共查询到20条相似文献,搜索用时 31 毫秒
1.
《生物化学与生物物理学报:生物膜》2014,1838(5):1338-1343
PbtA, a putative P1B-type ATPase from the Gram-negative soil bacterium Achromobacter xylosoxidans A8 responsible for Pb2 +/Zn2 +/Cd2 +-resistance in Escherichia coli, was heterologously expressed in Saccharomyces cerevisiae. When present in Zn2 +- and Pb2 +/Cd2 +-hypersensitive S. cerevisiae strains CM137 and DTY168, respectively, PbtA was able to restore Zn2 +- and Pb2 +-resistant phenotype. At the same time, the increase of Pb, Zn, and Cd accumulation in yeast was observed. However, Cd2 +-tolerance of the pbtA-bearing yeasts dramatically decreased. The PbtA-eGFP fusion protein was localized primarily in the tonoplast and also in the plasma membrane and the perinuclear region corresponding to the endoplasmic reticulum at later growth stages. This indicates that PbtA protein is successfully incorporated into membranes in yeasts. Since PbtA caused a substantial increase of Pb2 +/Zn2 +-resistance and accumulation in baker's yeast, we propose its further use for the genetic modification of suitable plant species in order to obtain an effective tool for the phytoremediation of sites polluted by toxic transition metals. 相似文献
2.
《Cellular signalling》2014,26(12):2826-2833
Eight paralogue members form the family of transmembrane channel-like (TMC) proteins that share considerable sequence homology to anoctamin 1 (Ano1, TMEM16A). Ano1 is a Ca2 + activated Cl− channel that is related to head and neck cancer, often caused by human papilloma virus (HPV) infection. Mutations in TMC 6 and 8 (EVER1, EVER2) cause epidermodysplasia verruciformis. This rare skin disease is characterized by abnormal susceptibility to HPV infection and cancer. We found that in contrast to Ano1 the common paralogues TMC4–TMC8 did not produce Ca2 + activated Cl− currents when expressed in HEK293 cells. On the contrary, TMC8 was found to be localized in the endoplasmic reticulum (ER), where it inhibited receptor mediated Ca2 + release, activation of Ano1 and volume regulated LRRC8-related Cl− currents. Zn2 + is co-released from the ER together with Ca2 + and thereby further augments Ca2 + store release. Because TMC8 is required to lower cytosolic Zn2 + concentrations by the Zn2 + transporter ZnT-1, we hypothesize that HPV infections and cancer caused by mutations in TMC8 are related to upregulated Zn2 +/Ca2 + signaling and activation of Ano1. 相似文献
3.
《Biochimica et Biophysica Acta - Proteins and Proteomics》2018,1866(2):205-213
We have analyzed the crystal structure of the dimeric form of d-glycero-d-manno-heptose-1,7-bisphosphate phosphatase from Burkholderia thailandensis (BtGmhB), catalyzing the removal of the phosphate at the 7 position of d-glycero-d-manno-heptose-1,7-bisphosphate. The crystal structure of BtGmhB revealed a dimeric form caused by a disruption of a short zinc-binding loop. The dimeric BtGmhB structure was induced by triggering the loss of Zn2 + via the protonation of cysteine residues at pH 4.8 of the crystallization condition. Similarly, the addition of EDTA also causes the dimerization of BtGmhB. It appears there are two dimeric forms in solution with and without the disulfide bridge mediated by Cys95. The disulfide-free dimer produced by the loss of Zn2 + in the short zinc-binding loop is further converted to a stable disulfide-bonded dimer in vitro. Though the two dimeric forms are reversible, both of them are inactive due to a deformation of the active site. Single and triple mutant experiments confirmed the presence of two dimeric forms in vitro. Phosphatase assay results showed that only a zinc-bound monomeric form contains catalytic activity in contrast to the inactive zinc-free dimeric forms. The monomer-to-dimer transition caused by the loss of Zn2 + observed in this study is an example of reversal phenomenon caused by artificial proteins containing protein engineered zinc-finger motifs where the monomer-to-dimer transitions occurred in the presence of Zn2 +. Therefore, this unusual dimerization process may be applicable to designing proteins possessing a short zinc-binding loop with a novel regulatory role. 相似文献
4.
《Bioorganic & medicinal chemistry》2014,22(6):1804-1808
The role of heart-type fatty acid-binding protein (FABP3) in human physiology as an intracellular carrier of fatty acids (FAs) has been well-documented. In this study, we aimed to develop an analytical method to study real-time interaction kinetics between FABP3 immobilized on the sensor surface and unsaturated C18 FAs using surface plasmon resonance (SPR). To establish the conditions for SPR experiments, we used an FABP3-selective inhibitor 4-(2-(1-(4-bromophenyl)-5-phenyl-1H-pyrazol-3-yl)-phenoxy)-butyric acid. The affinity index thus obtained was comparable to that reported previously, further supporting the usefulness of the SPR-based approach for evaluating interactions between FABPs and hydrophobic ligands. A pseudo-first-order affinity of FABP3 to K+ petroselinate (C18:1 Δ6 cis), K+ elaidate (C18:1 Δ9 trans), and K+ oleate (C18:1 Δ9 cis) was characterized by the dissociation constant (Kd) near micromolar ranges, whereas K+ linoleate (C18:2 Δ9,12 cis/cis) and K+ α-linolenate (C18:3 Δ9,12,15 cis/cis/cis) showed a higher affinity to FABP3 with Kd around 1 × 10−6 M. Interactions between FAPB3 and C18 FAs incorporated in large unilamellar vesicles consisting of 1,2-dimyristoyl-sn-glycero-3-phosphocholine and FAs (5:1 molar ratio) were also analysed. Control DMPC liposomes without FA showed only marginal binding to FABP3 immobilized on a sensor chip while liposome-incorporated FA revealed significant responses in sensorgrams, demonstrating that the affinity of FAs to FABP3 could be evaluated by using the liposome-incorporated analytes. Significant affinity to FABP3 was observed for monounsaturated fatty acids (Kd in the range of 1 × 10−7 M). These experiments demonstrated that highly hydrophobic compounds in a liposome-incorporated form could be subjected to SPR experiments for kinetic analysis. 相似文献
5.
《Biochimica et Biophysica Acta - Proteins and Proteomics》2007,1774(12):1500-1507
Salts inhibit the activity of sweet almond β-glucosidase. For cations (Cl− salts) the effectiveness follows the series: Cu+2, Fe+2 > Zn+2 > Li+ > Ca+2 > Mg+2 > Cs+ > NH4+ > Rb+ > K+ > Na+ and for anions (Na+ salts) the series is: I− > ClO4− > −SCN > Br− ≈ NO3− > Cl− ≈ −OAc > F− ≈ SO4− 2. The activity of the enzyme, like that of most glycohydrolases, depends on a deprotonated carboxylate (nucleophile) and a protonated carboxylic acid for optimal activity. The resulting pH-profile of kcat/Km for the β-glucosidase-catalyzed hydrolysis of p-nitrophenyl glucoside is characterized by a width at half height that is strongly sensitive to the nature and concentration of the salt. Most of the inhibition is due to a shift in the enzymic pKas and not to an effect on the pH-independent second-order rate constant, (kcat/Km)lim. For example, as the NaCl concentration is increased from 0.01 M to 1.0 M the apparent pKa1 increases (from 3.7 to 4.9) and the apparent pKa2 decreases (from 7.2 to 5.9). With p-nitrophenyl glucoside, the value of the pH-independent (kcat/Km)lim (= 9 × 104 M− 1 s− 1) is reduced by less than 4% as the NaCl concentration is increased. There is a similar shift in the pKas when the LiCl concentration is increased to 1.0 M. The results of these salt-induced pKa shifts rule out a significant contribution of reverse protonation to the catalytic efficiency of the enzyme. At low salt concentration, the fraction of the catalytically active monoprotonated enzyme in the reverse protonated form (i.e., proton on the group with a pKa of 3.7 and dissociated from the group with a pKa of 7.2) is very small (≈ 0.03%). At higher salt concentrations, where the two pKas become closer, the fraction of the monoprotonated enzyme in the reverse protonated form increases over 300-fold. However, there is no increase in the intrinsic reactivity, (kcat/Km)lim, of the monoprotonated species. For other enzymes which may show such salt-induced pKa shifts, this provides a convenient test for the role of reverse protonation. 相似文献
6.
《Journal of Asia》2014,17(1):67-71
While screening for cellulase-producing fungi from insect gut, a fungus with high endoglucanase (carboxymethyl cellulase; CMCase) activity was isolated from the larval gut of Bombyx mori. Based on morphological characteristics and using an 18S rRNA-based molecular phylogenetic approach, the fungus, strain BMC-2, was identified as a Mucor sp. expressing a novel alkalotolerant cellulase. The maximum production of cellulase by the BMC-2 strain was observed at 55 °C and pH 8.0. The CMCase activity was inhibited by Cu2 + > Na+ > Zn2 + > Mg2 + > Ba2 +, and induced by Ca2 +, Mn2 +, Fe2 +, and K+. 相似文献
7.
N,N'-dimethyl-4,4'-azopyridinium methyl sulfate (MAZP) was characterized as an electron transfer mediator for oxidation reactions catalyzed by NAD+- and pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases. The bimolecular rate constant of NADH reactivity with MAZP was defined as (2.2 ± 0.1) × 105 M−1 s−1, whereas the bimolecular rate constant of reactivity of the reduced form of PQQ-dependent alcohol dehydrogenase with MAZP was determined to be (4.7 ± 0.1) × 104 M−1 s−1. The use of MAZP for the regeneration of the cofactors was investigated by applying the electrochemical oxidation of the mediator. The total turnover numbers of mediator MAZP and cofactor NADH for ethanol oxidation catalyzed by NAD+-dependent alcohol dehydrogenase depended on the concentration of the substrate and the duration of the electrolysis, and the yield of the reaction was limited by the enzyme inactivation and the electrochemical process. The PQQ-dependent alcohol dehydrogenase was more stable, and the turnover number of the enzyme reached a value of 2.3 × 103. In addition, oxidation of 1,2-propanediol catalyzed by the PQQ-dependent alcohol dehydrogenase proceeded enantioselectively to yield l-lactic acid. 相似文献
8.
Jia Zhou Yong-Ming Lu Li-Qun Deng Zhong-Zhen Zhou Wen-Hua Chen 《Bioorganic & medicinal chemistry letters》2013,23(11):3145-3148
Three bis(choloyl) conjugates bearing a rigid p-phenylenediamine/p-bis(aminomethyl)benzene linker and amino/acetamido groups were synthesized, and fully characterized on the basis of 1H NMR, ESI-MS and HRMS. Their ionophoric activities were investigated by means of pH discharge assay. The results indicate that these conjugates exhibit potent ionophoric activities across egg-yolk l-α-phosphatidylcholine (EYPC)-based liposomal membranes, via a cation/proton antiport mechanism. They show moderate ion selectivity among alkali metal ions. Of the three conjugates, the ones having amino groups transport alkali metal ions in the order of Na+ > Li+ > K+ ≈ Rb+ ≈ Cs+, whereas the one having acetamido groups functions in the order of Li+ > Na+ > K+ ≈ Rb+ ≈ Cs+. 相似文献
9.
《生物化学与生物物理学报:生物膜》2015,1848(6):1376-1382
Magnesium (Mg2 +) plays a critical role in many physiological processes. Mg2 + transport systems in Salmonella have been well documented, but those in Escherichia coli have not been fully elucidated. We examined the effects of corA, mgtA, yhiD and corC gene deletion on Mg2 + transport in E. coli. We obtained every combination of double, triple and quadruple mutants. The corA and mgtA double mutant required addition of 10 mM Mg2 + to Luria-Bertani (LB) medium for growth, and the corA, mgtA and yhiD triple mutant TM2 required a higher Mg2 + concentration. The Mg2 + requirement of the quadruple mutant was similar to that of TM2. The results demonstrated that either CorA or MgtA is necessary for normal E. coli growth in LB medium and that YhiD plays a role in Mg2 + transport under high Mg2 + growth conditions in E. coli. The Arabidopsis Mg2 + transporters, AtMRS2-10 and AtMRS2-11, were heterologously expressed in TM2 cells. TM2 cells expressing AtMRS2-10 and AtMRS2-11 could grow in LB medium that had been supplemented with 1 mM Mg2 + and without Mg2 + supplementation, respectively, and cell growth was inhibited by 2 mM AlCl3. The results indicated that the growth of TM2 expressing AtMRS2-10 and AtMRS2-11 reflected these AtMRS2 function for Mg2 + and aluminum. The E. coli TM2 cells are useful for functional analysis of Arabidopsis MRS2 proteins. 相似文献
10.
Cytochrome c oxidase (CcO) catalyzes the reduction of molecular oxygen to water using ferrocytochrome c (cyt c2 +) as the electron donor. In this study, the oxidation of horse cyt c2 + by CcO from Rhodobacter sphaeroides, was monitored using stopped-flow spectrophotometry. A novel analytic procedure was applied in which the spectra were deconvoluted into the reduced and oxidized forms of cyt c by a least-squares fitting method, yielding the reaction rates at various concentrations of cyt c2 + and cyt c3 +. This allowed an analysis of the effects of cyt c3 + on the steady-state kinetics between CcO and cyt c2 +. The results show that cyt c3 + exhibits product inhibition by two mechanisms: competition with cyt c2 + at the catalytic site and, in addition, an interaction at a second site which further modulates the reaction of cyt c2 + at the catalytic site. These results are generally consistent with previous reports, indicating the reliability of the new procedure. We also find that a 6 × His-tag at the C-terminus of the subunit II of CcO affects the binding of cyt c at both sites. The approach presented here should be generally useful in spectrophotometric studies of complex enzyme kinetics. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). 相似文献
11.
Hai-Yan Li Dong-Wei Li Cai-Mei He Zuo-Ping Zhou Tao Mei Hong-Mei Xu 《Fungal Ecology》2012,5(3):309-315
The diversity and metal tolerance of endophytic fungi from six dominant plant species in a Pb–Zn mine wasteland in Yunnan, China were investigated. Four hundred and ninety-five endophytic fungi were isolated from 690 tissue segments. The endophytic fungal colonization extent and isolation extent ranged from 59 % to 75 %, and 0.42–0.93, respectively, and a positive correlation was detected between them. Stems harboured more endophytic fungi than leaves in each plant species, and the average colonization extent of stems was 82 %, being significantly higher than that of leaves (47 %) (P ≤ 0.001, chi-square test). The fungi were identified to 20 taxa in which Phoma, Alternaria and Peyronellaea were the dominant genera and the relative frequencies of them were 39.6 %, 19.0 % and 20.4 %, respectively. Metal tolerance test showed that 3.6 mM Pb2+ or 11.5 mM Zn2+ exhibited the greatest toxicity to some isolates and they did not grow on the metal-amended media. In contrast, some isolates were growth stimulated in the presence of tested metals. The isolates of Phoma were more sensitive to Zn2+ than the isolates of Alternaria and Peyronellaea. However, the sensitivity of isolates to Pb2+ was not significantly different among Phoma, Alternaria, Peyronellaea and other taxa (P > 0.05, chi-square test). Our results suggested that fungal endophyte colonization in Pb–Zn polluted plants is moderately abundant and some isolates have a marked adaptation to Pb2+ and Zn2+ metals, which has a potential application in phytoremediation in this area. 相似文献
12.
M.R. Islam M. Ishida S. Ando T. Nishida N. Yoshida 《Animal Feed Science and Technology》2011,163(2-4):222-230
The study investigated the suitability of stage of maturity and botanical fractions of whole crop rice (WCR) to predict yield and nutritive value of ensiled WCR for dairy cows. Eight varieties of WCR (i.e., Akichikara, Fukuhibiki, Habataki, Hamasari, Hokuriku 168, Kusanami, Tamakei 96, Yumetoiro) were harvested at four stages of maturity (i.e., 10, 22, 34, 45 days after flowering [DAF]) and ensiled. Dry matter (DM) yield at each harvest was determined. Silage samples were fractionated into four botanical fractions being: leaf blade, leaf sheath, stem and head. Silage samples were also analyzed for chemical composition, fermentation characteristics, in situ DM and N disappearance. Metabolizable energy (ME) and metabolizable protein (MP) content of samples were estimated according to Terada et al. (1988) and AFRC (1993), respectively. Relationships between maturity or proportions of botanical fractions and contents of WCR silage in terms of DM, ME and MP, and their yields, were estimated by correlation and regression analysis. Stage of maturity was positively related (P<0.001) to ME content (R2 = 0.46; y = 4.53 + 0.08X) and MP content (R2 = 0.56; y = 22.26 + 0.76X), and DM yield (R2 = 0.63; y = 9.21 + 0.12X), ME yield (R2 = 0.68, y = 36931 + 1708X) and MP yield (R2 = 0.72, y = 161.0 + 14.15X) of WCR. Proportion of leaf was negatively related to yields and nutritive value of ensiled WCR, whilst proportion of head was positively related (P<0.05 to <0.001). Proportion of head was best related to the ME content (R2 = 0.72; y = 3.26 + 0.009X), MP content (R2 = 0.72; y = 12.31 + 0.079X), and DM yield (R2 = 0.41; y = 9.02 + 0.009X), ME yield (R2 = 0.76, y = 19494 + 165.5X), and MP yield (R2 = 0.75, y = 34.37 + 1.32X) of WCR. Results suggest that to optimize yield and nutritive value, WCR should be ensiled within 40 DAF and the proportion of head should be equal to or more than 500 g per kg DM of WCR silage. Stage of maturity and proportion of head of WCR predict yields of DM, ME and MP of WCR, and their contents, in WCR silage with acceptable accuracy. However, these relationships need to be validated using large data sets and in vivo studies. 相似文献
13.
Xia Li Tongcheng Xu Hongbo Lu Xiaohang Ma Lei Kai Kangping Guo Yuhua Zhao 《Protein expression and purification》2010,69(1):16-20
Purification of a cis-epoxysuccinic acid hydrolase was achieved by ammonium sulfate precipitation, ionic exchange chromatography, hydrophobic interaction chromatography followed by size-exclusion chromatography. The enzyme was purified 177-fold with a yield of 14.4%. The apparent molecular mass of the enzyme was determined to be 33 kDa under denaturing conditions. The optimum pH for enzyme activity was 7.0, and the enzyme exhibited maximum activity at about 45 °C in 50 mM sodium phosphate buffer (pH 7.5). EDTA and o-phenanthrolin inhibited the enzyme activity remarkably, suggesting that the enzyme needs some metal cation to maintain its activity. Results of inductively coupled plasma mass spectrometry analysis indicated that the cis-epoxysuccinic acid hydrolase needs Zn2+ as a cofactor. Eight amino acids sequenced from the N-terminal region of the cis-epoxysuccinic acid hydrolase showed the same sequence as the N-terminal region of the beta subunit of the cis-epoxysuccinic acid hydrolase obtained from Alcaligenes sp. 相似文献
14.
A highly chitinolytic strain Penicillium ochrochloron MTCC 517 was procured from MTCC, Chandigarh, India. Culture medium supplemented with 1% chitin was found to be suitable for maximum production of chitinase. Purification of extracellular chitinase was done from the culture medium by organic solvent precipitation and DEAE-cellulose column chromatography. The chitinase was purified 6.92-fold with 29.9% yield. Molecular mass of purified chitinase was found to be 64 kDa by SDS-PAGE. The chitinase showed optimum temperature 40 °C and pH 7.0. The enzyme activity was completely inhibited by Hg2+, Zn2+, K+ and NH4+. The enzyme kinetic study of purified chitinase revealed the following characteristics, such as apparent Km 1.3 mg ml?1, Vmax 5.523 × 10?5 moles l?1 min?1 and Kcat 2.37 s?1 and catalytic efficiency 1.82 s?1 M?1. The enzyme hydrolyzed colloidal chitin, glycol chitin, chitosan, glycol chitosan, N,N′-diacetylchitobiose, p-nitrophenyl N-acetyl-β-d-glucosaminide and 4-methylumbelliferyl N-acetyl-β-d-glucosaminide. The chitinase of P. ochrochloron MTCC 517 is an exoenzyme, which gives N-acetylglucosamine as the main hydrolyzate after hydrolysis of colloidal chitin. Protoplasts with high regeneration capacity were obtained from Aspergillus niger using chitinase from P. ochrochloron MTCC 517. Since it also showed antifungal activity, P. ochrochloron MTCC 517 seems to be a promising biocontrol agent. 相似文献
15.
Melissa A. Liriano Kristen M. Varney Nathan T. Wright Cassandra L. Hoffman Eric A. Toth Rieko Ishima David J. Weber 《Journal of molecular biology》2012,423(3):365-385
Mutations in the second EF-hand (D61N, D63N, D65N, and E72A) of S100B were used to study its Ca2 + binding and dynamic properties in the absence and presence of a bound target, TRTK-12. With D63NS100B as an exception (D63NKD = 50 ± 9 μM), Ca2 + binding to EF2-hand mutants were reduced by more than 8-fold in the absence of TRTK-12 (D61NKD = 412 ± 67 μM, D65NKD = 968 ± 171 μM, and E72AKD = 471 ± 133 μM), when compared to wild-type protein (WTKD = 56 ± 9 μM). For the TRTK-12 complexes, the Ca2 +-binding affinity to wild type (WT + TRTKKD = 12 ± 10 μM) and the EF2 mutants was increased by 5- to 14-fold versus in the absence of target (D61N + TRTKKD = 29 ± 1.2 μM, D63N + TRTKKD = 10 ± 2.2 μM, D65N + TRTKKD = 73 ± 4.4 μM, and E72A + TRTKKD = 18 ± 3.7 μM). In addition, Rex, as measured using relaxation dispersion for side‐chain 15N resonances of Asn63 (D63NS100B), was reduced upon TRTK-12 binding when measured by NMR. Likewise, backbone motions on multiple timescales (picoseconds to milliseconds) throughout wild type, D61NS100B, D63NS100B, and D65NS100B were lowered upon binding TRTK-12. However, the X-ray structures of Ca2 +-bound (2.0 Å) and TRTK-bound (1.2 Å) D63NS100B showed no change in Ca2 + coordination; thus, these and analogous structural data for the wild-type protein could not be used to explain how target binding increased Ca2 +-binding affinity in solution. Therefore, a model for how S100B–TRTK‐12 complex formation increases Ca2 + binding is discussed, which considers changes in protein dynamics upon binding the target TRTK-12. 相似文献
16.
The performance of a mixed-culture on the removal of caffeine (CFN), sulfamethoxazole (SMX), ranitidine (RNT), carbamazepine (CZP) and ibuprofen (IBP) in a suspended growth reactor has been studied. The sorption and biodegradation of these compounds were examined when they were individually or simultaneously tested. The sorption of individual compounds was significantly low except from RNT (Kd = 0.42 L/g). In contrast, the sorption of SMX and CFN increased in detriment of RNT when all the pharmaceutical compounds were simultaneously present. The biodegradation removal also exhibited significant differences. Thus, the simultaneous treatment showed higher biodegradation rates (Kb up to 97.55 × 10−6 L/mg h) than the individual treatment (Kb up to 8.13 × 10−6 L/mg h) of the pharmaceuticals. In general, the simultaneous treatment leads to increased sorption distribution coefficients and biodegradation rates. Results seem to reveal that the enhanced biomass efficiency on the simultaneous elimination process was due to the synergistic effects of pharmaceutical compounds onto mixed-culture. During the simultaneous removal, CFN, SMX and CZP were removed consistently (5.3 ± 4.4%, 73.2 ± 21.3% and 4.2 ± 2.3%, respectively), whereas RNT and IBP showed an unsteady removal over time. Finally, a kinetic model capable of describing the influence of biomass growth and nutrients utilization on the sorption and biodegradation of the pollutants was successfully demonstrated. 相似文献
17.
《Aquatic Botany》2005,81(4):326-342
The effects of NH4+ or NO3− on growth, resource allocation and nitrogen (N) uptake kinetics of two common helophytes Phragmites australis (Cav.) Trin. ex Steudel and Glyceria maxima (Hartm.) Holmb. were studied in semi steady-state hydroponic cultures. At a steady-state nitrogen availability of 34 μM the growth rate of Phragmites was not affected by the N form (mean RGR = 35.4 mg g−1 d−1), whereas the growth rate of Glyceria was 16% higher in NH4+-N cultures than in NO3−-N cultures (mean = 66.7 and 57.4 mg g−1 d−1 of NH4+ and NO3− treated plants, respectively). Phragmites and Glyceria had higher S/R ratio in NH4+ cultures than in NO3− cultures, 123.5 and 129.7%, respectively.Species differed in the nitrogen utilisation. In Glyceria, the relative tissue N content was higher than in Phragmites and was increased in NH4+ treated plants by 16%. The tissue NH4+ concentration (mean = 1.6 μmol g fresh wt−1) was not affected by N treatment, whereas NO3− contents were higher in NO3− (mean = 1.5 μmol g fresh wt−1) than in NH4+ (mean = 0.4 μmol g fresh wt−1) treated plants. In Phragmites, NH4+ (mean = 1.6 μmol g fresh wt−1) and NO3− (mean = 0.2 μmol g fresh wt−1) contents were not affected by the N regime. Species did not differ in NH4+ (mean = 56.5 μmol g−1 root dry wt h−1) and NO3− (mean = 34.5 μmol g−1 root dry wt h−1) maximum uptake rates (Vmax), and Vmax for NH4+ uptake was not affected by N treatment. The uptake rate of NO3− was low in NH4+ treated plants, and an induction phase for NO3− was observed in NH4+ treated Phragmites but not in Glyceria. Phragmites had low Km (mean = 4.5 μM) and high affinity (10.3 l g−1 root dry wt h−1) for both ions compared to Glyceria (Km = 6.3 μM, affinity = 8.0 l g−1 root dry wt h−1). The results showed different plasticity of Phragmites and Glyceria toward N source. The positive response to NH4+-N source may participates in the observed success of Glyceria at NH4+ rich sites, although other factors have to be considered. Higher plasticity of Phragmites toward low nutrient availability may favour this species at oligotrophic sites. 相似文献
18.
The coastal shrub Limoniastrum monopetalum is capable of growth in soil containing extremely high concentrations of heavy metals. A greenhouse experiment was conducted in order to investigate the effects of a range of Zn concentrations (0–130 mmol l−1) on growth and photosynthetic performance, by measuring relative growth rate, total leaf area, plant height, gas exchange, chlorophyll fluorescence parameters and photosynthetic pigment concentrations. We also determined the total zinc, nitrogen, phosphorus, sulphur, calcium, magnesium, sodium, potassium, iron and copper concentrations in the plant tissues. The study species demonstrated hypertolerance to Zn stress, since survival was recorded with leaf concentrations of up to 1700 mg Zn kg−1 dry mass when treated with 130 mmol Zn l−1. L. monopetalum exhibited little overall effects on photosynthetic function at Zn levels of up to 90 mmol l−1. At greater external Zn concentration, plant growth was negatively affected, due in all probability to the recorded decline in net photosynthetic rate, which may be linked to the adverse effect of the metal on photosynthetic electron transport. Growth parameters were virtually unaffected by leaf tissue concentrations as high as 1400 mg Zn kg−1 dry mass thus indicating that this species could play an important role in the phytoremediation of Zn-polluted areas. 相似文献
19.
Kenneth R. Meehan Laleh Talebian Jillian Wu John M. Hill Zbigniew M. Szczepiorkowski Charles L. Sentman Marc S. Ernstoff 《Cytotherapy》2010,12(8):1013-1021
Background aimsA phase I trial examined the ability of immunotherapy to mobilize progenitor and activated T cells.MethodsInterleukin (IL)-2 was administered subcutaneously for 11 days, with granulocyte (G)-colony-stimulating factor (CSF) (5 mcg/kg/day) and granulocyte–macrophage (GM)-CSF (7.5 mcg/kg/day) added for the last 5 days. Leukapheresis was initiated on day 11. Thirteen patients were treated (myeloma n = 11, non-Hodgkin's lymphoma n = 2).ResultsToxicities were minimal. IL-2 was stopped in two patients because of capillary leak (n = 1) and diarrhea (n = 1). Each patient required 2.5 leukaphereses (median; range 1–3) to collect 3.2 × 106 CD34+ cells/kg (median; range 1.9–6.6 × 106/kg). Immune mobilization increased the number of CD3+ CD8+ T cells (P = 0.002), CD56+ natural killer (NK) cells (P = 0.0001), CD8+ CD56+ T cells (P = 0.002) and CD4+ CD25+ cells (P = 0.0001) compared with cancer patients mobilized with G-CSF alone. There was increased lysis of myeloma cells after 7 days (P = 0.03) or 11 days (P = 0.02). The maximum tolerated dose of IL-2 was 1 × 106 IU/m2/day.ConclusionsImmune mobilization is well tolerated with normal subsequent marrow engraftment. As cells within the graft influence lymphocyte recovery, an increased number of functional lymphocytes may result in more rapid immune reconstitution. 相似文献
20.
《Peptides》2016
Intermedin/adrenomedullin-2 (IMD) is a member of the adrenomedullin/CGRP peptide family. Less is known about the distribution of IMD than for other family members within the mammalian cardiovascular system, particularly in humans. The aim was to evaluate plasma IMD levels in healthy subjects and patients with chronic heart failure. IMD and its precursor fragments, preproIMD25–56 and preproIMD57–92, were measured by radioimmunoassay in 75 healthy subjects and levels of IMD were also compared to those of adrenomedullin (AM) and mid-region proadrenomedullin45–92 (MRproAM45–92) in 19 patients with systolic heart failure (LVEF < 45%). In healthy subjects, plasma levels (mean + SE) of IMD (6.3 + 0.6 pg ml−1) were lower than, but correlated with those of AM (25.8 + 1.8 pg ml−1; r = 0.49, p < 0.001). Plasma preproIMD25–56 (39.6 + 3.1 pg ml−1), preproIMD57–92 (25.9 + 3.8 pg ml−1) and MRproAM45–92 (200.2 + 6.7 pg ml−1) were greater than their respective bioactive peptides. IMD levels correlated positively with BMI but not age, and were elevated in heart failure (9.8 + 1.3 pg ml−1, p < 0.05), similarly to MRproAM45–92 (329.5 + 41.9 pg ml−1, p < 0.001) and AM (56.8 + 10.9 pg ml−1, p < 0.01). IMD levels were greater in heart failure patients with concomitant renal impairment (11.3 + 1.8 pg ml−1) than those without (6.5 + 1.0 pg ml−1; p < 0.05). IMD and AM were greater in patients receiving submaximal compared with maximal heart failure drug therapy and were decreased after 6 months of cardiac resynchronization therapy. In conclusion, IMD is present in the plasma of healthy subjects less abundantly than AM, but is similarly correlated weakly with BMI. IMD levels are elevated in heart failure, especially with concomitant renal impairment, and tend to be reduced by high intensity drug or pacing therapy. 相似文献