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1.
The phenolic extract of Acalypha leaves inhibited growth of Gloeophyllum sepiarium and Pleurotus sp. (test wood-rot fungi) in potato dextrose agar, starch agar, starch glucose agar, carboxyl methyl cellulose agar and carboxyl methyl cellulose glucose agar. Fungicidal or fungistatic concentration of the extract (10–14 mg/ml) depended on the medium. However a lower concentration of the extract (8–10 mg/ml) in combination with Trichoderma viride culture filtrate caused a similar inhibitory pattern. Degradation of obeche (Triplochiton scleroxylon), mahogany (Khaya ivorensis) and walnut (Lovoa trichilioides) by the test fungi was limited or prevented by extract treatment of 8–10 mg/g wood. A similar inhibitory effect again occurred when a combination of T. viride filtrate and lower extract concentration (6–8 mg extract per gram of wood) was used. On-going wood decay was limited or halted by a combined treatment involving 8–12 mg extract per gram of wood depending on the fungal residence period. Treated stakes exposed to 6 months of tropical wet season retained resistance to fungal attack including soft rot. The phenolic extract of A. hispida may prove useful in an integrated chemical and biological approach to wood treatment.  相似文献   

2.
The population of Daphnia galeata Sars from the fish pond Velký Pálenec (Blatná, Czechoslovakia) living in high food conditions (7 mgC l–1) was characterized by a small size of the filtering comb on the thoracic limb 3, measured as seta length, length of the base of the comb and number of setae (population 1). One month cultivation of this population in low food conditions (1.5 mgC l–1) in the laboratory resulted in twofold increase in size of the filtering comb (population 2). Filtering and ingestion rates of both populations were measured at eight concentrations of food (approximately 0.025–3.2 mgC l–1) using 14C labeled Scenedesmus acutus. The results show that size of the filtering combs influences considerably feeding behavior of Daphnia. The comparison of animals with the same body length suggests that the population with a large comb feeds at concentration of food below 0.4 mgC l–1 more intensively and reaches the maximum of the filtering rate at a lower concentration than the population with a small comb. The situation is opposite at concentration above 0.4 mgC l–1. The higher values of theoretical flow in population with a small projection of filtering area suggest that this population has to compensate disadvantage of a small comb with the higher appendages beat frequency.  相似文献   

3.
Hessen  Dag O.  Færøvig  Per J. 《Plant Ecology》2001,154(1-2):261-273
Cell numbers and fluorescence of the green algae Selenastrum capricornutuum and survival of Daphnia magna exposed to simulated sun-light was assessed along a gradient of DOC (0, 1, 5 10 and 50 mg C l–1). When exposed to UV-doses and spectral distribution (295–750 nm) closely resembling surface solar radiation during mid summer, Selenastrum showed major losses of cell fluorescence. In the absence of DOC, fluorescence was severely depressed, with successively decreasing effects with increased DOC. Surviving cells also required an extensive recovery period (10–12 d) for regrowth after exposure, while an almost immediate recovery was observed at concentrations above 1 mg DOC l–1. For Daphnia, survival was reduced to less than 10% after 4 h exposure, and almost zero after 8 h exposure in the absence of humus DOC, while no effects were observed in treatments with 10 and 50 mg C l–1. Selenastrum and Daphnia that were not directly irradiated, but exposed to UV-irradiated water with the same concentrations of DOC did not reveal negative effects. This indicates negligible indirect effects mediated by long-lived free radicals or other toxic compounds. Irradiation of Daphnia under increased oxygen concentration (200% saturation) did not indicate acute effects, suggesting that effects of ambient radicals and oxidants would be of minor importance relative to intracellular photoproducts.  相似文献   

4.
A reliable reversed-phase high-performance liquid chromatographic method has been developed for the determination of a new oral thrombin inhibitor (compound I) in the blood of rats and dogs. The analyte was deproteinized with a 1.5 volume of methanol and a 0.5 volume of 10% zinc sulfate, and the supernatant was injected into a 5-μm Capcell Pak C18 column (150×4.6 mm I.D.). The mobile phase was a mixture of acetonitrile and 0.2% triethylamine of pH 2.3 (31:69, v/v) with a flow-rate of 1.0 ml/min at UV 231 nm. The retention time of compound I was approximately 9.3 min. The calibration curve was linear over the concentration range of 0.05–100 mg/l for rat blood (r2>0.9995, n=6) and dog blood (r2>0.9993, n=6). The limit of quantitation was 0.05 mg/l for both bloods using a 100-μl sample. For the 5 concentrations (0.05, 0.1, 1, 10, and 100 mg/l), the within-day recovery (n=4) and precision (n=4) were 98.1–104.1% and 1.5–6.8% for rat blood and 95.4–105.7% and 1.4–5.3% for dog blood, respectively. The between-day recovery (n=6) and precision (n=6) were 99.8–105.3% and 3.7–12.6% for rat blood and 87.5–107.1% and 2.9–15.3% for dog blood, respectively. The absolute recoveries were 82.4–93.3%. No interferences from endogenous substances were observed. In conclusion, the presented simple, sensitive, and reproducible HPLC method proved and was used successfully for the determination of compound I in the preclinical pharmacokinetics.  相似文献   

5.
Termitomyces clypeatus produced 450 IU xylanase ml–1 in a medium containing starch-free wheat bran powder as the carbon source. Carboxymethyl cellulase (CMCase) activity in the culture filtrate was removed by keeping the filtrate at pH 10 for 60 min followed by a change to pH 6. Treatment of Kraft pulp (bamboo) with the filtrate at pH 7 decreased the kappa number from 10.5 to 5 with release of reducing groups equivalent to 0.15 mg glucose g–1 pulp.  相似文献   

6.
The growth rate of Phycomyces blakesleeanus sporangiophores was found to be very sensitive to sudden changes in the oxygen concentration. A change from 20% to 15% oxygen elicits a transient decrease in the growth rate which returns to normal 10 min after altering the concentration. After a step change to 10% oxygen, the growth rate shows two minima at 6–8 and 30–35 min and it reaches about 80% of its original value 50 min after this change. A threshold curve for this negative growth response shows that sporangiophores begin to sense a decrease in the oxygen concentration from 20% to 17%. Seven phototropically abnormal mutants with defects in the genes madA to madG were tested for the oxygen response. Two strains, C149madD120 and C316madF48, were found to have recoveries different from those of the wild type after step changes from 20% to 10% oxygen.  相似文献   

7.
The effect of liquid pulse treatment of growth regulators on in vitro propagation of banana (Musa spp. AAA) was studied. Optimal shoot proliferation rates were achieved due to the pulse treatment of 6-benzylaminopurine (BA) and kinetin combination (1:1) at the concentration of 50 mg l–1 for 60 min. Similarly high frequency of root induction was obtained due to pulse treatment with a NAA and IBA combination (1:1) at the concentration of 100 mg l–1 for 60 min.  相似文献   

8.
Photoinhibition of photosynthesis and its recovery in the cyanobacteriumSpirulina platensis was studied to find how photosynthetic rates were influenced by light and temperature. By exposing cell samples from a turbidostat culture to combinations of light and temperature, a connection between light, temperature and photoinhibition was found. The experiments showed that a 10 degree increase from 20 °C to 30 °C considerably reduced the photoinhibition. At 25 °C a photon flux density of 1720 µmol m–2 s–1 reduced the photosynthetic rate by 50 % in 1 h, but a similarly high photon flux density had nearly no negative effect at 35 °C. Reactivation in low light from 50% photoinhibition was fast and complete in 60 min at 30 °C, while at 20 °C only about 1/6 of the full capacity was regained in the same time. Addition of the protein synthesis inhibitor streptomycin to cultures undergoing photoinhibition and regeneration indicated the presence also in this organism of a repair mechanism based on protein synthesis.Author for correspondence  相似文献   

9.
A reliable reversed-phase high-performance liquid chromatographic method has been developed for the determination of LB71350 in the plasma of dogs. The analyte was deproteinized with 1.5 volumes of methanol and 0.5 volumes of 10% zinc sulfate, and the supernatant was injected into a 5-μm Capcell Pak C18 column (150×4.6 mm I.D.). The mobile phase was a stepwise gradient mixture of acetonitrile and 0.2% triethylamine–HCl with a flow-rate of 1 ml/min and detection at UV 245 nm. The proportion of acetonitrile was kept at 52% for the first 6 min, increased to 100% for the next 0.5 min, kept at 100% for the next 2 min, decreased to 52% for the next 0.5 min, and finally kept at 52% for the next 7 min. The retention time of LB71350 was 6.9 min. The calibration was linear over the concentration range of 0.1–100 mg/l for dog plasma (r>0.997) and the limit of quantitation was 0.1 mg/l using 0.1 ml plasma. The quality control samples were reproducible with acceptable accuracy and precision at 0.1, 1, 10 and 100 mg/l concentrations. The within-day recovery (n=5) was 90.2–93.9%, the between-day recovery (n=5) was 89.5–93.5%, and the absolute between-day recovery (n=5) was 77–81%. The within-day precision (n=5) and between-day precision (n=5) were 2.59–5.82% and 3.17–4.55%, respectively. No interferences from endogenous substances were observed. Taken together, the above HPLC assay method by deproteinization and UV detection was suitable for the determination of LB71350 in the preclinical pharmacokinetics.  相似文献   

10.
Summary The ability of embryos at different developmental stages to form plants in vitro has been studied in cultivated Cucumis sativus L. and in the wild species C. zeyheri 2 x Sond. and C. metuliferus Naud. On MS medium containing 3.5% sucrose, 0.1 mg 1–1 kinetin (Kn) and 0.01 mg 1–1 indoleacetic acid (IAA), proembryos (0.03–0.05 mm) and early globular embryos (0.05–0.08 mm) from the wild species developed into plants in low frequencies of 8% and 21%, respectively. These embryos should be surrounded by the embryo sac tissue. On the same medium late globular (0.08–0.1 mm) and early heart-stage embryos (0.1–0.3 mm) developed into plants in moderately high and high frequencies of 48% and 83%, respectively. The presence of the embryo sac at these stages was still beneficial, but no longer a prerequisite. Late heart-stage embryos (0.3–0.8 mm) also showed high frequencies of plant formation, 63%, if Kn was applied at a concentration of 1 mg 1–1. From the early cotyledon stage onwards, the frequency of plant formation gradually decreased, reaching a minimum at the late cotyledon stage. Subsequently it began to increase again up to the late maturation stage. The poor plant formation shown by the intermediate-aged embryos could be improved slightly by lowering the sucrose concentration to 0.5% and by increasing the Kn concentration to 10 mg 1–1. Relative to the wild species, embryos of C. sativus showed lower percentages of plant formation. The optimum sucrose concentration was 2% for the heart-stage C. sativus embryos. In all three species the ability to form plants strongly decreased with increasing embryo age, from early to late cotyledon. This is thought to be caused by the increasing tendency of the embryos at these stages to continue in vitro the normal embryo development.  相似文献   

11.
When the thermophilic mold Thermoascus aurantiacus var. levisporus was grown in a modified Czapek Dox medium containing casein the filtrate was found to contain proteolytic activity. The maximum production of activity occurred at 50 ° C in a medium containing 8% casein. The filtrate was subjected to ammonium sulfate fractionation and chromatography on DEAE-cellulose. Two proteases were separated. No further work was done on protease II. Protease I was further purified by gel filtration on Sephadex G 100–200. It showed a 40-fold purification with a final recovery of approximately 25%. It is a neutral protease with a pH optimum at 7.0. The optimal activity of the enzyme occurred in 0.02 M phosphate buffer but was completely inhibited at a concentration of 0.1 M. The optimum temperature for casein hydrolysis was found to be 55 ° C. The enzyme was inhibited by Hg++ but was greatly stimulated by Cu++ and mercaptoethanol. Metallo and sulfhydryl agents had no significant effect on enzyme activity.  相似文献   

12.
Polysaccharides production from Poria cocos was carried out using aqueous NaOH with the assistance of ultrasonic. Experimental design was used to investigate the effect of three parameters (extraction time, extraction concentration of NaOH, and ratio of aqueous NaOH to raw material) on polysaccharides yields. The ranges of the factors investigated were 1–3 min for extraction time (X1), 0.5–1.0 mol/L for extraction concentration of NaOH (X2), and 30–50 for ratio of aqueous NaOH to raw material (X3). The statistical analysis of the experiment indicated that extraction concentration of NaOH had significant effect on P. cocos polysaccharides yields. The central composite design showed that polynomial regression models were in good agreement with the experimental results with the coefficients of determination of 0.9935 for P. cocos polysaccharides yield. The optimal condition for P. cocos polysaccharides yield within the experimental range of the variables studied was at 2.44 min, 0.789 mol/L, and 53.0. At this condition, the predicted yield of polysaccharides extracted was 82.3%.  相似文献   

13.
Summary The effect of the carnitine palmitoyltransferase 1(CPT1) inhibitor, Etomoxir, on glucose oxidation rates was determined in ischemic hearts reperfused in the presence of fatty acids. Isolated working rat hearts were perfused with 11 mM (14C)-glucose and 1.2 mM palmitate at a 15 cm H2O preload, 80 mm Hg afterload. Hearts were subjected to either 60 min aerobic perfusion, or 15 min work followed by 25 min global ischemia then 60 min of aerobic reperfusion. Steady state glucose oxidation rates in reperfused ischemic hearts were not significantly different from non-ischemic hearts. If 10–9 M Etomoxir was added immediately prior to reperfusion no significant change in glucose oxidation occurred. Addition of 10–8 M and 10–6 M Etomoxir, however, significantly increased glucose oxidation. Etomoxir also significantly improved recovery of mechanical function at a concentration of 10i–8 M or greater. As we previously reported, no significant improvement of function was seen when 10–9 M Etomoxir was added to the perfusate (Lopaschuk GD et al., Circ Res 63: 1036–1043, 1988). Long chain acylcarnitine levels were significantly reduced in the presence of both 10–9 M and 10–8 M Etomoxir. These data demonstrate that the beneficial effect of Etomoxir on reperfusion recovery of ischemic hearts is not due to a lowering of long chain acylcarnitine levels. Etomoxir may improve recovery of function by overcoming fatty acid inhibition of glucose oxidation.  相似文献   

14.
The development of management techniques to improve the poor N use efficiency by lowland rice (Oryza sativa L.) and reduce the high N losses has been an important focus of agronomic research. The potential of an Azolla cover in combination with urea was assessed under field conditions in Laguna, Philippines. Two on-station field experiments were established in the 1998–1999 dry season and eight on-farm experiments per season were carried out in the 2000–2001 wet and dry seasons. Treatment combinations consisting of N levels applied alone or combined with Azolla were evaluated with respect to floodwater chemistry, 15N recovery, crop growth, and grain yield. A full Azolla cover on the floodwater surface at the time of urea application prevented the rapid and large increase in floodwater pH and floodwater temperature. As a consequence, the partial pressure of ammonia (NH3), which is an indicator of potential NH3 volatilization, was significantly depressed. 15N recovery was higher in plots covered with Azolla where the total 15N recovery ranged between 77 and 99%, and the aboveground (grain and straw) recovery by rice ranged between 32 and 61%. The tiller count in Azolla-covered plots was significantly increased by 50% more than the uncovered plots at all urea levels. Consequently, the grain yield was likewise improved. Grain yields from the 16 on-farm trials increased by as much as 40% at lower N rates (40 and 50 kg N ha–1) and by as much as 29% at higher N rates (80 and 100 kg N ha–1). In addition, response of rice to treatments with lower N rates with an Azolla cover was comparable to that obtained with the higher N rates without a cover. Thus, using Azolla as a surface cover in combination with urea can be an alternative management practice worth considering as a means to reduce NH3 volatilization losses and improve N use efficiency.  相似文献   

15.
The physiology of spore-negative and spore-positive nodules ofMyrica gale   总被引:1,自引:1,他引:0  
The physiology of spore-negative and spore-positive root nodules was investigated inMyrica gale L. grown in water culture in a growth chamber. Spore(–) nodules were induced withFrankia cultures and spore(+) nodules with crushed nodules. Gas exchange was measured in a flow-through system.The time course of acetylene reduction following addition of acetylene was essentially the same in both spore(–) and spore(+) nodules with a stable maximum between 2 and 4 minutes followed by a steep decline to a minimum (37% of the maximum) between 9 and 30 minutes depending on the plant. The minimum was followed by a partial recovery. Nodule CO2 evolution showed a similar pattern but the minimum rate (83% of the maximum) was not nearly as low.Plants nodulated with one spore(–) and one spore(+) strain were compared at 6, 8 and 10 weeks after inoculation. At 6 weeks the spore(–) plants had 52% greater specific nitrogenase activity and 46% more biomass than the spore(+) plants. At 8 and 10 weeks, however, the differences between plants with spore(–) and spore(+) nodules became smaller.Plants nodulated with 4 spore(–) and 5 spore(+) strains were compared at 8 weeks after inoculation. Collectively the spore(–) plants exhibited a 32% greater specific nitrogenase activity, a 15% lower energy cost of nitrogenase activity (CO2/C2H4), and invested 31% less biomass in nodules than the spore(+) plants. The spore(–) plants also produced 16% more biomass indicating that spore(–) strains are generally more desirable than spore(+) strains. However, two spore(+) strains were as effective as the spore(–) strains.  相似文献   

16.
Xylanases of marine fungi of potential use for biobleaching of paper pulp   总被引:1,自引:0,他引:1  
Microbial xylanases that are thermostable, active at alkaline pH and cellulase-free are generally preferred for biobleaching of paper pulp. We screened obligate and facultative marine fungi for xylanase activity with these desirable traits. Several fungal isolates obtained from marine habitats showed alkaline xylanase activity. The crude enzyme from NIOCC isolate 3 (Aspergillus niger), with high xylanase activity, cellulase-free and unique properties containing 580 U l–1 xylanase, could bring about bleaching of sugarcane bagasse pulp by a 60 min treatment at 55°C, resulting in a decrease of ten kappa numbers and a 30% reduction in consumption of chlorine during bleaching. The culture filtrate showed peaks of xylanase activity at pH 3.5 and pH 8.5. When assayed at pH 3.5, optimum activity was detected at 50°C, with a second peak of activity at 90°C. When assayed at pH 8.5, optimum activity was seen at 80°C. The crude enzyme was thermostable at 55°C for at least 4 h and retained about 60% activity. Gel filtration of the 50–80% ammonium sulphate-precipitated fraction of the crude culture filtrate separated into two peaks of xylanase with specific activities of 393 and 2,457 U (mg protein)–1. The two peaks showing xylanase activity had molecular masses of 13 and 18 kDa. Zymogram analysis of xylanase of crude culture filtrate as well as the 50–80% ammonium sulphate-precipitated fraction showed two distinct xylanase activity bands on native PAGE. The crude culture filtrate also showed moderate activities of -xylosidase and -l-arabinofuranosidase, which could act synergistically with xylanase in attacking xylan. This is the first report showing the potential application of crude culture filtrate of a marine fungal isolate possessing thermostable, cellulase-free alkaline xylanase activity in biobleaching of paper pulp.  相似文献   

17.
The susceptibility of the tick Boophilus microplus to Beauveria bassiana was evaluated by inoculating eggs, larvae and engorged females of the tick with five fungal isolates at concentrations of 106, 107 and 108 conidia/ml. Tick eggs (0.25 g) were immersed in 1 ml of a suspension of the different conidial concentrations for 1 min. Similar exposure was performed by immersion of 2000 larvae and homogeneous groups of nine engorged females in 2 and 20 ml of conidial suspension, respectively. Treated eggs, larvae and adults were placed in an incubator at 27 ± 1 °C and relative humidity above 80% for evaluation of the fungal action. All fungal isolates applied at all conidial concentrations reduced the hatching rate of larvae from treated eggs by 1.36–65.58% and increased the mortality rate of inoculated larvae by 0.8–70.49%. In the bioassay with engorged females, oviposition period was reduced by 9.69–47.80%, egg mass weight by 4.71–53.87%, estimated reproduction by 8.3–60.62%, egg production index by 5.03–54.20%, percent larval hatching by 0.27–13.96%, and the mortality rate of treated females was increased by 96.60–100%. The reduction of the estimated reproduction obtained for the treated groups ranged from 8.37 to 64.52%. The sporulation of the pathogen on dead females ranged from 3.70 to 88.88% depending on the isolate and concentration used. Isolates AM 09, CB 7 and JAB 07 were the most effective and effectiveness increased with increasing concentrations of conidia in the suspensions.  相似文献   

18.
To investigate the influence of temperature andholding time on the pyrolyzate yields of Chlorella protothecoides, the microalgal cells weresubjected to pyrolysis at 200, 300, 400, 500 and 600 °Cfor 5, 20, 60 and 120 min, separately. High oil yields above 40% dry weight cells wereobtained both at relatively low temperature (300 °C)with relatively long holding times (20–120min) and relatively high temperatures (400–500 °C)with relatively short holding times (5–20min). The maximum oil yield of 52.0% was achieved at500 °C for 5 min. The gas yield was generallyincreased with the increasing temperature and holdingtime. It could reach 63.3–76.0% at 600 °C.High pyrolytic rates of 72–87% were obtained at allexperiments except at 200 °C for 5–20 min or300 °C for 5 min. Thermogravimetric analysisindicated that the main thermal degradation of thismicroalga occurred at 200–520 °C. The resultsimply that C. protothecoides is a good candidatefor the production of renewable fuels by pyrolysis.  相似文献   

19.
Orientin (Ot) and Vicenin (Vc), two water-soluble flavonoids isolated from the leaves of Indian holy basil Ocimum sanctum have shown significant protection against radiation lethality and chromosomal aberrations in vivo. In the present study the protective effect of Ot and Vc against radiation induced chromosome damage in cultured human peripheral lymphocytes was determined by micronucleus test. In order to select the most effective drug concentration, fresh whole blood was exposed to 4 Gy of cobalt-60 γ-radiation with or without a 30 min pre-treatment with 6.25, 12.5, 15.0, 17.5 or 20 μM of Ot/Vc. Micronucleus (MN) assay was done by cytochalasin induced cytokinesis block method. Radiation significantly increased the MN frequency (16 times normal). Pre-treatment with either Ot or Vc at all concentrations significantly (P<0.05–0.001) reduced the MN count in a concentration dependent manner, with the optimum effect at 17.5 μM. Therefore, fresh blood samples were incubated with/without 17.5 μM Ot/Vc for 30 min and then exposed to 0.5–4 Gy of γ-radiation. Radiation increased the MN frequency linearly (r2=0.99) with dose. Pre-treatment with Ot or Vc significantly (P<0.01–0.001) reduced the MN counts to 51–67% of RT alone values, giving DMFs of 2.62 (Ot) and 2.48 (Vc). Both the compounds showed significant antioxidant activity in vitro at the above concentrations, which was significantly higher than that of DMSO at equimolar concentrations. Thus, the results demonstrate that both the flavonoids give significant protection to the human lymphocytes against the clastogenic effect of radiation at low, non-toxic concentrations. The radioprotection seems to be associated with their antioxidant activity. The clinical potential of these protectors in cancer therapy needs to be investigated.  相似文献   

20.
Membrane technologies were investigated with the aim to improve stability of C-Phycocyanin extracts resulting from ultrasonic breakage of Spirulina platensis. Five membranes, ranging from microfiltration to reverse osmosis, were utilized both for clarification and concentration steps. Nanofiltration with tubular organic membranes exhibited good performances: pigment recovery was 100%, mean permeation flux was 85 l h–1 m–2 for achieving a concentration factor of 7 with 30×105 Pa pressure and 1.5 m s–1 tangential velocity (turbulent flow).  相似文献   

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