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Biomedical subjects

M Kurachi

Publications and source records attributed to M Kurachi.

At least 19 recordsLinked to original sources
PubMed2000

Neonatal lesions of the left entorhinal cortex affect dopamine metabolism in the rat brain.

The present study was performed to determine the effects of neonatal excitotoxic lesions of the left entorhinal cortex on dopamine (DA) metabolism and release in limbic regions of the rat brain. Quinolinic acid or phosphate buffered saline was infused into the left entorhinal cortex of rat pups on postnatal day 7 (PD7). Concentrations of DA,3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the lateral amygdala, nucleus accumbens, caudate-putamen, and medial prefrontal cortex were determined in the postmortem brains of lesioned and sham-operated rats on PD35 and PD56. On PD35, concentrations of DA in the bilateral lateral amygdala and HVA in the left lateral amygdala were significantly increased in lesioned rats compared with sham-operated animals, while no significant change was observed in the other three brain areas. On PD56, in addition to the increased concentration of DA in the left lateral amygdala, those of DA, DOPAC and HVA in the caudate-putamen, and DA in the nucleus accumbens were found to be increased, but DA concentrations in the right medial prefrontal cortex were decreased. The DOPAC/DA concentration ratio was, however, decreased in the amygdala and nucleus accumbens of the lesioned rats. In an in vivo microdialysis study, methamphetamine (MAP: 2 mg/kg, i.p.)-induced DA release in the amygdala of lesioned rats was significantly enhanced compared with sham-operated rats on both PD35 and PD56. There were no significant differences in MAP-induced DA release in the caudate-putamen between the sham-operated and lesioned rats at any time point. These findings provide evidence that neonatally induced structural abnormalities in the entorhinal cortex affect DA transmission in the limbic regions at the adolescent stage.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

Plasma homovanillic acid in the prodromal phase of schizophrenia.

BACKGROUND: Plasma levels of homovanillic acid (pHVA) have been used as a peripheral measure of central dopaminergic activity. Despite a large body of studies investigating pHVA in schizophrenia, little is known about pHVA in patients in the prodromal phase of the illness. METHODS: Plasma HVA levels of 12 male outpatients meeting DSM-III-R criteria for the prodromal phase of schizophrenia at the time of blood sampling (who later developed psychotic symptoms) were compared with those of 12 normal male healthy volunteers. Task amounts in the Kraepelin arithmetic test at the time of blood sampling were compared between the prodromal patients and normal controls and were correlated with pHVA levels. RESULTS: The prodromal patients had significantly higher pHVA levels compared with normal control subjects. The mean amount of the arithmetic task for the prodromal patients was significantly less than that for controls. In the patient group, a significant negative correlation was observed between pHVA levels and the task amounts. CONCLUSIONS: Data from the present study indicate the presence of dopaminergic dysfunction in the prodromal stage of schizophrenia that is associated with neuropsychological impairment. Increased pHVA levels in the prodromal patients may have implications for early detection of schizophrenia.

Acute Disease↗
PubMed1999

Real-time observation of the disassembly of stable neuritic microtubules induced by laser transection: possible mechanisms of microtubule stabilization in neurites.

By dissolving the membrane with detergent perfusion, we have shown that the established neurites of dorsal root ganglion cells cultured for more than 5 days contained microtubules which persisted outside the cell for a few minutes to more than 1h [Tashiro et al., 1997: J. Neurosci. Res. 50:81-93]. To investigate their stabilization mechanism, we transected the exposed microtubules by laser microbeam irradiation and observed their length changes with video-enhanced differential interference contrast microscopy. Microtubule fragments started to shorten on both sides of the transection site. more rapidly from the newly generated plus ends than from the minus ends. The maximal rate as well as the pattern of shortening correlated with the time of transection; microtubules transected later than 30 min after membrane removal shortened at rates less than 20 microm/min and typically with intermittent pauses, while the more labile microtubules included in the earlier transections shortened continuously at higher rates. Microtubules in neurites were thus stabilized by 1) stopping disassembly at local sites including the plus ends, and 2) slowing disassembly along the length. Transection also suggested the presence of specialized points along microtubules which are involved in anchoring microtubules to the substratum. Cell Motil. Cytoskeleton 42:87-100, 1999.

Animals↗
PubMed1999

Clinical evaluation of 3D-CT cholangiography for preoperative examination in laparoscopic cholecystectomy.

Three-dimensional-computed tomography (3D-CT) cholangiography is a 3D shaded surface display image of the biliary tract obtained by using helical CT after intravenous cholangiography or cholangiography per percutaneous transhepatic cholangio-drainage tube. We investigated whether 3D-CT cholangiography could provide a useful image, for preoperative examination in laparoscopic cholecystectomy. Sixty-five patients with biliary diseases were examined by 3D-CT cholangiography. Helical scanning was performed on a Proceed Accell (GE Medical Systems, Waukesha, WI, USA). Three-dimensional images were created using an independent workstation. A clear image of the common bile duct was obtained for all patients (100%) by 3D-CT cholangiography. The gallbladder was well visualized in 54 (93%) and the cystic duct was shown to be opacified in 55 (95%) of the 58 patients with a gallbladder. Thirty-one patients were diagnosed as having gallstones by 3D-CT cholangiography (sensitivity. 72.1%; specificity, 100%; accuracy, 79.3%), while 43 were diagnosed as having cholecystolithiasis by ultrasonography. The advantages of 3D-CT cholangiography were a low level of invasiveness, easily obtained images compared to those obtained with endoscopic retrograde cholangiography (ERC), good opacification, and provision of a three-dimensional understanding of the biliary system, especially of the cystic duct. When combined with ultrasonography and routine liver function tests, 3D-CT cholangiography was considered very useful for obtaining information before laparoscopic cholecystectomy. It allowed the omission of ERC in many patients who were considered to have no common bile duct stone, by employment of 3D-CT cholangiography.

Adult↗
PubMed1999

Differential effects of mental stress on plasma homovanillic acid in schizophrenia and normal controls.

We previously reported that mental stress by Kraepelin's arithmetic test decreases plasma homovanillic acid (pHVA) levels in psychiatrically normal healthy human subjects. The present study was undertaken to determine whether this pattern of changes in pHVA concentrations resulting from mental stress is altered in patients with schizophrenia. Fourteen male patients with schizophrenia including those under ongoing neuroleptic treatment and 14 normal male volunteers participated in the study. Following overnight fast and restricted physical activity, the subjects performed Kraepelin's arithmetic test for 30 minutes. Plasma samples were collected immediately before and after the test for measurement of pHVA levels. A significant diagnosis by Kraepelin's test effect was observed due to a decrease in pHVA levels by the Kraepelin test in control subjects but not in patients with schizophrenia. Changes in pHVA levels during the Kraepelin test positively correlated with pre-test pHVA levels in control subjects, while this correlation was not observed in patients with schizophrenia. These results may be further support for the presence of a dopamine-dependent restitutive system in the brain. The absence of response of pHVA levels to mental stress in patients with schizophrenia may indicate that the dopamine restitutive system in these patients is disrupted or already down-regulated, as previously predicted.

Adolescent↗
PubMed1999

Treatment of obstructive sleep apnea syndrome with a Kampo-formula, San'o-shashin-to: a case report.

The following describes a 76-year-old male with obstructive sleep apnea syndrome successfully treated with a Kampo-formula, San'o-shashin-to (Formula medicamentorum tres ad dispellendi cordis). Polysomnography, performed before and after administration of San'o-shashin-to, revealed that the apnea index decreased from 11.1 events/hour to 4.1 events/hour, and that the apnea plus hypopnea index decreased from 18.4 events/hour to 10.7 events/hour. The patient was normo-weight (body mass index: 20.4 kg/m2), and events of sleep apnea and hypopnea were mostly noted during a non-rapid eye movement sleep. It is possible that San'o-shashin-to has some alleviating effects on the upper airway resistance during sleep.

Aged↗
PubMed1999

Intracellular elasticity and viscosity in the body, leading, and trailing regions of locomoting neutrophils.

To investigate the mechanisms underlying pseudopod protrusion in locomoting neutrophils, we measured the intracellular stiffness and viscosity in the leading region, main body, and trailing region from displacements of oscillating intracellular granules driven with an optical trap. Experiments were done in control conditions and after treatment with cytochalasin D or nocodazole. We found 1) in the body and trailing region, the granules divided into a "fixed" population (too stiff to measure) and a "free" population (easily oscillated; fixed fraction 65%, free fraction 35%). By contrast, the fixed fraction in the leading region was <5%. 2) In the body and trailing region, there was no difference in stiffness or viscosity, but both were sharply lower in the leading region (respectively, 20-fold and 5-fold). 3) Neither cytochalasin D nor nocodazole caused a decrease in stiffness, but both treatments markedly reduced the fixed fraction in the body and trailing region to <20% and <40%, respectively. These observations suggest a discrete lattice structure in the body and trailing region and suggest that the developing pseudopod has a core that is more fluidlike, in the sense of a much lower viscosity and an almost total loss of stiffness. This is consistent with the contraction/solation hypothesis of pseudopodial formation.

Cell Movement↗
PubMed1999

Ultrastructural observations of adherent cell pairs in hydra vulgaris

Previous morphological studies of cell sorting in Hydra vulgaris have considered only clusters of cells. Here, we present ultrastructural observations on the adherent region of cell pairs brought into contact (following dissociation) using a three-dimensional laser manipulator. There was a much larger area of close membrane contact between endodermal cell pairs in comparison with ectodermal cell pairs. Separation distances between membranes were categorized into three classes: closest distance (<4 nm); medium distance (5-25 nm); and cleavage (>25 nm). The sum of distances in the closest and medium categories as a proportion of total contact length was significantly greater (P<0.01) for endodermal cells (49.0+/-6.5 %) than for ectodermal cells (26.7+/-4. 4 %). In intact Hydra, this sum of distances was also significantly greater for endodermal cells, indicating that newly adherent cells, even after adhesion for only 10 min, display similar morphological characteristics to cells in intact Hydra. This suggests that close membrane contacts contribute to differential cell adhesion, which may form the basis of the cell sorting process.

Journal Article↗
PubMed1998

Effects of D2 dopamine receptor agonist and antagonist on brain activity in the rat assessed by functional magnetic resonance imaging.

The effects of D2 dopamine receptor agonist, bromocriptine (BROMO), and antagonist, haloperidol (HPD), on brain activity were investigated in rats by functional magnetic resonance imaging. T2*-weighted signal intensity was increased in the hypothalamus at 120 min after acute administration of BROMO, and in the ventral posterior and dorsomedial nuclei of the thalamus from 30 to 120 min. In contrast, the signal intensity was decreased in the caudate-putamen at 30 min after acute administration of HPD, in the hypothalamus from 30 to 60 min, and in the perirhinal cortex at 30 min. After chronic (2 weeks) HPD treatment, acute administration of HPD decreased signal intensity in the caudate-putamen at 60 min, in the hypothalamus at 30 min, the perirhinal cortex from 2 to 120 min, the dorsomedial and ventral posterior nuclei of the thalamus from 2 to 120 min, and the medial nucleus of the amygdala from 60 to 120 min. These results suggest that (1) the D2 receptor agonist increased the activity of the thalamic nuclei and the hypothalamus, while the D2 receptor antagonist suppressed brain activity in the regions where D2 receptors were present, (2) the suppression of brain activity in the thalamic nuclei and the perirhinal cortex by acute HPD administration was enhanced by chronic HPD treatment, and (3) the effects of antipsychotic drugs on the thalamus, amygdala, and perirhinal cortex may be related to their therapeutic efficacy, since clinical improvement in schizophrenic patients appears several days after the start of HPD treatment.

Amygdala↗
PubMed1998

Expression of Fos protein in the limbic regions of the rat following haloperidol decanoate.

To identify sites of antipsychotic drug action, the effects of acute and chronic haloperidol treatment on Fos protein expression in rat brain regions were examined by immunohistochemical methods. Male Wistar rats were injected with haloperidol decanoate (40 mg/kg, i.m. ) or vehicle. Fourteen days after injection, each rat was given an acute subcutaneous injection of haloperidol (0.25 mg/kg) or vehicle, and was transcardially perfused 2 h after the second injection. A single dose of haloperidol to chronic vehicle-treated rats produced significant increases in Fos-positive neurons in 18 of 21 brain regions examined including the several cortical areas, caudate-putamen, nucleus accumbens, lateral septum, thalamic nuclei, amygdala, hippocampus CA1, mesencephalic dopaminergic nuclei, and periaqueductal grey. The rats treated with acute vehicle after chronic haloperidol showed persistent Fos increases in confined brain regions comprising the lateral and central amygdala, lateral septum, and entorhinal cortex. Additional haloperidol injection to the chronic haloperidol-treated rats induced significant increases in Fos immunoreactivity in more widespread limbic-thalamo-cortical areas, whereas no significant increase was seen in the dorsolateral caudate-putamen. The persisting effects of haloperidol in the limbic and related structures, especially the amygdala, lateral septum, and entorhinal area may be of significance to the efficacy of long-term haloperidol treatment.

Analysis of Variance↗
PubMed1998

Direct measurement of DNA molecular length in solution using optical tweezers: detection of looping due to binding protein interactions.

DNA looping is caused by the interaction between DNA binding proteins located at separate positions on a DNA molecule and may play an important role in transcription regulation. We have developed a system to stretch single DNA molecules and to measure changes in molecular length. DNA molecules were prepared and 5' end-labeled by PCR amplification. Two beads and the intervening DNA molecule were trapped and manipulated independently with dual trap optical tweezers. The trapped DNA molecule was then stretched and the extension (the distance between the two beads) was measured. The extension at the specific tension force of 30 pN was calculated and used as a molecular length. The molecular length was found to be proportional to the base pair number. The rise per residue was calculated to be 3.31 +/- 0.05 A. The length measurement was applied to DNA fragments containing GC box sequences at two different locations separated by a distance of 2.428 kbp. The addition of GC box binding transcription factor Sp1 shortened the molecular length, suggesting DNA looping forms as a result of interaction between transcription factors.

Base Sequence↗
PubMed1998

Effect of mental stress on plasma homovanillic acid in healthy human subjects.

Plasma levels of homovanillic acid (pHVA) have been suggested to provide a measure of dopaminergic activity in the central nervous system. The present study investigated the effect of mental stress by the Kraepelin test, a test of continuous arithmetic addition of single-digit figures for 30 min, on pHVA levels in 13 male psychiatrically normal healthy volunteers. Following an overnight fast and restricted physical activity, plasma samples were collected immediately before and after the administration of the Kraepelin test. Plasma HVA levels following the administration of the Kraepelin test were significantly lower than the pretest pHVA levels. The percent change in pHVA levels by the Kraepelin test positively correlated with pretest pHVA levels. The observed reduction in pHVA levels by mental stress in normal subjects may reflect some aspects of a dopamine-dependent restitutive system in the brain.

Adult↗
PubMed1998

Widespread expression of Fos protein induced by acute haloperidol administration in the rat brain.

The effect of acute haloperidol administration on Fos protein expression was examined immunohistochemically in discrete regions of the rat brain. Male Wistar rats were injected subcutaneously (s.c.) with 0.1, 0.25, or 1.0 mg/kg of haloperidol. Two h after the injection, the rats were perfused, and the numbers of Fos immunoreactive neurons were counted in 24 brain regions. In contrast to the limited changes in Fos immunoreactivity at the low dose of haloperidol (0.1 mg/kg), the moderate dose (0.25 mg/kg) induced widespread increases in Fos-positive neurons in the rat brain. Large increases were produced in the caudate-putamen, nucleus accumbens, central amygdaloid nucleus, dorsomedial hypothalamic nucleus, hippocampus CA1 and substantia nigra pars compacta. Moderate increases were observed in the entorhinal cortex, lateral septum, lateral habenula, lateral amygdaloid nucleus, dentate gyrus, and mesencephalic central grey. Mild increases were induced in the anterior cingulate, temporal, occipital and perirhinal cortex, and central medial thalamic nucleus. The distribution of changes in Fos immunoreactivity at the high dose of haloperidol (1.0 mg/kg) were comparable to their distribution at the moderate dose. These findings indicate that the effect of acute haloperidol on Fos expression is widely distributed in the rat brain beyond the previously known dopamine-rich areas at the dose which produces plasma levels equivalent to those within the therapeutic range used clinically in humans. Further studies on the effects of chronic antipsychotic treatment are needed in order to identify the sites of the therapeutic action of antipsychotic drugs.

Animals↗
PubMed1998

A case of subwakefulness syndrome.

We report a patient, a 30-year-old male Japanese-Brazilian migrant construction worker, suffering from excessive daytime sleepiness for at least 6 months. Electroencephalogram recordings during his waking states showed that 10-Hz and 60-microV alpha activity was present prominently in the occipital regions. From the multiple sleep latency test, it was found that stages 1-2 NREM sleep episodes appeared repetitively without any REM episodes, and that the mean sleep latency was 10.2 min. These findings support the diagnosis that this patient suffers from subwakefulness syndrome.

Adult↗
PubMed1997

Direct visualization and characterization of stable microtubules from the neurites of cultured dorsal root ganglion cells.

We tested the stability of microtubules (MTs) in the neurites of cultured dorsal root ganglion cells by dissolving the cytoplasmic membrane with detergent and exposing them to defined extracellular medium under observation with a video-enhanced differential interference contrast (DIC) microscope. Smooth cytoplasmic filaments visualized after membrane removal were suggested to be MTs by the preservation of all of the filaments in the presence but not in the absence of taxol. They were further confirmed to be MTs by specific immunostaining with anti-tubulin antibody. A significant number of MTs in the established neurites of 6-day-old cultures remained longer than 10 min after membrane removal while MTs in the Schwann cell processes or in the distal regions of the growth cone-bearing neurites of 3-day-old cultures disappeared within 2 min. A population of very stable MTs persisting longer than 30 min was also found specifically in the 6-day-old cultures. Association with other structures or bundling seemed to stabilize the MTs to some degree. The most stable MTs, however, were not associated with some structure along the length but were mainly anchored at points, suggesting that specific point attachments may be another important mechanism operating in MT stabilization. The present method is thus capable of directly demonstrating the unusual stability of neuritic MTs, and provides a new system for further investigation on the mechanism of stabilization.

Animals↗
PubMed1997

Saccadic eye movements and regional cerebral blood flow in schizophrenic patients.

This study examined saccadic eye movements, using simple stationary targets, in schizophrenic patients. The targets were eight black points or eight arabic-numbered points placed in randomized order on the circumference of a circle. Self-paced eye movements during clockwise tracking of these points, by 23 patients and 23 controls, were recorded using an infrared eye-mark recorder. Then the relationship between the saccades and clinical symptoms was investigated. Finally, the relationship between the performance of the saccades and resting regional cerebral blood flow (rCBF) was examined using single photon emission computed tomography with 99mTc-hexamethyl propyleneamine oxime (HMPAO). The results indicate that patients track with significantly fewer correct scores and more deviant scores than controls, in agreement with our previous study. There were two groups of patients: an ordinary group who obtained a full-target-hitting score at a 200-ms setting and a fast group who obtained the full score at 100 ms but not at 200 ms. Some patients displayed significantly more hypermetria than controls. Significant correlations were found between hallucination and delusion symptoms and correct score. With respect to relative rCBF, fast-group patients showed significantly decreased rCBF in the left limbic and inferior parietal areas as compared with ordinary group patients. These findings suggest that some schizophrenic patients view the stationary targets too fast and this may be related to dysfunction in the limbic-parietal association area in the left hemisphere.

Adolescent↗
PubMed1996

Reduced microtubule-nucleation activity of tau after dephosphorylation.

Based on video-enhanced differential interference contrast (DIC) microscopy, we developed a small-scale method which is capable of measuring both the lengths and the number densities of microtubules (MTs) assembled in vitro. With this method, effect of dephosphorylation on the activity of bovine brain tau protein to promote the assembly of tubulin at physiological concentration (15 microM) was quantitatively analyzed. The MT number density was selectively reduced when tau isolated directly in the presence of phosphatase inhibitors (N-tau) was dephosphorylated in vitro (DP-tau), without significant changes in the mean MT length or the binding affinity toward preformed MTs. Tau obtained from brain MTs (MT-tau) also exhibited lower nucleation activity in spite of its high MT-binding affinity. The results indicate that nucleation, elongation and MT-binding are distinct aspects of tau function which are differentially affected by the phosphorylation state of tau.

Animals↗