Biomedical subjects

T Saiki

Publications and source records attributed to T Saiki.

At least 19 recordsLinked to original sources

PubMed2003

Near-field optical mapping of exciton wave functions in a GaAs quantum dot.

Near-field photoluminescence imaging spectroscopy of naturally occurring GaAs quantum dots (QDs) is presented. We successfully mapped out center-of -mass wave functions of an exciton confined in a GaAs QD in real space due to the enhancement of spatial resolution up to 30 nm. As a consequence, we discovered that the spatial profile of the exciton emission, which reflects the shape of a monolayer-high island, differs from that of biexciton emission, due to different distributions of the polarization field for the exciton and biexciton recombinations. This novel technique can be extensively applied to wave function engineering in the design and the fabrication of quantum devices.

Journal Article↗

PubMed2002

Two novel strains of Wolbachia coexisting in both species of mulberry leafhoppers.

Wolbachia is an intracellular symbiont that causes reproductive disorders in many insects. Its presence in the leafhoppers Hishimonoides sellatiformis and Hishimonus sellatus, vectors of mulberry dwarf-Phytoplasma, was confirmed by the PCR analysis of 16S rDNA, ftsZ and wsp. Sequencing of cloned PCR products revealed that two Wolbachia strains coexist in both leafhoppers. The phylogenetic analysis of wsp revealed that these strains belong in novel positions in the B-group of Wolbachia. These strains were detected by PCR and/or PCR-RFLP in all of the tested non-genital organs including salivary glands, as well as in the tested genital organs of Hishimonoides sellatiformis. In addition, Wolbachia-like organisms were observed by electron microscopy in all PCR-positive organs. We discuss the possible horizontal transmission of Wolbachia via mulberry trees.

Animals↗

PubMed2001

Trafficking of host- and donor-derived dendritic cells in rat cardiac transplantation: allosensitization in the spleen and hepatic nodes.

BACKGROUND: Kinetics and role of host and donor dendritic cells (DCs) in transplantation immunity are still ill-defined. Using a rat cardiac transplantation model, we studied DC trafficking and sites for allosensitization. METHODS: Host and donor DCs were defined as host- or donor-type class II major histocompatibility complex antigen single-positive cells by double-immunostaining. Proliferative response of both donor and host cells were also analyzed. RESULTS: Host DCs were recruited to the graft soon after transplantation. These cells represented definitive precursors because of high labeling index by a continuous bromodeoxyuridine infusion, their small round shape, and their putative bone marrow origin. Donor interstitial DCs showed a significant self-replicating capability. Both recruited host DCs in a regraft experiment and donor DCs preferentially performed blood-borne migration to the T-cell area of host spleen. Furthermore, they also migrated to the T-cell area of hepatic lymph nodes after executing the sinusoids-lymph translocation as a novel pathway for these DCs. Selectively at their migration sites, a strong T-cell proliferative response occurred, which preceded that in the graft tissues. Removal of spleen and hepatic lymph nodes significantly prolonged the mean graft survival time. CONCLUSION: We conclude that allogeneic heart transplantation induces the recruitment of host DC precursors to the graft tissues and the blood-borne migration of both recruited host and donor DCs to the host spleen and hepatic nodes where effector cells are predominantly sensitized.

Animals↗

PubMed2001

Design and optimization of tapered structure of near-field fibre probe based on finite-difference time-domain simulation.

The finite-difference time-domain method was employed to simulate light propagation in tapered near-field fibre probes with small metal aperture. By conducting large-volume simulations, including tapered metal-cladding waveguide and connected optical fibre waveguide, we illustrated the coupling between these guiding modes as well as the electric field distribution in the vicinity of the aperture. The high collection efficiency of a double-tapered probe was reproduced and was ascribed to the shortening of the cut-off region and the efficient coupling to the guiding mode of the optical fibre. The dependence of the efficiency on the tapered structure parameters was also examined.

Journal Article↗

PubMed2001

Near-field spectroscopy of single quantum dots at room temperature.

The observation of photoluminescence spectra of self-assembled single InGaAs quantum dots at room temperature was performed under weak excitation conditions using a near-field scanning optical microscope. Operation in illumination-collection mode with a highly sensitive double-tapered optical fibre probe enabled detection of weak photoluminescence signals at room temperature with high efficiency and high spatial resolution. Each single quantum dot was imaged with a spatial resolution of about 250 nm, which corresponded to a quarter of the wavelength of the photoluminescence from quantum dots. The photoluminescence yields of individual quantum dots were widely distributed and were found to decrease with photoluminescence energy. This result serves as a clue to be pursued for better understanding of the thermal excitation of the carrier from confined states in quantum dots.

Journal Article↗

PubMed2001

Near-field fluorescence imaging of single molecules with a resolution in the range of 10 nm.

We demonstrate fluorescence imaging of single molecules, by near-field scanning optical microscopy (NSOM), using the illumination-collection mode of operation, with an aperture probe. Fluorescence images of single dye molecules were obtained with a spatial resolution of 15 nm, which is smaller than the diameter of the aperture (20 nm) of the probe employed. Such super-resolution may be attributable to non-radiative energy transfer from the molecules to the coated metal of the probe since the resolution obtained in the case of conventional NSOM is limited to 30-50 nm due to penetration of light into the metal.

Journal Article↗

PubMed2001

Kupffer cell-mediated recruitment of rat dendritic cells to the liver: roles of N-acetylgalactosamine-specific sugar receptors.

BACKGROUND & AIMS: Tissue recruitment of dendritic cells (DCs) is essential for antigen presentation. This study aimed to examine cellular and molecular mechanisms for DC recruitment to the liver. METHODS: Purified rat DCs were injected into circulation and their traffics were analyzed in normal and Kupffer cell-depleted rats by intravital confocal microscopy and immunohistology. Affinities of DCs to sinusoidal cells were examined by a cell-binding assay. DC precursor recruitment was induced by particulate injection. RESULTS: Both DC precursors and DCs at the antigen-transporting stage could be recruited to the liver, and their majority initially showed a selective binding to Kupffer cells. In the Kupffer cell-depleted rats, DCs could neither be recruited to the liver nor adhere to sinusoidal walls. Pretreatment with varied monosaccharides showed that sugar residues consisting of N-acetylgalactosamine were necessary for this binding. The binding was calcium-dependent, implying the C-type lectin involvement. Furthermore, DCs could endocytose N-acetylgalactosamine polymers in a receptor-specific manner. CONCLUSIONS: The DC-Kupffer cell binding through N-acetylgalactosamine-specific C-type lectin-like receptors is crucial for DC recruitment to the liver. Rat DCs at least partly possess receptors for endocytosis of galactosylated antigens. These DC receptors as well as Kupffer cell lectins are presumably responsible for this binding.

Acetylgalactosamine↗

PubMed2001

In vivo roles of donor and host dendritic cells in allogeneic immune response: cluster formation with host proliferating T cells.

Possible roles of dendritic cells (DCs) in allogeneic immune responses in host lymphoid tissues were characterized in situ by using rat DC transfer and cardiac transplantation models. When allogeneic DCs were intravenously injected, these cells selectively migrated to the T-cell area of hepatic lymph nodes, with peak accumulation at 18 h after injection. Donor DCs and proliferating host T cells formed clusters (rosettes) in which the T-cell proliferative response started. The donor DCs were CD80(+) CD86(+) and, ultrastructurally, were in intimate contact with lymphoblasts within the rosettes. As a novel finding, some of the migrated donor DCs were quickly phagocytosed by putative host interdigitating DCS: By 48 h, the remaining donor DCs had disintegrated within the rosettes. Host interdigitating DCs also formed rosettes throughout the T-cell area, and their kinetics correlated well with that of the T-cell proliferation. In the cardiac allograft model, a few donor DCs selectively migrated to the host spleen and hepatic nodes. Rosette formation by donor and host DCs, phagocytosis of donor DCs, and the T-cell proliferative response occurred in much the same fashion as they did in the first experiment. We conclude that the donor rosettes at the early stage represent the sites of direct allosensitization and those at the late stage represent donor-DC killing. Host rosettes are the sites of T-cell proliferation. In this structure, phagocytosed donor-DC-derived antigens are presumably indirectly presented.

Adoptive Transfer↗

PubMed2000

Ossiculoplasty using hydroxyapatite prostheses: long-term results.

The surgical results of ossicular chain reconstruction using a hydroxyapatite prosthesis were evaluated in 106 ears of 101 patients who were followed up for > 5 years. Successful reconstruction was defined as: (1) postoperative air-bone gap of </= 20 db; or (2) postoperative air conduction better than 40 db; or (3) hearing gain better than 15 db. Success in hearing was obtained in 63/106 ears (59%) at 1 year; 44/65 ears (68%) in P-type (short columella) and 19/41 ears (46%) in T-type (long columella). By the fifth year, the overall success rate had deteriorated to 50%: i.e. 39/65 ears (60%) in P-type and 14/41 ears (34%) in T-type. Extrusion of the prosthesis occurred in 17 ears (16%) with a mean postoperative period of 27.7 months. The present results indicate that hydroxyapatite is a suitable material for an ossicular prosthesis, although the incidence of extrusion is high when it is placed in contact with the tympanic membrane.

Adolescent↗

PubMed1999

Production of D-lyxose from D-glucose by microbial and enzymatic reactions.

D-arabitol was first prepared from D-glucose using Candida famata R28. The reaction gave 5.0% D-arabitol from 10.0% D-glucose. D-arabitol was then almost completely converted to D-xylulose using Acetobacter aceti IFO 3281. Finally, D-lyxose was prepared from D-xylulose enzymatically using L-ribose isomerase from toluene-treated cells of Acinetobacter sp. strain DL-28. The isomerization reaction progressed steadily and the concentration of D-xylulose increased from 1.0 to 10.0%. About 70% of D-xylulose was converted to D-lyxose in all cases. Separation of residual D-xylulose from the reaction mixture is very difficult to achieve by column chromatography, but D-xylulose could be selectively degraded easily using Saccharomyces cerevisiae IFO 0841. The product was crystallized and was confirmed to be D-lyxose by HPLC, 13C-NMR spectra, IR spectra analysis, and optical rotation measurement.

Journal Article↗

PubMed1999

Butyrate from bacterial fermentation of germinated barley foodstuff preserves intestinal barrier function in experimental colitis in the rat model.

BACKGROUND AND AIMS: The consumption of germinated barley foodstuff (GBF) prevents inflammation and diarrhoea in a colitis model. In this study we investigated the mechanism of the preventative effect of GBF on experimental colitis in rats, in view of production of bacterial butyrate and preservation of intestinal barrier function. METHODS: Sprague-Dawley rats administered with diets supplemented with 3.5% dextran sodium sulphate were used as an experimental colitis model. Butyrate was given to rats orally or intracaecally. Intestinal barrier function was estimated by light microscopic observation of the mucosa, intestinal permeability and bacterial translocation. RESULTS: Mucosal damage was reduced by intracaecal administration of butyrate, but not by oral administration. Bacterial butyrate production and reduction of mucosal damage depended on the dose of GBF in diets. The action of endogenous bacterial butyrate, including the reduction of intestinal permeability and bacterial translocation, was inhibited by administration of an inhibitor of beta-oxidation of short-chain fatty acids. CONCLUSIONS: The feeding of GBF promotes bacterial butyrate production and improves intestinal barrier function in rats, resulting in mitigation of experimental colitis.

Animals↗

PubMed1999

Increased growth of Bifidobacterium and Eubacterium by germinated barley foodstuff, accompanied by enhanced butyrate production in healthy volunteers.

Germinated barley foodstuff (GBF) derived from the aleurone and scutellum fractions of germinated barley mainly consists of low-lignified hemicellulose and glutamine-rich protein. GBF improves the proliferation of intestinal epithelial cells and defecation, through the bacterial production of short chain fatty acids (SCFA), especially butyrate. In this study we investigated the mechanism of production of butyrate by microflora in humans and in vitro. Daily administration of 9 g GBF for 14 successive days significantly increased fecal butyrate content. Fecal Bifidobacterium and Eubacterium were also significantly increased by GBF administration in healthy volunteers. Ten anaerobic micro-organisms selected from intestinal microflora were cultured in vitro in the medium containing GBF as a sole carbon source (GBF medium). After a 3-day incubation, 7 strains (Bifidobacterium breve, Bifidobacterium longum, Lactobacillus acidophilus, Lactobacillus casei subsp. casei, Bacteroides ovatus, Clostridium butyricum, and Eubacterium limosum) lowered the medium pH producing SCFA. Eubacterium grown together with Bifidobacterium in GBF medium efficiently produced butyrate. On the other hand, GBF changed the intestinal microflora and increased probiotics such as Bifidobacterium in the intestinal tract. As a result, butyrate was produced by the mutual action of Eubacterium and Bifidobacterium. This butyrate is considered to enhance the proliferation of colonic epithelial cells.

Adult↗

PubMed1998

Aster-forming abilities of the egg, polar body, and sperm centrosomes in early starfish development.

Using ionophore-activated starfish eggs, the maternal centrosome accompanied by the female pronucleus (the egg centrosome) was confirmed to possess the ability for aster formation but generally not the capacity for reproduction. Inhibition of pronuclear fusion and removal of the male pronucleus and/or the sperm centrosome revealed that the egg centrosome lost its ability when it was only in the vicinity of the sperm centrosome. Hence, the entity that inactivated the egg centrosome was determined to be the adjacent sperm centrosome. When the second polar body was transplanted into a fertilized egg, its maternal centrosome (the polar body centrosome) organized an aster during cleavage; moreover, it possessed reproductive capacity. Furthermore, three different patterns of aster formation characterizing the sperm, egg, and polar body centrosomes occurred at each corresponding nucleus in the absence of nuclear fusion. When various kinds of centrosomes approached each other through nuclear fusion, there was observed only a pattern of aster formation at the fusion site that characterized a certain centrosome. Consequently, the sperm, polar body, and egg centrosomes were superior, intermediate, and inferior, respectively, in their ability for aster formation.

Animals↗

PubMed1998

Treatment of ulcerative colitis with germinated barley foodstuff feeding: a pilot study.

BACKGROUND: Germinated barley foodstuff (GBF) has been shown to attenuate intestinal injury in animal models, largely by increasing luminal short-chain fatty acid production. AIM: To investigate the safety and efficacy of GBF in the treatment of ulcerative colitis (UC). METHODS: Ten patients with active UC received 30 g of GBF daily for 4 weeks in an open-label treatment protocol while the baseline anti-inflammatory therapy was continued. The response to treatment was evaluated clinically and endoscopically. Pre- and post-treatment stool concentrations of short-chain fatty acids were measured by gas-liquid chromatography. RESULTS: Patients showed improvement in their clinical activity index scores, with a significant decrease in the score from 6.9+/-1.4 to 2.8+/-1.5 (mean+/-S.E.M., P < 0.05). The endoscopic index score fell from 6.1+/-2.3 to 3.8+/-2.3 (P < 0.0001). Patients showed an increase in stool butyrate concentrations after GBF treatment (P < 0.05). No side-effects were observed. CONCLUSIONS: Oral GBF therapy may have a place in management of ulcerative colitis, but controlled studies are needed to demonstrate its efficacy in the treatment of this disorder.

Adult↗

PubMed1998

Detection of pro- and anti-inflammatory cytokines in stools of patients with inflammatory bowel disease.

BACKGROUND: Cytokines play a predominant role in immune and inflammatory reactions in inflammatory bowel disease. Any cytokine that is produced locally as a result of gut inflammation may leak into the bowel lumen and appear in the stools. We examined the usefulness of determining cytokine profiles in the stools of patients with ulcerative colitis or Crohn's disease. METHODS: Cytokine concentrations in stool extracts were measured in 36 patients with ulcerative colitis, 32 patients with Crohn's disease, 9 controls with inflammatory disease, and 18 normal controls by means of enzyme-linked immunosorbent assays. RESULTS: Stool concentrations of interleukin-1beta and interleukin-1 receptor antagonist in patients with active inflammatory bowel disease increased significantly and correlated with various inflammatory factors and stool concentrations of polymorphonuclear cell elastase. The ratio of interleukin-1 receptor antagonist to interleukin-1beta in active disease was reduced significantly compared with that in inactive disease or in normal controls. Paired analysis showed a decrease in tumor necrosis factor-alpha and interleukin-1beta and interleukin-1 receptor antagonist and an increase in interleukin-4 and interleukin-10 concentrations after the resolution of disease exacerbation. CONCLUSIONS: Measurement of cytokines in stools may be a useful and noninvasive means of understanding pathophysiology and clinical monitoring in inflammatory bowel disease.

Adult↗

PubMed1998

Vascular endothelial growth factor in patients with rheumatoid arthritis.

To examine the role of vascular endothelial growth factor (VEGF), an endothelial cell specific growth factor, in rheumatoid arthritis (RA), serum concentration of VEGF was examined in patients with RA, osteoarthritis (OA), systemic lupus erythematosus (SLE), systemic sclerosis (SS) and control subjects. Serum C-reactive protein (CRP) level, erythrocyte sedimentation rate, white blood cell count and rheumatoid factor titer were also determined in patients with RA. The serum concentration of VEGF was significantly higher in patients with RA than in controls (p < 0.01), and patients with OA (p < 0.05), SLE (p < 0.05), and SS (p < 0.05). The serum concentration of VEGF correlated with serum levels of CRP (r = 0.698, p < 0.0001). The serum concentration of VEGF before treatment was significantly higher than that after treatment in patients with RA who experienced clinical remission (p < 0.05). Our data suggest that VEGF is involved in the pathogenesis of RA and that measurement of serum concentration of VEGF is a noninvasive, useful method for monitoring the disease activity of RA.

Adolescent↗

PubMed1998

Structure and property of model peptides of proline/arginine-rich region in bactenecin 5.

Bactenecin 5 (Bac 5), a cationic antibacterial peptide, contains a repeating region of Arg-Pro-Pro-X (X = hydrophobic residue). To investigate the structure and property of a Pro/Arg-rich region, we synthesized a series of repeating peptides, Ac-(Arg-Pro-Pro-Phe)n-NHCH3 (n = 2, 4, 6, 8 and 10) (PR2, PR4, PR6, PR8 and PR10) as models. The circular dichroism (CD) study suggested that the peptides with longer repeats, PR6, PR8 and PR10, formed a conformation similar to poly(proline)-II in aqueous solution. The CD spectra did not change in the presence of dipalmitoyl-DL-alpha-phosphatidylcholine (DPPC), but they changed in the presence of DPPC/ dipalmitoyl-DL-3-phosphatidylglycerol (DPPG). The gamma-helix, which is very similar in conformation to the poly(proline)-II helix, had the lowest energy conformation for the peptides by energy calculations. Peptides PR6, PR8 and PR10 caused slight leakage of fluorescent dye entrapped in DPPC vesicles, and in the presence of DPPC/DPPG, these peptides showed a considerable level of dye-leakage activity. In contrast, the shorter peptides PR2 and PR4 showed no activity. The same tendency was found in measurements of membrane-fusion activity. Judging from these results, the repeating region of Bac 5 may make a framework to hold a conformation resembling the poly(proline)-II structure in aqueous solution. In addition, this region may interact with acidic lipids, resulting in a change in conformation of the peptide.

Amino Acid Sequence↗

PubMed1998

Assessment of vasoactive agents and vascular aging by the second derivative of photoplethysmogram waveform.

To evaluate the clinical application of the second derivative of the fingertip photoplethysmogram waveform, we performed drug administration studies (study 1) and epidemiological studies (study 2). In study 1, ascending aortic pressure was recorded simultaneously with the fingertip photoplethysmogram and its second derivative in 39 patients with a mean+/-SD age of 54+/-11 years. The augmentation index was defined as the ratio of the height of the late systolic peak to that of the early systolic peak in the pulse. The second derivative consists of an a, b, c, and d wave in systole and an e wave in diastole. Ascending aortic pressure increased after injection of 2.5 microg angiotensin from 126/74 to 160/91 mm Hg and decreased after 0.3 mg sublingual nitroglycerin to 111/73 mm Hg. The d/a, the ratio of the height of the d wave to that of the a wave, decreased after angiotensin from -0.40+/-0.13 to -0.62+/-0.19 and increased after nitroglycerin to -0.25+/-0.12 (P<0.001 and P<0.001, respectively). The negative d/a increased with increases in plethysmographic and ascending aortic augmentation indices (r=0.79, P<0.001, and r=0.80, P<0.001, respectively). The negative d/a reflects the late systolic pressure augmentation in the ascending aorta and may be useful for noninvasive evaluation of the effects of vasoactive agents. In study 2, the second derivative of the plethysmogram waveform was measured in a total of 600 subjects (50 men and 50 women in each decade from the 3rd to the 8th) in our health assessment center. The b/a ratio increased with age, and c/a, d/a, and e/a ratios decreased with age. Thus, the second derivative aging index was defined as b-c-d-e/a. The second derivative wave aging index (y) increased with age (x) (r=0.80, P<0.001, y=0.023x-1.515). The second derivative aging index was higher in 126 subjects with any history of diabetes mellitus, hypertension, hypercholesterolemia, and ischemic heart disease than in age-matched subjects without such a history (-0.06+/-0.36 versus -0.22+/-0.41, P<0.01). Women had a higher aging index than men (P<0.01). The b-c-d-e/a ratio may be useful for evaluation of vascular aging and for screening of arteriosclerotic disease.

Aged↗