摘要:

AbstractTwo metabolically distinct cell populations were detected when two peaks of inorganic phosphate (Pi), corresponding to two pHivalues, were recorded by Phosphorus Magnetic Resonance Spectroscopy (31P MRS). One cell population, having intracellular pH (pHi) values less than 6.3, was thought to contain neither PCr (phosphocreatine) nor ATP and was thus considered metabolically unstable or inactive. The second cell population, having normal or near normal pHi, was considered metabolically active with adequate values of ATP and PCr. We can therefore further analyze the bioenergetics in this cell population.The results were based upon studies of 14 ischemic dogs that were anesthetized with 2% isoflurane and ventilated. The amount of Piassociated with the acidic cell population (low pHi) was used to calculate the fraction of metaboliacally inactive brain tissues. This value correlated well with the ATP depletion of the total cell population. This suggests that in the acidic cell population, PCr and ATP supplies were depleted by dephosphorylation during ischemia, leading to an accumulation of acidic Pi. In addition, ATP synthesis in this population may be inhibited by the low intracellular pH. On the other hand, the bioenergetic state of the metabolically stable cell population having a nearly neutral pHichanged markedly during ischemia. The PCr/Pidropped to 0.8 and the phosphorylation potential (PP) dropped to 10 mM−1from 40 mM−1. With reperfusion, two distinct patterns of responses were observed. One group showed the restoration of ATP (recovery group) whereas the second group did not (non‐recovery group). After 3 h of reperfusion, the ATP restored group showed complete recovery of PCr. The non‐recovery group showed no restoration of PCr or phosphorylation potential and no reductio

ISSN:0952-3480    

DOI:10.1002/nbm.1940030602

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

Abstract1H NMR spin‐echo spectroscopy has been used to study the metabolism of exogeneous compounds in human erythrocytes. The non‐invasive nature of the technique and the continuous monitoring makes it ideal to investigate both the conversion of substrates and the occurrence and the nature of the products. Hydrolysis rates may be determined and the hydrolysis of alkyl, vinyl, and aryl acetates are shown to be due to A‐esterase activity. The conversion products are normally observed, but in the case of dimethyl phthalate and methyl acetate only part of the methanol is found. An interesting case is the hydrolysis of vinyl acetate and the consecutive conversion of the vinyl alcohol to acetaldehyde (hydrate). Coupling of glutathione to a variety of vinyl derivatives is also observed. Oxidation of acetaldehyde can also be followed. Styrene and 5‐chloro‐2‐methylaniline are slowly converted in what is believed to be oxidation reactions. Changes in1H chemical shifts are observed for a number of compounds upon uptake into human erythrocytes, a shift that is suggested to be due to binding to

ISSN:0952-3480    

DOI:10.1002/nbm.1940030603

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractSerial31P nuclear magnetic resonance spectra were acquired from the brain in 19 rats following microsphere embolization of the right internal carotid artery. The brains were sectioned and stained with 2,3,5‐triphenyltetrazoline chloride 6 h post‐embolization to visualize infarcted areas. There was a narrow dosage range for the effect of embolism measured by maximum decline in pH at 20 min, mortality, and infarct size. This narrow range effect may be due to occlusion of collateral channels by the 16 micron microspheres. There was a strong correlation between decline in pH at 20 min post‐embolization and infarct size (r2= 0.76); this decline was the best early marker for eventual infarct in our study. This animal model for macroscopically heterogenous brain ischemia may be useful for the evaluation of therapeutic interventions in stroke, and as an aid in the interpretation of phosphorus spectra from mixed volumes of ischemic and non‐ischemi

ISSN:0952-3480    

DOI:10.1002/nbm.1940030604

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractFor a rapid determination of saturation factors in surface coil NMR spectroscopy, the recently published (90°–τ–180°–τ–90°–τ–) SUFIR sequence was modified with adiabatic pulse cycles. Signals were acquired after each of the two 90° pulses and they were stored in different memory blocks. The deleterious offset‐dependent saturation effects inherent in adiabatic 90° excitation pulses were minimized by suitable combinations of adiabatic pulses that sweep from either side of the spectrum onto resonance, and by setting the carrier frequency in the middle of the spectrum. The practical use of the proposed method is illustrated with the determination of31P NMR saturation factors

ISSN:0952-3480    

DOI:10.1002/nbm.1940030605

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of amphetamine on rat cerebral blood flow, lactate, and phosphate levels were studied usingin vivonuclear magnetic resonance (NMR) spectroscopy. Proton NMR imaging was used to determine the region of brain being studied. Blood flow was estimated by detecting the washout of trifluoromethane using19F NMR. A dose of 20 mg/kg D‐amphetamine sulphate stimulated flow fourfold over control values for at least 1 h. Even though amphetamine stimulated a large increase in flow, there were no significant changes in levels of inorganic phosphate, ATP, phosphocreatine, pH or Mg2+as determined by31P NMR. This was true for doses of 10 and 20 mg/kg D‐amphetamine sulphate. No significant changes occurred in1H NMR detected levels of lactate with a 20 mg/kg dose of amphetamines. Lactate levels increased slightly 30min after administration of 10 mg/kg D‐amphetamine sulphate. The results call into question the central role of changes in levels of phosphates in coupling increased cortical activity to increases in metab

ISSN:0952-3480    

DOI:10.1002/nbm.1940030606

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940030601

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY