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1.
We used the dual capability of hyperpolarized 129Xe for spectroscopy and imaging to develop new measures of xenon diffusing capacity in the rat lung that (analogously to the diffusing capacity of carbon monoxide or DLCO) are calculated as a product of total lung volume and gas transfer rate constants divided by the pressure gradient. Under conditions of known constant pressure breath-hold, the volume is measured by hyperpolarized 129Xe MRI, and the transfer rate is measured by dynamic spectroscopy. The new quantities (xenon diffusing capacity in lung parenchyma (DLXeLP)), xenon diffusing capacity in RBCs (DLXeRBC), and total lung xenon diffusing capacity (DLXe)) were measured in six normal rats and six rats with lung inflammation induced by instillation of fungal spores of Stachybotrys chartarum. DLXeLP, DLXeRBC, and DLXe were 56 +/- 10 ml/min/mmHg, 64 +/- 35 ml/min/mmHg, and 29 +/- 9 ml/min/mmHg, respectively, for normal rats, and 27 +/- 9 ml/min/mmHg, 42 +/- 27 ml/min/mmHg, and 16 +/- 7 ml/min/mmHg, respectively, for diseased rats. Lung volumes and gas transfer times for LP (TtrLP) were 16 +/- 2 ml and 22 +/- 3 ms, respectively, for normal rats and 12 +/- 2 ml and 35 +/- 8 ms, respectively, for diseased rats. Xenon diffusing capacities may be useful for measuring changes in gas exchange associated with inflammation and other lung diseases.  相似文献   
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Five out of 12 physically healthy patients with depression undergoing a tyramine pressor test developed cardiac arrhythmias. These arrhythmias occurred in drug-free patients in three out of 12 infusions following as little as 0.03 mg/kg of tyramine and after moclobemide, a reversible inhibitor of monoamine oxidase-A, in four out of 14 tyramine infusions with as little as 0.04 mg/kg of tyramine. The arrhythmias seen were independent of patient's age and occurred both before and after 30 mmHg elevations in systolic blood pressure. Electrocardiographic abnormalities and arrhythmias seen were a loss of p waves, sinus tachycardia, frequent atrial ectopic beats, atrial premature beats, Wenckebach phenomenon, junctional rhythm, ventricular ectopics, varying QRS configurations, and ventricular bigeminy. Tyramine, both oral and intravenous, caused similar reproducible changes in dogs, though not in rats, mice or guinea pigs. Practical implications are that tyramine pressor testing in humans should be performed cautiously and only with adequate cardiac monitoring and resuscitation facilities at hand. These findings suggest that a normal dietary component can induce serious cardiac arrhythmias, and that a low-tyramine diet may be of value for patients who are susceptible to cardiac arrhythmias.  相似文献   
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PURPOSE: To evaluate the feasibility and accuracy of automated analysis software for use with multidetector computed tomographic angiography (CTA) in the exact grading of internal carotid artery stenosis. METHODS: A retrospective pilot trial was performed using CTA datasets from 87 stenotic carotid arteries in 46 consecutive patients (34 men; median age 73.5 years) with known cerebrovascular disease. Internal carotid artery (ICA) stenosis was graded according to NASCET criteria by 2 experienced vascular radiologists in consensus using axial source images as well as curved planar reformations and digital subtraction angiography (DSA). These results were then compared to those obtained from the automated CTA analysis software and the results of manually adapted automated CTA analysis. RESULTS: Measurements from automated CTA analysis as well as manually adapted automated CTA analysis correlated significantly to those of axial/reformatted CTA and DSA (r=0.53 and r=0.82, r=0.58 and 0.70, respectively, all p<0.05). Compared to axial/reformatted CTA measurements, automated CTA analysis had a median difference of -16%, while manually adapted automated CTA had a difference of -10%. Corresponding differences in a comparison with DSA were +4% and -2%, respectively. Circumferential calcification or kinking of the ICA origin did not significantly interfere with these differences (all p>0.05). Sensitivities for the detection of ICA stenosis >70% by manually adapted automated CTA analysis and automated measurement were 44.2% and 34.9%, respectively, versus axial/reformatted CTA. Compared with DSA as the gold standard, the sensitivities were 54.2% and 62.5%, respectively. Specificities for both methods and gold standards all exceeded 90%. CONCLUSION: Commercially available automated CTA analysis is a feasible tool, but sensitivities are still not sufficient for clinical application.  相似文献   
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Alcohol and Platelet Function   总被引:3,自引:0,他引:3  
Epidemiological studies have shown that moderate consumption of alcoholic beverages is inversely related to the incidence of the complications of coronary artery disease. The protective effect of ethanol may be partially attributable to an inhibitory effect of ethanol on platelets. This article summarizes the experimental observations that ethanol inhibits platelet responses to specific physiological agonists. In alcoholics, various platelet defects have been observed, but these may be influenced by metabolic factors rather than the presence of ethanol alone. The acute effects of ethanol on platelet functions both in vivo and ex vivo will be reviewed. Evidence will be presented demonstrating that ethanol added acutely in vitro inhibits phospholipase A2 in stimulated platelets. The interaction of ethanol with other signal transduction pathways will also be discussed.  相似文献   
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Positive chronotropic responses of rat isolated atria to phenylephrine were reduced by propranolol (0.3 microM) and the residual response was further depressed by the selective alpha 1-adrenoceptor antagonist prazosin (1 nM) but not yohimbine (10 nM), confirming that a component of the response to phenylephrine was due to activation of alpha 1-adrenoceptors. When beta-adrenoceptors were blocked by propranolol, the positive chronotropic response to phenylephrine was enhanced by increasing the calcium concentration and by the calcium channel activator Bay K 8644 (0.1 microM), whereas the response was decreased by lowering the calcium concentration and by the calcium antagonists verapamil (10 nM), nifedipine (10 nM) and diltiazem (100 nM). In the presence of prazosin, when phenylephrine acts only on beta-adrenoceptors, calcium antagonists had no effect on the response. In rat isolated aortic strips in a calcium-free, high K+ (40 mM) solution, verapamil (10 nM), nifedipine (10 nM) and diltiazem (100 nM) shifted the calcium-induced contraction curves to the right, but prazosin (10 nM) had no effect, indicating that it is not a calcium antagonist. The calcium antagonists in the concentrations stated above had no effect on phenylephrine-induced contractions of rat aortic strips in normal Krebs-Henseleit solution, indicating that they did not block alpha 1-adrenoceptors in these concentrations. Taken together, these data suggest that the positive chronotropic effect of phenylephrine resulting from activation of alpha 1-adrenoceptors involves an increased influx of calcium through channels that are sensitive to organic calcium antagonists.  相似文献   
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Rilmenidine differs from clonidine in that it lacks histamine-like activity   总被引:1,自引:0,他引:1  
Studies were carried out to determine whether rilmenidine, a recently introduced antihypertensive agent with a similar mechanism of action of clonidine, possesses histamine-like activity on tissues responding to histamine H2-receptor agonists. In guinea-pig isolated atria, both histamine and clonidine caused concentration-dependent positive chronotropic effects which were blocked by the histamine H2-receptor antagonist cimetidine (5 microM); in contrast, rilmenidine produced a concentration-dependent negative chronotropic effect which was not altered by cimetidine. In stilboestrol-treated rat isolated uterus contracted by KCl, histamine and clonidine produces concentration-dependent relaxations which were blocked by cimetidine (5 microM); rilmenidine also produced relaxation, but this was not affected by cimetidine (5 microM). These findings suggest that rilmenidine, unlike clonidine, does not activate histamine H2-receptors in either guinea-pig atria or rat uterus.  相似文献   
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In erythropoietic protoporphyria (EPP), there is excessive production of protoporphyrin, primarily in the bone marrow, resulting in increased biliary excretion of this heme precursor. Some patients will develop progressive liver disease that may ultimately require liver transplantation. However, excessive production of protoporphyrin by the bone marrow continues after transplantation, which may cause recurrent disease in the allograft. This study was performed to define post-transplant survival, the risk of recurrent disease, and specific management issues in patients transplanted for EPP liver disease. The patients studied consisted of twelve males and eight females, with an average age of 31 (range, 13-56) years at the time of transplantation. The estimated maximum MELD score prior to transplant was 21 (range, 15-29). Unique complications in the perioperative period were light induced tissue damage in four patients and neuropathy in six, requiring prolonged mechanical ventilation in four. Patient and graft survival rates were 85% at 1 year, 69% at 5 years, and 47% at 10 years. Recurrent EPP liver disease occurred in 11 of 17 patients (65%) who survived more than 2 months. Three patients were retransplanted at 1.8, 12.6, and 14.5 years after the initial transplant for recurrent EPP liver disease. In conclusion, the 5-year patient survival rate in patients transplanted for EPP liver disease is good, but the recurrence of EPP liver disease appears to diminish long term graft and patient survival.  相似文献   
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