Studies on the labeling of streptokinase with 99mTc for use as a radiopharmaceutical in the detection of deep-vein thrombosis: concise communication.
Streptokinase was labeled with 99mTc using both stannous chloride and stannous pyrophosphate as reducing agents. Sixty to seventy-five percent of the 99m Tc was incorporated into streptokinase using stannous chloride as a reducing agent at pH 1-2, wheras 50-60% was incorporated using stannous pyrophosphate at neutral pH. Increasing the pH from 2 to 7 in the presence of stannous chloride caused the release of 15-20% of the protein-bound 99mTc. Incorporation of 99mTc into protein was relatively slow: labeling required 2-3 hr at room temperature. The concentration of stannous pyrophosphate required for optimum labeling varied between 10(-5) and 10(-2) M. Polyacrylamide-gel electrophoresis showed that the filler substance in commercial streptokinase was also labeled with 99mTc. However pure streptokinase gave a homogenous protein band after polyacrylamide-gel electrophoresis. This protein band coincided with the peak of streptokinase-bound 99mTc. The results obtained may partially explain why 99mTc-labeled streptokinase lacks the necessary specificity for the satisfactory location of blood clots in vivo. (+info)
Myocardial uptake of technetium-99m stannous pyrophosphate in experimental viral myopericarditis.
Distribution of technetium-99m stannous pyrophosphate was studied in mice with experimentally induced viral myopericarditis. Myocardial and bone uptakes of Tc-PPi were compared in 55 mice inoculated with coxsackievirus B3 (Nancy strain). The myocardium-to-bone uptake ratio in 33 mice with myopericarditis was increased to a greater extent than that seen in 22 mice without myopericarditis (p less than 0.001). In the severely involved heart, the uptake per gram exceeded that in the bone. Myocardial uptake in myopericarditis can be visualized on a whole-body image using a pinhole collimator and a left lateral view. Our experimental studies suggest the potential clinical usefulness of myocardial scintigraphy in viral myopericarditis. (+info)
Postural exercise abnormalities in symptomatic patients with mitral valve prolapse.
The hemodynamics of the supine and upright exercise response in 16 symptomatic women with mitral valve prolapse (Group I) was compared with that in 8 asymptomatic normal control women (Group II). All subjects had supine and upright echocardiography and phonocardiography at rest and none demonstrated mitral regurgitation. All participants then underwent same day graded bicycle exercise, with simultaneous radionuclide angiography in both the upright and the supine posture. Catecholamines were measured, and a variety of volumetric and hemodynamic data were obtained. Group I (patients with mitral valve prolapse) demonstrated a reduced exercise tolerance, especially during upright exercise, as measured by both total exercise duration and maximal work load achieved. Mean total catecholamine measurements were similar between the two study groups at comparable mean heart rate, mean blood pressure and mean rate-pressure (double) product. No difference was observed in the ratio of right to left ventricular stroke counts at rest or during exercise regardless of posture, suggesting that exercise-induced mitral regurgitation did not occur. A difference was noted, however, in left ventricular end-diastolic volume index. At rest, Group I patients exhibited a 42% decrease in this index when sitting upright, and this difference from supine values persisted at submaximal (300 kpm/min) and peak work loads (34 and 29% difference, respectively). This contrasted with the control subjects whose upright end-diastolic volumes at rest, at 300 kpm/min and at peak exercise were reduced 21, 10 and 3%, respectively, compared with supine values. Cardiac index measurements reflected the reduced left ventricular end-diastolic volume observed.(ABSTRACT TRUNCATED AT 250 WORDS) (+info)
Effect of Sn(II) ion concentration and heparin on technetium-99m red blood cell labeling.
While convenience and economy favor the use of in vivo methods for labeling red blood cells (RBCs) with [99mTc]pertechnetate, previous reports suggested that patient medication such as heparin might interfere and thus result in inferior quality images. In this study, using a canine model, the role of stannous Sn(II) ion in in vivo and in vitro labeling of RBCs both in the presence and absence of a therapeutic dose of heparin was investigated. Our results showed that Sn(II) ion concentration of 20 micrograms/kg body weight levels provided better than 80% in vivo labeling efficiency enabling high quality blood-pool images even in the presence of therapeutic doses of heparin. (+info)
Acute myocardial infarction is being recognized as a spectrum of clinical subsets. This appreciation has been brought about to a large degree by the development of several new tools that can be applied clinically to aid in evaluation of patients with acute infarction, and in some cases to provide short and long-term prognostic information. In the realm of noninvasive methods, several tests utilizing radiopharmaceuticals and scintillation cameras have emerged and are rapidly becoming reliable diagnostic parameters in patients with coronary disease and infarction. Technetium 99m (stannous) pyrophosphate (TcPYP) scintigraphy, one of the first of these techniques to find clinical use, has been shown to be an accurate indicator of acute transmural myocardial infarction and provides added sensitivity and specificity to the diagnosis. Increased diagnostic accuracy, the dimension of visible localization and the potential for infarct sizing promise physicians better understanding of a patient's clinical presentation and a more rational approach to management. (+info)
Localization and stability of technetium-99m-Sn-pyrophosphate in rat neutrophils.
Technetium-99m has been suggested as an alternative radiolabel for white cells, and while its physical characteristics are nearly ideal, its stability and site of localization in this procedure are unclear. We examined these parameters by radiolabeling 10(8) neutrophils from rat peritoneum with 74 to 370 MBq technetium-99m-Sn-pyrophosphate. We found that the percentage of initial activity bound to neutrophils was quite variable, possibly because the radiolabel associated with several subfractions: 19.8 +/- 11.5% (mean +/- s.d.) with nuclei and plasma membranes, 25.6 +/- 3.9% with mitochondria, 26.6 +/- 9.8% with microsomes, and 29.2 +/- 6.9% with cytosol. Approximately 80-90% of the radioactivity associated with neutrophils was not bound to protein and only about one-half of the activity localized to cell membranes was removable over 4 hr by pepsin digestion. We concluded that the variable labeling efficiency was due to the radiolabel's rather loose association with several cellular subfractions rather than specific binding to a unique substrate. (+info)
The paradox image: a noninvasive index of regional left-ventricular dyskinesis.
The paradox image, a functional image of regional dyskinesis derived from the equilibrium (gated) radionuclide ventriculogram, was constructed by subtracting the background-corrected end-diastolic frame from the background-corrected end-systolic frame. In 11 patients showing dyskinesis by contract ventriculography, the percentage of left-ventricular picture elements containing paradox ranged from 3.6 to 55.6% (21.44% +/- 4.45 s.e.m.). In 11 patients with normokinesis and in eight patients with hypokinesis by contract ventriculography, the left-ventricular picture elements demonstrating paradox were less than 1.1% in all cases. In nine patients with akinesis, the percentage of left-ventricular picture elements containing paradox was 2.05% +/- 0.96 s.e.m. and was less tha 2% in seven patients. There was also an excellent agreement between the location of dyskinesis on the paradox image and that by contrast ventriculography. The paradox image is a sensitive indicator of left-ventricular dyskinesis and should be useful in the evaluation of patients with suspected left-ventricular asynergy. (+info)
Technetium-99m labeling of polymorphonuclear leukocytes: preparation with two different stannous agents.
A technique for in vitro labeling of human polymorphonuclear leukocytes with Tc-99m is described. Titration of stannous fluoride and stannous pyrophosphate concentrations for pretinning was performed, and optimal amounts of the stannous agents were added to polymorphonuclear leukocytes efficiently isolated from 100 ml of blood. Labeling with 10-15 mCi Tc-99m resulted, after three washings of cell suspensions, in yields of 1.6-4.8 mCi, corresponding to 20.5-33.5% of added tracer. Cell-bound activity in the final cell suspensions was 92.3% +/- 1.9 of the added dose. Cell function was not impaired by the labeling technique. Sterility and exclusion of bacterial endotoxins in the final cell suspensions were demonstrated. The method may prove of diagnostic value in the isolation, labeling, and reinjection of autologous leukocytes for scintigraphic imaging of acute inflammatory lesions. (+info)