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Biomedical subjects

M Taniguchi

Publications and source records attributed to M Taniguchi.

At least 181 records · Page 10Linked to original sources
PubMed2000

Decapitation in suicidal hanging--a case report with a review of the literature.

We report a case of self-decapitation by suicidal hanging from a river bridge and discuss the decapitation mechanism, reviewing the literature. The torso and the head of the victim, respectively, were found apart in a river approximately 100 m and 600 m, respectively, downstream from the bridge in two days. Morphological, serological and DNA analyses confirmed their identity. Torn ligaments between the atlas and axis accompanied by fractures in the axis at the partes interarticulares were indicative of a traction force combined with anteroflexion of the head by falling from a height, and the radial pressure due to a strong, single twisted nylon rope with a slip knot was considered to have contributed considerably to the subsequent skin laceration with wavy marginal abrasions. In the reviewed literature, cervical spine fractures were described only in two of six cases, suggesting head movement at the time of decapitation.

Journal Article↗
PubMed2000

Sudden infant death attributed to peracute pulmonary infection: two autopsy cases.

This report describes two autopsy cases of sudden infant death attributed to peracute pulmonary infection in which possible causative microorganisms could be identified despite only minor pathological findings. Both babies were 5-month-old boys, who had no symptomatic disorders and were found dead in bed. Their main macropathology was inflated heavy lungs with patchy bleedings. One case showed a pulmonary histopathological finding suggestive of viral infection, and adenovirus DNA was detected from the intrabronchial fluid. In the second case, pulmonary histopathology was a feature of early inflammatory reaction involving focal necrosis with some neutrophil infiltration and many intra-alveolar macrophages containing gram-positive cocci, and Staphylococcus aureus was identified in venous blood culture. These findings significantly support the presence of pathogenic microorganisms in sudden infant death.

Journal Article↗
PubMed2000

Antimicrobial effects of green tea polyphenols on thermophilic spore-forming bacteria.

The inhibitory action of tea polyphenols towards the development and growth of bacterial spores was examined. Among the tested Bacillus bacteria, tea polyphenols showed antibacterial effects towards Bacillus stearothermophilus, which is a thermophilic spore-forming bacterium. The heat resistance of B. stearothermophilus spores was reduced by the addition of tea polyphenols. Clostridium thermoaceticum, an anaerobic spore-forming bacterium, also exhibited reduced heat resistance of its spores in the presence of tea polyphenols. (-)-Epigallocatechin gallate, which is the main component of tea polyphenols, showed strong activity against both B. stearothermophilus and C. thermoaceticum. The heat resistance of these bacterial spores was more rapidly decreased by the addition of tea polyphenols at high temperatures.

Journal Article↗
PubMed2000

His-Asp phosphorelay signaling: a communication avenue between plants and their environment.

His-Asp phosphorelay systems have been recently discovered in plants and have emerged as some of the most important signaling systems. The phosphorelay systems in plants include components with sensor (His-protein kinase) domains, His-containing phosphotransfer (HPt) domains, and receiver (response regulator) domains. Recent studies implicate phosphorelay systems in sensing and propagating signals from a wide variety of external and/or internal stimuli such as ethylene, cytokinin, and osmolarity. In maize and Arabidopsis, some response regulators are up-regulated by both cytokinins and nitrate. These findings imply that the His-Asp phosphorelay may operate in an inorganic nitrogen-signaling pathway mediated by cytokinin in plants.

Aspartic Acid↗
PubMed2000

Potentiation of antitumor effect of NKT cell ligand, alpha-galactosylceramide by combination with IL-12 on lung metastasis of malignant melanoma cells.

The combined therapeutic effect of natural killer T (NKT) cell ligand alpha-galactosylceramide (alpha-GalCer) and IL-12 against highly metastatic B16-BL6-HM melanoma cells was investigated. In comparison with a single administration of alpha-GalCer or IL-12, the combined treatment of tumor-bearing mice with alpha-GalCer plus IL-12 caused a super-induction of serum IFN-gamma levels, though alpha-GalCer-induced IL-4 production was rather inhibited. In parallel with the augmented IFN-gamma production, the natural killing activity against YAC-1 cells and syngeneic B16-BL6-HM melanoma was greatly augmented by the combined therapy. The major effector cells responsible for natural killing activity induced by alpha-GalCer plus IL-12 were enriched in both NK1.1+ TCRalphabeta+ NKT cells and NK1.1+ TCRalphabeta- NK cells. The preventing effect of alpha-GalCer or IL-12 alone against lung metastasis of B16-BL6-HM was also enhanced by the combination therapy. The antitumor activity of alpha-GalCer was totally abolished in NKT-deficient mice. However, IL-12-induced antitumor activity was not eliminated in NKT-deficient mice though it was inhibited by anti-asialo GM1 Ab treatment. These findings suggested that alpha-GalCer synergistically act with IL-12 to activate both NKT cells and NK cells, which may play a critical role in the strong prevention of distant tumor metastasis at early stages of tumor-bearing. These data will provide a novel tool for the prevention of tumor metastasis using NKT-specific ligands alpha-GalCer and IL-12.

Animals↗
PubMed2000

Effects of magnesium and its mechanism on the incidence of reperfusion arrhythmias following severe ischemia in isolated rat hearts.

Magnesium sulfate (Mg) has been widely used for the treatment of ventricular arrhythmias (VF) in patients with coronary artery disease. However, the mechanisms of prevention on the incidence of VF have not been defined. The aim of study was to investigate the role of Mg in the prevention of VF and the mechanism of those effects. Series 1 studied antiarrhythmic effects on VF. Isolated rat hearts were perfused in the working heart mode with Krebs'-Henseleit bicarbonate buffer (KHB). Whole heart ischemia was induced by a one-way ball valve with 300 beats/min electrical pacing for 10 minutes followed by 20 minutes of aerobic reperfusion. After control perfusion, Mg was added from 5 minutes before ischemia and was continued to the end of ischemia (1.2 mM for the control group and 2.4, 3.6, 4.8, and 9.6 mM for the study animals) or during reperfusion (3.6 mM). Left ventricular pressure, aortic flow, and ECG were monitored. Series 2 studied the effect of Mg on [Ca2+]i. Hearts were perfused by the Langendorff mode and were loaded with 4 microM of Fura 2/AM as a [Ca2+]i indicator. Ca2+ was monitored using the ratio of Fura-2 fluorescence intensity at excitation wavelengths of 340 and 380 nm. The hearts were subjected to a 20 minutes of low-flow ischemia followed by 20 minutes of aerobic reperfusion. Then 3.6 mM Mg was added to the KHB medium during ischemia. The duration of VF was significantly suppressed in the 2.4, 3.6, and 4.8 mM/L Mg-added groups (472 +/- 173, 779 +/- 159, and 525 +/- 202 second, respectively) when compared with the control group (1200 seconds). Magnesium sulfate suppressed the fluorescence ratio of the diastolic Ca2+ level at the end of 20 minutes of ischemia from 40.5 +/- 3.6% to 9.0 +/- 1.0% (P < 0.05 vs. control hearts). These results suggested that Mg had a beneficial effect on VF and that the optimal Mg concentration was between 2.4 and 4.8 mM. The mechanism of the prevention of VF by Mg could be through the inhibition of [Ca2+]i retention during ischemia.

Animals↗
PubMed2000

Binding of cell type-specific nuclear proteins to the 5'-flanking region of maize C4 phosphoenolpyruvate carboxylase gene confers its differential transcription in mesophyll cells.

C4-type phosphenolpyruvate carboxylase (C4PEPC) acts as a primary carbon assimilatory enzyme in the C4 photosynthetic pathway. The maize C4PEPC gene (C4Ppc1) is specifically expressed in mesophyll cells (MC) of light-grown leaves, but the molecular mechanism responsible for its cell type-specific expression has not been characterized. In this study, we introduced a chimeric maize C4Ppc1 5'-flanking region/beta-glucuronidase (GUS) gene into maize plants by Agrobacterium-mediated transformation. Activity assay and histochemical staining showed that GUS is almost exclusively localized in leaf MC of transgenic maize plants. This observation suggests that the introduced 5' region of maize C4Ppc1 contains the necessary cis element(s) for its specific expression in MC. Next, we investigated whether the 5' region of the maize gene interacts with nuclear proteins in a cell type-specific manner. By gel shift assays with nuclear extracts prepared from MC or bundle sheath cells (BSC), cell type-specific DNA-protein interactions were detected: nuclear factors PEP(Ib) and PEP(Ic) are specific to MC whereas PEP(Ia) and PEP(IIa) are specific to BSC. Light alters the binding activity of these factors. These interactions were not detected in the assay with nuclear extract prepared from root, or competed out by oligonucleotides corresponding to the binding sites for the maize nuclear protein, PEP-I, which is known to bind specifically to the promoter region of C4Ppc1. The results suggest that novel cell type-specific positive and negative nuclear factors bind to the maize C4Ppc1 5'-flanking region and regulate its differential transcription in MC in a light-dependent manner.

Binding Sites↗
PubMed2000

Natural killer cells determine the outcome of B cell-mediated autoimmunity.

Natural killer (NK) cells can affect the outcome of adaptive immune responses. NK cells, but not NK1.1+T cells, were found to participate in the development of myasthenia gravis (a T cell-dependent, B cell- and antibody-mediated autoimmune disease) in C57BL/6 mice. The requirement for NK cells was reflected by the lack of a type I helper T cell response and antibodies to the acetylcholine receptor in both NK1.1+ cell-depleted and NK cell-deficient IL-18-/- mice. These findings establish a previously unrecognized link between NK cells and autoreactive T and B cells.

Amino Acid Sequence↗
PubMed2000

Deficiency of the macrophage migration inhibitory factor gene has no significant effect on endotoxaemia.

By targeted disruption of the MIF gene, we have established a mouse strain deficient in macrophage (Mphi) migration inhibitory factor (MIF). Despite previous reports indicating an essential role of MIF in endotoxaemia, an injection of lipopolysaccharide (LPS) into the MIF-deficient mice (maintained under specific pathogen-free conditions) caused shock. No significant difference was detected between the MIF-deficient mutant and normal mice in susceptibility to LPS for endotoxaemia or tumour necrosis factor-alpha (TNF-alpha) formation upon LPS injection. Peritoneal Mphi from the two strains produced TNF-alpha in response to LPS with similar dose responses. Dexamethasone suppressed the LPS-induced TNF-alpha response of Mphi, but no difference was detected between the Mphi from the two strains. These results suggest that endogenous MIF has no significant effect on the LPS-induced TNF-alpha production and no effect on suppression of the response by glucocorticoids. Thus, MIF is not crucial for LPS-induced immune responses leading to shock.

Animals↗
PubMed2000

Differences in the ligand specificity between CD1d-restricted T cells with limited and diverse T-cell receptor repertoire.

The natural killer (NK) T-lymphocyte population consists of two subsets utilizing a diverse and restricted T-cell receptor (TCR) repertoire, respectively. Both populations have been shown to include autoreactive cells. NKT cells carrying restricted Valpha14(AV14S1)Jalpha281/Vbeta8.2(BV8S2A1 ) TCR have been shown to recognize alpha-galactosylceramide (alphaGalCer) presented in the context of murine CD1d. In this study we screened a set of murine CD1d-autoreactive T-cell hybridomas with diverse TCR for their reactivity with several glycosylated variants of ceramide, including alphaGalCer. These hybridomas showed a different pattern of reactivity to CD1d-expressing antigen-presenting cells (APC) and were not reactive with any of the tested variants of ceramide. A second set of hybridomas had been selected for expression of Valpha14 and Vbeta8.2 TCR chains. These cells responded to alphaGalCer presented on CD1d, but were only weakly reactive to syngeneic splenocytes or CD1d-transfected cells. Their fine specificity in the response to glycosylation variants of ceramide demonstrated a homogenous reactivity pattern, including reactivity to alpha-galactosylsphingosine, the variant of alphaGalCer with truncated fatty acyl chain. These findings underline the differences in ligand specificity between the two subsets of CD1d-restricted NKT cells, and demonstrate a similarity in reactivity among the hybridomas using the Valpha14-Jalpha281/Vbeta8.2 TCR.

Animals↗
PubMed2000

The evolution of C4 plants: acquisition of cis-regulatory sequences in the promoter of C4-type pyruvate, orthophosphate dikinase gene.

In a previous study, we identified the C4-like pyruvate, orthophosphate dikinase gene (Pdk) in the C3 plant rice, with a similar structure to the C4-type Pdk in the C4 plant maize. In order to elucidate the differences between C4-type and C4-like Pdk genes in C4 and C3 plants, we have produced chimeric constructs with the beta-glucuronidase (GUS) reporter gene under the control of the Pdk promoters. In transgenic rice, both rice and maize promoters directed GUS expression in photosynthetic organs in a light-dependent manner. However, the maize promoter exhibited a much higher transcriptional activity than the rice promoter did. These results indicate that the rice C4-like Pdk gene resembles the maize C4-type Pdk gene in terms of regulation of expression. We also tested the activity of the rice promoter in transgenic maize. GUS activity was seen in both photosynthetic and non-photosynthetic organs. Thus, the rice promoter does not confer a strict organ-specific gene expression, as the maize promoter does. Moreover, the rice promoter directed GUS expression not only in mesophyll cells but also in bundle sheath cells, whereas the maize promoter directed expression only in mesophyll cells. Taken together, the results obtained from both transgenic maize and rice demonstrate that the rice and maize promoters differ not only quantitatively, but also qualitatively, in terms of their cell- and organ-specificity. Experiments with swapped promoters using the rice and maize promoters further demonstrated that a limited sequence region from -330 to -76 of the maize promoter confers light-regulated, high-level expression to the rice promoter in maize mesophyll protoplasts. We conclude the gain of cis-acting elements conferring high-level expression and mesophyll cell specificity was necessary for establishment of a C4-type Pdk gene during the course of evolution from C3 to C4 plants.

Evolution, Molecular↗
PubMed2000

Novel prenyltransferase gene encoding farnesylgeranyl diphosphate synthase from a hyperthermophilic archaeon, Aeropyrum pernix. Molecularevolution with alteration in product specificity.

Prenyltransferases catalyse sequential condensations of isopentenyl diphosphate with allylic diphosphates. Previously, we reported the presence of farnesylgeranyl diphosphate (FGPP) synthase activity synthesizing C25 isoprenyl diphosphate in Natronobacterium pharaonis which is a haloalkaliphilic archaeon having C20-C25 diether lipids in addition to C20-C20 diether lipids commonly occurring in archaea [Tachibana, A. (1994) FEBS Lett. 341, 291-294]. Recently, it was found that a newly isolated aerobic hyperthermophilic archaeon, Aeropyrum pernix, had only C25-C25 diether lipids, not the usual C20-containing lipids [Morii, H., Yagi, H., Akutsu, H., Nomura, N., Sako, Y. & Koga, Y. (1999) Biochim. Biophys. Acta 1436, 426-436]. In this report, we describe the isoloation from A. pernix of the novel prenyltransferase gene, fgs, encoding FGPP synthase. The protein encoded by fgs was expressed in Escherichia coli as a glutathione S-transferase fusion protein and produced FGPP as a final product. Phylogenetic analysis of fgs with other prenyltransferases revealed that the short-chain prenyltransferase family is divided into three subfamilies: bacterial subfamily I, eukaryotic subfamily II, and archaeal subfamily III. fgs is clearly contained within the archaeal geranylgeranyl diphosphate (GGPP) synthase group (subfamily III), suggesting that FGPP synthase evolved from an archaeal GGPP synthase with an alteration in product specificity.

Alkyl and Aryl Transferases↗
PubMed2000

Tumor necrosis factor-beta gene NcoI polymorphism decreases insulin resistance in Japanese men.

Given that the NcoI polymorphism of the tumor necrosis factor-beta (TNF-beta) gene has been shown to be associated with tumor necrosis factor-alpha (TNF-alpha) secretory capacity, we know that this TNF-beta gene polymorphism may influence insulin resistance. In Caucasians, 2 polymorphisms of the TNF-alpha promoter region (positions -308 and -238) have been reported to be associated with insulin resistance. Thus, we investigated how genetic variation in the TNF-beta and TNF-alpha genes was associated with insulin resistance in 211 Japanese men. The frequency of the TNF-beta gene polymorphism was 0.41, and insulin resistance, estimated by homeostasis model assessment (HOMA), was significantly lower in variant homozygotes versus wild-type allele. The frequencies of the -308 and -238 polymorphisms were 0.01 and 0.02, respectively, and these polymorphisms were not associated with insulin resistance. Our results suggest that the TNF-beta gene polymorphism decreases insulin resistance, and that the -308 and -238 polymorphisms of the TNF-alpha promoter region are not a major contributing factor to insulin resistance in Japanese men.

Adult↗
PubMed2000

Inhalation toxicity of potassium octatitanate fibers (TISMO) in rats following 13 weeks of aerosol exposure.

One hundred and forty male and 140 female rats were divided into 1 control and 3 test groups of 35 rats each, per sex, and exposed by whole-body inhalation to test compound at target concentrations of 0, 1 mg/m(3) (1700 fibers/cm(3), 123 WHO fibers/cm(3)), 10 mg/m(3) (5900 fibers/cm(3), 952 WHO fibers/cm(3)), and 100 mg/m(3) (112,700 fibers/cm(3), 7440 WHO fibers/cm(3)) for 6 h/day, 5 days/wk for 13 wk. Ten rats from each group were killed after 13 wk of exposure and 13 wk of recovery, respectively, for histopathological evaluation. The other 15 rats from each group were killed to study lung clearance after 91 days of exposure, and approximately 1.5 and 3 mo of recovery following the end of the 13 wk of exposure. The mean fiber length of the chamber atmosphere was 2.8, 2.7, and 2.8 microm, while the mean fiber width was 0.48, 0.48, and 0.45 microm for the 1-, 10-, and 100-mg/m(3) chambers, respectively. In the 1-mg/m(3) (123 WHO fibers/cm(3)) exposure group, inhaled particles were mostly retained in a few fiber-laden alveolar macrophages (AMs) within the alveoli adjacent to alveolar ducts without any adverse tissue response throughout 13 wk of exposure and following 13 wk of recovery. This exposure concentration was considered to be a no-observable-adverse-effect level (NOAEL), since the alveoli containing fiber-laden AMs preserved normal structure. After 13 wk of exposure to 10 mg/m(3) (952 WHO fibers/cm(3)), fiber-laden AMs were mainly retained at the alveoli adjacent to the alveolar ducts. Infrequently, slight fibrotic thickening was observed in the alveolar ducts and adjoining alveoli, with proliferating fibroblasts and hyperplastic Type II pneumocytes, and microgranulomas. Occasionally, trace amounts of collagenous material were deposited in the thickened alveolar ducts and adjoining alveolar walls. In addition, minimal alveolar bronchiolarization was occasionally found in the alveoli adjacent to the terminal bronchioles. The peribronchial lymphoid tissue and thymic lymph nodes contained migrated fiber-laden AMs. After 13 wk of recovery, fiber-laden AMs had mostly disappeared from alveoli located in the peripheral acini, but they localized in the alveolar ducts region, suggesting there was active lung clearance of fibers by the AMs via airways. Thickened alveolar ducts and adjacent alveoli were decreased in thickness, a reversible change manifested by reduction of proliferating Type II pneumocytes and fibroblasts. Collagenized fibrosis was slightly more pronounced in the thickened alveolar ducts and adjoining alveoli. The lung response following 13 wk of exposure to 100 mg/m(3) (7440 WHO fibers/cm(3)) and after 13 wk of recovery was similar to those findings of the 952 WHO fibers/cm(3) group but more pronounced, demonstrating a clear concentration-related response. Alveolar ducts and adjoining alveolar walls in the central acini were irregularly thickened with more frequent evidence of minimal collagenized fibrosis. The lung burden and clearance of fibers were estimated by measuring the total content of titanium (Ti) in the lungs, but high variability of Ti content in control and exposed groups prevented meaningful lung clearance analysis.

Administration, Inhalation↗
PubMed2000

Chemosensitive conductance and inositol 1,4,5-trisphosphate-induced conductance in snake vomeronasal receptor neurons.

Snake vomeronasal receptor neurons in slice preparations were studied using the patch-clamp technique in the conventional and nystatin-perforated whole-cell configurations. The mean resting potential was approximately -70 mV; the average input resistance was 3 GOmega. Neurons required current injection of only 1-10 pA to display a variety of spiking patterns. Intracellular dialysis of 100 microM inositol 1,4,5-trisphosphate (IP(3)) evoked an inward current in 38% of neurons, with an average peak amplitude of 16.4 +/- 2.8 pA at a holding potential of -70mV. Application of 100 microM 3-deoxy-3-fluoro-D-myo-inositol 1,4,5-trisphosphate (F-IP(3)), a derivative of IP(3), also evoked an inward current in 4/8 (50%) neurons (32.6 +/- 58 pA at -70 mV, n = 4). The reversal potentials of the induced components were estimated to be -14 +/- 5 mV for IP(3) and -17 +/- 3 mV for F-IP(3). Bathing the neurons in 10 microM ruthenium red solution greatly reduced the IP(3)-evoked inward current to 1.6 +/- 1.1 pA at -70 mV (n = 6). With Cs(+)-containing internal solution, neither the Ca(2+)-ATPase inhibitor thapsigargin (1-50 microM) nor the Ca(2+)-ionophore ionomycin (10 microM) evoked a significant current response, suggesting that IP(3) can elicit current response in the neurons without mediation by intracellular Ca(2+) stores. Intracellular application of 1 mM cAMP evoked no detectable current response. Extracellular application of chemoattractant for snakes evoked a very large inward current. The reversal potential of the chemoattractant-induced current was similar to that of the IP(3)-induced current. The present results suggest that IP(3) may act as a second messenger in the transduction of chemoattractants in the garter snake vomeronasal organ.

Animals↗
PubMed2000

Impaired Ca/calcineurin pathway in in vivo anergized CD4 T cells.

Clonal anergy is one of the mechanisms that may account for self tolerance induced in T cells in the periphery. In this study we used the well-documented system of in vivo administration of a superantigen, staphylococcal enterotoxin B (SEB), to induce a state of hyporesponsiveness (anergy) in murine peripheral T cells to decipher the intracellular biochemical basis for this process. The TCR-induced Ca response of in vitro activated T cells was found to be impaired with significant defects in the phosphorylation of phospholipase C-gamma 1. Experiments with calcium ionophore and newly established transgenic mouse lines that express an active form of calcineurin suggested that in vivo SEB-induced anergy is established and/or maintained by a selective impairment in the TCR-induced activation of the Ca/calcineurin pathway.

Animals↗