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Biomedical subjects

T Miyauchi

Publications and source records attributed to T Miyauchi.

At least 145 records · Page 8Linked to original sources
PubMed1993

Regional uptake of iodine-125-metaiodobenzylguanidine in the rat heart.

Regional uptake of iodine-125-metaiodobenzylguanidine ([125I]MIBG) was evaluated in normal (n = 12) and reserpinized (n = 12) rat hearts. At 15 min and 1, 3 and 6 h after injection of [125I]MIBG, tissue activities were calculated for the right ventricular myocardium (RV), the whole left ventricular myocardium (whole LV), the epicardial layer of the left ventricular myocardium (Ep LV), the endocardial layer of the left ventricular myocardium (En LV), the basal segment of the left ventricular myocardium and the apical segment of the left ventricular myocardium. The uptake of [125I]MIBG at 6 h after injection in the normal rat heart was higher in RV than in whole LV (0.45 +/- 0.09% vs 0.30 +/- 0.06% kg dose/g), and in Ep LV than in En LV (0.32 +/- 0.07% vs 0.25 +/- 0.05%). In the reserpinized rat heart, the difference in the uptake between Ep LV and En LV was smaller. This suggests that the difference in the regional [125I]MIBG uptake might reflect different intravesicular uptake in the layers of the heart. To our knowledge, the low uptake in the endocardial layer was a new finding which seems to indicate a difference in innervation between the epicardial and endocardial layers of the left ventricle in the rat heart. Autoradiographic study also showed the low uptake of [125I]MIBG in the endocardial layer, while homogeneous perfusion was observed with thallium-201, supporting the tissue uptake study. Thus, the endocardial and epicardial layers of the left ventricle in the rat heart were considered to be differently innervated.

3-Iodobenzylguanidine↗
PubMed1993

A new model of transient complete obstruction of retinal vessels induced by endothelin-1 injection into the posterior vitreous body in rabbits.

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide produced by vascular endothelial cells. In order to investigate the effects of ET-1 on retinal vessels, ET-1 (1-1000 pmol) was injected into the posterior vitreous body in rabbits. A high dose of ET-1 induced transient complete obstruction of the retinal vessels. In this experimental model of transient complete obstruction of the retinal vessels, the effects of ET-1 on retinal function were further analyzed by means of electroretinograms. The scotopic a-wave was not affected, but the amplitude of the scotopic b-wave was significantly elevated. The amplitude of oscillatory potentials was significantly reduced. These phenomena suggested that retinal ischemia without choroidal ischemia was brought about due to severe vasoconstriction of the retinal arteries. These findings indicate that intravitreal injection of ET-1 causes a transient cessation of blood supply from retinal vessels and that oscillatory potentials in electroretinograms appear to be sensitive for detecting changes of retinal circulation. This new model of transient complete obstruction of retinal vessels might be useful for studying the pathophysiology of severe retinal ischemia.

Animals↗
PubMed1993

Analysis of vasocontractile responses to endothelin-1 in rabbit retinal vessels using an ETA receptor antagonist and an ETB receptor agonist.

To study the role of endothelin receptor subtypes in rabbit retinal arteries, endothelin-1 (ET-1)-induced vasoconstriction was analyzed using the ETA receptor antagonist BQ-123 and the ETB receptor agonist BQ-3020. A cumulative injection of ET-1 (1 approximately 100 pmole) into the posterior vitreous body in anesthetized rabbits caused dose-dependent vasoconstriction in the retinal arteries, and ultimately caused complete obstruction. Fifteen minutes after BQ-123 (1 mumole) was injected into the posterior vitreous body, the dose-response curve of ET-1 was significantly shifted to the right. Intravitreal injection of BQ-3020 caused a significant retinal vasoconstriction only at the highest dose (1000 pmole). Therefore, in rabbit retinal arteries, ET-1-induced vasoconstriction appears to be mediated mainly through ETA receptors.

Animals↗
PubMed1993

Endothelin-1-induced gastric ulcer is attenuated by cetraxate.

We investigated the effect of the anti-ulcer drug cetraxate on the development of the gastric ulcer induced by the submucosal injection of endothelin-1 in the rat gastric body, and its effects on gastric mucosal hemodynamics and tissue oxygenation by Laser doppler flowmetry and tissue spectrophotometry. Endothelin-1 induced gastric ulcer (ulcer length: 11.85 +/- 0.89 mm, mean +/- SEM, n = 4) which was strongly attenuated by cetraxate (ulcer length: 3.27 +/- 0.3 mm, mean +/- SEM, n = 8, p < 0.0001). Cetraxate maintained also tissue oxygenation without causing any significant effect on the endothelin-1-induced changes in gastric mucosal blood flow and volume. These results show that cetraxate exerts its cytoprotective action partly by maintaining mucosal oxygenation.

Animals↗
PubMed1993

High resolution Tc-99m HMPAO SPECT in a patient with transient global amnesia.

This is a report of a patient who underwent high-resolution brain perfusion SPECT studies during and after an episode of transient global amnesia. During the attack, SPECT imaging showed increased perfusion in the left medial temporal region involving the amygdala and hippocampus. After recovery from amnesia, a follow-up SPECT examination showed slightly decreased perfusion in this region. These findings support the hypothesis that transient global amnesia is associated with transient hyperperfusion in the medial temporal brain structures, and confirm the utility of high-resolution SPECT imaging for the evaluation of the fine details of functional brain anatomy.

Adult↗
PubMed1993

Altered expression of ETB-receptor mRNA in the lung of rats with pulmonary hypertension.

To investigate the pathophysiologic role(s) of endothelin-1 (ET-1) in pulmonary hypertension, we studied the expression of ETB-receptor mRNA in the lung and venous plasma concentrations of ET-1 in rats with monocrotaline-induced pulmonary hypertension (PH). Three weeks after s.c. injection of monocrotaline (60 mg/kg), rats (PH rats, n = 6) were sacrificed. Vehicle-injected rats (n = 6) served as controls. The right ventricular systolic pressure of PH rats [58.0 +/- 4.7 mm Hg (mean +/- SEM)] was significantly higher than that in the vehicle-treated control rats (29.2 +/- 2.1; p < 0.01). Northern blot analysis showed that the expression of ETB-receptor mRNA decreased in the lung of PH rats. The venous plasma concentration of ET-1 measured by a sandwich-enzyme immunoassay was significantly higher in PH rats than in control rats (5.1 +/- 0.7 versus 1.3 +/- 0.2 pg/ml; p < 0.01). The present findings suggest that the expression of ETB-receptor mRNA decreases in the lung of PH rats, which might be closely related to the increase in plasma ET-1 concentration in these rats.

Animals↗
PubMed1993

Evaluation of suspected malignant pulmonary lesions with 201Tl single photon emission computed tomography.

201Tl single photon emission computed tomography (SPECT) was evaluated in 170 patients suspected of having a malignant pulmonary lesion greater than 20 mm in diameter on the surgical specimen. Delayed SPECT (at 3 h after injection) visualized all of the 147 malignant pulmonary lesions and 16 of the 23 (69.6%) benign pulmonary lesions, and generally exhibited the lesion more clearly than the early SPECT images (at 15 min after injection). There was no significant difference in delayed ratio (uptake ratio of the lesion to the normal lung on delayed scan) among the various histological groups except between the adenocarcinoma and large cell carcinoma groups (P < 0.05), and no difference was noted between the malignant and benign lesions. However, in retention index (degree of retention in the lesion) a significant difference was noted between the malignant and benign lesions (P < 0.01), although there was no significant difference in this index among malignant different histology groups. These results indicate that this method is useful for visualizing malignant pulmonary lesions greater than 20 mm in diameter to exclude the possibility of malignancy in the lesions when no abnormal 201Tl accumulation is observed. When the lesion shows abnormal 201Tl accumulation, the retention index seems to help differentiate malignant from benign lesions.

Adenocarcinoma↗
PubMed1993

Computerized EEG and brain imaging studies in untreated schizophrenic patients: a report of seven cases.

We undertook routine EEG, Z-map, CT and PET scans in seven acute untreated schizophrenics. Routine EEGs showed slower activity in only one case. However, the Z-map showed slower activity in all the cases. CT demonstrated brain atrophy in three of the cases, and PET revealed hypofrontality in two, right hypoparietality in four, and both conditions in one case. There was no relation between CT and PET or the Z-map. However, a significant increase in alpha 1 activity was demonstrated on the Z-map in cases who were found to be the parietal type on PET; this was not conspicuous in the frontal type on PET. Moreover, in three of the patients, the Z-map findings were similar to the lesion indicated on PET.

Adult↗
PubMed1993

Mechanism of rat uterine smooth muscle contraction induced by endothelin-1.

1. Endothelin (ET)-1 has been demonstrated to cause contraction of uterine smooth muscle. We investigated the role of ET receptor subtypes (ETA and ETB receptors) in ET-1-induced contraction of rat uterine smooth muscle by using the ETA receptor antagonist BQ-123 and the ETB receptor agonist BQ-3020. 2. ET-1 caused a contraction with superimposed oscillations of the rat isolated uterus suspended in Krebs-Ringer solution; both the amplitude of contraction as well as the oscillation frequency increased in a dose-dependent manner (10(-11)-10(-7)M). 3. BQ-123 (10(-6)M) markedly shifted the dose-response curve of ET-1 for both contractile effects and oscillation frequency to the right. 4. BQ-3020 (10(-11)-3 x 10(-7) M) did not cause uterine contraction; neither did it affect the dose-response curve of ET-1 for either the contractile effect or the increase in oscillation frequency. Thus, stimulation of ETB receptors is not involved in these responses. 5. The present findings suggest that ET-1-induced contractile responses and the increase in oscillation frequency in rat uterine smooth muscle is mediated through ETA receptors, and that ETB receptors play no role in these responses.

Amino Acid Sequence↗
PubMed1993

Gastric ulcer induced by submucosal injection of ET-1: role of potent vasoconstriction and intraluminal acid.

To investigate whether submucosally applied endothelin-1 (ET-1) can induce gastric ulcer, ET-1 (62.5, 125, 250, and 500 pmol/kg) was injected in the submucosal layer of the rat gastric body. Twenty-four hours later, gastric ulcer (ulcer area: 10.31 +/- 5.13 mm2, mean +/- SE, at 500 pmol/kg, n = 8) was induced. The mucosal damage induced by the two highest doses was present even at 2 wk after their injection. Measurement of the mucosal blood flow at the injected area with three different methods (laser-Doppler flowmetry, hydrogen gas clearance, and reflectance spectrophotometry) revealed that injected ET-1 produced an extremely long-lasting vasoconstriction. Pretreatment with nicardipine, a Ca(2+)-channel blocker (1 mg/kg iv), significantly attenuated the ET-1-induced mucosal damage as well as the decrease in mucosal blood flow. Pretreatment with omeprazole (5-40 mumol/kg) also, significantly attenuated the ET-1-induced mucosal damage. Combined pretreatment with omeprazole (40 mumol/kg) and nicardipine almost abolished the ET-1-induced damage. The present study shows that a novel model for experimental ulcers can be induced by submucosal injection of ET-1.

Acids↗
PubMed1993

Contribution of endogenous endothelin-1 to the progression of cardiopulmonary alterations in rats with monocrotaline-induced pulmonary hypertension.

Endothelin-1 (ET-1) is known to have potent contractile and proliferative effects on vascular smooth muscle cells and is known to induce myocardial cell hypertrophy. We studied the pathophysiological role of endogenous ET-1 in rats with monocrotaline-induced pulmonary hypertension. Four-week-old rats were given a single subcutaneous injection of 60 mg/kg monocrotaline (MCT rats) or saline (control rats) and were killed after 6, 10, 14, 18, and 25 days. In the MCT rats, right ventricular systolic pressure progressively increased and right ventricular hypertrophy developed in a parallel fashion. The venous plasma ET-1 concentration also progressively increased, and this increase preceded the development of pulmonary hypertension. The isolated pulmonary artery exhibited a significantly weaker response to ET-1 in the MCT rats on day 25 but not on days 6 and 14. In the MCT rats, the expression of prepro ET-1 mRNA as measured by Northern blot analysis significantly increased in the heart on days 18 and 25, whereas it gradually decreased in the lungs. The peptide level of ET-1 in the lungs also significantly decreased in the pulmonary hypertensive stage. The expression of prepro ET-1 mRNA had increased by day 6 only in the kidneys. Continuous infusion of BQ-123, a selective ETA receptor antagonist, by an osmotic minipump (14.3 mg per day per rat for 18 days) significantly inhibited the progression of both pulmonary hypertension (right ventricular systolic pressure, 77.8 +/- 4.2 [mean +/- SEM] mm Hg [n = 10] versus 52.3 +/- 2.4 mm Hg [n = 7]; P < .01) and right ventricular hypertrophy (right ventricle/[left ventricle +/- septum], 0.56 +/- 0.03 [n = 10] versus 0.41 +/- 0.02 [n = 7]; P < .01). Histological examination revealed that BQ-123 also effectively prevented pulmonary arterial medial thickening. The inhibition of right ventricular hypertrophy by BQ-123 may be partly ascribed to the blockade of excessive stimulation of the heart by ET-1, in addition to the prevention of pulmonary hypertension. The present findings suggest that endogenous ET-1 contributes to the progression of cardiopulmonary alterations in rats with MCT-induced pulmonary hypertension.

Animals↗
PubMed1993

[Laboratory diagnosis of left atrial thrombi in patients with mitral stenosis].

Left atrial (LA) thrombi sometimes occur in patients with mitral stenosis (MS) and may cause systemic embolization resulting in serious and fatal complications. Several clinical techniques are used to detect the presence of LA thrombi, but even echocardiography, the most widely used, has some drawbacks depending on the sizes and locations of the thrombi. This study evaluated D-dimer, fibrinopeptide A(FPA), and thrombin-antithrombin III complex (TAT) as molecular markers for diagnosing the presence of LA thrombi in 26 patients with MS who underwent cardiac surgery. Atrial fibrillation was detected in all patients. Patients with episodes of obvious thromboembolic diseases were excluded. Blood was obtained from the brachial vein before the surgery (3 +/- 1 days; mean +/- SD). The presence or absence of thrombi was confirmed at surgery in all patients. Levels of both D-dimer and TAT were significantly higher in patients with thrombi than in those without thrombi or in normal subjects. FPA levels did not differ significantly between the three groups. The levels of D-dimer and TAT correlated significantly with the weights of the LA thrombi. LA thrombi (ca > or = 2 g) were always confirmed at surgery in patients with levels of D-dimer higher than 200 ng/ml and/or levels of TAT higher than 4 ng/ml. These results indicate that D-dimer and TAT are simple and useful diagnostic markers for determining LA thrombi in patients with MS.

Antithrombin III↗
PubMed1993

[A case report of cor triatriatum benefit of MRI for preoperative diagnosis and surgical method].

Cor triatriatum is uncommon in all congenital heart diseases. It is a malformation resulting in a separation of the left atrium or right atrium into two chambers due to a congenitally abnormal diaphragm. We wish to present a case of cor triatriatum in which MRI was found most useful for preoperative diagnosis and surgical procedure. A 2-year-old girl was transferred to us for severe pulmonary congestion as shown on chest X-ray. Echocardiography showed abnormal diaphragm in the left atrium. MRI demonstrated clearly the relationship between left pulmonary vein and the abnormal diaphragm. Therefore we should preoperatively determine type I A according to the Lucas and Schmidt's classification. Cardiac catheterization showed moderate pulmonary hypertension and confirmed cor triatriatum. The resection of the abnormal diaphragm was performed under extracorporeal circulation with moderate hypothermia. The postoperative course was uneventful. MRI is a very useful non-invasive technique in making a diagnosis and in choosing the appropriate surgical procedure for cor triatriatum.

Child, Preschool↗
PubMed1993

[Endothelin-1-induced vasoconstriction in retinal blood vessels in the rabbit].

Endothelin-1 (ET-1) is an endothelium-derived potent vasoconstrictor peptide which is synthesized in retinal vessels. In order to investigate its effect on retinal blood vessels, we injected ET-1 intravitreally (10(-12), 3 x 10(-12), 10(-11), 3 x 10(-11), 10(-10) mole) and examined the change in diameters of retinal arteries in rabbits by fundus photography. After injection of a high dose (10(-10) mole) of ET-1, fluorescein angiography was used to investigate whether complete occlusions of retinal blood vessels occurred or not. 3 x 10(-12) mole ET-1 induced contraction of retinal arteries and the contraction of those induced by 10(-10) mole ET-1 showed complete occlusion. A medium dose (10(-11) mole) of ET-1 caused repeated vasospasms and segmental vasoconstrictions of retinal blood vessels. Fluorescein angiograms revealed that retinal blood flow was interrupted transiently by injection of a high dose (10(-10) mole) of ET-1. These findings suggested that intravitreal injection of ET-1 could provide a new model of experimental transient occlusion of retinal vessels in rabbits.

Animals↗
PubMed1993

[Verrucous carcinoma of the penis: a case report and MRI findings].

A 54-year-old male visited our cancer center with the chief complaint of penile tumor in May, 1992. Magnetic resonance imaging (MRI) demonstrated a penile tumor and showed that this tumor invaded the submucosa but neither corpora cavernosa nor corpus spongiosum. Partial penectomy was performed in June, 1992. Histopathological examination of the resected tumor showed verrucous carcinoma. MRI was useful to investigate the degree of invasion of the penile tumor.

Carcinoma, Papillary↗
PubMed1993

[A case of tetralogy of Fallot associated with isolation of a subclavian artery and partial DiGeorge syndrome].

A month old girl was referred to our hospital for heart murmur and congestive heart failure. After the UCG and angiography, clinical diagnosis was tetralogy of Fallot, right aortic arch, isolation of left subclavian artery (Victorica type I), and a patent ductus arteriosus that originated from left subclavian artery. The direction of blood flow in the patent ductus arteriosus was from a subclavian artery to pulmonary artery, so she was in the condition of pulmonary over flow and appeared congestive heart failure, although she associated with tetralogy of Fallot. With intraoperative and postoperative examinations, we diagnosed the association of partial DiGeorge syndrome. Isolation of subclavian artery is uncommon, but this anomaly was classified by Victorica. Embryology of this anomaly was explained with hypothesis of double arch system. We had seen no reports of DiGeorge syndrome associated with isolation of a subclavian artery. But DiGeorge Syndrome is hypoplasia of branchiogenic organs, and subclavian arteries is differentiated from brachial arteries. So we supposed that this two lesions have the possibility of combination.

Aorta, Thoracic↗