Biomedical subjects

M Taira

Publications and source records attributed to M Taira.

At least 37 records · Page 2Linked to original sources

PubMed2001

A Xenopus homolog of a human p53-activated gene, PA26, is specifically expressed in the notochord.

The LIM class homeodomain protein Xlim-1 is specifically expressed in the organizer and later in the notochord in Xenopus. By seeking genes which are activated by Xlim-1 in animal caps, we isolated a gene which encodes a protein highly homologous to human PA26-T2, a p53-inducible nuclear factor, which we refer to as XPA26. Northern blot analysis showed that maternal transcripts of XPA26 are detected at cleavage stages and reduced during gastrulation. Whole-mount in situ hybridization showed that zygotic transcripts of XPA26 were initially detected in the anterior portion of developing notochord at neurula stages, and later in the entire notochord except its posterior region at tailbud stages. Thus the zygotic expression of XPA26 was detected exclusively in the notochord.

Amino Acid Sequence↗

PubMed2001

Early patterning of the prospective midbrain-hindbrain boundary by the HES-related gene XHR1 in Xenopus embryos.

The molecular mechanisms that govern early patterning of anterior neuroectoderm (ANE) for the prospective brain region in vertebrates are largely unknown. Screening a cDNA library of Xenopus ANE led to the isolation of a Hairy and Enhancer of split- (HES)-related transcriptional repressor gene, Xenopus HES-related 1 (XHR1). XHR1 is specifically expressed in the midbrain-hindbrain boundary (MHB) region at the tailbud stage. The localized expression of XHR1 was detected as early as the early gastrula stage in the presumptive MHB region, an area just anterior to the involuting dorsal mesoderm that is demarcated by the expression of the gene Xbra. Expression of XHR1 was detected much earlier than that of other known MHB genes, XPax-2 and En-2, and also before the formation of the expression boundary between Xotx2 and Xgbx-2, suggesting that the early patterning of the presumptive MHB is independent of Xotx2 and Xgbx-2. Instead, the location of XHR1 expression appears to be determined in relation to the Xbra expression domain, since reduced or ectopic expression of Xbra altered the XHR1 expression domain according to the location of Xbra expression. In functional assays using mRNA injection, overexpression of dominant-negative forms of XHR1 in the MHB region led to marked reduction of XPax-2 and En-2 expression, and this phenotype was rescued by coexpression of wild-type XHR1. Furthermore, ectopically expressed wild-type XHR1 near the MHB region enhanced En-2 expression only in the MHB region but not in the region outside the MHB. These data suggest that XHR1 is required, but not sufficient by itself, to initiate MHB marker gene expression. Based on these data, we propose that XHR1 demarcates the prospective MHB region in the neuroectoderm in Xenopus early gastrulae.

Amino Acid Sequence↗

PubMed2001

Studies on cytotoxic effect of nickel ions on three cultured fibroblasts.

Cytotoxicity of Ni ions on three fibroblasts such as L929, Balb/3T3 clone A31 and MC3T3-E1 were examined by cell count (CC) and Neutral Red assay (NR). Three cells were incubated for 6 days in 1 ml DME medium containing Ni ions which ranged from 0 to 2 mM/l. The results clarified that Ni ions had dose-dependent cytotoxicity. L929 possessed the largest TC50 values (the amount of Ni ion that caused 50% cell death or 50% cell viability) of 0.12 mM/l (CC) and 0.32 mM/l (NR), and Balb/3T3 clone A31 had the least values of 0.05 mM/l (CC) and 0.09 mM/l (NR), whilst MC3T3-E1 had the intermediate values of 0.08 mM/l (CC) and 0.15 mM/l (NR). The dissolution of Ni ions from Ni-containing metallic restorations must be lower than these concentration levels so that body tissues might not be severely damaged.

Journal Article↗

PubMed2001

Studies on polishing of Ti and Ag-Pd-Cu-Au alloy with five dental abrasives.

Titanium (Ti) and Ag-Pd-Cu-Au alloy were examined for their polishing behaviour by conducting manually controlled polishing tests using five dental abrasives [carborundum point (CR) and silicone points (R1 and R2)] driven by a high torque micromotor with rotational speeds ranging from 2000 to 15 000 r.p.m. Polishing of Ti resulted in less volume of removal upon polishing, a rougher surface and larger loss of abrasives, compared with polishing of Ag-Pd-Cu-Au alloy. Polishing of Ti with a rotational speed of 15 000 r.p.m. led to the largest volume of removal upon polishing, whilst that of 10 000 r.p.m. produced the optimal volume for Ag-Pd-Cu-Au alloy. It was concluded that Ti was much more difficult to polish, requiring special care (e.g. frequent exchange of abrasives). Development of new abrasives for polishing Ti is required.

Carbon Compounds, Inorganic↗

PubMed2001

Integration of perspective and disparity cues in surface-orientation-selective neurons of area CIP.

We investigated the effects of linear perspective and binocular disparity, as monocular and binocular depth cues, respectively, on the response of surface-orientation-selective (SOS) neurons in the caudal part of the lateral bank of the intraparietal sulcus (area CIP). During the single-unit recording, monkeys were required to perform the delayed-matching-to-sample (successive same/different discrimination) of discriminating surface orientation in stereoscopic computer graphics. Of 211 visually responsive neurons, 66 were intensively tested using the solid-figure stereogram (SFS) of a square plate with both disparity and perspective cues (D+P condition), and 62 of these were identified as SOS neurons for responding selectively to the orientation of stimuli. All these neurons were further tested using a solid figure with perspective cues alone (P-only condition), and 58% (36/62) of these showed selective response to the orientation of the stimuli. Of the 62 SOS neurons, 35 neurons were also tested using SFS with disparity cues alone (D-only condition) in addition to the D+P and P-only conditions. We classified these 35 neurons into four groups by comparing the response selectivity under the P-only and D-only conditions. More than one-half of these (19/35) were sensitive to both perspective and disparity cues (DP neurons), and nearly one-third (11/35) of these were sensitive to disparity cues alone (D neurons), but a few (2/35) were sensitive to perspective cues alone (P neurons). The remaining (3/35) neurons exhibited orientation selectivity only when both cues were present. In DP neurons, the preferred orientation under the D+P condition was correlated to those under the D-only and P-only conditions, and the response magnitude under the D+P condition was greater than those under the D-only and P-only conditions, suggesting the integration of both cues for the perception of surface orientation. However, in these neurons, the orientation tuning sharpness under the D+P and D-only conditions was higher than that under the P-only condition, suggesting the dominance of disparity cues. After the single-unit recording experiments, muscimol was microinjected into the recording site to temporarily inactivate its function. In all three effective cases out of six microinjection experiments, discrimination of a three-dimensional (3D) surface orientation was impaired when disparity cues alone were present. In only one effective case, when a relatively large amount of muscimol was microinjected, discrimination of a 3D surface orientation was impaired even when both disparity and perspective cues were present. These results suggest that linear perspective is an important cue for representations of a 3D surface of SOS neurons in area CIP, although it is less effective than binocular disparity, and that both of these depth cues may be integrated in area CIP for the perception of surface orientation in depth.

Algorithms↗

PubMed2001

A study of Xlim1 function in the Spemann-Mangold organizer.

The Spemann-Mangold organizer is required in amphibian embryos to coordinate cell fate specification, differentiation of dorsal cell types and morphogenetic movements at early stages of development. A great number of genes are specifically expressed within the organizer, most of them encoding secreted proteins and transcription factors. The challenge is now to uncover genetic cascades and networks of interactions between these genes, in order to understand how the organizer functions. The task is immense and requires loss-of-function approaches to test the requirement for a given factor in a specific process. For transcription factors, it is possible to generate inhibitory molecules by fusing the DNA binding region to a repressor or activator domain, which should in principle antagonize the activity of the endogenous protein at the level of the DNA targets. We used this strategy to design activated and inhibitory forms of the LIM homeodomain transcription factor Lim1, which is encoded by an organizer gene involved in head development, as revealed by analyses of knockout mice. We found that Lim1 is a transcriptional activator, and can trigger dorso-anterior development upon ventral expression of hyperactive forms, in which Ldb1 is fused to Lim1. Using inhibitory Lim1 fusion proteins, we found that Lim1, or genes closely related to it, is required for head formation as well as for notochord development. Co-expression experiments revealed that Lim1 is required downstream of the early organizer factor Siamois, first, to establish the genetic program of the organizer and second, to mediate the action of organizer agents that are responsible for blocking ventralizing activities in the gastrula.

Animals↗

PubMed2001

[Clinical features in six patients with liver abscess caused by Streptococcus milleri].

Among 39 patients with pyogenic liver abscess who were admitted to our institute, six (15%) were infected by Streptococcus milleri (S. milleri). We investigated clinical features of these six patients. There were five males and one female, aged 43-81 years old (mean: 61). Five of the six patients had underlying illness. All patients had fever, and three of them complained of abdominal pain. Three patients had mixed infections; particularly intraoral anaerobes, Fusobacterium, were found in two of the three patients. There were no differences in clinical features between patients with S. milleri liver abscess and those with other bacterial liver abscess. In conclusion, on selecting antibiotics for the treatment of liver abscess, it is necessary to consider the S. milleri and intraoral anaerobes.

Adult↗

PubMed2000

Xlim-1 and LIM domain binding protein 1 cooperate with various transcription factors in the regulation of the goosecoid promoter.

The homeobox genes Xlim-1 and goosecoid (gsc) are coexpressed in the Spemann organizer and later in the prechordal plate that acts as head organizer. Based on our previous finding that gsc is a possible target gene for Xlim-1, we studied the regulation of gsc transcription by Xlim-1 and other regulatory genes expressed at gastrula stages, by using gsc-luciferase reporter constructs injected into animal explants. A 492-bp upstream region of the gsc promoter responds to Xlim-1/3m, an activated form of Xlim-1, and to a combination of wild-type Xlim-1 and Ldb1, a LIM domain binding protein, supporting the view that gsc is a direct target of Xlim-1. Footprint and electrophoretic mobility shift assays with GST-homeodomain fusion proteins and embryo extracts overexpressing FLAG-tagged full-length proteins showed that the Xlim-1 homeodomain or Xlim-1/Ldb1 complex recognize several TAATXY core elements in the 492-bp upstream region, where XY is TA, TG, CA, or GG. Some of these elements are also bound by the ventral factor PV.1, whereas a TAATCT element did not bind Xlim-1 or PV.1 but did bind the anterior factors Otx2 and Gsc. These proteins modulate the activity of the gsc reporter in animal caps: Otx2 activates the reporter synergistically with Xlim-1 plus Ldb1, whereas Gsc and PV.1 strongly repress reporter activity. We show further, using animal cap assays, that the endogenous gsc gene was synergistically activated by Xlim-1, Ldb1, and Otx2 and that the endogenous otx2 gene was activated by Xlim-1/3m, and this activation was suppressed by the posterior factor Xbra. Based on these data, we propose a model for gene interactions in the specification of dorsoventral and anteroposterior differences in the mesoderm during gastrulation.

Animals↗

PubMed2000

RNA interference for the organizer-specific gene Xlim-1 in Xenopus embryos.

Double-stranded RNA (dsRNA) interferes with gene expression in various species, a phenomenon known as RNA interference (RNAi). We show here that RNAi is also effective in modifying gene expression in Xenopus embryos. First, expression of an exogenous luciferase gene as a reporter in embryos was reduced by coinjection with dsRNA corresponding to the luciferase gene. Next, injection of dsRNA for Xlim-1, a homeobox gene suggested to be involved in Spemann organizer functions, reduced the endogenous level of Xlim-1 mRNA and produced embryos with reduced eyes or anterior truncation at high efficiency. In addition, injection of an antisense expression construct of Xlim-1 elicited phenotypes very similar to those of Xlim-1 dsRNA-injected embryos. These results indicate the effectiveness of RNAi for loss of function studies in Xenopus embryos, and the importance of Xlim-1 in head formation.

Animals↗

PubMed2000

Evaluation of heterologous insulator function with regard to chromosomal position effect in the mouse blastocyst and fetus.

Insulators are located at the boundaries of differentially regulated genes and delimit their interactions by establishing independent chromatin structures. Recently, an insulator sequence has been found in the 5'-flanking region of arylsulfatase (ARS) gene from sea urchin. To investigate functional conservation of this ARS insulator in mice, we performed blastocyst assays to evaluate the effect of this insulator on the chromosomal position effect, quantitatively. We constructed transgenes that have a luciferase gene under the control of the CMV-IE enhancer and the human elongation factor 1 alpha promoter in the presence or absence of the ARS insulator in both flanking regions. These transgenes were microinjected into 1-cell mouse embryos and luciferase activity was measured at the blastocyst stage. We found that the presence of ARS insulator sequence doubled the number of luciferase-expressing blastocysts, and that the proportion of the blastocysts with high-level expression (> or = 1 x 10(4) relative light units (RLU)) was increased more than tenfold. In the case of transgenic fetuses, however, the presence of ARS insulator did not seem to improve transgene expression. These results suggest that the sea urchin ARS insulator confers position-independent expression driven by the human elongation factor 1 alpha promoter, at least in the blastocyst stage of the mouse.

Animals↗

PubMed2000

Voglibose administration before the evening meal improves nocturnal hypoglycemia in insulin-dependent diabetic patients with intensive insulin therapy.

Nocturnal hypoglycemia is one of the serious complications of intensive insulin therapy in patients with insulin-dependent diabetes mellitus (IDDM; type 1 DM). We assessed the effect of voglibose (alpha-glucosidase inhibitor) administration before the evening meal on nocturnal hypoglycemia in IDDM patients with intensive insulin therapy. Ten IDDM patients received 0.3 mg voglibose just before the evening meal for 5 days. The diet and insulin regimen were not changed throughout the study. Nocturnal plasma glucose levels (10 PM, 3 AM, and 7 AM) were studied in these patients before and during voglibose administration. Blood glucose levels were measured at 3 AM before and during voglibose treatment. The mean plasma glucose level at 3 AM was 3.4+/-0.4 mmol/L before voglibose treatment and 7.3+/-1.0 mmol/L during treatment. Plasma glucose at 3 AM was elevated in 9 of 10 patients with voglibose. The decrease in plasma glucose from 10 PM to 3 AM was 6.5+/-0.8 mmol/L before voglibose administration but 3.2+/-0.9 mmol/L during treatment (P < .01). The hypoglycemia rate was 52% (17 of 33 nights) before voglibose administration but only 9.1% (3 of 33 nights) during treatment. We conclude that voglibose administration before the evening meal improves nocturnal hypoglycemia in IDDM patients with intensive insulin therapy.

Adolescent↗

PubMed2000

Transforming growth factor-beta5 expression during early development of Xenopus laevis.

Members of the transforming growth factor-beta (TGF-beta) superfamily play various roles during development in both vertebrates and invertebrates. Two isoforms, TGF-beta2 and -beta5, have been isolated from Xenopus laevis. We describe here the localization of TGF-beta5 mRNA in early embryos of X. laevis, assessed by whole-mount in situ hybridization. The first detectable expression of TGF-beta5 was seen in the stage 14 embryo at the posterior tip of notochord, which continued to later stages, accompanied by the expression in bilateral regions of posterior wall in the tail region next to the notochord. At later stages, transient expression was seen in the cement gland (around stage 21) and in the somites (stages 24-27). In addition, expression was present in the branchial arches (stage 29-36) and olfactory placodes (stage 36).

Animals↗

PubMed2000

Xenopus crescent encoding a Frizzled-like domain is expressed in the Spemann organizer and pronephros.

The Spemann organizer can be subdivided into head- and trunk-inducing tissues along the anteroposterior axis (Mangold, 1933. Naturwiisenschaften 43, 761-766; Spemann, 1931. Wilhelm Roux Arch. Entwicklungsmech. Org. 123, 389-517). Recent studies have suggested that head formation is brought about by repression of both Wnt and BMP signalling (Glinka et al., 1998. Nature 391, 357-362; Glinka et al., 1997. Nature 389, 517-519). Several Wnt inhibitors secreted from the head organizer region have been identified in Xenopus, such as Cerberus (Bouwmeester et al., 1996. Nature 382, 595-601), Frzb-1 (Leyns et al., 1997. Cell 88, 747-756; Lin et al., 1997. Proc. Natl. Acad. Sci. USA 94, 11196-11200), and Dkk-1 (Glinka et al., 1998. Nature 391, 357-362), supporting this two-inhibitor model. To isolate genes expressed in the head organizer, we screened a prechordal plate cDNA library by sequencing and expression pattern, and isolated the Xenopus ortholog of chick crescent encoding a Frizzled-like domain that is related to Wnt-binding regions of the Frizzled-family proteins. Expression of Xenopus crescent was first detected in the Spemann organizer region at the early gastrula stage and later in prechordal plate cells lining the boundary of mesoderm and ectoderm layers and in the anterior endoderm. At tailbud stages, the expression in the endomesoderm region was diminished, while expression in the pronephros became detectable. In animal cap assays, crescent gene was synergistically upregulated by coexpression of Xlim1, Ldb1, and Siamois, but not by Activin treatment.

Amino Acid Sequence↗

PubMed2000

Inhibition of airway smooth muscle tone by Chinese herbal medicines.

The aim of the present study was to elucidate whether Chinese traditional herbal drugs, Gorei-San (TJ-17) and Toki-Shakuyaku-San (TJ-23), affect airway smooth muscle tone and, if so, to determine what the mechanism of action is. Rabbit tracheal segments were isolated and the contractile responses to electrical field stimulation and acetylcholine were measured before and after the application of TJ-17 or TJ-23 under isometric conditions in vitro. Ouabain-sensitive rubidium-86 (86Rb) uptake by tissues in response to each drug was also measured. Each herbal medicine attenuated the contractile responses to electrical field stimulation and acetylcholine in a concentration-dependent manner, the maximal inhibition of acetylcholine-induced contraction being 37.5+/-4.9% for TJ-17 and 42.4+/-5.3% for TJ-23 (p<0.05 for each). These effects were not altered by mechanical removal of the epithelium, indomethacin, the nitric oxide synthase inhibitor NG -nitro-L-arginine methyl ester, the cyclic adenosine monophosphate (cAMP)-dependent protein kinase inhibitor adenosine 3'5'-cyclic monophosphorothioate (Rp-cAMPS), the cyclic guanosine monophosphate (cGMP)-dependent protein kinase inhibitor KT5823, or the calcium (Ca2+)-activated potassium (K+) channel inhibitor charybdotoxin, but were greatly inhibited in the presence of the sodium (Na+)-K+ adenosine triphosphatase (ATPase) inhibitor ouabain. Incubation of tissues with TJ-17 and TJ-23 dose dependently increased ouabain-sensitive 86Rb uptake. The results of the study suggest that both Gorei-San and Toki-Shakuyaku-San reduce airway smooth muscle tone via a postjunctional mechanism probably through stimulation of the sodium pump and the subsequent hyperpolarization/repolarization of the cell membrane. These effects may contribute to the antiasthmatic properties of these herbal medicines.

Acetylcholine↗

PubMed2000

Effects of four mixing methods on setting expansion and compressive strength of six commercial phosphate-bonded silica investments.

Six commercial phosphate-bonded silica investments were mixed with four different mixing methods such as hand, two conventional blade-driven vacuum mixers and a new planetary mixing device, and examined for their setting expansion and compressive strength. The two properties often altered, depending upon the mixing method and the investment. The setting expansion of three investments were significantly affected by the mixing method while those of the other three were not. Compressive strength of all six investments varied by changing the mixing method. It is emphasized here that a mixing method and mixing condition must be properly set for each investment to improve the fit of the final metallic castings. This study also suggests that the planetary mixing device is a useful substitute for conventional blade-driven vacuum mixers.

Compressive Strength↗

PubMed2000

Studies on cytotoxicity of nickel ions using C3H10T1/2 fibroblast cells.

Cytotoxicity of Ni ions were examined using C3H mouse derived 10T1/2 fibroblast cells. It became evident that Ni ions had dose-dependent cytotoxicity. The cell number incubated in DME medium containing 0.04 mM/L Ni ion for 6 days was reduced to half that in control DME medium without Ni. The cell totally disappeared in DME medium containing 2 mM/L Ni ion. The dissolution of Ni ions from Ni-containing metallic restorations must be lower than these concentration levels so that oral tissues might not be damaged. No neoplastic transformation was found on all cells examined.

Animals↗

PubMed2000

Molecular analysis of hepatitis D virus infection in Miyako Island, a small Japanese island.

The present investigation attempted to determine the exact prevalence of hepatitis D virus (HDV) infection among inhabitants of Miyako Island (a remote island in the Okinawa Prefecture) and the molecular characteristics of the HDV genome that was isolated. Among the 4728 inhabitants, 375 (7.9%) were hepatitis B surface antigen (HBsAg) positive. Antibody to HDV (anti-HDV) was present in 32 (8. 5%) of these 375 subjects, and liver function tests were normal in most subjects. The presence of HDV RNA was analysed by nested polymerase chain reaction (PCR). Thirteen out of the 32 anti-HDV antibody-positive subjects were HDV RNA positive. Thus, 3.5% of HBsAg-positive subjects on Miyako Island were HDV RNA positive. Among the HDV RNA-positive subjects, liver function tests were within normal limits or were mildly abnormal. Nucleotide sequence analysis revealed that the HDV genomes on Miyako Island were similar to the Japanese and Taiwan isolates of HDV genotype II. Taiwan is geographically close to Miyako Island. Even though the races are different, a geographical factor was revealed to be significant with regard to HDV infection, which was spread in a closed environment.

Aged↗

PubMed2000

Impairment of airway mucociliary transport in patients with sinobronchial syndrome: role of nitric oxide.

Nitric oxide (NO) produced within the respiratory tract can stimulate ciliary motility of airway epithelial cells and hence mucociliary transport. In this study, to determine the role of NO in mucociliary dysfunction in sinobronchial syndrome (SBS), we measured NO concentrations in the exhaled air by chemiluminescence analyzer and nasal clearance time (NCT) by saccharin test. Exhaled NO concentrations in patients with SBS were 39% of those in healthy nonsmokers and 55% of those in healthy smokers. The patients also showed prolonged NCT compared with healthy subjects, and there was a significant negative correlation between exhaled NO concentrations and NCT. Furthermore, concentrations of chloride (Cl) in the sputum supernatant were higher in SBS patients than in healthy subjects, and there was a significant negative correlation between sputum Cl concentrations and exhaled NO concentrations. These results suggest that airway mucociliary clearance is impaired in patients with SBS and that this impairment might result from the reduced production of NO and the impaired availability of the molecule in the mucociliary apparatus.

Adult↗