bluuebunny/crossref_metadata_2025 huggingface dataset:
The cysteine-rich domain regulates ADAM protease function in vivo
Authors: Smith Katherine M. , Gaultier Alban , Cousin Helene , Alfandari Dominique , White Judith M. , DeSimone Douglas W.
Published: December 2002

ADAMs are membrane-anchored proteases that regulate cell behavior by proteolytically modifying the cell surface and ECM. Like other membrane-anchored proteases, ADAMs contain candidate “adhesive” domains downstream of their metalloprotease domains. The mechanism by which membrane-anchored cell surface proteases utilize these putative adhesive domains to regulate protease function in vivo is not well understood. We address this important question by analyzing the relative contributions of downstream extracellular domains (disintegrin, cysteine rich, and EGF-like repeat) of the ADAM13 metalloprotease during Xenopus laevis development. When expressed in embryos, ADAM13 induces hyperplasia of the cement gland, whereas ADAM10 does not. Using chimeric constructs, we find that the metalloprotease domain of ADAM10 can substitute for that of ADAM13, but that specificity for cement gland expansion requires a downstream extracellular domain of ADAM13. Analysis of finer resolution chimeras indicates an essential role for the cysteine-rich domain and a supporting role for the disintegrin domain. These and other results reveal that the cysteine-rich domain of ADAM13 cooperates intramolecularly with the ADAM13 metalloprotease domain to regulate its function in vivo. Our findings thus provide the first evidence that a downstream extracellular adhesive domain plays an active role in regulating ADAM protease function in vivo. These findings are likely relevant to other membrane-anchored cell surface proteases.
Gene density and transcription influence the localization of chromatin outside of chromosome territories detectable by FISH
Authors: Mahy Nicola L. , Perry Paul E. , Bickmore Wendy A.
Published: December 2002

Genes can be transcribed from within chromosome territories; however, the major histocompatibilty complex locus has been reported extending away from chromosome territories, and the incidence of this correlates with transcription from the region. A similar result has been seen for the epidermal differentiation complex region of chromosome 1. These data suggested that chromatin decondensation away from the surface of chromosome territories may result from, and/or may facilitate, transcription of densely packed genes subject to coordinate regulation.

To investigate whether localization outside of the visible confines of chromosome territories can also occur for regions that are not coordinately regulated, we have examined the spatial organization of human 11p15.5 and the syntenic region on mouse chromosome 7. This region is gene rich but its genes are not coordinately expressed, rather overall high levels of transcription occur in several cell types. We found that chromatin from 11p15.5 frequently extends away from the chromosome 11 territory. Localization outside of territories was also detected for other regions of high gene density and high levels of transcription. This is shown to be partly dependent on ongoing transcription. We suggest that local gene density and transcription, rather than the activity of individual genes, influences the organization of chromosomes in the nucleus.
The targeting of the atToc159 preprotein receptor to the chloroplast outer membrane is mediated by its GTPase domain and is regulated by GTP
Authors: Smith Matthew D. , Hiltbrunner Andreas , Kessler Felix , Schnell Danny J.
Published: December 2002

The multimeric translocon at the outer envelope membrane of chloroplasts (Toc) initiates the recognition and import of nuclear-encoded preproteins into chloroplasts. Two Toc GTPases, Toc159 and Toc33/34, mediate preprotein recognition and regulate preprotein translocation. Although these two proteins account for the requirement of GTP hydrolysis for import, the functional significance of GTP binding and hydrolysis by either GTPase has not been defined. A recent study indicates that Toc159 is equally distributed between a soluble cytoplasmic form and a membrane-inserted form, raising the possibility that it might cycle between the cytoplasm and chloroplast as a soluble preprotein receptor. In the present study, we examined the mechanism of targeting and insertion of the Arabidopsis thaliana orthologue of Toc159, atToc159, to chloroplasts. Targeting of atToc159 to the outer envelope membrane is strictly dependent only on guanine nucleotides. Although GTP is not required for initial binding, the productive insertion and assembly of atToc159 into the Toc complex requires its intrinsic GTPase activity. Targeting is mediated by direct binding between the GTPase domain of atToc159 and the homologous GTPase domain of atToc33, the Arabidopsis Toc33/34 orthologue. Our findings demonstrate a role for the coordinate action of the Toc GTPases in assembly of the functional Toc complex at the chloroplast outer envelope membrane.
BDNF-induced TrkB activation down-regulates the K+–Cl− cotransporter KCC2 and impairs neuronal Cl− extrusion
Authors: Rivera Claudio , Li Hong , Thomas-Crusells Judith , Lahtinen Hannele , Viitanen Tero , Nanobashvili Avtandil , Kokaia Zaal , Airaksinen Matti S. , Voipio Juha , Kaila Kai , Saarma Mart
Published: December 2002

Pathophysiological activity and various kinds of traumatic insults are known to have deleterious long-term effects on neuronal Cl− regulation, which can lead to a suppression of fast postsynaptic GABAergic responses. Brain-derived neurotrophic factor (BDNF) increases neuronal excitability through a conjunction of mechanisms that include regulation of the efficacy of GABAergic transmission. Here, we show that exposure of rat hippocampal slice cultures and acute slices to exogenous BDNF or neurotrophin-4 produces a TrkB-mediated fall in the neuron-specific K+–Cl− cotransporter KCC2 mRNA and protein, as well as a consequent impairment in neuronal Cl− extrusion capacity. After kindling-induced seizures in vivo, the expression of KCC2 is down-regulated in the mouse hippocampus with a spatiotemporal profile complementary to the up-regulation of TrkB and BDNF. The present data demonstrate a novel mechanism whereby BDNF/TrkB signaling suppresses chloride-dependent fast GABAergic inhibition, which most likely contributes to the well-known role of TrkB-activated signaling cascades in the induction and establishment of epileptic activity.
Vps10p Cycles between the TGN and the Late Endosome via the Plasma Membrane in Clathrin Mutants
Authors: Deloche Olivier , Schekman Randy W.
Published: December 2002

Clathrin-coated vesicles mediate the transport of the soluble vacuolar protein CPY from the TGN to the endosomal/prevacuolar compartment. Surprisingly, CPY sorting is not affected in clathrin deletion mutant cells. Here, we have investigated the clathrin-independent pathway that allows CPY transport to the vacuole. We find that CPY transport is mediated by the endosome and requires normal trafficking of its sorting receptor, Vps10p, the steady state distribution of which is not altered in chc1 cells. In contrast, Vps10p accumulates at the cell surface in achc1/end3 double mutant, suggesting that Vps10p is rerouted to the cell surface in the absence of clathrin. We used a chimeric protein containing the first 50 amino acids of CPY fused to a green fluorescent protein (CPY-GFP) to mimic CPY transport inchc1. In the absence of clathrin, CPY-GFP resides in the lumen of the vacuole as in wild-type cells. However, inchc1/sec6 double mutants, CPY-GFP is present in internal structures, possibly endosomal membranes, that do not colocalize with the vacuole. We propose that Vps10p must be transported to and retrieved from the plasma membrane to mediate CPY sorting to the vacuole in the absence of clathrin-coated vesicles. In this circumstance, precursor CPY may be captured by retrieved Vps10p in an early or late endosome, rather than as it normally is in the trans-Golgi, and delivered to the vacuole by the normalVPS gene-dependent process. Once relieved of cargo protein, Vps10p would be recycled to the trans-Golgi and then to the cell surface for further rounds of sorting.
Human Adipose Tissue Is a Source of Multipotent Stem Cells
Authors: Zuk Patricia A. , Zhu Min , Ashjian Peter , De Ugarte Daniel A. , Huang Jerry I. , Mizuno Hiroshi , Alfonso Zeni C. , Fraser John K. , Benhaim Prosper , Hedrick Marc H.
Published: December 2002

Much of the work conducted on adult stem cells has focused on mesenchymal stem cells (MSCs) found within the bone marrow stroma. Adipose tissue, like bone marrow, is derived from the embryonic mesenchyme and contains a stroma that is easily isolated. Preliminary studies have recently identified a putative stem cell population within the adipose stromal compartment. This cell population, termed processed lipoaspirate (PLA) cells, can be isolated from human lipoaspirates and, like MSCs, differentiate toward the osteogenic, adipogenic, myogenic, and chondrogenic lineages. To confirm whether adipose tissue contains stem cells, the PLA population and multiple clonal isolates were analyzed using several molecular and biochemical approaches. PLA cells expressed multiple CD marker antigens similar to those observed on MSCs. Mesodermal lineage induction of PLA cells and clones resulted in the expression of multiple lineage-specific genes and proteins. Furthermore, biochemical analysis also confirmed lineage-specific activity. In addition to mesodermal capacity, PLA cells and clones differentiated into putative neurogenic cells, exhibiting a neuronal-like morphology and expressing several proteins consistent with the neuronal phenotype. Finally, PLA cells exhibited unique characteristics distinct from those seen in MSCs, including differences in CD marker profile and gene expression.
A Specific Structural Requirement for Ergosterol in Long-chain Fatty Acid Synthesis Mutants Important for Maintaining Raft Domains in Yeast
Authors: Eisenkolb Marlis , Zenzmaier Christoph , Leitner Erich , Schneiter Roger
Published: December 2002

Fungal sphingolipids contain ceramide with a very-long-chain fatty acid (C26). To investigate the physiological significance of the C26-substitution on this lipid, we performed a screen for mutants that are synthetically lethal with ELO3. Elo3p is a component of the ER-associated fatty acid elongase and is required for the final elongation cycle to produce C26 from C22/C24 fatty acids.elo3Δ mutant cells thus contain C22/C24- instead of the natural C26-substituted ceramide. We now report that under these conditions, an otherwise nonessential, but also fungal-specific, structural modification of the major sterol of yeast, ergosterol, becomes essential, because mutations in ELO3 are synthetically lethal with mutations in ERG6. Erg6p catalyzes the methylation of carbon atom 24 in the aliphatic side chain of sterol. The lethality of an elo3Δ erg6Δ double mutant is rescued by supplementation with ergosterol but not with cholesterol, indicating a vital structural requirement for the ergosterol-specific methyl group. To characterize this structural requirement in more detail, we generated a strain that is temperature sensitive for the function of Erg6p in an elo3Δ mutant background. Examination of raft association of the GPI-anchored Gas1p and plasma membrane ATPase, Pma1p, in the conditional elo3Δ erg6tsdouble mutant, revealed a specific defect of the mutant to maintain raft association of preexisting Pma1p. Interestingly, in an elo3Δ mutant at 37°C, newly synthesized Pma1p failed to enter raft domains early in the biosynthetic pathway, and upon arrival at the plasma membrane was rerouted to the vacuole for degradation. These observations indicate that the C26 fatty acid substitution on lipids is important for establishing raft association of Pma1p and stabilizing the protein at the cell surface. Analysis of raft lipids in the conditional mutant strain revealed a selective enrichment of ergosterol in detergent-resistant membrane domains, indicating that specific structural determinants on both sterols and sphingolipids are required for their association into raft domains.
Calcium Regulation of GM-CSF by Calmodulin-Dependent Kinase II Phosphorylation of Ets1
Authors: Liu Hebin , Grundström Thomas
Published: December 2002

The multipotent cytokine granulocyte macrophage-colony stimulating factor (GM-CSF) is involved in particular in the physiological response to infection and in inflammatory responses. GM-CSF is produced by many cell types, including T lymphocytes responding to T-cell receptor activation and mantle zone B lymphocytes. B-cell receptor and T-cell receptor activation generates two major signals: an increase in intracellular Ca2+concentration and a protein kinase cascade. Previous studies have shown that the Ca2+/calmodulin-dependent phosphatase calcineurin mediates stimulation of GM-CSF transcription in response to Ca2+. In this study, we show that Ca2+signaling also regulates GM-CSF transcription negatively through Ca2+/calmodulin-dependent kinase II (CaMK II) phosphorylation of serines in the autoinhibitory domain for DNA binding of the transcription factor Ets1. Wild-type Ets1 negatively affects GM-CSF transcription on Ca2+stimulation in the presence of cyclosporin A, which inhibits calcineurin. Conversely, Ets1 with mutated CaMK II target serines showed an increase in transactivation of the GM-CSF promoter/enhancer. Moreover, constitutively active CaMK II inhibited transactivation of GM-CSF by wild-type Ets1 but not by Ets1 with mutated CaMK II sites. Mutation of CaMK II target serines in Ets1 also relieves inhibition of cooperative transactivation of GM-CSF with the Runx1/AML1 transcription factor. In addition, the Ca2+-dependent phosphorylation of Ets1 reduces the binding of Ets1 to the GM-CSF promoter in vivo.
EB1 Targets to Kinetochores with Attached, Polymerizing Microtubules
Authors: Tirnauer Jennifer S. , Canman Julie C. , Salmon E.D. , Mitchison Timothy J.
Published: December 2002

Microtubule polymerization dynamics at kinetochores is coupled to chromosome movements, but its regulation there is poorly understood. The plus end tracking protein EB1 is required both for regulating microtubule dynamics and for maintaining a euploid genome. To address the role of EB1 in aneuploidy, we visualized its targeting in mitotic PtK1 cells. Fluorescent EB1, which localized to polymerizing ends of astral and spindle microtubules, was used to track their polymerization. EB1 also associated with a subset of attached kinetochores in late prometaphase and metaphase, and rarely in anaphase. Localization occurred in a narrow crescent, concave toward the centromere, consistent with targeting to the microtubule plus end–kinetochore interface. EB1 did not localize to kinetochores lacking attached kinetochore microtubules in prophase or early prometaphase, or upon nocodazole treatment. By time lapse, EB1 specifically targeted to kinetochores moving antipoleward, coupled to microtubule plus end polymerization, and not during plus end depolymerization. It localized independently of spindle bipolarity, the spindle checkpoint, and dynein/dynactin function. EB1 is the first protein whose targeting reflects kinetochore directionality, unlike other plus end tracking proteins that show enhanced kinetochore binding in the absence of microtubules. Our results suggest EB1 may modulate kinetochore microtubule polymerization and/or attachment.
Pink-eyed Dilution Protein Modulates Arsenic Sensitivity and Intracellular Glutathione Metabolism
Authors: Staleva Liliana , Manga Prashiela , Orlow Seth J.
Published: December 2002

Mutations in the mouse p (pink-eyed dilution) and human P genes lead to melanosomal defects and ocular developmental abnormalities. Despite the critical role played by the p gene product in controlling tyrosinase processing and melanosome biogenesis, its precise biological function is still not defined. We have expressed p heterologously in the yeast Saccharomyces cerevisiae to study its function in greater detail. Immunofluorescence studies revealed that p reaches the yeast vacuolar membrane via the prevacuolar compartment. Yeast cells expressing p exhibited increased sensitivity to a number of toxic compounds, including arsenicals. Similarly, cultured murine melanocytes expressing a functional p gene were also found to be more sensitive to arsenical compounds compared with p-null cell lines. Intracellular glutathione, known to play a role in detoxification of arsenicals, was diminished by 50% in p-expressing yeast. By using the glutathione-conjugating dye monochlorobimane, in combination with acivicin, an inhibitor of vacuolar gamma-glutamyl cysteine transpeptidase, involved in the breakdown of glutathione, we found that p facilitates the vacuolar accumulation of glutathione. Our data demonstrate that the pink-eyed dilution protein increases cellular sensitivity to arsenicals and other metalloids and can modulate intracellular glutathione metabolism.
A Subset of Chaperones and Folding Enzymes Form Multiprotein Complexes in Endoplasmic Reticulum to Bind Nascent Proteins
Authors: Meunier Laurent , Usherwood Young-Kwang , Chung Kyung Tae , Hendershot Linda M.
Published: December 2002

We demonstrate the existence of a large endoplasmic reticulum (ER)-localized multiprotein complex that is comprised of the molecular chaperones BiP; GRP94; CaBP1; protein disulfide isomerase (PDI); ERdj3, a recently identified ER Hsp40 cochaperone; cyclophilin B; ERp72; GRP170; UDP-glucosyltransferase; and SDF2-L1. This complex is associated with unassembled, incompletely folded immunoglobulin heavy chains. Except for ERdj3, and to a lesser extent PDI, this complex also forms in the absence of nascent protein synthesis and is found in a variety of cell types. Cross-linking studies reveal that the majority of these chaperones are included in the complex. Our data suggest that this subset of ER chaperones forms an ER network that can bind to unfolded protein substrates instead of existing as free pools that assembled onto substrate proteins. It is noticeable that most of the components of the calnexin/calreticulin system, which include some of the most abundant chaperones inside the ER, are either not detected in this complex or only very poorly represented. This study demonstrates an organization of ER chaperones and folding enzymes that has not been previously appreciated and suggests a spatial separation of the two chaperone systems that may account for the temporal interactions observed in other studies.
Peroxisome Senescence in Human Fibroblasts
Authors: Legakis Julie E. , Koepke Jay I. , Jedeszko Chris , Barlaskar Ferdous , Terlecky Laura J. , Edwards Holly J. , Walton Paul A. , Terlecky Stanley R.
Published: December 2002

The molecular mechanisms of peroxisome biogenesis have begun to emerge; in contrast, relatively little is known about how the organelle functions as cells age. In this report, we characterize age-related changes in peroxisomes of human cells. We show that aging compromises peroxisomal targeting signal 1 (PTS1) protein import, affecting in particular the critical antioxidant enzyme catalase. The number and appearance of peroxisomes are altered in these cells, and the organelles accumulate the PTS1-import receptor, Pex5p, on their membranes. Concomitantly, cells produce increasing amounts of the toxic metabolite hydrogen peroxide, and we present evidence that this increased load of reactive oxygen species may further reduce peroxisomal protein import and exacerbate the effects of aging.
Mitochondrial Fusion in Human Cells Is Efficient, Requires the Inner Membrane Potential, and Is Mediated by Mitofusins
Authors: Legros Frédéric , Lombès Anne , Frachon Paule , Rojo Manuel
Published: December 2002

Mitochondrial fusion remains a largely unknown process despite its observation by live microscopy and the identification of few implicated proteins. Using green and red fluorescent proteins targeted to the mitochondrial matrix, we show that mitochondrial fusion in human cells is efficient and achieves complete mixing of matrix contents within 12 h. This process is maintained in the absence of a functional respiratory chain, despite disruption of microtubules or after significant reduction of cellular ATP levels. In contrast, mitochondrial fusion is completely inhibited by protonophores that dissipate the inner membrane potential. This inhibition, which results in rapid fragmentation of mitochondrial filaments, is reversible: small and punctate mitochondria fuse to reform elongated and interconnected ones upon withdrawal of protonophores. Expression of wild-type or dominant-negative dynamin-related protein 1 showed that fragmentation is due to dynamin-related protein 1-mediated mitochondrial division. On the other hand, expression of mitofusin 1 (Mfn1), one of the human Fzo homologues, increased mitochondrial length and interconnectivity. This process, but not Mfn1 targeting, was dependent on the inner membrane potential, indicating that overexpressed Mfn1 stimulates fusion. These results show that human mitochondria represent a single cellular compartment whose exchanges and interconnectivity are dynamically regulated by the balance between continuous fusion and fission reactions.
Entamoeba histolyticaExpressing a Dominant Negative N-Truncated Light Subunit of Its Gal-Lectin Are Less Virulent
Authors: Katz Uriel , Ankri Serge , Stolarsky Tamara , Nuchamowitz Yael , Mirelman David
Published: December 2002

The 260-kDa heterodimeric Gal/GalNAc-specific Lectin (Gal-lectin) of Entamoeba histolytica dissociates under reducing conditions into a heavy (hgl, 170 kDa) and a light subunit (lgl, 35 kDa). We have previously shown that inhibition of expression of the 35-kDa subunit by antisense RNA causes a decrease in virulence. To further understand the role of the light subunit of the Gal-lectin in pathogenesis, amoebae were transfected with plasmids encoding intact, mutated, and truncated forms of the light subunit lgl1 gene. A transfectant in which the 55 N-terminal amino acids of the lgl were removed, overproduced an N-truncated lgl protein (32 kDa), which replaced most of the native 35-kDa lgl in the formation of the Gal-lectin heterodimeric complex and exerted a dominant negative effect. Amoebae transfected with this construct showed a significant decrease in their ability to adhere to and kill mammalian cells as well as in their capacity to form rosettes with and to phagocytose erythrocytes. In addition, immunofluorescence confocal microscopy of this transfectant with anti–Gal-lectin antibodies showed an impaired ability to cap. These results indicate that the light subunit has a role in enabling the clustering of Gal-lectin complexes and that its N-truncation affects this function, which is required for virulence.
Characterization of an A-Kinase Anchoring Protein in Human Ciliary Axonemes
Authors: Kultgen Patricia L. , Byrd Sherell K. , Ostrowski Lawrence E. , Milgram Sharon L.
Published: December 2002

Although protein kinase A (PKA) activation is known to increase ciliary beat frequency in humans the molecular mechanisms involved are unknown. We demonstrate that PKA is associated with ciliary axonemes where it specifically phosphorylates a 23-kDa protein. Because PKA is often localized to subcellular compartments in proximity to its substrate(s) via interactions with A-kinase–anchoring proteins (AKAPs), we investigated whether an AKAP was also associated with ciliary axonemes. This study has identified a novel 28 kDa AKAP (AKAP28)that is highly enriched in airway axonemes. The mRNA for AKAP28 is up-regulated as primary airway cells differentiate and is specifically expressed in tissues containing cilia and/or flagella. Additionally, both Western blot and immunostaining data show that AKAP28 is enriched in airway cilia. These data demonstrate that we have identified the first human axonemal AKAP, a protein that likely plays a role in the signaling necessary for efficient modulation of ciliary beat frequency.
Identification of the Nuclear Localization Signal inXenopusCyclin E and Analysis of Its Role in Replication and Mitosis
Authors: Moore Jonathan D. , Kornbluth Sally , Hunt Tim
Published: December 2002

Cyclin-dependent kinase (Cdk)2/cyclin E is imported into nuclei assembled in Xenopus egg extracts by a pathway that requires importin-α and -β. Here, we identify a basic nuclear localization sequence (NLS) in the N-terminus ofXenopus cyclin E. Mutation of the NLS eliminated nuclear accumulation of both cyclin E and Cdk2, and such versions of cyclin E were unable to trigger DNA replication. Addition of a heterologous NLS from SV40 large T antigen restored both nuclear targeting of Cdk2/cyclin E and DNA replication. We present evidence indicating that Cdk2/cyclin E complexes must become highly concentrated within nuclei to support replication and find that cyclin A can trigger replication at much lower intranuclear concentrations. We confirmed that depletion of endogenous cyclin E increases the concentration of cyclin B necessary to promote entry into mitosis. In contrast to its inability to promote DNA replication, cyclin E lacking its NLS was able to cooperate with cyclin B in promoting mitotic entry.
Lamin A/C Binding Protein LAP2α Is Required for Nuclear Anchorage of Retinoblastoma Protein
Authors: Markiewicz Ewa , Dechat Thomas , Foisner Roland , Quinlan Roy. A , Hutchison Christopher J.
Published: December 2002

The phosphorylation-dependent anchorage of retinoblastoma protein Rb in the nucleus is essential for its function. We show that its pocket C domain is both necessary and sufficient for nuclear anchorage by transiently expressing green fluorescent protein (GFP) chimeras of Rb fragments in tissue culture cells and by extracting the cells with hypotonic solutions. Solid phase binding assays using glutathioneS-transferase-fusion of Rb pockets A, B, and C revealed a direct association of lamin C exclusively to pocket C. Lamina-associated polypeptide (LAP) 2α, a binding partner of lamins A/C, bound strongly to pocket C and weakly to pocket B. When LAP2α was immunoprecipitated from soluble nuclear fractions, lamins A/C and hypophosphorylated Rb were coprecipitated efficiently. Similarly, immunoprecipitation of expressed GFP-Rb fragments by using anti-GFP antibodies coprecipitated LAP2α, provided that pocket C was present in the GFP chimeras. On redistribution of endogenous lamin A/C and LAP2α into nuclear aggregates by overexpressing dominant negative lamin mutants in tissue culture cells, Rb was also sequestered into these aggregates. In primary skin fibroblasts, LAP2α is expressed in a growth-dependent manner. Anchorage of hypophosphorylated Rb in the nucleus was weakened significantly in the absence of LAP2α. Together, these data suggest that hypophosphorylated Rb is anchored in the nucleus by the interaction of pocket C with LAP2α–lamin A/C complexes.
URBANIZATION AND HEALTH CARE IN RURAL CHINA
Authors: Liu Gordon G. , Wu Xiaodong , Peng Chaoyang , Fu Alex Z.
Published: December 2002

Strong economic growth has led to remarkable urbanization in China. Using the China Health and Nutrition Survey, this study provides the first empirical evidence documenting the impact of urbanization on rural health care and insurance. The primary finding is that urbanization leads to a significant and equitable increase in insurance coverage, which in turn plays a critical role in access to care. In addition, adverse selection exists in the demand for insurance. Income is also a significant determinant of insurance coverage. This study concludes that urbanization can help make substantial changes in rural health care and insurance status.
IDENTIFYING AND ESTIMATING SOURCES OF TECHNICAL INEFFICIENCY IN KOREAN MANUFACTURING INDUSTRIES
Authors: Kim Sangho
Published: December 2002

This study estimated translog stochastic frontier production functions using an unbalanced panel of Korean manufacturing firms in the food, textile, paper, chemical, basic‐metal, and fabrication sectors. The sectors were estimated individually to investigate whether technical efficiency is systematically related to firm size, dependency on external funds, research and development investments, and exports. The empirical results suggest that firm size has a positive and significant effect in every sector. The effects of the other factors are less systematic and vary across sectors.
HABITAT–FISHERY LINKAGES AND MANGROVE LOSS IN THAILAND
Authors: Barbier Edward B.
Published: December 2002

The article develops a dynamic model of habitat–fishery linkage in which the habitat is being converted. The basic model is applied to a case study of the impacts of mangrove deforestation on the artisanal marine demersal and shellfish fisheries in Thailand. The comparative static effects of a change in mangrove area on the long‐run equilibrium level of effort and fish stocks, as well as on the resulting market harvesting supply of the fishery, are determined. By estimating parameters through pooled timE‐series and cross‐sectional data over the 1983–96 period for the five coastal zones along the Gulf of Thailand and Andaman Sea, the welfare impacts of mangrove deforestation are estimated. Mangrove conversion is expected to be a function of the return to shrimp farming and the input costs to farming shrimp, plus exogenous economic factors. The resulting aggregate reduced‐form level of mangrove clearing by all farmers in coastal areas is empirically estimated across the five coastal zones in Thailand over 1983–96. The policy implications of the findings are discussed with respect to Thailand and the modeling of habitat–fishery linkages.
CUTTING CARBON EMISSIONS AT A PROFIT (PART II): IMPACTS ON U.S. COMPETITIVENESS AND JOBS
Authors: Krause Florentin , DeCanio Stephen J. , Hoerner J. Andrew , Baer Paul
Published: December 2002

This article examines how an integrated least‐cost implementation of the Kyoto Protocol in the United States would affect U.S. competitiveness and jobs. Drawing on previous work, the authors analyze integrated emission reduction strategies based on a $50/ton carbon tax (including border tax adjustments), a payroll tax cut, energy‐productivity–oriented market reforms, and international flexibility mechanisms. This policy portfolios is compared to conventional approaches that omit market and fiscal reforms.

Input‐output data are used to estimate the impact on export prices of goods and services produced in the United States. Similar data are used to translate changes in GDP and energy production into employment impacts in energy and nonenergy sectors. The costs of providing transitional assistance for workers in the coal industry are compared to the GDP benefits of a profitable Kyoto strategy.

The analysis shows that relative to purchasing international emission rights, productivity‐raising domestic market, institutional, and fiscal reforms offer much broader advantages for tradE‐exposed U.S. industries. Though allowance purchases alone increase export prices of U.S. manufactured goods and services, an integrated no‐regrets strategy reduces export prices for the large majority of U.S. industries and limits the impact of climate protection policies on the few most energy‐intensive basic materials industries to very small levels. Relative to the baseline, an integrated least‐cost implementation of the Kyoto target increases economy‐wide employment levels by several hundred thousand jobs in 2010.
The Min system is not required for precise placement of the midcell Z ring in Bacillus subtilis
Authors: Migocki Margaret D. , Freeman Marcelle K. , Wake R. Gerry , Harry Elizabeth J.
Published: December 2002

In bacteria, the Min system plays a role in positioning the midcell division site by inhibiting the formation of the earliest precursor of cell division, the Z ring, at the cell poles. However, whether the Min system also contributes to establishing the precise placement of the midcell Z ring is unresolved. We show that the Z ring is positioned at midcell with a high degree of precision in Bacillus subtilis, and this is completely maintained in the absence of the Min system. Min is therefore not required for correct midcell Z ring placement in B. subtilis. Our results strongly support the idea that the primary role of the Min system is to block Z ring formation at the cell poles and that a separate mechanism must exist to ensure cell division occurs precisely at midcell.
PVF2, a PDGF/VEGF‐like growth factor, induces hemocyte proliferation in Drosophila larvae
Authors: Munier Anne‐Isabelle , Doucet Daniel , Perrodou Emmanuel , Zachary Daniel , Meister Marie , Hoffmann Jules A. , Janeway Charles A. , Lagueux Marie
Published: December 2002

Blood cells play a crucial role in both morphogenetic and immunological processes in Drosophila, yet the factors regulating their proliferation remain largely unknown. In order to address this question, we raised antibodies against a tumorous blood cell line and identified an antigenic determinant that marks the surface of prohemocytes and also circulating plasmatocytes in larvae. This antigen was identified as a Drosophila homolog of the mammalian receptor for platelet‐derived growth factor (PDGF)/vascular endothelial growth factor (VEGF). The Drosophila receptor controls cell proliferation in vitro. By overexpressing in vivo one of its putative ligands, PVF2, we induced a dramatic increase in circulating hemocytes. These results identify the PDGF/VEGF receptor homolog and one of its ligands as important players in Drosophila hematopoiesis.
Synthesis, characterization, and structures of zircona- and boracyclosiloxanes with ferrocenyl substituents
Authors: Thieme Karena , Bourke Sara C , Zheng Juan , MacLachlan Mark J , Zamanian Fojan , Lough Alan J , Manners Ian
Published: December 2002

The novel zirconatetraferrocenylcyclotrisiloxane Cp2Zr(OSiFc2)2O (6), dizirconatetraferrocenylcyclotetrasiloxane [Cp2Zr(OSiFc2)O]2 (7), boratetraferrocenylcyclotrisiloxane (C6H5)B(OSiFc2)2O (8), and diboratetraferrocenylcyclotetrasiloxane [(C6H5)B(OSiFc2)O]2 (9) with ferrocenyl (Fc = Fe(η-C5H4)(η-C5H5)) substituents at silicon have been prepared from the reactions of Cp2Zr(NMe2)2 and PhBCl2 with diferrocenylsilanediol Fc2Si(OH)2 (3) and tetraferrocenyldisiloxanediol [Fc2SiOH]2O (5). The compounds were characterized by mass spectrometry, elemental analysis, UVvis, IR, Raman, and multinuclear NMR spectroscopy, as well as single crystal X-ray diffraction. Thermogravimetric analysis and differential scanning calorimetry investigation of 69 showed that the cycles decompose before they can undergo any thermal ring-opening polymerization. In addition, no polymerization was detected in the presence of either KOSiMe3 or HOTf. The bulky ferrocenyl substituents on the Si atoms are likely to be at least partially responsible for the inability of these heterocycles to undergo ring-opening polymerization. Key words: heterocyclosiloxanes, ferrocenyl.
Sequential dehydrochloride coupling of trichlorophosphine with 2,6-di-isopropylaniline: aminophosphine precursors to phosphetidines
Authors: Burford Neil , Cameron T Stanley , Conroy Korey D , Ellis Bobby , Macdonald Charles LB , Ovans Robyn , Phillips Andrew D , Ragogna Paul J , Walsh Denise
Published: December 2002

Various stoichiometric combinations of PCl3 with DippNH2 (Dipp = 2,6-di-isopropylphenyl) have been examined using 31P NMR spectroscopy. The dehydrochloride coupling reaction is mediated by the moderate steric bulk of the Dipp substituent. Isolation procedures and characterization data are reported for the aminodichlorophosphine (1), the aminotetrachlorodiphosphine (4), and the dichlorophosphetidine (7). The observations offer new appreciation of dehydrochloride coupling products of halophosphines with primary amines.Key words: phosphorus, nitrogen, phosphazanes, phosphetidines, iminophosphine.
Earnings Management Surrounding Top Executive Turnover in Japanese Firms
Authors: Lam Detzler Miranda , Machuga Susan M.
Published: December 2002

This study examines the patterns of four discretionary financial variables surrounding president turnovers in Japanese firms. A new theory for earnings management, the coaching hypothesis, and three previously tested theories, the horizon, cover-up, and big bath hypotheses, are investigated. Our empirical results reinforce the importance of controlling for firm performance when testing earnings management. For routine turnovers, the evidence is consistent with the coaching hypothesis, which predicts mutual interests between incoming and outgoing presidents to portray a triumphant transition. We also find evidence for the horizon hypothesis, in that outgoing presidents in routine turnovers attempt to increase earnings during their last years, but the extent of the horizon problem may be curtailed by incentives to preserve a successful transition, the coaching hypothesis. For non-routine turnovers, we find little evidence of outgoing presidents attempting to cover up poor performance by employing income-increasing strategies. We also find weak support for the big bath hypothesis, which predicts incoming presidents of non-routine turnovers to decrease earnings in the transition year in order to report improved earnings in the following year.
Further Study on the Performance of Mergers among Credit Associations in Japan
Authors: Hoshino Yasuo , Turnbull Stephen J.
Published: December 2002

The recent trends toward consolidation in financial markets, both global and national, and the difficult state of the Japanese financial industry suggest the importance of an examination of consolidation in the Japanese financial industry. Recent mega-mergers have produced enormous banks such as the Bank of Tokyo-Mitsubishi, but as usual in Japan the health of the financial industry depends substantially on small and medium-size institutions. There the recent trend toward merger extends back a few decades.

This study reports a further examination of performance of mergers among credit associations (CA) in Japan, using a sample of 25 pairs of merging and non-merging institutions. Each pair is chosen for comparability in terms of variates such as size and geography. Performance is measured by 19 financial ratios sampled during the period of 1983–1998. Considering pre-versus post-merger values of various ratios, mergers have significant positive effects on ratios such as non-personnel expenses ratio, income ratio after tax, loan-deposit ratio, deposit per office and deposit per association's member. But mergers have rather negative effects on net equity ratio and ratio of current expense to current income. On balance mergers are a positive factor in the CA industry. These results contradict the conclusions of earlier studies (Hoshino, 1988).

Among relative financial ratios (comparing merging and non-merging CA), the effect of merger on yield on interest received and non-personnel expenses ratio are shown to be positive in this sample, contradicting previous results. However, in general the financial characteristics of merging CA are rather inferior to those of non-merging CA.
Lifetime Risk for Developing Congestive Heart Failure
Authors: Lloyd-Jones Donald M. , Larson Martin G. , Leip Eric P. , Beiser Alexa , D’Agostino Ralph B. , Kannel William B. , Murabito Joanne M. , Vasan Ramachandran S. , Benjamin Emelia J. , Levy Daniel
Published: December 2002

Background—

Congestive heart failure (CHF) is an increasing public health problem.

Methods and Results—

Among Framingham Heart Study subjects who were free of CHF at baseline, we determined the lifetime risk for developing overt CHF at selected index ages. We followed 3757 men and 4472 women from 1971 to 1996 for 124 262 person-years; 583 subjects developed CHF and 2002 died without prior CHF. At age 40 years, the lifetime risk for CHF was 21.0% (95% CI 18.7% to 23.2%) for men and 20.3% (95% CI 18.2% to 22.5%) for women. Remaining lifetime risk did not change with advancing index age because of rapidly increasing CHF incidence rates. At age 80 years, the lifetime risk was 20.2% (95% CI 16.1% to 24.2%) for men and 19.3% (95% CI 16.5% to 22.2%) for women. Lifetime risk for CHF doubled for subjects with blood pressure ≥160/100 versus <140/90 mm Hg. In a secondary analysis, we only considered those who developed CHF without an antecedent myocardial infarction; at age 40 years, the lifetime risk for CHF was 11.4% (95% CI 9.6% to 13.2%) for men and 15.4% (95% CI 13.5% to 17.3%) for women.

Conclusions—

When established clinical criteria are used to define overt CHF, the lifetime risk for CHF is 1 in 5 for both men and women. For CHF occurring in the absence of myocardial infarction, the lifetime risk is 1 in 9 for men and 1 in 6 for women, which highlights the risk of CHF that is largely attributable to hypertension. These results should assist in predicting the population burden of CHF and placing greater emphasis on prevention of CHF through hypertension control and prevention of myocardial infarction.
FrzA, a Secreted Frizzled Related Protein, Induced Angiogenic Response
Authors: Dufourcq Pascale , Couffinhal Thierry , Ezan Jérome , Barandon Laurent , Moreau Catherine , Daret Danièle , Duplàa Cécile
Published: December 2002

Background—

The secreted frizzled related proteins (sFRP) are soluble proteins thought to interfere with the Wnt signaling. Our group previously demonstrated that one of these members, sFRP-1/FrzA, is strongly expressed during early phases of the vascularization process in embryonic vasculature and in the endothelium of arteries and capillaries in adults and modulated vascular cell proliferation.

Methods and Results—

Analysis of the expression of
sFRP-1
during cyclic ovarian angiogenesis revealed that
sFRP-1
is expressed during the formation of neovessels and becomes undetectable when the vasculature is fully maturated. We then studied the role of FrzA in several distinct angiogenic models. FrzA induced angiogenesis in a chick chorioallantoic membrane model. Moreover, gene transfer of AdFrzA in grafted mesenchymal and glioma cells increased vessel density and tumor growth. FrzA induced formation of vessels, which were enlarged, longer, and appeared to be more mature compared with vessels formed under control treatments. In vitro, FrzA increased migration and tube formation of endothelial cells and seemed to protect them from apoptosis. FrzA-angiogenic effect in vitro was independent of vascular endothelial growth factor, fibroblast growth factor-2, or angiopiotin-1 induction and Akt activation. In contrast, FrzA decreased glycogen synthase kinase-3 phosphorylation.

Conclusions—

These results showed that FrzA has proangiogenic effects and suggest that Wnt signaling may be involved in normal differentiation as well as in the pathological development of vasculature.
Use of Emergency Medical Services in Acute Myocardial Infarction and Subsequent Quality of Care
Authors: Canto John G. , Zalenski Robert J. , Ornato Joseph P. , Rogers William J. , Kiefe Catarina I. , Magid David , Shlipak Michael G. , Frederick Paul D. , Lambrew Costas G. , Littrell Katherine A. , Barron Hal V.
Published: December 2002

Background—

National practice guidelines strongly recommend activation of the 9-1-1 Emergency Medical Systems (EMS) by patients with symptoms consistent with an acute myocardial infarction (MI). We examined use of the EMS in the United States and ascertained the factors that may influence its use by patients with acute MI.

Methods and Results—

From June 1994 to March 1998, the National Registry of Myocardial Infarction 2 enrolled 772 586 patients hospitalized with MI. We excluded those who transferred in, arrived at the hospital >6 hours from symptom onset, or who were in cardiogenic shock. We compared baseline characteristics and initial management for patients who arrived by ambulance versus self-transport. EMS was used in 53.4% of patients with MI, a proportion that did not vary significantly over the 4-year study period. Nonusers of the EMS were on average younger, male, and at relatively lower risk on presentation. In addition, payer status was significantly associated with EMS use. Use of EMS was independently associated with slightly wider use of acute reperfusion therapies and faster time intervals from door to fibrinolytic therapy (12.1 minutes faster,
P
<0.001) or to urgent PTCA (31.2 minutes faster,
P
<0.001).

Conclusions—

Only half of patients with MI were transported to the hospital by ambulance, and these patients had greater and significantly faster receipt of initial reperfusion therapies. Wider use of EMS by patients with suspected MI may offer considerable opportunity for improvement in public health.
S
-Nitrosoglutathione Reduces Asymptomatic Embolization After Carotid Angioplasty
Authors: Kaposzta Zoltan , Clifton Andrew , Molloy Jane , Martin John F. , Markus Hugh S.
Published: December 2002

Background—

The major complication of carotid angioplasty is embolic stroke, which may occur after balloon inflation and deflation or in the early postintervention period. Platelet adhesion and aggregation to the angioplasty site with subsequent embolization seems to plays a major role in early postangioplasty embolization and stroke. During this period, asymptomatic embolic signals can be detected in patients by transcranial Doppler ultrasound despite aspirin and heparin treatment.
S
-Nitrosoglutathione (GSNO) is a nitric oxide donor that appears to have relative platelet specificity. We evaluated its effectiveness in reducing embolization after carotid angioplasty.

Methods and Results—

Sixteen patients undergoing carotid angioplasty and stenting for symptomatic ≥70% internal carotid artery stenosis were randomized in a double-blind manner to GSNO or placebo given after surgery for 90 minutes. All patients were pretreated with aspirin and given heparin for 24 hours after the procedure. Transcranial Doppler recordings were made from the ipsilateral middle cerebral artery for 1 hour before treatment and at 0 to 3, 6, and 24 hours after treatment. GSNO resulted in a rapid reduction in the frequency of embolic signals of 95% at 0 to 3 hours and 100% at 6 hours (
P
=0.007 and
P
=0.01 versus placebo, respectively). In the placebo group, 2 patients experienced ipsilateral stroke after the angioplasty. No cerebrovascular events occurred in the GSNO group.

Conclusions—

S
-Nitrosoglutathione was highly effective in rapidly reducing the frequency of embolic signals after endovascular treatment for symptomatic high-grade carotid stenosis.
Low-Density Lipoprotein Receptor Gene Mutations and Cardiovascular Risk in a Large Genetic Cascade Screening Population
Authors: Umans-Eckenhausen Marina A.W. , Sijbrands Eric J.G. , Kastelein John J.P. , Defesche Joep C.
Published: December 2002

Background—

A large cohort of patients with familial hypercholesterolemia (FH), free from selection for cardiovascular disease (CVD), and their unaffected relatives was collected by genetic cascade screening and examined for the influence of different mutations of the LDL receptor gene on lipoprotein levels and the risk of CVD. Multivariate analyses with adjustment for age, sex, and specific family ties were performed.

Methods and Results—

Significant variation of LDL levels was observed among 399 patients with FH with different mutations. Null alleles were associated with more severely elevated LDL cholesterol, whereas the frequent N543H/2393del9 mutation led to less elevated LDL cholesterol. The type of mutation did not influence HDL cholesterol levels. Patients with FH had CVD 8.5 times more often compared with their unaffected relatives (RR, 8.54; 95% CI, 5.29 to 13.80). The N543H/2393del9 mutation was associated with a smaller increase of risk compared with other mutations (
P
<0.0001). After exclusion of families with the N543H/2393del9 mutation, null alleles and other allele mutations no longer differed with regard to LDL cholesterol levels and CVD risk.

Conclusions—

LDL receptor mutations only partly contributed to the variation of LDL cholesterol levels and cardiovascular burden in FH. Additional, so far unidentified, familial risk factors must underlie the differences of CVD risk, most likely independent of lipids and lipoproteins.