bluuebunny/crossref_metadata_2025_split huggingface dataset:
Excess Copper Predisposes Photosystem II to Photoinhibition in Vivo by Outcompeting Iron and Causing Decrease in Leaf Chlorophyll
Authors: Pätsikkä Eija , Kairavuo Marja , Šeršen Frantisek , Aro Eva-Mari , Tyystjärvi Esa 
Published: July 2002

Abstract
Photoinhibition of photosystem II was studied in vivo with bean (Phaseolus vulgaris) plants grown in the presence of 0.3 (control), 4, or 15 μm Cu2+. Although photoinhibition, measured in the presence of lincomycin to block concurrent recovery, is faster in leaves of Cu2+-treated plants than in control leaves, thylakoids isolated from Cu-treated plants did not show high sensitivity to photoinhibition. Direct effects of excess Cu2+ on chloroplast metabolism are actually unlikely, because the Cu concentration of chloroplasts of Cu-treated plants was lower than that of their leaves. Excess Cu in the growth medium did not cause severe oxidative stress, collapse of antioxidative defenses, or loss of photoprotection. Thus, these hypothetical effects can be eliminated as causes for Cu-enhanced photoinhibition in intact leaves. However, Cu treatment lowered the leaf chlorophyll (Chl) concentration and reduced the thylakoid membrane network. The loss of Chl and sensitivity to photoinhibition could be overcome by adding excess Fe together with excess Cu to the growth medium. The addition of Fe lowered the Cu2+ concentration of the leaves, suggesting that Cu outcompetes Fe in Fe uptake. We suggest that the reduction of leaf Chl concentration, caused by the Cu-induced iron deficiency, causes the high photosensitivity of photosystem II in Cu2+-treated plants. A causal relationship between the susceptibility to photoinhibition and the leaf optical density was established in several plant species. Plant species adapted to high-light habitats apparently benefit from thick leaves because the rate of photoinhibition is directly proportional to light intensity, but photosynthesis becomes saturated by moderate light.
Targeting Tryptophan Decarboxylase to Selected Subcellular Compartments of Tobacco Plants Affects Enzyme Stability and in Vivo Function and Leads to a Lesion-Mimic Phenotype
Authors: Di Fiore Stefano , Li Qiurong , Leech Mark James , Schuster Flora , Emans Neil , Fischer Rainer , Schillberg Stefan 
Published: July 2002

AbstractTryptophan decarboxylase (TDC) is a cytosolic enzyme that catalyzes an early step of the terpenoid indole alkaloid biosynthetic pathway by decarboxylation of l-tryptophan to produce the protoalkaloid tryptamine. In the present study, recombinant TDC was targeted to the chloroplast, cytosol, and endoplasmic reticulum (ER) of tobacco (Nicotiana tabacum) plants to evaluate the effects of subcellular compartmentation on the accumulation of functional enzyme and its corresponding enzymatic product. TDC accumulation and in vivo function was significantly affected by the subcellular localization. Immunoblot analysis demonstrated that chloroplast-targeted TDC had improved accumulation and/or stability when compared with the cytosolic enzyme. Because ER-targeted TDC was not detectable by immunoblot analysis and tryptamine levels found in transient expression studies and in transgenic plants were low, it was concluded that the recombinant TDC was most likely unstable if ER retained. Targeting TDC to the chloroplast stroma resulted in the highest accumulation level of tryptamine so far reported in the literature for studies on heterologous TDC expression in tobacco. However, plants accumulating high levels of functional TDC in the chloroplast developed a lesion-mimic phenotype that was probably triggered by the relatively high accumulation of tryptamine in this compartment. We demonstrate that subcellular targeting may provide a useful strategy for enhancing accumulation and/or stability of enzymes involved in secondary metabolism and to divert metabolic flux toward desired end products. However, metabolic engineering of plants is a very demanding task because unexpected, and possibly unwanted, effects may be observed on plant metabolism and/or phenotype.
The White Clover enod40 Gene Family. Expression Patterns of Two Types of Genes Indicate a Role in Vascular Function
Authors: Varkonyi-Gasic Erika , White Derek William Richard 
Published: July 2002

Abstract
Enod40 is one of the genes associated with legume nodule development and has a putative role in general plant organogenesis. We have isolated a small enod40 gene family from white clover (Trifolium repens), with three genes designated Trenod40-1, Trenod40-2, and Trenod40-3, all containing the conservedenod40 regions I and II. Trenod40-1 andTrenod40-2 share over 90% homology in the transcribed regions and high levels of similarity in their upstream regulatory sequences. Trenod40-1 and Trenod40-2 are similar to the enod40 genes of legumes forming indeterminate nodules (group II) and are predominantly expressed in nodules. Trenod40-3 shares only 32.8% identity withTrenod40-1 and Trenod40-2 within the transcribed region. Trenod40-3 is similar to theenod40 genes of legumes with determinate nodules (group I) and is not predominantly expressed in nodules. To our knowledge, this is the first report of both group I- and group II-typeenod40 genes being expressed in a single legume species. In situ hybridization studies revealed that Trenod40genes were highly expressed in non-symbiotic tissues, particularly in stolon nodes during nodal root and lateral shoot development. High levels of Trenod40 transcripts were also present in the vascular bundles of mature plant organs, mainly at sites of intensive lateral transport, suggesting a role in vascular tissue function. The expression pattern of Trenod40 genes was analyzed further using Trenod40 promoter-gusfusions in transgenic white clover and tobacco (Nicotiana tabacum), indicating that white clover and tobacco share the regulatory mechanisms for Trenod40-1/2 promoters and some aspects of Trenod40-3 regulation.
Reorientation of Seedlings in the Earth's Gravitational Field Induces Cytosolic Calcium Transients
Authors: Plieth Christoph , Trewavas Anthony J. 
Published: July 2002

Abstract
The gravitational field controls plant growth, morphology, and development. However, the underlying transduction mechanisms are not well understood. Much indirect evidence has implicated the cytoplasmic free calcium concentration ([Ca2+]c) as an important factor, but direct evidence for changes in [Ca2+]c is currently lacking. We now have made measurements of [Ca2+]c in groups of young seedlings of Arabidopsis expressing aequorin in the cytoplasm and reconstituted in vivo with cp-coelenterazine, a synthetic high-affinity luminophore. Distinct [Ca2+]c signaling occurs in response to gravistimulation with kinetics very different from [Ca2+]c transients evoked by other mechanical stimuli (e.g. movement and wind). [Ca2+]cchanges produced in response to gravistimulation are transient but with a duration of many minutes and dependent on stimulus strength (i.e. the angle of displacement). The auxin transport blockers 2,3,5-tri-iodo benzoic acid and N-(1-naphthyl) phthalamic acid interfere with gravi-induced [Ca2+]cresponses and addition of methyl indole-3-acetic acid to whole seedlings induces long-lived [Ca2+]ctransients, suggesting that changes in auxin transport may interact with [Ca2+]c. Permanent nonaxial rotation of seedlings on a two-dimensional clinostat, however, produced a sustained elevation of the [Ca2+]c level. This probably reflects permanent displacement of gravity-sensing cellular components and/or disturbance of cytoskeletal tension. It is concluded that [Ca2+]c is part of the gravity transduction mechanism in young Arabidopsis seedlings.
A Cell Plate–Specific Callose Synthase and Its Interaction with Phragmoplastin
Authors: Hong Zonglie , Delauney Ashton J. , Verma Desh Pal S. 
Published: July 2002

Abstract
Callose is synthesized on the forming cell plate and several other locations in the plant. We cloned an Arabidopsis cDNA encoding a callose synthase (CalS1) catalytic subunit. The CalS1 gene comprises 42 exons with 41 introns and is transcribed into a 6.0-kb mRNA. The deduced peptide, with an approximate molecular mass of 226 kD, showed sequence homology with the yeast 1,3-β-glucan synthases and is distinct from plant cellulose synthases. CalS1 contains 16 predicted transmembrane helices with the N-terminal region and a large central loop facing the cytoplasm. CalS1 interacts with two cell plate–associated proteins, phragmoplastin and a novel UDP-glucose transferase that copurifies with the CalS complex. That CalS1 is a cell plate–specific enzyme is demonstrated by the observations that the green fluorescent protein–CalS1 fusion protein was localized at the growing cell plate, that expression of CalS1 in transgenic tobacco cells enhanced callose synthesis on the forming cell plate, and that these cell lines exhibited higher levels of CalS activity. These data also suggest that plant CalS may form a complex with UDP-glucose transferase to facilitate the transfer of substrate for callose synthesis.
E. coli methionine sulfoxide reductase with a truncated N terminus or C terminus, or both, retains the ability to reduce methionine sulfoxide
Authors: Boschi‐Muller Sandrine , Azza Saïd , Branlant Guy 
Published: July 2002

AbstractThe monomeric peptide methionine sulfoxide reductase (MsrA) catalyzes the irreversible thioredoxin‐dependent reduction of methionine sulfoxide. The crystal structure of MsrAs from Escherichia coli and Bos taurus can be described as a central core of about 140 amino acids that contains the active site. The core is wrapped by two long N‐ and C‐terminal extended chains. The catalytic mechanism of the E. coli enzyme has been recently postulated to take place through formation of a sulfenic acid intermediate, followed by reduction of the intermediate via intrathiol‐disulfide exchanges and thioredoxin oxidation. In the present work, truncated MsrAs at the N‐ or C‐terminal end or at both were produced as folded entities. All forms are able to reduce methionine sulfoxide in the presence of dithiothreitol. However, only the N‐terminal truncated form, which possesses the two cysteines located at the C‐terminus, reduces the sulfenic acid intermediate in a thioredoxin‐dependent manner. The wild type displays a ping‐pong mechanism with either thioredoxin or dithiothreitol as reductant. Kinetic saturation is only observed with thioredoxin with a low KM value of 10 μM. Thus, thioredoxin is likely the reductant in vivo. Truncations do not significantly modify the kinetic properties, except for the double truncated form, which displays a 17‐fold decrease in kcat/KMetSO. Alternative mechanisms for sulfenic acid reduction are also presented based on analysis of available MsrA sequences.
Potential Therapeutic Role of Cationic Peptides in Three Experimental Models of Septic Shock
Authors: Giacometti Andrea , Cirioni Oscar , Ghiselli Roberto , Mocchegiani Federico , Del Prete Maria Simona , Viticchi Claudio , Kamysz Wojciech , Łempicka Elżbieta , Saba Vittorio , Scalise Giorgio 
Published: July 2002

ABSTRACTThe therapeutic efficacies of buforin II, indolicidin, and KFFKFFKFF were investigated in three rat models of septic shock: (i) rats injected intraperitoneally with 10 μg ofEscherichia coliO111:B4 lipopolysaccharide, (ii) rats given an intraperitoneal injection of 2 × 1010CFU ofEscherichia coliATCC 25922, and (iii) rats in which intra-abdominal sepsis was induced via cecal ligation and single puncture. All animals were randomized to receive parenterally isotonic sodium chloride solution, 1 mg of buforin II per kg of body weight, 1 mg of indolicidin per kg, 1 mg of KFFKFFKFF per kg, and 20 mg of imipenem per kg. The main outcome measures were bacterial growth in abdominal exudate and plasma, endotoxin and tumor necrosis factor alpha (TNF-α) concentrations in plasma, and lethality. Treatment with all peptides resulted in significant reductions in plasma endotoxin and TNF-α concentrations compared with those resulting from the imipenem and saline treatments. On the other hand, imipenem treatment significantly reduced the levels of bacterial growth compared with the reductions achieved with the peptide and saline treatments. All compounds reduced the rates of death compared to that for the controls. Although the peptides demonstrated lower levels of antimicrobial activity than imipenem, they exhibited the dual properties of antimicrobial and antiendotoxin agents.
New Carbenicillin-Hydrolyzing β-Lactamase (CARB-7) from
Vibrio cholerae
Non-O1, Non-O139 Strains Encoded by the VCR Region of the
V. cholerae
Genome
Authors: Melano Roberto , Petroni Alejandro , Garutti Alicia , Saka Héctor Alex , Mange Laura , Pasterán Fernando , Rapoport Melina , Rossi Alicia , Galas Marcelo 
Published: July 2002

ABSTRACT

In a previous study, an analysis of 77 ampicillin-nonsusceptible (resistant plus intermediate categories) strains of
Vibrio cholerae
non-O1, non-O139, isolated from aquatic environment and diarrheal stool, showed that all of them produced a β-lactamase with a pI of 5.4. Hybridization or amplification by PCR with a probe for
bla
TEM
or primers for
bla
CARB
gene families was negative. In this work, an environmental ampicillin-resistant strain from this sample, ME11762, isolated from a waterway in the west region of Argentina, was studied. The nucleotide sequence of the structural gene of the β-lactamase was determined by bidirectional sequencing of a
Sau
3AI fragment belonging to this isolate. The gene encodes a new 288-amino-acid protein, designated CARB-7, that shares 88.5% homology with the CARB-6 enzyme; an overall 83.2% homology with PSE-4, PSE-1, CARB-3, and the
Proteus mirabilis
N29 enzymes; and 79% homology with CARB-4 enzyme. The gene for this β-lactamase could not be transferred to
Escherichia coli
by conjugation. The nucleotide sequence of the flanking regions of the
bla
CARB-7
gene showed the occurrence of three 123-bp
V. cholerae
repeated sequences, all of which were found outside the predicted open reading frame. The upstream fragment of the
bla
CARB-7
gene shared 93% identity with a locus situated inside
V. cholerae
's chromosome 2. These results strongly suggest the chromosomal location of the
bla
CARB-7
gene, making this the first communication of a β-lactamase gene located on the VCR island of the
V. cholerae
genome.
Amino Acid Residues Essential for Function of the MexF Efflux Pump Protein of
Pseudomonas aeruginosa
Authors: Aires Julio Ramos , Pechère Jean-Claude , Van Delden Christian , Köhler Thilo 
Published: July 2002

ABSTRACT

At least four broad-spectrum efflux pumps (Mex) are involved in elevated intrinsic antibiotic resistance as well as in acquired multidrug resistance in
Pseudomonas aeruginosa
. Substrate specificity of the Mex pumps has been shown to be determined by the cytoplasmic membrane component (MexB, MexD, MexF, and MexY) of the tripartite efflux pump system. Alignment of their amino acid sequences with those of the homologous AcrB and AcrD pump proteins of
Escherichia coli
showed conservation of five charged amino acid residues located in or next to transmembrane segments (TMS). These residues were mutated in the MexF gene by site-directed mutagenesis and replaced by residues of opposite or neutral charge. MexF proteins containing combined D410A and A411G substitutions located in TMS4 were completely inactive. Similarly, the substitutions E417K (next to TMS4) and K951E (TMS10) also caused loss of activity towards all tested antibiotics. The substitution E349K in TMS2 resulted in a MexF mutant protein which was unable to transport trimethoprim and quinolones but retained partial activity for the transport of chloramphenicol. All mutated MexF proteins were expressed at comparable levels when tested by Western blot analysis. It is concluded that charged residues located in or close to TMS are essential for proper function of MexF.
Comparison of Corticosteroids for Treatment of Respiratory Syncytial Virus Bronchiolitis and Pneumonia in Cotton Rats
Authors: Ottolini Martin G. , Curtis Spencer J. , Porter David D. , Mathews Amy , Richardson Joann Y. , Hemming Val G. , Prince Gregory A. 
Published: July 2002

ABSTRACT
Triamcinolone acetonide, methylprednisolone, and dexamethasone were each evaluated in combination with palivizumab (Synagis) for the therapy of established respiratory syncytial virus infection in the cotton rat. Triamcinolone and methylprednisolone proved to be more effective than dexamethasone in reducing lung pathology. No recurrence of viral replication or pulmonary pathology followed the cessation of therapy.
Analysis of Penicillin-Binding Protein Genes of Clinical Isolates of
Streptococcus pneumoniae
with Reduced Susceptibility to Amoxicillin
Authors: du Plessis Mignon , Bingen Edouard , Klugman Keith P. 
Published: July 2002

ABSTRACT

The recent emergence of pneumococcal isolates exhibiting an unusual resistance phenotype of higher amoxicillin MICs in relation to the penicillin MICs prompted an analysis of the
pbp
genes from three such strains isolated in France. For comparison, three amoxicillin-susceptible strains were included in the study. DNA sequence analysis of the
pbp2x
,
pbp2b
, and
pbp1a
genes revealed extensive sequence divergence in all six isolates compared to the sequences of the genes of penicillin-susceptible strain R6. With the exception of
pbp2b
, no amino acid mutations were unique to the resistant isolates. Transformation experiments with cloned
pbp
genes isolated from one of the resistant isolates demonstrated a stepwise development of amoxicillin resistance involving penicillin-binding proteins (PBPs) 2X, 2B, and 1A. Full resistance, equivalent to that of the donor strain, was achieved only when genomic DNA was transformed into R6
2x/2b/1a
mutants, suggesting that full resistance development in this isolate is mediated by a non-PBP determinant. Moreover, the recently identified
murMN
resistance determinant does not appear to have any impact on resistance in this isolate. This determinant (from the French isolate) was, however, able to transform an R6 mutant harboring
pbp2x
,
pbp2b
, and
pbp1a
genes from a Hungarian clone with an extremely high level of penicillin resistance so that it had increased levels of penicillin resistance. These results indicate that the development of high-level β-lactam resistance is a complex process and that the involvement of MurMN in penicillin resistance appears to be dependent on specific mutations in PBPs 2X, 2B, and/or 1A. Furthermore, an additional (as yet unidentified) non-PBP-mediated resistance determinant is required for full resistance development in some pneumococci.
Preclinical and Toxicology Studies of 1263W94, a Potent and Selective Inhibitor of Human Cytomegalovirus Replication
Authors: Koszalka George W. , Johnson Nelson W. , Good Steven S. , Boyd Leslie , Chamberlain Stanley C. , Townsend Leroy B. , Drach John C. , Biron Karen K. 
Published: July 2002

ABSTRACT
1263W94 is a novel benzimidazole compound being developed for treatment of human cytomegalovirus infection. No adverse pharmacological effects were demonstrated in safety pharmacology studies with 1263W94. The minimal-effect dose in a 1-month rat study was 100 mg/kg/day, and the no-effect dose in a 1-month monkey study was 180 mg/kg/day. Toxic effects were limited to increases in liver weights, neutrophils, and monocytes at higher doses in female rats. 1263W94 was not genotoxic in the Ames or micronucleus assays. In the mouse lymphoma assay, 1263W94 was mutagenic in the absence of the rat liver S-9 metabolic activation system, with equivocal results in the presence of the S-9 mix. Mean oral bioavailability of 1263W94 was >90% in rats and ∼50% in monkeys. Clearance in rats and monkeys was primarily by biliary secretion, with evidence of enterohepatic recirculation. In 1-month studies in rats and monkeys, mean peak concentrations and exposures to 1263W94 increased in near proportion to dose. Metabolism of 1263W94 to its primary metabolite, an N-dealkylated analog, appeared to be mediated via the isozyme CYP3A4 in humans. 1263W94 was primarily distributed in the gastrointestinal tract of rats but did not cross the blood-brain barrier. In monkeys, 1263W94 levels in the brain, cerebrospinal fluid, and vitreous humor ranged from 4 to 20%, 1 to 2%, and <1%, of corresponding concentrations in plasma, respectively. The high level of binding by 1263W94 to human plasma proteins (primarily albumin) was readily reversible, with less protein binding seen in the monkey, rat, and mouse. Results of these studies demonstrate a favorable safety profile for 1263W94.
Class 1 Integron Containing a New Gene Cassette,aadA10, Associated with Tn1404from R151
Authors: Partridge Sally R. , Collis Christina M. , Hall Ruth M. 
Published: July 2002

ABSTRACTThe carbenicillin, gentamicin, kanamycin, streptomycin, spectinomycin, sulfonamide, and tobramycin resistance determinants found onPseudomonas aeruginosaplasmid R151 have previously been shown to translocate to another plasmid, R388, and it was inferred that a transposon, Tn1404, carried the resistance determinants. Sequencing of the cassette array from the plasmid known as R388::Tn1404revealed two known gene cassettes,oxa10andaadB, and a previously unidentified cassette determining resistance to streptomycin and spectinomycin, here designatedaadA10, in the orderoxa10-aadB-aadA10.These cassettes replaced thedfrB2-orfAcassette array of R388, indicating that movement of the resistance determinants from R151 to R388 resulted from recombinational exchange between two class 1 integrons rather than transposition. The AadA10 protein is most closely related to AadA6 (85% identical) and AadA7 (80% identical). TheaadA10cassette found here has only a simple site containing a 7-bp spacer derived fromattI1in place of a 59-base element and is likely to represent a derivative of the complete cassette. IntI1-mediated deletion of theaadA10cassette was not detected, indicating that this single simple site is either inactive or only weakly active.
Sulfadoxine-Pyrimethamine Resistance in the Rodent Malaria Parasite
Plasmodium chabaudi
Authors: Hayton Karen , Ranford-Cartwright Lisa C. , Walliker David 
Published: July 2002

ABSTRACT

We have studied resistance to sulfadoxine-pyrimethamine (S/P) in the rodent malaria parasite
Plasmodium chabaudi
. A stable S/P-resistant mutant, AS(50S/P), was selected by drug treatment of a clone, AS(PYR), already resistant to pyrimethamine. The sequences of the
P. chabaudi dhfr
and
dhps
genes were obtained and found to be identical in AS(50S/P) and AS(PYR), showing that resistance to S/P in AS(50S/P) was not due to additional mutations in either gene. AS(50S/P) was crossed with a drug-sensitive clone, AJ, and 16 independent recombinant progeny were obtained. These clones were phenotyped for their susceptibility to S/P and to sulfadoxine and pyrimethamine separately. Pyrimethamine resistance was invariably associated with S/P resistance, but no correlation was found between resistance to S/P and resistance to sulfadoxine. Quantitative trait locus analysis of the progeny with 31 chromosome-specific markers showed that mutant
P. chabaudi dhfr,
or one or more genes closely linked to it, was a major determinant of S/P resistance. In addition, the inheritance of genes on chromosomes 5 and 13 from the sensitive parent appeared to contribute to the level of resistance observed. These results demonstrate that the S/P resistance of the AS(50S/P) mutant of
P. chabaudi
does not involve mutation in
dhps
and is not due simply to a combination of two genes determining resistance to pyrimethamine and sulfadoxine separately.