bluuebunny/crossref_metadata_2025 huggingface dataset:
Stochastic game theory: For playing games, not just for doing theory
Authors: Goeree Jacob K. , Holt Charles A.
Published: July 2002

Recent theoretical advances have
dramatically increased the relevance of game theory for predicting
human behavior in interactive situations. By relaxing the classical
assumptions of perfect rationality and perfect foresight, we obtain
much improved explanations of initial decisions, dynamic patterns of
learning and adjustment, and equilibrium steady-state distributions.
Interferon gene transfer by a hepatitis B virus vector efficiently suppresses wild-type virus infection
Authors: Protzer Ulrike , Nassal Michael , Chiang Pei-Wen , Kirschfink Michael , Schaller Heinz
Published: July 2002

Hepatitis B viruses specifically target the liver, where they efficiently infect quiescent hepatocytes. Here we show that human and avian hepatitis B viruses can be converted into vectors for liver-directed gene transfer. These vectors allow hepatocyte-specific expression of a green fluorescent protein
in vitro
and
in vivo
. Moreover, when used to transduce a type I interferon gene, expression of interferon efficiently suppresses wild-type virus replication in the duck model of hepatitis B virus infection. These data suggest local cytokine production after hepatitis-B-virus-mediated gene transfer as a promising concept for the treatment of acquired liver diseases, including chronic hepatitis B.
Unusual carotenoid composition and a new type of xanthophyll cycle in plants
Authors: Bungard Ralph A. , Ruban Alexander V. , Hibberd Julian M. , Press Malcolm C. , Horton Peter , Scholes Julie D.
Published: July 2002

The capture of photons by the photosynthetic apparatus is the first step in photosynthesis in all autotrophic higher plants. This light capture is dominated by pigment-containing proteins known as light-harvesting complexes (LHCs). The xanthophyll–carotenoid complement of these LHCs (neoxanthin, violaxanthin, and lutein) is highly conserved, with no deletions and few, uncommon additions. We report that neoxanthin, considered an integral component of LHCs, is stoichiometrically replaced by lutein-5,6-epoxide in the parasitic angiosperm
Cuscuta reflexa
, without compromising the structural integrity of the LHCs. Lutein-5,6-epoxide differs from neoxanthin in that it is involved in a light-driven deepoxidation cycle similar to the deepoxidation of violaxanthin in the xanthophyll cycle, which is implicated in protection against photodamage. The absence of neoxanthin and its replacement by lutein-5,6-epoxide changes our understanding of the structure-function relationship in LHCs, has implications for biosynthetic pathways involving neoxanthin (such as the plant hormone abscisic acid), and identifies one of the early steps associated with the evolution of heterotrophy from autotrophy in plants.
Structure of the ternary complex of human 17β-hydroxysteroid dehydrogenase type 1 with 3-hydroxyestra-1,3,5,7-tetraen-17-one (equilin) and NADP
+
Authors: Sawicki Mark W. , Erman Mary , Puranen Terhi , Vihko Pirkko , Ghosh Debashis
Published: July 2002

Excess 17β-estradiol (E
2
), the most potent of human estrogens, is known to act as a stimulus for the growth of breast tumors. Human estrogenic 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1), which catalyzes the reduction of inactive estrone (E
1
) to the active 17β-estradiol in breast tissues, is a key enzyme responsible for elevated levels of E
2
in breast tumor tissues. We present here the structure of the ternary complex of 17β-HSD1 with the cofactor NADP
+
and 3-hydroxyestra-1,3,5,7-tetraen-17-one (equilin), an equine estrogen used in estrogen replacement therapy. The ternary complex has been crystallized with a homodimer, the active form of the enzyme, in the asymmetric unit. Structural and kinetic data presented here show that the 17β-HSD1-catalyzed reduction of E
1
to E
2
in vitro
is specifically inhibited by equilin. The crystal structure determined at 3.0-Å resolution reveals that the equilin molecule is bound at the active site in a mode similar to the binding of substrate. The orientation of the 17-keto group with respect to the nicotinamide ring of NADP
+
and catalytic residues Tyr-155 and Ser-142 is different from that of E
2
in the 17β-HSD1–E
2
complex. The ligand and substrate-entry loop densities are well defined in one subunit. The substrate-entry loop adopts a
closed
conformation in this subunit. The result demonstrates that binding of equilin at the active site of 17β-HSD1 is the basis for inhibition of E
1
-to-E
2
reduction by this equine estrogen
in vitro
. One possible outcome of estrogen replacement therapy
in vivo
could be reduction of E
2
levels in breast tissues and hence the reduced risk of estrogen-dependent breast cancer.
Stretching lattice models of protein folding
Authors: Socci Nicholas D. , Onuchic José Nelson , Wolynes Peter G.
Published: July 2002

A new class of experiments that probe folding of individual protein domains uses mechanical stretching to cause the transition. We show how stretching forces can be incorporated in lattice models of folding. For fast folding proteins, the analysis suggests a complex relation between the force dependence and the reaction coordinate for folding.
The dynamics of mass migration
Authors: Massey Douglas S. , Zenteno Rene M.
Published: July 2002

We specify a set of equations defining a dynamic model of international migration and estimate its parameters by using data specially collected in Mexico. We then used it to project the a hypothetical Mexican community population forward in time. Beginning with a stable population of 10,000 people, we project ahead 50 years under three different assumptions: no international migration; constant probabilities of in- and out-migration, and dynamic schedules of out- and in-migration that change as migratory experience accumulates. This exercise represents an attempt to model the self-feeding character of international migration noted by prior observers and theorists. Our model quantifies the mechanisms of cumulative causation predicted by social capital theory and illustrates the shortcomings of standard projection methodologies. The failure to model dynamically changing migration schedules yields a 5% overstatement of the projected size of the Mexican population after 50 years, an 11% understatement of the total number of U.S. migrants, a 15% understatement of the prevalence of U.S. migratory experience in the Mexican population, and an 85% understatement of the size of the Mexican population living in the United States.
Toward a new synthesis: Major evolutionary trends in the angiosperm fossil record
Authors: Dilcher David
Published: July 2002

Angiosperm paleobotany has widened its horizons, incorporated new
techniques, developed new databases, and accepted new questions that
can now focus on the evolution of the group. The fossil record of early
flowering plants is now playing an active role in addressing questions
of angiosperm phylogeny, angiosperm origins, and angiosperm radiations.
Three basic nodes of angiosperm radiations are identified:
(
i
) the closed carpel and showy radially
symmetrical flower, (
ii
) the bilateral flower,
and (
iii
) fleshy fruits and nutritious nuts and
seeds. These are all coevolutionary events and spread out through time
during angiosperm evolution. The proposal is made that the genetics of
the angiosperms pressured the evolution of the group toward
reproductive systems that favored outcrossing. This resulted in the
strongest selection in the angiosperms being directed toward the
flower, fruits, and seeds. That is why these organs often provide the
best systematic characters for the group.
Proapoptotic BH3-only Bcl-2 family members induce cytochromecrelease, but not mitochondrial membrane potential loss, and do not directly modulate voltage-dependent anion channel activity
Authors: Shimizu Shigeomi , Tsujimoto Yoshihide
Published: July 2002

Through direct interaction with the voltage-dependent anion channel (VDAC), proapoptotic Bcl-2 family members such as Bax and Bak induce apoptogenic mitochondrial cytochromecrelease and membrane potential (Δψ) loss in isolated mitochondria. Using isolated mitochondria, we showed that Bid and Bik, BH3-only proteins from the Bcl-2 family, induced cytochromecrelease but not Δψ loss. Unlike Bax/Bak, the cytochromecrelease induced by Bid/Bik was Ca2+-independent, cyclosporin A-insensitive, and respiration-independent. Furthermore, in contrast to Bax/Bak, Bid/Bik neither interacted with VDAC nor directly affected the VDAC activity in liposomes. Consistently, Bid/Bik induced apoptosis without Δψ loss, whereas Bax induced apoptosis with Δψ loss. These findings indicated the involvement of a different mechanism in BH3-only, protein-induced apoptogenic cytochromecrelease.
Cationic microparticles: A potent delivery system for DNA vaccines
Authors: Singh Manmohan , Briones Maylene , Ott Gary , O'Hagan Derek
Published: July 2002

An approach involving the preparation of biodegradable microparticles with a cationic surface was developed to improve the delivery of adsorbed DNA into antigen-presenting cells after i.m. injection. The microparticles released intact and functional DNA over 2 weeks
in vitro
. In addition, the microparticles induced higher levels of marker gene expression
in vivo
. After i.m. immunization, the microparticles induced significantly enhanced serum antibody responses in comparison to naked DNA. Moreover, the level of antibodies induced by the microparticles was significantly enhanced by the addition of a vaccine adjuvant, aluminum phosphate. In addition, in contrast to naked DNA, the cationic microparticles induced potent cytotoxic T lymphocyte responses at a low dose.
Monolayers of derivatized poly(
l
-lysine)-grafted poly(ethylene glycol) on metal oxides as a class of biomolecular interfaces
Authors: Ruiz-Taylor L. A. , Martin T. L. , Zaugg F. G. , Witte K. , Indermuhle P. , Nock S. , Wagner P.
Published: July 2002

We report on the design and characterization of a class of
biomolecular interfaces based on derivatized
poly(
l
-lysine)-grafted poly(ethylene glycol) copolymers
adsorbed on negatively charged surfaces. As a model system, we
synthesized biotin-derivatized poly(
l
-lysine)-grafted
poly(ethylene glycol) copolymers, PLL-g-[(PEGm)
(1−x)
(PEG-biotin)

x

], where
x
varies
from 0 to 1. Monolayers were produced on titanium dioxide substrates
and characterized by x-ray photoelectron spectroscopy. The specific
biorecognition properties of these biotinylated surfaces were
investigated with the use of radiolabeled streptavidin alone and within
complex protein mixtures. The PLL-g-PEG-biotin monolayers specifically
capture streptavidin, even from a complex protein mixture, while still
preventing nonspecific adsorption of other proteins. This streptavidin
layer can subsequently capture biotinylated proteins. Finally,
with the use of microfluidic networks and protein arraying, we
demonstrate the potential of this class of biomolecular interfaces for
applications based on protein patterning.
Culture and Conflict
Authors: Triandis Harry C.
Published: July 2002

Members of different cultures sample with diverse probabilities different kinds of information from their environment. Some sample the content of communications more than the context (e.g. tone of voice, gestures), whereas others do the reverse. Some sample processes internal to individuals (e.g. attitudes, beliefs) whereas others sample processes external to individuals (e.g. social influences, roles) with higher probabilities. Some give greater weights to ascribed attributes of persons, such as ethnicity, race, religion, and others to achieved attributes, such as beliefs, attitudes, or a record of achievements. These differences have profound implications for the probability of conflict and the type of conflict that will develop between individuals and groups.
Prague PEN and Central European Cultural Nationalism, 1924–1935
Authors: Orzoff Andrea
Published: July 2002

In “Our Guests and Ourselves,” an article written in 1924 for the Prague daily newspaperLidové noviny, Czech playwright and novelist Karelclarified for his readers the failings in Czech habits of sociability, and the unfortunate consequences of those habits for the new Czechoslovak nation. Each nationality in Prague, and each political grouping within the nationalities, tended to socialize in different clubs and cafes. The Czechs preferred to socialize only with each other, complained, and foreigners visiting Prague tended to socialize with Germans. When Czechs set themselves the task of entertaining visiting foreigners, they did so in a manner overly officious and overtly “national”: that is, Czechs dragged foreigners around from function to banquet, forcing them to listen endlessly to official pronouncements of the glories of the long-overlooked Czech nation. As yet,wrote, Prague lacked a single genuinely neutral club or grouping open to all, and comfortable for all, particularly foreigners, whom the Czechs needed badly to impress. In contrast,told his readers, he himself had just visited the kind of club the Czechs should create: the “Penklub”, in London. In the International Pen Club's London chapter, writers of different nationalities were able to enjoy one another's company, and perhaps develop a greater understanding for other countries' perspectives. The club's existence demonstrated that even England, one of the historical great powers of Europe, put great weight on creating international ties.reminded his readers that “we here have more, and more urgent, reasons for needing such [clubs].” Those “more urgent” reasons for changing Czech habits were first and foremost political reasons, in an age when sociability was politicized—and, as's comments make clear, nationalized.
Gender differences in older adults’ everyday cognitive collaboration
Authors: Margrett Jennifer A. , Marsiske Michael
Published: July 2002

Collaborative cognition research has demonstrated that social partners can positively impact individuals’ thinking and problem-solving performance. Research in adulthood and aging has been less clear about dyadic effects, such as partner gender, on collaborative cognition. The current study examined the objective and subjective experiences of older men and women’s collaboration on three everyday problems. Tasks included comprehension of everyday printed materials, a social dilemma task, and an errand-planning task. A sample of 98 older married couples ( N = 196) worked both collaboratively and individually with either their spouse ( N = 52 dyads) or a stranger of the other gender ( N = 46 dyads). Analyses conducted using the actor-partner methodology (e.g., Gonzalez & Griffin, 1997; Kenny, 1996) suggest that men tended to be more influential during dyadic problem solving, particularly on more ambiguous tasks. Subjective appraisals of collaboration also varied between male and female partners, with familiarity of partner playing a large role in expectations of collaboration. Most notably, women assigned to work with an unfamiliar male partner tended to rate their satisfaction with collaborative teamwork less positively. Both self and partner-rated subjective appraisals, particularly expectations of competitiveness, were predictive of collaborative performance.
Expression of Matrix Metalloproteinases during Rat Skin Wound Healing: Evidence that Membrane Type-1 Matrix Metalloproteinase Is a Stromal Activator of Pro-Gelatinase A
Authors: Okada Akiko , Tomasetto Catherine , Lutz Yves , Bellocq Jean-Pierre , Rio Marie-Christine , Basset Paul
Published: July 2002

Skin wound healing depends on cell migration and extracellular matrix remodeling. Both processes, which are necessary for reepithelization and restoration of the underlying connective tissue, are believed to involve the action of extracellular proteinases. We screened cDNA libraries and we found that six matrix metalloproteinase genes were highly expressed during rat skin wound healing. They were namely those of stromelysin 1, stromelysin 3, collagenase 3, gelatinase A (GelA), gelatinase B, and membrane type-1 matrix metalloproteinase (MT1-MMP). The expression kinetics of these MMP genes, the tissue distribution of their transcripts, the results of cotransfection experiments in COS-1 cells, and zymographic analyses performed using microdissected rat wound tissues support the possibility that during cutaneous wound healing pro-GelA and pro-gelatinase B are activated by MT1-MMP and stromelysin 1, respectively. Since MT1-MMP has been demonstrated to be a membrane-associated protein (Sato, H., T. Takino, Y. Okada, J. Cao, A. Shinagawa, E. Yamamoto, and M. Seiki. 1994. Nature (Lond.). 370: 61–65), our finding that GelA and MT1-MMP transcripts were expressed in stromal cells exhibiting a similar tissue distribution suggests that MT1-MMP activates pro-GelA at the stromal cell surface. This possibility is further supported by our observation that the processing of proGelA to its mature form correlated to the detection of MT1-MMP in cell membranes of rat fibroblasts expressing the MT1-MMP and GelA genes. These observations, together with the detection of high levels of the mature GelA form in the granulation tissue but not in the regenerating epidermis, suggest that MT1-MMP and GelA contribute to the restoration of connective tissue during rat skin wound healing.
The Membrane Transport Factor TAP/p115 Cycles between the Golgi and Earlier Secretory Compartments and Contains Distinct Domains Required for Its Localization and Function
Authors: Nelson David S. , Alvarez Cecilia , Gao Ya-sheng , García-Mata Rafael , Fialkowski Elizabeth , Sztul Elizabeth
Published: July 2002

The mammalian protein TAP/p115 and its yeast homologue Uso1p have an essential role in membrane traffic (Nakajima et al., 1991; Waters et al., 1992; Sztul et al., 1993; Rabouille et al., 1995). To inquire into the site and mechanism of TAP/p115 action, we aimed to localize it and to identify domains required for its function. We show that in interphase cells, TAP/p115 localizes predominantly to the Golgi and to peripheral structures that represent vesicular tubular clusters (VTCs) involved in ER to Golgi transport. Using BFA/ nocodazole treatments we confirm that TAP/p115 is present on ER to Golgi transport intermediates. TAP/ p115 redistributes to peripheral structures containing ERGIC-53 during a 15°C treatment, suggesting that it is a cycling protein. Within the Golgi, TAP/p115 is associated with pleiomorphic structures on the cis side of the cis-Golgi cisterna and the cis-most cisterna, but is not detected in more distal compartments of the Golgi.

TAP/p115 binds the cis-Golgi protein GM130, and the COOH-terminal acidic domain of TAP/p115 is required for this interaction. TAP/p115 interaction with GM130 occurs only in the Golgi and is not required for TAP/p115 association with peripheral VTCs. To examine whether interaction with GM130 is required to recruit TAP/p115 to the Golgi, TAP/p115 mutants lacking the acidic domain were expressed and localized in transfected cells. Mutants lacking the GM130-binding domain showed normal Golgi localization, indicating that TAP/p115 is recruited to the Golgi independently of its ability to bind GM130. Such mutants were also able to associate with peripheral VTCs. Interestingly, TAP/p115 mutants containing the GM130-binding domain but lacking portions of the NH2-terminal region were restricted from the Golgi and localized to the ER. The COOH-terminal domain required for GM130 binding and the NH2-terminal region required for Golgi localization appear functionally relevant since expression of TAP/p115 mutants lacking either of these domains leads to loss of normal Golgi morphology.
Functional Domains of α-Catenin Required for the Strong State of Cadherin-based Cell Adhesion
Authors: Imamura Yuzo , Itoh Masahiko , Maeno Yoshito , Tsukita Shoichiro , Nagafuchi Akira
Published: July 2002

The interaction of cadherin–catenin complex with the actin-based cytoskeleton through α-catenin is indispensable for cadherin-based cell adhesion activity. We reported previously that E-cadherin–α-catenin fusion molecules showed cell adhesion and cytoskeleton binding activities when expressed in nonepithelial L cells. Here, we constructed deletion mutants of E-cadherin–α-catenin fusion molecules lacking various domains of α-catenin and introduced them into L cells. Detailed analysis identified three distinct functional domains of α-catenin: a vinculin/α-actinin-binding domain, a ZO-1-binding domain, and an adhesion-modulation domain. Furthermore, cell dissociation assay revealed that the fusion molecules containing the ZO-1-binding domain in addition to the adhesion-modulation domain conferred the strong state of cell adhesion activity on transfectants, although those lacking the ZO-1-binding domain conferred only the weak state. The disorganization of actin-based cytoskeleton by cytochalasin D treatment shifted the cadherin-based cell adhesion from the strong to the weak state. In the epithelial cells, where α-catenin was not precisely colocalized with ZO-1, the ZO-1-binding domain did not completely support the strong state of cell adhesion activity. Our studies showed that the interaction of α-catenin with the actin-based cytoskeleton through the ZO-1-binding domain is required for the strong state of E-cadherin–based cell adhesion activity.
Airway Epithelial Cell Migration Dynamics: MMP-9 Role in Cell–Extracellular Matrix Remodeling
Authors: Legrand Claire , Gilles Christine , Zahm Jean-Marie , Polette Myriam , Buisson Anne-Cécile , Kaplan Hervé , Birembaut Philippe , Tournier Jean-Marie
Published: July 2002

Cell spreading and migration associated with the expression of the 92-kD gelatinase (matrix metalloproteinase 9 or MMP-9) are important mechanisms involved in the repair of the respiratory epithelium. We investigated the location of MMP-9 and its potential role in migrating human bronchial epithelial cells (HBEC). In vivo and in vitro, MMP-9 accumulated in migrating HBEC located at the leading edge of a wound and MMP-9 expression paralleled cell migration speed. MMP-9 accumulated through an actin-dependent pathway in the advancing lamellipodia of migrating cells and was subsequently found active in the extracellular matrix (ECM). Lamellipodia became anchored through primordial contacts established with type IV collagen. MMP-9 became amassed behind collagen IV where there were fewer cell–ECM contacts. Both collagen IV and MMP-9 were involved in cell migration because when cell–collagen IV interaction was blocked, cells spread slightly but did not migrate; and when MMP-9 activation was prevented, cells remained fixed on primordial contacts and did not advance at all. These observations suggest that MMP-9 controls the migration of repairing HBEC by remodeling the provisional ECM implicated in primordial contacts.
Tissue Transglutaminase Is an Integrin-Binding Adhesion Coreceptor for Fibronectin
Authors: Akimov Sergey S. , Krylov Dmitry , Fleischman Laurie F. , Belkin Alexey M.
Published: July 2002

The protein cross-linking enzyme tissue transglutaminase binds in vitro with high affinity to fibronectin via its 42-kD gelatin-binding domain. Here we report that cell surface transglutaminase mediates adhesion and spreading of cells on the 42-kD fibronectin fragment, which lacks integrin-binding motifs. Overexpression of tissue transglutaminase increases its amount on the cell surface, enhances adhesion and spreading on fibronectin and its 42-kD fragment, enlarges focal adhesions, and amplifies adhesion-dependent phosphorylation of focal adhesion kinase. These effects are specific for tissue transglutaminase and are not shared by its functional homologue, a catalytic subunit of factor XIII. Adhesive function of tissue transglutaminase does not require its cross-linking activity but depends on its stable noncovalent association with integrins. Transglutaminase interacts directly with multiple integrins of β1 and β3 subfamilies, but not with β2 integrins. Complexes of transglutaminase with integrins are formed inside the cell during biosynthesis and accumulate on the surface and in focal adhesions. Together our results demonstrate that tissue transglutaminase mediates the interaction of integrins with fibronectin, thereby acting as an integrin-associated coreceptor to promote cell adhesion and spreading.
Synaptotagmin VII Regulates Ca2+-Dependent Exocytosis of Lysosomes in Fibroblasts
Authors: Martinez Iñigo , Chakrabarti Sabyasachi , Hellevik Turid , Morehead Jennifer , Fowler Kimberly , Andrews Norma W.
Published: July 2002

Synaptotagmins (Syts) are transmembrane proteins with two Ca2+-binding C2 domains in their cytosolic region. Syt I, the most widely studied isoform, has been proposed to function as a Ca2+ sensor in synaptic vesicle exocytosis. Several of the twelve known Syts are expressed primarily in brain, while a few are ubiquitous (Sudhof, T.C., and J. Rizo. 1996. Neuron. 17: 379–388; Butz, S., R. Fernandez-Chacon, F. Schmitz, R. Jahn, and T.C. Sudhof. 1999. J. Biol. Chem. 274:18290–18296). The ubiquitously expressed Syt VII binds syntaxin at free Ca2+ concentrations ([Ca2+]) below 10 μM, whereas other isoforms require 200–500 μM [Ca2+] or show no Ca2+-dependent syntaxin binding (Li, C., B. Ullrich, Z. Zhang, R.G.W. Anderson, N. Brose, and T.C. Sudhof. 1995. Nature. 375:594–599). We investigated the involvement of Syt VII in the exocytosis of lysosomes, which is triggered in several cell types at 1–5 μM [Ca2+] (Rodríguez, A., P. Webster, J. Ortego, and N.W. Andrews. 1997. J. Cell Biol. 137:93–104). Here, we show that Syt VII is localized on dense lysosomes in normal rat kidney (NRK) fibroblasts, and that GFP-tagged Syt VII is targeted to lysosomes after transfection. Recombinant fragments containing the C2A domain of Syt VII inhibit Ca2+-triggered secretion of β-hexosaminidase and surface translocation of Lgp120, whereas the C2A domain of the neuronal- specific isoform, Syt I, has no effect. Antibodies against the Syt VII C2A domain are also inhibitory in both assays, indicating that Syt VII plays a key role in the regulation of Ca2+-dependent lysosome exocytosis.
Activated R-Ras, Rac1, Pi 3-Kinase and Pkcε Can Each Restore Cell Spreading Inhibited by Isolated Integrin β1 Cytoplasmic Domains
Authors: Berrier Allison L. , Mastrangelo Anthony M. , Downward Julian , Ginsberg Mark , LaFlamme Susan E.
Published: July 2002

Attachment of many cell types to extracellular matrix proteins triggers cell spreading, a process that strengthens cell adhesion and is a prerequisite for many adhesion-dependent processes including cell migration, survival, and proliferation. Cell spreading requires integrins with intact β cytoplasmic domains, presumably to connect integrins with the actin cytoskeleton and to activate signaling pathways that promote cell spreading. Several signaling proteins are known to regulate cell spreading, including R-Ras, PI 3-kinase, PKCε and Rac1; however, it is not known whether they do so through a mechanism involving integrin β cytoplasmic domains. To study the mechanisms whereby cell spreading is regulated by integrin β cytoplasmic domains, we inhibited cell spreading on collagen I or fibrinogen by expressing tac-β1, a dominant-negative inhibitor of integrin function, and examined whether cell spreading could be restored by the coexpression of either V38R-Ras, p110α-CAAX, myr-PKCε, or L61Rac1. Each of these activated signaling proteins was able to restore cell spreading as assayed by an increase in the area of cells expressing tac-β1. R-Ras and Rac1 rescued cell spreading in a GTP-dependent manner, whereas PKCε required an intact kinase domain. Importantly, each of these signaling proteins required intact β cytoplasmic domains on the integrins mediating adhesion in order to restore cell spreading. In addition, the rescue of cell spreading by V38R-Ras was inhibited by LY294002, suggesting that PI 3-kinase activity is required for V38R-Ras to restore cell spreading. In contrast, L61Rac1 and myr-PKCε each increased cell spreading independent of PI 3-kinase activity. Additionally, the dominant-negative mutant of Rac1, N17Rac1, abrogated cell spreading and inhibited the ability of p110α-CAAX and myr-PKCε to increase cell spreading. These studies suggest that R-Ras, PI 3-kinase, Rac1 and PKCε require the function of integrin β cytoplasmic domains to regulate cell spreading and that Rac1 is downstream of PI 3-kinase and PKCε in a pathway involving integrin β cytoplasmic domain function in cell spreading.
Loss of Calpain 3 Proteolytic Activity Leads to Muscular Dystrophy and to Apoptosis-Associated Iκbα/Nuclear Factor κb Pathway Perturbation in Mice
Authors: Richard Isabelle , Roudaut Carinne , Marchand Sylvie , Baghdiguian Stephen , Herasse Muriel , Stockholm Daniel , Ono Yasuko , Suel Laurence , Bourg Nathalie , Sorimachi Hiroyuki , Lefranc Gérard , Fardeau Michel , Sébille Alain , Beckmann Jacques S.
Published: July 2002

Calpain 3 is known as the skeletal muscle–specific member of the calpains, a family of intracellular nonlysosomal cysteine proteases. It was previously shown that defects in the human calpain 3 gene are responsible for limb girdle muscular dystrophy type 2A (LGMD2A), an inherited disease affecting predominantly the proximal limb muscles. To better understand the function of calpain 3 and the pathophysiological mechanisms of LGMD2A and also to develop an adequate model for therapy research, we generated capn3-deficient mice by gene targeting. capn3-deficient mice are fully fertile and viable. Allele transmission in intercross progeny demonstrated a statistically significant departure from Mendel's law. capn3-deficient mice show a mild progressive muscular dystrophy that affects a specific group of muscles. The age of appearance of myopathic features varies with the genetic background, suggesting the involvement of modifier genes. Affected muscles manifest a similar apoptosis-associated perturbation of the IκBα/nuclear factor κB pathway as seen in LGMD2A patients. In addition, Evans blue staining of muscle fibers reveals that the pathological process due to calpain 3 deficiency is associated with membrane alterations.
The Macrophage Scavenger Receptor Type A Is Expressed by Activated Macrophages and Protects the Host Against Lethal Endotoxic Shock
Authors: Haworth Richard , Platt Nick , Keshav Satish , Hughes Derralynn , Darley Elisabeth , Suzuki Hiroshi , Kurihara Yukiko , Kodama Tatsuhiko , Gordon Siamon
Published: July 2002

During gram-negative bacterial infections, lipopolysaccharide (LPS) stimulates primed macrophages (Mφ) to release inflammatory mediators such as tumor necrosis factor (TNF)-α, which can cause hypotension, organ failure, and often death. Several different receptors on Mφ have been shown to bind LPS, including the type A scavenger receptor (SR-A). This receptor is able to bind a broad range of polyanionic ligands such as modified lipoproteins and lipoteichoic acid of gram-positive bacteria, which suggests that SR-A plays a role in host defense. In this study, we used mice lacking the SR-A (SRKO) to investigate the role of SR-A in acquired immunity using a viable bacillus Calmette Guérin (BCG) infection model. We show that activated Mφ express SR-A and that this molecule is functional in assays of adhesion and endocytic uptake. After BCG infection, SRKO mice are able to recruit Mφ to sites of granuloma formation where they become activated and restrict BCG replication. However, infected mice lacking the SR-A are more susceptible to endotoxic shock and produce more TNF-α and interleukin-6 in response to LPS. In addition, we show that an antibody which blocks TNF-α activity reduces LPS-induced mortality in these mice. Thus SR-A, expressed by activated Mφ, plays a protective role in host defense by scavenging LPS as well as by reducing the release by activated Mφ of proinflammatory cytokines. Modulation of SR-A may provide a novel therapeutic approach to control endotoxic shock.
The Transcription Factor Interferon Regulatory Factor 1 Is Expressed after Cerebral Ischemia and Contributes to Ischemic Brain Injury
Authors: Iadecola Costantino , Salkowski Cindy A. , Zhang Fangyi , Aber Tracy , Nagayama Masao , Vogel Stefanie N. , Elizabeth Ross M.
Published: July 2002

The transcription factor interferon regulatory factor 1 (IRF-1) is involved in the molecular mechanisms of inflammation and apoptosis, processes that contribute to ischemic brain injury. In this study, the induction of IRF-1 in response to cerebral ischemia and its role in ischemic brain injury were investigated. IRF-1 gene expression was markedly upregulated within 12 h of occlusion of the middle cerebral artery in C57BL/6 mice. The expression reached a peak 4 d after ischemia (6.0 ± 1.8-fold; P < 0.001) and was restricted to the ischemic regions of the brain. The volume of ischemic injury was reduced by 23 ± 3% in IRF-1+/− and by 46 ± 9% in IRF-1−/− mice (P < 0.05). The reduction in infarct volume was paralleled by a substantial attenuation in neurological deficits. Thus, IRF-1 is the first nuclear transacting factor demonstrated to contribute directly to cerebral ischemic damage and may be a novel therapeutic target in ischemic stroke.
Induction of Lymphocyte Apoptosis by Tumor Cell Secretion of FasL-bearing Microvesicles
Authors: Andreola Giovanna , Rivoltini Licia , Castelli Chiara , Huber Veronica , Perego Paola , Deho Paola , Squarcina Paola , Accornero Paola , Lozupone Francesco , Lugini Luana , Stringaro Annarita , Molinari Agnese , Arancia Giuseppe , Gentile Massimo , Parmiani Giorgio , Fais Stefano
Published: July 2002

The hypothesis that FasL expression by tumor cells may impair the in vivo efficacy of antitumor immune responses, through a mechanism known as ‘Fas tumor counterattack,’ has been recently questioned, becoming the object of an intense debate based on conflicting results. Here we definitely show that FasL is indeed detectable in the cytoplasm of melanoma cells and its expression is confined to multivesicular bodies that contain melanosomes. In these structures FasL colocalizes with both melanosomal (i.e., gp100) and lysosomal (i.e., CD63) antigens. Isolated melanosomes express FasL, as detected by Western blot and cytofluorimetry, and they can exert Fas-mediated apoptosis in Jurkat cells. We additionally show that melanosome-containing multivesicular bodies degranulate extracellularly and release FasL-bearing microvesicles, that coexpress both gp100 and CD63 and retain their functional activity in triggering Fas-dependent apoptosis of lymphoid cells. Hence our data provide evidence for a novel mechanism potentially operating in Fas tumor counterattack through the secretion of subcellular particles expressing functional FasL. Such vesicles may form a sort of front line hindering lymphocytes and other immunocompetent cells from entering neoplastic lesions and exert their antitumor activity.
Toll-like Receptor 4 Resides in the Golgi Apparatus and Colocalizes with Internalized Lipopolysaccharide in Intestinal Epithelial Cells
Authors: Hornef Mathias W. , Frisan Teresa , Vandewalle Alain , Normark Staffan , Richter-Dahlfors Agneta
Published: July 2002

Toll-like receptor (TLR) 4 is mainly found on cells of the myelopoietic lineage. It recognizes lipopolysaccharide (LPS) and mediates cellular activation and production of proinflammatory cytokines. Less is known about the distribution and role of TLR4 in epithelial cells that are continuously exposed to microbes and microbial products. Here we show that the murine small intestinal epithelial cell line m-ICcl2 is highly responsive to LPS and expresses both CD14 and TLR4. Transcription and surface membrane staining for CD14 were up-regulated upon LPS exposure. Surprisingly, TLR4 immunostaining revealed a strictly cytoplasmic paranuclear distribution. This paranuclear compartment could be identified as the Golgi apparatus. LPS added to the supernatant was internalized by m-ICcl2 cells and colocalized with TLR4. Continuous exposure to LPS led to a tolerant phenotype but did not alter TLR4 expression nor cellular distribution. Thus, intestinal epithelial cells might be able to provide the initial proinflammatory signal to attract professional immune cells to the side of infection. The cytoplasmic location of TLR4, which is identical to the final location of internalized LPS, further indicates an important role of cellular internalization and cytoplasmic traffic in the process of innate immune recognition.
Natural Killer T Cell Ligand α-Galactosylceramide Enhances Protective Immunity Induced by Malaria Vaccines
Authors: Gonzalez-Aseguinolaza Gloria , Van Kaer Luc , Bergmann Cornelia C. , Wilson James M. , Schmieg John , Kronenberg Mitchell , Nakayama Toshinori , Taniguchi Masaru , Koezuka Yasuhiko , Tsuji Moriya
Published: July 2002

The important role played by CD8+ T lymphocytes in the control of parasitic and viral infections, as well as tumor development, has raised the need for the development of adjuvants capable of enhancing cell-mediated immunity. It is well established that protective immunity against liver stages of malaria parasites is primarily mediated by CD8+ T cells in mice. Activation of natural killer T (NKT) cells by the glycolipid ligand, α-galactosylceramide (α-GalCer), causes bystander activation of NK, B, CD4+, and CD8+ T cells. Our study shows that coadministration of α-GalCer with suboptimal doses of irradiated sporozoites or recombinant viruses expressing a malaria antigen greatly enhances the level of protective anti-malaria immunity in mice. We also show that coadministration of α-GalCer with various different immunogens strongly enhances antigen-specific CD8+ T cell responses, and to a lesser degree, Th1-type responses. The adjuvant effects of α-GalCer require CD1d molecules, Vα14 NKT cells, and interferon γ. As α-GalCer stimulates both human and murine NKT cells, these findings should contribute to the design of more effective vaccines against malaria and other intracellular pathogens, as well as tumors.
Effects of Partial Sarcoplasmic Reticulum Calcium Depletion on Calcium Release in Frog Cut Muscle Fibers Equilibrated with 20 mM EGTA
Authors: Pape Paul C. , Jong De-Shien , Knox Chandler W.
Published: July 2002

Resting sarcoplasmic reticulum (SR) Ca content ([CaSR]R) was varied in cut fibers equilibrated with an internal solution that contained 20 mM EGTA and 0–1.76 mM Ca. SR Ca release and [CaSR]R were measured with the EGTA–phenol red method (Pape et al. 1995. J. Gen. Physiol. 106:259–336). After an action potential, the fractional amount of Ca released from the SR increased from 0.17 to 0.50 when [CaSR]R was reduced from 1,200 to 140 μM. This increase was associated with a prolongation of release (final time constant, from 1–2 to 10–15 ms) and of the action potential (by 1–2 ms). Similar changes in release were observed with brief stimulations to −20 mV in voltage-clamped fibers, in which charge movement (Qcm) could be measured. The peak values of Qcm and the fractional rate of SR Ca release, as well as their ON time courses, were little affected by reducing [CaSR]R from 1,200 to 140 μM. After repolarization, however, the OFF time courses of Qcm and the rate of SR Ca release were slowed by factors of 1.5–1.7 and 6.5, respectively. These and other results suggest that, after action potential stimulation of fibers in normal physiological condition, the increase in myoplasmic free [Ca] that accompanies SR Ca release exerts three negative feedback effects that tend to reduce additional release: (a) the action potential is shortened by current through Ca-activated potassium channels in the surface and/or tubular membranes; (b) the OFF kinetics of Qcm is accelerated; and (c) Ca inactivation of Ca release is increased. Some of these effects of Ca on an SR Ca channel or its voltage sensor appear to be regulated by the value of [Ca] within 22 nm of the mouth of the channel.
Quadratic forms for the 1-D semilinear Schrödinger equation
Authors: Kenig Carlos , Ponce Gustavo , Vega Luis
Published: July 2002

This paper is concerned with 1-D quadratic semilinear Schrödinger equations. We study local well posedness in classical Sobolev space

H
s

H^s

of the associated initial value problem and periodic boundary value problem. Our main interest is to obtain the lowest value of

s
s

which guarantees the desired local well posedness result. We prove that at least for the quadratic cases these values are negative and depend on the structure of the nonlinearity considered.
Equivalent formulae for the supremum and stability of weighted pseudoinverses
Authors: Wei Musheng
Published: July 2002

During recent decades, there have been a great number of research articles studying interior-point methods for solving problems in mathematical programming and constrained optimization. Stewart and O’Leary obtained an upper bound for scaled pseudoinverses
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="sup Underscript upper W element-of script upper P Endscripts double-vertical-bar left-parenthesis upper W Superscript one half Baseline upper X right-parenthesis Superscript plus Baseline upper W Superscript one half Baseline double-vertical-bar Subscript 2">

sup

W
∈

P

‖
(

W

1
2

X

)

+

W

1
2

‖

2

\underset {W\in \mathcal {P} }{\text {sup}}\|(W^{\frac {1}{2}}X)^{+}W^{\frac {1}{2}}\|_{2}

of a matrix

X
X

where

P

\mathcal {P}

is a set of diagonal positive definite matrices. We improved their results to obtain the supremum of scaled pseudoinverses and derived the stability property of scaled pseudoinverses. Forsgren further generalized these results to derive the supremum of weighted pseudoinverses
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="sup Underscript upper W element-of script upper P Endscripts double-vertical-bar left-parenthesis upper W Superscript one half Baseline upper X right-parenthesis Superscript plus Baseline upper W Superscript one half Baseline double-vertical-bar Subscript 2">

sup

W
∈

P

‖
(

W

1
2

X

)

+

W

1
2

‖

2

\underset {W\in \mathcal {P} }{\text {sup}}\|(W^{\frac {1}{2}}X)^{+}W^{\frac {1}{2}}\|_{2}

where

P

\mathcal {P}

is a set of diagonally dominant positive semidefinite matrices, by using a signature decomposition of weighting matrices

W
W

and by applying the Binet-Cauchy formula and Cramer’s rule for determinants. The results are also extended to equality constrained linear least squares problems. In this paper we extend Forsgren’s results to a general complex matrix

X
X

to establish several equivalent formulae for
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="sup Underscript upper W element-of script upper P Endscripts double-vertical-bar left-parenthesis upper W Superscript one half Baseline upper X right-parenthesis Superscript plus Baseline upper W Superscript one half Baseline double-vertical-bar Subscript 2">

sup

W
∈

P

‖
(

W

1
2

X

)

+

W

1
2

‖

2

\underset {W\in \mathcal {P} }{\text {sup}}\|(W^{\frac {1}{2}}X)^{+}W^{\frac {1}{2}}\|_{2}

, where

P

\mathcal {P}

is a set of diagonally dominant positive semidefinite matrices, or a set of weighting matrices arising from solving equality constrained least squares problems. We also discuss the stability property of these weighted pseudoinverses.
Multilevel additive Schwarz method for the ℎ-𝑝 version of the Galerkin boundary element method
Authors: Heuer Norbert , Stephan Ernst , Tran Thanh
Published: July 2002

We study a multilevel additive Schwarz method for the

h
h

-

p
p

version of the Galerkin boundary element method with geometrically graded meshes. Both hypersingular and weakly singular integral equations of the first kind are considered. As it is well known the

h
h

-

p
p

version with geometric meshes converges exponentially fast in the energy norm. However, the condition number of the Galerkin matrix in this case blows up exponentially in the number of unknowns

M
M

. We prove that the condition number

κ
(
P
)

\kappa (P)

of the multilevel additive Schwarz operator behaves like

O
(

M

log
2

⁡
M
)

O(\sqrt {M}\log ^2M)

. As a direct consequence of this we also give the results for the

2
2

-level preconditioner and also for the

h
h

-

p
p

version with quasi-uniform meshes. Numerical results supporting our theory are presented.
The 𝑘^{𝑡ℎ} prime is greater than 𝑘(ln𝑘+lnln𝑘-1) for 𝑘≥2
Authors: Dusart Pierre
Published: July 2002

Rosser and Schoenfeld have used the fact that the first 3,500,000 zeros of the Riemann zeta function lie on the critical line to give estimates on

ψ
(
x
)

\psi (x)

and

θ
(
x
)

\theta (x)

. With an improvement of the above result by Brent et al., we are able to improve these estimates and to show that the

k

t
h

k^{th}

prime is greater than

k
(
ln
⁡
k
+
ln
⁡
ln
⁡
k
−
1
)

k(\ln k +\ln \ln k -1)

for

k
≥
2

k\geq 2

. We give further results without proof.
Symbolic dynamics and Markov partitions
Authors: Adler Roy
Published: July 2002

The decimal expansion of real numbers, familiar to us all, has a dramatic generalization to representation of dynamical system orbits by symbolic sequences. The natural way to associate a symbolic sequence with an orbit is to track its history through a partition. But in order to get a useful symbolism, one needs to construct a partition with special properties. In this work we develop a general theory of representing dynamical systems by symbolic systems by means of so-called Markov partitions. We apply the results to one of the more tractable examples: namely, hyperbolic automorphisms of the two dimensional torus. While there are some results in higher dimensions, this area remains a fertile one for research.
On positive entire solutions to the Yamabe-type problem on the Heisenberg and stratified groups
Authors: Lu Guozhen , Wei Juncheng
Published: July 2002

Let

G

\mathbb {G}

be a nilpotent, stratified homogeneous group, and let

X

1

X_{1}

, …,

X

m

X_{m}

be left invariant vector fields generating the Lie algebra

G

\mathcal {G}

associated to

G

\mathbb {G}

. The main goal of this paper is to study the Yamabe type equations associated with the sub-Laplacian

Δ

G

=

∑

k
=
1

m

X
k
2

(
x
)

\Delta _{\mathbb {G}} = \sum _{k=1}^m X_k^2(x)

on

G

\mathbb {G}

:
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartLayout 1st Row with Label left-parenthesis asterisk right-parenthesis EndLabel normal upper Delta Subscript double-struck upper G Baseline u plus upper K left-parenthesis x right-parenthesis u Superscript p Baseline equals 0 period EndLayout">

(*)

Δ

G

u
+
K
(
x
)

u

p

=
0.

\begin{equation}\tag {*} \Delta _{\mathbb {G}} u+K(x)u^{p}=0. \end{equation}

Especially, we will establish the existence, nonexistence and asymptotic behavior of positive solutions to (

∗
*

). Our results include the Yamabe type problem on the Heisenberg group as a special case, which is of particular importance and interest and also appears to be new even in this case.
Localization of Large ADP-Ribosylation Factor-Guanine Nucleotide Exchange Factors to Different Golgi Compartments: Evidence for Distinct Functions in Protein Traffic
Authors: Zhao Xinhua , Lasell Troy K.R. , Melancİon Paul
Published: July 2002

Activation of several ADP-ribosylation factors (ARFs) by guanine nucleotide exchange factors (GEFs) regulates recruitment of coat proteins (COPs) on the Golgi complex and is generally assumed to be the target of brefeldin A (BFA). The large ARF-GEFs Golgi-specific BFA resistance factor 1 (GBF1) and BFA-inhibited GEFs (BIGs) localize to this organelle but catalyze exchange preferentially on class II and class I ARFs, respectively. We now demonstrate using quantitative confocal microscopy that these GEFs show a very limited overlap with each other (15 and 23%). In contrast, GBF1 colocalizes with the cis-marker p115 (86%), whereas BIGs overlap extensively with TGN38 (83%). Consistent with these distributions, GBF1, but not BIG1, partially relocalized to peripheral sites after incubation at 15°C. The new GBF1 structures represent peripheral vesicular tubular clusters (VTCs) because 88% of structures analyzed stained for both GBF1 and p115. Furthermore, as expected of VTCs, they rapidly reclustered to the Golgi complex in a microtubule-dependent manner upon warm-up. These observations suggest that GBF1 and BIGs activate distinct subclasses of ARFs in specific locations to regulate different types of reactions. In agreement with this possibility, COPI overlapped to a greater extent with GBF1 (64%) than BIG1 (31%), whereas clathrin showed limited overlap with BIG1, and virtually none with GBF1.