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Biomedical subjects

N Sakai

Publications and source records attributed to N Sakai.

At least 343 records · Page 19Linked to original sources
PubMed1996

Suppressed expression of CD44 variant isoforms during human glioma A172 cell differentiation induced by cyclic AMP.

CD44 is a major receptor for hyaluronic acid, which is the most frequent route of malignant glioma invasion. Multiple isoforms of CD44 are generated by alternative mRNA splicing. We have examined differential expression of CD44 variant isoforms (CD44vs) during dibutyryl cyclic AMP (dbcAMP)/theophylline-induced differentiation of human glioma A172 cells using reverse transcriptase-polymerase chain reaction (RT-PCR). Treatment of cells with dbcAMP and theophylline caused decreased expression of all CD44 isoforms after 24 h. The CD44 standard form was observed to return to the unstimulated level after 72 h, whereas the variant isoforms, CD44 8v-10v and 10v, remained at the low level after 24-72 h. Changes of CD44vs were correlated with the level of expression of c-jun. These results suggested that the expression patterns of CD44vs might correlate with cellular differentiation in human glioma cells.).

Brain Neoplasms↗
PubMed1996

Regional cerebral blood flow in patients with schizophrenia: relevance to symptom structures.

Regional cerebral blood flow (rCBF) was measured with technetium-99m hexamethylpropyleneamine oxime single photon emission computed tomography in 38 neuroleptic-treated schizophrenic patients. To improve the validity of the evaluation of symptomatology, we applied findings previously derived in a principal component analysis (PCA) of the Positive and Negative Syndrome Scale. The PCA had disclosed five orthogonal independent symptom structures (i.e., negative, hostile/excited, thought disordered, delusional/hallucinatory, and depressive components), and obtained factor scores for 70 schizophrenic subjects, including the present sample. Stepwise regression analysis elucidated some of the cortical regions in which relative rCBF predicted the severity of symptoms--namely, lateral and orbital prefrontal, lateral temporal, inferior parietal, and medial temporal regions. Findings suggested that symptom structures derived from PCA could prove helpful in elucidating the pathophysiology of neural mechanisms.

Adult↗
PubMed1996

Lecithin:cholesterol acyltransferase overexpression generates hyperalpha-lipoproteinemia and a nonatherogenic lipoprotein pattern in transgenic rabbits.

Cholesterol esterification within plasma lipoprotein particles is catalyzed by lecithin:cholesterol acyltransferase (LCAT). The impact of the overexpression of this enzyme on plasma concentrations of the different plasma lipoproteins in an animal model expressing cholesteryl ester transfer protein was evaluated by generating rabbits expressing human LCAT. A 6.2-kilobase human genomic DNA construct was injected into the pronuclei of rabbit embryos. Of the 1002 embryos that were injected, 3 founder rabbits were characterized that expressed the human LCAT gene. As in mice and humans, the principal sites of mRNA expression in these rabbits is in the liver and brain, indicating that the regulatory elements required for tissue-specific expression among these species are similar. The alpha-LCAT activity correlated with the number of copies of LCAT that integrated into the rabbit DNA. Compared with controls, the high expressor LCAT-transgenic rabbits total and high density lipoprotein (HDL) cholesterol concentrations were increased 1.5-2.5-fold with a 3.1-fold increase in the plasma cholesterol esterification rate. Analysis of the plasma lipoproteins by fast protein liquid chromatography indicates that these changes reflected an increased concentration of apolipoprotein E-enriched, HDL1-sized particles, whereas atherogenic apolipoprotein B particles disappeared from the plasma. The concentrations of plasma HDL cholesterol were highly correlated with both human LCAT mass (r = 0.93; p = 0.001) and the log LCAT activity (r = 0.94; p < 0.001) in the transgenic rabbits. These results indicate that overexpression of LCAT in the presence of cholesteryl ester transfer protein leads to both hyperalpha-lipoproteinemia and reduced concentrations of atherogenic lipoproteins.

Animals↗
PubMed1996

Presynaptic and Ca(2+)-independent PKC subspecies modulates NMDAR1 current.

We have studied the properties of the protein kinase C (PKC) subspecies that modulates the NMDA receptor (NMDAR1). The current through homomeric NMDAR1 expressed in Xenopus oocytes was increased by 200-500% by phorbol ester and also by activation of a metabotropic glutamate receptor (mGluR1) expressed in the same oocytes. This potentiation of the NMDAR1 current was not inhibited by the intracellular injection of EGTA. Intracellular injection of epsilon-PKC, a presynaptic PKC subspecies, potentiated the NMDAR1 current more efficiently that did the Ca(2+)-dependent gamma-PKC, a postsynaptic subspecies of the enzyme. Our findings suggested that the presynaptic NMDA receptor could be potentiated in a Ca(2+)-independent manner by the activation of presynaptic PKC subspecies.

Animals↗
PubMed1996

Von Hippel-Lindau tumour suppressor gene. Localization of expression by in situ hybridization.

Inactivation of the von Hippel-Lindau (VHL) tumour suppressor gene is responsible not only for VHL disease, but also for sporadic renal cell carcinoma and cerebellar haemangioblastoma. The distribution of VHL gene expression in the mouse embryo was recently studied by in situ hybridization, along with human VHL in 14-week-old fetal kidney: there was widely distributed expression in the former and expression in the tubules and blastema in the latter. Adult human tissue and other fetal organs were not examined. The present paper describes an in situ hybridization study to assess the function of the VHL gene in adult human tissues and in tissues of human fetus at 28 weeks of gestation. The expression of the VHL gene was limited to the adult and fetal brain and kidney, and the adult prostate. Nerve cells in adult and fetal brain were positive, including the cerebellar Purkinje cells. In adult and fetal kidney, the proximal tubular epithelium, the putative origin of the common type of renal cell carcinoma, showed intense signal, whereas the distal nephron, glomeruli, and nephrogenic blastema showed no significant signal. The prostate showed significant signal in the basal epithelium. The adrenal, pancreas, and epidydimis showed no significant signal, in spite of the frequent occurrence at these sites of neoplastic or hamartomatous lesions in VHL disease.

Animals↗
PubMed1996

A case of chromophobe renal cell carcinoma associated with low chromosome number and microsatellite instability.

Cytogenetic study in a case of a human chromophobe renal cell carcinoma revealed a hypodiploid chromosome number of 36 with loss of chromosomes 1, 2, 5, 6, 10, 13, 15, 17, 21, and X. The tumor DNA showed microsatellite instability in dinucleotide repeat microsatellite markers. This is the fourth case that has been fully karyotyped and showed a low chromosome number in a chromophobe renal cell carcinoma. Our data in the present study are consistent with those in the literature. It is suggested that human chromophobe renal cell carcinoma may possibly be characterized by tumor cells with low chromosome number or microsatellite instability.

Adult↗
PubMed1996

Behavioral studies on rats with transient cerebral ischemia induced by occlusion of the middle cerebral artery.

The behavioral effects of transient cerebral ischemia in adult Wistar rats were studied. In Experiment 1, rats were subjected to 90-min occlusion of the unilateral, left or right, middle cerebral artery (MCA) followed by recirculation. The locomotor activity had not changed 3 and 30 days after the occlusion, except that the number of rearing was significantly decreased by left MCA occlusion. Rats were examined in a radial maze system for learning and memory ability during 4 weeks from the 3rd day after ischemia (the 3rd day was counted as day 1 of the experiment). Maze performance was slightly disturbed due to focal brain damage by MCA occlusion, but the disturbance was statistically significant only on days 6, 11, and 15 in the right occlusion. In Experiment 2, rats were trained to master a radial maze task completely for 4 weeks, and then subjected to transient unilateral (right) ischemia as described above. These rats showed an increase in incorrect entry in the radial maze task from day 4 to day 14. However, on day 21, the number of incorrect entry decreased to the control level of the sham-operated group. The numbers of correct choice were inversely related with those of incorrect entry, though slightly blunted. Coincidentally, the time required to solve the maze task was also prolonged from day 4 to day 14, but returned to the control time on day 21. These results suggest that unilateral ischemia transiently suppresses both acquiring radial maze performance and maintenance of learned performance and that it is a good model for studying human focal cerebral ischemia.

Adult↗
PubMed1996

Neuronal and glial localization of two GABA transporters (GAT1 and GAT3) in the rat cerebellum.

The localization of GABA transporters (GAT1 and GAT3) was examined immunocytochemically in the rat cerebellum at both light and electron microscopic levels using antibodies specific for each subtype. Immunoblot analysis showed that the antibodies against GAT1 and GAT3 specifically recognized their respective antigens in the cerebellum. Both GAT1 and GAT3 were found in the neuropil but not in neuronal somata or glial cell bodies. GAT1 immunoreactivity was seen throughout all layers of the cerebellar cortex with the highest immunoreactivity in the molecular layer, but little immunoreactivity was found in the deep cerebellar nuclei. GAT1 immunoreactivity was seen in the pinceau area of the Purkinje cell layer and in the mossy fiber glomeruli in addition to the neuropil of the molecular layer. Weak GAT3 immunoreactivity was found in the granular layer of the cerebellar cortex, and intense immunoreactivity was observed around the unstained large neurons in the deep cerebellar nuclei. Electron microscopic analysis of the cerebellum revealed that GAT1 immunoreactivity was predominantly localized in the presynaptic terminals, while GAT3 immunoreactivity was localized in the glial processes. These results suggested that GABAergic transmission at synapses is terminated by three GABA uptake systems, (1) only neuronal uptake through GAT1, (2) only glial uptake through GAT3, and (3) both neuronal and glial uptake through GAT1 and GAT3 respectively, and also that the GABA uptake system is different in each type of GABAergic neuron.

Animals↗
PubMed1996

Endoscopic resection of large pedunculated colorectal polyps using a detachable snare.

BACKGROUND: Colonoscopic resection of pedunculated polyps with heads 1 cm or greater in diameter is difficult because of the risk of bleeding. To minimize this complication, we used a detachable snare that allowed endoscopic ligation of the stalk of a large pedunculated polyp and evaluated its safety and effectiveness in comparison with conventional endoscopic snare polypectomy. METHODS: Patients with pedunculated polyps with heads 1 cm or greater in diameter were randomly assigned to colonoscopic polypectomy with (N = 47) or without (N = 42) a detachable snare. Arterial pumping bleeding immediately after colonoscopic polypectomy or hematochezia resulting in a 10% or greater drop in hematocrit was defined as "bleeding." RESULTS: No bleeding occurred during or after polypectomy with a detachable snare, but bleeding occurred significantly more frequently (five patients, 12%) without a snare. Moreover, the use of a detachable snare reduced the duration of hospitalization after polypectomy. CONCLUSIONS: Colonoscopic polypectomy with a detachable snare may be safer than conventional polypectomy without a detachable snare for resection of large, pedunculated polyps.

Blood Loss, Surgical↗
PubMed1996

Dome formation induced by v-H-ras oncogene in a human choriocarcinoma cell line.

To investigate the role of ras genes in trophoblastic cell lineage, we transfected the viral H- or K-ras oncogene into a human choriocarcinoma cell line, CCI, and analysed the biological properties of CCI cells expressing an activated ras oncogene. All v-H-ras-expressing clones distinctively formed the hemispherical domes, which represents an in vitro morphological expression of vectorial transport function and are characteristic of the polarized epithelial cells, but none of v-K-ras-expressing clones and control clones did. Microscopic observation demonstrated that those domes were cavities filled with fluid which accumulated between the cell layer and the surface of culture dish. Scanning electron microscopy revealed that the domes were aggregates of round cells with long numerous microvilli and were morphologically similar to a blastocyst. Furthermore, Na(+)-K(+)-ATPase activity, which is associated with the vectorial fluid transport in transporting epithelial cells, was significantly higher in the v-H-ras-expressing clones than that in the v-K-ras-expressing clones and the parental cells. Those domes flattened within 24 h after treatment with a specific inhibitor of Na(+)-K(+)-ATPase, ouabain, and the number of domes decreased in dose-dependent manner, indicating that Na(+)-K(+)-ATPase activity was required for maintainance of domes. These results suggest that up-regulated activity of H-ras but not of K-ras facilitates the vectorial fluid transport through a chorionic cell layer and leads to the dome formation. The function of II-ras in trophoblasts, may therefore, be essential for embryogenesis, especially for supplying the nutrients.

Biological Transport↗
PubMed1996

Simultaneous observation of regional cerebral blood flow and event-related potential during performance of an auditory task.

Reduced amplitude of the P300 component has been reported consistently in patients with neurological and psychiatric disorders. It is unclear, however, how such patients' cognitive dysfunction is related to their P300 abnormality. Further basic knowledge regarding neural substrates for P300 generation is required for gaining an understanding of the pathological significance of the P300 amplitude reduction. To determine the brain structures involved in P300 generation, we observed the event-related potential and the regional cerebral blood flow (rCBF) in 10 normal subjects performing an oddball discrimination of pure tones. The rCBF value was assessed quantitatively with the aid of single photon emission computed tomography using technetium-99m hexamethylpropylene amine oxime. During the task performance, significant activation was observed in the posterior superior temporal and inferior parietal regions of the right hemisphere. In addition, positive correlation of the task-related increase in rCBF with the simultaneously recorded P300 amplitude was observed in the right but not the left posterior superior temporal region. These findings indicate that activation of the right non-verbal auditory area might modulate P300 generation during pure-tone discrimination.

Acoustic Stimulation↗
PubMed1996

Influence of baseline airway calibre and pulmonary emphysema on bronchial responsiveness in patients with chronic obstructive pulmonary disease.

STUDY OBJECTIVE: Bronchial hyper-responsiveness (BHR) is widely observed in patients with chronic obstructive pulmonary disease (COPD). However, its clinical significance in COPD has not yet been established. To determine the factors that influence BHR in COPD, multiple linear regression analysis was used to analyse the relationship between BHR to methacholine and baseline forced expiratory volume in 1 s (FEV1), vital capacity (VC), residual volume (RV)/total lung capacity (TLC), static compliance (Cst), transfer coefficient of the lung (Kco), and the percentage of low attenuation area (%LAA) determined by computed tomographic (CT) scan. METHODS: Bronchial responsiveness to methacholine was determined in 63 patients with COPD by the dosimeter method and expressed as PD20FEV1. Residual volume and TLC were determined by body plethysmography. The percentage of low attenuation area was defined as the percentage of area less than -960 Hounsfield unit on a CT scan of the thorax. RESULTS: Forced expiratory volume in 1s (%predicted) and %LAA correlated with BHR (P = 0.023 and 0.020, respectively), while VC (%pred), RV/TLC, Cst and Kco did not. The coefficient of determination was 0.43. The regression analysis showed that a 10% increase in FEV1 (%pred) and a 10% decrease in %LAA would increase log(PD20FEV1) by 0.145 and 0.117, respectively. CONCLUSIONS: A considerable proportion of the BHR in COPD is related to functional abnormalities and morphologic changes of emphysema, such as decreased baseline airway calibre and destruction of the lung parenchyma.

Aged↗
PubMed1996

Molecular cloning and expression of cDNA for murine galactocerebrosidase and mutation analysis of the twitcher mouse, a model of Krabbe's disease.

The cDNA for a murine galactocerebrosidase was isolated from a murine testis cDNA library on the basis of its homology with the cDNA for human galactocerebrosidase and a PCR method was used to clone the 5' end. It has a 2,278-nucleotide sequence including a 2,004-nucleotide open reading frame, which encodes 668 amino acid residues. The identity between the human and murine amino acid sequences was very high, being calculated to be 84%. Sequencing of cDNA from liver of the twitcher mouse revealed a nonsense mutation at codon 339 (TGG-->TGA). The most abundant mRNA of the murine galactocerebrosidase gave a 3.6-kb band, which was not detected in twitcher mice. This suggests that the cDNA (2,278 bp) we characterized represents a minor species generated by an alternate poly(A) signal and that most of the mRNA has a much longer 3'-untranslated region. Genome analysis revealed that this mutation was homozygous in the twitcher and heterozygous in the carrier but was not present in normal mice. The normal mouse cDNA but not the mutant cDNA of the galactocerebrosidase transfected into COS1 cells gave rise to an increase in enzymatic activity. We concluded that this mutation results in the deficiency of galactocerebrosidase in the twitcher mouse.

Amino Acid Sequence↗
PubMed1996

Clinoidal meningioma arising from falciforme process of optic canal: case report and review.

A 56-year-old female with an initial symptom of unilateral progressive visual disturbance presented with a clinoidal meningioma arising from a falciforme process of the optic canal. Magnetic resonance images with gadolinium-diethylenetriaminepenta-acetic acid demonstrated marked enhancement of a small mass, approximately 1 cm in diameter, roofing the right optic nerve at the intracranial opening of the optic canal. The clinoidal meningioma is rarely reported and the precise originating location of the neoplasm has not been clarified. This is the first case of clinoidal meningioma, which is confirmed by the operative observation as the origin of the neoplasm is a falciforme process of the optic canal. Magnetic resonance images with enhancement are useful for the diagnosis of such a small neoplastic lesion adjacent to bone structure and total removal without a deterioration of visual function is achieved by careful microsurgical procedure.

Animals↗
PubMed1996

Free radical-independent protection by nerve growth factor and Bcl-2 of PC12 cells from hydrogen peroxide-triggered apoptosis.

To investigate the mechanism of oxidative stress induced death of PC12 cells, we performed confocal and flow cytometric analysis with a reactive oxygen species (ROS)-specific fluorogen, 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA). Hydrogen peroxide significantly decreased the number of viable PC12 cells after 24 h. Hydrogen peroxide caused membrane blebbing, nuclear condensation and DNA fragmentation, indicating that the PC12 cells died due to apoptosis. The hydrogen peroxide-triggered apoptosis of PC12 cells was associated with enhanced ROS production in a dose-dependent manner by measuring with C-DCDHF-DA. Nerve growth factor (NGF) and Bcl-2 inhibited the hydrogen peroxide-induced apoptosis of PC12 cells. Neither of them, however, reduced the ROS production in PC12 cells. These data suggest that NGF or Bcl-2 protects PC12 cells from hydrogen peroxide-triggered apoptosis independently from ROS production.

Animals↗
PubMed1996

Selective hypothermic perfusion of canine brain.

A method for selective brain cooling by profound hemodilution with cold Ringer's lactate solution was previously reported in 1992. We recently modified this technique by combining it with an ultrafiltration and rewarming circuit between the left jugular vein and the inferior vena cava. We used 12 beagle dogs to study the efficacy of selective cerebral hypothermia induced by this modified technique. The brain temperature decreased to 28 degrees C within 5.4 +/- 2.7 minutes and to 20 degrees C within 15.5 +/- 9.4 minutes. The lowest brain and rectal temperatures were 17.0 +/- 1.8 degrees C and 32.1 +/- 2.2 degrees C, respectively. All animals survived in good condition without evidence of neurological deficits until they were killed at 10 weeks. Histological examination of the brains with 2,3,5-triphenyltetrazolim chloride demonstrated no evidence of ischemic lesions, and even in the hippocampus, there was no evidence of ischemic neuronal damage.

Animals↗