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T Takabatake

Publications and source records attributed to T Takabatake.

At least 19 recordsLinked to original sources
PubMed2005

Magnetic-field-induced band-structure change in CeBiPt.

We report on a field-induced change of the electronic band structure of CeBiPt as evidenced by electrical-transport measurements in pulsed magnetic fields. Above approximately 25 T, the charge-carrier concentration increases nearly 30% with a concomitant disappearance of the Shubnikov-de Haas signal. These features are intimately related to the Ce 4f electrons since for the non-4f compound LaBiPt the Fermi surface remains unaffected. Electronic band-structure calculations point to a 4f-polarization-induced change of the Fermi-surface topology.

Journal Article↗
PubMed2004

Determination of the orbital polarization in YTiO3 by using soft X-ray linear dichroism.

We report measurements of linear dichroism in x-ray absorption at Ti L(2,3) edges of a Mott-insulating ferromagnet YTiO3, where orbital ordering occurs in the triply degenerate Ti 3d t(2g) states. Dichroic spectra and their integrated intensities are obtained for the incident electric field with polarizations parallel to a, b, and c axes. The comparison of the spectra with atomic multiplet calculations removes the ambiguity about the orbital polarization, i.e., the relative weights of |xy>, |yz>, and |zx> orbits, which are crucial for the origin of ferromagnetism. The result is consistent with the previous analysis of nuclear magnetic resonance in the Mizokawa-Fujimori scheme.

Journal Article↗
PubMed2003

No lengthening of life span in mice continuously exposed to gamma rays at very low dose rates.

Late effects of continuous exposure to ionizing radiation are potential hazards to workers in radiation facilities as well as to the general public. Recently, low-dose-rate and low-dose effects have become a serious concern. Using a total of 4000 mice, we studied the late biological effects of chronic exposure to low-dose-rate radiation as assayed by life span. Two thousand male and 2000 female 8-week-old specific-pathogen-free (SPF) B6C3F1 mice were randomly divided into four groups (one nonirradiated control and three irradiated). Irradiation was carried out for approximately 400 days using (137)Cs gamma rays at dose rates of 21 mGy day(-1), 1.1 mGy day(-1) and 0.05 mGy day(-1) with total doses equivalent to 8000 mGy, 400 mGy and 20 mGy, respectively. All mice were kept under SPF conditions until they died spontaneously. Statistical analyses showed that the life spans of mice of both sexes irradiated with 21 mGy day(-1) (P < 0.0001) and of females irradiated with 1.1 mGy day(-1) (P < 0.05) were significantly shorter than those of the control group. Our results show no evidence of lengthened life span in mice continuously exposed to very low dose rates of gamma rays.

Animals↗
PubMed2001

Redox regulation of MAPK pathways and cardiac hypertrophy in adult rat cardiac myocyte.

OBJECTIVES: We analyzed the regulatory function of reactive oxygen species (ROS) on the hypertrophic signaling in adult rat cardiac myocytes: BACKGROUND: The ROS regulate mitogenic signal transduction in various cell types. In neonatal rat cardiac myocyte, antioxidants have been shown to inhibit cardiac hypertrophy, and ROS are suggested to modulate the hypertrophic signaling. However, the conclusion may not reflect the situation of mature heart, because of the different natures between neonatal and adult cardiac myocytes. METHODS: Cultured adult rat cardiac myocytes were stimulated with endothelin-1 (ET-1) or phenylephrine (PE), and intracellular ROS levels, the activities of mitogen-activated protein kinases (MAPKs; ERK, p38, and JNK), and 3H-phenylalanine incorporation were examined. We also examined the effects of antioxidant pretreatment of myocytes on MAPK activities and cardiac hypertrophy to analyze the modulatory function of redox state on MAPK-mediated hypertrophic signaling. RESULTS: The ROS levels in ET-1- or PE-stimulated myocytes were maximally increased at 5 min after stimulation. The origin of ROS appears to be from NADH/NADPH oxidase, because the increase in ROS was suppressed by pretreatment of myocytes with NADH/NADPH oxidase inhibitor diphenyleneiodonium. Extracellular signal-regulated kinase (ERK) activity was increased by the stimulation of ET-1 or PE. In contrast, p38 and c-Jun-N-terminal protein kinase (JNK) activities did not change after these stimulations. Antioxidant treatment of myocytes suppressed the increase in ROS and blocked ERK activation and the subsequent cardiac hypertrophy induced by these stimuli. CONCLUSIONS: These data demonstrate that ROS mediate signal transduction of cardiac hypertrophy induced by ET-1 or PE in adult rat cardiac myocytes.

Animals↗
PubMed2001

[Formations and reactions of aromatic furazan compounds].

A reaction from various kinds of nitroquinoline with hydroxylamine in potassium hydroxide alkalinity produced a novel product, furazanoquinoline, besides the known amino derivatives. The products obtained were furazano [3,4-f] quinoline (5) from 5-nitroquinoline (1) and 6-nitroquinoline (6), and furazano [3,4-h] quinoline (10) from 7-nitroquinoline (8) and 8-nitroquinoline (11). The reaction mechanism was believed to be as shown in Figs. 2 and 3. The photoreaction of benzofuroxan (19) in acetonitrile containing a little water, under a high pressure mercury lamp, produced 1H-azepine-2,7-dione (20), while under irradiation using a low pressure lamp, 6H-furazano [4,5-c] carbazole-3-oxide (21) and compound 20 were obtained. Then the photoproduct 20 produced photodimer 22 by irradiation in acetonitrile: water (9:1, v/v) using a high or low pressure mercury lamp, while photolysis with alkali proceeded as in the photoreaction of N-alkylimide to give 7-hydroxy-1H-azepine-2-one (23). When pyrido [2,3-c] furoxan (24) was irradiated in acetonitrile containing a little water with a low pressure mercury lamp, 3-nitro-2-pyridone (25) was obtained. When compound 24 was irradiated in the presence of morpholine with a low pressure mercury lamp in an argon atmosphere, 6-morpholinopyridine 2,3-dioxime (26) was produced. Quinoxaline 1,4-dioxide derivatives (31, 33), phenazine 5,10-dioxide derivatives (36, 37) and pyrido [2,3-b] pyrazine derivatives (38, 39) were synthesized from the corresponding furoxan catalyzed by silica gel or molecular sieves, and their antibacterial properties were evaluated. The results of antibacterial screening tests in vitro, revealed strong activity against Bacteroides fragilis.

Bacteroides fragilis↗
PubMed2000

Isolation and characterization of three novel serine protease genes from Xenopus laevis.

Three novel cDNAs encoding serine proteases, that may play a role in early vertebrate development, have been identified from Xenopus laevis. These Xenopus cDNAs encode trypsin-like serine proteases and are designated Xenopus embryonic serine protease (Xesp)-1, Xesp-2, and XMT-SP1, a homolog of human MT-SP1. Xesp-1 is likely to be a secreted protein that functions in the extracellular space. Xesp-2 and XMP-SP1 are likely to be type II membrane proteases with multidomain structures. Xesp-2 has eight low density lipoprotein receptor (LDLR) domains and one scavenger receptor cysteine-rich (SRCR) domain, and XMT-SP1 has four LDLR domains and two CUB domains. The temporal expressions of these serine protease genes show distinct and characteristic patterns during embryogenesis, and they are differently distributed in adult tissues. Overexpression of Xesp-1 caused no significant defect in embryonic development, but overexpression of Xesp-2 or XMT-SP1 caused defective gastrulation or apoptosis, respectively. These results suggest that these proteases may play important roles during early Xenopus development, such as regulation of cell movement in gastrulae.

Amino Acid Sequence↗
PubMed2000

Distribution of dorsal-forming activity in precleavage embryos of the Japanese newt, Cynops pyrrhogaster: effects of deletion of vegetal cytoplasm, UV irradiation, and lithium treatment.

Two types of axis-deficient embryos developed after deletion of the vegetal cytoplasm: wasp-shaped embryos and permanent-blastula-type embryos. In situ hybridization revealed that neither type of axis-deficient embryo expressed goosecoid or pax-6. brachyury was expressed in the constricted waist region of the wasp-shaped embryos but was not expressed in the permanent-blastula-type embryos. Further, we examined the effect of UV irradiation on Japanese newt embryos. Surprisingly, UV-irradiated Japanese newt eggs formed hyperdorsalized embryos. These embryos gastrulated in an irregular circular fashion with goosecoid expression in the circular equatorial region. At tailbud stage, these embryos formed a proboscis which is very reminiscent of that formed in hyperdorsalized Xenopus embryos. Transplantation of the marginal region of the UV-irradiated embryos revealed that the entire marginal zone had organizer activity. Thus we conclude that UV hyperdorsalizes Japanese newt embryos. Finally, lithium treatment of normal embryos at the 32-cell stage also resulted in hyperdorsalization. Lithium treatment of vegetally deleted embryos had two distinct results. Lithium treatment of permanent-blastula-type embryos did not result in the formation of dorsal axial structures, while the same treatment reinduced gastrulation and dorsal axis formation in the wasp-shaped embryos. Based on these results, we propose a model for early axis specification in Japanese newt embryos. The model presented here is fundamentally identical to the Xenopus model, with some important modifications. The vegetally located determinants required for dorsal development (dorsal determinants, DDs) are distributed over a wider region at fertilization in Japanese newt embryos than in Xenopus embryos. The marginal region of the Japanese newt embryo at the beginning of development overlaps with the field of the DDs. Gastrulation is very likely to be a dorsal marginal-specific property, while self-constriction is most probably a ventral marginal-specific property in Japanese newt embryos.

Animals↗
PubMed2000

Conserved and divergent expression of T-box genes Tbx2-Tbx5 in Xenopus.

We report here the identification of four members of T-box family genes, Xltbx2-Xltbx5, in Xenopus. Two of them are probable pseudovariant genes of XTbx5 and ET, a putative Xenopus ortholog of Tbx3. We compared their expression patterns in both embryos and limbs. In embryos, expression of Xltbx2 and Xltbx3 showed novel diversities, such as Xltbx2 in the neural crest cells and Xltbx3 in the ventral spinal cord, together with mutual similarities in the following regions: dorsal retina, proctoderm, lateral line organ, cement gland and cranial ganglia. The patterns in limbs were highly conserved with mouse and chick orthologs, including the limb-type specific expression of Xltbx4 and Xltbx5. In addition, RT-PCR analysis showed that they are expressed weakly even in adult limbs as previously reported in the newt.

Amino Acid Sequence↗
PubMed2000

Distinct expression of two types of Xenopus Patched genes during early embryogenesis and hindlimb development.

Patched (Ptc) is a putative twelve transmembrane domain protein that is both a Hedgehog (Hh) receptor and transcriptional target of Hh. In this study, we isolated Xenopus Ptc cDNAs, Ptc-1 and Ptc-2, and carried out comparative analyses on their expression patterns. The putative Ptc-2 protein has a long C-terminal extension that has similarities in both length and sequence to those of Ptc-1 proteins in mouse, chick and human. In both early embryogenesis and hindlimb development, Ptc-2 expression is restricted to cells that receive a Hh signal, a pattern similar to that of Gli-1. Ptc-1, however, shows a broader distribution, mainly non-overlapping with that of Ptc-2. Despite the difference in their expression patterns, both are induced in animal cap explants synergistically by Shh and Noggin, showing a conserved regulation in their activation mechanisms.

Amino Acid Sequence↗
PubMed1999

The early expression control of Xepsin by nonaxial and planar posteriorizing signals in Xenopus epidermis.

The control mechanism of the anteroposterior axis specification in Xenopus epidermis was studied by comparing the expression of a novel anterior marker, Xepsin, with that of a panepidermal marker, type I keratin. Xepsin mRNA, which encodes a novel Xenopus serine protease, is transcribed zygotically with the expression peak in neurula stages. In normal development, its expression is limited to the anterior and anterior-dorsal portions within epidermis during neurula and tailbud stages, respectively. In UV-irradiated ventralized embryos (dorsoanterior index, DAI 0 and 1), an expression boundary for Xepsin is apparently formed within the epidermis. In contrast, Xepsin expression was observed throughout the epidermis in LiCl-treated dorsalized embryos (DAI 10), as seen from an expression pattern indistinguishable from that of type I keratin. These data suggest that posteriorizing signals which suppress the transcription of Xepsin are present in nonaxial regions and absent in the anterior dorsal mesoderm. That posteriorizing signals were present in nonaxial regions was also supported by a conjugation experiment in which Xepsin expression was suppressed in ectodermal explants conjugated with lateral or ventral marginal zone. Moreover, the partly suppressed expression of Xepsin in the epidermal region of exogastrulae indicates that the signals may travel horizontally within the plane of the epidermis. We also present data showing that both treatment with retinoic acid and the overexpression of a constitutively active form of a retinoic acid receptor caused the suppression of Xepsin mRNA transcription, suggesting that anterior-posterior patterning in the central nervous system and in the epidermis may share common endogenous factors, i.e. , retinoids, in the Xenopus embryo.

Amino Acid Sequence↗
PubMed1999

Expression and secretion of a biologically active mouse sonic hedgehog protein by the methylotrophic yeast Pichia pastoris.

We have successfully secreted the amino-terminal functional domain of mouse sonic hedgehog protein (SHH) into culture fluid using a yeast Pichia pastoris expression system. A cDNA fragment encoding the amino-terminal domain of mouse SHH was inserted downstream of the Saccharomyces cerevisiae alpha-mating factor secretion signal. The DNA fragment was introduced into the host genome by the spheroplast transformation method. Transformants were selected based on their resistance to G418: His+ transformants which showed resistance to over 8 mg G418/ml were selected and analyzed for determination of the plasmid copy number. One His+ clone which has eight copies of the expression cassette per genome was cultured in minimal medium deficient for histidine, and further cultured in buffered medium supplemented with methanol which activates the AOX1 promoter. SDS-PAGE analysis indicated efficient expression and secretion of mouse SHH into culture fluid. The yield of secreted SHH was estimated to be 50 micrograms/ml. Purified protein was assayed for biological activity and found to activate the transcription of the Patched genes (Ptc-1 and Ptc-2) encoding receptors for SHH.

Animals↗
PubMed1999

Renal effects of efonidipine hydrochloride, a new calcium antagonist, in spontaneously hypertensive rats with glomerular injury.

1. To obtain some insight into the renoprotective mechanism of the new calcium antagonist efonidipine hydrochloride, we evaluated the acute effects of efonidipine on proteinuria, glomerular haemodynamics and the tubuloglomerular feedback (TGF) mechanism in anaesthetized 24-25-week-old spontaneously hypertensive rats (SHR) with glomerular injury. 2. Efonidipine infusion at 10 micrograms/kg per h following a bolus dose of 10 micrograms/kg, i.v., reduced systemic blood pressure (BP) and renal vascular resistance, whereas renal plasma flow (RPF), glomerular filtration rate (GFR), filtration fraction, urine volume and urinary sodium excretion were unaltered. Urinary protein excretion was clearly diminished from 163 +/- 25 to 105 +/- 24 ng/min per g kidney weight. 3. Micropuncture experiments revealed that the maximal reduction of proximal stop-flow pressure (SFP), an index of glomerular capillary pressure (Pgc), induced by loop of Henle perfusion was significantly less with efonidipine treatment (6.7 +/- 1.0% of SFP with no loop flow) than in control (23.8 +/- 3.1%). In the presence of efonidipine, SFP at half-maximal reduction (SFP1/2max), which approximates Pgc at the in vivo steady state tubular flow rate, remained unchanged compared with control (36.9 +/- 0.8 vs 35.3 +/- 0.7 mmHg, respectively) and the slope of dependency on mean BP was not different between control and efonidipine. 4. These results indicate that efonidipine attenuates the TGF response in SHR by dilating the afferent arteriole, thus maintaining the level of RPF and GFR despite reduced renal perfusion pressure. Constant GFR and SFP1/2max under efonidipine suggest that single nephron GFR and Pgc remain unaltered and that a marked reduction in proteinuria is achieved without changes in single nephron GFR or Pgc of superficial nephrons.

Animals↗
PubMed1999

Expression of five novel T-box genes and brachyury during embryogenesis, and in developing and regenerating limbs and tails of newts.

Several T-box genes are considered to play important roles in developing limbs, tails and neural retinae. Five novel T-box genes in the Japanese newt were isolated and their expression was analyzed, together with another T-box gene of brachyury, during embryogenesis and in the developing and regenerating limbs and tail. Four are designated CpTbx2, CpTbx3, CpTbx6R and CpEomesodermin based on molecular phylogenetic analyses, and the other is named CpUbiqT from its ubiquitous expression. While all were expressed during embryogenesis, only four of them (CpTbx2, CpTbx3, CpUbiqT and brachyury) were detected in developing limbs and/or tails. Except for brachyury, they were continuously expressed in normal adult appendages and showed elevated expression levels in regenerating limbs, whereas only CpTbx2 showed significant up-regulation in regenerating tails. Compared with orthologous genes in other species, CpTbx2, CpTbx3 and CpEomesodermin showed several notable differences such as an abundance of maternal transcripts of CpEomesodermin, a unique insertion sequence within the T-box domain of CpTbx2, and a lack of visible expression of CpTbx2and CpTbx3 in the apical ectodermal region of developing limbs. In view of the uniqueness of the newt, these results are discussed with respect to the possibility of their involvement in regeneration.

Amino Acid Sequence↗
PubMed1999

A calcium antagonist protects against doxorubicin-induced impairment of calcium handling in neonatal rat cardiac myocytes.

The effects of doxorubicin (DOX) on intracellular calcium transients and the cardioprotective effects of a calcium antagonist on DOX-induced impairment of calcium handling were examined in neonatal rat cultured cardiac myocytes. Cultured cardiac myocytes isolated from neonatal Wistar-Kyoto rats were treated with DOX for 24 h. Field-stimulated calcium transients in single myocytes were measured in the presence or absence of isoproterenol using fura-2/AM. Calcium transients were also measured after the addition of DOX to myocytes pretreated with a calcium antagonist, benidipine. DOX reduced the amplitude, maximum velocity of increase and decrease of calcium transients and prolonged the time course of calcium transients and impaired the beta-adrenoceptor responsiveness of calcium transients in a concentration-dependent manner. The DOX-induced impairment of calcium transients and beta-adrenoceptor responsiveness was improved by 10(-8) mol/L of benidipine. However, these improvements decreased with increasing concentrations of benidipine. DOX impaired both the mobilization and removal of intracellular calcium ions in contraction-relaxation cycles and the response of calcium transients to beta-adrenoceptor stimulation. Appropriate concentration of benidipine ameliorated DOX-induced impairment of calcium dynamics, suggesting that benidipine, a long-acting calcium antagonist, has potential clinical usefulness on DOX-induced abnormal calcium handling.

Animals↗
PubMed1998

Overlapping and non-overlapping Ptch2 expression with Shh during mouse embryogenesis.

In Drosophila, patched encodes a negative regulator of Hedgehog signaling. Biochemical experiments have demonstrated that vertebrate patched homologues might function as a Sonic hedgehog (Shh) receptor. In mice, two patched homologues, Ptch and Ptch2, have been identified. Sequence comparison have suggested that they might possess distinct properties in Shh signaling. In the developing tooth, hair and whisker, Shh and Ptch2 are co-expressed in the epithelium while Ptch is strongly expressed in the mesenchymal cells. We report here the chromosomal localization of Ptch2 and further analysis of Ptch2 expression. Throughout mouse development, the level of Ptch2 expression is significantly lower than that of Ptch. In early mouse embryos, Ptch and Ptch2 were found to be co-expressed in regions adjacent to Shh-expressing cells in the developing CNS. Similar to other epidermal structures, Shh and Ptch2 also show overlapping expression in the developing nasal gland and eyelids. Thus, during mouse development, Ptch2 is expressed in both Shh-producing and -nonproducing cells.

Animals↗
PubMed1998

Isolation and characterization of a gene expressed mainly in the gastric epithelium, a novel member of the ep37 family that belongs to the betagamma-crystallin superfamily.

EP37 family proteins are non-lens members of the betagamma-crystallin superfamily, of which expression is observed in integumental tissues of the Japanese newt, Cynops pyrrhogaster. In the present study, a gene was isolated that has high homology with ep37 and is transcribed mainly in the gastric epithelial cells and hence designated gep. The predicted amino acid sequence of the gep cDNA contains four betagamma-crystallin motifs in the N-terminal half, as is the case in the integumental EP37 proteins. Immunohistochemical analysis showed that GEP protein was mainly localized on the luminal content of the surface mucous cells of the gastric epithelium in both premetamorphic larvae and adults. In addition, GEP protein was also expressed in fundic glands after metamorphosis. Considering the fact that beta- and gamma-crystallins are evolutionarily related to stress-induced proteins, this localization suggests that GEP protein may have an evolutionarily conserved role in protection against physico-chemical stresses, such as physical abrasion and autodigestion, during assimilation.

Amino Acid Sequence↗