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81.
Among carbon sources studied, cellobiose and mannitol provided the highest laccase (Lac) activity (648 and 742 U1-1, respectively) of Trametes versicolor 775 while glucose gave maximum manganese peroxidase (MnP) and peroxidase activities (44 and 114U1-1, respectively). Citrus fruit peel as growth substrate enhanced Lac activity 7-fold when compared to the medium with cellobiose, whereas grape vine sawdust increased MnP and peroxidase activity up to 148 and 677U1-1, respectively. 相似文献
82.
Human activities play a major role in toxic and carcinogenic metal pollution of the environment. This study was undertaken
to evaluate the effects of copper and mercury at the 400-to 1000-μM concentration range on some biochemical markers of oxidative
stress, such as lipid peroxidation (LPO), glutathione-S-transferase (GST) activity, and reduced glutathione (GSH) content
in the rainbow trout gill homogenates with or without supplementation of manganese, selenium, and bovine serum albumin (BSA).
The integrity of DNA was also measured to assess metal ion toxicity. The results showed that the LPO and specific activity
of GST were elevated. This indicated that cell-protecting antioxidant mechanisms were overtaxed and could not prevent membrane
peroxidation. Following the addition of metals, the GSH content was also significantly reduced in a concentration-dependent
manner. Mercury was found to be more effective than copper. The application of antioxidants proved beneficial in inhibiting
LPO, reducing GST activity, and elevating the GSH levels in the gill samples. Manganese was more effective than selenium and
BSA. Surprisingly, when BSA (1.0%) was added to the gill homogenates treated with a 1000-μM concentration of metal ions, instead
of alleviating malondialdehyde (MDA) generation, a drastic elevation in the MDA levels, alleviation in GST activity, and a
further decrease in glutathione (GSH) levels were observed, which were most likely the result of pro-oxidant activity of BSA.
The results also indicated that mercury and copper functioned as genotoxic pollutants, which altered the DNA integrity by
inducing the single and double-stranded DNA breaks in the gill cell nuclei. Collectively, toxicity of metal ions is related
to the depletion of GSH content and inhibition of antioxidant enzyme GST, resulting in the propagation of LPO and DNA damage. 相似文献
83.
Ninety-six crossbred growing pigs were used to evaluate the effects of fluoride levels on growth performance, nutrient digestibility,
and the retention of minerals in tissues. Four dietary treatments were formulated by supplementing fluorine (as NaF) to a
corn-soybean basal diet (39.75 mg/kg F) to provide the following added fluorine levels: 0, 50 100, and 150 mg/kg fluorine.
The results showed pigs of the 100 and 150 mg/kg fluorine-added groups had decreased average daily gain (ADG) and increased
feed gain ratio (F/G) compared to the control (p<0.05). Apparent digestibility of protein and calcium in 100 and 150 mg/kg fluorinetreated groups was significantly lower
than that of the control (p<0.05). On the other hand, iron, copper, zinc, and manganese levels in most tissues of the 100 and 150 mg/kg fluorine groups
were markedly changed compared to the control (p<0.05). However, growth performance, nutrient digestibility, and mineral concentrations in all tissues of pigs were not significantly
affected by the addition of 50 mg/kg fluorine (p>0.05). Thus, this study suggested that excess fluoride levels could decrease growth performance and change the retention
of iron, copper, zinc, and manganese in pigs. 相似文献
84.
It is shown that restoration of photoinduced electron flow with added Mn2+ (measured by photoreduction of DCPIP and photoinduced change of chlorophyll fluorescence yield) in Mn-depleted Photosystem II (PS II) membrane fragments isolated from spinach chloroplasts, is considerably increased by exogenous histidine (His). The stimulating effect of His is not observed if other electron donors (NH2OH or diphenylcarbazide) are used instead of Mn2+. His added alone does not induce electron transfer in Mn-depleted PS II preparations. Investigation of pH dependence of the stimulating effect of 2 mM His shows that the effect is observed only at pH > 5.0, it gives a 50% activation around pH 6.0 and saturates at pH 7.0–7.5. Nearly 200 μM His is required for a 50 effect at pH 7.0. It is suggested that the added His can be involved in stimulation of electron transfer on the donor side of PS II through direct interaction of Mn2+ with deprotonated form(s) of His resulting in formation of Mn–His complexes capable of efficient electron donation to PS II (though it is not excluded that His serves as a base that takes part in proton exchange coupled with redox reactions on the donor side of PS II or as an electron donor to the oxidized Mn). 相似文献
85.
This study addresses the impact of small-scale gold mining on the environment and communities of the Puyango River basin in
the southwest of Ecuador between 1999 and 2001. Our primary objectives were to measure mercury, manganese, and lead in the
river, to identify pathways of population exposure, and biological indicators of human exposure. A multi-method design at
the catchment scale was applied to the analysis of water, sediments, and particulate matter for mercury, lead, and manganese
over two different seasons. A household survey was undertaken, and individuals were assessed for lead (blood samples), and
for mercury (urine and hair samples). River water samples had high concentrations of particulate matter (700 mg/L). Mercury
and lead levels in water at the gold processing plants were very high in both seasons (250 ng Hg/L and 160 μg Pb/L). Mercury
and lead, there was a downstream gradient with the areas adjacent to the gold processing plants having the highest levels.
In Portovelo, the Upper Basin city, 14% of the population reported occupational exposure to inorganic mercury. Although no
one in Portovelo consumes water from the river, 10% of the population consume local fish. This contrasts the Lower Basin where
98% of the population consume fish, and 100% use river water for drinking and cooking. Lead blood levels over 20 μg/dl were
found in 39.4% of the study population and blood mercury over 10 μg/L only in 10.0%. Urinary mercury over 4 μg/L was found
in 66.5% of the examined persons. Hair methylmercury did not exceed the safe limit of 2 μg/g, the mean concentration was 1.2 μg/g.
Mining activity and erosion contributes to heavy-metal contamination (mercury, lead, and manganese) throughout the Puyango
Basin. The relation between environmental contamination is complex and further research is being conducted to understand these
relations. 相似文献
86.
In the present work, the oxidative degradation of gum arabic by colloidal manganese dioxide (MnO2) was carried out. Monitoring the disappearance of the MnO2 spectrophotometrically at 375 nm was used to follow the kinetics. The oxidation obeyed fractional-order kinetics with respect to the [gum arabic]. Effect of various experimental parameters such as the initial colloidal [MnO2], [HClO4], temperature, and complexing agents (P2O7(4-), F-, and Mn2+) for the oxidation of gum arabic was studied. The reaction was acid catalyzed. Addition of P2O(7)4-, F-, and Mn2+ ions enhances the rate of oxidation significantly. Gum arabic adsorbs onto the surface of the colloidal MnO2 through the equatorial -OH groups of the rhamnose moiety, and the complex breaks down into products. The Arrhenius equation was valid for the oxidation kinetics between 40 and 60 degrees C. To explain the observed kinetic results, a suitable mechanism and rate law for the reaction taking place at the surface of the colloidal particle has been proposed. The reducing nature of gum arabic is found be due to the presence of -OH group in the skeleton. 相似文献
87.
Montes S Pérez-Severiano F Vergara P Segovia J Ríos C Muriel P 《Neurochemical research》2006,31(1):11-20
Ammonium and manganese are neurotoxic agents related to brain metabolic disturbances observed after prolonged liver damage.
The aim of this study was to assess the production of nitric oxide (NO) in the brain of cirrhotic rats exposed to manganese.
We induced cirrhosis by bile duct ligation for 4 weeks in rats. From brain, striatum and globus pallidus were dissected out,
and NO synthase activity and the content of nitrites plus nitrates (NOx) were determined. In pallidum we found a diminished constitutive NO synthase activity from cirrhotic rats, independently
of manganese exposure. This result was confirmed by low levels of NOx in the same brain area (P<0.05, two-way ANOVA). This finding was not related to protein expression of NO synthase since no differences were observed
in immunoblot signals between cirrhotic and sham-operated animals. Results from present study suggest that the production
of NO is reduced in basal ganglia during cirrhosis. 相似文献
88.
89.
Shinichi Yoshida Saori Yonehara Shigemi Minami Hyo-cheol Ha Kenji Iwahara Takashi Watanabe Yoichi Honda Masaaki Kuwahara 《Mycoscience》1996,37(4):417-425
Manganese peroxidase (MnP) and lignin peroxidase (LiP) were produced by growing a white-rot fungusBjerkandera adusta statically, on a wood meal/wheat bran culture in flasks. MnP and LiP reached their maximum activity after 6 and 19 days of
inoculation, respectively. Both MnP and LiP are thought to be important enzymes in lignin biodegradation byB. adusta. Ion exchange chromatography showed thatB. adusta produced a single LiP and a single MnP enzyme in wood meal/wheat bran culture. These enzymes were separated and characterized.
The molecular weight of MnP was 46,500 with a pl of 3.9. The molecular weight of LiP was estimated to be 47,000 with a pl of 3.5. Spectral analysis demonstrated that both enzymes are heme proteins. Production of these enzymes was also achieved
using a rotarysolid culture fermenter. MnP, LiP and veratryl alcohol oxidase were produced byB. adusta in the fermenter. 相似文献
90.
Resuspension studies in cylindrical microcosms: Effects of stirring velocity on the dynamics of redox sensitive elements in a coastal sediment 总被引:4,自引:1,他引:3
Mario Hose Calado Laima Henning Matthiesen Lars Chresten Lund-Hansen Christian Christiansen 《Biogeochemistry》1998,43(3):293-309
Effects of resuspension on the release of dissolved, redox sensitive elements (Fe, Mn) was studied in cylindrical microcosms. Effects from changing water stirring velocity in sediment pools were evaluated through measurements of pore water profiles of dissolved Mn, Fe and redox potential. Mn was a good natural marker to follow such effects. At current velocities below the threshold velocity for resuspension (37 cm s-1), Mn release rates to overlying water were 100 times higher compared to steady-state values. Pulse increases in Mn concentration were the result of convective currents inside flow chambers. These results were strongly supported by measurements of Eh profiles in the sediment pore water. Furthermore, impacts from increasing stirring velocity were found down to 1.9 cm depth below the resuspended layer of sediment. 相似文献