首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
To investigate the effect of doxorubicin(DOX) on gene expression of the myocardial sarcoplasmic reticulum (SR) Ca2+ transport proteins and the mechanism of taurine(Tau) protecting cardiac muscle cells, 9 rabbits were injected with DOX, 8 rabbits with DOX and Tau, and 9 rabbits with normal saline. Cardiac function, concentration of calcium in cardiomycocytes (Myo [Ca2+] i ), activity of SR Ca2+-ATPase (SERCA2a), level of SERCA2a mRNA and Ca2+ released channels (RYR2) mRNA were detected. The left ventricle tissues were observed by electron microscopy. The results showed that cardiac index, left ventricular systolic pressure, activity of SR Ca2+-ATPase and level of SERCA2a mRNA decreased, while Myo[Ca2+] i increased in DOX-treated rabbits. DOX could not affect the level of RYR2 mRNA. Tau intervention could alleviate the increase of left ventricular diastolic pressure, Myo[Ca2+] i and the decrease of SERCA2a mRNA induced by doxorubicin. The results suggested that downregulation of SERCA2a gene expression was an important mechanism of DOX-induced cardiomyopathy and that Tau could partially improve the heart function by reducing calcium overload and alleviating downregulation of SERCA2a mRNA.  相似文献   

2.
The authors investigated the influence of green tea polyphenols (GTPs) on the liver mitochondria permeability transition pore (PTP) opening through mitochondria swelling and change of mitochondria membrane potential. The data showed that GTPs had obvious protective effect on the Ca2+-induced PTP opening in a dose-dependent manner detected by mitochondria swelling. The results were obtained by measuring the change of mitochondria membrane potential through Rh 123. Further experiments were conducted to examine the detailed influence of GTPs on Ca2+ import and export of mitochondria. The results showed that GTPs had remarkably inhibitory effect on the Ca2+-induced Ca2+ import in mitochondria; and that they could accelerate Ca2+-release from mitochondria. Our data provide an alternate interpretation of the potent protective function of GTPs on cell against apoptosis.  相似文献   

3.
Extracts from various vegetables and fruits were investigated for their abilities to reduce nitro-polycyclic aromatic hydrocarbons (NPAHs). The extracts from grape and onion exhibited an interesting selectivity, yielding corresponding hydroxylamines or amines as major products under mild conditions of 30 °C and pH 7.0. Grape extracts reduced the 4-nitro-1,8-naphthalic anhydride with the highest conversion rate (>99%) and the highest ratio of hydroxylamine to amine (95:5). In contrast, the onion extracts reduced 4-nitro-1,8-naphthalic anhydride with a conversion rate of 94% and a ratio of hydroxylamine to amine of 8:92. The thiol-reducing agent, β-mercaptoethanol, and metal cations, Ca2+ and Mg2+, greatly increased the reductive efficiency. This work provides an alternative strategy for biotransformation of nitro-polycyclic compounds.  相似文献   

4.
The Rhodobacter capsulatus hemA gene, which encodes 5-aminolevulinic acid synthase (ALAS), was expressed in Escherichia coli Rosetta (DE3) and the enzymatic properties of the purified recombinant ALAS (RC-ALAS) were studied. Compared with ALASs encoded by hemA genes from Agrobacterium radiobacter (AR-ALAS) and Rhodobacter sphaeroides (RS-ALAS), the specific activity of RC-ALAS reached 198.2 U/mg, which was about 31.2% and 69.5% higher than those of AR-ALAS (151.1 U/mg) and RS-ALAS (116.9 U/mg), respectively. The optimum pH values and temperatures of the three above mentioned enzymes were all pH 7.5 and 37 °C, respectively. Moreover, RC-ALAS was more sensitive to pH, while the other two were sensitive to temperature. The effects of metals, ethylene diamine tetraacetic acid (EDTA), and sodium dodecyl sulfate (SDS) on the three ALASs were also investigated. The results indicate that they had the same effects on the activities of the three ALASs. SDS and metal ions such as Co2+, Zn2+, and Cu2+ strongly inhibited the activities of the ALASs, while Mn2+ exerted slight inhibition, and K+, Ca2+, Ba2+, Mg2+, or EDTA had no significant effect. The specificity constant of succinyl coenzyme A [(k cat/K m)S-CoA] of RC-ALAS was 1.4989, which was higher than those of AR-ALAS (0.7456) and RS-ALAS (1.1699), showing its high catalytic efficiency. The fed-batch fermentation was conducted using the recombinant strain containing the R. capsulatus hemA gene, and the yield of 5-aminolevulinic acid (ALA) achieved was 8.8 g/L (67 mmol/L) under the appropriate conditions.  相似文献   

5.
INTRODUCTION Left ventricular hypertrophy has been thought to be the principal predicators of predisposing risk factor of cardiac morbidity and mortality (Devereux, 1995; Levy et al., 1990). The pathogenesis that mediates cardiac hypertrophy is poorly understood. Cardiachypertrophy can be induced by hemodynamic over-load, ischemic disease, neurohumoral factors and intrinsic defects in cardiac structural protein genes (Sadoshima and Izumo, 1997; Vikstrom and Lein-wand, 1996). Another in…  相似文献   

6.
The effects of salinity(50 mmol/L NaCl) and Cd(1 μmol/L CdCl2) as sole and combined on growth and photosyn-thetic parameters were studied using two soybean genotypes,Huachun 18 and NGB.The concentrations of Cd2 ,Zn2 ,Ca2 ,Mg2 ,K and Na were also determined in seeds and pods.Huachun 18 suffered a more serious decrease than NGB in net photosynthetic rate(Pn) in the treatments of salinity stress alone and combined stress(NaCl Cd),showing that it is relatively sensitive to salinity.The decrease in Pn caused by salt stress in Huachun 18 was mainly due to the reduced total chlorophyll content and photosynthetic efficiency(the ratio of variable fluorescence to maximal fluorescence,Fv/Fm),whereas the decease in NGB was mainly related to reduced stomatal conductance(Gs).The combined stress of both Na and Cd did not induce further decrease in photosynthesis and fluorescence in the two genotypes relative to salt or Cd stress alone.Greater change in the pod concentrations of Zn2 ,Ca2 ,Mg2 ,K and Na was detected under salt stress for Huachun 18 than for NGB.The results suggested that the interactive effect of NaCl-Cd on growth and nutrient uptake differs between the two soybean genotypes.  相似文献   

7.
T-wave alternans, a specific form of cardiac alternans, has been associated with the increased susceptibility to cardiac arrhythmias and sudden cardiac death (SCD). Plenty of evidence has related cardiac alternans at the tissue level to the instability of voltage kinetics or Ca2+ handling dynamics at the cellular level. However, to date, none of the existing experiments could identify the exact cellular mechanism of cardiac alternans due to the bi-directional coupling between voltage kinetics and Ca2+ handling dynamics. Either of these systems could be the origin of alternans and the other follows as a secondary change, therefore making the cellular mechanism of alternans a difficult chicken or egg problem. In this context, theoretical analysis combined with experimental techniques provides a possibility to explore this problem. In this review, we will summarize the experimental and theoretical advances in understanding the cellular mechanism of alternans. We focus on the roles of action potential duration (APD) restitution and Ca2+ handling dynamics in the genesis of alternans and show how the theoretical analysis combined with experimental techniques has provided us a new insight into the cellular mechanism of alternans. We also discuss the possible reasons of increased propensity for alternans in heart failure (HF) and the new possible therapeutic targets. Finally, according to the level of electrophysiological recording techniques and theoretical strategies, we list some critical experimental or theoretical challenges which may help to determine the origin of alternans and to find more effective therapeutic targets in the future.  相似文献   

8.
Systematic studies of the transport properties of La0.67Ca0.33Mn1?xFe x O3 (x=0–0.3) systems showed that with increasing Fe-doping contentx the resistance increases and the insulator-metal transition temperature moves to lower temperature. For small doping content, the transport property satisfies metal transport behavior below the transition temperature, and above the transition temperature it satisfies the small polaron model. This behavior can be explained by Fe3+ doping, which easily forms Fe3+?O2??Mn4+ channel, suppressing the double exchange Mn3+?O2??Mn4+ channel and enhancing the spin scattering of Mn ions induced by antiferromagnetic clusters of Fe ions.  相似文献   

9.
ZnNiO thin films with different contents of Ni (0–10 at.%) were fabricated on quartz and Si (100) substrates by pulsed laser deposition (PLD). We measured the samples by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectrometer (UV-VIS), and Hall testing. When the Ni contents were below 3 at.%, partial Zn2+ ions were replaced by the Ni2+ ions without forming any other phases, which enhanced the conductivity of the film. When the Ni contents were above 3 at.%, Ni ions were at the interstitial sites, and Ni-related clusters and defects were able to emerge in the films, resulting in a worsening of electrical and optical properties. A ferromagnetic hysteresis with a coercive force of approximately 30 Oe was observed in the ZnNiO film with a Ni content of 3 at.% at room temperature.  相似文献   

10.
This work investigated the microwave dielectric properties of A-site substitution by rare earth La3+in(Pb0.5Ca0.5)(Fe0.5Ta0.5)O3(PCFT) system.A single perovskite phase was obtained only when the doping content was 2%.Suitable La3+ doping improved microwave dielectric performances.Excessive La3+doping caused the formation of secondary phase,which resulted in the decreasing of permittivity εrand quality factor Qfvalues.Especially,when the doping content is 2%-5%,permittivity εrwas above 75 and Qfvalues were 6...  相似文献   

11.
β-glucanase was purified from a solid-state culture ofTrichoderma reesei on wheat bran in three steps which comprised ammonium sulfate precipitation, Sephadex G-100 chromatography, and DEAE-Sephadex A-50 chromatography. The molecular mass was determined to be 35.21 kilodaltons by sodium dodecyl sulfate-12.5% polyacrylamide gel electrophoresis. The β-glucanase at low pHs was more stable than that at high pHs, and optimum pH was 5.0. The optimum temperature was 60°C, and β-glucanase was relatively stable at below 40°C for 60 min. TheK m of the enzyme on β-glucan was 10.86 mg/ml, and theV max on β-glucan was 14286 μmol of glucose equivalents per mg of the pure enzyme per min. The β-glucanase activity was significantly inhibited by Fe3+ ions, and was reduced in the presence of Cu2+ ions, Mn2+ ions and Mg2+ ions at 5 mmol/L and 10 mmol/L, respectively. The β-glucanase activity was stimulated by Co2+ ions, Ca2+ ions, Zn2+ ions, and Fe2+ ions at 1 mmol/L and 5 mmol/L, respectively. Project supported by Foundation for University Key Teacher of the State Ministry of Education, the National Natural Science Foundation of China (No. 30000118) and Zhejiang Provincial Natural Science Foundation of China (No. 399409).  相似文献   

12.
纳米银对黄瓜和小麦的毒性效应研究   总被引:1,自引:0,他引:1  
研究目的:研究纳米银对黄瓜和小麦的毒性及在植物中的转运和分布,探讨其毒性机制,为纳米银的环境风险评估提供科学依据。创新要点:1.选取单子叶和双子叶植物为对象,比较研究纳米银对其萌发阶段和生长阶段的毒性效应及其影响因素;2.多数研究中的纳米银均有表面修饰,本研究选择无表面修饰的纳米银材料,排除表面活性剂的干扰因素;3.以络合剂半胱氨酸掩蔽解离出的银离子,探讨纳米银颗粒对植物毒性的贡献。研究方法:通过植物根长(图2)和生物量(图3)分别评价萌发和生长阶段纳米银的植物毒性。利用电感耦合等离子体质谱(ICP-MS)测定植物组织银元素的含量(图7)。通过组织切片,利用透射电镜(TEM)观察植物根中银的微观分布(图6)。通过在暴露介质中添加半胱氨酸掩蔽银离子来评价纳米银颗粒对植物毒性的贡献(图3和5)。重要结论:在较高暴露浓度情况下,纳米银和银离子对小麦和黄瓜都具有明显的毒性。但当纳米银浓度低于200 mg/L,银离子浓度低于5 mg/L时,两者均能促进黄瓜根系的生长。两种植物在营养生长阶段比萌发阶段对纳米银的毒性更敏感。纳米银暴露后,银首先积聚于植物的根,然后被转移到地上部。为评价纳米银释放的银离子的作用,我们测定了暴露后介质中银离子的浓度。在种子萌发阶段,黄瓜和小麦的暴露液中约0.03%和0.01%的纳米银溶解,而在营养生长阶段,溶解的纳米银达到0.17%和0.06%。半胱氨酸作为银离子的强络合剂,能够彻底消除纳米银对黄瓜和小麦的作用,说明纳米银的植物效应可能来自于其释放的银离子。  相似文献   

13.
The gene AtCSR encodes peptidyl-prolyl cis/trans isomerases (PPIases) that accelerate energetically unfavorable cis/trans isomerization of the peptide bond preceding proline production.In our studies,we found that AtCSR was associated with cadmium (Cd)-sensitive response in Arabidopsis.Our results show that AtCSR expression was triggered by Cd-stress in wild type Arabidopsis.The expression of some genes responsible for Cd2+ transportation into vacuoles was induced,and the expression of the iron-regulated transporter 1 (IRT1) related to Cd2+ absorption from the environment was not induced in wild type with Cd2+ treatment.The expression of Cd-transportation related genes was not in response to Cd-stress,whereas IRT expression increased dramatically in atcsr-2 with Cd2+ treatment.The expression of glutathione 1 (GSH1) was consistent with GSH being much lower in atcsr-2 in comparison with the wild type with Cd2+ treatment.Additionally,malondialdehyde (MDA),hydrogen peroxide,and Cd2+ contents,and activities of some antioxidative enzymes,differed between the wild type and atcsr-2.Hydrogen sulfide (H2S) has been confirmed as the third gas-transmitter over recent years.The findings revealed that the expression pattern of H2 S-releasing related genes and that of Cd-induced chelation and transportation genes matched well in the wild type and atcsr-2,and H2S could regulate the expression of the Cd-induced genes and alleviate Cd-triggered toxicity.Finally,one possible suggestion was given:down-regulation of atcsr-2,depending on H2S gas-transmitter not only weakened Cd2+ chelation,but also reduced Cd2+ transportation into vacuoles,as well as enhancing the Cd2+ assimilation,thus rendering atcsr-2 mutant sensitive to Cd-stress.  相似文献   

14.
猕猴桃果实采后呼吸作用的研究   总被引:1,自引:0,他引:1  
本试验以中华猕猴桃通山5号、武植3号和美味猕猴桃海沃德果实为试材,探讨了猕猴桃果实采后呼吸作用的变化。结果表明:通山5号、武植3号和海沃德果实采后都有明显的呼吸高峰,且不同品种、不同成熟度的果实呼吸强度有明显差异,呼吸高峰出现时期亦不同。采收时果实成熟度越高,呼吸强度越大,呼吸高峰亦越早。以研究结果看,猕猴桃属明显呼吸跃变果实。  相似文献   

15.
Astaxanthin (AST), a carotenoid molecule extensively found in marine organisms and increasingly used as a dietary supplement, has been reported to have beneficial effects against oxidative stress. In the current paper, the effects of AST on viability of prostate cells were investigated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay; cell apoptosis and intracellular reactive oxygen species (ROS) levels were determined by flow cytometry; the mitochondrial membrane potential (MMP) was measured by fluorospectrophotometer; and activities of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were evaluated by a detection kit. The results show that copper ion (Cu2+) induced apoptosis, along with the accumulation of intracellular ROS and MDA, in both prostate cell lines (RWPE-1 and PC-3). AST treatments could decrease the MDA levels, increase MMP, and keep ROS stable in RWPE-1 cell line. An addition of AST decreased the SOD, GSH-Px, and CAT activities in PC-3 cell line treated with Cu2+, but had a contrary reaction in RWPE-1 cell lines. In conclusion, AST could contribute to protecting RWPE-1 cells against Cu2+-induced injuries but could cause damage to the antioxidant enzyme system in PC-3 cells.  相似文献   

16.
Abstract

The aim of this study was to examine the effects of two different instructional models (i.e. direct instructional model (DIM) and tactical games model (TGM)) with primary education students. Perceived exertion, affective valence, physical activity (PA) level, instruction time, active learning time, and relation of instruction/active learning time were measured with 256 primary education students during DIM and TGM 8 weeks’ intervention programs. Significant differences were found between the DIM and TGM in perceived exertion, PA level, instruction time and in the relation between instruction/active learning time (p?<?.01, ES=?0.4 to 1.1). By age group, the DIM had significantly higher PA level in students of 3rd grade of primary education (G3), 4th grade (G4) and 6th grade (G6) (p?<?.05 or p?<?.01, ES=?0.8 to ?0.4). The instructional model used during physical education classes can affect perceived exertion, PA level, instruction time, and the relation instruction/active learning time.  相似文献   

17.
Previous work with rats showed slower active avoidance (AA) and passive avoidance (PA) learning in a light-go/noise-light no-go task (L+NL?) than in a noise-go/light-noise no-go task (N+LN?), independently of noise intensity and of presence or absence of AA pretraining. Experiment I compared these two tasks and the corresponding discriminations with a compound AA and a simple PA signal. The latter were learned at a faster rate, with only negligible differences between the two types of stimulus arrangements (NL+L? vs LN+N?). Experiment II investigated the acquisition and reversal of four go/no-go tasks with a simple AA signal, with either a simple or a compound no-go signal and asymmetrical reinforcement, i.e., with an extinction instead of a PA contingency during the presentation of no-go signals. As in previous experiments with symmetrical reinforcement, the groups with a simple no-go signal (L+N?, N+L?) acquired AA with little or no generalization to the other stimulus. In reversal, however, the L+N? group (formerly N+L?) responded to the no-go signal much more frequently than the other (N+L?, formerly L+N?). Both the L+NL? and the N+LN? groups gave a large number of responses to the extinction signal, but the differences between the two groups were at least as large as in previous work with a PA contingency. These data show that perceptual or attentional phenomena cannot explain stimulus nonequivalences in situations with a compound no-go signal. Furthermore, the similar nonequivalences found in situations with and without differential fear conditioning (AA-extinction tests vs AA-PA tests) leads to complex, highly speculative models concerning possible interactions between response and drive-modulating properties of various stimuli.  相似文献   

18.
纳米颗粒在水中的悬浮和团聚性能是决定它们在环境中迁移行为及潜在健康和环境风险影响范围的关键。表面活性剂不仅在环境中普遍存在,而且是工业制备纳米颗粒稳定悬浮液的主要分散剂。本文以单壁纳米碳管为代表,研究震荡扰动及稀释等模拟环境条件下其在阴离子表面活性剂溶液中的分散悬浮和团聚沉降性能,为评价纳米颗粒排放进入环境后的潜在风险提供依据。创新要点:现有研究认为,纳米颗粒由于能在水中稳定悬浮,其排放到环境中会产生长距离迁移并存在造成大范围污染的可能性和生态健康风险。在本文中,震荡扰动及稀释等模拟环境条件的研究表明,单壁碳纳米管在环境中长距离迁移并造成大范围污染的可能性和风险较小。研究方法:通过比较震荡扰动(模拟环境条件)和超声辅助两种分散悬浮方式及有无添加十二烷基苯磺酸钠(SDBS)阴离子表面活性剂条件下的单壁碳纳米管在水中的悬浮性能(图1),研究单壁碳纳米管能否在环境中被分散悬浮。通过研究 Na+,K+,Ca2+和 Mg2+等环境主要阳离子存在时 SDBS 稳定悬浮的单壁碳纳米管悬浮性能及与 SDBS 浓度等的相关性(图6和8),探明稳定悬浮的单壁碳纳米管能否在环境稀释过程中和环境阳离子存在下保持稳定悬浮。重要结论:在超声辅助下,单壁碳纳米管可以在 SDBS阴离子表面活性剂溶液中稳定分散悬浮,但不能在水中稳定分散悬浮。在无超声辅助、仅通过机械震荡的情况下,单壁碳纳米管无法在水中和 SDBS溶液中稳定分散悬浮。对于已经在 SDBS溶液中稳定悬浮的单壁碳纳米管,它们在 Na+,K+,Ca2+和 Mg2+等环境主要阳离子存在时也会脱稳形成团聚沉降,且该团聚沉降行为取决于悬浮溶液中 SDBS的浓度。当 SDBS稳定悬浮的单壁碳纳米管在环境中被稀释?  相似文献   

19.
Cucumber and rice plants with varying ammonium (NH4 +) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO3 )-grown plants, cucumber plants grown under NH4 +-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO2) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O2-independent alternative electron flux, and increased O2-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH4 +-grown plants had a higher O2-independent alternative electron flux than NO3 -grown plants. NO3 reduction activity was rarely detected in leaves of NH4 +-grown cucumber plants, but was high in NH4 +-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO3 assimilation, an effect more significant in NO3 -grown plants than in NH4 +-grown plants. Meanwhile, NH4 +-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO3 reduction, regardless of the N form supplied, while NH4 +-sensitive plants had a high water-water cycle activity when NH4 + was supplied as the sole N source.  相似文献   

20.
Aim: To explore teacher’s perceptions of barriers and facilitators to physical activity (PA), including enabling, reinforcing and predisposing factors amongst children and young people (CYP) with intellectual disabilities (ID). Method and procedures: The Youth Physical Activity Promotion (YPAP) Model was used to inform semi-structured focus groups to explore PA of CYP with ID. Participants were 23 (9 male) teachers and teaching assistants, from three special educational needs (SEN) schools (1?=?Primary, 2?=?Secondary) within North West England. Three focus groups were held with between six and eight participants, audio and video recorded and data transcribed. Data were inductively and deductively analysed using Nvivo and represented through pen profiles. Results: Three pen profiles were developed and structured around YPAP Model to display themes within the data. Enabling factors (facilities (n?=?23) and activity type (n?=?39)); reinforcing factors (influences of peers (n?=?23), family (n?=?10) and teachers (n?=?19) to PA engagement); and predisposing factors (healthy lifestyle (n?=?15), enjoyment of PA (n?=?14), adaptations for PA (n?=?10), structured play (n?=?10), effects of disability on PA (n?=?8) and the CYPs attitudes towards PA (n?=?8)). Conclusion: CYP with ID enjoy engaging in PA, particularly activities that are of a fun and unstructured nature which allow for progression of skills and promote independence. Participants recognised that they, as teachers, had an influence on the CYP’s PA engagement, however suggested that parents have the most influential role. Similar to previous research, participants noted that CYP with ID had a lack of understanding as regards the importance of PA engagement and its benefits to health. It is suggested a strong home–school link for CYP within SEN schools could prove to be a key facilitator for active and healthy lifestyles education and choices.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号