摘要:

AbstractA new gating NMR technique triggered by pulses for the cardiac pacing of isolated, perfused rat heart is described. This technique is suitable for obtaining spectra at the same positions over the cardiac cycle with the same RF pulse repetition time and with constant heart rate. Accordingly, each recovered magnetization level at these positions during the cycle can be kept constant. It also allows a qualitative analysis of the myocardial energy level during the cycle under the condition of the same or different cardiac workload (rate pressure product, HR X LVP). This method was used to observe cyclical changes in the concentration of adenosine triphosphate (ATP), phosphocreatine (PCr), Pi, and in pH during the cardiac cycle, and confirmed that the levels of ATP and PCr showed reversible decreases, and Pishowed an antiphasic increase at the peak systole. On the other hand, no significant changes in pH were noted during the cardiac cycle. This pacing‐gated technique is an improvement over other gated NMR techniques triggered by the blood pressure or by ECG trace

ISSN:0952-3480    

DOI:10.1002/nbm.1940050602

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractExperimental brain tumors produced in rats (n = 10) by stereotactic implantation of cells from the F98 anaplastic glioma clone into the right caudate nucleus were studiedin vivousing localized proton NMR andin vitrousing high‐resolution proton NMR, bioluminescent imaging of lactate, ATP and glucose distributions, and fluorescent imaging of regional pH.In vivospectra from normal brain contralateral to the tumor regions showed resonances assignable to N‐acetyl aspartate (NAA), creatines, choline‐containing compounds,myo‐inositol, glutamate and glucose in a pattern similar to those obtained from normal anaesthetized rats.In vivotumor spectra were characterized by the almost complete absence of NAA, a substantial reduction of total creatine and glucose, and an increase of cholines. Based on thein vitrospectra the increase of themyo‐inositol signal observedin vivowas mainly attributed to glycine. Histological examination as well as bioluminescent and fluorescent imaging indicated two stages of tumor development, i.e., solid vital tumors and tumors with necrosis. However, there was no consistent relationship between proton NMR observations and tumor de

ISSN:0952-3480    

DOI:10.1002/nbm.1940050603

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractA simple method for measuring absolute concentrations of31P metabolites in rat liver using an external reference is described. It neutralizes systematic errors due to conductive losses by calibration of the matching capacitor and selects liver signals via an electrically driven, surface spoiling magnetic field gradient. The technique avoids the chemical shift problems associated with linear field gradient localization methods at 4.7 T and allows combinaton with the double standard method for absolute metabolite concentration determination. Application of the method to thein vivomeasurement of the absolute concentrations of ATP and Piin eight rat livers yields results that are in good agreement with literature values. Absolute phosphomonoester concentrations were also obtained, but no literature data were available.

ISSN:0952-3480    

DOI:10.1002/nbm.1940050604

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractA novel iodoacetamide label 4‐perfluoro‐tert‐butyl‐phenyliodoacetamide (PFP) containing nine fluorine atoms in equivalent positions has been synthesized. It provides a homogeneous19F NMR resonance line which can be detected with high sensitivity when coupled to proteins. As an example, the sulfhydryl groups of actin have been labeled with PFP;<100 nmol of this medium sized protein (corresponding to 2.5 mL of a 40μM solution) can be detected easily in a single scan at

ISSN:0952-3480    

DOI:10.1002/nbm.1940050605

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe contribution of extracellular components to the measurement of pHMRSof a variety of rat tumours (nitrosomethyl urea induced mammary tumours, GH3 prolactinomas, Hepatoma 9618a, UA hepatomas and Walker sarcomas) has been assessed. Acid extractable Piwas between 2.6 and 12.5 μmol/g wet wt depending on tumour type, and of this 53±4.8% (mean ± SEM) was MRS‐visible. The Picontent of tumour exudate was 2–3 mM, of interstitial fluid (sampled from a micropore chamber incorporated within a tumour) 1.7 mM, and of blood plasma 1.95 mM. The mean extracellular volumes of the tumours, measured by distribution of3H2O and [14C]inulin, were 49‐55% depending on tumour type and were at least twice that found in normal liver. Calculations suggested that for most tumours with an extracellular volume not exceeding 55%, at least 65% of the Pi(MRS)signal was derived from intracellular Pi, and thus that pHMRSis a measure of pHi. For each tumour type, pHMRSwas measured both in “pulse‐acquire” mode at 1.9T which may include signals from surrounding tissue, and in localized mode at 4.7 T where the signal came uniquely from tumour tissue. The steady state pHMRSwas either neutral or on the alkaline side of neutrality (pH range 7.04–7.37). Raised lactate content and decreased buffering capacity (compared to normal tissues) accompanied these neutral to alkaline pH values. The extracellular pH of all the tumour types was found to be significantly lower than pHiwhen calculated from the distribution of lactate across the plasma membrane ([lactate−]out/[lactate−]in= [H+]in/[H+]out) by the method of Veech [Veech, R. L.NMR Biomed.4, 53–58 (1991)] whereas in control tissue (liver) the extracellular pH was higher

ISSN:0952-3480    

DOI:10.1002/nbm.1940050606

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe objective of this study was to compare pH measurements made in biological samples using31P NMR (pHNMR) with those made with a novel, dye‐based fibreoptic pH measurement system (pHF), which is compatible with use in electromagnetic fields without field perturbation. Using protein‐free model solutions, pHNMRwas calibrated against pHF, giving a correlation coefficient of 0.969 and a mean difference (± SD) between pHNMRand pHFof 0.037±0.054 over the pH range 6.8–7.7. Further calibration of pHNMRwith pHFwas carried out for human red blood lysates and then pHNMRwas compared with pHFfor whole, packed red blood cells over the pH range 7.0–7.8. Values for pHNMR, the intracellular pH, were consistently lower than for pHF, the extracellular pH, by a mean (±SD) of 0.15±0.02 units. A close correlation of extracellular pHNMRwith pHFwas demonstrated for a blood sample exhibiting two Pipeaks, over the pH range 7.03–7.71. We conclude that concurrent use of NMR and the fibreoptic pH meter provides a reliable method of simultaneous measurement of intracellular and extracellular pH in biolo

ISSN:0952-3480    

DOI:10.1002/nbm.1940050607

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIt is not sufficiently appreciated that chemical exchange can markedly affect the appearance of31P tissue extract NMR spectra. In addition to the commonly recognized31P chemical shift effects of divalent metal cation (e.g. Mg2+) binding upon ATP resonances, multiple resonances for phosphoethanolamine (PE) and phosphocreatine (PCr) are observed under certain conditions of pH, temperature, and D2O and bicarbonate concentrations. In the presence of bicarbonate ion (commonly used to neutralize acidic extractions) carbamate formation causes a second31P resonance for PE to appear. This effect has been described previously for13C and1H amino acid resonances in tissue extracts [Sherryet al. J. Magn. Reson.89, 391––398 (1990)]. The observation of a splitting of the PCr31P resonance in aqueous solutions containing D2O has been recently ascribed to proton scalar coupling but was described earlier in an underappreciated report [Kupriyanovet al. Biochem. Biophys. Res. Comm.114, 1117–1125 (1983)] as due to a deuterium isotope effect. These effects, carbamate formation and deuterium isotope shift, are verified herein to cause marked shifts in PE and PCr31P resonances. The dependence upon experimental parameters is exp

ISSN:0952-3480    

DOI:10.1002/nbm.1940050608

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940050609

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940050610

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940050601

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY