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Biomedical subjects

Y Nakayama

Publications and source records attributed to Y Nakayama.

At least 37 records · Page 2Linked to original sources
PubMed2002

Low fractional diastolic pressure in the ascending aorta increased the risk of coronary heart disease.

Although the fractional pulse pressure in the ascending aorta is related to the occurrence of coronary heart disease (CHD) and restenosis after percutaneous transluminal coronary angioplasty, the relative values of diastolic pressure in the ascending aorta at the onset of CHD have not been reported. The purpose of this study was to evaluate whether the relative values of diastolic pressure are associated with the risk of CHD. For this study, we enrolled 406 patients with chest pain, normal contractions, no local asynergy, and no history of myocardial infarction. We measured the ascending aortic pressure using a fluid-filled system. To quantify the relative diastolic pressure, we normalised the diastolic pressures to the mean pressure and referred to this value as the fractional diastolic pressure (FDP). We investigated the association between the FDP and the risk of CHD. Low FDP in the ascending aorta was associated with an increased risk of CHD. The multiple-adjusted odds ratio of CHD was 1.68 (95% CI, 0.67-4.22) in FDP for the middle tertile of the level. The multiple-adjusted odds ratio of CHD was 2.20 (1.16-4.75) in FDP for the lowest tertile compared with the highest tertile. FDP was associated with the risk of CHD.

Adult↗
PubMed2002

Improved filler-matrix coupling in resin composites.

Ineffective silane coupling between filler and matrix within dental composites is prone to accelerated in vivo degradation. In this study, we examined to what degree a procedure involving chemical decontamination of filler prior to silanization could improve the filler-matrix bonding, and thus the physico-mechanical properties, of composites. X-ray photoelectron spectroscopy revealed that filler-matrix coupling largely depended upon siloxane bridge (Si-O-Si) formation between the silica surface and the silane molecule, rather than on intermolecular bonding between adjacent silane molecules. Pre-silanization decontamination based upon boiling silica in 0.05-5% sodium peroxodisulfate, followed by ultrasonic rinsing in acetone, most effectively decontaminated filler. Consequently, it significantly improved the bonding of silane molecules to silanol groups at the silica surface. Experimental composites produced following pre-silanization decontamination of filler revealed a diametral tensile strength that was resistant to degradation by thermocycling.

Composite Resins↗
PubMed2002

Changes in membrane potential induced by compound 48/80 in the peritoneal mast cells of rats.

The changes in membrane potential induced by compound 48/80 were studied using rat peritoneal mast cells. The mean resting membrane potential of rat mast cells was -12.3 +/- 0.7 mM. When compound 48/80 was added to the mast cells, the cells were degranulated approximately 120 sec after the addition of the drug, after which immediate depolarization occurred. Degranulation of mast cells was not observed, even under the depolarization or hyperpolarization conditions caused by the replacement of a high K+ medium or the removal of K+ from the medium, respectively. Under both conditions, when compound 48/80 was added to the mast cells, degranulation was observed. Abrupt and marked depolarization was induced 30-60 sec after compound 48/80 was added. In addition, repolarization followed by gradual depolarization was observed without degranulation in mast cells treated with cytochalasin D after the addition of compound 48/80. These results suggest that the mast cells were depolarized by compound 48/80 independently of degranulation. It is also feasible that the gradual depolarization and repolarization induced by compound 48/80 in mast cells pretreated with cytochalasin D participated in the extracellular Na+ and Na+/K(+)-pump, respectively.

Animals↗
PubMed2002

[The use of a circulatory assistance device during replacement of descending aorta to treat chronic aortic dissection; report of a case].

A 70-year-old woman with Marfan syndrome had undergone Y-graft replacement for abdominal aortic aneurysm at the age of 61. She recently underwent axillo-bifemoral bypass to treat ischemia of the lower extremities caused by acute aortic dissection. The patient was admitted for surgical treatment to treat a remaining dissecting descending aortic aneurysm. Aortography revealed that the entry was present at the takeoff of the left subclavian artery, and that the false lumen extended up the proximal anastomosis of the Y-graft to where the true lumen ended. All the abdominal vessels originated from this false lumen, with the lower extremities being supplied via an axillo-bifemoral bypass. No re-entry was detected. Replacement of the descending aorta was carried out using a 28 mm woven Dacron graft. First, double-barreled distal anastomosis under single clamping was performed; then, proximal anastomosis was carried out under antegrade perfusion from the graft to shorten the ischemic time of the abdominal organs. The patient suffered no postoperative complications.

Aged↗
PubMed2001

Development of high-performance stent: gelatinous photogel-coated stent that permits drug delivery and gene transfer.

Hydrogel-coated metallic stents may provide supplementary functions such as local drug delivery and gene transfer in addition to mechanical dilation function. To this end, we used a photoreactive material consisting of gelatin macromer (multiple styrene-derivatized gelatin) and carboxylated camphorquinone (photo-initiator). A few minutes of visible light irradiation of a stent after dip-coating of an aqueous solution of the photoreactive material resulted in the formation of a homogeneously crosslinked gelatinous layer on the entire exterior surface of the stent. As the metal stent, gold stents under development were used. Rhodamine-conjugated albumin as a model drug or adenoviral vector expressing bacterial beta-galactosidase (AdLacZ) as a model gene were photo-immobilized in the gelatinous gel layer. In vitro experiments using hybrid tubular tissue, which is a self-shrinkaged, vascular smooth muscle cell-incorporated type-I collagen gel, as a vascular model, showed that the immobilized dye-derivatized albumin was released on and permeated into tissues, as observed by confocal laser microscopy, and that the cells transfected with immobilized AdLacZ produced beta-galactosidase up to almost 3 weeks, as observed by x-gal staining. In preliminary in vivo experiments these drug- or adenovirus-immobilized stents were implanted in rabbit common carotid arteries. Within 3 weeks of implantation, drug permeation and gene expression in the vascular tissues were observed, indicating that the gelatinous photogel effectively serves as a matrix or coating for a bioactive stent,which permits drug release as well as gene transfer. This intraluminal approach has the potential to realize drug and gene therapy in atherosclerotic plaque.

Albumins↗
PubMed2001

Oscillating rows of vortices in superconductors.

Superconductors can be used as dissipation-free electrical conductors as long as vortices are pinned. Vortices in high-temperature superconductors, however, behave anomalously, reflecting the anisotropic layered structure, and can move readily, thus preventing their practical use. Specifically, in a magnetic field tilted toward the layer plane, a special vortex arrangement (chain-lattice state) is formed. Real-time observation of vortices using high-resolution Lorentz microscopy revealed that the images of chain vortices begin to disappear at a much lower temperature, Td, than the superconducting transition temperature, Tc. We attribute this image disappearance to the longitudinal oscillation of vortices along the chains.

Journal Article↗
PubMed2001

Heart rate-independent vagal effect on end-systolic elastance of the canine left ventricle under various levels of sympathetic tone.

BACKGROUND: Although we have shown that in rabbits the direct (heart rate [HR]-independent) vagal effect on left ventricular end-systolic elastance (E(es)) was negligible under minimal sympathetic tone, how underlying sympathetic tone modulates the inotropic response to vagal stimulation remains unknown. METHODS AND RESULTS: We used an isolated canine heart preparation with functioning autonomic nerves. We examined the direct vagal inotropic effect by measuring E(es) under fixed-rate atrial pacing with or without concomitant sympathetic nerve stimulation. Right and left vagal stimulation at 20 Hz decreased HR by 27+/-3% and 14+/-2%, respectively, and decreased E(es) by 11+/-2% and 6+/-2%, respectively. When we fixed HR by atrial pacing, right and left vagal stimulation at 20 Hz did not decrease E(es) (0.01+/-0.3% and 0.3+/-0.4%; NS). Concomitant left sympathetic nerve stimulation at 4 Hz enhanced direct vagal negative inotropism to -19+/-3% and -34+/-5% for 20-Hz right and left vagal stimulation (interaction, P<0.01). CONCLUSIONS: Direct vagal negative inotropism was unobservable with minimal sympathetic tone in dogs but was enhanced with concomitant sympathetic stimulation.

Animals↗
PubMed2001

Self-similar fluctuation and large deviation statistics in the shell model of turbulence.

Both static and dynamic multiscalings of fluctuations of energy flux and energy dissipation rate in the Gledzer-Ohkitani-Yamada (GOY) shell model of turbulence are numerically investigated. We compute the large deviation rate function of energy flux not only in the inertial range (IR) but also around the crossover between the inertial range and the dissipation range (DR). The rate function in IR exists to be concave, which assures the applicability of the Legendre transformation with the anomalous scaling exponents that have been investigated so far, and turns out to be independent of the Reynolds number. On the contrary, near the crossover scale, an intermediate dissipation range (IMDR) scaling is observed with the rate function in IMDR, which is accounted with the argument on dissipation scale fluctuation dominated by the energy flux fluctuation in the inertial range. Furthermore, to study the difference between IR intermittency and DR intermittency, we compute finite time-averaged quantities of energy flux and energy dissipation rate and investigate their multiscaling behavior. The difference observed in terms of their dynamic multiscaling is discussed.

Journal Article↗
PubMed2001

Observation of individual vortices trapped along columnar defects in high-temperature superconductors.

Many superconductors do not entirely expel magnetic flux-rather, magnetic flux can penetrate the superconducting state in the form of vortices. Moving vortices create resistance, so they must be 'pinned' to permit dissipationless current flow. This is a particularly important issue for the high-transition-temperature superconductors, in which the vortices move very easily. Irradiation of superconducting samples by heavy ions produces columnar defects, which are considered to be the optimal pinning traps when the orientation of the column coincides with that of the vortex line. Although columnar defect pinning has been investigated using macroscopic techniques, it has hitherto been impossible to resolve individual vortices intersecting with individual defects. Here we achieve the resolution required to image vortex lines and columnar defects in Bi2Sr2CaCu2O8+delta (Bi-2212) thin films, using a 1-MV field-emission electron microscope. For our thin films, we find that the vortex lines at higher temperatures are trapped and oriented along tilted columnar defects, irrespective of the orientation of the applied magnetic field. At lower temperatures, however, vortex penetration always takes place perpendicular to the film plane, suggesting that intrinsic 'background' pinning in the material now dominates.

Journal Article↗
PubMed2001

BXMAS1 identifies a cluster of homologous genes differentially expressed in B cells.

Characterization of genes activated by anti-IgM crosslinking of BL2 cells identified one gene, designated BXMAS1, that is predicted to be a novel cell surface receptor. The time course of activation indicates maximal transcriptional induction after 24 h. The predicted protein contains 977 aa residues, with a cytoplasmic domain containing 2 ITIM motifs. The ectodomain of the protein contains 6 repeats of characteristic 93 aa sequences which we have designated BXMAS1 domains. These domains correspond to 6 out of 8 Ig-like domains in BXMAS1. A search of the human genome revealed 5 additional closely linked homologous genes many of which contain BXMAS1 domains as well. Analysis of expression in cell lines and tissues suggests a general restriction of expression of these genes to B cells. These genes may be involved in B cell development and differentiation in peripheral lymphoid organs and may be useful markers of B cell stages.

Amino Acid Motifs↗
PubMed2001

Influence of biomaterial surface chemistry on the apoptosis of adherent cells.

A common component of the foreign-body response to implanted materials is the presence of adherent macrophages that fuse to form foreign-body giant cells (FBGCs). These multinucleated cells have been shown to concentrate the phagocytic and degradative properties of macrophages at the implant surface and are responsible for the damage and failure of the implant. Therefore, the modulation of the presence or actions of macrophages and FBGCs at the material-tissue interface is an extensive area of recent investigations. A possible mechanism to achieve this is through the induction of the apoptosis of adherent macrophages, which results in no inflammatory consequence. We hypothesize that the induction of the apoptosis of biomaterial adherent cells can be influenced by the chemistry of the surface of adhesion. Herein, we demonstrate that surfaces displaying hydrophilic and anionic chemistries induce apoptosis of adherent macrophages at a higher magnitude than hydrophobic or cationic surfaces. Additionally, the level of apoptosis for a given surface is inversely related to that surface's ability to promote the fusion of macrophages into FBGCs. This suggests that macrophages fuse into FBGCs to escape apoptosis.

Apoptosis↗
PubMed2001

Small-diameter compliant arterial graft prosthesis: Design concept of coaxial double tubular graft and its fabrication.

To minimize compliance mismatch between native artery and arterial graft prosthesis over the entire pressure regions, we proposed a coaxial double tubular artificial graft which consists of an enhanced compliant inner tube and a less compliant outer tube, both of which were fabricated using well-controlled multiply micropored segmented polyurethane (SPU) films. Double tubular grafts were coaxially assembled by inserting the inner tube into the outer tube. First, the pressure-diameter (P-D) relationship of canine common carotid arteries, which exhibited a "J" curve, was determined as a targeted artery. Two determinant variables, the pressure-induced distensibility of each tube and the intertubular space distance, were defined and formulated in several models of coaxial double tubular SPU grafts, which had various intertubular space distances, micropore densities, and wall thicknesses. The distensibility of the inner tube determined the distensibility in the low-pressure regions, which was adjusted using wall thickness and microporosity. Thinner films with higher porosities resulted in a high pressure-induced distensibility. On the other hand, a low pressure-induced distensibility in the high-pressure regions was realized using an outer tube with a thicker wall and lower microporosity. The transition point from low- to high-pressure regions was determined by the intertubular distance using the theoretical values. On the basis of these results, we presented a prototype model of a coaxial double tubular graft that exhibited well-matched compliance with canine carotid artery.

Animals↗
PubMed2001

Follicle-stimulating hormone promotes the growth of human epithelial ovarian cancer cells through the protein kinase C-mediated system.

We have previously described that follicle-stimulating hormone (FSH) stimulated the growth of human epithelial ovarian cancer tissues and cells. In order to determine the signaling pathway on FSH action in ovarian cancer, we used an epithelial ovarian cancer cell line (HRA line) which constitutively FSH receptors (FSHRs). FSH significantly increased cell proliferation (230.1 +/- 20.5%, P < 0.05) and (3)H-thymidine uptake (443.5 +/- 35.1%, P < 0.01). 1-(5-Isoquinolinesulfonyl)-2-methyipiperazine (H7, 1 5 nM), staurosponine (STR, 5 nM) and calphostin C (5 nM), specific protein kinase C (PKC) inhibitors, significantly suppressed the FSH-stimulated cell growth (120.2-140.2%, P < 0.05) and (3)H-thymidine uptake (140.5-173.9%, P < 0.05), whereas N-(2-guanidinoethyl)-5-isoquinoline-sulfon-amide (HA1004, l5 nM), which is a derivant of H7 and inhibits most of protein kinases except PKC, showed no effect on the FSH-stimulated cell growth and (3)H-thymidine uptake. A pretreatment with 12-0-tetradecanoylphorbol-13 acetate (TPA, 100 ng/ml) or STR (20 nM) significantly suppressed the subsequent FSH-stimulated cell growth (TPA; 152.3 +/-10.3%, STR; 160.4 +/- 15.9%, P < 0.05) and (3)H-thymidine uptake (TPA; 250.4 +/-18.3%, STR; 208.7 +/- 15.9%, P < 0.05). STR abolished the suppression of TPA preincubation on the subsequent FSH-stimulated cell growth and (3)H-thymidine uptake. HRA cells constitutively expressed PKCalpha but not PKCbeta nor PKCgamma. The levels of either expression of PKCalpha protein and mRNA were significantly amplified by FSH. These data suggest that stimulation of PKCalpha transcription is involved in the FSH-stimulated cell growth and DNA synthesis in epithelial ovarian cancer cells.

Cell Division↗
PubMed2001

Recent progress in the Na(+)-translocating NADH-quinone reductase from the marine Vibrio alginolyticus.

The respiratory chain of Gram-negative marine and halophilic bacteria has a Na(+)-dependent NADH-quinone reductase that functions as a primary Na(+) pump. The Na(+)-translocating NADH-quinone reductase (NQR) from the marine Vibrio alginolyticus is composed of six structural genes (nqrA to nqrF). The NqrF subunit has non-covalently bound FAD. There are conflicting results on the existence of other flavin cofactors. Recent studies revealed that the NqrB and NqrC subunits have a covalently bound flavin, possibly FMN, which is attached to a specified threonine residue. A novel antibiotic, korormicin, was found to specifically inhibit the NQR complex. From the homology search of the nqr operon, it was found that the Na(+)-pumping NQR complex is widely distributed among Gram-negative pathogenic bacteria.

Amino Acid Sequence↗
PubMed2001

Cloning of dynein intermediate chain cDNA of the newt Cynops pyrrhogaster.

To isolate genes whose expression is up-regulated after initiation of meiosis, we employed an mRNA differential display method using RNA extracted from newt testis fragments in the spermatogonial and spermatocyte stages. We report here isolation of a spermatocyte stage-specific cDNA clone encoding a newt homologue of dynein intermediate chain (IC). The newt dynein IC cDNA was found to encode a polypeptide consisting of 694 amino acid residues with 66.8% and 45.8% amino acid sequence similarity to sea urchin dynein IC3 and Chlamydomonas IC69, respectively. The predicted protein contains five WD repeats and a novel repeated motif in the C-terminal region. Northern blot analysis revealed that newt dynein IC mRNA was expressed in the spermatocyte and round spermatid stages, suggesting that dynein IC plays a role in formation of flagella as well as in meiotic events.

Animals↗
PubMed2001

Forced oral opening for cadavers with rigor mortis: two approaches for the myotomy on the temporal muscles.

Forensic dentistry plays an essential role in personal identification procedures. An adequate interincisal space of cadavers with rigor mortis is required to obtain detailed dental findings. We have developed intraoral and two directional approaches, for myotomy of the temporal muscles. The intraoral approach, in which the temporalis was dissected with scissors inserted via an intraoral incision, was adopted for elderly cadavers, females and emaciated or exhausted bodies, and had a merit of no incision on the face. The two directional approach, in which myotomy was performed with thread-wire saw from behind and with scissors via the intraoral incision, was designed for male muscular youths. Both approaches were effective to obtain a desired degree of an interincisal opening without facial damage.

Adult↗
PubMed2001

Cloning of the rat Slc14a2 gene and genomic organization of the UT-A urea transporter.

We cloned the Slc14a2 gene and determined the genomic organization of the rat urea transporter UT-A. Slc14a2, the gene encoding the rat UT-A transporter, extends for more that 300 kb. The four known rat mRNA isoforms: UT-A1, UT-A2, UT-A3, and UT-A4 are transcribed from 24 exons. The Slc14a2 genomic map also accounts for 3'-untranslated sequences expressed alternatively in UT-A1, UT-A2, and UT-A3. We previously identified a TATA-less, tonicity-responsive promoter controlling the transcription of UT-A1, UT-A3, and UT-A4 from a single initiation site in the 5'-flanking region of the gene. Here, we describe a second, internal promoter in intron 12, which controls the transcription of UT-A2 starting from exon 13. This region contains a TATA motif upstream from the UT-A2 transcription start site, and shows consensus sequences for the cAMP response element (CRE) and for the tonicity enhancer (TonE) motif. Stimulation by cAMP induces UT-A2 mRNA expression in mIMCD3 cells, and luciferase activity in mIMCD3 cells transfected with those pGL3 constructs including the CRE sequences. Although long-term exposure to hypertonicity induces UT-A2 expression in mIMCD3 cells, hypertonicity does not induce significantly the activity of the promoter in intron 12. In summary, we describe the genomic structure of the rat UT-A urea transporter, encoded by the Slc14a2 gene. Our findings suggest that two promoters regulate transcription of the four UT-A isoforms, and that stimulation of transcription by vasopressin, mediated by cAMP and CRE sequences, and controlled by an intronic promoter, may contribute to the increase in UT-A2 expression during water deprivation.

Animals↗