bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Polar Auxin Transport InhibitorN-1-Naphthylphthalamic Acid Disrupts Leaf Initiation, KNOX Protein Regulation, and Formation of Leaf Margins in Maize
Authors: Scanlon Michael J. 
Published: October 2003

AbstractMaize (Zea mays) leaves develop basipetally (tip to base); the upper blade emerges from the shoot apical meristem (SAM) before the expansion of the lower sheath. Founder cells, leaf initials located in the periphery of the SAM, are distinguished from the SAM proper by the differential accumulation of KNOX proteins. KNOX proteins accumulate in the SAM, but are excluded from maize leaf primordia and leaf founder cells. As in Arabidopsis and tomato (Lycopersicon esculentum), maize shoots failed to initiate new leaves when cultured in the polar auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). We demonstrate that NPA-induced arrest of leaf initiation in maize is correlated with the failure to down-regulate KNOX accumulation in the SAM. In addition, NPA-cultured shoots formed abnormal tubular leaf bases in which the margins failed to separate in the lower leaf zone. The tubular leaf bases always formed in the fourth leaf from the arrested meristem. Moreover, the unseparated margin domains of these tubular leaf bases accumulated ectopic KNOX protein(s). Transfer of NPA-cultured apices to NPA-free media resulted in the resumption of leaf initiation from the SAM and the restoration of normal patterns of KNOX down-regulation, accordingly. These data suggest that the lower sheath margins emerge from the leaf base late in maize leaf development and that the separation of these leaf margin domains is correlated with auxin transport and down-regulation of KNOX proteins. In addition, these results suggest that the down-regulation of KNOX accumulation in maize apices is not upstream of polar auxin transport, although a more complicated feedback network may exist. A model for L1-derived margin development in maize leaves is presented.
Mechanisms of Arsenical and Diamidine Uptake and Resistance in
Trypanosoma brucei
Authors: Matovu Enock , Stewart Mhairi L. , Geiser Federico , Brun Reto , Mäser Pascal , Wallace Lynsey J. M. , Burchmore Richard J. , Enyaru John C. K. , Barrett Michael P. , Kaminsky Ronald , Seebeck Thomas , de Koning Harry P. 
Published: October 2003

ABSTRACT

Sleeping sickness, caused by
Trypanosoma brucei
spp., has become resurgent in sub-Saharan Africa. Moreover, there is an alarming increase in treatment failures with melarsoprol, the principal agent used against late-stage sleeping sickness. In
T. brucei
, the uptake of melarsoprol as well as diamidines is thought to be mediated by the P2 aminopurine transporter, and loss of P2 function has been implicated in resistance to these agents. The trypanosomal gene
TbAT1
has been found to encode a P2-type transporter when expressed in yeast. Here we investigate the role of
TbAT1
in drug uptake and drug resistance in
T. brucei
by genetic knockout of
TbAT1. Tbat1
-null trypanosomes were deficient in P2-type adenosine transport and lacked adenosine-sensitive transport of pentamidine and melaminophenyl arsenicals. However, the null mutants were only slightly resistant to melaminophenyl arsenicals and pentamidine, while resistance to other diamidines such as diminazene was more pronounced. Nevertheless, the reduction in drug sensitivity might be of clinical significance, since mice infected with
tbat1
-null trypanosomes could not be cured with 2 mg of melarsoprol/kg of body weight for four consecutive days, whereas mice infected with the parental line were all cured by using this protocol. Two additional pentamidine transporters, HAPT1 and LAPT1, were still present in the null mutant, and evidence is presented that HAPT1 may be responsible for the residual uptake of melaminophenyl arsenicals. High-level arsenical resistance therefore appears to involve the loss of more than one transporter.
Rabbit knee model of post‐traumatic joint contractures: The long‐term natural history of motion loss and myofibroblasts
Authors: Hildebrand Kevin A. , Sutherland Craig , Zhang Mei 
Published: October 2003

AbstractOur objective is to describe the natural history of motion loss with time and myofibroblast numbers in a rabbit knee model of post‐traumatic joint contractures. Twenty‐eight skeletally mature New Zealand White female rabbits had five‐mm‐squares of cortical bone removed from the medial and lateral femoral condyles of the right knee. A Kirschner wire (K‐wire) was used to immobilize the knee joint in maximum flexion. A second operation was performed 8 weeks later to remove the K‐wire. The rabbits were divided into four groups depending on the time of remobilization; 0, 8, 16 or 32 weeks.The average flexion contracture of the experimental knees in the 0‐week and 8‐week remobilization groups (38° and 33°, respectively) were significantly greater when compared with the values of the unoperated contralateral knees (8°). The average flexion contractures of the experimental knees in the 16‐week and 32‐week remobilization groups were also greater than the unoperated contralateral knees, although they were not statistically significant. The average flexion contractures of the 16‐week and 32‐week groups were 19° and 18°, respectively, indicating a stabilization of the motion loss. Myofibroblast numbers in the posterior joint capsules were elevated 4–5×in the knees with contractures when compared to the contralateral knees. The initial decrease in severity followed by stabilization of motion loss and the association of motion loss with myofibroblasts mimics the human scenario of permanent post‐traumatic joint contractures. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Identification of previously undiagnosed left ventricular systolic dysfunction: community screening using natriuretic peptides and electrocardiography
Authors: Ng Leong L. , Loke Ian , Davies Joan E. , Khunti Kamlesh , Stone Margaret , Abrams Keith R. , Chin Derek T. , Squire Iain B. 
Published: October 2003

AbstractAims: We examined strategies to improve the positive predictive value of natriuretic peptides in screening for undiagnosed left ventricular systolic dysfunction (LVSD) in the community. Methods and results: The value of B‐type(BNP), N‐terminal proB‐type (N‐BNP) and N‐terminal proAtrial(N‐ANP) natriuretic peptides was prospectively assessed in 1360 subjects (45–80 years) together with echocardiography and electrocardiography. Seventeen individuals had definite and 13 had borderline, LVSD. Receiver‐operating‐characteristic (ROC) curve analysis showed the superiority of BNP (ROC areas 0.942 for definite LVSD, P<0.03; 0.934 for borderline LVSD, P<0.003) compared to N‐BNP or N‐ANP. Peptide levels, major ECG abnormality and ischaemic heart disease (IHD) history were independent predictors of LVSD. Logistic regression modelling incorporating these factors improved ROC areas for all natriuretic peptides. The specificity of all natriuretic peptides is enhanced by consideration of these factors. Conclusions: In population screening for definite LVSD, consideration of plasma natriuretic peptide levels together with the presence of major ECG abnormalities and IHD history reduces by a factor of six (in comparison to consideration of plasma natriuretic peptide levels in isolation) the number of subjects requiring echocardiography to detect one case of LVSD (for BNP, 44 falling to seven). Similar improvements were evident for N‐ANP and N‐BNP. Inclusion of major ECG abnormalities and IHD history improves the performance of any natriuretic peptide used in screening programmes for ruling in undiagnosed LVSD.
RNA Interference in the Moss Physcomitrella patens
Authors: Bezanilla Magdalena , Pan Aihong , Quatrano Ralph S. 
Published: October 2003

Abstract
The moss Physcomitrella patens performs efficient homologous recombination, which allows for the study of individual gene function by generating gene disruptions. Yet, if the gene of study is essential, gene disruptions cannot be isolated in the predominantly haploid P. patens. Additionally, disruption of a gene does not always generate observable phenotypes due to redundant functions from related genes. However, RNA interference (RNAi) can provide mutants for both of these situations. We show that RNAi disrupts gene expression in P. patens, adding a significant tool for the study of plant gene function. To assay for RNAi in moss, we constructed a line (NLS-4) expressing a nuclearly localized green fluorescent protein (GFP):β-glucuronidase (GUS) fusion reporter protein. We targeted the reporter protein with two RNAi constructs, GUS-RNAi and GFP-RNAi, expressed transiently by particle bombardment. Transformed protonemal cells are marked by cobombardment with dsRed2, which diffuses between the nucleus and cytoplasm. Cells transformed with control constructs have nuclear/cytoplasmic red fluorescence and nuclear green fluorescence. In cells transformed with GUS-RNAi or GFP-RNAi constructs, the nuclear green fluorescence was reduced on average 9-fold as soon as 48 h after transformation. Moreover, isolated lines of NLS-4 stably transformed with GUS-RNAi construct have silenced nuclear GFP, indicating that RNAi is propagated stably. Thus, RNAi adds a powerful tool for functional analysis of plant genes in moss.
The Penalty of a Long, Hot Summer. Photosynthetic Acclimation to High CO2 and Continuous Light in “Living Fossil” Conifers
Authors: Osborne Colin P. , Beerling David J. 
Published: October 2003

Abstract
Deciduous forests covered the ice-free polar regions 280 to 40 million years ago under warm “greenhouse” climates and high atmospheric pCO2. Their deciduous habit is frequently interpreted as an adaptation for minimizing carbon losses during winter, but experiments with “living fossils” in a simulated warm polar environment refute this explanation. Measured carbon losses through leaf abscission of deciduous trees are significantly greater than losses through winter respiration in evergreens, yet annual rates of primary productivity are similar in all species. Here, we investigate mechanisms underlying this apparent paradox by measuring the seasonal patterns of leaf photosynthesis (A) under pCO2 enrichment in the same trees. During spring, A increased significantly in coastal redwood (Sequoia sempervirens), dawn redwood (Metasequoia glyptostroboides), and swamp cypress (Taxodium distichum) at an elevated pCO2 of 80 Pa compared with controls at 40 Pa. However, strong acclimation in Rubisco carboxylation capacity (V c,max) completely offset the CO2 response of A in all species by the end of 6 weeks of continuous illumination in the simulated polar summer. Further measurements demonstrated the temporary nature of acclimation, with increases in V c,max during autumn restoring the CO2 sensitivity of A. Contrary to expectations, the acclimation of V c,max was not always accompanied by accumulation of leaf carbohydrates, but was associated with a decline in leaf nitrogen in summer, suggesting an alteration of the balance in plant sources and sinks for carbon and nitrogen. Preliminary calculations using A indicated that winter carbon losses through deciduous leaf abscission and respiration were recovered by 10 to 25 d of canopy carbon fixation during summer, thereby explaining the productivity paradox.
Neutral-Lipid Analysis Reveals Elevation of Acylglycerols and Lack of Cholesterol Esters in
Plasmodium falciparum
-Infected Erythrocytes
Authors: Nawabi Parwez , Lykidis Athanasios , Ji Darder , Haldar Kasturi 
Published: October 2003

ABSTRACT

Here we show that blood-stage
Plasmodium falciparum
organisms accumulate a high mass of triacylglycerol and diacylglycerol. However, we failed to detect cholesterol esters, a second neutral lipid species reported to be important for a related apicomplexan,
Toxoplasma gondii
. Evidence for
P. falciparum
and
T. gondii
homologues of acyl coenzyme A:diacylglycerol acyltransferase suggests that acylglycerols may be the conserved neutral lipids in apicomplexans.
Ask10p Mediates the Oxidative Stress-Induced Destruction of the
Saccharomyces cerevisiae
C-Type Cyclin Ume3p/Srb11p
Authors: Cohen Todd J. , Lee Kun , Rutkowski Lisa H. , Strich Randy 
Published: October 2003

ABSTRACT

Srb11p-Srb10p is the budding yeast C-type cyclin-cyclin-dependent kinase that is required for the repression of several stress response genes. To relieve this repression, Srb11p is destroyed in cells exposed to stressors, including heat shock and oxidative stress. In the present study, we identified Ask10p (for activator of Skn7) by two-hybrid analysis as an interactor with Srb11p. Coimmunoprecipitation studies confirmed this association, and we found that, similar to Srb11p-Srb10p, Ask10p is a component of the RNA polymerase II holoenzyme. Ask10p is required for Srb11p destruction in response to oxidative stress but not heat shock. Moreover, this destruction is important since the hypersensitivity of an
ask10
mutant strain to oxidative stress is rescued by deleting
SRB11
. We further show that Ask10p is phosphorylated in response to oxidative stress but not heat shock. This modification requires the redundant mitogen-activated protein (MAP) kinase kinase Mkk1/2 but not their normal MAP kinase target Slt2p. Moreover, the other vegetative MAP kinases—Hog1p, Fus3p, or Kss1p—are not required for Ask10p phosphorylation, suggesting the existence of an alternative pathway for transducing the Pkc1p→Bck1→Mkk1/2 oxidative stress signal. In conclusion, Ask10p is a new component of the RNA polymerase II holoenzyme and an important regulator of the oxidative stress response. In addition, these results define a new role for the Pkc1p MAP kinase cascade (except the MAP kinase itself) in transducing the oxidative damage signal directly to the RNA polymerase II holoenzyme, thereby bypassing the stress-activated transcription factors.
Conservation of RNase III Processing Pathways and Specificity in Hemiascomycetes
Authors: Chanfreau Guillaume 
Published: October 2003

ABSTRACT

Rnt1p, the only known
Saccharomyces cerevisiae
RNase III endonuclease, plays important functions in the processing of precursors of rRNAs (pre-rRNAs) and of a large number of small nuclear RNAs (snRNAs) and small nucleolar RNAs (snoRNAs). While most eukaryotic RNases III, including the
Schizosaccharomyces pombe
enzyme Pac1p, cleave double-stranded RNA without sequence specificity, Rnt1p cleavage relies on the presence of terminal tetraloop structures that carry the consensus sequence AGNN. To search for the conservation of these processing signals, I have systematically analyzed predicted secondary structures of the 3′ external transcribed spacer (ETS) sequences of the pre-rRNAs and of flanking sequences of snRNAs and snoRNAs from sequences available in 13 other Hemiascomycetes species. In most of these species, except in
Yarrowia lipolytica
, double-stranded RNA regions capped by terminal AGNN tetraloops can be found in the 3′ ETS sequences of rRNA, in the 5′- or 3′-end flanking sequences of sn(o)RNAs, or in the intergenic spacers of polycistronic snoRNA transcription units. This analysis shows that RNase III processing signals and RNase III cleavage specificity are conserved in most Hemiascomycetes species but probably not in the evolutionarily more distant species
Y. lipolytica
.
Occupational exposures associated with work‐related asthma and work‐related wheezing among U.S. workers
Authors: Arif Ahmed A. , Delclos George L. , Whitehead Lawrence W. , Tortolero Susan R. , Lee Eun S. 
Published: September 2003

AbstractBackgroundNational estimates of occupational asthma (OA) in the United States are sparse.MethodsUsing data from the Third National Health and Nutrition Examination Survey (NHANES III) 1988–1994, we analyzed associations between occupation and work‐related asthma and work‐related wheezing among U.S. workers.ResultsThis study identified several occupations that were at risk of developing work‐related asthma and/or wheezing, with cleaners and equipment cleaners showing the highest risks. Other major occupations identified were farm and agriculture; entertainment; protective services; construction; mechanics and repairers; textile; fabricators and assemblers; other transportation and material moving occupations; freight, stock, and material movers; and motor vehicle operators. The population attributable risks for work‐related asthma and work‐related wheezing were 26% and 27%, respectively.ConclusionsThis study adds evidence to the literature that identifies work‐related asthma as an important public health problem. Several occupations are targeted for additional evaluation and study. Of particular interest are cleaners, which are being increasingly reported as a risk group for asthma. Future intervention strategies need to be developed for effective control and prevention of asthma in the workplace. Am. J. Ind. Med. 44:368–376, 2003. © 2003 Wiley‐Liss, Inc.
Recent Developments in the Catalytic Asymmetric Synthesis of α‐ and β‐Amino Acids
Authors: Ma Jun‐An 
Published: September 2003

AbstractThe stereoselective synthesis of amino acids is of great importance for the construction of optically active natural products and pharmaceuticals. Apart from enzymes, a broad repertoire of chiral reagents, auxiliaries, and catalysts can be used for the formation of amino acids. Asymmetric reactions using catalytic amounts of chiral molecules provide efficient methods for the generation of optically active proteinogenic and nonproteinogenic amino acids. This minireview collects recent work on catalytic asymmetric synthesis of α‐ and β‐amino acids.
Molecular Structure–Activity Relationships for the Oxidation of Organic Compounds Using Mesoporous Silica Catalysts Derivatised with Bis(halogeno)dioxomolybdenum(VI) Complexes
Authors: Nunes Carla D. , Valente Anabela A. , Pillinger Martyn , Rocha João , Gonçalves Isabel S. 
Published: September 2003

AbstractMo K‐edge XAFS spectra have been measured for ordered mesoporous silica MCM‐41 grafted with the complexes [MoO2X2(thf)2] (X=Cl, Br). For grafting reactions in the absence of triethylamine, materials with 1 wt. % Mo are obtained; the Mo K‐edge EXAFS results indicate the co‐existence of isolated surface‐fixed monomeric species {MoO2[(O)3SiO]2(thf)n} and {MoO2[(O)3SiO]X(thf)n}. When Et3N is used in the grafting reactions, materials with 4 wt. % Mo are obtained. The EXAFS data for the material prepared using [MoO2Cl2(thf)2] and Et3N indicate the presence of dinuclear species with two MoVI centres, each with two MoO groups and each linked by one or two oxo bridges (Mo⋅⋅⋅Mo 3.27 Å). The molybdenum centres in the material prepared using the dibromo complex comprise mainly isolated four‐coordinate dioxomolybdenum(VI) and trioxomolybdenum(VI) monomeric species, with a small contribution from dimeric species. All materials were further characterised in the solid state by powder X‐ray diffraction, N2 adsorption analysis, MAS NMR (13C, 29Si) and FTIR spectroscopy. The derivatised MCMs perform differently as catalysts in the liquid‐phase oxidation of various olefins and alcohols with tert‐butyl hydroperoxide. The highest alkene epoxidation activity was recorded for the catalysts with low metal loading, whereas the material containing oxo‐bridged dimers had the highest activity for oxidation of alcohols. The recyclability of all the catalysts was tested: the catalytic activity of the derivatised materials tended to stabilize with ageing.
Molecular Scale Speciation of First‐Row Transition Elements Bound to Ligneous Material by Using X‐ray Absorption Spectroscopy
Authors: Guillon Emmanuel , Merdy Patricia , Aplincourt Michel 
Published: September 2003

AbstractTo develop a solid scientific basis for maintaining soil quality and formulating effective remediation strategies, it is critical to determine how environmentally‐important trace metals are sequestered in soils at the molecular scale. The speciation of Mn, Fe and Cu in soil organic matter has been determined by synchrotron‐based techniques: extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near edge structure (XANES). We show the structural similarity between the surface complexes of MnII, FeIII and CuII. These cations are bound to the surface through oxygen atoms. Each one presents a more or less tetragonal‐distorted octahedral geometry. The use of X‐ray absorption spectroscopy provides a relevant method for determining trace‐metal speciation in both natural and contaminated environmental materials.
Relevance of the Electronegativity of Boron in η5‐Coordinating Ligands: Regioselective Monoalkylation and Monoarylation in Cobaltabisdicarbollide [3,3′‐Co(1,2‐C2B9H11)2]− Clusters
Authors: Rojo Isabel , Teixidor Francesc , Viñas Clara , Kivekäs Raikko , Sillanpää Reijo 
Published: September 2003

AbstractRegioselective monoalkylation and monoarylation in cobaltabisdicarbollide clusters has been achieved starting from Cs[8‐I‐3,3′‐Co(1,2‐C2B9H10)(1′,2′‐C2B9H11)] by cross‐coupling reactions between a BI fragment and an appropriate Grignard reagent in the presence of a Pd catalyst and CuI. A considerable number of monoalkylated and monoarylated derivatives have been synthesized, which allowed study of the influence of boron in metallocene‐type ligands and the effect of alkyl and aryl substituents on boron in boron anionic clusters. Experimental data from UV/Vis spectroscopy, E1/2 measurements, and X‐ray diffraction analysis, and supported by EHMO and ab initio analyses, indicate that the participation of metal d orbitals in the HOMO is less than that in typical metallocene complexes. This can be explained in terms of the lower electronegativity of boron compared to carbon. Related to this is the −I character of alkyl groups when bonded to boron in boron anionic clusters, contrary to the common belief that alkyl groups are generally electron‐releasing moieties.
An Accurate Barrier for the Hydrogen Exchange Reaction from Valence Bond Theory: Is this Theory Coming of Age?
Authors: Song Lingchun , Wu Wei , Hiberty Philippe C. , Danovich David , Shaik Sason 
Published: September 2003

AbstractOne of the landmark achievements of quantum chemistry, specifically of MO‐based methods that include electron correlation, was the precise calculation of the barrier for the hydrogen‐exchange reaction (B. Liu, J. Chem. Phys. 1973, 58, 1925; P. Siegbahn, B. Liu, J. Chem. Phys. 1978, 68, 2457). This paper reports an accurate calculation of this barrier by two recently developed VB methods that use only the eight classical VB structures. To our knowledge, the present work is the first accurate ab initio VB barrier that matches an experimental value. Along with the accurate barrier, the VB method provides accurate bond energies and diabatic quantities that enable the barrier height to be analyzed by the VB state correlation diagram approach, VBSCD (S. Shaik, A. Shurki, Angew. Chem. 1999, 111, 616; Angew. Chem. Int. Ed. Engl. 1999, 38, 586). This is a proof of principal that VB theory with appropriate account of dynamic electron correlation can achieve quantitative accuracy of reaction barriers, and still retain a compact and interpretable wave function. A sample of SN2 barriers and dihalogen bonding energies, which are close to CCSD(T) and G2(+) values, show that the H3 problem is not an isolated case, and while it is premature to conclude that VB theory has come of age, the occurrence of this event is clearly within sight.