bluuebunny/crossref_metadata_2025 huggingface dataset:
Homologous Chromosome Pairing in Drosophila melanogaster Proceeds through Multiple Independent Initiations
Authors: Fung Jennifer C. , Marshall Wallace F. , Dernburg Abby , Agard David A. , Sedat John W.
Published: July 2002

The dynamics by which homologous chromosomes pair is currently unknown. Here, we use fluorescence in situ hybridization in combination with three-dimensional optical microscopy to show that homologous pairing of the somatic chromosome arm 2L in Drosophila occurs by independent initiation of pairing at discrete loci rather than by a processive zippering of sites along the length of chromosome. By evaluating the pairing frequencies of 11 loci on chromosome arm 2L over several timepoints during Drosophila embryonic development, we show that all 11 loci are paired very early in Drosophila development, within 13 h after egg deposition. To elucidate whether such pairing occurs by directed or undirected motion, we analyzed the pairing kinetics of histone loci during nuclear cycle 14. By measuring changes of nuclear length and correlating these changes with progression of time during cycle 14, we were able to express the pairing frequency and distance between homologous loci as a function of time. Comparing the experimentally determined dynamics of pairing to simulations based on previously proposed models of pairing motion, we show that the observed pairing kinetics are most consistent with a constrained random walk model and not consistent with a directed motion model. Thus, we conclude that simple random contacts through diffusion could suffice to allow pairing of homologous sites.
Coordination of an Array of Signaling Proteins through Homo- and Heteromeric Interactions Between PDZ Domains and Target Proteins
Authors: Xu Xian-Zhong Shawn , Choudhury Atish , Li Xiaoling , Montell Craig
Published: July 2002

The rapid activation and feedback regulation of many G protein signaling cascades raises the possibility that the critical signaling proteins may be tightly coupled. Previous studies show that the PDZ domain containing protein INAD, which functions in Drosophila vision, coordinates a signaling complex by binding directly to the light-sensitive ion channel, TRP, and to phospholipase C (PLC). The INAD signaling complex also includes rhodopsin, protein kinase C (PKC), and calmodulin, though it is not known whether these proteins bind to INAD. In the current work, we show that rhodopsin, calmodulin, and PKC associate with the signaling complex by direct binding to INAD. We also found that a second ion channel, TRPL, bound to INAD. Thus, most of the proteins involved directly in phototransduction appear to bind to INAD. Furthermore, we found that INAD formed homopolymers and the homomultimerization occurred through two PDZ domains. Thus, we propose that the INAD supramolecular complex is a higher order signaling web consisting of an extended network of INAD molecules through which a G protein–coupled cascade is tethered.
Detection by Epitope-defined Monoclonal Antibodies of Werner DNA Helicases in the Nucleoplasm and Their Upregulation by Cell Transformation and Immortalization
Authors: Shiratori Miwa , Sakamoto Sakae , Suzuki Noriyuki , Tokutake Yoshiki , Kawabe Yoichi , Enomoto Takemi , Sugimoto Masanobu , Goto Makoto , Matsumoto Takehisa , Furuichi Yasuhiro
Published: July 2002

We prepared several monoclonal antibodies (mAbs) specific for the NH2- and COOH-terminal regions of the DNA helicase (WRN helicase) responsible for Werner's syndrome known as a premature aging disease. With these antibodies, we detected by immunoblot analysis the endogenous WRN helicase of a relative mass of 180 kD in several lines of cultured cells, but not in patient cells with a defined mutation. Immunocytochemical staining of proliferating fibroblasts and tumor cells showed that the major part of WRN helicase is in the nucleoplasm and not in the nucleolus. Similar experiments with a rat mAb specific to the mouse homologue of human WRN helicase yielded an identical conclusion. Although this nucleoplasmic staining was evident in cells in interphase, the condensed chromatin structure in metaphase was not stained by the same mAbs, suggesting that WRN helicases exist perhaps in a soluble form or bound to the unfolded chromatin structure. From quantitative immunoblot analysis, higher levels of WRN helicase were observed in all transformed cells and tumor cells examined than those of normal cells. The expression of WRN helicase was enhanced consistently in fibroblasts and B-lymphoblastoid cells by transformation with SV-40 and Epstein-Barr virus, respectively, suggesting that rapidly proliferating cells require a high copy numbers of WRN helicase.
A Conserved LIM Protein That Affects Muscular Adherens Junction Integrity and Mechanosensory Function in Caenorhabditis elegans
Authors: Hobert Oliver , Moerman Donald G. , Clark Kathleen A. , Beckerle Mary C. , Ruvkun Gary
Published: July 2002

We describe here the molecular and functional characterization of the Caenorhabditis elegans unc-97 gene, whose gene product constitutes a novel component of muscular adherens junctions. UNC-97 and homologues from several other species define the PINCH family, a family of LIM proteins whose modular composition of five LIM domains implicates them as potential adapter molecules. unc-97 expression is restricted to tissue types that attach to the hypodermis, specifically body wall muscles, vulval muscles, and mechanosensory neurons. In body wall muscles, the UNC-97 protein colocalizes with the β-integrin PAT-3 to the focal adhesion-like attachment sites of muscles. Partial and complete loss-of-function studies demonstrate that UNC-97 affects the structural integrity of the integrin containing muscle adherens junctions and contributes to the mechanosensory functions of touch neurons. The expression of a Drosophila homologue of unc-97 in two integrin containing cell types, muscles, and muscle-attached epidermal cells, suggests that unc-97 function in adherens junction assembly and stability has been conserved across phylogeny. In addition to its localization to adherens junctions UNC-97 can also be detected in the nucleus, suggesting multiple functions for this LIM domain protein.
Cytoplasmic Dynein Is Required for the Nuclear Attachment and Migration of Centrosomes during Mitosis inDrosophila
Authors: Robinson John T. , Wojcik Edward J. , Sanders Mark A. , McGrail Maura , Hays Thomas S.
Published: July 2002

Cytoplasmic dynein is a multisubunit minus-end–directed microtubule motor that serves multiple cellular functions. Genetic studies in Drosophila and mouse have demonstrated that dynein function is essential in metazoan organisms. However, whether the essential function of dynein reflects a mitotic requirement, and what specific mitotic tasks require dynein remains controversial. Drosophila is an excellent genetic system in which to analyze dynein function in mitosis, providing excellent cytology in embryonic and somatic cells. We have used previously characterized recessive lethal mutations in the dynein heavy chain gene, Dhc64C, to reveal the contributions of the dynein motor to mitotic centrosome behavior in the syncytial embryo. Embryos lacking wild-type cytoplasmic dynein heavy chain were analyzed by in vivo analysis of rhodamine-labeled microtubules, as well as by immu-nofluorescence in situ methods. Comparisons between wild-type and Dhc64C mutant embryos reveal that dynein function is required for the attachment and migration of centrosomes along the nuclear envelope during interphase/prophase, and to maintain the attachment of centrosomes to mitotic spindle poles. The disruption of these centrosome attachments in mutant embryos reveals a critical role for dynein function and centrosome positioning in the spatial organization of the syncytial cytoplasm of the developing embryo.
Adenine Nucleotide Translocase-1, a Component of the Permeability Transition Pore, Can Dominantly Induce Apoptosis
Authors: Bauer Manuel K.A. , Schubert Alexis , Rocks Oliver , Grimm Stefan
Published: July 2002

Here, we describe the isolation of adenine nucleotide translocase-1 (ANT-1) in a screen for dominant, apoptosis-inducing genes. ANT-1 is a component of the mitochondrial permeability transition complex, a protein aggregate connecting the inner with the outer mitochondrial membrane that has recently been implicated in apoptosis. ANT-1 expression led to all features of apoptosis, such as phenotypic alterations, collapse of the mitochondrial membrane potential, cytochrome c release, caspase activation, and DNA degradation. Both point mutations that impair ANT-1 in its known activity to transport ADP and ATP as well as the NH2-terminal half of the protein could still induce apoptosis. Interestingly, ANT-2, a highly homologous protein could not lead to cell death, demonstrating the specificity of the signal for apoptosis induction. In contrast to Bax, a proapoptotic Bcl-2 gene, ANT-1 was unable to elicit a form of cell death in yeast. This and the observed repression of apoptosis by the ANT-1–interacting protein cyclophilin D suggest that the suicidal effect of ANT-1 is mediated by specific protein–protein interactions within the permeability transition pore.
Actin-Dependent Propulsion of Endosomes and Lysosomes by Recruitment of N-Wasp✪
Authors: Taunton Jack , Rowning Brian A. , Coughlin Margaret L. , Wu Michael , Moon Randall T. , Mitchison Timothy J. , Larabell Carolyn A.
Published: July 2002

We examined the spatial and temporal control of actin assembly in living Xenopus eggs. Within minutes of egg activation, dynamic actin-rich comet tails appeared on a subset of cytoplasmic vesicles that were enriched in protein kinase C (PKC), causing the vesicles to move through the cytoplasm. Actin comet tail formation in vivo was stimulated by the PKC activator phorbol myristate acetate (PMA), and this process could be reconstituted in a cell-free system. We used this system to define the characteristics that distinguish vesicles associated with actin comet tails from other vesicles in the extract. We found that the protein, N-WASP, was recruited to the surface of every vesicle associated with an actin comet tail, suggesting that vesicle movement results from actin assembly nucleated by the Arp2/3 complex, the immediate downstream target of N-WASP. The motile vesicles accumulated the dye acridine orange, a marker for endosomes and lysosomes. Furthermore, vesicles associated with actin comet tails had the morphological features of multivesicular endosomes as revealed by electron microscopy. Endosomes and lysosomes from mammalian cells preferentially nucleated actin assembly and moved in the Xenopus egg extract system. These results define endosomes and lysosomes as recruitment sites for the actin nucleation machinery and demonstrate that actin assembly contributes to organelle movement. Conversely, by nucleating actin assembly, intracellular membranes may contribute to the dynamic organization of the actin cytoskeleton.
A Small Chloroplast-Encoded Protein as a Novel Architectural Component of the Light-Harvesting Antenna
Authors: Ruf Stephanie , Biehler Klaus , Bock Ralph
Published: July 2002

A small conserved open reading frame in the plastid genome, ycf9, encodes a putative membrane protein of 62 amino acids. To determine the function of this reading frame we have constructed a knockout allele for targeted disruption of ycf9. This allele was introduced into the tobacco plastid genome by biolistic transformation to replace the wild-type ycf9 allele. Homoplasmic ycf9 knockout plants displayed no phenotype under normal growth conditions. However, under low light conditions, their growth rate was significantly reduced as compared with the wild-type, due to a lowered efficiency of the light reaction of photosynthesis. We show that this phenotype is caused by the deficiency in a pigment–protein complex of the light-harvesting antenna of photosystem II and hence by a reduced efficiency of photon capture when light availability is limiting. Our results indicate that, in contrast to the current view, light-harvesting complexes do not only consist of the classical pigment-binding proteins, but may contain small structural subunits in addition. These subunits appear to be crucial architectural factors for the assembly and/or maintenance of stable light-harvesting complexes.
Selective Disruption of Nuclear Import by a Functional Mutant Nuclear Transport Carrier
Authors: Lane Cynthia M. , Cushman Ian , Moore Mary Shannon
Published: July 2002

p10/NTF2 is a nuclear transport carrier that mediates the uptake of cytoplasmic RanGDP into the nucleus. We constructed a point mutant of p10, D23A, that exhibited unexpected behavior both in digitonin-permeabilized and microinjected mammalian cells. D23A p10 was markedly more efficient than wild-type (wt) p10 at supporting Ran import, but simultaneously acted as a dominant-negative inhibitor of classical nuclear localization sequence (cNLS)-mediated nuclear import supported by karyopherins (Kaps) α and β1. Binding studies indicated that these two nuclear transport carriers of different classes, p10 and Kap-β1, compete for identical and/or overlapping binding sites at the nuclear pore complex (NPC) and that D23A p10 has an increased affinity relative to wt p10 and Kap-β1 for these shared binding sites. Because of this increased affinity, D23A p10 is able to import its own cargo (RanGDP) more efficiently than wt p10, but Kap-β1 can no longer compete efficiently for shared NPC docking sites, thus the import of cNLS cargo is inhibited. The competition of different nuclear carriers for shared NPC docking sites observed here predicts a dynamic equilibrium between multiple nuclear transport pathways inside the cell that could be easily shifted by a transient modification of one of the carriers.
D-Titin
Authors: Machado Cristina , Andrew Deborah J.
Published: July 2002

Previously, we reported that chromosomes contain a giant filamentous protein, which we identified as titin, a component of muscle sarcomeres. Here, we report the sequence of the entire titin gene in Drosophila melanogaster, D-Titin, and show that it encodes a two-megadalton protein with significant colinear homology to the NH2-terminal half of vertebrate titin. Mutations in D-Titin cause chromosome undercondensation, chromosome breakage, loss of diploidy, and premature sister chromatid separation. Additionally, D-Titin mutants have defects in myoblast fusion and muscle organization. The phenotypes of the D-Titin mutants suggest parallel roles for titin in both muscle and chromosome structure and elasticity, and provide new insight into chromosome structure.
Phosphorylation of Adf/Cofilin Abolishes Egf-Induced Actin Nucleation at the Leading Edge and Subsequent Lamellipod Extension
Authors: Zebda Noureddine , Bernard Ora , Bailly Maryse , Welti Susan , Lawrence David S. , Condeelis John S.
Published: July 2002

In metastatic rat mammary adenocarcinoma cells, cell motility can be induced by epidermal growth factor. One of the early events in this process is the massive generation of actin barbed ends, which elongate to form filaments immediately adjacent to the plasma membrane at the tip of the leading edge. As a result, the membrane moves outward and forms a protrusion. To test the involvement of ADF/cofilin in the stimulus-induced barbed end generation at the leading edge, we inhibited ADF/cofilin's activity in vivo by increasing its phosphorylation level using the kinase domain of LIM-kinase 1 (GFP-K). We report here that expression of GFP-K in rat cells results in the near total phosphorylation of ADF/cofilin, without changing either the G/F-actin ratio or signaling from the EGF receptor in vivo. Phosphorylation of ADF/cofilin is sufficient to completely inhibit the appearance of barbed ends and lamellipod protrusion, even in the continued presence of abundant G-actin. Coexpression of GFP-K, together with an active, nonphosphorylatable mutant of cofilin (S3A cofilin), rescues barbed end formation and lamellipod protrusion, indicating that the effects of kinase expression are caused by the phosphorylation of ADF/cofilin. These results indicate a direct role for ADF/cofilin in the generation of the barbed ends that are required for lamellipod extension in response to EGF stimulation.
Cargo of Kinesin Identified as Jip Scaffolding Proteins and Associated Signaling Molecules
Authors: Verhey Kristen J. , Meyer Debra , Deehan Reneé , Blenis John , Schnapp Bruce J. , Rapoport Tom A. , Margolis Ben
Published: July 2002

The cargo that the molecular motor kinesin moves along microtubules has been elusive. We searched for binding partners of the COOH terminus of kinesin light chain, which contains tetratricopeptide repeat (TPR) motifs. Three proteins were found, the c-jun NH2-terminal kinase (JNK)–interacting proteins (JIPs) JIP-1, JIP-2, and JIP-3, which are scaffolding proteins for the JNK signaling pathway. Concentration of JIPs in nerve terminals requires kinesin, as evident from the analysis of JIP COOH-terminal mutants and dominant negative kinesin constructs. Coprecipitation experiments suggest that kinesin carries the JIP scaffolds preloaded with cytoplasmic (dual leucine zipper–bearing kinase) and transmembrane signaling molecules (the Reelin receptor, ApoER2). These results demonstrate a direct interaction between conventional kinesin and a cargo, indicate that motor proteins are linked to their membranous cargo via scaffolding proteins, and support a role for motor proteins in spatial regulation of signal transduction pathways.
A novel Dbl family RhoGEF promotes Rho-dependent axon attraction to the central nervous system midline in Drosophila and overcomes Robo repulsion
Authors: Bashaw Greg J. , Hu Hailan , Nobes Catherine D. , Goodman Corey S.
Published: July 2002

The key role of the Rho family GTPases Rac, Rho, and CDC42 in regulating the actin cytoskeleton is well established (Hall, A. 1998. Science. 279:509–514). Increasing evidence suggests that the Rho GTPases and their upstream positive regulators, guanine nucleotide exchange factors (GEFs), also play important roles in the control of growth cone guidance in the developing nervous system (Luo, L. 2000. Nat. Rev. Neurosci. 1:173–180; Dickson, B.J. 2001. Curr. Opin. Neurobiol. 11:103–110). Here, we present the identification and molecular characterization of a novel Dbl family Rho GEF, GEF64C, that promotes axon attraction to the central nervous system midline in the embryonic Drosophila nervous system. In sensitized genetic backgrounds, loss of GEF64C function causes a phenotype where too few axons cross the midline. In contrast, ectopic expression of GEF64C throughout the nervous system results in a phenotype in which far too many axons cross the midline, a phenotype reminiscent of loss of function mutations in the Roundabout (Robo) repulsive guidance receptor. Genetic analysis indicates that GEF64C expression can in fact overcome Robo repulsion. Surprisingly, evidence from genetic, biochemical, and cell culture experiments suggests that the promotion of axon attraction by GEF64C is dependent on the activation of Rho, but not Rac or Cdc42.
The Motheaten Mutation Rescues B Cell Signaling and Development in CD45-deficient Mice
Authors: Pani Giovanni , Siminovitch Katherine A. , Paige Christopher J.
Published: July 2002

The cytosolic SHP-1 and transmembrane CD45 protein tyrosine phosphatases (PTP) play critical roles in regulating signal transduction via the B cell antigen receptor (BCR). These PTPs differ, however, in their effects on BCR function. For example, BCR-mediated mitogenesis is essentially ablated in mice lacking CD45 (CD45−), but is enhanced in SHP-1–deficient motheaten (me) and viable motheaten (mev) mice. To determine whether these PTPs act independently or coordinately in modulating the physiologic outcome of BCR engagement, we assessed B cell development and signaling in CD45-deficient mev (CD45−/SHP-1−) mice. Here we report that the CD45−/SHP-1− cells undergo appropriate induction of protein kinase activity, mitogen-activated protein kinase activation, and proliferative responses after BCR aggregation. However, BCR-elicited increases in the tyrosine phosphorylation of several SHP-1–associated phosphoproteins, including CD19, were substantially enhanced in CD45−/SHP-1−, compared to wild-type and CD45− cells. In addition, we observed that the patterns of cell surface expression of μ, δ, and CD5, which distinguish the PTP-deficient from normal mice, are largely restored to normal levels in the double mutant animals. These findings indicate a critical role for the balance of SHP-1 and CD45 activities in determining the outcome of BCR stimulation and suggest that these PTPs act in a coordinate fashion to couple antigen receptor engagement to B cell activation and maturation.
How Many Thymocytes Audition for Selection?
Authors: Merkenschlager Matthias , Graf Daniel , Lovatt Matthew , Bommhardt Ursula , Zamoyska Rose , Fisher Amanda G.
Published: July 2002

T cell maturation requires the rearrangement of clonotypic T cell receptors (TCR) capable of interacting with major histocompatibility complex (MHC) ligands to initiate positive and negative selection. Only 3–5% of thymocytes mature to join the peripheral T cell pool. To investigate the basis for this low success rate, we have measured the frequency of preselection thymocytes capable of responding to MHC. As many as one in five MHC-naive thymocytes show upregulation of activation markers on exposure to MHC-expressing thymic stroma in short-term reaggregate culture. The majority of these cells display physiological changes consistent with entry into the selection process within 24 h. By exposing TCR transgenic thymocytes to a range of MHC–peptide complexes, we show that CD69 induction is indicative of thymocyte selection, positive or negative. Our data provide evidence that the fraction of thymocytes that qualify to enter the thymic selection process far exceeds the fraction that successfully complete it, and suggest that most MHC-reactive thymocytes are actively eliminated in the course of selection.
Inhibition of Apoptosis in Chlamydia-infected Cells: Blockade of Mitochondrial Cytochrome c Release and Caspase Activation
Authors: Fan Tao , Lu Hang , Hu He , Shi Lianfa , McClarty Grant A. , Nance Dwight M. , Greenberg Arnold H. , Zhong Guangming
Published: July 2002

We report that chlamydiae, which are obligate intracellular bacterial pathogens, possess a novel antiapoptotic mechanism. Chlamydia-infected host cells are profoundly resistant to apoptosis induced by a wide spectrum of proapoptotic stimuli including the kinase inhibitor staurosporine, the DNA-damaging agent etoposide, and several immunological apoptosis-inducing molecules such as tumor necrosis factor-α, Fas antibody, and granzyme B/perforin. The antiapoptotic activity was dependent on chlamydial but not host protein synthesis. These observations suggest that chlamydia may encode factors that interrupt many different host cell apoptotic pathways. We found that activation of the downstream caspase 3 and cleavage of poly (ADP-ribose) polymerase were inhibited in chlamydia-infected cells. Mitochondrial cytochrome c release into the cytosol induced by proapoptotic factors was also prevented by chlamydial infection. These observations suggest that chlamydial proteins may interrupt diverse apoptotic pathways by blocking mitochondrial cytochrome c release, a central step proposed to convert the upstream private pathways into an effector apoptotic pathway for amplification of downstream caspases. Thus, we have identified a chlamydial antiapoptosis mechanism(s) that will help define chlamydial pathogenesis and may also provide information about the central mechanisms regulating host cell apoptosis.
Transendothelial Migration of Megakaryocytes in Response to Stromal Cell-derived Factor 1 (SDF-1) Enhances Platelet Formation
Authors: Hamada Tsuneyoshi , Möhle Robert , Hesselgesser Joseph , Hoxie James , Nachman Ralph L. , Moore Malcolm A.S. , Rafii Shahin
Published: July 2002

Although thrombopoietin has been shown to promote megakaryocyte (MK) proliferation and maturation, the exact mechanism and site of platelet formation are not well defined. Studies have shown that MKs may transmigrate through bone marrow endothelial cells (BMEC), and release platelets within the sinusoidal space or lung capillaries. In search for chemotactic factor(s) that may mediate transmigration of MKs, we have discovered that mature polyploid MKs express the G protein–coupled chemokine receptor CXCR4 (Fusin, LESTR). Therefore, we explored the possibility that stromal cell–derived factor 1 (SDF-1), the ligand for CXCR4, may also induce transendothelial migration of mature MKs. SDF-1, but not other CXC or CC chemokines, was able to mediate MK migration (ED50 = 125 pmol/liter). The MK chemotaxis induced by SDF-1 was inhibited by the CXCR4-specific mAb (12G5) and by pertussis toxin, demonstrating that signaling via the G protein–coupled receptor CXCR4 was necessary for migration. SDF-1 also induced MKs to migrate through confluent monolayers of BMEC by increasing the affinity of MKs for BMEC. Activation of BMEC with interleukin 1β resulted in a threefold increase in the migration of MKs in response to SDF-1. Neutralizing mAb to the endothelial-specific adhesion molecule E-selectin blocked the migration of MKs by 50%, suggesting that cellular interaction of MKs with BMEC is critical for the migration of MKs. Light microscopy and ploidy determination of transmigrated MKs demonstrated predominance of polyploid MKs. Virtually all platelets generated in the lower chamber also expressed CXCR4. Platelets formed in the lower chamber were functional and expressed P-selectin (CD62P) in response to thrombin stimulation. Electron microscopy of the cells that transmigrated through the BMEC monolayers in response to SDF-1 demonstrated the presence of intact polyploid MKs as well as MKs in the process of platelet formation. These results suggest that SDF-1 is a potent chemotactic factor for mature MKs. Expression of CXCR4 may be the critical cellular signal for transmigration of MKs and platelet formation.
Mechanisms of Acute Eosinophil Mobilization from the Bone Marrow Stimulated by Interleukin 5: The Role of Specific Adhesion Molecules and Phosphatidylinositol 3-Kinase
Authors: Palframan Roger T. , Collins Paul D. , Severs Nicholas J. , Rothery Stephen , Williams Timothy J. , Rankin Sara M.
Published: July 2002

Mobilization of bone marrow eosinophils is a critical early step in their trafficking to the lung during allergic inflammatory reactions. We have shown previously that the cytokine interleukin (IL)-5, generated during an allergic inflammatory reaction in the guinea pig, acts systemically to mobilize eosinophils from the bone marrow. Here, we have investigated the mechanisms underlying this release process. Examination by light and electron microscopy revealed the rapid migration of eosinophils from the hematopoietic compartment and across the bone marrow sinus endothelium in response to IL-5. Using an in situ perfusion system of the guinea pig hind limb, we showed that IL-5 stimulated a dose-dependent selective release of eosinophils from the bone marrow. Eosinophils released from the bone marrow in response to IL-5 expressed increased levels of β2 integrin and a decrease in L-selectin, but no change in α4 integrin levels. A β2 integrin–blocking antibody markedly inhibited the mobilization of eosinophils from the bone marrow stimulated by IL-5. In contrast, an α4 integrin blocking antibody increased the rate of eosinophil mobilization induced by IL-5. In vitro we demonstrated that IL-5 stimulates the selective chemokinesis of bone marrow eosinophils, a process markedly inhibited by two structurally distinct inhibitors of phosphatidylinositol 3-kinase, wortmannin and LY294002. Wortmannin was also shown to block eosinophil release induced by IL-5 in the perfused bone marrow system. The parallel observations on the bone marrow eosinophil release process and responses in isolated eosinophils in vitro suggest that eosinophil chemokinesis is the driving force for release in vivo and that this release process is regulated by α4 and β2 integrins acting in opposite directions.
Regulation of Apoptosis in Myeloid Cells by Interferon Consensus Sequence–Binding Protein
Authors: Gabriele Lucia , Phung Jan , Fukumoto Jon , Segal David , Wang I-Ming , Giannakakou Paraskevi , Giese Nathalie A. , Ozato Keiko , Morse Herbert C.
Published: July 2002

Mice with a null mutation of the gene encoding interferon consensus sequence–binding protein (ICSBP) develop a disease with marked expansion of granulocytes and macrophages that frequently progresses to a fatal blast crisis, thus resembling human chronic myelogenous leukemia (CML). One important feature of CML is decreased responsiveness of myeloid cells to apoptotic stimuli. Here we show that myeloid cells from mice deficient in ICSBP exhibit reduced spontaneous apoptosis and a significant decrease in sensitivity to apoptosis induced by DNA damage. In contrast, apoptosis in thymocytes from ICSBP-deficient mice is unaffected. We also show that overexpression of ICSBP in the human U937 monocytic cell line enhances the rate of spontaneous apoptosis and the sensitivity to apoptosis induced by etoposide, lipopolysaccharide plus ATP, or rapamycin. Programmed cell death induced by etoposide was specifically blocked by peptides inhibitory for the caspase-1 or caspase-3 subfamilies of caspases. Studies of proapoptotic genes showed that cells overexpressing ICSBP have enhanced expression of caspase-3 precursor protein. In addition, analyses of antiapoptotic genes showed that overexpression of ICSBP results in decreased expression of Bcl-XL. These data suggest that ICSBP modulates survival of myeloid cells by regulating expression of apoptosis-related genes.
The Cc Chemokine Thymus-Derived Chemotactic Agent 4 (Tca-4, Secondary Lymphoid Tissue Chemokine, 6ckine, Exodus-2) Triggers Lymphocyte Function–Associated Antigen 1–Mediated Arrest of Rolling T Lymphocytes in Peripheral Lymph Node High Endothelial Venules
Authors: Stein Jens V. , Rot Antal , Luo Yi , Narasimhaswamy Manjunath , Nakano Hideki , Gunn Michael D. , Matsuzawa Akio , Quackenbush Elizabeth J. , Dorf Martin E. , von Andrian Ulrich H.
Published: July 2002

T cell homing to peripheral lymph nodes (PLNs) is defined by a multistep sequence of interactions between lymphocytes and endothelial cells in high endothelial venules (HEVs). After initial tethering and rolling via L-selectin, firm adhesion of T cells requires rapid upregulation of lymphocyte function–associated antigen 1 (LFA-1) adhesiveness by a previously unknown pathway that activates a Gαi-linked receptor. Here, we used intravital microscopy of murine PLNs to study the role of thymus-derived chemotactic agent (TCA)-4 (secondary lymphoid tissue chemokine, 6Ckine, Exodus-2) in homing of adoptively transferred T cells from T-GFP mice, a transgenic strain that expresses green fluorescent protein (GFP) selectively in naive T lymphocytes (TGFP cells). TCA-4 was constitutively presented on the luminal surface of HEVs, where it was required for LFA-1 activation on rolling TGFP cells. Desensitization of the TCA-4 receptor, CC chemokine receptor 7 (CCR7), blocked TGFP cell adherence in wild-type HEVs, whereas desensitization to stromal cell–derived factor (SDF)-1α (the ligand for CXC chemokine receptor 4 [CXCR4]) did not affect TGFP cell behavior. TCA-4 protein was not detected on the luminal surface of PLN HEVs in plt/plt mice, which have a congenital defect in T cell homing to PLNs. Accordingly, TGFP cells rolled but did not arrest in plt/plt HEVs. When TCA-4 was injected intracutaneously into plt/plt mice, the chemokine entered afferent lymph vessels and accumulated in draining PLNs. 2 h after intracutaneous injection, luminal presentation of TCA-4 was detectable in a subset of HEVs, and LFA-1–mediated TGFP cell adhesion was restored in these vessels. We conclude that TCA-4 is both required and sufficient for LFA-1 activation on rolling T cells in PLN HEVs. This study also highlights a hitherto undocumented role for chemokines contained in afferent lymph, which may modulate leukocyte recruitment in draining PLNs.
The Extracellular Domain of CD83 Inhibits Dendritic Cell–mediated T Cell Stimulation and Binds to a Ligand on Dendritic Cells
Authors: Lechmann Matthias , Krooshoop Daniëlle J.E.B. , Dudziak Diana , Kremmer Elisabeth , Kuhnt Christine , Figdor Carl G. , Schuler Gerold , Steinkasserer Alexander
Published: July 2002

CD83 is an immunoglobulin (Ig) superfamily member that is upregulated during the maturation of dendritic cells (DCs). It has been widely used as a marker for mature DCs, but its function is still unknown. To approach its potential functional role, we have expressed the extracellular Ig domain of human CD83 (hCD83ext) as a soluble protein. Using this tool we could show that immature as well as mature DCs bind to CD83. Since CD83 binds a ligand also expressed on immature DCs, which do not express CD83, indicates that binding is not a homophilic interaction. In addition we demonstrate that hCD83ext interferes with DC maturation downmodulating the expression of CD80 and CD83, while no phenotypical effects were observed on T cells. Finally, we show that hCD83ext inhibits DC-dependent allogeneic and peptide-specific T cell proliferation in a concentration dependent manner in vitro. This is the first report regarding functional aspects of CD83 and the binding of CD83 to DCs.
Mutation of a Single Residue in the S2–S3 Loop of Cng Channels Alters the Gating Properties and Sensitivity to Inhibitors
Authors: Crary Jennifer I. , Dean Dylan M. , Maroof Farahnaz , Zimmerman Anita L.
Published: July 2002

We previously found that native cyclic nucleotide–gated (CNG) cation channels from amphibian rod cells are directly and reversibly inhibited by analogues of diacylglycerol (DAG), but little is known about the mechanism of this inhibition. We recently determined that, at saturating cGMP concentrations, DAG completely inhibits cloned bovine rod (Brod) CNG channels while only partially inhibiting cloned rat olfactory (Rolf) channels (Crary, J.I., D.M. Dean, W. Nguitragool, P.T. Kurshan, and A.L. Zimmerman. 2000. J. Gen. Phys. 116:755–768; in this issue). Here, we report that a point mutation at position 204 in the S2–S3 loop of Rolf and a mouse CNG channel (Molf) found in olfactory epithelium and heart, increased DAG sensitivity to that of the Brod channel. Mutation of this residue from the wild-type glycine to a glutamate (Molf G204E) or aspartate (Molf G204D) gave dramatic increases in DAG sensitivity without changing the apparent cGMP or cAMP affinities or efficacies. However, unlike the wild-type olfactory channels, these mutants demonstrated voltage-dependent gating with obvious activation and deactivation kinetics. Interestingly, the mutants were also more sensitive to inhibition by the local anesthetic, tetracaine. Replacement of the position 204 glycine with a tryptophan residue (Rolf G204W) not only gave voltage-dependent gating and an increased sensitivity to DAG and tetracaine, but also showed reduced apparent agonist affinity and cAMP efficacy. Sequence comparisons show that the glycine at position 204 in the S2–S3 loop is highly conserved, and our findings indicate that its alteration can have critical consequences for channel gating and inhibition.
On Burgess’s theorem and related problems
Authors: Kato Hisao , Ye Xiangdong
Published: July 2002

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be

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K
K

is a graph, then

K
K

is not

G

i

G_{i}

-like for some integer

i
i

with

1
≤
i
≤
m

1\le i\le m

. This generalizes a well known theorem of Burgess.
Connected sums of manifolds which induce approximate fibrations
Authors: Kim Yongkuk
Published: July 2002

Codimension-2 fibrators are

n
n

-manifolds which automatically induce approximate fibration, in the following sense: given any proper mapping

p
p

from an

(
n
+
2
)

(n+2)

-manifold onto a

2
2

-manifold such that each point-preimage is a copy of the codimension-2 fibrator,

p
p

is necessarily an approximate fibration. In this paper, we give some answers to the following question: given an

n
n

-manifold

N
N

which is a nontrivial connected sum, when is

N
N

a codimension-2 fibrator?
On the existence of doubling measures with certain regularity properties
Authors: Bylund Per , Gudayol Jaume
Published: July 2002

Given a compact pseudo-metric space, we associate to it upper and lower dimensions, depending only on the pseudo-metric. Then we construct a doubling measure for which the measure of a dilated ball is closely related to these dimensions.
On the number of generators of Cohen-Macaulay ideals
Authors: D’Cruz Clare , Verma J.
Published: July 2002

Several bounds on the number of generators of Cohen-Macaulay ideals known in the literature follow from a simple inequality which bounds the number of generators of such ideals in terms of mixed multiplicities. Results of Cohen and Akizuki, Abhyankar, Sally, Rees and Boratynski-Eisenbud-Rees are deduced very easily from this inequality.
A classification of prime segments in simple artinian rings
Authors: Brungs H. , Marubayashi H. , Osmanagic E.
Published: July 2002

Let

A
A

be a simple artinian ring. A valuation ring of

A
A

is a Bézout order

R
R

of

A
A

so that

R

/

J
(
R
)

R/J(R)

is simple artinian, a Goldie prime is a prime ideal

P
P

of

R
R

so that

R

/

P

R/P

is Goldie, and a prime segment of

A
A

is a pair of neighbouring Goldie primes of

R
.

R.

A prime segment

P

1

⊃

P

2

P_{1}\supset P_{2}

is archimedean if

K
(

P

1

)
=
{
a
∈

P

1

|

P

1

a

P

1

⊂

P

1

}

K(P_{1})=\{a\in P_{1}\vert P_{1} aP_{1}\subset P_{1}\}

is equal to

P

1

,

P_{1},

it is simple if

K
(

P

1

)
=

P

2

K(P_{1})=P_{2}

and it is exceptional if

P

1

⊃
K
(

P

1

)
⊃

P

2

.

P_{1}\supset K(P_{1})\supset P_{2}.

In this last case,

K
(

P

1

)

K(P_{1})

is a prime ideal of

R
R

so that

R

/

K
(

P

1

)

R/K(P_{1})

is not Goldie. Using the group of divisorial ideals, these results are applied to classify rank one valuation rings according to the structure of their ideal lattices. The exceptional case splits further into infinitely many cases depending on the minimal

n
n

so that

K
(

P

1

)

n

K(P_{1})^{n}

is not divisorial for

n
≥
2.

n\ge 2.
Remarks on commuting exponentials in Banach algebras, II
Authors: Schmoeger Christoph
Published: July 2002

Suppose that

a
a

and

b
b

are elements of a complex unital Banach algebra such that the spectrum of

a
a

is

2
π
i

2\pi i

-congruence-free and

e
a

e
b

=

e
b

e
a

e^ae^b = e^be^a

. We show that then

a
b
−
b
a

ab-ba

is the sum of nilpotent elements. If

r
(
b
)

r(b)

denotes the spectral radius of

b
b

, then we show that the additional assumption

r
(
b
)
>
2
π

r(b)>2 \pi

implies that

b
(
a
b
−
b
a

)
2

=
(
a
b
−
b
a

)
2

b
.

\begin{equation*} b (ab-ba)^2 = (ab-ba)^2 b. \end{equation*}
A property of subgroups of infinite index in a free group
Authors: Arzhantseva G.
Published: July 2002

We prove that if

H
H

is a finitely generated subgroup of infinite index in a free group

F
m

F_m

, then, in a certain statistical meaning, the normal subgroup generated by “randomly” chosen elements

r
1

,
…
,

r
n

r_1,\dots ,r_n

of

F
m

F_m

has trivial intersection with

H
H

.
A hierarchy of thin sets related to the boundedness of trigonometric series
Authors: Eliaš Peter
Published: July 2002

We study the family 

B

0

\mathcal {B}_0

of the sets on which some series of the form

∑

k
∈

N

|
sin
⁡
π

n
k

x
|

\sum _{k\in \mathbb {N}}\left |\sin \pi n_kx\right |

is uniformly bounded. We show that the families 

B

0
c

\mathcal {B}_0^c

of all sets admitting the boundary 

c
c

form a hierarchy which is incontinuous with respect to the operations of intersection and union.
Adjoints and the image of the ball
Authors: Richman Fred
Published: July 2002

A bounded operator between Hilbert spaces has an adjoint if and only if the image of the unit ball is located.
On fiber-preserving isotopies of surface homeomorphisms
Authors: Fuller Terry
Published: July 2002

We show that there are homeomorphisms of closed oriented genus

g
g

surfaces

Σ
g

\Sigma _g

which are fiber-preserving with respect to an irregular branched covering

Σ
g

→

S
2

\Sigma _g \to S^2

and isotopic to the identity, but which are not fiber-isotopic to the identity.
Every Σ-CS-module has an indecomposable decomposition
Authors: Gómez Pardo José , Guil Asensio Pedro
Published: July 2002

We show that every

Σ
\Sigma

-CS module is a direct sum of uniform modules, thus solving an open problem posed in 1994 by Dung, Huynh, Smith and Wisbauer. With the help of this result we also answer several other questions related to indecomposable decompositions of CS-modules.
Elements in a commutative Banach algebra determining the norm topology
Authors: Villena A.
Published: July 2002

For an element

a
a

of a commutative complex Banach algebra

(
A
,
‖
⋅
‖
)

(A,\|\cdot \|)

we investigate the following property: every complete norm

|

⋅

|

|\cdot |

on

A
A

making the multiplication by

a
a

from

(
A
,

|

⋅

|

)

(A,|\cdot |)

to itself continuous is equivalent to

‖
⋅
‖

\|\cdot \|

.
On complete graphs with negative r-mean curvature
Authors: Elbert Maria
Published: July 2002

We generalize Efimov’s Theorem for graphs in Euclidean space using the scalar curvature, with an additional hypothesis on the second fundamental form.
Normalizers of the congruence subgroups of the Hecke group II
Authors: Lang Mong-Lung , Tan Ser-Peow
Published: July 2002

Let

λ
=
2
cos
⁡
(
π

/

5
)

\lambda = 2\cos (\pi /5)

. Let

(
τ
)

(\tau )

be an ideal of

Z

[
λ
]

\mathbb {Z}[\lambda ]

and let

(

τ
0

)

(\tau _0)

be the maximal ideal of

Z

[
λ
]

\mathbb {Z}[\lambda ]

such that

(

τ
0
2

)
⊆
(
τ
)

(\tau _0^2)\subseteq (\tau )

. Then

N
(

G
0

(
τ
)
)
≤

G
0

(

τ
0

)

N(G_0(\tau ))\le G_0(\tau _0)

. In particular, if

τ
\tau

is square free, then

G

0

(
τ
)

G_{0}(\tau )

is self-normalized in

P
S

L

2

(

R

)

PSL_{2}(\mathbb {R})

.
Non-linearity of the pluricomplex Green function
Authors: Wikström Frank
Published: July 2002

We consider the pluricomplex Green function with multiple poles as introduced by Lelong. We give a partial solution to a question concerning the set where the multipole Green function coincides with the sum of the corresponding single pole Green functions.
FS-property for 𝐶*-algebras
Authors: Kodaka Kazunori , Osaka Hiroyuki
Published: July 2002

A

C

∗

C^{\ast }

-algebra

A
A

is said to have the FS-property if the set of all self-adjoint elements in

A
A

has a dense subset of elements with finite spectrum. We shall show that this property is not stable under taking the minimal

C

∗

C^{\ast }

-tensor products even in case of separable nuclear

C

∗

C^{\ast }

-algebras.
Single elements of finite CSL algebras
Authors: Longstaff W. , Panaia Oreste
Published: July 2002

An element

s
s

of an (abstract) algebra

A

{\mathcal {A}}

is a single element of

A

{\mathcal {A}}

if

a
s
b
=
0

asb=0

and

a
,
b
∈

A

a,b\in {\mathcal {A}}

imply that

a
s
=
0

as=0

or

s
b
=
0

sb=0

. Let

X
X

be a real or complex reflexive Banach space, and let

B

{\mathcal {B}}

be a finite atomic Boolean subspace lattice on

X
X

, with the property that the vector sum

K
+
L

K+L

is closed, for every

K
,
L
∈

B

K,L\in {\mathcal {B}}

. For any subspace lattice

D

⊆

B

{\mathcal {D}}\subseteq {\mathcal {B}}

the single elements of Alg

D

{\mathcal {D}}

are characterised in terms of a coordinatisation of

D

{\mathcal {D}}

involving

B

{\mathcal {B}}

. (On separable complex Hilbert space the finite distributive subspace lattices

D

{\mathcal {D}}

which arise in this way are precisely those which are similar to finite commutative subspace lattices. Every distributive subspace lattice on complex, finite-dimensional Hilbert space is of this type.) The result uses a characterisation of the single elements of matrix incidence algebras, recently obtained by the authors.
An order characterization of commutativity for 𝐶*-algebras
Authors: Wu Wei
Published: July 2002

In this paper, we investigate the problem of when a

C

∗

C^{\ast }

-algebra is commutative through operator-monotonic increasing functions. The principal result is that the function

e

t

,
t
∈
[
0
,
∞
)
,

e^{t}, t\in [0, \infty ),

is operator-monotonic increasing on a

C

∗

C^{\ast }

-algebra

A

\mathcal {A}

if and only if

A

\mathcal {A}

is commutative. Therefore,

C

∗

C^{\ast }

-algebra

A

\mathcal {A}

is commutative if and only if

e

x
+
y

=

e

x

e

y

e^{x+y}=e^{x}e^{y}

in

A

+
˙

C

\mathcal {A} \dot + \mathbf {C}

for all positive elements

x
,
y

x, y

in

A

\mathcal {A}

.
The Mitchell-Richter filtration of loops on Stiefel manifolds stably splits
Authors: Arone Greg
Published: July 2002

We prove that the Mitchell-Richter filtration of the space of loops on complex Stiefel manifolds stably splits. The result is obtained as a special case of a more general splitting theorem. Another special case is H. Miller’s splitting of Stiefel manifolds. The proof uses the theory of orthogonal calculus developed by M. Weiss. The argument is inspired by an old argument of Goodwillie for a different, but closely related, general splitting result.
Une preuve courte du principe de Selberg pour un groupe 𝑝-adique
Authors: Dat J.-F.
Published: July 2002

In 1992, Blanc and Brylinski showed the following property for a

p
p

-adic group

G
G

, called the “abstract Selberg principle”: the orbital integrals on conjugacy classes of non-compact elements of the Hattori rank of a finitely generated projective smooth representation of

G
G

vanish. The proof is by explicit computations of “low” level (

0
0

and

1
)

1)

cyclic and Hochschild cohomologies. Here we intend to show that this property is actually a direct consequence of two facts: Clozel’s integration formula (which leads us to assume the defining characteristic to be zero) and the triviality of the action of unramified characters on the

K
0

K_0

of

G
G

(which is also proven here, using a standard

K
K

-theoretic argument due to Grothendieck).
Orthogonality of the range and the kernel of some elementary operators
Authors: Kečkić Dragoljub
Published: July 2002

We prove the orthogonality of the range and the kernel of an important class of elementary operators with respect to the unitarily invariant norms associated with norm ideals of operators. This class consists of those mappings

E
:
B
(
H
)
→
B
(
H
)

E:B(H)\to B(H)

,

E
(
X
)
=
A
X
B
+
C
X
D

E(X)=AXB+CXD

, where

B
(
H
)

B(H)

is the algebra of all bounded Hilbert space operators, and

A
A

,

B
B

,

C
C

,

D
D

are normal operators, such that

A
C
=
C
A

AC=CA

,

B
D
=
D
B

BD=DB

and

ker
⁡
A
∩
ker
⁡
C
=
ker
⁡
B
∩
ker
⁡
D
=
{
0
}

\ker A\cap \ker C=\ker B\cap \ker D=\{0\}

. Also we establish that this class is, in a certain sense, the widest class for which such an orthogonality result is valid. Some other related results are also given.
Inequalities for products of spectral radii
Authors: Omladič M. , Radjavi H. , Rosenthal P. , Sourour A.
Published: July 2002

It is shown that submultiplicative inequalities for spectral radii often imply supermultiplicative inequalities, and vice versa.
Symmetric numerical semigroups with arbitrary multiplicity and embedding dimension
Authors: Rosales J.
Published: July 2002

We construct symmetric numerical semigroups

S
S

for every minimal number of generators

μ
(
S
)

\mu (S)

and multiplicity

m

(
S
)

\mathsf {m}(S)

,

2
≤
μ
(
S
)
≤

m

(
S
)
−
1

2\leq \mu (S)\leq \mathsf {m}(S)-1

. Furthermore we show that the set of their defining congruence is minimally generated by

μ
(
S
)
(
μ
(
S
)
−
1
)

/

2
−
1

\mu (S)(\mu (S)-1)/2-1

elements.