bluuebunny/crossref_metadata_2025 huggingface dataset:
Successful percutaneous transluminal angioplasty for hepatic artery stenosis in an infant undergoing living‐related liver transplantation
Authors: Hasegawa Toshimichi , Sasaki Takashi , Kimura Takuya , Okada Akira , Nakatsuchi Yoshiaki , Sugiura Takashi , Kato Hiromi , Nakajima Yoshikazu
Published: March 2003

Abstract: A 1‐yr‐old girl underwent a living‐related liver transplant, with reconstruction of hepatic artery of 2 mm in diameter under microscopy. She developed intestinal perforation requiring closure on day 4 post‐transplant and suffered from hepatic artery stenosis (HAS) on post‐transplant day 9. Conservative therapies, such as intravenous or transluminal administration of anti‐coagulants, vasodilators or fluids, were unsuccessful and caused remarkable general edema and multiple arrhythmias as a result of increased preload. On day 15 post‐transplant, because flow velocity was remarkably reduced (as shown by Doppler ultrasound) the patient underwent percutaneous transluminal angioplasty (PTA) using a kit for coronary angioplasty. The balloon catheter was inflated [first: 1.5 mm diameter, 4 atmospheric pressure (a.p.) for 30 seconds (s); second: 2.0 mm diameter, 4 a.p. for 30 s; third: 2.5 mm diameter, 10 a.p. for 30 s]. The stenosis was successfully dilated without any complication. The patient has been doing well with normal liver functions for 4 months after PTA. From this experience, PTA can be performed for HAS after liver transplantation, even in an infantile case, with a careful technique and a special device.
Changes in hepatitis B virus serology in bone marrow transplanted children
Authors: Küpeli Serhan , Özen Hasan , Uçkan Duygu , Çetin Mualla , Tuncer Murat , Aypar Ebru , Tezcan Ilhan
Published: March 2003

Abstract: Suppression of the immune system and reconstitution of the donor's immune system may affect the course of a chronic viral infection in the recipients. The aim of this study is to evaluate changes in hepatitis B virus (HBV) serology after bone marrow transplantation (BMT). HBV serology and hepatic function tests were examined in 45 children before and after BMT. Before BMT, 40 patients were HBsAg negative and 5 positive. There were no HBsAg positive donors. HBsAg disappeared in two patients and anti‐HBs became positive in one. Donors of these patients were anti‐HBs positive. In a third patient, acute HBV infection developed and lasted without complication. This patient also seroconverted to anti‐HBs. Anti‐HBs disappeared in 7 of 21 anti‐HBs positive patients. Among 18 patients who were HBsAg and anti‐HBs negative, 11 seroconverted to anti‐HBs positivity. Our findings support the notion that having an anti‐HBs positive donor is important for adoptive immunity transfer and for preventing HBV replication.
Growth following solid‐organ transplantation
Authors: Fine Richard N.
Published: March 2003

Abstract: One of the ultimate goals of successful transplantation (Tx) in pediatric solid‐organ transplant recipients is the attainment of optimal final adult height. Except for kidney Tx there are limited data to address this issue. Remarkably similar factors impact on growth in pediatric kidney, liver, and heart recipients. Age is a primary factor, with younger recipients exhibiting the greatest immediate catch‐up growth. Graft function is a significant contributory factor: a reduction in glomerular filtration rate (GFR) correlates with poor growth in kidney recipients, and the need for re‐Tx is associated with impaired growth in liver recipients. The known adverse impact of corticosteroids on growth has led transplant physicians/surgeons to either modify the dose or attempt steroid withdrawal. In kidney and liver recipients this is associated with the development of acute rejection episodes. In infant heart transplant recipients the avoidance of maintenance corticosteroid immunosuppression is associated with normal growth velocity in the majority of recipients. With the marked improvement in patient and graft survival rates in pediatric solid‐organ graft recipients, it is timely that the quality‐of‐life issues receive paramount attention. In children, normal growth following solid‐organ Tx should be an achievable goal that results in normal final adult height.
Use of radiolabeled antibodies in the treatment of childhood acute leukemia
Authors: Nemecek Eneida R. , Matthews Dana C.
Published: March 2003

Abstract: Despite advances in therapy for acute leukemia, relapse continues to be the major cause of treatment failure. Hematopoietic stem cell transplant can rescue some patients after relapse, but the ability to escalate the intensity of preparative regimens is limited by toxicity to normal organs. Radiolabeled monoclonal antibodies against hematopoietic antigens have emerged as an alternative to deliver targeted supplemental radiation to sites of leukemic involvement while relatively sparing normal organs. This paper will review the rationale for using this approach, our current experience with radiolabeled anti‐CD45 antibody, and the potential challenges encountered in treating children with radiolabeled antibodies.
Na+ and K+ transport in excised soybean roots
Authors: Lacan D. , Durand M.
Published: March 2003

Uptake, accumulation and xylem transport of K+ and Na+ in excised roots of soybean were investigated by use of a perfusion technique. This technique permitted independent quantification of, on the one hand, entry of ions into the roots and their transport through the cortex to the xylem vessels, and on the other hand reabsorption from the xylem vessels to the neighbouring cells and the external medium. Data are consistent with a low degree of selective uptake of K+ over Na+. However, Na+ depletion of the xylem stream by reabsorption limits, although weakly, its translocation to the shoots. Na+ reabsorbed is for a great part reexcreted into the external medium. The low efficiency of these processes is discussed in relation to the Na+ sensitivity of soybean.
Phosphorylation/dephosphorylation of Komatsuna (Brassica campestris) leaf nitrate reductase in vivo and in vitro in response to environmental light conditions: Effects of protein kinase and protein phosphatase inhibitors
Authors: Kojima Michiko , Wu Sheng‐Jun , Fukui Hajime , Sugimoto Toshio , Nanmori Takashi , Oji Yoshikiyo
Published: March 2003

Activity of nitrate reductase (NR; EC 1.6.6.1) in leaves of Komatsuna (Brassica campestris L. ssp. rapifera cv. Osome) was decreased by sudden darkness, and rapidly recovered upon reillumination. However, the amount of NR protein, estimated by western blots, did not fluctuate during short‐term light/dark/light transitions. This suggests that rapid changes of NR activity in response to light/dark regimes are due to reversible modulation of the protein and not to de novo synthesis/degradation. In mannose‐fed leaves, such light/dark changes in NR activity were not observed. When extracts from illuminated leaves were incubated with MgATP, NR activity decreased in a time‐dependent manner. K‐252a, a specific inhibitor of protein kinases, prevented the in vitro inactivation of NR. The radiolabel of [γ‐32P] ATP was incorporated into NR protein in vitro and the labelling of NR was blocked by K‐252a. On the other hand, extractable NR from darkened leaves was activated by incubation at 30°C without further additions. The in vitro activation of NR was prevented by calyculin A, a potent and specific inhibitor of protein phosphatase. Moreover calyculin A abolished the in vivo activation of NR by illumination. Our results confirm a regulatory system by phosphorylation/dephosphorylation of NR. The data also suggest that the activity of NR depends on the relative phosphorylation/dephosphorylation activities subtly controlled in response to photon flux density.
Light‐dependent phosphorylation of D1 reaction centre protein of photosystem II: hypothesis for the functional role in vivo
Authors: Rintamäki Eevi , Kettunen Reetta , Tyystjärvi Esa , Aro Eva‐Mari
Published: March 2003

Reversible phosphorylation of the D1 reaction centre protein of photosystem II (PSII) occurs in thylakoid membranes of higher plants. The significance of D1 protein phosphorylation in the function of PSII is not yet clear. This paper summarizes the data implying that phosphorylation of D1 protein in higher plants is involved in the regulation of the repair cycle of photoinhibited PSII centres. Photoinhibition of PSII, D1 protein phosphorylation and degradation have been studied in vivo in higher plant leaves acclimated to different growth irradiances. It is shown that photoinhibitory illumination induces maximal phosphorylation of the D1 protein. Under these conditions D1 turnover is also saturated. We postulate that phosphorylation retards the degradation of damaged D1 protein under conditions where rapid replacement by a new D1 copy is not possible. This would protect PSII from total disassembly and degradation of all PSII subunits. We conclude that the phosphorylation of D1 protein and the regulation of D1 protein degradation may have evolved together. Furthermore, these characteristics seem to be related to the highly organized structure of higher‐plant type thylakoid membranes, since the capability to phosphorylate D1 protein is restricted to seed plants.
Differential IAA dose response relations of the axr1 and axr2 mutants of Arabidopsis
Authors: Knee Emma M. , Hangarter Roger P.
Published: March 2003

In comparison to wild type Arabidopsis thaliana, the auxin resistant mutants axr1 and axr2 exhibit reduced inhibition of root elongation in response to auxins. Several auxin‐regulated physiological processes are also altered in the mutant plants. When wild‐type, axr1 and axr2 seedlings were grown in darkness on media containing indoleacetic acid (IAA), promotion of root growth was observed at low concentrations of IAA (10−11 to 10−7M) in 5‐day‐old axr2 seedlings, but not in axr1 or wild‐type seedlings. In axr1 there was little or no measurable root growth response over the same concentration range. In wild type, root growth was inhibited at concentrations greater than 10−10M and no detectable root growth response was observed at lower concentrations. In addition, production of lateral roots in response to IAA increased in axr2 seedlings and decreased in axr1 seedlings relative to wild type. Promotion of root elongation and initiation of lateral roots in axr2 seedlings in response to auxin indicate that axr2 seedlings are able to perceive and respond to IAA.
The role of activated oxygen species in plant disease resistance
Authors: Mehdy Mona C. , Sharma Yogesh K. , Sathasivan Kanagasabapathi , Bays Nathan W.
Published: March 2003

One of the earliest responses of plant cells to pathogens is the production of activated oxygen species. In several plant species, this oxidative burst appears to be generated by a signalling pathway similar to that employed by mammalian neutrophils during immune responses. Similar to neutrophils, elicitor receptors in the plant plasma membrane likely activate G proteins and phospholipase C leading to increased intracellular Ca2+ and protein phosphorylation and ultimately, formation of an active NADPH oxidase complex in the plasma membrane. The NADPH oxidase produces O2− which can be rapidly converted to H2O2. Work from a number of laboratories supports the concept that H2O2 plays a central role in mediating diverse aspects of disease resistance. Potential functions of H2O2 include its participation in direct killing of pathogen cells as part of the hypersensitive response, oxidative cross‐linking of plant cell wall proteins to render the wall less digestible by microbial enzymes, and as an intracellular signal regulating defense‐related gene expression.
Oxygen reduction in the Mehler reaction is insufficient to protect photosystems I and II of leaves against photoinactivation
Authors: Wiese Christian , Shi Lan‐bo , Heber Ulrich
Published: March 2003

The relative roles of assimilatory and photorespiratory electron flows on one side and of the Mehler‐peroxidase pathway on the other side in sustaining electron transport and providing protection against photoinhibition were investigated in leaves of spinach (Spinacia oleracea L.) and sunflower (Helianthus annuus L.). After inhibiting photosynthesis and photorespiration of intact leaves by either HCN or glycolaldehyde, light‐dependent linear electron transport was decreased by more than 90% at a photon flux density of 800 µmol m−2 s−1. Remaining electron transport exhibited characteristics of the Mehler reaction. Nonphotochemical quenching of chlorophyll fluorescence increased after inhibition of CO2 assimilation and photorespiration indicating effective dissipation of excess excitation energy. Nevertheless, appreciable photoinactivation was observed under these conditions not only of photosystem II but also of photosystem I. This damage was oxygen‐dependent. It was much reduced or absent when the oxygen concentration of the atmosphere was reduced from 21 to 1%.
Adventitious root initiation in hypocotyl and epicotyl cuttings of eastern white pine (Pinus strobus) seedlings
Authors: Goldfarb Barry , Hackett Wesley P. , Furnier Glenn R. , Mohn Carl A. , Plietzsch Andreas
Published: March 2003

The present paper reports results of experiments to develop a system for studying adventitious root initiation in cuttings derived from seedlings. Hypocotyl cuttings of 2‐week‐old eastern white pine (Pinus strobus L.) seedlings were treated for 5 min with 0, 100, 200, 300, 400, 500 or 600 mg l−1 (0, 0.54, 1.07, 1.61, 2.15, 2.69 or 3.22 mM) 1‐naphthaleneacetic acid (NAA) to determine the effect on root initiation. The number of root primordia per cutting was correlated with NAA concentration and the square of NAA concentration. Thus, the number increased from less than one per cutting in the 0 NAA treatment to approximately 40 per cutting at 300 mg l‐1 NAA, above which no substantial further increase was observed. The larger number of root primordia formed in response to increasing concentrations of NAA was due to the formation of primordia over a larger proportion of the hypocotyls. Histological analysis of the timing of root primordium formation in hypocotyl cuttings revealed three discernible stages. Progression through these stages was relatively synchronous among NAA‐treated hypocotyl cuttings and within a given cutting, but variation was observed in the portion of different cuttings undergoing root formation. Control‐treated hypocotyl cuttings formed root primordia at lower frequencies and more slowly than NAA‐treated cuttings, with fewer primordia per cutting. Epicotyl cuttings from 11‐week‐old seedlings also formed adventitious roots, but more slowly than hypocotyl cuttings. NAA treatment of epicotyl cuttings caused more rapid root initiation and also affected the origin of adventitious roots in comparison with nontreated cuttings. NAA‐treated epicotyl cuttings formed roots in a manner analogous to that of the hypocotyl cuttings, directly from preformed vascular tissue, while control‐treated epicotyl cuttings first formed a wound or callus tissue and subsequently differentiated root primordia within that tissue. This system of inducing adventitious roots in pine stem cuttings lends itself to studying the molecular and biochemical steps that occur during root initiation and development.
Action potentials and variation potentials in sunflower: An analysis of their relationships and distinguishing characteristics
Authors: Stanković Bratislav , Witters Daniel L. , Zawadzki Tadeusz , Davies Eric
Published: March 2003

Sunflower plants (Helianthus annuus L.) were given an electrical stimulus to the stem or a heat (flame)‐wound to a single leaf or a cotyledon. The resulting electrical activity was monitored with extracellular electrodes. An electrical stimulus applied to the stem frequently evoked an action potential (AP), but never a variation potential (VP). In contrast, a heat‐wound applied to a leaf virtually always elicited a VP, which was often accompanied by one or more superimposed spikes (putative APs). The kinetic parameters of the AP and the VP were investigated. The AP appears to propagate without decrement in velocity or magnitude, whereas the VP parameters decrease significantly with distance. The heat stimulus triggered rapid alterations in stem elongation/contraction, which preceded changes in electrical potential, indicating the transmission of a hydraulic signal. Light‐off and light‐on stimuli evoked negative‐ and positive‐going changes in extracellular electrical potential, respectively, corresponding to de‐ and hyper‐polarization of the plasma membrane. Membrane depolarization (extracellularly manifested as a VP) evoked by both the light‐off and heat‐wounding stimuli was able to trigger one or more APs. We interpret these results to suggest that APs are “genuine” electrical signals involving voltage‐gated ion channels or pumps, which can be evoked directly by electrical stimulation or indirectly by changes in membrane potential occurring during the VP or after the light‐off stimulus. In contrast, VPs appear to be a local (non‐transmissible) electrical consequence of the passage of a rapidly transmitted hydraulic signal in the xylem, presumably acting on mechanosensitive ion channels or pumps in adjacent living cells.
BiP, HSP70, NDK and PDI in wheat endosperm. II. Effects of high temperature on protein and mRNA accumulation
Authors: Hurkman William J. , DuPont Frances M. , Altenbach Susan B. , Combs Allison , Chan Ronald , Tanaka Charlene K. , Reuveni Moshe , Bernardin John E.
Published: March 2003

The effects of high temperature on accumulation of the 70‐kDa heat shock protein (HSP70) and nucleoside diphosphate kinase (NDK) as well as two other proteins that have roles in the biosynthesis of storage proteins were examined during grain development. An HSP70 homolog and a 17‐kDa NDK were co‐purified from wheat endosperm, their identity verified, and a cDNA for an HSP70 expressed in endosperm was isolated. Wheat plants (Triticum aestivum, cvs Butte and Vulcan) were heat shocked at 40°C or exposed to maximum daily temperatures of 37 or 40°C during early or mid‐grain fill. Antibodies and cDNA probes for BiP, HSP70, NDK and PDI were used to examine the effect of high temperatures on the accumulation of protein and mRNA in the endosperm. HSP70 mRNA levels increased substantially when plants were exposed to heat shock or to a 1‐day gradual increase to 40°C. The effects of a 5‐day heat treatment on mRNA levels were more complicated and depended on the developmental stage of the grain. A treatment that began at 7 days post‐anthesis (DPA) decreased the level of mRNA for HSP70, BiP, PDI and NDK, whereas a treatment that began at 14 DPA slightly increased mRNA levels. The same treatments increased the accumulation of HSP70 but did not affect BiP, PDI, or NDK protein levels. This is the first detailed report on the effects of heat on mRNA and protein levels for HSP70 in a developing seed storage tissue.
Continuous secretion of organic acids is related to aluminium resistance during relatively long‐term exposure to aluminium stress
Authors: Zheng Shao Jian , Ma Jian Feng , Matsumoto Hideaki
Published: March 2003

Secretion of organic acid has been suggested to be one of the mechanisms for Al resistance in short‐term experiments. In the present study, relatively long‐term response of roots to Al stress was investigated in terms of organic acid secretion. Eight plant cultivars belonging to 5 species that exhibited differential sensitivity to Al were used. Ten days of intermittent exposure to Al (one day in 0.5 mM CaCl2 containing 50 µM AlCl3 at pH 4.5, alternating with one day in nutrient solution without Al) inhibited root growth by 65% in an Al‐sensitive cultivar of wheat (Triticum aestivum L. Scout 66) and by 25‐50% in two cultivars of oilseed rape (Brassica napus L. 94008 and H166), two cultivars of oat (Avena sativa L. Tochiyutaka and Heoats), and an Al‐tolerant cultivar of wheat (Atlas 66). However, root growth was hardly affected by the same treatment in buckwheat (Fagopyrum esculentum Moench Jianxi) and radish (Raphanus sativus L. Guangxi). Organic acids were monitored during the first 6 h of each day of Al treatment, and both the kind and amount of organic acids secreted were found to differ among different species. Roots of buckwheat secreted oxalic acid, those of wheat exuded malic acid, while those of rapeseed, oats, and radish secreted both citric and malic acids. Three different patterns in response to relatively long‐term treatment of Al were found in terms of total amount of organic acids secreted: (1) the amount secreted was very low during the treatment (wheat cv. Scout 66, oat), (2) the amount gradually decreased with duration of treatment (wheat cv. Atlas 66, oilseed rape), and (3) the amount maintained at a high level during the whole period of Al treatment (buckwheat and radish). Combined with the results of growth inhibition, it is suggested that the continuous secretion of organic acids at a high level is related to high Al resistance.
Elevated CO2 and water deficit effects on photosynthesis, ribulose bisphosphate carboxylase‐oxygenase, and carbohydrate metabolism in rice
Authors: Vu Joseph C. V. , Baker Jeffrey T. , Pennanen Arja H. , Allen, Jr L. Hartwell , Bowes George , Boote Kenneth J.
Published: March 2003

Rice (Oryza sativa[L.] cv. IR‐72) was grown for a season in sunlit, controlled‐environment chambers at 350 or 700 µmol CO2 mol−1 under continuously flooded (unstressed) or drought‐imposed periods at panicle initiation (stressed). The midday canopy photosynthetic rates (Pn), measured at the CO2 concentration ([CO2]) used for growth, were enhanced by high [CO2] but reduced by drought. High [CO2] increased Pn by 18 to 34% for the unstressed plants, and 6 to 12% for the stressed plants. In the unstressed plants, CO2 enrichment increased water‐use efficiency (WUE) by 26%, and reduced evapotranspiration (ET) by 8 to 14%. Both high [CO2] and severe drought decreased the activity and content of ribulose bisphosphate carboxylase‐oxygenase (Rubisco). High‐CO2‐unstressed plants had 6 to 22% smaller content and 5 to 25%, lower activity of Rubisco than ambient‐CO2‐unstressed plants. Under severe drought, reductions of Rubisco were 53 and 27% in activity and 40 and 12% in content, respectively, for ambient‐ and high‐CO2 treatments. The apparent catalytic turnover rate (Kcat) of midday fully activated Rubisco was not altered by high [CO2], but severe drought reduced Kcat by 17 to 23%. Chloroplasts of the high‐CO2 leaves contained more, and larger starch grains than those of the ambient CO2 leaves. High [CO2] did not affect the leaf sucrose content of unstressed plants. In contrast, severe drought reduced the leaf starch and increased the sucrose content in both CO2 treatments. The activity of leaf sucrose phosphate synthase of unstressed plants was not affected by high [CO2], whereas that of ambient‐CO2‐grown plants was reduced 45% by severe drought. Reduction in ET and enhancements in both Pn and WUE for rice grown under high [CO2] helped to delay the adverse effects of severe drought and allowed the stressed plants to assimilate CO2 for an extra day. Thus, rice grown in the next century may utilize less water, use water more efficiently, and be able to tolerate drought better under some situations.
Proteins functionally and immunogenically related to pathogenesis‐related proteins are induced during parsley leaf senescence
Authors: Lers Amnon , Jiang Wei Bo , Lomaniec Ella , Aharoni Nehemia
Published: March 2003

The advancement of leaf senescence is accompanied by a reduction in cellular protein content together with the induction of specific proteins which are probably involved in the process. In the present study, with parsley, we followed the changes in the levels of proteins functionally and immunogenically related to pathogenesis‐related proteins during both senescence of detached leaves and natural senescence of attached leaves. Both chitinase activity and protein level were found to be induced during senescence, as was the level of two other proteins immunologically related to β‐1,3‐glucanase and P4 pathogenesis‐related proteins of citrus and tomato, respectively. A high correlation between the advancement of senescence and the induction of these proteins was demonstrated. Treatments with CO2 or gibberellic acid, which retard senescence, reduced both chitinase activity and the level of the pathogenesis‐related proteins, whereas enhancement of senescence with ethylene induced them further. The induction of pathogenesis‐related proteins during senescence suggests that these proteins may have a primary role in this process.
Responses of the transcriptional apparatus of barley chloroplasts to a prolonged dark period and to subsequent reillumination
Authors: Krause Kirsten , Falk Jon , Humbeck Klaus , Krupinska Karin
Published: March 2003

In this study the responses of the chloroplast transcriptional apparatus in barley (Hordeum vulgare L. cv. Carina) primary foliage leaves were examined during and after interruption of the light/dark growth regime by a two‐day period of light deprivation on days 10 and 11 after sowing.

Run‐on transcript assays and northern blot analyses showed that transcripts in chloroplasts can be divided into at least three groups that differ in their levels during the dark period and in the kinetics of their resynthesis during the reillumination phase. Group I transcripts (rbcL, psaA,B, atpB) show decreased expression as well as reduced transcript accumulation during the dark period both of which are restored within 32 h after reillumination of the plants. Group II (psbA, psbD) and group III (16S rRNA, trnE) transcripts show a delayed or no detectable response to prolonged darkness at the transcript level. While group II transcription does not change significantly upon reillumination, transcription of group III genes increases substantially above the initial value within a very short time after retransfer into light.

Changes in gene specificity of the transcriptional apparatus are accompanied by a changing sensitivity of the chloroplast transcriptional apparatus towards the transcription inhibitor tagetitoxin. The strongest inhibitory effect of tagetitoxin could be observed in leaves recovering from the dark‐induced stress situation.
Role of sodium in the ABA‐mediated long‐term growth response of bean to salt stress
Authors: Sibole John V. , Montero Elena , Cabot Catalina , Poschenrieder Charlotte , Barceló Juan
Published: March 2003

Long‐term salt effects on plant growth have often been related to direct ion toxicity due to the accumulation of high ion concentrations in plant tissue. This work examines the relative importance of endogenous ABA, as well as Na+ and Cl− toxicity, in the inhibition of leaf growth and photosynthesis, in bean plants grown at 1, 25, 50 and 75 mM NaCl until the fruit‐bearing stage. All salt‐treated plants showed very high leaf Cl− concentrations, with little difference between plants exposed to 50 or 75 mM NaCl. The 25 and 50 mM salt‐treated plants were able to successfully exclude Na+ from their leaves, and only suffered an initial decline in the rate of leaf growth. Plants exposed to 75 mM NaCl showed an increase in Na+ leaf concentrations with an accompanying decrease in growth and photosynthesis as salt exposure progressed. A high correlation was found between leaf Na+ and leaf growth. Leaf ABA significantly increased with salt supply, and was highly correlated with both leaf Na+ and leaf growth. Our results suggest that in bean plants under long‐term salt stress, leaf ABA may participate in the regulation of leaf growth, and leaf Na+ would be at least partly responsible for increased ABA levels.
Preferential allocation of sulphur into y‐glutamylcysteinyl peptides in wheat plants grown at low sulphur nutrition in the presence of cadmium
Authors: McMahon Peter J. , Anderson John W.
Published: March 2003

Plants respond to Cd by synthesising phytochelatins (PC) and similar S‐rich peptides which are important in alleviating Cd toxicity. The hypothesis that S nutrition influences the sensitivity of plants to Cd was examined by measuring the growth, PC and Cd content of wheat plants (Triticum aestivum cv. Condor) grown at 10–1000 µM S with and without 30 µM Cd. In the absence of Cd, 100 µM S was marginally S‐limiting. Cd severely inhibited root growth at 100 µM S but the concentrations of PC, Cd–PC complexes and Cd in the root were similar to those of plants grown at 1000 µM S which exhibited no evidence of Cd toxicity. Plants grown at low S (10 and 30 µM) contained lower concentrations of Cd. However, they produced very low amounts of PC and were very sensitive to Cd. At 10–300 µM S (but not at 1000 µM), Cd enhanced the concentration of S in the root. The data are consistent with a model in which plants preferentially allocate S to PC synthesis. When S was marginally limiting (100 µM), the S supply was sufficient for PC synthesis but not root growth, effectively causing Cd‐induced S deficiency. This did not occur at high S (1000 µM). Conversely, at low S (10 and 30 µM), the synthesis of PC2–PC4 was decreased by 87 and 66%, respectively, thereby resulting in decreased Cd uptake while also making the plants especially sensitive to Cd.
Are there connections between phenol metabolism, ascorbate metabolism and membrane integrity in leaves of boron‐deficient sunflower plants?
Authors: Pfeffer Heidrun , Dannel Frank , Römheld Volker
Published: March 2003

The influence of soluble phenol concentration and polyphenoloxidase activity in leaves of both B‐deficient and B‐sufficient sunflower plants (Helianthus annuus L. cv. Frankasol) on plasma membrane permeability was investigated, A study was also undertaken as to whether or not the incubation of B‐deficient leaves in ascorbate‐ and calcium‐containing solutions has a beneficial effect on plasma membrane integrity. Plants were cultivated under controlled environmental conditions with deficient and sufficient B supply and different light intensity to provoke changes in phenol metabolism. Analysis of membrane permeability (measured by potassium efflux), soluble phenol concentration and polyphenoloxidase (EC 1.10.3.1) activity of leaves showed that there was no correlation between these parameters. Furthermore, incubation in solutions containing ascorbate and calcium did not decrease the enhanced membrane permeability due to B deficiency, which could, however, be lowered by boric acid application. In summary, the results suggest that B does not maintain plasma membrane integrity by complexing phenols or inhibiting polyphenoloxidase activity, thereby preventing damage by oxygen free radicals. Ascorbate metabolism or calcium‐related disorders seem also not to be involved. It is therefore likely that B has a direct function at the membrane, possibly by stimulating membrane‐related enzymes, or in a structural role similar to that reported for the cell wall.
Facilitated diffusion drives transport of oxidised ascorbate molecules into purified plasma membrane vesicles of Phaseolus vulgaris
Authors: Horemans N. , Asard H. , Van Gestelen P. , Caubergs R. J.
Published: March 2003

Recently, the presence of a carrier‐mediated transport system for ascorbate was demonstrated in the plant plasma membrane. To investigate the possible physiological importance of this system in apoplastic ascorbate metabolism we further characterized this carrier. Transport of Asc was measured by incubating freshly‐purified plasma membrane vesicles from hypocotylar hooks of Phaseolus vulgaris together with [14C]‐labelled Asc. In this paper we show that ascorbate transport is detectable over a relatively broad pH range (6 to 7.5) and is not affected by protonophore addition. [14C]‐Ascorbate is not taken up into vesicle fractions consisting of sealed inside‐out oriented vesicles, suggesting that it is transported only from the apoplast to the cytoplasm. Asc uptake into vesicles previously loaded with ascorbate was also tested. Surprisingly, uptake of radioactive molecules was up to 3‐fold higher in the ascorbate‐loaded vesicles compared to non‐loaded control vesicles (P < 0.001). The uptake of [14C]‐ascorbate in both the ascorbate‐loaded as the non‐loaded membrane vesicles was inhibited by addition of DTT and not by glutathione or ferricyanide. Based on various observations such as cis‐inhibition, trans‐stimulation and insensitivity towards proton gradients, a facilitated uptake mechanism is suggested. Our results strongly indicate that dehydroascorbate is the preferred transported species from the apoplastic to the cytoplasmic side of the membrane. This transport system is possibly involved in the regeneration of apoplastic ascorbate.
Cell wall modifications in bean (Phaseolus vulgaris) callus cultures tolerant to isoxaben
Authors: Díaz‐Cacho Pilar , Moral Rosa , Encina Antonio , Luis Acebes José , Alvarez Jesús
Published: March 2003

Cultures of bean (Phaseolus vulgaris L.) callus were adapted for growth in a 12 μM concentration of the herbicide isoxaben; 1 200‐fold greater than the I50 calculated. Tolerant calluses grew slower, were browner and harder than nontolerant ones and formed large globular corpuscles on their surface. Cell wall fractionation of tolerant cells indicated that the mechanism of adaptation depends on the ability of these cells to divide and expand with a modified wall. The walls of tolerant cells growing on isoxaben differ from those of nontolerant cells by having reduced levels of cellulose and hemicelluloses and a higher uronic acid content. These differences are already found in adaptations to low concentrations of isoxaben and keep to the highest adaptation levels tested without any great change.
Relative contributions of photochemical and non‐photochemical routes to excitation energy dissipation in rice and barley illuminated at a chilling temperature
Authors: Xu Chang Cheng , Jeon Young Ah , Lee Choon‐Hwan
Published: March 2003

The mechanistic basis for differential sensitivities to chilling‐induced photoinhibition among two rice (Oryza sativa L.) cultivars (an Indica and a Japonica type) and one barley cultivar (Hordeum vulgare L. cv. Albori) was examined. When leaf segments were exposed to moderate illumination at 4°C, a sustained decrease in the photochemical efficiency of photosystem (PS) II measured as the ratio of variable to maximal fluorescence (Fv/Fm) was observed for several hours. An analysis of fluorescence quenching revealed a sudden drop in PSII‐driven electron transport rate (ETR) and a rapid rise in the reduction state of the primary electron acceptor QA upon exposure to chilling in moderate light. There was no appreciable difference in the level of non‐photochemical quenching (NPQ) nor in the xanthophyll cycle activity between Japonica rice and barley. However, barley was capable of sustaining a higher ETR, thereby keeping a lower reduction state of QA throughout the chilling for 6 h. The Indica rice was characterized by the lowest ability to develop the xanthophyll cycle‐associated NPQ, particularly the fast relaxing NPQ component (qf), accompanied by the highest reduction state of QA and photoinhibitory quenching (qI). It is concluded that the lower susceptibility of barley to chilling‐induced photoinhibition than Japonica rice is attributable to its higher potential to dissipate excess light energy via a photochemical mechanism, whereas Indica rice is more sensitive to photoinhibition at a chilling temperature than Japonica rice, due primarily to its lower capacity to develop an efficient NPQ pathway.
Sugar phosphorylation modulates ADP inhibition of maize mitochondrial hexokinase
Authors: Galina Antonio , Logullo Carlos , Fernandes de Souza Edmilson , Lazzaro Rezende Gustavo , Seixas da Silva Wagner
Published: March 2003

The preference of maize (Zea mays L.) mitochondrial hexokinase (EC 2.7.1.1.) for glucose and fructose and the ADP regulation were evaluated. The Michaelis‐Menten constants (Km) varied between 0.02 and 0.09 mM for glucose and from 2 to 6 mM for fructose as substrates. The value of Vmax was five times higher in the presence of glucose as compared with fructose in membrane‐bound enzyme preparations. It was shown that ADP produced from the reaction inhibits the hexokinase activity (Ki=20–50 μM). However, the inhibition was very specific for adenine nucleotide. Only a small inhibition was observed when 1 mM of UDP, CDP or GDP was included in the assay medium. Nevertheless, the ADP inhibition was observed only when glucose was phosphorylated. In assay conditions where fructose serves as substrate, the affinity for ADP decreased by 10‐fold (Ki varied between 500 and 1 000 μM). These kinetics properties were also observed in partially purified soluble enzyme preparations. These data suggest that the type of hexose bound to the catalytic site modulates the ADP control of maize mitochondrial hexokinase.
Oligomeric state of the tonoplast proteins: Structure of the putative malate transporter in Catharanthus roseus
Authors: Lahjouji Karim , Canut Hervé
Published: March 2003

Vacuolar malate transport in Catharanthus roseus is probably mediated by a 37 kDa intrinsic tonoplast protein identified with a photolyzable malate analog. Antibodies raised against the protein inhibit malate uptake in isolated vacuoles. We report here the native molecular mass and the oligomeric state of the putative malate transporter which were determined from two‐dimensional native electrophoresis. In its first dimension, the electrophoresis used a charge shift method developed for isolating native membrane protein complexes from purified tonoplast vesicles. In combination with a second dimension of sodium dodecylsulfate electrophoresis, it enables the determination of the oligomeric state and subunit composition of non‐dissociated complexes. In such analyses, most of the tonoplast proteins of Catharanthus roseus appear to have a complex structure. In native gels (first dimension), both the photoprobe and the antibodies recognized a 160 kDa protein. The photolabelling characteristics correlate well with the main features of malate transport activity. The 160 kDa protein, when analyzed in the second dimension, contained the 37 kDa polypeptide as a subunit. In addition, cross‐linking with dimethyl suberimidate (DMS) in the intact tonoplast vesicles resulted in the disappearance of the 37 kDa monomer protein band with concomitant appearance of additional bands of molecular masses higher than the monomer, i.e. 73 and 160 kDa. These results, taken together, suggest that the putative malate transporter exists in the tonoplast as a tetramer.
Thermal stress induces differential degradation of Rubisco in heat‐sensitive and heat‐tolerant rice
Authors: Bose Anindita , Tiwari Bs , Chattopadhyay Manas K , Gupta Sudhiranjan , Ghosh Bharati
Published: March 2003

Degradation of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco, EC.4.1.1.39), due to elevation in atmospheric temperature, and extent of enzyme damage, due to varietal differences, were studied by [ S]‐methionine pulse‐chase, transcript level of the large subunit (LSU), and protease activity in two rice cultivars. The cultivars N 22 and IR 8 are certified as thermotolerant and thermosensitive, respectively. Differential responses were observed in both cultivars, with the N 22 showing greater thermostability of the Rubisco protein up to 45°C, whereas IR 8 was thermolabile. Elevation of the temperature to 50°C favored the degradation of the protein in both cultivars. The transcript level of the LSU, as studied by Northern blot hybridization, also showed thermostability in N 22, whereas it was thermosensitive in IR 8. Protease activity, as measured by Western blot analysis using purified Rubisco, revealed the same trend in both cultivars and was correlated with protein turnover by [ S]‐methionine and Northern blot analysis. The results indicate that genetic differences exist in two rice cultivars and that the heat‐tolerant cultivar has a protective mechanism against thermal degradation of Rubisco.
Parameters interacting with mannose selection employed for the production of transgenic sugar beet
Authors: Joersbo Morten , Guldager Petersen Steen , Okkels Finn T.
Published: March 2003

The mannose selection system employs the phosphomannose isomerase (PMI) gene as selectable gene and mannose, converted to mannose‐6‐phosphate by endogenous hexokinase, as selective agent. The transgenic PMI‐expressing cells have acquired the ability to convert mannose‐6‐phosphate to fructose‐6‐phosphate, while the non‐transgenic cells accumulate mannose‐6‐phosphate with a concomitant consumption of the intracellular pools of phosphate and ATP. Thus, certain steps of mannose selection depend on the cells’ own metabolism which may be affected by a number of factors, some of which are studied here using Agrobacterium tumefaciens‐mediated gene transfer to sugar beet cotyledonary explants. Four frequently employed saccharides (sucrose, glucose, fructose, and maltose) were tested at various concentrations and were found to interact strongly with the phytotoxic effect of mannose, glucose being able to counteract nearly 100% of an almost complete mannose‐induced growth inhibition. Sucrose, maltose, and fructose also alleviated significantly the mannose‐induced growth inhibition, but were 4‐, 5‐, and 7‐fold less potent than glucose, respectively (calculated as hexose equivalents). The transformation frequencies were also dependent on the nature and concentration of the added carbohydrates, but in this respect sucrose resulted in the highest transformation frequencies, about 1.0%, while glucose and fructose gave significantly lower frequencies. The selection efficiencies were highest in the presence of maltose where no non‐transgenic escapes were found over a range of concentrations. The effect of the light intensity was also investigated and the transformation frequencies were positively correlated to light intensity, although the relative impact of light on growth in the presence of mannose appeared not to be dependent on the mannose concentration. Additional phosphate in the selection media had a strong positive effect on the transformation frequencies, suggesting phosphate limitation during selection. The mannose selection system was found to be relatively genotype‐independent, provided a slight optimization of the mannose concentrations during selection. Analysis of F1‐offspring showed that all studied primary transformants resulted in PMI‐expressing plantlets and that the segregational patterns were in accordance with expectations in at least 50% of the transformants, confirming the stable and active inheritance of the PMI‐gene.
Insulin‐stimulated ribosomal protein synthesis in maize embryonic axes during germination
Authors: Sánchez de Jiménez Estela , Beltrán‐Peña Elda , Ortíz‐López Adriana
Published: March 2003

Addition of insulin to maize seed (Zea mays L. cv. Chalqueño) was found to accelerate germination and seedling growth. Insulin‐stimulated maize axes showed enhancement of

S‐methionine incorporation into ribosomal proteins (rp) and mobilization of S6 rp mRNA into polysomes. Increase in S6 rp phosphorylation of the small ribosomal subunit (40S) was observed in

P‐orthophosphate pulse‐labeled experiments when maize axes were stimulated by insulin. Application of either wortmannin or rapamycin, inhibitors of protein kinases of the insulin transduction pathway, abolished the insulin stimulatory effect on S6 rp phosphorylation and on ribosomal protein synthesis. The above data are interpreted as an indication of the existence of an insulin‐stimulated signal transduction pathway in maize tissues that is involved in the regulation of translation.
Polyamine levels during the development of zygotic and somatic embryos of Pinus radiata
Authors: Minocha Rakesh , Smith Dale R. , Reeves Cathie , Steele Kevin D. , Minocha Subhash C.
Published: March 2003

Changes in the cellular content of three polyamines (putrescine, spermidine and spermine) were compared at different stages of development in zygotic and somatic embryos of Pinus radiata D. Don. During embryo development, both the zygotic and the somatic embryos showed a steady increase in spermidine content, with either a small decrease or no significant change in putrescine. This led to a several‐fold increase in spermidine/putrescine ratios during development of both types of embryos. Cell cultures of plant‐forming and non‐plant‐forming lines derived from the same clone and growing on proliferation (maintenance) medium differed significantly in their polyamine levels. Mature, cotyledonary stage somatic embryos capable of germination and formation of plants could be distinguished by their higher spermidine/putrescine ratios from abnormal cotyledonary stage somatic embryos which were incapable of forming plants.
Respiratory activities in chloramphenicol‐treated tobacco cells
Authors: Zhang Q. , Wiskich J.T. , Soole K.L.
Published: March 2003

Chloramphenicol (CAP) inhibited tobacco cell growth as shown by a reduction (34%) of cell mass 4 days after treatment. The rates of cell respiration were slightly higher than control under coupled conditions. However, CAP‐treated cells showed a decreased maximal capacity of the cytochrome pathway (48%) and an increased maximal capacity of alternative path (56%) 4 days after treatment. In purified mitochondria, the rates of NADH or malate oxidation under state 4 conditions were not significantly changed by CAP treatment. However, the state 3 rates were 34–40% lower in CAP‐treated than in control mitochondria. Succinate oxidation decreased by 31–46% under both state 4 and state 3 conditions after CAP treatment. The activities of complexes I, III, and IV, which contain mitochondrially encoded subunits, decreased by about 50% in CAP‐treated mitochondria. There was also a decrease in the contents of mitochondrial cytochromes. Unexpectedly, the activities of complex II and the matrix‐facing rotenone‐insensitive NADH dehydrogenase, which are thought to be nuclear‐encoded, also declined. The activities of external NADH dehydrogenase, NAD‐linked malic enzyme, and fumarase remained unchanged after CAP treatment. There was a slight increase in the activity and protein level of alternative oxidase. An electrochemical gradient across the mitochondrial membranes was observed by Rhodamine 123 staining in CAP‐treated cells. However, the morphology of most of the mitochondria changed from spherical to vermicular. A method for purifying a high yield of intact mitochondria from tobacco cell suspension cultures is described.
Abscisic acid immunolocalization and ultrastructural changes in water‐stressed lavender (Lavandula stoechas L.) plants
Authors: Pastor Alicia , López‐Carbonell Marta , Alegre Leonor
Published: March 2003

The relationship between the bulk abscisic acid (ABA) content, ABA compartmental redistribution, and chloroplast ultrastructural changes was studied in leaves of lavender (Lavandula stoechas L.) plants subjected to water stress. ABA was uniformly distributed in the cytosol, nucleus, chloroplasts, and cell walls of mesophyll cells in well‐watered plants. In plants subjected to water stress (−2.6 MPa water potential) the bulk leaf ABA increased from 900 to 3 600 pmol g−1 fresh weight. At the ultrastructural level, the first indication of this rise in ABA was a 4‐fold increase in ABA immunolabeling in the cell wall in which the highest labeling values were recorded. This increase in apoplastic ABA in lavender was not attributable to ABA release from the chloroplast, because a simultaneous increase in ABA labeling was observed in both the chloroplast and nucleus (2‐ and 3‐fold, respectively). Water stress induced a progressive increase in bulk leaf ABA concentration to 13 600 pmol g−1 fresh weight coincident, with the highest immunolabeling of ABA in the nucleus and chloroplast. Under severe water stress, the chloroplast membrane broke down, resulting in leakage of ABA from the chloroplast. The stress‐induced increase of ABA in chloroplasts and nuclei may serve a function other than affecting stomatal movement.