bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations on the links between the architecture of a tree (Dicorynia guianensis Amshoff) and Cerambycidae activity in French Guiana
Authors: CARAGLIO YVES , NICOLINI ERIC , PETRONELLI PASCAL 
Published: July 2002

The development of a given species in a natural forest depends on a multitude of factors. Insects are one of the factors
that have an important impact. We would like to present initial observations about the behaviour of longicorns of the
Onciderini tribe and their impact on the development of Dicorynia guianensis.A study of the development of D. guianensis was conducted in French Guiana (5°18'N, 5°48'W), at the Paracou
silvicultural facility. We studied plots where the Dicorynia inventory was extended to trees 1 m tall or over. In order
to describe the impact of longicorn activity on a Dicorynia stand in which spatial distribution is aggregative (Kokou
1992), we chose trees (156 observed trees) in a control plot (plot 11, area: 17 500 m2). Height, trunk basal diameter
and DBH were measured on each tree. A precise morphological description was established for each tree. It was
during morphological description that the signs of longicorn attacks were sought. In all the species of the genus
Oncideres, the female girdles the tree by removing the bark and some of the wood using its mandibles. It then digs
deep into the wood above the cut and lays its eggs. The branch then breaks and falls to the ground (Hequet 1996). All
that is left on the tree is a stump with characteristic signs of insect activity (Figure 1a). When such signs were seen
on a plant, the type of structure (trunk, branch) was noted.
Constructive points of powerlocales
Authors: VICKERS STEVEN 
Published: July 2002

Results of Bunge and Funk and of Johnstone, providing constructively
sound
descriptions of the global points of the lower and upper powerlocales,
are extended
here to describe the generalized points and proved in a way that displays
in a
symmetric fashion two complementary treatments of frames: as suplattices
and as
preframes. Also described here are the points of the Vietoris powerlocale.In each of two special cases, an exponential $D
($ being the Sierpiński locale) is
shown to be homeomorphic to a powerlocale: to the lower
powerlocale when D is
discrete, and to the upper powerlocale when D is compact regular.
Isolation and Characterization of Homogentisate Phytyltransferase Genes from Synechocystis sp. PCC 6803 and Arabidopsis
Authors: Savidge Beth , Weiss James D. , Wong Yun-Hua H. , Lassner Michael W. , Mitsky Timothy A. , Shewmaker Christine K. , Post-Beittenmiller Dusty , Valentin Henry E. 
Published: July 2002

Abstract
Tocopherols, synthesized by photosynthetic organisms, are micronutrients with antioxidant properties that play important roles in animal and human nutrition. Because of these health benefits, there is considerable interest in identifying the genes involved in tocopherol biosynthesis to allow transgenic alteration of both tocopherol levels and composition in agricultural crops. Tocopherols are generated from the condensation of phytyldiphosphate and homogentisic acid (HGA), followed by cyclization and methylation reactions. Homogentisate phytyltransferase (HPT) performs the first committed step in this pathway, the phytylation of HGA. In this study, bioinformatics techniques were used to identify candidate genes,slr1736 and HPT1, that encode HPT fromSynechocystis sp. PCC 6803 and Arabidopsis, respectively. These two genes encode putative membrane-bound proteins, and contain amino acid residues highly conserved with other prenyltransferases of the aromatic type. A Synechocystissp. PCC 6803 slr1736 null mutant obtained by insertional inactivation did not accumulate tocopherols, and was rescued by the Arabidopsis HPT1 ortholog. The membrane fraction of wild-type Synechocystis sp. PCC 6803 was capable of catalyzing the phytylation of HGA, whereas the membrane fraction from the slr1736 null mutant was not. The microsomal membrane fraction of baculovirus-infected insect cells expressing the Synechocystis sp. PCC 6803slr1736 were also able to perform the phytylation reaction, verifying HPT activity of the protein encoded by this gene. In addition, evidence that antisense expression of HPT1in Arabidopsis resulted in reduced seed tocopherol levels, whereas seed-specific sense expression resulted in increased seed tocopherol levels, is presented.
Molecular Responses to Aphid Feeding in Arabidopsis in Relation to Plant Defense Pathways
Authors: Moran Patrick J. , Thompson Gary A. 
Published: July 2002

Abstract
Little is known about molecular responses in plants to phloem feeding by insects. The induction of genes associated with wound and pathogen response pathways was investigated following green peach aphid (Myzus persicae) feeding on Arabidopsis. Aphid feeding on rosette leaves induced transcription of two genes associated with salicylic acid (SA)-dependent responses to pathogens (PR-1 and BGL2) 10- and 23-fold, respectively. Induction of PR-1 and BGL2mRNA was reduced in npr1 mutant plants, which are deficient in SA signaling. Application of the SA analog benzothiadiazole led to decreases in aphid reproduction on leaves of both wild-type plants and mutant plants deficient in responsiveness to SA, suggesting that wild-type SA-dependent responses do not influence resistance to aphids. Two-fold increases occurred in mRNA levels ofPDF1.2, which encodes defensin, a peptide involved in the jasmonate (JA)-/ethylene-dependent response pathway. Transcripts encoding JA-inducible lipoxygenase (LOX2) and SA/JA-inducible Phe-ammonia lyase increased 1.5- to 2-fold.PDF1.2 and LOX2 induction by aphids did not occur in infested leaves of the JA-resistant coi1-1mutant. Aphid feeding induced 10-fold increases in mRNA levels of a stress-related monosaccharide symporter gene, STP4. Phloem feeding on Arabidopsis leads to stimulation of response pathways associated with both pathogen infection and wounding.
Production of Dwarf Lettuce by Overexpressing a Pumpkin Gibberellin 20-Oxidase Gene
Authors: Niki Tomoya , Nishijima Takaaki , Nakayama Masayoshi , Hisamatsu Tamotsu , Oyama-Okubo Naomi , Yamazaki Hiroko , Hedden Peter , Lange Theo , Mander Lewis N. , Koshioka Masaji 
Published: July 2002

Abstract
We investigated the effect of overexpressing a pumpkin gibberellin (GA) 20-oxidase gene encoding an enzyme that forms predominantly biologically inactive products on GA biosynthesis and plant morphology in transgenic lettuce (Lactuca sativa cv Vanguard) plants. Lettuce was transformed with the pumpkin GA 20-oxidase gene downstream of a strong constitutive promoter cassette (El2–35S-Ω). The transgenic plants in which the pumpkin gene was detected by polymerase chain reaction were dwarfed in the T2generation, whereas transformants with a normal growth phenotype did not contain the transgene. The result of Southern-blot analysis showed that the transgene was integrated as a single copy; the plants segregated three dwarfs to one normal in the T2 generation, indicating that the transgene was stable and dominant. The endogenous levels of GA1 and GA4 were reduced in the dwarfs, whereas large amounts of GA17 and GA25, which are inactive products of the pumpkin GA 20-oxidase, accumulated in these lines. These results indicate that a functional pumpkin GA 20-oxidase is expressed in the transgenic lettuce, resulting in a diversion of the normal pathway of GA biosynthesis to inactive products. Furthermore, this technique may be useful for controlling plant stature in other agricultural and horticultural species.
Long-Distance Phloem Transport of Glucosinolates in Arabidopsis
Authors: Chen Sixue , Petersen Bent Larsen , Olsen Carl Erik , Schulz Alexander , Halkier Barbara Ann 
Published: July 2002

Abstract
Glucosinolates are a large group of plant secondary metabolites found mainly in the order Capparales, which includes a large number of economically important Brassica crops and the model plant Arabidopsis. In the present study, several lines of evidence are provided for phloem transport of glucosinolates in Arabidopsis. When radiolabeled p-hydroxybenzylglucosinolate (p-OHBG) and sucrose were co-applied to the tip of detached leaves, both tracers were collected in the phloem exudates at the petioles. Long-distance transport of [14C]p-OHBG was investigated in wild-type and transgenic 35S::CYP79A1 plants, synthesizing high amounts of p-OHBG, which is not a natural constituent of wild-type Arabidopsis. In both wild-type and 35S::CYP79A1 plants, radiolabeled p-OHBG was rapidly transported from the application site into the whole plant and intactp-OHBG was recovered from different tissues. The pattern of distribution of the radioactivity corresponded to that expected for transport of photoassimilates such as sucrose, and was consistent with translocation in phloem following the source-sink relationship. Radiolabeled p-OHBG was shown to accumulate in the seeds of wild-type and 35S::CYP79A1 plants, wherep-OHBG had been either exogenously applied or endogenously synthesized from Tyr in the leaves. p-OHBG was found in phloem exudates collected from cut petioles of leaves from both wild-type and 35S::CYP79A1 plants. Phloem exudates were shown to contain intact glucosinolates, and not desulphoglucosinolates, as the transport form. It is concluded that intact glucosinolates are readily loaded into and transported by the phloem.
Neutron Rietveld refinement of the incommensurate phase of the ordered perovskite Pb2CoWO6
Authors: Baldinozzi G. , Calvarin G. , Sciau Ph. , Grebille D. , Suard E. 
Published: July 2002

The incommensurate structure of lead cobalt tungstate has been refined by the Rietveld method on neutron data collected at 250 K. The space group is planar monoclinic I2/m(\alpha0\gamma)0s [a = 7.9602 (4), b = 5.6779 (3), c = 5.6967 (3) Å, \beta = 90.047 (5)°, \bf q_{\rm inc} = 0.9000 (9)\bf a^* + 0.1735 (6)\bf c^*]. The use of powder diffraction techniques to investigate ferroelastic modulated phases is discussed and compared with a previous polydomain single-crystal structural analysis. The modulated displacements of light atoms have been determined, allowing an accurate description of the modulation of both the cations and the O-atom framework. The refinement suggests a displacive model for the phase transition, involving significant atomic shifts for Pb atoms and a quite complex mixing of tilt and deformation of the oxygen octahedra. The average character of this modulated structure is antiferroelectric.
Structure and complex twinning of dysprosium disilicate (Dy2Si2O7), Type B
Authors: Fleet Michael E. , Liu Xiaoyang 
Published: July 2002

Dysprosium disilicate (Dy2Si2O7) is triclinic with a = 6.6158 (2), b = 6.6604 (2), c = 12.0551 (4) Å, α = 94.373 (2), β = 90.836 (2), γ = 91.512 (2)°, V = 529.4 (1) Å3, space group P\overline 1, Z = 4 and D

x
= 6.156 g cm−3. The structure (single-crystal X-ray, R = 0.033, wR = 0.041) is built from a linear triple tetrahedral group [Si3O10] and isolated [SiO4] tetrahedron cross-linked by Dy3+ in one sixfold and three eightfold coordinated positions, and corresponds to the presently revised type B structure of Ho2Si2O7. The formation of the unusual linear triple tetrahedral group in the type B structure allows for a more continuous transition in the mean size of REE3+O
n
(REE = rare earth element) polyhedra in REE disilicates through the 4f transition metal series. The crystal of Dy2Si2O7 investigated was complexly twinned such that the diffraction pattern was also consistent with a larger dimensionally monoclinic unit cell (a = 22.5354, b = 14.2102, c = 6.6158 Å, β = 91.788°), which resulted in an apparent superstructure of the type B structure in space group C1¯. Lattice coincidence with the type B unit cell appears to have been maintained during crystal synthesis and quenching by the complex sector-zoned growth twin.
Polymorphs and pseudopolymorphs of N,N′-dithiobisphthalimide
Authors: Farrell Dorcas M. M. , Glidewell Christopher , Low John N. , Skakle Janet M. S. , Zakaria Choudhury M. 
Published: July 2002

N,N′-Dithiobisphthalimide, C16H8N2O4S2 (I), forms a wide range of polymorphs and solvates (pseudopolymorphs). When (I) is crystallized from methanol it yields a solvent-free polymorph (4), in Pna21 with Z′ = 1, in which the molecules are linked into chains by a single C—H...O hydrogen bond: crystallization from either acetonitrile or dimethylformamide produces a monoclinic polymorph (5), in P21/c with Z′ = 2, also solvent-free, in which the molecules are linked into molecular ladders. Nitromethane forms a monosolvate, C16H8N2O4S2·CH3NO2 (6), in P21/c with Z′ = 1, in which the solvent molecules are linked to the molecules of (I) not only via a conventional C—H...O hydrogen bond but also via a polarized multicentre interaction involving all three C—H bonds of the solvent molecule. Chlorobenzene forms a precise hemisolvate, C16H8N2O4S2·0.5C6H5Cl (7), in P{\bar 1 } with Z′ = 1, while ethylbenzene forms an approximate hemisolvate 2C16H8N2O4S2·0.913C6H5C2H5·0.087H2O (8), in P21/c with eight molecules of (I) per unit cell. In both solvates the molecules of (I) are linked, in (7) by π...π stacking interactions augmented by weak C—H...O hydrogen bonds and in (8) by stronger C—H...O hydrogen bonds: the solvent molecules lie in isolated cavities, disordered across inversion centres in (7) and fully ordered in general positions in (8). Crystallization of (I) either from tetrahydrofuran or from wet tert-butanol yields isomorphous solvates (9) and (10), respectively, in C2/c with Z′ = 0.5, in which molecules of (I) lie across twofold rotation axes and are linked by π...π stacking interactions and very weak C—H...O hydrogen bonds, forming a framework enclosing continuous channels: highly disordered solvent molecules lie within these channels. p-Xylene and toluene form isomorphous hemisolvates (11) and (12) with unit cells metrically very similar to those of (9) and (10), but in P21/n with Z′ = 1: in these two solvates the molecules of (I) are linked into a framework by very short C—H...O hydrogen bonds; the solvent molecules lie within continuous channels, but they are localized across inversion centres so that the toluene is disordered across an inversion centre.
Mixed Alkali Systems: Structure and 29Si MASNMR of Li2Si2O5 and K2Si2O5
Authors: de Jong B. H. W. S. , Supèr H. T. J. , Spek A. L. , Veldman N. , Nachtegaal G. , Fischer J. C. 
Published: July 2002

Li2Si2O5,
M

r
= 150.05, λ(Mo Kα) = 0.71073 Å, 293 K, orthorhombic, Ccc2, a = 5.807 (2), b = 14.582 (7), c = 4.773 (3) Å, V = 404.2 (3) Å3, μ(Mo Kα) = 0.78 mm−1, Z = 4, D

x
= 2.466 Mg m−3, R
1 = 0.045 for 249 reflections with I > 2.0σ(I), wR
2 = 0.1138 for all 261 reflections. K2Si2O5, M

r
= 214.36, λ(Mo Kα) = 0.71073 Å, 150 K, monoclinic, Cc, a = 16.322 (2), b = 11.243 (2), c = 9.919 (1) Å, β = 115.97 (1)°, V = 1636.4 (4) Å3, μ(Mo Kα) = 2.11 mm−1, Z = 12, D

x
= 2.610 Mg m−3, R
1 = 0.0385 for 2370 reflections with I > 2.0σ(I), wR
2 = 0.0785 for all 2711 reflections. The crystal structures of Li2Si2O5 and K2Si2O5 have been determined and refined. The lithium phyllosilicate sheet topology and structure based on three-dimensional data and refined in the orthorhombic space group Ccc2 confirm the previous determination by Liebau [Acta Cryst. (1961), 14, 389–395] from two-dimensional data, but described in the lower monoclinic Cc space-group symmetry. Potassium disilicate, on the other hand, is not a phyllosilicate but forms a three-dimensional defect cristobalite structure built from Q
3 silica units. In this structure, one Si—O—Si bridge, common to four six-membered T-rings, i.e. rings consisting of six silica tetrahedra in the chair conformation, is missing, resulting in 14-membered T-rings. Continuous sheets built up from these rings form a layer connected to layers above and below by six-membered T-rings in the chair conformation. 29Si MASNMR shows a good correlation between Si—O—Si angle and 29Si chemical shift for K2Si2O5, Li2Si2O5 and KLiSi2O5. The 29Si spin lattice relaxation times, T
1, are 335, 689 and 〈1256〉 s for Li2Si2O5, KLiSi2O5 and K2Si2O5, respectively. The pronounced non-linearity in hygroscopicity in glassy potassium–lithium disilicates is not observed in the osmolality of 0.8M potassium–lithium chloride aqueous solutions.
Crystallization and preliminary X-ray crystallographic analysis of a vancomycin–N-acetyl-D-Ala-D-Ala complex
Authors: McPhail Deborah , Cooper Alan , Freer Andy 
Published: July 2002

A vancomycin–N-acetyl-D-Ala-D-Ala complex has been crystallized by the sitting-drop vapour-diffusion method using imidazole maleic buffer at pH 7.6. The novel crystals obtained belong to the space group P6322 with unit-cell parameters a = b = 73.43 (1), c = 277.17 (4) Å, γ = 120°. The crystal density was determined as 1.106 g cm−3 which gives a supercell of 24 molecules (12 dimers) per asymmetric unit for an acceptable Matthews number and an estimated solvent content of 42%. Data were collected at room temperature to 2.8 Å.
Crystallization and preliminary X-ray diffraction studies of monomeric isocitrate dehydrogenase from Corynebacterium glutamicum
Authors: Audette Gerald F. , Quail J. Wilson , Hayakawa Koto , Bai Cheng , Chen Ridong , Delbaere Louis T. J. 
Published: July 2002

A monomeric isocitrate dehydrogenase has been crystallized for the first time. This enzyme catalyzes the conversion of isocitrate to oxalosuccinate and subsequently to α-ketoglutarate and CO2; the coenzyme NADP+ is reduced to NADPH during the reaction. Polyethylene glycol 2000 monomethyl ether was used to crystallize the enzyme in space group C2 with unit-cell parameters a = 137.1, b = 54.6, c = 126.4 Å, β = 108.2°. The very small crystal (0.05 × 0.20 × 0.05 mm) diffracted to 3.5 Å d spacing using synchrotron radiation.
Preparation and preliminary X-ray diffraction studies of a new crystal form of L-asparaginase from Escherichia coli
Authors: Polikarpov I. , de Oliveira R. T. , Abrahão-Neto J. 
Published: July 2002

L-Asparaginase is an enzyme which hydrolyzes asparagine to produce aspartic acid and ammonia. It is an effective chemotherapeutic drug, especially in the treatment of acute lymphoblastic leukaemia in children. The enzyme from Escherichia coli was crystallized in a new crystal form with space group C2, unit-cell parameters a = 76.3 (0), b = 134.6 (2), c = 64.8 (7) Å, β = 110.5 (1)° and a dimer in the asymmetric unit. Synchrotron-radiation diffraction data have been collected to 1.95 Å resolution.
Three-dimensional structure of the Gly121Tyr dimeric form of ornithine decarboxylase from Lactobacillus 30a
Authors: Vitali Jacqueline , Carroll Donald , Chaudhry Rochika G. , Hackert Marvin L. 
Published: July 2002

Ornithine decarboxylases catalyze the conversion of ornithine to putrescine at the beginning of the polyamine pathway. Ornithine decarboxylase (ODC) from Lactobacillus 30a is a 990612 Da dodecamer composed of six homodimers. A single point mutation (Gly121Tyr) was found to prevent association of dimers into dodecamers. The dimeric protein has been crystallized at pH 7.0 in the presence of guanosine triphosphate (GTP). Crystals belong to space group P3221, with unit-cell parameters a = 111.8, c = 135.9 Å and one monomer in the asymmetric unit. The structure was determined by molecular replacement and refined using simulated annealing to R = 0.211 at 2.7 Å resolution. The GTP-binding site was analyzed in detail. The protein exhibits a novel binding mode for GTP which is different from that seen in most G-proteins or GTPases. Central to this binding scheme appear to be three lysines, Lys190, Lys374 and Lys382, which form salt bridges with the three phosphates, and Thr191, which hydrogen bonds with the guanine base. Furthermore, the structure suggests that there is some flexibility in the wing domain, which can change its orientation as the protein adapts to its environment. The active site is similar to that of the native enzyme, consistent with the observation that the enzyme activity does not depend on its dodecameric state.
Cytochrome P-450 2C9 Sensitizes Human Prostate Tumor Cells to Cyclophosphamide via a Bystander Effect
Authors: Zhou Diansong , Lu Yi , Steiner Mitchell S. , Dalton James T. 
Published: July 2002

ABSTRACT

The goal of the present study was to examine the ability of cytochrome P450-2C9 (CYP2C9) to activate cyclophosphamide (CPA) and elicit tumor cell death. A CYP2C9-deficient human lymphoblastoid cell line (AHH-1 cells) and a derivative cell line (H2C9 cells) stably transfected with a cDNA encoding CYP2C9 were used. The catalytic activity present in cell lines was examined by measuring the conversion of diclofenac, a CYP2C9-specific substrate, to its 4′-hydroxy metabolite by high-pressure liquid chromatography. Initial rate plots were constructed and the maximal rate of formation (
V
max
) and the Michaelis-Menten constant (

K
m

) for diclofenac metabolism were determined. Cytotoxicity was studied by exposing the cells to 0.01 to 4 mM CPA in the presence or absence of sulfaphenazole, a CYP2C9-specific inhibitor. Cell survival was quantitated by determination of the level of tritiated thymidine incorporation. H2C9 cells quickly metabolized diclofenac, indicating the presence of high levels of CYP2C9. Kinetic experiments demonstrated a
V
max
and

K
m

of 0.62 ± 0.012 pmol/min/10
6
cells and 6.16 ± 0.62 μM, respectively, for diclofenac metabolism. Diclofenac 4′-hydroxylase activity was undetectable in AHH-1 cells. H2C9 cells were more sensitive to the cytotoxic effects of CPA (50% inhibitory concentration [IC
50
], 0.80 ± 0.03 mM) than AHH-1 cells (IC
50
, 4.07 ± 0.35 mM). The cytotoxicity (IC
50
, 1.99 ± 0.14 mM) of CPA to H2C9 cells was blocked by sulfaphenazole, demonstrating that the chemosensitivity of these cells is a consequence of intracellular prodrug activation. H2C9 cells mediated a bystander killing effect for CYP2C9-negative PPC-1 cells, reducing the IC
50
of CPA from about 14 to 3.62 ± 0.73 mM in PPC-1 cells when they were cocultured with H2C9 cells. These results suggest that the enzyme-prodrug system of CYP2C9 and CPA may be an effective combination for gene-directed enzyme prodrug therapy. Ongoing studies are examining the utility of this system for use in prostate cancer cells.
Comparison of Human Immunodeficiency Virus Type 1 Pr55
Gag
and Pr160
Gag-Pol
Processing Intermediates That Accumulate in Primary and Transformed Cells Treated with Peptidic and Nonpeptidic Protease Inhibitors
Authors: Speck R. Renae , Flexner Charles , Tian Chun-Juan , Yu Xiao-Fang 
Published: July 2002

ABSTRACT

Human immunodeficiency virus type 1 (HIV-1) produces two polyproteins, Pr55
Gag
and Pr160
Gag-Pol
, that are cleaved into mature functional subunits by the virally encoded protease. Drugs that inhibit this protease are an important part of anti-HIV therapy. We studied the ordered accumulation of Gag and Gag-Pol processing intermediates by variably blocking the protease with HIV-1 protease inhibitors (PIs). Variable protease inhibition caused accumulation of a complex pattern of processing intermediates, which was the same after incubating HIV-1-infected cells with increasing concentrations of either one of the peptidomimetic inhibitors indinavir, saquinavir (SQV), ritonavir (RTV), nelfinavir, and SC-52151 or one of the nonpeptidomimetic inhibitors DMP450, DMP323, PNU-140135, and PNU-109112 for 3 days. The patterns of Gag and Gag-Pol processing intermediate accumulation were nearly identical when the following were compared: cell- versus virion-associated proteins, HIV-1-infected transformed cell lines versus primary human peripheral blood mononuclear cells (PBMCs) and HIV-1
MN
versus HIV-1
IIIB
virus strains. RTV was a more potent inhibitor of p24 production in PBMCs than SQV by approximately 7-fold, whereas SQV was a more potent inhibitor in transformed cells than RTV by approximately 30-fold. Although the antiretroviral potency of HIV-1 PIs may change as a function of cell type, the polyprotein intermediates that accumulate with increasing drug concentrations are the same. These results support sequential processing of Gag and Gag-Pol polyproteins by the HIV-1 protease and may have important implications for understanding common cross-resistance pathways.