Biomedical subjects

M Machida

Publications and source records attributed to M Machida.

At least 19 recordsLinked to original sources

PubMed2005

Structure of a quantized vortex near the BCS-BEC crossover in an atomic Fermi gas.

In order to clarify the structure of a singly quantized vortex in a superfluid fermion gas near the Feshbach resonance, we numerically solve the generalized Bogoliubov-de Gennes equation in the boson-fermion model. The superfluid gap, which contains contributions from both condensed fermion pairs and condensed bosons, is self-consistently determined, and the quasiparticle excitation levels bound in the vortex core are explicitly shown. We find that the boson condensate contributes to enhance the matter density depletion and the discreteness of localized quasiparticle spectrum inside the core. It is predicted that the matter density depletion and the discrete core levels are detectable in the vicinity of the BCS-Bose-Einstein condensation crossover point.

Journal Article↗

PubMed2004

Novel superfluidity in a trapped gas of Fermi atoms with repulsive interaction loaded on an optical lattice.

We investigate a possibility of superfluidity in a trapped gas of Fermi atoms with a repulsive interaction in the presence of an optical lattice. Applying the exact diagonalization method to a one-dimensional Hubbard model including the trap potential, we find that, when the strength of the repulsive interaction exceeds a critical value, the binding energy of two Fermi atoms becomes negative below the half-filling case, indicating that an attractive interaction effectively works between Fermi atoms. In this case, a "Mott insulating core" appears in the center of the trap, where each site is occupied by one atom. The Cooper-pair correlation strongly develops between atoms in the left- and right-hand sides of this core.

Journal Article↗

PubMed2004

Probe of bending motion following the 1s(-1)pi* excitation of N2O.

The doubly degenerate core-excited Pi state of N2O splits into two due to the static Renner-Teller effect. The lower state, A1, has a bent stable geometry and the molecule excited to this state starts to deform itself toward this bent geometry. To probe the effect of the potential energy surfaces of the core-excited A1 states on the nuclear motion, we measure the momenta of the three atomic ions in coincidence by means of the ion momentum imaging technique. We find that the potential energy surface affects the molecular deformation significantly. N2O in the terminal N 1s(-1)3piA1 excited state is observed to be bent more than that in the central N 1s(-1)3piA1 excited state. This means that N2O in the terminal N 1s(-1)3piA1 excited state bends faster than that in the central N 1s(-1)3piA1 excited state. When the excitation energy is decreased within the 1s(-1)3pi resonances, the nuclear motion in the A1 states becomes faster. This is interpreted by the notion that the excitation occurs onto the steeper slope part of the potential energy surface of the excited state for the lower excitation energy. The branching ratio of the A1 excitation increases with the decrease in the excitation energy.

Journal Article↗

PubMed2004

Comparative study of the effects of isatin, an endogenous MAO-inhibitor, and selegiline on bradykinesia and dopamine levels in a rat model of Parkinson's disease induced by the Japanese encephalitis virus.

We previously reported that exogenously administered isatin, an endogenous monoamine oxidase (MAO) inhibitor, significantly increased acetylcholine (ACh) and dopamine (DA) levels in the rat striatum. Selegiline [(-)-deprenil] was developed as a MAO-B inhibitor more than 30 years ago and widely used in the treatment of Parkinson's disease. Effects of isatin or selegiline were investigated in Japanese encephalitis virus (JEV)-induced post-encephalitic parkinsonism rats by a pole test for detecting motor activity and by the determination of biogenic amine levels. Motor activity of JEV-induced rats receiving isatin (100 mg/kg per day for 1 week, i.p.) or selegiline (0.2 mg/kg per day for 1 week, i.p.) was significantly improved compared with that of untreated JEV-infected rats. Both isatin and selegiline prevented the decrease in striatal DA levels in JEV-rats. The increased turnover of DA (DOPAC/DA) induced by JEV was significantly inhibited by isatin, but not by selegiline. These results suggested that exogenously administered isatin and selegiline can improve JEV-induced parkinsonism by increasing DA concentrations in the striatum.

Animals↗

PubMed2003

Friedel oscillation in charge profile and position dependent screening around a superconducting vortex core.

We calculate microscopically the charge distribution around a vortex in type II superconductors by solving the Bogoliubov-de Gennes equation and the Poisson equation simultaneously. Our calculations show that the charge density depletion occurs in the vortex center and the Friedel oscillation appears over the coherence length when k(F)xi is small. We also calculate the density-density correlation function K(r,r(')) as a function of two spatial variables, r and r('), and find that K(r,r(')) is strongly dependent on the distance from the vortex center. We clarify the spatial dependent screening properties on the basis of the correlation function in the core region.

Journal Article↗

PubMed2003

Dynamical matching of Josephson vortex lattice with sample edge in layered high-Tc superconductors: origin of the periodic oscillation of flux flow resistance.

We numerically investigate Josephson vortex flow states in layered high-T(c) superconductors motivated by a recent experimental observation for accurate periodic magnetic field dependences of the Josephson vortex flow resistance over a wide range of magnetic field (0.5-4.0 T). We confirm in our mesoscale simulations that dynamical matching of Josephson vortex lattice with sample edge is responsible for the periodic dependence. The present simulations reveal that the Josephson vortex lattice flow speed is particularly suppressed when the moment of vortex entry matches that of vortex escape. Thus, the possible matching situations are taken into account and the observed periodicity is successfully explained.

Journal Article↗

PubMed2003

Multipurpose robot for automated cycle sequencing.

Paramagnetic beads have the superior advantages of easy separation and resuspension by controlling the magnetic filed. Previously, we have developed Magtration technology to automate paramagnetic bead handling and have built several automated instruments that handle 1-12 samples simultaneously. To achieve more high-throughput sample processing, two types of a 96-arrayed Integrated Magtration Unit (IMU) were developed, one installed with electromagnets and the other with thin rod-shaped magnets made of neodymium. A multipurpose robot (SX-96GC) equipped with the IMU was also developed for fully automatic processing of 96 samples in parallel. The cleanup of dye-terminator sequencing products was performed using the robot installed with the permanent magnet version of IMU. The results had quality comparable to those by the same protocol in manual handling or to those by the conventional protocols. The robot processed 96 samples in a microplate within 30 min. The protocol that can purify 384 samples within 1 h by processing two microplates concurrently was successfully designed.

Equipment Design↗

PubMed2002

Symmetry-dependent multielectron excitations near the C 1s ionization threshold and distortion of the shape resonance in CO(2).

Satellite bands accompanying the C 1s photoline for the CO2 molecule parallel to the electric vector of the incident radiation E are found to be more intense than those for CO2 perpendicular to E in the shape resonance region. This indicates that multielectron excitations are caused in part by the interaction of the outgoing C 1s photoelectron with the valence electrons. The photoelectron-impact valence excitations couple with the C 1s single-hole ionization and distort the shape resonance significantly. We assign the broad resonance at approximately 312 eV to a distorted Sigma(u) shape resonance.

Journal Article↗

PubMed2002

Successfully treated case of cervical abscess and mediastinitis due to esophageal perforation after gastrointestinal endoscopy.

Perforations of the esophagus are uncommon complications of flexible gastrointestinal endoscopy. Perforations after endoscopy are likely to occur in the cervical esophagus, where fiber insertion is difficult anatomically. The diagnosis should be made as soon as possible, because mediastinitis and sepsis frequently develop following esophageal perforations. The surgical strategies are dependent on the location of the perforations and the condition of the patients. For a successful outcome, surgery is a preferred treatment for most perforation cases, and non-operative treatment, such as antibiotics, parental nutrition, and no food intake by mouth, should be applied carefully.

Abscess↗

PubMed2002

Plasma endothelin, nitric oxide and atrial natriuretic peptide levels in humans after abdominal angiography.

PURPOSE: To clarify the effect of the contrast medium iopamidol on endothelial function and response of vasoactive peptide, as measured by changes in the levels of plasma endothelin, nitric oxide and atrial natriuretic peptide. MATERIAL AND METHODS: Thirteen patients received iopamidol 300 mg I/ml intra-arterially during routine abdominal angiography. The mean volume of contrast medium administered was 208.1+/-32.5 ml. Endothelin, nitric oxide and atrial natriuretic peptide were measured before and after angiography. RESULTS: Endothelin levels increased significantly (from 1.45+/-0.12 pg/ml to 1.90+/-0.10 pg/ml) after exposure to contrast medium. Nitric oxide levels decreased significantly (from 34.56+/-2.23 micromol/ to 25.43+/-1.83 micromol/l). Atrial natriuretic peptide levels increased significantly (from 11.43+/-1.68 pg/ml to 21.28+/-2.89 pg/ml). CONCLUSION: Exposure to contrast medium in humans is associated with an increase in plasma endothelin levels and a decrease in nitric oxide levels, and atrial natriuretic peptide levels also increase following CM injection.

Abdomen↗

PubMed2001

Shapiro step response in the coherent Josephson flux flow state of Bi2Sr2CaCu2O8+delta.

We report the first observation of Shapiro steps in the Josephson flux flow state of Bi2Sr2CaCu2O8+delta stacked junctions. When the junction is irradiated at microwave frequencies in a strong parallel magnetic field ( H> or =1 T), a steep increase of the current is observed in the dc current-voltage characteristics when the external microwave frequency and the Josephson frequency are harmonically related. The existence of Shapiro steps in the Josephson flux flow state is strong evidence of coherent motion of the Josephson vortex lattice through the whole thickness of the stack.

Journal Article↗

PubMed2001

Optimized conditions of bio-mimetic artificial membrane permeation assay.

Effects of pH and co-solvents on the bio-mimetic artificial membrane permeation assay were investigated to determine the optimal conditions for the prediction of oral absorption. The permeability (P(am)) of 33 structurally diverse drugs to the PC/PE/PS/PI/CHO/1,7-octadiene membrane system (bio-mimetic lipid (BML) membrane) was measured at pH 5.5, 6.5, and 7.4. The pH dependence of P(am) was in accordance with the pH partition theory. The better prediction of oral absorption (fraction of a dose absorbed) was shown under the pH 5.5 condition (r=0.866, n=25) and/or pH 6.5 (r=0.865, n=28), rather than pH 7.4 (r=0.767, n=24). Then, the appropriate conditions for determining the permeability of poorly soluble compounds were examined. Dimethysulfoxide (DMSO), ethanol (EtOH) and polyoxyethyleneglycol 400 (PEG 400) were added up to 30% to the transport medium as solubilizers. DMSO, EtOH and PEG 400 decreased P(am) of hydrocortisone and propranolol. For example, DMSO (30%) decreased P(am) of hydrocortisone by 60% and by 70% in the case of propranolol. DMSO and PEG 400 also decreased P(am) of ketoprofen. In contrast, EtOH produced an opposite effect on permeability, i.e. an increased P(am) of ketoprofen. Therefore, the high concentration of these co-solvents could lead to the under- or overestimation of drug permeability.

Algorithms↗

PubMed2001

Pathologic mechanism of experimental scoliosis in pinealectomized chickens.

STUDY DESIGN: This study was designed to investigate the pathologic mechanisms of idiopathic scoliosis using experimentally induced scoliosis in chickens. OBJECTIVE: To understand the process of producing a scoliotic deformity in pinealectomized chickens. SUMMARY OF BACKGROUND DATA: Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. Pinealectomized chickens are an important animal model for the study of idiopathic scoliosis. METHODS: In this study, 40 chickens were divided into two groups; 20 chickens treated with pinealectomy and 20 with a sham operation as control subjects on the second after hatching. The chickens in both groups then were killed at intervals ranging from 1 to 20 weeks after surgery. Their spines were examined visually and radiologically for the presence of a scoliotic curve and vertebral deformities. RESULTS: Rotational lordoscoliosis developed in pinealectomized chickens. The chickens with severe scoliosis were characterized by apically wedge-shaped vertebrae. In contrast, no scoliosis with any vertebral deformity developed in any of the chickens that received a sham operation. CONCLUSIONS: Because there normally is evidence of lordosis in the thoracic spine of chickens, the rotational instability of the spine induced by pinealectomy may produce a scoliotic deformity as a secondary phenomenon. Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. The authors believe that disturbance of the equilibrium and the posture mechanism associated with a defect in melatonin synthesis after pinealectomy may promote the development of rotational lordoscoliosis.

Animals↗

PubMed2001

Deletion analysis of the enolase gene (enoA) promoter from the filamentous fungus Aspegillus oryzae.

The enolase gene (enoA) is one of the most strongly expressed genes in Aspergillus oryzae. To elucidate the transcription regulatory element for this strong expression and the process of glucose induction, the transcription activity of a series of truncated enoA promoters was measured by using the Escherichia coli uidA gene as a reporter. Deletion of a 104-bp region located -224 nt to -121 nt upstream of the translation initiation site caused both a drastic decrease in the beta-glucuronidase (GUS) activity and a loss of glucose induction. Northern blot analysis confirmed that the decrease in GUS activity was achieved at the transcriptional level. In addition, electrophoretic gel mobility shift assays indicated that the 104-bp region contained a 15-bp element, to which one or more A. oryzae cellular factors specifically bind. These results suggest that the 15-bp element between -195 nt and -181 nt includes the sequence essential for the transcription regulation of the A. oryzae enoA gene.

Aspergillus oryzae↗

PubMed2001

Method for orienting DNA molecules on mica surfaces in one direction for atomic force microscopy imaging.

An efficient method was developed to stretch DNA molecules on an atomically flat surface for AFM imaging. This method involves anchoring DNA molecules from their 5' ends to amino silanized mica surfaces. N-Succinimidyl6-[3'-(2-pyridyldithio) propionamido]hexanoate (LC-SPDP), a heterobifunctional cross-linker with a flexible spacer arm was used for this purpose. Immobilization was carried out by introducing a thiol group to the 5' end of DNA by PCR. Thiolated molecules were then reacted with the cross linker to conjugate with its 2-pyridyl disulphide group via sulfhydryl exchange. The resulting complex was deposited on amino silanized mica where NHS-ester moiety of the cross linker reacted with the primary amino group on the surface. Samples were washed by a current of water and dried by an air jet in one direction parallel to the surface. DNA molecules were fully stretched in one direction on imaging them by AFM.

Aluminum Silicates↗

PubMed2001

High throughput prediction of oral absorption: improvement of the composition of the lipid solution used in parallel artificial membrane permeation assay.

The purpose of the present study was to improve the composition of the lipid solution used in parallel artificial membrane permeation assay for the precise prediction of oral absorption. We modified the composition of lipid solution, which was used to make a lipid membrane on the filter support. First, we changed the chain length of organic solvent (PC/alkyldienes [C7-C10]). A negative charge was then added to the membrane to mimic the intestinal membrane (PC/stearic acid/1,7-octadiene and PC/PE/PS/PI/cholesterol/1,7-octadiene). Finally, we examined the predictability of the PC/PE/PS/PI/CHO/1,7-octadiene membrane using structurally diverse compounds. Permeability coefficients of tested compounds were increased as the chain length of alkyldiene became shorter. The addition of a negative charge to the membrane increased the permeability of the basic compounds. However, the negatively charged membrane with stearic acid showed different permeability profiles from PC/PE/PS/PI/CHO. The predictability of the PC/PE/PS/PI/CHO/1,7-octadiene membrane was adequate (r = 0.858, n = 31) for use during the early stages of the drug discovery/development process.

Absorption↗

PubMed2001

Electrophoretic mobility shift scanning using an automated infrared DNA sequencer.

Electrophoretic mobility shift assay (EMSA) is widely used in the study of sequence-specific DNA-binding proteins, including transcription factors and mismatch binding proteins. We have established a non-radioisotope-based protocol for EMSA that features an automated DNA sequencer with an infrared fluorescent dye (IRDye) detection unit. Our modification of the elec- trophoresis unit, which includes cooling the gel plates with a reduced well-to-read length, has made it possible to detect shifted bands within 1 h. Further, we have developed a rapid ligation-based method for generating IRDye-labeled probes with an approximately 60% cost reduction. This method has the advantages of real-time scanning, stability of labeled probes, and better safety associated with nonradioactive methods of detection. Analysis of a promoter from an industrially important filamentous fungus, Aspergillus oryzae, in a prototype experiment revealed that the method we describe has potential for use in systematic scanning and identification of the functionally important elements to which cellular factors bind in a sequence-specific manner.

DNA↗

PubMed2001

[Possible role of the pineal gland in the pathogenesis of idiopathic scoliosis. Experimental and clinical studies].

The unexpected finding in 1959 by Marie-Jeanne Thillard that pinealectomy in young chickens gives way to spinal deformities was confirmed by the authors. In another experiment they found that injected melatonine to the chick at adequate dose and at the same time as surgery, lessen or even totally prevents the occurrence of deformities. On the other hand, at too low dose or delayed after pinealectomy melatonine injection, may not prevent the deformity which will be persisting or even increasing. In a subsequent series of experiments on the rat, pinealectomy results in decreasing the plasmatic amount of melatonine as well as giving way to spinal deformities. The nature of these deformities observed here is dependent on the stature between of the animal. The normal quadrupede rat develops after pinealectomy a standard scoliosis. Inversely the scoliotic deformity occurs when the animal has been forced to a bipede condition, which may be achieved by removing its forelimbs when baby, then forcing it to stand and remain in erect posture by high enough feeding. Melatonine depressing and erect position are in two conditions, when associated, likely to give way to experimental scoliosis. In human, a low nycthemeral level of plasmatic melatonine is correlated with progressive scoliosis. The level of platelets calmoduline, when is normally modulated by melatonine, has been proved by Kindsfater to be increased in progressive scoliosis. Then raises the hypothesis that human idiopathic scoliosis may be due to an inherited disorder of neuro-transmitters from neuro-hormonal origin, associated with bipedal condition, where an horizontal localized neuro-muscular imbalance starts and produces the scoliotic deformity of the fibro-elastic and bony structures axial spinal pilar.

Animals↗