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Biomedical subjects

M Imazu

Publications and source records attributed to M Imazu.

At least 37 records · Page 2Linked to original sources
PubMed1998

Prediction of short- and intermediate-term prognoses of patients with acute myocardial infarction using myocardial contrast echocardiography one day after recanalization.

OBJECTIVES: This study sought to determine whether microvascular integrity in the risk area (RA) for myocardial infarction (MI) one day after recanalization predicts the outcome in patients with first acute MI. BACKGROUND: Immediately after recanalization, microcirculation in the RA is modified by both hyperemic response and microvascular impairment. METHODS: Fifty consecutive patients who underwent serial myocardial contrast echocardiography before and one day after recanalization (day 2) were studied. All patients had a completely occluded lesion in the left anterior descending coronary artery alone, and underwent successful reperfusion therapy. The relative size of the initial RA (RA ratio) and peak gray scale ratio (PGSR) within the RA on day 2 were determined. Patients were followed for a median of 22 months to evaluate clinical outcome. RESULTS: On day 2, PGSR was a median of 0.46. Study patients were subdivided into two groups, group A of 24 patients with acceptable opacification (PGSR > 0.46 on day 2) and group B of 26 patients without it. Major cardiac events (cardiac death, nonfatal MI and repeat admission for congestive heart failure) were more frequently observed in group B (28% vs. 4%, Cox hazard ratio=8.5, p=0.05, 95% confidence interval [CI] 1.03 to 69.9). The median value of the RA ratio was 0.45. Patients (n=15) with RA ratio > 0.45 on day 1 and PGSR on day 2 < or = 0.46 exhibited a 10.7-fold relative risk for major cardiac events (p=0.005, 95% CI 2.06 to 55.8) and a 3.69-fold relative risk for composite cardiac events (major cardiac events and target lesion revascularizations) after the initial intervention (p=0.004, 95% CI 1.51 to 9.04). CONCLUSIONS: The assessment of both the size of the initial RA and microvascular integrity on day 2 enables precise determination of the efficacy of reperfusion therapy and prediction of the short- and intermediate-term prognoses of patients with recanalized MI.

Adult↗
PubMed1998

Differences in histopathologic findings in restenotic lesions after directional coronary atherectomy or balloon angioplasty.

BACKGROUND: Directional coronary atherectomy (DCA) and balloon angioplasty (percutaneous transluminal coronary angioplasty, PTCA) differ in their method of dilating stenotic vessels. It is not known whether there is any morphologic difference between restenotic lesions that occur after DCA and those occurring after PTCA. METHODS: To evaluate histopathologic differences between restenotic lesions after DCA or PTCA, we reviewed coronary atherectomy specimens excised from 37 patients with stable angina. Patients were classified into three groups: those with restenotic lesions after DCA (n = 8), those with restenotic lesions after PTCA (n = 14), and those with primary lesions (n = 15). Specimens were analyzed immunohistochemically using monoclonal antibodies specific for smooth muscle cells (HHF35), endothelial cells (CD31), macrophage-derived foam cells (CD6B) and cell replication activity (Ki-67). In seven patients undergoing repeat DCA, de novo plaques and restenotic plaques were compared. RESULTS: Stellate smooth muscle cell (S-SMC) content in restenotic lesions after DCA (87%) was significantly greater than that in primary lesions (40%; P = 0.032) and that in restenotic lesions after PTCA (43%; P = 0.045). Foam cells tended to be more prevalent in primary lesions (67%) than in restenotic lesions after DCA (25%; P = 0.062) or after PTCA (36%; P = 0.10). Restenotic lesions after DCA had more S-SMC proliferation and fewer foam cells than did primary lesions. There were no differences in the presence of thrombus, calcification, cholesterin, hemosiderin, the percentage of HHF35-positive cells or Ki-67-positive cells, or neovascularization among the three groups. CONCLUSIONS: Smooth muscle cell proliferation may have an important role in the development of restenosis after DCA. Fewer foam cells are present in restenotic lesions after DCA or PTCA than are present in primary lesions.

Aged↗
PubMed1998

Comparative study of dobutamine stress electron-beam computed tomography and exercise thallium scintigraphy in the diagnosis of patients with suspected coronary artery disease.

To evaluate the diagnostic value of dobutamine stress electron-beam computed tomography (EBCT) as compared with exercise stress thallium-201 single-photon emission computed tomography (201T1-SPECT) for the detection of myocardial ischemia, 10 patients with proven or suspected coronary artery disease underwent both tests. Nine of the 10 patients also underwent coronary angiography. EBCT images were analyzed objectively to evaluate systolic wall thickening and analyzed segmentally to determine the distribution of the coronary arteries. Dobutamine stress EBCT revealed the presence of ischemia in 59 segments, whereas exercise stress 201T1-SPECT revealed ischemia in 51 segments (agreement = 73%). The advantage of dobutamine stress EBCT was demonstrated in the inferior/posterior segments as compared with the results of exercise stress 201T1-SPECT. The overall sensitivity for detecting ischemic regions supplied by coronary arteries with significant stenosis (diameter stenosis > 50%) was 83% for dobutamine stress EBCT and 79% for exercise stress 201T1-SPECT (p = NS), with specificities of 75% and 82% (p = NS). Thus, dobutamine stress EBCT presents a reasonable alternative to exercise stress 201T1-SPECT for the objective assessment of patients with suspected coronary artery disease.

Adult↗
PubMed1997

Immunohistochemical analysis of hepatocyte growth factor in human coronary atherectomy specimens: comparison with transforming growth factor beta isoforms.

The expression and localization of hepatocyte growth factor/scatter factor (HGF/SF) were examined immunohistochemically in 59 human coronary artery lesions retrieved by directional coronary atherectomy and compared with the localization of transforming growth factor beta isoforms (TGF-beta 1, -beta 2, and -beta 3). In 21 of the 59 specimens (35.6%) HGF-like immunoreactivity (HGF-IR) was revealed. The HGF immunopositivity rate of 45% (14/31) in thrombotic tissue was significantly (P < 0.05) higher than the rates of 7.3% (4/55), 7.1% (3/42), and 0% (0/14) in fibrous tissue, neointimal hyperplasia and atheromatous gruel, respectively. Immunoreactivity for HGF was much weaker than that for TGF-beta isoforms in these components except in thrombotic tissue. These cells exhibiting strong HGF-IR were inflammatory cells such as monocytes/macrophages in thrombotic tissue, in tissue lesions adjacent to a thrombus, and outside the capillary walls in a portion of the neovascularized lesions. Smooth muscle cells (SMCs) hardly demonstrated HGF-IR. In contrast, in control coronary arteries obtained at autopsy, the HGF-IR was strongly expressed in SMCs. These findings suggest that HGF produced by macrophages play a part in the process of coronary plaque formation attributable to thrombus in man.

Adult↗
PubMed1997

Comparison of proliferative activity in coronary plaques from patients with coronary ischemia. Histopathological and immunohistochemical analysis.

The overgrowth of cells of the vessel wall, especially of the smooth muscle cells (SMCs), contributes to the pathogenesis of coronary atherosclerosis and wound repair after coronary angioplasty. However, the association between cellular proliferation in coronary lesions and clinical pathophysiology remains to be clarified in humans. Thus, we investigated proliferative activity in coronary tissues obtained from patients with coronary ischemia. The proliferative activity in tissues obtained by using directional coronary atherectomy (DCA) from 87 coronary lesions was assessed by immunohistochemical staining for the proliferating cell nuclear antigen (PCNA). The lesions were divided into 34 primary lesions and 53 postangioplasty lesions. The 34 primary tissue samples were obtained from 9 patients with stable angina pectoris (SAP) and 25 patients with acute coronary syndromes (ACS). Collectively, the 53 postangioplasty tissue samples were obtained from 37 patients with SAP and 16 patients with ACS. The PCNA labeling index (LI) was quantified as the mean percentage of PCNA-positive cells in the 3 most positive high-power fields (x 200). The mean LIs were high in the primary ACS samples [8.9 +/- 2.1% (p = 0.01)] and postangioplasty samples [2.3 +/- 0.8% (p = 0.08) in SAP cases and 4.1 +/- 2.4% (p = 0.06) in ACS cases] compared with the primary SAP samples (0.2 +/- 0.2%). Intimal hyperplasia, a random proliferation of SMCs (alpha-actin positive) was marked in the primary ACS samples (76%) as well as in the postangioplasty SAP (92%) and ACS (81%) samples, as compared with the primary SAP samples (33%) (p < 0.01). PCNA expression was mainly evident in the nucleus of the SMCs and CD68-positive macrophages. Many PCNA-positive cells were localized in plaque areas, as follows: intimal hyperplasia, neovascularized lesions, lesions with macrophage clusters, and lesions near areas of disrupted internal elastic lamina. The levels of PCNA expression in coronary lesions were not associated with the subsequent development of restenosis after DCA. Our findings suggest that the excessive proliferation of vascular wall cells, especially SMCs, is involved in the pathogenesis of ACS and in the process of wound repair after angioplasty in humans.

Adult↗
PubMed1997

[Assessment of ventricular wall motion and volume by fast cine MRI using Fastcard sequence].

Left ventricular wall motion and volume are important factors for assessment of cardiac function. Recent advances in magnetic resonance imaging(MRI) have allowed fast cine MR sequences. Fastcard sequence is an electrocardiographically triggered gradient echo sequence with k-space segmentation and have enabled fast cine acquisition of the heart during breath holding. Improvement in image quality and contrast between myocardium and intraventricular cavity may facilitate assessment of cardiac function using the phased array coil. Drug stress MRI for detection of significant coronary artery stenosis could be more easily performed by this sequence than conventional cine MR sequences. Sequential short axis images obtained with Fastcard sequence also provide an accurate method without assumption of ventricular shape.

Cardiac Volume↗
PubMed1997

Cyclic GMP-dependent protein kinase regulates the L-type calcium current in rat ventricular myocytes.

This study aimed to elucidate the mechanism of cyclic granosine monophosphate (cGMP)-dependent protein kinase (PK-G) regulation of the L-type Ca2+ channel current (ICa(L) in young rat ventricular myocytes using whole-cell voltage clamp with internal perfusion. ICa(L) was usually elicited from a holding potential (HP) of -40 mV. Stimulated ICa(L) (by 2 microM isoproterenol) was inhibited to the basal level by internal perfusion with 50 nM PK-G (activated by 8Br-cGMP, 0.1 microM). Basal ICa(L) (non-stimulated through the cyclic adenosine monophosphate (cAMP)/PK-A pathway) was also inhibited to various degrees (large, medium, or small) by internal application of PK-G (25 nM). The average inhibition was 42.1%, and there were no differences in the inhibition during development. The inhibition by PK-G was blocked by the PK-G substrate peptide (300 microM) and by heart-inactivation of PK-G. The inhibited ICa(L) was reversed by ISO (seven of eight cells). When an HP of -80 mV was used, the inhibition produced by PK-G was much less. The inhibitory effects of PK-G were not mediated by activating phosphodiesterases or protein phosphatases, but most likely by a direct phosphorylation of the Ca2+ channel or associated regulatory protein. The inhibitory effect of PK-G may be explained by a balance between the activities of PK-A and PK-G in regulating the slow Ca2+ channels at two separate sites.

Animals↗
PubMed1996

A comparison of the prevalence and risk factors of high blood pressure among Japanese living in Japan, Hawaii, and Los Angeles.

THE AUTHORS STUDIED THE PREVALENCE AND RISK FACTORS of hypertension in samples of 2053 Japanese ages 40 to 70 in Hiroshima, Hawaii, and Los Angeles. The prevalence of hypertension (systolic blood pressure greater than or equal to 140 mmHg, diastolic blood pressure greater than or equal to 90 mmHg, or receiving antihypertensive drug treatment) was higher in Hawaii and Los Angeles for both sexes and almost all ages than in Hiroshima. The age- and sex-adjusted prevalence of hypertension in Hawaii, Los Angeles, and Hiroshima was 42.6%, 37.2%, and 29.7%. Hypertension was associated with a significant elevation in serum glucose, insulin, triglyceride, and total cholesterol levels in the combined participant population of Hawaii, Los Angeles, and Hiroshima. Age- and sex-adjusted mean values of serum total cholesterol, triglyceride, and insulin were highest in Hawaii and lowest in Hiroshima. The mean body mass index and 2-hour serum glucose levels were greatest in Hawaii and equal in the two other cohorts. These results suggest that hyperinsulinemia and hyperlipidemia may explain the prevalence of hypertension in the research participants.

Adult↗
PubMed1995

Risk factors for restenosis after percutaneous transluminal coronary angioplasty: role of lipoprotein (a).

To evaluate serum levels of lipoprotein (a) (Lp[a]) as a predictor of restenosis after percutaneous transluminal coronary angioplasty (PTCA), we evaluated 71 patients who underwent elective single-vessel angioplasty. Patients were divided into two groups according to the presence (n = 24 [34%]; group R) or absence (n = 47 [66%]; group N) of restenosis. Serum insulin levels were similar before and after the glucose challenge test in both groups. The median level of serum Lp(a) was 34.9 mg/dl in group R compared with 19.4 mg/dl in group N (p < 0.01). The frequency of the apo E4 allele was 4 (17%) in group R and 4 (9%) in group N (p = NS). The incidence of restenosis was significantly higher in patients with Lp(a) levels > or = 30 mg/dl than in those with Lp(a) levels < 30 mg/dl (65% vs 26%; p < 0.01). Our results indicate that a serum Lp(a) level > or = 30 mg/dl is a risk factor for restenosis.

Aged↗
PubMed1995

Effect of cilazapril on vascular restenosis after percutaneous transluminal coronary angioplasty.

BACKGROUND: In experimental studies using cilazapril, the strongest inhibition of neointima formation was obtained when treatment was initiated 6 days before injury. The MERCATOR trial showed no reduction in restenosis with cilazapril given after percutaneous transluminal coronary angioplasty (PTCA). The purpose of this study is to determine whether previous administration of cilazapril could prevent restenosis. METHODS: A total of 167 patients were randomly and prospectively assigned to the cilazapril group or the control group. In the cilazapril group, 78 patients received a 2 mg dose of cilazparil daily, starting 7 days before PTCA and continuing for 6 months. Only 128 patients (cilazapril 56, control 72) completed the study because 39 dropped out. Coronary angiograms were evaluated by the quantitative coronary angiogram (QCA) system. RESULTS: There were no differences between the two groups of patients with regard to baseline clinical and angiographic characteristics. QCA analysis (cilazapril 66 lesions, control 101 lesions): the loss at follow-up in minimal lumen diameter was 0.36 +/- 0.57 mm in the cilazapril group and 0.57 +/- 0.75 mm in the control group (P < 0.05). Restenosis rate: in the cilazapril group, 16 of 56 patients (28.6%) had restenosis in contrast to 36 of 72 patients (50.0%) in the control group (P < 0.02). When vessel restenosis was evaluated, 16 of 63 vessels (25.4%) demonstrated restenosis in the cilazapril group, in contrast to 41 of 82 vessels (50.0%) in the control group (P < 0.01). CONCLUSIONS: Treatment using cilazapril 7 days before PTCA significantly reduced the rate of restenosis. These data suggest that previous administration of cilazapril might be important for preventing restenosis.

Aged↗
PubMed1988

Three distinct forms of type 2A protein phosphatase in human erythrocyte cytosol.

Two type 2A protein phosphatases, phosphatases I (Mr = 180,000) and III (Mr = 177,000), were purified to near homogeneity from human erythrocyte cytosol. Phosphatase I was composed of alpha (34 kDa), beta (63 kDa), and delta (74 kDa) subunits in a ratio of 1:1:1. Phosphatase III comprised alpha, beta, and gamma (53 kDa) subunits in the same ratio. Heparin-Sepharose column chromatography converted most of phosphatase I and 20% of phosphatase III into alpha 1 beta 1 which were indistinguishable from phosphatase IV (Usui, H., Kinohara, N., Yoshikawa, K., Imazu, M., Imaoka, T., and Takeda, M. (1983) J. Biol. Chem. 258, 10455-10463). The catalytic subunit alpha and the beta subunit of phosphatases I, III, and IV displayed identical V8 and papain peptide maps, respectively, while the peptide maps of the alpha, beta, gamma, and delta subunits were clearly distinct. The molar ratio of phosphatases I, III, and IV in erythrocyte cytosol was estimated to be 6:1:14. Comparison of molecular activities of alpha, alpha 1 beta 1, alpha 1 beta 1 delta 1, and alpha 1 beta 1 gamma 1 revealed that beta suppressed phosphorylase and P-H2B histone phosphatase activities of alpha but stimulated the P-H1 histone phosphatase activity, and delta suppressed all the phosphatase activities of alpha 1 beta 1. The gamma subunit stimulated the P-histone phosphatase activity of alpha 1 beta 1 but inhibited the phosphorylase and P-spectrin phosphatase activities. The beta subunit increased the Mg2+ or Mn2+ requirement for P-H2B histone phosphatase activity of alpha, an effect which was counteracted by delta. The effects of heparin, H1 histone, protamine, and polylysine on the phosphorylase phosphatase activity of phosphatases I, III, IV, and alpha were described and discussed in connection with the functions of the subunits.

Cytosol↗
PubMed1985

Comparison of tyrosine protein kinases in membrane fractions from mouse liver and Ehrlich ascites tumor.

Tubulin was phosphorylated mainly at tyrosine residues by membranes from mouse liver and Ehrlich ascites tumor with ATP in the presence of MnCl2, ZnCl2, NaVO3, and Nonidet P-40 in an epidermal growth factor (EGF)- and insulin-independent manner. The tyrosine tubulin kinase activity in the tumor membranes is comparable to the activity in liver membranes. Two tyrosine tubulin kinases, namely I (Mr = 64,000) and II (Mr = 46,000), were purified 5-17-fold and were free of the EGF receptor and the insulin receptor. Phosphorylation of endogenous proteins produced major alkali-resistant phosphoproteins of 56 and 53 kDa in kinase I preparations and of 46 and 37 kDa in kinase II preparations. These kinases phosphorylated tubulin stoichiometrically at tyrosine and had a preference of alpha-subunit to beta-subunit of tubulin. Apparent Km values of kinases I and II for tubulin were about 4 and 8 microM and for ATP were about 2 and 4 microM, respectively. Thiol reagents inhibited their reactions. N alpha-p-Tosyl-L-lysine chloromethyl ketone stimulated the reactions at 1 mM but inhibited them at 5 mM. Although kinases I and II also phosphorylated angiotensin II, tyrosine-glutamate copolymers, and heavy chains of anti-pp60src IgG, they differed from each other in preferences for the substrates. More than 95% of the enzyme activities was not immunoprecipitated with the anti-pp60src IgG which cross-reacts with pp60c-src. In comparison with the corresponding liver enzymes, tumor enzymes were more stable to heat and incorporated more phosphate into tubulin, but showed lower activity toward angiotensin II and anti-pp60src IgG.

Adenosine Triphosphate↗
PubMed1985

Comparison of tyrosine phosphorylation of proteins by membrane fractions from mouse liver, Ehrlich ascites tumor and MH134 hepatoma.

When membrane fractions from mouse liver, Ehrlich ascites tumor and MH134 hepatoma were incubated with [gamma-32P]ATP at 0 degree C in the presence of MnCl2, ZnCl2 and NaVO3, proteins were phosphorylated on tyrosines to a larger extent in liver membranes than in tumor membranes. Separation of labelled proteins by SDS-gel electrophoresis showed phosphorylated alkali-resistant bands of 170, 140, 130, 80, 56, 53 and 46 kDa proteins in Ehrlich ascites tumor membranes; liver membranes exhibited more strongly phosphorylated bands of 170, 56, 53 and 46 kDa proteins. Epidermal growth factor stimulated the tyrosine phosphorylation of only a 170 kDa protein, which was more significant in liver membranes. Liver membranes exhibited slightly higher levels of tyrosine protein kinase activity compared to tumor membranes.

Animals↗
PubMed1984

Multiple phosphorylation of rat-liver glycogen synthase by protein kinases.

The phosphorylation sites in liver synthase were studied using gel filtration and high performance liquid chromatography of 32P-labeled tryptic peptides. Phosphorylase b kinase, calmodulin-dependent glycogen synthase kinase and glycogen synthase kinase 4 from liver phosphorylated the same low Mr tryptic peptide. cAMP-dependent protein kinase mainly phosphorylated the low Mr tryptic peptide, but also incorporated phosphate into two other peptides. Glycogen synthase kinase 5 phosphorylated a single tryptic peptide, whereas glycogen synthase kinase 3 phosphorylated several tryptic peptides. Calcium-phospholipid-dependent protein kinase phosphorylated two tryptic peptides, the major one of which had the same chromatographic properties as the low Mr peptide described above. These findings confirm that liver glycogen synthase undergoes multi-site phosphorylation and suggest that the topography of the sites is generally similar to that in muscle glycogen synthase.

Animals↗