Search PubMed⌕ Search

Biomedical subjects

T Yabe

Publications and source records attributed to T Yabe.

At least 19 recordsLinked to original sources
PubMed1995

Quantitative measurements of cardiac phosphorus metabolites in coronary artery disease by 31P magnetic resonance spectroscopy.

BACKGROUND: 31P metabolite measurements in the human heart by magnetic resonance spectroscopy (MRS) have been reported previously. By use of a method in which metabolite content was quantified with reference to a standard located outside the chest, it has become possible to measure the content of phosphocreatine (PCr) and ATP in vivo in the human heart. In this study, PCr and ATP contents were measured by 31P MRS and compared in human myocardium with reversible ischemia or scar diagnosed by exercise thallium scintigraphy. METHODS AND RESULTS: Forty-one subjects with stenosis of the left anterior descending coronary artery (> 50%) and 11 healthy control subjects (C) composed the present study group. Patients were divided into two groups on the basis of exercise 201Tl scintigraphy: a reversible 201Tl defect group (RD[+], n = 29) who demonstrated redistribution at late image and a fixed 201Tl defect group (RD[-], n = 12). While the subjects lay supine within the magnet, 31P MR spectra were obtained from the anterior and apical regions of the left ventricle by slice-selected one-dimensional chemical shift imaging. For metabolite quantification, a standard was placed at the center of the surface coil. ANOVA revealed significant differences among the three groups with respect to the mean (+/- SD) PCr at rest (C, 12.14 +/- 4.25 > RD[+], 7.64 +/- 3.00 > RD[-], 3.94 +/- 2.21 mumol/g wet heart tissue, P < .05) as well as a significant decrease in ATP in the RD(-) group (C, 7.72 +/- 2.97; RD[+], 6.35 +/- 3.17 > RD[-], 4.35 +/- 1.52 mumol/g wet heart tissue, P < .05). CONCLUSIONS: Compared with healthy control subjects, PCr content decreased significantly in patients with both reversible and fixed 201Tl defects, and ATP content decreased significantly in subjects with fixed thallium defects. These results suggest that the measurement of ATP content in the human heart by 31P MRS is a clinically important method for the evaluation of myocardial viability.

Adenosine Triphosphate↗
PubMed1995

Determinants of exercise capacity in the hypertensive elderly--a study based on the assessment of cardiac reserve by dipyridamole radionuclide angiography.

To evaluate the determinants of exercise capacity in the hypertensive elderly with an assessment of cardiac reserve by dipyridamole radionuclide angiography, 31 elderly subjects (aged 62 to 78 years, 15 hypertensive and 16 normotensive) underwent symptom-limited maximum treadmill exercise with measurement of maximal oxygen consumption along with radionuclide angiography in list mode at rest and after dipyridamole infusion. In the normotensive elderly, maximal oxygen consumption correlated with relative filling volume during the rapid filling period at rest (r = 0.58; p < 0.05), and correlated inversely with the percent change in the peak ejection rate with dipyridamole (r = -0.63; p < 0.01). In contrast, maximal oxygen consumption correlated with atrial contribution at rest (r = 0.69; p < 0.005), and correlated inversely with the percent change in atrial contribution with dipyridamole (r = -0.87; p < 0.0001) in the hypertensive elderly. These results indicate that the mechanisms for maintaining exercise capacity are different in elderly subjects with or without hypertension.

Aged↗
PubMed1995

[Diagnosis and prognosis of elderly patients with coronary artery disease: assessment with dipyridamole thallium imaging].

Noninvasive evaluation of coronary artery disease is difficult in elderly patients because of their limited exercise-capacity. The diagnostic and prognostic value of dipyridamole perfusion scintigraphy was assessed in 147 patients aged 65 years and older. All patients underwent coronary angiography. Initially, 32 patients had percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG). The other 115 patients were first treated medically and followed for a mean of 29 +/- 22 months. Nine patients (7.9%) had cardiac events including cardiac death and coronary intervention (PTCA or CABG) during the follow-up. Dipyridamole perfusion scintigraphy was performed safely in all patients, whereas treadmill exercise testing could not be adequately performed in 24 patients, 18 of whom had multivessel disease. Multiple regression analysis showed that: fixed defect and reversible defect were powerful detectors of coronary lesions (p = 0.0001, p = 0.0027, respectively), all patients with fixed disease and 94% of patients with only reversible defect had significant coronary lesion; Diffuse slow washout and ST depression were statistically significant for detecting multivessel coronary lesions in patients with fixed disease (p = 0.0001, p = 0.017, respectively), the sensitivity and specificity of diffuse slow washout and/or ST depression for detecting multivessel coronary lesions ware 85% and 74%, respectively, and ST depression was statistically significant for detecting multivessel coronary lesions (p = 0.0002) in patients with only reversible defect, the sensitivity and specificity of ST depression were 88% and 64%, respectively. Cox survival analysis identified diffuse slow washout as the best predictor of future cardiac events among the scintigraphic variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1995

Partially implantable piezoelectric middle ear hearing device. Long-term results.

In accordance with the 1992-1993 Japanese government approval of production and implementation in the health insurance system of the partially implantable piezoelectric middle ear device (P-MEI), we are conducting follow-up studies on the implanted patients. This article reports the results of the 16 cases, which are regarded as successful implantations because these patients are using the device every day as long as they are awake. A successful case is presented to illustrate the efficacy of the device.

Adult↗
PubMed1995

[Tympanosclerosis--clinical and pathological investigation].

Fifty-nine cases of tympanosclerosis were investigated clinically and pathologically, and the following results were obtained: 1) The male to female ratio was about 1:1.8 2) Calcification in the tympanic membrane was most common in the upper quadrants of the pars tensa, and never seen in the pars flaccida. 3) Calcification in the middle ear cavity was most common around the malleus. 4) Chronic otitis media was the most common complication of tympanosclerosis. 5) Preoperative audiometry revealed a stiffness curve with elevated bone conduction thresholds. 6) 54% of the patient had chronic otitis media in the contralateral ear. 7) Microscopic examination revealed calcification in the submucosa of the middle ear. 8) Postoperative hearing was improved in 49 ears (79.7%). Because there was no difference in the average postoperative hearing gain after type I and type III tympanoplasty, type III tympanoplasty is recommended to remove sclerotic masses completely.

Adolescent↗
PubMed1994

Absence of hemodynamic tolerance to nicorandil in patients with severe congestive heart failure.

To evaluate whether hemodynamic tolerance develops to nicorandil, a nitrate and potassium channel opener, 14 patients with chronic heart failure (CHF) were treated with nicorandil and 11 were treated with nitroglycerin (GTN). Doses of GTN or nicorandil were titrated to achieve a > or = 20% reduction in pulmonary capillary wedge pressure (PCWP) within 1 hour, and the infusion was maintained at a constant rate for 24 hours. Both groups of patients had comparable hemodynamic parameters before drug infusions were started. The fall in PCWP was identical after 1 hour infusion of either GTN or nicorandil. In the GTN group, PCWP was not significantly different from the baseline value at 12 hours; however, in the nicorandil group, PCWP remained significantly lower than the preinfusion value for 24 hours. During the study period changes in plasma atrial natriuretic peptide (ANP) concentrations paralleled and correlated with changes in PCWP (r = 0.84, p < 0.001). These findings indicate that CHF patients develop hemodynamic tolerance to GTN within 12 hours of continuous infusion, but not to nicorandil, which remained hemodynamically effective during the 24-hour period of infusion. Furthermore, plasma ANP concentration may be a useful noninvasive index of hemodynamic tolerance during GTN or nicorandil therapy in patients with CHF.

Adult↗
PubMed1994

Cloning of the Saccharomyces cerevisiae gene whose overexpression overcomes the effects of HM-1 killer toxin, which inhibits beta-glucan synthesis.

A gene whose overexpression can endow Saccharomyces cerevisiae cells with resistance to HM-1 killer toxin was cloned from an S. cerevisiae genomic library. This gene, designated HKR1 (Hansenula mrakii killer toxin-resistant gene 1), contains a 5.4-kb open reading frame. The predicted amino acid sequence of the protein specified by HKR1 indicates that the protein consists of 1,802 amino acids and is very rich in serine and threonine, which could serve as O-glycosylation sites. The protein also contains two hydrophobic domains at the N-terminal end and in the C-terminal half, which could function as a signal peptide and transmembrane domain, respectively. Hkr1p is found to contain an EF hand motif of the calcium-binding consensus sequence in the C-terminal cytoplasmic domain. Thus, Hkr1p is expected to be a calcium-binding, glycosylated type I membrane protein. Southern and Northern (RNA) analyses demonstrated that there is a single copy of the HKR1 gene in the S. cerevisiae genome, and the transcriptional level of HKR1 is extremely low. Gene disruption followed by tetrad analysis showed that HKR1 is an essential gene. Overexpression of the truncated HKR1 encoding the C-terminal half of Hkr1p made the cells more resistant to HM-1 killer toxin than the full-length HKR1 did, demonstrating that the C-terminal half of Hkr1p is essential for overcoming the effect of HM-1 killer toxin. Furthermore, overexpression of HKR1 increased the beta-glucan content in the cell wall without affecting in vitro beta-glucan synthase activity, suggesting that HKR1 regulates beta-glucan synthesis in vivo.

Amino Acid Sequence↗
PubMed1994

Detection of myocardial ischemia by 31P magnetic resonance spectroscopy during handgrip exercise.

BACKGROUND: The metabolic changes of myocardial ischemia in patients with coronary artery disease assessed by 31P magnetic resonance spectroscopy (MRS) have been reported previously. A significant decrease in the ratio of phosphocreatine (PCr) to ATP during handgrip exercise in a group of patients with severe coronary artery disease has been demonstrated. However, there are no reports at present that directly compare cardiac 31P MRS data with exercise 201Tl myocardial scintigraphy, now established as one of the most important clinical methods to assess myocardial ischemia. The purpose of this study was to investigate whether 31P MRS with handgrip exercise testing is able to detect myocardial ischemia, demonstrated by exercise 201Tl scintigraphy. METHODS AND RESULTS: Twenty-seven patients with severe stenosis of the left anterior descending coronary artery (> or = 75%) and 11 normal control subjects composed the present study. Patients were divided into two groups on the basis of exercise 201Tl scintigraphy: a reversible 201Tl defect group (RD[+]) who demonstrated redistribution at the late image and a fixed 201Tl defect group (RD[-]). While lying supine within the magnet, subjects performed handgrip exercise at 30% of maximal force once in every two cardiac cycles. 31P MR spectra were collected before and during handgrip exercise. Data were corrected for the saturation factor. ANOVA revealed significant differences among the three groups with respect to the mean +/- SD PCr/ATP ratio at rest (control, 1.85 +/- 0.28 > RD(+), 1.60 +/- 0.19 > RD(-), 1.24 +/- 0.30; P < .05). The PCr/ATP ratio decreased significantly from 1.60 +/- 0.19 at rest to 0.96 +/- 0.28 during exercise (P < .001) in the RD(+) group (n = 15). However, in the RD(-) group (n = 12), the ratio did not change significantly during handgrip exercise (1.24 +/- 0.30 at rest versus 1.19 +/- 0.28 during exercise). Similarly, the ratio did not change in the control group (n = 11) (1.85 +/- 0.28 at rest versus 1.90 +/- 0.23 during exercise). CONCLUSIONS: Contrary to normal subjects or patients with fixed thallium defects, the PCr/ATP ratio was significantly altered by exercise in patients with reversible thallium defects. These results suggest that 31P MRS with handgrip exercise testing is a sensitive method for detecting myocardial ischemia.

Adenosine Triphosphate↗
PubMed1994

Sound evaluation of partially implantable piezoelectric middle ear implant: comparative study of frequency responses.

Two comparative studies were performed in six subjects using partially implantable middle ear implants (MEI). The sound quality was evaluated by speech discrimination tests and sound evaluation tests. In the first experiment, the performance of the output transducer of the MEI and an ear phone of a conventional hearing aid was compared. The MEI showed better results than the hearing aid in both the speech discrimination tests and sound quality rating. In the second experiment, four kinds of frequency responses for the external component of the MEI were compared. Sound quality evaluation in a wide frequency response with a peak at 4000 Hz were superior to those with the frequency response of the present MEI model. In conclusion, improvement of the external component in the frequency response can provide better performance of the MEI.

Audiometry↗
PubMed1993

Genomic structure of NKG5, a human NK and T cell-specific activation gene.

We reported previously the isolation of a cDNA clone, designated NKG5, encoding a secreted protein that is expressed only in natural killer and T cells and is strongly upregulated upon cell activation. In this report we have isolated the NKG5 gene from a human placental genomic library and sequenced the gene and two kilobases of 5'-flanking DNA. Comparison with the cDNA sequence reveals that the NKG5 gene consists of five exons and four introns. Intron 1 contains a DNA segment that was reported to occur as an exon in 519, a closely related cDNA clone that was isolated from a T-cell library. This result indicates that NKG5 and 519 are alternative splicing products of a single gene. The 5'-flanking region of the NKG5 gene was analyzed for homology with the promoter regions of cytokines and other activation-induced genes showing lymphocyte-specific expression. Several segments displaying sequence similarity were identified. We also identified numerous sequence elements that have strong similarity to known binding sites for transcriptional regulatory proteins including T cell-specific and activation-specific regulatory factors. These findings are consistent with the cell-specific expression and the tight regulatory control that is observed for the NKG5 gene.

Alternative Splicing↗
PubMed1993

Medial vestibular nucleus in the guinea-pig: apamin-induced rhythmic burst firing--an in vitro and in vivo study.

In a previous in vitro study, we have shown that guinea-pig medial vestibular nucleus neurons (MVNn) can be grouped into two main cell types based on their intrinsic membrane properties. Subsequent in vivo and in vitro studies demonstrated that these neurons are endowed with N-methyl-D-aspartate (NMDA) receptors and that NMDA induces rhythmic bursts in B MVNn. We now report the occurrence of rhythmic bursts in B MVNn (and in the subclass of B+LTS MVNn) which are induced by long-lasting perfusion of either apamin, a selective blocker of one type of Ca(2+)-dependent K+ conductance (SK channels), or by a high Mg2+/low Ca2+ artificial cerebrospinal fluid. Apamin-induced bursts were studied in vitro in brainstem slices, and in vivo in the alert unrestrained guinea-pig. In vitro, intracellular recordings demonstrated that the frequency of the bursts was voltage dependent. These bursts were insensitive to D-2-amino-5-phosphopentanoic acid but could be abolished by tetrodotoxin or blocked by the bath application of 20-50 microM of ouabain, a blocker of the sodium pump. In the in vivo preparation, unilateral infusion of apamin into the vestibular nuclei induced oscillatory head and eye movements. Our data show that the blockade of a Ca(2+)-activated K+ conductance may switch, in vitro and probably in vivo, the B MVn firing pattern from a regular to a bursting firing pattern.

2-Amino-5-phosphonovalerate↗
PubMed1993

Evaluation of left ventricular mass: comparison of ultrafast computed tomography, magnetic resonance imaging, and contrast left ventriculography.

We measured and compared left ventricular mass in 20 patients by ultrafast computed tomography (UFCT), magnetic resonance imaging (MRI), and contrast left ventriculography (LVG). Left ventricular mass was calculated by UFCT and MRI in two ways: (1) excluding papillary muscles and trabeculae (LV mass), and (2) including papillary muscles and trabeculae (LV mass + PM&T) by Simpson's method. Left ventricular mass excluding papillary muscles and trabeculae (LV mass) in LVG was calculated by Rackley's method by biplane angiocardiography. LV mass was significantly larger in LVG than in MRI and UFCT (p < 0.01). Although LV mass was significantly larger in MRI than in UFCT (p < 0.01), there was no significant difference in LV mass + PM&T between UFCT and MRI. Interobserver and intraobserver variability showed good correlation of coefficient in both UFCT and MRI. We therefore conclude that left ventricular mass is best measured by including papillary muscles and trabeculae by Simpson's method in UFCT or MRI.

Adult↗
PubMed1993

Effects of nivalenol on hepatic drug-metabolizing activity in rats.

Effects of nivalenol (NIV), a trichothecene mycotoxin, on hepatic drug-metabolizing activity and aflatoxin B1 (AFB1) metabolism were investigated in male rats. In rats fed the diets containing 6-12 ppm NIV for 2 or 4 wk, decreases in initial feed uptake, terminal weight gain and organ weights were evident. An increase in cytochrome P-450 activity was observed in the hepatic microsomes, and Western blot analysis revealed a transient increase in P4502B1/2, together with a slight induction of P4501A2. The activity of cytosolic glutathione S-transferase (GST) enzymes was also enhanced in the rats, and Western blot analysis demonstrated an elevation of GST 1-2. The formation of aflatoxin B1-DNA adducts (AFB1-DNA) was increased in experiments using hepatic microsomal preparations from rats fed the NIV diet, whereas supplementation with cytosol prepared from NIV-treated rats reduced the microsomal potential for adduct formation. In in vivo experiments, the AFB1-DNA concentration in NIV-treated rats was lower than that in the controls. These results suggest that activities of cytochrome P-450 and GST enzymes were increased in rats fed NIV for several weeks. Alteration of these phase I and phase 2 enzyme levels resulted in the modulation of AFB1 adduction to DNA in vitro and in vivo.

Administration, Oral↗