bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative analysis by 31P magnetic resonance spectroscopy of abnormal mitochondrial oxidation in skeletal muscle during recovery from exercise
Authors: Kemp G. J. , Taylor D. J. , Thompson C. H. , Hands L. J. , Rajagopalan B. , Styles P. , Radda G. K. 
Published: March 2007

AbstractWe use the hyperbolic relationship between cytosolic [ADP] and the rate of phosphocreatine (PCr) resynthesis after exercise to estimate the apparent maximum rate of oxidative ATP synthesis (QMAX). We examine data from some human diseases in which mitochondrial oxidation may be impaired (due to reduced mitochondrial numbers, intrinsic mitochondrial defect or impaired vascular supply). Muscle responds to impaired oxidation by stimulating anaerobic ATP synthesis and/or by increasing [ADP], the stimulus to the mitochondrion. However, these responses interact: [ADP] depends on pH and [PCr], and lactic acid production tends to lower [ADP] (by lowering pH), while proton efflux has the opposite effect. We identify four patterns of results: (A) in mitochondrial myopathy, apparent QMAX is reduced and [ADP] is appropriately increased, because increased proton efflux reduces the pH change in exercise despite increased lactic acid production; (B) in some conditions (e.g., cyanotic congenital heart disease) apparent QMAX is reduced but there is no compensatory rise in [ADP], probably because anaerobic ATP synthesis during exercise is increased without increase in proton efflux; (C) in other conditions (e.g., myotonic dystrophy) [ADP] is increased during exercise but apparent QMAX is normal, suggesting either an increase in proton efflux and/or decrease in anaerobic ATP synthesis during exercise; (D) there are also conditions (e.g., respiratory failure) where, despite impaired oxygen supply, both apparent QMAX and end‐exercise [ADP] are normal. We also discuss the metabolic conditions under which end‐exercise [ADP] is increased by a mitochondrial defect. Finally, we discuss some technical aspects, including the effects of an altered mitochondrial Km for ADP and the relationship of the analysis to the halftime of PCr recovery and an alternative calculation of apparent QMAX.
Differential diagnosis of solid renal tumors by MRI. Comparison of In Situ relaxation times measured with a 0.1 T imager and histological findings
Authors: Takeda Masayuki , Katayama Yasushi , Tsutsui Toshiki , Komeyama Takeshi , Mizusawa Takaki , Saito Kazuhide , Takahashi Hitoshi , Tamaki Makoto , Sato Shotaro 
Published: March 2007

AbstractThe T1 and T2 of kidneys in 5 normal volunteers and 27 patients with renal tumors were evaluated preoperatively using a magnetic resonance imager with a 0.1 T resistive electromagnet, and the T1 and T2 of the renal tumors were compared with the pathological findings: (i) the T1 and T2 of the normal renal medulla were longer than those of the normal renal cortex and psoas muscle; (ii) both T1 and T2 of renal pelvic cancer (RPC) were shorter than those of renal cell cancer (RCC, p<0.05); (iii) the T2 values of RPC were significantly shorter than those of renal medulla (P<0.01); (iv) the T1 and T2 of the normal renal cortex of subjects <50 years old were shorter than those of subjects ⩾50 years old (p<0.05 and p<0.01, respectively). These findings suggest that preoperative evaluation of the pathological findings of renal tumors may be possible by calculating the relaxation time using MRI under low magnetic field.
Effect of hypoxia on bicuculline seizures of rat: NMR spectroscopy and bioluminescence imaging
Authors: Kloiber O. , Bockhorst K. , Hoehn‐Berlage M. , Hossmann K.‐A. 
Published: March 2007

AbstractPrevious studies suggested that hypoxia reduces the severity of brain injury after epileptic seizures. To test this hypothesis, the effect of hypoxic arrest of epileptic seizures on brain metabolism was investigated in rats by combining in vivo NMR spectroscopy with imaging techniques for the pictorial evaluation of energy metabolism and pH. Seizures were produced by i.v. injection of bicuculline, and measurements were compared in animals with and without 5 min exposure to 5% oxygen after the onset of seizures. Transient hypoxia persistently reduced seizure activity, even after return to normoxia. Hypoxia or seizure alone had little effect on brain metabolism but the combination of both led to marked albeit reversible deterioration of energy and acid/base status. In normoxic animals pictorial measurements of energy state 2 h after the onset of seizures revealed a regional decline of ATP in the hippocampus. In animals in which seizures were arrested by transient hypoxia ATP depletion was additionally observed in the border zones of vascular territories. These results demonstrate that hypoxic arrest of seizure activity leads to the aggravation of metabolic disturbances and is therefore not suited to preventing permanent brain injury.
Diffusion into rat brain of contrast and shift reagents for magnetic resonance imaging and spectroscopy
Authors: Preston Edward , Foster David O. 
Published: March 2007

AbstractA sensitive radiotracer technique was used to measure transfer constants (Kis) for blood to brain diffusion of the MR contrast reagent gadolinium diethylenetriaminepentaacetate (GdDTPA2−) and the MR shift reagent dysprosium triethylenetetraminehexaacetate (DyTTHA3−) across the normal and the ischemically injured blood‐brain barrier (BBB) of rats. In rats with a normal BBB mean Kis (nL/g/s) for these reagents ranged from 0.3 to 1.4 across eight brain regions and were significantly lower in each region than Kis for sucrose (1.5–3.2), a substance known to be a poor permeant of the intact BBB. Kis measured 6h after a 10min period of normothermic forebrain ischemia were increased to 4.0–6.2 (reagents) and 6.6–7.5 (sucrose) in two brain regions, striatum and hippocampus, known to be especially vulnerable to ischemic injury. Measurements of BBB permeability to DyTTHA3− after osmotic opening of the barrier with hypertonic arabinose gave Kis of 25–30 in forebrain regions. Estimates of reagent concentrations in brain interstitial fluid 30 min after dosing the animals indicated that both an extremely high dose of DyTTHA3− and severe disruption of the BBB would be required to shift the resonance frequency of extracellular Na+ appreciably. With the moderate degrees of BBB injury produced by short‐term ischemia, a dose of GdDTPA2− about 25 times the usual clinical dose of 0.1 mmol/kg would be required to quantify the injury by dynamic MRI.
Localized T1 measurements using an inversion‐recovery osiris method
Authors: Girard F. , Poulet P. , Steibel J. , Chambron J. 
Published: March 2007

AbstractThis work presents a new method for localized T1 measurements, based upon the OSIRIS scheme. It relies on the use of a non‐selective 180° pulse applied before the OSIRIS preparation cycle. The accuracy of the method has been verified with test tubes and in vivo for two nuclei, 1H and 19F. The accuracy of the T1 values is discussed, as well as possible applications of the inversion‐recovery method to non‐invasive in vivo pO2 measurements.
In Situ13C NMR quantification of hepatic glycogen
Authors: Borgs Maria , Van Hecke Paul , Overloop Kristin , Decanniere Caroline , Van Huffel Sabine , Stalmans Willy , Vanstapel Florent 
Published: March 2007

AbstractWe report on the 13C NMR visibility of the C‐1 glycosidic carbon of α‐particulate glycogen in perfused rat liver. We used rats fed ad libitum, animals refed after a 48 h fast with a sucrose supplement with or without glucocorticoid treatment, and gsd/gsd rats with a hepatic glycogen storage disease due to phosphorylase kinase deficiency. Thus we studied a wide range of glycogen levels (25‐140 mg/g liver). All livers were perfused with 15 mM glucose, to maintain constant glycogen levels. Failure to activate glycogen phosphorylase ensures stable glycogen levels in gsd/gsd livers. Natural abundance 13C NMR signals were calibrated against a phantom containing a fixed amount of glycogen. Accumulated free induction decays were analysed after Fourier transformation by numerical integration, or by direct analysis of the signal in the time domain using a non‐iterative method based on singular value decomposition. NMR quantification of the glycogen correlated well with the chemical determination over the whole concentration range. However, the precision (reproducibility) of glycogen determinations (be it by chemical methods or by NMR spectroscopy) may pose problems. Authors should be encouraged to report systematically on the precision of their methods.
In vivo19F one‐dimensional chemical shift imaging study of isoflurane uptake in rabbit brain
Authors: Venkatasubramanian P. N. , Shen Y. J. , Wyrwicz A. M. 
Published: March 2007

Abstract19F one‐dimensional chemical shift imaging and one‐pulse techniques were used to follow the uptake of isoflurane in rabbit brain in vivo. Brain isoflurane appeared mainly in two adjacent slices of cerebral cortex. Both slices showed increase in anesthetic content at similar rates. A biphasic first‐order uptake pattern with an initial fast component and a slower rate for the duration of the uptake was observed by the one‐pulse technique. Only the slower kinetic was followed by chemical shift imaging due to constraints on temporal resolution. Anesthetic levels in arterial blood reached equilibrium significantly earlier than in brain, suggesting a ‚restricted’︁ diffusion into brain tissue for this agent.
Non‐invasive investigation of parenchymal liver disease using 31P NMR spectroscopy
Authors: Roelsgaard Klaus , Stødkilde‐Jørgensen Hans , Dønstrup Sune , Djurhuus Jens Christian 
Published: March 2007

AbstractFour 31P NMR spectroscopy parameters were measured non‐invasively in the liver of 11 healthy pigs and 9 pigs with CCI4‐induced liver disease: (i) absolute molar concentration of phosphorous metabolites; (ii) pH based on the chemical shift of the Pi peak; (iii) T1 of the peaks in the 31P NMR spectrum; and (iv) changes in ATP, Pi and phosphomonoester after fructose administration. Liver disease was verified by histology and blood chemistry. The concentration of ATP decreased from 3.0(2.8–3.1) to 2.0(2.0–2.4) mM (median and quartiles) when liver disease was induced (p<0.05). The concentration of phosphodiesters (PDEs) decreased from 14.8(11.4–19.5) to 8.7(7.4–11.6) mM (p<0.05). pH increased by 0.1 unit. Ti relaxation times for the γ‐, α‐ and β‐ATP peaks increased from 320(249–471) to 577(506–638) ms (p<0.01), from 765(611–786) to 906(820–1058) ms (p<0.05) and from 402(327–509) to 579(543–743) ms (p<0.01), respectively, while T1 for the PDE peak decreased from 2204(1909–2404) to 1758(1502‐1894) ms (p<0.05). In the healthy animals injection of fructose was followed by a reduction of ATP (β‐ATP). In diseased livers this reduction was significantly smaller. In conclusion, it was possible non‐invasively to show differences between healthy and diseased livers in all NMR parameters evaluated. This means that 31P NMR Spectroscopy may have a potential as a non‐invasive diagnostic method for studying liver disease.
Effects of hyperoxia on T and resonance frequency weighted magnetic resonance images of rodent tumours
Authors: Karczmar G. S. , River J. N. , Li J. , Vijayakumar S. , Goldman Z. , Lewis M. Z. 
Published: March 2007

AbstractExperiments were performed to determine whether T and resonance frequency weighted MR images are sensitive to effects of hyperoxia on model tumors. Hyperoxia can increase tumor oxygen tension and thus affect T and/or the average resonance frequency within each image voxel due to the paramagnetism of oxygen itself or through modulation of the oxidation state of hemoglobin. Alternatively, changes in T during hyperoxia may reflect changes in tumor water content due to changes in systemic blood pressure. Mammary adenocarcinomas implanted in the flanks of rats were studied. Imaging sequences were preceded by two 90° pulses separated by an evolution period of 50 or 75 ms and followed by a crusher gradient to eliminate transverse magnetization. This pulse sequence produced images which were sensitized to both T and the average resonance frequency of each voxel. Images were produced at 2 T using a gradient echo imaging method with a TR of 3 s. Images obtained during inhalation of air and 100% O2 were compared. Significant increases in image intensity were observed in most tumors during hyperoxia, particularly at the tumor center. The increase was accentuated when the evolution period was increased and greatly reduced when a 180° refocusing pulse was placed at the center of the evolution period. These results suggest that hyperoxia reduces local magnetic susceptibility gradients leading to an increase in T or causes a shift in resonance frequency. The magnitude of this change may be a function of the rate at which oxygen is delivered to and metabolized by tumors and may also reflect tumor oxygen tension under normoxic conditions. Therefore, response to hyperoxia may provide useful contrast in MR images which could aid identification and characterization of tumors and provide an indirect measure of tumor blood flow and oxygenation.
Monitoring the initial expansion of focal ischaemic changes by diffusion‐weighted MRI using a remote controlled method of occlusion
Authors: Roussel S. A. , van Bruggen N. , King M. D. , Houseman J. , Williams S. R. , Gadian D. G. 
Published: March 2007

AbstractThe purpose of the present study was to quantify the early changes which occur on diffusion‐weighted imaging following focal cerebral ischaemia. We have developed a method for the remote occlusion of the middle cerebral artery in the rat, allowing early changes to be monitored and images to be acquired before and after ischaemia under identical conditions. Sequential diffusion‐weighted images were acquired before and for up to 6h following the occlusion. The data show that a hyperintense area appears soon after occlusion which expands during the first 2 h. It has previously been shown that the hyperintensity observed after ischaemia is linked to events associated with energy failure. Our findings are in good agreement with previous pathophysiological studies of focal ischaemia, which suggest a growing of the energy depleted area. In conclusion, our data extend the usefulness of diffusion‐weighted imaging to the study of the early spatial evolution of the most compromised area after focal ischaemia. Diffusion‐weighted imaging may constitute a very powerful tool to investigate pharmacological therapies which may interact with this evolution, both in experimental and clinical studies.
2D and 3D high resolution gradient echo functional imaging of the brain: Venous contributions to signal in motor cortex studies
Authors: Haacke E. M. , Hopkins A. , Lai S. , Buckley P. , Friedman L. , Meltzer H. , Hedera P. , Friedland R. , Klein S. , Thompson L. , Detterman D. , Tkach J. , Lewin J. S. 
Published: March 2007

AbstractRecent emphasis on high resolution gradient echo studies in functional imaging has led to the conclusion that there are likely three domains of response to the blood circulation in the brain when considering field inhomogeneity effects of the venous blood pre‐ and during activation. The first is a coherent effect due to large or macroscopic vessels on the order of the size of the voxel (ca 200–500 μm in most studies). These can lead to very large signal changes (up to 100%). The second is at the venule level (ca 50–200 μm) and is associated with smaller parenchymal changes (usually ca 10% or less). The third is at the capillary level and is associated with much smaller signal changes at 1.5T and even up to 4 T. The actual signal changes depend on field strength and sequence design. In this paper, we present our experience in detecting the first two domains with 2D and 3D gradient echo imaging at 1.5T. We find that high resolution enables visualization of the larger small veins in motor cortex studies and that, on occasion, it is possible to see the venule effects as well. We suggest a simple model to explain the large signal changes based on susceptibility changes and partial volume effects. Comparisons of the functional imaging data to this model and to MR angiographic studies are also shown as evidence of the venous sources of the susceptibility changes.
Potential pitfalls of functional MRI using conventional gradient‐recalled echo techniques
Authors: Kim Seong‐Gi , Hendrich Kristy , Hu Xiaoping , Merkle Hellmut , Uǧurbil Kâmil 
Published: March 2007

AbstractThe conventional gradient‐recalled echo technique, FLASH, has widely been used for functional MRI. FLASH results at 4 T with short TEs of 10–20 ms mimic those at 1.5 T with TEs of 25–50 ms or longer. Under these conditions, large venous vessels dominate the activated area; however, the use of longer TEs at 4 T reveals activation in gray matter areas as well as large vessels. Inflow effects of large vessels can be greatly reduced with centric‐reordering of phase‐encoding steps and inter‐image delay. Finger and toe movement paradigms show that functional activation maps are consistent with classical somatotopic maps, and are specific to the tasks. Navigator‐based motion correction generates functional maps with larger activation areas by reducing physiological noise.
Tissue specific perfusion imaging using arterial spin labeling
Authors: Detre John A. , Zhang Weiguo , Roberts David A. , Silva Afonso C. , Williams Donald S. , Grandis Donald J. , Koretsky Alan P. , Leigh John S. 
Published: March 2007

AbstractQuantitative magnetic resonance measurements of regional tissue perfusion can be obtained using magnetically labeled arterial water as a diffusable tracer. Continuous labeling is achieved in flowing spins using adiabatic inversion. The effects of continuous labeling of proximal arterial spins and T1 relaxation in distal tissue magnetization result in a steady‐state change in tissue magnetization which is tissue specific, i.e., it can be quantified in units of blood flow per gram of tissue per unit time. This magnetization is sampled using standard imaging sequences. The theoretical basis for this method, including the effects of macromolecular spin saturation, is reviewed. Recent results demonstrating the successful implementation of this technique in vitro and in vivo in rat brain, heart, and kidney, and in human brain and kidney are presented, as well as the use of a separate RF coil for arterial labeling to produce selective perfusion images in rat brain. This approach allows quantitative perfusion images to be obtained completely non‐invasively at the resolution of 1H MRI, and is useful in the clinical and investigational evaluation of organ physiology.
Effect of cardiac flow on gradient recalled echo images of the canine heart
Authors: Balaban Robert S. , Taylor Joni F. , Turner R. 
Published: March 2007

AbstractThe effect of coronary flow on the signal intensity of gradient recalled echo (GRE) MR images of the canine heart was evaluated at 4 T. Using a fully instrumented canine model, hyperperfusion (local adenosine infusion) and ischemia (local occlusion) were evaluated while coronary blood flow and venous oxygen tension were monitored. These studies demonstrated an increase in GRE signal intensity with increases in coronary blood flow and venous oxygenation. A local occlusion resulted in a small decrease in signal intensity in the affected area of the heart. The dependence of the signal changes on TE and TR indicated that the effects of high flow were associated with changes in the apparent T2 and T1. Both relaxation effects could reflect changes in tissue blood volume associated with the conditions studied. In addition, the apparent T2 changes were consistent with alterations in total tissue deoxyhemoglobin concentration and the changes in apparent T1 were consistent with inflow effects.
Reduction in myocardial high energy phosphate spin lattice relaxation times using manganese
Authors: Scholz Thomas D. 
Published: March 2007

AbstractParamagnetic contrast agents are being widely used in proton magnetic resonance imaging. The present study demonstrates the potential usefulness of paramagnetic contrast agents in 31P NMR spectroscopy. Using the Langendorff perfused rat heart, manganese chloride (Mn2+) at a concentration of 50 μM/L was added to the perfusate for 10 or 30 min. 31P NMR Ti relaxation times were subsequently measured at 121.5 MHz. After the 10 min exposure to Mn2+, 31P NMR Ti measurements of phosphocreatine and ATP were reduced by ca 25 and 50%, respectively, with no significant change in linewidths. A small additional decrease in Ti relaxation times after infusion of Mn2+ for 30 min was not significantly different from the values at 10 min. Potential uses of Mn2+ in 31P NMR spectroscopy include improving the S/N ratio of spectra and assessment of calcium ion channel activity.
The accuracy and reproducibility of measuring blood flow in murine tumours by the D2O uptake and clearance techniques
Authors: Bradley J. K. , Counsell C. J. R. , Bremner J. C. M. , Sansom J. M. , Adams G. E. 
Published: March 2007

AbstractThe use of D2O as an NMR visible tracer to monitor murine tumour blood flow (TBF) by both the wash‐in and wash‐out methods has been investigated. The factors that influence the models used to fit the data and the error on the measurement of the clearance and uptake rates have been assessed. The study concentrates on the uptake method which allows TBF to be measured without the need to use anaesthetic. Also, administering the D2O remotely to the mouse means it can remain undisturbed, in the magnet bore, between control and post‐treatment readings. The uptake method in KHT and RIF‐1 transplanted murine tumours has been investigated in a series of control experiments and after modifying TBF by hydralazine (5 mg/kg) and photodynamic therapy. These studies showed that four uptake measurements could be made on the same mouse at 20 min intervals without affecting TBF, control values were the same for anaesthetized and unanaesthetized mice and the values obtained for RIF‐1 tumours were marginally higher than those obtained for the KHT tumours. The decrease in TBF seen after modification was in good agreement with published data where TBF results were obtained by using D2O clearance, radioactive tracers or laser Doppler flowmetry.
1H MRS of high grade astrocytomas: Mobile lipid accumulation in necrotic tissue
Authors: Kuesel Annette C. , Sutherland Garnette R. , Halliday William , Smith Ian C. P. 
Published: March 2007

AbstractSixty‐four samples from six grade 4 astrocytomas were investigated ex vivo by 1H MRS at 360 MHz and subsequently by histopathology to obtain percentages of viable and necrotic tumour and grey and white matter. MR‐visible lipids were detected in 87% of tumour samples. Necrotic foci were <3 × 3 × 6 mm3. The means of the intensities/unit weight tissue of the lipid resonances at 5.33, 2.80, 1.29 and 0.89 ppm were significantly higher (p<0.05) for three sets of comparisons: samples with 85–100% vs 50–75%; with 50–75% vs 10–40% and with 10–40% vs 0–5% necrosis. For the lipid resonance at 2.04 ppm the difference in the means was significant only for samples with 50–75% compared to those with 85–100% necrosis, because for samples with <50% necrosis resonances from glutamine and possibly small amounts of glutamate, γ‐aminobutyrate and N‐acetylaspartate anions contribute significantly to the spectral area at 2.0 ppm. We conclude that necrotic foci below MRI resolution yield the resonances at 1.3 and 0.9 ppm, and contribute to the intense resonance at 2.0 ppm observed in in vivo 1H spectra of some high grade astrocytomas.