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Biomedical subjects

S Aoki

Publications and source records attributed to S Aoki.

At least 145 records · Page 8Linked to original sources
PubMed1999

Alterations in sarcoplasmic reticulum and angiotensin II receptor type 1 gene expression in spontaneously hypertensive rat hearts.

Left ventricular hypertrophy (LVH) is an adaptive change in response to hypertensive pressure overload. Some evidence indicates that the decrease in sarcoplasmic reticulum (SR) Ca2+-ATPase mRNA expression, which may contribute to a diastolic dysfunction of the heart, occurs in the experimental pressure overload model. Also, recent studies have demonstrated that angiotensin II (Ang II) and angiotensin II receptor type 1 (AT1) play important roles in LVH. The purpose of this study was to investigate the function of the SR and the role of AT1 in genetic hypertension in spontaneously hypertensive rats (SHR) at ages 10 and 18 weeks. In SHR, cardiac hypertrophy has already developed at 10 weeks of age. SR Ca2+-ATPase activity and mRNA expression were significantly lower in SHR than in Wistar-Kyoto rats (WKY). Plasma renin activity in SHR was unchanged compared with WKY, whereas the Ang II concentration in SHR was significantly higher than that in WKY. AT1 mRNA expression in SHR was similar to that in WKY. These results suggest that in the early stage of hypertension in SHR Ang II may stimulate hypertrophy in the cardiomyocytes through the AT1, which is not downregulated by a high concentration of Ang II.

Angiotensin II↗
PubMed1999

Generation of free radicals and the damage done to the sarcoplasmic reticulum during reperfusion injury following brief ischemia in the canine heart.

Free radical generation was studied by the electron spin resonance (ESR) technique using alpha-phenyl N tert butyl nitrone (PBN) in a brief ischemia-reperfusion model of the canine heart, and correlated with biochemical changes of the sarcoplasmic reticulum (SR). ESR spectra (aH=0.3-0.4mT, aN=1.43-1.58mT) were observed as PBN spin adducts, which peaked at levels 5-fold above the control levels at 5 min after reperfusion. The simulated coupling constants of PBN spin adducts suggested that the sample should contain at least 2 carbon-centered radicals at 5 min after reperfusion (radical A: aH=0.350mT, aN=1.485mT; radical B: aH=0.370mT, aN=1.615 mT). At this time point, a significant reduction in Ca-ATPase activity of the SR was found without degradation of the major ATPase protein. Superoxide dismutase (SOD) significantly reduced the intensity of the PBN spin adduct signals and preserved the Ca-ATPase activity of the SR to 80% of the control level. Reperfusion injury after brief ischemia may be the result of inactivation of intracellular Ca-ATPase by free radicals generated during reperfusion, and SOD contributes to the protective effect by scavenging the radicals.

Animals↗
PubMed1999

Promoter polymorphism of the beta2 bradykinin receptor gene is associated with essential hypertension.

The present study examined the genetic contribution of the human beta2 bradykinin receptor gene in Japanese subjects with essential hypertension, and identified a -58T/C polymorphism of the core promoter that might be responsible for essential hypertension in Japanese. The study consisted of 100 hypertensive subjects and 100 age- and sex-matched controls. The allelic frequencies were 0.575 for the C allele and 0.425 for the T allele in hypertensive subjects, and 0.465 for the C allele and 0.535 for the T allele in normotensive subjects. The allelic frequencies were in Hardy-Weinberg equilibrium. Significant differences between hypertensive and normotensive subjects were seen in the genotypes distribution (p=0.049) and allelic frequencies (p=0.028), and the beta2 bradykinin receptor gene variant was associated with human essential hypertension in this Japanese population. This new marker may provide a valuable tool for assessing the risk for putative bradykinin-associated common diseases, such as hypertension, and cardiovascular diseases with genetic determinism. These results suggest that the -58 polymorphism of the human beta2 bradykinin receptor gene is an independent risk factor for essential hypertension in the Japanese population.

Adult↗
PubMed1999

Spontaneous hemothorax secondary to immature teratoma of the mediastinum.

Spontaneous hemothorax in a 20-year-old boy was caused by rupture of an immature teratoma of the mediastinum. The tumor bled spontaneously into the right pleural space. This life-threatening complication necessitated emergency surgery. The unusual cause and the interesting clinical course of spontaneous hemothorax are described.

Adult↗
PubMed1999

Perfusion MR imaging with a superparamagnetic iron oxide using T2-weighted and susceptibility-sensitive echoplanar sequences: evaluation of tumor vascularity in hepatocellular carcinoma.

OBJECTIVE: The study purpose was to examine the usefulness of perfusion echoplanar MR imaging with a superparamagnetic iron oxide (SHU-555A) for evaluating the vascularity of hepatocellular carcinomas. SUBJECTS AND METHODS: Twenty-two patients with 32 hepatocellular carcinomas underwent perfusion imaging with bolus injection (0.7-1.1 ml) of SHU-555A. Echoplanar sequences included multishot spin-echo (17 patients) and single-shot gradient-echo (five patients) imaging. Image acquisition was repeated every 30 sec for 3 min with the multishot spin-echo sequence and every 2 sec for 100 sec with the single-shot gradient-echo sequence. Lesion signal intensity versus time curves were created for quantitative analysis. RESULTS: Transient decreases in tumor signal intensity (28.8% with multishot spin-echo and 63.3% with the single-shot gradient-echo) were seen in the perfusion phase. These decreases in signal intensity were statistically significantly (p < .01) different for each histologic type of hepatocellular carcinoma (poorly differentiated, 43.3%; well differentiated, 18.4%; and moderately differentiated, 24.8%). After the perfusion phase, the tumor signal intensities rapidly recovered. The multishot spin-echo sequence could detect some signal changes even in lesions smaller than 1 cm. CONCLUSION: Hepatocellular carcinoma vascularity can be evaluated with perfusion echoplanar imaging with SHU-555A. Because of its excellent temporal resolution, the single-shot gradient-echo echoplanar sequence detects the transient signal decrease in most lesions. The high image quality of the multishot spin-echo echoplanar sequence allows evaluation of the vascularity of even very small lesions.

Aged↗
PubMed1999

[Seven cases of marked pulmonary fibrosis in the upper lobe].

We report on 7 patients with marked idiopathic pulmonary fibrosis in the upper lung lobes. The patients were generally characterized by the following pathological and clinical features: (1) marked subpleural pulmonary opacities and reticular shadows mainly in the upper lobes, with a progressive reduction in lung volume; (2) nonspecific fibrosis (subpleural, zonal, rather well-defined fibrosis with small cysts and honeycomb lesions) in 5 patients and interstitial pneumonia in 2, mainly in the upper lobes; and (3) a slender build, and a family history of recurrent spontaneous pneumothorax. Clinically, all 7 cases resembled idiopathic upper-lobe fibrosis as described by Amitani in 1992. Further clinical and experimental research will be required to delineate the characteristics of idiopathic fibrosis affecting primarily the upper lobes.

Adult↗
PubMed1999

[Application of MR-guided intravascular procedures by passive tracking utilizing the magnetic susceptibility effect: a preliminary report].

In MR-guided intravascular procedures, the position of catheters must be confirmed on near-real-time MR images. One way of monitoring this is by passive tracking utilizing the magnetic susceptibility effect. A catheter with a stainless steel braid had suitable visibility when tracked by magnetic susceptibility on fast GRE images, although the direction of the static magnetic field affected the apparent width of the catheter. Passive tracking with a 1.5T MRI unit was performed in a patient at one image/2 seconds with fast GRE. The catheter could be introduced to the SMA and celiac artery from the aorta with passive tracking.

Animals↗
PubMed1999

Comparison between hockey stick and reversed hockey stick incision: gently curved single linear neck incisions for oral cancer.

Hockey stick incision (HSI) and reversed-HSI are known to be useful incisions for lymph node dissections of the neck. Both are gently curved single linear incisions without three-point suture line junctions, but are different at the base of the skin flap. The HSI allows the elevation of a superiorly-based single cervical skin flap and the reversed-HSI allows for an inferiorly-based flap. We compared the viability of the skin flaps, exposure of the operation field and cosmetic results to evaluate the characteristics of each incision. HSI appeared to be the suitable incision for radical neck dissection due to adequate exposure of the operation field while rendering excellent cosmetic results. Reversed-HSI was applied in combination with block resection of parts of the oral cavity because it provided much better exposure of the operation field than HSI, while still achieving acceptable cosmetic results. Using this technique, a small area of marginal necrosis was occasionally seen at the apex of the skin flap due to poor blood supply.

Aged↗
PubMed1999

[Current techniques in MR imaging of cerebral infarction].

The imaging of cerebral infarction is a current topic now that the usefulness of both thrombolysis for hyperacute infarction and carotid endarterectomy has been established. Diffusion-weighted imaging (DWI) by EPI is a highly sensitive method of detecting hyperacute infarction. Further, the combination of DWI and perfusion MR makes it possible to detect hyperacute infarction as well as predict the final size of infarction. Contrast-enhanced MRA can demonstrate carotid bifurcation without flow-related signal loss within 30 seconds and can visualize major cervical arteries from the aortic arch to the circle of Willis.

Adult↗
PubMed1999

[Evaluation of two-dimensional thick-slice MR DSA: preliminary study].

We have used two-dimensional contrast-enhanced MR angiography for a single thick slice and called it MR DSA. This technique realizes nearly subsecond scanning per image and is therefore superior to other types of contrast-enhanced MR angiography in temporal resolution. To determine the optimal parameters of this technique, we calculated SSR (the signal of brain to the signal of contrast agent ratio) in various settings. We also obtained MR DSA images of 26 cases. We believe that MR DSA may play a supportive role in conventional MR imaging or angiography, since its high temporal resolution is of value in the evaluation of cerebrovascular diseases.

Angiography, Digital Subtraction↗
PubMed1999

Pharmacokinetic and pharmacodynamic interactions among haloperidol, carteolol hydrochloride and biperiden hydrochloride.

A beta-adrenoceptor blocker and an anticholinergic agent are often prescribed concomitantly for the treatment of neuroleptic-induced akathisia. The aim of this study was to investigate possible pharmacokinetic interactions of neuroleptic haloperidol with the beta-blocker carteolol and the anticholinergic biperiden. In a 5-step, open-labeled, oral single-dose study, eight healthy male volunteers received 2 mg haloperidol, 10 mg carteolol hydrochloride, and 2 mg biperiden hydrochloride: first each drug alone, then a combination of haloperidol and carteolol, and then all three drugs concurrently. Serum concentrations of haloperidol, carteolol, and biperiden were determined up to 24 hr postdosing, and a safety evaluation was conducted throughout the study. Carteolol increased the area under the haloperidol serum concentration-time curve (AUC0-t) 1.4-fold (P = 0.0014) and decreased the serum clearance of haloperidol up to 67% (P = 0.0127). Biperiden reduced the serum haloperidol concentrations increased by the administration of carteolol. No significant changes of the serum pharmacokinetics of carteolol and biperiden were found as a result of any drug combinations. Adverse events of the central nervous system such as sleepiness and changes in pupil size were observed, but all were mild with clinical insignificance.

Adrenergic beta-Antagonists↗
PubMed1999

[Quantitative measurement of prefrontal lobe volume on three dimensional magnetic resonance imaging scan].

This article describes the measurement of the frontal and prefrontal lobe volumes on three dimensional (3-D) MRI in 13 children aged 5 months to 14 years and in 3 adults aged 27 to 39 years. The 3-D MRI data were acquired by the fast spoiled gradient recalled (SPGR) sequence using a 1.5 T MR imager. The frontal and prefrontal lobe volumes were measured by the volume measurement function of the Workstation. We confirmed that this technique to analyze segmental brain volumes achieved acceptable levels of reliability and accuracy. There was an increase in the frontal and prefrontal lobe volumes with advancing age, being rapid between 8 and 15 years of age. The prefrontal to frontal lobe volume ratio also increased gradually, with spurts between 8 and 15 years of age. This approach may be particularly useful for studies on patients with frontal and prefrontal lobe dysfunctions.

Adolescent↗
PubMed1999

[Practical compensation method of downscattered component due to high energy photon in 123I imaging].

We looked into the problem that the quantitative values of 123I data vary according to collimator type. First, we made the assumption that the quantitative values of 123I data are degraded by the scattered photons from the 529 keV component which contaminate the 159 keV imaging data. Then, the 123I Dual Window (IDW) method was proposed to improve the quantitative values of the 123I data. The IDW method uses the energy window on the high-energy side to estimate the amount of scattered 529 keV photons which contaminate the 159 keV data. Since only a dual-energy window acquisition and a simple image processing are needed, the IDW method can be performed in most conventional gamma camera systems. In the torso phantom studies, the IDW method reduced the error in the semi-quantitative value 'heart/mediastinum (H/M) ratio' in 123I-MIBG myocardial scintigraphy from 22% to 1%. The results of the phantom studies indicate that the IDW method can improve the quantitative values of 123I data.

3-Iodobenzylguanidine↗
PubMed1999

[A trial of clonazepam treatment for manic-depressive psychoses].

Clonazepam, which is a benzodiazepine structurally related to chlordiazepoxide hydrochloride, diazepam and nitrazepam, has been available for the treatment of seizure disorders in the USA since 1976 and in Japan since 1981. Recently, clonazepam has attracted interest as drug for the treatment of manic-depressive psychosis. Chouinard et al (1983), Victor et al (1984), Freinhar and Alvarez (1985) and Santos and Morton (1987) have reported on the antimanic properties of clonazepam, and Jones and Chouinard (1985), Zetine and Freedman (1986), Mas et al (1993) and Kishimoto et al(1987) have reported on the antidepressive properties of clonazepam. We have observed the antimanic and antidepressive properties of clonazepam as well. Clonazepam is a useful therapeutic adjunct and the onset of its effect is rapid. We cannot, however, advocate the use of only the therapeutic agent for amelioration of manic-depressive psychosis. Clonazepam is a useful supplement and has a diverse optimum daily dose for acute manic and depressive states. Clonazepam should, at the time, be considered only as an alternative treatment for patients nonresponsive to conventional therapy, and should be used at a dosage of 3-6 mg/day for depressive state and 10 mg/day for acute manic state in combination with other psychotropic drugs.

Anticonvulsants↗
PubMed1998

Expression of a gene cluster kaiABC as a circadian feedback process in cyanobacteria.

Cyanobacteria are the simplest organisms known to have a circadian clock. A circadian clock gene cluster kaiABC was cloned from the cyanobacterium Synechococcus. Nineteen clock mutations were mapped to the three kai genes. Promoter activities upstream of the kaiA and kaiB genes showed circadian rhythms of expression, and both kaiA and kaiBC messenger RNAs displayed circadian cycling. Inactivation of any single kai gene abolished these rhythms and reduced kaiBC-promoter activity. Continuous kaiC overexpression repressed the kaiBC promoter, whereas kaiA overexpression enhanced it. Temporal kaiC overexpression reset the phase of the rhythms. Thus, a negative feedback control of kaiC expression by KaiC generates a circadian oscillation in cyanobacteria, and KaiA sustains the oscillation by enhancing kaiC expression.

Amino Acid Sequence↗
PubMed1998

Imaging soft X-ray microscope at Rits Synchrotron Radiation Center.

An imaging soft X-ray microscope with zone plates has been installed at Rits SR Center (Ritsumeikan University, Kusatsu, Japan). With this microscope, specimens were set in air, which made it possible to investigate the specimens without breaking the vacuum of the microscope. The specimens can be prefocused with an optical microscope. Dry and wet biospecimens in air were observed. A new optical system was designed to improve the resolution.

Journal Article↗
PubMed1998

Imaging X-ray fluorescence microscope with a Wolter-type grazing-incidence mirror.

A Wolter-type grazing-incidence mirror was used as an objective for an imaging X-ray fluorescence microscope. The microscope was constructed at the beamline 6C2 of the Photon Factory. The shortest wavelength used was approximately 0. 1 nm, which was limited by the grazing-incidence angle of the mirror. To demonstrate the possibility of recording X-ray fluorescence images, several fine grids were used as test specimens. Characteristic X-rays emitted from each specimen could be clearly imaged. Spatial resolution was estimated to be better than 10 micro m.

Journal Article↗