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Biomedical subjects

T Ono

Publications and source records attributed to T Ono.

At least 253 records · Page 14Linked to original sources
PubMed1999

Identification of a bile acid-responsive element in the human ileal bile acid-binding protein gene. Involvement of the farnesoid X receptor/9-cis-retinoic acid receptor heterodimer.

Intestinal bile acid-binding protein (I-BABP) is a cytosolic protein that binds bile acids (BAs) with a high affinity. In the small intestine, its expression is restricted to the ileum where it is involved in the enterohepatic circulation of BAs. Using the human enterocyte-like Caco-2 cell line, we have recently shown that BAs increased I-BABP gene expression. To determine whether this regulation occurs in vivo, the effect of BA depletion or supplementation was studied in mice. A dramatic drop in I-BABP mRNA levels was observed in mice treated with the BA-binding resin cholestyramine, whereas an increase was found in animals fed with taurocholic acid. BAs are physiological ligands for the nuclear farnesoid X receptor (FXR). Both FXR and I-BABP are co-expressed along the small intestine and in Caco-2 cells. To determine the role of FXR in the regulation of I-BABP expression, the promoter of the human I-BABP gene was cloned. In Caco-2 cells, cotransfection of FXR and RXRalpha is required to obtain the full transactivation of the I-BABP promoter by BAs. Deletion and mutation analyses demonstrate that the FXR/RXRalpha heterodimer activates transcription through an inverted repeat bile acid responsive element located in position -160/-148 of the human I-BABP promoter. In conclusion, we show that FXR is a physiological BA sensor that is likely to play an essential role in BA homeostasis through the regulation of genes involved in their enterohepatic circulation.

Animals↗
PubMed1999

Age-dependent alterations in mRNA level and promoter methylation of collagen alpha1(I) gene in human periodontal ligament.

In an attempt to understand the molecular mechanisms of age-dependent degenerative alteration in human periodontal tissues, we examined mRNA level and DNA methylation of collagen alpha1(I) gene. Using healthy periodontal ligament tissues from humans aged 9-76 years, we found that the collagen alpha1(I) mRNA level decreased almost linearly with age. It was observed in both Northern blot and dot blot hybridization. Examination of DNA methylation in the collagen alpha1(I) gene promoter region by its susceptibility to methylation-sensitive restriction enzyme followed by Southern blot analysis showed age-dependent increase of DNA methylation at -1705 and -80 positions located upstream of the gene. The data suggest the possible importance of alterations in collagen alpha1(I) gene expression and its DNA methylation in promoter region in age-dependent degeneration of periodontal ligament.

5' Untranslated Regions↗
PubMed1999

Cloning and characterization of novel mouse and human secretory phospholipase A(2)s.

Mammalian secretory phospholipase A(2)s (sPLA(2)s) are classified into several groups according to molecular structure and the localization of intramolecular disulfide bridges. Among them, group IIA sPLA(2) has been thought to be one of the key enzymes in the pathogenesis of inflammatory diseases owing to its augmented expression under various inflammatory conditions. However, in a number of inbred mouse strains, the group IIA sPLA(2) gene is naturally disrupted by a frameshift mutation. Here, we report the cloning of a cDNA encoding a novel sPLA(2) expressed in the spleen of group IIA sPLA(2)-deficient mouse. We also cloned its human homolog and mapped its gene location on chromosome 1p36.12 near the loci of group IIA and V sPLA(2) genes. The human mature sPLA(2) protein consists of 125 amino acids (M(r) = 14,500) preceded by a 20-residue prepeptide and is most similar to group IIA sPLA(2) with respect to the number and positions of cysteine residues as well as overall identity (48%). Based on these structural properties, the novel sPLA(2) should be categorized into group II, called group IID to follow the already identified IIA to IIC sPLA(2)s. When the cDNA was expressed in COS-7 cells, PLA(2) activity preferentially accumulated in the culture medium. It is maximally active at neutral to alkaline pH and with 2 mM Ca(2+). In assays with individual substrates, L-alpha-1-palmitoyl-2-linoleoyl phosphatidylethanolamine was more efficiently hydrolyzed than the other phospholipids examined. An RNA blot hybridized with the cDNA exhibited two transcripts (2.0 and 1.0 kb) in human spleen, thymus, and colon. The expression of a novel sPLA(2) mRNA was elevated in the thymus after treatment with endotoxin in rats as well as in group IIA sPLA(2)-deficient mice, suggesting its functional role in the progression of the inflammatory process.

Amino Acid Sequence↗
PubMed1999

Protocadherin 2C: a new member of the protocadherin 2 subfamily expressed in a redundant manner with OL-protocadherin in the developing brain.

Using cDNA of human protocadherin 2A (pc2A; originally known as protocadherin 2) as a probe, we cloned a new member of the protocadherin 2 subfamily from mouse brain cDNA libraries and named it protocadherin 2C (pc2C). It was similar to pc2A throughout its entire coding region, and its C-terminal region was highly conserved. The locus of the pc2C gene was on the mouse chromosome 18C where the pc2A gene is located, suggesting that genes of the pc2 subfamily form a gene cluster. The expression of pc2C was restricted to the nervous system, and the expression started in the embryonic stage and increased up to the adult stage. The expression pattern was quite similar to that of OL-protocadherin, a distinct class of protocadherin, although the timing and relative strength of expression were different. These results suggest that pc2C may be involved in neural development along with other classes of protocadherins.

Amino Acid Sequence↗
PubMed1999

Single amino acid replacements in an antigenic peptide are sufficient to alter the TCR V beta repertoire of the responding CD8+ cytotoxic lymphocyte population.

Cytotoxic CD8+ T lymphocytes are activated upon the engagement of their Ag-specific receptors by MHC class I molecules loaded with peptides 8-11 amino acids long. T cell responses triggered by certain antigenic peptides are restricted to a limited number of TCR V beta elements. The precise role of the peptide in causing this restricted TCR V beta expansion in vivo remains unclear. To address this issue, we immunized C57BL/6 mice with the immunodominant peptide of the vesicular stomatitis virus (VSV) and several peptide variants carrying single substitutions at TCR-contact residues. We observed the expansion of a limited set of TCR V beta elements responding to each peptide variant. To focus our analysis solely on the TCR beta-chain, we created a transgenic mouse expressing exclusively the TCR alpha-chain from a VSV peptide-specific CD8+ T cell clone. These mice showed an even more restricted TCR V beta usage consequent to peptide immunization. However, in both C57BL/6 and TCR alpha transgenic mice, single amino acid replacements in TCR-contact residues of the VSV peptide could alter the TCR V beta usage of the responding CD8+ T lymphocytes. These results provide in vivo evidence for an interaction between the antigenic peptide and the germline-encoded complementarity-determining region-beta loops that can influence the selection of the responding TCR repertoire. Furthermore, only replacements at residues near the C terminus of the peptide were able to alter the TCR V beta usage, which is consistent with the notion that the TCR beta-chain interacts in vivo preferentially with this region of the MHC/peptide complex.

Amino Acid Substitution↗
PubMed1999

Effects of T-588, a newly synthesized cognitive enhancer, on hippocampal CA1 neurons in rat brain tissue slices.

The effects of a newly synthesized cognitive enhancer, (-)-R-alpha-[[2-(diethylamino) ethoxy] methyl] benzo [b] thiophene-5-methanol hydrochloride (T-588), on the membrane properties of hippocampal CA1 neurons were investigated in a rat brain slice preparation. T-588 produced a slow and long-lasting depolarization of CA1 neurons with an increase in membrane resistance; this action showed close similarity to that of acetylcholine (ACh). However, the action of T-588 was not affected by atropine, tetrodotoxin or DL-2-amino-5-phosphonovalerate, while the action of ACh was blocked by atropine. The estimated reversal potential of this T-588 effect was near -90 mV which is the reversal potential of potassium ions in CA1 neurons. In the whole-cell voltage-clamp study, T-588 produced a reversible block of the outward potassium current in CA1 neurons. T-588 did not block the afterhyperpolarization evoked by an intracellular current injection, while ACh suppressed it. These results suggest that T-588 has a direct effect on CA1 neurons independent of its cholinergic activity, resulting from blockade of a conductance carried predominantly by potassium ions.

2-Amino-5-phosphonovalerate↗
PubMed1999

No requirement of P2X1 purinoceptors for platelet aggregation.

ADP produces a series of responses in rabbit platelets such as shape changes, aggregation and intracellular Ca2+ mobilization. In human platelets, the P2X1 receptor mediates a rapid increase in intracellular Ca2+ concentration ([Ca2+]i) upon stimulation with ADP. We investigated whether this phenomenon is also present in rabbit platelets. We found that the P2X1 receptor-mediated response was absent because there was (1) no elevation of [Ca2+]i in response to alpha,beta-methylene-ATP, a selective P2X1 receptor agonist, in fura-2-loaded platelets; (2) no change in the ADP-induced [Ca2+]i increase and platelet aggregation after P2X1 receptor desensitization with alpha,beta-methylene-ATP; (3) complete inhibition of the ADP-induced [Ca2+]i elevation by the P2Y1 receptor specific antagonist, A3'P5'PS, with a similar ID50 value both in the presence and absence of external Ca2+. These results indicate that ADP-induced [Ca2+]i elevation is mainly mediated by P2Y1 receptors in rabbit platelets. We conclude that the P2X1 receptor does not play a significant role in the ADP-induced platelet shape changes and aggregation.

Adenosine Diphosphate↗
PubMed1999

Suppression of murine endotoxic shock by sPLA2 inhibitor, indoxam, through group IIA sPLA2-independent mechanisms.

Endotoxic shock is a systemic inflammatory process, involving a variety of proinflammatory mediators. Two types of secretory phospholipase A2 (sPLA2) have been implicated in this process. Group IB sPLA2 (PLA2-IB) binds to the PLA2 receptor (PLA2R), and PLA2R-deficient mice exhibit resistance to endotoxin-induced lethality with reduced plasma levels of proinflammatory cytokines, such as TNF-alpha. Group IIA sPLA2 (PLA2-IIA) is found in many tissues and cell types, and local and systemic levels are elevated under numerous inflammatory conditions including sepsis. In this study, we investigated the effect of a specific sPLA2 inhibitor, indoxam, on murine endotoxic shock. Indoxam suppressed the elevation of plasma TNF-alpha with a similar potency in PLA2-IIA-expressing and PLA2-IIA-deficient mice after LPS challenge. In PLA2-IIA-deficient mice, indoxam also suppressed the elevation of plasma IL-1beta, IL-6 and NO, and prolonged survival after LPS challenge. Indoxam was found to block the PLA2-IB binding to murine PLA2R with a high potency (Ki=30 nM). The inhibitory effects of indoxam on the LPS-induced elevation of plasma TNF-alpha levels could not be observed in mice deficient in PLA2R. These findings suggest that indoxam blocks the production of proinflammatory cytokines during endotoxemia through PLA2-IIA-independent mechanisms, possibly via blockade of the PLA2R function.

Animals↗
PubMed1999

Propagation of a magnetic domain wall in a submicrometer magnetic wire

The motion of a magnetic domain wall in a submicrometer magnetic wire was detected by use of the giant magnetoresistance effect. Magnetization reversal in a submicrometer magnetic wire takes place by the propagation of a magnetic domain wall, which can be treated as a "particle." The propagation velocity of the magnetic domain wall was determined as a function of the applied magnetic field.

Journal Article↗
PubMed1999

Spatial- and task-dependent neuronal responses during real and virtual translocation in the monkey hippocampal formation.

Neuropsychological data in humans demonstrated a pivotal role of the medial temporal lobe, including the hippocampal formation (HF) and the parahippocampal gyrus (PH), in allocentric (environment-centered) spatial learning and memory. In the present study, the functional significance of the monkey HF and PH neurons in allocentric spatial processing was analyzed during performance of the spatial tasks. In the tasks, the monkey either freely moved to one of four reward areas in the experimental field by driving a cab that the monkey rode (real translocation task) or freely moved a pointer to one of four reward areas on the monitor (virtual translocation task) by manipulating a joystick. Of 389 neurons recorded from the monkey HF and PH, 166 had place fields that displayed increased activity in a specific area in the experimental field and/or on the monitor (location-differential neurons). More HF and PH neurons responded in the real translocation task. These neurons had low mean spontaneous firing rates (0.96 spikes/sec), similar to those of rodent HF place cells. The remaining nonresponsive neurons had significantly higher mean firing rates (8. 39 spikes/sec), similar to interneurons or theta cells in the rodent HF. Furthermore, most location-differential neurons showed different responses in different tasks. These results suggest that the HF and PH are crucial in allocentric information processing and, moreover, that the HF can encode different reference frames that are context or task-dependent. This may be the neural basis of episodic memory.

Animals↗
PubMed1999

Isolation of MHC class I-restricted tumor antigen peptide and its precursors associated with heat shock proteins hsp70, hsp90, and gp96.

We have previously demonstrated that vaccination with heat shock proteins hsp70, hsp90, and gp96 elicits specific immunity against the tumor from which the hsps were purified. Although the association of tumor Ag peptides with these hsps have been suggested, the identification of the peptides or their precursors stripped from the hsps remained to be resolved. We show in this report that an Ld-restricted cytotoxic T lymphocyte epitope of a mouse leukemia RLmale symbol1 and its precursors are associated with the chaperones hsp90 and hsp70 in the cytosol and gp96 in the lumen of the endoplasmic reticulum. Hsp70 was associated with only final sized octamer, while hsp90 was found to associate with the octamer and two distinct precursor peptides. The gp96 was associated with the octamer and one of the two precursors. Thus, each of the hsps bound a distinct set of peptides. Our results have demonstrated for the first time that the hsps associate not only with final sized tumor Ag peptide but also with its precursors. The implication of this evidence is also discussed in terms of the roles of hsps in MHC class I Ag processing/presentation.

Animals↗
PubMed1999

Molecular cloning and chromosomal mapping of mouse intronless myc gene acting as a potent apoptosis inducer.

Our previous findings suggest that the activation of the rat intronless myc gene provides a selective advantage in tumor suppression through apoptosis induction. In the present study, to examine whether intronless myc gene acting as an apoptosis inducer is evolutionarily conserved in mammalian cells, we isolated the mouse intronless myc gene and characterized it. A sequence analysis demonstrated that mouse intronless myc gene, ms-myc, has a linearly opened translatable frame consisting of 1293bp with 90% homology with that of rat s-myc. The chromosomal locus of ms-myc was identified on chromosome 19B by a fluorescent in situ hybridization (FISH) analysis. Gene transfection experiments showed that the transient overexpression of ms-Myc with transactivation activity effectively induces cell death in a wild-type p53-independent manner. In addition, cells stably expressing transfected ms-myc became more susceptible to apoptosis induced by genotoxic stress such as UV-irradiation and hydrogen peroxide compared with untransfected control cells. These observations suggest that the rodents commonly contain an s-myc-type of intronless myc gene with apoptosis-inducing activity.

Amino Acid Sequence↗
PubMed1999

Two forms of Vibrio cholerae O1 El Tor hemolysin derived from identical precursor protein.

Vibrio cholerae O1 grown in heart infusion broth produces two forms of El Tor hemolysin (ETH) monomers of 65 and 50 kDa. These monomers form several different sizes of mixed oligomers ranging from 180 to 280 kDa in the liposomal membranes. We found that the N-terminal amino acid sequences, NH2-Trp-Pro-Ala-Pro-Ala-Asn-Ser-Glu, of both the 65- and 50-kDa toxins were identical. We assumed, therefore, that the 65- and 50-kDa toxins were derivatives of the identical precursor protein and the 50-kDa protein was a truncated derivative of 65-kDa ETH. To substantiate this assumption, we treated the 260-kDa oligomer with trypsin and obtained a 190-kDa oligomer. This 190-kDa oligomer consisted of only the 50-kDa subunits. Both 260- and 190-kDa oligomers formed ion channels indistinguishable from each other in planar lipid bilayers. These results suggest that the essential part of the ETH in forming the membrane-damaging aggregate is a 50-kDa protein.

Bacterial Proteins↗
PubMed1999

Sunlight mutagenesis: changes in mutational specificity during the irradiation of phage M13mp2.

We reported previously that the mutations in phage M13mp2, a single-stranded DNA phage, induced by sunlight exposure are predominated by G-to-C transversions. We have now made an unexpected observation that an exposure to sunlight for a short period of time results in induction mainly of C-to-T transitions while a longer exposure results in the induction of G-to-C transversions. This peculiar phenomenon suggests that DNA damage formed by initial sunlight exposure can be transformed during an elongated exposure. 7, 8-Dihydro-8-oxoguanine (8-oxoG) in DNA might be involved in the shift of the mutational specificity, as 8-oxoG was formed in the phage DNA upon the sunlight exposure. We also compared the mutagenic activity of UVB irradiation with that of sunlight exposure. The results demonstrate that the genotoxic properties of sunlight and UVB in phage M13mp2 mutagenesis are different. The shift in the mutational specificity associated with the dose of the sunlight may call for general cautions in the studies of agent-induced mutagenesis.

Bacteriophage M13↗
PubMed1999

Comparison of medial and lateral septal neuron activity during performance of spatial tasks in rats.

The septal complex, having close and reciprocal connections with the hippocampus, is known to play an important role in learning and memory. Anatomically, the septal complex is divided into the medial and lateral areas (MS and LS). In the present study, in order to elucidate functional differences between the MS and LS, we recorded single unit activity in the MS or LS and electroencephalogram (EEG) in the hippocampus simultaneously while the rats performed the following 2 spatial tasks in an open-field chamber. In task 1, the rat received rewarding intracranial electrical stimulation (ICES) when it entered in a reward place that was set randomly in the open field in each trial. In task 2, the rat received rewarding ICES when it alternately visited two fixed reward places in the open field. Unit activity was analyzed in relation to the pattern of hippocampal EEG, and rat's location, locomotion direction and locomotion speed in the spatial tasks. A total of 47 neurons were recorded in the septal complex (MS, 19; LS, 28). The majority of neurons with activity correlated with hippocampal EEG were found in the MS (14/19). All of the neurons with place-related activity (an increase in unit activity when the rat was in a specific location in the open field) were found in the LS (n = 15). The majority of neurons with direction-related activity were found in the LS (18/23). Twenty-one neurons displayed speed-related activity (MS, 9; LS, 12). The present results indicate that (1) the MS is directly involved in the formation and control of hippocampal EEG patterns, and (2) the LS is important for the processing and integration of spatial information in the environment.

Animals↗
PubMed1999

Active spatial information processing in the septo-hippocampal system.

The hippocampal formation (HF) receives the final outputs from all association cortices, and processes and integrates this diverse information. Our neurophysiological data in rats and monkeys suggest active selection of relevant sensory information in the HF. In an open field, rat HF neurons strengthened their sensitivity to more relevant variables among various movement variables such as movement speed, direction, and turning angle based on navigation contexts. The HF place-related activity in the monkey, which rode on a movable cab, became obscure in passive translocation of a monkey by an experimenter. This suggests that the animal actively senses the environment surrounding it during spatial navigation, and that spatial correlates of HF neurons depend on this active sensing. In the monkey septal nuclei that receive hippocampal outputs, some neurons were differential to specific views from 4 specific locations in an experimental room (place-differential responses). Multidimensional scaling (MDS) analysis of place-differential responses indicated that the 4 locations represented in a 2-dimensional virtual space at relative positions were similar to those in the real experimental room. This might be a neurophysiological basis of a cognitive map and path finding. These results are consistent with recent human PET studies that indicated HF involvement in recalling routes and landmarks. Thus, a cognitive mapping system represented in the HF plays a pivotal role in active computation for path finding.

Animals↗
PubMed1999

Increased serum levels of 5-S-cysteinyldopa and intercellular adhesion molecule-1 in a patient with a uterine amelanotic metastasis from a primary vaginal malignant melanoma.

A 75-year-old Japanese woman, who had an enlarged uterus and two nodules on the anterior vaginal wall, underwent wide excision of the anterior vaginal wall, bilateral inguinal lymphadenectomy, modified radical hysterectomy, and pelvic lymph node dissection. Her serum level of 5-S-cysteinyldopa (5-S-CD) was elevated, but her serum intercellular adhesion molecule-1 (ICAM-1) level was within normal limits. Histologic examination of the vaginal wall revealed atypical melanocytes at the dermoepidermal junction and numerous melanin-containing granules in the cytoplasm of the tumor cells. The tumor in the uterus consisted of sheets of anaplastic cells with evidence of diminished melanization. Five months after her initial presentation, she developed a recurrence and expired. The serum level of ICAM-1 was beyond the normal limit at the time of recurrence. Both the serum 5-S-CD and the ICAM-1 levels became elevated after recurrence and appeared to be correlated with disease progression.

Aged↗