Biomedical subjects

T Takeda

Publications and source records attributed to T Takeda.

At least 271 records · Page 15Linked to original sources

PubMed1998

Development of a two-dimensional imaging system for clinical applications of intravenous coronary angiography using intense synchrotron radiation produced by a multipole wiggler.

A two-dimensional clinical intravenous coronary angiography system, comprising a large-size view area produced by asymmetrical reflection from a silicon crystal using intense synchrotron radiation from a multipole wiggler and a two-dimensional detector with an image intensifier, has been completed. An advantage of the imaging system is that two-dimensional dynamic imaging of the cardiovascular system can be achieved due to its two-dimensional radiation field. This world-first two-dimensional system has been successfully adapted to clinical applications. Details of the imaging system are described in this paper.

Journal Article↗

PubMed1998

Medical applications with synchrotron radiation in Japan.

In Japan, various medical applications of synchrotron X-ray imaging, such as angiography, monochromatic X-ray computed tomography (CT), radiography and radiation therapy, are being developed. In particular, coronary arteriography (CAG) is quite an important clinical application of synchrotron radiation. Using a two-dimensional imaging method, the first human intravenous CAG was carried out at KEK in May 1996; however, further improvements of image quality are required in clinical practice. On the other hand, two-dimensional aortographic CAG revealed canine coronary arteries as clearly as those on selective CAG, and coronary arteries less than 0.2 mm in diameter. Among applications of synchrotron radiation to X-ray CT, phase-contrast X-ray CT and fluorescent X-ray CT are expected to be very interesting future applications of synchrotron radiation. For actual clinical applications of synchrotron radiation, a medical beamline and a laboratory are now being constructed at SPring-8 in Harima.

Journal Article↗

PubMed1998

Phase-contrast X-ray CT image of breast tumor.

Phase-contrast X-ray CT images generated by differences in refractive indices can be used to visualize the internal structures of soft tissues without contrast enhancement. In this study, imaging of human breast tumor was performed on formalin-fixed samples. Experiments were carried out at the synchrotron source of the Photon Factory, Tsukuba, Japan. The X-ray energy was adjusted to 17.7 keV. Phase-contrast X-ray CT images revealed various structures of human breast tumor as clearly as optical images.

Journal Article↗

PubMed1998

High-spatial-resolution and real-time medical imaging using a high-sensitivity HARPICON camera.

A HARPICON(TM) camera has been applied to a digital angiography system with fluorescent-screen optical-lens coupling. It uses avalanche multiplication in the photoconductive layer for high-sensitivity imaging. The limiting spatial resolutions in the 1050 scanning-line mode of the camera are about 30 and 50 micro m at input field sizes of 20 x 20 and 50 x 50 mm on the screen, respectively. For high-speed imaging, the 525 scanning-line mode at a rate of 60 images s(-1) can be selected. High-quality images of coronary arteries in dogs were obtained by intra-aortic coronary angiography and superselective coronary angiography using a single-energy X-ray above the iodine K-edge energy.

Journal Article↗

PubMed1998

Spontaneous and artificial lesions of magnocellular reticular formation of brainstem deteriorate avoidance learning in senescence-accelerated mouse SAM.

The role of the magnocellular reticular formation (MGRF) of the brainstem on learning and memory was examined in memory-deficient mice with spontaneous spongy degeneration in the brainstem (senescence-accelerated mouse, SAMP8) and control mice (accelerated-senescence resistant mouse, SAMR 1). SAMP8 showed spontaneous age-related impairment of learning and memory, as determined by passive and active avoidance responses. The deficits of learning and memory function in passive avoidance performances began at two months of age and increased with ageing. In the brains of SAMP8 at one month of age and older, spongy degeneration was mainly observed in the brainstem, while no vacuoles were evident in SAMR1 control (normal ageing mouse) brains in the age range tested (up to 12 months). The vacuolization in SAMP8 was marked in the MGRF, especially in the dorsomedial MGRF. Quantitative analysis of the vacuolization showed that the total area and number of vacuoles in the MGRF increased with age, and they were affected by the degree of deficits in learning and memory. The latency 24 h after footshock in passive avoidance tests decreased with the increase in total area and number of vacuoles in MGRF. The number of shocks in active avoidance tests increased with the increase in total number and area of vacuoles. Thus, learning and memory ability in passive and active avoidance responses deteriorated with enlargement in the vacuolated area in MGRF, and it was assumed that MGRF (especially, the dorsomedial part) possesses functions related to learning and memory. To confirm this notion, behavior and memory tests (passive avoidance and active avoidance tests, open field tests and shock sensitivity measurements) were carried out in SAMR1 mice, whose bilateral dorsomedial MGRF was destroyed electrolytically (MGRF-lesioned mice). The MGRF-lesioned mice showed no difference from sham mice in sensory threshold or open field activity; however, there was severe deterioration in passive avoidance behavior and impairment in the active avoidance performances. From the results in SAMP8 and MGRF-lesioned mice, it was confirmed that MGRF (especially the dorsomedial part) has functions related to learning and memory, and is one part in the learning and memory system of the brain. Thus, SAMP8 can serve as a model of RF-lesioned mice with impaired learning and memory functions.

Aging↗

PubMed1998

Schizophrenic psychoses and the CNTF null mutation.

Genetic susceptibility plays an important role in the development of schizophrenic psychoses, and the neural maldevelopment hypothesis is suggested by neuropathological and neuroimaging findings. We investigated the association between a null mutation in the ciliary neurotrophic factor (CNTF) gene and functional psychoses including schizophrenia and schizoaffective disorder. The frequency of mutant allele was significantly increased in patients with schizoaffective disorder, but not in those with schizophrenia in comparison with controls. The CNTF null mutation resulting in CNTF deficiency may confer potential susceptibility to schizoaffective disorder.

Adult↗

PubMed1998

Temporal structure of implicit motor imagery in visual hand-shape discrimination as revealed by MEG.

We investigated the spatio-temporal brain activity on the time scale of several milliseconds related to the mental rotation task requiring judgements of hand orientation, using a whole-cortex MEG (magnetoencephalography) system. Neuronal activity in the visual cortex was observed approximately 100-200 ms from stimulus onset, and that in inferior parietal lobe followed (after 200 ms). Both of these activities showed a contralateral dominance to visual stimulus hemifield. Premotor activity started later than the inferior parietal lobe activity, and these activities partially overlapped. Activity in primary motor and/or motosensory areas was observed in some subjects. The whole-cortex neuromagnetic measurements provided the time course of activity in the human brain associated with the implicit motor imagery: visual cortex-->inferior parietal lobe<-->premotor cortex. This process is considered to be the transformation process of retinotopic locations into a body-centered reference frame necessary for the mental rotation task.

Adult↗

PubMed1998

Increased cellular resistance to oxidative stress by expression of cyanobacterium catalase-peroxidase in animal cells.

To exploit prokaryotic antioxidant enzymes for protection of animal cells from oxidative damage, we expressed catalase-peroxidase of cyanobacterium Synechococcus PCC 7942 in 104C1 cells. The gene for this enzyme was inserted into the mammalian expression vector pRc/CMV. The stable transfectants obtained had higher specific activities of catalase and as a result became more resistant to H2O2 or paraquat than the parental cells. Subcellular fractionation and immunoblot analysis revealed that the expressed catalase-peroxidase was confined to the cytosol; this localization may be the basis for the effective protection of the transfectants from the oxidative cell damage.

Animals↗

PubMed1998

Human chorionic gonadotropin-alpha gene is transcriptionally activated by epidermal growth factor through cAMP response element in trophoblast cells.

The purpose of this study was to analyze the mechanism of transcriptional activation of human chorionic gonadotropin-alpha (hCGalpha) gene by epidermal growth factor (EGF) in trophoblast cells. We stably transfected hCGalpha promoter-chloramphenicol acetyltransferase constructs into Rcho-1 trophoblast cells and monitored the promoter activities. -290-base pair hCGalpha promoter containing a tandem repeat of cAMP response element (CRE) was activated by EGF in a dose- and time-dependent manner. Deletion analysis of hCGalpha promoter suggested an involvement of CRE in EGF-induced hCGalpha transcriptional activation. Moreover, the hCGalpha promoter, of which both CREs were mutated, did not respond to EGF. These results indicate that EGF activates the hCGalpha gene transcription through CRE. Although EGF did not alter the amount of CRE-binding protein (CREB), EGF induced CREB phosphorylation. We next examined the mechanism of CREB phosphorylation by EGF. Protein kinase C inhibitors (H7, staurosporin, and chelerythrine) inhibited EGF-induced CREB phosphorylation, whereas either mitogen-activated protein kinase kinase-1 inhibitor (PD98059) or protein kinase A inhibitor (H8) showed no effect. Furthermore, H7 and staurosporin but not H8 inhibited hCGalpha promoter activation by EGF. In conclusion, EGF promotes hCGalpha gene transcription via the CRE region probably by phosphorylating CREB mainly through the protein kinase C pathway in trophoblast cells.

Dose-Response Relationship, Drug↗

PubMed1998

Acquisition of a new type of fructose-1,6-bisphosphatase with resistance to hydrogen peroxide in cyanobacteria: molecular characterization of the enzyme from Synechocystis PCC 6803.

We have previously described that Synechococcus PCC 7942 cells contain two fructose-1,6-bisphosphatase isozymes, designated F-I and F-II the former belongs to a new type of fructose-1,6-bisphosphatase, while the latter is a typical enzyme similar to the cytosolic and chloroplastic forms from eukaryotic cells [Tamoi et al., Arch. Biochem. Biophys., 334, 1996, 27-36]. The genes of F-I and F-II were found in three species of cyanobacteria, Synechocystis PCC 6803, Anabaena 7120, and Plectonema boryanum according to the results of Southern hybridization with a probe from the S. 7942 F-I and F-II genes. In Western blotting, antibody raised against the S. 7942 F-I cross-reacted with a protein band corresponding to the F-I in each crude extract from cyanobacterial cells, whereas the antibody against F-II failed to cross-react with any protein band corresponding to the F-II. In cyanobacterial cells, only one form of F-I has been resolved by ion-exchange chromatography at same concentration of NaCl as shown in the F-I of S. 7942. The F-I from Synechocystis 6803 has been purified to electrophoretic homogeneity. The enzyme hydrolyzed both fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate. The apparent K(m) values of the enzyme for fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate were 57 +/- 2.4 and 180 +/- 6.3 microM, respectively. The enzyme activity was inhibited by AMP with a Ki value of 0.57 +/- 0.03 mM for fructose 1,6-bisphosphate and 0.35 +/- 0.02 mM for sedoheptulose 1,7-bisphosphate. The enzyme showed a molecular mass of 168 kDa which was composed of four identical subunits. The activities of FBPase and SBPase from the F-I were resistant to hydrogen peroxide up to 1 mM. The nucleotide sequence of the S. 6803 F-I gene showed an open reading frame of 1164 bp that encoded a protein of 388 amino acid residues (approx. molecular mass of 41.6 kDa). The deduced amino acid sequences had homologous sequences with the S. 7942 F-I.

Amino Acid Sequence↗

PubMed1998

RT-PCR analysis of mRNA expression of natriuretic peptide family and their receptors in rat inner ear.

To assess the possible physiological role of the atrial natriuretic peptide (ANP) family, we investigated the expression of mRNA of ANP, brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP), and their receptors in rat inner ear using the reverse transcription-polymerase chain reaction method. ANP and CNP message bands were detected in the inner ear, but the BNP message band was not. Amplification products of the expected sizes of ANP-A, ANP-B and ANP-C receptors were detected in the inner ear. These results suggest that natriuretic peptide family may influence the function of the inner ear through the ANP-A, ANP-B, and ANP-C receptors.

Animals↗

PubMed1998

Rise of cytosolic Ca2+ and activation of membrane-bound guanylyl cyclase activity in rat enterocytes by heat-stable enterotoxin of Vibrio cholerae non-01.

The cytosolic calcium level ([Ca2+]i) and the membrane-bound guanylyl cyclase activity in the isolated rat intestinal epithelial cells were investigated. Heat-stable enterotoxin of Vibrio cholerae non-01 (NAG-ST) was found to increase both the [Ca2+]i and the enzyme activity. These changes occur similarly until 5 min of incubation with NAG-ST, indicating that these changes might be involved in NAG-ST induced signal transduction in rat enterocytes.

Animals↗

PubMed1998

Neurotoxicity of intrathecal Shiga toxin 2 and protection by intrathecal injection of anti-Shiga toxin 2 antiserum in rabbits.

The initial brain lesions in rabbits given intravenous Shiga toxin 2 (Stx2) were noted at 24 h in an area around the third ventricle (Fujii et al., Infect Immun 1996, 64: 5053-60). This result implied that Stx2 is present in the cerebrospinal fluid (CSF) despite the fact that the toxin was administered intravenously. We measured Stx2 activity in CSF by using a Vero cell cytotoxicity assay at various times after an intravenous injection of Stx2. Stx2 was detected from 2 h after the injection, and its concentration in CSF remained at a high level for a further 6 h. Fifty percent lethal doses (LD 50) of Stx2 were measured in rabbits after intravenous and intrathecal Stx2 injections; The LD 50 after an intrathecal injection of Stx2 was 0. 36 microg/kg, which was 9.2-fold lower than that of an intravenous injection of Stx2 (3.4 microg/kg). Magnetic resonance images obtained after an intrathecal Stx2 injection (5 microg/kg) were compared with those obtained after an intravenous Stx2 injection (5 microg/kg). At 48 h, the cerebellar lesions had spread from the area in contact with the CSF on a T2-weighted image, which suggests that the intrathecal Stx2 may invade the cerebellum directly. We then examined whether anti-Stx2 antiserum injected intrathecally protects rabbits against brain damage. Eighty percent of the rabbits infected with Stx2 at 5 microg/kg died within 8 days from brain damage. Rabbit anti-Stx2 sera (with titres of x16 and x64 by the Ouchterlony precipitation method) were administered into the CSF space through the cisterna magna. All the rabbits ( n=10) survived when they were given an intrathecal injection of rabbit anti-Stx2 antiserum 2 h before the intravenous injection of Stx2. Our results suggest that a leakage of Stx2 into the CSF from the choroid plexus causes brain damage, and that an intrathecal injection of anti-Stx2 antiserum could be a therapy for acute encephalopathy caused by Stx2-producing Escherichia coli.

Animals↗

PubMed1998

Tc-99m diethylenetriamine pentaacetic acid (DTPA)-human serum albumin (HSA) radionuclide lymphography for detecting the location of chyluria.

The cause of chyluria cannot be easily detected by CT scan or other imaging methods, except conventional lymphography, but Tc-99m diethylenetriamine pentaacetic acid radionuclide lymphography clearly revealed the location of chyluria in the left renal pelvic area. Radionuclide lymphography is one of the choices in investigating chyluria due to its noninvasive and simple technique.

Aged↗

PubMed1998

Protection of islet allografts transplanted together with Fas ligand expressing testicular allografts.

Fas ligand (FasL) is highly expressed in testicular tissues and thought to be responsible for protection from allograft rejection by inducing apoptosis of anti-graft activated T cells. FasL-expressing islets have been shown to induce a granulocyte-mediated inflammatory reaction. We investigated whether a graft can be protected from alloimmune responses by manipulating the Fas/FasL-system. We transplanted allogeneic islets under the kidney capsule of streptozotocin-induced diabetic mice together with testicular tissue. Significant prolongation of survival of C3H islet allograft was observed in C57BL/6 (B6) recipients transplanted with C3H testicular tissue, but not in those transplanted with C3H-gld testicular tissue expressing non-functional FasL. No significant prolongation was observed in B6-lpr recipients expressing non-functional Fas. Immunohistochemical staining of C3H testicular tissue in the composite graft showed a high expression of FasL, but not that of the C3H-gld testicular tissue. In situ terminal deoxynucleotidyl transferase-mediated dUDP-biotin catalysed DNA nick-end labelling (TUNEL) staining of a composite graft of C3H islet and testicular tissue in B6 recipients demonstrated extensive apoptosis of infiltrating mononuclear cells around the graft. The protective effect of C3H testicular tissue was abrogated when anti-FasL monoclonal antibody was administered i.p. postoperatively. Our results suggest that FasL-positive testicular allografts protect composite islet allografts and indicate that manipulation of Fas/FasL mediated apoptosis is a suitable strategy for controlling rejection of islet allografts.

Animals↗

PubMed1998

Natural course of portal hemodynamics in patients with chronic liver diseases, evaluated by per-rectal portal scintigraphy with Tc-99m pertechnetate.

Portal circulation can be evaluated in a relatively noninvasive way by per-rectal portal scintigraphy. We used this method to evaluate portal hemodynamics in patients with chronic liver diseases and underlying hepatic viral infection; the patients did not need surgery or sclerotherapy, or refused it, so changes in the natural course were identified. A solution of Tc-99m pertechnetate was instilled into the rectum, and serial scintigrams were taken while radioactivity curves for the liver and heart were produced. The per-rectal portal shunt index was calculated from the curves. In a longitudinal study, 70 patients (9 with mild chronic hepatitis, 10 with moderate chronic hepatitis, 7 with severe chronic hepatitis, 22 with cirrhosis but without varices, and 22 with both cirrhosis and varices) were examined at least twice at intervals of 12-102 months (mean, 39 months). The shunt index was higher for more severe disorders, increasing in the order of mild chronic hepatitis, moderate chronic hepatitis, severe chronic hepatitis, cirrhosis without varices, and cirrhosis with varices. The mean annual changes in the mean shunt index were 1.0% in mild chronic hepatitis, 4.4% in moderate chronic hepatitis, 6.1% in severe chronic hepatitis, 10.7% in cirrhosis without varices, and 6.2% in cirrhosis and varices. Cirrhotic patients were arbitrarily divided into two groups of roughly equal size on the basis of the shunt index at the first examination. In those with a shunt index of 30% or more, the mean annual change was 4.7%. The patients with a shunt index of less than 30% had a mean annual change of 11.8%. Changes in the portal hemodynamics were not steady. The shunt index rose gradually as disease advanced from mild to moderate and to severe chronic hepatitis and cirrhosis of the liver, after which the index rose rapidly when varices developed, slowing later.

Cross-Sectional Studies↗

PubMed1998

Vector manometric study of the sphincter of Oddi in the dog: functional and morphological correlation.

The relationship between sphincter of Oddi pressure and the morphological structure of the sphincter was studied in eight dogs prepared with a duodenal cannula. Sphincter of Oddi manometry was performed in awake animals in three directions, ventral, left dorsal, and right dorsal, using a catheter with three radial side holes for recording at one level. The pressure in the ventral direction (26.6+/-1.06 mmHg) (mean+/-SEM) was significantly lower than that in the left and right dorsal directions (30.6+/-1.42 and 31.2+/-1.23 mmHg, respectively). This functional manometric difference in the three directions correlated closely with the morphological structure of the sphincter of Oddi; the sum of the thickness of the sphincter of Oddi muscle and duodenal proper muscle was greater on the dorsal than on the ventral side. To our knowledge, this is the first report of axial asymmetry in sphincter of Oddi pressure.

Analysis of Variance↗

PubMed1998

Age-related changes in cortical bone in women: metacarpal bone mass measurement study.

The mechanism of age-related cortical bone loss was investigated in 229 Japanese women, 41-94 years of age, by metacarpal bone mass measurement. While no significant correlation was found between bone width and age, a significant increase in bone marrow width, and significant decreases in cortical bone density and total bone mass were observed in association with aging (P < 0.0001). There was a significant negative correlation between total bone mass and bone marrow width (r = -0.239; P < 0.0005), and significant positive correlations between both total bone mass and cortical bone density (r = 0.539; P < 0.0001) and cortical bone width (r = 0.839; P < 0.0001). The findings suggested that age-related cortical bone loss in middle-aged and elderly women resulted from two different factors; a decrease in cortical bone density caused by progression of intracortical porosity, and a decrease in cortical bone width as a result of bone loss on the endosteal surface. The latter had a greater influence on an age-related cortical bone loss than the former.

Absorptiometry, Photon↗