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Biomedical subjects

T Nagata

Publications and source records attributed to T Nagata.

At least 73 records · Page 4Linked to original sources
PubMed2001

Extracellular glutamate changes in rat striatum during ischemia determined by a novel dialysis electrode and conventional microdialysis.

Our newly developed method using a dialysis electrode has made it possible to perform real time monitoring of extracellular glutamate concentration ([Glu]e) utilizing the oxygen-independent reaction with glutamate oxidase and ferrocene. In this study, we therefore, investigated [Glu]e changes during brain ischemia using both the conventional microdialysis method and the dialysis electrode method. A comparison between our newly developed dialysis electrode and conventional microdialysis methods provided the following results. When the conventional microdialysis method was employed: (1) the elevation of [Glu]e during complete global ischemia was delayed; and (2) the elevation of concentration and reuptake of glutamate were delayed during 10-min transient ischemia, and the elevation of [Glu]e reached a maximum later using conventional microdialysis than using our dialysis electrode. (3) The biphasic [Glu]e elevation of glutamate concentration detected using the dialysis electrode method was not observed using the conventional microdialysis method. It was additionally investigated why the conventional microdialysis method provides inferior time resolution. In this study, we also demonstrated with the chromatographic SMART procedure coupled to UV detection that biogenic substances, i.e. low molecular weight proteins and peptides, are released during ischemic injury, and they may cause a delay in the time resolution in the microdialysis method.

Animals↗
PubMed2001

Effect of round-edged acrylic intraocular lenses on preventing posterior capsule opacification.

PURPOSE: To clarify the extent to which the adhesiveness of an acrylic material influences the formation of posterior capsule opacification (PCO). SETTING: Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. METHODS: Two types of AcrySof(R) intraocular lenses (IOLs) were prepared: round edged and tumbled. The AcrySof with round edges was implanted in 1 eye in a group of 4 rabbits and the tumbled IOL, in 1 eye in a group of 5 rabbits. In both groups, the contralateral eye received a conventional AcrySof with sharp optic edges. A histopathological examination was performed 3 weeks after surgery. RESULTS: With the round-edged AcrySof IOL, no capsular bend formed at the optic edge and abundant lens epithelial cells (LECs) migrated posteriorly. With the sharp-edged AcrySof lens, a sharp capsular bend formed and LEC migration was significantly inhibited. In eyes with a tumbled IOL, a capsular bend was created, but it was less marked than that created by the sharp-edged lens and there was slightly more LEC migration posteriorly. CONCLUSIONS: The AcrySof IOL lost its preventive effect on PCO when the optic was rounded. The effect of the AcrySof lens in preventing PCO is mainly a result of its rectangular, sharp-edged optic design. The acrylic material may play a complementary role by helping create a sharp capsular bend. Capsular bend formation is the key to the PCO preventive effect of an IOL.

Acrylic Resins↗
PubMed2001

Three-dimensional high voltage electron microscopy of thick biological specimens.

The procedures recently developed in our laboratory to observe three-dimensional structures of cell organelles in thick biological specimens by means of high voltage electron microscopy are reviewed. Thick biological specimens such as whole mount cultured cells seeded and grown on grid meshes in culture vessels or thick sections cut from embedded tissues and stained by histochemical reactions can be readily observed three-dimensionally by high voltage transmission electron microscopy at 400-1000kV. Cultured cells used were both primary cultures from animal tissues and established cell lines maintained in our laboratory. The livers of adult Wistar rats were isolated by collagenase perfusion, and hepatocytes were suspended in a Leibovitz medium and seeded on formval coated gold grid meshes in Petri dishes, incubated in a CO(2) incubator in a humidified atmosphere containing 5% CO(2) in air at 37 degrees C for a few days. Established cell lines, CHO-K1 cells, were cultured in Ham's F12 medium, while HeLa cells were cultured in Eagle's MEM under the same condition. Some of the cells were cultured under experimental conditions such as hepatocyte culture in the medium containing peroxisome proliferating agents such as clofibrate or bezafibrate and some of them were labeled with (3)H-thymidine, (3)H-uridine, (3)H-labeled precursors and (14)C-bezafibrate. Also some cells were incubated in medium containing HRP to induce pinocytosis. All the whole mount cultured cells on grid meshes were prefixed in buffered 2.5% glutaraldehyde, stained with various histochemical reactions and postfixed in 1% osmium tetroxide. The histochemical reactions used were glucose-6-phosphatase (G-6-Pase), thiamine pyrophosphatase (TPPase), cytochrome oxidase, acid phosphatase (AcPase), DAB, ZIO, PA-TCH-SP reactions and radioautography was performed after labeling with radiolabeled compounds. The whole mount cultured cells were dried in a critical point dryer and were observed with JEOL JEM-4000EX or Hitachi H-1250M high voltage electron microscopes at 400-1000kV. By tilting the specimens' stereo-pair micrographs were recorded and they were observed with stereoscopes. Rat liver, mouse intestine and pancreas tissues, fixed and stained as above, were embedded in Epoxy resin, thick sectioned at 1-2 microm and were observed as for the whole mount cultured cells at 1000kV. Stereo-pairs were further analyzed with an image analyzer JEOL JIM-5000 (JEOL, Tokyo, Japan), producing two contour lines plotted from the micrographs at a thickness of 0.2 microm and were observed with anaglyph type glasses, demonstrating the depth or heights of respective cell organelles. The results show that whole mount cultured cells and thick sections stained with histochemical reactions reveal cell organelles corresponding to marker enzymes, such as G-6-Pase in endoplasmic reticulum, TPPase and ZIO in Golgi apparatus, cytochrome oxidase in mitochondria, AcPase in lysosomes, DAB in peroxisomes and pinocytotic vesicles, PA-TCH-SP in secretory granules, (3)H-thymidine and (3)H-uridine in nuclei, (3)H-animo acids in endoplasmic reticulum and secretory granules, (14)C-bezafibrate around ER and peroxisomes. The ultrastructure of these cell organelles as well as the structural relationship between them can be demonstrated three-dimensionally with stereo-pair images. Overall, these procedures are useful for analyzing stereologically the ultrastructure of cell organelles in cells and tissues.

Animals↗
PubMed2001

Structural analysis of a novel antimutagenic compound, 4-Hydroxypanduratin A, and the antimutagenic activity of flavonoids in a Thai spice, fingerroot (Boesenbergia pandurata Schult.) against mutagenic heterocyclic amines.

Six compounds were isolated from fresh rhizomes of fingerroot (Boesenbergia pandurata Schult.) as strong antimutagens toward 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) in Salmonella typhimurium TA98. These compounds were 2',4',6'-trihydroxychalcone (pinocembrin chalcone; 1), 2',4'-dihydroxy-6'-methoxychalcone (cardamonin; 2), 5,7-dihydroxyflavanone (pinocembrin; 3), 5-hydroxy-7-methoxyflavanone (pinostrobin; 4), (2,4,6-trihydroxyphenyl)-[3'-methyl-2'-(3' '-methylbut-2' '-enyl)-6'-phenylcyclohex-3'-enyl]methanone (5), and (2,6-dihydroxy-4-methoxyphenyl)-[3'-methyl-2'-(3' '-methylbut-2' '-enyl)-6'-phenylcyclohex-3'-enyl]methanone (panduratin A; 6). Compound 5 was a novel compound (tentatively termed 4-hydroxypanduratin A), and 1 was not previously reported in this plant, whereas 2-4 and 6 were known compounds. The antimutagenic IC(50) values of compounds 1-6 were 5.2 +/- 0.4, 5.9 +/- 0.7, 6.9 +/- 0.8, 5.3 +/- 1.0, 12.7 +/- 0.7, and 12.1 +/- 0.8 microM in the preincubation mixture, respectively. They also similarly inhibited the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). All of them strongly inhibited the N-hydroxylation of Trp-P-2. Thus, the antimutagenic effect of compounds 1-6 was mainly due to the inhibition of the first step of enzymatic activation of heterocyclic amines.

Amines↗
PubMed2001

Osteopontin in gingival crevicular fluid.

Osteopontin (OPN) is a major glycosylated phosphoprotein in bone matrix and is produced by several cells including osteoblasts, osteoclasts and macrophages. OPN levels increase in active sites of bone metabolism. Recently, several bone-related proteins were identified in gingival crevicular fluid (GCF) to seek markers of alveolar bone resorption in periodontal disease. In this study, we investigated the existence of OPN in GCF and the correlation between OPN level in GCF and probing depth (PD) of sampling sites in 98 periodontitis patients and 35 healthy subjects. An immunoblotting analysis using 10% polyacrylamide gel showed that two forms of OPN with molecular masses of 54 and 66 kDa and several degraded fragments were detected in most GCF samples from diseased sites (PD > 4 mm). In GCF samples from healthy sites (PD < or = 3 mm), only one form (54 kDa) was observed, but any degraded fragments were not detected. When OPN amounts in GCF samples were determined by ELISA, a weak. but significant correlation was observed between OPN amount in GCF and PD (r=0.32, p=0.0013). These results demonstrate that OPN exists in GCF and that OPN level in GCF increases with the progression of periodontal disease.

Adult↗
PubMed2001

The gene mutated in ataxia-ocular apraxia 1 encodes the new HIT/Zn-finger protein aprataxin.

The newly recognized ataxia-ocular apraxia 1 (AOA1; MIM 208920) is the most frequent cause of autosomal recessive ataxia in Japan and is second only to Friedreich ataxia in Portugal. It shares several neurological features with ataxia-telangiectasia, including early onset ataxia, oculomotor apraxia and cerebellar atrophy, but does not share its extraneurological features (immune deficiency, chromosomal instability and hypersensitivity to X-rays). AOA1 is also characterized by axonal motor neuropathy and the later decrease of serum albumin levels and elevation of total cholesterol. We have identified the gene causing AOA1 and the major Portuguese and Japanese mutations. This gene encodes a new, ubiquitously expressed protein that we named aprataxin. This protein is composed of three domains that share distant homology with the amino-terminal domain of polynucleotide kinase 3'- phosphatase (PNKP), with histidine-triad (HIT) proteins and with DNA-binding C2H2 zinc-finger proteins, respectively. PNKP is involved in DNA single-strand break repair (SSBR) following exposure to ionizing radiation and reactive oxygen species. Fragile-HIT proteins (FHIT) cleave diadenosine tetraphosphate, which is potentially produced during activation of the SSBR complex. The results suggest that aprataxin is a nuclear protein with a role in DNA repair reminiscent of the function of the protein defective in ataxia-telangiectasia, but that would cause a phenotype restricted to neurological signs when mutant.

Amino Acid Sequence↗
PubMed2001

Physical and sexual abuse histories in patients with eating disorders: a comparison of Japanese and American patients.

Physical and sexual abuse among patients with eating disorders has been a focus of attention in Western countries, however, there is no study comparing the incidence of these factors in Western and Asian countries. Japanese subjects consisted of 38 patients with anorexia nervosa restricting type (AN-R), 46 patients with anorexia nervosa binge eating/purging type (AN-BP), 76 patients with bulimia nervosa purging type (BN) and 99 controls. Subjects from the USA consisted of 29 AN-R, 34 AN-BP and 16 BN. The Physical and Sexual Abuse Questionnaire was administered to all subjects. Minor sexual abuse such as confronting exhibitionism or being fondled by a stranger tended to be more prevalent among Japanese subjects, while victimization by rape or incest was more prevalent among USA subjects. Conversely, physical abuse history was similarly distributed across each diagnostic subgroup in both countries. Events related to physical abuse, such as an abusive family background, may contribute whether eating disorder patients are restricting or bulimic and regardless of culture.

Analysis of Variance↗
PubMed2001

Outcome of severe anorexia nervosa patients receiving inpatient treatment in Japan: an 8-year follow-up study.

Sixty-one subjects with anorexia nervosa (AN) were followed for a minimum of 4 years after discharge (mean 8.3 years). They were evaluated using the Morgan-Russell Outcome Assessment Scale. Thirty-one (51%) were categorized as having good outcome, eight (13%) as intermediate, 15 (25%) as poor, and seven (11%) had died. As predictors of outcome, later onset (after 20 years of age) and low minimum body mass index were associated with poor prognosis. The outcome of AN in Japan is relatively similar to those in Western countries, irrespective of different sociocultural backgrounds and health systems.

Adolescent↗
PubMed2001

Ghrelin is an appetite-stimulatory signal from stomach with structural resemblance to motilin.

BACKGROUND & AIMS: : Ghrelin, an endogenous ligand for growth hormone secretagogue receptor, was recently identified in the rat stomach. We examined the effects of the gastric peptide ghrelin on energy balance in association with leptin and vagal nerve activity. METHODS: : Food intake, oxygen consumption, gastric emptying, and hypothalamic neuropeptide Y (NPY) messenger RNA expression were measured after intra-third cerebroventricular or intraperitoneal injections of ghrelin in mice. The gastric vagal nerve activity was recorded after intravenous administration in rats. Gastric ghrelin gene expression was assessed by Northern blot analysis. Repeated coadministration of ghrelin and interleukin (IL)-1 beta was continued for 5 days. RESULTS: : Ghrelin exhibited gastroprokinetic activity with structural resemblance to motilin and potent orexigenic activity through action on the hypothalamic neuropeptide Y (NPY) and Y(1) receptor, which was lost after vagotomy. Ghrelin decreased gastric vagal afferent discharge in contrast to other anorexigenic peptides that increased the activity. Ghrelin gene expression in the stomach was increased by fasting and in ob/ob mice, and was decreased by administration of leptin and IL-1 beta. Peripherally administered ghrelin blocked IL-1 beta-induced anorexia and produced positive energy balance by promoting food intake and decreasing energy expenditure. CONCLUSIONS: : Ghrelin, which is negatively regulated by leptin and IL-1 beta, is secreted by the stomach and increases arcuate NPY expression, which in turn acts through Y(1) receptors to increase food intake and decrease energy expenditure. Gastric peptide ghrelin may thus function as part of the orexigenic pathway downstream from leptin and is a potential therapeutic target not only for obesity but also for anorexia and cachexia.

Amino Acid Sequence↗
PubMed2001

Cocaine-amphetamine-regulated transcript influences energy metabolism, anxiety and gastric emptying in mice.

This study was designed to investigate the effects of cocaine-amphetamine-regulated transcript (CART), a recently discovered hypothalamic neuropeptide, on food intake, anxiety, oxygen consumption and gastric emptying in mice. Intracerebroventricular (i. c. v.) injection of CART (1 - 100 pmol) markedly reduced food intake in a dose-related manner. A significant decrease was observed 20 min after i. c. v. injection of CART and continued for four hours. In the elevated plus maze test, i. c. v. CART injection significantly raised the normal preference for the closed arms. Furthermore, the i. c. v. injection of CART significantly reduced oxygen consumption and gastric emptying rate. These results suggest that CART modulates feeding, emotion, and autonomic functions in mice.

Animals↗
PubMed2001

Development of apoptosis and changes in lymphocyte subsets in thymus, mesenteric lymph nodes and Peyer's patches of mice orally inoculated with T-2 toxin.

Development of apoptosis and changes in lymphocyte subsets were examined mainly by flow cytometer in thymus, mesenteric lymph nodes and Peyer's patches of mice up to 24 hours after oral inoculation with T-2 toxin (10 mg/kg). T-2 toxin attacked Peyer's patches first, then mesenteric lymph nodes, and finally thymus in relation to the course of enteric absorption of orally inoculated T-2 toxin. The degree of lymphocyte apoptosis was prominent in the thymus, moderate in the Peyer's patches, and somewhat mild in the mesenteric lymph nodes, suggesting the difference in lymphocyte population susceptible to T-2 toxin. As to the changes in lymphocyte subsets, CD4+ CD8+ T cells were most sensitive to T-2 toxin, and CD4+ CD8- T cells were more severely depressed than CD4- CD8+ T cells in the thymus. In the mesenteric lymph nodes, CD3+ cells was more clearly affected than CD19+ cells, and the numbers of CD4+ and CD8+ cells were similarly decreased. In the Peyer's patches, the numbers of CD3+, CD 19+, CD4+ and CD8+ cells were unexceptionally decreased. In addition, among IgM+, IgG+ and IgA+ B cells, the number of IA+ B cells which are more important in the mucosal immunity was most severely affected.

Administration, Oral↗
PubMed2001

Propofol inhibits FMLP-stimulated phosphorylation of p42 mitogen-activated protein kinase and chemotaxis in human neutrophils.

Propofol is used in the peri-operative setting and may affect some neutrophil functions. The effects of propofol on the function and intracellular signal transduction systems of neutrophils is controversial. Mitogen-activated protein kinase families (MAPKs) are members of the intracellular signal-transducing systems in eukaryotes. MAPKs have been shown to be involved in neutrophil chemotaxis by the use of PD98059, the specific inhibitor of MAPK/ERK kinase (MEK). The effects of propofol in dimethyl sulfoxide on phosphorylation of MAPKs and chemotaxis were investigated in human neutrophils. Isolated neutrophils (2 x 10(7) cells per ml) from healthy volunteers were incubated with propofol (2-500 microM) and stimulated by N-formyl-L-methionyl-phenylalanine (FMLP) (100 nM). The effects of propofol on the phosphorylation of p44/42 MAPK were investigated by immunoblotting. The effects of FMLP (1 microM) on chemotaxis were investigated with the under-agarose method. The phosphorylation of p42 MAPK and chemotaxis stimulated by FMLP were both inhibited by propofol at clinically relevant concentrations (> or = 10 and > or = 20 microM respectively). PD98059 (50 microM) also inhibited chemotaxis stimulated by FMLP, suggesting the involvement of p42 MAPK in the response. Propofol might therefore inhibit human neutrophil chemotaxis, at least in part, by suppressing the p44/42 MAPK pathway.

Anesthetics, Intravenous↗
PubMed2001

A simple and rapid system for the quantitation of RNA interference in plant cultured cells.

The phenomenon known as RNA interference (RNAi) by double-stranded RNA (dsRNA) that was reported recently in the nematode Caenorhabditis elegans has been shown to operate by a mechanism that is widely conserved among species including plant cells. No quantitative analysis of the effects of RNAi on the expression of specific genes in plant cultured cells has been reported. An RNAi effect was observed 24 h after the introduction of dsRNA expression plasmids into tobacco BY-2 cells by electroporation. The simple system for suppression of specific genes in plant cells should be useful in attempts to elucidate the roles of individual genes in plant cells.

Cell Line↗
PubMed2001

Fate of nascent microtubules organized at the M/G1 interface, as visualized by synchronized tobacco BY-2 cells stably expressing GFP-tubulin: time-sequence observations of the reorganization of cortical microtubules in living plant cells.

Transgenic BY-2 cells stably expressing a GFP (green fluorescent protein)-tubulin fusion protein (BY-GT16) were subcultured in a modified Linsmaier and Skoog medium. The BY-GT16 cells could be synchronized by aphidicolin and the dynamics of their microtubules (MTs) were monitored by the confocal laser scanning microscopy (CLSM). We have succeeded in investigating the mode of reorganization of cortical MTs at the M/G1 interface. The cortical MTs were initially organized in the perinuclear regions and then they elongated to reach the cell cortex, forming the bright spots there. Subsequently, the first cortical MTs rapidly elongated from the spots and they were oriented parallel to the long axis towards the distal end of the cells. Around the time when the tips of the parallel MTs reached the distal end, the formation of transverse cortical MTs followed in the cortex near the division site, as we had previously suggested [Hasezawa and Nagata (1991) Bot. Acta 104: 206, Nagata et al. (1994) Planta 193: 567]. It was confirmed in independent observations that the appearance of the parallel MTs was followed by the appearance of the transverse MTs in each cell. We found that the transverse MTs spread through the whole cell cortex within about 20-30 min, while the parallel MTs disappeared. The significance of these observations on the mode of cortical MT organization is discussed.

Cell Line↗
PubMed2001

Immunohistochemical localization of osteopontin in human pulp stones.

The organic matrix component of human pulp stones was investigated by immunohistochemistry. Two pulp stones were extracted from the upper molar teeth of two patients suffering from irreversible pulpitis. Both were formed in the center of the pulp cavity and located apart from the dentin walls. After demineralization, serial sections of the stones were prepared and subjected to immunohistochemical procedures using specific antibodies to type I collagen and noncollagenous proteins (osteopontin, osteonectin, and osteocalcin), which are reported to be involved in calcified matrix formation. Type I collagen was localized evenly in the stones, indicating that it is a major matrix component of pulp stones. Strong immunostaining of osteopontin appeared in the peripheral area of the stones, whereas osteonectin and osteocalcin were not detected. We previously reported that dental pulp cells produced osteopontin in vitro. Osteopontin has been commonly found in other pathological calcification, such as urinary stones, atherosclerotic plaques, and dental calculus. Taken together, the present findings suggest that osteopontin produced by dental pulp cells is possibly associated with calcification of the pulp stone matrix.

Antibodies↗
PubMed2001

Characteristics of somatosensory feedback in postural control during standing.

In the present study, the function of the somatosensory feedback system in postural control was investigated. For the sake of simplicity, the present study considered only balancing in the anteroposterior direction using the ankle strategy, in which the ankle moment is mainly used to maintain balance. To suppress the vestibular and visual feedback paths, a subject stood on a force-measuring platform with a fixed back support. Because the subject's body was immovable under these conditions, the subject controlled a computer model that simulated the subject's load at the ankles. Information about the sway angle of the model was fed through the somatosensory feedback path. Frequency response functions of the ankle moment in response to the sway angle were calculated. The experimental results suggest that the human somatosensory feedback system has derivative characteristics and, consequently, can maintain an upright posture by itself. The results were compared with those of previous studies on vestibular and visual feedback systems. The comparison reveals that subject-to-subject variance in the somatosensory system is significantly smaller than that in the other systems. This may indicate that the somatosensory feedback is the most automatic of the systems and plays a dominant role when a subject maintains an upright posture using the ankle strategy.

Adult↗