bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence of a dramatic decline of the red-necked ostrich Struthio camelus camelus in the Aïr and Ténéré National Nature Reserve, Niger
Authors: Ostrowski Stéphane , Massalatchi Mahaman Sani , Mamane Mamadou 
Published: March 2003

AbstractIn 1990 the population of the red-necked ostrich Struthio camelus camelus in the Aïr and Ténéré National Nature Reserve, Niger, was estimated at c. 1600 individuals. During a 14-day survey carried out in the protected area in October and November 2000 no evidence of recent occurrence of ostriches was found, and it appears that the population size has dramatically declined in its favoured habitat. The species seems to have been severely persecuted during the civil war of 1991–1997. Although a small population had remained in the protected area after the conflict, the occurrence of further poaching suggests that remaining individuals are threatened with extirpation.
Cellular responses to Schistosoma japonicum cathepsin D aspartic protease
Authors: Verity Christiana K. , Mcmanus Donald P. , Brindley Paul J. 
Published: March 2003

Summary Lymphocyte proliferation and cytokine production were measured in groups of mice vaccinated (but not subsequently challenge infected) with recombinant forms of Schistosoma japonicum cathepsin D aspartic protease, rSjASP1 (expressed in bacteria; enzymatically inactive) and rSjASP2 (expressed in insect cells; enzymatically active). Both forms of the schistosome enzyme induced significant proliferation of splenocytes recovered from vaccinated mice, and expression of interferon (IFN)‐γ, interleukin (IL)‐4 and IL‐10 mRNA in these cells was detected using reverse transcriptase‐polymerase chain reaction. Secretion of IFN‐γ, IL‐4 and IL‐10 by splenocytes from vaccinated mice was confirmed and quantified using enzyme‐linked immunosorbent assay. IFN‐γ was the most abundant cytokine produced, followed by IL‐4 and IL‐10 in rank order. These findings indicated that vaccination of mice with the schistosome protease induces a mixed Th1/Th2 cytokine response, which may explain the modest level of protection after challenge infection in cathepsin d‐vaccinated mice, reported previously.
Increased levels of interleukin‐12 in Plasmodium falciparum malaria: correlation with the severity of disease
Authors: Malaguarnera Lucia , Imbesi Rosa Maria , Pignatelli Salvatore , Simporè Jacques , Malaguarnera Mariano , Musumeci Salvatore 
Published: March 2003

Summary Interleukin (IL)‐12, produced by mononuclear phagocytes, activates the T‐helper 1 (Th1) cells and helps, as a mediator, the innate immune response to intracellular microbes. In Plasmodium falciparum infection, this proinflammatory cytokine has immunoregulatory functions with effects on the immune response to the blood stage of disease, but also induces protection and reduces malarial anaemia. In this study, the levels of IL‐12 were determined in 73 African children, aged 2–144 months (median 19·5 months), who had severe or mild P. falciparum malaria. IL‐12 was determined using the enzyme‐linked immunosorbent assay. The levels of IL‐12 were found to be significantly elevated (21·6 ± 18·3 pg/ml) in patients who suffered less severely from the disease. In contrast, the levels of IL‐12 were found to be lower (13·1 ± 7·11 pg/ml) in patients who suffered more severely from the disease.
Regulation by ABA of osmotic‐stress‐induced changes in protein synthesis in tomato roots
Authors: Jin S. , Chen C. C. S. , Plant A. L. 
Published: March 2003

ABSTRACTPolypeptide synthesis and accumulation were examined in the roots of tomato seedlings exposed to a polyethylene glycol‐imposed water deficit stress. In these roots, the synthesis of a number of polypeptides was induced, while that of several others was enhanced or repressed. To examine the role played by abscisic acid (ABA) in co‐ordinating the accumulation of these proteins, water‐deficit‐stress‐responsive polypeptide synthesis was investigated in the roots of the ABA‐deficient mutant flacca. In the roots of this mutant, the ability to accumulate a complete set of water‐deficit‐stress‐responsive polypeptides was impaired, indicating that ABA is required for their synthesis. The role of ABA was further examined by exposing the roots of both genotypes to exogenous ABA, which, with one exception, elicited the accumulation of all water‐deficit‐stress‐responsive proteins. Polyethylene glycol‐induced polypeptide accumulation was accompanied by a 1·6‐fold increase in the level of endogenous ABA in the roots of wild‐type plants and a 5‐fold increase in the roots of flc. Thus, although the absolute level was lower than that of the wild‐type, flc has the capacity to accumulate ABA in its roots. When fluridone was used to prevent the biosynthesis of ABA, the accumulation of several water‐deficit‐stress‐responsive polypeptides was reduced further. The synthesis of polypeptides was also examined in the roots of salt‐treated seedlings. Salt altered the accumulation of several polypeptides, all of which were previously observed in water‐deficit‐stressed roots, indicating that their synthesis was the result of the osmotic component of the salt stress. However, the accumulation of these polypeptides was not impaired in flc roots, indicating that the role played by ABA in regulating their accumulation in salt‐and polyethylene glycol‐treated roots differs. As such, salt‐ and water‐deficit‐stress‐induced changes in gene expression may be effected by different mechanisms, at least at the level of polypeptide accumulation.
Characterization and possible redox regulation of the purified calmodulin‐dependent NAD+ kinase from Lycopersicon pimpinellifolium
Authors: Delumeau O. , Renard M. , Montrichard F. 
Published: March 2003

ABSTRACTThe soluble and calmodulin (CaM)‐dependent NAD+ kinase from Lycopersicon pimpinellifolium was previously shown to be largely inactivated in isolated cells exposed to a short‐term NaCl stress (Delumeau, Morère‐Le Paven, Montrichard, Laval‐Martin (2000) Plant Cell & Environment 23, 329–336). Nevertheless, the activity could be restored by adding a high dithiothreitol concentration to the protein extract, suggesting that the salt stress triggers an oxidation of the enzyme which leads to its inactivation. It was then interesting to investigate the effect of thiol‐modifying reagents and disulphide reductants on the activity of L. pimpinellifolium NAD+ kinase. A three‐step purification procedure was then established and allowed isolation of the enzyme which exists under two forms: a monomer and a dimer of a 56 kDa subunit, characterized, respectively, by pIs of 6·8 and 7·1. Isolated NAD+ kinase had a high affinity for CaM, half saturation being obtained for 7 ng mL−1 bovine CaM. The activity of NAD+ kinase was strongly inhibited by thiol‐modifying reagents and oxidized glutathione. NAD+ kinase was also found to be air‐inactivated, the residual activity being stimulated by disulphide reductants. The most efficient of them is reduced thioredoxin from Escherichia coli which induced a five‐fold increase in activity and restored 80% of the initial activity. These results which can be related to those previously observed in vivo suggest that the activity of the L. pimpinellifolium NAD+ kinase, besides its dependence on CaM, is also dependent on the reduction state of the protein which could be regulated by the thioredoxin h/NADP‐thioredoxin reductase system.
Cloning and characterization of an 18 kiloDalton protein in the roots of the perennial weed Taraxacum officinale Weber (Dandelion) which has allergen‐ and pathogenesis‐related protein properties
Authors: Xu X.‐Y. , Bewley J. D. , Greenwood J. S. 
Published: March 2003

ABSTRACTThe root of the persistent weed, dandelion (Taraxacum officinale Weber), contains a predominant 18 kDa protein which undergoes small seasonal fluctuations in amount, increasing in the late autumn months, and declining in the spring. This protein has been purified and found to consist of two major isoforms of pI 5·56 and pI 5·49. A full‐length cDNA has been obtained, coding for the pI 5·56 isoform, and the 156‐amino‐acid sequence deduced. The protein shows homologies in amino acid composition to several allergen and intracellular pathogenesis‐related proteins. The deduced protein does not contain a signal peptide nor any known organelle‐targeting sequences, and thus is likely to be cytosolic. Expression of the 18 kDa protein gene is exclusive to the roots and stem tissues; transcripts accumulate during the late autumn months, and decline in the early spring. Changes in the amount of protein in the root are much less. The mRNA for the 18 kDa protein is not present in the dry seed, but appears in the roots within 16–18 h from the start of imbibition, and is expressed constitutively thereafter. Although it is the predominant protein in dandelion roots, its properties are different from those commonly associated with vegetative storage proteins.
Regulation of root hair density by phosphorus availability in Arabidopsis thaliana
Authors: Ma Z. , Bielenberg D. G. , Brown K. M. , Lynch J. P. 
Published: March 2003

ABSTRACTWe characterized the response of root hair density to phosphorus (P) availability in Arabidopsis thaliana. Arabidopsis plants were grown aseptically in growth media with varied phosphorus concentrations, ranging from 1 mmol m−3 to 2000 mmol m−3 phosphorus. Root hair density (number of root hairs per mm of root length) was analysed starting at 7 d of growth. Root hair density was highly regulated by phosphorus availability, increasing significantly in roots exposed to low‐phosphorus availability. The initial root hairs produced by the radicle were not sensitive to phosphorus availability, but began to respond after 9 d of growth. Root hair density was about five times greater in low phosphorus (1 mmol m−3) than in high phosphorus (1000 mmol m−3) media. Root hair density decreased logarithmically in response to increasing phosphorus concentrations within that range. Root hair density also increased in response to deficiencies of several other nutrients, but not as strongly as to low phosphorus. Indoleacetic acid (IAA), the auxin transport inhibitor 2‐(p‐chlorophenoxy)‐2‐methylpropionic acid (CMPA), the ethylene precursor 1‐aminocyclopropane‐1‐carboxylic acid (ACC), and the ethylene synthesis inhibitor amino‐oxyacetic acid (AOA) all increased root hair density under high phosphorus but had very little effect under low phosphorus. Low phosphorus significantly changed root anatomy, causing a 9% increase in root diameter, a 31% decrease in the cross‐sectional area of individual trichoblasts, a 40% decrease in the cross‐sectional area of individual atrichoblasts, and 45% more cortical cells in cross‐section. The larger number of cortical cells and smaller epidermal cell size in low phosphorus roots increased the number of trichoblast files from eight to 12. Two‐thirds of increased root hair density in low phosphorus roots was caused by increased likelihood of trichoblasts to form hairs, and 33% of the increase was accounted for by changes in low phosphorus root anatomy resulting in an increased number of trichoblast files. These results show that phosphorus availability can fundamentally alter root anatomy, leading to changes in root hair density, which are presumably important for phosphorus acquisition.
Seasonal patterns of photosynthesis in Douglas fir seedlings during the third and fourth year of exposure to elevated CO2 and temperature
Authors: Lewis J. D. , Lucash M. , Olszyk D. , Tingey D. T. 
Published: March 2003

ABSTRACTThe interactive effects of elevated atmospheric CO2 and temperature on seasonal patterns of photosynthesis in Douglas fir (Psuedotsuga menziesii (Mirb.) Franco) seedlings were examined. Seedlings were grown in sunlit chambers controlled to track either ambient (~400 p.p.m.) CO2 or ambient +200 p.p.m. CO2, and either ambient temperature or ambient +4 °C. Light‐saturated net photosynthetic rates were measured approximately monthly over a 21 month period. Elevated CO2 increased net photosynthetic rates by an average of 21% across temperature treatments during both the 1996 hydrologic year, the third year of exposure, and the 1997 hydrologic year. Elevated mean annual temperature increased net photosynthetic rates by an average of 33% across CO2 treatments during both years. Seasonal temperature changes also affected net photosynthetic rates. Across treatments, net photosynthetic rates were highest in the spring and autumn, and lowest in July, August and December–January. Seasonal increases in temperature were not correlated with increases in the relative photosynthetic response to elevated CO2. Seasonal shifts in the photosynthetic temperature optimum reduced temperature effects on the relative response to elevated CO2. These results suggest that the effects of elevated CO2 on net photosynthetic rates in Douglas fir are largely independent of temperature.
Co‐ordination of vapour and liquid phase water transport properties in plants
Authors: Meinzer F. C. 
Published: March 2003

AbstractThe pathway for water movement from the soil through plants to the atmosphere can be represented by a series of liquid and vapour phase resistances. Stomatal regulation of vapour phase resistance balances transpiration with the efficiency of water supply to the leaves, avoiding leaf desiccation at one extreme, and unnecessary restriction of carbon dioxide uptake at the other. In addition to maintaining a long‐term balance between vapour and liquid phase water transport resistances in plants, stomata are exquisitely sensitive to short‐term, dynamic perturbations of liquid water transport. In balancing vapour and liquid phase water transport, stomata do not seem to distinguish among potential sources of variation in the apparent efficiency of delivery of water per guard cell complex. Therefore, an apparent soil‐to‐leaf hydraulic conductance based on relationships between liquid water fluxes and driving forces in situ seems to be the most versatile for interpretation of stomatal regulatory behaviour that achieves relative homeostasis of leaf water status in intact plants. Components of dynamic variation in apparent hydraulic conductance in intact plants include, exchange of water between the transpiration stream and internal storage compartments via capacitive discharge and recharge, cavitation and its reversal, temperature‐induced changes in the viscosity of water, direct effects of xylem sap composition on xylem hydraulic properties, and endogenous and environmentally induced variation in the activity of membrane water channels in the hydraulic pathway. Stomatal responses to humidity must also be considered in interpreting co‐ordination of vapour and liquid phase water transport because homeostasis of bulk leaf water status can only be achieved through regulation of the actual transpirational flux. Results of studies conducted with multiple species point to considerable convergence with regard to co‐ordination of stomatal and hydraulic properties. Because stomata apparently sense and respond to integrated and dynamic soil‐to‐leaf water transport properties, studies involving intact plants under both natural and controlled conditions are likely to yield the most useful new insights concerning stomatal co‐ordination of transpiration with soil and plant hydraulic properties.
Leaf dispersion and light partitioning in three‐dimensionally digitized tall fescue–white clover mixtures
Authors: Sonohat G. , Sinoquet H. , Varlet‐Grancher C. , Rakocevic M. , Jacquet A. , Simon J.‐C. , Adam B. 
Published: March 2003

AbstractA three‐dimensional digitizing method was used to assess the canopy structure of six Festuca arundinacea (FA)–Trifolium repens (TR) mixtures during the installation stage. Virtual canopy images were synthesized and used to derive light interception and partitioning between species. Computations from images were compared with a simple light model based on Beer’s law, in order to analyse within‐ and between‐species foliage dispersion. The total leaf area index of the mixtures ranged from 0·6 to 4·5. The fraction of FA foliage overtopping TR was 9–30%. The mean inclination of FA and TR was 66 and 57°, respectively. Within‐species dispersion parameters of FA and TR were about 0·8 and 1·0, namely clumped and random foliage dispersion, respectively. Although FA was sown in rows, between‐species dispersion was random. Lower leaf inclination and lesser clumping in TR compensated foliage overtopping by FA, so that light partitioning between FA and TR (about 80 and 20%, respectively) was similar to the species contribution to total canopy foliage. Since between‐species dispersion was random, a simple two‐layer light model based on Beer’s law provided correct estimations of light partitioning (RMSE = 0·05), although light interception by FA was slightly overestimated because of its clumped dispersion.
Inulin metabolism in dicots: chicory as a model system
Authors: Van Laere A. , Van Den Ende W. 
Published: March 2003

AbstractFructans are fructose‐based oligo‐ and polymers that serve as reserve carbohydrates in many plant species. The original Edelman and Jefford model for GFn inulin type fructan biosynthesis was confirmed by the de novo synthesis of fructans in vitro as well as by heterologous expression of the respective cDNAs in non‐fructan plants. Now the model can be extended for the biosynthesis of Fn inulin type fructans. Recent progress has now succeeded in elucidating the biochemistry and molecular biology of fructan biodegradation in chicory, an economically important species used for commercial inulin extraction. Unlike fructan biosynthetic genes that originated from vacuolar type invertase, plant fructan exohydrolases seem to have evolved from a cell wall invertase ancestor gene that later obtained a low iso‐electric point and a vacuolar targeting signal. Using chicory as a model system, expression analysis revealed that fructan enzymes are mainly controlled at the transcriptional level.
Membrane stabilization by abscisic acid under cold aids proline in alleviating chilling injury in maize (Zea mays L.) cultured cells
Authors: Chen W. P. , Li P. H. 
Published: March 2003

AbstractPrevious studies of maize suspension‐cultured cells showed that abscisic acid (ABA) treatment at warm temperatures improved the tolerance of cells to subsequent chilling. In the present study, it is shown that both ABA‐treated and untreated maize cells accumulated proline in response to chilling. However, ABA‐treated cells displayed less lipid peroxidation during chilling, and thus, unlike untreated cells, were able to retain the accumulated proline intracellularly. Proline application experiments indicate that an intracellular proline level higher than 2 µmole (g FW)−1 prior to chilling was needed to meaningfully reduce chilling‐enhanced lipid peroxidation and significantly improve chilling tolerance. The results suggest that total proline accumulation in ABA‐treated as well as untreated cells during chilling was enough to potentially improve chilling tolerance, but proline leakage rendered the control cells unable to benefit from the endogenous synthesis of proline in relation to the alleviation of chilling injury. Proline participated in chilling tolerance improvement in ABA‐treated maize cells, as evidenced by: (1) the inhibition of proline accumulation by l‐methionine‐d, l‐sulphoximine (MSO), an inhibitor of glutamine synthetase, reduced ABA‐improved chilling tolerance, and (2) the addition of glutamine into the medium prevented the MSO‐induced reduction in chilling tolerance. The revised relationship between proline accumulation and membrane stability at cold is discussed in the light of these current findings.
Diurnal variation in the stable isotope composition of water and dry matter in fruiting Lupinus angustifolius under field conditions
Authors: Cernusak L. A. , Pate J. S. , Farquhar G. D. 
Published: March 2003

AbstractIn this paper, we present an integrated account of the diurnal variation in the stable isotopes of water (δD and δ18O) and dry matter (δ15N, δ13C, and δ18O) in the long‐distance transport fluids (xylem sap and phloem sap), leaves, pod walls, and seeds of Lupinus angustifolius under field conditions in Western Australia. The δD and δ18O of leaf water showed a pronounced diurnal variation, ranging from early morning minima near 0‰ for both δD and δ18O to early afternoon maxima of 62 and 23‰, respectively. Xylem sap water showed no diurnal variation in isotopic composition and had mean values of −13·2 and −2·3‰ for δD and δ18O. Phloem sap water collected from pod tips was intermediate in isotopic composition between xylem sap and leaf water and exhibited only a moderate diurnal fluctuation. Isotopic compositions of pod wall and seed water were intermediate between those of phloem and xylem sap water. A model of average leaf water enrichment in the steady state (Craig & Gordon, pp. 9–130 in Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Palaeotemperatures, Lischi and Figli, Pisa, Italy, 1965; Dongmann et al., Radiation and Environmental Biophysics 11, 41–52, 1974; Farquhar & Lloyd, pp. 47–70 in Stable Isotopes and Plant Carbon–Water Relations, Academic Press, San Diego, CA, USA, 1993) agreed closely with observed leaf water enrichment in the morning and early afternoon, but poorly during the night. A modified model taking into account non‐steady‐state effects (Farquhar and Cernusak, unpublished) gave better predictions of observed leaf water enrichments over a full diurnal cycle. The δ15N, δ13C, and δ18O of dry matter varied appreciably among components. Dry matter δ15N was highest in xylem sap and lowest in leaves, whereas dry matter δ13C was lowest in leaves and highest in phloem sap and seeds, and dry matter δ18O was lowest in leaves and highest in pod walls. Phloem sap, leaf, and fruit dry matter δ18O varied diurnally, as did phloem sap dry matter δ13C. These results demonstrate the importance of considering the non‐steady‐state when modelling biological fractionation of stable isotopes in the natural environment.
Root respiration and associated costs in deciduous and evergreen species of Quercus
Authors: Martínez F. , Lazo Y. O. , Fernández‐Galiano J. M. , Merino J. 
Published: March 2003

AbstractRoot construction and maintenance costs were estimated in four evergreen and three deciduous Quercus species that are typical in the landscape of southern Spain. The cost quantification was based on analysis of the growth–­respiration ratio. Values observed for both construction cost (ranging from 1·17 to 1·29 g glucose g−1 dry weight) and maintenance   cost   (ranging   from   6·22   to   11·71 mg glucose g−1 dry weight d−1) were generally lower than those reported in other studies. The results showed non‐significant differences between deciduous and evergreen species. The lack of significant differences between species appeared to be due to the homogeneity of growth conditions. Hydroponic culture, with unrestricted nutrient and water supply, would lead to low tissue carbon content and low respiration rates, leading to the low costs observed. Furthermore, the fact that root organs are clearly importers of organic molecules inevitably entails some underestimation of the respiration associated with growth and, to a lesser extent, with maintenance respiration. This leads in turn to underestimation of the corresponding construction and maintenance costs. All this raises doubts as to the suitability of this method for studying root systems.