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Biomedical subjects

T Isshiki

Publications and source records attributed to T Isshiki.

At least 73 records · Page 4Linked to original sources
PubMed1993

High-resolution transmission electron microscopy of hexagonal and rhombohedral molybdenum disulfide crystals.

Natural (molybdenite) and synthesized molybdenum disulfide crystals have been studied by high-resolution transmission electron microscopy. The image simulation demonstrates that the [0001] and [0110] HRTEM images of hexagonal and rhombohedral MoS2 crystals hardly disclose their stacking sequences, and that the [2110] images can distinguish the Mo and S columns along the incident electron beam and enable one to determine not only the crystal structure but also the fault structure. Observed [0001] images of cleaved molybdenite and synthesized MoS2 crystals, however, reveal the strain field around partial dislocations limiting an extended dislocation. A cross-sectional image of a single molecular (S-Mo-S) layer cleaved from molybdenite has been observed. Synthesized MoS2 flakes which were prepared by grinding have been found to be rhombohedral crystals containing many stacking faults caused by glides between S/S layers.

Crystallography↗
PubMed1993

A new inherited prion disease (PrP-P105L mutation) showing spastic paraparesis.

We report the clinicopathological findings of 5 patients with an inherited prion disease with a codon 105 (Pro to Leu) mutation. All of the patients had a spastic gait disturbance and progressive dementia without either cerebellar signs, myoclonus, or periodic synchronous discharges. Autopsy of 3 patients revealed numerous amyloid plaques in the cerebral cortex, especially in the motor cortex and the frontal lobe where neuronal loss and severe gliosis were observed in the absence of spongiform changes. The cerebellum was preserved histologically except for only a few amyloid plaques. The pyramidal tracts in the brainstem and spinal cord showed vacuolated changes and a loss of myelin, but no prion protein accumulations. Thus, the prion protein codon 105 mutation is considered to correspond to a new variant of the Gerstmann-Sträussler syndrome with spastic paraparesis.

Adult↗
PubMed1993

Transluminal extraction atherectomy and adjunctive balloon angioplasty for restenosis after Palmaz-Schatz coronary stent implantation.

Two patients who developed restenosis after implantation of Palmaz-Schatz coronary stents were successfully treated by transluminal extraction atherectomy and there has been no recurrence on follow-up angiograms. The optimum strategy for managing restenosis after coronary stenting remains unclear, but transluminal extraction atherectomy appears to be a safe and effective option.

Angioplasty, Balloon, Coronary↗
PubMed1993

Myocardial reperfusion can be predicted by myoglobin/creatine kinase ratio of a single blood sample obtained at the time of admission.

To evaluate noninvasive markers for determining the reperfusion status without coronary angiography (CAG) or serial blood sampling in patients with acute myocardial infarction (AMI), two markers were examined: (1) serum myoglobin (Mb) level and (2) serum myoglobin/creatine kinase ratio (Mb/CK). Before emergency CAG a blood sample was drawn from 72 AMI patients within 6 hours after the onset of AMI. CAG revealed thrombolysis in myocardial infarction grades (TIMI) 0 to 1 in 56 and TIMI 2 to 3 in 16 patients (spontaneous reperfusion). No patients had received thrombolytic therapy before admission. TIMI 0 to 1 patients were characterized with lower Mb levels than TIMI 2 to 3 patients at admission (346 +/- 476 vs 1558 +/- 2005, mean +/- SD, p < 0.001). Furthermore, the mean Mb0/CK0 ratio in TIMI 2 to 3 patients, who had already achieved the reperfusion at admission, was significantly higher than that in patients with TIMI 0 to 1 patients (6.5 +/- 3.9 vs 2.1 +/- 1.8, mean +/- SD, p < 0.0001). When Mb0/CK0 > 5.0 was assumed to indicate the sufficient reperfusion at admission, the sensitivity, specificity, and accuracy evaluating the reperfusion status were 75%, 96%, and 92%, respectively. It can be concluded that the reperfusion status can be predicted satisfactorily by a single blood sample obtained at the time of admission without CAG.

Aged↗
PubMed1993

Percutaneous angioplasty of stenosed gastroepiploic artery grafts.

OBJECTIVES: This report describes our early experience and results with percutaneous transluminal coronary angioplasty of gastroepiploic artery grafts in 12 patients. BACKGROUND: Angioplasty has been successfully performed in saphenous vein and internal thoracic artery grafts; however, experience with angioplasty in gastroepiploic artery/coronary artery bypass grafts is limited. METHODS: Balloon angioplasty was performed in 12 patients (11 men, 1 woman; mean age 58 +/- 8 years) with either total occlusion (6 patients) or severe stenosis (6 patients) of a gastroepiploic artery/coronary artery anastomosis. In seven patients, a guide wire/balloon catheter system was used through a 7F sheath inserted into the celiac trunk. In seven patients, including two who had unsuccessful wire/balloon angioplasty, an over the wire system was used through a 6.5F Cobra or 7F JR4 guide catheter, selectively inserted into the gastroduodenal artery. RESULTS: Angioplasty was successful in five (83%) of six patients with stenosis and in one of six patients with total occlusion (p = 0.08, 1 - beta = 0.68). The guide wire could not be advanced through the lesion in five patients, and the balloon catheter did not cross the lesion in one patient whose gastroepiploic artery was tortuous. Catheters exhibited better trackability and pushability when the over the wire system was used, and five of the six successes were achieved using this approach. Follow-up arteriography was performed in five patients, and all of the gastroepiploic artery grafts were patent without stenosis. CONCLUSIONS: Angioplasty can be safely performed in stenosed gastroepiploic artery grafts. An over the wire system that uses a thin balloon catheter inserted through a guide catheter in the gastroduodenal artery seems optimal.

Aged↗
PubMed1992

Structures of grain boundaries in long-chain Te crystals observed by high-resolution transmission electron microscopy.

Vacuum-deposited Te crystals, composed of endless chains of the right-handed or left-handed spiral, have been investigated by high-resolution electron microscopy with the aid of image simulation. A (010) grain boundary, which accompanies edge dislocations having an extra layer of the width of one Te chain, has been observed. A through-focal series of images reveal that it is not a reflectional nor a rotational twin boundary but a small angle grain boundary in a single crystal or an inversion twin. The lattice on one side of the boundary is shifted from that on the other side by [001]c/3 + [120]a/8, and inclined at 1.1 degrees around the c-axis of the other side. Also found between crystallites of [100] and [011] orientation is a grain boundary which is built with the (011) facets on one side of the boundary and the (211) or (0,1,10) facets on another side.

Crystallization↗
PubMed1992

Anomalous origin of the left coronary artery from the pulmonary artery: direct assessment of anomalous and collateral coronary flow by pulsed Doppler echocardiography.

We directly assessed the anomalous and collateral coronary flow profiles of a 58 year-old-man with Bland-White-Garland syndrome using pulsed Doppler echocardiography. Doppler recordings in this patient document the utility of pulsed Doppler echocardiography in the assessment of a cardiac shunt associated with a congenital coronary anomaly in an adult.

Blood Flow Velocity↗
PubMed1992

Inclusion bodies in cerebral cortical astrocytes: a new change of astrocytes.

A unique pathological finding of astrocytes was observed in the brain of a 20-year-old man who had severe physical and mental retardation. The brain was malformed showing micropolygyria in several cortical areas. A large number of hypertrophic astrocytes with eosinophilic granular substances in their cytoplasm were found throughout the cerebral cortex. Several staining procedures and electron microscopical examinations were carried out on these intracytoplasmic inclusion. It was found that the appearance and staining character of these inclusions were different from other astrocytic changes, especially the Rosenthal fiber, described so far. The authors consider that these inclusion bodies in cerebral cortical astrocytes represent new pathological changes of astrocytes that appear to be associated with malformation of the brain.

Adult↗
PubMed1992

Characterization of a fission yeast gene, gpa2, that encodes a G alpha subunit involved in the monitoring of nutrition.

The Schizosaccharomyces pombe gpa2 gene was cloned by hybridization with a cDNA for Dictyostelium discoideum G alpha 1. It encodes a homolog of G-protein alpha-subunits with 354 amino acids and a predicted molecular mass of 40,522. Disruption of gpa2 slows cell growth but is not lethal. Cells defective in gpa2 mate and sporulate readily in the presence of plentiful nutrition, bypassing the requirement of nitrogen starvation for the initiation of sexual development. These phenotypes mimic those of cells defective in cyr1 encoding adenylyl cyclase. The level of cAMP in gpa2 null mutants is only one-third of the wild-type level. Mutations in gpa2 that are likely to inhibit the GTPase activity of the gene product cause a slight increase in intracellular cAMP levels and result in leaky sterility. The cAMP level reaches 20 times as high as the wild-type level if a cell carries both this type of gpa2 mutation and a null mutation in pde1 encoding phosphodiesterase. Cells defective in gpa2 fail to produce cAMP in response to glucose stimulation. These results suggest that Gpa2 is involved in the determination of the cAMP level according to nutritional conditions, most likely as a positive regulator of adenylyl cyclase.

Amino Acid Sequence↗
PubMed1992

Coronary angiographic findings and in-hospital outcome of aggressive treatment in impending myocardial infarction.

The influence of coronary angiographic findings and treatment on clinical outcome was determined in 104 patients with impending myocardial infarction (unstable angina with prolonged chest pain and persistent electrocardiographic changes on admission). Coronary arteriography was performed on day one (aggressive strategy) in 50 patients and following medical treatment (conservative strategy) in 48 patients, of whom 40 were unstable. Six elderly patients were treated medically without angiography. A complex eccentric morphology of the coronary vessels was the most common finding in both groups, but the incidence of intracoronary thrombus was significantly higher in the aggressive strategy group (78%) and in unstable patients (77%) compared with patients controlled medically (24%). Severe multivessel disease was also common in refractory patients without thrombus. Percutaneous transluminal coronary angioplasty was less successful and produced more distal emboli in patients with thrombus. Emergency intervention was applied to 90% of the aggressive strategy group-it failed to improve the in-hospital outcome, but shortened hospitalization significantly. Elderly patients treated medically without angiography had the highest mortality. We concluded that intracoronary thrombus plays a major role in the pathogenesis of impending infarction, and that the majority of such patients cannot be stabilized medically. An aggressive strategy can be applied safely to impending infarction and will shorten hospitalization.

Aged↗
PubMed1992

[Percutaneous transluminal coronary angioplasty and coronary bypass grafting for refractory angina in chronic dialysis patients].

Between June 1983 and July 1989, 25 consecutive chronic dialysis patients with medically refractory angina pectoris underwent revascularization, either percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) (21 males and 4 females, mean age of 57 +/- 10 years, and mean duration of dialysis of 3.7 +/- 5.0 years). Patients with single-vessel disease and/or mildly calcified lesions received PTCA (n = 15), while those with multi-vessel disease and/or severely calcified lesions received CABG (n = 10). As controls for PTCA-treated dialysis patients, 208 non-dialysis patients who received initial PTCA in 1988 were used. The mean number of diseased vessels was 2.7 +/- 0.7 for CABG group, and 1.5 +/- 0.8 for PTCA group (p < 0.01). In both groups, 80% of patients were successfully revascularized. In CABG group, however, 7 of 10 patients had major complications including 2 hospital deaths, while no complications occurred in the PTCA group. During the follow-up period after CABG (35 +/- 30 months), recurrent angina developed in one patient, who was successfully treated with PTCA. In the PTCA group, angiographic success was initially obtained in 16 of 21 lesions (76%), which was significantly lower than that in the control group (92%, p < 0.05). Follow-up angiography revealed restenosis in 6 of 16 lesions with successful PTCA (38%), similar to that observed in the control group (32%, p = ns). A second PTCA was successful in 5 of 6 patients with restenosis, however, 4/5 patients developed recurrent angina. Three of 4 patients with a second episode of restenosis underwent a third PTCA, and angina recurred in 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Efficacy of intracoronary thrombolysis versus percutaneous transluminal coronary angioplasty for treating acute myocardial infarction].

The usefulness of percutaneous transluminal coronary angioplasty (PTCA) in patients with evolving myocardial infarction remains controversial. We retrospectively assessed the efficacy of PTCA on myocardial salvage in acute myocardial infarction in comparison with the efficacy of intracoronary thrombolysis (ICT). Sixty-two patients with initial anteroseptal myocardial infarction who had been treated within 6 hrs after the onset of chest pain were categorized into 4 groups: 1) spontaneous recanalization: n = 14, 2) successful PTCA: n = 25 (this group was further subdivided into 2 groups: direct PTCA group, primary PTCA without prior ICT: n = 19; and rescue PTCA group, PTCA after unsuccessful ICT: n = 6), 3) successful ICT group (n = 12), and 4) unsuccessful recanalization group (n = 11). Left ventricular function in the chronic phase was assessed by contrast ventriculography using the global ejection fraction (EF) and regional wall motion (RWM) was assessed by the centerline method. Patients with recanalization had a significantly higher EF than did those without (62 +/- 12 vs 50 +/- 13%, p < 0.01). The mean EFs for groups with successful reperfusion were as follows: 65 +/- 8% for the spontaneous recanalization group, 61 +/- 14% for PTCA group (64 +/- 13% for direct PTCA group, 51 +/- 13% for rescue PTCA group) and 60 +/- 12% for the ICT group. The EFs for the spontaneous recanalization group and the direct PTCA group were significantly greater than that for the rescue PTCA group. The time to reperfusion and the thrombolysis in myocardial infarction (TIMI) flow grade before reperfusion did not affect the preservation of global left ventricular function. RWM of the infarcted area in patients with recanalization were less hypokinetic than that in patients without (p < 0.01). The mean RWM (SD/chord) in the successfully reperfused groups were -2.3 +/- 1.2 for the spontaneous recanalization group, -2.6 +/- 1.2 for the PTCA group (-2.3 +/- 1.1 for the direct PTCA group, -3.3 +/- 1.0 for rescue PTCA group) and -3.0 +/- 0.5 for the ICT group. Hypokinesis of the infarcted area was more severe in the rescue PTCA group than in the spontaneous recanalization group and the direct PTCA group (multiple comparison test p < 0.01, respectively), and hypokinesis was more severe in the ICT group than in the direct PTCA group (Student's t-test, p < 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Responses of human gastroepiploic arteries to vasoactive substances: comparison with responses of internal mammary arteries and saphenous veins.

We examined the responses of human gastroepiploic arteries to histamine, serotonin, and norepinephrine, comparing those of internal mammary arteries and saphenous veins. Fresh specimens of the vessels were obtained intraoperatively from 21 patients. The vessels were suspended in organ chambers to record isometric tensions. With gastroepiploic arteries, histamine induced relaxations in the endothelial rings (85% +/- 7%) but failed to induce any contractions or relaxations in the rings without endothelium. The relaxations were prevented by methylene blue or hemoglobin and the H1-histaminergic receptor antagonist chlorpheniramine. With internal mammary artery rings with endothelium, histamine at a low concentration (10(-8) to 10(-5.5) mol/L) induced relaxations (53% +/- 12%) but evoked contractions at a higher concentration (10(-5) to 10(-4.5) mol/L). With saphenous veins, histamine caused only contractions. Serotonin induced markedly greater contractions in saphenous veins than in either artery. The endothelium inhibited the maximal contraction in response to serotonin in both arteries but not in veins. With the gastroepiploic artery, the responses to norepinephrine and serotonin were similar to those of the internal mammary artery. Histamine induces endothelium-dependent relaxations only, and histaminergic receptors that induce contractions may be absent on vascular smooth muscle cells. These vasoactive properties may contribute to the high patency as a coronary graft.

Acetylcholine↗
PubMed1991

Comparative study between the gastroepiploic and the internal thoracic artery as a coronary bypass graft. Size, flow, patency, histology.

Ninety-two gastroepiploic artery (GEA) and 322 internal thoracic artery (ITA) grafts which underwent postoperative angiography (0.5-24 postoperative months, mean 2.0 months) were compared. The sites of GEA anastomosis were 5 left anterior descending, 3 diagonal, 16 circumflex and 68 right coronary arteries and for ITA grafts, 241 left anterior descending, 40 diagonal, 36 circumflex and 5 right coronary arteries. Patency rates were 96% (88/92) of GEA and 98% (314/322) of ITA, respectively. No focal stenosis in the graft trunk was found in both GEA and ITA except occasional spasm in GEA. Six (6%) GEAs were opacified via the superior mesenteric artery. Mean diameter of grafts just proximal to the anastomosis measured by angiogram was 2.3 mm in GEA and 1.9 mm in ITA (P less than 0.01). Free flow after intraluminal papaverine injection was 90.6 ml/min (50-300 ml/min) in 48 GEAs and 81.3 ml/min (50-150 ml/min) in 98 ITAs. Histology showed normal to mild intimal sclerotic changes in 58 of 63 (92%) GEAs and in 94 of 95 (99%) ITAs. From these results, we concluded that GEA is a suitable conduit and good long term patency similar to ITA grafting can be expected in coronary artery bypass grafting.

Arteries↗
PubMed1991

Spontaneously hypertensive rats demonstrate increased renal vascular alpha 1-adrenergic receptor responsiveness.

To determine alpha 1-adrenergic receptor responsiveness of the renal vasculature in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR), phenylephrine (2.5 or 5.0 micrograms.kg-1.min-1 iv) or saline was infused. Effective renal blood flow (ERBF) and glomerular filtration rate were determined by p-aminohippuric acid and inulin clearances, respectively. Peritubular capillary, proximal tubular, and stop-flow pressures (SFP) were measured by micropuncture. Phenylephrine decreased ERBF (6.27 +/- 0.48 to 4.55 +/- 0.65 ml.min-1.g-1; P less than 0.05) and increased arterial pressure and SFP (31.5 +/- 0.9 to 34.2 +/- 1.0 mmHg) in SHR. It only increased arterial pressure and ERBF in WKY without changing SFP. Afferent arteriolar resistance (RA) and glomerular capillary pressure (PG) remained unchanged, whereas efferent resistance (RE) decreased in WKY; in contrast, RA, RE, and PG increased in SHR (RA 21.2 +/- 2.0 to 38.1 +/- 7.1 mmHg.ml-1.min.g, RE 6.9 +/- 0.6 to 13.9 +/- 3.8 mmHg.ml-1.min.g; and PG 49.6 +/- 0.9 to 53.7 +/- 1.1 mmHg; all P less than 0.05). These data demonstrated increased SHR afferent and efferent arteriolar responsiveness; WKY efferent arteriolar hyperresponsiveness was not observed. The findings support the concept of augmented intrarenal vascular alpha 1-adrenergic responsiveness in hypertension that may predispose to subsequent glomerular hypertension.

Animals↗
PubMed1991

[Long-term prognosis in patients with echocardiographic left ventricular dysfunction masquerading as dilated cardiomyopathy].

The long-term prognosis and prognostic factors were assessed in patients with left ventricular dilatation with impaired function secondary to idiopathic dilated cardiomyopathy (DCM) or to heart diseases of various pathogeneses masquerading as DCM (DCM-like). The echocardiographic criteria for DCM-like disease were 1) left ventricular end-diastolic dimension exceeding 60 mm and 2) fractional shortening less than 15%. Those who showed improvement in either of these 2 parameters within 3 months were excluded from this study. One hundred and fifty-eight of 35,250 serially examined patients fulfilled the definitions. The pathogeneses of diseases were valvular heart disease (VHD) in 30 patients, ischemic heart disease (IHD) in 37, alcoholic cardiomyopathy (AC) in 12, hypertensive heart disease (HHD) in 31 and DCM in 48. All of the survivors were followed for more than 24 months; an average of 40 months. During this period, there were a total of 75 deaths, 18 (27%) of whom were judged as sudden death. Five-year survival rates calculated using the Kaplan-Meier method in AC and HHD were 86% and 77%, respectively, which were significantly higher than those in DCM (48%; p < 0.05); whereas, patients with VHD and IHD had lower values (60% and 46%, respectively) which were nearly equal to those in DCM. Factors that contributed to the increase in total cardiac mortality were advanced age, higher NYHA functional class, larger cardiac size on chest radiograph and history of heavy alcohol intake. Each of these factors were closely related to the specific pathogeneses as follows: age to IHD, cardiac size to VHD, and NYHA functional class to DCM. Long-term prognosis of DCM-like heart diseases, especially those of IHD and VHD, seemed to be as bad as those of DCM.

Adult↗