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1.
Y. Jia  V. M. Gray 《Photosynthetica》2004,42(4):535-542
The influence of phosphorus (P) and nitrogen (N) supply on biomass, leaf area, photon saturated photosynthetic rate (Pmax), quantum yield efficiency (), intercellular CO2 concentration (Ci), and carboxylation efficiency (CE) was investigated in Vicia faba. The influence of P on N accumulation, biomass, and leaf area production was also investigated. An increase in P supply was consistently associated with an increase in N accumulation and N productivity in terms of biomass and leaf area production. Furthermore, P increased the photosynthetic N use efficiency (NUE) in terms of Pmax and . An increase in P supply was also associated with an increase in CE and a decrease in Ci. Under variable daily meteorological conditions specific leaf nitrogen content (NL), specific leaf phosphorus content (PL), specific leaf area (L), root mass fraction (Rf), Pmax, and remained constant for a given N and P supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. L increased with increasing N supply or with increasing NL. We tested also the hypothesis that P supply positively affects both N demand and photosynthetic NUE by influencing the upper limit of the asymptotic values for Pmax and CE, and the lower limit for Ci in response to increasing N.This revised version was published online in March 2005 with corrections to the page numbers.  相似文献   

2.
Scaling CO2-photosynthesis relationships from the leaf to the canopy   总被引:11,自引:0,他引:11  
Responses of individual leaves to short-term changes in CO2 partial pressure have been relatively well studied. Whole-plant and plant community responses to elevated CO2 are less well understood and scaling up from leaves to canopies will be complicated if feedbacks at the small scale differ from feedbacks at the large scale. Mathematical models of leaf, canopy, and ecosystem processes are important tools in the study of effects on plants and ecosystems of global environmental change, and in particular increasing atmospheric CO2, and might be used to scale from leaves to canopies. Models are also important in assessing effects of the biosphere on the atmosphere. Presently, multilayer and big leaf models of canopy photosynthesis and energy exchange exist. Big leaf models — which are advocated here as being applicable to the evaluation of impacts of global change on the biosphere — simplify much of the underlying leaf-level physics, physiology, and biochemistry, yet can retain the important features of plant-environment interactions with respect to leaf CO2 exchange processes and are able to make useful, quantitative predictions of canopy and community responses to environmental change. The basis of some big leaf models of photosynthesis, including a new model described herein, is that photosynthetic capacity and activity are scaled vertically within a canopy (by plants themselves) to match approximately the vertical profile of PPFD. The new big leaf model combines physically based models of leaf and canopy level transport processes with a biochemically based model of CO2 assimilation. Predictions made by the model are consistent with canopy CO2 exchange measurements, although a need exists for further testing of this and other canopy physiology models with independent measurements of canopy mass and energy exchange at the time scale of 1 h or less.Abbreviations LAI leaf area index - NIR near infrared (700–3000 nm) radiation - PAR photosynthetically active (400–700 nm) radiation - PI photosynthetic irradiance (400–700 nm) - PPFD photosynthetic photon flux area density (400–700 nm) - PS I Photosystem I - PS II Photosystem II - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - RuP2 ribulose-1,5-bisphosphate  相似文献   

3.
Measurements were made of the concentration and stable oxygen isotopic ratio of carbon dioxide in air samples collected on a diurnal basis at two heights within a Pinus resinosa canopy. Large changes in CO2 concentration and isotopic composition were observed during diurnal time courses on all three symple dates. In addition, there was strong vertical stratification in the forest canopy, with higher CO2 concentrations and more negative 18O values observed closer to the soil surface. The observed daily increases in 18O values of forest CO2 were dependent on relative humidity consistent with the modelled predictions of isotopic fractionation during photosynthetic gas exchange. During photosynthetic gas exchange, a portion of the CO2 that enters the leaf and equilibrates with leaf water is not fixed and diffuses back out of the leaf with an altered oxygen isotopic ratio. The oxygen isotope ratio of CO2 diffusing out of a leaf depends primarily on the 18O content of leaf water which changes in response to relative humidity. In contrast, soil respiration caused a decline in the 18O values of forest CO2 at night, because CO2 released from the soil has equilibrated with soil water which has a lower 18O content than leaf water. The observed relationship between diurnal changes in CO2 concentration and oxygen isotopic composition in the forest environment were consistent with a gas mixing model that considered the relative magnitudes of CO2 fluxes associated with photosynthesis, respiration and turbulent exchange between the forest and the bulk atmosphere.  相似文献   

4.
Summary Seedlings of five tropical trees, Cecropia obtusifolia, Myriocarpa longipes, Piper auritum, Senna multijuga and Trichospermum mexicanum, were grown both as individuals, and in competition with each other at ambient (350) and two levels of elevated CO2 (525 and 700 l l-1) for a period of 111 days. Growth, allocation, canopy architecture, mid-day leaf water potential and soil moisture content were assessed three times over this period for individually grown plants, and at the end of the experiment for competitively grown plants. In addition, leaf photosynthesis and conductance were assessed for the individually grown plants midway through the experiment, and light profile curves were determined for the competitive arrays at three stages of development. Elevated CO2 did not affect photosynthesis or overall growth of the individually-grown plants but did affect canopy architecture; mean canopy height increased with CO2 in Piper and Trichospermum and decreased in Senna. Stomatal conductance decreased slightly as CO2 increased from 350 to 525 l l-1 but this had no significant effect upon whole plant water use of leaf water potential. Soil moisture content for the individuals increased marginally as CO2 increased, but this did not occur in the competitive arrays. There was a marked effect of CO2 upon species composition of the competitive arrays; Senna decreased in importance as CO2 increased while Cecropia, Trichospermum and Piper increased in importance. Stepwise regression analysis using competitive performance as the independent variable, and the various morphological and physiological parameters measured on the individually grown plants as independent variables, suggested that canopy height was the single most important variable determining competitive ability. Also significant were photosynthetic rate (particularly at low light levels) and allocation to roots early in the experiment. Light profiles in the canopy revealed that less than 15% of incident light penetrated to the level of mean canopy height. Results suggest that competition for light was the major factor determining community composition, and that CO2 affected competitive outcome through its affect upon canopy architecture.This study was supported by a grant from the US Department of Energy  相似文献   

5.
Elevated CO2 may increase dry mass production of canopies directly through increasing net assimilation rate of leaves and also indirectly through increasing leaf area index (LAI). We studied the effects of CO2 elevation on canopy productivity and development in monospecific and mixed (1:1) stands of two co-occurring C3 annual species, Abutilon theophrasti, and Ambrosia artemisiifolia. The stands were established in the glasshouse with two CO2 levels (360 and 700 l/l) under natural light conditions. The planting density was 100 per m2 and LAI increased up to 2.6 in 53 days of growth. Root competition was excluded by growing each plant in an individual pot. However, interference was apparent in the amount of photons absorbed by the plants and in photon absorption per unit leaf area. Greater photon absorption by Abutilon in the mixed stand was due to different canopy structures: Abutilon distributed leaves in the upper layers in the canopy while Ambrosia distributed leaves more to the lower layers. CO2 elevation did not affect the relative performance and light interception of the two species in mixed stands. Total aboveground dry mass was significantly increased with CO2 elevation, while no significant effects on leaf area development were observed. CO2 elevation increased dry mass production by 30–50%, which was mediated by 35–38% increase in the net assimilation rate (NAR) and 37–60% increase in the nitrogen use efficiency (NUE, net assimilation rate per unit leaf nitrogen). Since there was a strong overall correlation between LAI and aboveground nitrogen and no significant difference was found in the regression of LAI against aboveground nitrogen between the two CO2 levels, we hypothesized that leaf area development was controlled by the amount of nitrogen taken up from the soil. This hypothesis suggests that the increased LAI with CO2 elevation observed by several authors might be due to increased uptake of nitrogen with increased root growth.  相似文献   

6.
Photosystem II chlorophyll fluorescence and leaf net gas exchanges (CO2 and H2O) were measured simultaneously on bean leaves (Phaseolus vulgaris L.) submitted either to different ambient CO2 concentrations or to a drought stress. When leaves are under photorespiratory conditions, a simple fluorescence parameter F/ Fm (B. Genty et al. 1989, Biochem. Biophys. Acta 990, 87–92; F = difference between maximum, Fm, and steady-state fluorescence emissions) allows the calculation of the total rate of photosynthetic electron-transport and the rate of electron transport to O2. These rates are in agreement with the measurements of leaf O2 absorption using 18O2 and the kinetic properties of ribulose-1,5bisphosphate carboxylase/oxygenase. The fluorescence parameter, F/Fm, showed that the allocation of photosynthetic electrons to O2 was increased during the desiccation of a leaf. Decreasing leaf net CO2 uptake, either by decreasing the ambient CO2 concentration or by dehydrating a leaf, had the same effect on the partitioning of photosynthetic electrons between CO2 and O2 reduction. It is concluded that the decline of net CO2 uptake of a leaf under drought stress is only due, at least for a mild reversible stress (causing at most a leaf water deficit of 35%), to stomatal closure which leads to a decrease in leaf internal CO2 concentration. Since, during the dehydration of a leaf, the calculated internal CO2 concentration remained constant or even increased we conclude that this calculation is misleading under such conditions.Abbreviations Ca, Ci ambient, leaf internal CO2 concentrations - Fm, Fo, Fs maximum, minimal, steady-state fluorescence emission - Fv variable fluorescence emission - PPFD photosynthetic photon flux density - qp, qN photochemical, non-photochemical fluorescence quenching - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase  相似文献   

7.
Minimal photosynthetic catalytic F1() core complexes, containing equimolar ratios of the and subunits, were isolated from membrane-bound spinach chloroplast CF1 and Rhodospirillum rubrum chromatophore RrF1. A CF1-33 hexamer and RrF1-11 dimer, which were purified from the respective F1() complexes, exhibit lower rates and different properties from their parent F1-ATPases. Most interesting is their complete resistance to inhibition by the general F1 inhibitor azide and the specific CF1 inhibitor tentoxin. These inhibitors were earlier reported to inhibit multisite, but not unisite, catalysis in all sensitive F1-ATPases and were therefore suggested to block catalytic site cooperativity. The absence of this typical property of all F1-ATPases in the 11 dimer is consistant with the view that the dimer contains only a single catalytic site. The 33 hexamer contains however all F1 catalytic sites. Therefore the observation that CF1-33 can bind tentoxin and is stimulated by it suggests that the F1 subunit, which is required for obtaining inhibition by tentoxin as well as azide, plays an important role in the cooperative interactions between the F1-catalytic sites.Abbreviations CF0F1 chloroplast F0F1 - CF1 chloroplast F1 - CF1 chloroplast F1 subunit - CF1 chloroplast F1 subunit - CF1() a complex containing equal amounts of the CF1 and subunits - MF1 mitochondrial F1 - RrF0F1 Rhodospirillum rubrum F0F1 - RrF1 R. rubrum F1 - RrF1 R. rubrum F1 subunit - RrF1 R. rubrum F1 subunit - RrF1() a complex containing equal amounts of the RrF1 and subunits - Rubisco Ribulose-1,5-bisphosphate carboxylase - TF1 thermophilic bacterium PS3 F1  相似文献   

8.
The cultivation of the hyperthermophilic archaeobacterium Pyrococcus woesei on starch under continuous gassing (80% H2:20% CO2) caused the formation of 250 U/l of an extremely thermoactive and thermostable -amylase. In a complex medium without elemental sulphur under 80% N2 and 20% CO2 atmosphere enzyme production could be elevated up to 1000 U/l. Pyrococcus woesei grew preferentially on poly-and oligosaccharides. The amylolytic enzyme formation was constitutive. Enzyme production was also observed in continuous culture at dilution rates from 0.1 to 0.4 h-1. A 20-fold enrichment of -amylase was achieved after adsorption of the enzyme onto starch and its desorption by preparative gel electrophoresis. The -amylase consisted of a single subunit with a molecular mass of 70 000 and was catalytically active at a temperature range between 40°C and 130°C. Enzymatic activity was detected even after autoclaving at a pressure of 2 bars at 120°C for 5 h. The purified enzyme hydrolyzed exclusively -1,4-glycosidic linkages present in glucose polymers of various sizes. Unlike many -amylases from anaerobes the enzyme from P. woesei was unable to attack short chain oligosaccharides with a chain length between 2 and 6 glucose units.  相似文献   

9.
The effect of temperature on photosynthesis at constant water-vapor pressure in the air was investigated using two sclerophyll species, Arbutus unedo and Quercus suber, and one mesophytic species, Spinacia oleracea. Photosynthesis and transpiration were measured over a range of temperatures, 20–39° C. The external concentration of CO2 was varied from 340 bar to near CO2 compensation. The initial slope (carboxylation efficiency, CE) of the photosynthetic response to intercellular CO2 concentration, the CO2 compensation point (), and the extrapolated rate of CO2 released into CO2-free air (R i) were calculated. At an external CO2 concentration of 320–340 bar CO2, photosynthesis decreased with temperature in all species. The effect of temperature on was similar in all species. While CE in S. oleracea changed little with temperature, CE decreased by 50% in Q. suber as temperature increased from 25 to 34° C. Arbutus unedo also exhibited a decrease in CE at higher temperatures but not as marked as Q. suber. The absolut value of R i increased with temperature in S. oleracea, while changing little or decreasing in the sclerophylls. Variations in and R i of the sclerophyll species are not consistent with greater increase of respiration with temperature in the light in these species compared with S. oleracea.Abbreviations and symbols A net photosynthetic rate - C and C i CO2 concentration in the air and in the intercellular airspace of the leaf, respectively - CE carboxylation efficiency - E transpiration rate - R i CO2 release into CO2-free air estimated from extrapolation to 0 bar CO2 - T i leaf temerature - VPD difference in water-vapor pressure between mesophyll and air - CO2 compensation point  相似文献   

10.
GABAA-receptors, the major synaptic targets for the neutotransmitter GABA, are gated chloride channels. By their allosteric drug-induced modulation they serve as molecular control elements through which the levels of anxiety, vigilance, muscle tension and epileptiform activity can be regulated. Despite their functional prominence, the structural requirements of fully functional GABAA-receptors are still elusive. Expression of cDNAs coding for the 1- and 1-subunits of rat brain yielded GABA-gated chloride channels which were modulated by barbiturates but displayed only agonistic responses to ligands of the benzodiazepine receptor. GABAA-receptors with fully functional benzodiazepine receptor sites were formed when the 1- and 1-subunits were coexpressed with the 2-subunit of rat brain. These receptors, however, failed to show cooperativity of GABA in gating the channel. In order to determine the subunit repertoire available for receptor assembly in different neuronal populations in vivo, the sites of subunit gene expression were (1, 2, 3, 5, 6, 1, 2, 3, 2) mapped by in situ hybridization histochemistry in brain sections. The mRNAs of the 1-, 1- and 2-subunits were co-localized e.g. in mitral cells of olfactory bulb, pyramidal cells of hippocampus as well as granule cells of dentate gyrus and cerebellum. The lack of colocalization in various other brain areas points to an extensive receptor heterogeneity. The presence of multiple GABAA-receptors in brain may contribute to synaptic plasticity, differential responsiveness of neurons to GABA and to variations in drug profiles.Special issue dedicated to Dr. Erminio Costa  相似文献   

11.
Summary The characteristics of the photosynthetic apparatus of 11 Hawaiian Euphorbia species, all of which possess C4 photosynthesis but range from arid habitat, drought-deciduous shrubs to mesic or wet forest evergreen trees and shrubs, were investigated under uniform greenhouse conditions. Nine species exhibited CO2 response curves typical of C4 plants, but differed markedly in photosynthetic capacity. Light-saturated CO2 uptake rates ranged from 48 to 52 mol m-2 s-1 in arid habitat species to 18 to 20 mol m-2 s-1 in mesic and wet forest species. Two possessed unusual CO2 response curves in which photosynthesis was not saturated above intercellular CO2 pressures [p(CO2)] of 10 to 15 Pa, as typically occurs in C4 plants.Both leaf (g1) and mesophyll (gm) conductances to CO2 varied widely between species. At an atmospheric p(CO2) of 32 Pa, g1 regulated intercellular p(CO2) at 12–15 Pa in most species, which supported nearly maximum CO2 uptake rates, but did not result in excessive transpiration. Intercellular p(CO2) was higher in the two species with unusual CO2 response curves. This was especially apparent in E. remyi, which is native to a bog habitat. The regulation of g1 and intercellular p(CO2) yielded high photosynthetic water use efficiencies (P/E) in the species with typical CO2 response curves, whereas P/E was much lower in E. remyi.Photosynthetic capacity was closely related to leaf nitrogen content, whereas correlations with leaf morphological characteristics and leaf cell surface area were not significant. Thus, differences in photosynthetic capacity may be determined primarily by investment in the biochemical components of the photosynthetic apparatus rather than by differences in diffusion limitations. The lower photosynthetic capacities in the wet habitat species may reflect the lower light availability. However, other factors, such as reduced nutrient availability, may also be important.  相似文献   

12.
Li ZY  Li YJ  Guo CY  Shi YW  Xu MQ  Trommer WE  Yuan JM 《Biotechnology letters》2004,26(23):1765-1769
An open reading frame of the -subunit 1-205 residues (205) of human acetylcholine receptor (AchR) was amplified by PCR with pUC-AChR205 as the template and inserted into vector pMAL-c2X. The constructed pMAR205 was transferred into E. coli BL21 which were then grown in LB medium. The amount of soluble MBP-AChR205 protein reached about 25% of total soluble proteins from the cell lysate. Using amylose-affinity chromatography, about 35 mg MBP-AChR205 could be obtained from 1 l culture. Western blot analysis and ELISA showed that immunoreactivities of both MBP-AChR205 and AChR205 were similar to that of AChR -subunit from Torpedo.Revisions received 23 September 2004  相似文献   

13.
Summary Well watered plants of Vigna unguiculata (L.) Walp cv. California Blackeye No. 5 had maximum photosynthetic rates of 16 mol m-2 s-1 (at ambient CO2 concentration and environmental parameters optimal for high CO2 uptake). Leaf conductance declined with increasing water vapour concentration difference between leaf and air (w), but it increased with increasing leaf temperature at a constant small w. When light was varied, CO2 assimilation and leaf conductance were correlated linearly. We tested the hypothesis that g was controlled by photosynthesis via intercellular CO2 concentration (c i). No unique relationship between (1) c i, (2) the difference between ambient CO2 concentration (c a) and c i, namely c a-c i, or (3) the c i/c a ratio and g was found. g and A appeared to respond to environmental factors fairly independently of each other. The effects of different rates of soil drying on leaf gas exchange were studied. At unchanged air humidity, different rates of soil drying were produced by using (a) different soils, (b) different irrigation schemes and (c) different soil volumes per plant. Although the soil dried to wilting point the relative leaf water content was little affected. Different soil drying rates always resulted in the same response of photosynthetic capacity (A max) and corresponding leaf conductance (g(Amax)) when plotted against percent relative plant-extractable soil water content (W e %) but the relationship with relative soil water content (W e ) was less clear. Above a range of W e of 15%–25%, A max and g(Amax) were both high and responded little to decreasing W e . As soon as W e fell below this range, A max and g(Amax) declined. The data suggest root-to-leaf communication not mediated via relative leaf water content. However, g(Amax) was initially more affected than A max.List of abbreviations A CO2 assimilation - A max photosynthetic capacity at favourable ambient conditions - c a CO2 concentration of the air in the leaf chamber - c i intercellular - CO2 concentration - E transpiration - g leaf conductance - g(Amax) leaf conductance corresponding to photosynthetic capacity - I photon flux rate - T l leaf temperature - W e relative plant-extractable soil water content - W e absolute plant-extractable soil water content - W l relative leaf water content - W s relative soil water content - w difference in water vapour mole fraction between leaf and air - leaf water potential  相似文献   

14.
I. Nijs  I. Impens  T. Behaeghe 《Planta》1989,177(3):312-320
The relationship between leaf photosynthetic capacity (p n, max), net canopy CO2- and H2O-exchange rate (NCER and E t, respectively) and canopy dry-matter production was examined in Lollium perenne L. cv. Vigor in ambient (363±30 l· l-1) and elevated (631±43 l·l-1) CO2 concentrations. An open system for continuous and simultaneous regulation of atmospheric CO2 concentration and NCER and E t measurement was designed and used over an entire growth cycle to calculate a carbon and a water balance. While NCERmax of full-grown canopies was 49% higher at elevated CO2 level, stimulation of p n, max was only 46% (in spite of a 50% rise in one-sided stomatal resistance for water-vapour diffusion), clearly indicating the effect of a higher leaf-area index under high CO2 (approx. 10% in one growing period examined). A larger amount of CO2-deficient leaves resulted in higher canopy dark-respiration rates and higher canopy light compensation points. The structural component of the high-CO2 effect was therefore a disadvantage at low irradiance, but a far greater benefit at high irradiance. Higher canopy darkrespiration rates under elevated CO2 level and low irradiance during the growing period are the primary causes for the increase in dry-matter production (19%) being much lower than expected merely based on the NCERmax difference. While total water use was the same under high and low CO2 levels, water-use efficiency increased 25% on the canopy level and 87% on a leaf basis. In the course of canopy development, allocation towards the root system became greater, while stimulation of shoot dry-matter accumulation was inversely affected. Over an entire growing season the root/shoot production ratio was 22% higher under high CO2 concentration.Abbreviations and symbols C350 ambient CO2, 363±30 l·l-1 - C600 high CO2, 631±43 l·l-1 - c a atmospheric CO2 level - c i CO2 concentration in the intracellular spaces of the leaf - Et canopy evapotranspiration - I o canopy light compensation point - NCER canopy CO2-exchange rate - p n leaf photosynthetic rate - PPFD photosynthetic photon flux density - r a leaf boundary-layer resistance - RD canopy dark-respiration rate - r s stomatal resistance - WUE water use efficiency  相似文献   

15.
Sites of photoinhibition and photo-oxidative damage to the photosynthetic electrontransport system of the unicellular cyanobacterium Microcystis aeruginosa were identified by studies of the kinetics of chlorophyll fluorescence induction by whole cells at room temperature and from partial photosynthetic electron-transport reactions in vitro in thylakoid preparations. Chlorophyll fluorescence intensity decreased following photoinhibitory light treatment. This was attributed to decreases both in the activity of photosystem II and in electron flow through the primary electron acceptor, Q. This inhibition was only partially reversed over a 50-min dark recovery period. Partial photosynthetic electron-transport experiments in vitro demonstrated that photosystem I was not affected by the photoinhibitory treatment. Light damage was associated exclusively with the light reactions, of photosystem II, at a site close to the reaction centre, between the site where diphenylcarbazide can donate electrons and the site where silicomolybdate can accept electrons. This damage presumably reduced production of ATP by noncyclic photophosphorylation and production of NADPH by photosystem I, decreasing the availability of these co-factors for reducing CO2 in the dark reactions of photosynthesis. The importance of these findings is discussed.Abbreviations Chl chlorophyll - DCPIP 2,6-dichlorophenolindophenol - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DPC diphenylcarbazide - PSI photosystem I - PSH photosystem II  相似文献   

16.
We have investigated the activity of CMP-Neu5Ac:Gal\1-3GalNAc -2,3-sialyltransferase (EC 2.4.99.4) in FR3T3 cells transformed by the Ha-ras oncogene in which we have previously demonstrated the higher expression of the -galactosidase -2,6-sialyltransferase (EC 2.4.99.1) [21]. We demonstrate that the presence of the activatedras gene decreases the activity of this specific -2,3-sialyltransferase fourfold. According to the kinetic parameters and to mixing experiments, we can assume that this decreased enzymatic activity reflects a decrease in the number of activeO-glycan -2,3-sialyltransferase polypeptides inras-transformed cells. However, no change in the binding of Peanut agglutinin was observed on the cell surface ofras-transformed FR3T3 suggesting that no change in the sialylation ofO-glycan core 1 appeared in these cells, although the activity of the -2,3-sialyltransferase was decreased.Abbreviations -2,3-ST(O) CMP-Neu5Ac:Gal1-3GalNAc-R -2,3-sialyltransferase - -2,3-ST(N/O) CMP-Neu5Ac:Gal1-3/4GlcNAc-R -2,3-sialyltransferase - -2,6-ST(N) CMP-Neu5Ac:Gal1-4GlcNAc-R -2,6-sialyltransferase - -2,6-ST(O)I CMP-Neu5Ac:R-GalNAc(1-O)Ser -2,6-sialyltransferase - -2,6-ST(O)II CMP-Neu5Ac:Neu5Ac2-3Gal1-3GalNAc-R -2,6-sialyltransferase - ASFet asialofetuin - FR3T3 Fisher rat fibroblast - FRras Ha-ras-transfected FR3T3 fibroblasts - NaCl/Pi sodium phosphate 10mm, NaCl 0.15m, pH 7.4, buffer - pNp p-nitrophenol  相似文献   

17.
Wheat plants were grown from sowing to day 18 in 26-dm3 chambers at three different CO2 concentrations: 150 (-CO2), 350 (C, control), 800 (+CO2) mol mol-1. Afterwards, plants of the three variants were grown at the same natural CO2 concentration. Plant characteristics were measured just before the transfer (0 days after CO2 treatment, DAT), and at 5 – 8 DAT on the 1st leaf, and at 12 – 22 DAT on the 4th leaf. Decreased or increased CO2 concentrations caused acclimations which persisted after transplantation to natural CO2 concentration. At 5 – 8 DAT, stomatal density, stomatal conductance (gs), CO2 saturated net photosynthetic rate (PNsat0), radiation saturated net photosynthetic rate (PNsat1), and carboxylation efficiency () were higher in -CO2 plants and lower in +CO2 plants than in C plants. As compared with C plants, the photochemical efficiency () was lower in -CO2 and higher in -CO2 plants, however, chlorophyll (Chl) a, Chl b, Chl a–b and carotenoid contents were lower in both -CO2 and +CO2 plants. On the 4th leaf, which emerged on plant after finishing CO2 treatments, at 12 – 22 DAT, no differences in stomatal density and g, between treatments were observed. In -CO2 plants, pigment content and PNsat0 were higher, was lower, and PNsat1 and were not different from C plants. In contrast, in +CO2 plants, pigment content, PNsat1 and were lower, and PNsat0 and were unchanged. Leaf area, dry mass, and tiller development increased in +CO2 plants and decreased in -CO2 plants. In the interval between 8 and 22 DAT, lower net assimilation rate in +CO2 than in -CO2 plants was observed.  相似文献   

18.
Desensitization of prostaglandin (PG) F2 receptor-mediated phosphoinositide (PI) hydrolysis was investigated in cultured rat astrocytes. Prolonged exposure of astrocytes differentiated by dibutyryl cyclic AMP-treatment to PGF2 caused the desensitization of subsequent PGF2-induced PI hydrolysis. The desensitization was time- and PGF2 dose-dependent; maximal decrease in the PI hydrolysis was observed after exposure to 10 M PGF2 for 4 h and the degree of the desensitization was 31.7±2.7% of control. Pretreatment with either PGD2 or PGE2 also induced the desensitization of subsequent PGF2-stimulated PI hydrolysis and conversely pretreatment of PGF2 decreased the PI responses to PGD2 and PGE2. The desensitization prevented by phloretin and was reversible upon removal of the agonist. Protein synthesis inhibitors blocked the recovery of the desensitization. Treatment of the cells with phorbol 12-myristate 13-acetate had no effect on the desensitization. These results suggest that prolonged exposure of the astrocytes to PGF2 caused the desensitization of the receptors.  相似文献   

19.
To examine the possible role of basic fibroblast growth factor (FGF) in regulating the effects of TNF, we tested the effect of FGF on TNF-mediated PGE2 production and TNF receptor expression in human fibroblasts. We found that, while FGF alone had no effect on PGE2 production, it enhanced the amount of PGE2 produced in response to TNF between 3 and 11-fold. FGF stimulated TNF-induced PGE2 production independent of potential TNF-mediated IL-1 production, as neither anti-IL-1 mAbs nor IL-1 receptor antagonist protein (IRAP) inhibited TNF induced-PGE2 production or the stimulatory effect of FGF. A one minute exposure of cells to FGF prior to removal was sufficient to significantly enhance TNF-induced PGE2 production; the maximal FGF effect was reached after a 6 h preincubation. We also found that FGF significantly enhanced TNF receptor expression. Untreated fibroblasts expressed 3,900 receptors/cell, while cells treated with FGF for 6h expressed 9,500 receptors/cell, a 2.4-fold increase in receptor number; there was no apparent change in affinity for TNF (Kd 3.8×10–11 M). The FGF-mediated increase in TNF receptor expression and TNF-mediated PGE2 production could be abolished by FGF mAbs, indicating a specific FGF effect. These results show that FGF increases TNF receptor expression and suggest that this may account, at least in part, for the ability of FGF to enhance TNF-mediated PGE2 production in human fibroblasts.  相似文献   

20.
Summary In the Far East two types of -thalassemia genes, namely -thalassemia1 (-thal1) and -thalassemia2 (-thal2) exist. Definite diagnosis of the -thal1 and -thal2 traits is very difficult because their hematological findings are minimally abnormal or normal. This study attempts to characterize the heterozygotes by hemoglobin chain synthesis in reticulocytes from obligatory cases of the -thal1 and -thal2 traits. Twelve parents of babies with hemoglobin Bart's hydrops fetalis (obligatory -thal1 trait) had the mean total radioactivity / ratio of 0.76±SD 0.04, while that of 7 normal controls was 1.06±SD 0.04. The / globin chain ratios of 16 cases, who were either parents or offspring of patients with hemoglobin H disease, were found to segregate into 2 groups, i.e. 0.78±SD 0.03 (10 cases) and 0.92±SD 0.03 (6 cases), probably representing the -thal1 and -thal2 traits respectively. The hematological data of the first group showed definite hypochromic microcytic red cells, similar to thoseof the parents of the hydrops. The second group had significantly higher mean corpuscular hemoglobin than the first group, compatible with -thal2 trait. Our globin chain synthesis study thus appears to be capable of discriminating normal, -thal1 and -thal2 traits.A preliminary report of the results was presented at the XV Congress of the International Society of Haematology, Israel, September, 1974.  相似文献   

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