bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrate uptake into Pisum sativum L. cv. Feltham First seedlings: commonality with nitrate uptake into Chara corallina and Hordeum vulgare through a substrate cycling model
Authors: DEANE‐DRUMMOND C. E. 
Published: April 2006

Abstract Net NO3−, uptake into Pisum sativum L. seedlings temporarily ceased in the presence of very low NH4 concentrations (δmmol m−3). The sensitivity to NH4+ was apparent for seedlings grown in nitrogen‐free conditions with or without NO3− pretreatment, although in the latter case the inhibitory effects were more obvious because net NO3− uptake was higher. NO3− influx, measured using 36ClO3− tracer, was unaffected by NH4+ though pretreatment with NO3− for 24 h slightly stimulated influx. The inhibitory effects of NH4+ were attributed to its effects on stimulating NOJ efflux, which, under certain conditions, was moving against its electrochemical gradient.A theoretical model has been devised that involves NO3− cycling across the plasmalemma, with distinct parallel influx and efflux pathways, which improves the sensitivity to substrate and effectors and provides a means for control of internal pool size. The sensitivity of net flux (J) to effectors of the influx step (I) is a function of (1 +E/J), and the sensitivity of J to effectors of the efflux step (E) is a function of ‐ E/J. The model has been used to quantify the relative sensitivity of nitrate influx and efflux processes to nitrate and ammonium for Pisum sativum, Chara corallina and Hordeum vulgare. As steady state is reached, sensitivity of net flux (J) to NO3− increases, whereas sensitivity to NH4+ decreases.
Endogenous ion currents traverse growing roots and root hairs of Trifolium repens
Authors: MILLER A. L. , RAVEN J. A. , SPRENT J. I. , WEISENSEEL M. H. 
Published: April 2006

Abstract The patterns of naturally growing ion currents associated with horizontally growing roots of Trifolium repens L. seedlings were measured in a simple low‐salt bathing medium using a highly sensitive vibrating electrode. Current consistently enters the main elongation zone of the root and leaves from mature, elongated tissue. This current enters and leaves with densities of ca. 4.0–11.0 mA m−2 and 4.0 mA m−2, respectively. Current was also delected entering the zone of emerging root hairs and also the root‐hair tips themselves.These results are a further example of the involvement of self‐generated electrical fields in plant developmental processes. Possible, secondary rhizosphere‐associated effects of the extracellular loop of the developmental current are also suggested.
Leaf expansion in sunflower as influenced by salinity and short‐term changes in carbon fixation
Authors: RAWSON H. M. , MUNNS RANA 
Published: April 2006

Abstract With a view to defining factors regulating the growth responses of sunflower to salinity, plants were grown in solution culture (0, 50 or 100 mol m−3 NaCl) and under natural light, and the areas of every leaf measured once or twice daily from 22 until 38 d after germination. During this period, carbon availability for growth was manipulated by changing light levels and by the use of a photosynthesis inhibitor, DCMU.Salinity reduced relative leaf expansion rates per plant (RLER) by an average of 0.04 (50 mol m−3) and 0.08 (100 mol m−3) m2 m−2 d−1 compared with control plants of equivalent leaf area: the effects were found in expanding leaves regardless of age or size.Control plants expanded faster during the day than the night, but plants grown in salt had an almost constant RLER throughout the 24 h, indicating that salt influences the rate of utilization of assimilates independently of their production. DCMU reduced RLER considerably in both control and salt‐treated plants and reduced the advantage of control plants during the day. Conditions of low light also reduced the differences in RLER between control and salt‐treated plants.When salt was removed from the root medium of non‐DCMU plants, the expansion rates equalled that of the controls within 24 h and remained at the same levels for the following 3 d measurement period: this recovery applied to leaves of all ages. Salt‐grown plants with no photosynthesis (DCMU treatments) also increased their expansion rates upon removal of salt from the root medium, thus providing further evidence that growth was not limited by carbohydrate status, i.e. that salt influences growth primarily via its effects on the rate of utilization of stored assimilates.
Increase in calmodulin level in the early phases of radish seed (Raphanus sativus) germination
Authors: COCUCCI MAURIZIO 
Published: April 2006

Abstract Calmodulin (Cam), the heat‐stable, ubiquitous, Ca2+‐dependent regulator protein, has been purified to apparent homogeneity from germinating radish seeds (Raphanus sativus). The characteristics of radish Cam‐molecular weight, absorption spectrum, Ca2+‐dependent activation of brain phosphodiesterase (PDE)‐are very similar to those described for Cam from other plant materials. Radish Cam, like other plant Cam, shows some differences to Cam of calf brain.The total amount of Cam in radish embryos at 24 h of germination is ca. 37 μg g−1 fresh weight. Approximately 95% of the total amount of Cam is present in the soluble fraction (supernatant at 100,000 g).The level in the embryo axis strongly increases in the first 24 h of germination (+540%); this increase is strongly reduced when the germination is inhibited by abscisic acid (ABA). In the presence of Ca2+, no ‘free’ Cam (i.e. not bound to other structures) is present in the soluble fraction, suggesting that, during early germination, Cam level is a limiting factor for the activities of Ca2+ ‐Cam‐dependent systems. These studies suggest that Cam plays an important role in the early phases of seed germination.An inhibitor of the Ca2+‐Cam‐dependent phosphodiesterase is present in the soluble fraction from radish embryos; this substance decreases during germination. A possible role of this inhibitor during the early germination phases is hypothesized.
Abscisic‐acid‐induced turion formation in Spirodela polyrrhiza L. IV. Comparative ion flux characteristics of the turion and the vegetative frond and the effect of ABA during early turion development
Authors: SMART CHERYL C. , TREWAVAS ANTHONY J. 
Published: April 2006

Abstract Using the method of compartmental analysis, the ion fluxes and compartment concentrations of Ca2+, K+ and Cl‐ have been compared in the untreated vegetative frond and the abscisic acid (ABA) induced turion of Spirodela polyrrhiza. The ABA‐induced turion is characterized by reduced Ca2+ exchange across the tonoplast and low vacuolar Ca2+ concentration relative to the vegetative frond. In addition the turion exhibits a higher plasmalemma flux with a correspondingly high Ca2+ concentration in the cytoplasm. The concentration of K+ and Cl‐ is much lower in the cytoplasm of the ABA‐induced turion than in the vegetative frond with the influx/efflux ratio at both the plasmalemma and the tonoplast being less than 1, a finding exhibited also in dormant storage tissue.Treatment of vegetative fronds with ABA for 18 h resulted in a reduced K+ plasmalemma efflux relative to untreated vegetative fronds and a concomitant increase in the cytoplasmic concentration. There was no rapid effect of ABA on Ca2+, K+ or Cl‐ fluxes through either membrane. These results are consistent with the notion that drastic changes in ion fluxes and concentrations in the turion are a secondary consequence of ABA‐induced development, possibly due to prior regulation by ABA of enzymes inherent to processes involved in membrane transport.
Crassulacean acid metabolism in the epiphytic ferns Drymoglossum piloselloides and Pyrrosia longifolia: studies on responses to environmental signals
Authors: ONG B. L. , KLUGE M. , FRIEMERT V. 
Published: April 2006

Abstract The paper reports the results of the comprehensive study of crassulacean acid metabolism in two epiphytic tropical ferns, Drymoglossum piloselloides and Pyrrosia longifolia. The plants were investigated under different light, temperature and water status. It was found that both species are obligate CAM plants. The diurnal acidity rhythm is due to the fluctuation in malic acid concentration, which accounts for the change in titratable acidity. Besides malic acid, shikimate and oxalate are found to be present, but not contributing to the CAM acid rhythm. The diurnal rhythm of malic acid content results in a corresponding rhythm in leaf water relations. Both ΦΦ and Φtotal, were lowest at the end of the night, i.e. when the level of malic acid was highest.The effects of temperature on CO2 exchange were inverse to those observed in other CAM plants. In both ferns studied, dark CO2 fixation increased when the night temperature was increased. Increase in day temperature reduced CO2 uptake during phase IV and during the following night. The observed responses of the ferns to temperature changes suggest that the in situ environmental conditions are optimal for their CAM performance. In weak light, the plants showed net CO2 output during the midday deacidification period. Increases in light intensity reduced such CO2 output.Under drought conditions, the CO2 exchange in the ferns was reduced to zero within 5–6 d, indicating that the ferns studied are more susceptible to water deficiency than other CAM plants. This could be due to a higher cuticular conductance for water.The results are discussed, in particular, in relation to CAM performance of epiphytes growing in the wet tropics.
Effects of external NaCl on the growth of Atriplex amnicola and the ion relations and carbohydrate status of the leaves
Authors: ASLAM Z. , JESCHKE W. D. , BARRETT‐LENNARD E. G. , SETTER T. L. , WATKIN E. , GREENWAY H. 
Published: April 2006

Abstract Atriplex amnicola, was grown in nutrient solution cultures with concentrations of NaCl up to 750 mol m−3. The growth optimum was at 25–50 mol m−3 NaCl and growth was 10–15% of that value at 750 mol m−3 NaCl. Sodium chloride at 200 mol m−3 and higher reduced the rate of leaf extension and increased the time taken for a leaf to reach its maximal length.Concentrations of Na+, K+ and Mg2+ in leaves of different ages were investigated for plants grown at 25, 200 and 400 mol m−3 NaCl. Although leaves of plants grown at 200 and 400 mol m−3 NaCl had high Na+ concentrations at young developmental stages, much of this Na+ was located in the salt bladders. Leaves excluding bladders had low Na+ concentrations when young, but very high in Na+ when old.In contrast to Na+, K+ concentrations were similar in bladders and leaves excluding bladders. Concentrations of K+ were higher in the rapidly expanding than in the old leaves. At 400 mol m−3 NaCl, the K+:Na+ ratios of the leaves excluding bladders were 0.4–0.6 and 0.1 for rapidly expanding and oldest leaves, respectively. The Na+ content in moles per leaf, excluding bladders, increased linearly with the age of the leaves; concurrent increases in succulence were closely correlated with the Na + concentration in the leaves excluding the bladders.Soluble sugars and starch in leaves, stems and buds were determined at dusk and dawn.There was a pronounced diurnal fluctation in concentrations of carbohydrates. During the night, most plant parts showed large decreases in starch and sugar. Concentrations of carbohydrates in most plant organs were similar for plants grown at 25 and 400 mol m−3 NaCl. One notable exception was buds at dusk, where sugar and starch concentrations were 30–35% less in plants grown at 400 mol m−3 NaCl than in plants grown at 25 mol m−3 NaCl.The data indicate that the growth of A. amnicola at 400 mol m−3 NaCl is not limited by the availability of photosynthate in the plant as a whole. However, there could have been a growth limitation due to inadequate organic solutes for osmotic regulation.
Nocturnal enuresis and the use of desmopressin: is it helpful?
Authors: Bath R , Morton R , Uing A , Williams C 
Published: April 2006

SummaryWe assessed the outcome of the use of an enuretic alarm and desmopressin according to conventional guidelines and investigated the reasons for resistance to desmopressin. Children were given a 4 month course using an enuretic alarm if they had not previously used one; 12 out of 21 were dry (57%) after 4 months and one relapsed 1 month later. Those who had previously failed with an alarm or were considered poorly motivated to use it, were given a 4 month course of intranasal desmopressin. Of these 26 children, 10 (38%) were dry at the end of 4 months but only two (7%) remained dry after this was withdrawn. After the initial treatment with alarm or desmopressin, 27 children were still enuretic and attending the clinic. They were shown how to use the alarm and eight also used the dry bed training technique: 15 had become dry after a further 6 months. Of the 12 children who made no response to intranasal desmopressin, nine were given this medication under supervision in hospital; seven of these children still wet the bed despite producing small amounts of concentrated urine overnight. They also had small measured diurnal bladder capacities. We conclude that if a 4 month course with an enuretic alarm is unsuccessful, rather than using desmopressin, the alarm should be continued with relearning and consideration given to additional use of the dry bed training technique. The major factor causing nocturnal enuresis in children is likely to be a small nocturnal bladder capacity.
TH2‐polarized immunological memory to inhalant allergens in atopies is established during infaney and early childhood
Authors: YABUHARA A. , MACAUBAS C. , PRESCOTT S. L. , VENAILLE T. J. , HOLT B. J. , HABRE W. , SLY P. D. , HOLT P. G. 
Published: April 2006

SummaryBackground
There is increasing evidence that the T‐cell reactivity to environmental allergens underlying expression of allergic disease in adulthood, develops initially during childhood. However, there is little information available on the kinetics of these early responses, or on the patterns of cytokine production during this period.Objective
The purpose of this study was twofold: to obtain further information on the reported differences between responses to food versus inhalant allergens during early childhood, and to ascertain the age‐range over which T‐cell responses to inhalant allergens become polarized towards the TH2 cytokine profile, in potentially atopic children.Methods
In vitro cytokine responses to house dust mite (HDM) and egg (OVA) were assessed by semiquantitative RT‐PCR in panels of 2‐ and 5‐year‐old children and adults; lymphoproliferative responses to OVA were subjected to epitope analysis.Results
At age 2 years IL‐4/IL‐5 responses to HDM grouped with positive atopic family history, and by age 5 years cytokine responses correlated strongly with individual SPT reactivity to HDM. In contrast, OVA responses were restricted to weak and transient IL‐5 signals in the 2‐year‐old family history positive group. Lymphoproliferation assays performed in parallel indicate a log‐scale greater postnatal expansion of T‐cell reactivity to the inhalant allergen; preliminary epitope analysis of OVA responses indicate that the number of OVA epitopes recognised decrease during early childhood.Conclusions
Inhalant allergen‐specific in vitro cytokine production associated with positive skin‐prick test (SPT) reactions, one of the hallmarks of adult atopy, manifests in children at or before 5 years of age; additionally, cytokine responses in SPT negative 5 year‐olds are restricted to IFNγ, as per normal adults. In contrast, T‐cell responses to a typical food allergen appear to be deleted during early childhood.
Expression of interleukin (IL)‐4 and IL‐5 proteins in asthma induced by toluene diisocyanate (TDI)
Authors: MAESTRELLI P. , OCCARI P. , TURATO G. , PAPIRIS S. A. , DI STEEANO A. , MAPP C. E. , MILANI G. F. , EABBRI L. M. , SAETTA M. 
Published: April 2006

SummaryBackground
TDI‐induced asthma exhibits clinical, functional and morphological similarities with allergen‐induced asthma, suggesting that an immunological mechanism is involved in the sensitization to TDL In vitro studies using the technique of cloning lymphocytes demonstrated that a great proportion of T‐cell clones derived from bronchial mucosa of subjects with TDI‐induced asthma produced IL‐5 and interferon‐gamma, but not IL‐4, upon in vitro stimulation.Objectives
To investigate in vivo the role of IL‐4 and IL‐5 on the inflammatory response of the bronchial mucosa to TDI in sensitized subjects, we performed a quantitative analysis of bronchial biopsies.Methods
We obtained bronchial biopsies from six subjects with TDI asthrha 48 h after an asthmatic reaction induced by TDI challenge (challenged group), in six subjects with TDI asthma 1–4 weeks after the last exposure to TDI (chronic group), and in six non‐asthmatic controls. The number of eosinophils, mast cells, T‐lymphocytes, and IL‐4 and IL‐5 protein positive cells was determined by immunohistochemistry in the area 100 μn beneath the epithelial basement membrane.Results
The characteristic increase of submucosal eosinophils, but not of mast cells and T‐lymphocytes, was observed in the subjects with TDI‐induced asthma when compared with controls. No differences were detected between the two groups of asthmatics. In the subjects with TDI‐induced asthma, cell immunoreactivity for IL‐5 was increased when compared with normal controls. There was no difference in the expression of IL‐5 protein between challenged and chronic asthmatics. In contrast, the expression of IL‐4 protein was increased only in the asthmatic subjects tested after recent exposure to TDI.Conclusions
We demonstrated that TDI asthma 48 h after specific bronchial challenge was associated with increased numbers of cells expressing IL‐4 and IL‐5, whereas chronic TDI asthma was associated with increased expression of IL‐5, but not of IL‐4. The results suggest that subjects who developed TDI asthma exhibit increased production of IL‐5 even in the absence of a recent trigger by the exogenous sensitizer and that production of TH2‐like cytokines in TDI‐induced asthma may not always be co‐ordinately regulated in vivo.
Substance P is generated in vivo following nasal challenge of allergic individuals with bradykinin
Authors: BAUMGARTEN C. R. , O'CONNOR A. , DOKIC D. , SCHULTZ K. D. , KUNKEL G. 
Published: April 2006

SummaryBackground
Bradykinin, a potent inflammatory mediator, is released during allergic and non‐allergic rhinitis and asthma in man. Nasal bradykinin challenge induces a dose‐dependent plasma leakage into the nasal cavity and relevant symptoms of rhinitis.Objective
We now report on substance P generation during nasal bradykinin challenge in vivo.Methods
The effect ot locally applied bradykinin on substance P generation was studied in nine individuals, allergic to grass pollen and six non‐allergic controls. In the allergies TAME‐esterase activity, histamine and substance P concentrations were measured in nasal lavages and correlated to the clinical symptoms.Results
Substance P concentrations in nasal lavages increased in a dose‐dependent fashion during nasal bradykinin challenge in both groups. In the allergic group Substance P‐increases correlated with the production of TAME‐esterase activity (r= 0.9. P < 0.05) whereas these allergic individuals did not produce any histamine increases. The generation of substance P and the increase of TAME‐esterase activity was associated with the onset of clinical symptoms. Correlation of oedema and hypersecretion to substance P were signiticant by linear regression analysis (r = 0.88, P < 0.005 and r= 0.89. P < 0.02, respectively). Bradykinin induced irritations like burning and itching were shortterm and rare. Serial dilutions of nasal washes produced Substance P‐RIA displacement curves that paralleled the standard curve and recovery of standard substance P that was added to nasal washes was 76 ± 4% (mean ± sem), n= 8.Conclusion
Bradykinin induces in vivo a dose‐dependent plasma leakage into the nasal cavity without affecting mast cells, but stimulates nerve endings resulting in the release of the neuropeptide substance P.
The effect of stratification on the endogenous levels of gibberellins and cytokinins in seeds of douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) and sugar pine (Pinus lambertiana Dougl.)
Authors: TAYLOR J. S. , WAREING P. F. 
Published: April 2006

Abstract Seeds of Douglas‐fir and sugar pine which had been exposed to various periods of moist chilling (stratification) were extracted and bioassayed for gibberellin and cytokinin activity. In Douglas‐fir a peak of gibberellin activity increased progressively during stratification and was seven times higher after 7 weeks, but declined subsequently. No change in the level of cytokinin activity was observed during stratification. However, a slight increase (1.7‐fold) occurred in stratified seeds placed at 22°C for 3 days.In sugar pine a high level of gibberellin activity, approximately 20‐fold higher than in unstratified controls, was present in extracts of seeds which had been stratified for 8 weeks. After 10 weeks of stratification cytokinin levels had increased approximately 200‐fold. Four cytokinin‐like substances were detected in seeds. Three of the substances are similar in their chromatographic properties to zeatin glucoside, zeatin riboside and zeatin, respectively. Both gibberellin and cytokinin activity declined rapidly after reaching maximum levels.In seeds with the coats removed, germination was rapid and complete in the absence of stratification. Prior to radicle emergence in coatless seeds cytokinin activity increased to a maximum (approximately a 1‐7‐fold increase) within 24 h. Significant levels of gibberellin‐like substances were present after 8 h. Gibberellin activity could not be detected in coatless seeds which were imbibed in AMO‐1618, and germination was inhibited significantly.
Interaction of polyamines and light on biochemical processes involved in leaf senescence
Authors: KAUR‐SAWHNEY RAVINDAR , GALSTON ARTHUR W. 
Published: April 2006

Abstract The rapid senescence of detached oat leaves in darkness is first manifested by a sharp rise in RNase activity (about 50% within 1 h), then by a rise in protease activity (indicated by an increase in non‐protein α‐amino nitrogen within 6 h) and ultimately by chlorophyll degradation (beginning after 18 h). These degradative changes are delayed or prevented by low concentrations (1–10 mM) of the naturally‐occurring polyamines cadaverine, putrescine, spermidine and spermine. The tetraamine spermine is generally more active than the triamine spermidine, which is in turn more active than the diamines putrescine and cadaverine. All the polyamines are more active than kinetin or cycloheximide. As little as 10 min of exposure to 1 mM spermine, especially at the beginning of the dark period, produces a marked retardation of chlorophyll degradation over a 48 h period, and 60 min of exposure saturates the effect.In the light, all polyamines promote, rather than retard, the disappearance of chlorophyll but, as in the dark, they inhibit the rise in RNase and non‐protein α‐amino nitrogen. The photobleaching of chlorophyll in the presence of polyamines is proportional to the duration of exposure to high irradiance (16.5 Wm−2) fluorescent light. Such light is more effective toward the end of the 48 h post‐excision test period than at the beginning.Calcium ion (1–10 mM) supplied together with the polyamines diminishes their action in dark and light, indicating probable involvement of an initial ionic attachment mechanism.The loss of chlorophyll from the leaves of four species of dicotyledonous plants (pea, bean, rape, tobacco) in the darkness is similarly retarded by 1–10 mM polyamines. In rape, the most rapidly senescing species, 1 mM spermine almost completely arrests chlorophyll degradation over a 96 h period. It is suggested that polyamine metabolism in plants may be related to normal physiological control mechanisms as in microorganisms and animals, and that polyamines could find use as anti‐senescence agents for plants.