bluuebunny/crossref_metadata_2025_split huggingface dataset:
Drying Increases Intracellular Partitioning of Amphiphilic Substances into the Lipid Phase
Authors: Golovina Elena A. , Hoekstra Folkert A. , Hemminga Marcus A. 
Published: July 2002

Abstract
Previously we proposed that endogenous amphiphilic substances may partition from the aqueous cytoplasm into the lipid phase during dehydration of desiccation-tolerant organ(ism)s and vice versa during rehydration. Their perturbing presence in membranes could thus explain the transient leakage from imbibing organisms. To study the mechanism of this phenomenon, amphiphilic nitroxide spin probes were introduced into the pollen of a model organism, Typha latifolia, and their partitioning behavior during dehydration and rehydration was analyzed by electron paramagnetic resonance spectroscopy. In hydrated pollen the spin probes mainly occurred in the aqueous phase; during dehydration, however, the amphiphilic spin probes partitioned into the lipid phase and had disappeared from the aqueous phase below 0.4 g water g−1 dry weight. During rehydration the probes reappeared in the aqueous phase above 0.4 g water g−1 dry weight. The partitioning back into the cytoplasm coincided with the decrease of the initially high plasma membrane permeability. A charged polar spin probe was trapped in the cytoplasm during drying. Liposome experiments showed that partitioning of an amphiphilic spin probe into the bilayer during dehydration caused transient leakage during rehydration. This was also observed with endogenous amphipaths that were extracted from pollen, implying similar partitioning behavior. In view of the fluidizing effect on membranes and the antioxidant properties of many endogenous amphipaths, we suggest that partitioning with drying may be pivotal to desiccation tolerance, despite the risk of imbibitional leakage.
Molecular Analysis of (R)-(+)-Mandelonitrile Lyase Microheterogeneity in Black Cherry1
Authors: Hu Zihua , Poulton Jonathan E. 
Published: July 2002

AbstractThe flavoprotein (R)-(+)-mandelonitrile lyase (MDL; EC 4.1.2.10), which plays a key role in cyanogenesis in rosaceous stone fruits, occurs in black cherry (Prunus serotina Ehrh.) homogenates as several closely related isoforms. Biochemical and molecular biological methods were used to investigate MDL microheterogeneity and function in this species. Three novel MDL cDNAs of high sequence identity (designated MDL2, MDL4, and MDL5) were isolated. Like MDL1 and MDL3 cDNAs (Z. Hu, J.E. Poulton [1997] Plant Physiol 115: 1359–1369), they had open reading frames that predicted a flavin adenine dinucleotide-binding site, multipleN-glycosylation sites, and an N-terminal signal sequence. The N terminus of an MDL isoform purified from seedlings matched the derived amino acid sequence of the MDL4 cDNA. Genomic sequences corresponding to the MDL1, MDL2, and MDL4 cDNAs were obtained by polymerase chain reaction amplification of genomic DNA. Like the previously reported mdl3 gene, these genes are interrupted at identical positions by three short, conserved introns. Given their overall similarity, we conclude that the genesmdl1, mdl2, mdl3,mdl4, and mdl5 are derived from a common ancestral gene and constitute members of a gene family. Genomic Southern-blot analysis showed that this family has approximately eight members. Northern-blot analysis using gene-specific probes revealed differential expression of the genes mdl1,mdl2, mdl3, mdl4, andmdl5.
Regions of the Pea Lhcb1*4 Promoter Necessary for Blue-Light Regulation in Transgenic Arabidopsis1
Authors: Folta Kevin M. , Kaufman Lon S. 
Published: July 2002

Abstract
Pea (Pisum sativum) and Arabidopsis contain similar, if not identical, blue-light (BL)-responsive systems that alter expression of specific members of the Lhcb (light-harvestingchlorophyll-binding) gene family. In both plants a single, short pulse of low-fluence BL (threshold = 10−1 μmol m−2) causes an increase in the rate of transcription from specific members of the Lhcbgene family in etiolated seedlings. Constructs of the BL-regulated peaLhcb1*4 promoter (PsLhcb1*4) were created, which altered sequences previously implicated in light responses, deleted the 5′-promoter sequence, or removed the 5′-untranslated region. These constructs were tested for BL induction in transgenic Arabidopsis. The PsLhcb1*4 promoter deletions to −150 bp maintained normal fluence response, time course, and reciprocity characteristics. The 5′- untranslated region contained enhancer elements, but was not necessary for BL induction. The −95 to +2 promoter was capable of responding to BL, whereas sequences from −50 were not. Promoters that lack conserved light-regulatory elements or sequences directly implicated in phytochrome and circadian responses retained BL activity, suggesting that the low-fluence BL response utilizes regions of the promoter independent of those that modulate the phytochrome and circadian responses.
Early Events in the Signal Pathway for the Oxidative Burst in Soybean Cells Exposed to Avirulent Pseudomonas syringaepv glycinea1
Authors: Rajasekhar Vinagolu K. , Lamb Chris , Dixon Richard A. 
Published: July 2002

Abstract
Soybean (Glycine max) cv Williams 82 suspension cultures exhibit an oxidative burst approximately 3 h after challenge withPseudomonas syringae pv glycinea(Psg) harboring the avrA (avirulence) gene. Pretreatment with the tyrosine (Tyr) kinase inhibitor herbimycin A or the serine/threonine kinase inhibitor K252a abolished the burst and subsequent induction of glutathioneS-transferase. However, imposition of a 45-min rest period between pathogen challenge and subsequent addition of the kinase inhibitors resulted in escape from inhibition by herbimycin A, whereas inhibition by K252a persisted. Suramin, a G-protein inhibitor, inhibited the burst if added up to 90 min after pathogen challenge. The burst was also induced by the ion channel generator amphotericin B, and this induction was sensitive to suramin and K252a. Conversely, the ion channel blocker anthracene-9-carboxylate inhibited thePsg:avrA-induced burst.Psg:avrA rapidly induced Tyr phosphorylation of several proteins, and this was inhibited by herbimycin A or anthracene 9-carboxylic acid. These data suggest that the activation of ion channels is followed by an upstream Tyr kinase before the serine/threonine kinase-dependent steps in the signal pathway leading to the oxidative burst.Psg:avrA-dependent induction of phenylalanine ammonia-lyase was not inhibited by herbimycin or suramin, suggesting the operation of different signal pathways for the oxidative burst and phenylpropanoid-derived defense responses.
Conservation of Matrix Attachment Region-Binding Filament-Like Protein 1 among Higher Plants
Authors: Harder Patricia A. , Silverstein Rebecca A. , Meier Iris 
Published: July 2002

Abstract
The interaction of chromatin with the nuclear matrix via matrix attachment regions (MARs) on the DNA is considered to be of fundamental importance for higher-order chromatin organization and the regulation of gene expression. We have previously isolated a novel nuclear matrix-localized protein (MFP1) from tomato (Lycopersicon esculentum) that preferentially binds to MAR DNA. Tomato MFP1 has a predicted filament-protein-like structure and is associated with the nuclear envelope via an N-terminal targeting domain. Based on the antigenic relationship, we report here that MFP1 is conserved in a large number of dicot and monocot species. Several cDNAs were cloned from tobacco (Nicotiana tabacum) and shown to correspond to two tobacco MFP1 genes. Comparison of the primary and predicted secondary structures of MFP1 from tomato, tobacco, and Arabidopsis indicates a high degree of conservation of the N-terminal targeting domain, the overall putative coiled-coil structure of the protein, and the C-terminal DNA-binding domain. In addition, we show that tobacco MFP1 is regulated in an organ-specific and developmental fashion, and that this regulation occurs at the level of transcription or RNA stability.
The Effects of Elevated CO2 Concentrations on Cell Division Rates, Growth Patterns, and Blade Anatomy in Young Wheat Plants Are Modulated by Factors Related to Leaf Position, Vernalization, and Genotype
Authors: Masle Josette 
Published: July 2002

Abstract
This study demonstrates that elevated [CO2] has profound effects on cell division and expansion in developing wheat (Triticum aestivum L.) leaves and on the quantitative integration of these processes in whole-leaf growth kinetics, anatomy, and carbon content. The expression of these effects, however, is modified by intrinsic factors related to genetic makeup and leaf position, and also by exposure to low vernalizing temperatures at germination. Beyond these interactions, leaf developmental responses to elevated [CO2] in wheat share several remarkable features that were conserved across all leaves examined. Most significantly: (a) the contribution of [CO2] effects on meristem size and activity in driving differences in whole-blade growth kinetics and final dimensions; (b) an anisotropy in cellular growth responses to elevated [CO2], with final cell length and expansion in the paradermal plane being highly conserved, even when the rates and duration of cell elongation were modified, while cell cross-sectional areas were increased; (c) tissue-specific effects of elevated [CO2], with significant modifications of mesophyll anatomy, including an increased extension of intercellular air spaces and the formation of, on average, one extra cell layer, while epidermal anatomy was mostly unaltered. Our results indicate complex developmental regulations of sugar effects in expanding leaves that are subjected to genetic variation and influenced by environmental cues important in the promotion of floral initiation. They also provide insights into apparently contradictory and inconsistent conclusions of published CO2 enrichment studies in wheat.
Covalent Binding of the Benzamide RH-4032 to Tubulin in Suspension-Cultured Tobacco Cells and Its Application in a Cell-Based Competitive-Binding Assay
Authors: Young David H. , Lewandowski Veronica T. 
Published: July 2002

Abstract
The benzamide, RH-4032, was found to be a potent antimicrotubule agent in tobacco (Nicotiana tabacum) cells. It strongly inhibited root growth and produced swollen club-shaped roots, an accumulation of cells in arrested metaphase, and loss of microtubules. RH-4032 inhibited the in vitro assembly of bovine tubulin into microtubules, with inhibition requiring a relatively long incubation period. Treatment of tobacco suspension-cultured cells or isolated bovine tubulin with [14C]RH-4032, and analysis of radiolabeled protein revealed a highly specific covalent attachment to β-tubulin. Binding of [3H]RH-4032 in tobacco suspension-cultured cells was shown to be saturable and to be influenced by pre-incubation of the cells with various antimicrotubule agents: Binding of [3H]RH-4032 was inhibited by the benzamides, pronamide and zarilamide, theN-phenylcarbamate, chlorpropham, and the microtubule-stabilizing drug, paclitaxel, whereas trifluralin and amiprophosmethyl were not inhibitory. A common characteristic of agents that cause microtubule disassembly was a slight enhancement of [3H]RH-4032 binding at low concentrations, which did not occur with the microtubule-stabilizing agent paclitaxel. For structural analogs of RH-4032 and various N-phenylcarbamates, it was shown that the ability to inhibit binding of [3H]RH-4032 was correlated with the ability to inhibit tobacco root elongation. The results suggest a common binding site on β-tubulin for RH-4032, pronamide, zarilamide, and chlorpropham, which is distinct from the binding site(s) for trifluralin and amiprophosmethyl. RH-4032 provides a unique approach to studying effects of antimicrotubule agents on plant cells by allowing competitive tubulin binding assays to be conducted in whole cells.
An Increase in Pectin Methyl Esterase Activity Accompanies Dormancy Breakage and Germination of Yellow Cedar Seeds
Authors: Ren Chengwei , Kermode Allison R. 
Published: July 2002

AbstractPectin methyl esterase (PME) (EC 3.1.1.11) catalyzes the hydrolysis of methylester groups of cell wall pectins. We investigated the role of this enzyme in dormancy termination and germination of yellow cedar (Chamaecyparis nootkatensis [D. Don] Spach) seeds. PME activity was not detected in dormant seeds of yellow cedar but was induced and gradually increased during moist chilling; high activity coincided with dormancy breakage and germination. PME activity was positively correlated to the degree of dormancy breakage of yellow cedar seeds. The enzyme produced in different seed parts and in seeds at different times during moist chilling, germination, and early post-germinative growth consisted of two isoforms, both basic with isoelectric points of 8.7 and 8.9 and the same molecular mass of 62 kD. The pH optimum for the enzyme was between 7.4 and 8.4. In intact yellow cedar seeds, activities of the two basic isoforms of PME that were induced in embryos and in megagametophytes following dormancy breakage were significantly suppressed by abscisic acid. Gibberellic acid had a stimulatory effect on the activities of these isoforms in embryos and megagametophytes of intact seeds at the germinative stage. We hypothesize that PME plays a role in weakening of the megagametophyte, allowing radicle emergence and the completion of germination.
Tuber Physiology and Properties of Starch from Tubers of Transgenic Potato Plants with Altered Plastidic Adenylate Transporter Activity
Authors: Geigenberger Peter , Stamme Claudia , Tjaden Joachim , Schulz Alexander , Quick Paul W. , Betsche Thomas , Kersting H. J. , Neuhaus H. Ekkehard 
Published: July 2002

Abstract
We showed recently that antisense plants with decreased activity of the plastidic ATP/ADP-transporter protein exhibit drastically reduced levels of starch and a decreased amylose/amylopectin ratio, whereas sense plants with increased activity of the transporter possessed more starch than wild-type plants and an increased amylose/amylopectin ratio. In this paper we investigate the effect of altered plastidic ATP/ADP-transporter protein expression on primary metabolism and granule morphology in more detail. Tuber tissues from antisense and sense plants exhibited substantially increased respiratory activity compared with the wild type. Tubers from antisense plants contained markedly increased levels of free sugars, UDP-Glc, and hexose phosphates, whereas phosphoenolpyruvate, isocitrate, ATP, ADP, AMP, UTP, UDP, and inorganic pyrophosphate levels were slightly decreased. In contrast, tubers from sense plants revealed a slight increase in adenine and uridine nucleotides and in the levels of inorganic pyrophosphate, whereas no significant changes in the levels of soluble sugars and metabolites were observed. Antisense tubers contained 50% reduced levels of ADP-Glc, whereas sense tubers contained up to 2-fold increased levels of this sole precursor for starch biosynthesis. Microscopic examination of starch grain morphology revealed that the size of starch grains from antisense tubers was substantially smaller (50%) compared with the wild type. The large starch grains from sense tubers appeared of a more angular morphology, which differed to the more ellipsoid shape of wild type grains. The results suggest a close interaction between plastidial adenylate transport and starch biosynthesis, indicating that ADP-Glc pyrophosphorylase is ATP-limited in vivo and that changes in ADP-Glc concentration determine starch yield, as well as granule morphology. Possible factors linking starch synthesis and respiration are discussed.
Conformational propagation with prion‐like characteristics in a simple model of protein folding
Authors: Harrison Paul M. , Chan Hue Sun , Prusiner Stanley B. , Cohen Fred E. 
Published: July 2002

AbstractProtein refolding/misfolding to an alternative form plays an aetiologic role in many diseases in humans, including Alzheimer's disease, the systemic amyloidoses, and the prion diseases. Here we have discovered that such refolding can occur readily for a simple lattice model of proteins in a propagatable manner without designing for any particular alternative native state. The model uses a simple contact energy function for interactions between residues and does not consider the peculiarities of polypeptide geometry. In this model, under conditions where the normal (N) native state is marginally stable or unstable, two chains refold from the N native state to an alternative multimeric energetic minimum comprising a single refolded conformation that can then propagate itself to other protein chains. The only requirement for efficient propagation is that a two‐faced mode of packing must be in the ground state as a dimer (a higher‐energy state for this packing leads to less efficient propagation). For random sequences, these ground‐state dimeric configurations tend to have more β‐sheet‐like extended structure than almost any other sort of dimeric ground‐state assembly. This implies that propagating states (such as for prions) are β‐sheet rich because the only likely propagating forms are β‐sheet rich. We examine the details of our simulations to see to what extent the observed properties of prion propagation can be predicted by a simple protein folding model. The formation of the alternative state in the present model shows several distinct features of amyloidogenesis and of prion propagation. For example, an analog of the phenomenon of conformationally distinct strains in prions is observed. We find a parallel between ‘glassy’ behavior in liquids and the formation of a propagatable state in proteins. This is the first report of simulation of conformational propagation using any heteropolymer model. The results imply that some (but not most) small protein sequences must maintain a sequence signal that resists refolding to propagatable alternative native states and that the ability to form such states is not limited to polypeptides (or reliant on regular hydrogen bonding per se) but can occur for other protein‐like heteropolymers.
Attribution of Tumour Lethality and Estimation of the time to Onset of Occult Tumours in the Absence of Cause-of-Death Information
Authors: Ahn Hongshik , Moon Hojin , Kodell Ralph L. 
Published: July 2002

SUMMARY
A new statistical approach is developed for estimating the carcinogenic potential of drugs and other chemical substances used by humans. Improved statistical methods are developed for rodent tumorigenicity assays that have interval sacrifices but not cause-of-death data. For such experiments, this paper proposes a nonparametric maximum likelihood estimation method for estimating the distributions of the time to onset of and the time to death from the tumour. The log-likelihood function is optimized using a constrained direct search procedure. Using the maximum likelihood estimators, the number of fatal tumours in an experiment can be imputed. By applying the procedure proposed to a real data set, the effect of calorie restriction is investigated. In this study, we found that calorie restriction delays the tumour onset time significantly for pituitary tumours. The present method can result in substantial economic savings by relieving the need for a case-by-case assignment of the cause of death or context of observation by pathologists. The ultimate goal of the method proposed is to use the imputed number of fatal tumours to modify Peto’s International Agency for Research on Cancer test for application to tumorigenicity assays that lack cause-of-death data.
A Kinetic Investigation of the Role of Changes in the Composition of
Natural Gas in Engine Applications
Authors: Khalil E. B. , Karim G. A. 
Published: July 2002

Abstract
The influence of variations in the composition of natural gas on the ignition and combustion processes in engines is investigated. Particular attention is given to changes in the relatively small concentrations of high molar mass alkanes that may be present in the fuel. A detailed chemical kinetic scheme for the oxidation of the higher hydrocarbon components of up to n-heptane was used to investigate analytically the combustion reactions of different fuel mixtures under constant volume adiabatic conditions with initial states that are similar to those during the ignition delay of a typical internal combustion engine. These comprehensive simulation calculations require much computing capacity and time that would preclude their incorporation in full simulation models of engine processes. A simplification is introduced based on replacing artificially the small concentrations of any higher hydrocarbons that may be present in the natural gas by a kinetically equivalent amount of propane in the fuel mixture. This is done such that the resulting equivalent fuel has the same ignition delay as the original fuel under constant volume engine T.D.C. conditions. This “propane equivalent” concept was used in full engine simulation models while employing a relatively short scheme of 150 steps for the oxidation of fuel mixtures of propane, ethane, and methane in air.
Sensitivity Analysis and Optimization of Undamped Rotor Critical
Speeds to Supports Stiffness
Authors: Huang Shyh-Chin , Lin Chin-Ann 
Published: July 2002

Abstract
This paper introduced a new approach that employed the assumed-modes method and the receptance method, to the sensitivity analysis and the optimization of rotor-bearing systems. First, the frequency equation in terms of receptances was derived. The natural frequencies and the critical speeds for a typical rotor system were then illustrated. Beginning with the receptance equation, the authors, for the first time, derived a sensitivity matrix and employed it into an optimization process. The topographical method in conjunction with the variable metric method followed for the optimal solution. In the solution process, the sensitivity matrix provided important information for search direction. Examples of critical speeds adjustment via supports change in an optimal sense were illustrated. Numerical results showed that the approach was very efficient and the solutions were very accurate. This approach, in addition, provided such valuable information as which supports dominated specific critical speeds. The developed approach proved to be very helpful to rotor engineers in both rotor modification and rotor design.
Molecular Characterization of Integrons in
Acinetobacter baumannii
: Description of a Hybrid Class 2 Integron
Authors: Ploy Marie-Cécile , Denis François , Courvalin Patrice , Lambert Thierry 
Published: July 2002

ABSTRACT

Twenty
Acinetobacter baumannii
strains resistant to various antibiotics were analyzed for integron content and sequences of the amplification products. Sixteen clinical isolates had a class 1 integron, 2 contained an additional class 1 or class 2 integron, but no class 3 integron was detected. Thirteen strains had integrons with a single cassette:
aac
(
3
)-
Ia
(9 strains),
ant
(
2
")-
Ia
(2 strains), or
aac
(
6
′)-
Ib
(2 strains); 1 had
aac
(
6
′)-
Ib
and
oxa20
cassettes and an unknown gene; and 1 had an integron containing
ant
(
2
")-
Ia
and an
oxa3
cassette truncated by IS
6100
. The remaining strains harbored class 1 integrons with gene cassettes previously found in
Enterobacteriaceae
. One integron had a hybrid structure composed of
intI2
and the 3′ conserved segment of class 1 integrons. These data indicate that integrons play a major role in multidrug resistance in
Acinetobacter
.