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Hideki Kato

Publications and source records attributed to Hideki Kato.

32 records · Page 2Linked to original sources
PubMed2004

[Method of calculating side scatter factor for diagnostic X-rays].

When computing the amount of leakage from a diagnostic X-ray room, the amount of scattered radiation released from the irradiated body in the lateral direction must be evaluated correctly. The side-scatter factor varies owing to change in the area and/or shape of the field, but the amount of variation is not always linearly proportional to the area of the field. Because the X-ray spectrum depends on the total filtration of the X-ray tube even if the irradiation geometry, X-ray equipment, and tube potential are the same, the side-scatter factor, too, is subject to change. In this paper, we propose a new method of calculation that uses the differential side-scatter factor computed by means of a Monte Carlo simulation, for obtaining the side-scatter factor of diagnostic X-rays. This method, which can calculate the side-scatter factor under any conditions of irradiation, is useful in evaluating the side-scatter factor of diagnostic X-rays.

Monte Carlo Method↗
PubMed2004

[Method of calculating percentage depth dose for diagnostic X-rays].

Data on the percentage depth-dose of diagnostic X-rays are important in evaluating patient dose from medical exposure. We developed a new method of calculating central-axis depth-dose in a homogeneous tissue phantom irradiated by diagnostic X-rays. First, primary and scattered components of percentage depth-dose for mono-energetic X-rays were calculated by means of Monte Carlo simulation, and the data were stored in data tables. Then, percentage depth-doses for individual X-rays were calculated by making use of the data tables, the photon spectrum of X-rays, and exposure conditions such as field size. This method, which can calculate depth-dose under any condition of irradiation by combining with the approximating equation of the X-ray spectrum, is useful in evaluating the percentage depth-dose of diagnostic X-rays.

Humans↗
PubMed2003

An essential role for angiotensin II type 1a receptor in pregnancy-associated hypertension with intrauterine growth retardation.

Little is known about an in vivo significance of angiotensin II Type-1 receptor (AT1) for pregnancy-associated diseases, including hypertension and intrauterine growth retardation (IUGR). We previously demonstrated that female mice carrying the human angiotensinogen gene (hAG+/+), when mated with human renin transgenic (hRN+/+) male mice, displayed hypertension in late pregnancy due to secretion of human renin from the fetal side into the maternal circulation. In the present study, to investigate a role for AT1 in pregnancy-associated hypertension, we generated a new strain of hAG+/+/mAT1a-/- mice by genetically deleting the AT1a gene from hAG+/+ mice. When mated with hRN+/+ male mice, excessive increases in human renin, angiotensin, and plasma renin activity were detected in the plasma of pregnant hAG+/+/mAT1a-/- mice as found in that of pregnant hAG+/+ mice. Surprisingly, however, blood pressure of hAG+/+/mAT1a-/- mice was not elevated in late pregnancy despite the presence of AT1b, a subtype of AT1. The maternal and fetal defects, such as cardiac and placental abnormalities, and IUGR observed in pregnant hypertensive hAG+/+ mice were not recognized in pregnant hAG+/+/mAT1a-/- mice. The limited term administration of AT1 antagonists to hypertensive hAG+/+ mice in late pregnancy dramatically improved hypertension and IUGR, showing the clinical importance of AT1a.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2003

Inhibitory effect of the small heterodimer partner on hepatocyte nuclear factor-4 mediates bile acid-induced repression of the human angiotensinogen gene.

Bile acids function as transcriptional regulators for the genes important in bile acid synthesis and cholesterol homeostasis. In this study, we identified angiotensinogen (ANG), the precursor of vasoactive octapeptide angiotensin II, as a novel target gene of bile acids. In human ANG transgenic mice, administration of cholic acid resulted in the down-regulation of human ANG gene expression in the liver. ANG gene expression in HepG2 cells was also repressed by chenodeoxycholic acid. Because the expression of small heterodimer partner (SHP) mRNA was induced by chenodeoxycholic acid in HepG2 cells, we analyzed the effects of SHP on the human ANG promoter. Promoter mutation analysis demonstrated that SHP repressed human ANG promoter activity through the element, which has been previously determined as a binding site for hepatocyte nuclear factor-4 (HNF-4). SHP repressed human ANG promoter activity only when the HNF-4 expression vector was cotransfected in HeLa cells. Furthermore, we found that SHP bound to the HNF-4 N-terminal region including the DNA-binding domain and activation function-1 and that SHP prevented HNF-4 from binding to the human ANG promoter. These results suggest that bile acids negatively regulate the human ANG gene through the inhibitory effect of SHP on HNF-4.

Angiotensinogen↗
PubMed2003

Identification, cDNA cloning and possible roles of seed-specific rice asparaginyl endopeptidase, REP-2.

We previously showed that two major cysteine endopeptidases, REP-1 and REP-2, were present in germinated rice ( Oryza sativa L.) seeds, and that REP-1 was the enzyme that digests seed storage proteins. The present study shows that REP-2 is an asparaginyl endopeptidase that acts as an activator of REP-1, and we separated it into two forms, REP-2alpha (39 kDa) and REP-2beta (40 kDa), using ion-exchange chromatography and gel filtration chromatography. Although analysis of the amino terminals revealed that 10 amino acids of both forms were identical, their isoelectric points were different. SDS-PAGE/immunoblot analysis using an antiserum raised against legumain, an asparaginyl endopeptidase from jack bean, indicated that both forms were present in maturing and germinating rice seeds, and that their amounts transiently decreased in dry seeds. Northern blot analysis indicated that REP-2 mRNA was expressed in both maturing and germinating seeds. In germinating seeds, the mRNA was detected in aleurone layers but not in shoot and root tissues. Incubation of the de-embryonated seeds in 10(-6) M gibberellic acid induced the production of large amounts of REP-1, whereas REP-2beta levels declined rapidly. Southern blot analysis showed that there is one gene for REP-2 in the genome, indicating that both REP-2 enzymes are generated from a single gene. The structure of the gene was similar to that of beta-VPE and gamma-VPE isolated from Arabidopsis thaliana.

Abscisic Acid↗
PubMed2003

Highly efficient water splitting into H2 and O2 over lanthanum-doped NaTaO3 photocatalysts with high crystallinity and surface nanostructure.

NiO-loaded NaTaO(3) doped with lanthanum showed a high photocatalytic activity for water splitting into H(2) and O(2) in a stoichiometric amount under UV irradiation. The photocatalytic activity of NiO-loaded NaTaO(3) doped with lanthanum was 9 times higher than that of nondoped NiO-loaded NaTaO(3). The maximum apparent quantum yield of the NiO/NaTaO(3):La photocatalyst was 56% at 270 nm. The factors affecting the highly efficient photocatalytic water splitting were examined by using various characterization techniques. Electron microscope observations revealed that the particle sizes of NaTaO(3):La crystals (0.1-0.7 microm) were smaller than that of the nondoped NaTaO(3) crystal (2-3 microm) and that the ordered surface nanostructure with many characteristic steps was created by the lanthanum doping. The small particle size with a high crystallinity was advantageous to an increase in the probability of the reaction of photogenerated electrons and holes with water molecules toward the recombination. Transmission electron microscope observations and extended X-ray absorption fine structure analyses indicated that NiO cocatalysts were loaded on the edge of the nanostep structure of NaTaO(3):La photocatalysts as ultrafine particles. The H(2) evolution proceeded on the ultrafine NiO particles loaded on the edge while the O(2) evolution occurred at the groove of the nanostep structure. Thus, the reaction sites for H(2) evolution were separated from those of O(2) evolution over the ordered nanostep structure. The small particle size and the ordered surface nanostep structure of the NiO/NaTaO(3):La photocatalyst powder contributed to the highly efficient water splitting into H(2) and O(2).

Journal Article↗
PubMed2003

[Effective dose transmission of diagnostic X-rays through concrete and lead shields].

When computing the amount of leakage from a diagnostic X-ray room, the transmission data of X-ray beams through the shielding material, which are used in the computation, must agree with the conditions of use of the X-ray equipment. Even if the tube potential is the same, the energy spectrum of generated X-rays depends on conditions such as high voltage rectification and total filtration, and transmission through the shielding material, too, is subject to change. In this paper, we propose a new method of calculation, which uses transmission data of mono-energetic photon beams computed by means of a Monte Carlo simulation, for obtaining effective dose transmission data through the shielding material of an X-ray beam with spectral distribution. We also present effective dose transmission data of primary X-ray beams and 90 degrees scattered X-ray beams through concrete and lead shields as determined by this method. This method, which can calculate the transmission data of X-ray beams with any spectral distribution, is useful in evaluating the leakage dose of diagnostic X-ray facilities.

Calcium Sulfate↗
PubMed2003

[Complexity evaluation of data transfer in the Z-axis direction in 4-row multislice spiral CT using fractal dimension analysis].

Image reconstruction in multislice spiral/helical computed tomography (MSCT) consists of a package of data on the arbitrary direction of the Z-axis that can be collected by active detector arrays. Thus the recombined data vary with each spiral pitch. In certain cases of spiral pitch, data compression can occur, and the spiral artifacts that are characteristic of MSCT would change. In our study, we evaluated image complications by fractal dimensions, because the geometrical patterns from a conic phantom are closely related to data transfer in the direction of the Z-axis in spiral pitches. We hoped to establish useful spiral pitches and slice collimation for clinical use in a 4-row MSCT scanner. By employing a conic phantom of 120 mm in diameter and a cone angle of 100 degrees, we measured the fractal dimension of the conic phantom image by making a binary to outline from 2.0 to 8.0 of various slice collimations. Moreover, in order to evaluate the correlation between fractal dimensions and image artifacts, we confirmed the influence of spiral pitch and reconstruction slice thickness for clinical use. We found that, when the reconstruction slice thickness was the same, the cross section of the conic phantom that was from thin-slice collimations was more similar to an actual circle than that of wide-slice collimations. The former deserved a low value and showed slight changes, and, therefore, its fractal dimensions were fixed. As a phenomenon worthy of attention, when we employed wide-slice collimations (4x5.0 mm) during peculiar low spiral pitches of 2.5 to 3.0 fractal dimensions remained low and similar to an actual circle. By these analyses of the influence of data transfer in the direction of the Z-axis, we found that spiral pitch influenced the rate of slice collimation used for data acquisition closely to the reconstruction slice thickness. Based on these findings, when slice collimations and reconstruction slice thickness should be made equal, we estimated that spiral pitches of low image artifacts in 4row MSCT ranged from 2.5 to 3.0 using fractal dimensions. We consider that a new adaptation of fractal dimension analysis is possible when it is used as an index in determining protocols.

Artifacts↗
PubMed2003

[Cytokines in MS lesion].

A variety of cytokines are involved in the pathogenesis of multiple sclerosis(MS), either in induction phase and effector phase. In order to interact with immune cells, the cells in the brain have to express MHC antigens which they do not usually express. Cytokines such as IFN gamma, IL-3 and TNF alpha induce MHC antigen expression on neural cells. IFN gamma also induces costimulatory molecule for antigen presentation and also induce IL-12, a critical cytokine in T helper cell differentiation, in microglia. Although TNF alpha is a critical cytokines in effector phase, other cytokines and chemokines have also been shown to play roles on the development of inflammatory demyelination and gliosis. In this chapter, we will review the cytokine profile of MS lesions.

Animals↗
PubMed2002

The curved DNA structure in the 5'-upstream region of the light-responsive genes: its universality, binding factor and function for cyanobacterial psbA transcription.

A unique DNA curvature, the CIT, has been found in the 5'-upstream region of the psbA2 gene, which exhibits basal, light-responsive and circadian rhythmic transcription, in a unicellular photosynthetic cyanobacterium, Microcystis aeruginosa K-81. In this study, we report the universality of curvatures found in 5'-upstream regions in the psbA family and the function of the curvature in gene expression. Intrinsic curvatures were identified within 1000 bp upstream from the psbA genes in another cyanobacterium, a red alga and in plants (monocot and dicot). Mutagenized curvatures were constructed and confirmed to have disrupted architecture by gel electrophoresis and atomic force microscopy. Relatively small amounts but light-responsive transcripts of psbA2 were observed in cyanobacterial transformants harboring the mutagenized curvature under light/dark and light/high-light conditions. This shows that the curvature is important for basal transcription. In vitro primer extension and DNA mobility shift assay revealed that factors which might bind to the region upstream from the bending center contribute to the effective basal transcription of psbA2.

5' Flanking Region↗
PubMed2002

AgInZn7S9 solid solution photocatalyst for H2 evolution from aqueous solutions under visible light irradiation.

AgInZn7S9 with a 2.3 eV band gap, which was a solid solution of AgInS2 and ZnS semiconductors, showed photocatalytic activity for H2 evolution from an aqueous solution containing sacrificial reagents SO3(2-) and S2- under visible light irradiation (lambda > 420 nm) even without a Pt cocatalyst, and loading of the Pt cocatalyst improved the photocatalytic activity.

Journal Article↗
PubMed2002

[Basic examination of in-plane spatial resolution in multi-slice CT].

In computed tomography(single-slice spiral CT, conventional CT), in-plane(x-y plane) spatial resolution is consistently identified as depending on the detector density of the in-plane(x-y plane). However, we considered that the in-plane(x-y plane) spatial resolution of multi-slice CT (MSCT) was influenced by an error in the detector's sensitivity to the Z-axis and by the frequency of use of direct row data and complementary row data when the image of spiral pitches(SP) was reconstructed. Our goal in this experiment was to analyze the relationship of the in-plane(x-y plane)spatial resolution of an asymmetric-type detector in MSCT to SP, tube current, and rotation time. By employing a tungsten wire phantom of 0.2 mm in diameter, we examined modulation transfer functions(MTF) by point-spread functions(PSF) of CT-images. Next, using the mean-square-root bandwidth theory, we analyzed the MTF of wire phantoms. The analysis of in-plane(x-y plane) spatial resolution revealed that various tube currents had no effect on the value of the mean-square-root bandwidth. However, rotation time and high spiral pitch did have an effect on mean-square-root bandwidth. Considering the results mentioned above, spiral pitch(z-axis reconstruction algorithm) had a slight effect on in-plane(x-y plane) spatial resolution of asymmetric-type detectors in MSCT. Accordingly, we proposed a new general view of VDDz(view/mm) in MSCT that considered view data density on the Z-axis according to spiral pitch(mm/rotation), rotation time(view/rotation), and slice collimation.

Tomography, Spiral Computed↗