摘要:

AbstractTwenty‐three pairs of normal mucosa and colonic adenocarcinoma biopsy specimens have been examined in this pilot study by1H NMR spectroscopy at 9.4 T to determine whether it was possible to find spectral malignancy markers. The 3.2 ppm (trimethylamine‐containing compounds)/0.9 ppm (methyl of fatty acids) resonance intensity ratio in water suppressed spectra, proposed by other authors as a malignancy marker, results in our hands, using resonance areas, in partial overlap between tumor and mucosa values, which reduces its diagnostic value. Furthermore, we have found that submucosa contamination could mask the normal mucosa pattern and artifactually decrease the 3.2/0.9 ppm, ratio value by increasing the 0.9 ppm resonance due to the known triglyceride content of normal submucosa. On the other hand, we have observed in the Hahn spin‐echo spectra of intact biopsies resonances arising from taurine and exogenous polyethyleneglycol (PEG). Their assignment and quantification has been carried out in perchloric acid extracts of the tissue biopsies. The taurine (3.4 ppm)/creatine (3.0 ppm) area ratio produced an excellent discrimination between normal mucosa and tumour groups while the PEG (3.7 ppm)/creatine (3.0 ppm) area ratio presented a large overlap, although it was clearly higher in the mucosae than in the tumors for paired samples. These two NMR observable parameters are in our hands highly discriminating and are accordingly proposed as malignancy markers in tissue biopsies although their possible utility forin vivostudies remains to be demonst

ISSN:0952-3480    

DOI:10.1002/nbm.1940060202

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractTo study whether acute or chronic hyponatremia alters blood‐brain barrier (BBB) permeability, rats made hyponatremic by constant desmopressin acetate infusion were studied by NMR spectroscopy and imaging. On constant volume ventilation and nitrous oxide, acute (1‐ and 2‐day) and chronic (7‐ and 14‐day) hyponatremic and normonatremic controls were infused with 0.25 M HCI. Despite reducing blood pH by at least 0.35 in<50min, brain pH, measured by31P NMR, was unaffected in any group. As a second test of BBB function, gadolinium‐DTPA (Gd‐DTPA) was injected intravenously in these five groups. Coronal slice1H NMR images obtained before and after Gd‐DTPA showed image intensity changes in multiple areas outside brain, but neither control nor hyponatremic rats showed any differences in cortex, white matter or cerebellum. To ascertain whether the threshold for BBB disruption was altered, hypertonic mannitol (1.5, 2.0 or 3.0 mL) was injected rapidly into one internal carotid artery and pre‐ and post‐Gd‐DTPA images obtained. In both control and hyponatremic rats only the largest dose caused detectable Gd‐DTPA leakage into brain. Thus, BBB function appears intact in both acute and chronic hyponatremia since neither H+nor GD‐DTPA penetrated the barrier and resistance to mannitol disruption was u

ISSN:0952-3480    

DOI:10.1002/nbm.1940060203

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe relevance of bulk magnetic susceptibility (BMS) induced broadening toin vivoNMR studies of intact cells has been examined and the significance of the contribution of BMS difference to the resolution of intra‐ and extracellular resonances was demonstrated. BMS difference between intra‐ and extracellular compartments was found to limit the resolution of intra‐ and extracellular19F resonances of fluoro compounds in leukemic

ISSN:0952-3480    

DOI:10.1002/nbm.1940060204

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractBiomedical NMR experiments rely frequently on data obtained sequentially over time. A method is presented for analysis of time based NMR data, which allows modelling of continuous and discontinuous functions to observed intensity changes by non‐linear regression and which uses variance ratio analysis to compare these models statistically. The method eliminates many of the usual problems in the parametric analysis of experimental values obtained at discrete time points and of comparison of the coefficients of model functions which require unsubstantiated assumptions about the distribution of parameters and ignore internal correlations which may exist between such parameters. The variance ratio method is illustrated for multiple time courses obtained with23Na NMR of perfused rat kidney undergoing hypoxic perturbation in the presence of different treatment

ISSN:0952-3480    

DOI:10.1002/nbm.1940060205

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn erythrocytes suspended in isotonic medium, a number of fluorinated anions showed well resolved19F NMR resonances from the solute populations in the intra‐ and extracellular compartments; theintracellularresonances were shifted tohigherfrequency (low field). In addition19F NMR resonances ofextracellularsolutes were shifted tohigherfrequency when bovine serum albumin was incorporated into the extracellular medium. The dependence of19F NMR chemical shift on protein concentration was also demonstrated using resealed red cell ghosts and liposomes; in the presence of external hemoglobin, lysozyme and bovine serum albumin, the shift of theexternalresonances was tohigherfrequency. In addition, significant high frequency shifts of19F NMR resonances were evident along with an increase of temperature. The results of the present study further support the contention that the principal physical basis for the shifts is the disruption of direct hydrogen bonds between19F of the solutes and (primarily) solvent H2O by protein hydration. The ‘split peak’ phenomenon is of general importance in biological systems where a transmembrane protein‐concentration difference

ISSN:0952-3480    

DOI:10.1002/nbm.1940060206

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe relationship between blood flow and metabolism was studied in halothane‐anaesthetized, normothermic rats submitted to 30 min global ischemia by four‐vessel occlusion. Phosphocreatine (PCr), ATP, intracellular pH and intracellular magnesium (pMg) were measured by31P NMR spectroscopy, and blood flow by laser Doppler flowmetry. Prior to ischemia the PCr/ATP ratio of fully relaxed spectra was 2.4±0.3, intracellular pH was 7.26±0.15 and pMg was 3.26±0.13. Vascular occlusion led to complete cessation of blood flow in four out of eight rats, and to incomplete ischaemia (<10% of control) in the other four animals. During vascular occlusion EEG flattened and energy metabolism broke down in all but one animal with a residual blood flow of 8% of control. pH declined to 6.70±0.08. The speed of electrophysiological and metabolic recovery after 30 min ischemia varied considerably from animal to animal. Variability depended mainly on the recirculation delay (i.e., the interval from vascular release to normalization of blood flow) but was independent of residual blood flow during ischemia, pre‐ischemic glucose, ischemic or post‐ischemic acidosis, or the degree of post‐ischemic hypoperfusion. After 3 h recirculation PCr and intracellular pH returned to normal but pMg was slightly increased, and ATP was reduced by up to 50% in all animals except the rat with incomplete breakdown of energy metabolism during ischemia. The dissociation between PCr and ATP is attributed to a loss of total adenylate, the severity of which depends on the quality of post‐ischemic recirculation. The data refute the hypothesis that the quality of post‐ischemic metabolic recovery depends mainly on the severity of tissue acidosis but stress the importance of post‐ischemic haemodynamic factors for the speed and quality of

ISSN:0952-3480    

DOI:10.1002/nbm.1940060207

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this paper we describe features of an NMR probe designed for the study of small, superfused muscles. We also present the results of an empirical study of the performance characteristics of several configurations of small solenoid coils, ca 2 mm diameter. Our data show that optimal use of the available volume of sample becomes the prime consideration in coil design at this scale. In contrast to large biological samples, for such small coils the equivalent resistance associated with the sample is minor relative to the resistance of the RF coil itself. Thus, substantial improvements in the S/N ratio can be obtained by adopting coil configurations that are inferior electrically, but which can sample a greater volume of tissue.

ISSN:0952-3480    

DOI:10.1002/nbm.1940060208

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of ω3 fatty acids on the metabolism of the normal liver was studied using31P NMR spectroscopy. Human subjects were examined before and after 1, 3 and 7 days of supplementation with 50 mL fish oil per day (12 g ω3 fatty acids).31P NMR spectra (1.6 T) revealed a significant increase in phosphodiester (PDE) to ATP ratios after 1 and 3 days of fish oil. After 7 days, [PDE]/[ATP]ratios at aTRof 1 s had returned to baseline levels, but [PDE]/[ATP]at aTRof 5 s appeared to remain high. Rats were fed diets containing 50% of the energy from fish oil or normal rat chow (controls) for 14 days.31P NMR liver spectrain vivo(4.7 T) confirmed increased [PDE]/[ATP]in rats fed fish oil compared to controls, although the difference was only statistically significant at aTRof 1.5 s but not at aTRof 8s.31P NMR spectra of rat liver extracts (8.7 T) suggested that increased concentrations of glycerophosphocoline and possibly glycerophosphoethanolamine were responsible for rising PDE levelsin vivo. Phosphocholine (PC) concentrations were markedly reduced in rat liver after fish oil. The combined rise in glycerophosphocholine and reduction in PC would be consistent with a shift from the phospholipase C to the phospholipase A1/A2 pathway of phosphatidylcholine breakdown after fish oil consumptio

ISSN:0952-3480    

DOI:10.1002/nbm.1940060209

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

Abstract1H NMR spectra have been measured at 500 and 600 MHz on 23 human cerebrospinal fluid samples obtained at autopsy from Alzheimer's disease patients and controls. The spectra at 500 MHz were quantified using 42 descriptors based on NMR peak heights and it was shown that differences between the two classes were apparent in the δ2.4–2.9 region. Remeasured at 600 MHz a detailed examination of this chemical shift range identified citrate, aspartate,N‐acetyl aspartate, methionine and glutamate in this region of the spectra. Principal components analysis showed that a separation of the two classes was possible and detailed statistics indicated that citrate level was the principal marker. Patient age and the interval between death and autopsy (parameters not closely matched between the two groups) were examined statistically to establish whether these might account for the citrate differences. Although they could possibly account for them to some extent, the relationship between citrate levels and disease state remained significant atp<0.05. The data invite a test of the importance of citrate levels in Alzheimer's disease using samples takenex

ISSN:0952-3480    

DOI:10.1002/nbm.1940060210

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractFourteen patients with liver cirrhosis of differing severity participated in a one‐dimensional chemical shift imaging31P MRS study of the liver. Patients were divided into two groups according to the severity of their liver disease using Child's classification and the aminopyrine breath test (AB test). Seven normal volunteers without liver disease acted as controls. The phosphomonester (PME) peak in normal subjects was 4.77% (95% confidence interval, CI: 4.11–5.42) of total phosphorus. The PME peak was significantly elevated in both mild cirrhosis [5.80% (95% CI: 5.46–6.14),p=0.0051, vs normal subjects] and severe cirrhosis [9.64% (95% CI: 8.71–10.57),p=0.0002, vs normal subjects andp=0.001, vs mild cirrhosis]. There was a significant negative linear correlation (r=0.88, p<0.01) of PME with the percentage dose of14CO2excreted over 2 h in the AB test. pH values in patients with mild cirrhosis [7.45 (95% CI: 7.35–7.55)] but not severe cirrhosis [7.36 (95% CI: 7.25–7.47)]were significantly elevated (p=0.04) compared to normal subjects [7.29 (95% CI: 7.17–7.41)]. Comparison of the peak area of PME atTR= 0.5 s against that usingTR= 5.0 s in cirrhotic liver suggested no reduction inT1of phosphorus metabolites in cirrhosis. A relationship between the severity of liver cirrhosis and a relative increase in PME was demonstrated and this was not due to a reduction ofT1. This study highlights the clinical potential of31P MRS as a non‐invasive means of assessing the severity of

ISSN:0952-3480    

DOI:10.1002/nbm.1940060211

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY