bluuebunny/crossref_metadata_2025 huggingface dataset:
Mon Van Genechten (1903–1974), Flemish Missionary and Chinese Painter: Inculturation of Christian Art in China. By Lorry Swerts and Koen De Ridder. [Leuven: Leuven University Press and the Ferdinand Verbiest Foundation, 2002. 188 pp. €16.15. ISBN 90-5867-222-0.]
Authors: Lufkin Felicity
Published: February 2004

This books offers an appreciation of the life and work of Father Mon Van Genechten, a Belgian artist-priest who was a missionary in China from 1930 to 1946. It presents Father Van Genechten as an open-hearted and creative man of faith, and also makes the rather dramatic claim that Van Genechten, whose art combined Chinese styles with Christian iconography, should be seen as a Chinese artist.

The book contains two essays: one by De Ridder, on the art-historical context of Van Genechten's work; and the other by Swerts, giving fuller biographical detail. It also includes a brief memoir of Van Genechten by a former student; reproductions of his paintings, woodcuts and photographs; a list of his exhibitions; and a catalog of his known works. This catalogue is, unfortunately, less useful than it might be as it gives neither the current location of a work nor where it is reproduced.

Van Genechten is no neglected genius, but he is potentially interesting to students of Christian missionary work in China, of the modern development of Christian art, and also to students of modern Chinese art. His career – which encompassed decorating churches in Inner Mongolia, teaching at the Catholic University of Peking, and being prisoner of war in Shandong – offers a fresh perspective on East–West artistic interchange. But while the book introduces a worthwhile subject, it falls short in analysis and historical contextualization.
Autonomous Queenship in Cambodia, 1st–9th Centuries AD
Authors: Jacobsen Trudy
Published: February 2004

A brief glance at any bibliography for a history of Cambodia written in the last hundred years will reveal the immense preoccupation that historians have had with the institution of kingship. Yet nothing has been written on autonomously ruling queens, despite the acceptance by some twentieth-century historians that at least two such queens apparently ruled in pre-classical Cambodia (c. 50-802). These female sovereigns have been considered an anomaly, their reigns evidence that the political and social fabric of pre-classical society was rent asunder by the intrusion of female rulers into a male domain. Such a scenario is at variance with epigraphic evidence. One of the queens accepted by twentieth-century historians as an autonomous female ruler belongs to the eleventh century, not the seventh, as previously determined. Moreover, it appears that in most pre-classical Cambodian polities, women held the power of sovereignty, even if they did not rule independently. This not only raises questions regarding the accepted understanding of gender and power in pre-classical Cambodia, but also calls for a revision of pre-classical Cambodian history.
Cybersuizid oder Werther-Effekt online: Suizidchatrooms und -foren im Internet
Authors: Becker Katja , El-Faddagh Mahha , Schmidt Martin H.
Published: February 2004

Zusammenfassung. Die Beratung der Medien zur Verhinderung von Imitationssuiziden hat einen festen Stellenwert in der Suizidprävention. Das zunehmend an Bedeutung gewinnende Internet birgt für vulnerable Jugendliche mit Suizidgedanken sowohl zusätzliche Gefahren als auch erweiterte Möglichkeiten des Austauschs. In speziellen Chatrooms nehmen suizidgefährdete respektive suizidinteressierte Jugendliche Kontakt miteinander auf, wodurch Suizidalität ausagiert und reduziert, aber auch aufrechterhalten und potenziert werden könnte. Wissenschaftliche Untersuchungen sind dringend notwendig, um mediale Effekte des Internets objektiv zu erfassen. Implikationen für die Praxis sind unter anderem Kenntnisse von Bezugspersonen, Ärzten und Psychotherapeuten über Suizid-Chatrooms, die Forderung nach Einhaltung internetspezifischer Presserichtlinien, international geltende Gesetze sowie suffiziente Online-Informationen und Hilfeangebote für gefährdete Jugendliche.
Jugendliche in stationärer psychiatrischer Behandlung: Parasuizidale Symptome und psychische Störungen
Authors: Braun-Scharm Hellmuth , Goth Kirsten , Freisleder Franz Josef , Althoff Angelika
Published: February 2004

Zusammenfassung. Psychische Störungen zählen zu den wichtigsten Ursachen für Parasuizide und Suizide. Dies gilt für das Erwachsenenalter und mit gewissen Abstrichen auch für das Jugendalter. Die häufigsten psychischen Störungen im Zusammenhang mit Suizidalität im Jugendalter sind akute Belastungsreaktionen, affektive Störungen, Substanzmissbrauch sowie Borderline-Syndrome und andere beginnende Persönlichkeitsstörungen. Essstörungen und Schizophrenien sind dagegen im Jugendalter noch nicht mit erhöhten Parasuiziden verknüpft. Anhand einer Gesamtstichprobe von 537 konsekutiv aufgenommenen und nach ICD-10 diagnostizierten stationär behandelten jugendpsychiatrischen Patienten konnten 163 mit parasuizidalen Symptomen bei Aufnahme ermittelt werden, die etwa zur Hälfte aus parasuizidalen Gedanken und parasuizidalen Handlungen bestanden. Der Anteil parasuizidaler Jugendlicher auf der Aufnahmestation lag bei etwa 66 %, auf der Therapiestation (Rottmannshöhe) bei etwa 30 %. Dies spricht für die Relevanz von Selektionsfaktoren bei Häufigkeits- und vermutlich auch Schweregradangaben von Suizidalität im stationären jugendpsychiatrischen Bereich.
Prävention parasuizidalen Verhaltens in der Adoleszenz: Möglichkeiten und Grenzen
Authors: van Engeland Herman
Published: February 2004

Zusammenfassung. In der vorliegenden Arbeit wird ein Literaturüberblick über Charakteristiken von jugendlichen Parasuizidenten gegeben und Möglichkeiten von Präventionen für Parasuizide werden aufgezeigt. Eine Metaanalyse randomisierter Studien, die die Effektivität von psychosozialer Therapie auf die Wiederholungsrate von Parasuiziden prüfte, ergab, dass zwei von zwölf Studien einen kleinen positiven Effekt zeigten. Basierend auf diesen beiden Studien wurde eine randomisierte klinische Studie mit dem Schwerpunkt auf intensiver psychosozialer Intervention gestartet. Die psychologische Intervention wurde mit der üblichen Standardbehandlung verglichen und alle Patienten (n = 274) wurden über ein Jahr lang nach dem Index-Parasuizid nachuntersucht. Kaplan-Meyers Survival Analysen zeigten keinen signifikanten Unterschied zwischen den beiden Behandlungsansätzen. Möglichkeiten für zukünftige Studien werden diskutiert.
Episodic enhancement of phytoplankton stocks in New Zealand subantarctic waters: Contribution of atmospheric and oceanic iron supply
Authors: Boyd P. W. , McTainsh G. , Sherlock V. , Richardson K. , Nichol S. , Ellwood M. , Frew R.
Published: February 2004

Around 30% of oceanic waters are high nitrate low chlorophyll (HNLC) where low iron levels limit algal growth. HNLC waters have mainly been studied using shipboard and lab experiments. Since 1997, remote‐sensing of phytoplankton via SeaWiFS Ocean Color has permitted monitoring of the constancy of this “HNLC condition,” i.e., spatial homogeneity and low temporal variability of chlorophyll over annual cycles. These trends can be exploited, as episodic iron inputs should be conspicuous by subsequent expression as iron‐elevated algal stocks. Subantarctic (SA) waters near New Zealand are HNLC, and the proximity of the arid Australian landmass, and the iron‐rich Subtropical Front, provide natural laboratories to detect episodic atmospheric and oceanic iron supply, respectively. Two approaches were used: Oceanic supply was inferred from episodic increases in chlorophyll concentrations in SA waters, detected using Ocean Color archives. Additional archives were used to confirm the oceanic provenance of iron supply, and identify supply mechanism(s). Atmospheric supply was assessed using data on source areas and loads for dust storms monitored in central Australia. Dust transport and its fate was assessed using air mass forward trajectories and SeaWiFS Ocean Color and Aerosol Optical Depth maps. During 1997–2001, episodic elevated chlorophyll events occurred in SA waters southeast of New Zealand. There was no evidence of these events being mediated by atmospheric iron supply; however, neither wind‐driven lateral advection or vertical mixing alone could account for these episodes. Dust storms, over this period sent plumes either into high iron SubTropical (ST) waters or into SA waters in early spring, when cells are probably light‐ rather than iron‐limited.
A comparison of techniques for mapping total electron content over Europe using GPS signals
Authors: Meggs Robert W. , Mitchell Cathryn N. , Spencer Paul S. J.
Published: February 2004

Two different analysis techniques for mapping ionospheric total electron content (TEC) are compared. The first technique approximates the ionospheric electron concentration as a thin shell at a fixed altitude. In this case, slant TEC observations are converted into vertical TEC values using a mapping function and interpolated across a grid. Other slant TEC values are then calculated from the vertical TEC grid using another mapping function. The second technique applies an advanced tomographic algorithm to invert the slant TEC observations into a time‐evolving three‐dimensional grid of electron concentration. Either slant or vertical TEC can then be extracted from the electron concentration images without the need for a mapping function. Results based on both simulated and experimental data are presented. The results indicate that the inversion offers improvements over a thin shell in the mapping of TEC at middle latitudes.
Miocene extension and extensional folding in an anticlinal segment of the Black Mountains accommodation zone, Colorado River extensional corridor, southwestern United States
Authors: Varga Robert J. , Faulds James E. , Snee Lawrence W. , Harlan Stephen S. , Bettison‐Varga Lori
Published: February 2004

Recent studies demonstrate that rifts are characterized by linked tilt domains, each containing a consistent polarity of normal faults and stratal tilt directions, and that the transition between domains is typically through formation of accommodation zones and generally not through production of throughgoing transfer faults. The mid‐Miocene Black Mountains accommodation zone of southern Nevada and western Arizona is a well‐exposed example of an accommodation zone linking two regionally extensive and opposing tilt domains. In the southeastern part of this zone near Kingman, Arizona, east dipping normal faults of the Whipple tilt domain and west dipping normal faults of the Lake Mead domain coalesce across a relatively narrow region characterized by a series of linked, extensional folds. The geometry of these folds in this strike‐parallel portion of the accommodation zone is dictated by the geometry of the interdigitating normal faults of opposed polarity. Synclines formed where normal faults of opposite polarity face away from each other whereas anticlines formed where the opposed normal faults face each other. Opposed normal faults with small overlaps produced short folds with axial trends at significant angles to regional strike directions, whereas large fault overlaps produce elongate folds parallel to faults. Analysis of faults shows that the folds are purely extensional and result from east/northeast stretching and fault‐related tilting. The structural geometry of this portion of the accommodation zone mirrors that of the Black Mountains accommodation zone more regionally, with both transverse and strike‐parallel antithetic segments. Normal faults of both tilt domains lose displacement and terminate within the accommodation zone northwest of Kingman, Arizona. However, isotopic dating of growth sequences and crosscutting relationships show that the initiation of the two fault systems in this area was not entirely synchronous and that west dipping faults of the Lake Mead domain began to form between 1 m.y. to 0.2 m.y. prior to east dipping faults of the Whipple domain. The accommodation zone formed above an active and evolving magmatic center that, prior to rifting, produced intermediate‐composition volcanic rocks and that, during rifting, produced voluminous rhyolite and basalt magmas.
Dynamic modeling of geomagnetic cutoff for the 23–24 November 2001 solar energetic particle event
Authors: Kress B. T. , Hudson M. K. , Perry K. L. , Slocum P. L.
Published: February 2004

We investigate numerically the time variations of geomagnetic cutoffs of solar energetic particles. As a test case, the geomagnetic cutoff of 25 MeV protons is modeled for the 23–24 November 2001 solar energetic particle (SEP) event. Following Smart and Shea [2001], solar energetic particle access is determined by computing the reverse particle trajectories. Magnetospheric fields are obtained from the Lyon‐Feder‐Mobarry (LFM) global MHD model, which is driven by measured solar wind parameters at the sunward boundary. We find well‐defined surfaces of constant cutoff that exhibit dynamic behavior in response to solar wind conditions. We show that dynamic modeling of cutoff surfaces may be used as a tool to investigate SEP access to the inner magnetosphere. The numerical results are compared with proton observations from a highly elliptical orbit (HEO) satellite. The results suggest that an enhancement in the solar wind dynamic pressure plays a role in the observed ion injection.
The depth of magma fractionation in the oceanic mantle: Insights from garnet‐ bearing xenoliths from Oahu, Hawaii
Authors: Keshav Shantanu , Sen Gautam
Published: February 2004

A suite of garnet‐bearing xenoliths that is dominantly composed of olivine, clinopyroxene, and garnet, from Oahu, Hawaii is discussed. All the minerals are in Mg# equilibrium with each other. High Fe/Mg of constituent minerals, high TiO2, Al2O3, Na2O of cpx, and low Cr‐garnet preclude these xenoliths from being residues of partial melting. Combined petrography, mineral chemistry, and high‐pressure liquidus phase equilibria indicate that these xenoliths are high pressure cumulates and originated as products of magma fractionation at a depth of >100 km, corresponding to the uppermost part of the asthenosphere. These depth constraints are about 15 km more than the seismically detected lithosphere‐asthenosphere boundary. It is proposed here that the top of the asthenosphere beneath Oahu, Hawaii is a network of magma chambers where considerable amount of magma ponding and subsequent fractionation takes place.
Trends in time‐varying percentiles of daily minimum and maximum temperature over North America
Authors: Robeson Scott M.
Published: February 2004

With the recent development of high‐quality, digital daily air‐temperature archives over North America, flexible approaches that evaluate trends in time‐varying percentiles are capable of estimating climate‐change parameters from all portions of air‐temperature frequency distributions. Using these methods, intense warming is found in the lowest minimum temperatures over western and central North America. During the months of January through March, the lower tail of the daily minimum air‐temperature distribution over western North America has warmed at rates exceeding 3°C/50yr. Daily maximum air temperatures also are increasing over western Canada and Alaska at this time, but all parts of the frequency distribution are warming equally. Other times of year in western North America, as well as much of eastern North America, show little change in either minimum or maximum air temperature during the last half‐century.
Tharsis as a consequence of Mars' dichotomy and layered mantle
Authors: Wenzel Mark J. , Manga Michael , Jellinek A. Mark
Published: February 2004

The two most striking features of the martian surface topography are the Tharsis rise and the crustal dichotomy. Closely associated with Tharsis are several large volcanoes, active in the geologically recent past, indicating a longevity of volcanic activity at Tharsis that is unique in the solar system. Using analogue laboratory experiments we examine the dynamical effects of the crustal dichotomy and a layered mantle on the thermal evolution of Mars. We show that in combination these two effects lead to the formation of a large‐scale upwelling under the southern highlands that appears early and endures for many billions of years. The upwelling comprises several persistent narrow plumes, which can explain the long‐lived Tharsis volcanoes.
Numerical simulation of the 12 May 1997 interplanetary CME event
Authors: Odstrcil D. , Riley P. , Zhao X. P.
Published: February 2004

Numerical three‐dimensional magnetohydrodynamic models are capable of predicting large‐scale solar wind structures at Earth, provided that appropriate time‐dependent boundary conditions are specified near the Sun. Since knowledge of such conditions is at present insufficient to directly drive the models, various approximations are used. In this paper, we introduce the main features and approximations of a numerical model where (1) the ambient solar wind is derived from coronal models utilizing photospheric magnetic field observations and (2) transient disturbances are derived from geometrical and kinematic fitting of coronagraph observations of coronal mass ejections (CMEs). We have chosen the well‐defined halo‐CME event of 12 May 1997 as our initial event because it is characterized by a relatively quiet solar and interplanetary background into which the ejecta was launched. The numerical simulation has enabled us to predict the arrival of the shock and ejecta and provided us with a global picture of transient disturbance interacting with a moderately fast solar wind stream.
Olivine‐wadsleyite transition in the system (Mg,Fe)2SiO4
Authors: Katsura Tomoo , Yamada Hitoshi , Nishikawa Osamu , Song Maoshuang , Kubo Atsushi , Shinmei Toru , Yokoshi Sho , Aizawa Yoshitaka , Yoshino Takashi , Walter Michael J. , Ito Eiji , Funakoshi Ken‐ichi
Published: February 2004

Phase relations of the olivine‐wadsleyite transition in the system (Mg,Fe)2SiO4 have been determined at 1600 and 1900 K using the quench method in a Kawai‐type high‐pressure apparatus. Pressure was determined at a precision better than 0.2 GPa using in situ X‐ray diffraction with MgO as a pressure standard. The transition pressures of the end‐member Mg2SiO4 are estimated to be 14.2 and 15.4 GPa at 1600 and 1900 K, respectively. Partition coefficients for Fe and Mg between olivine and wadsleyite are 0.51 at 1600 K and 0.61 at 1900 K. By comparing the depth of the discontinuity with the transition pressure, the temperature at 410 km depth is estimated to be 1760 ± 45 K for a pyrolitic upper mantle. The mantle potential temperature is estimated to be in the range 1550–1650 K. The temperature at the bottom of the upper mantle is estimated to be 1880 ± 50 K. The thickness of the olivine‐wadsleyite transition in a pyrolitic mantle is determined to be between 7 and 13 km for a pyrolitic mantle, depending on the efficiency of vertical heat transfer. Regions of rapid vertical flow (e.g., convection limbs), in which thermal diffusion is negligible, should have a larger transition interval than stagnant regions, where thermal diffusion is effective. This is in apparent contradiction to short‐period seismic wave observations that indicate a maximum thickness of <5 km. An upper mantle in the region of the 410 km discontinuity with about 40% olivine and an Mg# of at least 89 can possibly explain both the transition thickness and velocity perturbation at the 410 km discontinuity.
Measurement and simulation of snow and superimposed ice at the Kongsvegen glacier, Svalbard (Spitzbergen)
Authors: Obleitner Friedrich , Lehning Michael
Published: February 2004

Multiyear glaciometeorological data have been collected at about the equilibrium line of Kongsvegen glacier in Svalbard. During the first summer of the investigation period, about 0.6 m of superimposed ice (SI) was built up because of effective meltwater refreeze upon the former glacier surface. Thus winter accumulation is completely retained from runoff, and latent heat is released equivalent to 27% of July net radiation. This ice layer, as well as part of the former year's ice, disappeared during the subsequent summer. Using a physically based snow model, the evolution of the snow pack properties as well as the observed amount of SI is successfully reproduced. However, the latter is only possible by modifying the model's water transport routine to also treat effects of ponding water, which have been observed. Two distinct phases of SI formation can be distinguished. A first one (15 cm) is initiated as soon as meltwater has penetrated to the underlying cold glacier ice. Toward the end of the melt period, however, the remaining body of SI is rapidly formed because of intense atmospheric cooling. The availability of ponding water plays an essential role in this context. During the following summer the initial refreezing phase was terminated by exposure of the newly built SI at the surface. The whole amount of the actual year and the major part of the former year's SI was melted then. A positive ice‐albedo feedback process plays an additional role there. Sensitivity studies prove that the model results and their interpretation do not critically depend on possible uncertainties of input data and model parameters. Despite their local nature these studies are valuable steps toward understanding the regional distribution of SI on Arctic glaciers as well as their climate sensitivity. Remote sensing studies indicate that SI presently covers 35% of Kongsvegen's surface area.
Influence of a mutation in the ATP-binding region of Ca2+/calmodulin-dependent protein kinase II on its interaction with peptide substrates
Authors: PRASEEDA Mullasseril , PRADEEP Kurup K. , KRUPA Ananth , KRISHNA S. Sri , LEENA Suseela , KUMAR R. Rajeev , CHERIYAN John , MAYADEVI Madhavan , SRINIVASAN Narayanaswamy , OMKUMAR Ramakrishnapillai V.
Published: February 2004

CaMKII (Ca2+/calmodulin-dependent protein kinase II) is expressed in high concentrations in the brain and is found enriched in the postsynaptic densities. The enzyme is activated by the binding of calmodulin to the autoregulatory domain in the presence of high levels of intracellular Ca2+, which causes removal of auto-inhibition from the N-terminal catalytic domain. Knowledge of the 3D (three-dimensional) structure of this enzyme at atomic resolution is restricted to the association domain, a region at the extreme C-terminus. The catalytic domain of CaMKII shares high sequence similarity with CaMKI. The 3D structure of the catalytic core of CaMKI comprises ATP- and substrate-binding regions in a cleft between two distinct lobes, similar to the structures of all protein kinases solved to date. Mutation of Glu-60, a residue in the ATP-binding region of CaMKII, to glycine exerts different effects on phosphorylation of two peptide substrates, syntide and NR2B (N-methyl-d-aspartate receptor subunit 2B) 17-mer. Although the mutation caused increases in the Km values for phosphorylation for both the peptide substrates, the effect on the kcat values for each was different. The kcat value decreased in the case of syntide, whereas it increased in the case of the NR2B peptide as a result of the mutation. This resulted in a significant decrease in the apparent kcat/Km value for syntide, but the change was minimal for the NR2B peptide. These results indicate that different catalytic mechanisms are employed by the kinase for the two peptides. Molecular modelling suggests structural changes are likely to occur at the peptide-binding pocket in the active state of the enzyme as a consequence of the Glu-60→Gly mutation.
Calcium mobilization and Rac1 activation are required for VCAM-1 (vascular cell adhesion molecule-1) stimulation of NADPH oxidase activity
Authors: COOK-MILLS Joan M. , JOHNSON Jacob D. , DEEM Tracy L. , OCHI Atsuo , WANG Lei , ZHENG Yi
Published: February 2004

VCAM-1 (vascular cell adhesion molecule-1) plays an important role in the regulation of inflammation in atherosclerosis, asthma, inflammatory bowel disease and transplantation. VCAM-1 activates endothelial cell NADPH oxidase, and this oxidase activity is required for VCAM-1-dependent lymphocyte migration. We reported previously that a mouse microvascular endothelial cell line promotes lymphocyte migration that is dependent on VCAM-1, but not on other known adhesion molecules. Here we have investigated the signalling mechanisms underlying VCAM-1 function. Lymphocyte binding to VCAM-1 on the endothelial cell surface activated an endothelial cell calcium flux that could be inhibited with anti-α4-integrin and mimicked by anti-VCAM-1-coated beads. VCAM-1 stimulation of calcium responses could be blocked by an inhibitor of intracellular calcium mobilization, a calcium channel inhibitor or a calcium chelator, resulting in the inhibition of NADPH oxidase activity. Addition of ionomycin overcame the calcium channel blocker suppression of VCAM-1-stimulated NADPH oxidase activity, but could not reverse the inhibitory effect imposed by intracellular calcium blockage, indicating that both intracellular and extracellular calcium mobilization are required for VCAM-1-mediated activation of NADPH oxidase. Furthermore, VCAM-1 specifically activated the Rho-family GTPase Rac1, and VCAM-1 activation of NADPH oxidase was blocked by a dominant negative Rac1. Thus VCAM-1 stimulates the mobilization of intracellular and extracellular calcium and Rac1 activity that are required for the activation of NADPH oxidase.
An activating mutant of Rac1 that fails to interact with Rho GDP-dissociation inhibitor stimulates membrane ruffling in mammalian cells
Authors: GANDHI Payal N. , GIBSON Richard M. , TONG Xiaofeng , MIYOSHI Jun , TAKAI Yoshimi , KONIECZKOWSKI Martha , SEDOR John R. , WILSON-DELFOSSE Amy L.
Published: February 2004

Rac1, a member of the Rho family of small GTP-binding proteins, is involved in the regulation of the actin cytoskeleton via activation of lamellipodia and membrane ruffle formation. RhoGDI (Rho-family-specific GDP-dissociation inhibitor) forms a complex with Rho proteins in the cytosol of mammalian cells. It not only regulates guanine nucleotide binding to Rho proteins, but may also function as a molecular shuttle to carry Rho proteins from an inactive cytosolic pool to the membrane for activation. These studies tested if RhoGDI is necessary for the translocation of Rac1 from the cytosol to the plasma membrane for the formation of membrane ruffles. We describe a novel mutant of Rac1, R66E (Arg66→Glu), that fails to bind RhoGDI. This RhoGDI-binding-defective mutation is combined with a Rac1-activating mutation G12V, resulting in a double-mutant [Rac1(G12V/R66E)] that fails to interact with RhoGDI in COS-7 cells, but remains constitutively activated. This double mutant stimulates membrane ruffling to a similar extent as that observed after epidermal growth factor treatment of non-transfected cells. To confirm that Rac1 can signal ruffle formation in the absence of interaction with RhoGDI, Rac1(G12V) was overexpressed in cultured mesangial cells derived from a RhoGDI knockout mouse. Rac1-mediated membrane ruffling was indistinguishable between the RhoGDI(−/−) and RhoGDI(+/+) cell lines. In both the COS-7 and cultured mesangial cells, Rac1(G12V) and Rac1(G12V/R66E) co-localize with membrane ruffles. These findings suggest that interaction with RhoGDI is not essential in the mechanism by which Rac1 translocates to the plasma membrane to stimulate ruffle formation.
Stimulated initiation of mitogen-activated protein kinase phosphatase-1 (MKP-1) gene transcription involves the synergistic action of multiple cis-acting elements in the proximal promoter
Authors: RYSER Stephan , MASSIHA Abbas , PIUZ Isabelle , SCHLEGEL Werner
Published: February 2004

Mitogen-activated protein kinases (MAPKs) are inactivated by a dual specificity phosphatase, MAPK phosphatase-1 (MKP-1). MKP-1 is transcribed as an immediate early response gene (IEG) following various stimuli. In the pituitary cell line GH4C1, MKP-1 gene transcription is strongly induced by thyrotropin-releasing hormone (TRH) as well as by epidermal growth factor (EGF) as a consequence of activated MAPK/extracellular-signal-regulated kinase (ERK) signalling. Intriguingly, reporter gene analysis with the MKP-1 promoter showed strong basal transcription, but only limited induction by TRH and EGF. Site-directed mutagenesis of the reporter construct combined with band-shift and in vivo studies revealed that part of the constitutive activity of the MKP-1 promoter resides in two GC boxes bound by Sp1 and Sp3 transcription factors in the minimal promoter. Basal transcription of transiently transfected luciferase reporter can be initiated by either of the two GC boxes or also by either of the two cAMP/Ca2+ responsive elements or by the E-box present in the proximal promoter. On the other hand, when analysed by stable transfection, the five responsive elements are acting in synergy to transactivate the MKP-1 proximal promoter. We show in this study that the MKP-1 promoter can function as a constitutive promoter or as a rapid and transient sensor for the activation state of MAPKs/ERKs. This dual mode of transcription initiation may have different consequences for the control of a block to elongation situated in the first exon of the MKP-1 gene, as described previously [Ryser, Tortola, van Haasteren, Muda, Li and Schlegel (2001) J. Biol. Chem. 276, 33319–33327].
Cellular mechanisms of redox cell signalling: role of cysteine modification in controlling antioxidant defences in response to electrophilic lipid oxidation products
Authors: LEVONEN Anna-Liisa , LANDAR Aimee , RAMACHANDRAN Anup , CEASER Erin K. , DICKINSON Dale A. , ZANONI Giuseppe , MORROW Jason D. , DARLEY-USMAR Victor M.
Published: February 2004

The molecular mechanisms through which oxidized lipids and their electrophilic decomposition products mediate redox cell signalling is not well understood and may involve direct modification of signal-transduction proteins or the secondary production of reactive oxygen or nitrogen species in the cell. Critical in the adaptation of cells to oxidative stress, including exposure to subtoxic concentrations of oxidized lipids, is the transcriptional regulation of antioxidant enzymes, many of which are controlled by antioxidant-responsive elements (AREs), also known as electrophile-responsive elements. The central regulator of the ARE response is the transcription factor Nrf2 (NF-E2-related factor 2), which on stimulation dissociates from its cytoplasmic inhibitor Keap1, translocates to the nucleus and transactivates ARE-dependent genes. We hypothesized that electrophilic lipids are capable of activating ARE through thiol modification of Keap1 and we have tested this concept in an intact cell system using induction of glutathione synthesis by the cyclopentenone prostaglandin, 15-deoxy-Δ12,14-prostaglandin J2. On exposure to 15-deoxy-Δ12,14-prostaglandin J2, the dissociation of Nrf2 from Keap1 occurred and this was dependent on the modification of thiols in Keap1. This mechanism appears to encompass other electrophilic lipids, since 15-A2t-isoprostane and the lipid aldehyde 4-hydroxynonenal were also shown to modify Keap1 and activate ARE. We propose that activation of ARE through this mechanism will have a major impact on inflammatory situations such as atherosclerosis, in which both enzymic as well as non-enzymic formation of electrophilic lipid oxidation products are increased.
Methyl-beta-cyclodextrin stimulates glucose uptake in Clone 9 cells: a possible role for lipid rafts
Authors: BARNES Kay , INGRAM Jean C. , BENNETT Matthew D. M. , STEWART Gordon W. , BALDWIN Stephen A.
Published: February 2004

An acute increase in the Vmax for glucose uptake occurs in many mammalian cell types after exposure to osmotic or metabolic stress. In the rat epithelial Clone 9 cell line, the glucose transporter isoform GLUT1 is responsible for this enhanced uptake. Although stimulation of transport in these cells is known to result from the unmasking of ‘cryptic’ exofacial permeant-binding sites in GLUT1 molecules resident in the plasma membrane, the mechanism of such unmasking remains unclear. One possibility involves changes in the lipid environment of the transporter: reconstitution experiments have shown that transport activity in vitro is acutely sensitive to the phospholipid and cholesterol composition of the membrane. In the current study we found that treatment of Clone 9 cells with methyl-β-cyclodextrin, which removed >80% of the cell cholesterol, led to a 3.5-fold increase in the Vmax for 3-O-methyl-d-glucose transport while having little effect on the Km. In contrast to the metabolic stress induced by inhibition of oxidative phosphorylation, cholesterol depletion led neither to depletion of cellular ATP nor stimulation of AMP-activated protein kinase. Similarly, it did not result in stimulation of members of the stress- and mitogen-activated protein kinase families. In unstressed, cholesterol-replete cells, a substantial proportion of GLUT1 in detergent lysates co-fractionated with the lipid-raft proteins caveolin and stomatin on density-gradient centrifugation. Immunocytochemistry also revealed the presence of GLUT1-enriched domains, some of which co-localized with stomatin, in the plasma membrane. Both techniques revealed that the abundance of such putative GLUT1-containing domains was decreased not only by cholesterol depletion but also in cells subjected to metabolic stress. Taken together, these data suggest that a change in the lipid environment of GLUT1, possibly associated with its re-distribution between different microdomains of the plasma membrane, could play a role in its activation in response to stress.
Distinct roles of PTCH2 splice variants in Hedgehog signalling
Authors: RAHNAMA Fahimeh , TOFTGÅRD Rune , ZAPHIROPOULOS Peter G.
Published: February 2004

The human PTCH2 gene is highly similar to PTCH1, a tumour suppressor gene frequently mutated in basal cell carcinoma and several other tumour types. PTCH1 is a transmembrane protein believed to inhibit another transmembrane protein SMO (Smoothened), which mediates HH (Hedgehog) signalling. In this study, we analysed the biological properties of several PTCH2 splice variants. An mRNA form that lacked the last exon was abundantly expressed in all tissues examined, in contrast with the one that included it. Moreover, a transcript lacking exon 9, which is a part of a conserved sterol-sensing domain, was identified in intestine, prostate and cerebellum. In ovary, spleen, testis, cerebellum and skin, an mRNA lacking both exons 9 and 10 could also be observed. The different PTCH2 isoforms localized in the cytoplasm were capable of internalizing the N-terminal fragment of Sonic HH (Shh-N). Additionally, the PTCH2 gene was found to be a target of HH signalling. PTCH2 promoter regulation assays demonstrated that only one of the PTCH2 variants could inhibit the activity of SHH-N, whereas none was capable of inhibiting the activated form of SMO (SMO-M2) and this contrasts with PTCH1. Despite the fact that the PTCH2 isoforms lacked the ability to inhibit SMO-M2 activity, all PTCH2 variants as well as PTCH1, on co-transfection with Smo, were able to change Smo localization from being largely dispersed in the cytoplasm to the juxtanuclear region. Furthermore, the PTCH2 isoforms and PTCH1 co-localized in doubly transfected cells and an interaction between them was confirmed using immunoprecipitation assays. Using Ptch1−/− mouse cells, it was shown that the PTCH2 variants and PTCH1 differentially act to reconstitute not only the SHH but also the Desert HH-dependent transcriptional response. We conclude that in spite of their structural similarities, the PTCH2 isoforms have distinct functional properties when compared with PTCH1.
Alternative quinone substrates and inhibitors of human electron-transfer flavoprotein-ubiquinone oxidoreductase
Authors: ŠIMKOVIČ Martin , FRERMAN Frank E.
Published: February 2004

Electron-transfer flavoprotein (ETF)-ubiquinone (2,3-dimethoxy-5-methyl-1,4-benzoquinone) oxidoreductase (ETF-QO) is a membrane-bound iron–sulphur flavoprotein that participates in an electron-transport pathway between eleven mitochondrial flavoprotein dehydrogenases and the ubiquinone pool. ETF is the intermediate electron carrier between the dehydrogenases and ETF-QO. The steady-state kinetic constants of human ETF-QO were determined with ubiquinone homologues and analogues that contained saturated n-alkyl substituents at the 6 position. These experiments show that optimal substrates contain a ten-carbon-atom side chain, consistent with a preliminary crystal structure that shows that only the first two of ten isoprene units of co-enzyme Q10 (CoQ10) interact with the protein. Derivatives with saturated alkyl side chains are very good substrates, indicating that, unlike other ubiquinone oxidoreductases, there is little preference for the methyl branches or rigidity of the CoQ side chain. Few of the compounds that inhibit ubiquinone oxidoreductases inhibit ETF-QO. Compounds found to act as inhibitors of ETF-QO include 2-n-heptyl-4-hydroxyquinoline N-oxide, a naphthoquinone analogue, 2-(3-methylpentyl)-4,6-dinitrophenol and pentachlorophenol. 2,5-Dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), which inhibits the mitochondrial bc1 complex and the chloroplast b6f complex in redox-dependent fashion, can serve as an electron acceptor for human ETF-QO. The observation of simple Michaelis–Menten kinetic patterns and a single type of quinone-binding site, determined by fluorescence titrations of the protein with DBMIB and 6-(10-bromodecyl)ubiquinone, are consistent with one ubiquinone-binding site per ETF-QO monomer.
Isomerization of the uncomplexed actinidin molecule: kinetic accessibility of additional steps in enzyme catalysis provided by solvent perturbation
Authors: REID James D. , HUSSAIN Syeed , BAILEY Tamara S. F. , SONKARIA Sanjiv , SREEDHARAN Suneal K. , THOMAS Emrys W. , RESMINI Marina , BROCKLEHURST Keith
Published: February 2004

The effects of increasing the content of the aprotic dipolar organic co-solvent acetonitrile on the observed first-order rate constant (kobs) of the pre-steady state acylation phases of the hydrolysis of N-acetyl-Phe-Gly methyl thionester catalysed by the cysteine proteinase variants actinidin and papain in sodium acetate buffer, pH 5.3, were investigated by stopped-flow spectral analysis. With low acetonitrile content, plots of kobs against [S]0 for the actinidin reaction are linear with an ordinate intercept of magnitude consistent with a five-step mechanism involving a post-acylation conformational change. Increasing the acetonitrile content results in marked deviations of the plots from linearity with a rate minimum around [S]0=150 µM. The unusual negative dependence of kobs on [S]0 in the range 25–150 µM is characteristic of a rate-determining isomerization of the free enzyme before substrate binding, additional to the five-step mechanism. There was no evidence for this phenomenon nor for the post-acylation conformational change in the analogous reaction with papain. For this enzyme, however, acetonitrile acts as an inhibitor with approximately uncompetitive characteristics. Possible mechanistic consequences of the differential solvent-perturbed kinetics are indicated. The free enzyme isomerization of actinidin may provide an explanation for the marked difference in sensitivity between this enzyme and papain of binding site–catalytic site signalling in reactions of substrate-derived 2-pyridyl disulphide reactivity probes.
A novel Gal(beta1-4)Gal(beta1-4)Fuc(alpha1-6)-core modification attached to the proximal N-acetylglucosamine of keyhole limpet haemocyanin (KLH) N-glycans
Authors: WUHRER Manfred , ROBIJN Marjolein L. M. , KOELEMAN Carolien A. M. , BALOG Crina I. A. , GEYER Rudolf , DEELDER André M. , HOKKE Cornelis H.
Published: February 2004

KLH (keyhole limpet haemocyanin), the oxygen-carrying molecule of the marine snail Megathura crenulata, is often used as an adjuvant or as a hapten carrier for immunizations with peptides, oligosaccharides or other low-molecular-mass organic compounds. KLH exhibits several carbohydrate determinants, at least some of which are immunogenic: it shares an antigenic Fuc(α1-3)GalNAc-determinant with schistosomes and contains unique Gal-(β1-6)Man-structural motifs on its N-glycans. This study reveals the presence of N-glycans with unusual ±Gal(β1-4)Gal(β1-4)Fuc- units (α1-6)-linked to the reducing end N-acetylglucosamine residue. The following novel structures of KLH N-glycans were deduced by linkage analysis, exoglycosidase digestion, matrix-assisted laser-desorption ionization-tandem MS and nano-LC-ESI-IT-MS (where LC stands for liquid chromatography, ESI for electrospray ionization and IT for ion trap): Man(α1-6)[±Man(α1-3)]Man(β1-4)GlcNAc(β1-4)[Gal(β1-4)Fuc(α1-6)]GlcNAc and Man(α1-6)Man(β1-4)GlcNAc(β1-4)[Gal(β1-4)Gal(β1-4)Fuc(α1-6)]GlcNAc. The Gal(β1-4)Fuc- and Gal(β1-4)Gal(β1-4)Fuc- core modifications are expected to be immunogenic, similar to other non-mammalian-type core modifications, and to contribute to the immunostimulatory properties of KLH.
Activated Src increases adhesion, survival and alpha2-integrin expression in human breast cancer cells
Authors: PARK Hee Boong , GOLUBOVSKAYA Vita , XU Lihui , YANG Xihui , LEE Jin Woo , SCULLY Sean , CRAVEN Rolf Joseph , CANCE William G.
Published: February 2004

Focal adhesion kinase (FAK) is an intracellular kinase that localizes to focal adhesions. FAK is overexpressed in human tumours, and FAK regulates both cellular adhesion and anti-apoptotic survival signalling. Disruption of FAK function by overexpression of the FAK C-terminal domain [FAK-CD, analogous to the FRNK (FAK-related non-kinase) protein] leads to loss of adhesion and apoptosis in tumour cells. We have shown that overexpression of an activated form of the Src tyrosine kinase suppressed the loss of adhesion induced by dominant-negative; adenoviral FAK-CD and decreased the apoptotic response in BT474 and MCF-7 breast cancer cell lines. This adhesion-dependent apoptosis was increased by the Src-family kinase inhibitor PP2 {4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine}. We have also shown that expression of activated Src in breast cancer cells increased the expression of α2-integrin and that overexpression of α2-integrin suppressed FAK-CD-mediated loss of adhesion. Our results suggest a model in which Src regulates adhesion and survival through enhanced expression of the α2-integrin. This provides a mechanism through which Src promotes cellular adhesion and alters the adhesive function of FAK.
Overexpression of phospholipase D prevents actinomycin D-induced apoptosis through potentiation of phosphoinositide 3-kinase signalling pathways in Chinese-hamster ovary cells
Authors: YAMADA Momoko , BANNO Yoshiko , TAKUWA Yoh , KODA Masahiro , HARA Akira , NOZAWA Yoshinori
Published: February 2004

To examine the roles of PLD (phospholipase D) in the regulation of the apoptotic process, PLD1 and PLD2 were stably overexpressed in S1P3-CHO cells [CHO (Chinese-hamster ovary) cells expressing the S1P (sphingosine 1-phosphate) receptor S1P3]. Treatment of S1P3-CHO cells with ActD (actinomycin D) induced apoptosis, as shown by the occurrence of nuclear fragmentation and the caspase-dependent proteolytic cleavage of PARP [poly(ADP-ribose) polymerase] and protein kinase Cδ. Overexpression of either PLD1 or PLD2 protected S1P3-CHO cells from ActD-induced apoptosis, as demonstrated by an increased number of viable cells and inhibition of PARP and protein kinase Cδ cleavage. However, in the early phase of apoptosis, ActD induced an increase in PLD activity and activation of key factors in the cell-survival signalling pathways, such as PI3K (phosphoinositide 3-kinase), Akt, p70S6K (p70 S6 kinase) and ERK (extracellular-signal-regulated kinase). Furthermore, the ActD-induced activation of these survival signalling enzymes was potentiated by overexpression of either PLD1 or PLD2. The PI3K inhibitor LY294002 inhibited the ActD-induced activation of Akt and p70S6K, and completely abolished the effects of PLD1 or PLD2, whereas inhibition of ERK activity by the MEK inhibitor U0126 had a milder effect. The ActD-induced activation of p70S6K and ERKs was blocked by 1-butanol, but not by t-butanol; similar to S1P, exogenous PLD suppressed the ActD-induced events in the apoptosis signalling pathways. These results show that, in S1P3-CHO cells, increased expression of PLDs prevents ActD-induced apoptosis by enhanced activation of the PI3K signalling pathways.
Bicarbonate enhances alpha-synuclein oligomerization and nitration: intermediacy of carbonate radical anion and nitrogen dioxide radical
Authors: ANDREKOPOULOS Christopher , ZHANG Hao , JOSEPH Joy , KALIVENDI Shasi , KALYANARAMAN B.
Published: February 2004

α-Synuclein, a neuronal presynaptic protein, has been reported to undergo oligomerization to form toxic Lewy bodies in neurodegenerative disorders. One of the proposed mechanisms for aggregation of α-synuclein involves oxidative and nitrative modifications. In the present study, we show that addition of 3-morpholino-sydnonimine chloride (SIN-1) or slow infusion of pre-formed peroxynitrite (ONOO−) to mixtures containing α-synuclein and HCO3− markedly enhanced both nitration and aggregation of α-synuclein through dityrosine formation. Bicarbonate-dependent peroxidase activity of Cu,Zn-superoxide dismutase (SOD1) also induced covalent aggregation of α-synuclein via a CO3•−-dependent mechanism. Nitrone spin traps completely inhibited CO3•−-mediated oxidation/nitration and aggregation of α-synuclein. Conversely, α-synuclein inhibited CO3•−-induced spin adduct formation. Independent evidence for CO3•−-mediated oxidation and dimerization of α-synuclein was obtained from UV photolysis of [(NH3)5CoCO3]+, which generates authentic CO3•−. Irradiation of [(NH3)5CoCO3]+ and NO2− in the presence of α-synuclein yielded nitration and aggregation products that were similar to those obtained from a SIN-1 (or slowly infused ONOO−) and HCO3− or a myeloperoxidase/H2O2/NO2− system. Hydrophobic membranes greatly influenced α-synuclein aggregation and nitration in these systems. We conclude that both CO3•− and NO2• could play a major role in the nitration/aggregation of α-synuclein.
Identification and biochemical characterization of vivapains, cysteine proteases of the malaria parasite Plasmodium vivax
Authors: NA Byoung-Kuk , SHENAI Bhaskar R. , SIJWALI Puran S. , CHOE Youngchool , PANDEY Kailash C. , SINGH Ajay , CRAIK Charles S. , ROSENTHAL Philip J.
Published: February 2004

Cysteine proteases play important roles in the life cycles of malaria parasites. Cysteine protease inhibitors block haemoglobin hydrolysis and development in Plasmodium falciparum, suggesting that the cysteine proteases of this major human pathogen, termed falcipains, are appropriate therapeutic targets. To expand our understanding of plasmodial proteases to Plasmodium vivax, the other prevalent human malaria parasite, we identified and cloned genes encoding the P. vivax cysteine proteases, vivapain-2 and vivapain-3, and functionally expressed the proteases in Escherichia coli. The vivapain-2 and vivapain-3 genes predicted papain-family cysteine proteases, which shared a number of unusual features with falcipain-2 and falcipain-3, including large prodomains and short N-terminal extensions on the catalytic domain. Recombinant vivapain-2 and vivapain-3 shared properties with the falcipains, including acidic pH optima, requirements for reducing conditions for activity and hydrolysis of substrates with positively charged residues at P1 and Leu at P2. Both enzymes hydrolysed native haemoglobin at acidic pH and the erythrocyte cytoskeletal protein 4.1 at neutral pH, suggesting similar biological roles to the falcipains. Considering inhibitor profiles, the vivapains were inhibited by fluoromethylketone and vinyl sulphone inhibitors that also inhibited falcipains and have demonstrated potent antimalarial activity.