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Biomedical subjects

T Yaguchi

Publications and source records attributed to T Yaguchi.

At least 19 recordsLinked to original sources
PubMed2005

The linoleic acid derivative FR236924 facilitates hippocampal synaptic transmission by enhancing activity of presynaptic alpha7 acetylcholine receptors on the glutamatergic terminals.

The present study aimed at understanding the effect of FR236924, a newly synthesized linoleic acid derivative with cyclopropane rings instead of cis-double bonds, on hippocampal synaptic transmission in both the in vitro and in vivo systems. FR236924 increased the rate of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor-mediated miniature excitatory postsynaptic currents, without affecting the amplitude, triggered by nicotine in CA1 pyramidal neurons of rat hippocampal slices, that is inhibited by GF109203X, a selective protein kinase C (PKC) inhibitor or alpha-bungarotoxin, an inhibitor of alpha7 acetylcholine (ACh) receptors. FR236924 stimulated glutamate release from rat hippocampal slices and in the hippocampus of freely behaving rats, and the effect was also inhibited by GF109203X or alpha-bungarotoxin. FR236924 induced a transient huge potentiation followed by a long-lasting potentiation in the slope of field excitatory postsynaptic potentials recorded from the CA1 region of rat hippocampal slices, and the latter effect was blocked by GF109203X or alpha-bungarotoxin. Likewise, the compound persistently facilitated hippocampal synaptic transmission in the CA1 region of the intact rat hippocampus. It is concluded from these results that FR236924 stimulates glutamate release by functionally targeting presynaptic alpha7 ACh receptors on the glutamatergic terminals under the influence of PKC, responsible for the facilitatory action on hippocampal synaptic transmission. This may provide evidence for a link between cis-unsaturated free fatty acids and presynaptic alpha7 ACh receptors in hippocampal synaptic plasticity.

Alkanes↗
PubMed2001

Involvement of endogenous PACAP expression in the activity-dependent survival of mouse cerebellar granule cells.

Membrane depolarization causes Ca2+ influx through L-type voltage-dependent calcium channels (L-VDCC), which promotes the activity-dependent survival of mouse cerebellar granule cells (CGCs). Although exogenously added pituitary adenylate cyclase activating polypeptide (PACAP) is effective in promoting the survival of CGCs, it is unknown whether PACAP is synthesized in CGCs and involved in the activity-dependent survival of CGCs. In this study, we found that the PACAP gene was activated in depolarized CGCs cultured at 25 mM KCl (high K+), independently of de novo protein synthesis. In addition, the PACAP immunoreactivity increased through the activation of L-VDCC in depolarized CGCs, indicating that PACAP is concomitantly produced with PACAP mRNA in an activity-dependent manner. Exogenously added PACAP attenuated the apoptosis of CGCs through a specific interaction with PACAP receptors. Furthermore, a PACAP receptor antagonist, PACAP(6-38), reduced the survival of CGCs at high K+. These findings indicate that endogenous PACAP production induced by Ca2+ signals exerts a survival effect on CGCs via PACAP receptors, which, at least in part, accounts for the activity-dependent survival of CGCs.

Actins↗
PubMed2001

Observation of human dentine by focused ion beam and energy-filtering transmission electron microscopy.

Molar dentine was sliced into 100 nm ultrathin sections, by means of a focused ion beam, for observation by energy-filtering transmission electron microscopy (EFTEM). Within the matrix, crystals approximately 10 nm wide and 50-100 nm long were clearly observed. When carbon and calcium were mapped in electron spectroscopic images by EFTEM, carbon failed to localize in crystals. However, it was found in other regions, especially those adjacent to crystals. Because carbon localizations were thought to reflect the presence of organic components, carbon concentration in regions near crystals suggested the interaction of crystals and organics, leading to organic control of apatite formation and growth. Ca was present in almost all regions. The majority of Ca localizing in regions other than crystals may be bound to organic substances present in dentine matrix. These substances are thought to both accumulate Ca and act as reservoirs for crystallization of apatite in dentine.

Calcification, Physiologic↗
PubMed2001

A method for characterizing carbon nanotubes.

High-resolution transmission electron microscopy and electron energy-loss spectroscopy of a multi-walled carbon nanotube (MWCNT) at elevated temperatures were studied. Although the observation was carried out at 200 kV, the crystal structures of the MWCNT were observed without introducing defects. In addition, contamination on the MWCNT, such as nanobubbles, was removed during the observation at 600 degrees C. In this paper, we report the observation conditions and experimental results. The experimental results obtained both at 600 degrees C and at room temperature were compared.

Letter↗
PubMed2000

The metabolism and distribution of docosapentaenoic acid (n-6) in rats and rat hepatocytes.

In this study, a new marine oil that contains 45% docosahexaenoic acid (DHA, 22:6n-3) and 13% docosapentaenoic acid (DPA, 22:5n-6) was administered to rats. The metabolism and distribution of DPA in rats was investigated. In experiment 1, the effects of DHA and n-6 fatty acids (linoleic acid, LA; arachidonic acid, AA; and DPA) on AA contents were investigated in vivo. LA group: LA 25%, DHA 30%; LA-DPA group: LA 15%, DPA 10%, DHA 35%; LA-AA-DPA group: LA 10%, AA 5%, DPA 10%, DHA 35% were administered to rats for 4 wk. In the liver, the AA content in the LA-DPA and LA-AA-DPA groups was significantly higher than in the LA group. The decreased AA contents in the LA group might be caused by DHA administration. Although DHA also was administered in the LA-DPA and LA-AA-DPA groups, the AA contents in these two groups did not decrease. These results suggested that DPA retroconverted to AA, blunting the decrease in AA content caused by DHA administration. To conduct a detailed investigation on DPA metabolism and its relation with AA and DHA, rat hepatocytes were cultured with purified DPA and DHA for 24 h. We discovered the retroconversion of DPA to AA occurred only when AA content was decreased by a high DHA administration; it did not occur when AA content was maintained at a normal level.

Animals↗
PubMed2000

Antifungal substances against pathogenic fungi, talaroconvolutins, from talaromyces convolutus.

The dichloromethane extract of Talaromyces convolutus cultivated on barley exhibited antifungal activity against Candida albicans. In the course of a search for the active compounds, four new tetramic acid derivatives, talaroconvolutins A (1), B (2), C (3), and D (4), were isolated along with ZG-1494alpha (5), and mitorubrin derivatives. The structures of talaroconvolutins A-D (1-4) were established on the basis of spectroscopic and chemical investigations and chemical correlations. The antifungal activity of the talaroconvolutins against the pathogenic fungi Aspergillus fumigates, Aspergillus niger, C. albicans, and Cryptococcus neoformans was determined.

Antifungal Agents↗
PubMed2000

PF1163A and B, new antifungal antibiotics produced by Penicillium sp. I. Taxonomy of producing strain, fermentation, isolation and biological activities.

Two novel antifungal antibiotics, PF1163A and B, were isolated from the fermentation broth of Penicillium sp. They were purified from the solid cultures of rice media using ethyl acetate extraction, silica gel and Sephadex LH-20 column chromatographies. PF1163A and B showed potent growth inhibitory activity against pathogenic fungal strain Candida albicans but did not show cytotoxic activity against mammalian cells. These compounds inhibited the ergosterol biosynthesis in Candida albicans.

Antifungal Agents↗
PubMed2000

Cross-sectional Specimen Preparation and Observation of a Plasma Sprayed Coating Using a Focused Ion Beam/Transmission Electron Microscopy System.

A focused ion beam (FIB) technique was applied to cross-sectional specimen preparation to observe an interface between a plasma sprayed coating and an aluminum (Al) substrate by transmission electron microscopy (TEM). The surface of the sprayed coating film has a roughness of several tens of microns. Sputter rates for the coating film and the substrate are greatly different. The rough surface and the difference in sputter rate cause problems in making TEM specimens with smooth side walls. The top surface of the coating film was planerized by the FIB before fabricating the TEM specimen. The interfaces were investigated by TEM and energy-dispersive X-ray (EDX) analysis. The TEM observation revealed that there is a 10 nm thick amorphous layer at the interface between the coating film and substrate. The coating film consists of two kinds of sublayers with bright and dark contrast. The bright contrast sublayers were amorphous layers with thickness of 2 approximately 10 nm. The Al/Fe X-ray intensity ratio was larger in bright contrast sublayers than that in dark contrast sublayers.

Journal Article↗
PubMed1999

A successful surgical repair of the hepatic hydrothorax using pneumoperitoneum: report of a case.

A successful surgical repair of a right hepatic hydrothorax in the absence of ascites is reported. A technetium-99m scintigram that was injected intraperitoneally provided evidence of a one-way flow of fluid from the peritoneal to pleural cavity. To identify any possible minute defects in the diaphragm, carbon dioxide was insufflated into the peritoneal cavity during the operation. We performed a direct suture of the defect observed on the diaphragm. The pleural effusion subsequently vanished after the operation.

Humans↗
PubMed1999

Method for Cross-sectional Transmission Electron Microscopy Specimen Preparation of Composite Materials Using a Dedicated Focused Ion Beam System.

: A new method for transmission electron microscope (TEM) specimen preparation using a focused ion beam (FIB) system that results in a lower rate of gallium (Ga) implantation has been developed. The method was applied to structural and analytical studies of composite materials such as silicon (Si)-devices and magneto-optical disk. To protect the specimens against Ga ion irradiation, amorphous tungsten (W) was deposited on the surface of the specimen prior to FIB milling. The deposition was quite effective in reducing the Ga implantation rate, and energy-dispersive X-ray (EDX) analysis of these specimens detected 0.3-1.5% Ga incorporated in the thinned area. FIB milling times for these specimens were 1.5-2 hr, with a starting thickness of about 50 µm. Although the milling rate was high, all the materials were properly prepared for TEM study, and clear crystal lattice images were observed on all specimens.

Journal Article↗
PubMed1999

Mitorubrin derivatives on ascomata of some talaromyces species of ascomycetous fungi

Two groups, producers of (+)- and (-)-mitorubrin derivatives, coexist in the series Lutei of the genus Talaromyces. The optical rotations of mitorubrins from T. emodensis, T. hachijoensis, and T. wortmannii var. sublevisporus, which produced mitorubrinol acetate (5), were all positive, whereas those from T. austrocalifornicus and T. convolutus, which produced mitorubrinal (3) and mitorubrinic acid (4), were all negative.

Journal Article↗
PubMed1998

Phylogenetic position of an obligately chemoautotrophic, marine hydrogen-oxidizing bacterium, Hydrogenovibrio marinus, on the basis of 16S rRNA gene sequences and two form I RuBisCO gene sequences.

Two form ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) genes from the obligately autotrophic, marine hydrogen oxidizer Hydrogenovibrio marinus were sequenced. The deduced amino acid sequences of both RuBisCOs revealed that they are similar to those of sulfur oxidizers (Thiobacillus) and a purple sulfur bacterium (Chromatium vinosum). According to the 16S rRNA gene sequences, H. marinus is also affiliated with these microorganisms, members of Thiomicrospira being the closest relatives. Sequence similarities of the 16S rRNA genes and of the RuBisCO genes among these gamma-Proteobacteria suggest a common autotrophic ancestry. An ancestor of purple sulfur bacteria might be a common root of H. marinus and related sulfur oxidizers.

Bacterial Proteins↗
PubMed1998

Coexistence of generalized morphea with hisotological changes in lichen sclerosus et atrophicus and lichen planus.

We reported a 44-year-old Japanese woman with generalized multiple sclerotic plaques, which showed histological findings of morphea. This patient also had an erosive lesion on her mouth; its histological findings were consistent with lichen planus. A sclerotic lesion on her thigh showed the histological findings of lichen sclerosus et atrophicus (LSA). These data suggest that similar etiologic events or closely related pathologic processes are involved in morphea, lichen planus, and LSA.

Adult↗
PubMed1998

Immunohistochemical and gelatin zymography studies for matrix metalloproteinases in bleomycin-induced pulmonary fibrosis.

The role of various matrix metalloproteinases (MMP) and tissue inhibitor of metalloproteinases-2 (TIMP-2), and the gelatinolytic activities of MMP involved in the process of bleomycin-induced pulmonary fibrosis in rabbits were investigated. Male Japanese white rabbits were intubated with tracheal tubes under anesthesia, and bleomycin hydrochloride in sterile saline or only sterile saline was administered through the tracheal tubes. The animals were killed 1, 3, 7, 14 and 28 days after the administration of bleomycin (n = 3) or saline (n = 2). Light microscopic immunohistochemistry for MMP-1 (interstitial collagenase), MMP-2 (gelatinase A), MMP-9 (gelatinase B) and TIMP-2 was performed. The gelatinolytic activities of lung tissue homogenates were studied by gelatin zymography. In the early stages, the gelatinolytic activity of MMP-9 was predominant. MMP-9 localized in the infiltrating neutrophils, macrophages, bronchial and bronchiolar epithelial cells. The alveolar epithelial basement membrane was frequently disrupted in the early stages, where MMP-9 possibly contributed to the disruption. In the late stages, the gelatinolytic activities of the latent and active forms of MMP-2 were predominant, and MMP-2 localized in the regenerated alveolar epithelial cells in addition to the bronchial epithelial cells. MMP-2, especially its active form, possibly plays a role in alveolar epithelial cell regeneration. The localization of MMP-1 was similar to that of MMP-9. TIMP-2 localized in the epithelial cells and in some fibroblasts in fibrotic lesions. TIMP-2 possibly plays a role in extracellular matrix deposition in balance with MMP.

Animals↗
PubMed1997

PF1092A, B and C, new nonsteroidal progesterone receptor ligands produced by Penicillium oblatum. I. Taxonomy of producing strain, fermentation, isolation and biological activities.

Three new nonsteroidal progesterone receptor ligands, PF1092A, B and C, have been isolated from Penicillium oblatum. They were purified from the solid cultures of rice media using ethyl acetate extraction, silica gel and Sephadex LH-20 column chromatographies, and crystallization. All three ligands competitively inhibited [3H]-progesterone binding to porcine uteri cytosol preparations with IC50 of 3.0 x 10 nM (PF1092A), 2.2 x 10(2) nM (PF1092B) and 2.2 x 10(3) nM (PF1092C).

Animals↗
PubMed1996

Cross-sectional sample preparation by focused ion beam: a review of ion-sample interaction.

A focused ion beam (FIB) was applied for cross-sectional sample preparation with both transmission electron microscopes (TEM) and scanning electron microscopes (SEM). The FIB sample preparation has the advantage of high positioning accuracy for cross sections. On the other hand, a broad ion beam (BIB) has been conventionally used for thinning TEM samples. Although both FIB and BIB use energetic ion beams, they are essentially different from each other in many aspects such as beam size, beam current density, incident angle of the beam with respect to cross sections, and beam scanning (i.e., dynamic or static beam). In this study, FIB cross-sectioning is compared with BIB thinning. We review inherent characteristics such as positioning accuracy and uniformity of cross section, radiation damage, and beam heating. Discussion is held from a view-point of ion beam and sample interaction.

Ions↗