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Biomedical subjects

O Iimura

Publications and source records attributed to O Iimura.

At least 127 records · Page 7Linked to original sources
PubMed1991

Does myocardial stunning contribute to infarct size limitation by ischemic preconditioning?

BACKGROUND: The mechanism through which ischemic preconditioning causes cardioprotection is unknown. The present study investigated the role of stunning in preconditioning. METHODS AND RESULTS: We studied three different protocols of preconditioning: two cycles of 2-minute ischemia separated by 5-minute reperfusion (2'PC), one cycle of 5-minute ischemia by 5-minute reperfusion (5'PC1), and two cycles of 5-minute ischemia separated by 5-minute reperfusion (5'PC2). In the first series of experiments, the stunning associated with 2'PC, 5'PC1, or 5'PC2 was assessed using an epicardial Doppler transducer in anesthetized open-chest rabbits. The thickening fraction (percent baseline) of the preconditioned region was 76.8 +/- 7.2% (mean +/- SEM) after 2'PC but 31.4 +/- 9.2% and 34.3 +/- 9.7% after 5'PC1 and 5'PC2, respectively, which were significantly lower, thus indicating more severe stunning than that after 2'PC. In the second series of experiments, a branch of the left circumflex artery was occluded for 30 minutes and then reperfused for 72 hours in four groups of rabbits. One group was not preconditioned and three groups were preconditioned with 2'PC, 5'PC1, or 5'PC2 protocols before the 30-minute ischemia. In contrast to the differences observed in the stunning in the first series of experiments, histological infarct size was similar in the three preconditioned groups (21.1 +/- 3.0% of area at risk after 2'PC, 20.1 +/- 3.4% after 5'PC1, 16.4 +/- 4.2% after 5'PC2), all of which were significantly smaller than that in the unpreconditioned group (43.9 +/- 5.0%). The third series of experiments examined the degree of stunning by 2'PC, 5'PC1, or 5'PC2 and the size of infarct (tetrazolium staining) in the same animal after 30-minute ischemia/3-hour reperfusion; again, the results showed no significant correlation between degree of stunning and infarct size. CONCLUSIONS: The myocardial infarct size-limiting effect of preconditioning did not correlate with the degree of myocardial stunning accompanying preconditioning. Thus, it is unlikely that myocardial stunning contributes to the cardioprotective effect of ischemic preconditioning.

Animals↗
PubMed1991

Inhibition of thromboxane A2 synthetase failed to limit myocardial infarct size in a rabbit ischemia-reperfusion model.

The role of thromboxane A2 (TXA2) in myocardial necrosis during coronary occlusion and reperfusion was investigated by using a new long-acting TXA2 synthetase inhibitor, DP1904. A rabbit coronary branch was occluded for 30 min and then reperfused for 72h. Infarct size and area at risk were determined histologically and by fluorescent particles, respectively, for 4 groups; a saline receiving control group (C group), a DP1904 treated group (DP group), a heparin treated group (H group), and a DP1904 plus heparin treated group (DP-H group). The H group and DP-H group were included to examine the influence of heparinization on the effect of DP1904. In the DP and DP-H groups, 10 mg/kg of DP1904 was injected i.v. 2h before coronary occlusion, as well as 24 and 48h after reperfusion. This dose of DP1904 (10 mg/kg i.v.) was able to inhibit serum thromboxane B2 formation ex vivo to 1.1% of the control level 2h after its administration, and to 39.5% at 24h, in the rabbit (n = 5). The H and DP-H groups received 1000 units of heparin i.v. 3 min prior to coronary occlusion. The size of the area at risk, heart rate, blood pressure, and rate-pressure products were comparable between the 4 groups. Mortality was not significantly different in any group. Myocardial infarct size as the percentage of area at risk was 43.6 +/- 3.9% in C group (n = 10), 41.1 +/- 4.4% in DP group (n = 9), 47.8 +/- 3.0% in H group (n = 13), and 44.7 +/- 4.0% in DP-H group (n = 10), which were not significantly different. These findings suggest that TXA2 does not contribute directly to myocardial necrosis during coronary occlusion and reperfusion in the rabbit.

Animals↗
PubMed1991

A case of congenital left ventricular diverticulum with pulmonary stenosis and its scintigraphic characteristics.

We encountered a 31-year-old female patient with mild valvular pulmonary stenosis who had no abnormality in the electrocardiogram but pulmonary dilatation in the chest radiograph. Two-dimensional echocardiography and magnetic resonance imaging demonstrated two small protrusions at the interventricular septum indicating diverticula. Large perfusion defects were observed at the anterior wall in the thallium-201 myocardial tomograms. Short axial and vertical long axial images by ECG-gated blood pool tomography revealed an out-pouching best seen during diastole and a good contraction during systole in the corresponding areas. These findings suggested the presence of thin but normal myocardium in the anterior wall, i.e. a muscular type of left ventricular diverticulum. The presence of the muscular type of left ventricular diverticulum at the anterior and septal walls was confirmed by contrast left ventriculography. A congenital diverticulum at the anterior and septal walls with pulmonary stenosis is very rare. Furthermore, its scintigraphic images were quite characteristic and useful for its diagnosis.

Adult↗
PubMed1991

[The coefficient of variation of RR intervals (CVRR) on electrocardiogram in patients with essential hypertension with reference to aging, hemodynamics and sympatho-adrenomedullary function].

To evaluate the significance of parasympathetic nerve activity in essential hypertension, we measured the coefficients of variation of RR intervals (CVRR) on electrocardiogram and examined the relationships between CVRR and aging, hemodynamics and sympatho-adrenomedullary function in normotensive subjects (NT) and in patients with essential hypertension (EHT). Mean arterial pressure (MAP), heart rate (HR), plasma noradrenaline concentration (pNA), plasma adrenaline concentration (pAd) and CVRR resting in a supine position were simultaneously measured in 37 NT (33.8 +/- 2.0 years) and 47 mild-to-moderate EHT (51.3 +/- 1.5 years). In both NT and EHT, significantly negative correlations between CVRR and age (NT: r = -0.54, p less than 0.001, EHT: r = -0.41, p less than 0.005) were observed, however, CVRR correlated with neither MAP, HR nor pAd. CVRR tended to correlate negatively with pNA (r = -0.27, p less than 0.1) in NT, unlike in EHT. The mean value of CVRR in EHT (n = 10, age: 38.3 +/- 1.6 years, CVRR: 3.61 +/- 0.37%) was significantly (p less than 0.005) lower than in age-matched NT (n = 10, age: 38.3 +/- 2.5 years, CVRR: 5.76 +/- 0.45%). These results indicate that the parasympathetic tone suggested by CVRR may be related to aging and sympathetic nerve activity, and that parasympathetic function might be impaired in EHT.

Adolescent↗
PubMed1991

[Shy-Drager syndrome: its autonomic function, alpha 2 receptor density and mechanism of postprandial hypotension].

The autonomic function, platelet alpha 2 receptor (alpha 2R) density, and mechanism of postprandial hypotension were examined in a 58-year-old man with Shy-Drager syndrome (SDS). His chief complaints were orthostatic syncope and impotence. His blood pressure was kept within normal limits in a supine position, but severe hypotension and fainting occurred when he assumed an upright posture. There were diminished sweating response to warm stress, abnormal pupil reactions to drugs, lack of blood pressure elevation at phase IV during the Valsalva maneuver, and a lack of pressor response to hyperventilation and cold stress. The plasma norepinephrine levels (pNE) were very low in a supine position at rest and in a head-up tilt position. Severe blood pressure fall (hypotension) associated with a lack of pNE elevation occurred during an oral glucose tolerance test (oGTT). Platelet alpha 2R density increased and the pressor response to infused norepinephrine (NE-R) was pronounced. The heart rate response to injected atropine was clearly attenuated. The coefficient of the R-R interval variation in the ECG (CVRR), which may reflect parasympathetic activity, was markedly low at rest. In addition, a decrease in a head-up tilt position and increase during oGTT also resolved. These results indicate that a dysfunction of the parasympathetic and sympathetic nervous systems and the up-regulation in the alpha 2R system that leads to an increase in alpha 2R density in SDS are involved in this disease and that the mechanism of postprandial hypotension in SDS may be different from that in normal elderly subjects.

Atropine↗
PubMed1991

Normalized left ventricular filling indexes to detect diastolic dysfunction in hypertension and in hypertrophic cardiomyopathy.

In order to establish a normalizing method for left ventricular filling indexes, peak filling rate (PFR) and time to peak filling rate (TPFR), derived from resting radionuclide ventriculography using Fourier analysis with third-order harmonics, were analyzed in 45 normal subjects, 40 hypertensive patients, and 29 patients with hypertrophic cardiomyopathy. PFR was significantly negatively correlated with age (r = -0.62) and significantly positively correlated with peak ejection rate (PER) (r = 0.58) in normals. TPFR normalized for heart rate (N-TPFR) was correlated positively with age in normals (r = 0.60) and hypertensives (r = 0.49) but not in patients with hypertrophic cardiomyopathy. N-TPFR was not significantly correlated with systolic parameters. A significant relationship between PFR normalized to PER (PFR/PER) and age was observed in normals (r = -0.58) but not in patients with hypertension or hypertrophic cardiomyopathy. To cancel the ageing effect, individual data of PFR/PER and N-TPFR were expressed as a percentage of the predicted regression value in normal subjects (%PFR/PER and %N-TPFR, respectively). Per cent PFR/PER was significantly lower and %N-TPFR was significantly greater in patients with hypertension and hypertrophic cardiomyopathy compared to normals. When normal limits of these indexes were defined as %PFR/PER greater than 80% and %N-TPFR less than 120%, the sensitivity, specificity and diagnostic accuracy of differentiating normals from patients with hypertension or hypertrophic cardiomyopathy were 41 of 45 (91%), 44 of 68 (65%), and 85 of 113 (75%), respectively. These findings indicate that %PFR/PER and %N-TPFR might be more reasonably normalized parameters for describing diastolic filling and its abnormality.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Myocardial accumulation of monoclonal antimyosin Fab in hypertrophic cardiomyopathy and postpartum cardiomyopathy.

Indium-111-antimyosin Fab scan was performed in patients with hypertrophic and postpartum cardiomyopathies to assess whether or not myocardial damage can be delineated. In two patients with hypertrophic cardiomyopathy, intense and diffuse antimyosin uptake was observed, although there was no evidence of acute myocardial damage or wall motion abnormality. A patient with postpartum cardiomyopathy showed a dense and relatively localized accumulation in the left ventricular anterior wall in association with thallium perfusion and wall motion abnormalities. Thus, antimyosin scanning can delineate not only manifested but also subclinical myocardial damage in hypertrophic and postpartum cardiomyopathies which may not be detectable by other techniques.

Adult↗
PubMed1991

Effect of prednisolone on myocardial infarct healing: characteristics and comparison with indomethacin.

OBJECTIVE: To characterize retardation of myocardial infarct healing by corticosteroid administration, and to examine the role of suppression of prostaglandin production in its effect. DESIGN: The left circumflex coronary artery of the rabbit was occluded for 30 mins and reperfused for 72 h. Rabbits were divided into four groups: a control group, a low dose prednisolone group (L-PSL) that was treated with 5 mg/kg/24 h prednisolone, a high dose prednisolone group (H-PSL) that was treated with 10 mg/kg/24 h prednisolone, and an indomethacin group that received a 5 mg/kg intravenous bolus of indomethacin followed by 10 mg/kg/24 h. The status of infarct healing and infarcted wall thinning was assessed 72 h after ischemia by the percentage of infarct mass organized (%O/I) and the ratio of infarcted wall thickness to noninfarcted wall thickness (thinning ratio). MAIN RESULTS: The %O/I was 61.4 +/- 4.2% (mean +/- SEM) in the control group. The L-PSL and H-PSL groups had %O/Is of 48.3 +/- 3.7% and 29.1 +/- 2.1%, respectively, which were significantly lower than the control value. The difference in %O/I between the H-PSL and L-PSL groups was also significant. However, the %O/I of the indomethacin group (55.1 +/- 3.3%) was not significantly different from control. When the myocardial infarcts were retrospectively subgrouped into small infarcts (infarct volume less than 0.31 cm3) and large infarcts (greater than or equal to 0.31 cm3), infarct healing delay in large infarcts was evident only for H-PSL and not for L-PSL, while both L-PSL and H-PSL treatment retarded healing of small infarcts. No significant difference was observed in the thinning ratio for any group. CONCLUSION: Infarct healing delay by prednisolone is dosage dependent, and smaller infarcts may be more sensitive to its effect. Retardation of infarct healing by prednisolone is unlikely to be mediated by suppression of prostaglandins from the cyclo-oxygenase pathway.

Animals↗
PubMed1991

Acute thrombocytopenia after intravenous infusion of radiographic contrast medium.

Acute thrombocytopenia due to intravenous infusion of radiographic contrast media is extremely rare. We report the first such case in Japan. A 52-year-old male was admitted to hospital because of right ureteral stone. Two hours after drip infusion pyelography, the patient experienced chills and fever. It was shown that his platelet count had decreased abruptly from 233,000 to 8000/mm3. Platelet associated immunoglobulin was not detected. An in vitro test for platelet aggregation by contrast media was negative. Following infusion of hydrocortisone, the platelet count recovered to a normal level within several days.

Blood Platelets↗
PubMed1991

[Correlations between the coefficient of variation of RR intervals and sympathetic nerve activity following superior tilting in normotensive subjects and in patients with essential hypertension].

The relationship between changes in sympathetic nerve activity and those in parasympathetic tone with a change in position was investigated in patients with essential hypertension using the coefficient of variation of RR intervals on electrocardiograms (CVRR). Mean arterial pressure (MAP), heart rate (HR), plasma noradrenaline concentration (pNA) and CVRR were measured in a supine position at rest and 20 min after having the head tilted 60 degrees superiorly in 10 normotensives (NT: 51.9 +/- 3.0 yrs) and 7 essential hypertensive patients (EHT: 51.0 +/- 2.8 yrs). After changing the position, CVRR decreased significantly in the NT, but not in the EHT; whereas, significant increases of both HR and pNA without significant changes in MAP were shown in both groups. A significant negative correlation between percentage changes in CVRR (% delta CVRR) and pNA (% delta pNA) were observed in the NT, but not in the EHT. However, there was no relationship of % delta CVRR to % delta MAP or to % delta HR in either group. It was suggested from the changes in CVRR that suppression of the parasympathetic tone, which occurs in the NT group corresponding to sympathetic augmentation to present a decrease in blood pressure with a change in position, may be impaired in the EHT group.

Blood Pressure↗
PubMed1991

Myocardial distribution of indium-111-antimyosin Fab in acute inferior and right ventricular infarction: comparison with technetium-99m-pyrophosphate imaging and histologic examination.

In a postmortem study of a 69-yr-old female patient who had suffered 2 yr previously a non-Q-wave anterior infarction and who had sustained just seven days earlier a left inferior and right ventricular infarction, the distribution of 111In-antimyosin Fab was compared to the results of 99mTc-pyrophosphate imaging and histologic examination. Indium-111-antimyosin Fab imaging could not be performed because of cardiogenic shock. However, postmortem gamma scintillation counting revealed increased activities of antimyosin Fab in the inferoapical and right ventricular infarcted regions in which 99mTc-pyrophosphate positive imagings were observed; in contrast, a histologically confirmed old subendocardial anterior infarction had no definite activity. Thus, the myocardial distribution of 111In-antimyosin Fab corresponded well to the results of 99mTc scintigrams and histologic examinations in a human heart, suggesting that this technique could be useful in vivo for detecting several-day-old myocardial infarction of the right ventricle as well as the left ventricle. Tissue from the 2-yr-old infarction was not identified by this technique.

Aged↗
PubMed1991

[Scintigraphic diagnosis of postinfarction left ventricular aneurysm and the prediction of the residual left ventricular function after aneurysmectomy using ECG gated blood pool SPECT].

The diagnostic accuracy of ECG gated blood pool SPECT (blood pool SPECT) for detecting and quantify postinfarction left ventricular aneurysm (LVA) was assessed in 49 patients with myocardial infarction and 15 control subjects. LVA, which was detected in 35 of 49 patients, was defined as a regional protrusion through a cardiac cycle in contrast ventriculography and as a non-contracting segment with a markedly delayed phase angle in the tomographic functional images derived from phase analysis. The blood pool SPECT technique showed a high sensitivity (100%), specificity (78.6%) and accuracy (93.3%) for detecting LVA and was very useful for precisely determining LVA location and sizing contractile and non-contractile volume of left ventricle in patients with LVA. Furthermore, left ventricular ejection fraction (LVEF) after the excision of LVA was predicted using preoperative pool SPECT images in 9 patients. The predicted LVEF was closely correlated with the measured LVEF after the operation (y = 1.09x-4.37, r = 0.87, p less than 0.01). Thus, gated blood pool SPECT can be a useful non-invasive technique not only for detecting and quantifying left ventricular aneurysm but also for predicting a residual left ventricular function after aneurysmectomy.

Adult↗
PubMed1991

[Usefulness of high resolution transesophageal echocardiography for diagnosis of ruptured chordae tendineae of the mitral valve: clinical and echocardiographic characteristics].

Transesophageal echocardiography with high resolution (TEE; 5 MHz, convex type probe) revealed ruptured chordae tendinae of the mitral valve (RCT) in seven patients. However transthoracic echocardiography (TTE) was diagnostic only in two patients. These all seven patients had mitral valve prolapse and mitral regurgitation documentated by TTE. Six of seven patients were 59 years or older, and four patients had only mild symptoms. TEE showed the systolic appearance of an edge echo, suggesting an edge of ruptured chordae tendineae within the left atrium. These results show that TEE is a useful method for detecting RCT of the mitral valve, especially in the aged patients with MVP and mitral regurgitation. It is because of the availability of high resolution and nearfield in TEE.

Adult↗
PubMed1991

Effects of early and later reperfusion on healing speed of experimental myocardial infarct.

The effects of reperfusion on myocardial infarct healing in the rabbit were analyzed using two morphometric indexes: the ratio of the volume of the organized portion of infarct to the volume of the whole infarct (%O/I), and the ratio of the minimal thickness of the infarct zone to the normal zone thickness (thinning ratio). In the nonreperfused infarcts, %O/I increased from 43.8 +/- 3.1% (mean +/- SEM) at 48 h to 85.7 +/- 2.5% at seven days, which supported the validity of this index. The thinning ratio was 0.50 +/- 0.03 at 48 h and did not change during the following five days. In other groups of rabbits, the coronary artery was temporarily occluded for 30 mins (early reperfusion) or 60 mins (late reperfusion), and the hearts were analyzed at 72 h or seven days. Early reperfusion limited infarct size as a percentage of the area at risk (%I/AAR) by approximately 50%, but late reperfusion did not. In both nonreperfused and reperfused infarcts, %O/I correlated significantly with absolute infarct size. Furthermore, the regression lines of the relationship of infarct size to %O/I of early and late reperfused infarcts shifted towards higher %O/I values compared with that of nonreperfused infarcts at seven days, which suggested accelerated organization. However, such a regression line shift by reperfusion was not detected at 72 h after infarction. The thinning ratio was higher in early reperfused infarcts compared to nonreperfused or late perfused infarcts, and there was a weak inverse correlation between thinning ratio and %I/AAR when the data of reperfused and nonreperfused infarcts were pooled.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The transient increase of urinary digitalis-like substance excreted during excess sodium intake in reduced renal mass rats.

Urinary immunoreactive endogenous digitalis-like substance (EDLS) excretion was studied in gradually reduced renal mass rats (RRM). Urinary EDLS increased immediately after the start of 1% NaCl ingestion, then it returned to the basal level 2 weeks later. Both urinary sodium excretion and urinary EDLS were significantly higher in 3/6 and 4/6 RRM than in control until 2 weeks after starting 1% NaCl. However, there was no difference in blood pressure between the groups. Transient EDLS increase may play an important role in maintaining sodium and water homeostasis, but its transient increase apparently does not contribute to blood pressure elevation.

Animals↗