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Biomedical subjects

H Takano

Publications and source records attributed to H Takano.

At least 19 recordsLinked to original sources
PubMed2002

Development of a multilayer Fresnel zone plate for high-energy synchrotron radiation X-rays by DC sputtering deposition.

Hard X-ray microscopy with high spatial resolution ( or=20 keV) because a large thickness (aspect ratio) can be available. Various types of multilayer FZPs have been fabricated by DC sputtering deposition. Their focusing characteristics have been evaluated at the high-brilliance undulator beamline BL47XU of SPring-8. An optical system using a Cu/Al multilayer FZP (with an outermost zone width of 0.25 microm) as the focusing optics fabricated by the optimum deposition condition with precise film (zone) thickness control has attained an almost diffraction-limited microbeam of 0.3-0.35 microm at 8.9 keV. A line-and-space resolution test pattern has been observed: fine structures up to 0.2 microm were clearly observed in the measured image. This FZP has been working since 1995, keeping good focusing characteristics. It can be said from these results that a spatial resolution better than 0.1 microm in the high-energy X-ray region is in prospect by the development of a multilayer FZP with a narrower outermost zone width in the near future.

Journal Article↗
PubMed2002

Hard X-ray microbeam experiments with a sputtered-sliced Fresnel zone plate and its applications.

Hard X-ray microbeam experiments with sputtered-sliced Fresnel zone plates have been performed. Zone plates with an outermost zone width of 0.25 microm (#FZP1) and 0.1 microm (#FZP2) were fabricated and evaluated. In a scanning X-ray microscopy experiment, a line-and-space pattern with structure as fine as 0.1 microm was resolved using #FZP2 at an X-ray wavelength of 1 A. As an application of the microbeam technique, a two-dimensional distribution of constituent elements in forensic samples has been obtained (e.g. section view of human and elephant hairs) using fluorescent scanning microscopy.

Animals↗
PubMed2002

Zernike-type X-ray imaging microscopy at 25 keV with Fresnel zone plate optics.

A Zernike-type imaging microscope using a sputtered-sliced Fresnel zone plate (SS-FZP) has been developed and tested at an X-ray energy of 25 keV. The SS-FZP was used as an objective. A copper (Cu) phase plate was placed at the back focal plane of the SS-FZP in order to produce phase contrast. The performance of the Zernike-type imaging microscope was tested with a gold (Au) mesh and a resolution test pattern at undulator beamline 47 of SPring-8. The Au mesh and the resolution test pattern could be imaged in transmission with a magnification of x10.2. Owing to the Cu phase plate, different image contrast was observed compared with the bright-field image contrast. Tantalum microstructures down to 0.5 microm line-and-space have been observed on spatial resolution test patterns.

Journal Article↗
PubMed2002

Modulators of internal Ca2+ stores and the spontaneous electrical and contractile activity of the guinea-pig renal pelvis.

1. The role of internal Ca(2+) stores in the generation of the rhythmic electrical and contractile activity in the guinea-pig proximal renal pelvis was examined using intracellular microelectrode and muscle tension recording techniques. 2. Ryanodine (30 microM) transiently increased contraction amplitude, while caffeine (0.5 - 3 mM) reduced contraction amplitude and frequency. Contractility was also reduced by 2-aminoethoxy-diphenylborate (2-APB 60 microM), xestospongin C (1 microM), U73122 (5 microM) and neomycin (4 mM), blockers of IP(3)-dependent release from Ca(2+) stores. 3. 60 mM K(+) saline-evoked contractions were reduced by caffeine (1 mM), U73122 (5 microM) and neomycin (4 mM), but little affected by ryanodine or 2-APB (60 microM). 4. Spontaneous action potentials consisting of an initial spike followed by a long plateau were recorded (frequency 8.6+/-1.0 min(-1)) in small urothelium-denuded strips of proximal renal pelvis. 5. Action potential discharge was blocked in 75 and 35% of cells by 2-APB (60 microM) and caffeine (1 mM), respectively. In the remaining cells, only a truncation of the plateau phase was observed. 6. Cyclopiazonic acid (CPA 10 microM for 10 - 180 min), blocker of CaATPase, transiently increased contraction frequency and amplitude. Action potential durations were increased 3.6 fold. Contraction amplitude and frequency slowly declined during a prolonged (>60 min) CPA exposure. 7. We conclude that the action potential in caffeine-sensitive cells and the shoulder component of caffeine-insensitive action potential arise from the entry of Ca(2+) through Ca(2+) channels. The inhibitory actions of modulators of internal Ca(2+) release were partially explained by a blockade of Ca(2+) entry.

Animals↗
PubMed2001

Reactive oxygen species in mechanical stress-induced cardiac hypertrophy.

Mechanical stress induces various hypertrophic responses including activation of mitogen-activated protein kinases (MAPKs) in cardiac myocytes. Here we examined the role of the small GTP-binding proteins of Rho family and reactive oxygen species (ROS) in stretch-induced activation of p38MAPK in cardiomyocytes. Overexpression of dominant-negative mutants of Rac1 (D.N. Rac1), D.N.RhoA and D.N.Cdc42 suppressed stretch-induced activation of p38MAPK. Overexpression of constitutively active mutants of Rac1 (C.A.Rac1) and C.A.Cdc42 increased the p38MAPK activity in the absence of mechanical stress. Pretreatment with N-acetyl-L-cysteine and N-(2-mercaptopropionyl)-glycine (NAC) suppressed stretch-induced activation of p38MAPK. Mechanical stretch increased intracellular ROS generation, which was abrogated by overexpression of D.N.Rac1 and attenuated by overexpression of D.N.RhoA and D.N.Cdc42. An increase in protein synthesis evoked by mechanical stretch was suppressed by overexpression of D.N.Rac1 and pretreatment with NAC. These results suggest that mechanical stress induces cardiac hypertrophy through the Rac1-ROS-p38MAPK pathway in cardiac myocytes.

Animals↗
PubMed2001

Exposure to diesel exhaust exacerbates allergen-induced airway responses in guinea pigs.

Diesel exhaust (DE) is a major air pollutant in urban areas. To clarify the effects of DE on the exacerbation of asthma, guinea pigs were exposed 12 h daily to 3 mg/m(3) DE or air for 8 wk with or without sensitization to ovalbumin (OVA). In the DE-exposed sensitized animals, both immediate (IAR) and late (LAR) airway responses were enhanced after the inhalation challenge by OVA, compared with the DE-unexposed sensitized animals. Mucus was greatly accumulated in the airways of DE-exposed sensitized animals during IAR. The number of eosinophils and level of sialic acid concentration in bronchial lavage fluids were also significantly higher in the DE-exposed sensitized animals than in the DE-unexposed control animals. During LAR, intercellular spaces of the bronchial epithelium became enlarged in the DE-exposed sensitized animals, showing infiltration by numerous eosinophils. Albumin concentration was significantly higher in the bronchial lavage fluids from the DE-exposed sensitized animals than in those from the DE-unexposed control animals. These results suggest that exposure to DE enhances mucus hypersecretion and eosinophilic inflammation during IAR. DE exposure also increases airway permeability and airway inflammation during LAR. Thus, DE exposure exacerbates allergen-induced airway responses in guinea pigs.

Allergens↗
PubMed2001

Amino acid sequences flanking polyglutamine stretches influence their potential for aggregate formation.

Expanded polyglutamine stretches have been shown to form aggregates and to be toxic to cells. In this study, we hypothesized that amino acid sequences flanking the polyglutamine stretches influence the aggregate formation potential of these stretches. Green fluorescent protein (GFP) fusion proteins containing glutamine repeats of various lengths and a fixed number of flanking amino acids of ataxin-2, huntingtin, dentatorubral-pallidoluysian atrophy protein (DRPLAP) or ataxin-3 were transiently expressed in COS-7 cells. The aggregate formation potential of ataxin-2 and DRPLAP increased in a CAG-repeat-length-dependent manner, with a threshold between 34 and 36. Truncated ataxin-2-Q56-GFP and truncated huntingtin-Q56-GFP showed a significantly higher aggregate formation potential than truncated DRPLAP-Q56-GFP or truncated ataxin-3-Q56-GFP. These results are in agreement with the clinical observation that ages of disease onset in patients with spinocerebellar ataxia type 2 or Huntington's disease are lower than those in patients with DRPLA or Machado-Joseph disease having expanded CAG repeats of the same length. Furthermore, mutagenesis of the flanking sequence of ataxin-2 markedly reduced its aggregate formation potential. These results indicate that the amino acid sequences flanking the polyglutamine stretches significantly influence their aggregate formation potential.

Amino Acid Sequence↗
PubMed2001

Beta-amyloid induces neuronal apoptosis via a mechanism that involves the c-Jun N-terminal kinase pathway and the induction of Fas ligand.

Elevated levels of beta-Amyloid (Abeta) are present in the brains of individuals with either the sporadic or familial form of Alzheimer's disease (AD), and the deposition of Abeta within the senile plaques that are a hallmark of AD is thought to be a primary cause of the cognitive dysfunction that occurs in AD. Recent evidence suggests that Abeta induces neuronal apoptosis in the brain and in primary neuronal cultures, and that this Abeta-induced neuronal death may be responsible in part for the cognitive decline found in AD patients. In this study we have characterized one mechanism by which Abeta induces neuronal death. We found that in cortical neurons exposed to Abeta, activated c-Jun N-terminal kinase (JNK) is required for the phosphorylation and activation of the c-Jun transcription factor, which in turn stimulates the transcription of several key target genes, including the death inducer Fas ligand. The binding of Fas ligand to its receptor Fas then induces a cascade of events that lead to caspase activation and ultimately cell death. By analyzing the effects of mutations in each of the components of the JNK-c-Jun-Fas ligand-Fas pathway, we demonstrate that this pathway plays a critical role in mediating Abeta-induced death of cultured neurons. These findings raise the possibility that the JNK pathway may also contribute to Abeta-dependent death in AD patients.

Alzheimer Disease↗
PubMed2001

Nitroglycerin induces late preconditioning against myocardial infarction in conscious rabbits despite development of nitrate tolerance.

BACKGROUND: Recent studies suggest that the late phase of ischemic preconditioning (PC) can be mimicked by pretreatment with NO donors. The ability of clinically relevant NO donors to induce PC against infarction, however, has not been evaluated. Furthermore, it is unknown whether tolerance to the hemodynamic actions of nitrates also extends to their PC effects. METHODS AND RESULTS: Conscious rabbits underwent a 30-minute coronary occlusion and 3 days of reperfusion. A 60-minute intravenous (IV) infusion of nitroglycerin (NTG) ending 1 hour before occlusion reduced infarct size, indicating an early PC effect. When the time interval between NTG infusion and occlusion was extended to 24 or 72 hours, the infarct-sparing action of NTG became even more pronounced, indicating a robust late PC effect. Transdermal NTG patches elicited a late PC effect that was (1) equivalent to that induced by IV NTG, demonstrating the efficacy of transdermal NTG as an alternative form of NTG delivery for inducing late PC, and (2) similar in nitrate-tolerant and -nontolerant rabbits, demonstrating that tolerance does not extend to the PC effects of NTG. CONCLUSIONS: In conscious rabbits, administration of NTG via either the IV or the transdermal route elicits a robust protective effect against infarction that lasts for 72 hours. The magnitude of NTG-induced cardioprotection is equivalent to that observed during the late phase of ischemic PC and is not affected by the development of tolerance. These findings reveal a new action of nitrates and support novel applications of these drugs for protecting the ischemic myocardium in patients.

Administration, Cutaneous↗
PubMed2001

Differentiation of monocytes into multinucleated giant bone-resorbing cells: two-step differentiation induced by nurse-like cells and cytokines.

Bone resorption in the joints is the characteristic finding in patients with rheumatoid arthritis (RA). Osteoclast-like cells are present in the synovial tissues and invade the bone of patients with RA. The characteristics of these cells are not completely known. In the work reported here, we generated these cells from peripheral-blood monocytes from healthy individuals. The monocytes were co-cultured with nurse-like cells from synovial tissues of patients with RA (RA-NLCs). Within 5 weeks of culture, the monocytes were activated and differentiated into mononuclear cells positive for CD14 and tartrate-resistant acid phosphatase (TRAP). These mononuclear cells then differentiated into multinucleated giant bone-resorbing cells after stimulation with IL-3, IL-5, IL-7, and/or granulocyte-macrophage-colony-stimulating factor. TRAP-positive cells with similar characteristics were found in synovial fluid from patients with RA. These results indicate that multinucleated giant bone-resorbing cells are generated from monocytes in two steps: first, RA-NLCs induce monocytes to differentiate into TRAP-positive mononuclear cells, which are then induced by cytokines to differentiate into multinucleated giant bone-resorbing cells.

Acid Phosphatase↗
PubMed2001

Mechanical responses evoked by nerve stimulation in gastric muscles of mouse lacking inositol trisphosphate receptor.

Alteration of mechanical responses elicited by transmural nerve stimulation (TNS) was investigated in pylorus muscle of stomach isolated from mutant mice lacking expression of IP, type-1 receptor. In wild and mutant mice. TNS inhibited spontaneous contractions and generated an off-response at the cessation. The effects of inhibitors of neurotransmission revealed that in wild mice, acetylcholine and nitric oxide were involved as excitatory and inhibitory mediators, respectively. In mutant mice, a lack of nitroxidergic component with associated attenuation of cholinergic transmission was found. The off-response was inhibited by apamin in both mice. In mutant mice, spantide-sensitive excitatory response appeared in the presence of apamin. Acetylcholine and substance P enhanced while noradrenaline and sodium nitroprusside inhibited spontaneous contractions, in both wild and mutant mice; the actions were weaker in mutant mice than in wild mice for any agonists. The results indicate that pylorus smooth muscles receive cholinergic excitatory and nitroxidergic and non-adrenergic non-cholinergic inhibitory projections, and a lack of IP, type-1 receptor results in an impairment of cholinergic and nitroxidergic components, with no alteration of non-adrenergic non-cholinergic inhibitory projections. In addition, the mutation induces a substance P projection which is not detected in wild mice.

Acetylcholine↗
PubMed2001

A(1) or A(3) adenosine receptors induce late preconditioning against infarction in conscious rabbits by different mechanisms.

We investigated whether activation of A(1) or A(3) adenosine receptors (ARs) induces late preconditioning (PC) against infarction in conscious rabbits using the selective AR agonists 2-chloro-N(6)-cyclopentyladenosine (CCPA) and N(6)-3-iodobenzyladenosine-5'-N-methylcarboxamide (IB-MECA). In vitro radioligand binding and cAMP assays demonstrated CCPA to be approximately 200- to 400-fold selective for the rabbit A(1)AR and IB-MECA to be approximately 20-fold selective for the rabbit A(3)AR. We observed that (1) pretreatment of rabbits 24 hours earlier with CCPA (100 microgram/kg IV bolus) or IB-MECA (100 or 300 microgram/kg) resulted in an approximately 35% to 40% reduction in the size of the infarct induced by 30 minutes of coronary artery occlusion and 72 hours of reperfusion compared with vehicle-treated rabbits, whereas pretreatment with the selective A(2A)AR agonist CGS 21680 (100 microgram/kg) had no effect; (2) the delayed cardioprotective effect of CCPA, but not that of IB-MECA, was completely blocked by coadministration of the highly selective A(1)AR antagonist N-0861; (3) inhibition of nitric oxide synthase (NOS) with N(omega)-nitro-L-arginine during the 30-minute occlusion abrogated the infarct-sparing action of CCPA but not that of IB-MECA; and (4) inhibition of ATP-sensitive potassium (K(ATP)) channels with sodium 5-hydroxydecanoate during the 30-minute occlusion blocked the cardioprotective effects of both CCPA and IB-MECA. Taken together, these results indicate that activation of either A(1)ARs or A(3)ARs (but not A(2A)ARs) elicits delayed protection against infarction in conscious rabbits and that both A(1)AR- and A(3)AR-induced cardioprotection involves opening of K(ATP) channels. However, A(1)AR-induced late PC uses an NOS-dependent pathway whereas A(3)AR-induced late PC is mediated by an NOS-independent pathway.

Adenine↗
PubMed2001

Transcriptional activation of the human HMG1 gene in cisplatin-resistant human cancer cells.

The nonhistone chromosomal protein, high mobility group 1 (HMG1), which is ubiquitously expressed in higher eukaryotic cells, preferentially binds to cisplatin-modified DNA. The observation that HMG1 is overexpressed in cisplatin-resistant human cancer cells suggests that cisplatin resistance may be closely associated with HMG1. To decipher the mechanism of HMG1 overexpression in cisplatin-resistant cells, we isolated two overlapping genomic DNA clones containing the entire human HMG1 gene. These clones, which span approximately 15 kb of contiguous DNA, include 5 kb of the 5' flanking region as well as the entire coding sequence. We sequenced 1500 bp upstream of the first exon. The segment proximal to the transcription initiation site did not contain a TATA box but did possess an activating transcription factor site, an activator protein-2 site, one CCAAT box, and two CCAAT-binding transcription factor/nuclear factor-1 (CTF/NF-1) sites. HMG1 promoter activity was 3-10-fold higher in cisplatin-resistant KB-CP20 cells than in parental KB cells. An in vivo footprint experiment showed several differences of dimethyl sulfate modifications between KB and KB-CP20 cells in the area around the CTF/NF-1 sites. In addition, electrophoretic gel mobility shift assays showed that binding of a nuclear factor from cisplatin-resistant cells to the CTF/NF-1 site was significantly higher than the binding of the same factor from parental cells. Semiquantitative reverse transcription-PCR and Western blot analysis also showed that expression of CTF/NF-1 was 3-20-fold higher in the resistant cell line than in its parental counterpart. These findings suggest that, in cisplatin-resistant cells, the expression of HMG1 gene product is enhanced at the transcriptional level and that this probably occurs through the enhanced expression of the CCAAT binding factor, CTF/NF-1.

Antineoplastic Agents↗
PubMed2001

Origin and propagation of spontaneous excitation in smooth muscle of the guinea-pig urinary bladder.

The origin and propagation of waves of spontaneous excitation in bundles of smooth muscle of the guinea-pig bladder were examined using intracellular recording techniques and visualization of the changes in the intracellular calcium concentration ([Ca2+]i). Bladder smooth muscle cells exhibited spontaneous transient increases in [Ca2+]i which originated along a boundary of each smooth muscle bundle and then spread to the other boundary with a conduction velocity of 2.0 1r1r>mm1> s-1. Spontaneous increases in [Ca2+]i were always preceded by action potentials. Nifedipine (10 microM) abolished increases in both [Ca2+]i and action potentials. Caffeine (10 1s1sFmM1F), ryanodine (50 microM) and cyclopiazonic acid (10 microM reduced the amplitude of the associated increases in [Ca2+]i without preventing the generation of action potentials. Spontaneous action potentials had conduction velocities of 40 1t1t>mm 1> s-1 in the axial direction and 1.3 1u1u>mm 1> s-1 in the transverse direction. The electrical length constants of the bundles of muscle were 425 microM in the axial direction and 12.5 microM in the transverse direction. Neurobiotin, injected into an impaled smooth muscle cell, spread more readily to neighbouring cells located in the axial direction than those located in the transverse direction. The spread of neurobiotin was inhibited by 18beta-glycyrrhetinic acid (18beta-GA, 40 microM), a gap junction blocker. Immunohistochemistry for Connexin 43 showed abundant punctate staining on the smooth muscle cell membranes. These results suggested that spontaneous action potentials and associated calcium waves occur almost simultaneously along the boundary of bladder smooth muscle bundles and then propagate to the other boundary probably through gap junctions.

Action Potentials↗
PubMed2001

Detection of human papillomaviruses in cervical neoplasias using multiple sets of generic polymerase chain reaction primers.

OBJECTIVE: The aim of this study was to evaluate precisely the differences in the spectra of human papillomavirus (HPV) types detected by different generic primer pairs commonly used for detection of this extraordinarily heterogeneous virus. METHODS: Three sets of polymerase chain reaction (PCR) primers for the L1 open reading frame (ORF) and two sets for E6/E7 ORFs were used to detect HPVs in DNAs from 107 cervical tissues, including 77 cervical neoplasias. HPV types were determined by analysis of restriction fragment length polymorphisms (RFLPs) and nucleotide sequencing. RESULTS: A high overall detection rate of HPV in cervical neoplasias (76/77, 98.7%) was achieved by polymerase chain reaction (PCR) amplification with multiple sets of generic primers, while the detection rate for each individual primer pair varied from 48/77 (62%) to 70/77 (91%). Only in 34 of 77 cases (44%) were HPV DNAs positive for all sets of primer pairs. Further determination of HPV types by RFLPs and nucleotide sequencing showed inconsistencies between the PCR primer pairs used. CONCLUSION: Our study revealed that the HPV detection rate is critically affected by the choice of PCR primers, and that appropriate use of combinations of generic PCR primer sets followed by RFLP analyses is both necessary and sufficient for typing most HPVs in cervical lesions. More precise methods such as sequencing would be necessary in only a few cases.

Consensus Sequence↗