运动性疲劳的线粒体膜分子机理研究.Ⅳ.线粒体质子跨膜势能、质子漏与运动性内源活性氧生成的相互关系

目的以运动、外源性补充CoQ以及运动合并补充CoQ作为干预手段,观察线粒体能量转换速率、质子漏与活性氧产生之间的相互关系,进一步探讨运动性内源活性氧生成和代谢途径及可能机制.方法雄性SD大鼠36只,随机分为1)安静对照组(R,n=6);2)运动中对照组(Em,n=6);3)力竭对照组(Ei,n=6);4)安静补药组(QR,n=6);5)运动中补药组(Qm,n=6);6)力竭补药组(Qi,n=6).采用三级递增负荷力竭运动模型,测定心肌线粒体ROS产生速率、线粒体膜电子传递与质子泵出比值(H+/2e)以及线粒体态4呼吸速率.结果(1)Em和Qm组心肌线粒体ROS产生、H+/2e和态4呼吸分别比R和QR组显著增高,并且,Qm组三项指标显著高于Em组.(2)相关分析表明,ROS产生速率分别与H+/2e和态4呼吸速率呈正相关.结论运动所致的心肌线粒体质子跨膜势能升高引发了活性氧的生成增加,并进而增加质子漏,"活性氧循环”与Q循环和质子循环并存和共同运转可能是运动性内源活性氧生成及代谢的重要机制.     

运动性疲劳的线粒体膜分子机理研究.IV.线粒体质子跨膜势能、质子漏与运动性内源活性氧生成的相互关系

目的 :以运动、外源性补充CoQ以及运动合并补充CoQ作为干预手段 ,观察线粒体能量转换速率、质子漏与活性氧产生之间的相互关系 ,进一步探讨运动性内源活性氧生成和代谢途径及可能机制。方法 :雄性SD大鼠 36只 ,随机分为 :1)安静对照组 (R ,n =6 ) ;2 )运动中对照组 (Em ,n =6 ) ;3)力竭对照组 (Ei,n =6 ) ;4)安静补药组 (QR ,n =6 ) ;5 )运动中补药组 (Qm ,n =6 ) ;6 )力竭补药组 (Qi,n =6 )。采用三级递增负荷力竭运动模型 ,测定心肌线粒体ROS产生速率、线粒体膜电子传递与质子泵出比值 (H / 2e)以及线粒体态 4呼吸速率。结果 :(1)Em和Qm组心肌线粒体ROS产生、H / 2e和态 4呼吸分别比R和QR组显著增高 ,并且 ,Qm组三项指标显著高于Em组。 (2 )相关分析表明 ,ROS产生速率分别与H / 2e和态 4呼吸速率呈正相关。结论 :运动所致的心肌线粒体质子跨膜势能升高引发了活性氧的生成增加 ,并进而增加质子漏 ,“活性氧循环”与Q循环和质子循环并存和共同运转可能是运动性内源活性氧生成及代谢的重要机制。     

运动性疲劳的线粒体膜分子机理研究.III.线粒体质子跨膜势能与运动性内源自由基生成的关系

目的 :以外源性补充线粒体电子传递载体CoQ10 为干预手段 ,观察一次急性运动后线粒体能量转换速率与线粒体脂质过氧化水平改变的关系 ,进一步探讨运动性内源自由基生成和代谢的途径及可能机理。方法 :雄性SD大鼠 2 4只 ,随机分为 1)正常对照组 (NC ,n =6 ) ;2 )正常运动组 (NE ,n =6 ) ;3)单纯补充CoQ10 对照组 (QC ,n =6 ) ;4)补充CoQ10 运动组 (QE ,n =6 )。以递增负荷达次最大强度急性运动为运动模型 ,测定运动后即刻肝脏线粒体膜CoQ10 和CoQ9结合含量 ,线粒体膜质子泵出与电子传递比值 (H / 2e)以及线粒体MDA含量。结果 :(1)NE、QC和QE组线粒体MDA含量均较NC组显著增高 (P <0 .0 5 ) ;(2 )线粒体H / 2e呈现与MDA含量相同的显著性变化 (P <0 0 5 ) ;(3)QC和QE组线粒体膜CoQ10 结合含量均较未补充的NC和NE组显著增高 (P <0 0 5 ) ,而线粒体膜内源CoQ9含量则在运动组 (NE和QE)呈显著增高 (P <0 0 5 )。结论 :线粒体膜CoQ结合含量和 /或动员的增加明显提高电子传递和质子跨膜偶联速率。运动性内源自由基生成可能与呼吸链电子流被所建立的高跨膜质子电化学势能抑制 ,而经电子漏途径代谢的能量重新分配有关。     

运动延缓衰老的可能机理:活性氧生成对线粒体膜通透性转换的作用

目的 :以游泳训练为有氧运动模型 ,观察运动对衰老大鼠肝脏线粒体活性氧 (ROS)产生的影响及ROS对线粒体膜通透性转换 (MPT)的作用 ,以探讨运动延缓衰老的线粒体膜分子机理。方法 :1 2只SD大鼠随机分为衰老对照组 (C ,n =6)和衰老训练组 (T ,n =6) ;测定肝脏线粒体ROS生成、MDA含量和MPT。结果 :T组肝脏线粒体ROS生成和MDA含量均显著低于C组 (分别P <0 .0 5和P <0 .0 0 5 ) ;T组线粒体膜通透性转换孔 (PTP)半时开放时间较C组延长 ,即对Ca2 + 的敏感性降低 (P <0 .0 5 )。线粒体PTP半时开放时间与ROS生成和MDA含量呈负相关 (分别为r=-0 .494和r=-0 .479,均P <0 .0 0 1 )。结论 :有氧运动训练可能通过降低衰老组织线粒体ROS产生和减轻氧化损伤 ,而降低线粒体PTP开放的敏感性。     

补充辅酶Q_(10)与递增负荷训练对一次力竭运动大鼠骨骼肌线粒体呼吸链酶复合体活性的影响

目的:探讨补充外源性辅酶Q10(CoQ10)及递增负荷运动训练对一次力竭运动大鼠骨骼肌线粒体呼吸链酶复合体Ⅰ、Ⅱ和Ⅲ活性的影响。方法:36只2月龄健康雄性Wister大鼠随机分为4组(n=9):对照组(NC)、补充CoQ10组(QC)、训练组(NE)和补充CoQ10+训练组(QE)。喂养及训练时间共7周。QC组和QE组每天按2mg/100g体重剂量灌胃补充CoQ10一次。NC组和QC组不进行运动训练,NE组和QE组进行递增负荷水平跑台运动训练。7周后各组均进行一次力竭运动,运动后即刻断头处死,迅速取出股四头肌。差速离心提取骨骼肌线粒体,分光光度法测定线粒体呼吸链酶复合体(CⅠ~CⅢ)活性。结果:(1)CⅠ活性:与NC组比较,QC组和QE组均显著下降(P<0.05,P<0.01);与NE组比较,QE组显著下降(P<0.05)。(2)CⅡ活性:与NC组比较,QC组显著升高(P<0.01);与QC组比较,QE组显著下降(P<0.01);与NE组比较,QE组显著上升(P<0.05)。(3)CⅢ活性:与NC组比较,QC组和NE组均显著上升(P<0.01)。结果提示:(1)单纯补充CoQ10和递增负荷训练均可提高力竭性运动后即刻骨骼肌线粒体呼吸链功能,且单纯补充CoQ10效果更佳。(2)递增负荷运动训练与补充CoQ10在提高力竭性运动后即刻骨骼肌线粒体功能方面无协同作用。     

力竭运动后不同时相大鼠心肌线粒体转录因子A的变化

目的:探讨力竭运动后不同时相大鼠心肌线粒体转录因子A(mtTFA)表达的变化特点.方法:90只健康成年雄性SD大鼠,分为一次力竭游泳运动组(n=40)、2周反复力竭游泳运动组(n=40)及安静对照组(n=10),分别于力竭运动后0、6、12及24小时取材,应用免疫荧光技术和图像分析方法研究大鼠心肌mtTFA含量的变化.结果:在一次力竭和反复力竭运动后,大鼠心肌各部位mtTFA表达含量均显著低于对照组(P＜0.01).一次力竭运动后,大鼠心肌室间隔、右心室mtTFA含量在运动后12小时达到最低(P＜0.01),左心室mtTFA含量在运动后24小时达到最低;反复力竭运动后,室间隔、右心室mtTFA含量在运动后12小时达到最低(P＜0.01),而左心室mtTFA含量在运动后6小时达到最低.结论:一次力竭运动和反复力竭运动可导致mtTFA表达明显降低,直接影响心肌纤维线粒体的氧化能力和能量产生,可能是运动性心肌微损伤和心律失常发生的诱导因素和重要机制之一.此外,上述改变在运动后24小时出现不同程度的回升也提示急性大强度运动后心肌mtTFA的改变是可恢复性的,有别于病理性心肌损伤.     

不同磷脂补充对力竭运动小鼠心肌线粒体NO、Ca~(2+)和ATP含量的影响

目的:探讨不同磷脂补充对小鼠心肌线粒体功能的影响。方法:雄性昆明种小鼠48只,随机分为4组:安静对照组、运动对照组、大豆磷脂补充组和肝磷脂补充组。后3组每天早、晚两次灌胃,肝磷脂补充组为18mg/ml的肝磷脂悬浊液,大豆磷脂补充组为18mg/ml的大豆磷脂悬浊液,运动对照组灌胃生理盐水,共2周。饲养2周后除安静对照组外,其余各组均进行一次力竭游泳。运动后即刻分别测定小鼠心肌线粒体NO、游离Ca2+和ATP含量。结果:(1)力竭运动后运动对照组NO含量显著高于安静对照组,磷脂补充组显著低于运动对照组;3个运动组力竭运动后Ca2+和ATP含量均显著低于安静对照组,两个磷脂补充组Ca2+和ATP含量显著高于运动对照组。两磷脂补充组各指标均无明显差异。(2)两个磷脂补充组小鼠游泳力竭时间均显著长于运动对照组,且肝磷脂补充组小鼠力竭游泳时间略长于大豆磷脂补充组,但无统计学意义。结论:磷脂补充可以削弱力竭运动对线粒体的影响,使ATP生成增多,运动时间延长。两种磷脂补充效果无明显不同。     

急性运动心肌缺氧时线粒体膜损伤的实验研究

目的 研究急性耗竭运动缺氧应激后心肌线粒体膜结构和功能的变化。方法 采用递增负荷耗竭性运动为急性缺氧应激源,观察SD大鼠急性运动至力竭后心肌线粒体超微结构、线粒体膜过氧化脂质含量和线粒体内膜NADH-CoQ还原酶活性变化。结果 心肌能量需求过高性映氧应激后大鼠心肌线粒体超微结构呈损伤性改变,线粒体膜过氧化脂质含量增高39．4％(P<0．05),线粒体内膜NADH-CoQ还原酶活性较安静时下降61．6％(P<0．05)。结论 急性运动心肌缺氧时线粒体膜结构及功能有明显改变。     

牛磺酸对运动力竭大鼠心肌线粒体的保护作用

以大鼠力竭运动为模型，研究了牛磺酸对心肌线粒体脂质过氧化、抗氧化系统及游离钙浓度的影响。结果发现：牛磺酸可降低大鼠力竭运动后心肌线粒体脂质过氧化水平，提高大鼠力竭运动后心肌线粒体超氧化物歧化酶（ＳＯＤ）的活性，保持大鼠力竭运动后心肌线粒体还原性谷脱甘肽含量及游离钙浓度。结果提示牛磺酸可减少力竭运动后因脂质过氧化而产生的自由基，降低自由基对心肌线粒体的攻击，维持线粒体膜的功能，说明牛磺酸有保护心肌线粒体的功能和防止心肌损伤的作用。     

力竭运动后不同时相大鼠心肌CnAβ的变化

目的:探讨力竭运动后不同时相大鼠心肌CnAβ表达的变化特点。方法:90只健康成年雄性SD大鼠,分为一次力竭游泳运动组(n=40)、2周反复力竭游泳运动组(n=40)及安静对照组(n=10),两运动组根据取材时间不同又分别分为力竭运动后0、6、12及24小时组(n=10)。应用免疫荧光技术和免疫印迹法检测大鼠心肌CnAβ含量。结果:免疫荧光检测结果显示一次性力竭运动各组大鼠心肌CnAβ灰度值与对照组相比均无显著性差异(P>0.05);而反复力竭运动各组大鼠心肌CnAβ灰度值均高于对照组,其中运动后即刻组显著高于对照组(P<0.05)。免疫印迹法检测两种不同力竭运动后心肌CnAβ的积分灰度值比值变化趋势与免疫荧光法检测心肌CnAβ灰度值变化基本一致。结果提示,反复力竭运动大鼠心肌CnAβ蛋白含量的升高可能与运动性心肌微损伤发生有关。     

Water and tissue equivalence properties of biological materials for photons,electrons, protons and alpha particles in the energy region 10 keV–1 GeV: a comparative study

Purpose: To compare some biological materials in respect to the water and tissue equivalence properties for photon, electron, proton and alpha particle interactions as means of the effective atomic number (Z_eff) and electron density (N_e).

Methods: A Z-wise interpolation procedure has been adopted for calculation of Z_eff using the mass attenuation coefficients for photons and the mass stopping powers for charged particles.

Results: At relatively low energies (100?keV–3?MeV), Z_eff and N_e for photons and electrons were found to be constant while they vary much more for protons and alpha particles. In contrast, Z_eff and N_e for protons and alpha particles were found to be constant after 3?MeV whereas for photons and electrons they were found to increase with the increasing energy. Also, muscle eq. liquid (with sucrose) have Z_eff and N_e values close to the Muscle Skeletal (ICRP) and Muscle Striated (ICRU) within low relative differences below 9%. Muscle eq. liquid (without sucrose) have Z_eff and N_e values close to the Muscle Skeletal (ICRP) and Muscle Striated (ICRU) with difference below 10%.

Conclusions: The reported data should be useful in determining best water as well as tissue equivalent materials for photon, electron, proton and alpha particle interactions.     

Proton beam output measurement with an extrapolation chamber

A variable air-volume, parallel-plate extrapolation chamber forming an integral part of a polystyrene phantom was used in measurement of dose rate in a 250 MeV clinical proton beam. The sensitive air-volume of the extrapolation chamber is controlled through the movement of the chamber piston by means of a micrometer mounted on the phantom body. The relative displacement of the piston is monitored by a calibrated mechanical distance travel indicator. The proton beam dose rate determined with the uncalibrated extrapolation chamber was 5% lower than the dose rate determined with a calibrated Farmer-type thimble chamber at the same depth in the polystyrene phantom. Despite the current 5% discrepancy, uncalibrated extrapolation chambers may offer a simple and practical alternative to current techniques used in output measurements of proton beam machines.     

Incorporation of Lactate Measurement in Multi-Spin-Echo Proton Spectroscopic Imaging

An improved multi-slice, multi-spin-echo proton spectro-scopic imaging method for human brain is presented. The technique allows the reconstruction of lactate images, along with choline plus creatine, N-acetylaspartate, and lipid images from one single data set processed in three separate ways. The discrimination between resonances of lipid protons and lactate methyl protons is based on homonuclear spin-spin coupling. The reliability of the separation of the lipid and lactate contribution depends on the T2 of the lipid resonances. Measurements were performed on a standard 1.5 Tesla clinical scanner on healthy volunteers and a patient with high grade CNS lymphoma, demonstrating the ability to obtain high quality metabolite maps within 11 min.     

Quantitative proton spectroscopy of canine brain: in Vivo and in Vitro correlations

Quantitative, single-voxel proton NMR spectroscopy of normal brain was performed in five adult beagle dogs using the cerebral water signal as an internal intensity reference. The same brain regions were then rapidly isolated and frozen using a pneumatic biopsy drill, perchloric acid extracted, and analyzed by biochemical assay and high-resolution NMR spectroscopy. The concentrations of the major resonances in the in vivo and in vitro spectra were compared, and good agreement was found between the different measurements. The in vivo spectra contained three peaks at 3.21, 3.04, and 2.02 ppm, which are usually assigned to trimethylamines (TMA), creatines, and N-acetyl derivatives (NAc), which corresponded to be the following metabolite concentration values: 1.7 ± 0.6, 7.7 ± 2.1, and 10.9 ± 2.7 μmol/g wet weight respectively. In vitro, the following metabolite concentrations were measured: glycerophosphocholine (GPC) 1.3 ± 0.2, phosphocholine (PC) 0.5 ± 0.1, phosphocreatine (PCr) 2.6 ± 0.4, creatine (Cr) 5.9 ± 1.4, and N-Acetyl aspartate (NAA) 8.9 ± 1.8 μmol/g wet weight. Therefore, the 3.21 ppm resonance observed in the in vivo spectrum is predominantly GPC and PC in a ratio of 2.6:1, the 3.04 ppm resonance is Cr and PCr in a ratio of 2.3:1, and the 2.02 ppm resonance is predominantly (≈?80%) NAA with small contributions from N-acetylaspartyl-glutamate (NAAG) and glutamate. The data presented here validate the technique of water referencing as a simple and convenient means of quantitating single-voxel in vivo proton NMR spectra of the brain.     

Partial volume effects in volume localized phased-array proton spectroscopy of the temporal lobe

MRS techniques can aide in confirming the location of seizure foci in temporal lobe epilepsy. N-acetyl aspartate (NAA). creatine plus phosphocreatine. choline-containing compounds, and lactate arc most often the clinically relevant metabolites in these studies. We examined the importance of partial volume effects from tissue heterogeneity in temporal lobe spectroscopy on the metabolite ratios. Our study shows that localized spectroscopy, using three different voxel slzes. centered on the anterior body of the hippocampus. produces significantly different values for the NAA to the creatine ratio. The spectroscopy was performed at 1.5 T wing the PRESS pulse sequence and a phased-array coil system specifically designed for the temporal lobe. The data exhibits a clear trend of increasing NM to creatine ratios with increasing voxel size. This trend demonstrates that partial volume effects can contribute to variation of NAA to creatine ratios in healthy subjects.     

鞍旁海绵状血管瘤的CT和MRI诊断

目的总结7例鞍旁海绵状血管瘤CT、MRI和磁共振波谱（MRS）表现,探讨其诊断和鉴别诊断。资料与方法7例均经手术病理证实,均行CT和MR平扫,2例行CT增强扫描,7例行MR增强扫描,5例行MR扩散加权成像（DWI）,6例行^1H MRS检查。结果鞍旁海绵状血管瘤体积大,并同时伸入到鞍内。CT平扫病变呈等或稍高密度,密度均匀,MR T1WI呈等或稍低于脑灰质信号,T2WI呈类似脑脊液高信号。增强扫描病变呈非常显著强化。DWI呈等或稍低信号,但表观扩散系数（ADC）值明显高于正常脑实质。。HMRS表现为NAA峰、Cr峰和Cho峰消失。可出现Lip峰。结论CT检查时鞍旁海绵状血管瘤与脑膜瘤和垂体瘤鉴别困难,MRI表现很有特点,T2WI呈极高信号,增强扫描非常显著强化,ADC值明显升高而DWI接近等信号,MRS检查无NAA峰、Cr峰和Cho峰,MRI可以对海绵窦海绵状血管瘤作出定性诊断。     

Sensitive CEST agents based on nucleic acid imino proton exchange: detection of poly(rU) and of a dendrimer-poly(rU) model for nucleic acid delivery and pharmacology.

It is shown that the exchange properties of the imino and hydroxyl protons of polyuridilic acid (poly(rU)) allow use of this compound as a chemical-exchange saturation transfer (CEST) contrast agent. A proton/proton sensitivity enhancement factor of over 5000 per imino proton allowed the detection of a few micromolar of polymer (2000 uridine units; 644 kD) with a 50% change in the water signal. The enhancement factor would increase further at even lower concentrations, opening up the submicromolar range. When poly(rU) was complexed to a dendrimer carrying 250 positive charges, the stoichiometry was approximately one RNA for 10 dendrimers. The sensitivity enhancement was reduced but remained large (2300/imino proton), bringing enhanced CEST visibility to the dendrimers. The net charge of the complex was positive, suggesting that the complexed dendrimers would still interact with cell membranes, and that the RNA-dendrimer complex could provide a model for a gene delivery system with good CEST visibility.     

Construction of a 28-mm 1H/13C probe and actively shielded Z-gradient set for operation in a 9.4 T/89 mm magnet

In this work, we present a new RF and gradient assembly for operation in a 9.4 Tesla 189 mm magnet. This assembly was designed in order to enable ¹H-NMR perfusion studies that are based on proton-observed carbon-edited approaches or gradient selected double quantum coherence. The RF portion of this probe assembly is comprised of a modified Alderman-Grant coil and a saddle coil operating at 400 and 100 MHz, respectively. These coils are surrounded by an actively shielded Z gradient, which also allows for the use of gradient-based water suppression without the need for carbon selection. We demonstrate that this probe can be used to implement gradient selected double quantum coherence experiments resulting in a high degree of water suppression.     

Single-voxel long TE 1H-MR spectroscopy of the normal brainstem and cerebellum

PURPOSE: To evaluate the feasibility of single voxel 1H-MRS of the CNS structures contained in the posterior cranial fossa and to determine the distribution of the normal metabolite ratios, concentrations, and T2 relaxation times in the midbrain, pons, medulla, dentate nucleus and cerebellar vermis. MATERIALS AND METHODS: A total of 147 single voxel 1H-MR spectra with a point-resolved proton spectroscopy sequence (PRESS) sequence and echo time (TE) of 136 or 272 msec were obtained in the midbrain, pons, medulla, dentate, and vermis of 31 healthy volunteers. In seven additional patients; the concentrations and T2 relaxation times of metabolites were obtained in the same locations (except the medulla) with an external phantom calibration method and a four TE PRESS technique. RESULTS: Ten (27%) of 36 spectra acquired in the medulla were of poor quality. A similar ranking of the N-acetyl aspartate (NAA)/creatine (Cr) ratio and choline(Cho)/Cr ratios in the five locations for the two TEs was observed, with the highest values in the pons (mean NAA/Cr = 4.16 +/- 0.6 and Cho/Cr =2.66 +/- 0.6 at TE 272) and the lowest values in the dentate and vermis (mean NAA/Cr = 1.66 +/- 0.2 and Cho/Cr = 1.20 +/- 0.2 at TE 272). The analysis of variance showed significant regional differences of the NAA and Cr concentrations, which had the highest values in the dentate. Non-significant regional differences were observed for the concentration of Cho and for the T2 of the metabolites. CONCLUSION: With the exception of the medulla, single voxel 1H-MRS enables an in vivo biochemical analysis of the CNS structures contained in the posterior cranial fossa. Regional differences in the metabolite ratios and concentrations must be considered when employing 1H-MRS for evaluation of diseases of the brainstem and cerebellum.