Effects of anoxia and ischemia on thallium exchange in rabbit myocardium (Conference) OSTI.GOV anoxia definition

The isolated, arterially perfused rabbit interventricular septum was used to study the effects of anoxia and ischemia on thallium (tl-201) exchange. Anoxia or ischemia was introduced for periods of 20, 40, or 60 minutes during either uptake or washout of tl-201. These interventions were followed by a reperfusion period. Effluent samples were collected during washout experiments. Anoxia lasting 20, 40, or 60 minutes during uptake resulted in a decrease in net tl-201 uptake, which was promptly reversed upon reoxygenation. Effluent washout curves demonstrated that an increased efflux of tl-201 anoxic encephalopathy icd 10 occurred during 20 and 40 minutes of anoxia. Surprisingly, comparison of the tl loss due to anoxia during uptake with the loss of tl during washout was consistent with an increased influx of tl-201 during the first 40 minutes of anoxia.


Between 40 and 60 minutes of anoxia, the increased efflux of tl-201 was reversed and the increase in tl-201 influx was absent. Total ischemia for 20, 40, or 60 minutes during uptake was followed by continued accumulation of tl-201 in 8 of 9 septa. Total ischemia during washout was followed by an immediate rapid washout of tl-201 before a new steady-rate was achieved. The authors conclude that these results represent more » important differences from those reported previously using K-42. Anoxia did not increase the influx of K-42 observed with tl-201. Also, 60 minutes of ischemia did not result in progressive loss of TL-201 as previously noted for K-42. This implies there are different sensitivities and/or mechanisms for tl as compared to K uptake. « less

Authors: krivokapich, J.; watanabe, C.R.; shine, K.I. Publication anxiety attack help date: sun jan 01 00:00:00 EST 1984 research org.: UCLA center for the health sciences, los angeles, CA OSTI identifier: 6932087 alternate identifier(s): OSTI ID: 6932087 report number(s): CONF-840619- journal ID: CODEN: JNMEA resource type: conference resource relation: journal name: J. Nucl. Med.; (united states); journal volume: 25:5; conference: 31. Annual meeting of the society of nuclear medicine, los angeles, CA, USA, 5 jun 1984 country of publication: united states language: english subject: 62 RADIOLOGY AND NUCLEAR MEDICINE; ANOXIA; DIAGNOSIS; ISCHEMIA; KRYPTON ISOTOPES; DIAGNOSTIC USES; UPTAKE; MYOCARDIUM; RADIOISOTOPE SCANNING; RABBITS; THALLIUM 201; PERFUSED ORGANS; SENSITIVITY ANALYSIS; TIME DEPENDENCE; ANIMALS; BETA DECAY RADIOISOTOPES; BODY anoxia at birth; CARDIOVASCULAR DISEASES; CARDIOVASCULAR SYSTEM; COUNTING TECHNIQUES; DAYS LIVING RADIOISOTOPES; DISEASES; ELECTRON CAPTURE RADIOISOTOPES; HEART; HEAVY NUCLEI; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; MAMMALS; MUSCLES; NUCLEI; ODD-EVEN NUCLEI; ORGANS; RADIOISOTOPES; SECONDS LIVING RADIOISOTOPES; THALLIUM ISOTOPES; USES; VASCULAR DISEASES; VERTEBRATES 550601* — medicine– unsealed radionuclides in diagnostics

AbstractNote = {the isolated, arterially perfused rabbit interventricular septum was used to study the effects of anoxia and ischemia on thallium (tl-201) exchange. Anoxia or ischemia was introduced for periods of 20, 40, or 60 minutes during either uptake or washout of tl-201. These interventions were followed by a reperfusion period. Effluent samples were collected during washout experiments. Anoxia lasting 20, 40, or 60 minutes during uptake resulted in a decrease in net nanoxia deep silence 5 tl-201 uptake, which was promptly reversed upon reoxygenation. Effluent washout curves demonstrated that an increased efflux of tl-201 occurred during 20 and 40 minutes of anoxia. Surprisingly, comparison of the tl loss due to anoxia during uptake with the loss of tl during washout was consistent with an increased influx of tl-201 during the first 40 minutes of anoxia. Between 40 and 60 minutes of anoxia, the increased efflux of tl-201 was reversed and the increase in tl-201 influx was absent. Total ischemia for 20, 40, or 60 minutes during uptake was followed by continued accumulation of tl-201 in 8 of 9 septa. Total ischemia during washout was followed by an immediate rapid washout of tl-201 before a new steady-rate was achieved. The authors conclude that these results represent important differences from those reported previously using K-42. Anoxia did not increase the influx of K-42 observed with tl-201. Also, 60 minutes of ischemia did not result in progressive loss of TL-201 as previously noted for K-42. This implies there are different sensitivities and/or mechanisms for tl as compared to K uptake.},

The effects of hypoxia and ischemia, as well as altered contractility, on thallium-201 (/sup 201/TI) kinetics were evaluated in 42 isolated isovolumetrically contracting rabbit hearts. In group A, three subgroups (n = 7 each) were studied that had either normal flow and oxygenation, hypoxia and normal flow, or ischemic flow and normal perfusate oxygen content. In group B, three subgroups (n = 7 each) were studied and all hearts had normal flow but the contractile state was either enhanced with isoproterenol or impaired by hypocalcemia. A hemoglobin-free buffer perfusate was used in all experiments and multiple timed collections of arterial more » and coronary anoxic brain damage symptoms sinus effluent were used to model myocardial isotope activity during 30 min of constant uptake followed by 30 min of tracer clearance. During ischemia, hypoxia and hypocalcemia peak developed pressure and peak positive and negative dp/dt were all significantly reduced when compared to normal hemodynamic parameters (p less than 0.01). As expected, isoproterenol significantly elevated these parameters (p less than 0.04). Myocardial /sup 201/TI kinetics were adequately described utilizing a bi-exponential model having a fast and slow component. Only ischemic hearts had significantly lower rate constants for /sup 201/TI uptake and clearance than normal hearts (p less than 0.001). The mean (+/- s.D.) myocardial uptake acute posthypoxic myoclonus treatment and clearance rates for /sup 201/TI (%/min) varied between 4.86 +/- 0.87 and 7.18 +/- 1.45 for the remaining groups of hearts. Therefore, myocardial /sup 201/TI kinetics appear to be dominated by coronary flow and may not reflect marked alterations in the metabolic and contractile state. These data suggest that normal /sup 201/TI uptake in impaired or hypercontractile cells, receiving normal flow, may not represent normal cellular function. « less

Positron emission tomography is a unique noninvasive imaging technique that provides cross-sectional images of radiotracer concentrations in myocardium and permits measurement of blood flow as well as metabolism. Ammonia and glutamate have been labeled with the positron-emitter /sup 13/N (half-life 10 minutes) for use with positron emission tomography as tracers of flow and metabolism, respectively. In order to characterize the fate of these /sup 13/N-labelled compounds in myocardium, isolated rabbit interventricular septa were used to study the kinetics of (/sup 13/N) glutamate ((/sup 13/N)glu) and /sup 13/NH/sub 3/ under aerobic nanoxia ncore retro review and anoxic conditions. Tissue analyses 6 minutes after injection of more » a (/sup 13/N)glu bolus into myocardium revealed that 70% of the /sup 13/N-label was present in (/sup 13/N)glu 12%, 11%, and 4% in (/sup 13/N)alanine ((/sup 13/N)ala), (/sup 13/N)aspartate ((/sup 13/N)asp), and (/sup 13/N)glutamine ((/sup 13/N)gln), respectively. The corresponding relative specific activities were 1.0:0.4:0.5:0.01. Anoxia resulted in a significant increase in (/sup 13/N)ala with a reduction in (/sup 13/N)glu. This was consistent with increased pyruvate production due to increased anaerobic glycolysis and transamination of pyruvate with (/sup 13/N)glu to yield (/sup 13/N)ala. In support of this, addition of 2 mm pyruvate to the perfusate under control conditions produced a tissue distribution of /sup 13/N similar to that with anoxia. Six minutes after a bolus of /sup 13/NH/sub 3/ during both control and anoxic conditions, 60% of the tissue /sup 13/N-label was in (/sup 13/N)gln with no detectable amounts in other amino acids. The rest of the /sup 13/N-label was in /sup 13/NH/sub 3/. Time-activity curve analyses demonstrated that anxieux en anglais anoxia significantly reduced the tissue retention of /sup 13/N-label from /sup 13/NH/sub 3/ but not from (/sup 13/N)glu. « less

The primary purpose of this study was to determine the effect of anoxia on the fate of N-13 labeled glutamate (glu) in myocardial tissue. Boluses of N-13-glu were injected arterially into isolated, arterially perfused rabbit interventricular septa under control conditions, during anoxia, and during perfusion with 2 mm pyruvate or lactate. In one set of experiments, time-activity curves were generated after the boluses. In another set of experiments, –0.1g of tissue was cut from the septum at 6 minutes after each injection. These samples were analyzed by reverse-phase HPLC. Under control anxiety attack symptoms in teenager conditions, glu accounted for 58% of the total N-13 more » radioactivity present in the sample and aspartate (asp), alanine (ala) and glutamine (gln) accounting for 20%, 16%, and 4%, respectively. During anoxia, the dominant change was an increase in ala to 40% of the N-13 radioactivity with an accompanying decrease in glu to 35%. Pyruvate perfusion produced a decrease in glu and increase in ala similar to the changes induced by anoxia. The changes due to lactate were in the same direction but less profound. Analysis of the time-activity curves revealed 2 components. The fraction of N-13 in the residual fraction was not different during anoxia as compared to control conditions. The t 1/2 of this fraction, however, became much shorter. The authors conclude that anoxia induces an increase severe diffuse axonal brain injury in ala secondary to increased pyruvate availability. This is reflected in the time-activity curves as a faster washout of N-13 from the septa. « less

To determine the effect of ischemia on myocardial clearance of thallium-201 (/sup 201/tl), we studied 12 dogs with ischemia produced after the injection of tl. Tl was given I.V. 10 minutes before left anterior descending (LAD) coronary artery ligation. /sup 85/sr-microspheres (MS) were administered 5 minutes later, and control biopsies were obtained from the myocardium. The LAD was tied and repeat biopsies obtained from the ischemic zone (IZ) and normal zone (NZ) 15 minutes and 2 h later. /sup 46/sc-MS were given just before the final biopsy. Tl activity in the IZ was not significantly different from that in the more » NZ either before LAD occlusion or 15 minutes and 2 h later. Tl clearance at the end of 2 h was not significantly different (27 +- 5% vs 28 +- 5%, IZ vs NZ respectively) between the two zones. The half-time of tl clearance from both the IZ and NZ was calculated at 4.5 hours (consistent with previously reported normal values). This occurred despite a decrease in regional myocardial blood flow to 24 +- 6% of control anoxic brain injury nursing diagnosis (P less than 0.01) in the IZ and an increase to 47 +- 14% of control (P less than 0.01) in the NZ during the study. We conclude that myocardial ischemia does not alter the normal rate of tl clearance from the myocardium. « less

The authors have noted that the pattern of reverse redistribution (RR) on rest-redistribution tl-201 scintigrams is a common finding in patients who have undergone streptokinase therapy (SKT) in evolving myocardial infarction. Thus they studied the significance of RR pattern in 70 patients who underwent SKT as well as rest-redistribution tl-201 study (7-10 days after SKT), coronary arteriography and resting radionuclide ventriculography. Tl-201 images were visually interpreted by consensus of three experienced observers with a 4-point scoring system (0=nl,3=severe defect), and RR was defined as decrease by at least 1 score between rest and 4-hr studies. Fifty of 70 patients (group more » I) showed RR pattern and the remaining 20 (group II) did not. On angiography, coronary arteries supplying the myocardial segments with RR were patent, suggesting that coronary flow has been reestablished to these regions. In 23 patients tl-201 % washout rate was quantitated anoxic tank retention time and showed significantly higher (p <.001) values in the regions demonstrating RR pattern compared to the adjacent normal regions (49+-15% vs. 24+-15%). Normal or near-normal wall motion was observed in 80% of myocardial segments with marked RR (2 score change) and 54% of those with mild RR (1 score change). The authors conclude that in patients who have undergone streptokinase therapy, reverse tl-201 redistribution is common in previously jeopardized myocardial segments with subsequent successful reperfusion and partial myocardial salvage. The reverse redistribution phenomenon may indicate higher than normal flow rates to the salvaged epicardial regions resulting in faster washout of tl-201. « less