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Biomedical subjects

Seiji Kawamura

Publications and source records attributed to Seiji Kawamura.

At least 19 recordsLinked to original sources
PubMed2006

[Development of automatic analyses for star-shot images using computed radiography (CR)].

Recent progress in radiation therapy has been greatly enhanced in many facilities by the development of new machines for treatment, improved computer technology for radiotherapy treatment planning systems (RTPs), increased accuracy of radiation therapy such as stereotactic irradiation, and intensity-modulated radiation therapy (IMRT). Quality control (QC) of the isocenter, which has consisted of gantry rotation and limiting the radiation field, is important for greater accuracy of these radiation therapy technologies. Star-shot analyses using computed radiography (CR) for evaluation of the isocenter were employed in this study. Devices to support CR were created, and a method of automatically analyzing images obtained by the star-shot technique, which calculated the error (distance) from the isocenter and the incident beam angle, were developed. In terms of the accuracy of our method, the average maximum error was 0.33 mm (less than 2 pixels: 0.35 mm), the average absolute error and incident beam angle errors were 0.3 mm and 0.4 degrees at maximum and at one standard deviation (SD), respectively. In this study, the processing times were 16 sec at minimum, 152 sec at maximum, 18 sec at most frequencies, and 23.6 sec on average. In conclusion, it was considered that our newly developed method for analyzing star-shot images using CR enabled immediate, quantitative evaluation of the isocenter.

Algorithms↗
PubMed2006

Interferometers for displacement-noise-free gravitational-wave detection.

We propose a class of displacement- and laser-noise-free gravitational-wave-interferometer configurations, which does not sense nongeodesic mirror motion and laser noise, but provides a nonvanishing gravitational-wave signal. Our interferometers consist of four mirrors and two beam splitters, which form four Mach-Zehnder interferometers. By contrast to previous works, no composite mirrors with multiple reflective surfaces are required. Each mirror in our configuration is sensed redundantly, by at least two pairs of incident and reflected beams. Displacement- and laser-noise-free detection is achieved when output signals from these four interferometers are combined appropriately. Our 3-dimensional interferometer configuration has a low-frequency response proportional to f2, which is better than the f3 achievable by previous 2-dimensional configurations.

Journal Article↗
PubMed2006

Displacement- and timing-noise-free gravitational-wave detection.

Motivated by a recently invented scheme of displacement-noise-free gravitational-wave detection, we demonstrate the existence of gravitational-wave detection schemes insusceptible to both displacement and timing (laser) noises and are thus realizable by shot-noise-limited laser interferometry. This is possible due to two reasons: first, gravitational waves and displacement disturbances contribute to light propagation times in different manners; second, for an N-detector system, the number of signal channels is of the order Omicron(N(2)), while the total number of timing- and displacement-noise channels is of the order Omicron(N).

Journal Article↗
PubMed2005

[Research on time-course differential imaging by bone scintigraphy].

The temporal image subtraction technique was applied to bone scintigraphy, using Photoshop (commercially available image processing software) and Morpher (public domain warping software). For the temporal subtraction images, 81 subtraction images (19 cases) were prepared by a method used to subtract the previous images from the current ones. Registration of the current and previous images was performed by manual operation using Photoshop, and warping was done using the warping function of Morpher. In addition, difference images prepared after correcting the distributions of radioactive isotopes of the current and previous images using the count of the pelvic region were also examined. Compared with manual operation, alignment of images by warping improved registration and reduced the generation of pseudo-images of subtraction images. The rate of identification of abnormal accumulation-enhanced regions and subjective evaluation by doctors was improved for warping more than for manual operation. Furthermore, abnormal hot regions, which are difficult to find in film images, could be found in three subtraction images. In addition, it was confirmed that abnormal hot regions become more visible in many cases by preparing subtraction images after correcting the count between images using the count of the pelvic region. Thus, it is suggested that the temporal image subtraction technique in bone scintigraphy enables more accurate observation of enhancement of or changes in abnormal hot regions, which will support diagnostic reading. It is considered that enhancement of or changes in abnormal hot regions will be more accurately understood through further detailed discussion in the future.

Bone and Bones↗
PubMed2005

Power-recycled resonant sideband extraction interferometer with polarization detection.

Second-generation interferometric gravitational-wave detectors will use a technique called resonant sideband extraction (RSE) to improve the sensitivity in a narrow, tunable, frequency band. We present a configuration in which we use polarization detection to allow a continuously tunable power-recycled RSE interferometer for a control scheme similar to those of the first-generation detectors. A mathematical model describing this configuration and the results from a tabletop prototype are presented that demonstrate this configuration.

Journal Article↗
PubMed2005

Development of a frequency-detuned interferometer as a prototype experiment for next-generation gravitational-wave detectors.

We report on our prototype experiment that uses a 4-m detuned resonant sideband extraction interferometer with suspended mirrors, which has almost the same configuration as the next-generation, gravitational-wave detectors. We have developed a new control scheme and have succeeded in the operation of such an interferometer with suspended mirrors for the first time ever as far as we know. We believe that this is the first such instrument that can see the radiation pressure signal enhancement, which can improve the sensitivity of next-generation gravitational-wave detectors.

Journal Article↗
PubMed2005

No regional differences of cytochrome P450 expression in the liver of Cynomolgus monkeys (Macaca fascicularis).

Non-human primates are frequently used in toxicological studies the result of which are extrapolated to humans, but background data on drug metabolism ability among monkeys derived from different countries has not been published, especially on the key enzyme, cytochrome P450 (CYP450). We assessed the amounts of hepatic CYP450 obtained from cynomolgus monkeys of different ages and from different countries in this study. There were no regional differences of total P450 content, as well as major CYP450 isozymes (CYP 1A, 2A, 2B, 2C, 2D, 2E1 and 3A4) in cynomolgus monkeys by westernblot analysis. Similarly, there were no significant differences with hybrid cynomolgus monkeys, but variations in individual values were large. As for aging, total P450 contents declined in old cynomolgus monkeys (12-32 years of age). These results indicate the usefulness of basic data of hepatic CYP450 obtained from cynomolgus monkeys of different ages and from different countries.

Aging↗
PubMed2004

Displacement-noise-free gravitational-wave detection.

We present a new idea that allows us to detect gravitational waves without being disturbed by any kind of displacement noise, based on the fact that gravitational waves and test-mass motions affect the propagations of light differently. We demonstrate this idea by analyzing a simple toy model consisting of three equally-separated objects on a line. By taking a certain combination of light travel times between these objects, we construct an observable free from the displacement of each object, which has a reasonable sensitivity to gravitational waves.

Journal Article↗
PubMed2004

[Estimation of daily intake of phenols in hospital meal samples].

Daily intakes of 12 phenols which are possible endocrine disruptors were estimated in hospital meals from 2000 to 2001. 4-Nonylphenol (4-NP (mix)) and bisphenol A (BPA) were detected at levels of 5.0 to 19.4 ng/g and 0.2 to 1.1 ng/g, respectively. 4-tert-Butylphenol, 4-n-pentylphenol, 4 -tert-pentylphenol, 4-n-hexylphenol, 4-n-heptylphenol and 4-tert-octylphenol were detected at levels of 0.1 to 2.4 microg/g. The daily intakes of 4-NP (mix) and BPA were 5.8 microg/day and 0.42 microg/day, respectively. The daily intakes of other phenols were less than 1 microg/day.

Environmental Pollutants↗
PubMed2004

[Investigation of pesticide residues in foods distributed in Kitakyushu City].

We investigated 160 kinds of pesticide residues in 715 samples of 116 kinds of foods distributed in Kitakyushu city. Sixty kinds of pesticides were detected in 55 kinds of foods (204 samples) in the range of 0.002-22 mg/kg. Five kinds of pesticides in 7 samples violated the residue standards and the indication of "unused". The detection ratios of unregulated pesticide in domestic and imported foods were 27.8 and 33.0%, respectively. Iprodione, dicofol, diethofencarb, procymidone and chlorfenapyr (for domestic food) and total bromine, benomyl, chlorpyrifos, dicofol, fenvalerate, cypermethrin and dimethoate (for imported food) showed relatively high detection ratios. Chinese cabbage, garland chrysanthemum, tomatoes and green teas (domestic) and broccoli, bananas, grapefruit, lemons, oranges, frozen edamame and frozen kidney beans (imported) showed high relative pesticide detection ratios. Residual pesticides were detected with relatively high frequency in imported fruits, imported frozen foods and imported processed foods.

Chromatography, Gel↗
PubMed2003

Technetium-99 m sestamibi imaging in patients with subacute thyroiditis.

To determine if subacute thyroiditis (SAT) is associated with changes in the regional perfusion of the thyroid gland, we performed Tc-99 m sestamibi scans on eleven patients with SAT who had painful goiter and clinical thyrotoxicosis. Eleven patients had Tc-99 m pertechnetate and Tc-99 m sestamibi scintigraphy during the acute stage of SAT. The thyroid uptake ratio of sestamibi was compared with the laboratory data and color Doppler ultrasonography. Tc-99 m pertechnetate scintigraphy in the thyroid was markedly reduced during the acute stage of SAT. Conversely, Tc-99 m sestamibi showed diffuse increased uptake in the thyroid region, suggesting increased perfusion. On the other hand, there was near absence of vascularization in the acute phase and slight increase in the recovery phase by color Doppler ultrasonography. The clearance rate of Tc-99 m sestamibi during the early phase (from 10 min to 1 h) was decreased in the acute stage of SAT. The sestamibi uptake ratio correlated with serum immunosuppressive acidic protein (IAP) in the acute stage of SAT and the sestamibi uptake ratio in the recovery stage of SAT was correlated with serum thyrotropin levels. Tc-99 m sestamibi uptake in the early phase in the acute stage of SAT may reflect the inflammatory process associated with SAT.

Adult↗
PubMed2003

D-galactosamine induced hepatocyte apoptosis is inhibited in vivo and in cell culture by a calcium calmodulin antagonist, chlorpromazine, and a calcium channel blocker, verapamil.

Studies were conducted in C57BL/6N Crj male mice and in cultured hepatocytes to clarify the relationship between galactosamine (GaIN) induced apoptosis and [Ca2+]i kinetics. Chlorpromazine (CPZ), a Ca(2+)-calmodulin antagonist, and verapamil (VR), a Ca(2+)-channel blocker each inhibited GaIN-induced DNA fragmentation and the appearance of apoptotic bodies. The kinetics of calcium uptake were evaluated using a calcium analyzer with the acetoxymethyl ester of fura-PE3 (fura-PE3/AM, 2.5 microM) as the calcium reporter. An increase in [Ca2+]i was detected in the cultured hepatocytes within 3 hours after treatment with 20 mM GaIN; this increase was inhibited by pretreatment with either 20 microM CPZ or 30 microM VR. Ca2+ imaging by confocal laser scanning microscopy showed that increase in [Ca2+]i after treatment with GaIN was initially localized around nuclei, while [Ca2+]i signals were later diffuse and observed throughout the cytoplasm. The activities of lactate dehydrogenase (LDH) and serum glutamate-pyruvate transaminase (sGPT), used as indicators of plasma membrane damage and leakage, however, were not reduced by pretreatment with CPZ or VR. From these findings, we infer that the DNA fragmentation in GaIN-induced hepatocyte apoptosis is associated with an elevation in the perinuclear concentration of Ca2+, but GaIN-induced necrotic cell death is triggered through pathway(s) that are insensitive to blockage of Ca2+ influx and therefore appear to occur independently of elevation in [Ca2+]i. These results help to clarify the role of calcium flux in hepatocyte apoptosis and necrosis induced by exposure to hepatotoxins in vivo and in vitro.

Animals↗
PubMed2003

Differences between BALB/c and C57BL/6 mice in mouse hepatitis virus replication in primary hepatocyte culture.

We previously showed that an intraperitoneal infection with mouse hepatitis virus (MHV) resulted in acute hepatic failure accompanying extremely elevated viral growth in the liver in interferon-gamma-deficient BALB/c (BALB-GKO), but not C57BL/6 (B6-GKO) mice. To examine the basis of the strain difference against MHV infection in interferon-gamma-deficient mice, viral replication in primary hepatocyte cultures from BALB/c and B6 mice with or without the IFN-gamma gene was compared in vitro. The MHV replication in BALB/c hepatocytes with or without the IFN-gamma gene was significantly higher than that in B6 hepatocytes with or without the IFN-gamma gene, suggesting that there is a strain difference in MHV replication in hepatocytes. Since a significant difference in MHV replication in hepatocytes was not observed between wild type and IFN-gamma-deficient mice of the same genetic background, the phenomenon is thought to be independent of IFN-gamma. However, pretreatment of hepatocytes with recombinant mouse interferon-gamma inhibited MHV replication in a dose-dependent fashion. The results are discussed with respect to the pathology of MHV infection in mice with or without the IFN-gamma gene.

Animals↗
PubMed2002

Cryopreservation and primary culture of cerebral neurons from cynomolgus monkeys (Macaca fascicularis).

We established the procedures for cryopreservation and primary culture of fetal cerebral neurons of cynomolgus monkeys (Macaca fascicularis). Three developmental stages of fetuses (80, 93, and 102 days of gestation) were compared to determine the optimal stage of cerebrum development for primary culture. Among the three fetuses, the 80-day-old fetus produced the most process-rich neurons with the highest survival. The number of total recovery cells from the cryopreserved 80-day-old fetus corresponded to 83.4% of that from fresh tissue. Besides, synchronous oscillations of intracellular calcium were first seen in primate cerebral neurons, which suggested the formation of synapse-networks. Cultured neurons expressed synaptophysin protein. Successful cryopreservation and subsequent cell culture of primate neurons would be useful tools for neuroscience research with species specificity.

Animals↗