鼠S180肉瘤的体内31P MRS研究

利用表面线圈³¹P NMR研究了小鼠S180肉瘤生长过程中能量代谢和磷脂类变化的特点.结果发现:随着肿瘤体积的增大,(1)Pi和PME升高;(2)PCr降低,在肿瘤体积较大时常检测不到;(3)β-NTP(通常用来表示ATP的量)变化较小;(4)PDE波动性较大;(5)PCr/Pi和β-NTP/Pi比值均下降,且PCr/Pi比β-NTP/Pi下降得快;(6)PME/β-NTP比值升高;(7)肿瘤pH下降,且与PCr/Pi、β-NTP/Pi或(PCr+β-NTP)/Pi比值有相关性.讨论了与这些参数变化相关联的生物学意义.     

活体动物代谢过程的31P NMR研究——方法与初步结果

利用表面线圈探头测得了小鼠大脑,大腿肌肉和肝脏的体内³¹P NMR谱图。观察到PCr,ATP,PME,PDE,P_i等化合物的共振峰,并确定了各谱峰的化学位移。由大脑的P_i化学位移计算得到其细胞内pH值为7.15.用差谱方法解决了因定位不准而造成的肝脏谱图不纯。观察了小鼠大脑在缺氧状态下的代谢变化过程。当O₂浓度降至2%时,PCr开始下降,降到1%时,P_i明显升高。从空气变化到1%的O₂含量,致使小鼠死亡,小鼠大脑的pH值从7.16降到6.46。     

小鼠大脑急性缺血过程中31P NMR研究

利用³¹P NMR研究了小鼠大脑在急性缺血状态下能量代谢的特点,结扎带迷走神经的颈总动脉后,PCr/Pi、β-ATP/Pi比值迅速下降,且PCr/Pi下降速度较快,同时脑细胞内酸中毒加重.缺血5min后恢复供血,可部分地逆转缺血造成的损伤.     

急性低氧大鼠脑31P核磁共振波谱研究

³¹P磁共振波谱是目前唯一可以用作在体无损伤的检测细胞水平能量代谢变化的非侵入性技术,可测得脑内多种能量代谢产物.目的：急性低氧大鼠脑组织的³¹P MRS检测.方法：(1)20只成年SD大鼠分为4组：低氧0min(对照),5min,10min,15min后,迅速液氮冷冻;(2)将脑组织研碎后,加入高氯酸(PCA),冷冻干燥;(3)将提取物用0.5mL D\-2O溶解后进行MRS检测.结果：(1)急性低氧早期即引起³¹P MRS中PCr和ATP峰降低,ADP和Pi峰增高,PCr/Pi和ATP/Pi降低,而ADP/ATP增高.可交换磷池(EPP)中PCr的正常值为42.4%,低氧5min后降到28.9%, ATP从33.8%降到19.2%,Pi从17.7%升到42.0%.(2)急性低氧时³¹P MRS中脑内磷酯分解代谢产物GPC、GPE含量增加,说明低氧早期脑内即有膜磷酯的分解增加.结论：³¹P磁共振波谱可用于脑低氧性疾病的诊断,我们波谱中最敏感的指标是PCr/Pi和ATP/Pi,尤其早期降低更为显著.     

维拉帕米对离体大鼠心脏缺血-再灌注损伤保护作用的31P核磁共振研究

为评价维拉帕米(Ver)防治心脏缺血-再灌注损伤的作用,采用³¹P核磁共振(^3lP NMR)技术对大鼠心肌缺血前,缺血过程中及缺血后高能磷化物的含量及细胞内pH (pH_i)的变化过程进行了动态跟踪测定,离体心脏于37℃下平衡灌流30min,停止灌流30min,再灌注30min.灌流液中始终含有Ver (0.2μmol·L^-1).Ver可使再灌注后心脏的冠脉流量有较高程度的恢复,^3lP NMR测定显示Ver可使心脏产生代谢上的改善作用.缺血10min后对照组心脏即检测不到磷酸肌酸(PCr),而Ver组心脏PCr仍保持在缺血前的20%.缺血过程中治疗组比未治疗组心脏ATP下降减缓,至缺血结束时心肌ATP分别为缺血前的53%和34%.再灌注后两组心肌的ATP均未回升,但Ver使PCr的恢复显著提高(P<0.05),给药心脏PCr/P_i(无机磷酸盐)无论在缺血前或再灌注阶段,都非常显著(P<0.01)地高于对照组心脏.Ver还可显著减轻缺血过程中的酸中毒并防止再灌注后心肌出现严重酸化的区域.     

光谱法研究不同pH范围内三磷酸腺苷与Mg2+的相互作用

研究金属离子与ATP的相互作用方式,对于阐明金属离子与ATP参与的酶反应过程具有重要的意义.31P NMR光谱结果表明ATP分子的a-P在pH 2-8研究范围内都不参与键合作用,而β-P 和γ-P都参与键合作用.1H NMR光谱结果表明,当ATP与Mg2+发生相互作用时,其磷酸根阴离子与腺嘌呤碱基都会参与配位作用.紫外吸收光谱结果表明在碱性条件时,Mg2+会引起ATP分子发生碱基堆积,而在酸性条件时,碱基堆积则不会发生.     

大鼠急性缺血心肌31P磁共振波谱的基础研究

利用³¹P磁共振波谱（MRS）检测了急性缺血心肌组织提取物中高能磷酸化合物的变化. 方法：成年SD大鼠在心肌梗塞后0、5、 20、45 min后进行取材,梗塞区、边缘区及正常区的心肌组织经高氯酸萃取后进行高分辨MRS检测. 结果：梗塞区,缺血5 min PCr/Pi比值下降到对照组的12 ％;20 min ATP/Pi 比值下降至0.05,Pi/EPP比值上升至0.8;45 min 梗塞区PDE/ATP上升至1.93,与45 min心肌的不可逆损伤超微结构相吻合. 边缘区各代谢产物出现改变的程度要小于梗塞区,大于正常区. 正常区也有能量代谢的改变. 结论：心肌组织的³¹P MRS能够反映心肌缺血后心肌不同部位的动态能量代谢改变. PDE/ATP是判断心肌不可拟性损伤的可靠指标.     

体内31P NMR表面线圈探头的研制

报道一种为进行活体小动物核磁共振实验而研制的体内³¹P NMK表面线圈探头.该探头工作频率为161.83MHz,无载Q值为300,可无损伤地研究生命体内各部位的性质.本文给出了用该探头所测得的小鼠体内肝脏、大腿肌肉、大脑以及大脑缺氧状态下³¹P NMR谱图实例.     

紫杉醇治疗小鼠S180肉瘤的体内31P MRS研究

为了研究紫杉醇治疗小鼠S180肉瘤的³¹P MRS参数的变化及这些参数的变化是否早于常规观察的瘤体积的变化.方法:利用表面线圈³¹P NMR方法,研究小鼠皮下接种的S180肉瘤.结果:用药48h后给药组的PCr/Pi、β-NTP/Pi、PME/β-NTP比值与对照组有显著性差别(P<0.05),而肿瘤体积在给药组和对照组之间无显著性差别,³¹P MRS参数的变化早于瘤体积变化.结论:小鼠S180肉瘤³¹P MRS不仅可以给出定量的结果,而且可以较早地显示出治疗的效果.     

体内￣（31）PNMR表面线圈探头的研制

报道一种为进行活体小动物核磁共振实验而研制的体内￣（３１）ＰＮＭＫ表面线圈探头．该探头工作频率为１６１．８３ＭＨｚ，无载Ｑ值为３００，可无损伤地研究生命体内各部位的性质．本文给出了用该探头所测得的小鼠体内肝脏、大腿肌肉、大脑以及大脑缺氧状态下￣（３１）ＰＮＭＲ谱图实例．     

Considerations for brain pH assessment by 31P NMR

Recently in vivo NMR spectroscopy has been used to measure brain pH non-invasively. Both the inorganic orthophosphate (Pi) chemical shift (delta) and the difference between the chemical shifts of phosphocreatine (PCr) and Pi(delta delta PCr-Pi) have been proposed as indicators of brain pH. However, the precise delta of Pi may be difficult to determine under normoxic conditions as is the delta of PCr under hypoxic/ischemic conditions. Ideally one needs a NMR delta parameter that: (1) linearly changes between pH 6.0-8.0, (2) is either relatively unaffected or predictably affected by cations (e.g., Mg2+) other than H+, and that (3) comes from readily observable 31P NMR resonances whose delta's can be accurately assessed under all physiological conditions. Therefore, we undertook a systematic 31P NMR study of the pH and Mg2+ titration curves for 16 phosphorus-containing metabolites observed in brain by 31P NMR. On the basis of the titration curves, the delta delta's for PCr-Pi, phosphoethanolamine (PE)-Pi, and PCr-PE fulfill criteria (1) and (2), but not criterion (3). However, the delta delta of ATP gamma-alpha fulfills all three criteria and potentially provides information on the intracellular Mg2+ concentration.     

Phosphorus-31 MR spectroscopic imaging (MRSI) of normal and pathological human brains.

The goals of this study were to evaluate 31P MR spectroscopic imaging (MRSI) for clinical studies and to survey potentially significant spatial variations of 31P metabolite signals in normal and pathological human brains. In normal brains, chemical shifts and metabolite ratios corrected for saturation were similar to previous studies using single-volume localization techniques (n = 10; pH = 7.01 +/- 0.02; PCr/Pi = 2.0 +/- 0.4; PCr/ATP = 1.4 +/- 0.2; ATP/Pi = 1.6 +/- 0.2; PCr/PDE = 0.52 +/- 0.06; PCr/PME = 1.3 +/- 0.2; [Mg2+]free = 0.26 +/- 0.02 mM.) In 17 pathological case studies, ratios of 31P metabolite signals between the pathological regions and normal-appearing (usually homologous contralateral) regions were obtained. First, in subacute and chronic infarctions (n = 9) decreased Pi (65 +/- 12%), PCr (38 +/- 6%), ATP (55 +/- 6%), PDE (47 +/- 9%), and total 31P metabolite signals (50 +/- 8%) were observed. Second, regions of decreased total 31P metabolite signals were observed in normal pressure hydrocephalus (NPH, n = 2), glioblastoma (n = 2), temporal lobe epilepsy (n = 2), and transient ischemic attacks (TIAs, n = 2). Third, alkalosis was detected in the NPH periventricular tissue, glioblastoma, epilepsy ipsilateral ictal foci, and chronic infarction regions; acidosis was detected in subacute infarction regions. Fourth, in TIAs with no MRI-detected infarction, regions consistent with transient neurological deficits were detected with decreased Pi, ATP, and total 31P metabolite signals. These results demonstrate an advantage of 31P MRSI over single-volume 31P MRS techniques in that metabolite information is derived simultaneously from multiple regions of brain, including those outside the primary pathological region of interest. These preliminary findings also suggest that abnormal metabolite distributions may be detected in regions that appear normal on MR images.     

Bio-energetic impairment in human calf muscle in thyroid disorders: a P MRS study

Mitochondrial metabolism particularly oxidative phosphorylation is greatly influenced by thyroid hormones. Earlier studies have described neuromuscular symptoms as well as impaired muscle metabolism in hypothyroid and hyperthyroid patients. In this study, we intend to look in to the muscle bioenergetics including phosphocreatine recovery kinetics based oxidative metabolism in thyroid dysfunction using in vivo ³¹P nuclear magnetic resonance spectroscopy (MRS). ³¹P MRS was carried out at resting state on 32 hypothyroid, 10 hyperthyroid patients and 25 control subjects. Nine out of 32 hypothyroid patients and 17 out of 25 control subjects under went exercise protocol for oxidative metabolism study and performed plantar flexion exercise while lying supine in 1.5 T magnetic resonance scanner using custom built exercise device. MRS measurements of inorganic phosphate (Pi), phosphocreatine (PCr), phosphodiesters (PDE) and adenosine triphosphate (ATP) of the calf muscle were acquired during rest, exercise and recovery phase. PCr recovery rate constant (k_PCr) and oxidative capacity were calculated by monoexponential fit of PCr versus time (t) at the beginning of recovery. During resting condition in hypothyroid patients, PCr/Pi ratio was reduced whereas PDE/ATP and Pi/ATP were increased. However, in case of hyperthyroidism, an increased PCr/Pi ratio and reduced PDE/ATP and Pi/ATP were observed. The results confirmed differential energy status of the muscle due to increased or decreased levels of thyroid hormone. Our results also demonstrate reduced oxidative metabolism in hypothyroid patients based on PCr recovery kinetics. PCr recovery kinetics study after exercise revealed decreased PCr recovery rate constant (k_PCr) in hypothyroid patients compared to controls that resulted in decrease in oxidative capacity of muscle by 50% in hypothyroids. These findings are consistent with a defect of high energy phosphate mitochondrial metabolism in thyroid dysfunction.     

Spin-lattice relaxation times and nuclear overhauser enhancement effect for P metabolites in model solutions at two frequencies: Implications for in vivo spectroscopy

The relaxation time T₁ values and nuclear Overhauser enhancement factor for ³¹P signal were determined in model solutions of metabolites ATP, PCr and Pi, and AMP at two frequencies and in H₂O and ²H₂O solutions. The data were analyzed to resolve the contribution of different relaxation mechanisms. A knowledge of NOE is important in the light of recent applications of double resonance methods to enhance the sensitivity of in vivo ³¹P spectroscopy. The results show that chemical shift anisotropy is the dominant mechanism for ³¹P in ATP at the high field, whereas the dipolar interaction mechanism is the main feature for the ³¹P relaxation of PCr and Pi. The dipolar mechanism responsible for NOE originates from interactions of solvent water with ³¹P moiety. Implications for in vivo spectroscopy are indicated.     

Relayed magnetization transfer from nuclear Overhauser effect and chemical exchange observed by in vivo ³¹P MRS in rat brain

The ³¹P magnetization transfer effects among nuclear magnetic resonances (NMRs) of phosphocreatine (PCr), γ-adenosine-5'-triphosphate (γ-ATP) and inorganic phosphate (Pi) have been attributed to the chemical exchange reactions among PCr, ATP and Pi catalyzed by creatine kinase (CK) and ATPase enzymes and, therefore, are commonly applied in situ to measure chemical exchange fluxes involving two chemically coupled CK and ATPase reactions (i.e., PCr↔ATP↔Pi) by selectively saturating γ-ATP resonance. Besides the expected reductions in the Pi and PCr NMR signals upon saturating γ-ATP resonance, one particularly interesting phenomenon showing decreases in α-ATP and β-ATP signals was also observed. The underlying mechanism was investigated and identified via saturating NMR of β-ATP in the present study. The unique relayed magnetization transfer effects through spin diffusion were observed in the rat brain using in vivo ³¹P magnetic resonance spectroscopy.