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Biomedical subjects

Y Sakurai

Publications and source records attributed to Y Sakurai.

At least 181 records · Page 10Linked to original sources

Allowable aperture size of the front end for the high-heat-load undulator beamlines of SPring-8.

A systematic study to determinine the allowable aperture size of the front end for the SPring-8 high-heat-load undulator beamlines has been performed, from the viewpoint of protecting the front-end Be window from thermomechanical failure, and based on the results of ANSYS finite-element analyses. These results have revealed that the allowable aperture size of the front end ranges approximately from 1.06 mm(2) to 3.2 mm(2) depending on the K-parameter and the filter thickness.

Journal Article↗

Electronics for SPring-8 X-ray beam monitors.

A sensitive current-measuring system is required to construct a highly sensitive X-ray beam-position monitor (XBPM). A current-voltage converter (I/V) which can measure currents between 0.1 nA and 10 mA was designed, and the signal processing system of the XBPM was constucted using this I/V. This system was used in beamline commissioning. Beam-position data standard deviations of sigma approximately 3 micro m for the bending-magnet beamline, and sigma(x) approximately 3 micro m and sigma(y) approximately 1 micro m for the insertion-device beamline were obtained during the beamline commissioning.

Journal Article↗

Bent-crystal monochromators for high-energy synchrotron radiation.

Two kinds of monochromators covering the energy ranges 100-150 keV and approximately 300 keV have been designed for inelastic (Compton) scattering experiments at the elliptical multipole wiggler beamline, BL08W, of SPring-8. Finite-element analyses using ANSYS for bent crystals indicate that thermal problems are not serious for the 300 keV monochromator, while an energy spread of about 10(-3) for the 100-150 keV monochromator is possible in the centre of the crystal. Detailed calculations of X-ray interaction with the silicon crystal were performed. The results show that Compton scattering is a dominant process and deposits about 100 W continuously.

Journal Article↗

High-energy inelastic-scattering beamline for electron momentum density study.

The advent of synchrotron radiation sources for well polarized and high-energy X-rays offers new opportunities for exploiting Compton scattering spectroscopy as a tool for investigating the electronic and magnetic structures of materials. Recent high-resolution Compton scattering experiments show the unique capability for the study of Fermiology-related issues and electron-electron correlation effects. Intense, high-energy and circularly polarized X-ray sources have improved magnetic Compton scattering spectroscopy from the point of statistical accuracy and momentum resolution. As a next advance, a high-energy inelastic scattering beamline dedicated to Compton scattering spectroscopies is being constructed at SPring-8. The light source is an elliptic multipole wiggler with a periodic length of 12 cm. The beamline includes two experimental stations: one is for high-resolution spectroscopy using 100-150 keV X-rays and the other is for magnetic Compton scattering experiments using circularly polarized 300 keV X-rays. The use of such high-energy X-rays makes it possible to carry out experiments efficiently on samples including heavier elements, such as high-T(c) superconductors and 4f and 5f magnetic materials.

Journal Article↗

Effect of molecular architecture of hydrophobically modified poly(N-isopropylacrylamide) on the formation of thermoresponsive core-shell micellar drug carriers.

Terminal-incorporation of hydrophilic or hydrophobic groups dramatically influences the phase transition of poly(N-isopropylacrylamide) (PIPAAm) because of a critical role of the polymer chain ends in initiation of the phase transition. Incorporation of an amino or hydroxyl group to one end of PIPAAm remarkably raised the LCST (lower critical solution temperature) and slowed down the rate of the phase transition, and these effects were more pronounced as the mole fraction of hydrophilic groups increased compared to the random copolymers of PIPAAm and hydrophilic co-monomers, such as acrylic acid (AAc) or dimethylacrylamide (DMAAm). Hydrophilic effects were more remarkable for hydroxyl groups, due to stronger hydrogen bonding with water. Terminal-modification (hydrophobization) was also more effective in producing hydrophobic effects on the PIPAAm phase transition in comparison with PIPAAm copolymers that were randomly modified along the main chain with hydrophobic co-monomers. Moreover, terminal-located hydrophobic groups were able to form hydrophobic microdomains that were clearly isolated from PIPAAm chains in aqueous media by the aggregation of hydrophobic segments. As a result, the obtained micellar aqueous solution showed the same LCST as pure PIPAAm, while the PIPAAm random copolymer with hydrophobic co-monomers formed incompletely separated microdomains. The LCST for this random copolymer was reduced with increasing hydrophobic co-monomer mole fraction. Hydrophobically terminal-modified PIPAAm produced thermo-responsive core-shell structures that exhibited the same LCST and the same thermal response rate as those of free linear PIPAAm chains. Such polymeric micellar structures show reversible thermoresponsive aggregation/dispersion and deformation/reformation in heating/cooling cycles through the LCST for pure PIPAAm. These properties indicate the possibility of using such a system as a thermoresponsive drug carrier with double targeting mechanisms, in both passive and active manners.

Acrylic Resins↗

Differentiation of oligodendrocyte occurs in contact with astrocyte.

We have generated stage-specific oligodendrocytes, which are identified as immature oligodendrocytes by the expression of specific markers. These cells were generated by using 3 types of intrinsic and extrinsic factors for influencing the characteristics of oligodendrocyte-lineage cells. The factors included 10% serum in the medium to induce cell proliferation, bFGF in serum-free medium to increase survival and induce differentiation, and 0.25% trypsin to remove nonoligodendrocyte lineage cells. We have also demonstrated that it is possible to supply a huge amount of homogeneous populations of stage-specific immature oligodendrocytes after 35 days' culture. The maturation of these cells is controlled by interacting with astrocytes in vitro, resulting in the expression of MBP isoforms (14.0 and 18.5 kDa) that may participate in mature oligodendrocyte membrane compaction.

Animals↗

Purification and amino acid sequence of halystase from snake venom of Agkistrodon halys blomhoffii, a serine protease that cleaves specifically fibrinogen and kininogen.

We have isolated a serine protease, halystase, from Agkistrodon halys blomhoffii venom by chromatography on DEAE-Sepharose, heparin-Sepharose and Q-Sepharose columns, and have determined the complete amino acid sequence by Edman degradation and by mass spectral analysis of peptides generated by enzymatic and chemical cleavage. The 238-residue sequence of halystase, containing N-linked carbohydrates (about 13%) at two sites showed significant similarity to other thrombin-like snake venom serine proteases (66-72%), mammalian tissue kallikrein (42%) and thrombin (26%). Halystase contained the tentative catalytic triad of His43, Asp88 and Ser184 common to all serine proteases and Asp178 in the primary substrate-binding site. Although halystase contained an RGD sequence at residues 181-183, it did not inhibit platelet aggregation induced by ADP or collagen. It hydrolyzed most efficiently a tissue-kallikrein substrate, prolylphenylalanylarginyl-4-methyl-coumaryl-7-amide, and released bradykinin from bovine kininogen. Halystase did not coagulate human plasma, but it cleaved the fibrinogen B beta chain at the carboxyl side of Arg42 and cleaved slowly the fibrogen A alpha chain. Fibrinogen thus treated gradually became insensitive to thrombin. The proteolytic activity was inhibited with diisopropyl fluorophosphate, phenylmethylsulfonyl fluoride or leupeptin. These results indicate that halystase is a serine protease structurally similar to coagulating thrombin-like snake venom proteases, but it specifically cleaves fibrinogen at sites different from thrombin without inducing fibrin clotting, and hydrolyzes kininogen to produce bradykinin, resulting in the reduction of blood pressure.

Agkistrodon↗

Regular physical activity and coronary risk factors in Japanese men.

BACKGROUND: Physical activity decreases the risk of coronary heart disease (CHD), but its effects on risk factors require further exploration. METHODS AND RESULTS: The study included 3331 adult Japanese men in whom health benefits, especially CHD risk factors, were compared among those who were sedentary and those who were engaged in continuous physical activity of 30 minutes or more per day for 1, 2 and > or =3 days per week. Significantly higher HDL cholesterol values; lower triceps, scapula, and iliac subcutaneous fat thickness; and lower smoking rates were noted in all physically active groups compared with the sedentary group, whereas body mass index did not differ significantly. Waist-to-height ratios and the prevalence of fatty liver were significantly lower in the groups who exercised 2 or > or =3 days per week than in the sedentary group. The lowest triglyceride values were noted in the group who exercised > or =3 days per week. Multiple regression analysis revealed both the frequency of physical activity and smoking status to be independent positive and negative factors, respectively, for the HDL cholesterol value. The sum of the risk factor scores for hypertension, abnormal glucose tolerance, hypertriglyceridemia, hypercholesterolemia, and low HDL cholesterol level (one point for each if present) was highest in the sedentary group (1.38, 1.19, 1.19, 0.99 for the sedentary group and the groups who exercised 1, 2, and > or =3 days per week). CONCLUSIONS: Those who engaged in regular physical activity > or =3 days per week appeared to have the fewest coronary risk factors. However, even those engaged in physical activity once per week had fewer CHD risk factors than sedentary individuals.

Adult↗

Mechanism of short-term memory and repetition in conduction aphasia and related cognitive disorders: a neuropsychological, audiological and neuroimaging study.

To evaluate the role of the sub-cortical white matter and cortical areas of the supramarginal gyrus in short-term memory impairment (shortened digit or letter span) and repetition difficulty, four patients with conduction aphasia and impaired short-term memory and two patients with only short-term memory impairment were given digit span, letter span, speech audiometry and dichotic listening tests. The results showed that in most of the patients letter span was inferior to digit span and that bilateral ear suppression in the dichotic listening test was observed in two patients with a lesion in the inferior part of the supramarginal gyrus, suggesting that what was affected was phonological information and that the supramarginal gyrus was the storage site. The overlapped lesion of conduction aphasia patients with short-term memory impairment was the periventricular white matter at the upper to middle part of the trigone, while patients with only short-term memory impairment had a lesion in the inferior supramarginal gyrus in common. Thus, damage to the periventricular white matter at the trigone may yield the phonemic paraphasia characteristic of conduction aphasia, while damage to the inferior part of the supramarginal gyrus may result in the impairment of short-term memory. We believe that as a part of the mechanisms of short-term memory and repetition, phonological information is processed in the primary auditory cortex and goes through the periventricular white matter to the inferior part of the supramarginal gyrus and is temporarily stored there.

Aged↗

Characterization of physical entrapment and chemical conjugation of adriamycin in polymeric micelles and their design for in vivo delivery to a solid tumor.

An anticancer drug adriamycin (ADR) was incorporated into polymeric micelles forming from poly(ethylene glycol)-poly(aspartic acid) block copolymer by chemical conjugation and physical entrapment. Structural stability of the polymeric micelles was found to be dependent on both the contents of chemically conjugated and physically entrapped ADR. The polymeric micelle with high contents of the chemically conjugated ADR and the physically entrapped ADR expressed very high in vivo antitumor activity against murine C 26 tumor, while the polymeric micelle with only the chemically conjugated ADR showed negligible in vivo activity. This indicates that the physically entrapped ADR played a major role in antitumor activity in vivo. For the polymeric micelle with the high ADR contents, it was found that a dimer of adriamycin molecules formed and that this dimer was physically entrapped in the inner core of the micelle as well as intact ADR.

Animals↗

Active platelet movements on hydrophobic/hydrophilic microdomain-structured surfaces.

The early motion and interaction of platelets on a microdomain-structured block copolymer surface composed of 2-hydroxyethyl methacrylate (HEMA)-styrene were analyzed and compared with those on a compositionally identical random copolymer, homopolymer poly (HEMA) (hydrophilic) and polystyrene (hydrophobic) surfaces. Contacting platelets were quantitatively more active, with motions including rolling, detachment, oscillatory vibration, and change of direction only on the HEMA-St block copolymer surface. Active platelet movements were observed for long time periods (>20 min) on HEMA-St block copolymer surfaces and were distinct from those for inert PSt latex particles on these same surfaces, demonstrating that platelet movements were not due to physical forces such as convection, hydrophobic interactions, or microbrownian movement. To study the cause and mechanism underlying the platelet movements, platelets treated with an adenosine triphosphate (ATP) synthesis inhibition, NaN3, or a membrane skeleton-disrupting chemical agent, dibucaine, were also studied on these surfaces. Both treatments reduced platelet movement and demonstrated that platelets in contact with the HEMA-St block copolymer surface require metabolic processes consuming ATP and involve dynamics of their membrane skeleton. These energy-consuming active movements might explain the previously observed lower platelet activation and low thrombogenicity of the HEMA-St block copolymers. Enhanced platelet movements on the HEMA-St block copolymer surface show that the microdomain surface interacts uniquely with platelets to hinder activation and preserve passive platelet function despite surface contact.

Adenosine Triphosphate↗

Metabolic alteration in patients with cancer: nutritional implications.

During the past 20 years, efforts have been made to elucidate the metabolic changes observed in patients with cancer by using stable and radioactive isotopic tracers. These metabolic changes in patients with cancer may be similar to those in other stress conditions, in which glucose production and utilization, lipolysis and free fatty acid flux, and net protein catabolism are increased. Stress hormones, such as glucagon and catecholamines, and certain cytokines may be responsible for these metabolic changes. Although it has been shown that cachexia in patients with cancer signals a poor prognosis, efforts to improve the clinical outcomes with nutritional support have been disappointing. The failure of cancer patients to respond to nutritional support may be related to an alteration in the intermediate metabolism. Therefore, further research evaluating the metabolic abnormalities associated with cancer may lead to more effective nutritional therapies.

Cachexia↗

Cervical myelocystocele with Chiari II malformation: magnetic resonance imaging and surgical treatment.

BACKGROUND: The myelocystocele is a rare clinical entity, and there have only been six case reports concerning the cervical myelocystocele, including ours. METHODS: The case of a female neonate with cervical myelocystocele, who presented with respiratory distress beginning at birth is reported. RESULTS: Magnetic resonance (MR) imaging disclosed a cystic lesion surrounded by two layers of membrane, which were recognized to be the dural and arachnoid layer and the ependymal lining layer, respectively, during operation and on histopathologic examination. Hydromyelia at C2-C7 with Chiari II malformation was also observed. After a thorough repair and untethering surgery, the hydromyelia was diminished on a follow-up MR examination. The patient's respiratory status normalized several days postoperatively, and her growth and development were within normal limits at the 2-year follow-up. CONCLUSIONS: In cases of cervical myelocystocele with Chiari II malformation, untethering through intradural exploration to treat the tethered cord and outer decompression of the foramen magnum are needed. MR imaging is the best modality for preoperative determination of anatomic relationships.

Arnold-Chiari Malformation↗

The search for cell assemblies in the working brain.

This paper discusses why population ensemble coding by multiple neurons is a tenable view of the brain's basic neuronal code. The discussion is based on features of neuronal activity in working brains of behaving animals. The key concept to elucidate population ensemble coding is the 'cell assembly', i.e. overlapped populations of neurons with flexible functional connections within and among the populations. Recent examples of experimental approaches which indicate the cell-assembly coding of memory in the working brain are given. These experiments used a strategy that reveals two main properties of cell assemblies; the overlapping of neurons and the dynamic changes of synaptic connections in processing different kinds of memory. Several possible features of cell-assembly coding that might be explored in future experimental research are enumerated.

Animals↗

A paired wedge filter system for compensation in dose differences.

OBJECTIVE: In radiotherapy, it is important to conform the high dose volume to the planned target volume. A variable thickness paired wedge filter system was developed to compensate for dose inhomogeneity arising from field width segment variation in conformal irradiation. MATERIALS AND METHODS: The present study used a 6 MV linear accelerator equipped with multileaf collimator leaves and a paired wedge compensating filter system. The dose variation due to field width was measured in each field segment width. The variation in attenuation of the compensators was measured as a function of filter position. As the field width increases, the relative absorbed dose also increases; this is the point of requiring compensation, so it can be in reverse proportion. RESULTS: As the field width increases, the relative absorbed dose also increases; this is why compensation is required and thus it must be in reverse proportion. Attenuation of the absorbed dose by the paired filters was in proportion to the filter position. The filter position to compensate for the difference of absorbed doses was defined by the square root of the field width. For a field varying in width from 4 to 16 cm, the variation in the absorbed dose across the field was reduced from 12% to 2.7%. CONCLUSION: This paired wedge filter system reduced absorbed dose variations across multileaf collimator shaped fields and can facilitate treatment planning in conformal therapy.

Humans↗

Insertion/deletion polymorphism in intron 16 of the ACE gene and left ventricular hypertrophy in patients with end-stage renal disease.

We studied the relationship between polymorphism in intron 16 of the angiotensin-converting enzyme (ACE) gene and left ventricular (LV) hypertrophy in uremic patients treated with hemodialysis therapy. The LV parameters were not different for age-, hematocrit-, and blood pressure-matched patients in DD, ID, and II genotype groups. The most important factor for LV hypertrophy was systolic blood pressure, which correlated with the posterior wall thickness (r=0.35; P=0.001) and LV mass index (LVMI; r=0.23; P=0.032). Among nonhypertensive patients, the frequency of interventricular septum (IVS) hypertrophy (>12 mm) and hypertrophy in LVMI (>145 g/m2) was significantly greater in patients with the DD genotype than in I allele-positive (+) patients. The odds rate for IVS hypertrophy was 5.04 (95% confidence interval, 1.15 to 24.8). These data suggest that the DD genotype of the ACE gene polymorphism is a contributory factor for the development of LV hypertrophy in patients with end-stage renal disease (ESRD).

Age Factors↗

Establishment of a new murine-phenotypic angiosarcoma cell line (ISOS-1).

A cell line, designated ISOS-1, was established from a tumor formed by transplantation of a human angiosarcoma into mice with severe combined immunodeficiency (SCID). The cells showed endothelial properties, based on the uptake of Dil-Ac-LDL and binding of UEA-I/GSA-I lectins, but were negative for CD11b and Pan Cytokeratin. However, the cells lost differentiated characteristics such as expression of von Willebrand factor, contact inhibition growth and tube formation activity. These findings indicate that ISOS-1 is a poorly-differentiated endothelial cell line. At the 81st passage, all of the cells were positive for H-2Dd in various intensity, but not HLA-ABC. The metaphase chromosomes consistently showed a characteristic mouse, but not human, telocentric form. Furthermore, this cell line produced fatal tumor growth in SCID mice and also in BALB/c mice. These results suggest that ISOS-1 is a murine-phenotypic angiosarcoma cell line.

Animals↗