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Biomedical subjects

K Hirano

Publications and source records attributed to K Hirano.

At least 235 records · Page 13Linked to original sources
PubMed1998

Phase-Contrast Tomographic Imaging Using an X-ray Interferometer.

Apparatus for phase-contrast X-ray computed tomography using a monolithic X-ray interferometer is presented with some observational results for human breast tissues. Structures characteristic of the tissues were revealed in the phase-contrast tomograms. The procedure of image analysis consists of phase retrieval from X-ray interference patterns and tomographic image reconstruction from the retrieved phase shift. Next, feasibility of phase-contrast imaging using a two-crystal X-ray interferometer was studied aiming at in vivo observation in the future. In a preliminary study, the two-crystal X-ray interferometer was capable of generating fringes of 70% visibility using synchrotron X-rays.

Journal Article↗
PubMed1998

New methods for semiconductor charge-diffusion-length measurements using synchrotron radiation.

The extension of a new theory on the X-ray energy response of semiconductor detectors is carried out to characterize the X-ray response of a multichannel semiconductor detector fabricated on one silicon wafer. Recently, these multichannel detectors have been widely utilized for position-sensitive observations in various research fields, including synchrotron radiation research and fusion-plasma investigations. This article represents the verification of the physics essentials of a proposed theory on the X-ray response of semiconductor detectors. The three-dimensional charge-diffusion effects on the adjoining detector-channel signals are experimentally demonstrated at the Photon Factory for two types of multichannel detectors. These findings are conveniently applicable for measuring diffusion lengths for industrial requirements.

Journal Article↗
PubMed1998

X-ray diffraction with a Bragg angle near pi/2 and its applications.

X-ray dynamical diffraction phenomena at a Bragg angle near pi/2 are studied. The X-ray transmissivity as well as the reflectivity from the (991) lattice plane of a silicon thin plate is observed. It agrees fairly well with the diffraction pattern calculated on the basis of the Darwin approach. The possibility is discussed whether a set of two crystal plates arranged face to face, in which the diffraction condition with a Bragg angle near pi/2 is satisfied, may be used as a very high resolution monochromator.

Journal Article↗
PubMed1998

X-ray parametric scattering by a diamond crystal.

Spontaneous X-ray parametric scattering from a diamond single crystal has been observed at the Photon Factory. The high perfection of the diamond single crystal and the small angular divergence of synchrotron radiation has enabled down-converted X-ray photon pairs to scatter into two small solid angles which satisfy the phase-matching condition. High-efficiency noise reduction was performed using avalanche photodiode detectors with good time resolution.

Journal Article↗
PubMed1998

Characterization and interpretation of the quantum efficiencies of multilayer semiconductor detectors using a new theory.

On the basis of a new theory of semiconductor X-ray detector response, a new type of multilayer semiconductor detector was designed and developed for convenient energy analyses of intense incident X-ray flux in a cumulative-current mode. Another anticipated useful property of the developed detector is a drastic improvement in high-energy X-ray response ranging over several hundred eV. The formula for the quantum efficiency of multilayer semiconductor detectors and its physical interpretations are proposed and have been successfully verified by synchrotron radiation experiments at the Photon Factory. These detectors are useful for data analyses under strong radiation-field conditions, including fusion-plasma-emitting X-rays and energetic heavy-particle beams, without the use of high-bias applications.

Journal Article↗
PubMed1998

Determination of interactions between structured nucleic acids by fluorescence resonance energy transfer (FRET): selection of target sites for functional nucleic acids.

We previously developed a method for monitoring the integrity of oligonucleotides in vitro and in vivo by quantitating fluorescence resonance energy transfer (FRET) between two different fluorochromes attached to a single oligonucleotide. As an extension of this analysis, we examined changes in the extent of FRET in the presence or absence of target nucleic acids with a specific sequence and a higher-ordered structure. In this system FRET was maximal when probes were free in solution and a decrease in FRET was evidence of successful hybridization. We used a single-stranded oligodeoxyribonucleotide labeled at its 5'-end and its 3'-end with 6-carboxyfluorescein and 6-carboxytetramethylrhodamine, respectively. Incubation of the probe with a single-stranded complementary oligonucleotide reduced the FRET. Moreover, a small change in FRET was also observed when the probe was incubated with an oligonucleotide in which the target site had been embedded in a stable hairpin structure. The decrease in the extent of FRET depended on the length of the stem region of the hairpin structure and also on the higher-ordered structure of the probe. These results indicate that this spectrofluorometric method and FRET probes can be used to estimate the efficacy of hybridization between a probe and its target site within highly ordered structures. This conclusion based on changes in FRET was confirmed by gel-shift assays.

DNA↗
PubMed1998

Ethanolamine stimulates repair processes in acute CCl4 damage of mouse liver.

Ethanolamine, a positively charged hydrophilic component of the phosphatidylethanolamine (PE) which is also a precursor of phosphatidylcholine (PC), enhances the repair processes 24 h after carbon tetrachloride (CCl4) intoxication of mouse liver. Ethanolamine quickly reduced aminotransferase activity released in the serum, increased the hepatocellular nuclear BrdU uptake, a marker of S phase, and the epidermal growth factor (EGF) receptor content in the liver injured with CCl4. Thus, exogenous administration of ethanolamine may function as a liver proliferating factor in CCl4 intoxicated mouse liver.

Alanine Transaminase↗
PubMed1998

Expression and function of alpha1-adrenoceptor subtypes in the porcine renal artery.

We investigated the expression and function of alpha1-adrenoceptor subtypes in the porcine renal artery. Reverse transcription polymerase chain reaction (RT-PCR) and nucleotide sequencing indicated that the mRNAs for alpha1a- and alpha1b-adrenoceptors were expressed in the porcine renal artery. Chloroethylclonidine, an alpha1B- and alpha1D-adrenoceptor antagonist, partially inhibited the phenylephrine-induced contraction, while 3 nM BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]dec ane-7,9-dione dihydrochloride), an alpha1D-adrenoceptor antagonist, had no effect. In contrast, 5-methylurapidil, an alpha1A-adrenoceptor antagonist, induced a rightward shift of the phenylephrine concentration-response curve. The simultaneous measurement of cytosolic Ca2+ concentration ([Ca2+]i) and tension revealed that chloroethylclonidine pretreatment abolished the phenylephrine-induced increases in [Ca2+]i and tension in the Ca2+-free solution. The application of 5-methylurapidil (3 nM) to the chloroethylclonidine-pretreated strips completely inhibited the 3 microM phenylephrine-induced [Ca2+]i and tension increase in normal PSS. We concluded that both alpha1A- and alpha1B-adrenoceptors mediate the phenylephrine-induced contraction of the porcine renal artery accompanied by an increase in [Ca2+]i, and that alpha1A-adrenoceptors cause Ca2+ influx whereas alpha1B-adrenoceptors mainly mediate Ca2+ release.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1998

Immunolocalization of anti-placental alkaline phosphatase monoclonal antibody in mice with testicular tumors and lymph node metastasis.

To evaluate the ability of an anti-placental alkaline phosphatase (PLAP) monoclonal antibody (MAb) to localize to PLAP-expressing tumors, we established a model of testicular tumor with metastasis to lymph nodes and liver in severe combined immunodeficient (SCID) mice. 131I-labeled or 125I-labeled MAb was simultaneously administered via the intravenous or lymphatic route, respectively. Preferential accumulation of MAb in PLAP-expressing tumors at primary as well as metastatic sites was demonstrated. The percentage of the injected dose of MAb found in the tumor was generally higher when MAb was administered intravenously. Identical tumor/blood ratios were found with the two routes of administration. These data suggest that intravenous administration of a radiolabeled MAb is superior to lymphatic administration for tumor imaging and radioimmunotherapy.

Alkaline Phosphatase↗
PubMed1998

Natural interferon enhances expression of placental alkaline phosphatase in human seminoma xenograft.

The purpose of this study was to investigate the effect of natural interferon (IFN) on the expression of placental alkaline phosphatase (PLAP) in a human seminoma xenograft in severe combined immunodeficient mice. Mice were injected intramuscularly with 3x10(5) U/mouse of IFN, twice a day, for five consecutive days. A significant increase in PLAP level of the xenografts followed IFN treatment. A radiolabeled anti-PLAP monoclonal antibody (MAb) was intravenously injected on the first day of IFN administration in order to determine if IFN has the potential to enhance the efficacy of an anti-PLAP MAb in the detection of seminoma. Enhanced retention of the anti-PLAP MAb was observed at 7 and 11 days after MAb administration. Thus, IFN treatment appears to have some effect on the efficacy of the anti-PLAP MAb in the detection of seminoma xenografts.

Alkaline Phosphatase↗
PubMed1998

Expression of sucrase and intestinal-type alkaline phosphatase in colorectal carcinomas in rats treated with methylazoxymethanol acetate.

In this study the small-intestine phenotype in rat colonic tumors was investigated in terms of sucrase and intestinal-type alkaline phosphatase (I-ALP) activity. F344 rats were given intraperitoneal injections of methylazoxymethanol acetate at a dose level of 25 mg/kg body weight once a week for 8 weeks and were killed 40 weeks after the first injection. Sucrase and I-ALP activities in proximal and distal colon adenocarcinomas were significantly higher than those in the normal colon epithelium. In the jejunum, by contrast, normal tissue had significantly higher levels than tumors. Immunohistochemical staining of I-ALP was also strong in striated cell borders of colon adenocarcinoma cells. These data suggest that, whereas absorptive cells of the small intestine lose their own traits with tumor development, colonocytes acquire phenotypic features of the small intestine. Intestinal enzymes associated with the striated-cell border, such as sucrase and I-ALP, may be useful markers for malignant phenotypic expression in colonocytes.

Adenocarcinoma↗
PubMed1998

Hydrogen peroxide-induced cellular injury is associated with increase in endogenous fluorescence from rat gastric mucosal epithelial cell culture: A new method for detecting oxidative cellular injury by fluorescence measurement.

To develop a new method of detecting cellular injury caused by oxygen radicals, we studied endogenous fluorescence from the cultured cells of a rat gastric mucosal epithelial cell line. Measurement with an ultra-high sensitivity camera-image processor system under an inverted epifluorescence microscope showed that the fluorescence intensity of the cells increased time- and dose-dependently after the addition of hydrogen peroxide (H2O2), an oxygen radical precursor, to the medium. This increase was inhibited by the presence of catalase. Phase-contrast and fluorescence microscopy revealed that the fluorescence was emitted from granular substances in the cytoplasm of the injured cells. The spectral pattern of excitation and emission indicated that the fluorescent substances were flavins. In cell-free experiments, glutathione reductase which has flavin adenine dinucleotide (FAD) at the active site, increased in fluorescence after incubation with H2O2 in the presence of reduced glutathione and glutathione peroxidase. These findings indicate that FAD in the cytoplasm of cells injured by H2O2 increased in endogenous fluorescence according to the extent of injury, and suggest that fluorescence measurement may be a simple method in cellular toxicology to detect oxygen radical-induced injuries.

Animals↗
PubMed1998

An alternatively spliced form of apobec-1 messenger RNA is overexpressed in human colon cancer.

BACKGROUND & AIMS: Apobec-1 is an RNA-specific cytidine deaminase whose forced overexpression in transgenic animals is associated with hepatic carcinogenesis. Apobec-1 messenger RNA (mRNA) undergoes alternative splicing, generating a catalytically inactive peptide, apobec-T. We have examined apobec-1 gene expression in human gastrointestinal tumors and in colon cancer-derived cell lines. METHODS: Levels of the full-length (apobec-1) and alternatively spliced (apobec-T) mRNAs were measured by RNase protection assay, and apobec-T distribution was determined by immunocytochemical localization. RESULTS: Apobec-1 mRNA was detectable in normal and colon cancer tissue, metastatic nodules, and certain colon cancer-derived cell lines. Apobec-T mRNA abundance was increased an average of 3.5-fold in colon cancers compared with paired control tissue (range, 0.5-14-fold). Immunocytochemical analysis showed apobec-T expression in normal fetal and adult colon and in gastric and small intestinal adenocarcinomas, colonic tubular adenomas, and both primary and metastatic colonic tumors. Overexpression of apobec-T in a tetracycline-responsive cell line decreased cellular proliferation. CONCLUSIONS: Apobec-T is expressed in normal, adenomatous, and cancerous gastrointestinal tissues, and levels of the mRNA encoding this peptide are significantly increased in colon cancer. Although its relationship to colon carcinogenesis has not been defined, the regulated overexpression of apobec-T is associated with an altered growth phenotype.

3T3 Cells↗
PubMed1998

Isomerization of ceftibuten in aqueous solution.

The isomerization reactions of ceftibuten and ceftibuten-related compounds in aqueous solution were investigated to estimate the substitution effect on the isomerization reaction and identify the three proximal dissociation constants of ceftibuten kinetically from the pH-rate profiles. The isomerization reaction of ceftibuten-related compounds was influenced by the substituents near the double bond at the C7-side chain, and the electron-withdrawing substituent was found to increase the isomerization rate. Ceftibuten isomerized at the C7-side chain, and the isomerization rate was influenced by the dissociation of the C7-side chain carboxylic acid and aminothiazole in the acidic pH region. The dissociation constants of ceftibuten were assigned by comparing the isomerization rates of ceftibuten with its related compounds at various pH conditions, and the pKas 2.3, 3.2, and 4.5 were attributed to the 4-carboxylic acid, 7-carboxylic acid, and 7-aminothiazole, respectively.

Ceftibuten↗
PubMed1998

Mechanisms of galanin-induced contraction in the rat myometrium.

A neuropeptide, galanin, regulates the reproductive process and directly induces myometrial contraction. The aim of this study was to determine the mechanism of galanin-induced myometrial contraction. For this purpose, we simultaneously measured intracellular Ca2+ concentration ([Ca2+]i) and tension using fura-PE3-fluorometry and the rat longitudinal myometrium. The effect of galanin on the Ca2+ sensitivity of the contractile apparatus was examined in beta-escin permeabilized strips. The expression of galanin and the galanin receptors mRNAs in the rat myometrium were determined by reverse transcription polymerase chain reaction (RT-PCR). Galanin (10-300 nM) induced phasic contraction with or without oscillation in the pregnant rat myometrium in a concentration-dependent manner. The maximal response was obtained at 100 nM. There was no significant difference either in the maximal responses or EC50 values for galanin-induced myometrial contractions among myometriums from non-pregnant and pregnant (day 4, day 11, day 20, day 22) rats. In the day 20 and 22 pregnant myometriums, assigning the levels of [Ca2+]i and tension at 40 mM K+-depolarization to be 100%, galanin increased the [Ca2+]i and tension to 126.9+/-2.9% and 116.3+/-2.7%, respectively. Diltiazem (10 microM) inhibited the galanin-induced elevation of [Ca2+]i and tension to 71.9+/-2.4% and 16.2+/-0.7%, respectively. Ni2+, by itself, decreased the basal [Ca2+]i to -50.2+/-3.9% without affecting resting tension. After Ni2+ treatment, galanin-induced increases in [Ca2+]i and tension were -19.6+/-3.4% and 0.9+/-0.1%, respectively. In myometrium treated with diltiazem, no oscillation in [Ca2+]i and tension was observed. In Ca2+-free solution with 0.1 mM EGTA, galanin increased [Ca2+]i from -40.2+/-2.7% to -18.0+/-2.6% and induced transient contraction (3.6+/-0.8%). In beta-escin permeabilized myometrium, galanin enhanced the contraction induced by 0.3 microM Ca2+ in the presence of GTP. In the presence of GDPbetaS (1 mM) instead of GTP, galanin failed to increase the Ca2+ sensitivity of the contractile apparatus. RT-PCR revealed that galanin mRNA was hardly expressed in the non-pregnant rat myometrium and increased to reach a maximal level at mid pregnancy (day 11), but decreased to the same level as in the non-pregnant myometrium at term (day 22). Type 2 galanin receptor (GALR2) mRNA was found to be expressed in the rat myometrium whereas type 1 galanin receptor (GALR1) mRNA expression was not detected. In conclusion, galanin induces contraction of the rat myometrium by increasing [Ca2+]i as well as by increasing Ca2+ sensitivity of the contractile apparatus. Galanin-induced increases in [Ca2+]i are caused by both intracellular Ca2+ release and Ca2+ influx from extracellular space. The responsiveness of the rat myometrium to galanin does not change during pregnancy. The galanin mRNA is expressed in the rat myometrium and it is upregulated during mid-pregnancy. Rat myometrium expresses GALR2 but not GALR1 mRNA. By changing mRNA expression in the myometrium during pregnancy, galanin may act as a paracrine or autocrine mediator in the regulation of myometrial contractility.

Animals↗
PubMed1998

Analysis of blood pressure responses during exercise by logistic function curve in hypertension: effects of age, gender and physical training.

During exercise blood pressure fluctuates from minute to minute and does not rise linearly with time. Blood pressure responses were evaluated during exercise by a logistic function curve. Thirty-nine hypertensive patients underwent exercise testing with an ergometer, employing a multistage method (25 watts increment, every 3 min). We plotted the exercise duration on the X-coordinate and systolic blood pressure on the Y-coordinate and blood pressure was assumed to form a logistic curve for exercise duration. The relationship of systolic blood pressure vs. exercise duration was better fitted into a logistic function curve than a linear regression model. The logistic curve was defined by lower plateau, upper plateau, SPX (the X-coordinate at the shift point) and df (SPX), the maximal slope at the shift point. The effects of aging, gender and physical training were then analyzed on the curve. Aging did not affect lower plateau, upper plateau and SPX but augmented df (SPX), indicating greater blood pressure responses in older subjects during exercise. In females the curve was shifted to the left compared to males (SPX: 4.9 vs. 8.3 min, P < 0.05) without changes in plateaux and df (SPX), indicating greater blood pressure responses than males. Physical training for 3 weeks decreased the lower plateau from 157 to 144 mmHg (P < 0.05) and shifted the curve to the right (SPX: 7.1 vs. 8.6 min, P < 0.05), indicating unchanged blood pressure responses after training because of the opposite effects by decreases in the lower plateau vs. the curve shift to the right. In conclusion, blood pressure during exercise is better delineated by a logistic function curve than a linear regression model. The biological or physiological significance of df (SPX) is not clear at present and needs further investigations.

Adult↗