bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nodal Endoplasmic Reticulum, a Specialized Form of Endoplasmic Reticulum Found in Gravity-Sensing Root Tip Columella Cells
Authors: Zheng Hui Qiong , Staehelin L. Andrew 
Published: July 2002

Abstract
The endoplasmic reticulum (ER) of columella root cap cells has been postulated to play a role in gravity sensing. We have re-examined the ultrastructure of columella cells in tobacco (Nicotiana tabacum) root tips preserved by high-pressure freezing/freeze-substitution techniques to gain more precise information about the organization of the ER in such cells. The most notable findings are: the identification of a specialized form of ER, termed “nodal ER,” which is found exclusively in columella cells; the demonstration that the bulk of the ER is organized in the form of a tubular network that is confined to a peripheral layer under the plasma membrane; and the discovery that this ER-rich peripheral region excludes Golgi stacks, vacuoles, and amyloplasts but not mitochondria. Nodal ER domains consist of an approximately 100-nm-diameter central rod composed of oblong subunits to which usually seven sheets of rough ER are attached along their margins. These domains form patches at the interface between the peripheral ER network and the ER-free central region of the cells, and they occupy defined positions within central and flanking columella cells. Over one-half of the nodal ER domains are located along the outer tangential walls of the flanking cells. Cytochalasin D and latrunculin A cause an increase in size and a decrease in numbers of nodal ER domains. We postulate that the nodal ER membranes locally modulate the gravisensing signals produced by the sedimenting amyloplasts, and that the confinement of all ER membranes to the cell periphery serves to enhance the sedimentability of the amyloplasts in the central region of columella cells.
A Comparison of the Effects of DNA-Damaging Agents and Biotic Elicitors on the Induction of Plant Defense Genes, Nuclear Distortion, and Cell Death
Authors: Choi Jane Junghae , Klosterman Steven J. , Hadwiger Lee A. 
Published: July 2002

Abstract
Pea (Pisum sativum L. cv Alcan) endocarp tissue challenged with an incompatible fungal pathogen, Fusarium solani f. sp. phaseoli or fungal elicitors results in the induction of pathogenesis-related (PR) genes and the accumulation of pisatin, a phytoalexin. Essentially the same response occurs in pea tissue exposed to DNA-specific agents that crosslink or intercalate DNA. In this study, the effects of DNA-damaging agents were assessed relative to the inducible expression of several pea PR genes: phenylalanine ammonia lyase, chalcone synthase, and DRR206. Mitomycin C and actinomycin D mimicked the biotic elicitors in enhancing the expression of all three PR genes. The activities of these PR gene promoters, isolated from different plants, were evaluated heterologously in transgenic tobacco. It is remarkable that β-glucuronidase expression was induced when plants containing the heterologous phenylalanine ammonia lyase, chalcone synthase, and DRR206 promoter-β-glucuronidase chimeric reporter genes were treated by DNA-damaging agents. Finally, cytological analyses indicated that many of these agents caused nuclear distortion and collapse of the treated pea cells. Yet we observed that cell death is not necessary for the induction of the PR gene promoters assessed in this study. Based on these observations and previously published results, we propose that DNA damage or the associated alteration of chromatin can signal the transcriptional activation of plant defense genes.
Screening of the Rice Viviparous Mutants Generated by Endogenous Retrotransposon Tos17 Insertion. Tagging of a Zeaxanthin Epoxidase Gene and a Novel OsTATCGene
Authors: Agrawal Ganesh Kumar , Yamazaki Muneo , Kobayashi Masatomo , Hirochika Rei , Miyao Akio , Hirochika Hirohiko 
Published: July 2002

Abstract
The rice (Oryza sativa) retrotransposonTos17 is one of a few active retrotransposons in plants and its transposition is activated by tissue culture. Here, we present the characterization of viviparous mutants of rice induced by tissue culture to demonstrate the feasibility of the use of retrotransposonTos17 as an endogenous insertional mutagen and cloning of the tagged gene for forward genetics in unraveling the gene function. Two mutants were shown to be caused by the insertion ofTos17. Osaba1, a strong viviparous mutant with wilty phenotype, displayed low abscisic acid level and almost no further increase in its levels upon drought. The mutant is shown to be impaired in the epoxidation of zeaxanthin. On the other hand,Ostatc, a mutant with weak phenotype, exhibited the pale green phenotype and slight increase in abscisic acid levels upon drought. Deduced amino acids of the causative genes ofOsaba1 and Ostatc manifested a significantly high homology with zeaxanthin epoxidase isolated from other plant species and with bacterial Sec-independent translocase TATC protein, respectively. This is the first example of transposon tagging in rice.
Quantitative Trait Locus Mapping of Loci Influencing Elongation Factor 1α Content in Maize Endosperm
Authors: Wang Xuelu , Woo Young-min , Kim Cheol Soo , Larkins Brian A. 
Published: July 2002

Abstract
The nutritional value of maize (Zea mays) seed is most limited by its protein quality because its storage proteins are devoid of the essential amino acid lysine (Lys). The Lys content of the kernel can be significantly increased by the opaque-2 mutation, which reduces zein synthesis and increases accumulation of proteins that contain Lys. Elongation factor 1α (eEF1A) is one of these proteins, and its concentration is highly correlated with the Lys content of the endosperm. We investigated the genetic regulation of eEF1A and the basis for its relationship with other Lys-containing proteins by analyzing the progeny of a cross between a high (Oh51Ao2) and a low (Oh545o2) eEF1A maize inbred. We identified 83 simple sequence repeat loci that are polymorphic between these inbreds; the markers are broadly distributed over the genome (1,402 cM) with an average interval of 17 cM. Genotypic analysis of the F2 progeny revealed two significant quantitative trait loci that account for 25% of the variance for eEF1A content. One of these is on the short arm of chromosome 4 and is linked with a cluster of 22-kD α-zein coding sequences; the other quantitative trait locus is on the long arm of chromosome 7. The content of α-zein and γ-zein was measured in pools of high- and low-eEF1A individuals obtained from this cross, and a higher level of α-zein was found to cosegregate with high eEF1A content. Allelic variation at the 22-kD α-zein locus may contribute to the difference of eEF1A content between Oh51Ao2 and Oh545o2 by increasing the surface area of protein bodies in the endosperm and creating a more extensive network of cytoskeletal proteins.
Altered Expression of SPINDLY Affects Gibberellin Response and Plant Development
Authors: Swain Stephen M. , Tseng Tong-seung , Olszewski Neil E. 
Published: July 2002

Abstract
Gibberellins (GAs) are plant hormones with diverse roles in plant growth and development. SPINDLY (SPY) is one of several genes identified in Arabidopsis that are involved in GA response and it is thought to encode an O-GlcNAc transferase. Genetic analysis suggests that SPY negatively regulates GA response. To test the hypothesis that SPY acts specifically as a negatively acting component of GA signal transduction,spy mutants and plants containing a 35S:SPY construct have been examined. A detailed investigation of the spymutant phenotype suggests that SPY may play a role in plant development beyond its role in GA signaling. Consistent with this suggestion, the analysis of spy er plants suggests that theERECTA (ER) gene, which has not been implicated as having a role in GA signaling, appears to enhance the non-GA spy mutant phenotypes. Arabidopsis plants containing a 35S:SPY construct possess reduced GA response at seed germination, but also possess phenotypes consistent with increased GA response, although not identical to spy mutants, during later vegetative and reproductive development. Based on these results, the hypothesis that SPY is specific for GA signaling is rejected. Instead, it is proposed that SPY is a negative regulator of GA response that has additional roles in plant development.
Influence of Growth Conditions and Developmental Stage onN-Glycan Heterogeneity of Transgenic Immunoglobulin G and Endogenous Proteins in Tobacco Leaves
Authors: Elbers Ingrid J.W. , Stoopen Geert M. , Bakker Hans , Stevens Lucas H. , Bardor Muriel , Molthoff Jos W. , Jordi Wilco J.R.M. , Bosch Dirk , Lommen Arjen 
Published: July 2002

Abstract
Plants are regarded as a promising system for the production of heterologous proteins. However, little is known about the influence of plant development and growth conditions on N-linked glycosylation. To investigate this, transgenic tobacco (Nicotiana tabacum cv Samsun NN) plants expressing a mouse immunoglobulin G antibody (MGR48) were grown in climate rooms under four different climate conditions, i.e. at 15°C and 25°C and at either low or high light conditions. N-glycans on plantibodies and soluble endogenous proteins were analyzed with matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS). Antibodies isolated from young leaves have a relatively high amount of high- mannose glycans compared with antibodies from older leaves, which contain more terminal N-acetylglucosamine. Senescence was shown to affect the glycosylation profile of endogenous proteins. The relative amount of N-glycans without terminalN-acetylglucosamine increased with leaf age. Major differences were observed between glycan structures on endogenous proteins versus those on antibodies, probably to be attributed to their subcellular localization. The relatively high percentage of antibodyN-glycan lacking both xylose and fucose is interesting.
A Noncontact, Nondestructive Method for Quantifying Intratissue Deformations and Strains
Authors: Bey M. J. , Song H. K. , Wehrli F. W. , Soslowsky L. J. 
Published: July 2002

AbstractThe function of soft connective tissues is frequently characterized by quantifying tissue strain (e.g., during joint motion). Conventional techniques for quantifying tendon and ligament strain typically provide surface measures, using markers, stain lines or instrumentation that may influence the tissue. An alternative approach is to quantify intratendinous strain by applying texture correlation analysis to magnetic resonance (MR) images. This paper reports the accuracy and reproducibility of this approach by (1) assessing the reproducibility of MR images, (2) assessing texture correlation accuracy using simulated displacements, and (3) comparing texture correlation measures of displacement and strain from MR images to conventional techniques.
Analysis of In-Flight Oxidation During Reactive Spray Atomization and
Deposition Processing of Aluminum
Authors: Delplanque J.-P. , Lavernia E. J. , Rangel R. H. 
Published: July 2002

Abstract
This work defines a model to predict the characteristics of materials processed using reactive spray atomization and deposition. The materials considered are aluminum alloys while target dispersoids are primarily oxides. These may be obtained by the reaction of oxygen-containing atomization gas mixtures with molten alloy droplets. Droplet position and velocity histories are obtained from the numerical solution of the one-dimensional equation of motion. The energy equation inside the droplet is solved numerically using finite differences to predict the spatially resolved temperature field. The solid/liquid interface progression rate is estimated using a power law while an oxidation rate expression based on the Mott-Cabrera theory is used for the oxide thickness. Such a model should prove very valuable in determining the parameters controlling the volume fraction and the size distribution of the dispersoids for various systems. [S0022-1481(00)02901-7]
Abstract: Intense field-emission ion source of liquid metals
Authors: Clampitt R. , Aitken K. L. , Jefferies D. K. 
Published: July 2002

Intense ion beams are of interest in fusion research for plasma heating, diagnostics, and target compression and in industry for implantation, microfabrication, etc.
We report the generation of intense beams of metal ions of Li, Cs, Sn, Ga, and Hg by field-ion emission of molten metal films on solid wire needles. The source is extremely simple and is based on electrohydrodynamic instabilities induced in liquid films under electric stress. In practice, for a point-source or needle emitter, a tungsten needle protrudes from the surface of the molten metal which, with good wetting, flows as a thin film to the needle apex. Application of a potential difference between the needle anode and an apertured cathode results in an electrohydrodynamic instability in the film which is manifested as a filamentary cusp at the needle apex. The electric field intensity at the cusp is sufficient to produce intense atomic-ion emission by field ionization. When the protruding length of the needle through the molten metal pool is appropriately adjusted, the tip becomes self-feeding and continuous ion emission occurs.
Direct currents of 50–700 μA can be readily produced from single needles at modest voltages (3–10 kV). Examination of the liquid cusp in an electron microscope shows that the radius of the emitting zone is ?104 Å, suggesting ion current densities in excess of 104 A/cm2. Source scaling can be achieved with an array of needles. Alternatively, one can use a linear or annular edge over which the molten metal flows as a thin film. In the latter source the ion emitting sites are generated along the edge by the field at a frequency given by λ=8πS/3ε0E2, where S is surface tension and E is field strength.
Ion emission is accompanied by light emission from a microscopic spot (10–50 μm) at the anode apex. The anode emission process bears some phenomenological similarities to anode spots and cathode spots in vacuum arcs and to pulsed high-current pinched plasma jets formed on pointed anodes or from exploding wires. Such plasmas are known to be dynamic linear pinches. What we have produced is a microscopic metal-vapor plasma ball, and we have found a way of anchoring this to allow continuous operation. We do not know by what mechanism the intense plasma spot forms; almost certainly it is initiated by field ionization, the electrons perhaps being generated by ion collisions with the metal vapor. Heating and evaporation of the anode jet could be by I2R heating or by electrons accelerated across the anode drop between plasma ball and liquid surface.
As a stable plasma ball it is novel and readily lends itself to plasma diagnostics. Also by rapidly discharging a high current at high voltage through the anode it should provide a source of a minute dense plasma more reproducibly than presently attained and an intense pulsed source of ions, light, and x rays.
Interfaces in GaAs/AlAs: Perfection and applications
Authors: Bode Michael H. , Ourmazd Abbas 
Published: July 2002

This article presents a short review of our present understanding of the structure of semiconductor interfaces and the way they may be used to investigate solid state processes at the atomic level. Until recently it was customary to claim the fabrication of atomically perfect interfaces, based on the results of photoluminescence (PL) experiments. This was based on the splitting of PL lines into closely spaced satellites, thought to stem from the recombination of excitons within large, atomically perfect terraces. However, quantitative microscopic data, obtained by chemical mapping [A. Ourmazd, F. Baumann, M. Bode, and Y. Kim, Ultramicroscopy 34, 237 (1990)], clearly indicate the presence of significant atomic scale roughness [A. Ourmazd, D. W. Taylor, J. Cunningham, and C. W. Tu, Phys. Rev. Lett. 62, 933 (1989)]. This has been confirmed more recently by high resolution PL and photoluminescence excitation experiments [C. A. Warwick, W. Y. Jan, A. Ourmazd, and T. D. Harris, Appl. Phys. Lett. 56, 2666 (1990)], by Raman scattering [D. Gammon, B. V. Shannabrook, and D. S. Katzer, Phys. Rev. Lett. 67, 1547 (1991)] and by high resolution x-ray measurements [M. Lagally, presented at the MRS Fall Meeting in Boston, 1991, Ca5.2]. All these experiments reveal a more complex interfacial configuration, produced by the interplay of roughness at different length scales.
The quantitative microscopic techniques developed for the study of interfacial structure also makes possible a class of experiments, where the interface is used as a ‘‘photographic emulsion’’ layer, capable of recording the passage of defects. This allows one to investigate solid state processes at the atomic level. For example, the intermixing caused by the passage of an implanted ion through a GaAs/AlAs interface of a multilayer may be used to track the ion and investigate the microscopics of its interaction with the host material [M. Bode, A. Ourmazd, J. A. Rentschler, M. Hong, L. C. Feldman, and J. P. Mannaerts, Mater. Res. Soc. Symp. Proc. 1989 157, 197 (1990)]. From this type of experiments it is possible to deduce the microscopic damage signature produced by individual implanted Ga+ ions [M. Bode, A. Ourmazd, J. Cunningham, and M. Hong, Phys. Rev. Lett. 67, 843 (1991)]. Intriguingly, the damage is charged, and thus strongly influenced by internal electric fields in the solid. This may be exploited to microscopically steer ion implantation damage in solids.
Sex and Conflict
Authors: Partridge Linda , Hurst Laurence D. 
Published: July 2002

REVIEW
Evolutionary conflict occurs when the deterministic spread of an allele lowers the fitness either of its bearer or of other individuals in the population, leading to selection for suppressors. Sex promotes conflict because associations between alleles are temporary. Differing selection on males and females, sexual selection, and differences in transmission patterns between classes of nuclear and cytoplasmic genes can all give rise to conflict. Inert Y chromosomes, uniparental inheritance of cytoplasmic genes, mating strains and sexes, and many features of sexual behavior may have evolved in part as a result of evolutionary conflict. Estimates of its quantitative importance, however, are still needed.
In Vitro and In Vivo Potentiation of Artemisinin and Synthetic Endoperoxide Antimalarial Drugs by Metalloporphyrins
Authors: Benoit-Vical Françoise , Robert Anne , Meunier Bernard 
Published: July 2002

ABSTRACT

The in vitro potentiation of artemisinin by synthetic manganese porphyrin complexes has been recently reported (F. Benoit-Vical, A. Robert, and B. Meunier, Antimicrob. Agents Chemother. 43:2555–2558, 1999). Since the activity of artemisinin and synthetic antimalarial endoperoxides is related to their interaction with heme (S. R. Meshnick, A. Thomas, A. Ranz, C. M. Xu, and H. Z. Pan, Mol. Biochem. Parasitol. 49:181–190, 1991), an improvement of their efficiency may be expected in the presence of a synthetic metalloporphyrin having the same activating role as endogenous heme. With the aim to boost the activity of antimalarial endoperoxide drugs, we were thus led to evaluate the in vitro and in vivo potentiation of natural and synthetic drugs of this family by a nontoxic and cheap metalloporphyrin. The potentiation of artemisinin, β-artemether, and arteflene (Ro 42-1611) by synthetic heme models is reported. In vitro studies on the chloroquine-resistant
Plasmodium falciparum
FcB1-Columbia strain indicate a synergistic effect of the manganese complex of
meso
-tetrakis(4-sulfonatophenylporphyrin) (Mn-TPPS) on the activity of artemisinin or β-artemether, whereas this heme model has no influence on the activity of arteflene. A significant synergistic effect on rodent malaria was also observed in vivo between artemisinin and Mn-TPPS using
Plasmodium vinckei petteri
strain.
Fluoroquinolone Resistance in Clinical Isolates of
Streptococcus pneumoniae
: Contributions of Type II Topoisomerase Mutations and Efflux to Levels of Resistance
Authors: Bast Darrin J. , Low Donald E. , Duncan Carla L. , Kilburn Laurie , Mandell Lionel A. , Davidson Ross J. , de Azavedo Joyce C. S. 
Published: July 2002

ABSTRACT

We report on amino acid substitutions in the quinolone resistance-determining region of type II topisomerases and the prevalence of reserpine-inhibited efflux for 70 clinical isolates of
S. pneumoniae
for which the ciprofloxacin MIC is ≥4 μg/ml and 28 isolates for which the ciprofloxacin MIC is ≤2 μg/ml. The amino acid substitutions in ParC conferring low-level resistance (MICs, 4 to 8 μg/ml) included Phe, Tyr, and Ala for Ser-79; Asn, Ala, Gly, Tyr, and Val for Asp-83; Asn for Asp-78; and Pro for Ala-115. Isolates with intermediate-level (MICs, 16 to 32 μg/ml) and high-level (MICs, 64 μg/ml) resistance harbored substitutions of Phe and Tyr for Ser-79 or Asn and Ala for Asp-83 in ParC and an additional substitution in GyrA which included either Glu-85-Lys (Gly) or Ser-81-Phe (Tyr). Glu-85-Lys was found exclusively in isolates with high-level resistance. Efflux contributed primarily to low-level resistance in isolates with or without an amino acid substitution in ParC. The impact of amino acid substitutions in ParE was minimal, and no substitutions in GyrB were identified.
Effects of the Movement of Insertion Sequences on the Structure of VanA Glycopeptide Resistance Elements in
Enterococcus faecium
Authors: Darini Ana L. C. , Palepou Marie-France I. , Woodford Neil 
Published: July 2002

ABSTRACT

A Tn
1546
-related element with IS
1216V
at position 8839 underwent a structural change after storage of the host strain of
Enterococcus faecium
at 4°C. The element acquired IS
1542
at position 3932, nucleotides 8732 to 8831 were deleted, and the first 3417 nucleotides were lost and replaced by an inverted copy of the IS
1216V–vanY–vanZ
-inverted-repeat block from the 3′ end. Insertion sequence movement is likely to play a key role in the evolution of VanA resistance elements.