bluuebunny/crossref_metadata_2025 huggingface dataset:
DISTANCE MEASUREMENT AND κ-DEFORMED PROPAGATION OF LIGHT AND HEAVY PROBES
Authors: AMELINO-CAMELIA GIOVANNI , LUKIERSKI JERZY , NOWICKI ANATOL
Published: April 2003

We investigate the implications for the measurability of distances of a covariant dimensionful "κ" deformation of D=4 relativistic symmetries, with quantum time coordinate and modified Heisenberg algebra. We show that the structure of the deformed mass-shell condition has significant implications for measurement procedures relying on light probes, whereas in the case of heavy probes the most sizeable effect is due to the nontrivial commutation relation between three-momenta and quantum time coordinate. We argue that these findings might indicate that κ-Poincaré symmetries capture some aspects of the physics of the quantum-gravity vacuum.
EXCITED SCALAR MESONS IN A CHIRAL QUARK MODEL
Authors: VOLKOV M. K. , YUDICHEV V. L.
Published: April 2003

First radial excitations of the scalar and pseudoscalar meson nonets as well as their ground states are described as quark–antiquark bound systems in the framework of a nonlocal chiral quark model of the NJL type. Glueball states and their possible mixing with members of the [Formula: see text] multiplets are not considered.

Radial excitations are described by means of simple polynomial form factors in the momentum–space which are introduced into the four-quark vertices of the quark Lagrangian. The form factors are chosen in the regime of spontaneous chiral symmetry breaking so that the gap equations do not change their standard form, which provides fulfillment of the low energy theorems. All free parameters of the form factors are fixed by experimentally observed masses of pseudoscalar mesons. All masses of the scalar mesons are predicted.

The local six-quark 't Hooft interaction is introduced to solve the so-called UA(1)-problem. The (four particle) singlet–octet mixing for the ground and radially excited states of scalar and pseudoscalar mesons is taken into account. The widths of the main strong decays of the first radial excitation of the scalar meson nonet are calculatedin satisfactory agreement with experimental data.

Classification of the considered meson nonets is given. It is shown that the meson states a0(1450), f0(1370), fJ(1710) and [Formula: see text] are the first radial excitations of a0(980), f0(400-1200), f0(980), [Formula: see text].
OPERATOR-PRODUCT EXPANSION AND ANALYTICITY
Authors: FISCHER JAN , VRKOČ IVO
Published: April 2003

We discuss the current use of the operator-product expansion in QCD calculations. Treating the OPE as an expansion in inverse powers of an energy-squared variable (with possible exponential terms added), approximating the vacuum expectation value of the operator product by several terms and assuming a bound on the remainder along the Euclidean region, we observe how the bound varies with increasing deflection from the Euclidean ray down to the cut (Minkowski region). We argue that the assumption that the remainder is constant for all angles in the cut complex plane down to the Minkowski region is not justified.

Making specific assumptions on the properties of the expanded function, we obtain bounds on the remainder in explicit form and show that they are very sensitive both to the deflection angle and to the class of functions considered. The results obtained are discussed in connection with calculations of the coupling constant αs from the τ decay.
DUALITIES BETWEEN POISSON BRACKETS AND ANTIBRACKETS
Authors: BATALIN IGOR , MARNELIUS ROBERT
Published: April 2003

Recently it has been shown that antibrackets may be expressed in terms of Poisson brackets and vice versa for commuting functions in the original bracket. Here we also introduce generalized brackets involving higher antibrackets or higher Poisson brackets where the latter are of a new type. We give generating functions for these brackets for functions in arbitrary involutions in the original bracket. We also give master equations for generalized Maurer–Cartan equations. The presentation is completely symmetric with respect to Poisson brackets and antibrackets.
CHIRALITY IN ELECTRODYNAMICS
Authors: MARQUES G. C. , SPEHLER D.
Published: April 2003

We show that a not necessarily totally symmetric Bargman–Wigner second rank spinor field is able to accommodate a left–right symmetric U (1)L⊗ U (1)R Abelian gauge theory. We show that some features of the standard QED, such as vectorial gauge invariance, invariance under gauge transformation of the second kind, and the nonexistence of monopoles, follow from imposing left–right asymmetry on the level of self-interaction of the spinorial constituents.
MODIFIED BACKJUMPING ALGORITHMS FOR SOLVING CONSTRAINT SATISFACTION PROBLEMS
Authors: CHOWDHURY U. , GUPTA D. K.
Published: April 2003

The backtracking algorithm is a prominent search technique in AI, particularly due to its use in Constraint Satisfaction Problems (CSPs), Truth Maintenance Systems (TMS), and PROLOG. In the context of CSPs, Dechter5 and Gashnig10 proposed two variants of the backtracking algorithm known as backjumping algorithms. One is graph-based and the other is failure-based backjumping algorithm. These algorithms attempt to backjump to the source of failure in case of a dead-end situation. This improves the backtracking performance. However, these algorithms are not consistent in the selection of the variable to backjump.

In this paper, the modifications of both types of backjumping algorithms are proposed. These algorithms adopt a technique to select the variable to backjump in a consistent manner. This further increases the search efficiency in them. The merits of these modified algorithms are investigated theoretically. Experimental results on the zebra problem and random problems show that the modified algorithms give better results on most occasions.
STATISTICAL INFERENCE AS DEFAULT REASONING
Authors: KYBURG HENRY E. , TENG CHOH MAN
Published: April 2003

Classical statistical inference is nonmonotonic in nature. We show how it can be formalized in the default logic framework. The structure of statistical inference is the same as that represented by default rules. In particular, the prerequisite corresponds to the sample statistics, the justifications require that we do not have any reason to believe that the sample is misleading, and the consequence corresponds to the conclusion sanctioned by the statistical test.
SOLUTION OF A DELAYED INFORMATION LINEAR PURSUIT-EVASION GAME WITH BOUNDED CONTROLS
Authors: SHINAR JOSEF , GLIZER VALERY Y.
Published: April 2003

A class of linear pursuit-evasion games with first-order acceleration dynamics and bounded controls is considered, where the evader has perfect information and the pursuer has delayed information on the lateral acceleration of the evader. The other state variables are perfectly known to the pursuer. This game can be transformed to a perfect information delayed control game with a single state variable, the centre of the uncertainty domain created by the information delay. The delayed dynamics of the game is transformed to a linear first-order partial differential equation coupled with an integral-differential equation, both without delay. These equations are approximated by a set of K + 1 ordinary differential equations of first order, creating an auxiliary game. The necessary conditions of optimality derived for the auxiliary game lead to the solution of the delayed control game by a limit process as K → + ∞. The solution has the same structure as the other, already solved, perfect information linear pursuit-evasion games with bounded controls and indicates that the value of the delayed information pursuit-evasion game is never zero. Asymptotic expressions of the value of the game for small and large values of the information delay are derived.
UNIQUE NASH IMPLEMENTATION FOR A CLASS OF BARGAINING SOLUTIONS
Authors: TROCKEL WALTER
Published: April 2003

The paper presents a method of supporting certain solutions of two-person bargaining games by unique Nash equilibria of associated games in strategic form. Among the supported solutions is the Kalai-Smorodinsky solution.
THE H-STRATEGIES IN EXTENSIVE FORM GAMES
Authors: LIAPOUNOV ANDREY N.
Published: April 2003

The paper is devoted to the problem of the equivalence of the strategies in extensive form games. The notion of H-strategies is introduced and it is proved that every strategy is equivalent to a certain H-strategy.
A REMOTE COOPERATIVE DESIGN SYSTEM USING INTERACTIVE 3D GRAPHICS
Authors: LUO YUHUA , GALLI RICARDO , SÁNCHEZ DAVID , BENNASAR ANTONIO , FORNÉS JUAN , SERRA JUAN CARLOS , HUÉSCAR JUAN MANUEL , GAYÀ JOSEP
Published: April 2003

This paper presents a distributed system for the cooperative design in a 3D virtual environment with full interactive 3D graphics functionality. The system includes a multi-site 3D cooperative editor, a database and a cooperative support platform. The users can design and modify a common 3D virtual world from remote sites simultaneously and cooperatively via long distance communication network. The design information can be stored into the design database and retrieved from it. The cooperative and communication support platform keeps the application away from the network process detail.
Empirically downscaled temperature scenarios for Svalbard
Authors: Benestad R. E. , Førland E. J. , Hanssen‐Bauer I.
Published: April 2003

Empirically downscaled climate scenarios are presented for the Svalbard region, based on mixed 2‐meter temperature and sea level pressure fields. The scenarios are derived using the large‐scale fields from the ECHAM4‐GSDIO, HadCM3, and NCAR‐CSM climate change experiments, and utilizing common empirical orthogonal functions.

There are substantial differences between the scenarios derived from the various models. Those downscaled from the HadCM3 model indicate significantly stronger warming than those based on the ECHAM4‐GSDIO and NCAR‐CSM models. Much of these differences can be explained in terms of the different descriptions of the sea‐ice extent. The sea‐ice in the HadCM3 scenario is subject to a substantial retreat in the Barents Sea, whereas there is no melting in the same region in the NCAR‐CSM model. Copyright © 2003 Royal Meteorological Society.
Abrupt Cooling of Antarctic Surface Waters and Sea Ice Expansion in the South Atlantic Sector of the Southern Ocean at 5000 cal yr B.P.
Authors: Hodell David A. , Kanfoush Sharon L. , Shemesh Aldo , Crosta Xavier , Charles Christopher D. , Guilderson Thomas P.
Published: April 2003

Antarctic surface waters were warm and ice free between 10,000 and 5000 cal yr B.P., as judged from ice-rafted debris and microfossils in a piston core at 53°S in the South Atlantic. This evidence shows that about 5000 cal yr B.P., sea surface temperatures cooled, sea ice advanced, and the delivery of ice-rafted detritus (IRD) to the subantarctic South Atlantic increased abruptly. These changes mark the end of the Hypsithermal and onset of Neoglacial conditions. They coincide with an early Neoglacial advance of mountain glaciers in South America and New Zealand between 5400 and 4900 cal yr B.P., rapid middle Holocene climate changes inferred from the Taylor Dome Ice Core (Antarctica), cooling and increased IRD in the North Atlantic, and the end of the African humid period. The near synchrony and abruptness of all these climate changes suggest links among the tropics and both poles that involved nonlinear response to gradual changes in Northern Hemisphere insolation. Sea ice expansion in the Southern Ocean may have provided positive feedback that hastened the end of the Hypsithermal and African humid periods in the middle Holocene.
Late Pleistocene Cosmogenic 36Cl Glacial Chronology of the Southwestern Ahklun Mountains, Alaska
Authors: Briner Jason P. , Swanson Terry W. , Caffee Marc
Published: April 2003

Thirty-two cosmogenic 36Cl surface exposure ages constrain the timing of two late Pleistocene glacial advances in the western Ahklun Mountains, southwestern Alaska. Boulders were sampled from one early Wisconsin (sensu lato) and six late Wisconsin moraines deposited by ice-cap outlet glaciers and local alpine glaciers. Four moraine boulders deposited during an extensive early Wisconsin ice-cap outlet glacier advance have a mean surface exposure age of 60,300±3200 yr. A moraine deposited by an ice-cap outlet glacier during the restricted late Wisconsin advance has a mean surface exposure age of 19,600±1400 yr. Five moraines deposited by late Wisconsin alpine glaciers have mean ages that range between 30,000 and 17,000 yr. The 36Cl ages are consistent with limiting 14C and thermoluminescence ages from related deposits and indicate that Ahklun Mountains glaciers reached their most extensive position of the last glaciation early during the late Pleistocene, in contrast to the deep-sea isotopic record of global ice volume.1
Late Quaternary Climate Changes in Central Africa as Inferred from Terrigenous Input to the Niger Fan
Authors: Zabel Matthias , Schneider Ralph R. , Wagner Thomas , Adegbie Adesina T. , de Vries Uwe , Kolonic Sadat
Published: April 2003

Time series of terrigenous source elements (Al, K, Ti, Zr) from core GeoB4901-8 recovered from the deep-sea fan of the Niger River record variations in riverine sediment discharge over the past 245,000 yr. Although the flux rates of all the elements depend on physical erosion, which is mainly controlled by the extent of vegetation coverage in central Africa, element/Al ratios reflect conditions for chemical weathering in the river basin. Maximum sediment input to the ocean occurs during cold and arid periods, when precipitation intensity and associated freshwater runoff are reduced. High carbonate contents during the same periods indicate that the sediment supply has a positive effect on river-induced marine productivity. In general, variations in the terrestrial signals contain a strong precessional component in tune with changes in low-latitude solar radiation. However, the terrestrial signal lags the insolation signal by several thousand years. K/Al, Ti/Al, and Zr/Al records reveal that African monsoonal precipitation depends on high-latitude forcing. We attribute the shift between insolation cycle and river discharge to the frequently reported nonlinear response of African climate to primary orbital configurations, which may be caused by a complex interaction of the secondary control parameters, such as surface albedo and/or thermohaline circulation.
Late Pleistocene Environments of the Central Ukraine
Authors: Rousseau Denis-Didier , Gerasimenko Natalia , Matviischina Zhanna , Kukla George
Published: April 2003

The Vyazivok loess sequence from the Dnieper Plain, Ukraine, documents regional environmental changes during the late Pleistocene and Holocene. Pedological and palynological analyses and low-field magnetic susceptibility document changes from dense temperate forest during the last interglacial maximum to open, harsh, loess–steppe during the latest Pleistocene. The Vyazivok section overlies hillwash derived from a lower Pleistocene terrace and consists of two stratified soil complexes (Kaydaky and Pryluky; marine isotope stage [MIS] 5 equivalent) separated by a layer of eolian dust (Tyasmyn silt). The lower soils in both complexes formed within forest. These soils are overlain by the Uday (MIS4) and Bug (MIS2) loess units, which are separated by boreal soils of the Vytachiv (MIS3) complex. The coldest conditions within the record occurred in the youngest loess. Holocene soils cap the Bug loess. The Vyazivok section shows remarkable similarities with other classical loess sequences in western Europe, the Czech Republic, and Austria. The Kaydaky, Pryluky, and Vytachiv deposits, correlate with the PKIII, PKII, and PKI soil complexes, respectively, of the Czech Republic. The Tyasmyn and Prylyky silt layers correspond to marker horizons from central Europe.
Age of the Cutler Dam Alloformation (Late Pleistocene), Bonneville Basin, Utah
Authors: Kaufman Darrell S. , Forman Steve L. , Bright Jordon
Published: April 2003

Luminescence geochronology, especially infrared stimulated luminescence analyses on marsh mud, shows that a relatively deep lake reached its peak (∼1340 m above sea level) in the Bonneville basin 59,000±5000 yr ago. The age is consistent with nonfinite14C ages and with amino acid geochronology on ostracodes. The Cutler Dam Alloformation was deposited during this lake cycle, which, like the subsequent Bonneville lake cycle, appears to have reached its maximum highstand following the peak of a global glacial stage (marine oxygen-isotope stage 4) but at a time when other records from North America show evidence for cold climate and expanded glacier ice.
Stable Isotopes in Pocket Gopher Teeth as Evidence of a Late Matuyama Climate Shift in the Southern Rocky Mountains
Authors: Rogers Karel L. , Wang Yang
Published: April 2003

Previous work in the San Luis Valley of south-central Colorado and northern New Mexico at the Hansen Bluff and SAM Cave localities has allowed reconstruction of the paleoclimate in the region during the interval from ∼0.6 myr to ∼2.6 myr. Surface exposures at Hansen Bluff have been correlated to deep-sea oxygen isotope core stages 18–23 and one of the glacial periods contained therein to the oldest “Nebraskan” till in southwestern Iowa. Deposits in SAM Cave correlate to Hansen Bluff on the basis of paleomagnetics, climate interpretation, and microtine rodent biochronology. In this paper, carbon and oxygen stable isotope data of herbivorous rodent teeth are used as indicators of change in the predominance of C3, C4, and CAM plants and of changes in temperature and precipitation. Taken together with other previously analyzed data from these localities, the evidence indicates a shift in the severity of glacial events that is mainly related to the hydrologic characteristics of the climate. This shift may have been caused by broad regional uplift that may have been instrumental in shifting global climate cycles from the 41,000-yr Matuyama cycles to the Brunhes 100,000-yr-dominated cycles.
Holocene History of Desertification along the Woodland-Steppe Border in Northern China
Authors: Liu Hongyan , Xu Lihong , Cui Haiting
Published: April 2003

The woodland-steppe ecotone of the southeastern Inner Mongolian Plateau in northern China is located at the northwestern limit of the Pacific monsoon influence, where the landscape may have been a sensitive recorder of past climatic changes. Physical, chemical, and biological analyses of AMS14C-dated sediment sequences from two lakes of this region were used to reconstruct the Holocene vegetation and desertification history and distinguish four periods: (1) a cold and humid period from 10000 to 800014C yr B.P., (2) a warm and humid period from 8000 to 590014C yr B.P., (3) a warm and dry period from 5900 to 290014C yr B.P., and (4) a cool and dry period from 290014C yr B.P. to the present. The increased aridity during the middle Holocene was likely caused by increased winter temperatures and enhanced winter evaporation. The transition from a humid to an arid climate after ∼590014C yr B.P. coincided with enhanced aeolian activity, and deciduous woodlands were replaced by pine woodlands and then by steppes in response to the climatic deterioration. These transitions led to the present desertification. The records suggest that a simple association of thermal and moisture conditions, such as warm/wet or cold/dry, may be misleading.
Wetland Diagenesis and Traces of Early Hominids, Olduvai Gorge, Tanzania
Authors: Deocampo Daniel M. , Blumenschine Robert J. , Ashley Gail M.
Published: April 2003

Lateral variations in whole-rock and clay geochemistry of basal Bed II claystones in Olduvai Gorge, Tanzania, reflect water quality differences across the Eastern Lacustrine Plain ∼1.75 myr ago. Bulk Ba/Sr and (Na2O+K2O+MgO)/Al2O3range from 1.4 to 4.2 and from 0.7 to 1.4, respectively, and indicate leaching of lacustrine claystones beneath freshwater wetlands at times following lake retreat. Bulk MgO/Al2O3(0.3–1.0) and molar Mg/Al (0.5–3.9) ratios of <0.2-μm clays reflect alteration of Mg-rich lacustrine clays. These indicators point to freshest conditions near Locality 43 of Hay (1976; HWK-East; Leakey, 1971), moderate conditions to the east (Locality 40-MCK), and high salinity and alkalinity to the west (Localities 85-VEK, 45-FLK).

Clay geochemistry and artifact abundances are well correlated (r=−0.67,p<0.005), suggesting a relationship between paleo-water quality and hominid paleoecology. This pattern is consistent with predictions of greatest artifact discard/loss around freshwater sources where scavanging opportunities were greatest for hominids. This quantifies a relationship between artifact density distribution and a paleoecological proxy over landscape scales for the first time in Early Stone Age archaeology. In contrast, fossil bone abundance is uncorrelated (r=0.14,p=0.6), reflecting more complex taphonomic processes. Quantitative tests of landscape-scale land-use models are important for understanding early hominid behavior and its evolution.
Enzymatic activity of a developmentally regulated member of the sialyltransferase family (STX): evidence for α2,8‐sialyltransferase activity toward N‐linked oligosaccharides
Authors: Kojima Naoya , Yoshida Yukiko , Kurosawa Nobuyuki , Lee Young-Choon , Tsuji Shuichi
Published: April 2003

We have detected sialyltransferase activity of recombinant mouse STX, which was cloned from rat brain as a new member of the sialyltransferase family, but sialyltransferase activity of which had not been detected previously [Livingston and Paulson, J. Biol. Chem. (1993) 268, 11504–11507]. The activity of mouse STX was specific toward sialylated glycoproteins. N‐Glycanase treatment and linkage‐specific sialidase treatment of glycoproteins revealed that STX transfers sialic acids through α2,8‐linkages to only N‐linked oligosaccharides of glycoproteins. However, polymerase activity for polysialic acid synthesis was not detected for this sialyltransferase. Since this α2,8‐sialyltransferase gene is highly restricted in fetal and newborn brain, it may be involved in the polysialylation of glycoproteins, especially of N‐CAM.
Colony‐stimulating factors and interferon‐γ activate a protein related to MGF‐Stat 5 to cause formation of the differentiation‐induced factor in myeloid cells
Authors: Barahmand-pour Fariba , Meinke Andreas , Eilers Andreas , Gouilleux Fabrice , Groner Bernd , Decker Thomas
Published: April 2003

The Jak‐Stat pathway of intracellular signals is used by growth factor‐ and cytokine receptors to induce gene transcription. We have recently reported that differentiation of myeloid cells, induced by phorbol ester, interferon‐γ (IFN‐γ) or colony‐stimulating factor‐1 (CSF‐1) is accompanied by the activation of the differentiation‐induced factor (DIF). Activated DIF specifically associates with a subclass of gamma‐interferon activation site (GAS)‐like DNA elements. We now report that GM‐CSF, which like CSF‐1 promotes the generation of mature macrophages, activates DIF. No activation was observed after treatment with the granulocyte growth and differentiation factor G‐ CSF. Antibodies raised against a Stat family protein, designated mammary gland factor‐Stat 5 (MGF‐Stat 5), reacted with DIF induced by either CSF‐1, GM‐CSF or IFN‐γ. Antisera to other known Stats were without effect on the DIF complex in electrophoretic mobility shift assays (EMSA). A 112 kDa protein could be isolated from either GM‐CSF‐ or IFN‐γ‐treated cells by GAS oligonucleotide precipitation. This protein reacted with antibodies to both MGF‐Stat 5 and phosphotyrosine. MGF‐Stat 5 and closely related proteins thus define a subfamily of Stat transcription factors that are present in a variety of cell types and are required for the onset of immediate gene expression in response to differentiating stimuli.
Modulation of the levels of ouabain‐like compound by central catecholamine neurons in rats
Authors: Yamada Kaoru , Goto Atsuo , Omata Masao
Published: April 2003

Catecholamine regulates the Na+,K+‐ATPase activity in the central nervous system and the Na+,K+‐ATPase has been shown to have endogenous ligands (ouabain‐like compound; OLC). To examine the relationship between OLC and central adrenergic neurons, we evaluated the effects of central sympathectomies with intracerebroventricular (i.c.v.) injection of 6‐hydroxydopamine (6‐OHDA; 250 μg) on brain and plasma OLC levels and brain catecholamine levels. In centrally sympathectomized rats, hypothalamic OLC content and plasma OLC level were significantly decreased by 90% (P < 0.01) and 70% (P < 0.01), respectively, in accordance with reduced brain norepinephrine content compared with control rats pretreated by i.c.v. injection of vehicle (ascorbic acid). On the other hand, peripheral sympathectomy with a similar manner did not affect plasma OLC level at all. These findings suggest that central adrenergic neurons may be involved in the synthesis and/or release of circulating OLC.
Fas antigen signals proliferation of normal human diploid fibroblast and its mechanism is different from tumor necrosis factor receptor
Authors: Aggarwal Bharat B. , Singh Sanjaya , LaPushin Ruth , Totpal Klara
Published: April 2003

Recent cloning of the cDNA for Fas/Apo‐1 and its ligand has revealed that they belong to the tumor necrosis factor (TNF) receptor and TNF family, respectively, and play an important role in apoptosis (programmed cell death). Like TNF, antibodies against the Fas antigen (anti‐Fas) have been shown to be cytotoxic to Fas‐expressing cells. Whether Fas, like TNF receptor, also mediates proliferation of normal human diploid fibroblasts (HDF), is not known. In this study, we show that HDF expresses Fas antigen and the engagement of this antigen signals proliferation of these cells in a dose‐dependent manner. Unlike TNF receptor, however, Fas‐mediated proliferation of HDF could not be blocked by orthovanadate, a tyrosine phosphatase inhibitor. The difference in the signaling was further evident from our observation that TNF induced the expression of interleukin‐6 but anti‐Fas did not. Overall, our results demonstrate for the first time that besides cell killing, Fas also mediates proliferation of HDF and that its mechanism is different from that of TNF receptor.
DAMGO, a μ‐opioid receptor selective ligand, distinguishes between μ‐and κ‐opioid receptors at a different region from that for the distinction between μ‐ and δ‐opioid receptors
Authors: Minami Masabumi , Onogi Tatsuhiro , Nakagawa Takayuki , Katao Yoshikazu , Aoki Yasuhide , Katsumata Seishi , Satoh Masamichi
Published: April 2003

The structural basis of opioid receptors (OPRs) for the subtype‐selective binding of DAMGO, a μ‐opioid receptor selective ligand, was investigated using chimeric μ/κ‐OPRs. Replacement of the region from the middle of the fifth transmembrane domain to the C‐terminal of μ‐OPR with the corresponding region of μ‐OPR remarkably decreased the binding affinity to DAMGO, while the reciprocal chimera revealed the high affinity to DAMGO. These results indicate that DAMGO distinguishes between μ‐ and μ‐OPRs at the region around the third extracellular loop, different from the case of the distinction between μ‐and δ‐OPRs in which the region around the first extracellular loop is important. Furthermore, displacement studies revealed that the region around the third extracellular loop is involved in the discrimination between μ‐ and κ‐OPRs not only by peptidic μ‐ selective ligands but also by non‐peptidic ligands, such as morphine and naloxone.
High‐pressure stabilization of α‐chymotrypsin entrapped in reversed micelles of aerosol OT in octane against thermal inactivation
Authors: Rariy Roman V. , Bec Nicole , Saldana J.-L. , Nametkin Sergey N. , Mozhaev Vadim V. , Klyachko Natalia L. , Levashov Andrey V. , Balny Claude
Published: April 2003

α‐Chymotrypsin (CT) solubilized in reversed micelles of sodium bis‐(2‐ethylhexyl)‐sulfosuccinate (AOT) undergoes thermal inactivation and the enzyme stability decreases significantly when temperature increases (25–40°C). The half‐life of CT in micelles shows a bell‐shaped dependence on the degree of hydration of AOT (w
0) analogous to the previously obtained dependence on w
0 for the enzyme activity. The optima of catalytic activity and thermal stability have been observed under conditions where the diameter of the inner aqueous cavity of the micelle is close to the size of the enzyme molecule (w
0 = 10). Application of high hydrostatic pressure in the range of 1–1500 atm (bar) stabilizes CT against thermal inactivation at all hydration degrees (w
0) from 7 to 20; the stabilization effect is most pronounced under the experimental conditions being far from the optimum for catalytic activity.
Mapping regions of Gαq interacting with PLCβ1 using multiple overlapping synthetic peptides
Authors: Arkinstall Steve , Chabert Christian , Maundrell Kinsey , Peitsch Manuel
Published: April 2003

The heterotrimeric G‐protein α‐chain Gαp plays a critical role mediating receptor‐linked activation of the β isoforms of PLC which hydrolyse membrane inositol‐containing phospholipids to generate the second messengers inositol 1,4,5‐trisphosphate and diacylglycerol. Despite knowledge of the three‐dimensional structure of two G‐protein α‐chains (Gαt and Gα1 as well as high regional amino acid conservation between members of the G‐protein α‐chain family, the precise molecular domains of Gαp mediating activation of PLCβ1 are unknown. To map sites responsible for effector interaction we employed 188 peptides each of 15 residues and corresponding to overlapping regions of the complete G
αq sequence. These were tested for their ability to inhibit G
αq‐dependent activation of recombinant PLCJβ1 using an in vitro reconstitution assay. Peptides from two regions of Gαq mediated up to 100% inhibition of GTPγS‐stimulated PLCβ1 activity, and representative peptides from each of these regions were half‐maximally effective at 69.3 ± 27.4 μM (n = 4) (G
αq: 251–265) and 110.0 ± 41.9 μM (n = 4) (G
αq: 306–319). Gαq regions described by inhibitory peptides are conserved selectively in other G‐protein a‐chains linked to PLCβ1 activation (Gα11, Gα4) and correspond spatially to sites of effector interaction identified in Gαs by scanning mutagenesis and in transducin using site‐specific antibodies and peptides. Computer homology modelling of Gαq based on the crystal structure of transducin indicates that regions interacting with PLCβ1 form two parallel α‐helices lying at the surface of the Gαq structure. These observations provide the first description of two regions within Gαq critically important for activating PLCβ1, and moreover, indicate that effector binding domains identified in transducin and Gαs are also conserved spatially in Gαq.
Preferential inhibition of phorbol ester‐induced hydrolysis of phosphatidylethanolamine by N‐acetylsphingosine in NIH 3T3 fibroblasts
Authors: Kiss Zoltan , Deli Eva
Published: April 2003

It has been reported that in rat fibroblasts cell‐permeable ceramide analogs inhibit agonist‐induced phospholipase D (PLD)‐mediated hydrolysis of phosphatidylcholine (PtdCho). Here we demonstrate that relatively short (30 min) treatments of NIH 3T3 fibroblasts with 15–60 μM concentrations of N‐acetylsphingosine result in preferential, although not exclusive, inhibition of phorbol 12‐myristate 13‐acetate‐induced PLD‐mediated hydrolysis of phosphatidylethanolamine (PtdEtn). The results suggest that in different cell types the PtdEtn‐ and PtdCho‐hydrolyzing PLD activities are differentially sensitive to the inhibitory effect of ceramide.
Polyamine induced Z‐conformation of native calf thymus DNA
Authors: Hasan Rashid , Alam Moinuddin K. , Ali Rashid
Published: April 2003

Conformational isomerization of native calf thymus DNA under the influence of spermine, spermidine and putrescine was monitored by UV absorption and immunospecific anti‐Z‐DNA antibodies. Immunological data indicated increased binding of anti‐Z‐DNA antibodies to polyamine‐perturbed conformations of native DNA and double stranded poly(dG‐dC). In the absence of polyamines, anti‐Z‐DNA antibodies did not bind to either polymers. Analysis of UV absorption studies indicates a left handed conformation of nDNA in the presence of polyamines. Moreover, we observed total aggregation of DNA in the presence of spermine on prolongued incubation. These perturbations in conformation were dependent on polyamine concentration. The results clearly suggest that certain regions of nDNA are sensitive to elevated levels of polyamines and are capable of undergoing B → Z transition.
Control of p62 binding to TGN38/41 by phosphorylation
Authors: Zehavi-Feferman Revital , Burgess James W. , Stanley Keith K.
Published: April 2003

TGN38/41 cycles between the trans‐Golgi network (TGN) and plasma membrane, traversing three sorting compartments: the TGN, plasma membrane and early endosome. The targeting signals responsible for this complex itinerary reside in a short cytoplasmic domain of 33 amino acid residues. We show that phosphorylation of the cytoplasmic domain of TGN38 prevents binding of p62 — a cytoplasmic protein essential for exocytic vesicle formation. Thus the cycle of TGN38/41 traffic, and by implication the pathway of exocytosis, could be controlled by phosphorylation of the TGN38 cytoplasmic domain.
Rapid purification of wildtype and mutant cytochrome c oxidase from Rhodobacter sphaeroides by Ni2+‐NTA affinity chromatography
Authors: Mitchell David M. , Gennis Robert B.
Published: April 2003

A rapid and highly efficient method of purifying the aa
3‐type cytochrome c oxidase from Rhodobacter sphaeroides has been developed. This method relies upon a six‐histidine affinity tag fused to the C‐terminus of subunit I, which confers to the oxidase a high affinity for Ni2+‐nitrilotriacetic acid (NTA) agarose. The histidine‐tagged oxidase can be purified rapidly and with high yield by one affinity chromatography step, starting with solubilized membranes. The purified oxidase is >95% pure and possesses structural and functional characteristics of the wildtype enzyme. The six‐histidine tag can be easily added to pre‐constructed site‐directed mutants of subunit I, increasing the availability of purified cytochrome c oxidase mutants for biophysical and biochemical studies.
Antioxidant potential of intermediates in phenylpropanoid metabolism in higher plants
Authors: Castelluccio Cinzia , Paganga George , Melikian Narbeh , Paul Bolwell G. , Pridham John , Sampson Julia , Rice-Evans Catherine
Published: April 2003

In this study the antioxidant activities of the hydroxycinnamic acids, chlorogenic, caffeic, ferulic and p‐coumaric have been investigated in peroxidising lipid systems mediated by metmyoglobin. The results show that the order of effectiveness in increasing the resistance of LDL to peroxidation, in protecting LDL cholesterol from oxidation and preventing the oxidative modification of the LDL apoprotein B100 is caffeic = chlorogenic > ferulic > p‐coumaric acid. Assessment of the rates of reaction of the hydroxycinnamates with ferrylmyoglobin, a product of the reductive decomposition of lipid hydroperoxides, reveals that the compounds are more effective as peroxyl radical scavengers than reductants of ferryl myoglobin in peroxidising LDL systems mediated by haem proteins.
G protein βγ subunit activates Ras, Raf, and MAP kinase in HEK 293 cells
Authors: Ito Akiko , Satoh Takaya , Kaziro Yoshito , Itoh Hiroshi
Published: April 2003

Using transient transfection of HEK 293 cells, we have studied the activation of Ras, c‐Raf, and MAP kinase by G protein‐coupled receptors, activated G protein α subunit (Gα), and βγ subunits (Gβγ). The expression of constitutively activated Gsα, Giα, and Gaaα did not have any effect on MAP kinase phosphorylation. In contrast, overexpression of Gβγ could stimulate the phosphorylation of MAP kinase and enhance the MEK kinase activity of c‐Raf. Coexpression of dominant negative Ras inhibited Gβγ‐induced phosphorylation of MAP kinase. Furthermore, the GTP‐bound form of Ras was increased by overexpression of Gβγ. These results strongly suggest that the Gβγ may play an important role in signaling from G protein‐coupled receptors to the MAP kinase pathway, and the activation of Ras and c‐Raf may be involved in this signaling cascade in HEK 293 cells.
Occurrence of heme O in photoheterotrophically growing, semi‐anaerobic cyanobacterium Synechocystis sp. PCC6803
Authors: Peschek Günter A. , Wastyn Marnik , Fromwald Susanne , Mayer Bernhard
Published: April 2003

Extraction and identification of the non‐covalently bound heme groups from crude membrane preparations of photoheterotrophically grown Synechocystis sp. PCC 6803 by reversed phase high performance liquid chromatography and optical spectrophotometry led to the detection of heme O in addition to hemes B and A which latter was to be expected from the known presence of aa3‐type cytochrome oxidase in cyanobacteria. In fully aerated cells (245 μM dissolved O2 in the medium) besides heme B only heme A was found while in low‐oxygen cells (<10 μM dissolved O2) heme O was present at a concentration even higher than that of heme A. Given the possible role of heme O as a biosynthetic intermediate between heme B and heme A, together with generally much higher K
m values of 5–50 μM O2 for oxygenase as compared to K
m values of 40–70 nM O2 for typical cytochrome‐c oxidase, our findings may permit the conclusion that the conversion of heme O to heme A is an obligately oxygen‐requiring process catalyzed by some oxygenase directly introducing oxygen from O2 into the 8‐methyl group of heme O. At the same time thus the occurrence of heme O (cytochrome o) in cyanobacteria does of course not imply the existence of an ‘alternative oxidase’ since according to the well‐known ‘promiscuity of heme groups’ both hemes O and A are likely to combine with one and the same apoprotein.
Effects of the uncI gene on expression of uncB, the gene coding for the a subunit of the F1F0 ATPase of Escherichia coli
Authors: Hsu Debbie K.W. , Brusilow William S.A.
Published: April 2003

The eight genes coding for the subunits of the E. coli F1F0 ATPase are preceded by a gene, designated uncI. A homologous gene, or a gene coding for an analagous protein, is found preceding the ATPase genes of several microorganisms. No function for the I gene has been described. Using lac fusions to measure gene expression in vivo, we tested the effects of deleting uncI on the expression of the adjacent gene uncB, which codes for the a subunit of the F0 sector of the ATPase. Deleting uncI reduced the expression of three uncB′‐′lacZ fusion genes in vivo, but had no effect on the expression of two uncB′‐′lacZ fusion genes containing a relatively smaller amount of the uncB coding region. The uncI deletion also reduced the relative synthesis of the a subunit in vitro. The I gene therefore appears to specifically affect the expression of uncB or the synthesis of the a subunit at some step after translational initiation of uncB.
Protein insertion into the endoplasmic reticulum of permeabilized cells
Authors: Jadot M. , Hofmann M.W. , Graf R. , Quader H. , Martoglio B.
Published: April 2003

We have established efficient translocation of newly synthesized proteins into the endoplasmic reticulum of permeabilized Mel Juso cells. By site‐specific photo‐crosslinking we show that translocating polypeptide chains contact the same components of permeabilized cells ER as in dog pancreas rough microsomes. This cellular assay system has the potential to overcome the limitations of isolated microsomes in investigating the molecular environment of a newly synthesized protein after they have left the ER translocation site.
Accumulation of cyclic ADP‐ribose measured by a specific radioimmunoassay in differentiated human leukemic HL‐60 cells with all‐trans‐retinoic acid
Authors: Takahashi Katsunobu , Kukimoto Iwao , Tokita Ken-ichi , Inageda Kiyoshi , Inoue Shin-ichi , Kontani Kenji , Hoshino Shin-ichi , Nishina Hiroshi , Kanaho Yasunori , Katada Toshiaki
Published: April 2003

Cyclic adenosine diphosphoribose (cADPR) is a novel candidate for the mediator of Ca2+ release from intracellular Ca2+ stores. The formation of this cyclic nucleotide is catalyzed by not only Aplysia ADP‐ribosyl cyclase but also an ecto‐form enzyme of NAD+ glycohydrolase (NADase), which was previously identified as all‐trans‐retinoic acid (RA)‐inducible CD38 in human leukemic HL‐60 cells. In the present study, we developed a radioimmunoassay specific for cADPR, by which more than 100 fmol of cADPR could be detected without any interference by other nucleotides. The possible involvement of CD38 in the formation of cellular cADPR was investigated with the radioimmunoassay method. A marked increase in cellular cADPR was accompanied by all‐trans‐RA‐induced differentiation of HL‐60 cells. Moreover, a high level of cellular cADPR was observed in other leukemic cell lines, in which CD38 mRNA was expressed. Thus, CD38, which was initially identified as an NADase, appeared to be responsible for the formation of cellular cADPR.
The mouse prostaglandin E receptor EP2 subtype: cloning, expression, and Northern blot analysis
Authors: Katsuyama Masato , Nishigaki Nobuhiro , Sugimoto Yukihiko , Morimoto Kimiko , Negishi Manabu , Narumiya Shuh , Ichikawa Atsushi
Published: April 2003

A functional cDNA clone for the mouse prostaglandin (PG) E receptor EP2 subtype was isolated from a mouse cDNA library. The mouse EP2 receptor consists of 362 amino acid residues with seven putative transmembrane domains. [3H]PGE2 bound specifically to the membrane of Chinese hamster ovary cells stably expressing the cloned receptor. This binding was displaced by unlabeled prostanoids in the order of iloprost, a stable PGI2 agonist > PGF2α
> PGD2. Binding was also inhibited by butaprost (an EP2 agonist) and to a lesser extent by M&B 28767 (an EP3 agonist), but not by sulprostone (an EP1 and EP3 agonist) or SC‐19220 (an EP1 antagonist). PGE2 and butaprost increased the cAMP level in the Chinese hamster ovary cells in a concentration‐dependent manner. Northern blot analysis revealed that EP2 mRNA is expressed most abundantly in the uterus, followed by the spleen, lung, thymus, ileum, liver, and stomach.
Effect of substrate aglycon on enzyme mechanism in the reaction of sialidase from influenza virus
Authors: Tiralongo J. , Pegg M.S. , von Itzstein M.
Published: April 2003

The effect of substrate aglycon on enzyme mechanism of sialidase from influenza virus was investigated by kinetic isotope effects using the substrates acid (Neu5Acα2MU) and acid (Neu5Acα2PNP). The kinetic isotope effect on , at pH 6.0, as revealed by direct comparison of rates obtained with Neu5Acα2MU and the [3,3‐2H]‐substituted substrate analogue, was shown to be inverse. This indicates that sialidase‐catalysed hydrolysis of Neu5Acα2MU proceeds with substantial positive charge development at the reaction centre in the transition state for the formation of the glycosyl cation‐enzyme intermediate. However, no such inverse effect on V
max at pH 6.0 was observed when using Neu5Acα2PNP and the [3,32H]‐substituted substrate. A mechanism by which hydrolysis proceeds through an α‐lactone intermediate has been proposed by Guo et al. [8]. We propose that the differences in
βD
V for the substrates investigated are due primarily to the differing properties of the aglycon leaving groups, which may result in influenza virus sialidase catalysing substrate hydrolysis by a similar mechanism with alternative stabilisation of transition state.
Histidine and tyrosine phosphorylation in pea mitochondria: evidence for protein phosphorylation in respiratory redox signalling
Authors: Håkansson Gunilla , Allen John F.
Published: April 2003

A 37 kDa protein in pea mitochondria was found to contain phosphorylated residues. Phosphorylation was acid‐labile but stable in alkali solution, a unique property of phosphorylation on histidine, indicating that a signal transduction pathway with homology to bacterial two‐component systems might exist in plant mitochondria. We also describe the first example of tyrosine phosphorylation in plant organelles and the first indication of protein phosphorylation as part of a redox signalling mechanism in mitochondria. Labelling of three proteins (28, 27 and 12 kDa) was found to be dependent on the redox state of the reaction medium. Their phospho‐groups were resistant to alkali as well as acid treatment and labelling was inhibited by the tyrosine kinase inhibitor genistein.
Molecular cloning of a widely expressed human homologue for the Drosophila trp gene
Authors: Zhu Xi , Chu Phillip B. , Peyton Michael , Birnbaumer Lutz
Published: April 2003

The Drosophila transient receptor potential (trp) gene and its homologue, trpl, have been suggested to mediate calcium entry during the insect's phototransduction process. We isolated a human cDNA, human trp‐1 (Htrp‐1), encoding a polypeptide of 793 amino acids that is 37% identical (62% similar) to Drosophila trp and trpl. Northern analysis showed that the Htrp‐1 transcript is approximately 5.5 kb and expressed in most human tissues, with higher amounts in ovary, testis, heart, and brain. Isolation of Htrp‐1 suggests that a trp‐type protein is present in mammals and should provide a useful tool in studying calcium‐depletion induced calcium influx processes.
The expression of the imprinted H19 and IGF‐2 genes in human bladder carcinoma
Authors: Elkin Michael , Shevelev Alexander , Schulze Ekkehard , Tykocinsky Mark , Cooper Mark , Ariel Ilana , Pode Dov , Kopf Eliezer , de Groot Nathan , Hochberg A.
Published: April 2003

The imprinted H19 gene is highly expressed in human embryos, fetal tissues and is nearly completely shut off in adults. However, it is reexpressed in a number of tumors including bladder carcinoma, demonstrating that H19 RNA is an oncofetal RNA. Tumors induced by injection of bladder carcinoma cell lines express H19 in contrast to the cells before injection. These observations support the notion of a positive correlation between H19 expression and bladder carcinoma. Loss of imprinting of H19 and IGF‐2 was observed in samples of human bladder carcinoma.
Specific RNA cleavages induced by manganese ions
Authors: Wrzesinski Jan , Michałowski Daniel , Ciesiołka Jerzy , Krzyżosiak Wlodzimierz J.
Published: April 2003

The specificity and efficiency of manganese ion‐induced RNA hydrolysis was studied with several tRNA molecules. In case of yeast tRNAPhe, the main cleavage occurs at p16 and minor cuts at p17–18, p20–21, p34 and p36–37. The major Mn(II)‐induced cut in yeast elongator tRNAMet is also located in the D‐loop at p16 and it is stronger than that observed in tRNAPhe. In initiator tRNAMet from yeast two strong Mn(II) cleavages of equal intensity occur at p16 and p17. This is in contrast with single, much weaker cuts induced in the D‐loop of that tRNA by Mg(II), Eu(III) and Pb(II) ions. Interestingly, in case of yeast tRNAGlu the main cleavage caused by Mn(II), Mg(II) and Pb(II) ions occurs in the anticodon loop. The involvement of hypermodified base mnm5s2U in this cleavage was ruled out based on results obtained with in vitro transcript of yeast tRNAGlu anticodon arm. Mutation of a single base A37G in the anticodon loop of the transcript drastically reduced the specificity of Mn(II)‐induced hydrolysis.
An immunodominant antigen of Brugia malayi is an asparaginyl‐tRNA synthetase
Authors: Kron Michael , Marquard Kristine , Härtlein Michael , Price Steven , Leberman Reuben
Published: April 2003

Lymphatic filariasis is caused by infection with the filarial nematodes Brugia malayi, Brugia timori, Wuchereria bancrofti and Onchocerca volvulus which collectively infect about 200 million persons throughout the world. Protein sequence homology analysis of a major nematode antigen suggested that it was a class II aminoacyl‐tRNA synthetase. The overproduction, purification and verification that the major B. malayi antigen is an asparaginyl‐tRNA synthetase is described.