bluuebunny/crossref_metadata_2025 huggingface dataset:
Significance of Epstein–Barr virus status and post‐transplant lymphoproliferative disease in pediatric thoracic transplantation
Authors: Harwood J. S. , Gould F. K. , McMaster A. , Hamilton J. R. L. , Corris P. A. , Hasan A. , Gennery A. R. , Dark J. H.
Published: March 2003

Abstract: Epstein‐Barr virus (EBV)‐associated post‐transplant lymphoproliferative disease (PTLD) is a serious complication of organ and bone marrow transplantation. The importance of EBV matching between recipient and donor remains unclear. Between October 1987 and December 1997, 64 pediatric cardio‐pulmonary transplants were performed at this center (58 hearts, two heart/lungs, four sequential single lungs). The EBV viral capsid antigen (VCA) immunoglobulin G (IgG) status of both donor and recipient was determined at the time of transplant. Of 56 patients from whom paired sera was available for analysis, 27 (50%) were recipient and donor EBV IgG positive, four (7%) were recipient EBV IgG positive and donor EBV IgG negative, and 12 (20%) were recipient EBV IgG negative and donor EBV IgG negative. The remaining 13 (23%) patients were EBV IgG negative but received organs from EBV IgG‐positive donors. The EBV immunoglobulin M (IgM) status was determined from 6 weeks post‐transplant in the 11 mismatches who survived for longer than 28 d. Seven became EBV IgM positive, two remained EBV IgM negative; the status of the remaining two remains unknown. The EBV IgM status was also determined retrospectively in patients who were EBV IgG negative pretransplant and received organs from EBV IgG‐negative donors. Nine became EBV IgM positive; the rest remained negative. PTLD was diagnosed in two of 56 patients from whom paired sera was available; one was donor and recipient EBV IgG negative; the other was donor and recipient EBV IgG positive. No cases of PTLD were diagnosed in the remaining eight patients from whom paired sera was not available. Our experience suggests that PTLD does not occur with any greater frequency in the ‘mismatch’ group, and does not justify EBV matching in pediatric thoracic transplantation where there is a higher proportion of EBV‐negative recipients than in adults.
Renal transplantation in children: Psychological and donation‐related aspects from the parental perspective
Authors: Kärrfelt Helena M. E. , Berg Ulla B. , Lindblad Frank I. E.
Published: March 2003

Abstract: Parent(s) accompanying their 18 children to the annual medical follow‐up after renal transplantation were interviewed by a child psychiatric social worker. Thirteen of the children had received their grafts from one of their parents, two from other relatives, and three from cadaveric donors. The aims of this interview were to study the decision‐making process regarding donation, and the consequences, reflections, and psychological reactions from the parental perspective. Although most parents reported improved psychosocial functioning of the family, many parents also reported significant psychological distress, in many cases complicated by unemployment related to the care of the child. Most parent donors reported that the relationship with their child had improved. For most parents, the decision about the donation seemed to have been a matter of course. However, the process may have induced suffering in those parents who had felt obliged to donate. Thus, questions regarding donation must be approached in a professional and non‐judgmental manner when parents are informed about the preconditions of transplantation. The present results indicate a need of psychosocial support for all families during the transplantation process. Therefore, a psychologist and a social worker have been included in the pediatric nephrology team at our unit. The donors also require further information concerning the operative details as well as in regard to the post‐operative pain.
Epstein–Barr virus‐related lymphoproliferation in children after liver transplant: Role of immunity, diagnosis, and management
Authors: Smets F. , Sokal E. M.
Published: March 2003

Abstract: Tumor occurrence following immunosuppression remains a major concern in children after liver transplantation. More than 50% of these tumors belong to the post‐transplant lymphoproliferative diseases (PTLD) and are diagnosed during childhood. These PTLD are mostly related to primary Epstein–Barr virus (EBV) infection and a heavy immunosuppressive regimen. Improvement in their prognosis was reached thanks to a better knowledge of their pathogenesis, risk factors and clinical presentation, linked probably to earlier management. However, their incidence remains stable (occurring in 5–15% of children after liver transplantation) despite different pre‐emptive strategies based on these parameters. Moreover, acute graft rejection and subsequent risk of graft loss is a common side‐effect of PTLD treatment. EBV viral load determination by quantitative polymerase chain reaction (PCR) is so far the only predictive marker proposed for PTLD prevention and PTLD treatment monitoring, although limited by a lack of specificity. New immunologic techniques have allowed the demonstration of a defect of the EBV‐specific cellular immunity in the patients with PTLD. The level of immunity is correlated to the viral load and improves during recovery from PTLD. These recent findings add further knowledge to PTLD pathogenesis and management.
Atorvastatin treatment for hyperlipidemia in pediatric renal transplant recipients
Authors: Argent Elizabeth , Kainer Gad , Aitken Maggie , Rosenberg Andrew R. , Mackie Fiona E.
Published: March 2003

Abstract: The objective of this prospective study was to determine the prevalence of hyperlipidemia in our pediatric renal transplant patients and to treat those with persistently elevated cholesterol and/or low‐density lipoprotein (LDL) levels. All patients with a functioning renal allograft for greater than 6 months were studied (n = 18). Patients with cholesterol and/or LDL levels greater than the 95th percentile (n = 9) were commenced on an HMG‐CoA reductase inhibitor, Atorvastatin and monitoring was performed for efficacy and adverse effects. Total serum cholesterol was elevated in 11 of 18 (61%) and triglyceride (TG) was elevated in 12 of 18 (67%) patients. Atorvastatin treatment was effective with a mean percentage reduction of total cholesterol of 41 ± 10% (p < 0.01 vs. before treatment), LDL 57 ± 7% (p < 0.01 vs. before treatment) and TG 44 ±25% (p = 0.05 vs. before treatment). No adverse effects on allograft function or cyclosporin levels were experienced. Hyperlipidemia is a common problem and Atorvastatin is a safe and effective treatment in pediatric renal transplant recipients.
Increased expression of cytotoxic effector molecules: Different interpretations for steroid‐based and steroid‐free immunosuppression
Authors: Satterwhite Thomas , Chua Mei‐Sze , Hsieh Szu‐Chuan , Chang Stella , Scandling John , Salvatierra Oscar , Sarwal Minnie M.
Published: March 2003

Abstract: Cytotoxic T lymphocyte (CTL) effector molecules have been studied as markers of acute rejection in renal allograft recipients on steroid‐based immunosuppression. We hypothesized that basal CTL gene expression may vary with time post‐transplantation as well as with different immunosuppression protocols (steroid‐based or steroid‐free). Variations in CTL gene expression may thus impact on the ability to predict acute allograft rejection. We used the non‐invasive method of quantitative competitive‐reverse transcription‐polymerase chain reaction (QC‐RT‐PCR) to quantify the amounts of CTL effector molecules (granulysin, GL; perforin, P; granzyme B, GB) in serial peripheral blood lymphocyte (PBL) samples from steroid‐free and steroid‐based adult and pediatric renal allograft recipients. Patients on both protocols were clinically monitored by protocol biopsies at 1, 3, 6, and 12 months post‐transplantation and for graft function at 1 yr post‐transplantation in a separate clinical study. Steroid‐free patients with stable graft function showed an increase in GL, P, and GB gene expression over time post‐transplantation with the increase being seen largely by the first post‐transplant month. A further increase in GL expression was noted at the end of the first post‐transplant year in the absence of acute rejection, whereas GB and P levels were unchanged. At comparative time‐points post‐transplantation, CTL genes were found to be higher in steroid‐free patients with stable graft function, compared to steroid‐based recipients with either clinically stable graft function or acute rejection. This study suggests that levels of CTL gene expression, although important in a steroid‐based regimen to monitor the risk of acute rejection, may not be similarly applied in patients on steroid‐free immunosuppression. The early increase in levels seen in steroid‐free patients appears to correlate with the total absence of steroids. As steroid‐free patients seem to have a lower incidence of acute rejection and better long‐term graft function at 1 yr, the early increase in CTL genes in the absence of acute rejection may suggest an early adaptive immune activation response, promoting early graft acceptance in this protocol.
Megadose transplantation of highly purified haploidentical stem cells: current results and future prospects
Authors: Handgretinger Rupert , Klingebiel Thomas , Lang Peter , Gordon Paul , Niethammer Dietrich
Published: March 2003

Abstract: The transplantation of megadoses of haploidentical hematopoietic stem cells is for a number of children with malignant or nonmalignant diseases the only curative approach. In order to prevent severe GvHD, the removal of T lymphocytes from the stem cell graft either by positive selection of CD34+ stem cells or by negative depletion of CD3+ T lymphocytes is necessary. We present the results obtained so far by CD34+ positive selection and discuss new techniques of graft engineering which might hopefully further improve the outcome of haploidentical stem cell transplantation.
Enhancement of photosystem II photoreactions and high pH stability in thylakoids from cotyledonary leaves of Brassica juncea raised under sodium chloride stress
Authors: Saradhi Alia, P. Pardha , Mohanty Prasanna
Published: March 2003

Enhancement in the rates of photosystem (PS) II‐catalysed O2 evolution was observed with thylakoids isolated from cotyledonary leaves of Brassica juncea seedlings raised in medium containing 200 mM NaCl compared to controls. The nature of this enhancement in PS II activity by NaCl treatment has been investigated. The pH profile showed an optimal PS 11(H2O→FeCN) activity at pH 7.5 in thylakoids of both controls and NaCl‐raised seedlings. However, the thylakoids from NaCl‐raised plants showed significantly higher PS II activity at all the pHs (from 6.0 to 9.0) with maximal difference occurring at alkaline pHs. Besides the enhanced electron transport rates, light‐induced proton uptake was about 30% higher in the thylakoids from NaCl‐raised plants than in the control thylakoids. The 3‐(3,4‐dichlorophenyl)‐1, 1‐dimethylurea (DCMU)‐induced enhancement in the room temperature fluorescence was significantly higher in thylakoids from NaCl‐grown plants compared to controls, suggesting more efficient PS II photochemical reactions in thylakoids from NaCl‐raised seedlings. The analysis of the changes in the fluorescence yield of Chl also showed an enhancement in Fv level in NaCl‐raised plants, suggesting that NaCl treatment stimulates the photochemistry of PS II. Analysis of light saturation kinetics of PS II [H2O→2,6‐dichloro‐p‐benzoquinone (DCBQ) or phenylenediamine (PD)] activity showed that the extent of stimulation by NaCl under rate‐limiting light intensities was greater than at rate‐saturating intensities. This result indicates that NaCl treatment not only alters the electron transport rates but also the relative quantum yield. Incubation of thylakoids at pH 9.0 inhibited FeCN‐supported PS II activity more drastically in control than in NaCl‐treated thylakoids. Recovery from alkaline‐pH‐induced inhibition occurred when the thylakoids were resuspended at pH 7.5. Reversal in PS II activity was significantly higher in the thylakoids of NaCl‐raised plants than in the control thylakoids. These results suggest that the seedlings raised at moderately elevated levels of NaCl have thylakoids with enhanced stability and PS II photochemical functions.
Induction of a specific isoenzyme of glutamate dehydrogenase during isolation and the first 48 h of culture of Brassica napus leaf protoplasts
Authors: Watanabe Masami , Nakayama Hiroyuki , Watanabe Yukio , Shimada Noritsugu
Published: March 2003

The specific activity of NADH‐glutamate dehydrogenase (GDH, EC 1.4.1.2) in leaf protoplasts (Brassica napus L. cv. Bronowski) was initially low and progressively increased during culture in Murashige and Skoog (MS) medium and MS (−NH4) (ammonium nitrate‐free MS) medium in the dark. Native polyacrylamide gel electrophoresis (PAGE) and tetrazolium staining revealed that the high specific activity of NAD‐GDH (deamination) in leaves correlated with the cathodal isoenzymes, and the high specific activity of NADH‐GDH (amination) in leaf protoplasts to the anodal ones. Changes in isoenzyme pattern were correlated with an increase in the specific activity of NADH‐GDH but not with the NADH‐GDH/NAD‐GDH ratio. The increase in NADH‐GDH (amination) activity of leaf protoplasts was correlated with the occurrence of the isoenzyme GDH7, which was not detected in leaves.
Laser‐mediated gene transfer in rice
Authors: Guo Yande , Liang Hong , Berns Michael W.
Published: March 2003

We report an effective system for introducing exogenous DNA into cells of embryonic calli of Oryza sativa L. cv. Japonica. Plant cells were pretreated in hypertonic buffer to draw some of the water from the cells and were then put into medium of less negative osmotic potential containing exogenous DNA and treated immediately with a laser microbeam (λ=355 nm) to puncture holes in the cell wall and membrane. The pretreatment of the cells generated a gradient of osmotic pressure between the inside and outside of the cells, which facilitated the uptake of material into cells through the laser perforations. Bright yellow‐green fluorescence could be detected inside cells that had been bathed in a solution containing the fluorescent molecule calcein. β‐Glucuronidase (GUS) genes were successfully introduced into rice cells as indicated by gene expression both in post‐treated cells and in plantlets derived from kanamycin‐resistant calli that had been treated by this method.
Growth and maintenance respiration in stems of Quercus alba after four years of CO2 enrichment
Authors: Wullschleger Stan D. , Norby Richard J. , Hanson Paul J.
Published: March 2003

Atmospheric CO2 enrichment is increasingly being reported to inhibit leaf and whole‐plant respiration. It is not known, however, whether this response is unique to foliage or whether woody‐tissue respiration might be affected as well. This was examined for mid‐canopy stem segments of white oak (Quercus alba L.) trees that had been grown in open‐top field chambers and exposed to either ambient or ambient + 300 µmol mol−1 CO2 over a 4‐year period. Stem respiration measurements were made throughout 1992 by using an infrared gas analyzer and a specially designed in situ cuvette. Rates of woody‐tissue respiration were similar between CO2 treatments prior to leaf initiation and after leaf senescence, but were several fold greater for saplings grown at elevated concentrations of CO2 during much of the growing season. These effects were most evident on 7 July when stem respiration rates for trees exposed to elevated CO2 concentrations were 7.25 compared to 3.44 µmol CO2 m−2 s−1 for ambient‐grown saplings. While other explanations must be explored, greater rates of stem respiration for saplings grown at elevated CO2 concentrations were consistent with greater rates of stem growth and more stem‐wood volume present at the time of measurement. When rates of stem growth were at their maximum (7 July to 3 August), growth respiration accounted for about 80 to 85% of the total respiratory costs of stems at both CO2 treatments, while 15 to 20% supported the costs of stem‐wood maintenance. Integrating growth and maintenance respiration throughout the season, taking into account treatment differences in stem growth and volume, indicated that there were no significant effects of elevated CO2 concentration on either respiratory process. Quantitative estimates that could be used in modeling the costs of woody‐tissue growth and maintenance respiration are provided.
Diurnal fluctuation in the composition of chlorophyll a/b light harvesting antenna of photosystem II in young wheat leaves
Authors: Liker Erika , Garab Gyõzõ
Published: March 2003

We investigated the diurnal fluctuation in the composition of the light harvesting chlorophyll a/b antenna of photosystem II in young wheat (Triticum aestivum) leaves grown under periodic day/night irradiation. By means of gel electrophoresis of the polypeptides of thylakoid membranes, we determined the amount of 25 kDa and 27 kDa polypeptides, which are the main components of the peripheral and inner antenna subpopulations, respectively. Our data show a preferential fluctuation in the amount of the 25 kDa protein relative to the 27 kDa polypeptide, in parallel to the fluctuation in the amount of chlorophyll a/b antenna of photosystem II, which suggests that the peripheral antenna plays a role in the diurnal adjustment of the antenna size.
Nature of enhanced respiration during sprouting of aged potato seed‐tubers
Authors: Kumar G. N. Mohan , Knowles N. Richard
Published: March 2003

Respiration of 18‐month‐old Solarium tuberosum L. tubers was about 53% greater than that of 6‐month‐old tubers during sprouting at 23°C; yet, a significant loss of sprout vigor in the older tubers was apparent. Involvement of alternative oxidase (AO) in the age‐induced difference in tuber respiration was assessed. AO was only detected in immunoblots if tissue disks from tubers were pre‐incubated for 24 h prior to isolation of submitochondrial membrane particles (SMPs). No AO1 was detected in SMPs from nonincubated tuber tissue of either age, indicating that it was not contributing to tuber respiration during sprouting as previously thought. Respiratory control and ADP/O ratios indicated that oxidative phosphorylation was fully coupled to electron transport in mitochondria isolated from 6‐ and 18‐month‐old tubers. Cytochrome c oxidase (EC 1.9.3.1) activities of intact mitochondria were also not affected by tuber age. The difference in respiration during sprouting was unique to whole tubers, as oxygen consumption by mitochondria from young and oid tubers was equal on a milligram protein basis. Sprouting 18‐month‐old tubers had 15% more mitochondrial protein per gram fresh weight than did 6‐month‐old tubers. Older tubers also produced more ATP than younger tubers prior to and during sprouting, through a fully coupled, Cyt‐mediated respiratory pathway, reduced sprout vigor notwithstanding. From 5 to 10 days of sprouting, coinciding with development of the age‐induced difference in whole‐tuber respiration, ATP concentration in 18‐month‐old tubers increased to become 52% higher than that in 6‐month‐old tubers. ATP synthase (EC 3.6.1.34), assessed by SDS‐PAGE and immunoblots of β‐ and oligomycin‐sensitivity conferring protein‐subunits, also increased as a proportion of SMP protein in older tubers during this period. Relative to 6‐month‐old tubers, the increased respiration and associated oxidative phosphorylation of 18‐rnonth‐old tubers during sprouting were probably in response to a lower adenylate energy charge (AEC) prior to sprouting (from 0 fo 5 days). From 5 to 10 days of sprouting, AEC of 18‐rnonth‐old tubers increased to equal that of 6‐month‐old tubers and the two tuber ages maintained the same AEC for the remainder of the 20‐day sprouting interval. Higher respiration and lower AEC of older tubers in storage at 4°C, along with the fact that older tubers respired at a higher rate to achieve the same AEC as younger tubers during sprouting, indicate greater utilization of ATP by older tubers.
Calcium reduces toxicity of aminoglycoside antibiotics in sugar beet explants in vitro
Authors: Joersbo M. , Okkels F. T.
Published: March 2003

Aminoglycoside antibiotics are frequently used for the selection of transgenic plant cells. However, for a number of species aminoglycoside selection is inefficient. The objective of the present study was to elucidate factors affecting the phytoloxic effects of aminoglycoside antibiotics. Using non‐transgenic sugar beet cotyledonary explants the interaction between three aminoglycoside antibiotics, kanamycin, neomycin and hygromycin. and Ca2+ was studied by monitoring the effects on growth and shoot formation. The phytotoxic effects of the aminoglycoside antibiotics were strongly dependent on the calcium concentration in the growth media. At comparable levels of the antibiotics (kanamycin 170 μM, neomycin 220 μM, hygromycin 9.5 μM, an elevation of the calcium concentration from 1 to 10 mM resulted in growth increases of approximately 3‐, 2.5‐ and 8‐fold, respectively, and shoot formation was enhanced 1.5‐, 2‐and 6‐fold, respectively. At lower concentrations of the antibiotics, the toxic effect was nearly abolished by increasing the calcium concentration. Additional magnesium, sodium and ammonium did not affect the phytotoxic effects of the aminoglycoside antibiotics. Moreover, the phytotoxic effects of the herbicides glyphosate and phosphinothricin were not decreased by additional calcium. These data suggest the existence of a specific interaction between calcium and aminoglycoside anfibiotics in plants. The implications of these results for the use of aminoglycosides as selective agents in plant transformation are discussed.
Seed dormancy in Avena fatua: Interacting effects of nitrate, water and seed coat injury
Authors: Mclntyre G. I. , Cessna A. J. , Hsiao A. I.
Published: March 2003

In experiments conducted under controlled conditions. KNO3 (50 or 100 mM) promoted germination of a dormant strain (AN 474) of Avena fatua when either one or two holes were pierced in the lower (adaxial) surface of the caryopsis in contact with the nitrate solution. Germination was increased by increasing either the KNO3 concentration or the number of holes in the seed coat. The germination response induced by the application of water to a hole pierced in the upper surface of the caryopsis was. increased by pre‐treatment of the intact caryopsis with KNO3. Treatment with either 50 or 100 mM KNO3 caused a transient reduction in embryo water content of intact cary‐opses, but increased the nitrate and amino‐N content of pierced caryopses prior to germination. Supplying a 100 mM solution of KNO3 to pierced caryopses reduced the total water potential and osmotic potential of the embryo, and increased its pressure potential by the same amount as an equimolar solution of KC1; however, while both treatments promoted germination, the KNO3 induced more rapid germination than the KCI. Both treatments also increased the K+ content of the embryo, the KNO3 again having the greater effect. These results are consistent with the hypothesis, based on our previous investigations, that KNO3 promotes germination of dormant caryopses by accumulating in the embryo where it acts osmotically to increase water uptake. It is also postulated, that, in contrast to KCI, KNG3 may combine an osmotic effect on water uptake with a nutritional effect on protein synthesis.
Cytokinin metabolites and gradients in wild type and transgenic tobacco with moderate cytokinin over‐production
Authors: Eklöf Staffan , Åstot Crister , Moritz Thomas , Blackwell John , Olsson Olof , Sandberg Göran
Published: March 2003

A binary T‐DNA plant expression vector carrying a promoterless isopentenyl transferase (ipt) gene was constructed and used to transform Nicotiana tabacum L. Several primary transformants were obtained that displayed a range of phenotypes characteristic of cytokinin over‐production. Two of the transformants with moderately altered phenotypes, both of which produced viable offspring and expressed the ipt gene at a low level, were selected for use in studies of the regulation of cytokinin metabolism. Both lines were found to contain high concentrations of zeatin‐7‐glucoside (Z7G), indicating that Z7G can accumulate in plants even when the rate of endogenous overproduction of cytokinins is low. This supports the hypothesis that 7‐glucosidation is an important step in the regulation of zeatin (Z) levels. Very sharp gradients in concentration of cytokinin riboside and ribotides, related to age of tissue and distance from the apex, were found in both wild type and transfomed plants, which could be important in developmental regulation and could also account for some of the discrepancies between reported cytokinin levels in various plants. Intriguingly, however, although the combined level of zeatin riboside and ribotide was much higher in the transformed plants than in wild type, the combined level of isopentenyl riboside and ribotide was lower.
K+ status and ABA affect both exudation rate and hydraulic conductivity in sunflower roots
Authors: Quintero José M. , Fournier José M. , Ramos José , Benlloch Manuel
Published: March 2003

Twenty‐day‐old sunflower plants (Helianthus annuus L. cv. Sun‐Gro 380) grown in nutrient solutions with different KCl levels were used to study the effects of K+ status of the root and of abcisic acid (ABA) on the exudation rate (Jv), the hydraulic conductivity of the root (Lp), the fluxes of exuded K+ and Na+ (JK and JNa), and the gradient of osmotic pressure between the xylem and the external medium. Jv and Lp increased in direct proportion to the K+ starvation of the root. Also addition of ABA (4 µM) at the onset of exudation in the external medium made Jv and Lp rise, and this effect also increased with the degree of K+ starvation. Similarly, K+ starvation and ABA promoted both the flux of exuded Na+ and the accumulation of Na+ in the root. We suggest that ABA acts as a regulating signal for the radial transport of water across the root, and that potassium may be an effector of this mechanism.
The cause of PSI photoinhibition at low temperatures in leaves of Cucumis sativus, a chilling‐sensitive plant
Authors: Terashima Ichiro , Noguchi Ko , Itoh‐Nemoto Tomoko , Park Yong‐Mok , Kuhn Akihiro , Tanaka Kiyoshi
Published: March 2003

In a chilling‐sensitive plant, cucumber, chilling of leaves in the light results in irreversible damage to PSI. Recent in vitro studies suggested that hydroxyl radicals, which are formed in the presence of H2O2 and reduced Fe‐S centers, are involved in the PSI inhibition. We therefore examined this possibility in vivo. Chilling of leaves at 5°C in the light caused a temporary increase in H2O2 concentration, which was probably due to the net H2O2 production in vivo. The activity, measured at 5°C, of the thylakoid ascorbate peroxidase (APX), a key enzyme of the H2O2‐scavenging system, was about 20% of that measured at 25°C. The isolated thylakoids retaining high thylakoid APX activity did not show light‐dependent net H2O2 production at 25°C. However, at 5°C, net production of H2O2 was observed. Since the rate of electron flow to molecular oxygen in the isolated thylakoids was ca 5 mmol e− mol−1 Chl s−1 at 5°C, the H2O2‐scavenging capacity was below this level. When intact leaves were illuminated at 5°C at an irradiance of 100 µmol m−2 s−1, the rate of electron transport through PSII was ca 20 mmol e− mol−1 Chl s−1 and more than 80% of QA was in the reduced state. Since thylakoids are uncoupled in cucumber leaves at 5°C in the light. ATP is not formed and energy dissipation in the form of heat is suppressed. Therefore, the electron flow to molecular oxygen would be greater than 5 mmol e− mol−1 Chl s−1. Moreover, under such conditions, components in the electron transport chain, including Fe‐S centers in PSI, were probably reduced. These features indicate that, when cucumber leaves are chilled in the light, hydroxyl radicals can be produced by the Fenton reaction and cause damage to PSI.
Changes in oxidation‐reduction state and antioxidant enzymes in the roots of jack pine seedlings during cold acclimation
Authors: Zhao Sheyun , Blumwald Eduardo
Published: March 2003

The role of glutathione and the response of components of the ascorbic acid‐glutathione cycle in cold acclimation and the acquired freezing tolerance of jack pine (Pinus banksiana Lamb.) seedlings were investigated. An increase in the reduced to oxidized glutathione mole ratio was correlated with the increase in root soluble and membrane‐bound protein thiol concentrations during cold acclimation and after a freeze and thaw event. All the enzymes involved in the ascorbic acid‐glutathione cycle were regulated by low temperatures and increased activities of ascorbic peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, and glutathione reductase were observed after the conditioning of the seedlings to low temperatures. Our results suggest that these enzymes play a protective role following the exposure of the seedlings to freezing temperatures.
Effect of hypoxia on sugar accumulation, respiration, activities of amylase and starch phosphorylase, and induction of alternative oxidase and acid invertase during storage of potato tubers (Solanum tuberosum cv. Russet Burbank) at 1°C
Authors: Zhou Dingbo , Solomos Theophanes
Published: March 2003

The transfer of potato (Solanum tuberosum) tubers from 10 to 1°C was associated with an initial decline in the rate of CO2 output followed by a rapid increase reaching, within some 12 days, a peak which was about 3‐fold higher than at 10°C. Thereafter the rate of CO2 evolution declined gradually for the duration of the experiment. The specific rate of mitochondrial O2 uptake decreased initially, followed by a rise to a level similar to that of mitochondria prepared from tubers stored at 10°C. Low temperature decreased by 30% the capacity of the cytochrome pathway while it sharply increased the capacity of the alternative pathway. Sucrose was the first sugar to accumulate at 1°C, followed after a delay of 6‐7 days by glucose and fructose. Low temperature induced within 4‐5 days a rise in amylase activity which increased by 10‐fold after 30 days. The increase was reflected in only two out of four existing isoforms. In addition a novel isoform of amylase was detected later in storage. The induction and the accumulation of invertase mRNA and extractable activity followed the increase in sucrose but preceded that of hexoses. The activity of starch phosphorylase isoforms was not affected by temperature. There was a 3‐fold increase in chlorogenic acid at 1°C. Hypoxia strongly inhibited the accumulation of sugars and chlorogenic acid, the increase in the amylase activity, and the appearance of the novel isoform. Low O2 totally suppressed the induction of invertase mRNA and increased the capacity of the alternative oxidase. It did not, however, prevent the decrease in cytochrome capacity; neither did it affect the activity of starch phosphorylase isoforms.
Loss of the precise control of photosynthesis and increased yield of non‐radiative dissipation of excitation energy after mild heat treatment of barley leaves
Authors: Bukhov N. G. , Boucher N. , Carpentier R.
Published: March 2003

The after effects of a short exposure of intact barley leaves to moderately elevated temperature (40°C, 5 min) on the induction transients and the irradiance dependencies of photosynthesis and chlorophyll fluorescence are presented. This mild heat treatment strongly reduced the oscillations in the rate of photosynthesis and in the yield of chlorophyll fluorescence. However, only a 25% irreversible inhibition of maximum photosynthetic capacity of photosystem II (PSII) measured by oxygen evolution was produced and the intrinsic quantum yield of PSII measured by the chlorophyll fluorescence ratio (Fm‐ Fo)/Fm decreased by only 15%. In contrast, the above treatment increased radiationless dissipation processes in PSII by a factor of two. In heat‐treated leaves, photosynthesis was not saturated even by strong light. Both ΔpH‐dependent quenching of excitons in PSII (including formation of zeaxanthin) and state 1/state 2 transition were found to be stimulated. Heat exposure enhanced the control of PSII activity by PSI, as evidenced by a significant increase in the quenching effect of far‐red light on the maximum yield of chlorophyll fluorescence. It was deduced that after mild heat treatment, the photosynthetic apparatus in leaves lacks the precise coordinating control of electron transport and carbon metabolism owing to the inability of PSII to support electron transport at a level adequate for carbon metabolism. This effect was not related to the small irreversible thermal damage to PSII, but was rather due to a significant increase in non‐photochemical quenching of excitation energy.
Superoxide dismutase and catalase activities in apple fruit during ripening and post‐harvest and with special reference to ethylene
Authors: Masia Andrea
Published: March 2003

Oxidative stress is involved in many biological systems, among which are fruit ripening and senescence. Free radicals play an important role in senescence and ageing processes. Plants have evolved antioxidative strategies in which superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6) are the most efficient antioxidant enzymes, influencing patterns of fruit ripening. Variations in total SOD and CAT activities were determined at regular intervals during ripening and senescence in on‐tree and cold‐stored apple fruits of the cultivars Fuji and Golden Delicious. In all fruits, internal ethylene concentration was also measured. The results suggest that the onset of ripening, signalled by ethylene burst, is closely related to SOD and CAT activities. In on‐tree fruits the climacteric peak in ethylene was associated with the peaks of SOD and CAT activity in both cultivars. Quite different results were obtained in cold‐stored fruits: Ethylene concentration increased in both cultivars during the storage. CAT activity doubled in both cultivars. SOD activity decreased in Golden Delicious and peaked in Fuji.
Differential impacts of aluminium on microtubule organisation depends on growth phase in suspension‐cultured tobacco cells
Authors: Sivaguru Mayandi , Yamamoto Yoko , Matsumoto Hideaki
Published: March 2003

We investigated the impacts of aluminium (Al) on the structural organisation of microtubules (MTs) in suspension‐cultured tobacco (Nicotiana tabacum L. cv. Samsun) cells using monoclonal anti‐tubulin antibodies coupled with confocal microscopy. Cells were treated with Al (50 μM) in a simple calcium solution (3 mM CaCl2 and 3% [w/v] sucrose, pH 4.5) up to 24 h. The impacts of Al on tobacco cells were found to be distinct, depending on the growth phase of cells. Cells at logarithmic (log) phase lost their structural integrity of phragmoplasts and spindle MTs during Al treatments. In log‐phase cells, the cortical microtubules (CMTs) showed no visible changes in the initial 1 h, but progressive alteration, such as less prominent (after 6 h) and intensive (from 12 h onwards) depolymerisation of MTs, was registered upon increasing Al treatment duration, which accompanied Al‐induced callose formation. The growth of log‐phase cells showed a tendency of inhibition between 6 and 12 h Al treatment, which led to significant growth inhibition from 12 h onwards, suggesting that Al‐induced depolymerisation of CMTs in log‐phase cells is closely linked to the Al‐induced inhibition of cell growth. In contrast, Al‐induced stabilisation of CMTs was found in stationary‐phase cells and these cells required higher Al levels (100 μM) for the depolymerisation of CMTs. These results provide first circumstantial evidence for both depolymerisation and stabilisation of MTs induced by Al, depending on the phases of plant cell growth.
Differential accumulation of ferredoxin‐ and NADH‐dependent glutamate synthase activities, peptides, and transcripts in developing soybean seedlings in response to light, nitrogen, and nodulation
Authors: Turano Frank J. , Muhitch Michael J.
Published: March 2003

Soybean (Glycine max [L.] Merr. cv. Century) seedlings were germinated in vermiculite, sub‐irrigated with a complete nutrient solution, without nitrogen or supplemented with 10 mM KNO3, 5 mM (NH4)2SO4, or 5 mM NH4NO3. After 14 days in the light, or 5 days in the dark, tissues from different organs were harvested separately. Similarly, tissues from different organs from 14‐ or 21‐day‐old nodulated or non‐nodulated soybean seedlings, maintained in the absence of nitrogen, were harvested. Proteins and total RNA were isolated from the different plant organs and used for immunoblot and RNA blot analyses, respectively. Protein or RNA blots were separately incubated with antisera or hybridized with probes specific for either ferredoxin‐dependent glutamate synthase (Fd‐GOGAT) or NADH‐dependent glutamate synthase (NADH‐GOGAT). The specific activity and the abundance of the Fd‐GOGAT peptide and transcript increased, approximately 3–10 times, in cotyledons and hypocotyls/stems in plants germinated in the light compared with those germinated in the dark. Fd‐GOGAT activity, peptide, and transcript were highest in leaves. Except for increases in the specific activity of samples from roots treated with (NH4)2SO4 or NH4NO3, there were minor or no changes in Fd‐GOGAT activity, peptide and transcript among organs of seedlings treated with different nitrogen sources or by nodulation. Low levels of NADH‐GOGAT transcript were detected in all organs. NADH‐GOGAT activity, peptide, and transcript increased in roots of seedlings treated with different nitrogen sources, but these changes were more apparent on RNA blots versus immunoblots. The highest NADH‐GOGAT activity and most abundant amounts of the peptide and transcript were observed in nodules. Despite being induced by different environmental factors, both GOGAT activities are controlled, at least in part, by either gene expression or by RNA stability, because in most instances, both isoenzymes exhibited paralleled changes in specific activity and the abundance of their corresponding peptides and transcripts on immunoblot and RNA blots, respectively. However, there were some exceptions to the parallel increases in specific activities, peptides and transcripts which suggest that post‐translational modification may also regulate the activties of the two GOGAT isoforms. Collectively, the results presented here suggest that the two GOGAT isoforms have distinct physiological functions in soybean.
Photosynthetic response of drought‐ and salt‐stressed tomato and turnip rape plants to foliar‐applied glycinebetaine
Authors: Mäkelä Pirjo , Kontturi Markku , Pehu Eija , Somersalo Susanne
Published: March 2003

The effect of foliar application of glycinebetaine (50 and 100 mM) on photosynthesis, stomatal conductance, photorespiration and transpiration in tomato cv. Bos 3155 (Lycopersicon esculentum Mill.) and summer turnip rape cv. Kulta (Brassica rapa L. ssp. oleifera) plants subjected to drought and salinity are reported. Glycinebetaine application increased net photosynthesis of stressed plants. This was mostly due to increased stomatal conductance following glycinebetaine application as there were no marked changes in light and CO2 saturated rates of O2 evolution. Moreover, glycinebetaine application resulted in a significant decrease of photorespiration both in drought‐ and salt‐stressed plants.
Progressive loss of desiccation tolerance in germinating pea (Pisum sativum) seeds
Authors: Reisdorph Nichole A. , Koster Karen L.
Published: March 2003

Loss of desiccation tolerance during germination has been described in general terms for many orthodox seeds and has been used as a framework to elucidate the mechanisms that confer tolerance to quiescent embryos. A more detailed description of the time course during which desiccation tolerance is lost will allow us to build a more comprehensive picture of the events that contribute to the loss of tolerance. To more thoroughly characterize the loss of desiccation tolerance, we monitored the viability of germinating pea (Pisum sativum L. cv. Alaska) seeds after drying them to a range of moisture contents. Desiccation tolerance is lost in different embryonic tissues at different times during germination. Thus, we looked separately at the effects of drying on radicle and epicotyl survival and on electrolyte leakage from the whole embryonic axis. Using statistical and graphical analysis, we calculated the moisture content at which the population of germinating seeds began to be damaged by dehydration (threshold moisture content, TMC) and at which dehydration damaged the majority of the population (critical moisture content, CMC). CMCs and TMCs differed for each tissue and increased as germination progressed. TMCs appeared at 18 h of imbibition for radicle survival and electrolyte leakage and at 24 h for epicotyl survival. CMCs appeared at 21 h for radicle survival and electrolyte leakage. Among the axis tissues, epicotyls were the least sensitive to dehydration during germination. CMCs for epicotyl survival did not appear until 30 h of imbibition and did not increase to the extent that they did for either radicle survival or electrolyte leakage. Results from these experiments can be used as a framework to correlate the progression of biochemical and anatomical changes to the progressive loss of desiccation tolerance in germinating pea embryos.
Localization of cytokinins in somatic and zygotic embryos of Tilia cordata using immunocytochemistry
Authors: Kärkönen Anna , Simola Liisa Kaarina
Published: March 2003

Immunofluorescent and immunogold labeling was used to study the localization of cytokinins in developing somatic and zygotic embryos of Tilia cordata Miller. Broad‐specificity polyclonal antibodies active against dihydrozeatin riboside (DHZR)/zeatin riboside (ZR)‐type and isopentenyladenosine (iPR)‐type cytokinins were used for immunolabeling. Immunofluorescent microscopy showed that these cytokinins were concentrated in highly cytoplasmic cells showing meristematic character. Cotyledon initials and primary meristems of heart‐stage somatic embryos, as well as heart‐stage zygotic embryos, were labeled. During elongation of embryos, cytokinin immunoreactive material was concentrated to areas having meristematic character. Root apex, shoot meristem, and cotyledon cells of somatic and zygotic cotyledonary embryos, as well as epidermal and subepidermal cell layers of the hypocotyl, showed the strongest immunoreaction. The nucleoli, especially, had a very strong signal. Results at the ultrastructural level with gold‐conjugated protein A supported these conclusions. Gold particles were distributed in the nuclei, especially in the nucleoli and throughout the ground cytoplasm. They were occasionally associated with plastids and mitochondria, but seldom with other organelles.
Physiological and genomic variations in rice cells recovered from direct immersion and storage in liquid nitrogen
Authors: Moukadiri O. , Lopes C. R. , Cornejo M. J.
Published: March 2003

The use of cryoprotectants and slow cooling rates are routine procedures for the cryopreservation of plant cell lines. However, our results with rice (Oryza sativa L., cv. Taipei 309) show that calli can be cryopreserved by direct immersion and stored in liquid nitrogen without any cryoprotection. The efficiency of recovery using this method, as well as a conventional method was generally increased with a previous abscisic acid (ABA) treatment. Following cryopreservation, calli demonstrated some differences with respect to unfrozen calli of the same lines. Thus, resistance to freezing stress (−20°C for 2 h) increased significantly in all lines tested, irrespective of their pre‐incubation with ABA. Calli that had been directly stored in liquid nitrogen also demonstrated a higher competence for genetic transformation than their unfrozen counterparts, as indicated by the transient gene expression levels obtained after particle bombardment. These differences might lead to further biotechnological applications. A genetic analysis of amplified DNA polymorphisms was performed with three independent lines that had been subjected to four combinations of ABA treatment and direct immersion in liquid nitrogen. At the loci screened with the randomly amplified polymorphic DNA (RAPD) markers tested, the genetic variations among lines and among calli of the same line akppear to be more related to tissue‐culture‐induced somaclonal variation than to cryoselection.
Induction of auxin biosynthetic enzymes by jasmonic acid and in clubroot diseased Chinese cabbage plants
Authors: Grsic Slobodanka , Kirchheim Brigitte , Pieper Kerstin , Fritsch Monika , Hilgenberg Willy , Ludwig‐Müller Jutta
Published: March 2003

Nitrilase (NIT) and myrosinase are important enzymes for auxin biosynthesis in Brassicaceae, which is increased during clubroot disease. Therefore, NIT and myrosinase levels during club development and possible regulation mechanisms were investigated. In addition, the occurrence of different nitrilase isoforms in Chinese cabbage has been shown. Nitrilase activity was enhanced in infected roots during later stages of club development (35–42 days after inoculation). However, no differences in nitrilase mRNA levels between infected and healthy roots were found during symptom development. Myrosinase expression was increased in clubbed roots at slightly earlier time points (28 days after inoculation) and also at later time points during infection. The activities of tryptophan oxidizing enzyme (TrpOxE), which catalyzes the first step in tryptophan‐dependent auxin biosynthesis in Brassicaceae, and nitrilase were enhanced after treatment with jasmonic acid (JA) and methyl jasmonate. Similarly, the amount of myrosinase mRNA was increased by JA. During clubroot disease the endogenous concentration of JA increased in infected roots 3–5 weeks after inoculation. From our results it can be concluded that: (1) de novo indole‐3‐acetic acid (IAA) biosynthesis plays a role for symptom development of clubroot disease in Brassicaceae during later developmental stages; and (2) JA which increased during club development, may be involved in the up‐regulation of three enzymes important for IAA synthesis.
Dispersion of energies in worldwide crop formations
Authors: Levengood W. C. , Talbott Nancy P.
Published: March 2003

The findings reported here lend further support to a decade of research which suggests that over 95% of worldwide crop formations involve organized ion plasma vortices that deliver lower atmosphere energy components of sufficient magnitude to produce significant bending, expansion and the formation of unique expulsion cavities in plant stem pulvini, as well as significant changes in seedling development. Here we demonstrated that, in a number of formations, quantitative node alterations can be directly related to fundamental concepts of electromagnetic energy absorption through the atmosphere. Also, in a detailed field study of simulated crop formations, we show that over‐fertilization or gravitropism cannot account for observed physiological alterations. In addition, we demonstrate that details of flattened, intertwined crop patterns can be described by the application of fluid dynamic principles governing the interaction of rectilinearly moving vortex pairs.