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1.
Transpiration and water absorption rates, stomatal and cuticular resistances to water vapour diffusion, were measured on Plantago maritima (halophyte) and Plantago lanceolata (glycophyte) grown in the presence of NaCl or Na 2SO 4. Water absorption was reduced in the presence of Na 2SO 4 and transpiration rate was increased when NaCl was added to the nutrient solution. The glycophyte daily water balance was
more disturbed than that of the halophyte in the presence of Na 2SO 4. 相似文献
2.
Seeds and seedlings of soft wheat ( Triticum vulgare Vill.) were used to study seed germination, leaf elongation, and the content of photosynthetic pigments (chlorophylls a, b and carotenoids) as affected by five concentrations of iron-containing nanoparticles (NP): spherical Fe 0 NP with the diameter of 80 ± 5 nm and the magnetite Fe 3O 4 NP measuring 50–80 nm in width and 4–10 nm in height. The effects of FeSO 4 solutions were also tested for comparison. The parameters examined varied as a function of the exogenous agent applied, the agent concentration, and the exposure duration. The highest sensitivity of seedlings was observed in the presence of increasing concentrations of iron (II) sulfate in the nutrient medium. This was evident from the decrease in seed germination percentage, inhibition of leaf growth, and the diminished content of photosynthetic pigments. The apparent toxicity of iron nanoforms varied depending on the parameter examined. (1) The strongest inhibition of germination was exerted by Fe 0 NP (toxicity assessed from germination percentage was 3.3% higher with Fe 0 NP than with magnetite NP); (2) the inhibition of leaf elongation on the 4th day after germination was most evident in the presence of Fe 0 NP (a 12% stronger inhibition in the presence of Fe 0 NP than in the presence of magnetite NP), whereas on the 7th day the inhibition was most pronounced with magnetite NP (a 9% stronger inhibition in the presence of Fe 3SO 4 NP than in the presence of Fe 0 NP); (3) the lowest total content of photosynthetic pigments on the 4th day of seedling growth was noted in the presence of magnetite NP (8% lower in the presence of Fe 3SO 4 NP than in the presence of Fe 0 NP), whereas on the 7th day the lowest pigment pool was observed in the presence Fe 0 NP (a 3% reduction compared to that in the presence of magnetite NP). The highest content of photosynthetic pigments was recorded in the presence of 0.125 and 0.001 g/L of Fe 0 NP, 0.5 g/L and 1 μg/L of Fe 3O 4 NP, and 1 mg/L FeSO 4. 相似文献
3.
Methanogenesis by a Syntrophomonas wolfei/ Methanospirillum hungatei coculture was inhibited in presence of ethylene and the hydrogenation catalyst Pd-BaSO 4. However, butyrate oxidation by S. wolfei continued and ethylene was reduced to ethane. Per mol of butyrate oxidized, 2.4 mol acetate was produced and 0.8 mol ethylene was reduced. Acetylene, propylene and butene were less effective as H 2 acceptors than ethylene, and addition of bromoethanesulfonic acid was necessary to inhibit methanogenesis in the presence of the two longer-chain olefins. Other hydrogenation catalysts were less effective in the order Pd-charcoal < PE-asbestos < Pd-PEI beads < Pt-Al 2O 3, Pd-CaCO 3. Optimal ethylene hydrogenation was achieved with still incubation in presence of 7.2 mg Pd-BaSO 4 and 0.7 g sand per ml medium. The higher catabolic rate of S. wolfei in presence of the methanogen indicated that the biological H 2 removal mechanism was more efficient than the catalytic olefin reduction.Abbreviations BES
bromoethane sulfonic acid
- VFA
volatile fatty acid 相似文献
4.
The benthic O 2 consumption and CO 2 production of sieved sediment cores containing a varied biomass of two polychaete species, Notomastus sp. (deep deposit-feeder) and Neanthes japonica (Izuka) (surface deposit-feeder), were measured simultaneously. Each species increased the benthic O 2 consumption and CO 2 production in proportion to its biomass. This increase was not explained by the respiration of the animals alone. The residual O 2 and CO 2 fluxes increased markedly in the presence of polychaetes. In the presence of Notomastus (the deeper burrowing species with low irrigation activity), the enhanced CO 2 flux was much higher than that in the presence of Neanthes, whereas the enhanced O 2 flux was lower in the presence of Notomastus. 相似文献
5.
Biological effects of angiotensin II (AngII) such as regulation of AngII target genes may be triggered by interaction of AngII with intracellular AngII receptor types 1 and 2 (AT1 and AT2), defined as intracrine response. The aim of this study was to examine the presence of AT1 and AT2 receptors in nuclear membrane of human mesangial cells (HMCs) and evaluate the possible biological effects mediated by intracellular AT1 through an intracrine mechanism. Subcellular distribution of AT1 and AT2 was evaluated by immunofluorescence and by western blot in isolated nuclear extract. Endogenous intracellular synthesis of AngII was stimulated by high glucose (HG). Effects of HG were analyzed in the presence of candesartan, which prevents AngII internalization. Both receptors were found in nuclear membrane. Fluorescein isothiocyanate (FITC)-labeled AngII added to isolated nuclei produced a fluorescence that was reduced in the presence of losartan or PD-123319 and quenched in the presence of both inhibitors simultaneously. HG induced overexpression of fibronectin and increased cell proliferation in the presence of candesartan, indicating an intracrine action of AngII induced by HG. Results showed the presence of nuclear receptors in HMCs that can be activated by AngII through an intracrine response independent of cytoplasmic membrane AngII receptors. 相似文献
6.
The interaction of pyrimidine oligonucleotides (OLN 15 and OLN 6) and their alkylating derivatives bearing 4-(3-amino)propyl- N-methyl and N-2-chloroethyl (RCl) aniline residues at the 5′-phosphate with a fragment of the human γ-interferon gene was studied. In the
presence of 150 mM NaCI at pH 5.4, the yield of dsDNA alkylation was 60% for RCl-OLN 15 and 10% for RCl-OLN 6; at pH 4.0 in the presence of 150 mM NaCI and 10 mM MgCl 2, the yield of the dsDNA modification product was 100% for RCl-OLN 6 and 50% for RCl-OLN 15. It was shown by native electrophoresis that OLN 15 could form with the target dsDNA complexes of two types in the presence of magnesium ions at pH 4.0. One of the complexes
was stable at pH 5.4 in the presence of magnesium ions, whereas the other was not. We found that only the complex stable in
10 mM Mg(OAc) 2, pH 5.4, was effectively alkylated. 相似文献
7.
Long chain fatty acid synthesis was studied using etiolated leek seedling microsomes. In the presence of ATP, [2- 14C]malonyl-CoA was incorporated into fatty acids of C 16C 26. The omission of ATP, even in the presence of acetyl-CoA, led to a complete loss of activity, which was restored by addition of exogeneous acyl-CoAs. Comparison of acyl-CoA (C 12C 24) elongation showed that stearoyl-CoA, in the presence of [2- 14C]malonyl-CoA, was the more efficient precursor leading to the formation of fatty acids having a chain length of C 20C 26. [1- 14C]C 16CoA and [1- 14C]C 18CoA were elongated in the presence of malonyl-CoA, without degradation of the acyl chain. The time-course and the malonyl-CoA concentration curves showed that [1- 14C]C 18CoA was a better primer than [1- 14C]C 16CoA. Acyl-CoA elongation was also studied over the concentration range 4.5–45 μM [1- 14C]C 18CoA. Comparison of the radioactivity incorporated into the fatty acids formed using [2- 14C]malonyl-CoA in the presence of C 18CoA, on the one hand, and [1- 14C]C 18CoA in the presence of malonyl-CoA, on the other, demonstrated clearly that the acyl chain of the acyl-CoA was elongated by malonyl-CoA. 相似文献
8.
A highly purified adenosine 3′,5′-monophosphate-dependent protein kinase from bovine brain has been found to catalyze its own phosphorylation. The incorporated phosphate was shown to be associated with the cyclic AMP-binding subunit (R-protein) of the protein kinase. The catalytic subunit exhibited no detectable incorporation of phosphate into itself, but was required for the phosphorylation of R-protein. The molecular weight of R-protein was determined by polyacrylamide gel electrophoresis to be about 48,000 in the presence of sodium dodecyl sulfate. Cyclic AMP strikingly inhibited the rate of autophosphorylation observed in the presence of ZnCl 2, CaCl 2, NiCl 2, or FeCl 2, but had no significant effect in the presence of MgCl 2 or CoCl 2. The concentration of cyclic AMP required to give half-maximal inhibition of phosphorylation was 3 × 10 ?7m in the presence of either CaCl 2 or ZnCl 2. Guanosine 3′,5′-monophosphate was far less effective under the same experimental conditions than cyclic AMP. R-protein appears to be similar to a phosphoprotein recently discovered in synaptic membrane fractions from rat and bovine cerebral cortex. 相似文献
9.
Summary We investigated the influence of Mg 2+ and Mn 2+ on the effects of adenosine and some derivatives on basal adenylate cyclase activity in rat fat cell membranes as well as on enzyme activity stimulated by isoprenaline or sodium fluoride. Adenosine and derivatives modified in the ribose function were inhibitory, irrespective of the stimulant used, both in the presence of MgCl 2 or MnCl 2. Inhibition of basal and sodium fluoride stimulated adenylate cyclase activity was more pronounced in the presence of MnCl 2 than in the presence of MgCl 2. N 6-substituted adenosine analogs proved to be inhibitory in the presence of 5 MM MgCl 2, but in the presence of 1 mM MnCl 2 the fluoride stimulated adenylate cyclase activity was potentiated, while basal and isoprenaline stimulated activity were not significantly inhibited. These effects of adenosine and derivatives could not be blocked by theophylline with or without guanyl nucleotides.The potentiating effect of N 6-substituted adenosine derivatives on sodium fluoride activated adenylate cyclase is dependent on the structure of the N 6-substitutent and consists of an enhancement of Vrnax in combination with a small decrease of the K m for MnATP 2–, indicative of an allosteric effect on adenylate cyclase. No potentiation by N 6-phenylisopropyladeno sine of sodium fluoride stimulated cyclase was found on digitonin solubilized cyclase, while the inhibitory effect of adenosine was retained. The relevance of these findings is discussed in connection with the current hypothesis concerning the presence of two adenosinesensitive sites on rat fat cell membranes. 相似文献
10.
In spinach thylakoids prepared from intact chloroplasts by shocking in the presence of ascorbate to preserve the operation of ascorbate peroxidase, the rate of oxygen uptake with methyl viologen as acceptor decreased in response to the addition of H 2O 2. Such a decrease was not observed in the presence of KCN or when the thylakoids lost ascorbate peroxidase activity. Illumination of intact chloroplasts in the presence of H 2O 2 and methyl viologen showed an initial rate of oxygen exchange, which is intermediate between the initial rate of oxygen evolution in the presence of H 2O 2 alone and steady-state oxygen uptake in the presence of methyl viologen. The data showed that monodehydroascorbate radical generated in ascorbate peroxidase reaction could compete with methyl viologen for electrons supplied by the electron transport chain in both thylakoids and intact chloroplasts. During the illumination of intact chloroplasts the rate of oxygen uptake increased. The presence of nigericin swiftly led to steady-state oxygen uptake, and to a clear-cut 1:1 relationship between the electron transport rate estimated from fluorescence assay and the electron transport rate determined from oxygen uptake, taking the stoichiometry 1O 2:4e. The increase in oxygen uptake was attributed to the cessation of monodehydroascorbate radical generation brought about by consumption of intrachloroplast ascorbate in the peroxidase reactions, and the effects of nigericin were explained by acceleration of such consumption. The competition between methyl viologen and monodehydroascorbate radical in the intact chloroplasts was estimated under various conditions. 相似文献
11.
介绍一种鉴别SOD类型的方法─—聚丙烯酰胺凝胶电泳的定位染色法. 由于不同类型的SOD对抑制剂的表现各异, 电泳后的凝胶经不同的抑制剂处理, 染色, 结果展示在凝胶上, CuZn-SOD酶带在H 2O 2或CN -的作用下消失, Mn-SOD在CHCl 3-CH 3OH作用下消失, Fe-SOD在H 2O 2或. CHCl 3-CH 3CH 2OH作用下失活, 从酶带消失或存活的情况, 可以判断SOD的类型. 相似文献
12.
This study reports the regulation of multiple xylanases produced by Myceliophthora sp. IMI 387099. Fructose was found to positively regulate the expression of multiple xylanase when used as sole carbon source.
The xylanases (EX 1 and EX 2) of acidic pI were expressed in the presence of simple sugars (glucose, arabinose, and xylose), whereas xylanase of both
acidic as well as basic pI (EX 1, EX 2, EX 3, and EX 5) were expressed in the presence of fructose, xylan, and combination of xylan and alcohol. The combination of fructose and
xylan also led to expression of an additional xylanase (EX 4). The positional isomer (iso-X4) was found to be the key transglycosylation product when cultures were grown in the presence
of fructose and xylan. In the presence of alcohols, the higher expression of xylanase was ascribed to the synergistic effect
of alkyl glycoside and other transglycosylation products present in the culture extracts. 相似文献
13.
The adenosine transport in cultured chromaffin cells was increased by the presence of triiodo- l-thyronine (T 3) throughout the prolonged period studied. The V max values of this transport obtained in absence and presence of 1 M T 3 were 36.21±2.1 and 44.17±3.5 (means±SD) pmol/10 6cells/min respectively for 26 hours incubation-time with the hormone. The K m values were not significantly modified. The number of adenosine transporters in cultured chromaffin cells, measured by [ 3H]nitrobenzylthioinosine (NBTI) binding, was increased by 1 M T 3 for 26 hours incubation-time. The values of binding sites per cell were 33,500±3,000 and 40,153±3,700 in absence and presence of T 3 respectively, without changing the K d constant. When the transport studies were carried out in presence of cycloheximide, an inhibitor of protein synthesis, the adenosine transport capacity decreased with a half-life values of 23.9±2.8 and 24.3±2.1 hours both in the presence or absence of T 3 respectively. When cells were incubated in the presence of both T 3 and cycloheximide, not only the activatory effect of T 3 was completely abolished but also adenosine transport was decreased to the same extent as with cycloheximide alone. These results indicated that T 3 activation of adenosine transport in chromaffin cells required the protein-synthesizing mechanism. 相似文献
14.
The inhibition of nitrous oxide (N 2O) reduction by acetylene (C 2H 2) in saltmarsh sediment was temporary; we investigated this phenomenon and possible causes. The reduction of N 2O in the presence of C 2H 2 was biological. N 2O consumption in the presence of C 2H 2 began when nitrate concentration became very low. The time course of N 2O consumption after periods of N 2O accumulation was unaffected by initial nitrate concentrations between 16 and 200 M, or C 2H 2 concentrations between 10 and 100% of the gas phase. Sulfide had no effect on the kinetics of N 2O reduction in the presence of C 2H 2. In more dilute slurries of saltmarsh sediments and in estuarine sediment, N 2O persisted in the presence of C 2H 2 unless sufficient organic carbon was added to deplete nitrate. In saltmarsh sediments, the rate of N 2O consumption in the presence of C 2H 2 was not changed by preincubation with C 2H 2. Initial positive rates of N 2O production in the presence of C 2H 2 occurred only when the block was apparently effective (i.e., at nitrate concentrations greater than about 5–10 M) and appeared to represent a valid estimate of denitrification. Conversely, and in agreement with previous studies, concentrations of NO 3
– below these levels resulted in reduced efficiency of C 2H 2 blockage of N 2O reductase. 相似文献
15.
Summary Net CO 2 fixation in Lemna gibba L. was inhibited by 0.5 m M L-methionine D,L-sulfoximine (MSX) both under photorespiratory conditions (21% O 2) and in 2% O 2. The inhibition was noticeably delayed by addition of 5 m M glutamine. Glutamine also delayed MSX-induced inactivation of glutamine synthetase. An increase in intracellular NH
4
+
concentration was noted in the presence of MSX only, and in the presence of 10 m M NH
4
+
only. However, presence of 10 m M NH
4
+
did not cause any inhibition of CO 2 fixation. 相似文献
16.
AbstractThe activity and stability of commercial peroxidase was investigated in the presence of five 1-alkyl-3-methylimidazolium-based ionic liquids (ILs) with either bromide or chloride anions: [C xmim][X]. The peroxidase activity and stability were better for the shorter alkyl chain lengths of the ILs and peroxidase was more stable in the presence of the bromide anion, rather than chloride. The thermal inactivation profile was studied from 45 to 60 °C in [C 4mim][Cl] and [C 4mim][Br]. The activation energy was also determined. Kinetic analysis of the enzyme in the presence of the [C 4mim][Br] or control (buffer solution) showed that the KM value increased 5-fold and Vm decreased 13-fold in the presence of the IL. The increase in KM indicates that this IL can reduce the binding affinity between substrate and enzyme. 相似文献
17.
Externally added quercetin (100 micromolar) was oxidized by intact spinach chloroplasts at a rate of 30 micromoles per mg chlorophyll per hour in the presence of 100 micromolar H 2O 2. The oxidation rate was increased by about 20% in a hypotonic reaction mixture. The thylakoid fraction also oxidized the flavonol in the presence of H 2O 2, and the rate was about 25% of that by intact chloroplasts. The oxidation of quercetin was inhibited by KCN and NaN 3. Ascorbate, which permeates slowly across chloroplast envelope, only slightly suppressed the initial rate of quercetin oxidation by intact chloroplasts, while the oxidation by ruptured chloroplasts was suppressed by ascorbate by about 60%. Quercetin glycosides, quercitrin and rutin, were also oxidized by chloroplasts in the presence of H 2O 2. These results suggest that flavonols are oxidized by peroxidase-like activity in chloroplasts and that externally added flavonols can permeate into the stroma through the envelope of intact chloroplasts. 相似文献
18.
The probable effect of increasing levels of ammonium nitrogen on the growth, efficiency of nitrogen fixation, and main cellular constituents of Azotobacter vinelandii was studied under shaking and static culture conditions. The presence of NH 4+-N up to 50 mgl -1 level has no harmful effect on the multiplication as well as the yield efficiency ratio of the tested organism. A. vinelandii was able to fix dinitrogen in the presence of NH 4+-N when both nitrogen sources were available in the culturing medium. The efficiency of nitrogen fixation was affected by the initial presence of NH 4+-N in the medium, it was quite low at the highest level. The crude protein efficiency ratio was correlated inversely with the initial NH 4+-N concentration, whereas the total carbohydrate efficiency ratio as well as the total lipid efficiency ratio were positively correlated with the NH 4+-N concentration. The presence of NH 4+-N in the culturing medium has no essential influence on the qualitative composition of the amino acids in the Azotobacter cells. 相似文献
19.
The activity of Aspergillus oryzae S 1 nuclease in solutions which destabilize DNA secondary structure was investigated. S 1 nuclease is able to degrade single-stranded DNA in the presence of various concentrations of formaldehyde, formamide, and glyoxal. It is further shown that S 1 nuclease can be used: (1) in the presence of formaldehyde to generate cleavage products from partially denatured duplex DNA; (2) to obtain thermal-melting profiles in the presence of formamide. 相似文献
20.
Studies show that uptake of long-chain fatty acids (LCFA) across the plasma membranes (PM) may occur partly via a carrier-mediated process and that the plasma membrane fatty acid-binding protein (FABP PM) may be a component of this system. To test the hypothesis that FABP PM is involved in transsarcolemmal transport of LCFA in muscle, we measured palmitate uptake in giant sarcolemmal vesicles and palmitate binding to PM proteins in rat muscles, (1) in the presence of increasing amounts of unbound palmitate and (2) in the absence or presence of antibody to FABP PM. Both palmitate uptake and binding were found to be saturable functions of the unbound palmitate concentration with calculated V max values of 10.5 ± 1.2 pmol/mg protein/15 sec and 45.6 ± 2.9 nmol/mg protein/15 min and K m values of 12.8 ± 3.8 and 18.4 ± 1.8 nmol/L, respectively. The V max values for both palmitate uptake and binding were significantly decreased by 75-79% in the presence of a polyclonal antibody to the rat hepatic FABP PM. Antibody inhibition was found to be dose-dependent and specific to LCFA. Glucose uptake was not affected by the presence of the antibody to FABP PM. Palmitate uptake and binding were also inhibited in the presence of trypsin and phloretin. These results support the hypothesis that transsarcolemmal LCFA transport occurs in part by a carrier-mediated process and that FABP PM is a component of this process in muscle. 相似文献
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