Metabolism and inflammatory mediators in the peritendinous space measured by microdialysis during intermittent isometric exercise in humans.
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1. The metabolic processes that occur around the tendon during mechanical loading and exercise are undescribed in man. These processes are important for understanding the development of overuse inflammation and injury. 2. A microdialysis technique was used to determine interstitial concentrations of glycerol, glucose, lactate, prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) as well as to calculate tissue substrate balance in the peritendinous region of the human Achilles tendon. Recovery of 48-62 % (range) at rest and 70-77 % during exercise were obtained for glycerol, glucose and PGE2. 3. Six young healthy humans were studied at rest, during 30 min of intermittent static plantar flexion of the ankle at a workload corresponding to individual body weight, and during 60 min of recovery. Microdialysis was performed in both legs with simultaneous determination of blood flow by 133Xe washout in the same area, and blood sampling from the radial artery. 4. With exercise, the net release of lactate as well as of glycerol from the peritendinous space of the Achilles tendon increased 2-fold (P < 0.05). Furthermore a 100 % increase in interstitial concentration of PGE2 and TXB2 was found, but it was only significant for TXB2(P < 0.05). As peritendinous blood flow increased 2- to 3-fold during intermittent static contractions, this indicates also that the output of these substances from the tissue increased during exercise. 5. This study indicates that both lipid and carbohydrate metabolism as well as inflammatory activity is accelerated in the peritendinous region of the human Achilles tendon with dynamic loading. (+info)
Laterality in functional brain imaging studies of schizophrenia.
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Brain laterality in schizophrenia has been examined through the application of functional neuroimaging methods. These methods have included the 133Xenon technique for measuring cerebral blood flow (CBF); positron emission tomography for assessing rates of glucose metabolism, CBF, and neuroreceptor functioning; single photon emission computerized tomography for studying CBF and neuroreceptors; and functional magnetic resonance imaging for measuring changes attributable to CBF. This article highlights the application of this technology in schizophrenia research, emphasizing more recent studies that have evaluated hemispheric differences. There is evidence for lateralized abnormalities in some studies that have examined this dimension. In general, the results implicate abnormalities in left hemispheric activity. Recent advances in basic and clinical neuroscience provide an opportunity for focused application of functional imaging in neurobiological studies of schizophrenia. (+info)
Remote regional cerebral blood flow consequences of focused infarcts of the medulla, pons and cerebellum.
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The aim of this study was to evaluate regional and remote diaschisis of inferior brain stem or cerebellar infarcts in 25 patients presenting with relatively limited lesions. Patients presented with medullary, pontine or cerebellar infarction. METHODS: Lesions were evaluated on MRI (0.5 T). Regional cerebral blood flow (rCBF) was assessed by means of SPECT, after injection of 9rmTc-hexamethyl propyleneamine oxime (HMPAO) and, when possible, inhalation of 133Xe in the same session. For each method, asymmetry indices (Als), comparing contralateral to ipsilateral rCBF values, were calculated in four areas of each cerebral hemisphere and in the cerebellum and later compared with values obtained in healthy subjects (P = 0.05). RESULTS: Higher rCBF values were observed in the contralateral cerebellum in 2 of 7 patients with selective lateral medullary lesions, and cerebellar Als were significantly increased. When a cerebellar infarct was associated with a lateral medullary lesion, the cerebellar and contralateral hemispheric asymmetries were more severe. Unilateral paramedian pontine infarcts had more frequent consequences on the cerebellum (2 of 3 cases), with rCBF or tracer uptake being reduced in the ipsilateral or the contralateral lobe. Inverse cerebral hemispheric asymmetry could then be observed. Bilateral pontine lesions were difficult to evaluate. Using 99mTc-HMPAO, discrete cerebellar asymmetry was observed in 3 of 6 cases. Pure cerebellar infarcts in the posterior inferior cerebellar artery territory were always associated with a severe ipsilateral flow drop in the cerebellum, and contralateral hemispheric diaschisis was frequent (3 of 4 patients), predominating in the frontotemporal cortex and subcortical structures. This was also more obvious using 99mTC-HMPAO than 133Xe. Variance analysis showed that hemispheric diaschisis was more severe in mixed brain stem and cerebellar infarcts than in pure cerebellar or brain stem lesions. Furthermore, cerebellar and hemispheric AI values were not correlated with measurements of clinical deficits, disability or handicap. CONCLUSION: Unilateral and limited inferior brain stem lesions can have ipsi- or contralateral consequences on the cerebellum and cerebral hemispheres rCBF. These remote effects are related to lesions of the main pathways joining these structures, resulting in deactivation and, in some cases, overactivation. Contrary to what has been suggested, consequences on cerebral hemispheres are more severe in mixed cerebellar and brain stem infarcts than in pure cerebellar lesions. (+info)
Noninvasive quantification of cerebral blood flow using 99mTc-ECD and SPECT.
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The aim of this study was to develop a simple, noninvasive method for quantifying regional cerebral blood flow (rCBF) using 99mTc-ethyl cysteinate dimer (ECD) by a single SPECT scan and single venous sampling. METHODS: Using a three-compartment model, we introduced the regional brain fractionation index (BFI), Cb(Ts)/integral of 0-Ts Ca(tau)dtau [Ca(t), arterial input; Cb(t), brain activity]. Regional BFI obtained at the optimum time Ts (min) was converted to rCBF using an exponential function, which was obtained by analyzing the relationship between regional BFI and rCBF (= F) obtained by the standard 133Xe inhalation SPECT method. The integral of the concentration of 99mTc-ECD in arterial blood corrected for physical decay [Ca(t)] in BFI was estimated from a single venous blood sample obtained at the optimum time Tv using the regression line obtained by analyzing the relationship between the integral of Ca(t) and venous sample data. The data come from three groups of patients. The first group of patients (n = 16) underwent a complete 99mTc-ECD BFI study with measurement of Ca(t) and dynamic SPECT scanning, as well as a 133Xe inhalation study to measure rCBF The results were used to analyze the relationship between regional BFI and rCBF (obtained with 133Xe) and to determine the optimum time Ts for obtaining BFI. Data from the second group of patients (n = 15) were used to analyze the relationship between the integral of Ca(t) and venous sample data and to determine the optimum time Tv for one-point venous blood sampling. Finally, the third group of patients (8 patients, 10 studies) was used to validate the current method by comparing the results with 133Xe inhalation SPECT. RESULTS: Regional BFI obtained at time Ts = 20 min showed good agreement (r = 0.907; a = 0.552, b = 0.962) with rCBF. The venous sample data obtained at time Tv = 6 min showed a good correlation (r = 0.988) with BFI. In comparing rCBF values thus obtained and those obtained by the 133Xe method, we found a good correlation (r = 0.917, slope = 1.01). CONCLUSION: The proposed method has three advantages: (a) accurate quantification of rCBF without underestimation in the high flow range, (b) simplicity and noninvasiveness and (c) the ability to use any type of SPECT camera for the study. (+info)
Effects of intracoronary radiation on thrombosis after balloon overstretch injury in the porcine model.
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BACKGROUND: The main complications of PTCA remain thrombosis and restenosis. Recent studies have demonstrated reduction in the neointimal hyperplasia after intracoronary radiation (IR) with doses of 10 to 25 Gy of ionizing radiation delivered by either beta- or gamma-emitters to injured vessels. The purpose of this study was to examine the effect of ionizing radiation on the thrombosis rate (TR) of injured porcine coronary arteries. METHODS AND RESULTS: Thirty-four juvenile swine (63 coronary arteries) were subjected to overstretch balloon injury followed by IR with doses of 0 to 18 Gy of either beta- or gamma-radiation. Two weeks after treatment, tissue sections were perfusion-fixed, stained with hematoxylin-eosin and Verhoeff-van Gieson's stain, and analyzed for presence of a thrombus, thrombus morphology, and neointima formation by computer-assisted histomorphometry techniques. Although the overall TR increased dose-dependently from 0 to 18 Gy prescribed dose, luminal thrombi decreased. Thrombus area also decreased with increasing radiation dose, whether assessed at the prescription point or at the luminal surface, which corresponded to decreased intimal area. Furthermore, luminal thrombi present after IR tended to consist mostly of fibrin and thus were less organized than in controls. CONCLUSIONS: These results suggest that IR induces thrombosis but does not necessarily compromise the lumen. Strategies for reducing TR may further decrease intimal area as well as increasing the safety of this therapy. (+info)
Serial measurement of cerebral blood flow using external counting of microspheres.
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Described is a modified method of measuring organ blood flow which combines the serial injection of a standard dose of microspheres and the external counting of their gamma activity when they are distributed to the tissues. The method produces similar results to measurements of grey matter blood flow by the clearance of 133xenon. (+info)
Radioactive contamination of packing materials from a xenon-133 shipment.
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OBJECTIVE: We report on radioactive contamination of packing materials from a 133Xe shipment. METHODS: A 2-vial 133Xe shipment was monitored using a survey meter before opening. Both vials were immediately assayed in a dose calibrator. The packing materials were monitored and contamination was detected. RESULTS: The maximum surface reading of the shipment was 7.0 microSv/h. This was higher than previous shipments (1.1 +/- 0.3 microSv/h). One vial was 544 MBq while the other vial was only 474 MBq. Previous shipments were 565 +/- 13 MBq/vial. Monitoring and imaging revealed 133Xe contamination within the packing materials. Xenon-133 escaped from the packing materials over time. The lower activity vial continued to leak 133Xe over time. CONCLUSION: Careful monitoring of 133Xe shipments before and after opening along with assaying vials on receipt can indicate vial leakage and radioactive contamination so steps can be taken to minimize radiation exposure to the staff. (+info)
Hypofixation and hyperfixation of 99mTc-hexamethyl propyleneamine oxime in subacute cerebral infarction.
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The relationship between hypofixation and hyperfixation of 99mTc-hexamethyl propyleneamine oxime (99mTc-HMPAO) remains unclear. The purpose of this study was to compare 99mTc-HMPAO SPECT with regional cerebral blood flow (CBF) imaging using 133Xe inhalation in patients with subacute cerebral infarction and to investigate the behavior of 99mTc-HMPAO in the infarct area using dynamic SPECT. METHODS: 133Xe and consecutive 99mTC-HMPAO SPECT studies, the latter of which consisted of dynamic and static scanning, were performed on 51 patients (22 women, 29 men; age range, 40-83 y; mean age, 61 y) with cortical infarction in the middle cerebral artery territory 13-15 d after stroke onset. One region of interest (ROI) was drawn in the infarct area. The control ROI was mirrored to the contralateral side, and the same set of ROIs was applied to all SPECT studies. Fractional fixation of 99mTc-HMPAO in the infarct area was evaluated relatively as the ratio of the infarct-to-control region in 99mTc-HMPAO static tomograms/the ratio of the infarct-to-control region in CBF images using 133Xe inhalation and was classified as hyperfixation when this value was >1.1 and hypofixation when this value was <0.9. To investigate the behavior of 99mTc-HMPAO in the infarct area, the second (36-72 s after tracer injection) and eighth (252-288 s after tracer injection) of 8 dynamic scans were selected, and the washout rate was calculated using the formula: 1 - (mean count in the eighth scan/mean count in the second scan). RESULTS: The infarct area showed hyperfixation of 99mTc-HMPAO when CBF in the area was 35 mL/100 g/min or less and showed hypofixation when CBF was >45 mL/U100 g/min. The washout rate was usually negative when CBF imaging using 133Xe inhalation was <20 mL/100 g/min but was positive when it was >45 mUL/100 g/min. The washout rate was negative when the infarct area showed hyperfixation of 99mTc-HMPAO but was positive when it showed hypofixation. CONCLUSION: 99mTc-HMPAO SPECT underestimates CBF in high-flow regions and overestimates CBF in low-flow regions of subacute cerebral infarction. 99mTc-HMPAO hypofixation and hyperfixation are associated with backdiffusion from the brain to blood and gradual accumulation of hydrophilic metabolites, respectively. Dynamic images should be useful for discriminating between 99mTc-HMPAO hypofixation and hyperfixation. (+info)