bluuebunny/crossref_metadata_2025_split huggingface dataset:
Xylem sap flow as a major pathway for oxygen supply to the sapwood of birch (Betula pubescens Ehr.)
Authors: GANSERT D. 
Published: November 2003

ABSTRACTThe role of xylem sap flow as an aqueous pathway for oxygen supply to the wood parenchyma of Betula pubescens saplings was investigated. Using micro‐optode sensors the oxygen status of the sapwood was quantified in relation to mass flow of xylem sap. Sap flow was gradually reduced by an increasing oxygen depletion in the root space. The effect of sap flow on radial O2 transport between stem and atmosphere was assessed by a stoichiometrical approach between respiratory CO2 production and O2 consumption. Restriction of sap flow set in 36.5 h after the onset of O2 depletion, and was complete after 71 h. Interruption of sap flow drastically increased the O2 deficit in the sapwood to 70%. Sap flow contributed about 60% to the total oxygen supply to the sapwood. Diurnal O2 flow rates varied between 3 and 6.3 nmol O2 m−2 leaf area (LA)  s−1 during night‐ and daytime, respectively. Maximum O2 flow rates of 20 nmol O2 m−2 LA s−1 were reached at highest sap flow rates of 5.7 mmol H2O m−2 LA s−1. Sap flow not only affected the oxygen status of the sapwood but also had an effect on radial O2 transport between stem and atmosphere.
Disentangling CO2 fluxes: direct measurements of mesocosm‐scale natural abundance 13CO2/12CO2 gas exchange, 13C discrimination, and labelling of CO2 exchange flux components in controlled environments
Authors: SCHNYDER H. , SCHÄUFELE R. , LÖTSCHER M. , GEBBING T. 
Published: November 2003

ABSTRACTA 13C/12C mass spectrometer was interfaced with a open gas exchange system including four growth chambers to investigate CO2 exchange components of perennial ryegrass (Lolium perenne L.) stands. Chambers were fed with air containing CO2 with known δ13C (δCΟ2−2.6 or −46.8‰). The system did not fractionate C isotopes and no extraneous CO2 leaked into chambers. The on‐line 13C discrimination (Δ) of ryegrass stands in light was independent of δCΟ2 when δCΟ2 was constant. The δ of CO2 exchanged by the stands in light (δNd) and darkness (δRn) differed by 0.7‰, suggesting some Δ in dark respiration at the stand‐level. However, Δ decreased by ∼ 10‰ when δCΟ2 was switched from −46.8 to −2.5‰, and increased by ∼ 10‰ following a shift from −2.6 to −46.7‰ due to isotopic disequilibria between photosynthetic and respiratory fluxes. Isotopic imbalances were used to assess (non‐photorespiratory) respiration in light and the replacement of the respiratory substrate pool(s) by new photosynthate. Respiration was partially inhibited by light, but increased during the light period and decreased in darkness, in association with temperature changes. The labelling kinetics of respiratory CO2 indicated the existence of two major respiratory substrate pools: a fast pool which was exchanged within hours, and a slow pool accounting for ∼ 60% of total respiration and having a mean residence time of 3.6 d.
Hydrogen fertilization of soils – is this a benefit of legumes in rotation?
Authors: DONG Z. , WU L. , KETTLEWELL B. , CALDWELL C. D. , LAYZELL D. B. 
Published: November 2003

ABSTRACTHydrogen gas (H2) is an obligate byproduct of the N2‐fixing enzyme, nitrogenase, claiming about 5–6% of the crops’ net photosynthesis but most, if not all of the H2 lost from nodules is oxidized by the soil surrounding the root system of the plant. When soils not recently used to support the growth of legumes were exposed to H2 gas at a rate and duration similar to that of soil adjacent to legume nodules, the fertility of the soil was enhanced in comparison with soil treated with air. Under growth‐chamber and field conditions, H2‐treated soils improved the growth performance of spring wheat, canola, barley and soybean (non‐symbiotic) when compared with untreated soils or with soils pretreated with air. The dry weights of 4‐ to 7‐week‐old plants were 15–48% greater in the H2‐treated soil, and in barley and spring wheat, tiller number of 7‐week‐old plants were 36 and 48% greater in the H2‐treated soils. These findings may contribute to an explanation for the persistence of H2 evolving associations in agricultural legume symbioses selected for high yields (Uratsu et al., Crop Science 22, 600–602, 1982) and suggest that it may be possible to isolate, identify and culture the micro‐organisms that are responsible for at least some of the benefits of legumes in crop rotation.
Characterization of a novel zinc metalloprotease involved in degrading targeting peptides in mitochondria and chloroplasts
Authors: Moberg Per , Ståhl Annelie , Bhushan Shashi , Wright Sarah J. , Eriksson AnnaCarin , Bruce Barry D. , Glaser Elzbieta 
Published: November 2003

SummaryWe have recently isolated and identified a novel mitochondrial metalloprotease, pre‐sequence protease (PreP) from potato and shown that it degrades mitochondrial pre‐sequences. PreP belongs to the pitrilysin protease family and contains an inverted zinc‐binding motif. To further investigate the degradation of targeting peptides, we have overexpressed the Arabidopsis thaliana homologue of PreP, zinc metalloprotease (Zn‐MP), in Escherichia coli. We have characterized the recombinant Zn‐MP with respect to its catalytic site, substrate specificity and intracellular localization. Mutagenesis studies of the residues involved in metal binding identified the histidines and the proximal glutamate as essential residues for the proteolytic activity. Substrate specificity studies showed that the Zn‐MP has the ability to degrade both mitochondrial pre‐sequences and chloroplastic transit peptides, as well as other unstructured peptides. The Zn‐MP does not recognize an amino acid sequence per se. Immunological studies and proteolytic activity measurements in isolated mitochondria and chloroplasts revealed the presence of the Zn‐MP in both organelles. Furthermore, the Zn‐MP was found to be dually imported to both mitochondria and chloroplasts in vitro. In summary, our data show that the Zn‐MP is present and serves the same function in chloroplasts as in mitochondria – degradation of targeting peptides.
Functional analysis of barley RAC/ROP G‐protein family members in susceptibility to the powdery mildew fungus
Authors: Schultheiss Holger , Dechert Cornelia , Kogel Karl‐Heinz , Hückelhoven Ralph 
Published: November 2003

SummarySmall monomeric G‐proteins of the plant ras (rat sarcome oncogene product) related C3 botulinum toxin substrate (RAC)/Rho of plants (ROP) family are molecular switches in signal transduction of many cellular processes. RAC/ROPs regulate hormone effects, subcellular gradients of Ca2+, the organisation of the actin cytoskeleton and the production of reactive oxygen intermediates. Therefore, we followed a genetic bottom‐up strategy to study the role of these proteins during the interaction of barley (Hordeum vulgare L.) with the fungal biotrophic pathogen Blumeria graminis f.sp. hordei (Bgh). We identified six barley RAC/ROP proteins and studied their gene expression. Five out of six Rac/Rop genes were expressed constitutively in the leaf epidermis, which is the site of interaction with Bgh. None of the genes showed enhancement of mRNA abundance after inoculation with Bgh. After microprojectile mediated transformation of single barley epidermal cells with constitutively activated mutant RAC/ROP proteins, we found an RAC/ROP‐specific enhancement of pathogen accessibility, tagging HvRACB, HvRAC3 and HvROP6 as host proteins potentially involved in the establishment of susceptibility to Bgh. Confocal laser scanning microscopy (CLSM) of green fluorescent protein (GFP):HvRAC/ROP‐transformed cells revealed varying strengths of plasma membrane association of barley RAC/ROPs. The C‐terminal CAAX motif for presumable prenylation or the C‐terminal hypervariable region (HVR), respectively, were required for membrane association of the RAC/ROPs. Proper intracellular localisation was essential for HvRACB and HvRAC3 function. Together, our data support the view that different paths of host signal transduction via RAC/ROP G‐proteins are involved in processes supporting parasitic entry into epidermal host cells.
Analysis of the Arabidopsis nuclear proteome and its response to cold stress
Authors: Bae Min Seok , Cho Eun Ju , Choi Eun‐Young , Park Ohkmae K. 
Published: November 2003

SummaryThe nucleus is the subcellular organelle that contains nearly all the genetic information required for the regulated expression of cellular proteins. In this study, we comprehensively characterized the Arabidopsis nuclear proteome. Nuclear proteins were isolated and analyzed using two‐dimensional (2D) gel electrophoresis and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). Approximately 500–700 spots were detected in reference 2D gels of nuclear proteins. Proteomic analyses led to the identification of 184 spots corresponding to 158 different proteins implicated in a variety of cellular functions. We additionally analyzed the changes in the nuclear proteome in response to cold stress. Of the 184 identified proteins, 54 were up‐ or downregulated with a greater than twofold change in response to cold treatment. Among these, six proteins were selected for further characterization. Northern analysis data revealed that gene expression of these proteins was also altered by cold stress. Following transient expression in BY‐2 protoplasts, two proteins were detected in both the cytoplasm and the nucleus and four others were detected exclusively in the nucleus, which correlates well with the nuclear localization patterns of the proteomic data. Our study provides an initial insight into the Arabidopsis nuclear proteome and its response to cold stress.
CUC1 gene activates the expression of SAM‐related genes to induce adventitious shoot formation
Authors: Hibara Ken‐ichiro , Takada Shinobu , Tasaka Masao 
Published: November 2003

Summary CUP‐SHAPED COTYLEDON (CUC)1 encodes members of the NAC family. These are functionally redundant genes that are involved in shoot apical meristem (SAM) formation and cotyledon separation during embryogenesis in Arabidopsis. We analyzed transgenic plants overexpressing CUC1 (35S::CUC1). The cotyledons of these transgenic seedlings regularly had two basal lobes, small and round epidermal cells between the sinuses, and adventitious SAMs on the adaxial surface of this region. This suggests that CUC1 promotes adventitious SAM formation by maintaining epidermal cells in an undifferentiated state. In 35S::CUC1 cotyledons, the class I knotted‐like homeobox (KNOX) genes, including SHOOT MERISTEMLESS (STM) and BREVIPEDICELLUS (BP), which are involved in SAM formation and/or maintenance, were ectopically expressed before adventitious SAM formation. In stm mutants, ectopic expression of CUC1 could not induce adventitious SAMs, whereas they continued to be observed in bp mutants. These results suggest that STM, but not BP, is necessary for the formation of adventitious SAMs in 35S::CUC1 cotyledons. Furthermore, we examined the relationship between CUC1 and ASYMMETRIC LEAVES (AS)1 and AS2. The as1 and as2 mutations genetically enhance 35S::CUC1 phenotypes even in the absence of STM function. Interestingly, the as1 mutation can partially rescue the mutant vegetative development phenotypes in the cuc1 cuc2 double mutant. Our results suggest that CUC1 positively regulates SAM formation not only through STM but also through an STM‐independent pathway that is negatively regulated by AS1 and AS2.
Unexpected presence of fructan 6‐exohydrolases (6‐FEHs) in non‐fructan plants: characterization, cloning, mass mapping and functional analysis of a novel ‘cell‐wall invertase‐like’ specific 6‐FEH from sugar beet (Beta vulgaris L.)
Authors: Van den Ende Wim , De Coninck Barbara , Clerens Stefan , Vergauwen Rudy , Van Laere André 
Published: November 2003

SummaryAbout 15% of flowering plant species synthesize fructans. Fructans serve mainly as reserve carbohydrates and are subject to breakdown by plant fructan exohydrolases (FEHs), among which 1‐FEHs (inulinases) and 6‐FEHs (levanases) can be differentiated. This paper describes the unexpected finding that 6‐FEHs also occur in plants that do not synthesize fructans. The purification, characterization, cloning and functional analysis of sugar beet (Beta vulgaris L.) 6‐FEH are described. Enzyme activity measurements during sugar beet development suggest a constitutive expression of the gene in sugar beet roots. Classical enzyme purification followed by in‐gel trypsin digestion and mass spectrometry (quadruple‐time‐of‐flight mass spectrometry (Q‐TOF) MS) led to peptide sequence information used in subsequent RT‐PCR based cloning. Levan‐type fructans (β‐2,6) are the best substrates for the enzyme, while inulin‐type fructans (β‐2,1) and sucrose are poorly or not degraded. Sugar beet 6‐FEH is more related to cell wall invertases than to vacuolar invertases and has a low iso‐electric point (pI), clearly different from typical high pI cell wall invertases. Poor sequence homology to bacterial or fungal FEHs makes an endophytic origin highly unlikely. The functionality of the 6‐FEH cDNA was further demonstrated by heterologous expression in Pichia pastoris. As fructans are absent in sugar beet, the role of 6‐FEH in planta is not obvious. Like chitinases and β‐glucanases hydrolysing cell‐surface components of fungal plant pathogens, a straightforward working hypothesis for further research might be that plant 6‐FEHs participate in hydrolysis (or prevent the formation) of levan‐containing slime surrounding endophytic or phytopathogenic bacteria.
Disrupted mucosal barrier in quiescent ulcerative colitis: effect of metronidazole and of a symbiotic preparation in a pilot cross‐over study
Authors: MAROTTA F , NAITO Y , TAJIRI H , LIGHTHOUSE J , YOSHIOKA M , OGLIARI C , BOZZANI A , FUJI H , FESCE E 
Published: November 2003

OBJECTIVES:  The aims of the present study were to investigate the plasma concentration of endotoxin in patients with inflammatory bowel disease (IBD), the effect of metronidazole (MNZ) and of symbiotics on that concentration, and the relationship to IBD activity.METHODS:  The study group comprised 26 patients with quiescent ulcerative colitis (UC), all of whom were on maintenance mesalazine treatment (1200− 2400 mg/day). The control group comprised 15 subjects. Blood samples were taken from all study subjects to measure: routine blood chemistry, endotoxin concentration, lipopolysaccharide binding protein (LBP) and macrophage‐colony stimulating factor (M‐CSF). All the IBD patients were randomly enrolled for a 2‐week oral daily treatment regimen with either MNZ (250 mg t.i.d.) or the symbiotic mixture SCM‐III (Lactobacillus acidophilus, L. helveticus and Bifidobacteria brevis in an ion‐ and vitamin‐enriched medium; 3 mL t.i.d.). Following a 6‐week washout period during which the patients continued their maintenance treatment, the cross‐over study of the new treatments was begun. Blood parameters were checked at entry and 2 weeks after each treatment schedule.RESULTS:  The concentration of endotoxin level in the UC patients, as a whole, was comparable with that of the control subjects. However, a separate group of patients with long‐standing disease and pancolitis showed a statistically significant increase in toxin. SCM‐III, but not MNZ, normalized this parameter. There was no statistical change in LBP and plasma endotoxin‐inhibiting capacity in the IBD patients. The M‐CSF concentration was increased in the UC group, particularly in the pancolitis subgroup. SCM‐III, but not MNZ, significantly decreased the M‐CSF concentration in the UC patients, but there was only an insignificant trend toward decrease in the subgroup. There was a significant correlation between M‐CSF and endotoxin in the pancolitis subgroup (r: 0.74, P < 0.05).CONCLUSIONS:  Although these preliminary results need to be treated with caution, they suggest the effectiveness of long‐term administration of probiotics/symbiotics in conjunction with standard treatment in patients with UC, even if there is not gross disease activity.
A preliminary study of liver cells derived from bone marrow
Authors: ZHU Wei , QIU De Kai , WANG Ya Dong , LAI Zhuo Shen 
Published: November 2003

OBJECTIVE:  To investigate whether hepatocytes can be derived from bone marrow cells in vivo.METHODS:  A cohort of lethally irradiated BALB/C female mice received whole bone marrow transplants from age‐matched male donors and were killed at 1, 2, 4 and 8 weeks post transplantation. Fluorescence in situ hybridization (FISH) for the Y‐chromosome was performed using liver tissue.RESULTS:  A few Y‐chromosome positive hepatocytes were found in the liver tissues at 2 months post transplantation.CONCLUSION:  Hepatocytes can be derived from bone marrow cells after transplantation in lethally irradiated mice without severe acute hepatic injury.
Impact of parvovirus H‐1 infection on the expression of genes related to the MAPK signaling pathway in gastric cancer cells
Authors: RAN Zhi Hua , LIU Jiong , FENG Ying , ZOU Jian , XIAO Shu Dong 
Published: November 2003

OBJECTIVE:  To investigate the cell cytotoxicity induced by the antineoplastic parvovirus H‐1 in gastric carcinoma cells.METHODS:  The cytotoxicity of the H‐1 virus in the gastric cancer cell strain HGC27 was measured by MTT test and FACS analysis. The mRNA expressions of genes related to the mitogen‐activated protein kinase (MAPK) signaling transduction pathway were measured by RT‐PCR in HGC27 cells infected by the H‐1 virus.RESULTS:  HGC27 cells were sensitive to the cytotoxicity of the H‐1 virus, although the cell cycle distribution was not significantly changed. The RT‐PCR results showed that 48 h after H‐1 virus infection of HGC27 cells the expression of creb was increased and that of erk1, stat2, p38‐γ, mek2, B‐raf and mtk1 was remarkably decreased. However, the expression of each of jnk2, ets and erk2 was unchanged.CONCLUSIONS:  The mechanism of the cytotoxic effect of parvovirus H‐1 in HGC27 cells might be interference with specific cellular signaling trans­duction pathways, which would induce cell death. A modified and reconstructed parvovirus H‐1 could be a very useful tool for antitumor biochemical therapy.
REM sleep enhancement induced by different procedures improves memory retention in rats
Authors: Wetzel Wolfram , Wagner Thomas , Balschun Detlef 
Published: November 2003

AbstractGrowing evidence supports the idea that sleep following learning is critically involved in memory formation. Recent studies suggest that information acquired during waking is reactivated and possibly consolidated during subsequent sleep, especially during rapid‐eye movement (REM) or paradoxical sleep (PS). Critical reviews, however, have questioned PS and memory relationships, particularly because of shortcomings of the PS deprivation paradigm applied in many studies. Therefore, in the present study we used an opposite strategy, i.e. we investigated the effects of PS enhancement on memory retention. In three experiments, we found that selective PS enhancement, induced by different procedures after discrimination training in rats, results in increased retention tested 24 h later. Moreover, calculated in all animals (n = 61), there was a highly significant correlation between post‐training PS values and retention scores. Our results suggest that an experimentally induced increase of PS after learning facilitates memory consolidation.
Excitotoxic lesions of the tegmental pedunculopontine nucleus impair copulation in naive male rats and block the rewarding effects of copulation in experienced male rats
Authors: Kippin Tod E. , Van Der Kooy Derek 
Published: November 2003

AbstractThe tegmental pedunculopontine nucleus (TPP) of the brainstem mediates food reward in food‐sated animals and opiate reward in drug‐naive animals. In the present study, we examine the effect of excitotoxic lesions of the TPP on sexual behaviour in naive and experienced male rats. Male, Long‐Evans rats received either 0.25 µL injections of NMDA (4.2 µg/side) or vehicle (shams) into the TPP. In sexually naive males, complete bilateral TPP lesions decreased all measure of copulation (i.e. mounts, intromissions and ejaculations), prevented acquisition of conditioned sexual excitement, decreased approach preference for a receptive female over a non‐receptive one, and decreased non‐contact erections; unilateral or bilateral posterior‐sparing TPP lesions did not affect any of these measures. Conversely, in sexually experienced males, lesions not only failed to disrupt copulation, but also increased conditioned sexual excitement, decreased post‐ejaculatory interval and blocked the effect of prolonged copulation on conditioned sexual excitement. Following differential pairing of distinctive environments with and without copulation, sham males with sexual experience displayed a significant preference for the environment paired with copulation, whereas the lesion males with sexual experience displayed a significant aversion for the environment paired with copulation. These findings indicate that the TPP is critical for the acquisition of copulation in naive males and mediates the rewarding consequences of copulation in experienced males. Together these findings demonstrate that the TPP mediates sexual reward, but that sexual experience is not sufficient to produce a deprivation state.
Dopamine depresses cholinergic oscillatory network activity in rat hippocampus
Authors: Weiss Torsten , Veh Rüdiger W. , Heinemann Uwe 
Published: November 2003

AbstractThe dopaminergic neuronal system is implicated in cognitive processes in a variety of brain regions including the mesolimbic system. We have investigated whether dopamine also affects synchronized network activity in the hippocampus, which has been ascribed to play a pivotal role in memory formation. Gamma frequency (20–80 Hz) oscillations were induced by the cholinergic agonist carbachol. Oscillatory activity was examined in area CA3 of Wistar rat hippocampal slices, employing field potential and intracellular recordings. Application of carbachol initiated synchronized population activity in the gamma band at 40 Hz. Induced gamma activity persisted over hours and required GABAA receptors. Dopamine reversibly decreased the integrated gamma band power of the carbachol rhythm by 62%, while its frequency was not changed. By contrast, individual pyramidal cells recorded during carbachol‐induced field gamma activity exhibited theta frequency (5–15 Hz) membrane potential oscillations that were not altered by dopamine. The dopamine effect on the field gamma activity was mimicked by the D1 receptor agonist SKF‐383393 and partially antagonized by the D1 antagonist SCH‐23390. Conversely, the D2 receptor agonist quinpirole failed to depress the oscillations, and the D2 antagonist sulpiride did not prevent the suppressive dopamine effect. The data indicate that dopamine strongly depresses cholinergic gamma oscillations in area CA3 of rat hippocampus by activation of D1‐like dopamine receptors and that this effect is most likely mediated via impairment of interneurons involved in generation and maintenance of the carbachol‐induced network rhythm.