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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↗
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↗
PubMed1992

Neurotransmitters in the vestibular commissural system of the cat.

The present study focused on the transmitters that control the vestibular neural activity and, in particular, that regulate commissural inhibition. Extracellular spikes of a single vestibular neuron were recorded in decerebrate cats. The seven barrels of the electrode, with the exception of the center barrel, were filled with transmitter candidates and their specific antagonists, while the center barrel was filled with 2 M NaCl for extracellular recording. After isolation of a type 1 neuron, chemicals were iontophoretically applied to examine their effects on its activity. The results were as follows: (1) GABA and glycine markedly decreased spontaneous firing of the neurons, while serotonin did not affect their activity. (2) Bicuculline abolished the inhibitory effects of GABA on the neurons. (3) Strychine abolished the effects of glycine. (4) Commissural inhibition induced by electrical stimulation of the contralateral labyrinth was not abolished by strychine but was abolished by bicuculline. We conclude that (1) vestibular type 1 neurons are controlled by GABAergic and glycinergic but not serotoninergic neurons, and (2) commissural inhibition is activated by the GABAA receptor, but not by the GABAB receptor.

Animals↗
PubMed1992

Effects of Ginkgo biloba extract (EGb 761) on the guinea pig vestibular system.

Previous studies have demonstrated that the administration of Ginkgo biloba extract (EGb 761) improves the compensation of the vestibular syndrome induced by transection of the VIIIth nerve. To investigate the mechanisms at play, the vestibular nuclei of alert guinea pigs were perfused with EGb 761. This perfusion always induced a stereotyped reversible postural syndrome that was the mirror image of the syndrome provoked by the unilateral lesion of the otolithical receptors. This result supports the hypothesis that EGb 761 has a direct excitatory effect on the lateral vestibular nuclei (LVN) neurons. In a second step, we quantified the horizontal vestibuloocular reflex (HVOR) of the normal guinea pig following IP injection of EGb 761. In normal guinea pig, IP administration of EGb 761 led to a reversible, dose-dependent decrease of the HVOR gain without affecting the phase of the reflex. These data help to explain the therapeutic effects of EGb 761 during vestibular syndromes and strongly suggest an impact at the neuronal level.

Animals↗
PubMed1992

Candidate natural killer cell receptors.

Among the high points of immunological discovery has been the identification of antigen-recognizing receptors on B and T cells. Of the lymphocyte populations, only the NK cell receptor remains unknown. Consequently, any newly-recognized, cell-surface molecules expressed selectively on NK cells, especially ones that can transmit a signal to the cell upon appropriate ligand interaction, are possible candidates. This article describes such candidates.

Animals↗
PubMed1992

Enhancement of GST-P-positive liver cell foci development by nivalenol, a trichothecene mycotoxin.

In order to elucidate whether T-2 toxin (T-2) and nivalenol (NIV), the naturally occurring trichothecene mycotoxins in food and feed, are carcinogenic or possess an ability to modulate aflatoxin B1 (AFB1)-induced hepatocarcinogenicity, a medium-term liver bioassay was carried out. F344 male rats were given a single i.p. injection of diethylnitrosamine (DEN, 200 mg/kg), and then fed the test trichothecenes in diet (2 and 5 p.p.m. T-2 or 6 p.p.m. NIV) for 6 weeks beginning 2 weeks after the injection. Some control groups received DEN alone. For synergism between AFB1 and the trichothecenes, DEN-initiated rats as above were given a single i.p. injection of AFB1 (0.5 mg/kg) 2 weeks later and were fed a NIV-containing diet (6 p.p.m.) for 6 weeks. The other control group received the vehicle alone. Control rats not initiated with DEN were also treated with AFB1, NIV or T-2 alone as above. All rats were subjected to a two-thirds partial hepatectomy (PH) at week 3 and killed at week 8, and liver sections were analyzed by glutathione S-transferase placental form (GST-P) expression. In rats that did not receive DEN, AFB1 alone enhanced both the numbers and areas of GST-P-positive foci as reported earlier, while NIV or T-2 alone induced no marked changes. In rats initiated with DEN, AFB1 caused a marked expression of GST-P, and thus the hepatocarcinogenicity of AFB1 was reconfirmed. The expression of GST-P foci in rats fed T-2 or NIV was found to be at background level, indicating that the hepatocarcinogenicity was not predicted for the trichothecene mycotoxins such as T-2 and NIV by this medium-term bioassay system. In the group initiated by DEN followed by AFB1, on the other hand, an elevation of both the numbers and areas of GST-P-positive foci was observed by the subsequent feeding of rats with NIV, and this elevation was statistically significant from the sum totals of individual data of AFB1 or NIV alone. From this evidence, it is predicted that NIV causes an enhancing effect on AFB1-induced hepatocarcinogenesis.

Animals↗
PubMed1992

Circadian blood pressure variation in patients with renovascular hypertension or primary aldosteronism.

Circadian blood pressure (BP) variation were studied in patients with renovascular hypertension (RVH) and primary aldosteronism (PA). Ambulatory BP (ABP) was monitored every 5 min for 24 hrs in a ward setting in 23 patients with PA and 17 patients with RVH (13 patients with unilateral renal arterial stenosis and 4 with bilateral stenosis). In patients with RVH, ABP was monitored before and after treatment with a converting enzyme inhibitor or percutaneous transluminal angioplasty. Plasma renin activity (PRA) was high before percutaneous transluminal angioplasty in almost all patients with RVH and low in those with PA. Ordinary circadian BP variation, i.e. nocturnal fall and diurnal rise in BP, was confirmed in the patients with unilateral or bilateral renal artery stenosis. Percutaneous transluminal angioplasty successfully normalized both BP and PRA in those with RVH. Normal circadian BP variation was observed in those with RVH before the treatment with a converting enzyme inhibitor or percutaneous transluminal angioplasty as well as during treatment with the former and after treatment with the latter. Circadian BP variation in the patients with RVH was affected by the pathogenesis of renal artery stenosis alone, i.e, fibromuscular hyperplasia and atherosclerosis; with fibromuscular hyperplasia normal circadian BP variation was observed, while with atherosclerosis, nocturnal BP fall was restricted or eliminated. Circadian BP variation in those with PA before and after excision of adrenal adenoma was essentially similar to that in normal subjects and essential hypertensive patients. From these it seems that in patients with RVH or PA, circadian BP variation is not affected by hypertension per se or by pathogenesis of hypertension.

Adenoma↗
PubMed1992

[Prognosis of asymptomatic elderly patients with aortic stenosis].

To elucidate the prognosis of elderly patients with asymptomatic aortic stenosis (AS) and to assess the timing of aortic valve replacement (AVR), 21 asymptomatic patients (8 men, 13 women, mean age: 75 +/- 8 years (54-89 years)), who had Doppler echocardiographic evidence of a significant aortic pressure gradient of greater than 40 mmHg (mean gradient: 75 +/- 31 mmHg), were followed for 33 +/- 10 months. During the follow-up, there were 4 cardiac events (2 cardiac deaths, 2 late AVRs), and 2 non-cardiac deaths (cerebro-vascular accidents). Among 15 survivors, 13 patients were in NYHA class I--II, and the remaining 2 patients were found to have malignant disease. Compared to the 17 patients without cardiac events, those with cardiac events had significantly larger CTR (58 +/- 6% vs. 53 +/- 3%; p less than 0.01), although there were no significant difference in electrocardiographic LVH, echocardiographic LV mass, and Doppler pressure gradient between the two groups. The prevalence of the development of cardiac symptoms during the follow-up was not high (12%) in patients without cardiac events. Among 4 patients with cardiac events, one patient who was 89 years-old at diagnosis died of heart failure, one patient had fatal myocardial infarction which seemed to be unrelated to AS, and two patients had successful late AVR because of new heart failure. The low incidence of fatal cardiac events in asymptomatic patients with aortic stenosis and the relatively high possibility of developing non-cardiac events in elderly patients indicate that the decision-making for AVR should not be solely based upon the pressure gradient detected by Doppler echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗