Biomedical subjects

T Imamura

Publications and source records attributed to T Imamura.

At least 91 records · Page 5Linked to original sources

PubMed2000

The tumor suppressor PTEN negatively regulates insulin signaling in 3T3-L1 adipocytes.

PTEN is a tumor suppressor with sequence homology to protein-tyrosine phosphatases and the cytoskeleton protein tensin. PTEN is capable of dephosphorylating phosphatidylinositol 3,4, 5-trisphosphate in vitro and down-regulating its levels in insulin-stimulated 293 cells. To study the role of PTEN in insulin signaling, we overexpressed PTEN in 3T3-L1 adipocytes approximately 30-fold above uninfected or control virus (green fluorescent protein)-infected cells, using an adenovirus gene transfer system. PTEN overexpression inhibited insulin-induced 2-deoxy-glucose uptake by 36%, GLUT4 translocation by 35%, and membrane ruffling by 50%, all of which are phosphatidylinositol 3-kinase-dependent processes, compared with uninfected cells or cells infected with control virus. Microinjection of an anti-PTEN antibody increased basal and insulin stimulated GLUT4 translocation, suggesting that inhibition of endogenous PTEN function led to an increase in intracellular phosphatidylinositol 3,4,5-trisphosphate levels, which stimulates GLUT4 translocation. Further, insulin-induced phosphorylation of downstream targets Akt and p70S6 kinase were also inhibited significantly by overexpression of PTEN, whereas tyrosine phosphorylation of the insulin receptor and IRS-1 or the phosphorylation of mitogen-activated protein kinase were not affected, suggesting that the Ras/mitogen-activated protein kinase pathway remains fully functional. Thus, we conclude that PTEN may regulate phosphatidylinositol 3-kinase-dependent insulin signaling pathways in 3T3-L1 adipocytes.

3T3 Cells↗

PubMed2000

Simple and simultaneous analysis of fenfluramine, amphetamine and methamphetamine in whole blood by gas chromatography-mass spectrometry after headspace-solid phase microextraction and derivatization.

A simple and sensitive method for the simultaneous analysis of fenfluramine, amphetamine and methamphetamine in whole blood was developed using a headspace-solid phase microextraction (SPME) and derivatization. A 0.5 g whole blood sample, 5 microl d(5)-methamphetamine (50 micrig/ml) as an internal standard, and 0.5 ml sodium hydroxide (1 M) were placed into a 12 ml vial, and sealed rapidly with a silicone septum and an aluminum cap. Immediately after the vial was heated to 70 degrees C in an aluminium block heater, the needle of the SPME device was inserted through the septum of the vial, and the extraction fiber was exposed in the headspace for 15 min. First, heptafluorobutyric anhydride was injected into the injection port of the GC-MS, and the compounds extracted by the fiber were then desorbed and derivatized simultaneously by exposing the fiber in the injection port. The calibration curves, using an internal standard method, demonstrated good linearity throughout the concentration range from 0.01 to 1.0 microg/g. The detection limits of this method were 5.0 ng/g for fenfluramine and methamphetamine, and 10 ng/g for amphetamine. No interferences were found, and the time for analysis was about 30 min for one sample. This method was applied to a suicide case in which the victim ingested fenfluramine. Fenfluramine was detected in the blood sample collected from the victim at the concentration of 7.7 microg/g.

Adult↗

PubMed2000

Activin receptor-like kinase 1 modulates transforming growth factor-beta 1 signaling in the regulation of angiogenesis.

The activin receptor-like kinase 1 (ALK1) is a type I receptor for transforming growth factor-beta (TGF-beta) family proteins. Expression of ALK1 in blood vessels and mutations of the ALK1 gene in human type II hereditary hemorrhagic telangiectasia patients suggest that ALK1 may have an important role during vascular development. To define the function of ALK1 during development, we inactivated the ALK1 gene in mice by gene targeting. The ALK1 homozygous embryos die at midgestation, exhibiting severe vascular abnormalities characterized by excessive fusion of capillary plexes into cavernous vessels and hyperdilation of large vessels. These vascular defects are associated with enhanced expression of angiogenic factors and proteases and are characterized by deficient differentiation and recruitment of vascular smooth muscle cells. The blood vessel defects in ALK1-deficient mice are reminiscent of mice lacking TGF-beta1, TGF-beta type II receptor (TbetaR-II), or endoglin, suggesting that ALK1 may mediate TGF-beta1 signal in endothelial cells. Consistent with this hypothesis, we demonstrate that ALK1 in endothelial cells binds to TGF-beta1 and TbetaR-II. Furthermore, the ALK1 signaling pathway can inhibit TGF-beta1-dependent transcriptional activation mediated by the known TGF-beta1 type I receptor, ALK5. Taken together, our results suggest that the balance between the ALK1 and ALK5 signaling pathways in endothelial cells plays a crucial role in determining vascular endothelial properties during angiogenesis.

Activin Receptors↗

PubMed2000

Direct colorimetric method for determination of organophosphates in human urine.

A simple and sensitive method for determination of organophosphorus pesticides in human urine was developed by detecting the color complexes which resulted from reactions of organophosphorus pesticides and 4-(4-nitrobenzyl)pyridine (NBP) in urine. Based on studies of reaction conditions, e.g. reaction temperature and time, and reagent concentration, a colorimetric method was established. A 0.1-ml volume of NBP (45% in acetone) was added to a 1.0-ml volume of a urine sample, and the mixture was heated at 100 degrees C for 20 min. After cooling, 0.1 ml of tetraethylenepentamine was added. The organophosphorus pesticides showed a characteristic purplish blue color and the coloring complexes which were produced were stable for several hours. Furthermore, these complexes could be determined spectrophotometrically. The detection limits were 0.10-10 microg/ml in urine. The required time for analysis was approximately 30 min for one sample. Comparing the result of the proposed method with those of the GC-MS method, the results were similar for the 12 poisoning cases studied. Thus, the proposed method is useful for detection of these pesticides in critical care practices.

Chelating Agents↗

PubMed2000

Visuoperceptual impairment in dementia with Lewy bodies.

BACKGROUND: In dementia with Lewy bodies (DLB), vision-related cognitive and behavioral symptoms are common, and involvement of the occipital visual cortices has been demonstrated in functional neuroimaging studies. OBJECTIVES: To delineate visuoperceptual disturbance in patients with DLB in comparison with that in patients with Alzheimer disease and to explore the relationship between visuoperceptual disturbance and the vision-related cognitive and behavioral symptoms. DESIGN: Case-control study. SETTING: Research-oriented hospital. PATIENTS: Twenty-four patients with probable DLB (based on criteria of the Consortium on DLB International Workshop) and 48 patients with probable Alzheimer disease (based on criteria of the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association) who were matched to those with DLB 2:1 by age, sex, education, and Mini-Mental State Examination score. MAIN OUTCOME MEASURES: Four test items to examine visuoperceptual functions, including the object size discrimination, form discrimination, overlapping figure identification, and visual counting tasks. RESULTS: Compared with patients with probable Alzheimer disease, patients with probable DLB scored significantly lower on all the visuoperceptive tasks (P<.04 to P<.001). In the DLB group, patients with visual hallucinations (n = 18) scored significantly lower on the overlapping figure identification (P = .01) than those without them (n = 6), and patients with television misidentifications (n = 5) scored significantly lower on the size discrimination (P<.001), form discrimination (P = .01), and visual counting (P = .007) than those without them (n = 19). CONCLUSIONS: Visual perception is defective in probable DLB. The defective visual perception plays a role in development of visual hallucinations, delusional misidentifications, visual agnosias, and visuoconstructive disability charcteristic of DLB.

Aged↗

PubMed2000

Comparison of pathogenic properties between two types of arginine-specific cysteine proteinases (gingipains-R) from Porphyromonas gingivalis.

Two major arginine-specific cysteine proteinases (gingipains R) from Porphyromonas gingivalis have been compared with regard to their potential participation in the pathology of periodontal disease. Both the high and low molecular mass forms, HRgpA and RgpB, cleaved oligopeptide fluorogenic substrates at the P1-arginine residue with essentially identical specificity but different efficiencies, with HRgpA being about 1.5 to seven-fold less potent than RgpB. In contrast HRgpA, which occurs as a non-covalent complex of catalytic and hemagglutinin/adhesion domains, was about two-fold more active than RgpB in degrading fibrinogen and fibrin, while both enzymes activated prekallikrein with similar efficiency. These data indicate the likelihood that both activities could be involved in both the bleeding tendency and production of gingival crevicular fluid, which occur at infected periodontitis sites. Significantly, however, is the fact that HRgpA, but not RgpB, was able to bind phospholipids in the presence of calcium ions, the effect dramatically enhancing the activation of clotting factors by this proteinase. This suggests that HRgpA may play a more important role in the virulence of Porphyromonas gingivalis, relative to RgpB, almost certainly because of the presence of the hemagglutinin/adhesion domain which can bind phospholipid and apparently modulate enzyme activity.

Adhesins, Bacterial↗

PubMed2000

Characterization of two cDNA clones encoding isozymes of the F(1)F(0)-ATPase inhibitor protein of rice mitochondria.

Two cDNA clones encoding F(1)F(0)-ATPase inhibitor proteins, which are loosely associated with the F(1) part of the mitochondrial F(1)F(0)-ATPase, were characterized from rice (Oryza sativa L. cv. Nipponbare). A Northern hybridization showed that the two genes (designated as IF(1)-1 and IF(1)-2) are transcribed in all the organs examined. However, the steady-state mRNA levels varied among organs. A comparison of the deduced amino acid sequences of the two IF(1) genes and the amino acid sequence of the mature IF(1) protein from potato revealed that IF(1)-1 and IF(1)-2 have N-terminal extensions with features that are characteristic of a mitochondrial targeting signal. To determine the subcellular localization of the gene products, the IF(1)-1 or IF(1)-2 proteins were fused in frame to the green fluorescent protein (GFP) or the fused GFP-beta-glucuronidase, and expressed transiently in onion or dayflower epidermal cells. Localized fluorescence was detected in mitochondria, confirming that the two IF(1) proteins are targeted to mitochondria.

Amino Acid Sequence↗

PubMed2000

Disturbances of spatial vision and object vision correlate differently with regional cerebral glucose metabolism in Alzheimer's disease.

There is evidence of two neuronal systems for visual cognition which are referred to as spatial vision and object vision. We subjected 49 patients with mild-to-moderate probable Alzheimer's disease (AD) to tasks associated with these two types of visual cognition. Visual counting was employed as a task to assess visuospatial recognition. Identification of overlapping figures and discrimination of visual forms were used as visuoperceptual tasks that require an ability to recognize objects. Regional cerebral glucose metabolism (rCMRglc) of the subjects was also determined by positron emission tomography. Multivariate statistics controlling for the confounding factors assessed the correlation between the task performances and the rCMRglc. The visual counting score significantly correlated with the metabolic rate of the bilateral inferior parietal lobules. On the other hand, the scores of the visuoperceptual tasks significantly correlated with the metabolic rate of the right middle temporal gyrus and the right inferior parietal lobule. The present study showed that visuospatial disturbance was related to bilateral parietal metabolism, and that visuoperceptual disturbance was related to right temporo-parietal metabolism in patients with mild-to-moderate AD.

Aged↗

PubMed2000

Expression of heat shock proteins in osteosarcoma and its relationship to prognosis.

The prognosis of osteosarcoma has been improved by chemotherapy. Heat shock proteins (HSPs) assist in folding proteins at posttranslation and degeneration under stress. We investigated the effect of HSPs on survival in osteosarcoma. Conventional osteosarcomas of the extremities from 70 patients aged 30 years or younger were used. Preoperational chemotherapy was performed in all cases. Tissues at surgery and biopsy were immunohistochemically stained with anti-HSP27, HSP47, HSP60, HSP70, HSP90alpha, HSP90beta, and p53 antibodies. We classified the cases in which more than 10% of tumor cells were positive into the overexpressing group. Overall survival was compared between the groups either overexpressing HSPs or not using Wilcoxon's test and Cox's proportional hazard model. The overexpression rate at biopsy was 22% (HSP27), 88% (HSP47), 66% (HSP60), 48% (HSP70(, 47% (HSP90alpha), 31% (HSP90beta), and 17% (p53), respectively. The rate at surgery was 33% (HSP27), 94% (HSP47), 60% (HSP60), 49% (HSP70), 28% (HSP90alpha), 40% (HSP90beta), and 17% (p53), respectively. HSP27 and p53 overexpression at biopsy had a negative prognostic value. HSP27 showed the strongest negative prognostic value in osteosarcoma. It is therefore important to investigate further its function in cellular regulation and drug resistance.

Bone Neoplasms↗

PubMed2000

Traumatic avulsion fracture of the occipital condyles and clivus: a case report.

A 25-year-old male was found dead on a river bank. Wounds and injuries were found on the corpse, and a bloodstain was found on the face from blood discharged from the oral and nasal cavities. Since the man was considered the victim of a traffic accident, a forensic autopsy was carried out. At the time of autopsy, severe bruises and wounds were found on the occiput, the nape and the dorsal side of the lower extremities. There was a fracture line in the bilateral occipital condyles through the lower part of the clivus and the head was unstable in relation to the neck. The medulla oblongata was severed near the fracture site and the basilar artery was also torn at the branching end of the posterior cerebral arteries. The fracture of the occipital condyles and clivus was considered to be avulsed due to hyperflexion of the neck joint by a blunt impact onto the occiput. Anterior traction of the skull following the fracture was supposed to have accompanied the injuries of the medulla oblongata and the basilar artery. In this autopsy case, the authors observed an unusual type of fracture in the posterior cranial fossa.

Journal Article↗

PubMed2000

Sensitive determination of pentazocine in human tissues by high-performance liquid chromatography.

The authors developed a simple, reliable and sensitive method for the determination of pentazocine in human solid tissues using high-performance liquid chromatography, combined with a three-step liquid-liquid extraction procedure. Levallorphan tartrate served as the internal standard. The extract was evaporated to dryness and dissolved in the mobile phase of acetonitrile/10 mM phosphate buffer (pH 4.0). The eluent was pumped at a flow rate of 0.4 ml/min through a Spherisorb Ph (2.1 mm I.D. x 150 mm) column. A fluorescence detector with excitation at 247 nm and emission at 320 nm was used. The lower limit of detection was about 0.5 ng/g. The calibration curve was linear over the concentration ranges from 1 to 500 ng/g in each tissue examined and could be determined up to at least 10.0 microg/g by means of reduction of injected volumes. Using this method, the concentrations of pentazocine could be determined in the tissues of an autopsied individual for toxicological evaluation.

Journal Article↗

PubMed2000

Tolerance mechanism of the ethanol-tolerant mutant of sake yeast.

Several ethanol-tolerant mutants have been bred from industrial sake yeasts, but the mechanism of ethanol tolerance in these mutants has not been elucidated. After the determination of the entire genome sequence of Saccharomyces cerevisiae, various methods to monitor the whole-gene expression of the yeast have been developed. In this study, we used a commercially available nylon membrane on which virtually every gene of S. cerevisiae was spotted to compare expression profiles between the ethanol-tolerant mutant and its parent sake yeast to investigate the mechanism of ethanol tolerance in this mutant. As a result, we found that several genes were highly expressed only in the ethanol-tolerant mutant but not in the parent strain. These genes were known to be induced in cells that were exposed to various stresses, such as ethanol, heat, and high osmolarity, or at the stationary-phase but not at the log-phase. In the ethanol-tolerant mutant, the expression level of these stress-responsive genes was further increased after exposure to ethanol. We also found that substances such as catalase, glycerol and trehalose that may have protective roles under stressful conditions were accumulated in high amounts in the ethanol-tolerant mutant. The ethanol-tolerant mutant also exhibited resistance to other stresses including heat, high osmolarity and oxidative stress in addition to ethanol tolerance. These results indicate that the mutant exhibits multiple stress tolerance because of elevated expression of stress-responsive genes, resulting in accumulation of stress protective substances.

Journal Article↗

PubMed2000

Engineering of an FGF-proteoglycan fusion protein with heparin-independent, mitogenic activity.

In the absence of heparan sulfate (HS) on the surface of target cells, or free heparin (HP) in the vicinity of their receptors, fibroblast growth factor (FGF) family members cannot exert their biological activity and are easily damaged by proteolysis. This limits the utility of FGFs in a variety of applications including treatment of surgical, burn, and periodontal tissue wounds, gastric ulcers, segmental bony defects, ligament and spinal cord injury. Here we describe an FGF analog engineered to overcome this limitation by fusing FGF-1 with HS proteoglycan (PG) core protein. The fusion protein (PG-FGF-1), which was expressed in Chinese hamster ovary cells and collected from the conditioned medium, possessed both HS and chondroitin sulfate sugar chains. After fractionation, intact PG-FGF-1 proteins with little affinity to immobilized HP and high-level HS modification, but not their heparitinase or heparinase digests, exerted mitogenic activity independent of exogenous HP toward HS-free Ba/F3 transfectants expressing FGF receptor. Although PG-FGF-1 was resistant to tryptic digestion, its physiological degradation with a combination of heparitinase and trypsin augmented its mitogenic activity toward human endothelial cells. The same treatment abolished the activity of simple FGF-1 protein. By constructing a biologically active proteoglycan-FGF-1 fusion protein, we have demonstrated an approach that may prove effective for engineering not only FGF family members, but other HP-binding molecules as well.

Amino Acid Sequence↗

PubMed2000

Increased sensitivity to the stimulant effects of morphine conferred by anti-adhesive glycoprotein SPARC in amygdala.

Repeated administration of morphine substantially increases its locomotor-enhancing activity, a phenomenon termed locomotor sensitization. Here we show that secreted protein acidic and rich in cysteine (SPARC), an anti-adhesive glycoprotein present in the basolateral amygdala, contributes to the establishment of locomotor sensitization. The morphine-induced increase in SPARC levels in the basolateral amygdala persisted after morphine withdrawal and coincided with the duration of locomotor sensitization. Moreover, a single injection of morphine after SPARC infusion into the basolateral amygdala of previously uninjected mice substantially enhanced locomotor activity. Thus, SPARC may be an important element for establishing locomotor sensitization to morphine.

Amygdala↗

PubMed2000

Effects of intravenous immunoglobulin in a patient with intermittent thrombotic thrombocytopenic purpura.

We describe a patient with a 9-year history of thrombotic thrombocytopenic purpura (TTP) who exhibited four relapses. Intravenous immunoglobulin (IVIg) was effective for these four episodes. The patient was well and the laboratory findings were within normal ranges between each episode, although unusually large von Willebrand factor multimers were observed during remission. Our results suggest the usefulness of IVIg at the time of relapse in the treatment of patients with TTP who have multiple relapses over a long period.

Electrophoresis, Agar Gel↗

PubMed2000

Fall-related injuries in dementia with Lewy bodies (DLB) and Alzheimer's disease.

Repeated falls are reported as one of the clinical characteristics in dementia with Lewy bodies (DLB). We examined the incidence of fall-related injuries in 561 dementia patients with various clinical diagnoses, including DLB and Alzheimer's disease (AD), in a ward established for dementia research. The incidence of fall-related injuries was significantly higher in DLB patients (10.7%) than in AD patients (1.1%) (P < 0.001). The high incidence in those patients with DLB cannot be attributed to Parkinsonism because none of the DLB patients with injuries showed extrapyramidal sign. Our observations suggest that patients with a clinical diagnosis of DLB have a high risk of fall-related injuries, even though they do not show Parkinsonism. An appropriate clinical discrimination between DLB and AD is recommended to manage and prevent fall-related injuries.

Accidental Falls↗

PubMed2000

Dual-mode regulation of hair growth cycle by two Fgf-5 gene products.

As the result of alternative mRNA splicing, Fgf-5, the gene encoding fibroblast growth factor-5, translates to both long and short forms of the protein, respectively, designated fibroblast growth factor-5 and fibroblast growth factor-5S. We previously showed that localization of fibroblast growth factor-5 and the level of fibroblast growth factor-5S in murine skin are hair-cycle dependent. In this study, we examined the effect of fibroblast growth factor-5 and fibroblast growth factor-5S on the hair growth cycle in mice. Once the anagen phase of the hair growth cycle was induced in the dorsal skin by depilation during telogen, and effects of subcutaneous injection of fibroblast growth factor-5 and fibroblast growth factor-5S into the affected region were analyzed. We found that fibroblast growth factor-5 inhibited hair growth during anagen and promoted the transition from anagen to catagen. Interestingly, whereas fibroblast growth factor-5S alone exerted no effect on hair growth, it significantly inhibited the catagen-promoting activity of fibroblast growth factor-5 when the two proteins were injected simultaneously. Because neither fibroblast growth factor-5 nor fibroblast growth factor-5S affected skin thickness, it is postulated that changes in skin thickness during hair cycle are separately regulated by factors other than those regulating hair and follicle growth. The present results, together with our earlier findings that fibroblast growth factor-5-producing cells gather around dermal papillae during catagen, whereas fibroblast growth factor-5S is abundantly expressed in the hair follicles only during the latter half of anagen, suggests that the mouse hair growth cycle is regulated by the two Fgf-5 gene products acting in concert: fibroblast growth factor-5 induces catagen, whereas fibroblast growth factor-5S antagonizes this activity during anagen.

Animals↗

PubMed2000

Pancreatoblastoma treated by delayed operation after effective chemotherapy.

A case of pancreatoblastoma in a 4-year-old girl is presented. She was admitted with an abdominal mass and vomiting in August 1994. Computed tomography scan showed a 10- x 8- x 7-cm mass occupying both the head and body of the pancreas. Serum alpha-fetoprotein (AFP) level was 9,600 ng/mL (normal, <8.3 ng/mL). Results of open biopsy of the tumor showed pancreatoblastoma. Chemotherapy was administered using the new A-1 regimen consisting of cyclophosphamide, etoposide, pirarubicin, and cisplatin. After 3 cycles of chemotherapy, the size of the tumor was reduced to 5 x 4 x 3 cm, the portal vein became patent, and the AFP value decreased to 98.1 ng/mL. Total removal of the tumor was performed leaving the head and tail of the pancreas. Postoperative chemotherapy continued for 2 years. The patient has been disease free for 5 years, and her serum AFP remained within normal levels.

Antineoplastic Combined Chemotherapy Protocols↗