bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of the Isochrysis C18-Δ9 Polyunsaturated Fatty Acid Specific Elongase Component Alters Arabidopsis Glycerolipid Profiles
Authors: Fraser Thomas Colin Michael , Qi Baoxiu , Elhussein Salah , Chatrattanakunchai Sunantha , Stobart Allan Keith , Lazarus Colin Michael
Published: June 2004

A cDNA isolated from the prymnesiophyte micro-alga Isochrysis galbana, designated IgASE1, encodes a fatty acid elongating component that is specific for linoleic acid (C18:2n-6) and α-linolenic acid (C18:3n-3). Constitutive expression of IgASE1 in Arabidopsis resulted in the accumulation of eicosadienoic acid (EDA; C20:2n-6) and eicosatrienoic acid (ETrA; C20:3n-3) in all tissues examined, with no visible effects on plant morphology. Positional analysis of the various lipid classes indicated that these novel fatty acids were largely excluded from the sn-2 position of chloroplast galactolipids and seed triacylglycerol, whereas they were enriched in the same position in phosphatidylcholine. EDA and ETrA are precursors of arachidonic acid (C20:4n-6), eicosapentaenoic acid (C20:5n-3), and docosahexaenoic acid (C22:6n-3) synthesized via the so-called ω6 Δ8 desaturase and ω3 Δ8 desaturase biosynthetic pathways, respectively. The synthesis of significant quantities of EDA and ETrA in a higher plant is therefore a key step in the production of very long chain polyunsaturated fatty acid in oil-seed species. The results are further discussed in terms of prokaryotic and eukaryotic pathways of lipid synthesis in plants.
Glucosinolate and Amino Acid Biosynthesis in Arabidopsis
Authors: Field Ben , Cardon Guillermo , Traka Maria , Botterman Johan , Vancanneyt Guy , Mithen Richard
Published: June 2004

Enzymes that catalyze the condensation of acetyl coenzyme A and 2-oxo acids are likely to be important in two distinct metabolic pathways in Arabidopsis. These are the synthesis of isopropylmalate, an intermediate of Leu biosynthesis in primary metabolism, and the synthesis of methylthioalkylmalates, intermediates of Met elongation in the synthesis of aliphatic glucosinolates (GSLs), in secondary metabolism. Four Arabidopsis genes in the ecotype Columbia potentially encode proteins that could catalyze these reactions. MAM1 and MAML are adjacent genes on chromosome 5 at the Gsl-elong locus, while MAML-3 and MAML-4 are at opposite ends of chr 1. The isopropylmalate synthase activity of each member of the MAM-like gene family was investigated by heterologous expression in an isopropylmalate synthase-null Escherichia coli mutant. Only the expression of MAML-3 restored the ability of the mutant to grow in the absence of Leu. A MAML knockout line (KO) lacked long-chain aliphatic GSLs, which were restored when the KO was transformed with a functional MAML gene. Variation in expression of MAML did not alter the total levels of Met-derived GSLs, but just the ratio of chain lengths. MAML overexpression in Columbia led to an increase in long-chain GSLs, and an increase in 3C GSLs. Moreover, plants overexpressing MAML contained at least two novel amino acids. One of these was positively identified via MS/MS as homo-Leu, while the other, with identical mass and fragmentation patterns, was likely to be homo-Ile. A MAML-4 KO did not exhibit any changes in GSL profile, but had perturbed soluble amino acid content.
Trehalose Mediated Growth Inhibition of Arabidopsis Seedlings Is Due to Trehalose-6-Phosphate Accumulation
Authors: Schluepmann Henriette , van Dijken Anja , Aghdasi Mahnaz , Wobbes Barry , Paul Matthew , Smeekens Sjef
Published: June 2004

Trehalose-6-phosphate (T6P) is required for carbon utilization during Arabidopsis development, and its absence is embryo lethal. Here we show that T6P accumulation inhibits seedling growth. Wild-type seedlings grown on 100 mm trehalose rapidly accumulate T6P and stop growing, but seedlings expressing Escherichia coli trehalose phosphate hydrolase develop normally on such medium. T6P accumulation likely results from much-reduced T6P dephosphorylation when trehalose levels are high. Metabolizable sugars added to trehalose medium rescue T6P inhibition of growth. In addition, Suc feeding leads to a progressive increase in T6P concentrations, suggesting that T6P control over carbon utilization is related to available carbon for growth. Expression analysis of genes from the Arabidopsis trehalose metabolism further supports this: Suc rapidly induces expression of trehalose phosphate synthase homolog AtTPS5 to high levels. In contrast, T6P accumulation after feeding trehalose in the absence of available carbon induces repression of genes encoding T6P synthases and expression of T6P phosphatases. To identify processes controlled by T6P, we clustered expression profile data from seedlings with altered T6P content. T6P levels correlate with expression of a specific set of genes, including the S6 ribosomal kinase ATPK19, independently of carbon status. Interestingly, Suc addition represses 15 of these genes, one of which is AtKIN11, encoding a Sucrose Non Fermenting 1 (SNF1)-related kinase known to play a role in Suc utilization.
A Family of Auxin-Conjugate Hydrolases That Contributes to Free Indole-3-Acetic Acid Levels during Arabidopsis Germination
Authors: Rampey Rebekah A. , LeClere Sherry , Kowalczyk Mariusz , Ljung Karin , Sandberg Göran , Bartel Bonnie
Published: June 2004

Auxins are hormones important for numerous processes throughout plant growth and development. Plants use several mechanisms to regulate levels of the auxin indole-3-acetic acid (IAA), including the formation and hydrolysis of amide-linked conjugates that act as storage or inactivation forms of the hormone. Certain members of an Arabidopsis amidohydrolase family hydrolyze these conjugates to free IAA in vitro. We examined amidohydrolase gene expression using northern and promoter-β-glucuronidase analyses and found overlapping but distinct patterns of expression. To examine the in vivo importance of auxin-conjugate hydrolysis, we generated a triple hydrolase mutant, ilr1 iar3 ill2, which is deficient in three of these hydrolases. We compared root and hypocotyl growth of the single, double, and triple hydrolase mutants on IAA-Ala, IAA-Leu, and IAA-Phe. The hydrolase mutant phenotypic profiles on different conjugates reveal the in vivo activities and relative importance of ILR1, IAR3, and ILL2 in IAA-conjugate hydrolysis. In addition to defective responses to exogenous conjugates, ilr1 iar3 ill2 roots are slightly less responsive to exogenous IAA. The triple mutant also has a shorter hypocotyl and fewer lateral roots than wild type on unsupplemented medium. As suggested by the mutant phenotypes, ilr1 iar3 ill2 imbibed seeds and seedlings have lower IAA levels than wild type and accumulate IAA-Ala and IAA-Leu, conjugates that are substrates of the absent hydrolases. These results indicate that amidohydrolases contribute free IAA to the auxin pool during germination in Arabidopsis.
Intracellular Localization of Arabidopsis Sulfurtransferases
Authors: Bauer Michael , Dietrich Christof , Nowak Katharina , Sierralta Walter D. , Papenbrock Jutta
Published: June 2004

Sulfurtransferases (Str) comprise a group of enzymes widely distributed in archaea, eubacteria, and eukaryota which catalyze the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors. In all organisms analyzed to date, small gene families encoding Str proteins have been identified. The gene products were localized to different compartments of the cells. Our interest concerns the localization of Str proteins encoded in the nuclear genome of Arabidopsis. Computer-based prediction methods revealed localization in different compartments of the cell for six putative AtStrs. Several methods were used to determine the localization of the AtStr proteins experimentally. For AtStr1, a mitochondrial localization was demonstrated by immunodetection in the proteome of isolated mitochondria resolved by one- and two-dimensional gel electrophoresis and subsequent blotting. The respective mature AtStr1 protein was identified by mass spectrometry sequencing. The same result was obtained by transient expression of fusion constructs with the green fluorescent protein in Arabidopsis protoplasts, whereas AtStr2 was exclusively localized to the cytoplasm by this method. Three members of the single-domain AtStr were localized in the chloroplasts as demonstrated by transient expression of green fluorescent protein fusions in protoplasts and stomata, whereas the single-domain AtStr18 was shown to be cytoplasmic. The remarkable subcellular distribution of AtStr15 was additionally analyzed by transmission electron immunomicroscopy using a monospecific antibody against green fluorescent protein, indicating an attachment to the thylakoid membrane. The knowledge of the intracellular localization of the members of this multiprotein family will help elucidate their specific functions in the organism.
IAR4, a Gene Required for Auxin Conjugate Sensitivity in Arabidopsis, Encodes a Pyruvate Dehydrogenase E1α Homolog
Authors: LeClere Sherry , Rampey Rebekah A. , Bartel Bonnie
Published: June 2004

The formation and hydrolysis of indole-3-acetic acid (IAA) conjugates represent a potentially important means for plants to regulate IAA levels and thereby auxin responses. The identification and characterization of mutants defective in these processes is advancing the understanding of auxin regulation and response. Here we report the isolation and characterization of the Arabidopsis iar4 mutant, which has reduced sensitivity to several IAA-amino acid conjugates. iar4 is less sensitive to a synthetic auxin and low concentrations of an ethylene precursor but responds to free IAA and other hormones tested similarly to wild type. The gene defective in iar4 encodes a homolog of the E1α-subunit of mitochondrial pyruvate dehydrogenase, which converts pyruvate to acetyl-coenzyme A. We did not detect glycolysis or Krebs-cycle-related defects in the iar4 mutant, and a T-DNA insertion in the IAR4 coding sequence conferred similar phenotypes as the originally identified missense allele. In contrast, we found that disruption of the previously described mitochondrial pyruvate dehydrogenase E1α-subunit does not alter IAA-Ala responsiveness or confer any obvious phenotypes. It is possible that IAR4 acts in the conversion of indole-3-pyruvate to indole-3-acetyl-coenzyme A, which is a potential precursor of IAA and IAA conjugates.
Fluorescent Screening of Transgenic Arabidopsis Seeds without Germination
Authors: Wei Shu , Bravdo Ben-Ami , Shoseyov Oded
Published: June 2004

In this paper, we describe a reliable method for the screening and selection of Arabidopsis transgenic seeds within minutes without germination. Expression of the Aspergillus niger β-glucosidase gene BGL1 in the plant's endoplasmic reticulum was used as a visual marker, together with 4-methylumbelliferyl-β-d-glucopyranoside (MUGluc) as a substrate. Subsequent to incubation in a solution of MUGluc at room temperature for 2 to 15 min, transgenic seeds expressing BGL1 demonstrated a distinct fluorescent signal under UV light. Optimal screening conditions at room temperature were achieved between 75 and 450 μ  m MUGluc, at a pH of 2.5 to 5.0 and 2 to 5 min of incubation. No significant loss of viability was detected in transgenic seeds that were redried and stored for 45 d after incubation in MUGluc solution for 2 to 150 min. Transgenic plants expressing BGL1 displayed normal phenotypes relative to the wild type. Selection frequency was 3.1% ± 0.34% for the fluorescence selection method, while kanamycin resistant selection resulted in only 0.56% ± 0.13% using the same seed batch. This novel selection method is nondestructive, practical, and efficient, and eliminates the use of antibiotic genes. In addition, the procedure shortens the selection time from weeks to minutes.
Salicylate Accumulation Inhibits Growth at Chilling Temperature in Arabidopsis
Authors: Scott Ian M. , Clarke Shannon M. , Wood Jacqueline E. , Mur Luis A.J.
Published: June 2004

The growth of Arabidopsis plants in chilling conditions could be related to their levels of salicylic acid (SA). Plants with the SA hydroxylase NahG transgene grew at similar rates to Col-0 wild types at 23°C, and growth of both genotypes was slowed by transfer to 5°C. However, at 5°C, NahG plants displayed relative growth rates about one-third greater than Col-0, so that by 2 months NahG plants were typically 2.7-fold larger. This resulted primarily from greater cell expansion in NahG rosette leaves. Specific leaf areas and leaf area ratios remained similar in both genotypes. Net assimilation rates were similar in both genotypes at 23°C, but higher in NahG at 5°C. Chlorophyll fluorescence measurements revealed no PSII photodamage in chilled leaves of either genotype. Col-0 shoots at 5°C accumulated SA, particularly in glucosylated form. SA in NahG shoots showed similar tendencies at 5°C, but at greatly depleted levels. Catechol was not detected as a metabolite of the NahG transgene product. We also examined growth and SA levels in SA signaling and metabolism mutants at 5°C. The partially SA-insensitive npr1 mutant displayed growth intermediate between NahG and Col-0, while the SA-deficient eds5 mutant behaved like NahG. In contrast, the cpr1 mutant at 5°C accumulated very high levels of SA and its growth was much more inhibited than wild type. At both temperatures, cpr1 was the only SA-responsive genotype in which oxidative damage (measured as thiobarbituric acid-reactive substances) was significantly different from wild type.
Chlamydomonas and Arabidopsis. A Dynamic Duo
Authors: Gutman Benjamin L. , Niyogi Krishna K.
Published: June 2004

A translational biology perspective on Chlamydomonas and Arabidopsis might be expected to focus on those genes, cellular components, or biological processes found first in Chlamydomonas and subsequently studied in Arabidopsis. There are indeed many such examples. There are also examples that flow from Arabidopsis to Chlamydomonas in terms of initial discovery and subsequent study. However, the differences can also be illuminating. In this brief essay, we make a case for the pairing of Chlamydomonas and Arabidopsis as model organisms that bracket a major subset of photosynthetic eukaryotes, the green plants (Mishler, 2000). By analogy with the yeast-mouse dyad, this green pair has tremendous potential as we enter an era of renewed interest in comparative biology.
AtCAND1, A HEAT-Repeat Protein That Participates in Auxin Signaling in Arabidopsis
Authors: Cheng Youfa , Dai Xinhua , Zhao Yunde
Published: June 2004

Auxin affects many aspects of plant growth and development. We previously used chemical genetics to dissect auxin-signaling mechanisms and identified a small molecule, sirtinol, that constitutively activated auxin signaling (Y. Zhao et al. [2003], Science 301: 1107–1110). Here we describe the isolation, characterization, and cloning of an Arabidopsis mutant Atcand1-1 that emerged from a genetic screen for mutants insensitive to sirtinol. Loss-of-function mutants of AtCAND1 were resistant to sirtinol and auxin, but not to gibberellins or brassinolide. Atcand1 displayed developmental phenotypes similar to those of axr1, namely, short petioles, downwardly curling leaves, short inflorescence, and reduced fertility. AtCAND1 is homologous to human CAND1, a protein that is composed almost entirely of HEAT-repeat units and has been implicated in regulating the assembly and disassembly of the SCF protein degradation machinery. Taken together with previous biochemical studies, this work helps to elucidate the roles of AtCAND1 in protein degradation and auxin signaling.
Customer value: a review of recent literature and an integrative configuration
Authors: Salem Khalifa Azaddin
Published: June 2004

The concept of customer value is becoming increasingly used in strategy and marketing literature in recent years. Customer value is considered central to competitive advantage and long‐term success of business organizations. Consequently, a great importance attached to this concept. This paper attempts to build an integrative configuration of the concept of customer value that reflects its richness and complexity. It reviews, synthesizes and extends the literature on the subject. The configuration includes three complementary models, namely: customer value in exchange, customer value buildup, and customer value dynamics. Thinking about customer value in this way is helpful in the designing of and studying service offerings.
Neural network analysis of leakage oil quantity in the design of partially hydrostatic slipper bearings
Authors: Canbulut Fazıl , Sinanoğlu Cem , Yildirim Şahin
Published: June 2004

This paper presents an investigation for analyzing the efficiency of axial piston pumps in a variety conditions using a proposed neural network. Since slippers affect the performance of the system considerably, the effects of surface roughness on lubrication have been studied in slippers with varying hydrostatic bearing areas and surface roughness. The neural network structure is very suitable for this kind of system. The network is capable of predicting the leakage oil quantity of the experimental system. The network has parallel structure and fast learning capacity. It is also easy to see from the experimental results that the leakage oil quantity was caused by surface roughness, orifice diameter and the size of hydrostatic bearing area, loading pressure and the number of rotations. It can be outlined from the results for both approaches, neural network could be modeled slipper bearing systems in real time applications.
Is Self‐Complexity Linked to Better Coping? A Review of the Literature
Authors: Koch Erika J. , Shepperd James A.
Published: June 2004

Abstract
Initial theorizing depicted self‐complexity as the number of nonoverlapping self‐aspects, such as traits, roles, and behaviors, and proposed that greater self‐complexity is linked to better coping in response to stress and negative events. A review of the literature, however, finds inconsistent results. The inconsistency apparently arises from variation in the measurement of self‐complexity. The different measures stem from disagreement over the definition of self‐complexity, and the various definitions apparently result from theoretical disagreement about how to conceptualize the structure of self‐knowledge. The present paper reviews the self‐complexity literature and suggests directions for future research. The present paper suggests a positive, moderating relationship between self‐complexity and coping, and additional research that includes careful measurement and definition of self‐complexity may provide stronger support for this relationship.
Sexual Identity Development in the Context of Compulsory Heterosexuality
Authors: Konik Julie , Stewart Abigail
Published: June 2004

Abstract
This study analyzed the implications of sexual identity development for global, political, religious, and occupational identity development in 358 college students. Participants completed a written survey packet including the Extended Objective Measure of Ego Identity Status (EOM‐EIS) and measures of sexual identity, physical/sexual preference, and emotional/affective preference. Data from the EOM‐EIS suggest that having a sexual minority identity (lesbian, gay, bisexual, or “other” nonheterosexual identity) and reporting strong same‐sex sexual or physical preferences are linked with more advanced global, political, religious, and occupational identity development. Heterosexual‐identified participants were more likely to score high on identity foreclosure, moratorium, and diffusion, while sexual‐minority‐identified individuals scored higher on identity achievement. Individuals with strong same‐sex physical/sexual preferences showed a pattern of results similar to those of sexual‐minority‐identified participants. Themes coded from a free‐response question highlighted the finding that sexual‐minority‐identified participants more often viewed their sexual identity as salient and involving an effortful process. These individuals also stressed the importance of having support or modeling for their sexual identity.
Acute desensitization of presynaptic GABAB‐mediated inhibition and induction of epileptiform discharges in the neonatal rat hippocampus
Authors: Tosetti P. , Bakels R. , Colin‐Le Brun I. , Ferrand N. , Gaiarsa J. L. , Caillard O.
Published: June 2004

The consequences of sustained activation of GABAB receptors on GABAB‐mediated inhibition and network activity were investigated in the neonatal rat hippocampus using whole‐cell and extracellular field recordings. GABAB‐mediated presynaptic control of γ‐aminobutyric acid (GABA) release progressively diminished with time in spite of the continued presence of the agonist (100 µm baclofen, 15 min), indicating acute desensitization of presynaptic GABAB‐mediated inhibition on GABAergic terminals. By contrast, neither GABAB‐mediated inhibition of glutamate release nor postsynaptic GABAB‐mediated inhibition seemed to produce this desensitization. Efficacy of presynaptic GABAB receptors was still reduced by 49% 30 min after baclofen washout, suggesting a long timeframe for recovery from desensitization. The 15‐min baclofen application was followed by a dramatic modification of the spontaneous network activity, with the occurrence of epileptiform events called ictal‐like discharges (ILDs). Extracellular field recordings confirmed the epileptic nature of the discharges that could be recorded up to 4 h after baclofen washout. ILDs did not occur when the GABAB receptor antagonist CGP35348 was coapplied with baclofen. This indicates that ILD induction is a consequence of the sustained activation of GABAB receptors and the correlated changes in GABAB‐mediated inhibition. Furthermore, ILDs were also induced when blocking with CGP35348 an amount of GABAB receptors that exactly mimicked the loss of inhibition obtained with desensitization. These results show that presynaptic GABAB‐mediated inhibition of GABA release acutely and specifically desensitizes following a sustained application of the GABAB receptor agonist baclofen. Conditions that induce desensitization of the GABAB‐mediated responses also trigger persistent epileptiform discharges in the neonatal rat hippocampus.
Anterior thalamic lesions stop immediate early gene activation in selective laminae of the retrosplenial cortex: evidence of covert pathology in rats?
Authors: Jenkins Trisha A. , Vann Seralynne D. , Amin Eman , Aggleton John P.
Published: June 2004

Lesions involving the anterior thalamic nuclei stopped immediate early gene (IEG) activity in specific regions of the rat retrosplenial cortex, even though there were no apparent cytoarchitectonic changes. Discrete anterior thalamic lesions were made either by excitotoxin (Experiment 1) or radiofrequency (Experiment 2) and, following recovery, the rats foraged in a radial‐arm maze in a novel room. Measurements made 6–12 weeks postsurgery showed that, in comparison with surgical controls, the thalamic lesions produced the same, selective patterns of Fos changes irrespective of method. Granular (caudal granular cortex and rostral granular cortex), but not dysgranular (dysgranular cortex), retrosplenial cortex showed a striking loss of Fos‐positive cells. While a loss of between 79 and 89% of Fos‐positive cells was found in the superficial laminae, the deeper layers appeared normal. In Experiments 3 and 4, rats 9–10 months postsurgery were placed in an activity box for 30 min. Anterior thalamic lesions (Experiment 3) led to a pronounced IEG decrease of both Fos and zif268 throughout the retrosplenial cortex that now included the dysgranular area. These IEG losses were found even though the same regions appeared normal using standard histological techniques. Lesions of the postrhinal cortex (Experiment 4) did not bring about a loss of retrosplenial IEG activity even though this region is also reciprocally connected with the retrosplenial cortex. This selective effect of anterior thalamic damage upon retrosplenial activity may both amplify the disruptive effects of anterior thalamic lesions and help to explain the posterior cingulate hypoactivity found in Alzheimer's disease.
Neonatal medial prefrontal cortex lesion enhances the sensitivity of the mesoaccumbal dopamine system
Authors: Bennay Mustapha , Gernert Manuela , Schwabe Kerstin , Enkel Thomas , Koch Michael
Published: June 2004

Neurodevelopmental models of schizophrenia posit that early brain damage leads to dys‐ or misconnection effects possibly altering synaptic transmission in brain sites distal of the lesion. We tested the hypothesis that neonatal medial prefrontal cortex (mPFC) lesions affect the sensitivity of the mesoaccumbal dopamine (DA) system. Using extracellular single‐unit recordings combined with systemic application of the DA agonist apomorphine, followed by the D2 receptor antagonist haloperidol or the D1 receptor antagonist SCH23390, we compared electrophysiological properties of nucleus accumbens core and shell neurons after bilateral excitotoxic lesions of mPFC induced at postnatal day 7 or in adult rats. Whereas animals with adult mPFC lesions showed an altered discharge pattern within the core region, neonatal mPFC lesions altered the discharge pattern within the shell region. Subcutaneous administration of apomorphine (4 mg/kg) reduced accumbal firing rate in 77% of all neurons. Onset and magnitude of apomorphine‐induced inhibition of neuronal activity was faster and stronger in rats with neonatal but not adult mPFC lesions in both core and shell regions. Apomorphine‐induced inhibition was partially reversed by 0.1 mg/kg haloperidol only in core region of neonatal lesioned rats. Apomorphine‐induced excitation of neuronal activity (in 21% of all neurons) was reversed by the D1 receptor antagonist SCH23390 (0.1 mg/kg) in all excited neurons. These data support the hypothesis that neonatal but not adult lesions of mPFC alter cortico‐striatal networks and suggest that disturbance of mPFC development leads to neurodevelopmental changes in mesoaccumbal DA system during adulthood.
Exposure to interferon‐γ during synaptogenesis increases inhibitory activity after a latent period in cultured rat hippocampal neurons
Authors: Brask Johan , Kristensson Krister , Hill Russell H.
Published: June 2004

Certain disorders of the nervous system may have their origin in disturbances in the development of synaptic connections and network structure that may not become overt until later in life. As inflammatory cytokines can influence synaptic activity in neuronal cultures, we analysed whether cytokine exposure during synaptogenesis can lead to imbalances in a neuronal network. Short‐term application of interferon‐γ (IFN‐γ), but not tumour necrosis factor‐α, during peak synaptogenesis (but not before or after) in Sprague–Dawley rat hippocampal cultures, caused both a decrease in the frequency of spontaneous excitatory postsynaptic currents (EPSCs) and an increase in the frequency of spontaneous inhibitory postsynaptic currents (IPSCs). These effects were only detected in recordings made weeks later. This was not due to a depression of glutamatergic synapses or to a change in the relative number of neurons containing glutamic acid decarboxylase (GAD). There was an increase in the average amplitude of miniature IPSCs, and in GAD‐expressing neurons the amplitude of miniature EPSCs were larger as well as the responses to glutamate. This indicates that IFN‐γ‐treatment induced increased inhibition via postsynaptic changes. These effects of IFN‐γ treatment were not observed when neuronal nitric oxide synthase was inhibited. Our study therefore shows that exposure to IFN‐γ during a restricted period of development, which coincides with the peak of excitatory synaptogenesis, can cause progressive changes in synaptic activity in the network. Thus, cytokine exposure at a critical period of development may constitute a ‘hit‐and‐run’ mechanism for certain nervous system disorders that become manifest after a latency period.
Preferential vulnerability of astroglia and glial precursors to combined opioid and HIV‐1 Tat exposure in vitro
Authors: Khurdayan Valeriya K. , Buch Shreya , El‐Hage Nazira , Lutz Sarah E. , Goebel Susan M. , Singh Indrapal N. , Knapp Pamela E. , Turchan‐Cholewo Jadwiga , Nath Avindra , Hauser Kurt F.
Published: June 2004

Human immunodeficiency virus (HIV)‐1 infection can cause characteristic neural defects such as progressive motor dysfunction, striatal pathology and gliosis. Recent evidence suggests that HIV‐induced pathogenesis is exacerbated by heroin abuse and that the synergistic neurotoxicity is a direct effect of heroin on the CNS, an alarming observation considering the high incidence of HIV infection with injection drug abuse. Although HIV infection results in neurodegeneration, neurons themselves are not directly infected. Instead, HIV affects microglia and astroglia, which subsequently contributes to the neurodegenerative changes. Opioid receptors are widely expressed by macroglia and macroglial precursors, and the activation of µ‐opioid receptors can modulate programmed cell death, as well as the response of neural cells to cytotoxic insults. For this reason, we questioned whether opioid drugs might modify the vulnerability of macroglia and macroglial precursors to HIV‐1 Tat protein. To address this problem, the effects of morphine and/or HIV Tat1−72 on the viability of macroglia and macroglial precursors were assessed in mixed‐glial cultures derived from mouse striatum. Our findings indicate that sustained exposure to morphine and Tat1−72 viral protein induces the preferential death of glial precursors and some astrocytes. Moreover, the increased cell death is mediated by µ‐opioid receptors and accompanied by the activation of caspase‐3. Our results imply that opiates can enhance the cytotoxicity of HIV‐1 Tat through direct actions on glial precursors and/or astroglia, suggesting novel cellular targets for HIV–opiate interactions.
SOME REMARKS ON ARBITRAGE AND PREFERENCES IN SECURITIES MARKET MODELS
Authors: Frittelli Marco
Published: June 2004

We introduce the notion of a market‐free‐lunch that depends on the preferences of all agents participating in the market. In semimartingale models of securities markets, we characterize no arbitrage (NA) and no‐free‐lunch‐with‐vanishing‐risk (NFLVR) in terms of the market‐free‐lunch and show that the difference between NA and NFLVR consists in the selection of the class of monotone, respectively monotone and continuous, utility functions that determines the absence of the market‐free‐lunch. We also provide a direct proof of the equivalence between the absence of a market‐free‐lunch, with respect to monotone concave preferences, and the existence of an equivalent (local/sigma) martingale measure.
A FAMILY OF TERM‐STRUCTURE MODELS FOR LONG‐TERM RISK MANAGEMENT AND DERIVATIVE PRICING
Authors: Cairns Andrew J. G.
Published: June 2004

In this paper we propose a new family of term‐structure models based on the Flesaker and Hughston (1996) positive‐interest framework. The models are Markov and time homogeneous, with correlated Ornstein‐Uhlenbeck processes as state variables. We provide a theoretical analysis of the one‐factor model and a thorough emprical analysis of the two‐factor model. This allows us to identify the key factors in the model affecting interest‐rate dynamics. We conclude that the new family of models should provide a useful tool for use in long‐term risk management. Suitably parameterized, they can satisfy a wide range of desirable criteria, including:

sustained periods of both high and low interest rates similar to the cycle lengths we have observed over the course of the 20th century in the United Kingdom and the United States

realistic probabilities of both high and low interest rates consistent with historical data and without the need for regular recalibration

a wide range of shapes of yield curves, again consistent with what we have observed in the past and including the recent Japanese yield curve.
QUANTO LOOKBACK OPTIONS
Authors: Dai Min , Wong Hoi Ying , Kwok Yue Kuen
Published: June 2004

The lookback feature in a quanto option refers to the payoff structure where the terminal payoff of the quanto option depends on the realized extreme value of either the stock price or the exchange rate. In this paper, we study the pricing models of European and American lookback options with the quanto feature. The analytic price formulas for two types of European‐style quanto lookback options are derived. The success of the analytic tractability of these quanto lookback options depends on the availability of a succinct analytic representation of the joint density function of the extreme value and terminal value of the stock price and exchange rate. We also analyze the early exercise policies and pricing behaviors of the quanto lookback options with the American feature. The early exercise boundaries of these American quanto lookback options exhibit properties that are distinctive from other two‐state American option models.
THE MOMENT FORMULA FOR IMPLIED VOLATILITY AT EXTREME STRIKES
Authors: Lee Roger W.
Published: June 2004

Consider options on a nonnegative underlying random variable with arbitrary distribution. In the absence of arbitrage, we show that at any maturity T, the large‐strike tail of the Black‐Scholes implied volatility skew is bounded by the square root of 2|x|/T, where x is log‐moneyness. The smallest coefficient that can replace the 2 depends only on the number of finite moments in the underlying distribution. We prove the moment formula, which expresses explicitly this model‐independent relationship. We prove also the reciprocal moment formula for the small‐strike tail, and we exhibit the symmetry between the formulas. The moment formula, which evaluates readily in many cases of practical interest, has applications to skew extrapolation and model calibration.
CHOQUET INSURANCE PRICING: A CAVEAT
Authors: Castagnoli Erio , Maccheroni Fabio , Marinacci Massimo
Published: June 2004

We show that, if prices in a market are Choquet expectations, the existence of one frictionless asset may force the whole market to be frictionless. Any risky asset will cause this collapse if prices depend only on the distribution with respect to a given nonatomic probability measure; the frictionless asset has to be fully revealing if such dependence is not assumed. Similar considerations apply to law‐invariant coherent risk measures.
A GENERAL FRAMEWORK FOR PRICING CREDIT RISK
Authors: BÉlanger Alain , Shreve Steven E. , Wong Dennis
Published: June 2004

A framework is provided for pricing derivatives on defaultable bonds and other credit‐risky contingent claims. The framework is in the spirit of reduced‐form models, but extends these models to include the case that default can occur only at specific times, such as coupon payment dates. Although the framework does not provide an efficient setting for obtaining results about structural models, it is sufficiently general to include most structural models, and thereby highlights the commonality between reduced‐form and structural models. Within the general framework, multiple recovery conventions for contingent claims are considered: recovery of a fraction of par, recovery of a fraction of a no‐default version of the same claim, and recovery of a fraction of the pre‐default value of the claim. A stochastic‐integral representation for credit‐risky contingent claims is provided, and the integrand for the credit exposure part of this representation is identified. In the case of intensity‐based, reduced‐form models, credit spread and credit‐risky term structure are studied.
Synchronicity in southern hemisphere squid stocks and the influence of the Southern Oscillation and Trans Polar Index
Authors: Waluda C. M. , Trathan P. N. , Rodhouse P. G.
Published: June 2004

Squid are short lived, with highly labile populations that respond rapidly to changes in environmental conditions. This makes them a good model for studying the response of recruitment processes to environmental signals. This study examines the influence of the Southern Oscillation Index (SOI) and Trans Polar Index (TPI) on the environment and abundance of six species of commercially important squid from the southern hemisphere, all linked to major current systems connected by the Antarctic Circumpolar Current: Dosidicus gigas (Southeast Pacific), Loligo vulgaris reynaudii (Southeast Atlantic), Nototodarus sloanii, N. gouldi (Southwest Pacific), Illex argentinus and L. gahi (Southwest Atlantic). All fisheries displayed a high level of inter‐annual variability and a degree of synchronicity was seen to occur in the abundance of the three Pacific species. The SOI signal was reflected in the environment of each fishery, particularly in Pacific regions. Both indices are correlated with squid abundance, particularly during the early life history stages (SOI) and adult stages (TPI), suggesting some degree of latitudinal separation, with juveniles potentially influenced by environmental variability at lower latitudes and adults at higher latitudes.
Distribution patterns of larval myctophid fish assemblages in the subtropical–tropical waters of the western North Pacific
Authors: Sassa Chiyuki , Kawaguchi Kouichi , Hirota Yuichi , Ishida Minoru
Published: June 2004

We examined larval myctophid fish assemblages and their distribution patterns, based on discrete depth sampling. Samples were collected at 19 stations along a transect that crossed the subtropical–tropical waters of the western North Pacific. In total, we collected 27 189 larvae of 40 myctophid species or types, belonging to 15 genera. Three assemblages were recognized, based on their species composition: Kuroshio Axis (KuA), Kuroshio Countercurrent (KCC), and Subtropical Countercurrent–North Equatorial Current (SCC–NEC) assemblages. The distributions of these assemblages were well defined by the positions of the KuA and the Subtropical Convergence. Each species had a specific distribution depth, and none showed diel vertical migration. Larvae of the subfamily Lampanyctinae were distributed in shallower waters (0–50 m) than larvae of the subfamily Myctophinae (50–150 m). Larvae of the same species were distributed at lower depths in the SCC–NEC area than in the KCC area. This corresponded to the abundance of chlorophyll a, which would reflect abundance of prey organisms such as copepod nauplii and copepodites.
Bluefin tuna (Thunnus thynnus) distribution in relation to sea surface temperature fronts in the Gulf of Maine (1994–96)
Authors: Schick R. S. , Goldstein J. , Lutcavage M. E.
Published: June 2004

Fishery‐linked aerial surveys for bluefin tuna (Thunnus thynnus) were conducted in the Gulf of Maine (GOM) from July through October, 1994–96. Each year, from 507 to 890 surface schools were detected and their locations examined in relation to oceanographic conditions. Correlations between bluefin tuna presence and environmental variables were explored for sea surface temperature (SST), distance to a SST front, frontal density (relative density of all SST fronts seen in a given 1 km area for 2 weeks prior to each tuna sighting), and bottom depth and slope. Mean SST associated with bluefin schools was 18.1°C (±2.8). Schools were located at a mean distance of 19.7 km (±19.6) from SST fronts, and in water masses with an average frontal density of 28.2 m km−2 (±35.7). Mean bottom depth of detected schools was 139.0 m (±70.3), and mean bottom slope was 0.7% rise (±0.7). A binomial generalized linear model fit to these variables indicated that bluefin are seen closer to fronts than locations in which no tuna were seen. Using simple and partial Mantel tests, we investigated the spatial correlation between bluefin tuna presence and the environmental variables, controlling for spatial autocorrelation. For each day that schools were sighted, we performed 24 Mantel tests, on a combination of response and predictor variables. The spatial relationship between bluefin tuna and SST fronts was inconsistent. Our analysis identified significant spatial structure in the bluefin school locations that had no significant correlation with any of the measured environmental features, suggesting that other untested features, such as prey density, may be important predictors of bluefin distribution in the GOM.
Fine scale spatial pattern of Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax) eggs
Authors: Alexandra Curtis K.
Published: June 2004

Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax) eggs exhibited different spatial structure on the scale of 0.75–2.5 km in two egg patches sampled in the Southern California Bight in April 2000. Plankton samples were collected at 4‐min intervals with a Continuous Underway Fish Egg Sampler (CUFES) on 5 × 5 km grids centered on surface drifters. Variograms were calculated for sardine and anchovy eggs in Lagrangian coordinates, using abundances of individual developmental stages grouped into daily cohorts. Model variograms for sardine eggs have a low nugget effect, about 10% of the total variance, indicating high autocorrelation between adjacent samples. In contrast, model variograms for anchovy eggs have a high nugget effect of 50–100%, indicating that most of the variance at the scales sampled is spatially unstructured. The difference between observed spatial patterns of sardine and anchovy eggs on this scale may reflect the behavior of the spawning adults: larger, faster, more abundant fish may organize into larger schools with greater structure and mobility that create smoother egg distributions. Size and mobility vary with population size in clupeoids. The current high abundance of sardines and low abundance of anchovy off California agree with the greater autocorrelation of sardine egg samples and the observed tendency for locations of anchovy spawning to be more persistent on the temporal scale of days to weeks. Thus the spatial pattern of eggs and the persistence of spawning areas are suggested to depend on species, population size and age structure, spawning intensity and characteristic physical scales of the spawning habitat.
Basking sharks (Cetorhinus maximus) schooling in the southern Gulf of Maine
Authors: Wilson Steven G.
Published: June 2004

Schools of up to 50 basking sharks (Cetorhinus maximus) were observed on the warm side of a persistent thermal front in the southern Gulf of Maine from early September through mid‐October 2002. Aerial photographs showed a variety of schooling patterns, including echelon, cartwheel and milling formations. While the function of these aggregations remains unknown, they may represent group courtship behaviour.
Rapid, large‐scale generation ofDstransposant lines and analysis of theDsinsertion sites in rice
Authors: Kim Chul Min , Piao Hai Long , Park Soon Ju , Chon Nam Soo , Je Byoung Il , Sun Bingyao , Park Sung Han , Park Jin Young , Lee Eun Jin , Kim Min Jung , Chung Woo Sik , Lee Kon Ho , Lee Young Suk , Lee Jeung Joo , Won Yong Jae , Yi GiHwan , Nam Min Hee , Cha Young Soon , Yun Doh Won , Eun Moo Young , Han Chang‐deok
Published: June 2004

Rapid, large‐scale generation of aDstransposant population was achieved using a regeneration procedure involving tissue culture of seed‐derived calli carryingAcand inactiveDselements. In the F2progeny from genetic crosses between the sameDsandAcstarter lines, most of the crosses produced an independent germinal transposition frequency of 10–20%. Also, manyDselements underwent immobilization even thoughAcwas expressed. By comparison, in a callus‐derived regenerated population, over 70% of plants carried independentDsinsertions, indicating transposition early in callus formation. In the remaining population, the majority of plants carried onlyAc. Most of the newDsinsertions were stably transmitted to a subsequent generation. An exceptionally high proportion of independent transposants in the regenerated population means that selection markers for transposedDsand continual monitoring ofAc/Dsactivities may not necessarily be required. By analyzing 1297Ds‐flanking DNA sequences, a genetic map of 1072Dsinsertion sites was developed. The map showed thatDselements were transposed onto all of the rice chromosomes, with preference not only near donor sites (36%) but also on certain physically unlinked arms. Populations from both genetic crossing and tissue culture showed the same distribution patterns ofDsinsertion sites. The information of these mappedDsinsertion sites was deposited in GenBank. Among them, 55% ofDselements were on predicted open‐reading frame (ORF) regions. Thus, we propose an optimal strategy for the rapid generation of a large population ofDstransposants in rice.
Refining a health‐related quality of life assessment strategy for solid organ transplant patients
Authors: Feurer Irene D , Moore Derek E , Speroff Theodore , Liu Hongxia , Payne Jerita , Harrison Connie , Pinson C Wright
Published: June 2004

Abstract:  Purpose:  The psychometric properties of generic health‐related quality of life (HRQOL) assessment instruments were evaluated to identify a reliable, valid, and non‐redundant battery to measure longitudinal outcomes in organ transplant patients.

Methods:  Objective functional performance and subjective HRQOL were assessed in 371 solid organ (liver, heart, kidney, lung) transplant patients using the Karnofsky scale, the SF‐36® Health Survey (SF‐36®), and Psychosocial Adjustment to Illness Scale (PAIS). The surveys' internal‐consistency reliability, criterion‐related validity, and redundancy were tested.

Results:  The SF‐36® mental (MCS) and physical components (PCS), and PAIS summary scales were internally consistent (all α ≥ 0.83). Four out of seven PAIS scales (vocational, domestic, sexual, social) were collectively associated with the PCS (R = 0.65, P < 0.001), as was functional performance (r = 0.52, P < 0.001). Three PAIS scales (family, social, psychological distress) were associated with the MCS (R = 0.72, P < 0.001). Only the PAIS healthcare orientation (satisfaction) scale was not associated with the SF‐36®. The relationship between functional performance and the PCS is stronger (r = 0.52, P < 0.001) than with the MCS (r = 0.25, P < 0.001) and the PAIS global score (r = 0.37, P < 0.001).

Conclusions:  The SF‐36® and PAIS are internally consistent and exhibit divergent criterion‐related validity but, with the exception of the PAIS healthcare orientation scale, are statistically redundant. The advantages of the SF‐36® include wider use, more norms, and a lesser response burden. A transplant‐specific patient satisfaction inventory was indicated and was developed.
Summer forage biomass and the importance of litterfall for a high‐density sika deer population
Authors: MIYAKI Masami , KAJI Koichi
Published: June 2004

The biomass of summer forage and their contributions were surveyed to show that litterfall supported a high‐density population of sika deer (Cervus nippon Temminck) in summer on Nakanoshima Island, Toya Lake, Japan. In July 1974, the grassland had the highest productivity among understory vegetations (228 ± 55 kg ha−1: mean ± SE). In deciduous forests, palatable plants occupied only 0.1% of the biomass of 0.872 ± 0.366 kg ha−1, and deciduous leaves within the reach of deer (=220 cm at height) produced 0.208 ± 0.070 kg ha−1. However, litterfall during this period had the highest productivity, 28.7 ± 5.3 kg ha−1. The deer consumed litterfall (75.6% in dry weight), short grasses (17.2%), deciduous forest understory (4.1%), deciduous leaves within the reach of deer (3.0%) and conifer plantation under story (0.1%). It is suggested that the high‐density deer population would be maintained by litterfall through the year instead of browsing in deciduous forests, which has been overlooked.