Biomedical subjects

Hiroshi Yokoyama

Publications and source records attributed to Hiroshi Yokoyama.

At least 19 recordsLinked to original sources

PubMed2006

Nitrogen removal from animal waste treatment water by anammox enrichment.

The aim of this work was to examine the applicability of the anaerobic ammonium oxidation (anammox) process to three kinds of low BOD/N ratio wastewaters from animal waste treatment processes in batch mode. A rapid decrease of NO(2)(-) and NH(4)(+) was observed during incubation with wastewaters from AS and UASB/trickling filter and their corresponding control artificial wastewaters. This nitrogen removal resulted from the anammox reaction, because the ratio of removed NO(2)(-) and NH(4)(+) was close to the theoretical ratio of the anammox reaction. Comparison of the inorganic nitrogen removal rate of the actual wastewater and that of control artificial wastewater showed that these two kinds of wastewater were very suitable for anammox treatment. Incubation with wastewater from RW did not show a clear anammox reaction; however, diluting it by half enabled the reaction, suggesting the presence of an inhibitory factor. This study showed that the three kinds of wastewater from animal waste treatment processes were suitable for anammox treatment.

Animals↗

PubMed2006

Effect of fermentation temperature on hydrogen production from cow waste slurry by using anaerobic microflora within the slurry.

We examined hydrogen production from a dairy cow waste slurry (13.4 g of volatile solids per liter) by batch cultures in a temperature range from 37 to 85 degrees C, using microflora naturally present within the slurry. Without the addition of seed bacteria, hydrogen was produced by simply incubating the slurry, using the microflora within the slurry. Interestingly, two peaks of fermentation temperatures for hydrogen production from the slurry were observed at 60 and 75 degrees C (392 and 248 ml H2 per liter of slurry, respectively). After the termination of the hydrogen evolution, the microflora cultured at 60 degrees C displayed hydrogen-consuming activity, but hydrogen-consuming activity of the microflora cultured at 75 degrees C was not detected, at least for 24 days. At both 60 and 75 degrees C, the main by-product was acetate, and the optimum pH of the slurry for hydrogen production was around neutral. Bacteria related to hydrogen-producing moderate and extreme thermophiles, Clostridium thermocellum and Caldanaerobacter subterraneus, were detected in the slurries cultured at 60 and 75 degrees C, respectively, by denaturing gradient gel electrophoresis analyses, using the V3 region of 16S rDNA.

Animals↗

PubMed2006

Numerical treatment of the dynamics of a conserved order parameter in the presence of walls.

We discuss how the diffusive dynamics of a conserved order parameter should be numerically treated when impenetrable wall surfaces are present and interact with the degrees of freedom characterized by the order parameter. We derive the discretization scheme for the dynamics, paying particular attention to the conservation of the order parameter in the strict numerical sense. The discretized chemical potential, or the functional derivative of the free energy, contains a surface contribution inversely proportional to the grid spacing Delta z, which was proposed heuristically in a recent paper of Henderson and Clarke [Macromol. Theory Simul. 14, 435 (2005)]. Although apparently that surface contribution diverges in the continuum limit Delta z --> 0, we can show, by an analytic argument and numerical calculations, that this divergence does not yield any anomalies, and that our discretization scheme is well defined in this limit. We also discuss the correspondence of our treatment to the model proposed by Puri and Binder [Phys. Rev. A 46, R4487 (1992)] extensively used for the present problem.

Journal Article↗

PubMed2006

Autotrophic denitrification and chemical phosphate removal of agro-industrial wastewater by filtration with granular medium.

A novel granular medium consisting (1.5-5 mm in diameter) of inert perlite particles as nuclei and an effective surface layer containing sulfur, CaCO3 and Mg(OH)2 was developed for advanced treatment of agro-industrial wastewater. The performance of the medium was examined with a laboratory-scale down-flow fixed-bed column reactor using piggery wastewater, which had been treated by an upflow anaerobic sludge blanket reactor and a trickling filter. The removal efficiency of NOx- -N was more than 70% with a NOx- -N loading rate of less than approximately 0.3 kg Nm(-3) d(-1); the removal efficiency dropped due to the accumulation of nitrite when the loading rate exceeded that value. A significant drop of phosphate and Mg2+ concentrations occurred when the effluent pH exceeded 7.9. Ammonium was removed with an average removal efficiency of 12.4%. These results indicated that the crystalline reaction of PO4(3-), Mg2+ and NH4+ (MAP reaction) under alkaline conditions contributed to the removal of phosphate. This medium could be useful for the simultaneous reduction of nitrogenous and phosphorus compounds in biologically treated agro-industrial wastewater.

Filtration↗

PubMed2006

Involvement of calcineurin-dependent degradation of Yap1p in Ca2+-induced G2 cell-cycle regulation in Saccharomyces cerevisiae.

The Ca2+-activated pathways in Saccharomyces cerevisiae induce a delay in the onset of mitosis through the activation of Swe1p, a negative regulatory kinase that inhibits the Cdc28p/Clb complex. We isolated the YAP1 gene as a multicopy suppressor of calcium sensitivity owing to the loss of ZDS1, a negative regulator of SWE1 and CLN2 gene expression. YAP1 deletion on a zds1delta background exacerbated the Ca2+-related phenotype. Yap1p was degraded in a calcineurin-dependent manner when cells were exposed to calcium. In yap1delta cells, the expression level of the RPN4 gene encoding a transcription factor for the subunits of the ubiquitin-proteasome system was diminished. The deletion of YAP1 gene or RPN4 gene led to the accumulation of Swe1p and Cln2p. Yap1p was a substrate of calcineurin in vivo and in vitro. The calcineurin-mediated Yap1p degradation seems to be a long adaptive response that assures a G2 delay in response to a stress that causes the activation of the calcium signalling pathways.

Calcineurin↗

PubMed2006

Constant surface-tension molecular-dynamics simulation methods for anisotropic systems.

We propose a simulation method for liquid-liquid interface under constant surface tension and constant normal pressure. The method introduces an anisotropic factor in the cell dynamics which avoids artifacts such as continuous expansion or contraction of the cell lengths. This allows simulation of a full range of surface tensions including when the value is 0, i. e, hydrostatic pressure.

Journal Article↗

PubMed2006

IL-10 deficiency leads to somatic mutations in a model of IBD.

Individuals with inflammatory bowel disease (IBD) are at increased risk of developing gastrointestinal cancer. Here, we have tested the possibility that chronic inflammation could trigger mutations. For this, we have used IL-10-deficient (IL-10-/-) mice, which spontaneously develop intestinal inflammation, in combination with a transgenic gpt gene and red/gam gene (gpt+IL-10-/-), which is a well-characterized mutation reporter locus. The total mutation frequency in the colon of gpt+IL-10-/- mice was about five times higher than that in normal gpt+IL-10+/+ mice. In the particular case of G:C to A:T transitions, the frequency of mutations in gpt+IL-10-/- mice was 4.1 times higher than that in control mice. Interestingly, the frequency of small deletions and insertions was also strikingly increased (approximately 10 times). The majority of the deletion or insertion mutations were observed in the monotonous base runs or adjacent repeats of short tandem sequences. In contrast, the frequency of large deletions, detected by loss of the Spi marker present in the red/gam transgene, was similar among the mouse strains. Finally, as a control, the mutation frequency in non-inflamed tissues, such as the liver, were similar between gpt+IL-10-/- mice and gpt+IL-10+/+ mice. Our data demonstrate that the chronic inflammatory environment in the colon promotes the generation of mutations.

Animals↗

PubMed2006

Interferon-related mental deterioration after craniotomy for removal of metastatic renal cancer.

Interferon-related severe adverse events on the central nervous system are relatively rare, because interferon-alpha (INF-alpha) can not cross an intact blood-brain barrier. We experienced remarkable mental deterioration caused by INF-alpha administration in a 43-year-old man with renal cell carcinoma after surgical removal of a metastatic brain tumor. We detected a high concentration of INF-alpha in a cerebrospinal fluid sample, which was comparable to that in the serum at 24 h after the administration of INF-alpha; 5x10(6) IU i.m., suggesting that the blood-brain barrier was damaged somehow by the craniotomy. The mental deterioration improved shortly after discontinuation of the INF-alpha administration.

Adult↗

PubMed2006

Differences in host selection of actinospores of two myxosporeans, Myxobolus arcticus and Thelohanellus hovorkai.

We investigated the host selection mechanism of actinospore stages of 2 myxosporeans, Myxobolus arcticus and Thelohanellus hovorkai, infecting masu salmon (Oncorhynchus masou) and common carp (Cyprinus carpio), respectively. Discharge of the polar filaments and sporoplasm release by M. arcticus actinospores occurred within the first 5 min of exposure to skin mucus of masu salmon. The actinospores also reacted to the mucus of nonsusceptible fish, i.e., sockeye salmon (Oncorhynchus nerka) and goldfish (Carassius auratus), although the reactivity was comparatively lower. After exposure of masu, and sockeye and chum salmon (Oncorhynchus keta) to M. arcticus actinospores, the penetration of sporoplasms was observed in the fins and gills of masu and sockeye salmon to a similar extent and to a lesser extent in chum salmon. Thelohanellus hovorkai actinospores exhibited a slow response of sporoplasm release to common carp mucus as well as penetration into the gills of common carp. Neither chemoresponse to mucus of nonsusceptible fish (goldfish and sockeye salmon) nor sporoplasm invasion in goldfish was observed for T. hovorkai actinospores. These results indicate notable differences in the host selection at the time of entry between M. arcticus and T. hovorkai; the former responds quickly to fish mucus with low host specificity, whereas the latter was highly host specific in a dilatory reaction.

Analysis of Variance↗

PubMed2006

The protective effects of angiotensin II blockade with olmesartan medoxomil on resistance vessel remodeling (The VIOS study): rationale and baseline characteristics.

BACKGROUND: The VIOS (Vascular Improvement with Olmesartan medoxomil Study) study is a randomized, parallel study to determine the relative effects of suppressing the renin-angiotensin system (RAS) with the angiotensin receptor antagonist olmesartan medoxomil versus suppressing sympathetic drive with the beta-adrenoceptor antagonist atenolol on remodeling of the subcutaneous small resistance vessel. Remodeling of small resistance vessels may be the earliest pathologic finding associated with hypertension. It may predate the onset of clinically apparent hypertension. METHODS: In this study, 100 patients with stage I hypertension are characterized at baseline before being treated for 1 year to obtain a goal BP of less than 140/90 mm Hg as defined by Joint National Committee (JNC)-7. Resistance vessel remodeling is determined using the gluteal fat biopsy technique in the hypertensive patients and a group of normotensive healthy volunteers. Additionally, efforts will be made to define whether noninvasive hemodynamic parameters, retinal vessel measurement changes, or biologic markers may predict and track the underlying vascular morphologic and physiologic changes induced by either regimen during the 12-month treatment period. RESULTS: The primary endpoint will be the degree of vascular remodeling as obtained from percutaneous biopsy of gluteal subcutaneous resistance vessels in each of two treatment arms compared with the normal volunteers. The design of the study and the pertinent baseline characteristics of these patients with uncomplicated essential hypertension are presented. CONCLUSION: The suppression of the RAS by the blockade of angiotensin II type 1 (AT(1)) receptors may demonstrate remodeling effects on the ubiquitous small resistance vessels similar to that seen in the myocardium and renal glomeruli, thus affording more complete end-organ protection.

Adult↗

PubMed2005

Optical isotropy and iridescence in a smectic 'blue phase'.

When liquid crystal molecules are chiral, the twisted structure competes with spatially uniform liquid crystalline orders, resulting in a variety of modulated liquid crystal phases, such as the cholesteric blue phase, twist grain boundary and smectic blue phases. Here we report a liquid crystal smectic blue phase (SmBP(iso)), formed from a two-component mixture containing a chiral monomer and a 'twin' containing two repeat units of the first molecule connected by a linear hydrocarbon spacer. The phase exhibits the simultaneous presence of finite local-order parameters of helices and smectic layers, without any discontinuity on a mesoscopic length scale. The anomalous softening of elasticity due to a strong reduction in entropy caused by mixing the monomer and the twin permits the seamless coexistence of these two competing liquid crystal orders. The new phase spontaneously exhibits an optically isotropic but uniformly iridescent colour and automatically acquires spherical symmetry, so that the associated photonic band gap maintains the same symmetry despite the local liquid crystalline order. We expect a range of unusual optical transmission properties based on this three-dimensional isotropic structure, and complete tunability due to the intrinsic softness and responsiveness of the liquid crystalline order against external fields.

Journal Article↗

PubMed2005

Spinal curvature of cultured Japanese mackerel Scomber japonicus associated with a brain myxosporean, Myxobolus acanthogobii.

Skeletal deformities were found in the cultured Japanese mackerel Scomber japonicus. External and radiographical observations showed the deformed fish to exhibit a dorso-ventral spinal curvature (kyphosis) without fracture or dislocation of the vertebrae. Numerous myxosporean cysts, ca. 0.3 to 1.0 mm in diameter, formed in the 4th ventricle, the cavity of the optic tectum, the surface of the olfactory lobe and bulb, the optic lobe and the inferior lobe of the brain. Spore morphology and molecular analysis of the small subunit ribosomal RNA gene sequence identified the myxosporean parasite as Myxobolus acanthogobii, a parasite which also causes scoliosis in yellowtail Seriola quinqeradiata. Histopathological observation showed that the myxosporean cysts were encapsulated within the host's collagenous layer although some had disintegrated to disperse mature spores into the cranial cavity. Occasionally, lymphocytic infiltration and local granulomatous inflammation were found to be associated with spore dispersion.

Animals↗

PubMed2005

Friction drag of a spherical particle in a liquid crystal above the isotropic-nematic transition.

We study the friction drag of a spherical particle in the isotropic phase of a nematic liquid crystal close to the isotropic-nematic transition point. To describe the orientational order in the liquid crystal, the second-rank tensor order parameter Qalphabeta is employed. We solve the hydrodynamic equations for Qalphabeta and the fluid velocity nu in order to determine the friction drag. In our discussion of the friction drag, we concentrate on four parameters: the temperature, the surface order parameter, the particle radius, and the Ericksen number Er (characterizing the ratio of the viscous force to the elastic force). The temperature dependence of the friction drag agrees well with experiments that show an increasing friction drag when the isotropic-nematic phase transition is approached from above. Furthermore the friction drag increases with the surface order parameter due to the more pronounced surface nematic layer, and for larger particles it is less affected by this layer. Finally, we observe that in the range of Er we study, the friction drag is almost independent of Er although flow-induced order occurs for sufficiently large Er and surface order parameter.

Journal Article↗

PubMed2005

Subsecond luminescence intensity fluctuations of single CdSe quantum dots.

Photoluminescence (PL) intermittency characteristics are examined for single quantum dots (QDs) in a CdSe QD sample synthesized at a slow rate at 75 degrees C. Although the PL quantum efficiency was relatively low ( approximately 0.25), we noticed that the PL intensity of single CdSe QDs fluctuated on a subsecond time scale with short-lived "on" and "off" states. The subsecond PL intensity fluctuations of CdSe QDs are different from "on" and "off" PL blinking generally observed for QDs fluctuating on a millisecond to minute time scale. We characterized single QDs by identifying polarized excitations, topographic imaging using atomic force microscopy (AFM), and transmission electron microscopy (TEM). From analysis of the PL intensity trajectories from >100 single CdSe QDs, the average intermittency time was 213 ms. From the PL quantum efficiency, slow growth of QDs, intensity trajectory analyses, and previous reports relating surface trap states and PL properties of QDs, we attribute the subsecond PL intensity fluctuations of single CdSe QDs and short-lived "on" and "off" states to a high-density distribution of homogeneous surface trap states.

Cadmium Compounds↗

PubMed2005

Temperature-sensitive photoluminescence of CdSe quantum dot clusters.

The formation of narrow size dispersed and nanometer size aggregates (clusters) of cadmium selenide (CdSe) quantum dots (QDs) and their temperature-sensitive photoluminescence (PL) spectral properties close to room temperature (298 K) are discussed. CdSe QDs formed stable clusters with an average diameter of approximately 27 nm in the absence of coordinating solvents. Using transmission electron microscopy (TEM) imaging, we identified the association of individual QDs with 2-5 nm diameters into clusters of uniform size. A suspension of these clusters in different solvents exhibited reversible PL intensity changes and PL spectral shifts which were correlated with temperature. Although the PL intensity of CdSe QDs encapsulated in host matrixes and the solid state showed a response to temperature under cryogenic conditions, the current work identified for the first time QD clusters showing temperature-sensitive PL intensity variations and spectral shifts at moderate temperatures above room temperature. Temperature-sensitive reversible PL changes of clusters are discussed with respect to reversible thermal trapping of electrons at inter-QD interfaces and dipole-dipole interactions in clusters. Reversible luminescence intensity variations and spectral shifts of QD clusters show the potential for developing sensors based on QD nanoscale assemblies.

Cadmium Compounds↗

PubMed2005

Separation-independent attractive force between like particles mediated by nematic-liquid-crystal distortions.

We investigate numerically with the aid of the Landau-de Gennes continuum theory the interaction between two spherical particles carrying the same topological charges +1 mediated by the elastic distortion of a nematic liquid crystal. We consider the case where an escaped nontopological ring disclination is situated between the particles; the director is continuous everywhere and no counterdefects are present. We find that the interaction is attractive and its potential energy depends linearly on the interparticle distance D. This behavior yields the D-independent interaction force, which was observed experimentally by Poulin, Cabuil, and Weitz [Phys. Rev. Lett. 79, 4862 (1997)] in the presence of narrow strings of birefringent regions ("bubble-gum" configuration) between the particles.

Journal Article↗

PubMed2005

Role of blood pressure reduction in prevention of cardiac and vascular hypertrophy.

We investigated whether prevention of cardiac and vascular remodeling associated with inhibition of angiotensin II is independent of the blood pressure (BP)-lowering action of angiotensin II type 1 (AT1) receptor blockade. Spontaneously hypertensive rats, 8 weeks old, were treated with olmesartan, atenolol, or vehicle in their drinking water for 56 days. At the end of each treatment, arterial pressure and heart rate were measured, the ratio of heart weight to body weight was calculated, collagen deposition in the heart was determined histochemically using picrosirius red staining, and wall-to-lumen ratio in isolated mesenteric arteries was measured by a videographic approach. At 3 weeks after the initiation of treatment, rats medicated with olmesartan showed lower values of systolic BP compared with rats given atenolol or vehicle, whereas no difference in directly measured BP were observed at the end of study in anesthetized rats given olmesartan or atenolol. Rats given atenolol showed sustained bradycardia, whereas cardiac hypertrophy and collagen deposition was prevented only in spontaneously hypertensive rats given olmesartan. Olmesartan or atenolol reduced arteriolar wall-to-lumen ratio (olmesartan: 11.5+/-0.4%; atenolol: 13.3+/-0.6%; vehicle: 18.4%+/-1.1); however, this effect was greatest in rats medicated with the angiotensin II type 1 antagonist. Although control of BP is a factor in the prevention of cardiac and vascular hypertrophy, our studies suggest that blockade of angiotensin II receptors may attenuate the structural changes in the heart and blood vessels of hypertensive animals independent of a reduction in BP.

Adrenergic beta-Antagonists↗

PubMed2005

Incidence of adrenal involvement and assessing adrenal function in patients with renal cell carcinoma: is ipsilateral adrenalectomy indispensable during radical nephrectomy?

OBJECTIVE: To determine the value of ipsilateral adrenalectomy with radical nephrectomy, by investigating the clinical aspects of adrenal involvement and adrenocortical function in patients with renal cell carcinoma (RCC). PATIENTS AND METHODS: The demographic, clinical and pathological data of adrenal involvement were reviewed in 247 patients with RCC. To evaluate adrenocortical function, 14 patients (adrenalectomy in eight, adrenal-sparing in six) had a rapid adrenocorticotropic hormone (ACTH) stimulation test before and 2 weeks after surgery. RESULTS: There was adrenal involvement with RCC in seven of the 247 (2.8%) patients (a solitary adrenal metastatic tumour in four and direct extension into the adrenal gland in three). All adrenal involvement was detectable on abdominal computed tomography before surgery, and these patients had a large primary renal tumour of > pT2 and/or distant metastasis. Plasma cortisol levels declined significantly more in response to the rapid ACTH stimulation test in those treated by adrenalectomy than in those with spared adrenal glands at 2 weeks after surgery (P < 0.05), while there was no significant difference between the groups before surgery. CONCLUSIONS: These results suggest that unconditional ipsilateral adrenalectomy with radical nephrectomy for RCC should be avoidable, and thus preserve the reserve of adrenocortical function, as preoperative imaging, especially thin-slice multidetector helical computed tomography, can detect adrenal involvement with RCC in most cases. Unilateral adrenalectomy might cause an irreversible impairment of the reserve of adrenocortical function.

Adrenal Gland Neoplasms↗