补充含铬能量糖能有效改善大学生有氧运动和无氧运动表现

本研究选择的受试者为12名大学运动训练专业男性学生(年龄:(20.3±2.26)岁; BMI:(21±1.17) kg/m2),采用双盲、安慰剂控制及平衡次序法进行不同补充处理(NBC, UBE或安慰剂,剂量皆为200μg)各1次,每次间隔1周,补充后15 min依序进行最大有氧运动表现测试,以及自行车30 s无氧温盖特测验,旨在探讨氧协同多重烟碱酸铬复合物(NBC)与含铬能量糖(UBE)补充对有氧及无氧运动表现的影响。结果表明:受试者在补充NBC和补充UBE后最大摄氧量分别增加5.1%和5.5%,衰竭时间分别延迟2.1%和3.5%,平均动力输出分别增加3.3%和3.8%,最大动力输出提升9.4%和12%,且皆显著优于安慰剂组,且补充UBE的衰竭时间也显著优于NBC,补充UBE在温盖特测验后血乳酸浓度显著高于补充NBC。本研究初步说明,补充NBC与UBE均能有效改善有氧运动和无氧运动表现。若单就运动衰竭时间而言,由于UBE内含NBC及碳水化合物等其他成分,所以补充UBE效果更佳。     

Tolerance of Ornamental Succulent Plant Crown of Thorns (Euphorbia milli) to Chromium and its Remediation

The potential of an ornamental shrub Crown of thorns (Euphorbia milli) was evaluated for remediation of soil contaminated with Cr. The plant is one of the rare succulent ornamental shrubs with a slow to moderate growth rate and is capable of blooming almost year-round. The plant could tolerate well up to 75 mg of applied Cr and beyond that there was mortality of plants. Though the plant could not be classified as a hyperaccumulator, the plant was still very efficient in translocating Cr from roots to shoots as evident from the data on uptake and translocation efficiency values. The translocation efficiency of over 80% in our study demonstrates that a large proportion of Cr has been translocated to the harvestable biomass of the plant and therefore, this plant could be effectively recommended for the remediation of soils contaminated with low to medium level of contamination i.e., up to 50 mg/kg soil.     

Potential of Mauritius Hemp (Furcraea gigantea Vent.) for the Remediation of Chromium Contaminated Soils

The present study was conducted to evaluate the ability of a high biomass producing, drought tolerant succulent plant Mauritius hemp (Furcraea gigantea Vent.) for its tolerance to different levels of Cr (0, 25, 50, 100 and 200 mg Cr kg soil^?1) and its potential for phytoremediation purposes. Based on the data on inhibition of the growth of plants with Cr, tolerance index and grade of growth inhibition, it was observed that the plant could tolerate up to 50 mg Cr kg ^?1 soil. Absorption of Cr from soil to plant and its translocation into plant tissues were discussed in terms of bio concentration factor (BCF), transfer factor (TF), and translocation efficiency (TE%). Cr was mainly accumulated in the roots and exclusion of Cr was found to be the principal physiological tolerance mechanism followed by a marked increase in proline, ascorbic acid, total free amino acids in the leaf tissue and malic acid in the rhizosphere samples to counter Cr stress. Based on the tissue concentration of Cr (< 300 μg g^?1 in the leaves and TF<1), it was concluded that, Furcraea gigantea could not be considered a hyperaccumulator and therefore unsuitable for phytoextraction of Cr. Nevertheless, Furcraea gigantea could be a suitable candidate for phytostablization of Cr contaminated soils.     

Removal of Chromium (VI) from Aqueous Solution Using Mycelial Pellets of Penicillium simplicissimum Impregnated with Powdered Biochar

The mycelia pellets of Penicillium simplicissimum impregnated with powdered biochar (MPPSIPB) were synthesized and applied to remove chromium (VI) from aqueous solution. The effects of pH, MPPSIPB dosage, initial Cr(VI) concentration, and contact time were investigated via batch experiments. Results indicated that the percentage removal of Cr(VI) was significantly dependent on the pH of the solution. Ten grams mycelial pellets and 0.2 g powdered biochar could form the most stable pellets. The maximum value of biosorption of Cr(VI) was 28.0 mg/g. Scanning electron microscopy (SEM) analysis showed that the mycelia pellets of Penicillium simplicissimum had abundant filamentous network, which entrapped powdered biochar firmly. Fourier transform infrared (FTIR) analysis suggested that O?H, N?H, C?H, C?O, and C?OH groups from MPPSIPB were involved in chromium binding and the subsequent reduction. Kinetic studies indicated that the pseudo-second-order equation fit best for Cr(VI) removal from aqueous solution. Freundlich isotherm was found to apply better for the adsorption equilibrium data with respect to the Langmuir isotherm. Furthermore, MPPSIPB can be separated from aqueous solution completely by filtration. Both experimental study and modeling results indicated that MPPSIPB exhibited remarkable affinity for chromate and had a potential application in Cr(VI) removal from water.     

Bioremediation of Cr(VI) from Chromium-Contaminated Wastewater by Free and Immobilized Cells of Cellulosimicrobium cellulans KUCr3

In this report, possible utilization of a chromium-reducing bacterial strain Cellulosimicrobium cellulans KUCr3 for effective bioremediation of hexavalent chromium (Cr(VI))-containing wastewater fed with tannery effluents has been discussed. Cr(VI) reduction and bioremediation were found to be related to the growth supportive conditions in wastewater, which is indicative of cell mass dependency for Cr(VI) reduction. Cr(VI) reduction was determined by measuring the residual Cr(VI) in the cell-free supernatant using colorimetric reagent S-diphenylcarbazide. Nutrient availability and initial cell density showed a positive relation with Cr(VI) reduction, but it was inhibited with increasing concentration of Cr(VI) under laboratory condition. The optimum temperature and pH for effective Cr(VI) reduction in wastewater were found to be 35°C and 7.5, respectively. The viable cells of KUCr3 were successfully entrapped in an agarose bead that was used in continuous column and batch culture for assaying Cr(VI) reduction. In packed bed column (continuous flow) experiment, approximately 25% Cr(VI) reduction occurred after 144 h. Cr(VI) was almost 75% and 52% reduced at concentrations of 0.5 mM and 2 mM Cr(VI), respectively, after 96 h in batch culture experiment in peptone-yeast extract-glucose medium, whereas it could decrease the Cr(VI) content up to 40% from the water containing tannery waste. This study suggests that KUCr3 could be used as a candidate for possible environmental clean up operation with respect to Cr(VI) bioremediation.     

Effects of concentrate type and chromium propionate on insulin sensitivity,productive and reproductive parameters of lactating dairy cows consuming excessive energy

This experiment compared insulin sensitivity parameters, milk production and reproductive outcomes in lactating dairy cows consuming excessive energy, and receiving in a 2×2 factorial arrangement design: (1) concentrate based on ground corn (CRN; n=13) or citrus pulp (PLP; n=13), and (2) supplemented (n=14) or not (n=12) with 2.5 g/day of chromium (Cr)-propionate. During the experiment (day 0 to 182), 26 multiparous, non-pregnant, lactating Gir×Holstein cows (initial days in milk=80±2) were offered corn silage for ad libitum consumption, and individually received concentrate formulated to allow diets to provide 160% of their daily requirements of net energy for lactation. Cow BW and body condition score (BCS) were recorded weekly. Milk production was recorded daily and milk samples collected weekly. Blood samples were collected weekly before the morning concentrate feeding. Glucose tolerance tests (GTT; 0.5 g of glucose/kg of BW) were performed on days −3, 60, 120 and 180. Follicle aspiration for in vitro embryo production was performed via transvaginal ovum pick-up on days −1, 82 and 162. No treatment differences were detected (P⩾0.25) for BW and BCS change during the experiment. Within weekly blood samples, concentrations of serum insulin and glucose, as well as insulin : glucose ratio were similar among treatments (P⩾0.19), whereas CRN had less (P<0.01) non-esterified fatty acid concentrations compared with PLP (0.177 v. 0.215 mmol/l; SEM=0.009). During the GTT, no treatment differences were detected (P⩾0.16) for serum glucose concentration, glucose clearance rate, glucose half-life and insulin : glucose ratio. Serum insulin concentrations were less (P=0.04) in CRN supplemented with Cr-propionate compared with non-supplemented CRN (8.2 v. 13.5 µIU/ml, respectively; SEM=1.7), whereas Cr-propionate supplementation did not impact (P=0.70) serum insulin within PLP cows. Milk production, milk fat and solid concentrations were similar (P⩾0.48) between treatments. However, CRN had greater (P<0.01) milk protein concentration compared with PLP (3.54% v. 3.14%, respectively; SEM=0.08). No treatment differences were detected (P⩾0.35) on number of viable oocytes collected and embryos produced within each aspiration. In summary, feeding a citrus pulp-based concentrate to lactating dairy cows consuming excessive energy did not improve insulin sensitivity, milk production and reproductive outcomes, whereas Cr-propionate supplementation only enhanced insulin sensitivity in cows receiving a corn-based concentrate during a GTT.     

Isolation and characterization of chromium(VI)-reducing Bacillus sp. FY1 and Arthrobacter sp. WZ2 and their bioremediation potential

Two native bacterial strains, FY1 and WZ2, that showed high chromium(VI)-reducing ability were respectively isolated from electroplating and tannery effluent–contaminated sites and identified as Bacillus and Arthrobacter. The objective of the present study was to evaluate their potential for future application in soil bioremediation. The results showed that both Bacillus sp. FY1 and Arthrobacter sp. WZ2 were tolerant to 1000 mg L^?1 Cr(VI) and capable of reducing 78–85% and 75–82% of Cr(VI) (100–200 mg L^?1) within 24 h, respectively. The Cr(VI) reduction rate decreased with increasing levels of Cr(VI) concentration (200–1000 mg L^?1). The optimum pH, temperature, and inoculum concentration for Cr(VI) reduction were found to be between pH 7.0 and 8.0; 30 and 35°C; and 1 × 10⁸ cells ml^?1, respectively. Further evidence for the bioremediation potential of Bacillus sp. FY1 and Arthrobacter sp. WZ2 was provided by the high capacity to reduce 100, 200, and 500 mg kg^?1 Cr(VI) in contaminated soil by 83–91%, 78–85%, and 71–78% within 7 days, respectively. These findings demonstrated the high potential of Bacillus sp. FY1 and Arthrobacter sp. WZ2 for application in future soil bioremediation.     

A low-GC Gram-positive Thermoanaerobacter-like bacterium isolated from an Indian hot spring contains Cr(VI) reduction activity both in the membrane and cytoplasm

Aim:  Characterization of an anaerobic thermophilic bacterium and subcellular localization of its Cr(VI)-reducing activity for potential bioremediation applications.
Methods and Results:  16S rRNA gene sequence-based analyses of bacterial strains isolated from sediment samples of a Bakreshwar (India) hot spring, enriched anaerobically in iron-reducing medium, found them to be 86–96% similar to reported Thermoanaerobacter strains. The most efficient iron reducer among these, BSB-33, could also reduce Cr(VI) at an optimum temperature of 60°C and pH 6·5. Filtered culture medium could reduce Cr(VI) but not Fe(III). Cell-free extracts reduced Cr(VI) inefficiently under aerobic conditions but efficiently anaerobically. Fractionation of the cell-free extracts showed that chromium reduction activity was present in both the cytoplasm and membrane.
Conclusions:  BSB-33 reduced Fe(III) and Cr(VI) anaerobically at 60°C optimally. After fractionation, the reducing activity of Cr(VI) was found in both cytoplasmic and membrane fractions.
Significance and Impact of the Study:  To the best of our knowledge, this is the first systematic study of anaerobic Cr(VI) reduction by a gram-positive thermophilic micro-organism and, in contrast to our results, none of the earlier reports has mentioned Cr(VI)-reducing activity to be present both in the cytoplasm and membrane of an organism. The strain may offer itself as a potential candidate for bioremediation.     

铬与胰岛素敏感性

铬可以提高动物机体组织对胰岛素的敏感性,但对其具体作用机制直到最近才有了较深入的认识.铬在吸收后主要由转铁蛋白运输.血液胰岛素水平升高可以促进转铁蛋白受体从细胞内的小泡中移位到细胞膜上.携带铬的转铁蛋白与细胞膜表面的转铁蛋白受体发生结合,通过内吞作用将铬转运到细胞内.在细胞内,内吞小泡中的酸性环境可使铬从转铁蛋白中释放,4个三价铬离子与apochromodulin形成有活性的holochromodulin. Holochromodulin 除了可与胰岛素和/或胰岛素受体直接结合起作用外,还可以通过激活AMPK激酶来降低细胞膜胆固醇含量,改善细胞骨架功能,促进GLUT4移位,然后又通过激活p38MAPK激酶增强GLUT4的内在活性,从而促进葡萄糖吸收.但其具体分子机制仍不完全清楚.本文就铬在提高动物机体组织对胰岛素的敏感性的作用机制问题进行综述.