Biomedical subjects

Shigeru Watanabe

Publications and source records attributed to Shigeru Watanabe.

42 records · Page 3Linked to original sources

PubMed2002

Enhancement of delayed release of dopamine in the amygdala induced by conditioned fear stress in methamphetamine-sensitized rats.

Behavior during conditioned fear stress, a form of psychological stress, and the release of dopamine in the amygdala were measured over time using methamphetamine-sensitized rats, which are considered to be a model of hypersensitivity and vulnerability to emotional stress associated with stimulant-induced psychosis and schizophrenia. Dopamine release in the amygdala showed a delayed increase following completion of freezing behavior induced by conditioned fear stress regardless of the presence or absence of methamphetamine-sensitization. Since methamphetamine treatment did not lower the basal level of dopamine in the amygdala, under the conditions of this study, methamphetamine was presumed not to show neurotoxicity. On the other hand, basal dopamine levels after 15 h of repeated electric foot shock were about 40% lower than those in the control group (p<0.0002). In addition, dopamine release following conditioned fear stress in animals repeatedly treated with methamphetamine increased significantly from 40 to 100 min after conditioned fear stress while the duration of freezing behavior or latency of the appearance of grooming were not different from those in the control group. The above results suggested that delayed dopamine release in the amygdala is a phenomenon strongly associated with the emotional context of conditioned fear stress, and hypersensitivity and vulnerability to stress are at least partially involved with the overreaction to stress.

Amygdala↗

PubMed2002

Measurement of aortic diameters and detection of asymptomatic aortic aneurysms in a mass screening program using a mobile helical computed tomography unit.

In a mass chest computed tomography (CT) screening using a mobile helical CT unit, we measured the aortic diameter at three segments to confirm standard values and also attempted to detect any asymptomatic aortic aneurysms. The population screened in the present study consisted of 6971 subjects (3847 men and 3124 women, mean age 60.3 +/- 12.1 years). They underwent a plain chest CT to screen for lung cancer and tuberculosis. The diameters of the ascending and descending aorta were measured at the level of the pulmonary artery bifurcation. The abdominal aorta was measured at the level of the celiac bifurcation, and the mean values for each measurement were calculated. In addition, we attempted to determine whether any correlation exists among aortic diameter, age, and indices of body size and investigated the frequency of asymptomatic aortic aneurysms among the general population. The mean aortic diameter of all three segments was significantly larger in men than in women and increased with age. It also correlated significantly with indices of body size (P < 0.01). A total of 11 subjects (0.16%) had asymptomatic aortic aneurysms (3 ascending, 4 descending, and 4 thoracoabdominal). The aortic diameter in each individual case was greater than the mean aortic diameter +3 standard deviations in each age group. Chest CT screening for lung cancer can thus detect asymptomatic aneurysms through simultaneous aortic measurement.

Adult↗

PubMed2002

Effects of hippocampal lesions on conditional spatial discrimination in pigeons.

Pigeons were trained on a conditional spatial discrimination with a three-key operant chamber. The position of the correct key was left when all the keys were red, center when all the keys were green, and right when all the keys were white. Pigeons with hippocampal damages could learn the task, as well as intact birds and those that received hippocampal lesions after acquisition of the task. These results suggest that the pigeon hippocampus does not play a role in conditional spatial discrimination.

Animals↗

PubMed2002

Two-layered appearance of noncompaction of the ventricular myocardium on magnetic resonance imaging.

A 60-year-old man with isolated noncompaction of the ventricular myocardium was evaluated by magnetic resonance imaging (MRI), which clearly showed excessively prominent trabeculations and deep intertrabecular recesses that correlated well with the findings on echocardiography and contrast enhanced computed tomography. On the T2-weighted and contrast enhanced MRI scans, the noncompacted myocardium was separated into 2 layers: a subendocardial and an endocardial layer. A difference in signal intensity may reflect myocardial damage that leads to ventricular dysfunction or arrhythmia.

Cardiomegaly↗

PubMed2002

In vivo measurement of superoxide in the cerebral cortex during anoxia-reoxygenation and ischemia-reperfusion.

Abstract. The exact time profile of superoxide generation during anoxia-reoxygenation and ischemia-reperfusion was assessed in the feline cerebral cortex in vivo using a chemiluminescence technique with a probe specific for superoxide, 2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazo[1,2-alpha]pyrazin-3-one (MCLA). MCLA solution was superfused on the cortex throughout the protocol, and MCLA chemiluminescence was measured using a newly developed photon counting system. Reflectance at 398 nm was simultaneously measured to compensate for hemodynamic artifacts resulting from cerebral blood volume changes. In 19 animals, a 90-second anoxia was induced by the inhalation of 100% nitrogen followed by a 40-minute reoxygenation. The chemiluminescence decreased during the period of anoxia (p < 0.01) and then exceeded the baseline level at 15 and 20 minutes after reoxygenation (p < 0.05). In six animals, superoxide dismutase (SOD) was continuously superfused and anoxia-reoxygenation was performed in the same manner. The chemiluminescence decreased during the period of anoxia (p < 0.05) but did not exceed the baseline level during the reoxygenation period, indicating that an increase in superoxide production was the main cause of the chemiluminescence increase. In eight animals, a 15-minute forebrain ischemia was induced by the occlusion of the bilateral common carotid arteries with systemic hypotension (systolic blood pressure less than 50 mmHg) followed by a 30-minute reperfusion. The chemiluminescence decreased during the period of ischemia (p < 0.01) and then increased at 20 and 25 minutes after reperfusion (p < 0.05). These results indicate that superoxide generation decreases during anoxia and ischemia and then increases within 20 minutes after reoxygenation or reperfusion.

Animals↗

PubMed2002

[The effect on other individual presentations of the goldfish by FG7142 injection].

To research the emotional effects on goldfish shoaling behavior, the change in time spent by the stimulus shoal sizes (0, 1, 2, and 5) was investigated. Consequently, as for shoaling behavior, a difference was seen only in the presence of a shoal, independent of size. The experimental goldfish were then injected with beta-carboline (FG7142, N-Methyl-beta-carboline-3-carboxyamide at 0.1, 1, 2, or 4 mg/kg) or the vehicle and exposed to the stimulus fish (1). In the beta-carboline group with the 1 and 2 mg/kg dose, the time spent within 10 cm of the stimulus fish increased compared with the vehicle, and this increase was maintained throughout the trial. In contrast, the time spent was unchanged in the high-dose group (4 mg/kg). The subject fish motility was unchanged in all dose groups. These results are discussed in their relationship to predator avoidance.

Animals↗