American Journal of Physiology-Heart and Circulatory Physiology, 1991
This study determined whether the rapidity of myocardial metabolic and contractile recovery after... more This study determined whether the rapidity of myocardial metabolic and contractile recovery after brief coronary occlusion depends upon the intensity of reactive hyperemia. We also tested the hypothesis that coronary flow rate modulates contractility after brief myocardial ischemia, independent of changes in phosphorus metabolites. Eight open-chest pigs were studied with phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy with 14 s time resolution. After a 29-s anterior descending coronary occlusion, peak Doppler coronary flow velocity was alternately unrestricted (normal hyperemia, 443 +/- 40% of control) or limited to 159 +/- 9% of control. During 29 s coronary occlusion, phosphocreatine-to-inorganic phosphate ratio (PCr/Pi) and systolic segment shortening in the ischemic region fell to 28 +/- 4 and 7 +/- 7% of control, respectively. With normal hyperemia, PCr/Pi and segment shortening recovered within 29 s. With blunted hyperemia, recovery of both parameters was delayed a...
American Journal of Physiology-Heart and Circulatory Physiology, 1990
This study used 31P nuclear magnetic resonance (NMR) spectroscopy to determine whether the magnit... more This study used 31P nuclear magnetic resonance (NMR) spectroscopy to determine whether the magnitude and duration of myocardial reactive hyperemia (RH) reflect a commensurate derangement of myocardial high-energy phosphate (HEP) metabolism, or if coronary blood flow (CBF) and HEP metabolism are dissociated during RH. Twelve open-chest anesthetized pigs were studied during and after 24 s occlusion of the anterior descending coronary artery. CBF velocity was measured with a Doppler probe. NMR time resolution (4.8 s) was obtained by summing corresponding short blocks of data from multiple occlusions. During occlusion, phosphocreatine (PCr) declined to 65 +/- 5% (mean +/- SE) of control accompanied by increased spectral intensity of the Pi + phosphomonester region. By 20 s of reflow, HEPs had returned to control levels, but CBF was still elevated at 282 +/- 18% of control and remained elevated for an additional 53 +/- 7 s, during which 44 +/- 6% of total RH flow occurred. Therefore, the...
Biomedical instrumentation & technology / Association for the Advancement of Medical Instrumentation
The authors sought to define a method to use magnetic resonance (MR) to assess cardiac function b... more The authors sought to define a method to use magnetic resonance (MR) to assess cardiac function by obtaining short-axis images of the left ventricle (LV) in humans. Sagittal and axial scout1H MR images were used in the protocol. The long axis of the LV was defined in both planes using the mitral valve and left ventricular apex as references. Based on this double angulation, the acquisition planes were created for a series of parallel short-axis images extending from the base to the apex of the left ventricular cavity. Cardiac images acquired with a fast-field echo technique, six slices with 16-20 phases per RR interval, were analyzed, representing the initial 75-80% of the cardiac cycle. For each slice, the endocardial border of the left ventricular chamber was manually traced. Using Simpson's rule, the total LV volume at a given phase was determined, considering the traced area, thickness, and position in three-dimensional space of each of the six constituent slices. The calcul...
Localized phosphorus-31 magnetic resonance (MR) spectroscopy in humans has previously been accomp... more Localized phosphorus-31 magnetic resonance (MR) spectroscopy in humans has previously been accomplished with surface coils by means of depth-resolved surface coil spectroscopy or rotating frame experiments, in which the extent of tissue sampled critically depends on surface coil placement. The authors' goal was to modify the surface coil image-selected in vivo spectroscopy (ISIS) experiment to accomplish three-dimensional volume selection through application of selective pulses in the presence of B0 gradients. Advantages of ISIS include the ability to use proton images to define the volume of interest (VOI) and reduced dependence on exact positioning of the surface coil. However, rapid replication of the surface coil ISIS experiment can cause spectral contamination from signals originating outside the VOI. A modified version of the ISIS experiment was developed to alleviate contamination under conditions of rapid replication. Applications of localized P-31 MR spectroscopy for ob...
... Martin CR, Cobb C, Tatter Q Johnson CS, Haywood U: Myocardial fibrosis and in-farction in sic... more ... Martin CR, Cobb C, Tatter Q Johnson CS, Haywood U: Myocardial fibrosis and in-farction in sickle cell disease, submitted for pub-lication. ... 10:141-144,1989. Norris S, Johnson CS and Haywood U: Sickle cell anemia: Does myocardial ischemia occur during cri-sis? ...
Changes in high-energy phosphate metabolism may be important in the regulation of myocardial cont... more Changes in high-energy phosphate metabolism may be important in the regulation of myocardial contractile function during ischemia. This study sought to determine the dynamic relation between myocardial contractile function and high-energy phosphate metabolism during and following brief (24-second) coronary occlusion, when large and rapid changes in both parameters occur. Eight anesthetized, open-chest pigs were instrumented with a Doppler flow probe and occluder on the anterior descending coronary artery, segment length crystals in the anterior left ventricular wall, and a surface coil for phosphorus-31 nuclear magnetic resonance spectroscopy. Phosphorus-31 spectra were reconstructed with a 4.8-second time resolution by summing corresponding short blocks of data from multiple occlusions. Metabolic and functional parameters were unchanged during the first 4.8 seconds of occlusion. During the remainder of occlusion, phosphocreatine progressively declined to 66 +/- 3% of control, inorg...
The changes in myocardial high energy phosphates and pH during regional ischemia, and their poten... more The changes in myocardial high energy phosphates and pH during regional ischemia, and their potential role in mediating functional abnormalities, is unclear. To determine the degree of regional blood flow reduction required to induce changes in high energy phosphates and pH, and to correlate these metabolic changes with alterations in blood flow, 31P nuclear magnetic resonance spectroscopy was employed in an in vivo porcine model of graded coronary stenosis. Simultaneous measurements of regional blood flow and phosphate compounds were made during various steady-state degrees of regional ischemia in which subendocardial blood flow was reduced by as much as 80%. ATP did not fall over the total range of graded ischemia, while phosphocreatine (PCr), inorganic phosphate (Pi), and pH all changed progressively after blood flow was reduced below 50% of normal. The ratio of PCr/Pi (a measure of the energy reserve of the myocardium) was strongly correlated to subendocardial blood flow (r = 0....
porcine myocardium in vivo. Response of myocardial metabolites to graded regional ischemia: 31P N... more porcine myocardium in vivo. Response of myocardial metabolites to graded regional ischemia: 31P NMR spectroscopy of
A 13C-NMR study of the long-acting opiate antagonists naloxazone (I) and naltrexazone (II) and th... more A 13C-NMR study of the long-acting opiate antagonists naloxazone (I) and naltrexazone (II) and the long-acting opiate agonist oxymorphazone (III) revealed that these compounds are formed as mixtures of their anti and syn isomers. The less crowded anti isomer was found to be the major product in all cases (ca. 80%). N,N-Dimethyl derivatives of naloxazone (IV), naltrexazone (V), and oxymorphazone (VI), which are sterically more crowded than the corresponding unsubstituted hydrazones I-III, were formed as almost exclusively anti isomers. Pure anti isomer of II was obtained as a 1:1 complex with ethanol. No syn-anti equilibration was observed during the 13C-NMR experiment in any of the cases studied. The relevance of our finding about the syn-anti isomerism of the opiate hydrazones to the understanding of their interactions with the opiate receptor is discussed.
American Journal of Physiology-Heart and Circulatory Physiology, 1991
This study determined whether the rapidity of myocardial metabolic and contractile recovery after... more This study determined whether the rapidity of myocardial metabolic and contractile recovery after brief coronary occlusion depends upon the intensity of reactive hyperemia. We also tested the hypothesis that coronary flow rate modulates contractility after brief myocardial ischemia, independent of changes in phosphorus metabolites. Eight open-chest pigs were studied with phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy with 14 s time resolution. After a 29-s anterior descending coronary occlusion, peak Doppler coronary flow velocity was alternately unrestricted (normal hyperemia, 443 +/- 40% of control) or limited to 159 +/- 9% of control. During 29 s coronary occlusion, phosphocreatine-to-inorganic phosphate ratio (PCr/Pi) and systolic segment shortening in the ischemic region fell to 28 +/- 4 and 7 +/- 7% of control, respectively. With normal hyperemia, PCr/Pi and segment shortening recovered within 29 s. With blunted hyperemia, recovery of both parameters was delayed a...
American Journal of Physiology-Heart and Circulatory Physiology, 1990
This study used 31P nuclear magnetic resonance (NMR) spectroscopy to determine whether the magnit... more This study used 31P nuclear magnetic resonance (NMR) spectroscopy to determine whether the magnitude and duration of myocardial reactive hyperemia (RH) reflect a commensurate derangement of myocardial high-energy phosphate (HEP) metabolism, or if coronary blood flow (CBF) and HEP metabolism are dissociated during RH. Twelve open-chest anesthetized pigs were studied during and after 24 s occlusion of the anterior descending coronary artery. CBF velocity was measured with a Doppler probe. NMR time resolution (4.8 s) was obtained by summing corresponding short blocks of data from multiple occlusions. During occlusion, phosphocreatine (PCr) declined to 65 +/- 5% (mean +/- SE) of control accompanied by increased spectral intensity of the Pi + phosphomonester region. By 20 s of reflow, HEPs had returned to control levels, but CBF was still elevated at 282 +/- 18% of control and remained elevated for an additional 53 +/- 7 s, during which 44 +/- 6% of total RH flow occurred. Therefore, the...
Biomedical instrumentation & technology / Association for the Advancement of Medical Instrumentation
The authors sought to define a method to use magnetic resonance (MR) to assess cardiac function b... more The authors sought to define a method to use magnetic resonance (MR) to assess cardiac function by obtaining short-axis images of the left ventricle (LV) in humans. Sagittal and axial scout1H MR images were used in the protocol. The long axis of the LV was defined in both planes using the mitral valve and left ventricular apex as references. Based on this double angulation, the acquisition planes were created for a series of parallel short-axis images extending from the base to the apex of the left ventricular cavity. Cardiac images acquired with a fast-field echo technique, six slices with 16-20 phases per RR interval, were analyzed, representing the initial 75-80% of the cardiac cycle. For each slice, the endocardial border of the left ventricular chamber was manually traced. Using Simpson's rule, the total LV volume at a given phase was determined, considering the traced area, thickness, and position in three-dimensional space of each of the six constituent slices. The calcul...
Localized phosphorus-31 magnetic resonance (MR) spectroscopy in humans has previously been accomp... more Localized phosphorus-31 magnetic resonance (MR) spectroscopy in humans has previously been accomplished with surface coils by means of depth-resolved surface coil spectroscopy or rotating frame experiments, in which the extent of tissue sampled critically depends on surface coil placement. The authors' goal was to modify the surface coil image-selected in vivo spectroscopy (ISIS) experiment to accomplish three-dimensional volume selection through application of selective pulses in the presence of B0 gradients. Advantages of ISIS include the ability to use proton images to define the volume of interest (VOI) and reduced dependence on exact positioning of the surface coil. However, rapid replication of the surface coil ISIS experiment can cause spectral contamination from signals originating outside the VOI. A modified version of the ISIS experiment was developed to alleviate contamination under conditions of rapid replication. Applications of localized P-31 MR spectroscopy for ob...
... Martin CR, Cobb C, Tatter Q Johnson CS, Haywood U: Myocardial fibrosis and in-farction in sic... more ... Martin CR, Cobb C, Tatter Q Johnson CS, Haywood U: Myocardial fibrosis and in-farction in sickle cell disease, submitted for pub-lication. ... 10:141-144,1989. Norris S, Johnson CS and Haywood U: Sickle cell anemia: Does myocardial ischemia occur during cri-sis? ...
Changes in high-energy phosphate metabolism may be important in the regulation of myocardial cont... more Changes in high-energy phosphate metabolism may be important in the regulation of myocardial contractile function during ischemia. This study sought to determine the dynamic relation between myocardial contractile function and high-energy phosphate metabolism during and following brief (24-second) coronary occlusion, when large and rapid changes in both parameters occur. Eight anesthetized, open-chest pigs were instrumented with a Doppler flow probe and occluder on the anterior descending coronary artery, segment length crystals in the anterior left ventricular wall, and a surface coil for phosphorus-31 nuclear magnetic resonance spectroscopy. Phosphorus-31 spectra were reconstructed with a 4.8-second time resolution by summing corresponding short blocks of data from multiple occlusions. Metabolic and functional parameters were unchanged during the first 4.8 seconds of occlusion. During the remainder of occlusion, phosphocreatine progressively declined to 66 +/- 3% of control, inorg...
The changes in myocardial high energy phosphates and pH during regional ischemia, and their poten... more The changes in myocardial high energy phosphates and pH during regional ischemia, and their potential role in mediating functional abnormalities, is unclear. To determine the degree of regional blood flow reduction required to induce changes in high energy phosphates and pH, and to correlate these metabolic changes with alterations in blood flow, 31P nuclear magnetic resonance spectroscopy was employed in an in vivo porcine model of graded coronary stenosis. Simultaneous measurements of regional blood flow and phosphate compounds were made during various steady-state degrees of regional ischemia in which subendocardial blood flow was reduced by as much as 80%. ATP did not fall over the total range of graded ischemia, while phosphocreatine (PCr), inorganic phosphate (Pi), and pH all changed progressively after blood flow was reduced below 50% of normal. The ratio of PCr/Pi (a measure of the energy reserve of the myocardium) was strongly correlated to subendocardial blood flow (r = 0....
porcine myocardium in vivo. Response of myocardial metabolites to graded regional ischemia: 31P N... more porcine myocardium in vivo. Response of myocardial metabolites to graded regional ischemia: 31P NMR spectroscopy of
A 13C-NMR study of the long-acting opiate antagonists naloxazone (I) and naltrexazone (II) and th... more A 13C-NMR study of the long-acting opiate antagonists naloxazone (I) and naltrexazone (II) and the long-acting opiate agonist oxymorphazone (III) revealed that these compounds are formed as mixtures of their anti and syn isomers. The less crowded anti isomer was found to be the major product in all cases (ca. 80%). N,N-Dimethyl derivatives of naloxazone (IV), naltrexazone (V), and oxymorphazone (VI), which are sterically more crowded than the corresponding unsubstituted hydrazones I-III, were formed as almost exclusively anti isomers. Pure anti isomer of II was obtained as a 1:1 complex with ethanol. No syn-anti equilibration was observed during the 13C-NMR experiment in any of the cases studied. The relevance of our finding about the syn-anti isomerism of the opiate hydrazones to the understanding of their interactions with the opiate receptor is discussed.
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