bluuebunny/crossref_metadata_2025 huggingface dataset:
Ambient Air Pollution: Health Hazards to Children
Authors:   Committee on Environmental Health
Published: December 2004

Ambient (outdoor) air pollution is now recognized as an important problem, both nationally and worldwide. Our scientific understanding of the spectrum of health effects of air pollution has increased, and numerous studies are finding important health effects from air pollution at levels once considered safe. Children and infants are among the most susceptible to many of the air pollutants. In addition to associations between air pollution and respiratory symptoms, asthma exacerbations, and asthma hospitalizations, recent studies have found links between air pollution and preterm birth, infant mortality, deficits in lung growth, and possibly, development of asthma. This policy statement summarizes the recent literature linking ambient air pollution to adverse health outcomes in children and includes a perspective on the current regulatory process. The statement provides advice to pediatricians on how to integrate issues regarding air quality and health into patient education and children's environmental health advocacy and concludes with recommendations to the government on promotion of effective air-pollution policies to ensure protection of children's health.
Thermoplastic elastomers based on recycled high‐density polyethylene, ethylene–propylene–diene monomer rubber, and ground tire rubber
Authors: Grigoryeva O. P. , Fainleib A. M. , Tolstov A. L. , Starostenko O. M. , Lievana E. , Karger‐Kocsis J.
Published: December 2004

High‐performance thermoplastic elastomers (TPEs), based on recycled high‐density polyethylene (HDPER), olefinic type ethylene–propylene–diene monomer rubber (EPDM), and ground tire rubber (GTR) treated with bitumen, were prepared by using dynamic vulcanization technology, and their structure–property relationships were investigated. It was established that special pretreatment of GTR by bitumen confers outstanding mechanical properties on the resulting TPEs. TPEs, containing GTR pretreated by bitumen, exhibit thermal behavior similar to that of the HDPER/EPDM basic blend in the temperature region up to about 340°C. Rheological measurements showed that bitumen acts as an effective plasticizer for the GTR‐containing TPEs. SEM, DSC, and DMTA results revealed improved adhesion between the particles of GTR treated by bitumen and the surrounding thermoplastic matrix, compared to that of the untreated GTR particles. It was concluded that bitumen acts as an effective devulcanizing agent in the GTR treatment stage. In the following steps of TPE production, bitumen acts simultaneously as a curing agent for the rubber components (EPDM/GTR) and as a compatibilizer for the blend components. GTR‐containing TPEs, prepared by extrusion technology, were reprocessed (by passing through the extruder six times) without any observable changes in their tensile properties, thermal stability, and melt viscosity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 659–671, 2005
Stimuli sensitive copolymer poly(N‐tert‐butylacrylamide‐ran‐acrylamide): Synthesis and characterization
Authors: Save Ninad S. , Jassal Manjeet , Agrawal Ashwini K.
Published: December 2004

Temperature sensitive random linear and crosslinked copolymers of N‐tert‐butylacrylamide (NTBA) and acrylamide (Am) were synthesized by the solution polymerization method, using regulated dosing of comonomer Am having a higher reactivity ratio (rAm = 1.5) than NTBA (rNTBA = 0.5). Copolymers with varying feed ratios of NTBA and Am (80 : 20 to 20 : 80 mol %) were synthesized and characterized. For the synthesis of copolymer hydrogels, N′, N‐methylene bisacrylamide (MBA) (1.13 mol %) was used along with monomers. The effect of composition on transition properties was evaluated for the linear copolymers and their hydrogels. A definite trend was observed. The incorporation of a higher percentage of the hydrophilic comonomer Am in the structure resulted in the shifting of the transition temperature towards a higher value. The transition temperatures of the copolymers synthesized with feed compositions of 80 : 20, 70 : 30, 60 : 40, 50 : 50, 40 : 60, 30 : 70, and 20 : 80 mol % were found to be 2, 10, 19, 27, 37, 45, and 58°C, respectively. Differential scanning calorimetry (DSC) studies confirmed the formation of random copolymers. The copolymers synthesized with a monomer feed ratio of 50 : 50 with regulated dosing showed a single glass transition temperature (Tg) at 168°C, while the copolymer synthesized with full dosing of Am at the beginning of the reaction showed two Tgs, at 134 and 189°C. The copolymer samples were analyzed by Fourier transform infrared spectroscopy (FTIR) for ascertaining the composition. The composition of the copolymers followed the trend of the feed ratio, but the incorporation of NTBA in the copolymers was found to be lower than the feed ratio because of lower than quantitative yields of the reactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 672–680, 2005
Influence of radiation structures on positive‐temperature‐coefficient and negative‐temperature‐coefficient effects of irradiated low‐density polyethylene/carbon black composites
Authors: Xie Hongfeng , Dong Lisong , Sun Jiazhen
Published: December 2004

The electrical‐resistivity/temperature behaviors of low‐density polyethylene (LDPE)/carbon black (CB) composites irradiated with 60Co γ rays were studied. The experimental results showed that the irradiated composites could be separated into insoluble crosslinking networks with CB (gel) and soluble components (sol) by solvent‐extraction techniques. When the sol of an irradiated LDPE/CB composite was extracted, the electrical conductivity of the system increased. The positive‐temperature‐coefficient (PTC) and negative‐temperature‐coefficient (NTC) intensities of the gels of the irradiated composites became extremely small and independent of the radiation dose. The sols and gels of the irradiated LDPE/CB composites, which had different thermal behaviors, played important roles in the appearances of the PTC and NTC effects. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 700–704, 2005
Expression of type 1 corticotropin‐releasing factor receptor in the guinea pig enteric nervous system
Authors: Liu Sumei , Gao Xiang , Gao Na , Wang Xiyu , Fang Xiucai , Hu Hong‐Zhen , Wang Guo‐Du , Xia Yun , Wood Jackie D.
Published: December 2004

Reverse transcription‐polymerase chain reaction (RT‐PCR), immunohistochemistry, electrophysiological recording, and intraneuronal injection of the neuronal tracer biocytin were integrated in a study of the functional expression of corticotropin‐releasing factor (CRF) receptors in the guinea pig enteric nervous system. RT‐PCR revealed expression of CRF1 receptor mRNA, but not CRF2, in both myenteric and submucosal plexuses. Immunoreactivity for the CRF1 receptor was distributed widely in the myenteric plexus of the stomach and small and large intestine and in the submucosal plexus of the small and large intestine. CRF1 receptor immunoreactivity was coexpressed with calbindin, choline acetyltransferase, and substance P in the myenteric plexus. In the submucosal plexus, CRF1 receptor immunoreactivity was found in neurons that expressed calbindin, substance P, choline acetyltransferase, or neuropeptide Y. Application of CRF evoked slowly activating depolarizing responses associated with elevated excitability in both myenteric and submucosal neurons. Histological analysis of biocytin‐filled neurons revealed that both uniaxonal neurons with S‐type electrophysiological behavior and neurons with AH‐type electrophysiological behavior and Dogiel II morphology responded to CRF. The CRF‐evoked depolarizing responses were suppressed by the CRF1/CRF2 receptor antagonist astressin and the selective CRF1 receptor antagonist NBI27914 and were unaffected by the selective CRF2 receptor antagonist antisauvagine‐30. The findings support the hypothesis that the CRF1 receptor mediates the excitatory actions of CRF on neurons in the enteric nervous system. Actions on enteric neurons might underlie the neural mechanisms by which stress‐related release of CRF in the periphery alters intestinal propulsive motor function, mucosal secretion, and barrier functions. J. Comp. Neurol. 481:284–298, 2005. © 2004 Wiley‐Liss, Inc.
Drosophila neuroblast 7‐3 cell lineage: A model system for studying programmed cell death, Notch/Numb signaling, and sequential specification of ganglion mother cell identity
Authors: Karcavich Rachel , Doe Chris Q.
Published: December 2004

Cell lineage studies provide an important foundation for experimental analysis in many systems. Drosophila neural precursors (neuroblasts) sequentially generate ganglion mother cells (GMCs), which generate neurons and/or glia, but the birth order, or cell lineage, of each neuroblast is poorly understood. The best‐characterized neuroblast is NB7‐3, in which GMC‐1 makes the EW1 serotonergic interneuron and GW motoneuron; GMC‐2 makes the EW2 serotonergic interneuron and a programmed cell death; and GMC‐3 gives rise to the EW3 interneuron. However, the end of this lineage has not been determined. Here, we use positively marked genetic clones, bromodeoxyuridine (BrdU) labeling, mutations that affect Notch signaling, and antibody markers to further define the end of the cell lineage of NB7‐3. We provide evidence that GMC‐3 directly differentiates into EW3 and that the sibling neuroblast undergoes programmed cell death. Our results confirm and extend previous work on the early portion of the NB7‐3 lineage (Novotny et al. [2002] Development 129:1027–1036; Lundell et al. [ 2003] Development 130:4109–4121). J. Comp. Neurol. 481:240–251, 2005. © 2004 Wiley‐Liss, Inc.
Rat retinal dopaminergic neurons: Differential maturation of somatodendritic and axonal compartments
Authors: Witkovsky Paul , Arango‐Gonzalez Blanca , Haycock John W. , Kohler Konrad
Published: December 2004

We examined developmental changes in dopaminergic (DA) neurons of rat pups between postnatal (P) days 3 and 21. DA cell bodies and dendrites grew progressively between P3–15. Voltage‐sensitive sodium channels were present in axons at P11, but the ring‐like DA axon terminals appeared only during the third postnatal week. The density of ring terminals increased markedly between P15 and P21. The vesicular monoamine transporter (VMAT2) was absent before P13 and became concentrated in DA ring terminals after P17. A steady increase in VMAT2‐containing rings around AII amacrine cells occurred during the third postnatal week. The presynaptic membrane protein SNAP‐25 colocalized with DA terminals, but several other presynaptic proteins tested, including synaptotagmin I, synapsin, bassoon, syntaxin, and synaptogyrin, appeared not to be associated with DA neurons. Our study shows that the somatodendritic compartment of DA neurons matures before the DA axon terminals do. Maturation of DA axons during the third postnatal week corresponds to the period of onset of visual function. J. Comp. Neurol. 481:352–362, 2005. © 2004 Wiley‐Liss, Inc.
Pheromone processing center in the protocerebrum of Bombyx mori revealed by nitric oxide‐induced anti‐cGMP immunocytochemistry
Authors: Seki Yoichi , Aonuma Hitoshi , Kanzaki Ryohei
Published: December 2004

The antennal lobe (AL) of the male silkworm moth Bombyx mori contains 60 ± 2 ventrally located antennal glomeruli and a dorsal macroglomerular complex (MGC) consisting of three subdivisions. The response patterns of MGC projection neurons (PNs) to pheromonal stimuli correlate with their dendritic arborization in the subdivisions of the MGC. However, the representation of this pheromonal information in the lateral protocerebrum (LPC), which is the target site of the AL PNs, is not well known. We performed nitric oxide (NO)‐induced anti‐cGMP immunohistochemistry and found that the PNs which respond to the major pheromone component (bombykol) express strong immunoreactivity. They project to a specific area, the delta area in the inferior lateral protocerebrum (ΔILPC), which clearly represents the processing center for the major pheromone component. Furthermore, to examine the projection sites in the LPC from each subdivision of the MGC, we performed double‐labeling of each type of MGC‐PNs, combined with NO‐induced anti‐cGMP immunohistochemistry. We revealed that projections from each subdivision of the MGC overlapped or separated in specific regions of the ΔILPC. These results suggest that integration and segregation of pheromone information may occur in the ΔILPC. J. Comp. Neurol. 481:340–351, 2005. © 2004 Wiley‐Liss, Inc.
Public reporting: A neglected aspect of nonprofit accountability
Authors: Lee Mordecai
Published: December 2004

Nonprofit organizations have a compulsory external accountability (largely involving financial reporting) to government agencies such as the Internal Revenue Service and state regulators. They also have a pragmatic “must‐do” accountability to their funders, clients, and other obvious stakeholders. But are nonprofits also accountable to the public at large? If so, how can such accountability be implemented, given the diffuseness and breadth of the public as an audience? This article suggests that nonprofits should consider the citizenry as a stakeholder, if only due to the substantial taxpayer subsidy of the sector. The theory of public reporting that emerged in public administration literature beginning in the 1920s and 1930s can be helpful. Using principles, templates, and examples from public administration, nonprofit organizations can pursue more vigorous public reporting as one method to increase citizen confidence in their activities and in the sector as a whole.
Balancing strategy and accountability: A model for the governance of professional associations
Authors: Friedman Andrew , Phillips Mary
Published: December 2004

An erratum has been published for this article in Nonprofit Management and Leadership 15(4) 2005, 487 [].

Professional associations are operating in a context of uncertainty and change, with which their traditional governance structures struggle to manage. After describing this context and presenting a brief overview of relevant governance literature, a project aimed at supporting the redesign of governance structures and procedures among five professional associations in the United Kingdom is outlined. Three specific governance issues are examined: size of councils (council is the term used for a governing body of a U.K. professional association), their composition in relation to electoral processes, and the development of inner councils, or executive boards, within councils. Finally, we present a normative model, the cupped hands model, that has arisen from the research. This model offers a possible means of balancing the representation required by their status as membership associations with the requirement that professional associations become more strategic and proactive.
Social accounting
Authors: Nitterhouse Denise
Published: December 2004

What Counts: Social Accounting for Nonprofits and Cooperatives, by Jack Quarter, Laurie Mook, and Betty Jane Richmond. Upper Saddle River, N.J.: Prentice Hall, 2003. 239 pp. $45.00 paper.
Glass transitions and mixed phases in block SBS
Authors: Masson J‐F. , Bundalo‐Perc Slađana , Delgado Ana
Published: December 2004

Differential scanning calorimetry (DSC) does not allow for easy determination of the glass‐transition temperature (Tg) of the polystyrene (PS) block in styrene–butadiene–styrene (SBS) block copolymers. Modulated DSC (MDSC), which deconvolutes the standard DSC signal into reversing and nonreversing signals, was used to determine the (Tg) of both the polybutadiene (PB) and PS blocks in SBS. The Tg of the PB block was sharp, at −92 °C, but that for the PS blocks was extremely broad, from −60 to 125 °C with a maximum at 68 °C because of blending with PB. PS blocks were found only to exist in a mixed PS–PB phase. This concurred with the results from dynamic mechanical analysis. Annealing did not allow for a segregation of the PS blocks into a pure phase, but allowed for the segregation of the mixed phase into two mixed phases, one that was PB‐rich and the other that was PS‐rich. It is concluded that three phases coexist in SBS: PB, PB‐rich, and PS‐rich phases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 276–279, 2005
Flexibility transitions and looped adsorption of wormlike chains
Authors: Dalhaimer P. , Wagner O. I. , Leterrier J.‐F. , Janmey P. A. , Aranda‐Espinoza H. , Discher D. E.
Published: December 2004

When deposited from a solution onto a surface, superpolymeric chains display revealing transitions in their apparent stiffness. With simulated chains in adsorption, we varied the backbone rigidity and measured the chain persistence length (lPads). As the three‐dimensional persistence length (lP3) increases toward the contour length, a transition can be seen from lPads = lP2 (i.e., the two‐dimensional persistence length) to lPads = lP3. Looped conformations decrease in frequency with a distinct nonlinear dependence. Finally, comparisons with experiments on polymeric worm micelles and purified neurofilaments demonstrate a simple new method for assessing the flexibility of these novel superpolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 280–286, 2005
Particle pair diffusion and persistent streamline topology in two-dimensional turbulence
Authors: S Goto and J C Vassilicos
Published: December 2004

There was a small error in equation (61) of this paper. The correct equation is as follows:
Fuzzy Decision Making in Politics: A Linguistic Fuzzy-Set Approach (LFSA)
Authors: Arfi Badredine
Published: December 2004

In this article I use linguistic fuzzy-set theory to analyze the process of decision making in politics. I first introduce a number of relevant elements of (numerical and linguistic) fuzzy-set theory that are needed to understand the terminology as well as to grasp the scope and depth of the approach. I then explicate a linguistic fuzzy-set approach (LFSA) to the process of decision making under conditions in which the decision makers are required to simultaneously satisfy multiple criteria. The LFSA approach is illustrated through a running (hypothetical) example of a situation in which state leaders need to decide how to combine trust and power to make a choice on security alignment.
The Statistical Properties and Empirical Performance of Double Regression
Authors: Zax Jeffrey S.
Published: December 2004

Voting rights litigation requires ecological inference to estimate the voting preferences of minority and nonminority groups within the electorate. Double regression has been the procedure most commonly employed for this purpose. This article presents the first formal examination of this procedure. The underlying structural model reveals that double regression estimators are neither unbiased nor consistent estimators of true within-group vote preferences or polarization. Simulations demonstrate that they can substantially exaggerate the differences between minority and nonminority vote choices when none are present, and dramatically understate them when differences exist. In sum, double regression cannot meet conventional statistical standards for reliability. Consequently, it should be abandoned.
Issue Attitudes and Survey Continuity across Interview Mode in the 2000 NES
Authors: Fogarty Brian J. , Kelly Nathan J. , Kilburn H. Whitt
Published: December 2004

Can researchers draw consistent inferences about the U.S. public's issue attitudes when studying survey results from both the in-person and telephone interview modes of the 2000 National Election Studies (NES) survey? We address this question through an analysis contrasting the distribution of issue attitudes across modes in the dual sample design of the 2000 NES. We find clear differences across mode even when applying a method devised by the NES to improve comparability by recoding issue attitude scales from the in-person mode. We present an alternative method of recoding these scales, which substantially improves comparability between modes. Through an analysis of the covariance structure of the issues and simple models of vote choice, we discuss the implications of the results for the study of issue attitudes in the 2000 NES.
Can Ca2+ Fluxes to the Root Xylem Be Sustained by Ca2+-ATPases in Exodermal and Endodermal Plasma Membranes?
Authors: Hayter Meghan L. , Peterson Carol A.
Published: December 2004

The pathway of Ca2+ movement from the soil solution into the root stele has been a subject of controversy. If transport through the endodermis is assumed to be through the cytoplasm, the limiting factor is believed to be the active pumping of Ca2+ from the cytoplasm into the stele apoplast through the plasma membrane lying on the stele side of the Casparian band. By analogy, for similar transport through the exodermis, the limiting step would be the active pumping into the apoplast on the central cortical side of the layer. Such effluxes are mediated by Ca2+-ATPases. To assess whether or not known Ca2+ fluxes to the stele in onion (Allium cepa) roots could be supported by Ca2+-ATPases, the percentages of total membrane protein particles required to effect the transport were calculated using measured values of membrane surface areas, an animal literature value for Ca2+-ATPase V max, plant literature values for Ca2+-ATPase K m, and protein densities of relevant membranes. Effects of a putative symplastic movement of Ca2+ from the exo- or endodermis into the next cell layer, which would increase the surface areas available for pumping, were also considered. Depending on the assumptions applied, densities of Ca2+ pumps, calculated as a percentage of total membrane protein particles, varied tremendously between three and 1,600 for the endodermis, and between 0.94 and 1,900 for the exodermis. On the basis of the data, the possibility of Ca2+ transport through the cytoplasm and membranes of the exodermis and endodermis cannot be discounted. Thus, it is premature to assign an entirely apoplastic pathway for Ca2+ movement from the soil solution to the tracheary elements of the xylem. To verify any conclusion with certainty, more detailed data are required for the characteristics of exo- and endodermal Ca2+-ATPases.
Amino Acid Metabolism in Maize Earshoots. Implications for Assimilate Preconditioning and Nitrogen Signaling
Authors: Seebauer Juliann R. , Moose Stephen P. , Fabbri Bradon J. , Crossland Lyle D. , Below Frederick E.
Published: December 2004

Nitrogen (N) is an essential requirement for kernel growth in maize (Zea mays); however, little is known about how N assimilates are metabolized in young earshoots during seed development. The objective of this study was to assess amino acid metabolism in cob and spikelet tissues during the critical 2 weeks following silking. Two maize hybrids were grown in the field for 2 years at two levels of supplemental N fertilizer (0 and 168 kg N/ha). The effects of the reproductive sink on cob N metabolism were examined by comparing pollinated to unpollinated earshoots. Earshoots were sampled at 2, 8, 14, and 18 d after silking; dissected into cob, spikelet, and/or pedicel and kernel fractions; then analyzed for amino acid profiles and key enzyme activities associated with amino acid metabolism. Major amino acids in the cob were glutamine (Gln), aspartic acid (Asp), asparagine (Asn), glutamate, and alanine. Gln concentrations dropped dramatically from 2 to 14 d after silking in both pollinated and unpollinated cobs, whereas all other measured amino acids accumulated over time in unpollinated spikelets and cobs, especially Asn. N supply had a variable effect on individual amino acid levels in young cobs and spikelets, with Asn being the most notably enhanced. We found that the cob performs significant enzymatic interconversions among Gln, alanine, Asp, and Asn during early reproductive development, which may precondition the N assimilate supply for sustained kernel growth. The measured amino acid profiles and enzymatic activities suggest that the Asn to Gln ratio in cobs may be part of a signal transduction pathway involving aspartate aminotransferase, Gln synthetase, and Asn synthetase to indicate plant N status for kernel development.
Effect of the Colorless non-ripening Mutation on Cell Wall Biochemistry and Gene Expression during Tomato Fruit Development and Ripening
Authors: Eriksson Emma M. , Bovy Arnaud , Manning Ken , Harrison Liz , Andrews John , De Silva Jacquie , Tucker Gregory A. , Seymour Graham B.
Published: December 2004

The Colorless non-ripening (Cnr) mutation in tomato (Solanum lycopersicum) results in mature fruits with colorless pericarp tissue showing an excessive loss of cell adhesion (A.J. Thompson, M. Tor, C.S. Barry, J. Vrebalov, C. Orfila, M.C. Jarvis, J.J. Giovannoni, D. Grierson, G.B. Seymour [1999] Plant Physiol 120: 383–390). This pleiotropic mutation is an important tool for investigating the biochemical and molecular basis of cell separation during ripening. This study reports on the changes in enzyme activity associated with cell wall disassembly in Cnr and the effect of the mutation on the program of ripening-related gene expression. Real-time PCR and biochemical analysis demonstrated that the expression and activity of a range of cell wall-degrading enzymes was altered in Cnr during both development and ripening. These enzymes included polygalacturonase, pectinesterase (PE), galactanase, and xyloglucan endotransglycosylase. In the case of PE, the protein product of the ripening-related isoform PE2 was not detected in the mutant. In contrast with wild type, Cnr fruits were rich in basic chitinase and peroxidase activity. A microarray and differential screen were used to profile the pattern of gene expression in wild-type and Cnr fruits. They revealed a picture of the gene expression in the mutant that was largely consistent with the real-time PCR and biochemical experiments. Additionally, these experiments demonstrated that the Cnr mutation had a profound effect on many aspects of ripening-related gene expression. This included a severe reduction in the expression of ripening-related genes in mature fruits and indications of premature expression of some of these genes in immature fruits. The program of gene expression in Cnr resembles to some degree that found in dehiscence or abscission zones. We speculate that there is a link between events controlling cell separation in tomato, a fleshy fruit, and those involved in the formation of dehiscence zones in dry fruits.
Identification and Characterization of a Ca2+-Dependent Actin Filament-Severing Protein from Lily Pollen
Authors: Fan Xiaoxue , Hou Jian , Chen Xiaoliang , Chaudhry Faisal , Staiger Christopher J. , Ren Haiyun
Published: December 2004

It is well known that a tip-focused intracellular Ca2+ gradient and the meshwork of short actin filaments at the tip region are necessary for pollen tube growth. However, little is known about the connections between the two factors. Here, a novel Ca2+-dependent actin-binding protein with molecular mass of 41 kD from lily (Lilium davidii) pollen (LdABP41) was isolated and purified with DNase I chromatography. Our purification procedure yielded about 0.6 mg of LdABP41 with >98% purity from 10 g of lily pollen. At least two isoforms with isoelectric points of 5.8 and 6.0 were detected on two-dimensional gels. The results of N-terminal sequencing and mass-spectrometry analysis of LdABP41 showed that both isoforms shared substantial similarity with trumpet lily (Lilium longiflorum) villin and other members of the gelsolin superfamily. Negative-stained electron microscope images showed that LdABP41 severed in vitro-polymerized lily pollen F-actin into short actin filaments in a Ca2+-sensitive manner. Microinjection of the anti-LdABP41 antibody into germinated lily pollen demonstrated that the protein was required for pollen tube growth. The results of immunolocalization of the protein showed that it existed in the cytoplasm of the pollen tube, especially focused in the tip region. Our results suggest that LdABP41 belongs to the gelsolin superfamily and may play an important role in controlling actin organization in the pollen tube tip by responding to the oscillatory, tip-focused Ca2+ gradient.
Analysis of Sequence, Map Position, and Gene Expression Reveals Conserved Essential Genes for Iron Uptake in Arabidopsis and Tomato
Authors: Bauer Petra , Thiel Thomas , Klatte Marco , Bereczky Zsolt , Brumbarova Tzvetina , Hell Rüdiger , Grosse Ivo
Published: December 2004

Arabidopsis (Arabidopsis thaliana) and tomato (Lycopersicon esculentum) show similar physiological responses to iron deficiency, suggesting that homologous genes are involved. Essential gene functions are generally considered to be carried out by orthologs that have remained conserved in sequence and map position in evolutionarily related species. This assumption has not yet been proven for plant genomes that underwent large genome rearrangements. We addressed this question in an attempt to deduce functional gene pairs for iron reduction, iron transport, and iron regulation between Arabidopsis and tomato. Iron uptake processes are essential for plant growth. We investigated iron uptake gene pairs from tomato and Arabidopsis, namely sequence, conserved gene content of the regions containing iron uptake homologs based on conserved orthologous set marker analysis, gene expression patterns, and, in two cases, genetic data. Compared to tomato, the Arabidopsis genome revealed more and larger gene families coding for the iron uptake functions. The number of possible homologous pairs was reduced if functional expression data were taken into account in addition to sequence and map position. We predict novel homologous as well as partially redundant functions of ferric reductase-like and iron-regulated transporter-like genes in Arabidopsis and tomato. Arabidopsis nicotianamine synthase genes encode a partially redundant family. In this study, Arabidopsis gene redundancy generally reflected the presumed genome duplication structure. In some cases, statistical analysis of conserved gene regions between tomato and Arabidopsis suggested a common evolutionary origin. Although involvement of conserved genes in iron uptake was found, these essential genes seem to be of paralogous rather than orthologous origin in tomato and Arabidopsis.
Short-Day Potentiation of Low Temperature-Induced Gene Expression of a C-Repeat-Binding Factor-Controlled Gene during Cold Acclimation in Silver Birch
Authors: Puhakainen Tuula , Li Chunyang , Boije-Malm Maria , Kangasjärvi Jaakko , Heino Pekka , Palva E. Tapio
Published: December 2004

Development of winter hardiness in trees is a two-stage process involving sequential perception of distinct environmental cues, short-day (SD) photoperiod and low temperature (LT). We have shown that both SD and LT are recognized by leaves of silver birch (Betula pendula cv Roth) leading to increased freezing tolerance, and thus leaves can be used as an experimental model to study the physiological and molecular events taking place during cold acclimation. To obtain a molecular marker for the acclimation process in birch we cloned a gene, designated Bplti36, encoding a 36-kD acidic SK2 type of dehydrin. The gene was responsive to LT, drought, salt, and exogenous abscisic acid. This responsiveness to abiotic stresses and abscisic acid was retained when Bplti36 was introduced to Arabidopsis (Arabidopsis thaliana). The LT induction of the gene appeared to be under the control of the C-repeat-binding factor pathway as suggested by the presence of several C-repeat/dehydration-responsive element/LT-responsive elements in the Bplti36 promoter and its constitutive expression in C-repeat-binding factor overproducing Arabidopsis. In birch SD photoperiod at normal-growth temperature did not result in significant induction of Bplti36. However, preexposure to SD followed by LT treatment resulted in a remarkable increase in Bplti36 transcript accumulation as compared to LT-treated plants grown at long-day photoperiod. This suggests that SD photoperiod potentiates the LT response by conditioning the leaf tissue to be more responsive to the LT stimulus.
Glutamate Dehydrogenase of Tobacco Is Mainly Induced in the Cytosol of Phloem Companion Cells When Ammonia Is Provided Either Externally or Released during Photorespiration
Authors: Tercé-Laforgue Thérèse , Dubois Frédéric , Ferrario-Méry Sylvie , Pou de Crecenzo Marie-Anne , Sangwan Rajbir , Hirel Bertrand
Published: December 2004

Glutamate (Glu) dehydrogenase (GDH) catalyses the reversible amination of 2-oxoglutarate for the synthesis of Glu using ammonium as a substrate. This enzyme preferentially occurs in the mitochondria of companion cells of a number of plant species grown on nitrate as the sole nitrogen source. For a better understanding of the controversial role of GDH either in ammonium assimilation or in the supply of 2-oxoglutarate (F. Dubois, T. Tercé-Laforgue, M.B. Gonzalez-Moro, M.B. Estavillo, R. Sangwan, A. Gallais, B. Hirel [2003] Plant Physiol Biochem 41: 565–576), we studied the localization of GDH in untransformed tobacco (Nicotiana tabacum) plants grown either on low nitrate or on ammonium and in ferredoxin-dependent Glu synthase antisense plants. Production of GDH and its activity were strongly induced when plants were grown on ammonium as the sole nitrogen source. The induction mainly occurred in highly vascularized organs such as stems and midribs and was likely to be due to accumulation of phloem-translocated ammonium in the sap. GDH induction occurred when ammonia was applied externally to untransformed control plants or resulted from photorespiratory activity in transgenic plants down-regulated for ferredoxin-dependent Glu synthase. GDH was increased in the mitochondria and appeared in the cytosol of companion cells. Taken together, our results suggest that the enzyme plays a dual role in companion cells, either in the mitochondria when mineral nitrogen availability is low or in the cytosol when ammonium concentration increases above a certain threshold.
Extracellular Calmodulin-Induced Stomatal Closure Is Mediated by Heterotrimeric G Protein and H2O2
Authors: Chen Yu-Ling , Huang Rongfeng , Xiao Yu-Mei , Lü Pin , Chen Jia , Wang Xue-Chen
Published: December 2004

Extracellular calmodulin (ExtCaM) exerts multiple functions in animals and plants, but the mode of ExtCaM action is not well understood. In this paper, we provide evidence that ExtCaM stimulates a cascade of intracellular signaling events to regulate stomatal movement. Analysis of the changes of cytosolic free Ca2+ ([Ca2+]cyt) and H2O2 in Vicia faba guard cells combined with epidermal strip bioassay suggests that ExtCaM induces an increase in both H2O2 levels and [Ca2+]cyt, leading to a reduction in stomatal aperture. Pharmacological studies implicate heterotrimeric G protein in transmitting the ExtCaM signal, acting upstream of [Ca2+]cyt elevation, and generating H2O2 in guard cell responses. To further test the role of heterotrimeric G protein in ExtCaM signaling in stomatal closure, we checked guard cell responses in the Arabidopsis (Arabidopsis thaliana) Gα-subunit-null gpa1 mutants and cGα overexpression lines. We found that gpa1 mutants were insensitive to ExtCaM stimulation of stomatal closure, whereas cGα overexpression enhanced the guard cell response to ExtCaM. Furthermore, gpa1 mutants are impaired in ExtCaM induction of H2O2 generation in guard cells. Taken together, our results strongly suggest that ExtCaM activates an intracellular signaling pathway involving activation of a heterotrimeric G protein, H2O2 generation, and changes in [Ca2+]cyt in the regulation of stomatal movements.
Phenolic Profiling of Caffeic Acid O-Methyltransferase-Deficient Poplar Reveals Novel Benzodioxane Oligolignols
Authors: Morreel Kris , Ralph John , Lu Fachuang , Goeminne Geert , Busson Roger , Herdewijn Piet , Goeman Jan L. , Van der Eycken Johan , Boerjan Wout , Messens Eric
Published: December 2004

Caffeic acid O-methyltransferase (COMT) catalyzes preferentially the methylation of 5-hydroxyconiferaldehyde to sinapaldehyde in monolignol biosynthesis. Here, we have compared HPLC profiles of the methanol-soluble phenolics fraction of xylem tissue from COMT-deficient and control poplars (Populus spp.), using statistical analysis of the peak heights. COMT down-regulation results in significant concentration differences for 25 of the 91 analyzed peaks. Eight peaks were exclusively detected in COMT-deficient poplar, of which four could be purified for further identification using mass spectrometry/mass spectrometry, nuclear magnetic resonance, and spiking of synthesized reference compounds. These new compounds were derived from 5-hydroxyconiferyl alcohol or 5-hydroxyconiferaldehyde and were characterized by benzodioxane moieties, a structural type that is also increased in the lignins of COMT-deficient plants. One of these four benzodioxanes amounted to the most abundant oligolignol in the HPLC profile. Furthermore, all of the differentially accumulating oligolignols involving sinapyl units were either reduced in abundance or undetectable. The concentration levels of all identified oligolignols were in agreement with the relative supply of monolignols and with their chemical coupling propensities, which supports the random coupling hypothesis. Chiral HPLC analysis of the most abundant benzodioxane dimer revealed the presence of both enantiomers in equal amounts, indicating that they were formed by radical coupling reactions under simple chemical control rather than guided by dirigent proteins.
Metabolic Engineering of the Chloroplast Genome Using the Echerichia coli ubiC Gene Reveals That Chorismate Is a Readily Abundant Plant Precursor for p-Hydroxybenzoic Acid Biosynthesis
Authors: Viitanen Paul V. , Devine Andrew L. , Khan Muhammad Sarwar , Deuel Deborah L. , Van Dyk Drew E. , Daniell Henry
Published: December 2004

p-Hydroxybenzoic acid (pHBA) is the major monomer in liquid crystal polymers. In this study, the Escherichia coli ubiC gene that codes for chorismate pyruvate-lyase (CPL) was integrated into the tobacco (Nicotiana tabacum) chloroplast genome under the control of the light-regulated psbA 5′ untranslated region. CPL catalyzes the direct conversion of chorismate, an important branch point intermediate in the shikimate pathway that is exclusively synthesized in plastids, to pHBA and pyruvate. The leaf content of pHBA glucose conjugates in fully mature T1 plants exposed to continuous light (total pooled material) varied between 13% and 18% dry weight, while the oldest leaves had levels as high as 26.5% dry weight. The latter value is 50-fold higher than the best value reported for nuclear-transformed tobacco plants expressing a chloroplast-targeted version of CPL. Despite the massive diversion of chorismate to pHBA, the plastid-transformed plants and control plants were indistinguishable. The highest CPL enzyme activity in pooled leaf material from adult T1 plants was 50,783 pkat/mg of protein, which is equivalent to approximately 35% of the total soluble protein and approximately 250 times higher than the highest reported value for nuclear transformation. These experiments demonstrate that the current limitation for pHBA production in nuclear-transformed plants is CPL enzyme activity, and that the process becomes substrate-limited only when the enzyme is present at very high levels in the compartment of interest, such as the case with plastid transformation. Integration of CPL into the chloroplast genome provides a dramatic demonstration of the high-flux potential of the shikimate pathway for chorismate biosynthesis, and could prove to be a cost-effective route to pHBA. Moreover, exploiting this strategy to create an artificial metabolic sink for chorismate could provide new insight on regulation of the plant shikimate pathway and its complex interactions with downstream branches of secondary metabolism, which is currently poorly understood.
Organization of Monoterpene Biosynthesis in Mentha. Immunocytochemical Localizations of Geranyl Diphosphate Synthase, Limonene-6-Hydroxylase, Isopiperitenol Dehydrogenase, and Pulegone Reductase
Authors: Turner Glenn W. , Croteau Rodney
Published: December 2004

We present immunocytochemical localizations of four enzymes involved in p-menthane monoterpene biosynthesis in mint: the large and small subunits of peppermint (Mentha x piperita) geranyl diphosphate synthase, spearmint (Mentha spicata) (−)-(4S)-limonene-6-hydroxylase, peppermint (−)-trans-isopiperitenol dehydrogenase, and peppermint (+)-pulegone reductase. All were localized to the secretory cells of peltate glandular trichomes with abundant labeling corresponding to the secretory phase of gland development. Immunogold labeling of geranyl diphosphate synthase occurred within secretory cell leucoplasts, (−)-4S-limonene-6-hydroxylase labeling was associated with gland cell endoplasmic reticulum, (−)-trans-isopiperitenol dehydrogenase labeling was restricted to secretory cell mitochondria, while (+)-pulegone reductase labeling occurred only in secretory cell cytoplasm. We discuss this pathway compartmentalization in relation to possible mechanisms for the intracellular movement of monoterpene metabolites, and for monoterpene secretion into the extracellular essential oil storage cavity.
Rice Contains Two Disparate ent-Copalyl Diphosphate Synthases with Distinct Metabolic Functions
Authors: Prisic Sladjana , Xu Meimei , Wilderman P. Ross , Peters Reuben J.
Published: December 2004

Rice (Oryza sativa) produces ent-copalyl diphosphate for both gibberellin (GA) phytohormone and defensive phytoalexin biosynthesis, raising the question of how this initial biosynthetic step is carried out for these distinct metabolic processes. Here, a functional genomics approach has been utilized to identify two disparate ent-copalyl diphosphate synthases from rice (OsCPS1ent and OsCPS2ent). Notably, it was very recently demonstrated that only one of these (OsCPS1ent) normally operates in GA biosynthesis as mutations in this gene result in severely impaired growth. Evidence is presented here strongly indicating that the other (OsCPS2ent) is involved in related secondary metabolism producing defensive phytochemicals. In particular, under appropriate conditions, OsCPS2ent mRNA is specifically induced in leaves prior to production of the corresponding phytoalexins. Thus, transcriptional control of OsCPS2ent seems to be an important means of regulating defensive phytochemical biosynthesis. Finally, OsCPS1ent is significantly more similar to the likewise GA-specific gene An1/ZmCPS1ent in maize (Zea mays) than its class II terpene synthase paralogs involved in rice secondary metabolism. Hence, we speculate that this cross-species conservation by biosynthetic process reflects derivation of related secondary metabolism from the GA primary biosynthetic pathway prior to the early divergence between the separate lineages within the cereal/grass family (Poaceae) resulting in modern rice and maize.
Green Fluorescent Protein-mTalin Causes Defects in Actin Organization and Cell Expansion in Arabidopsis and Inhibits Actin Depolymerizing Factor's Actin Depolymerizing Activity in Vitro
Authors: Ketelaar Tijs , Anthony Richard G. , Hussey Patrick J.
Published: December 2004

Expression of green fluorescent protein (GFP) linked to an actin binding domain is a commonly used method for live cell imaging of the actin cytoskeleton. One of these chimeric proteins is GFP-mTalin (GFP fused to the actin binding domain of mouse talin). Although it has been demonstrated that GFP-mTalin colocalizes with the actin cytoskeleton, its effect on actin dynamics and cell expansion has not been studied in detail. We created Arabidopsis (Arabidopsis thaliana) plants harboring alcohol inducible GFP-mTalin constructs to assess the effect of GFP-mTalin expression in vivo. We focused on the growing root hair as this is a model cell for studying cell expansion and root hair tip growth that requires a highly dynamic and polar actin cytoskeleton. We show that alcohol inducible expression of GFP-mTalin in root hairs causes severe defects in actin organization, resulting in either the termination of growth, cell death, and/or changes in cell shape. Fluorescence recovery after photobleaching experiments demonstrate that the interaction of GFP-mTalin and actin filaments is highly dynamic. To assess how GFP-mTalin affects actin dynamics we performed cosedimentation assays of GFP-mTalin with actin on its own or in the presence of the actin modulating protein, actin depolymerizing factor. We show that that GFP-mTalin does not affect actin polymerization but that it does inhibit the actin depolymerizing activity of actin depolymerizing factor. These observations demonstrate that GFP-mTalin can affect cell expansion, actin organization, and the interaction of actin binding proteins with actin.
The Role of Aquaporins and Membrane Damage in Chilling and Hydrogen Peroxide Induced Changes in the Hydraulic Conductance of Maize Roots
Authors: Aroca Ricardo , Amodeo Gabriela , Fernández-Illescas Silvia , Herman Eliot M. , Chaumont François , Chrispeels Maarten J.
Published: December 2004

When chilling-sensitive plants are chilled, root hydraulic conductance (L  o) declines precipitously; L  o also declines in chilling-tolerant plants, but it subsequently recovers, whereas in chilling-sensitive plants it does not. As a result, the chilling-sensitive plants dry out and may die. Using a chilling-sensitive and a chilling-tolerant maize genotype we investigated the effect of chilling on L  o, and its relationship to osmotic water permeability of isolated root cortex protoplasts, aquaporin gene expression, aquaporin abundance, and aquaporin phosphorylation, hydrogen peroxide (H2O2) accumulation in the roots and electrolyte leakage from the roots. Because chilling can cause H2O2 accumulation we also determined the effects of a short H2O2 treatment of the roots and examined the same parameters. We conclude from these studies that the recovery of L  o during chilling in the chilling-tolerant genotype is made possible by avoiding or repairing membrane damage and by a greater abundance and/or activity of aquaporins. The same changes in aquaporins take place in the chilling-sensitive genotype, but we postulate that membrane damage prevents the L  o recovery. It appears that the aquaporin response is necessary but not sufficient to respond to chilling injury. The plant must also be able to avoid the oxidative damage that accompanies chilling.
Progression through Meiosis I and Meiosis II in Arabidopsis Anthers Is Regulated by an A-Type Cyclin Predominately Expressed in Prophase I
Authors: Wang Yixing , Magnard Jean-Louis , McCormick Sheila , Yang Ming
Published: December 2004

Meiosis is often described as a special case of cell division since it differs from mitosis in having two nuclear divisions without an intervening S-phase. It will be of great interest to uncover what molecular mechanisms underlie these special features of meiosis. We previously reported that the tardy asynchronous meiosis (tam) mutant of Arabidopsis (Arabidopsis thaliana) is slower in cell cycle progression in male meiosis. Here we report that TAM encodes the A-type cyclin, CYCA1;2. The point mutation in tam replaced a conserved threonine with an isoleucine in the linker region between the α4 and α5 helices of the first cyclin fold. By studying the dynamics of a CYCA1;2-green fluorescent protein fusion protein under the control of the CYCA1;2 promoter, we found that the fusion protein was most abundant at pachytene, but was undetectable from late prophase I until telophase II. Nonetheless, cell cycle progression in tam was delayed in both pachytene and meiosis II. We conclude either that the CYCA1;2 produced in prophase I indirectly regulates meiosis II progression, or that a very low level of CYCA1;2 directly regulates meiosis II progression. Either of these scenarios is a deviation from the typical mode of action of mitotic cyclins in mitosis and meiosis I, in which each nuclear division is coupled with a peak of expression of mitotic cyclins.