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1.
Endocrine-disrupting genistein was treated with the white rot fungus Phanerochaete sordida YK-624 under ligninolytic condition with low-nitrogen and high-carbon culture medium. Genistein decreased by 93% after 4 days of treatment and the activities of ligninolytic enzymes, manganese peroxidase (MnP) and laccase, were detected during treatment, thus suggesting that the disappearance of genistein is related to ligninolytic enzymes produced extracellularly by white rot fungi. Therefore, genistein was treated with MnP, laccase, and the laccase-mediator system with 1-hydroxybenzotriazole (HBT) as a mediator. HPLC analysis demonstrated that genistein disappeared almost completely in the reaction mixture after 4 h of treatment with either MnP, laccase, or the laccase-HBT system. Using the yeast two-hybrid assay system, it was also confirmed that three enzymatic treatments completely removed the estrogenic activity of genistein after 4h. These results strongly suggest that ligninolytic enzymes are effective in removing the estrogenic activity of genistein.  相似文献   

2.
The toxicity of para-menthane-3,8-diol (PMD), the main arthropod-repellent compound in the oil of the lemon eucalyptus, Corymbia citriodora, was evaluated against nymphs of Ixodes ricinus using five methods (A–E) of a contact toxicity bioassay. Mortality rates were estimated by recording numbers of dead nymphs at 30 min intervals during the first 5 h after the start of exposure and at longer intervals thereafter. The mortality rate increased with increasing concentration of PMD and duration of exposure with a distinct effect after 3.5 h. From the results obtained by methods A, C and E, the LC50 range was 0.035–0.037 mg PMD/cm2 and the LC95 range was 0.095–0.097 mg PMD/cm2 at 4 h of exposure; the LT50 range was 2.1–2.8 h and the LT95 range was 3.9–4.2 h at 0.1 mg PMD/cm2. To determine the duration of toxic activity of PMD, different concentrations (0.002, 0.01, 0.1 mg PMD/cm2) were tested and mortality was recorded at each concentration after 1 h; thereafter new ticks were tested. This test revealed that the lethal activity of PMD remained for 24 h but appeared absent after 48 h. The overall results show that PMD is toxic to nymphs of I. ricinus and may be useful for tick control.  相似文献   

3.
We determined the structure of two compounds, namely, 5,8,11,14,17-eicosapentaenoic acid (EPA) and di-n-octylphthalate (DnOP), which have algicidal activity against the toxic dinoflagellate, Cochlodinium polykrikoides. The polyunsaturated fatty acid EPA and the anthropogenic DnOP were isolated from the MeOH extract of the red alga Corallina pilulifera. We also found that a commercial EPA has algicidal activity identical to that of the EPA purified from C. pilulifera. At low inoculum (5.0 × 102 cells mL−1), the highest algicidal activity of a commercial EPA exhibited approximately 92.6% algicidal activity after 1 h and 96.8% after 6 h treatment at 6 μg mL−1, respectively. At high inoculum (1.0 × 104 cells mL−1), the strongest algicidal activity of EPA showed 69.5% after 1 h and 75.5% algicidal activity after 6 h treatment at 6 μg mL−1, respectively. However, EPA did not show algicidal activity against several microalgae used in aquaculture such as Pavlova lutheri, Tetraselmis suecica, Isochrysis galbana, and Nannochloris oculata for 6 h treatment at 6 μg mL−1. The algicidal activity of the five red tide strains to EPA (3 μg mL−1) showed about 86.6%, 86.6%, and 67.3% algicidal activity against Skeletonema costatum, Chaetoceros curvisetus, and C. polykrikoides after 1 h treatment at low inoculum (5.0 × 102 cells mL−1), respectively, but not against Prorocentrum minimum and Scrippsiella trochoidea. We concluded that EPA might be useful as a controlling agent of harmful algal blooms.  相似文献   

4.
The purpose of this study was to determine whether 7 weeks of standardized (same number and duration of repetitions, sets and rest strictly identical) electromyostimulation training of the elbow flexor muscles would induce strength gains equivalent to those of voluntary isometric training in isometric, eccentric and concentric contractions. Twenty-five males were randomly assigned to an electromyostimulated group (EMS, n = 9), a voluntary isometric group (VOL, n = 8), or a control group (CON, n = 8). Maximal voluntary isometric, eccentric and concentric strength, electromyographic (EMG) activity of the biceps and triceps brachii muscles, elbow flexor muscle activation (twitch interpolation technique) and contractile properties were assessed before and after the training period. The main findings were that the isometric torque gains of EMS were greater than those of VOL after the training period (P < 0.01) and that the eccentric and concentric torque gains were equivalent. In both groups, we observed that the mechanical twitch (Pt) was increased (P < 0.05) and that torque improvements were not mediated by neural adaptations. Considering the respective intensities of the training programs (i.e., submaximal contractions for EMS versus maximal for VOL), it can be concluded that electromyostimulation training would be more efficient than voluntary isometric training to improve both isometric and dynamic strength.  相似文献   

5.
Two extracellular chitinases were purified from Paecilomyces variotii DG-3, a chitinase producer and a nematode egg-parasitic fungus, to homogeneity by DEAE Sephadex A-50 and Sephadex G-100 chromatography. The purified enzymes were a monomer with an apparent molecular mass of 32 kDa (Chi32) and 46 kDa (Chi46), respectively, and showed chitinase activity bands with 0.01% glycol chitin as a substrate after SDS-PAGE. The first 20 and 15 N-terminal amino acid sequences of Chi32 and Chi46 were determined to be Asp-Pro-Typ-Gln-Thr-Asn-Val-Val-Tyr-Thr-Gly-Gln-Asp-Phe-Val-Ser-Pro-Asp-Leu-Phe and Asp-Ala-X-X-Tyr-Arg-Ser-Val-Ala-Tyr-Phe-Val-Asn-Trp-Ala, respectively. Optimal temperature and pH of the Chi32 and Chi46 were found to be both 60°C, and 2.5 and 3.0, respectively. Chi32 was almost inhibited by metal ions Ag+ and Hg2+ while Chi46 by Hg2+ and Pb2+ at a 10 mM concentration but both enzymes were enhanced by 1 mM concentration of Co2+. On analyzing the hydrolyzates of chitin oligomers [(GlcNAc) n , n = 2–6)], it was considered that Chi32 degraded chitin oligomers as an exo-type chitinase while Chi46 as an endo-type chitinase.  相似文献   

6.
7.
Some plant species can increase the mass flow of water from the soil to the root surface in response to the appearance of nitrate in the rhizosphere by increasing root hydraulic conductivity. Such behavior can be seen as a powerful strategy to facilitate the uptake of nitrate in the patchy and dynamically changing soil environment. Despite the significance of such behavior, little is known about the dynamics and mechanism of this phenomenon. Here we examine root hydraulic response of nitrate starved Zea mays (L.) plants after a sudden exposure to 5 mM NO3 solution. In all cases the treatment resulted in a significant increase in pressure-induced (pressure gradient ~ 0.2 MPa) flow across the root system by ~50% within 4 h. Changes in osmotic gradient across the root were approximately 0.016 MPa (or 8.5%) and thus the results could only be explained by a true change in root hydraulic conductance. Anoxia treatment significantly reduced the effect of nitrate on xylem root hydraulic conductivity indicating an important role for aquaporins in this process. Despite a 1 h delay in the hydraulic response to nitrate treatment, we did not detect any change in the expression of six ZmPIP1 and seven ZmPIP2 genes, strongly suggesting that NO3 ions regulate root hydraulics at the protein level. Treatments with sodium tungstate (nitrate reductase inhibitor) aimed at resolving the information pathway regulating root hydraulic properties resulted in unexpected findings. Although this treatment blocked nitrate reductase activity and eliminated the nitrate-induced hydraulic response, it also produced changes in gene expression and nitrate uptake levels, precluding us from suggesting that nitrate acts on root hydraulic properties via the products of nitrate reductase.  相似文献   

8.
9.
In this study, human α-1,4-N-acetylglucosaminyltransferase (α4GnT) fused with GFPuv (GFPuv-α4GnT) was expressed using both a transformed cell system and silkworm larvae. A Tn-pXgp-GFPuv-α4GnT cell line, isolated after expression vector transfection, produced 106 mU/ml of α4GnT activity in suspension culture. When Bombyx mori nucleopolyhedrovirus containing a GFPuv-α4GnT fusion gene (BmNPV-CP /GFPuv-α4GnT) bacmid was injected into silkworm larvae, α4GnT activity in larval hemolymph was 352 mU/ml, which was 3.3-fold higher than that of the Tn-pXgp-GFPuv-α4GnT cell line. With human calnexin (CNX) or human immunoglobulin heavy chain-binding protein (BiP, GRP78) coexpressed under the control of the ie-2 promoter, α4GnT activity in larval hemolymph increased by 1.4–2.0-fold. Moreover, when BmNPV-CP /GFPuv-α4GnT bacmid injection was delayed for 3 h after BmNPV-CP /CNX injection, the α4GnT activity increased significantly to 922 mU/ml, which was 8.7-fold higher than that of the Tn-pXgp-GFPuv-α4GnT cell line. Molecular chaperone assisted-expression in silkworm larvae using the BmNPV bacmid is a promising tool for recombinant protein production. This system could lead to large-scale production of more complex recombinant proteins.  相似文献   

10.
The nature of photosynthetic recovery was investigated in 10-d-old wheat (Triticum aestivum L., cv. Moskovskaya-35) seedlings exposed to temperatures of 40 and 42 °C for 20 min and to temperature 42 °C for 40 min in the dark. The aftereffect of heat treatment was monitored by growing the heat-treated plants in low/moderate/high light at 20 °C for 72 h. The net photosynthetic rates (PN) and the fluorescence ratios Fv/Fm were evaluated in intact primary leaves and the rates of cyclic and non-cyclic photophosphorylation were measured in the isolated thylakoids. At least two temporally separated steps were identified in the path of recovery from heat stress at 40 and 42 °C in the plants growing in high and moderate/high light, respectively. Both photochemical activity of the photosystem II (PSII) and the activity of CO2 assimilation system were lowered during the first step in comparison with the corresponding activities immediately after heat treatment. During the second step, the photosynthetic activities completely or partly recovered. Recovery from heat stress at 40 °C was accompanied by an appreciably higher rate of cyclic photophosphorylation in comparison with control non-heated seedlings. In pre-heated seedlings, the tolerance of the PSII to photoinhibition was higher than in non-treated ones. The mode of acclimation to different light intensities after heat exposures is analyzed.  相似文献   

11.
A chitinase was purified from the stomach of a fish, the silver croaker Pennahia argentatus, by ammonium sulfate fractionation and column chromatography using Chitopearl Basic BL-03, CM-Toyopearl 650S, and Butyl-Toyopearl 650S. The molecular mass and isoelectric point were estimated at 42 kDa and 6.7, respectively. The N-terminal amino acid sequence showed a high level of homology with family 18 chitinases. The optimum pH of silver croaker chitinase toward p-nitrophenyl N-acetylchitobioside (pNp-(GlcNAc)2) and colloidal chitin were observed to be pH 2.5 and 4.0, respectively, while chitinase activity increased about 1.5- to 3-fold with the presence of NaCl. N-Acetylchitooligosaccharide ((GlcNAc)n, n = 2–6) hydrolysis products and their anomer formation ratios were analyzed by HPLC using a TSK-GEL Amide-80 column. Since the silver croaker chitinase hydrolyzed (GlcNAc)4–6 and produced (GlcNAc)2–4, it was judged to be an endo-type chitinase. Meanwhile, an increase in β-anomers was recognized in the hydrolysis products, the same as with family 18 chitinases. This enzyme hydrolyzed (GlcNAc)5 to produce (GlcNAc)2 (79.2%) and (GlcNAc)3 (20.8%). Chitinase activity towards various substrates in the order pNp-(GlcNAc)n (n = 2–4) was pNp-(GlcNAc)2 >> pNp-(GlcNAc)4 > pNp-(GlcNAc)3. From these results, silver croaker chitinase was judged to be an enzyme that preferentially hydrolyzes the 2nd glycosidic link from the non-reducing end of (GlcNAc)n. The chitinase also showed wide substrate specificity for degrading α-chitin of shrimp and crab shell and β-chitin of squid pen. This coincides well with the feeding habit of the silver croaker, which feeds mainly on these animals.  相似文献   

12.
The activities of antioxidative enzymes and the concentration of malondialdehyde were assayed in cucumber leaves (Cucumis sativus L.) 0, 6, 12, 24, 48, 72, and 96 h after the cucumber seedlings were infested by Bemisia tabaci (Gennadius). The results indicated that the activities of antioxidative enzymes were increased after herbivore infestation, including superoxide dismutase (SOD), and peroxidase (POD), and the levels of malondialdehyde (MDA), which is a product of membrane lipid peroxidation in the leaves. The enzymes and MDA showed peaks of different activity levels at 24 and 48 h after the infestation. SOD activity reached the highest peak, 10.4% higher than control, at 24 h, POD activity reached the highest peak, 213.2% higher than control, at 6 h, catalase (CAT) activity was not statistically significant compared with the control, and MDA content reached the highest peak, 59.9% higher than control, at 48 h. The results suggested that the enhanced activities of antioxidative enzymes and MDA content may contribute to bioprotection of cucumber plants against B. tabaci infestation. Handling editor: Henryk Czosnek  相似文献   

13.
Intertribal somatic hybrids between Brassica napus (2n = 38, AACC) and a dye and medicinal plant Isatis indigotica (2n = 14, II) were obtained by fusions of mesophyll protoplasts. From a total of 237 calli, only one symmetric hybrid (S2) and five asymmetric hybrids (As1, As4, As6, As7 and As12) were established in the field. These hybrids showed some morphological variations and had very low pollen fertility. Hybrids S2 and As1 possessed 2n = 52 (AACCII), the sum of the parental chromosomes, and As12 had 2n = 66 (possibly AACCIIII). Hybrids As4, As6 and As7 were mixoploids (2n = 48–62). Genomic in situ hybridization analysis revealed that pollen mother cells at diakinesis of As1 contained 26 bivalents comprising 19 from B. napus and 7 from I. indigotica and mainly showed the segregation 26:26 at anaphase I (AI) with 7 I. indigotica chromosomes in each polar group. Four BC1 plants from As1 after pollinated by B. napus resembled mainly B. napus in morphology but also exhibited some characteristics from I. indigotica. These plants produced some seeds on selfing or pollination by B. napus. They had 2n = 45 (AACCI) and underwent pairing among the I. indigotica chromosomes and/or between the chromosomes of two parents at diakinesis. All hybrids mainly had the AFLP banding patterns from the addition of two parents plus some alterations. B. napus contributed chloroplast genomes in majority of the hybrids but some also had from I. indigotica. Production of B. napusI. indigotica additions would be of considerable importance for genome analysis and breeding.  相似文献   

14.
Little is known about the vascular actions of angiotensin II (Ang II) and nitric oxide (NO) in Amphibia. This study investigated (1) Ang II contractility, (2) NO concentrations, and (3) correlations between Ang II contractility, NO concentration and mean arterial pressure (MAP) in isolated Bufo arenarum toad aortic rings. Contractility was measured in isometric conditions, NO concentrations were determined by the Griess reaction, and MAP was determined by a direct method. In isolated toad aortic rings, Ang II produced a contractile response (292.7 ± 89.2 mg; n = 20). Furthermore, a contractile response to norepinephrine (NE) was also obtained. A significant correlation between both the Ang II and NE contractile responses was found (r = 0.89; n = 11; P < 0.01). Administration of Ang II increased MAP values (Basal 16.8 ± 1.7; n = 19 vs. Ang II 28.4 ± 1.8 mmHg; n = 19; P < 0.001), and the increase of MAP by Ang II was positively correlated with the Ang II contractile response (P < 0.01). Administration of L-NAME also increased MAP values, and this effect was higher in those toads that presented a lower pressure response to Ang II (Pearson r = −0.68; P < 0.05). NO was present in all aortic rings, and its concentrations were negatively related to the Ang II contractile response (P < 0.036) and pressure response (Pearson r = −7.08; P < 0.001). These findings suggest that, in the B. arenarum toad, the NO system contra-regulates both the contractile and pressure Ang II responses, although its action could be different in each specimen.  相似文献   

15.
Both stability and catalytic activity of two commercial immobilized lipases were investigated in the presence of different organic solvents in ultrasound-assisted system. In a general way, for Novozym 435, the use of ethanol as solvent led to a loss of activity of 35% after 10 h of contact. The use of iso-octane conducted to a gradual increase in lipase activity in relation to the contact time, reaching a maximum value of relative activity of 126%. For Lipozyme RM IM, after 5 h of exposure, the enzyme presented no residual activity when ethanol was used as solvent. The solvents tert-butanol and iso-octane showed an enhancement of about 20 and 17% in the enzyme activity in 6 h of exposure, respectively. Novozym 435 and Lipozyme IM presented high stability to storage after treatment under ultrasound-assisted system using n-hexane and tert-butanol as solvents.  相似文献   

16.
We have investigated the cytotoxicity in Saccharomyces cerevisiae of the novel antitumor agent 3-bromopyruvate (3-BP). 3-BP enters the yeast cells through the lactate/pyruvate H+ symporter Jen1p and inhibits cell growth at minimal inhibitory concentration of 1.8 mM when grown on non-glucose conditions. It is not submitted to the efflux pumps conferring Pleiotropic Drug Resistance in yeast. Yeast growth is more sensitive to 3-BP than Gleevec (Imatinib methanesulfonate) which in contrast to 3-BP is submitted to the PDR network of efflux pumps. The sensitivity of yeast to 3-BP is increased considerably by mutations or chemical treatment by buthionine sulfoximine that decrease the intracellular concentration of glutathione.  相似文献   

17.
The cyanobacterium Synechococcus elongatus (SE) has been shown to rescue ischaemic heart muscle after myocardial infarction by photosynthetic oxygen production. Here, we investigated SE toxicity and hypothesized that systemic SE exposure does not elicit a significant immune response in rats. Wistar rats intravenously received SE (n = 12), sterile saline (n = 12) or E. coli lipopolysaccharide (LPS, n = 4), and a subset (8 SE, 8 saline) received a repeat injection 4 weeks later. At baseline, 4 h, 24 h, 48 h, 8 days and 4 weeks after injection, clinical assessments, blood cultures, blood counts, lymphocyte phenotypes, liver function tests, proinflammatory cytokines and immunoglobulins were assessed. Across all metrics, SE rats responded comparably to saline controls, displaying no clinically significant immune response. As expected, LPS rats exhibited severe immunological responses. Systemic SE administration does not induce sepsis or toxicity in rats, thereby supporting the safety of cyanobacteria–mammalian symbiotic therapeutics using this organism.  相似文献   

18.
Penicillium citrinum β-keto ester reductase (KER) can catalyze the reduction of methyl 4-bromo-3-oxobutyrate (BAM) to methyl (S)-4-bromo-3-hydroxybutyrate with high optical purity. To improve the thermostability of KER, protein engineering was performed using error-prone polymerase chain reaction-based random mutagenesis. Variants with the highest levels of thermostability contained the single amino acid substitutions L54Q, K245R, and N271D. The engineered L54Q variant of KER retained 62% of its initial activity after heat treatment at 30°C for 6 h, whereas wild-type KER showed only 15% activity. The L54Q substitution also conferred improved enantioselectivity by KER. An Escherichia coli cell biocatalyst that overproduced the L54Q mutant of KER and glucose dehydrogenase as a cofactor regeneration enzyme showed the highest level of BAM reduction in a water/butyl acetate two-phase system.  相似文献   

19.
An NADPH-dependent carbonyl reductase (PsCR) gene from Pichia stipitis was cloned. It contains an open reading frame of 849 bp encoding 283 amino acids whose sequence had less than 60% identity to known reductases that produce ethyl (S)-4-chloro-3-hydroxybutanoates (S-CHBE). When expressed in Escherichia coli, the recombinant PsCR exhibited an activity of 27 U/mg using ethyl 4-chloro-3-oxobutanoate (COBE) as a substrate. Reduction of COBE to (S)-CHBE by transformants in an aqueous mono-phase system for 18 h, gave a molar yield of 94% and an optical purity of the (S)-isomer of more than 99% enantiomeric excess.  相似文献   

20.
Germination of lettuce seeds was inhibited by 6-methoxy-2-benzoxazolinone (MBOA) at concentrations greater than 0.03 mmol/L. MBOA also inhibited the induction of α-amylase activity in the lettuce seeds at concentrations greater than 0.03 mmol/L. These two concentration–response curves for the germination and α-amylase indicate that the percentage of the germination was positively correlated with the activity of α-amylase in the seeds. Lettuce seeds germinated around 18 h after incubation and inhibition of α-amylase by MBOA occurred within 6 h after seed incubation. These results show that MBOA may inhibit the germination of lettuce seeds by inhibiting the induction of α-amylase activity.  相似文献   

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