bluuebunny/crossref_metadata_2025 huggingface dataset:
ATP-dependent interaction of the cytosolic domains of the inwardly rectifying K
+
channel Kir6.2 revealed by fluorescence resonance energy transfer
Authors: Tsuboi Takashi , Lippiat Jonathan D. , Ashcroft Frances M. , Rutter Guy A.
Published: January 2004

ATP-sensitive K
+
(K
ATP
) channels play important roles in the regulation of membrane excitability in many cell types. ATP inhibits channel activity by binding to a specific site formed by the N and C termini of the pore-forming subunit, Kir6.2, but the structural changes associated with this interaction remain unclear. Here, we use fluorescence resonance energy transfer (FRET) to study the ATP-dependent interaction between the N and C termini of Kir6.2 using a construct bearing fused cyan and yellow fluorescent proteins (ECFP-Kir6.2-EYFP). When expressed in human embryonic kidney cells, ECFP-Kir6.2-EYFP/SUR1 channels displayed FRET that was augmented by agonist stimulation and diminished by metabolic poisoning. Addition of ATP to permeabilized cells or isolated plasma membrane sheets increased FRET. FRET changes were abolished by Kir6.2 mutations that altered ATP-dependent channel closure and channel gating. In the wild-type channel, the ATP concentrations, which increased FRET (EC
50
= 1.36 mM), were significantly higher than those causing channel inhibition (IC
50
= 0.29 mM). Demonstrating the existence of intermolecular interactions, a dimeric construct comprising two molecules of Kir6.2 linked head-to-tail (ECFP-Kir6.2-Kir6.2-EYFP) displayed less FRET than the monomer in the absence of nucleotide but still exhibited ATP-dependent FRET increases (EC
50
= 1.52 mM) and channel inhibition. We conclude that binding of ATP to Kir6.2, (
i
) alters the interaction between the N- and C-terminal domains, (
ii
) probably involves both intrasubunit and intersubunit interactions, (
iii
) reflects ligand binding not channel gating, and (
iv
) occurs in intact cells when subplasmalemmal [ATP] changes in the millimolar range.
3D structure of the influenza virus polymerase complex: Localization of subunit domains
Authors: Area Estela , Martín-Benito Jaime , Gastaminza Pablo , Torreira Eva , Valpuesta José M. , Carrascosa José L. , Ortín Juan
Published: January 2004

The 3D structure of the influenza virus polymerase complex was determined by electron microscopy and image processing of recombinant ribonucleoproteins (RNPs). The RNPs were generated by
in vivo
amplification using cDNAs of the three polymerase subunits, the nucleoprotein, and a model virus-associated RNA containing 248 nt. The polymerase structure obtained is very compact, with no apparent boundaries among subunits. The position of specific regions of the PB1, PB2, and PA subunits was determined by 3D reconstruction of either RNP–mAb complexes or tagged RNPs. This structural model is available for the polymerase of a negative-stranded RNA virus and provides a general delineation of the complex and its interaction with the template-associated nucleoprotein monomers in the RNP.
APlasmodium falciparumcandidate vaccine based on a six-antigen polyprotein encoded by recombinant poxviruses
Authors: Prieur Eric , Gilbert Sarah C. , Schneider Joerg , Moore Anne C. , Sheu Eric G. , Goonetilleke Nilu , Robson Kathryn J. H. , Hill Adrian V. S.
Published: January 2004

To generate broadly protective T cell responses more similar to those acquired after vaccination with radiation-attenuatedPlasmodium falciparumsporozoites, we have constructed candidate subunit malaria vaccines expressing six preerythrocytic antigens linked together to produce a 3,240-aa-long polyprotein (L3SEPTL). This polyprotein was expressed by a plasmid DNA vaccine vector (DNA) and by two attenuated poxvirus vectors, modified vaccinia virus Ankara (MVA) and fowlpox virus of the FP9 strain. MVAL3SEPTL boosted anti-thrombospondin-related adhesive protein (anti-TRAP) and anti-liver stage antigen 1 (anti-LSA1) CD8+T cell responses when primed by single antigen TRAP- or LSA1-expressing DNAs, respectively, but not by DNA-L3SEPTL. However, prime boost regimes involving two heterologous viral vectors expressing L3SEPTL induced a strong cellular response directed against an LSA1 peptide located in the C-terminal region of the polyprotein. Peptide-specific T cells secreted IFN-γ and were cytotoxic. IFN-γ-secreting T cells specific for each of the six antigens were induced after vaccination with L3SEPTL, supporting the use of polyprotein inserts to induce multispecific T cells againstP. falciparum. The use of polyprotein constructs in nonreplicating poxviruses should broaden the target antigen range of vaccine-induced immunity and increase the number of potential epitopes available for immunogenetically diverse human populations.
Thymic selection can compensate for mutations affecting T cell activation and generate a normal T cell repertoire in mutant mice
Authors: Kissler Stephan , Lu Linrong , Cantor Harvey
Published: January 2004

Thymic selection adjusts the reactivity of the peripheral T cell repertoire to maximize recognition of pathogens and minimize stimulation by innocuous substances and self-antigen. The study of molecules implicated in T cell activation often involves the generation of knockout (-/-) mice. In many instances, knockout animals display revealing phenotypes. But should a lack of phenotype be interpreted as a lack of function? Bcl-xγ was shown previously to affect T cell activation
in vitro
, and here we note that overexpression of this molecule increases cell cycling after T cell receptor ligation by antibody. It was therefore surprising that Bcl-xγ
-/-
, Bcl-xγ transgenic, and WT T cells displayed similar levels of sensitivity to antigen according to
ex vivo
stimulation. Bcl-xγ could be demonstrated to influence competitiveness and selection of thymocytes in a manner that counteracted the effects of Bcl-xγ mutation on T cell activation. These findings suggest that thymic selection can overcome genetic defects in T cell activation to generate a T cell repertoire of normal reactivity.
Dominant-negative C/EBP disrupts mitotic clonal expansion and differentiation of 3T3-L1 preadipocytes
Authors: Zhang Jiang-Wen , Tang Qi-Qun , Vinson Charles , Lane M. Daniel
Published: January 2004

Hormonal induction of growth-arrested 3T3-L1 preadipocytes rapidly activates expression of CCAAT/enhancer-binding protein (C/EBP) β. Acquisition of DNA-binding activity by C/EBPβ, however, is delayed until the cells synchronously enter the S phase of mitotic clonal expansion (MCE). After MCE, C/EBPβ activates expression of C/EBPα and peroxisome proliferator-activated receptor γ, which then transcriptionally activate genes that give rise to the adipocyte phenotype. A-C/EBP, which possesses a leucine zipper but lacks functional DNA-binding and transactivation domains, forms stable inactive heterodimers with C/EBPβ
in vitro
. Infection of 3T3-L1 preadipocytes with an adenovirus A-C/EBP expression vector interferes with C/EBPβ function after induction of differentiation. A-C/EBP inhibited events associated with hormone-induced entry of S-phase of the cell cycle, including the turnover of p27/Kip1, a key cyclin-dependent kinase inhibitor, expression of cyclin A and cyclin-dependent kinase 2, DNA replication, MCE, and, subsequently, adipogenesis. Although A-C/EBP blocked cell proliferation associated with MCE, it did not inhibit normal proliferation of 3T3-L1 preadipocytes. Immunofluorescent staining of C/EBPβ revealed that A-C/EBP prevented the normal punctate nuclear staining of centromeres, an indicator of C/EBPβ binding to C/EBP regulatory elements in centromeric satellite DNA. The inhibitory effects of A-C/EBP appear to be due primarily to interference with nuclear import of C/EBPβ caused by obscuring its nuclear localization signal. These findings show that both MCE and adipogenesis are dependent on C/EBPβ.
An egalitarian network model for the emergence of simple and complex cells in visual cortex
Authors: Tao Louis , Shelley Michael , McLaughlin David , Shapley Robert
Published: January 2004

We explain how simple and complex cells arise in a large-scale neuronal network model of the primary visual cortex of the macaque. Our model consists of ≈4,000 integrate-and-fire, conductance-based point neurons, representing the cells in a small, 1-mm
2
patch of an input layer of the primary visual cortex. In the model the local connections are isotropic and nonspecific, and convergent input from the lateral geniculate nucleus confers cortical cells with orientation and spatial phase preference. The balance between lateral connections and lateral geniculate nucleus drive determines whether individual neurons in this recurrent circuit are simple or complex. The model reproduces qualitatively the experimentally observed distributions of both extracellular and intracellular measures of simple and complex response.
Loss of poly(ADP-ribose) glycohydrolase causes progressive neurodegeneration in
Drosophila melanogaster
Authors: Hanai Shuji , Kanai Masayuki , Ohashi Sayaka , Okamoto Keiji , Yamada Mitsunori , Takahashi Hitoshi , Miwa Masanao
Published: January 2004

Poly(ADP-ribosyl)ation has been suggested to be involved in regulation of DNA repair, transcription, centrosome duplication, and chromosome stability. However, the regulation of degradation of poly(ADP-ribose) and its significance are not well understood. Here we report a loss-of-function mutant
Drosophila
with regard to poly(ADP-ribose) glycohydrolase, a major hydrolyzing enzyme of poly(ADP-ribose). The mutant lacks the conserved catalytic domain of poly(ADP-ribose) glycohydrolase, and exhibits lethality in the larval stages at the normal development temperature of 25°C. However, one-fourth of the mutants progress to the adult stage at 29°C but showed progressive neurodegeneration with reduced locomotor activity and a short lifespan. In association with this, extensive accumulation of poly(ADP-ribose) could be detected in the central nervous system. These results suggest that poly(ADP-ribose) metabolism is required for maintenance of the normal function of neuronal cells. The phenotypes observed in the
parg
mutant might be useful to understand neurodegenerative conditions such as the Alzheimer's and Parkinson's diseases that are caused by abnormal accumulation of substances in nervous tissue.
Alleviating spatial conflict between people and biodiversity
Authors: Luck Gary W. , Ricketts Taylor H. , Daily Gretchen C. , Imhoff Marc
Published: January 2004

Human settlements are expanding in species-rich regions and pose a serious threat to biodiversity conservation. We quantify the degree to which this threat manifests itself in two contrasting continents, Australia and North America, and suggest how it can be substantially alleviated. Human population density has a strong positive correlation with species richness in Australia for birds, mammals, amphibians, and butterflies (but not reptiles) and in North America for all five taxa. Nevertheless, conservation investments could secure locations that harbor almost all species while greatly reducing overlap with densely populated regions. We compared two conservation-planning scenarios that each aimed to represent all species at least once in a minimum set of sampling sites. The first scenario assigned equal cost to each site (ignoring differences in human population density); the second assigned a cost proportional to the site's human population density. Under the equal-cost scenario, 13–40% of selected sites occurred where population density values were highest (in the top decile). However, this overlap was reduced to as low as 0%, and in almost all cases to <10%, under the population-cost scenario, when sites of high population density were avoided where possible. Moreover, this reduction of overlap was achieved with only small increases in the total amount of area requiring protection. As densely populated regions continue to expand rapidly and drive up land values, the strategic conservation investments of the kind highlighted in our analysis are best made now.
IFN-regulatory factor 3-dependent gene expression is defective in
Tbk1
-deficient mouse embryonic fibroblasts
Authors: McWhirter Sarah M. , Fitzgerald Katherine A. , Rosains Jacqueline , Rowe Daniel C. , Golenbock Douglas T. , Maniatis Tom
Published: January 2004

Virus infection, double-stranded RNA, and lipopolysaccharide each induce the expression of genes encoding IFN-α and -β and chemokines, such as RANTES (regulated on activation, normal T cell expressed and secreted) and IP-10 (IFN-γ inducible protein 10). This induction requires the coordinate activation of several transcription factors, including IFN-regulatory factor 3 (IRF3). The signaling pathways leading to IRF3 activation are triggered by the binding of pathogen-specific products to Toll-like receptors and culminate in the phosphorylation of specific serine residues in the C terminus of IRF3. Recent studies of human cell lines in culture have implicated two noncanonical IκB kinase (IKK)-related kinases, IKK-ε and Traf family member-associated NF-κB activator (TANK)-binding kinase 1 (TBK1), in the phosphorylation of IRF3. Here, we show that purified recombinant IKK-ε and TBK1 directly phosphorylate the critical serine residues in IRF3. We have also examined the expression of IRF3-dependent genes in mouse embryonic fibroblasts (MEFs) derived from
Tbk1
-/-
mice, and we show that TBK1 is required for the activation and nuclear translocation of IRF3 in these cells. Moreover,
Tbk1
-/-
MEFs show marked defects in
IFN
-α and -β,
IP-10
, and
RANTES
gene expression after infection with either Sendai or Newcastle disease viruses or after engagement of the Toll-like receptors 3 and 4 by double-stranded RNA and lipopolysaccharide, respectively. Finally, TRIF (TIR domain-containing adapter-inducing IFN-β), fails to activate IRF3-dependent genes in
Tbk1
-/-
MEFs. We conclude that TBK1 is essential for IRF3-dependent antiviral gene expression.
Anatomy of a chaotic attractor: Subtle model-predicted patterns revealed in population data
Authors: King Aaron A. , Costantino R. F. , Cushing J. M. , Henson Shandelle M. , Desharnais Robert A. , Dennis Brian
Published: January 2004

Mathematically, chaotic dynamics are not devoid of order but display episodes of near-cyclic temporal patterns. This is illustrated, in interesting ways, in the case of chaotic biological populations. Despite the individual nature of organisms and the noisy nature of biological time series, subtle temporal patterns have been detected. By using data drawn from chaotic insect populations, we show quantitatively that chaos manifests itself as a tapestry of identifiable and predictable patterns woven together by stochasticity. We show too that the mixture of patterns an experimentalist can expect to see depends on the scale of the system under study.
Learning rules and network repair in spike-timing-based computation networks
Authors: Hopfield J. J. , Brody Carlos D.
Published: January 2004

Plasticity in connections between neurons allows learning and adaptation, but it also allows noise to degrade the function of a network. Ongoing network self-repair is thus necessary. We describe a method to derive spike-timing-dependent plasticity rules for self-repair, based on the firing patterns of a functioning network. These plasticity rules for self-repair also provide the basis for unsupervised learning of new tasks. The particular plasticity rule derived for a network depends on the network and task. Here, self-repair is illustrated for a model of the mammalian olfactory system in which the computational task is that of odor recognition. In this olfactory example, the derived rule has qualitative similarity with experimental results seen in spike-timing-dependent plasticity. Unsupervised learning of new tasks by using the derived self-repair rule is demonstrated by learning to recognize new odors.
Hubble's diagram and cosmic expansion
Authors: Kirshner Robert P.
Published: January 2004

Edwin Hubble's classic article on the expanding universe appeared in PNAS in 1929 [Hubble, E. P. (1929)
Proc. Natl. Acad. Sci. USA
15, 168–173]. The chief result, that a galaxy's distance is proportional to its redshift, is so well known and so deeply embedded into the language of astronomy through the Hubble diagram, the Hubble constant, Hubble's Law, and the Hubble time, that the article itself is rarely referenced. Even though Hubble's distances have a large systematic error, Hubble's velocities come chiefly from Vesto Melvin Slipher, and the interpretation in terms of the de Sitter effect is out of the mainstream of modern cosmology, this article opened the way to investigation of the expanding, evolving, and accelerating universe that engages today's burgeoning field of cosmology.
Increased hippocampal neurogenesis in Alzheimer's disease
Authors: Jin Kunlin , Peel Alyson L. , Mao Xiao Ou , Xie Lin , Cottrell Barbara A. , Henshall David C. , Greenberg David A.
Published: January 2004

Neurogenesis, which persists in the adult mammalian brain, may provide a basis for neuronal replacement therapy in neurodegenerative diseases like Alzheimer's disease (AD). Neurogenesis is increased in certain acute neurological disorders, such as ischemia and epilepsy, but the effect of more chronic neurodegenerations is uncertain, and some animal models of AD show impaired neurogenesis. To determine how neurogenesis is affected in the brains of patients with AD, we investigated the expression of immature neuronal marker proteins that signal the birth of new neurons in the hippocampus of AD patients. Compared to controls, Alzheimer's brains showed increased expression of doublecortin, polysialylated nerve cell adhesion molecule, neurogenic differentiation factor and TUC-4. Expression of doublecortin and TUC-4 was associated with neurons in the neuroproliferative (subgranular) zone of the dentate gyrus, the physiological destination of these neurons (granule cell layer), and the CA1 region of Ammon's horn, which is the principal site of hippocampal pathology in AD. These findings suggest that neurogenesis is increased in AD hippocampus, where it may give rise to cells that replace neurons lost in the disease, and that stimulating hippocampal neurogenesis might provide a new treatment strategy.
Random walks in the history of life
Authors: Cornette James L. , Lieberman Bruce S.
Published: January 2004

The simplest null hypothesis for evolutionary time series is that the observed data follow a random walk. We examined whether aspects of Sepkoski's compilation of marine generic diversity depart from a random walk by using statistical tests from econometrics. Throughout most of the Phanerozoic, the random-walk null hypothesis is not rejected for marine diversity, accumulated origination or accumulated extinction, suggesting that either these variables were correlated with environmental variables that follow a random walk or so many mechanisms were affecting these variables, in different ways, that the resultant trends appear random. The only deviation from this pattern involves rejection of the null hypothesis for roughly the last 75 million years for the diversity and accumulated origination time series.
DNA-methyltransferase 1 mRNA is selectively overexpressed in telencephalic GABAergic interneurons of schizophrenia brains
Authors: Veldic M. , Caruncho H. J. , Liu W. S. , Davis J. , Satta R. , Grayson D. R. , Guidotti A. , Costa E.
Published: January 2004

A down-regulation of reelin and glutamic acid decarboxylase (GAD) 67 mRNAs was detected in γ-aminobutyric acid (GABA)ergic cortical interneurons of schizophrenia (SZ) postmortem brains (
10
), suggesting that the availability of GABA and reelin may be decreased in SZ cortex.
In situ
hybridization of the mRNA encoding for DNA-methyltransferase 1, which catalyzes the methylation of promoter CpG islands, shows that the expression of this mRNA is increased in cortical GABAergic interneurons but not in pyramidal neurons of SZ brains. Counts of reelin mRNA-positive neurons in Brodmann's area 10 of either nonpsychiatric subjects or SZ patients show that the expression of reelin mRNA is decreased in layer-I, -II, and -IV GABAergic interneurons of SZ patients. These findings are consistent with the hypothesis that the increase of DNA-methyltransferase 1 expression in telencephalic GABAergic interneurons of SZ patients causes a promoter hypermethylation of
reelin
and
GAD

67

and perhaps of other genes expressed in these interneurons. It is difficult to decide whether this dysfunction of GABAergic neurons detected in SZ is responsible for this disease or is a consequence of this disorder. Although at present we cannot differentiate between these two alternatives, it is important to consider that so far a molecular pathology of cortical GABAergic neurons appears to be the most consistent finding associated with SZ morbidity.
Biomimetic ratcheting motion of a soft, slender, sessile gel
Authors: Mahadevan L. , Daniel S. , Chaudhury M. K.
Published: January 2004

Inspired by the locomotion of terrestrial limbless animals, we study the motion of a lubricated rod of a hydrogel on a soft substrate. We show that it is possible to mimic observed biological gaits by vibrating the substrate and by using a variety of mechanisms to break longitudinal and lateral symmetry. Our simple theory and experiments provide a unified view of the creeping, undulating, and inchworming gaits observed in limbless locomotion on land, all of which originate as symmetry-breaking bifurcations of a simple base state associated with periodic longitudinal oscillations of a slender gel. These ideas are therefore also applicable to technological situations that involve moving small, soft solids on substrates.
Role of the hydrophobic domain in targeting caveolin-1 to lipid droplets
Authors: Ostermeyer Anne G. , Ramcharan Lynne T. , Zeng Youchun , Lublin Douglas M. , Brown Deborah A.
Published: January 2004

Although caveolins normally reside in caveolae, they can accumulate on the surface of cytoplasmic lipid droplets (LDs). Here, we first provided support for our model that overaccumulation of caveolins in the endoplasmic reticulum (ER) diverts the proteins to nascent LDs budding from the ER. Next, we found that a mutant H-Ras, present on the cytoplasmic surface of the ER but lacking a hydrophobic peptide domain, did not accumulate on LDs. We used the fact that wild-type caveolin-1 accumulates in LDs after brefeldin A treatment or when linked to an ER retrieval motif to search for mutants defective in LD targeting. The hydrophobic domain, but no specific sequence therein, was required for LD targeting of caveolin-1. Certain Leu insertions blocked LD targeting, independently of hydrophobic domain length, but dependent on their position in the domain. We propose that proper packing of putative hydrophobic helices may be required for LD targeting of caveolin-1.
PEX19 is a predominantly cytosolic chaperone and import receptor for class 1 peroxisomal membrane proteins
Authors: Jones Jacob M. , Morrell James C. , Gould Stephen J.
Published: January 2004

Integral peroxisomal membrane proteins (PMPs) are synthesized in the cytoplasm and imported posttranslationally. Here, we demonstrate that PEX19 binds and stabilizes newly synthesized PMPs in the cytosol, binds to multiple PMP targeting signals (mPTSs), interacts with the hydrophobic domains of PMP targeting signals, and is essential for PMP targeting and import. These results show that PEX19 functions as both a chaperone and an import receptor for newly synthesized PMPs. We also demonstrate the existence of two PMP import mechanisms and two classes of mPTSs: class 1 mPTSs, which are bound by PEX19 and imported in a PEX19-dependent manner, and class 2 mPTSs, which are not bound by PEX19 and mediate protein import independently of PEX19.
Amyloid-β peptide induces oligodendrocyte death by activating the neutral sphingomyelinase–ceramide pathway
Authors: Lee Jiunn-Tay , Xu Jan , Lee Jin-Moo , Ku Grace , Han Xianlin , Yang Ding-I , Chen Shawei , Hsu Chung Y.
Published: January 2004

Amyloid-β peptide (Aβ) accumulation in senile plaques, a pathological hallmark of Alzheimer's disease (AD), has been implicated in neuronal degeneration. We have recently demonstrated that Aβ induced oligodendrocyte (OLG) apoptosis, suggesting a role in white matter pathology in AD. Here, we explore the molecular mechanisms involved in Aβ-induced OLG death, examining the potential role of ceramide, a known apoptogenic mediator. Both Aβ and ceramide induced OLG death. In addition, Aβ activated neutral sphingomyelinase (nSMase), but not acidic sphingomyelinase, resulting in increased ceramide generation. Blocking ceramide degradation with N-oleoyl-ethanolamine exacerbated Aβ cytotoxicity; and addition of bacterial sphingomyelinase (mimicking cellular nSMase activity) induced OLG death. Furthermore, nSMase inhibition by 3-O-methyl-sphingomyelin or by gene knockdown using antisense oligonucleotides attenuated Aβ-induced OLG death. Glutathione (GSH) precursors inhibited Aβ activation of nSMase and prevented OLG death, whereas GSH depletors increased nSMase activity and Aβ-induced death. These results suggest that Aβ induces OLG death by activating the nSMase–ceramide cascade via an oxidative mechanism.
Optimal Truncation in Ionization of hydrogen by Electron Impact
Authors: Zhang Cheng-Hua  , Niu Ying-Yu  , Wu Wei  , Qiu Wei  , Xin Jun-Li  , Wang Xiao-Wei  , Wang Jing-Yang
Published: January 2004

An analytic expression for the ionization amplitude of hydrogen by electron impact is found to contain a polynomial by an optimal truncation in an asymptotic series and a convergent series. The ionization amplitude, i.e., the transition matrix element on the energy shell, is decomposed into two parts: the structure-scattering factor and correlation factor, based on an approximation of the projectile plane wave in coplanar asymmetric geometries. The contribution of these factors to the triple differential cross section is evaluated using the method of optional truncation of asymptotic and convergent series.
Neutrino masses and the number of neutrino species from WMAP and 2dFGRS
Authors: Steen Hannestad
Published: January 2004

We have performed a thorough analysis of the constraints which can be put on neutrino parameters from cosmological observations, most notably those from the WMAP satellite and the 2dF galaxy survey. For these data we find an upper limit on the sum of active neutrino mass eigenstates of ∑mν ⩽ 1.0 eV (95% conf.), but this limit is dependent on priors. We find that the WMAP and 2dF data alone cannot rule out the evidence from neutrinoless double beta decay reported by the Heidelberg–Moscow experiment. In terms of the relativistic energy density in neutrinos or other weakly interacting species we find, in units of the equivalent number of neutrino species,Nν, thatNν  =  4.0+3.0−2.1(95% conf.). When BBN constraints are added, the bound onNνis 2.6+0.4−0.3(95% conf.), suggesting thatNνcould possibly be lower than the standard model value of 3. This can, for instance, be the case in models with very low reheating temperature and incomplete neutrino thermalization. Conversely, ifNνis fixed to 3 then the data from WMAP and 2dFGRS predict that 0.2458 ⩽ YP ⩽ 0.2471 (95% conf.), which is significantly higher than the observationally measured value. The limit on relativistic energy density changes when a small νechemical potential is present during BBN. In this case the upper bound onNνfrom WMAP, 2dFGRS and BBN isNν ⩽ 6.5. Finally, we find that a non-zero ∑mνcan be compensated by an increase inNν. One result of this is that the LSND result is not yet ruled out by cosmological observations.
GSK-3 kinases enhance calcineurin signaling by phosphorylation of RCNs
Authors: Hilioti Zoe , Gallagher Deirdre A. , Low-Nam Shalini T. , Ramaswamy Priya , Gajer Pawel , Kingsbury Tami J. , Birchwood Christine J. , Levchenko Andre , Cunningham Kyle W.
Published: January 2004

The conserved RCN family of proteins can bind and directly regulate calcineurin, a Ca2+-activated protein phosphatase involved in immunity, heart growth, muscle development, learning, and other processes. Whereas high levels of RCNs can inhibit calcineurin signaling in fungal and animal cells, RCNs can also stimulate calcineurin signaling when expressed at endogenous levels. Here we show that the stimulatory effect of yeast Rcn1 involves phosphorylation of a conservedserine residue by Mck1, a member of the GSK-3 family of protein kinases. Mutations at the GSK-3 consensus site of Rcn1 and human DSCR1/MCIP1 abolish the stimulatory effects on calcineurin signaling. RCNs may therefore oscillate between stimulatory and inhibitory forms in vivo in a manner similar to the Inhibitor-2 regulators of type 1 protein phosphatase. Computational modeling indicates a biphasic response of calcineurin to increasing RCN concentration such that protein phosphatase activity is stimulated by low concentrations of phospho-RCN and inhibited by high concentrations of phospho- or dephospho-RCN. This prediction was verified experimentally in yeast cells expressing Rcn1 or DSCR1/MCIP1 at different concentrations. Through the phosphorylation of RCNs, GSK-3 kinases can potentially contribute to a positive feedback loop involving calcineurin-dependent up-regulation of RCN expression. Such feedback may help explain the large induction of DSCR1/MCIP1 observed in brain of Down syndrome individuals.
SETH1andSETH2, Two Components of the Glycosylphosphatidylinositol Anchor Biosynthetic Pathway, Are Required for Pollen Germination and Tube Growth in Arabidopsis [W]
Authors: Lalanne Eric , Honys David , Johnson Andrew , Borner Georg H. H. , Lilley Kathryn S. , Dupree Paul , Grossniklaus Ueli , Twell David
Published: January 2004

Glycosylphosphatidylinositol (GPI) anchoring provides an alternative to transmembrane domains for anchoring proteins to the cell surface in eukaryotes. GPI anchors are synthesized in the endoplasmic reticulum via the sequential addition of monosaccharides, fatty acids, and phosphoethanolamines to phosphatidylinositol. Deficiencies in GPI biosynthesis lead to embryonic lethality in animals and to conditional lethality in eukaryotic microbes by blocking cell growth, cell division, or morphogenesis. We report the genetic and phenotypic analysis of insertional mutations disrupting SETH1 and SETH2, which encode Arabidopsis homologs of two conserved proteins involved in the first step of the GPI biosynthetic pathway. seth1 and seth2 mutations specifically block male transmission and pollen function. This results from reduced pollen germination and tube growth, which are associated with abnormal callose deposition. This finding suggests an essential role for GPI anchor biosynthesis in pollen tube wall deposition or metabolism. Using transcriptomic and proteomic approaches, we identified 47 genes that encode potential GPI-anchored proteins that are expressed in pollen and demonstrated that at least 11 of these proteins are associated with pollen membranes by GPI anchoring. Many of the identified candidate proteins are homologous with proteins involved in cell wall synthesis and remodeling or intercellular signaling and adhesion, and they likely play important roles in the establishment and maintenance of polarized pollen tube growth.
Maize Mutants Lacking Chloroplast FtsY Exhibit Pleiotropic Defects in the Biogenesis of Thylakoid Membranes[W]
Authors: Asakura Yukari , Hirohashi Toshiya , Kikuchi Shingo , Belcher Susan , Osborne Erin , Yano Satoshi , Terashima Ichiro , Barkan Alice , Nakai Masato
Published: January 2004

A chloroplast signal recognition particle (SRP) that is related to the SRP involved in secretion in bacteria and eukaryotic cells is used for the insertion of light-harvesting chlorophyll proteins (LHCPs) into the thylakoid membranes. A conserved component of the SRP mechanism is a membrane-bound SRP receptor, denoted FtsY in bacteria. Plant genomes encode FtsY homologs that are targeted to the chloroplast (cpFtsY). To investigate the in vivo roles of cpFtsY, we characterized maize cpFtsY and maize mutants having a Mu transposon insertion in the corresponding gene (chloroplast SRP receptor1, or csr1). Maize cpFtsY accumulates to much higher levels in leaf tissue than in roots and stems. Interestingly, it is present at similar levels in etiolated and green leaf tissue and was found to bind the prolamellar bodies of etioplasts. A null cpFtsY mutant, csr1-1, showed a substantial loss of leaf chlorophyll, whereas a “leaky” allele, csr1-3, conditioned a more moderate chlorophyll deficiency. Both alleles caused the loss of various LHCPs and the thylakoid-bound photosynthetic enzyme complexes and were seedling lethal. By contrast, levels of the membrane-bound components of the thylakoid protein transport machineries were not altered. The thylakoid membranes in csr1-1 chloroplasts were unstacked and reduced in abundance, but the prolamellar bodies in mutant etioplasts appeared normal. These results demonstrate the essentiality of cpFtsY for the biogenesis not only of the LHCPs but also for the assembly of the other membrane-bound components of the photosynthetic apparatus.
Experimental Analysis of the Arabidopsis Mitochondrial Proteome Highlights Signaling and Regulatory Components, Provides Assessment of Targeting Prediction Programs, and Indicates Plant-Specific Mitochondrial Proteins [W]
Authors: Heazlewood Joshua L. , Tonti-Filippini Julian S. , Gout Alexander M. , Day David A. , Whelan James , Millar A. Harvey
Published: January 2004

A novel insight into Arabidopsis mitochondrial function was revealed from a large experimental proteome derived by liquid chromatography–tandem mass spectrometry. Within the experimental set of 416 identified proteins, a significant number of low-abundance proteins involved in DNA synthesis, transcriptional regulation, protein complex assembly, and cellular signaling were discovered. Nearly 20% of the experimentally identified proteins are of unknown function, suggesting a wealth of undiscovered mitochondrial functions in plants. Only approximately half of the experimental set is predicted to be mitochondrial by targeting prediction programs, allowing an assessment of the benefits and limitations of these programs in determining plant mitochondrial proteomes. Maps of putative orthology networks between yeast, human, and Arabidopsis mitochondrial proteomes and the Rickettsia prowazekii proteome provide detailed insights into the divergence of the plant mitochondrial proteome from those of other eukaryotes. These show a clear set of putative cross-species orthologs in the core metabolic functions of mitochondria, whereas considerable diversity exists in many signaling and regulatory functions.
Programmed Cell Death Remodels Lace Plant Leaf Shape during Development[W]
Authors: Gunawardena Arunika H. L. A. N. , Greenwood John S. , Dengler Nancy G.
Published: January 2004

Programmed cell death (PCD) functions in the developmental remodeling of leaf shape in higher plants, a process analogous to digit formation in the vertebrate limb. In this study, we provide a cytological characterization of the time course of events as PCD remodels young expanding leaves of the lace plant. Tonoplast rupture is the first PCD event in this system, indicated by alterations in cytoplasmic streaming, loss of anthocyanin color, and ultrastructural appearance. Nuclei become terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling positive soon afterward but do not become morphologically altered until late stages of PCD. Genomic DNA is fragmented, but not into internucleosomal units. Other cytoplasmic changes, such as shrinkage and degradation of organelles, occur later. This form of PCD resembles tracheary element differentiation in cytological execution but requires unique developmental regulation so that discrete panels of tissue located equidistantly between veins undergo PCD while surrounding cells do not.
Storage Protein Accumulation in the Absence of the Vacuolar Processing Enzyme Family of Cysteine Proteases[W]
Authors: Gruis Darren , Schulze Jan , Jung Rudolf
Published: January 2004

The role(s) of specific proteases in seed protein processing is only vaguely understood; indeed, the overall role of processing in stable protein deposition has been the subject of more speculation than direct investigation. Seed-type members of the vacuolar processing enzyme (VPE) family were hypothesized to perform a unique function in seed protein processing, but we demonstrated previously that Asn-specific protein processing in developing Arabidopsis seeds occurs independently of this VPE activity. Here, we describe the unexpected expression of vegetative-type VPEs in developing seeds and test the role(s) of all VPEs in seed storage protein accumulation by systematically stacking knockout mutant alleles of all four members (αVPE, βVPE, γVPE, and δVPE) of the VPE gene family in Arabidopsis. The complete removal of VPE function in the αvpe βvpe γvpe δvpe quadruple mutant resulted in a total shift of storage protein accumulation from wild-type processed polypeptides to a finite number of prominent alternatively processed polypeptides cleaved at sites other than the conserved Asn residues targeted by VPE. Although alternatively proteolyzed legumin-type globulin polypeptides largely accumulated as intrasubunit disulfide-linked polypeptides with apparent molecular masses similar to those of VPE-processed legumin polypeptides, they showed markedly altered solubility and protein assembly characteristics. Instead of forming 11S hexamers, alternatively processed legumin polypeptides were deposited primarily as 9S complexes. However, despite the impact on seed protein processing, plants devoid of all known functional VPE genes appeared unchanged with regard to protein content in mature seeds, relative mobilization rates of protein reserves during germination, and vegetative growth. These findings indicate that VPE-mediated Asn-specific proteolytic processing, and the physiochemical property changes attributed to this specific processing step, are not required for the successful deposition and mobilization of seed storage protein in the protein storage vacuoles of Arabidopsis seeds.
Overexpression of an Arabidopsis Formin Stimulates Supernumerary Actin Cable Formation from Pollen Tube Cell Membrane[W]
Authors: Cheung Alice Y. , Wu Hen-ming
Published: January 2004

Formins, actin-nucleating proteins that stimulate the de novo polymerization of actin filaments, are important for diverse cellular and developmental processes, especially those dependent on polarity establishment. A subset of plant formins, referred to as group I, is distinct from formins from other species in having evolved a unique N-terminal structure with a signal peptide, a Pro-rich, potentially glycosylated extracellular domain, and a transmembrane domain. We show here that overexpression of the Arabidopsis formin AFH1 in pollen tubes induces the formation of arrays of actin cables that project into the cytoplasm from the cell membrane and that its N-terminal structure targets AFH1 to the cell membrane. Pollen tube elongation is a polar cell growth process dependent on an active and tightly regulated actin cytoskeleton. Slight increases in AFH1 stimulate growth, but its overexpression induces tube broadening, growth depolarization, and growth arrest in transformed pollen tubes. These results suggest that AFH1-regulated actin polymerization is important for the polar pollen cell growth process. Moreover, severe membrane deformation was observed in the apical region of tip-expanded, AFH1-overexpressing pollen tubes in which an abundance of AFH1-induced membrane-associated actin cables was evident. These observations suggest that regulated AFH1 activity at the cell surface is important for maintaining tip-focused cell membrane expansion for the polar extension of pollen tubes. The cell surface–located group-I formins may play the integrin-analogous role as mediators of external stimuli to the actin cytoskeleton, and AFH1 could be important for mediating extracellular signals from female tissues to elicit the proper pollen tube growth response during pollination.
A Unique Set of 11,008 Onion Expressed Sequence Tags Reveals Expressed Sequence and Genomic Differences between the Monocot Orders Asparagales and Poales[W]
Authors: Kuhl Joseph C. , Cheung Foo , Yuan Qiaoping , Martin William , Zewdie Yayeh , McCallum John , Catanach Andrew , Rutherford Paul , Sink Kenneth C. , Jenderek Maria , Prince James P. , Town Christopher D. , Havey Michael J.
Published: January 2004

Enormous genomic resources have been developed for plants in the monocot order Poales; however, it is not clear how representative the Poales are for the monocots as a whole. The Asparagales are a monophyletic order sister to the lineage carrying the Poales and possess economically important plants such as asparagus, garlic, and onion. To assess the genomic differences between the Asparagales and Poales, we generated 11,008 unique ESTs from a normalized cDNA library of onion. Sequence analyses of these ESTs revealed microsatellite markers, single nucleotide polymorphisms, and homologs of transposable elements. Mean nucleotide similarity between rice and the Asparagales was 78% across coding regions. Expressed sequence and genomic comparisons revealed strong differences between the Asparagales and Poales for codon usage and mean GC content, GC distribution, and relative GC content at each codon position, indicating that genomic characteristics are not uniform across the monocots. The Asparagales were more similar to eudicots than to the Poales for these genomic characteristics.
The Tomato Homolog of CORONATINE-INSENSITIVE1 Is Required for the Maternal Control of Seed Maturation, Jasmonate-Signaled Defense Responses, and Glandular Trichome Development[W]
Authors: Li Lei , Zhao Youfu , McCaig Bonnie C. , Wingerd Byron A. , Wang Jihong , Whalon Mark E. , Pichersky Eran , Howe Gregg A.
Published: January 2004

Jasmonic acid (JA) is a fatty acid–derived signaling molecule that regulates a broad range of plant defense responses against herbivores and some microbial pathogens. Molecular genetic studies in Arabidopsis have established that JA also performs a critical role in anther and pollen development but is not essential for other developmental aspects of the plant's life cycle. Here, we describe the phenotypic and molecular characterization of a sterile mutant of tomato (jasmonic acid–insensitive1 [jai1]) that is defective in JA signaling. Although the mutant exhibited reduced pollen viability, sterility was caused by a defect in the maternal control of seed maturation, which was associated with the loss of accumulation of JA-regulated proteinase inhibitor proteins in reproductive tissues. jai1 plants exhibited several defense-related phenotypes, including the inability to express JA-responsive genes, severely compromised resistance to two-spotted spider mites, and abnormal development of glandular trichomes. We demonstrate that these defects are caused by the loss of function of the tomato homolog of CORONATINE-INSENSITIVE1 (COI1), an F-box protein that is required for JA-signaled processes in Arabidopsis. These findings indicate that the JA/COI1 signaling pathway regulates distinct developmental processes in different plants and suggest a role for JA in the promotion of glandular trichome–based defenses.
Traditions of Australian governance
Authors: Wanna John , Weller Patrick
Published: January 2004

Australia's traditions of governance tend to be pragmatic and to blend different ideologies. Its traditions are less dependent on political party ideologies, and more on competing conceptions of the significant problems and the way that they should be addressed. In this article we identify five principal traditions, namely: settler–state developmentalism; civilizing capitalism; the development of a social–liberal constitutional tradition; traditions of federalism; and the exclusiveness/ inclusiveness of the state and society. These traditions have been robust and have developed over time. We show how political actors operating from within this plurality of traditions have understood the public sector and how their understandings have led to changes in the way the public sector is structured.
Delegation as a Source of Law
Authors: Dewhurst Dale , Hampton David , Shiner Roger A.
Published: January 2004

The status of delegation as a strictly institutionalized source of law is controversial. In this article, we examine some instances of delegation, in order to explore their claim to be independent and strictly institutionalized sources of law. We consider primarily the instances of labour arbitration and of mediation. Our conclusion is that there is no straightforward answer in either instance to the question whether they constitute sources of law, although the claim of arbitration is strong and that of mediation is weak. We argue that the controversial character of delegation as a source of law is therefore to be expected, given its ambivalent character, and that in exploring the reasons for this ambivalence much can be learnt about the concept of a strictly institutionalized source of law.
The Politics of Foreign Aid: A Median Voter Perspective
Authors: Mayer Wolfgang , Raimondos‐Møller Pascalis
Published: January 2004

The paper presents a model where the median voter in the donor country determines the support of foreign aid. It is first established that an individual in the donor country is affected by the direct benefits (due to altruism) and costs (due to taxes) of giving aid, and by the indirect benefits or costs of a change in the terms of trade. Then it is shown that the latter effect works through changing both the donor country's average income and its distribution of income. Given the stylized facts of a capital‐abundant donor country and relatively capital‐poor median voter, it is shown how redistribution‐of‐income effects soften the impact of terms‐of‐trade changes on the political support for foreign aid.
An African Growth Trap: Production Technology and the Time‐Consistency of Agricultural Taxation, R&D and Investment
Authors: McMillan Margaret S. , Masters William A.
Published: January 2004

Why do so many African governments consistently impose high tax rates and make little investment in productive public goods, when alternative policies could yield greater tax revenues and higher national income? The authors posit and test an intertemporal political economy model in which the government sets tax and R&D levels while investors respond with production. Equilibrium policy and growth rates depend on the initial cost structure. It is found that in many (but not all) African countries, low tax/high investment regimes would be time‐inconsistent, primarily because production technology requires relatively large sunk costs. For pro‐growth policies to become sustainable, new political commitment mechanisms or new production techniques would be needed.
Trade Liberalization in the Presence of Foreign Direct Investment and Tax Credits: Estimates for Costa Rica
Authors: Abrego Lisandro
Published: January 2004

The paper uses a calibrated general‐equilibrium model to quantify the welfare impact of trade liberalization—and compute the optimal tariff structure—for Costa Rica when trade‐policy‐induced foreign direct investment and international capital taxation with credits are present. It shows that complete trade liberalization reduces Costa Rica's welfare, as it leads to an outflow of capital and loss of tax revenue which more than offset the efficiency gains from an enhanced resource allocation. The optimal tariff structure for the Costa Rican economy turns out to be a mixture of relatively small import tariffs and subsidies.