bluuebunny/crossref_metadata_2025_split huggingface dataset:
Export of amino acids to the phloem in relation to N supply in wheat
Authors: Caputo Carla , Barneix Atilio J. 
Published: May 2006

The effect of different N supply on amino acid export to the phloem was studied in young plants of wheat (Triticum aestivum L. cv. Klein Chamaco), using the exudation in EDTA technique. Plants were grown in a growth cabinet in pots with sand, and supplied with nutrient solutions of different NO3− concentrations. When plants were grown for 15 days with nutrient solutions containing 1.0, 3.0, 5.0, 10.0, 15.0 or 20.0 mM KNO3, the exudation rate of sugars from the phloem was unaffected by N supply, but sugars accumulated in the leaf tissue when the N supply was limiting for growth. On the other hand, the rate of exudation of amino acids was proportional to the NO3− concentration in the nutrient solution. When the supply of N to plants grown for 15 days with 15.0 mM NO3− was interrupted, the exudation of sugars was again unaffected, but there was a fast decrease in the amount of amino acids exudated, and of the concentration of amino acids and nitrogen in the tissues. Also, when 10‐day‐old plants grown without N were supplied with 15.0 mM NO3−, there was a sharp increase in the exudation of amino acids, without changes in the amount of sugar exudated. The rate of exudation of amino acids to the phloem was independent of the concentration of free amino acids in the leaves in all three types of experiment.Asp was the most abundant amino acid in the leaf tissue, while Glu was the one most abundant in the phloem exudate. Asp and Ala were exported to the phloem at a rate lower than expected from their leaf tissue concentrations, indicating some discrimination. On the contrary, Glu showed a preferential export at low N supply.It is concluded that the rate of amino acid export from the leaf to the phloem is dependent on the N available to the plant. This N is used for synthesis of leaf protein when the supply is low, exported to the phloem when supply is adequate, and accumulated in the storage pool when supply is above plant demand.
Update on the possible mode of action of the jasmonates: Focus on the metabolism of cell wall polysaccharides in relation to growth and development
Authors: Miyamoto Kensuke , Oka Mariko , Ueda Junichi 
Published: May 2006

Jasmonic acid (JA) and its related compounds (jasmonates) applied to plant tissues exert either inhibitory or promotive effects in growth and developmental processes, which in some ways are similar to abscisic acid. However, little is known about the mode of action of the jamonates at the tissue or organ levels. Here, we review partial evidence for the physiological action of the jasmonates on cell elongation and abscission.Jasmonates inhibit the IAA‐induced cell elongation of oat coleoptile segments not by affecting energy production, osmoregulation and cell wall loosening, but by inhibiting the synthesis of cell wall polysaccharides. The inhibition is partially reversed by simultaneous application of sucrose. Inhibition of IAA‐induced elongation by JA is only observed in monocotyledons, not in dicotyledons. These effects suggest that jasmonates exert their inhibitory effect on cell elongation by affecting the metabolism of the cell wall polysaccharides in monocotyledons.Jasmonates promote the abscission of bean petiole explants without enhancing ethylene production. Cells in the petiole adjacent to the abscission zone expand during abscission. In the abscission zone, jasmonates decrease the amount of cellulosic but not that of noncellulosic polysaccharides. Jasmonates increase the activities of cellulase and decrease the levels of UDP‐sugars, which are important intermediates for the synthesis of cell wall polysaccharides in the abscission zone, probably resulting in the decreased level of cellulose and the mechanical weakness of cell walls.Thus, it is suggested that jasmonates exert their multiple physiological effects by affecting the metabolic processes of cell wall polysaccharides.
Possible involvement of jasmonates in various morphogenic events
Authors: Koda Yasunori 
Published: May 2006

Jasmonates (jasmonic acid and related compounds) seem to be involved in various morphogenic events of plants, such as tuberization (potato, yam and Jerusalem artichoke), tuberous root formation (sweet potato), bulb formation (onion and garlic), determination of plant structure (soybean) and thigmomorphogenesis (coiling of tendrils of Bryonia dioica). The involvement of jasmonates in tuberization in these plants was inferred from their ability to induce tubers in vitro, and from changes in the levels of endogenous jasmonates during the growth of the plants, which can account for the initiation of tuberization. As to potato tuberization, jasmonic acid (JA) and its methyl ester (JA‐Me) have strong tuber‐inducing activity. These compounds seem to exert their tuber‐inducing effects by elicting the expansion of cells, because JA and JA‐Me are capable of causing the expansion of cells in potato tubers. The JA‐induced expansion of cells is attributable to both an increase in osmotic pressure due to the accumulation of sucrose and changes in cell wall architecture that appear to affect the extensibility of the wall. And, moreover, the synthesis of cellulose might be indispensable for the JA‐induced expansion. The tuberization and the expansion of cells induced by JA always involve the reorientation of cortical microtubules (MTs), suggesting that JA controls the direction of cell expansion by changing the arrangement of MTs. However, the reorientation of MTs itself seems to be insufficient for the induction of expansion of cells.Involvement of jasmonates in bulb formation and tuberous root formation is presumed from the fact that JA is able to induce these in vitro. The exact nature of the control that the jasmonates exert on morphogenesis remains to be elucidated.
Respiration of barley protoplasts before and after illumination
Authors: Igamberdiev Abir U. , Zhou Guoquing , Malmberg Gunilla , Gardeström Per 
Published: May 2006

Respiratory O2 consumption was investigated in dark‐adapted barley (Hordeum vulgare L. cv. Gunilla) protoplasts and after illumination for 10 min at high and very low CO2 in the presence of respiratory and photorespiratory inhibitors. In dark‐adapted protoplasts no difference was observed between inhibitor treatments in high and very low CO2. The respiratory rate increased somewhat after illumination and a difference in responce to inhibitors was in some cases observed between high and very low CO2. Thus, the operation of the mitochondrial electron transport chain is affected following a period of active photosynthesis. In all situations tested, oligomycin inhibited respiratiory O2 uptake indicating that respiration of mitochondria in protoplasts is not strictly ADP limited. Antimycin A inhibited respiration more in dark‐adapted protoplasts than after illumination whereas SHAM gave the opposite response. Rotenone inhibited respiration both in dark‐adapted protoplasts (about 30%) and after illumination where the inhibition was much greater in very low CO2 (50%) than in high CO2 (10%). After illumination in very low CO2. SHAM + rotenone inhibited respiration almost completely (70%). Photorespiratory inhibitors had very small effect on O2 consumption in darkness. After illumination the effect of aminoacetonitrile (AAN) was also very low whereas α‐hydroxypyridine‐2‐methane sulphonate (HPMS) in photorespiratory conditions inhibited O2 uptake much stronger (35%). The addition of glyoxylate enhanced respiration in the presence of HPMS up to the control level suggesting that alternative pathways of glyoxylate conversion might be operating.The differences in inhibitor responses may reflect fine mechanisms for the regulation of energetic balance in the plant cell which consists of switching from electron transport coupled to ATP production to non‐coupled transport. Photorespiratory flux is also very flexible, and the suppression of glycine decarboxylation can induce bypass reactions of glyoxylate metabolism.
Regulation of cytokinin oxidase activity in tobacco callus expressing the T‐DNA ipt gene
Authors: Redig Pascale , Motyka Václav , Van Onckelen Henri A. , Kamínek Miroslav 
Published: May 2006

There are indications that the cytokinin content in transgenic tissues expressing the cytokinin biosynthetic ipt gene is under metabolic control, which prevents the accumulation of cytokinins to lethal levels. The objective of this study was to investigate the relationships between the content of endogenous cytokinins and the activity of cytokinin oxidase (which is believed to be a copper‐containing amine oxidase, EC 1.4.3.6.) in ipt transgenic tobacco callus. In addition, the effect of exogenously applied N‐benzyladenine (BA) on this relationship was examined. Endogenous cytokinin concentrations were measured in callus of Nicotiana tabacum L. cv. Petit Havana SRI transformed with the ipt of Agrobacterium tumefaciens under the control of a light‐inducible promoter and in non‐transformed tissue using LC‐tandem mass spectrometry. The activity of cytokinin oxidase was estimated by measuring the conversion of [2,8‐3H]N6‐(Δ2‐isopentenyl)adenine to [3H]adenine by enzyme preparations in vitro.The 14‐day‐old ipt‐transformed callus contained a 25‐fold higher amount of cytokinins as compared to the non‐transformed tissue. Mainly zeatin‐ and dihydrozeatin‐types of cytokinins (free bases, ribosides, nucleotides and O‐glucosides) accumulated in the ipt transgenic tissue. The cytokinin pool of both ipt‐transformed and non‐transformed tissues consisted predominantly of cytokinins that are either resistant to cytokinin oxidase attack (nucleotides and O‐glucosides of cytokinins and cytokinins bearing N6‐saturated side chain) or have a low affinity for the enzyme (zeatin and its riboside). The former represented 71.6 and 74.8% and the latter 27.7 and 24.4% of the pool of endogenous cytokinins in ipt‐transformed and non‐transformed tissues, respectively. Enzyme preparations from ipt‐transformed tissue exhibited 1.5‐fold higher cytokinin oxidase activity compared with that observed in control tissues.Application of exogenous BA affected the total levels of cytokinins of the two tissue lines in different ways. The cytokinin content increased by 1.7‐ and 1.5‐fold in ipt‐transformed tissues 6 and 12 h after BA application, respectively, while it declined in the non‐transformed control by 1.6‐ to 2.0‐fold between 3 and 12 h after BA application. The increase in cytokinin content in the ipt callus is due to an increase of zeatin‐ and dihydrozeatin‐type cytokinins (nucleotides, ribosides and free bases) leading to an enhanced accumulation of O‐glucosides after 12 h. Following BA treatment, the cytokinin oxidase activity increased up to 1.8‐fold in ipt‐transformed and 1.6‐fold in non‐transformed tissues. The levels of isopentenyl‐type cytokinins were near the detection limit; however, the enhancement of cytokinin oxidase activity after BA treatment in both tissue lines was correlated with the content of preferred substrate of the enzyme, N6‐(Δ2‐isopentenyl)adenosine.
Effects of increased UV‐B radiation and elevated levels of tropospheric ozone on physiological processes in European beech (Fagus sylvatica)
Authors: Zeuthen Jakob , Mikkelsen Teis N. , Paludan‐Müller Georg , Ro‐Poulsen Helge 
Published: May 2006

As a consequence of the ongoing reduction of the stratospheric ozone layer, the vegetation is exposed to increasing levels of UV‐B radiation (280–320 nm). In addition ozone in the troposphere is a pollutant and also capable of affecting the photosynthetic machinery.In this study, 5‐year‐old European beech trees were exposed from 1 July to October 1993 to two levels of UV‐B radiation and two levels of ozone, alone and in combination, in open‐top chambers equipped with lamps. The simulated UV‐B levels corresponded to either clear sky ambient level or a 14% decrease in the stratospheric ozone column over eastern Denmark, resulting in a 23% difference in biologically effective UV‐B (UV‐BBE) irradiance. The maximum UV‐Bbe given was 8.61 kJ m−2 day−1. The ozone levels were either the ambient (average 32 nl l−1) or ambient with ozone addition (average resulting concentration 71 nl l−1). Compared to the control treatment (ambient UV‐B, ambient O3) the elevated levels of UV‐B and O3 affected the trees negatively, expressed as declines in net photosynthesis (Pn), stomatal conductance (gs), chlorophyll fluorescence (Fv/Fm) and acceleration of senescence, measured as yellowing of the leaves. The UV‐B treatment induced stomatal closure before the other treatments did. The magnitude of the decreases in Pn and Fv/Fm occurred in the order: control <UV‐B <O3 <UV‐B and O3. Compared to the control, the combination treatment with high levels accelerated the visual senescence processes by ca 27 days, while for high UV‐B and O3 alone, there was an acceleration by 14 and 21 days, respectively. UV‐B and O3 in combination enhanced the negative effects compared with UV‐B and O3 alone. The Pn and Fv/Fm results could be related to this acceleration process. The chamber effect was investigated by comparing the control plots with a plot without open‐top chamber. The trees in the chambers showed a higher Pn and Fv/Fm and a 14‐day delayed senescence compared to the trees outside, probably caused by higher temperatures, a more protected environment and altered conditions inside the chambers.
The Development of Same‐ and Opposite‐Sex Social Relations Among Adolescents: An Analogue Study
Authors: Hops Hyman , Alpert Anthony , Davis Betsy 
Published: May 2006

AbstractThe present study, utilizing an analogue procedure and a short‐term longitudinal design, examined the relative strength of observed behavior in predicting mid‐ to late‐adolescents' ratings of that behavior. Direct observations were made of 89 adolescents during videotaped problem‐solving interactions with groups of unfamiliar peers. Within 6‐member peer groups, counterbalanced for gender, the adolescents participated in a series of problem‐solving and discussion tasks. Peer groups met one hour daily for six consecutive days. The interactions were coded with the LIFE code and three behavioral constructs were assessed: facilitative, problem‐solving, and aggressive. Same‐ and opposite‐sex peer ratings of three factors, sociable, aggressive, and withdrawn, were obtained at the end of the second and sixth days. Hierarchical linear modeling analyses revealed that same‐sex sociability ratings were predicted by prosocial behaviors of both girls and boys whereas boys' aggressive behavior also predicted these ratings across gender. In contrast, aggressive behavior displayed by girls predicted boys' ratings of girls' aggression. Withdrawal ratings were related to low levels of all behaviors. The results provide further evidence that peer perceptions may be driven by characteristics associated with gender that have been determined by culturally proscribed practices and socialization efforts.
Observed and Reported Psychological and Physical Aggression in Young, At‐Risk Couples
Authors: Capaldi Deborah M. , Crosby Lynn 
Published: May 2006

AbstractThe occurrence of observed and reported physical and psychological aggression was examined for young, at‐risk mostly unmarried couples using reports from both partners and observational data. It was predicted that males higher in antisocial behavior would be more likely to have an antisocial partner and that antisocial behavior would predict aggression toward the partner. The prevalence of reported physical aggression was comparable to that found for prior studies and was generally higher for the young women than the young men. Observed aggression was significantly associated with reported aggression, and psychological aggression was associated with physical aggression. Assortative partnering by antisocial behavior was found. The young man's aggression toward his partner was predicted particularly by his antisocial behavior, whereas that of the young woman was predicted by depressive symptoms and low self‐esteem. Relationship satisfaction was associated with the occurrence of psychological aggression but not of physical aggression.
Children's Friends and Behavioral Similarity in Two Social Contexts
Authors: Poulin François , Cillessen Antonius H. N. , Hubbard Julie A. , Coie John D. , Dodge Kenneth A. , Schwartz David 
Published: May 2006

AbstractThe general purpose of this study was to examine similarity between friends with respect to behavior. The specific goals were to consider; 1) different sources of evaluation (peer ratings and direct observations); 2) different social contexts (classroom and play group); and 3) different subtypes of aggressive behavior (proactive and reactive aggression). In the first phase of the study, sociometric assessments and peer evaluations of behavior were conducted in the school setting with third‐grade boys and girls (n ‐ 268). In the second phase, a subsample of boys participated in a series of play group sessions (n = 66). Direct observations and peer ratings of children's behavior were conducted in those sessions. Results showed in both social contexts a tendency towards similarity among friends, especially with respect to aggressive behavior. Separate analyses for subtypes of aggressive behavior revealed that the similarity hypothesis applied for proactive aggression but not for reactive aggression.
Adult Problem Solving: Contributor to Parenting and Child Outcomes in Divorced Families
Authors: Forgatch Marion S. , DeGarmo David S. 
Published: May 2006

AbstractThis cross‐sectional study extends child outcome models by focusing on factors in the adult social domain as contributors to parenting. The sample included 138 divorced mothers, their focal sons, and their support confidants assessed approximately 5 years after marital separation. The multimethod latent variable analysis tested a hypothesized progression stating observed confidant support would enhance problem solving outcomes achieved by mothers and confidants. Resolving parenting and personal issues for the mother was expected to benefit parenting practices (i.e., monitoring, discipline, and mother/child problem solving), which in turn would predict a macro level measure of child antisocial behavior. Analysis of the simplex model supported the progression. The final model explained 36% of the variance in antisocial behavior, 15% of the variance in parenting, and 53% of the variance in problem solving outcome. Dyads with cohabiting partners scored higher on problem solving outcomes than did dyads with friends or family members. The model is discussed in the context of social interactional and social learning theory.
The Protease Complex Consisting of Dipeptidyl Peptidase IV and Seprase Plays a Role in the Migration and Invasion of Human Endothelial Cells in Collagenous Matrices
Authors: Ghersi Giulio , Zhao Qiang , Salamone Monica , Yeh Yunyun , Zucker Stanley , Chen Wen-Tien 
Published: May 2006

AbstractDipeptidyl peptidase IV (DPP4/CD26) and seprase/fibroblast activation protein α are homologous type II transmembrane, homodimeric glycoproteins that exhibit unique prolyl peptidase activities. Human DPP4 is ubiquitously expressed in epithelial and endothelial cells and serves multiple functions in cleaving the penultimate positioned prolyl bonds at the NH2 terminus of a variety of physiologically important peptides in the circulation. Recent studies showed a linkage between DPP4 and down-regulation of certain chemokines and mitogenic growth factors, and degradation of denatured collagens (gelatin), suggesting a role of DPP4 in the cell invasive phenotype. Here, we found the existence of a novel protease complex consisting of DPP4 and seprase in human endothelial cells that were activated to migrate and invade in the extracellular matrix in vitro. DPP4 and seprase were coexpressed with the three major protease systems (matrix metalloproteinase, plasminogen activator, and type II transmembrane serine protease) at the cell surface and organize as a complex at invadopodia-like protrusions. Both proteases were colocalized at the endothelial cells of capillaries, but not large blood vessels, in invasive breast ductal carcinoma in vivo. Importantly, monoclonal antibodies against the gelatin-binding domain of DPP4 blocked the local gelatin degradation by endothelial cells in the presence of the major metallo- and serine protease systems that modified pericellular collagenous matrices and subsequent cell migration and invasion. Thus, we have identified a novel mechanism involving the DPP4 gelatin-binding domain of the DPP4-seprase complex that facilitates the local degradation of the extracellular matrix and the invasion of the endothelial cells into collagenous matrices. (Cancer Res 2006; 66(9); 4652-61)
Combinational FLt3 Ligand and Granulocyte Macrophage Colony-Stimulating Factor Treatment Promotes Enhanced Tumor Infiltration by Dendritic Cells and Antitumor CD8+ T-Cell Cross-priming but Is Ineffective as a Therapy
Authors: Berhanu Aklile , Huang Jian , Alber Sean M. , Watkins Simon C. , Storkus Walter J. 
Published: May 2006

Abstract
Dendritic cells play significant roles in the development and maintenance of antitumor immune responses. Therapeutic recruitment of dendritic cells into the tumor microenvironment has the potential to result in enhanced antitumor T-cell cross-priming against a broad array of naturally processed and presented tumor-associated antigens. We have observed that the treatment of BALB/c mice bearing syngeneic CMS4 sarcomas with the combination of recombinant Flt3 ligand and recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) for five sequential days is sufficient to optimize the number of tumor-infiltrating dendritic cells (TIDC). However, despite the significant increase in the number of TIDCs, the therapeutic benefit of Flt3 ligand and GM-CSF treatment is minimal. Therapy-associated TIDCs do not exhibit a “suppressed” or “suppressor” phenotype in vitro, and their enhanced numbers in cytokine-treated mice were associated with increased levels of peripheral antitumor CD8+ T effector cells and with an augmented population of CD8+ tumor-infiltrating lymphocytes (TIL). These data suggest that Flt3 ligand + GM-CSF therapy of murine tumors fails at a mechanistic point that is downstream of specific T-cell priming by therapy-induced TIDCs and the recruitment of these T cells into the tumor microenvironment. Based on the enhanced infiltration of tumors by CD4+CD25+ TIL in Flt3 ligand + GM-CSF–treated mice, this could reflect the dominant influence of regulatory T cells in situ. (Cancer Res 2006; 66(9): 4895-903)