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Y Takamura

Publications and source records attributed to Y Takamura.

At least 19 recordsLinked to original sources
PubMed1996

Emotional and behavioral correlates of mediodorsal thalamic neurons during associative learning in rats.

Neuronal activity was recorded from the mediodorsal thalamic nucleus (MD) of behaving rats that were trained to lick a protruding spout just after a conditioned stimulus to obtain reward or to avoid shock. Conditioned stimuli included both elemental (auditory or visual stimuli) and configural (simultaneous presentation of auditory and visual stimuli predicting reward outcome opposite that predicted by each stimulus presented alone) stimuli. Of 122 MD neurons responding during the task, the activity of 13 increased just before licking only during the task, but not before spontaneous licking during the intertrial interval (conditioned behavior related). These conditioned behavior-related neurons were located mainly in the lateral MD, which has intimate anatomical connections with motor-related areas such as anterior cingulate and striatum. The activity of the other 109 neurons was related to conditioned stimulation (conditioned stimulus related). Most of these neurons responded differentially to both elemental and configural stimuli in terms of reward contingency, and also changed their responses during extinction and relearning trials. Conditioned stimulus-related neurons with latencies < 300 msec were located mainly in the rostromedial MD, which receives afferents from the basolateral nucleus of the amygdala in which sensory information from various sources converge. Furthermore, most differential neurons that were tested responded during the delay period in a reward task in which a delay was imposed between the conditioned stimulus and reward delivery. The present results, along with previous anatomical studies, suggest the existence of two limbic circuits: anterior cingulate-striatum-lateral MD (motor) and amygdala-medial MD-orbital prefrontal cortex (short-term memory/emotion).

Acoustic Stimulation↗
PubMed1995

[Magnetic resonance imaging of supratentorial and parafalcial empyema].

The authors report the MR imaging of two patients with multiple subdural empyemas, including one in the interhemispheric fissure. MRI demonstrated convexity and interhemispheric collections which were mild hyperintense relative to CSF, hypointense relative to gray and white matter on T1W1, and marked hyperintense relative to CSF, and brain on T2W1. On the basis of signal intensity differences, MRI can distinguish subdural empyemas from most sterile effusions and chronic subdural hematomas with similar CT appearances. MRI was found to be clearly more sensitive to subdural empyemas than CT, though such lesions missed on CT were considered to be relevant. MR was superior to CT in demonstrating the nature, presence, and extent of these lesions. In both cases, the capsule of the lesions demonstrated enhancement, and connection between each lesion was obvious on contrast-enhanced MRI. It seems that contrast-enhanced MR image may detect encapsulation of an abscess which can not be detected from contrast-enhanced CT. We emphasized that the most significant factor in the successful surgical management of multiple subdural empyema, particularly including interhemispheric collections is the accurate location of pus. This can be reliably achieved with MR imaging.

Adolescent↗
PubMed1994

Effects of intraventricular administration of neuropeptide Y on feeding behavior in fasted female rats with ventromedial hypothalamic lesions.

The role of ventromedial hypothalamic nucleus (VMN) in feeding behavior induced by central administration of porcine neuropeptide Y (NPY) in fasted female rats was investigated focusing on the effect of the intracerebroventricular (i.c.v.) injection of NPY on food intake in rats with VMN lesions after 24 h of food deprivation. Cumulative food intake was measured 1, 3 and 6 h after injection. In Exp. 1, the i.c.v. injection of NPY into intact rats stimulated food intake compared with the injection of saline 1 and 3 h after the injections in a dose dependent manner (1 h; NPY 1 microgram, 3.29 +/- 0.43, 2 micrograms, 4.64 +/- 0.88, 5 micrograms, 5.15 +/- 0.61 vs. saline 2.48 +/- 0.42 g, P < 0.05 in 2 and 5 micrograms). 5 micrograms of NPY significantly stimulated food intake 6 h later. In Exp. 2, i.c.v. injection of NPY (2 micrograms) in VMN-lesioned rats showed no significant effect on food intake compared with the injection of saline 3 weeks after VMN lesioning (1 h; NPY 2 micrograms, 2.46 +/- 0.58 vs. saline 2.39 +/- 0.12 g). These results suggest that central administration of NPY enhances food intake in fasted female rats and that the VMN is one of the crucial sites of NPY induced feeding.

Analysis of Variance↗
PubMed1994

An isolated dissecting aneurysm of the superior mesenteric artery: report of a case.

We report herein the case of a 56-year-old man found to have an isolated dissecting aneurysm of the superior mesenteric artery (SMA) after he presented with a 3-day history of postprandial epigastralgia of sudden onset. An echogram showed marked dilatation of the SMA and a high level of peripheral echoes in a linear fashion within its lumen. A thin-section contrast enhanced computed tomography revealed a thin flap, separating two distinct well-enhanced lumina. Angiography confirmed the presence of a localized dissecting aneurysm of the SMA. The patient was treated conservatively and has since been followed up as an outpatient. Following the presentation of this case, the problems regarding the diagnosis and management of this rare disease are discussed based on a review of the literature.

Aortic Dissection↗
PubMed1994

Gastric damage and body weight loss in LHA-lesioned rats: effects of cytoprotective geranylgeranylacetone.

We investigated the development of gastric damage and body weight (BW) loss in lateral hypothalamic area (LHA)-lesioned rats, measured 2 h and 1 and 3 days after the lesioning (experiment 1), as well as the effects of geranylgeranylacetone (GGA), a cytoprotective antiulcer agent, on these disorders (experiment 2). In experiment 1, BW of LHA-lesioned rats decreased throughout the 3-day experiment. In LHA-lesioned rats, gastric mucosal lesions appeared 1 day after lesioning in the glandular portion and persisted, whereas those in the rumenal portion appeared only after 3 days. Gastric transepithelial potential differences (PDs) of glandular portion began to decrease after 2 h and had decreased in both portions. Gastric acid output was increased transiently at 2 h but it was not high after 1 day and after 3 days was lower than that in sham-LHA-lesioned rats. In experiment 2, PDs of the rumenal decreased more in LHA-lesioned rats than in sham-LHA-lesioned rats pair fed to LHA-lesioned rats after 3 days. Three days of treatment with GGA (200 mg/kg ip) improved PDs of rumenal and glandular portions in LHA-lesioned rats and reduced lesions of the rumenal portion. Loss of BW in LHA-lesioned rats was significantly but not completely inhibited by GGA. These results indicate that disturbance to the gastric defensive mechanism plays an important role in the development of gastric lesions after LHA lesions and that the impairment of gastric functions may be a partial cause of the loss of BW in LHA-lesioned rats.

Animals↗
PubMed1994

Structural components of beta-eudesmol essential for its potentiating effect on succinylcholine-induced neuromuscular blockade in mice.

beta-Eudesmol, a sesquiterpenoid alcohol isolated from Atractylodes lancea rhizoma, potentiates the neuromuscular blocking effect of succinylcholine (SuCh). The potentiating effect is greater in diabetic muscles than in normal ones. To identify the structural components of beta-eudesmol contributing to this action, we examined the potentiating effect of newly synthesized tertiary alcohols related to beta-eudesmol in phrenic nerve-diaphragm muscle preparations of normal and alloxan-diabetic mice. Potentiating effects were exhibited by cyclohexylidene derivatives but not by cyclohexanone or cyclohexanol derivatives. The compound 2-(3-hydroxy-3-methylbutyl)cyclohexylidene exhibited a potentiating effect, but 3-(3-hydroxy-3-methylbutyl)cyclohexylidene did not. These results indicate that both the presence of an exo-methylene attached to a cyclohexane ring and the distance between the exo-methylene and the hydroxy group in beta-eudesmol are involved in the potentiating effect on SuCh-induced neuromuscular blockade.

Animals↗
PubMed1994

Positive chronotropic and inotropic effects of higenamine and its enhancing action on the aconitine-induced tachyarrhythmia in isolated murine atria.

Aconitine and higenamine are the components of aconite root. We investigated the cardiac effects of these compounds on murine right and left atria and the interaction of higenamine with aconitine on the rate of spontaneously beating right atria. Higenamine increased the rate (EC50 = 38 nM) and the force of contraction (EC50 = 97 nM), the maximal responses being comparable with those of isoproterenol. The positive chronotropic effect of higenamine was antagonized by propranolol (30-300 nM) and practolol (10 nM-3 microM), but not by butoxamine (1 microM), indicating that it was a beta 1-adrenoceptor-mediated action. The positive chronotropic effect of higenamine was not changed by pretreatment with reserpine (4 mg/kg, i.p., 4 hr). Aconitine (0.16-0.25 microM) induced tachyarrhythmia in right atria was attenuated by quinidine (1 microM), atropine (8.6 microM) and AF-DX 116 (8.6 microM), suggesting that aconitine activates sodium channels and muscarinic receptors. Higenamine (2.5 nM) and dobutamine (1 nM) did not cause chronotropic effects by themselves, but enhanced the aconitine-induced tachyarrhythmia. These results indicate that higenamine is a beta 1-adrenoceptor full agonist in murine atria and that the aconitine-induced tachyarrhythmia is augmented by the beta 1-adrenergic action of higenamine.

Aconitine↗
PubMed1994

Transformation of Pseudomonas putida by electroporation.

The optimum electrotransformation conditions were determined for Pseudomonas putida PpY101 with plasmid pSUP104 (9.5 kb) and pSR134 (18.6 kb). Field strength was a very important parameter for electrotransformation efficiency. Optimum efficiencies (1.1 x 10(5) transformants/micrograms DNA) with pSUP104 and pSR134 were obtained at a field strength of 12.5 kV/cm, a time constant of about 4.5 ms (resistance setting of 200 ohms), a supercoiled DNA concentration of 100 ng/ml, and a cell concentration of 10(9)/ml. Because the efficiency obtained is high enough, electrotransformation is useful for the direct cloning of P. putida PpY101. No significant relationship between plasmid size and electrotransformation efficiency was observed. These efficiencies were about 4.5 times higher than those using the MgCl2 method. Under these conditions, electrotransformation efficiencies of relaxed plasmid DNA treated with topoisomerase I and that linearized by EcoRI digestion were high.

Biotechnology↗
PubMed1994

[Clinical analysis of the fatal cases of adult malignant gliomas after aggressive treatment].

Six patients operated on for supratentorial malignant astrocytomas and seven patients operated on for glioblastoma multiforme were analyzed to evaluate the effect of aggressive surgical resection on the length of survival and causes of death. Early postoperative contrast enhanced CT scan was used to assess the extent of surgical resection. A gross total resection was considered to have been accomplished when there was no evidence of any residual enhanced mass. When 10% or less of the preoperative enhanced mass remained, the resection was classified as a subtotal resection. Subsequent follow-up CT scan showed that a gross total resection was accomplished in nine patients, and a subtotal resection was attained in four patients. The patients' ages ranged from 40 to 78 years (mean, 59 years). The median survival after the first aggressive surgical resection was 18.0 months in patients with malignant astrocytoma and 13.6 months in those with glioblastoma multiforme. The median duration between first operation and recurrence of tumor was 8.8 months in patients with malignant astrocytoma and 11.5 months in those with glioblastoma multiforme. A second aggressive surgical resection for recurrent malignant astrocytoma or glioblastoma multiforme was carried out in four patients (40%) of the evaluated ten patients. The median survival of these patients after reoperation was 8.25 months. Accordingly, aggressive surgical resection of malignant astrocytoma and glioblastoma multiforme is correlated with longer survival and is advocated in the treatment of recurrent tumors. Leptomeningeal dissemination was diagnosed in nine patients (90%) of evaluated ten patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Percutaneous transluminal angioplasty for progressing stroke caused by severe basilar artery stenosis: case report].

We encountered one case of progressing stroke caused by severe basilar artery stenosis. The patient was treated with emergent percutaneous transluminal angioplasty (PTA) with satisfactory results. A 54 year-old woman was admitted 15 minutes after the sudden onset of rt. hemiparesis, rt. hemidysesthesia, dysarthria and consciousness disturbance. CT scan on admission showed no abnormal findings. The consciousness level of the patient deteriorated rapidly from JCS 1 to JCS 20 within 30 minutes from the ictus. An emergent angiogram revealed severe basilar artery stenosis at its middle portion and poorly developed collateral circulation. One hour after the stroke occurred, PTA was performed. Using a 3mm diameter balloon catheter, we introduced the balloon into the stenotic lesion and inflated it 6 times from 4 atm to 8 atm pressure. The patient recovered immediately on the operating table improving from JCS 20 to JCS 1. Rt. hemiparesis also improved. Follow-up MRI showed a small area of ischemic change in the brain stem, but no large infarction appeared. The patient was discharged with no neurosurgical deficits after 30 days of PTA. PTA for basilar artery stenosis is still a controversial subject. One reason is the risk of basilar artery perforating branches occlusion by balloon catheter and the other is the difficulty of introducing a flexible balloon catheter into the basilar artery beyond the acute angulation of the vertebral artery. If those two problems were solved, PTA would be the first-choice therapy for basilar artery stenosis in both acute and chronic stages.

Acute Disease↗
PubMed1994

[Cerebellar infarcts that require differentiation from tumors: diagnosis with MRI].

It is often difficult to differentiate cerebellar infarct with cerebellar swelling from neoplastic disorders, because former can be shown as cerebellar mass with marked contrast enhancement on CT scan. We analyzed radiologically three cases with cerebellar infarction by using MRI, conventional CT scan and angiography. Two cases in the acute stage could be diagnosed as cerebellar infarction by MRI alone based on the following findings: 1) the lesion was distributed in the territory of cerebellar arteries; 2) the normal pattern of cerebellar folia and fissures was preserved in Gd enhancement MRI image; 3) characteristics of MRI intensity were compatible with hemorrhagic infarction. The other case in the chronic stage showed peculiar enhancement, which was unusual for infarction. It was diagnosed as cellular infarction with reference to the angiographic findings. MRI is generally useful to obtain early diagnosis of tumor-like cerebellar infarcts, and proper treatment should be started as early as possible.

Aged↗
PubMed1993

Glycine sensor in the hepato-portal system and their reflex effects on pancreatic efferents in the rat.

We earlier reported the existence of vagal arginine, alanine, and leucine sensors in the liver which modulate amino acid-induced pancreatic hormone secretion. To determine the possible existence of glycine sensors in the liver and their reflex effects, afferent discharges from the hepatic branch and efferent discharges from the pancreatic branch of the vagus nerve were recorded. Intraportal administration of 0.1, 1, and 10 mM of L-glycine solution (0.1 ml) depressed the afferent discharge rate of the hepatic branch of the nerve in a dose-dependent manner, and increased the efferent discharge rate of the pancreatic vagal branch. The results suggest the existence of glycine sensors in the hepato-portal system that exert reflex regulation on the pancreatic vagus nerve activity.

Animals↗
PubMed1993

Elevated serum thymidine kinase activity in patients with acute viral hepatitis.

To evaluate the clinical applications of serum thymidine kinase (TK) activity, we compared the results obtained with this parameter with those of other liver function tests in 27 patients with acute viral hepatitis and 16 normal controls. In those in the acute stage, the serum TK activity increased significantly to 55.5 +/- 66.5 U/L. There was no significant correlation between serum TK activity and findings for serum albumin, bilirubin, alkaline phosphatase or r-glutamyl transpeptidase. However, it did correlate significantly well with the serum activity of aspartate aminotransferase (AST) (r = 0.621, P < 0.01), alanine aminotransferase (ALT) (r = 0.551, P < 0.01), and lactate dehydrogenase (LDH) (r = 0.620, P < 0.01). Serum TK activity reached higher than 70 U/L in 8 of 11 patients with hepatitis A; however, no patients with the other types of hepatitis reached such a high level. During the recovery stage, the serum TK activity decreased significantly to 5.9 +/- 1.7 U/L (P < 0.01), and did not correlate with AST, ALT, LDH or other conventional liver function parameters. The data suggest that an elevation of serum TK in patients with acute viral hepatitis results from hepatocellular damage. A marked elevation of serum TK activity may thus provide a marker for acute hepatitis A infection.

Acute Disease↗
PubMed1993

Hepatic glucose-sensitive unit regulation of glucose-induced insulin secretion in rats.

Vagal glucose receptors, or glucose-sensitive units which modulate insulin secretion, exist in the liver. This study sought to determine the pathway of portal glucose-sensitive unit-regulated insulin secretion by measuring plasma insulin after intraperitoneal (IP) injection of glucose under unanesthetized and unrestrained conditions (Experiment 1), and by recording electrical discharge after intraportal injection of glucose (Experiment 2) in rats with hepatic and/or celiac vagotomy. In Experiment 1, plasma insulin was significantly reduced and plasma glucose elevated after IP glucose injection (1 g/kg) in the three groups of hepatic-, celiac-, and hepatic- and celiac-vagotomized rats in comparison with a sham-vagotomized group. There were no significant differences among the four groups in plasma insulin or glucose after IV glucose injection (0.5 g/kg). In Experiment 2, intraportal injection of 400 mg/dl of glucose solution, a similar concentration to that produced by 1 g/kg of IP glucose injection, caused a reduction in the discharge rate of hepatic vagal afferents and an increase in that of pancreatic vagal efferents. This increase was blocked by prior sectioning of the hepatic branch of the vagus nerve. These results suggested that hepatic glucose-sensitive units enhanced glucose-induced insulin secretion via the hepatic vagal afferents and the pancreatic vagal efferents mediated by the brain stem center in vivo. The physiological role of these hepatic glucose-sensitive units is assumed to maintain blood glucose homeostasis by enhancing glucose-induced insulin secretion.

Afferent Pathways↗
PubMed1993

Hepatic vagal amino acid sensors modulate amino acid induced insulin and glucagon secretion in the rat.

To clarify the physiological role of vagal amino acid sensors in the liver, the effect of hepatic vagotomy and/or celiac vagotomy (sectioning of the hepatic branch and/or the celiac branches of the vagus nerve) on the secretion of insulin and glucagon after intraperitoneal injection of neutral (L-alanine, L-leucine, and L-phenylalanine), acidic (L-glutamate), or nonmetabolized (cycloleucine) acids, was examined in rats. Hepatic vagotomy enhanced both plasma glucose and glucagon concentrations after intraperitoneal injection of alanine more than those in sham-vagotomized (control) rats, while after intraperitoneal injection of leucine, hepatic vagotomy decreased plasma glucose concentrations and enhanced plasma insulin concentrations more than in control animals. These effects, following both alanine and leucine administration, were blocked by celiac vagotomy. Glutamate, phenylalanine, and cycloleucine stimulation in hepatic-vagotomized rats caused no significant differences in plasma glucose, insulin, or glucagon levels as compared to those in sham-vagotomized rats. Celiac vagotomy alone did not affect plasma glucose, insulin, or glucagon concentrations after stimulation by these five amino acids. The physiological role of alanine and leucine sensors may be to prevent amino acid-induced exaggerated pancreatic hormone secretion and to maintain blood glucose homeostasis, while glutamate, phenylalanine, and cycloleucine have no effect on this pancreatic neuroendocrine system.

Amino Acids↗
PubMed1993

Acute and chronic effects of VMH lesions on circadian rhythms in food intake and metabolites.

In the dynamic phase, 3 weeks after surgery, food intake increased especially during the latter part of the light cycle in VMH-lesioned rats, and the difference between light and dark cycles disappeared. The rhythms of serum insulin, glucose, and triglyceride disappeared. Concentrations of glucose during the light cycle were lower than those of sham-operated rats, although concentrations of triglyceride and insulin were higher than those of sham-operated rats at all times. In the static phase, 12 weeks after surgery, the difference of food intake between light and dark cycle appeared in VMH-lesioned rats, but the loss of rhythmicity for serum glucose, insulin, and triglyceride remained. Concentrations of glucose except early light phase and concentrations of triglyceride and insulin at all times were higher than those of sham-operated rats. VMH lesions thus abolished circadian rhythmicity in serum insulin, glucose, and triglyceride for a long period; however, the disturbed rhythmicity of food intake was reversible.

Animals↗
PubMed1993

Age-related changes of DRG neuronal attachment to extracellular matrix proteins in vitro.

Attachment of dorsal root ganglion (DRG) neurones from 3-month-old (young adult) and 24-month-old (aged) mice to the following substrates was evaluated after 6 h in culture: (1) poly-L-lysine (PL), (2) PL + type I collagen (CL-I), (3) PL + type IV collagen (CL-IV), (4) PL + laminin (LM) and (5) PL + fibronectin (FN). In the young adult mice, each substrate coated onto PL, significantly increased the ratio of attachment, compared with PL alone. In the aged mice, CL-I and LM, but not CL-N or FN improved the attachment. There was no difference in cell survival or neurite extension after 48 h in culture between the two groups of mice. These results suggest that ageing causes selective changes of the neuronal cell-surface receptors respective to extracellular matrix proteins such as CL-IV and FN.

Aging↗