested experimentally. More generally, it provides a general explanation for adaptive functional changes following CNS lesions, based on the recruitment of existing cortical connections that are involved in normal integrative mechanisms.
Evidence for Two Populations of Bitter Responsive Taste Cells in Mice
Authors: Hacker Kyle , Laskowski Agnes , Feng Li , Restrepo Diego , Medler Kathryn
Published: January 2008

Taste receptor cells use multiple signaling mechanisms to detect different taste stimuli in the oral cavity. Ionic stimuli (sour, salty) interact directly with ion channels to elicit responses, whereas bitter, sweet, and umami tastants activate G protein–coupled receptors to initiate phospholipase C (PLC)-dependent release of calcium from intracellular stores. However, the precise role for PLC in taste responses remains unclear. One study reported that bitter, sweet, and umami detection is abolished in PLCβ2 knock-out animals, indicating that the perception of these stimuli depends solely on PLCβ2. In contrast, another study found that PLCβ2 knock-out mice have a reduced, but not abolished, capacity to detect these taste qualities, suggesting a PLCβ2-independent signaling pathway may be involved in the detection of taste stimuli. Since PLCβ2-expressing taste cells do not have conventional synapses or express voltage-gated calcium channels (VGCCs), we sought to determine if any taste cells responding to bitter express VGCCs. We characterized calcium responses generated by bitter stimuli to activate the PLC pathway and 50 mM KCl to activate VGCCs. Comparisons of evoked calcium responses found that these two stimuli generated significantly different responses. Surprisingly, although most responsive taste cells responded to bitter or 50 mM KCl, some taste cells responded to both. Analysis of dual responsive cells found that bitter responses were inhibited by the PLC inhibitor U73122. Immunocytochemical analysis detected PLCβ3 and IP3R1, indicating the presence of multiple PLC signaling pathways in taste cells.
Synaptic Responses of Neurons Controlling the Parotid and von Ebner Salivary Glands in Rats to Stimulation of the Solitary Nucleus and Tract
Authors: Suwabe Takeshi , Fukami Hideyuki , Bradley Robert M.
Published: January 2008

Salivary secretion results from reflex stimulation of autonomic neurons via afferent sensory information relayed to neurons in the rostral nucleus of the solitary tract (rNST), which synapse with autonomic neurons of the salivatory nuclei. We investigated the synaptic properties of the afferent sensory connection to neurons in the inferior salivatory nucleus (ISN) controlling the parotid and von Ebner salivary glands. Mean synaptic latency recorded from parotid gland neurons was significantly shorter than von Ebner gland neurons. Superfusion of GABA and glycine resulted in a concentration-dependent membrane hyperpolarization. Use of glutamate receptor antagonists indicated that both AMPA and N-methyl-d-aspartate (NMDA) receptors are involved in the evoked excitatory postsynaptic potentials (EPSPs). Inhibitory postsynaptic potential (IPSP) amplitude increased with higher intensity ST stimulation. Addition of the glycine antagonist strychnine did not affect the amplitude of the IPSPs significantly. The GABAA receptor antagonist, bicuculline (BMI) or mixture of strychnine and BMI abolished the IPSPs in all neurons. IPSP latency was longer than EPSP latency, suggesting that more than one synapse is involved in the inhibitory pathway. Results show that ISN neurons receive both excitatory and inhibitory afferent input mediated by glutamate and GABA respectively. The ISN neuron response to glycine probably derives from descending connections. Difference in the synaptic characteristics of ISN neurons controlling the parotid and von Ebner glands may relate to the different function of these two glands.
Data analysis and bioinformatics tools for tandem mass spectrometry in proteomics
Authors: Deutsch Eric W. , Lam Henry , Aebersold Ruedi
Published: January 2008

Data processing is a central and critical component of a successful proteomics experiment, and is often the most time-consuming step. There have been considerable advances in the field of proteomics informatics in the past 5 years, spurred mainly by free and open-source software tools. Along with the gains afforded by new software, the benefits of making raw data and processed results freely available to the community in data repositories are finally in evidence. In this review, we provide an overview of the general analysis approaches, software tools, and repositories that are enabling successful proteomics research via tandem mass spectrometry.
CXCR4 up-regulation by imatinib induces chronic myelogenous leukemia (CML) cell migration to bone marrow stroma and promotes survival of quiescent CML cells
Authors: Jin Linhua , Tabe Yoko , Konoplev Sergej , Xu Yuanyuan , Leysath Clinton E. , Lu Hongbo , Kimura Shinya , Ohsaka Akimichi , Rios Mary-Beth , Calvert Leslie , Kantarjian Hagop , Andreeff Michael , Konopleva Marina
Published: January 2008

Chronic myelogenous leukemia (CML) is driven by constitutively activated Bcr-Abl tyrosine kinase, which causes the defective adhesion of CML cells to bone marrow stroma. The overexpression of p210Bcr-Abl was reported to down-regulate CXCR4 expression, and this is associated with the cell migration defects in CML. We proposed that tyrosine kinase inhibitors, imatinib or INNO-406, may restore CXCR4 expression and cause the migration of CML cells to bone marrow microenvironment niches, which in turn results in acquisition of stroma-mediated chemoresistance of CML progenitor cells. In KBM5 and K562 cells, imatinib, INNO-406, or IFN-α increased CXCR4 expression and migration. This increase in CXCR4 levels on CML progenitor cells was likewise found in samples from CML patients treated with imatinib or IFN-α. Imatinib induced G0-G1 cell cycle block in CML cells, which was further enhanced in a mesenchymal stem cell (MSC) coculture system. MSC coculture protected KBM-5 cells from imatinib-induced cell death. These antiapoptotic effects were abrogated by the CXCR4 antagonist AMD3465 or by inhibitor of integrin-linked kinase QLT0267. Altogether, these findings suggest that the up-regulation of CXCR4 by imatinib promotes migration of CML cells to bone marrow stroma, causing the G0-G1 cell cycle arrest and hence ensuring the survival of quiescent CML progenitor cells. [Mol Cancer Ther 2008;7(1):48–58]
In vivo silencing of a molecular target by short interfering RNA electroporation: tumor vascularization correlates to delivery efficiency
Authors: Takei Yoshifumi , Nemoto Toshio , Mu Ping , Fujishima Tatsuya , Ishimoto Takuji , Hayakawa Yasuhiko , Yuzawa Yukio , Matsuo Seiichi , Muramatsu Takashi , Kadomatsu Kenji
Published: January 2008

Screening for a molecular target for cancer therapy requires multiple steps, of which an important one is evaluation of the knockdown effect of the target molecule on pregrown xenograft tumors. However, methods currently used for local administration of knockdown reagents, such as short interfering RNA (siRNA), are not satisfactory as to simplicity and efficiency. We established an electroporation method involving a constant voltage and “plate and fork” type electrodes and used it for in vivo delivery of siRNA. The delivery efficiency correlated to the electric current. The electric current correlated to the microvascular density and vascular endothelial growth factor (VEGF) expression and exhibited a threshold that guaranteed efficient delivery. Consequently, we showed that the vascularization and VEGF expression in tumors determined the efficiency of delivery of siRNA by electroporation. VEGF was chosen as a model target. VEGF siRNA electroporation suppressed the growth of tumors exhibiting high VEGF expression to less than 10% of the control level, but it had no effect on low VEGF-expressing tumors. Notably, a long interval (20 days) of electroporation was enough to obtain a satisfactory effect. Systemically injected siRNA could also be delivered into tumors by this method. Our data will provide the technical basis for in vivo electroporation, and this simple and efficient siRNA delivery method is applicable to in vivo comprehensive screening for a molecular target. [Mol Cancer Ther 2008;7(1):211–21]
Adenovirus-expressed human hyperplasia suppressor gene induces apoptosis in cancer cells
Authors: Wu Lina , Li Zhixin , Zhang Yingmei , Zhang Pei , Zhu Xiaohui , Huang Jing , Ma Teng , Lu Tian , Song Quansheng , Li Qian , Guo Yanhong , Tang Jian , Ma Dalong , Chen Kuang-Hueih , Qiu Xiaoyan
Published: January 2008

Hyperplasia suppressor gene (HSG), also called human mitofusin 2, is a novel gene that markedly suppresses the cell proliferation of hyperproliferative vascular smooth muscle cells from spontaneously hypertensive rat arteries. This gene encodes a mitochondrial membrane protein that participates in mitochondrial fusion and contributes to the maintenance and operation of the mitochondrial network. In this report, we showed that an adenovirus vector encoding human HSG (Ad5-hHSG) had an antitumor activity in a wide range of cancer cell lines. We further focused on the lung cancer cell line A549 and the colon cancer cell line HT-29 and then observed that Ad5-hHSG induced apoptosis both in vitro and in vivo. Confocal laser scanning microscopy and electron microscopy revealed that cells infected with Ad5-hHSG formed dose-dependent perinuclear clusters of fused mitochondria. Adenovirus-mediated hHSG overexpression induced apoptosis, cell cycle arrest, mitochondrial membrane potential (ΔΨm) reduction and release of cytochrome c, caspase-3 activation, and cleavage of PARP in vitro. Overexpression of hHSG also significantly suppressed the growth of subcutaneous tumors in nude mice both ex vivo and in vivo. In addition, Ad5-hHSG increased the sensitivity of these cell lines to two chemotherapeutic agents, VP16 and CHX, and radiation. These results suggest that Ad5-hHSG may serve as an effective therapeutic drug against tumors. [Mol Cancer Ther 2008;7(1):222–32]
Molecular profiling of angiogenesis with targeted ultrasound imaging: early assessment of antiangiogenic therapy effects
Authors: Palmowski Moritz , Huppert Jochen , Ladewig Gesa , Hauff Peter , Reinhardt Michael , Mueller Margareta M. , Woenne Eva C. , Jenne Juergen W. , Maurer Mathias , Kauffmann Guenter W. , Semmler Wolfhard , Kiessling Fabian
Published: January 2008

Molecular ultrasound is capable of elucidating the expression of angiogenic markers in vivo. However, the capability of the method for volumetric “multitarget quantification” and for the assessment of antiangiogenic therapy response has rather been investigated. Therefore, we generated cyanoacrylate microbubbles linked to vascular endothelial growth factor receptor 2 (VEGFR2) and αvβ3 integrin binding ligands and quantified their accumulation in squamous cell carcinoma xenografts (HaCaT-ras-A-5RT3) in mice with the quantitative volumetric ultrasound scanning technique, sensitive particle acoustic quantification. Specificity of VEGFR2 and αvβ3 integrin binding microbubbles was shown, and changes in marker expression during matrix metalloproteinase inhibitor treatment were investigated. In tumors, accumulation of targeted microbubbles was significantly higher compared with nonspecific ones and could be inhibited competitively by addition of the free ligand in excess. Also, multimarker imaging could successfully be done during the same imaging session. Molecular ultrasound further indicated a significant increase of VEGFR2 and αvβ3 integrin expression during tumor growth and a considerable decrease in both marker densities after matrix metalloproteinase inhibitor treatment. Histologic data suggested that the increasing VEGFR2 and αvβ3 integrin concentrations in tumors during growth are related to an up-regulation of its expression by the endothelial cells, whereas its decrease under therapy is more related to the decreasing relative vessel density. In conclusion, targeted ultrasound appears feasible for the longitudinal molecular profiling of tumor angiogenesis and for the sensitive assessment of therapy effects in vivo. [Mol Cancer Ther 2008;7(1):101–9]
Ataxia-telangiectasia and Rad3-related and DNA-dependent protein kinase cooperate in G2 checkpoint activation by the DNA strand-breaking nucleoside analogue 2′-C-cyano-2′-deoxy-1-β-d-arabino-pentofuranosylcytosine
Authors: Liu Xiaojun , Matsuda Akira , Plunkett William
Published: January 2008

2′-C-Cyano-2′-deoxy-1-β-d-arabino-pentofuranosylcytosine (CNDAC), the prodrug (sapacitabine) of which is in clinical trials, has the novel mechanism of action of causing single-strand breaks after incorporating into DNA. Cells respond to this unique lesion by activating the G2 checkpoint, affected by the Chk1-Cdc25C-cyclin-dependent kinase 1/cyclin B pathway. This study aims at defining DNA damage checkpoint sensors that activate this response to CNDAC, particularly focusing on the major phosphatidylinositol 3-kinase–like protein kinase family proteins. First, fibroblasts, deficient in ataxia-telangiectasia mutated (ATM), transfected with empty vector or repleted with ATM, were arrested in G2 by CNDAC to similar extents, suggesting ATM is not required to activate the G2 checkpoint. Second, chromatin associations of RPA70 and RPA32, subunits of the ssDNA-binding protein, and the ataxia-telangiectasia and Rad3-related (ATR) substrate Rad17 and its phosphorylated form were increased on CNDAC exposure, suggesting activation of ATR kinase. The G2 checkpoint was abrogated due to depletion of ATR by small interfering RNA, and impaired in ATR-Seckel cells, indicating participation of ATR in this G2 checkpoint pathway. Third, the G2 checkpoint was more stringent in glioma cells with wild-type DNA-dependent protein kinase catalytic subunit (DNA-PKcs) than those with mutant DNA-PKcs, as shown by mitotic index counting. CNDAC-induced G2 arrest was abrogated by specific DNA-PKcs inhibitors or small interfering RNA knockdown in ML-1 and/or HeLa cells. Finally, two phosphatidylinositol 3-kinase–like protein kinase inhibitors, caffeine and wortmannin, abolished the CNDAC-induced G2 checkpoint in a spectrum of cell lines. Together, our data showed that ATR and DNA-PK cooperate in CNDAC-induced activation of the G2 checkpoint pathway. [Mol Cancer Ther 2008;7(1):133–42]
z-Guggulsterone, a constituent of Ayurvedic medicinal plant Commiphora mukul, inhibits angiogenesis in vitro and in vivo
Authors: Xiao Dong , Singh Shivendra V.
Published: January 2008

Our previous studies have shown that z-guggulsterone, a constituent of Indian Ayurvedic medicinal plant Commiphora mukul, inhibits the growth of human prostate cancer cells by causing apoptosis. We now report a novel response to z-guggulsterone involving the inhibition of angiogenesis in vitro and in vivo. The z-guggulsterone treatment inhibited capillary-like tube formation (in vitro neovascularization) by human umbilical vein endothelial cells (HUVEC) and migration by HUVEC and DU145 human prostate cancer cells in a concentration- and time-dependent manner. The z- and E-isomers of guggulsterone seemed equipotent as inhibitors of HUVEC tube formation. The z-guggulsterone–mediated inhibition of angiogenesis in vitro correlated with the suppression of secretion of proangiogenic growth factors [e.g., vascular endothelial growth factor (VEGF) and granulocyte colony–stimulating factor], down-regulation of VEGF receptor 2 (VEGF-R2) protein level, and inactivation of Akt. The z-guggulsterone–mediated suppression of DU145 cell migration was increased by knockdown of VEGF-R2 protein level. Ectopic expression of constitutively active Akt in DU145 cells conferred protection against z-guggulsterone–mediated inhibition of cell migration. Oral gavage of 1 mg z-guggulsterone/d (five times/wk) to male nude mice inhibited in vivo angiogenesis in DU145-Matrigel plug assay as evidenced by a statistically significant decrease in tumor burden, microvessel area (staining for angiogenic markers factor VIII and CD31), and VEGF-R2 protein expression. In conclusion, the present study reveals that z-guggulsterone inhibits angiogenesis by suppressing the VEGF–VEGF-R2–Akt signaling axis. Together, our results provide compelling rationale for further preclinical and clinical investigation of z-guggulsterone for its efficacy against prostate cancer. [Mol Cancer Ther 2008;7(1):171–80]
Predicting Rapid Clinical Progression in Amnestic Mild Cognitive Impairment
Authors: Ahmed Samrah , Mitchell Joanna , Arnold Robert , Nestor Peter J. , Hodges John R.
Published: January 2008

Background/Aims: We investigated whether an initial neuropsychological assessment could predict rapid progression over 12 months, from amnestic mild cognitive impairment (aMCI) to Alzheimer’s disease (AD). Methods: A longitudinal study compared the neuropsychological profiles of 27 normal controls and 18 aMCI patients at baseline and 12 months. Results: At 12 months, 24 control subjects followed up remained cognitively normal. 7 aMCI patients (6 multiple-domain aMCI and 1 single-domain aMCI) progressed to AD, and 11 were non-progressors. Prognosis was best captured by a combination of associative learning, the paired associate learning task (PAL), and global cognition, the Addenbrooke’s Cognitive Examination (ACE). Conclusion: The PAL and ACE can sensitively detect meaningful differences in scores at baseline and may be used as prognostic indicators. Multiple-domain aMCI patients progressed rapidly to AD and may be more usefully labelled as early stage AD.
Calibrated automated thrombin generation in normal uncomplicated pregnancy
Authors: Rosenkranz Andrea , Hiden Michael , Leschnik Bettina , Eva-Christine Weiss , Schlembach Dietmar , Lang Uwe , Gallistl Siegfried , Muntean Wolfgang
Published: January 2008

Pregnancy is associated with substantial changes in the haemostatic system and a six-fold higher incidence of venous thromboembolism. Conventional global tests, such as prothrombin time and activated partial thromboplastin time, do not definitely detect this hypercoagulable condition. We investigated whether the changes in haemostatic system during pregnancy are reflected in the calibrated automated thrombography (CAT). Thrombin generation was measured in platelet-poor plasma (PPP) of 150 healthy pregnant women without any pregnancy associated diseases by means of CAT. In addition, prothrombin (FII), antithrombin (AT), protein S, protein C, tissue factor pathway inhibitor (TFPI), plasminogen activator inhibitor-1 (PAI-1), thrombin-antithrombin complex (TAT), and prothrombin fragments 1+2 (F1+2) were measured. Endogenous thrombin potential (ETP) and peak of thrombin generation increased significantly with gestational weeks, while lag time and time to peak remained unchanged. A significant increase of PAI-1,TFPI,F1+2 and TAT as well as a significant decrease of free protein S, protein S antigen, and protein S activity was observed. Levels of AT and protein C remained stable during pregnancy. Division of population in trimester of pregnancy and analysis of differences between the trimesters showed rather similar results. Our study shows that endogenous thrombin potential does increase with duration of normal uncomplicated pregnancy. Whether parameters of continuous thrombin generation will correlate with thrombembolic disease remains to be shown.
Effect of raloxifene therapy on venous thromboembolism in postmenopausal women: A meta-analysis
Authors: Adomaityte Jurga , Farooq Maria , Qayyum Rehan
Published: January 2008

Raloxifene, a selective estrogen receptor modulator, is indicated for the prevention of osteoporosis in postmenopausal women. However, its effect on the risk of deep venous thrombosis (DVT) and pulmonary embolism (PE) is unclear. Therefore, we conducted a meta-analysis to evaluate the effect of raloxifene on these outcomes. To identify randomized controlled trials of raloxifene, a systematic search of PubMed, EMBASE, and Cochrane Collaboration databases was performed from the date of inception of these databases to October 2007. Search was limited to trials that were published in peer-reviewed English-language medical journals. Articles were included in the meta-analysis if they had reported on DVT, PE, or thromboembolic events. Nine trials, including 24,523 postmenopausal women, (median age 59.4 years, range 55 to 67 years; median follow-up 24 months, range 3 to 67 months) met inclusion criteria. Therapy with raloxifene was associated with a 62% increase in odds of either DVT or PE (odds ratio = 1.62; 95% confidence interval = 1.25 to 2.09; p-value < 0.001). Similarly, raloxifene therapy was associated with 54% increase in odds of DVT (odds ratio = 1.54; 95% confidence interval = 1.13 to 2.11; p-value = 0.006) and 91% increase in odds of PE alone (odds ratio = 1.91;95% confidence interval = 1.05 to 3.47; p-value = 0.03). Raloxifene increases the risk of DVT and PE in postmenopausal women.
Deconstructing Reappraisal: Descriptions Preceding Arousing Pictures Modulate the Subsequent Neural Response
Authors: Foti Dan , Hajcak Greg
Published: January 2008

The late positive potential (LPP) is a sustained positive deflection in the event-related potential that is larger following the presentation of emotional compared to neutral visual stimuli. Recent studies have indicated that the magnitude of the LPP is sensitive to emotion regulation strategies such as reappraisal, which involves generating an alternate interpretation of emotional stimuli so that they are less negative. It is unclear, however, whether reappraisal-related reductions in the LPP reflect reduced emotional processing or increased cognitive demands following reappraisal instructions. In the present study, we sought to examine whether a more or less negative description preceding the presentation of unpleasant images would similarly modulate the LPP. The LPP was recorded from 26 subjects as they viewed unpleasant and neutral International Affective Picture System images. All participants heard a brief description of the upcoming picture; prior to unpleasant images, this description was either more neutral or more negative. Following the more neutral description, the magnitude of the LPP, unpleasant ratings, and arousal ratings were all reliably reduced. These results indicate that changes in narrative are sufficient to modulate the electrocortical response to the initial viewing of emotional pictures, and are discussed in terms of recent studies on reappraisal and emotion regulation.
Response Inhibition and Response Selection: Two Sides of the Same Coin
Authors: Mostofsky Stewart H. , Simmonds Daniel J.
Published: January 2008

Response inhibition refers to the suppression of actions that are inappropriate in a given context and that interfere with goal-driven behavior. Studies using a range of methodological approaches have implicated executive control processes mediated by frontal-subcortical circuits as being critical to response inhibition; however, localization within the frontal lobe has been inconsistent. In this review, we present evidence from behavioral, lesion, neuroimaging, electrophysiology, and neurological population studies. The findings lay the foundation for a construct in which response inhibition is akin to response selection, such that pre-SMA circuits are critical to selection of appropriate behavior, including both selecting to engage appropriate motor responses and selecting to withhold (inhibit) inappropriate motor responses. Recruitment of additional prefrontal and posterior cortical circuits, necessary to guide response selection, varies depending on the cognitive and behavioral demands of the task.
The Search for the Phonological Store: From Loop to Convolution
Authors: Buchsbaum Bradley R. , D'Esposito Mark
Published: January 2008

The phonological loop system of Baddeley and colleagues' Working Memory model is a major accomplishment of the modern era of cognitive psychology. It was one of the first information processing models to make an explicit attempt to accommodate both traditional behavioral data and the results of neuropsychological case studies in an integrated theoretical framework. In the early and middle 1990s, the purview of the phonological loop was expanded to include the emerging field of functional brain imaging. The modular and componential structure of the phonological loop seemed to disclose a structure that might well be transcribed, intact, onto the convolutions of the brain. It was the phonological store component, however, with its simple and modular quality, that most appealed to the neuroimaging field as the psychological “box” that might most plausibly be located in the brain. Functional neuroimaging studies initially designated regions in the parietal cortex as constituting the “neural correlate” of the phonological store, whereas later studies pointed to regions in the posterior temporal cortex. In this review, however, we argue the phonological store as a theoretical construct does not precisely correspond to a single, functionally discrete, brain region. Rather, converging evidence from neurology, cognitive psychology, and functional neuroimaging argue for a reconceptualization of phonological short-term memory as emerging from the integrated action of the neural processes that underlie the perception and production of speech.
The Temporal Features of Self-referential Processing Evoked by Chinese Handwriting
Authors: Chen Antao , Weng Xuchu , Yuan Jiajin , Lei Xu , Qiu Jiang , Yao Dezhong , Li Hong
Published: January 2008

To explore the temporal features and underlying brain structures of self-referential processing, participants were shown examples of Chinese handwriting, half of which were their own and the other half belonged to others, and asked to judge whether the handwriting was their own. In Experiment 1, the task was to categorize the handwriting by pressing the correct key as quickly as possible. In Experiment 2, after the participants recognized the stimuli, they were required to gaze at the handwriting for 3000 msec before making a response rather than responding immediately after stimulus onset. The results showed prominent differences in event-related potentials elicited by own and other handwriting conditions in the 200–500 msec and 1000–2000 msec time windows. Dipole analyses of the difference waves, own minus other, were conducted in both of these time windows. There were two dipoles in the 200–500 msec time window localized to the medial-temporal lobe and the anterior cingulate cortex (ACC), and MTL activation preceded ACC activation. Only one dipole at the posterior cingulate cortex was fitted to the 1000–2000 msec time window. These structures were activated sequentially in a temporal course, which provides evidence that the cortex middle structures potentially form a specific self-related processing unit, which is involved in processing various aspects of the self.