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Biomedical subjects

B H Oh

Publications and source records attributed to B H Oh.

At least 91 records · Page 5Linked to original sources
PubMed1993

Myocardial hypertrophy in the ischemic zone induced by exercise in rats after coronary reperfusion.

BACKGROUND: Factors influencing left ventricular (LV) remodeling after coronary artery reperfusion, including adaptive changes in the infarcted region and the role of exercise, have not been well defined. The common application of early reperfusion by thrombolysis after acute myocardial infarction lends potential significance to such remodeling, and a rat model with 45 minutes of regional ischemia followed by reperfusion was developed to study these events. We postulated that the effects of reperfusion in altering LV morphology would be further modified by exercise training, including induction of hypertrophic changes in the outer region of the nontransmural infarction. METHODS AND RESULTS: Female Sprague-Dawley rats were subjected either to 15 minutes of left anterior descending coronary artery occlusion followed by reperfusion or to sham operation, and at 5 days after the operation, animals were randomly assigned to sedentary conditions or to 3 weeks of swimming exercise. Animals completing the experiment included a reperfused sedentary group (n = 21), a reperfused exercised group (n = 20), a sham-operated group (n = 10), and a sham-operated group subjected to exercise (sham exercised group, n = 9). In addition, in seven rats, myocardial infarction was produced by permanent coronary occlusion, and the animals remained sedentary (permanent occlusion group). In each group, the morphology of the noninfarcted (septal) and the infarcted (anterolateral) regions of the left ventricle was examined 26 days after surgery from midventricular transverse sections 25 microns thick taken after perfusion fixation of the heart at an aortic pressure of 60 mm Hg and an LV cavity pressure of 10 mm Hg. Compared with the permanent occlusion group, LV cavity area in the sedentary reperfused group was smaller (33.5 versus 53.2 mm2, p < 0.001), the infarcted wall was thicker (1.36 versus 0.53 mm, p < 0.001), and the septal wall also was thicker (1.95 versus 1.62 mm, p < 0.05), whereas compared with the sham-operated group, the LV cavity area was increased, and infarcted wall thickness was reduced (both p < 0.01). Reperfusion resulted in less transmurality of infarction compared with permanent occlusion (38.3% versus 69.5%, p < 0.001), with increased subepicardial area in the infarcted zone after reperfusion (7.5 versus 1.9 mm2, p < 0.001). In the reperfused exercised group, transmurality was further decreased compared with the reperfused sedentary group (31.5% versus 38.3%, p < 0.05), and the viable subepicardial area of the infarct zone increased by 32%. CONCLUSIONS: Important remodeling of global and regional LV morphology was evident at 26 days in sedentary rats after 45 minutes of coronary occlusion with reperfusion compared with rats with permanent coronary occlusion, with reduced infarct transmurality and less LV dilation in the reperfused group. Exercise after reperfusion further affected ventricular remodeling by causing hypertrophy with increased wall thickness of the surviving subepicardium of the infarcted zone.

Animals↗
PubMed1993

Altered left ventricular remodeling with beta-adrenergic blockade and exercise after coronary reperfusion in rats.

BACKGROUND: beta-Adrenergic blockade is known to improve the survival of patients after acute myocardial infarction and to reduce myocardial infarct size in experimental coronary occlusion. However, the effects of beta-blockade on global and regional left ventricular (LV) remodeling have not been characterized after coronary occlusion with reperfusion. In rats subjected to coronary occlusion and reperfusion, we have demonstrated beneficial effects of reperfusion in sedentary rats with a hypertrophic response to exercise in the surviving outer wall of the infarcted zone, and in this study we investigated whether such remodeling is modified by beta-blockade in both sedentary and exercised rats. METHODS AND RESULTS: Female Sprague-Dawley rats were randomized into groups at 5 days after 45 minutes of left coronary artery occlusion followed by reperfusion to produce nontransmural infarction. Animals completing the experiment included a propranolol-treated sedentary group (750 mg/l drinking water) (n = 20) and a propranolol-treated exercised group (n = 19), and these groups were compared with two groups of simultaneously randomized rats (which were also part of a separate study): an untreated sedentary group (n = 21) and an untreated exercised group (n = 20). After 3 weeks of intervention, global and regional LV morphological changes were analyzed in 78 completed experiments from midventricular transverse slices of hearts after perfusion fixation. Compared with sedentary untreated rats, propranolol-treated sedentary rats showed significantly increased LV cavity area (41.6 versus 31.5 mm2, p < 0.001) and reduced wall thicknesses in the noninfarcted (1.77 versus 1.95 mm, p < 0.01) and infarcted regions (1.29 versus 1.36 mm, p < 0.01) (two-way ANOVA). In the propranolol-treated rats, exercise further increased the LV cavity area (44.6 versus 39.1 mm2, p < 0.001), reduced the noninfarcted wall thickness (1.62 versus 1.81 mm, p < 0.01), and increased the LV dimension/wall thickness ratio in the noninfarcted region (4.7 versus 3.95 mm, p < 0.001). Whereas exercise in the reperfused group in the absence of beta-blockade significantly increased the viable subepicardial area of the infarcted zone, as reported elsewhere, propranolol treatment prevented this exercise-induced increase of subepicardial area (7.8 rest versus 7.7 mm2 exercise, NS), and there was a significant reduction of total myocardial area in the propranolol-treated exercised group compared with the untreated exercised group (p < 0.05). Corresponding trends in LV weights were not statistically significant. CONCLUSIONS: These findings provide evidence for altered LV remodeling, including LV cavity dilation and reduced wall thickness, after 3 weeks of propranolol treatment in sedentary rats after coronary artery occlusion and reperfusion to produce nontransmural infarction. In addition, after 3 weeks of exercise together with propranolol treatment, morphological changes were consistent with suppression of exercise-induced myocardial hypertrophy globally and in the viable outer wall of the infarcted region, accompanied by further LV cavity dilation.

Adrenergic beta-Antagonists↗
PubMed1992

14,15N, 13C, 57Fe, and 1,2H Q-band ENDOR study of Fe-S proteins with clusters that have endogenous sulfur ligands.

The benefits of performing ENDOR experiments at higher microwave frequency are demonstrated in a Q-band (35 GHz) ENDOR investigation of a number of proteins with [nFe-mS] clusters, n = 2, 3, 4. Each protein displays several resonances in the frequency range of 0-20 MHz. In all instances, features are seen near v approximately 13 and 8 MHz that can be assigned, respectively, to "distant ENDOR" from 13C in natural-abundance (1.1%) and from 14N (the delta m1 = +/- 2 transitions); the nuclei involved in this phenomenon are remote from and have negligible hyperfine couplings to the cluster. In addition, a number of proteins show local 13C ENDOR signals with resolved hyperfine interactions; these are assigned to the beta carbons of cysteines bound to the cluster [A(13C) approximately 1.0 MHz]. Five proteins show resolved, local delta m1 = +/- 2 ENDOR signals from 14N with an isotropic hyperfine coupling, 0.4 less than or equal to A(14N) less than or equal to 1.0, similar to those seen in ESEEM studies; these most likely are associated with N-H...S hydrogen bonds to the cluster. Anabaena ferredoxin further shows a signal corresponding to A(14N) approximately 4 MHz. Quadrupole coupling constants are derived for both local and distant 14N signals. The interpretation of the data is supported by studies on 15N- and 13C-enriched ferredoxin (Fd) from Anabaena 7120, where the 15N signals can be clearly correlated with the corresponding 14N signals and where the 13C signals are strongly enhanced. Thus, the observation of 14N delta m1 = +/- 2 signals at Q-band provides a new technique for examining weak interactions with a cluster.(ABSTRACT TRUNCATED AT 250 WORDS)

Aconitate Hydratase↗
PubMed1992

Hemispheric asymmetry in visual recognition of words and motor response in schizophrenic and depressive patients.

Two-letter Hangul words were presented tachistoscopically as target words to either the right or left visual field of normal subjects, schizophrenics, and depressive patients. The subjects' task was to judge the similarity or difference between the target words and the words used for comparison. They were to signal as soon as possible by pressing a key with their hands. In normal subjects, the correct response rate was significantly higher in the left hemisphere; there was little difference in the speed of motor response between the two hemispheres, however. Compared with normal subjects, both patient groups showed generalized impairment. Schizophrenia was associated with impairment in the left hemisphere, depression was associated with impairment in the right hemisphere.

Adult↗
PubMed1992

Takayasu arteritis in Korea: clinical and angiographic features.

Clinical and angiographic features of Takayasu arteritis were investigated in 129 Korean patients. This disease affects females more frequently than males, in a ratio of 6.6 to 1. Of the total number of patients, 51 were in the third decade, 27 in the fourth decade, and 23 in the second decade. Common clinical symptoms were headache (60%), exertional dyspnea (42%), dizziness (36%), and malaise or weakness (34%). Takayasu arteritis affected the abdominal aorta (46%) and descending thoracic aorta (37%) more frequently than the ascending aorta (1%) and aortic arch (2%) According to Ueno's classification based on aortographic findings, the 129 patients were divided into type I (37), type II (25), and type III (67). Among the 48 patients who had coronary angiography, 11 (23%) showed coronary arterial involvement. Because the clinical features are determined by the extent and severity of the specific artery involved in the occlusive phase of the disease, total aortography including coronary angiography is very important in the initial evaluation of Takayasu arteritis.

Adolescent↗
PubMed1992

Evaluation of inotropic effect of endothelin-1 in vivo.

The vasoconstrictive peptide endothelin-1 (ET-1) has been reported to exert a very important positive inotropic effect in vitro. To assess the effect of ET-1 on myocardial contractility in vivo, we compared the effect of intracoronary infusion of 10(-8) M ET-1 (constant coronary blood flow) to that of 10(-8) M dobutamine in 8 swine. ET infusion did not produce changes in segmental shortening (control vs. drug, mean +/- SD): 33.8 +/- 14.3 vs. 30.8 +/- 12.1%, shortening velocity: 10.3 +/- 4.3 vs. 10.7 +/- 4.5 mm/s, or maximum +dP/dt: 1,691 +/- 701 vs. 1,772 +/- 773 mm Hg/s, whereas dobutamine infusion induced an important increase in these measurements; segmental shortening: 36.9 +/- 14 vs. 48.4 +/- 18.8%, shortening velocity: 10.1 +/- 2.6 vs. 14.7 +/- 4.5 mm/s, and maximum +dP/dt: 2,041 +/- 567 vs. 2,389 +/- 765 mm Hg/s (all p less than 0.05). Mean myocardial blood flow assessed by microspheres was unchanged by ET-1 despite a marked increase in coronary artery pressure (88.6 +/- 12.9 vs. 157 +/- 8.8 mm Hg, p less than 0.001). Regional infusion of ET-1 at a dose provoking extensive coronary vasoconstriction does not induce any change in regional or global myocardial function in swine.

Adenosine↗
PubMed1992

Enhancement of the force-frequency effect on myocardial contractility by adrenergic stimulation in conscious dogs.

BACKGROUND: The influence of changes in heart rate on myocardial contractility (the force-frequency effect) differs under various experimental conditions, including the anesthetized versus the conscious state. METHODS AND RESULTS: To assess the influence of beta-adrenergic stimulation on force-frequency effects on myocardial contraction and relaxation, seven instrumented conscious dogs were studied in which heart rate could be controlled by atrial pacing after the intrinsic rate was slowed with a bradycardiac agent (UL-FS 49 0.5-0.75 mg/kg). Left ventricular (LV) pressure was measured with a micromanometer under resting conditions and during dobutamine infusion at low, intermediate, and high doses (2.7, 5.4, and 10.7 micrograms/kg/min). At each dose, heart rate was progressively increased from 100 to 210 beats per minute. In the absence of dobutamine (control), no significant positive force-frequency effect was detected on LV dP/dtmax; this was probably due to the known effect of the observed decrease in preload to reduce LV dP/dtmax, thereby offsetting an effect of the force-frequency response to increased dP/dt. However, during dobutamine infusions, the force-frequency effect was observed to increase significantly in a dose-dependent manner with increases in heart rate. An increase in heart rate from 100 to 210 beats per minute increased LV dP/dtmax by 12.4 +/- 12.5% with low-dose, 22.7 +/- 13.1% with intermediate-dose, and 27.5 +/- 8.9% with high-dose dobutamine. Changes in preload and aortic pressure were within the same ranges under control conditions and at each of the three dobutamine doses. The time constant of LV pressure fall (tau) was significantly shorter with increases in heart rate during control, but only the highest dobutamine dose caused further significant shortening in tau with increased heart rate. CONCLUSIONS: These data indicate that there is a pronounced dose-dependent action of beta-adrenergic stimulation to enhance force-frequency-induced contractile responses in normal conscious dogs.

Adrenergic beta-Agonists↗
PubMed1992

Myocardial function and transmural blood flow during coronary venous retroperfusion in pigs.

BACKGROUND: The degree of recovery of regional myocardial contraction during coronary venous retroperfusion has not been well established, particularly in the absence of coronary collateral channels. Therefore, the maximal functional benefit attainable with coronary venous retroperfusion was assessed in pigs by means of using selective pump retroperfusion of the left anterior descending vein, with venting of the left anterior descending artery to zero pressure. METHODS AND RESULTS: In eight anesthetized open-chest pigs during selective left anterior descending venous retroperfusion over a range of retroperfusion flows, regional myocardial function (percent systolic wall thickening by sonomicrometry) increased progressively to an average of 62% of control values at a retroperfusion flow rate 200% of control arterial flow. Progressive thickening of the end-diastolic dimension of the anterior wall was observed with increasing retroperfusion flow (from 8.7 +/- 0.9 to 10.7 +/- 2.3 mm, p less than 0.001). Perfusion pressures within the left anterior descending vein increased linearly with increased retroperfusion flow rates (up to 132 +/- 57 mm Hg with retroperfusion flow 200% of control). A gradual increase of retrograde left anterior descending arterial outflow was observed with increasing retroperfusion flows; however, the absolute amount (maximum, 8.3 +/- 4.1 ml/min) was much too low to explain the extent of functional recovery. Transmural myocardial capillary blood flows in the anterior wall with retroperfusion flows of 100% and 200% of control arterial flow were 0.22 and 0.42 ml/min/g with corresponding subendocardial blood flows of 0.14 and 0.29 ml/min/g; ratios of endocardium to epicardium were 0.51 and 0.61, respectively. Thus, capillary blood flows during selective retroperfusion were relatively low despite considerable restoration of regional systolic wall thickening, and a significant difference was noted in the slopes of the relations between regional systolic wall thickening and myocardial blood flow during retroperfusion and anterograde arterial perfusion (p less than 0.05). With retrograde injection of silicone elastomer at different retroperfusion pressures (50, 75, and 100 mm Hg) in three pigs, capillaries were well visualized, and profuse intramyocardial venous anastomotic connections were seen at the highest retroperfusion pressure (100 mm Hg), whereas there was filling of small venules but little capillary filling at the lowest retroperfusion pressure (50 mm Hg). CONCLUSIONS: Considerable recovery of regional myocardial function with low regional capillary blood flows were observed during acute venous retroperfusion with high retroperfusion flows with arterial blood. These findings together with low levels of retrograde arterial outflow and visualization of retrograde capillary filling with a rich venous network provide evidence for possible oxygen delivery via the intramyocardial venous plexus.

Animals↗
PubMed1992

Myocardial cell hypertrophy after myocardial infarction with reperfusion in dogs.

BACKGROUND: The potential role of myocardial cell hypertrophy in the ischemic zone in the mechanism of late recovery of regional contractile function after myocardial infarction followed by reperfusion has not been examined. METHODS AND RESULTS: Eight chronically instrumented, conscious dogs were subjected to 90-120 minutes of circumflex coronary artery occlusion followed by reperfusion. The thickness and function of the anterior (AT) and posterior (PT) walls was measured by ultrasonic gauges at control, during occlusion, and after reperfusion. After 3 weeks, cross-sectional areas of surviving cells were determined from subepicardial (epi), midwall (mid), and subendocardial (endo) regions in six dogs and compared with those from six animals without infarction, including three sham-operated control dogs. PT systolic wall thickening showed dyskinesia during occlusion but recovered after reperfusion to 48% of control at 1 week and 67% at 3 weeks. End-diastolic thickness of the PT wall increased markedly after reperfusion, but AT and PT walls were only slightly thicker (p = NS) than in control dogs at 3 weeks. Cross-sectional areas of reperfused dogs in the infarct region averaged 279 (PTepi), 291 (PTmid), and 317 microns 2 (PTendo) and were significantly larger than in control animals (237 [PTepi], 241 [PTmid], and 233 microns 2 [PTendo]). PT cell areas were significantly larger than AT cells, ENDO cell areas were larger than EPI cells (both p < 0.05), and ENDO cells of the AT wall were larger than those of noninfarcted dogs (p < 0.05). CONCLUSIONS: In dogs with myocardial infarction followed by reperfusion, the cross-sectional areas of cells in the infarcted PT wall were larger than those in the noninfarcted AT wall, and within both the infarcted and noninfarcted zones, cell areas were larger in the endocardial than the epicardial region. In all regions of the infarcted wall and in the ENDO region of the noninfarcted wall, cell areas were generally larger than those of control dogs without infarction, and the control dogs showed no transmural differences in cell areas. The mechanisms responsible for this significant remodeling of the reperfused infarcted zone, which involves myocardial cellular hypertrophy, are unknown, but it is possible that hypertrophy of surviving regions of the infarcted wall played a role in the late recovery of regional function that accompanied this hypertrophic response.

Animals↗
PubMed1992

Percutaneous mitral valvuloplasty in a mid-term pregnant woman with severe rheumatic mitral stenosis.

A 28-year-old woman with severe mitral stenosis underwent percutaneous mitral valvuloplasty at 26 weeks' gestation. Balloon dilation using a double 18-18 mm balloon resulted in improvement in mean mitral pressure gradient (32 to 8 mmHg) and in calculated mitral valve area (0.9 to 2.4 cm2) without complications and any evidence of fetal distress during procedures with an estimated radiation exposure to the fetus of 0.13 rem. This procedure resulted in the disappearance of symptoms of congestive heart failure and allowed for normal full term spontaneous delivery of a 3.51 Kg boy without any complication.

Adult↗
PubMed1991

Two-dimensional magnetization exchange spectroscopy of Anabaena 7120 ferredoxin. Nuclear Overhauser effect and electron self-exchange cross peaks from amino acid residues surrounding the 2Fe-2S* cluster.

Hyperfine 1H NMR signals of the 2Fe-2S* vegetative ferredoxin from Anabaena 7120 have been studied by two-dimensional (2D) magnetization exchange spectroscopy. The rapid longitudinal relaxation rates of these signals required the use of very short nuclear Overhauser effect (NOE) mixing times (0.5-20 ms). The resulting pattern of NOE cross-relaxation peaks when combined with previous 1D NOE results [Dugad, L. B., La Mar, G. N., Banci, L., & Bertini, I. (1990) Biochemistry 29, 2263-2271] led to elucidation of the carbon-bound proton spin systems from each of the four cysteines ligated to the 2Fe-2S* cluster in the reduced ferredoxin. Additional NOE cross peaks were observed that provide information about other amino acid residues that interact with the iron-sulfur cluster. NOE cross peaks were assigned tentatively to Leu27, Arg42, and Ala43 on the basis of the X-ray coordinates of oxidized Anabaena 7120 ferredoxin [Rypniewski, W.R., Breiter, D.R., Benning, M.M., Wesenberg, G., Oh, B.-H., Markley, J.L., Rayment, I., & Holden, H. M. (1991) Biochemistry 30, 4126-4131]. Three chemical exchange cross peaks were detected in magnetization exchange spectra of half-reduced ferredoxin and assigned to the 1H alpha protons of Cys49 and Cys79 [both of whose sulfur atoms are ligated to Fe(III)] and Arg42 (whose amide nitrogen is hydrogen-bonded to one of the inorganic sulfurs of the 2Fe-2S* cluster). The chemical exchange cross peaks provide a means of extending assignments in the spectrum of reduced ferredoxin to assignments in the spectrum of the oxidized protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1991

Crystallization and structure determination to 2.5-A resolution of the oxidized [2Fe-2S] ferredoxin isolated from Anabaena 7120.

The molecular structure of the oxidized form of the [2Fe-2S] ferredoxin isolated from the cyanobacterium Anabaena species strain PCC 7120 has been determined by X-ray diffraction analysis to a nominal resolution of 2.5 A and refined to a crystallographic R factor of 18.7%. Crystals used in this investigation belong to the space group P2(1)2(1)2(1) with unit cell dimensions of a = 37.42 A, b = 38.12 A, and c = 147.12 A and two molecules in the asymmetric unit. The three-dimensional structure of this ferredoxin was solved by a method that combined X-ray data from one isomorphous heavy-atom derivative with noncrystallographic symmetry averaging and solvent flattening. As in other plant-type [2Fe-2S] ferredoxins, the iron-sulfur cluster is located toward the outer edge of the molecule, and the irons are tetrahedrally coordinated by both inorganic sulfurs and sulfurs provided by protein cysteine residues. The main secondary structural elements include four strands of beta-pleated sheet and three alpha-helical regions.

Crystallization↗
PubMed1990

Multinuclear magnetic resonance studies of the 2Fe.2S* ferredoxin from Anabaena species strain PCC 7120. 1. Sequence-specific hydrogen-1 resonance assignments and secondary structure in solution of the oxidized form.

Complete sequence-specific assignments were determined for the diamagnetic 1H resonances from Anabaena 7120 ferredoxin (Mr = 11,000). A novel assignment procedure was followed whose first step was the identification of the 13C spin systems of the amino acids by a 13C(13C) double quantum correlation experiment [Oh, B.-H., Westler, M. W., Darba, P., & Markley, J. L. (1988) Science 240, 908-911]. Then, the 1H spin systems of the amino acids were identified from the 13C spin systems by means of direct and relayed 1H(13C) single-bond correlations [Oh, B.-H., Westler, W. M., & Markley, J. L. (1989) J. Am. Chem. Soc. 111, 3083-3085]. The sequential resonance assignments were based mainly on conventional interresidue 1H alpha i-1HNi + 1 NOE connectivities. Resonances from 18 residues were not resolved in two-dimensional 1H NMR spectra. When these residues were mapped onto the X-ray crystal structure of the homologous ferredoxin from Spirulina platensis [Fukuyama, K., Hase, T., Matsumoto, S., Tsukihara, T., Katsube, Y., Tanaka, N., Kakudo, M., Wada, K., & Matsubara, H. (1980) Nature 286, 522-524], it was found that they correspond to amino acids close to the paramagnetic 2Fe.2S* cluster. Cross peaks in two-dimensional homonuclear 1H NMR spectra were not observed for any protons closer than about 7.8 A to both iron atoms. Secondary structural features identified in solution include two antiparallel beta-sheets, one parallel beta-sheet, and one alpha-helix.

Amino Acid Sequence↗
PubMed1990

Multinuclear magnetic resonance studies of the 2Fe.2S* ferredoxin from Anabaena species strain PCC 7120. 2. Sequence-specific carbon-13 and nitrogen-15 resonance assignments of the oxidized form.

Multinuclear two-dimensional NMR techniques were used to assign nearly all diamagnetic 13C and 15N resonances of the plant-type 2Fe.2S* ferredoxin from Anabaena sp. strain PCC 7120. Since a 13C spin system directed strategy had been used to identify the 1H spin systems [Oh, B.-H., Westler, W. M., & Markley, J. L. (1989) J. Am. Chem. Soc. 111, 3083-3085], the sequence-specific 1H assignments [Oh, B.-H., & Markley, J. L. (1990) Biochemistry (first paper of three in this issue)] also provided sequence-specific 13C assignments. Several resonances from 1H-13C groups were assigned independently of the 1H assignments by considering the distances between these nuclei and the paramagnetic 2Fe.2S* center. A 13C-15N correlation data set was used to assign additional carbonyl carbons and to analyze overlapping regions of the 13C-13C correlation spectrum. Sequence-specific assignments of backbone and side-chain nitrogens were based on 1H-15N and 13C-15N correlations obtained from various two-dimensional NMR experiments.

Amino Acid Sequence↗
PubMed1990

Multinuclear magnetic resonance studies of the 2Fe.2S* ferredoxin from Anabaena species strain PCC 7120. 3. Detection and characterization of hyperfine-shifted nitrogen-15 and hydrogen-1 resonances of the oxidized form.

All the nitrogen signals from the amino acid side chains and 80 of the total of 98 backbone nitrogen signals of the oxidized form of the 2Fe.2S* ferredoxin from Anabaena sp. strain PCC 7120 were assigned by means of a series of heteronuclear two-dimensional experiments [Oh, B.-H. Mooberry, E. S., & Markley, J. L. (1990) Biochemistry (second paper of three in this issue )]. Two additional nitrogen signals were observed in the one-dimensional 15N NMR spectrum and classified as backbone amide resonances from residues whose proton resonances experience paramagnetic broadening. The one-dimensional 15N NMR spectrum shows nine resonances that are hyperfine shifted and broadened. From this inventory of diamagnetic nitrogen signals and the available X-ray coordinates of a related ferredoxin [Tsukihara, T., Fukuyama, K., Nakamura, M., Katsube, Y., Tanaka, N., Kakudo, M., Wada, K., Hase, T., & Matsubara, H. (1981) J. Biochem. 90, 1763-1773], the resolved hyperfine-shifted 15N peaks were attributed to backbone amide nitrogens of the nine amino acids that share electrons with the 2Fe.2S* center or to backbone amide nitrogens of two other amino acids that are close to the 2Fe.2S* center. The seven 15N signals that are missing and unaccounted for probably are buried under the envelope of amide signals. 1H NMR signals from all the amide protons directly bonded to the seven missing and nine hyperfine-shifted nitrogens were too broad to be resolved in conventional 2D NMR spectra.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Mitral stenosis: evaluation with MR imaging after percutaneous balloon valvuloplasty.

To evaluate the pathoanatomic findings of mitral valve stenosis and changes after percutaneous balloon valvuloplasty (PBV), magnetic resonance (MR) imaging was performed in 23 patients. The patients were imaged with a 2.0-T system within 1 week before and 3-10 days after PBV. The angle of the interatrial septum was measured on the transverse image to facilitate a successful transseptal puncture. On MR images, the mean transverse and anteroposterior diameters of the left atrium at the level of the aortic root in the ventricular diastolic phase decreased significantly after PBV. Areas of flow-related intraluminal signal intensity detected in the left atrial cavity of 17 patients (74%) before the procedure disappeared in 15 patients after the procedure. Other MR imaging findings after PBV were the disappearance of intraluminal signal intensity in the pulmonary artery, normal curvature of the interatrial and interventricular septa, and pericardial effusion as a complication. MR imaging was thought to provide useful information before and after PBV in patients with mitral stenosis.

Adolescent↗