Biomedical subjects

T Yoshimoto

Publications and source records attributed to T Yoshimoto.

At least 379 records · Page 21Linked to original sources

PubMed1996

Deletion of CD4+ T cells by mouse mammary tumor virus (FM) superantigen with broad specificity of T cell receptor beta-chain variable region.

We previously identified a superantigen from the exogenous mouse mammary tumor virus carried by FM mice [MMTV (FM)], which can preferentially activate V beta 8.2+ CD4+ T cells by subcutaneous injection. In the present study we investigated the effect of neonatal infection with the virus on the T cell receptor (TCR) beta-chain variable region (V beta) repertoire, T cell immune response, and development of experimental allergic encephalomyelitis (EAE). The infection, surprisingly, resulted in deletion of a large portion of CD4+ T cells including V beta 2+, 6+, 8.1+, 8.3+, and 14+ CD4+ T cells in addition to V beta 8.2+ CD4+ T cells. Nevertheless, the infection marginally affected T cell immune response to various antigens such as ovalbumin (OVA) and alloantigen except the abrogated response to anti-V beta 8.2 antibody-mediated receptor cross-linking. Moreover, the infection exerted a protective effect on the development of EAE in (PL/J x SJL)F1 mice. Thus, MMTV (FM) superantigen has the ability to delete a large portion of CD4+ T cells with broad TCR V beta specificity, including V beta 8.2+ CD4+ T cells, and may have potential as a therapeutic agent against autoimmune diseases.

Animals↗

PubMed1996

Differential response in the release of hydrogen peroxide between astroglial cells and endothelial cells following hypoxia/reoxygenation.

Hydrogen peroxide (H2O2) and lactate dehydrogenase (LDH) released from cultured astroglial cells (AGs) and brain endothelial cells (BECs) were measured following hypoxia/reoxygenation. AGs released H2O2 to the extracellular space from 8 h of hypoxia with the cellular injury indicated by LDH increase. In contrast, BECs released H2O2 at 4 h of hypoxia, prior to the LDH increase. These results suggest that AGs and BECs play different roles in production and metabolism of oxygen free radicals in the blood-brain barrier (BBB), and AGs may protect the BBB disruption from oxidative stress after hypoxia/reoxygenation.

Animals↗

PubMed1996

Expression of heme oxygenase and inducible nitric oxide synthase mRNA in human brain tumors.

Heme oxygenase-1, a key enzyme in heme catabolism, and inducible nitric oxide synthase (iNOS) are responsible for production of carbon monoxide and nitric oxide (NO), respectively. Expression of each enzyme has been shown to be modulated by heme and NO, raising a possibility for the coordinated regulation of the two enzymes. We therefore analyzed the expression levels of both mRNA in humans using brain tumors. Either heme oxygenase-1 or iNOS mRNA was expressed at higher levels in brain tumors compared to the brain tissue, but their expression levels were not apparently correlated. In the brain tumor cell lines, treatment with cytokines increased the expression of iNOS mRNA but not heme oxygenase-1 mRNA, whereas treatment with an NO donor increased the expression of heme oxygenase-1 mRNA but not iNOS mRNA. These results suggest the separate regulation of expression of both enzyme mRNA in humans.

Adult↗

PubMed1996

Alterations of c-fos gene methylation in the processes of aging and tumorigenesis in human liver.

The state of DNA methylation in the c-fos gene was examined in human livers of different ages, cirrhosis and hepatocellular carcinoma. The degree of methylation in the intron 1 to exon 4 region increased with age, whereas all of the 10 cirrhosis samples revealed a decrease in methylation when compared to normal livers of similar ages. The 11 hepatocellular carcinomas showed varied alterations suggesting that the alteration of the c-fos gene methylation is related to aging as well as to early-step of hepatocarcinogenesis.

Adolescent↗

PubMed1996

Crystal structures of the binary and ternary complexes of 7 alpha-hydroxysteroid dehydrogenase from Escherichia coli.

7 alpha-Hydroxysteroid dehydrogenase (7 alpha-HSDH;1 EC 1.1.1.159) is an NAD+-dependent oxidoreductase belonging to the short-chain dehydrogenase/reductase (SDR) 1 family. It catalyzes the dehydrogenation of a hydroxyl group at position 7 of the steroid skeleton of bile acids. The crystal structure of the binary (complexed with NAD+) complex of 7 alpha-HSDH has been solved at 2.3 A resolution by the multiple isomorphous replacement method. The structure of the ternary complex [the enzyme complexed with NADH, 7-oxoglycochenodeoxycholic acid (as a reaction product), and possibly partially glycochenodeoxycholic acid (as a substrate)] has been determined by a difference Fourier method at 1.8 A resolution. The enzyme 7 alpha-HSDH is an alpha/beta doubly wound protein having a Rossmann-fold domain for NAD (H) binding. Upon substrate binding, large conformation changes occur at the substrate binding loop (between the beta F strand and alpha G helix) and the C-terminal segment (residues 250-255). The variable amino acid sequences of the substrate-binding loop appear to be responsible for the wide variety of substrate specificities observed among the enzymes of the SDR family. The crystal structure of the ternary complex of 7 alpha-HSDH, which is the only structure available as the ternary complex among the enzymes of the SDR family, indicates that the highly conserved Tyr159 and Ser146 residues most probably directly interact with the hydroxyl group of the substrates although this observation cannot be definite due to an insufficiently characterized nature of the ternary complex. The strictly conserved Lys163 is hydrogen-bonded to both the 2'- and 3'-hydroxyl groups of the nicotinamide ribose of NAD(H). We propose a new catalytic mechanism possibly common to all the enzymes belonging to the SDR family in which a tyrosine residue (Tyr159) acts as a catalytic base and a serine residue (Ser146) plays a subsidiary role of stabilizing substrate binding.

Amino Acid Sequence↗

PubMed1996

Induction of brain-derived neurotrophic factor (BDNF) and the receptor trk B mRNA following middle cerebral artery occlusion in rat.

Middle cerebral artery (MCA) occlusion in halothane-anesthetized rats induced brain-derived neurotrophic factor (BDNF) and the receptor, trk B mRNA, in brain. In situ hybridization studies showed that BDNF and trk B mRNAs were induced in a widespread region of the ipsilateral cortex outside the infarct at 4 h following MCA occlusion. They were also induced in the bilateral hippocampi which are remote from the ischemic MCA region. These data show that changes in neurotrophic factor and receptor gene expressions can occur in the areas outside the infarct which could survive.

Animals↗

PubMed1996

Gustatory evoked magnetic fields in humans.

Magnetic fields evoked by taste stimuli of the human tongue were measured over the whole head using a helmet-shaped 64 channel magnetoencephalography system in five normal subjects. The stimuli were 10% glucose and 0.3 M NaCl solutions and distilled water. The most prominent peak (N175m) appearing over the bilateral hemispheres had a latency of 150-210 ms. The N175m sources were located using a two-dipole model in a spherical conducting medium based on the individual head dimensions and superimposed on magnetic resonance images. The N175m dipoles due to 10% glucose and 0.3 M NaCl stimuli were located at the operculum and circum-insular areas in both hemispheres, but those due to distilled water could not be located accurately.

Adult↗

PubMed1996

Astroglial cells inhibit the increasing permeability of brain endothelial cell monolayer following hypoxia/reoxygenation.

Blood-brain barrier (BBB) is known to be structured with astroglial cells (AGs) and brain endothelial cells (BECs), and it has been proposed that these cells play different roles in the BBB. We cultivated AGs and BECs from infant rats (2-week-old), and these cells were cultured on the opposing side of collagen membrane to produce a co-culture model of the BBB in vitro. Permeability of the cell layer was evaluated by the electrical resistance through the membrane. To clarify the role of AGs in the BBB disruption following ischemia/reperfusion, electrical resistance of the co-culture model was compared to that of BEC monolayer following hypoxia/reoxygenation. The electrical resistance through BEC monolayer showed 55.5 +/- 15.1 percent reduction at 4 h of hypoxia, and 93.3 +/- 5.4 percent reduction at 8 h of hypoxia (n = 8). However, the co-culture model showed attenuation of the reduction (24.8 +/- 14.2 percent) at 4 h of hypoxia (n = 8, P < 0.01), but not at 8 h of hypoxia (95.3 +/- 5.0 percent). These results indicate that AGs reduce the increasing permeability of the BEC monolayer following short duration of hypoxia/reoxygenation. It is suggested that AGs may have a protective effect to the BBB disruption following ischemia/reperfusion.

Animals↗

PubMed1996

Suicide inactivation of porcine leukocyte 12-lipoxygenase associated with its incorporation of 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid derivative.

Two isozymes of arachidonate 12-lipoxygenase, platelet-type and leukocyte-type, which were distinguished by their substrate specificities and primary structures, were investigated with reference to 'suicide' inactivation. Upon reaction with arachidonic acid the leukocyte-type enzyme was inactivated rapidly during the catalysis, whereas the platelet-type enzyme did not show such a rapid inactivation. The two 12-lipoxygenase isozymes were incubated with various hydroperoxy and hydroxy products from arachidonic acid. (15S)-Hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) was found to be a unique substrate of the leukocyte-type 12-lipoxygenase as follows. (1) 15-HPETE was an active substrate for porcine leukocyte 12-lipoxygenase, and converted anaerobically to a 14,15-epoxy compound (14,15-leukotriene A4). (2) A rapid inactivation of the enzyme was observed within 2 min upon aerobic and anaerobic incubations with 15-HPETE. (3) 15-HPETE was rapidly incorporated into the enzyme in a nearly equimolar amount under both aerobic and anaerobic conditions. (4) Several findings suggested a covalent binding of 15-HPETE or its derivative to the enzyme. (5) Such a rapid and stoichiometric incorporation of 15-HPETE was not observed with the platelet-type 12-lipoxygenase. On the basis of these findings we presumed that 15-HPETE was transformed to 14,15-leukotriene A4, which was covalently bound to the leukocyte-type 12-lipoxygenase leading to the suicide inactivation of the enzyme.

Animals↗

PubMed1996

Deletion of peripheral V beta 14+ T cells by Mtv-2-encoded viral superantigen preceded by blastogenesis and DNA synthesis but not by specific expansion.

Exogenous and endogenous mouse mammary tumor viruses encode superantigen (SAG) in the 3' long terminal repeat. We investigated the immune response of lymph node cells to the viral SAG encoded by endogenous Mtv-2 (vSAG-2) by i.v. injecting splenocytes from Mtv-2+ mice into Mtv-2- congenic counterparts. vSAG-2 stimulation induced blastogenesis and DNA synthesis but not subsequent specific expansion of V beta 14+CD4+ or CD8+ T lymphocytes. Instead, immediate deletion of these T cells progressed after vSAG-2 stimulation, and it was more prominent in both rapidity and degree in CD4+ than CD8+ population and in I-E+ than I-E- mice. vSAG-7 stimulation caused specific expansion of V beta 6+ T cells prior to their deletion as reported. vSAG-7 but not vSAG-2 induced IL-2R expression in the specific T cells. Moreover, the percentage of 5-bromo-2'-deoxyuridine-incorporated cells was about twofold higher in Vbeta6+ T cells stimulated with vSAG-7 than in V beta 14+ T cells stimulated with vSAG-2. The results suggest that vSAG-2 may be a weak mitogen against specific T cells and that T cells weakly activated by SAG may die without preceding expansion. In addition, proliferation of lymphocytes, especially B cells, and enhancement of the expression of IL-2, IL-4, and IFN-gamma messenger RNA were observed. Thus, V beta 14+ T cells stimulated with vSAG-2 were activated to produce cytokines and depleted quickly.

Animals↗

PubMed1996

Molecular cloning and characterization of murine IL-12 genes.

IL-12 is a heterodimeric cytokine composed of two covalently linked chains, p40 and p35. p40 expression appears to be restricted to monocytes/macrophages and B cells and is highly regulated, while p35 is more ubiquitously and constitutively expressed. To investigate the mechanism involved in the regulation of IL-12 expression, we molecularly cloned and characterized the murine p40 and p35 genes. The p40 gene spans over 14 kb, consists of eight exons and seven introns, and was shown to be localized on chromosome 11A5-B2 by fluorescence in situ hybridization. A single major transcription initiation site was detected by primer extension analysis, and a TATA box was found at approximately 30 bp upstream from the transcription initiation site. The 5' flanking region preceding the transcription initiation site induced the enhanced expression of a promoterless reporter gene after LPS stimulation when transfected into a macrophage-like cell line. In contrast, the p35 gene spans over 8 kb and consists of seven exons and six introns on chromosome 6C, and multiple transcription initiation sites were detected. The 5' flanking region lacks canonical TATA and CAAT boxes at the appropriate position, but, instead, contains GC-rich sequences and constitutively mediated promoter activity when placed upstream of a promoterless reporter gene and transfected into a B cell lymphoma cell line. Thus, the characteristics of promoter regions of p40 and p35 genes are quite different, and this would account for the different regulations of p40 and p35 expression.

Amino Acid Sequence↗

PubMed1996

Angiotensin converting enzyme inhibitor normalizes vascular natriuretic peptide type A receptor gene expression via bradykinin-dependent mechanism in hypertensive rats.

We previously demonstrated that angiotensin converting enzyme (ACE) inhibitor normalizes the up-regulated gene expression of vascular natriuretic peptide type A (NP-A) receptor in hypertensive rats. To elucidate the mechanism, we examined the effect of angiotensin II receptor (AT1) antagonist (TCV-116) and bradykinin receptor (B2) antagonist (Hoe 140) on the NP-A receptor mRNA level in the aorta of genetically hypertensive rats (SHR-SP/Izm) using ribonuclease protection assay. The effect of ACE inhibitor on the NP-A receptor mRNA level was completely abolished by a concomitant administration of Hoe 140, while TCV-116 did not show any significant effect on the NP-A receptor mRNA level. These results suggest that bradykinin plays an important role in the regulation of the vascular NP-A receptor gene expression.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1996

Crystallization and preliminary X-ray crystallographic studies of 7alpha-hydroxysteroid dehydrogenase from Escherichia coli.

Crystals of 7alpha-hydroxysteroid dehydrogenase from E. coli, which is a tetramer in its active form, have been obtained by a hanging-drop vapor-diffusion method in the presence of the coenzyme NAD(+). Crystals as large as 0.25 x 0.25 x 0.75 mm could be grown within a month at pH 8.5 with polyethylene glycol as precipitating agent. Preliminary X-ray crystallographic analysis revealed that they belong to one of the enantiomorphic space groups P4(1)2(1)2 or P4(3)2(1)2 with dimensions a = b = 81.66 and c = 214.6 A, having two subunits in an asymmetric unit. The crystals diffract to at least 2.3 A resolution.

Journal Article↗

PubMed1996

Alteration of c-fos gene methylation in human gliomas.

In an attempt to find a common DNA alteration occurring in human glioma, we examined DNA methylation in 34 gliomas of various pathological grades and compared them with those in normal cerebral subcortex DNA. The total methylated cytosine levels in the genome did not differ appreciably between the tumors and the normal tissues; however, the degree of DNA methylation in several proto-oncogenes and suppressor oncogenes showed some alterations. Among them, the c-fos gene demonstrated deviation from that of normal tissues in all cases examined, suggesting that the alteration of c-fos gene methylation plays a role in the early steps of human glioma development.

Adult↗

PubMed1996

Management of pilocytic astrocytoma.

Pilocytic astrocytoma, when totally resected, has a favorable outcome compared to other astrocytomas. However, when residual tumor remains, the prognosis is less satisfactory. Our study addressed the issues of prognosis in cases of residual tumor and the effect of post-surgical radiation therapy on tumor recurrence. We analyzed 41 cases of pilocytic astrocytoma which were diagnosed by histologic examination. Twenty-six patients were 15 years old or younger, and 15 patients were 16 years old or older. An analysis of the relationship between age and tumor location revealed a cerebellar predominance in both age groups; however, there were more brain stem and basal ganglia tumors among adults. Overall prognosis was favorable, with a 2-year survival rate of 97.6%, 94.6% at 5 years, and 94.6% at 10 years. Children had a better prognosis than adults due to more favorable tumor location. Gross total resection resulted in the best prognosis, i.e., no recurrence during a 10-year follow-up period. Radiation treatment after surgery suppressed residual tumor. We concluded that the best treatment for pilocytic astrocytoma is: 1) total resection, if possible, followed by 2) irradiation of any residual tumor to suppress recurrence.

Adolescent↗

PubMed1996

Evaluation of regional cerebral blood flow using single photon emission tomography for the selection of patients for local fibrinolytic therapy of acute cerebral embolism.

To clarify the indications for local fibrinolytic therapy for acute cerebral embolism, correlation among initial regional cerebral blood flow (rCBF) abnormalities, recanalization timing, and computed tomographic scan (CT) findings two days later were evaluated in 17 cases. All cases included had embolic occlusion of middle cerebral or internal carotid arteries which showed no abnormal findings on initial CT corresponding to the acute events but did show abnormal CBF reduction on initial single photon emission computed tomography (SPECT). Relative rCBF was evaluated as the percentage radioisotope counts in the region of interest (ROI) of the affected side against the corresponding ROI in the unaffected contralateral side. Within 6 hours from onset, there was a tendency towards reversed time dependent tolerance of cortical infarction with residual relative rCBF. Hemorrhagic transformation was observed in one case whose relative rCBF was 35% or less. In 10 patients whose occluded arteries were not recanalized within 6 hours, cortical areas with residual relative rCBF of 70% or more did not develop infarction. In conclusions, a pre-therapeutic rCBF study using SPECT is considered to be mandatory: cases with moderate ischemia involving the cortex with residual relative rCBF of between 35% and 70% may be good candidates for local fibrinolytic therapy.

Aged↗

PubMed1996

Transcingulate approach to lateral ventricle tumors. Technical case report.

Surgical experience with treatment of two lateral ventricle tumors using the anterior transcingulate approach demonstrate that this route provides an excellent approach to tumors attached to the lateral wall of the anterior ventricle, without causing gross neurologic deficits. This approach deserves attention as an alternative to the transcallosal approach in selected patients.

Adolescent↗

PubMed1996

Types of unruptured cerebral aneurysms reviewed from operation video-recordings.

To estimate the proportion of unruptured cerebral aneurysms with thin-walled sac, we have analyzed the operative findings of 78 incidental cerebral aneurysms found in 51 consecutive surgical cases by reviewing of intra-operative videotape recordings. Among 78 unruptured aneurysms, 23 (30%) were evaluated as thick-walled aneurysms (Type A), 39 (50%) with partially thin-walled sac (Type B) and 16 (20%) with entirely thin wall sacs (Type C). The mean size of Type A aneurysms was 10.4 mm (ranging from 3 to 22 mm), in Type B it was 9.8 mm (ranging 4 to 25 mm) and in Type C it was 4.4 mm (between 2-12 mm). Approximately two-thirds of Type C aneurysms were 4 mm in size or smaller, and Type C aneurysms were significantly smaller than Type A aneurysms. In summary, this preliminary study has provided two original data. 1) About 70% of incidental unruptured aneurysms have a partially or entirely thin-walled sac. 2) Many of the small aneurysms have an entirely thin sac. Assuming that thin-walled aneurysms are at a high risk of subsequent rupture, the surgical intervention for incidental unruptured aneurysms may be recommended irrespective of their size if the surgical risk is considered low.

Adult↗