bluuebunny/crossref_metadata_2025 huggingface dataset:
A strategy to calculate cyclosporin A area under the time–concentration curve in pediatric renal transplantation
Authors: David‐Neto Elias , Araujo Lilian Pereira , Feres Alves Cristiane , Sumita Nairo , Romano Pascoalina , Yagyu Elisa Midori , Nahas William Carlos , Ianhez Luiz Estevam
Published: March 2003

Abstract:The complete area under the time–concentration curve (AUC) is considered the gold standard for cyclosporin A (CsA) monitoring, particularly in pediatric kidney graft recipients who have great absorption and drug clearance variability. However, completeAUCis time‐consuming and expensive. For this reason, we retrospectively reviewed 131 complete 4‐hAUC(AUC0−4) performed in 34 children (mean age 10.6 ± 2 yr) in order to construct an equation to calculateAUC0−4.The median time after transplantation was 540 (range: 247–1,358) days. Multiple regression analysis was performed either with a single variable or with a combination of two variables. CsA blood concentration at the second hour after the oral morning dose (C2) was the best predictor ofAUC0−4, where  AUC0−4 = 424 + (2.65 × C2),R2 = 0.81, p < 0.001. Only the combination of C1 and C2 offered mathematical improvement over the C2 equation. The same analysis was made for pharmacokinetic curves performed earlier than 6 months (79 ± 55 days, range 8–169 days) and after 1 yr of transplantation. In both time‐periods, C2 was the best parameter to use to calculateAUC0−4.The equations obtained during these two time‐periods were very close to the one for the whole population. Our data shows that C2 can be safely used to estimateAUC0−4. However, for values above 4,000 ng/h/mL, the formula overestimates the trapezoidalAUC0−4.The C2 equation simplifies the CsA monitoring as a result of its high predictive value and clinical feasibility.
Limited surgical interventions in children with posterior urethral valves can lead to better outcomes following renal transplantation
Authors: Bartsch Leah , Sarwal Minnie , Orlandi Pamela , Yorgin Peter D. , Salvatierra Jr Oscar
Published: March 2003

Abstract: There is currently no consensus as to the most appropriate means by which children with posterior urethral valves (PUV) are to be managed prior to transplantation. We compared (i) renal allograft survival and function in patients with PUV vs. those with non‐obstructive causes of ESRD and (ii) graft outcomes in children who had limited interventions (Group 1) vs. those with more extensive urologic surgeries to decompress the urinary tract (Group 2). Twenty‐six pediatric renal transplant recipients had ESRD due to PUV (Group 1, n = 16; Group 2, n = 10). The study group was compared to 23 matched controls with ESRD due to non‐obstructive causes. Five yr patient and graft survival was similar in all patients with PUV (Groups 1 and 2) when compared to all other kidney recipients in the transplant program, 96.2% vs. 98.0% and 87.5% vs. 87.0%, respectively. Although calculated creatinine clearance (Ccr), was similar between the PUV group and controls for the first 4 yr, the 5 yr graft function was significantly lower in the PUV group. (53.7 ± 15.7 vs. 70.2 ± 21.0 mL/min/1.73 m2; p = 0.03). When the two PUV groups were compared, graft survival was equivalent, but graft function was significantly better at 5 yr in Group 1(60.4 ± 10.8 vs. 33.8 ± 9.3 mL/min/1.73 m2; p = 0.02). Thus, patients with PUV managed by a limited intervention approach of vesicostomy with delayed valve ablation or primary valve ablation, had better outcomes. When ESRD is virtually certain, additional pre‐transplant surgeries affecting the urinary tract should be avoided.
Epstein–Barr virus associated disease following blood or marrow transplant
Authors: Gross Thomas G. , Loechelt Brett J.
Published: March 2003

Abstract: EBV associated disease continues to be a problem in the post‐BHT population. The pathogenesis, risk factors, and diagnosis of PTLD, as well as the rationale, efficacy and advantages/disadvantages of various prophylactic, pre‐emptive and treatment strategies are discussed.
Metabolism of starch synthesis in developing grains of the shx shrunken mutant of barley (Hordeum vulgare)
Authors: Tyynelä Jaana , Stitt Mark , Lönneborg Anders , Smeekens Sjef , Schulman Alan H.
Published: March 2003

The shx mutant of barley (Hordeum vulgare L. cv. Bomi) produces grains greatly decreased in starch content and containing smaller A‐starch granules together with normal B‐granules. Soluble starch synthase (SSS) and ADP‐glucose pyrophosphorylase (AGP) are reduced to about 20% normal activity. To help determine the position of the block to starch synthesis in shx, we measured enzyme activities and metabolite levels in developing grains of normal and mutant genotypes in a cv. Bomi background. We demonstrate that sucrose, free hexose, hexose phosphates and, critically, ADP‐Glc accumulate as a result of the mutation. In addition to AGP and SSS, several other enzyme activities are affected in the shx mutant, most of them showing activities 50‐80% of normal. Northern blots showed that transcripts for the AGP small subunit are much less abundant, but of normal size, in shx. These and earlier results together indicate that the metabolic block is at the end of the starch synthetic pathway, with a primary effect on a type I, primer‐independent soluble starch synthase.
Gravitropism in roots of intermediate‐starch mutants of Arabidopsis
Authors: Kiss John Z. , Wright Jonathan B. , Caspar Timothy
Published: March 2003

Gravitropism was studied in roots of wild type (WT) Arabidopsis thaliana (L.) Heynh. (strain Wassilewskija) and three starch‐deficient mutants that were generated, by T‐DNA insertional mutagenesis. One of these mutants was starchless while the other two were intermediate mutants, which had 51% and 60%, respectively, of the WT amount of starch as. determined by light and electron microscopy. The four parameters used to assay gravitropism were: orientation during vertical growth, time course of curvature, induction, and intermittent stimulation experiments. WT roots were much more responsive to gravity than were roots of the slarchless mutant, and the intermediate starch mutants exhibited an intermediate graviresponse. Our data suggest that lowered starch content in the mutants primarily affects gravitropism rather than differential growth because both phototropic curvature and growth rates were approximately equal among all four genotypes. Since responses of intermediate‐starch mutants were closer to the WT response than to that of the starchless mutant, it appears that 51–60% of the WT level of starch is near the threshold amount needed for full gravitropic sensitivity. While other interpretations are possible, the data are consistent with the starch statolith hypothesis for gravity perception in that the degree of graviresponsiveness is proportional to the total mass of plastids per cell.
In vitro synthesis of fractofuranosyl‐only oligosaccharides from inulin and fructose by purified chicory root fructan:fructan fructosyl transferase
Authors: Van den Ende Wim , Roover Joke De , Van Laere André
Published: March 2003

Besides the non‐reducing inulin series of gluco‐frueto oligosaccharides which are common in Asteraceae, two series of reducing fructofuranosyl‐only oligosaccharides occur in overwintering, forced, and sprouting chicory roots. Such inulo‐n‐oses could be produced by the action of an endo‐inulinase on gluco‐fructo oligosaccharides. We show here that similar series of inulo‐n‐oses as found in vivo can be produced by incubating fructose and inulin with a purified fructamfructan tructosyl transferase (FFT; EC 2.4.1.100) from chicory roots (Cichorium intybus L.). Therefore fructose (but not glucose) can act as an acceptor for FFT. Since the inulo‐n‐oses only appear in vivo once the endogenous fructose concentration increases, we conclude that they are not the result of a putative endo‐inulinase but of FFT activity.
Partial purification of a plasma membrane flavoprotein and NAD(P)H‐oxidoreductase activity
Authors: Van Gestelen Peter , Asard Han , Caubergs Roland J.
Published: March 2003

Plasma membrane flavins and pterins are considered to mediate important physiological functions such as blue light photoperception and redox activity. Therefore, the presence of flavins and pterins in the plasma membrane of higher plants was studied together with NAD(P)H‐dependent redox activities. Plasma membranes were isolated from the apical hooks of etiolated bean seedlings (Phaseolus vulgaris L. cv. Limburgse Vroege) by aqueous two‐phase partitioning. Fluorescence spectroscopy revealed the presence of two chromophores. The first showed excitation maxima at 370 and 460 nm and an emission peak at 520 nm and was identified as a flavin. The second chromophore was probably a pterin molecule with excitation peaks at 290 and 350 nm and emission at 440 nm. Both pigments are considered intrinsic to the plasma membrane since they could not be removed by treatment with hypotonic media containing high salt and low detergent concentrations. The flavin concentration was estimated at about 500 pmol mg−1 protein. However difficulties were encountered in quantifying the pterin concentrations. Protease treatments indicated that the flavins were non‐covalently bound to the proteins. Separation of the plasma membrane proteins after solubilisation by octylglucoside, on an ion exchange system (HPLC, Mono Q), resulted in a distinct protein fraction showing flavin and pterin fluorescence and NADH oxidoreductase activity. The flavin of this fraction was identified as flavin mononucleotide (FMN) by HPLC analysis. Other minor peaks of NADH:acceptor reductase activity were resolved on the column. The presence of distinct NAD(P)H oxidases at the plasma membrane was supported by nucleotide specificity and latency studies using intact vesicles. Our work demonstrates the presence of plasma membrane flavins as intrinsic chromophores, that may function in NAD(P)H‐oxidoreductase activity and suggests the presence of plasma membrane bound pterins.
Magnesium deficiency results in accumulation of carbohydrates and amino acids in source and sink leaves of spinach
Authors: Fischer E. S. , Lohaus G. , Heineke D. , Heldt H. W.
Published: March 2003

Accumulation of assimilates in source leaves of magnesium‐deficient plants is a well‐known feature. We had wished to determine whether metabolite concentrations in sink leaves and roots are affected by magnesium nutrition. Eight‐week‐old spinach plants were supplied either with a complete nutrient solution (control plants) or with one lacking Mg (deficient plants) for 12 days. Shoot and root fresh weights and dry weights were lower in deficient than in control plants. Mg concentrations in deficient plants were 11% of controls in source leaves, 12% in sink leaves and 26% in roots, respectively. As compared with controls, increases were found in starch and amino acids in source leaves and in sucrose, hexoses, starch and amino acids in sink leaves, whereas they were only slightly enhanced in roots. In phloem sap of magnesium‐deficient and control plants no differences in sucrose and amino acid concentrations were found. To prove that sink leaves were the importing organs they were shaded, which did not alter the response to magnesium deficiency as compared with that without shading. Since in the shaded sink leaves the photosynthetic production of metabolites could be excluded, those carbohydrates and amino acids that accumulated in the sink leaves of the deficient plants must have been imported from the source leaves. It is concluded that in magnesium‐deficient spinach plants the growth of sink leaves and roots was not limited by carbohydrate or amino acid supply. It is proposed that the accumulation of assimilates in the source leaves of Mg‐deficient plants results from a lack of utilization of assimilates in the sink leaves.
NaCl‐induced accumulation of glycinebetaine in four subtropical halophytes from Pakistan
Authors: Khan M. Ajmal , Ungar Irwin A. , Showalter Allan M. , Dewald Howard D.
Published: March 2003

Variation in both the total content and the concentration of glycinebetaine in response to increasing soil salinity was studied in the salt‐secreting Atriplex griffithii Moq., the leaf succulent Suaeda fruticosa (L.) Forssk., the stem succulent Haloxylon recurvum Bunge ex Boiss. and the osmotically adjusting desert grass Halopyrum mucronatum (L.) Stapf. collected from a subtropical maritime desert in Pakistan. Glycinebetaine content (mmol kg−1 dry weight) increased with increasing NaCl in Atriplex griffithii, Haloxylon recurvum and Halopyrum mucronatum, but peaked at 600 mM NaCl for Suaeda fruticosa and declined thereafter. Glycinebetaine concentration (mmol l−1 tissue water) increased with increasing salinity in all four halophyte species and was sufficiently high to serve as an osmoticum in all cases.
Elicitor‐induced changes of wall‐bound and secreted peroxidase activities in suspension‐cultured spruce (Picea abies) cells are attenuated by auxins
Authors: Mensen Ruth , Hager Achim , Salzer Peter
Published: March 2003

In ectomycorrhizae auxins are proposed to attenuate elicitor‐induced defence reactions in the host plant. To examine this hypothesis we compared the elicitor‐induced accumulation of peroxidase isoforms between suspension‐cultured spruce (Picea abies[L.] Karst.) cells incubated in media with and without auxins. In spruce cells changes in ionically and covalently wall‐bound as well as symplasmic peroxidase (EC 1.11.1.7) activities were observed when elicitors from the following fungal species were applied: (1) Hebeloma crustuliniforme, an ectomycorrhizal partner of spruce; (2) Suillus variegatus, an ectomycorrhizal fungus incompatible with spruce; (3) Heterobasidion annosum, a spruce pathogen. Activity staining after SDS‐PAGE and western blotting showed an accumulation of an ionically wall‐bound 38‐kDa peroxidase isoform. In addition, two covalently wall‐bound isoforms (34 and 53 kDa) that could be released from spruce cell walls by cellulase and pectinase treatment were also induced by elicitors from these fungi. Moreover, in cells cultured without auxins all the elicitors triggered a rapid and transient accumulation of ionically wall‐bound peroxidases, which reached a maximum activity 48 h after elicitor application. This early and transient peroxidase accumulation was diminished and delayed in cells cultured in the presence of auxins. In contrast, activity of peroxidases released into the culture medium of spruce cells or into the medium of protoplasts was suppressed by the elicitors of Hebeloma crustuliniforme. However, this suppression was attenuated by the action of auxins. It is suggested that under natural conditions, in infected spruce roots, the elicitors of the compatible fungus cause both suppression of the peroxidase (which is secreted to the free space of the roots), and induction of wall‐bound and symplasmic peroxidases. On the other hand, auxins synthesized by the fungus could weaken these different elicitor‐mediated effects.
Chitinase accumulates systemically in wounded poplar trees
Authors: Clarke Howard R. G. , Lawrence Susan D. , Flaskerud Jeff , Korhnak Theresa E. , Gordon Milton P. , Davis John M.
Published: March 2003

Young leaves of poplar (Populus spp.) trees accumulate novel messenger RNAs shortly after the mature leaves have been mechanically wounded. These systemically wound‐induced (win) mRNAs are thought to encode proteins involved in plant defense. In the present paper, transgenic tobacco plants that ectopically expressed a win6 cDNA contained a novel chitinase activity that was not present in normal tobacco. This demonstrated Win6 was a chitinase. Win6 and a related protein Win8 accumulated in wounded poplars. Win6 and Win8 had low isoelectric points (ca 4) as predicted from their nucleotide sequence. The wound‐inducible increase in Win6 and Win8 was correlated with an increase in chitinase (EC 3.2.1.14) activity in poplar leaf extracts. We conclude that mechanical wounding induces chitinase in poplar trees, and speculate that the induced chitinase activity could act to increase the tolerance of poplars to opportunistic wound pathogens.
Growth requirement for N as a criterion to assess the effects of physical manipulation on nitrate uptake fluxes in spinach
Authors: Steege Margreet W. Ter , Stulen Ineke , Wiersema Peter K. , Paans Anne J. M. , Vaalburg Wim , Kuiper Pieter J. C. , Clarkson David T.
Published: March 2003

The effects of physical manipulation of hydroponically grown plants of spinach (Spinacia oleracea L., cvs Subito and Glares) on nitrate uptake fluxes were studied in a long‐term experiment (3 days), and in short‐term label experiments (2 h) with 13N‐nitrate and 15N‐nitrate. In the long‐term experiment, net nitrate uptake rate (NNUR) was measured by following the nitrate depletion in the uptake solution, which was replaced at regular intervals. In the short‐term experiments, NNUR and nitrate influx were measured by simultaneous application of 13N‐nitrate and 15N‐nitrate. Plants were gently transferred into the labelled uptake solution, as is usually done in nutrient uptake studies. In addition, a more severe physical manipulation was carried out, including blotting of the roots, to mimic pretreatments which involve more handling of the plants prior to uptake measurements. Nitrate influx was measured immediately after physical manipulation and after 2 h of recovery. To assess the impact of the physical manipulation the experimentally determined nitrate uptake fluxes were compared with the N demand for growth, defined as relative growth rate (RGR) times plant nitrogen concentration (PNC) of parallel plants, which were left undisturbed. Nitrate influx and efflux were both subject to changes after physical manipulation of the plants. Physical handling, however, did not always result in an alteration of NNUR, which complicates the determination of the length of the recovery period. The impact of the handling and the time course of the recovery depended on the severity of the disturbance and were independent of the light conditions during the experiments. Even after a gentle transfer of the plants, recovery, in most cases, was not complete within 2 h. The data emphasise the need for minimal disturbance of plants during the last hours prior to nutrient uptake measurements.
Basic chitinases are correlated with the morphogenic response of flax cells
Authors: Roger David , Gallusci Philippe , Meyer Yves , David Alain , David Hélène
Published: March 2003

Flax (Linum usitatissimum) hypocotyl protoplasts immobilized in a calcium‐alginate matrix give rise to embryo‐like structures. A direct correlation was established between the presence of a set of ionically‐bound cell wall proteins, which includes the basic polypeptides P184 and P183 with an apparent molecular mass of 25 kDa, and this morphogenic response. Microsequencing of tryptic fragments from P184 and P183 indicated homologies with the chitinase family. These homologies were confirmed by demonstrating that, after renaturation, such proteins express a potential chitinase activity in SDS‐PAGE gel containing glycol chitin as synthetic substrate. Using degenerate primers from P184 internal sequences, we isolated one partial genomic sequence of a chitinase of 626 bp from which a putative 74‐amino acid sequence, disrupted by one intron, was deduced. High degrees of homology with several plant chitinases, including those expressed during somatic embryogenesis or in seeds, were observed. P184 microsequences match the corresponding sequence deduced from the chitinase PCR‐fragment perfectly.
Identification and characterisation of cultivar‐specific 22‐kDa heat shock proteins from mitochondria of Pisum sativum
Authors: Wood Carlton K. , Pratt James R. , Moore Anthony L.
Published: March 2003

Pea plants (Pisum sativum L. cv. Feltham First) exposed to a heat stress of 37°C for 6 h accumulated two low molecular weight (LMW) heat shock proteins (HSPs) of molecular mass 22 kDa. The two LMW HSPs were associated with purified mitochondria. N‐terminal amino acid sequencing analysis indicates that the more basic of these proteins is a novel protein. The response of other cultivars of P. sativum to heat shock revealed that up to three 22‐kDa HSPs were expressed in a cultivar‐specific manner. Evidence presented suggests that the different 22‐kDa HSPs arise as a result of there being multiple 22‐kDa HSP genes. The expression of the most basic novel HSP was studied in the Feltham First cultivar using two dimensional SDS‐PAGE. Treatment of intact plants with chloramphenicol and cycloheximide prior to heat stress treatment indicated that the LMW HSPs were nuclear encoded and de novo synthesised. The response to heat shock was rapid with protein expression detected within 45 min and the protein remained in excess of 6 days following removal of the stress. The protein accumulated to very high levels with maximal expression being 2% of the total mitochondrial protein. The results are discussed in relation to the likely role of LMW HSPs in thermotolerance.
Phosphate starvation‐inducible pyrophosphate‐dependent phosphofructokinase occurs in plants whose roots do not form symbiotic associations with mycorrhizal fungi
Authors: Murley Vanessa R. , Theodorou Maria E. , Plaxton William C.
Published: March 2003

Previously, we reported that phosphate (Pi) starvation of suspension cells or seedlings of Brassica nigra results in a large elevation in the activity of pyrophosphate‐dependent phosphofructokinase (EC 2.7.1.90) (PFP). However, other researchers have found that Pi deprivation either causes a significant reduction or no change in extractable PFP activity of Catharanthus roseus suspension cells, or roots of Nicotiana tabacum and Phaseolis vulgaris seedlings. The present study was undertaken to examine the prevalence of Pi starvation‐inducible PFP in seedlings, root cultures, or suspension cells of a variety of plant species differing in phylogenetic relatedness to B. nigra. In all species examined, fresh weights were decreased and acid phosphatase (EC 3.1.3.2) activities were increased by Pi limitation. Brassica napus suspension cells, Arabidopsis thaliana seedlings, and roots of B. napus, B. carinata, B. oleracea, Beta vulgaris, Fagopyrum esculentum, Sinapis alba, and S. arvensis seedlings grown with Pi‐limited media contained 170–510% greater PFP activity than did nutrient‐sufficient controls. In five of these species the induction of PFP activity by Pi limitation was based in part upon an increased susceptibility of the enzyme to its allosteric activator, fructose‐2,6‐bisphosphate. By contrast, the PFP activity in Pi‐deprived Lycopersicon esculentum root cultures and Nicotiana silvestris suspension cells decreased by 45–65% relative to Pi‐sufficient controls. Immunoblotting of extracts from A. thaliana seedlings, S. arvensis, F. esculentum and B. oleracea roots, and B. napus suspension cells probed with potato tuber PFP antibodies indicated that the upregulation of PFP activity by Pi stress in these species was not correlated with an alteration in the amount or subunit composition of PFP. Our findings suggest that induction of PFP during long‐term Pi starvation may be characteristic of members of the Cruciferae, Chenopodiaceae and Polygonaceae families whose roots do not form symbiotic associations with mycorrhizal fungi.
Organ‐specific localization and molecular properties of three soluble invertases from Lilium longiflorum flower buds
Authors: Ranwala Anil P. , Baird W. Vance , Miller William B.
Published: March 2003

Three soluble invertase (EC 3.2.1.26) isoforms from Easter lily (Lilium longiflorum Thunb. cv. Nellie White) flower buds were purified to apparent homogeneity. Non‐denaturing PAGE showed one band for all three invertases that corresponded to the invertase activity. SDS‐PAGE of purified invertase I gave a single band at 78 kDa, whereas invertases II and III gave three bands at 54, 52 and 24 kDa. Antibodies against tomato fruit acid invertase and Urtica dioica leaf acid invertase recognized all three invertase isoforms, whereas antibodies against wheat coleoptile acid invertase recognized only 56‐ and 54‐kDa bands of invertases II and III. Antibodies against wheat coleoptile invertase recognized the 54‐ and 52‐kDa proteins from crude extracts of all flower organs, and a 72‐kDa protein in both leaf and bulb scale extracts. All three invertases bound to Con‐A peroxidase. Deglycosylation of invertase I with glycopeptidase F was complete and resulted in a peptide of 75 kDa. Invertases II and III were deglycosylated partially by glycopeptidase F and resulted in proteins of 53, 51, 50 and 22 kDa. Invertase I was localized only in anther and filament, whereas the other two isoforms were present in all flower organs.
Acid invertase (sucrose hydrolysis) is not required for sucrose mobilization from the vacuole
Authors: Echeverria Ed
Published: March 2003

The possible involvement of acid invertase (sucrose hydrolysis) as a prerequisite for sucrose mobilization from the vacuole of storage cells was investigated. Sugarcane (Saccharum officinarum) stalks, carrot (Daucus carota) roots and red beet (Beta vulgaris) hypocotyls were planted under greenhouse conditions and allowed to resume growth. The plants, however, were not permitted to become photosynthetically autotrophic by removing the new expanded leaves. Sucrose levels declined significantly in all three tissues without the development of acid invertase (EC 3.2.1.26) during the 21‐day experimental period. Acid invertase and thus sucrose hydrolysis within the vacuole was, therefore, not required for sucrose mobilization.
The influence of the mycorrhiza Glomus etunicatum on drought acclimation in safflower and wheat
Authors: Bryla D. R. , Duniway J. M.
Published: March 2003

A study was done to determine the effects of vesicular‐arbuscular mycorrhizal (VAM) colonization on drought acclimation of host plants. Safflower (Carthamus tinctorius L. cv. S555) and wheat (Triticum aestivum L. cv. Anza) were grown under environmentally controlled conditions with or without the VAM fungus, Glomus etunicatum Becker and Gerd., and were either acclimated (by pre‐exposing plants to a 10–11 day drought period) or unacclimated to drought. Plants from all treatments were then exposed to drought for 9 days, and plant water status and root water uptake were measured. To minimize interactions between drought and P uptake, growth periods were adjusted so that acclimated and unacclimated plants were similar in size when measurements were made. When wheat was acclimated to drought, osmotic adjustment occurred (leaf solute potentials of leaf tissue rehydrated to full turgor were approximately 0.5 MPa lower in acclimated than unacclimated plants); in safflower, osmotic adjustment was minimal when plants were acclimated. Consequently, acclimated wheat plants were able to tolerate drought better than unacclimated plants, and maintained higher leaf water potentials and relative water contents as soil water was depleted. For both safflower and wheat, acclimated plants had higher water use efficiency, and therefore produced more biomass when water availability was limited, than unacclimated plants. However, mycorrhizal colonization did not affect osmotic adjustment, plant water status, water use efficiency or water uptake in either plant species, and therefore had no effect on drought acclimation or resistance.
Characterization of mitochondrial glutamate dehydrogenase from dark‐grown soybean seedlings
Authors: Turano Frank J.
Published: March 2003

Purified preparations of NAD(H)‐glutamate dehydrogenase (GDH, EC 1.4.1.2.) were assayed to determine the effects of mono‐ and divalent cations, nucleotides and select carbon compounds on NAD(H)‐dependent GDH activity. The amination reaction was stimulated 2‐ to 17‐fold by divalent cations (Ca2+ > Cd2+ > Co2+ > Mg2+ > Mn2+ > Zn2+ between 1 and 1000 µM), but the reaction was unaffected by monovalent cations (Na + and K +). The amination reaction was most responsive to changes in Ca2+ in a NADH‐dependent manner. The addition of EDTA or EGTA nullified the stimulatory effects of Ca2+. Calmodulin alone or in combination with calmodulin antagonists did not affect the amination reaction. Divalent cations (at 1 mM) inhibited the rate of the deamination reaction by 15 to 25%, while monovalent cations had no effect. ATP inhibited the amination reaction by 10 to 60%, while ADP had little or no effect. ATP or ADP decreased the rate of the deamination reaction 23 to 60 or 20 to 38%, respectively. Many tricarboxylic acid cycle intermediates inhibited the amination reaction, 20 to 50% of the inhibition could be attributed to the chelating capacity of intermediates. Conversely, most of the carbon sources tested did not affect the deamination reaction, the only appreciable differences were increases in activity with sucrose (21%) and glucose (41%) and a decrease in activity with pyruvate (34%). Inhibitors of sulfhydryl groups were used to examine the importance of reduced thiol groups in the amination or deamination reactions. The amination was not dependent on reduced thiol groups, whereas the deamination reaction was dependent on reduced thiol groups.
Dose responses of two pea lines to ultraviolet‐B radiation (280–315 nm)
Authors: González R. , Wellburn A. R. , Paul N. D.
Published: March 2003

UV‐B dose responses of two lines of pea were quantified at 2.3, 4.6, 6.9 and 9.2 kJ m−2 day−1 UV‐B (weighted according to Caldwell's generalised plant action spectrum) in controlled environments providing near‐field doses of photosynthetic radiation. Increasing UV‐B significantly increased UV‐B absorbing compounds in both lines. In the UV‐B sensitive line, JI1389, increasing UV‐B significantly inhibited most aspects of plant morphology and biomass. In the more UV‐B‐tolerant line, Scout, increasing UV‐B significantly reduced foliage area but had no effect on above‐ground biomass, although root biomass was significantly increased. Reduced plant height in JI1389 was caused by shorter internodes, in turn due to reduced cell number but not cell length. UV‐B had no significant effects on photosynthesis in either line. Significant dose responses were linear for the growth of the main stem in JI1389 but remaining significant dose responses were better fitted by quadratics with maximum UV‐B effects occurring in the range 5–7 kJ m−2 day−1 PAS300, due to stimulation of branch growth at the highest dose. However, growth stimulation by UV‐B was confined to PAS300 doses which at temperate latitudes would result only from rather extreme ozone depletions. We conclude that investigations using relatively low UV‐B doses, rather than those well above the current maximum, may be the best approach to both understanding of the fundamental mechanisms of plant responses to UV‐B and quantifying the magnitude of responses to stratospheric ozone depletion.
Physiological responses of resistant and susceptible plants to diclofop‐methyl and its antagonism by 2,4‐D and antioxidants
Authors: Shimabukuro Richard H. , Hoffer Barry L. , Biewer Kristi A. , Davis David G.
Published: March 2003

Diclofop‐methyl (DM) sprayed onto 6–8‐week‐old plants of leafy spurge (Euphorbia esula L.) caused senescence and abscission of older leaves, while the young leaves and apex remained attached. The phytotoxicity of DM was reversed by the antioxidant, α‐tocopherol (vitamin E), in leafy spurge and DM‐susceptible oat (Avena sativa L. cv. Gary). DM and 2,4‐dichlorophenoxyacetic acid (2,4‐D) increased ethylene evolution in mature leaves of leafy spurge. Vitamin E reduced the DM‐induced ethylene by ampproximately 50%, but had no effect on the 2,4‐D‐induced ethylene. DM did not increase ethylene in DM‐resistant pea or tobacco, but 2,4‐D induced a 3‐fold increase in ethylene evolution over controls in DM‐resistant tobacco. 2,4‐D amppears to act at a site different from that of DM in the pathway of ethylene formation. Ethylene evolution increased in DM‐treated susceptible biotypes of annual ryegrass (Lolium rigidum L.) and wild oat (Avena fatua L.), but not in resistant biotypes of these species. DM reduced root and shoot formation and dry weight in hypocotyl segments of etiolated leafy spurge seedlings grown in vitro. Organogenesis and dry weights were increased by the combination of DM+antioxidants. Vitamin E was a more effective antioxidant than ascorbic acid. These results sumpport the hypothesis that DM induces oxidative stress in susceptible plant tissues and that antioxidants reduce the damaging action of the phytotoxic free radicals.
Epidermal transmittance and phenolic composition in leaves of atrazine‐tolerant and atrazine‐sensitive cultivars of Brassica napus grown under enhanced UV‐B radiation
Authors: Olsson Louise C. , Veit Markus , Bornman Janet F.
Published: March 2003

Experiments were conducted on the atrazine‐tolerant mutant Stallion and the atrazine‐sensitive cv. Paroll of Brassica napus L., which were grown under either visible light or with the addition of UV‐B radiation (280–320 nm) for 15 days. The mutant has been shown to be sensitive to high levels of visible light as compared to the atrazine‐sensitive cultivar and therefore we wished to determine plant response to UV‐B radiation with respect to potential pigment changes, certain anatomical features, radiation penetration and partial photosynthesis. With regard to pigment changes, we were particularly interested in whether the compositional shift in flavonol pigments under enhanced UV‐B radiation, previously suggested to favour increased antioxidant activity, is confined to the adaxial epidermis, which generally receives most UV‐B radiation or whether the pigment shift is also inducible in the abaxial epidermis.As was to be expected, the penetration of UV‐B radiation (310 nm) was lower in the UV‐B‐exposed plants, which was correlated with an increased amount of UV‐screening pigments in the adaxial and abaxial epidermal layers. The main flavonoid glycosides showed the largest shift from kaempferol to quercetin as aglycone moiety in the adaxial epidermal layer. However, in the abaxial epidermal layer the hydroxycinnamic acid (HCA) derivatives and kaempferol glycosides were predominant. Penetration of 430 nm light was higher after UV‐B exposure, and probably contributed to the fact that photosynthetic efficiency of photosystem II was unchanged or higher after UV‐B exposure. UV‐B radiation decreased leaf area in the atrazine‐tolerant mutant only. Both cultivars showed an increased leaf thickness after UV‐B exposure due to cell elongation mainly of the palisade tissue. This was especially evident in the mutant.
Antioxidative defense activation in soybean cells
Authors: Knörzer Oliver C. , Lederer Barbara , Durner Jörg , Böger Peter
Published: March 2003

Suspension‐cultured, photoheterotrophically grown, green soybean cells (Glycine max L.) were used to investigate alterations in the cellular contents of ascorbate and glutathione, as well as specific activities of antioxidative enzymes, elicited by salicylic acid (SA) and BTH [benzo(1,2,3)thiadiazole‐7‐carbothioic acid S‐methylester]. Both antioxidants were positively regulated by 48‐h incubations with SA and BTH, respectively, the latter induced a stronger increase in antioxidant levels compared to SA. The specific activities of glutathione reductase, monodehydroascorbate reductase and glutathione S‐transferase increased strongly in soybean cells as a response to both SA and BTH. The enzyme activations observed were in the range of 2–8‐fold. Catalase activity was also increased 2‐fold by SA but decreased when cells were incubated with BTH. These results indicate an activation of the cellular antioxidative system at both the antioxidant and enzyme level. In addition, the effects of SA and BTH on phytotoxicity exerted by the peroxidizing herbicide oxyfluorfen were investigated. Both compounds protected soybean cells from herbicide‐induced lipid peroxidation in a time‐ and concentration‐dependent manner and strongly suppressed the herbicide‐induced accumulation of protoporphyrin IX. SA as well as BTH antagonize the action of peroxidizing herbicides.
Effect of inhibition of phenylalanine ammonia‐lyase activity on growth of alfalfa cell suspension culture: Alterations in mitotic index, ethylene production, and contents of phenolics, cytokinins and polyamines
Authors: Cvikrová Milena , Binarová Pavla , Eder Josef , Vágner Martin , Hrubcová Marie , Zoń Jerzy , Macháčková Ivana
Published: March 2003

The effect of inhibition of phenylpropanoid biosynthesis on the growth of Medicago sativa L. suspension culture was studied. 2‐Aminoindan‐2‐phosphonic acid (AIP), a potent inhibitor of phenylalanine ammonia‐lyase (PAL; EC 4.3.1.5), caused a marked reduction in the amount of hydroxycinnamic acid derivatives in a few hours after cell inoculation into AIP medium. The treatment of alfalfa suspension culture with this inhibitor increased the extractable PAL activity and elevated ethylene production during the growth cycle. The addition of AIP (10 μM) stimulated cell division activity during the growth cycle, although the onset of cell division was slightly delayed. The maxima of cytokinin content as well as of the mitotic index were postponed in AIP‐treated cells, however, the unchanged content of cytokinins did not correlate with increased mitotic activity of treated cells. The decreased level of hydroxycinnamic acid derivatives, which represent the phenolic conjugation partners of free polyamines (PAs), influenced the rate of PA conjugation. Consequently, the balance between free and conjugated PAs was shifted in favor of the free PA form. A potential role of the reduction of the pool of phenolic acids in the enhancement of cell division of alfalfa cell suspension culture is discussed.
Methylglyoxal(bis‐guanylhydrazone) inhibition of organogenesis is not due to S‐adenosylmethionine decarboxylase inhibition/polyamine depletion in tobacco thin layers
Authors: Scaramagli Sonia , Biondi Stefania , Torrigiani Patrizia
Published: March 2003

Previous results indicated that in shoot‐forming tobacco thin layers the putative inhibitor of S‐adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.21) activity methylglyoxal(bis‐guanylhydrazone) (MGBG) inhibited meristemoid/primordia formation while enhancing conjugated polyamine accumulation and ethylene biosynthesis, thus showing an inverse relationship between the two phenomena ( Scaramagli et al. 1999). In order to better understand how MGBG causes polyamine overproduction and by using the same model system, we further examined the effect of 0.5 mM MGBG on the incorporation of labelled methionine into spermidine and spermine, on SAMDC transcript levels and activity and on putrescine oxidising (DAO) activity at different times in culture. MGBG‐induced ethylene accumulation was also evaluated by gas chromatography (GC). In shoot‐forming controls (grown on a medium supplemented with IAA+BA) label was mainly incorporated into free spermidine (82–86% of the total amount incorporated into polyamines) while only 6–12% of radioactivity was recovered in free spermine. Some label was also found in putrescine. In the presence of MGBG, spermidine biosynthetic capacity was enhanced throughout the culture by 28–45% compared with controls. The same occurred for spermine and putrescine. MGBG‐enhanced spermidine synthesis was supported by increased SAMDC activity (days 1–2) and higher levels of SAMDC message (days 1–7). On the contrary, the effect of the drug on putrescine oxidation was inhibitory starting from day 2. These results, together with the previous ones, suggest that MGBG, in fact, does not behave as a SAMDC inhibitor in shoot‐forming tobacco thin layers and that its negative effect on organised growth is not due to SAMDC inhibition/polyamine depletion.
Apoplastic pH and inorganic ion levels in tomato fruit: A potential means for regulation of cell wall metabolism during ripening
Authors: Almeida Domingos P. F. , Huber Donald J.
Published: March 2003

Apoplastic pH and ionic conditions exert strong influence on cell wall metabolism of many plant tissues; however, the nature of the apoplastic environment of ripening fruit has been the subject of relatively few studies. In this report, a pressure‐bomb technique was used to extract apoplastic fluid from tomato fruit (Lycopersicon esculentum Mill.) pericarp at several developmental stages. pH and the levels of K+, Na+, Ca2+, Mg2+, Cl− and P were determined and compared with the values for the bulk pericarp and locule tissues. The pH of the apoplastic fluid from pericarp tissue decreased from 6.7 in immature and mature‐green fruits to 4.4 in fully‐ripe fruit. During the same period, the K+ concentration increased from 13 to 37 mM. The levels of Na+ and divalent cations did not change, whereas the anions P and Cl− increased in ripe fruit. Ca2+ levels remained relatively constant during ripening at 4–5 mM, concentrations that effectively limit pectin solubilization. The electrical conductivity of the apoplastic liquid increased 3‐fold during ripening, whereas osmotically active solutes increased 2‐fold. Pressure‐treated fruit retained the capacity to ripen. The decline in apoplastic pH and increase in ionic strength during tomato fruit ripening may regulate the activity of cell wall hydrolases. The potential role of apoplastic changes in fruit ripening and softening is discussed.
Phytochrome‐induced transmissible signal elicits germination response in turions of Spirodela polyrhiza
Authors: Tirlapur U. K. , Dahse I. , Probandt R. , Fischer W. , Akppenroth K.‐J.
Published: March 2003

The role of cell competence, including the spatiotemporal aspect of phytochrome‐induced long‐distance signal transmission, was investigated in turions of Spirodela polyrhiza (L.) Schleiden. Irradiation of the dorsal surface of the turions triggered a significant germination response, while identical treatment of the ventral surface was less effective. Red‐light (R) microbeam irradiation of a subregion (ca. 1 μm2) of the dorsal surface could induce the germination response. Therefore, photoactivation of phytochrome in a single cell or few cells is sufficient to trigger the photomorphogenetic response. The ultimate response occurs at the proximal end of the turion by way of growth and emergence of the frond primordia about 1.3 mm away from the microbeam‐irradiated distal cell(s). This photoinduction was reversible by a pulse of far‐red light (FR) given less than 24 h after R microbeam irradiation. Microsurgical separation of distal (irradiated) and proximal (primordium‐bearing) halves of the turions following microbeam irradiation further revealed that the light‐induced transmissible signal can be intercepted and that it required more than 48 h to traverse one half distance of the turions. Based on the kinetics of the signal transmission, the possible involvement of light scattering, light piping, or transfer of electrophysiological signals can be excluded. Taken together, the results indicate that a transmissible signal is generated by the irradiated cell(s) and propagated across to the non‐irradiated cells, leading to induction of the photomorphogenetic response.
Photothermal control of the imposition of summer dormancy in Poabulbosa, a perennial grass geophyte
Authors: Ofir Micha , Kigel Jaime
Published: March 2003

Poa bulbosa L., like many other Mediterranean geophytes, grows in the winter and enters a phase of summer dormancy in the spring. Summer dormancy enables these plants to survive the hot and dry summer. Long days are the main environmental factor active in the induction of summer dormancy in P. bulbosa and elevated temperatures accelerate dormancy development. P. bulbosa becomes dormant earlier than most other species that grow actively in the winter. Previous studies suggested that pre‐exposure of P. bulbosa to short days and low temperatures during the autumn and early winter increased its sensitivity to photoperiodic induction in late winter, and thus enabled the early imposition of dormancy. To study this hypothesis, experiments were carried out under controlled photothermal conditions in the phytotron, under natural daylight extended with artificial lighting. The critical photoperiod for induction of summer dormancy at an optimal temperature (22/17°C day/night) was between 11 and 12 h. Photoperiods shorter than 12 h were noninductive, while 14‐ and 16‐h days were fully inductive. A night break of 1 h of light given at the middle of the dark period of an 8‐h photoperiod also resulted in full induction of dormancy. Pre‐exposure to either low temperature (chilling at 5°C) or to short days of 8 h (SD) enhanced the inductive effect of subsequent 16‐h long days (LD). The enhancing effect of chilling and SD increased with longer duration, i.e. fewer LDs were required to impose dormancy. However, the day‐length during the low‐temperature pretreatment had no effect on the level of induction at the following LD. Chilling followed by SD did not induce dormancy. The relevance of these responses to the development and survival of P. bulbosa in its natural habitat is discussed.
Non‐destructive optical detection of pigment changes during leaf senescence and fruit ripening
Authors: Merzlyak Mark N. , Gitelson Anatoly A. , Chivkunova Olga B. , Rakitin Victor YU.
Published: March 2003

Reflectance spectra in the visible and near infra‐red range of the spectrum, acquired for maple (Acer platanoides L.), chestnut (Aesculus hippocastanum L.), potato (Solanum tuberosum L.), coleus (Coleus blumei Benth.), leaves and lemon (Citrus limon L.) and apple (Malus domestica Borkh.) fruits were studied. An increase of reflectance between 550 and 740 nm accompanied senescence‐induced degradation of chlorophyll (Chl), whereas in the range 400–500 nm it remained low, due to retention of carotenoids (Car). It was found that both leaf senescence and fruit ripening affect the difference between reflectance (R) near 670 and 500 nm (R678−R500), depending on pigment composition. The plant senescing reflectance index in the form (R678−R500)/R750 was found to be sensitive to the Car/Chl ratio, and was used as a quantitative measure of leaf senescence and fruit ripening. The changes in the index were followed during leaf senescence, and natural and ethylene‐induced fruit ripening. This novel index can be used for estimating the onset, the stage, relative rates and kinetics of senescence/ripening processes.
Isolation and expression of an elongation‐dependent gene of mung bean (Vigna radiata) hypocotyl
Authors: Hashimoto Hiroshi , T. Yamamoto Kotaro
Published: March 2003

A cDNA clone of an auxin up‐regulated gene, ARG8, was isolated from hypocotyl sections of etiolated mung bean [Vigna radiata (L.) Wilczek] seedlings by differential screening. The deduced amino acid sequence suggested that ARG8 may encode a cell wall protein. The steady state mRNA level of ARG8 increased by treatment of hypocotyl sections not only with indole‐3‐acetic acid (IAA) but also with fusicoccin, and the auxin inducibility was inhibited by the addition of 0.3 M mannitol in the incubation medium. This indicated that it was not auxin but elongation that regulated the expression of ARG8. The promoter activity of the 5′‐flanking region of ARG8 was determined by assaying the transient expression of a luciferase fusion gene that was introduced into mung bean hypocotyl sections by the particle bombardment technique. The basal activity of the ARG8 upstream region was about a few tenths of that of a modified cauliflower mosaic virus 35S promoter, and it was increased a few fold by treatment with IAA. The auxin inducibility was completely suppressed by the addition of mannitol. A 5′‐deletion analysis showed that a 53‐bp region in the ARG8 promoter was important for the basal and elongation‐dependent promoter activities.