Search PubMed⌕ Search

Biomedical subjects

H Yokoyama

Publications and source records attributed to H Yokoyama.

At least 19 recordsLinked to original sources
PubMed2006

Director-configurational transitions around microbubbles of hydrostatically regulated size in liquid crystals.

A high-pressure technique is introduced which allows a continuous variation of the inclusion size in liquid crystal colloids. We use a nematic liquid crystal host into which micrometer-sized gas bubbles are injected. By applying hydrostatic pressures, the diameter of these gas bubbles can be continuously decreased via compression and absorption of gas into the host liquid crystal, so that the director configurations around a single bubble can be investigated as a function of the bubble size. The theoretically predicted transition from a hyperbolic hedgehog to a Saturn-ring configuration, on reduction of the particle size below a certain threshold, is confirmed to occur at the radius of a few micrometers.

Journal Article↗
PubMed2006

Molecular basis for sensitivity and acquired resistance to gefitinib in HER2-overexpressing human gastric cancer cell lines derived from liver metastasis.

Gastric cancer metastasised to the liver was found to overexpress HER2 at a significantly higher incidence than primary gastric cancers. The purpose of the present study was to investigate the possibility of molecular therapy targeting HER2 overexpression in gastric cancer liver metastasis. We developed three new HER2-overexpressing gastric cancer cell lines (GLM-1, GLM-2, GLM-4) without epidermal growth factor receptor (EGFR) mutations derived from such liver metastasis, two of which had HER2 gene amplifications. All these GLM series of cell lines were highly sensitive to gefitinib in vitro, a specific inhibitor of EGFR tyrosine kinase (Iressa) rather than anti-HER2 antibody trastuzumab (Herceptin), whereas most of the HER2 low-expressing counterparts were not. In these HER2-overexpressing GLM series, protein kinase B (Akt), but not extracellular signal-regulated kinase 1/2 (ERK1/2), was constitutively phosphorylated, and gefitinib efficiently inhibited this Akt phosphorylation, induced strong apoptosis in vitro and exhibited antitumour activity in tumour xenografts in nude mice. This gefitinib-mediated antitumour effect in xenograft was significantly potentiated by trastuzumab treatment. On the other hand, gefitinib-resistant cells (GLM-1R) exhibited increased EGFR expression, followed by constitutive activation of mitogen-activated protein kinase (MAPK) pathway. These results suggest that the antitumour effect of gefitinib is due to the effective inhibition of HER2-driven constitutive activation of phosphatidylinositol-3-kinase (PI3K)/Akt pathway, and that the acquired resistance to gefitinib is due to the constitutive activation of Ras/MAPK pathway in compensation for PI3K/Akt pathway. Gastric cancer liver metastasis with HER2 overexpression would be a potential molecular target for gefitinib and trastuzumab.

Animals↗
PubMed2006

Effectiveness of an 'half elemental diet' as maintenance therapy for Crohn's disease: A randomized-controlled trial.

BACKGROUND: Although thiopurines have a proven role in maintenance therapy for Crohn's disease, an alternative therapy is needed for patients intolerant or resistant to thiopurines. AIM: To evaluate the effectiveness of home enteral nutrition as a maintenance therapy regimen in which half of the daily calorie requirement is provided by an elemental diet and the remaining half by a free diet. We refer to this home enteral nutrition therapy as 'half elemental diet'. METHODS: Between 2002 and 2005, 51 patients in remission from two hospitals were randomly assigned to a half elemental diet group (n = 26) or a free diet group (n = 25). The primary outcome measure of this study was the occurrence of relapse over the 2-year period. RESULTS: The relapse rate in the half elemental diet group was significantly lower [34.6% vs. 64.0%; multivariate hazard ratio 0.40 (95% CI: 0.16-0.98)] than that in the free diet group after a mean follow-up of 11.9 months. Compliance was similar in the two groups. No adverse event occurred in any of the patients throughout the study. CONCLUSION: This randomized-controlled trial shows the effectiveness of an half elemental diet, which is a promising maintenance therapy for Crohn's disease patients.

Adult↗
PubMed2006

Relationship between metabolic syndrome components and vascular properties in Japanese type 2 diabetic patients without cardiovascular disease or nephropathy.

To investigate the effect of metabolic syndrome (MS) components on early atherosclerosis markers, i.e., urinary albumin excretion rate (UAE), pulse wave velocity (PWV), and carotid intima-media thickness (IMT), we studied 536 Japanese patients with type 2 diabetes without cardiovascular disease or nephropathy. The MS definition by ATP III was employed. UAE, PWV, and IMT increased significantly with increasing the number of components even before fulfilling the diagnosis of MS. UAE was significantly influenced by high blood pressure, high triglycerides, and low HDL cholesterol. PWV was significantly increased by high blood pressure. IMT was significantly increased by high blood pressure and abdominal obesity. Multiple regression analysis, including MS components and putative risk factors, indicated that the number of MS components, age and glycosylated HbA1C were independent determinants of UAE, PWV, and IMT. LDL cholesterol and male gender were independent determinants of IMT. In conclusion, UAE, PWV, and IMT increased according to increasing the number of MS in type 2 diabetic patients without cardiovascular disease or diabetic nephropathy. The current observation considering the modifiable factors may help to identify patients who are at high risk of experiencing cardiovascular disease.

Adult↗
PubMed2006

[Three-dimensional image of Adamkiewicz artery detected by using multidetector CT: preoperative assessment of thoraco-abdominal aortic aneurysm].

Images were obtained with the following parameter 0.5 sec/r, 1 mm collimation, pitch 3.5, 120 kV, 300 mA. One hundred ml of contrast material containing 350 mg I/ml was injected with a power injector (dual shot type) into an antecubital vein at a rate of 3.5 ml/sec (70 ml). Then remaining 30 ml and same volume of saline were infused at a rate of 1.5 ml/sec simultaneously. Twenty-five seconds after the injection, scan was performed from the level of L2 to T5 vertebrae. Transverse sections were reconstructed with a 1 mm thickness at 0.7 mm intervals. Imaging was done with multiplanar and curved planar reformations. In case of vertebral deformity, however, 3D images were made to depict the Adamkiewicz artery. In 141 patients, 107 (76%) Adamkiewicz arteries from the interverbral foramen to the hairpin-shaped union with the anterior spinal artery were visualized. Seventy-nine arteries of Adamkiewicz (73%) originated from the left side. Our method is useful for depicting Adamkiewicz artery.

Angiography↗
PubMed2006

Blockade of VEGF accelerates proteinuria, via decrease in nephrin expression in rat crescentic glomerulonephritis.

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor that maintains the glomerular and peritubular capillary (PTC) network in the kidney. The soluble form of the VEGF receptor-1 (soluble fms-like tyrosine kinase 1 (sFlt-1)) is known to regulate VEGF activity by binding VEGF in the circulation. We hypothesized that VEGF may be beneficial for maintaining glomerular filtration barrier and vascular network in rats with progressive glomerulonephritis (GN). For blockade of VEGF activity in vivo, rats were transfected twice with plasmid DNA encoding the murine sFlt-1 gene into femoral muscle 3 days before and 2 weeks after the induction of antiglomerular basement membrane antibody-induced GN. Inhibition of VEGF with sFlt-1 resulted in massive urinary protein excretion, concomitantly with downregulated expression of nephrin in nephritic rats. Further, blockade of VEGF induced mild proteinuria in normal rats. Administration of sFlt-1 affected neither the infiltration of macrophages nor crescentic formation. In contrast, treatment of sFlt-1 accelerated the progression of glomerulosclerosis and interstitial fibrosis accompanied with renal dysfunction and PTC loss at day 56. VEGF may play a role in maintaining the podocyte function as well as renal vasculature, thereby protecting glomeruli and interstitium from progressive renal insults.

Animals↗
PubMed2006

Temperature effects on the development of Enteromyxum spp. (Myxozoa) in experimentally infected tiger puffer, Takifugu rubripes (Temminck & Schlegel).

The effects of water temperature on the development of the enteric myxosporeans, Enteromyxum fugu and Enteromyxum leei, were investigated in experimentally infected tiger puffer, Takifugu rubripes. After naïve tiger puffer were fed gut tissue infected with both E. fugu and E. leei, they were divided into separate tanks and kept at different constant temperature regimes between 10 and 25 degrees C. Regardless of the water temperature tested, E. fugu was consistently detected with a high prevalence of infection (60-100%), although no sporulation occurred at 10 and 15 degrees C. Development of E. leei and the onset of disease were suppressed by low water temperatures (<15 degrees C). However, a temperature increase to 20 degrees C promoted the development of E. leei, followed by an increase of disease rate in the fish. The present study demonstrates that water temperatures below 15 degrees C have an inhibitory effect on the development of E. fugu and E. leei, resulting in suppression of enteromyxosis at low temperatures.

Animals↗
PubMed2005

Paranematic interaction between nanoparticles of ordinary shape.

We propose a general approach to the description of the long-ranged interaction between nanoparticles (1-10 nm) of ordinary shape in the paranematic phase, i.e., nematic liquid crystal in the isotropic phase. In general case interaction potential is attractive of Yukawa form with derivatives. But it can be anisotropic despite the isotropy of the paranematic phase. The origin of such anisotropy is the shape of nanoparticles. Particular potentials for spherical and cylindrical particles are considered. For the case of nanocylinders anisotropic part of the interaction potential can lead to the orientational ordering of them in the isotropic phase of nematic liquid crystals.

Journal Article↗
PubMed2005

Significance of colonoscopy in patients with intestinal graft-versus-host disease after hematopoietic stem cell transplantation.

BACKGROUND AND STUDY AIMS: Patients with intestinal graft-versus-host disease (GVHD) are generally in poor clinical condition. In this study we aimed to establish the clinical significance of endoscopic diagnosis of this condition, observing only the distal section of the large intestine. PATIENTS AND METHODS: Endoscopic and pathological findings at colonoscopy were evaluated retrospectively in 12 patients who were diagnosed with intestinal GVHD after undergoing hematopoietic stem cell transplantation. RESULTS: The main mucosal changes observed at endoscopy were granular change, edema, "spotty redness", and sloughing. These were clearly displayed after enhancement with Indigo carmine staining, and with insertion of the colonoscope only as far as the distal section of the large intestine. A histological diagnosis of intestinal GVHD was made in 50 % of the patients, whose intestinal epithelium specimens showed numerous apoptotic bodies. It was possible to perform total colonoscopy in two patients who were in relatively good condition clinically, but there were no remarkable differences in the endoscopic findings throughout the large intestine, from the terminal ileum to the rectum. In terms of clinical outcomes of the 12 patients, their prognosis was poor in that they all either went on to suffer from chronic GVHD or died. CONCLUSIONS: Endoscopic and histological findings on distal colonoscopy are clinically significant in the diagnosis of intestinal GVHD, and limiting this examination to the distal section of the large intestine avoids causing further clinical deterioration in patients who are already in very poor general condition and the possibility of causing endoscopy-related complications.

Adolescent↗
PubMed2005

Henneguya pagri n. sp. (Myxozoa: Myxosporea) causing cardiac henneguyosis in red sea bream, Pagrus major (Temminck & Schlegel).

Henneguya pagri n. sp. (Myxozoa: Myxosporea) is described from netpen-cultured red sea bream, Pagrus major, in Japan. Affected fish displayed anaemic gills, an enlarged bulbus arteriosus and internal haemorrhaging in the pericardial cavity. Disease outbreaks occurred during the summer and the prevalence of infection reached 75% in August. Plasmodia of H. pagri developed in the bulbus arteriosus of red sea bream, in which degenerative cardiomyopathy was observed. Following maturation of the parasite, the influx of spores into the gills caused congestion of the gill capillaries, resulting in proliferative branchitis. Spores (10.5 x 7.5 microm) were ovoid with two caudal appendages (29.6 microm in average length), with a whip-like extension from the end. Partial small subunit ribosomal RNA gene sequences of H. pagri are closely related to those of H. lateolabracis infecting the bulbus arteriosus of Chinese sea bass, Lateolabrax sp.

Animals↗
PubMed2005

Two multivalvulid myxozoans causing postmortem myoliquefaction: Kudoa megacapsula n. sp. from red barracuda (Sphyraena pinguis) and Kudoa thyrsites from splendid alfonso (Beryx splendens).

Postmortem myoliquefaction associated with multivalvulid myxozoans was found in fillets of red barracuda (Sphyraena pinguis) and splendid alfonso (Beryx splendens), which were imported to Japan from China and South Africa, respectively. Morphological examinations of the myxozoans from the somatic muscle of red barracuda revealed that spores (30.3-44.7 microm in maximum thickness) had 4 distinct winglike valves, in which 1 extremely large (12.7 x 5.8 microm), 2 small, and 1 vestigial polar capsule were present. The small subunit ribosomal DNA sequence analysis showed that the myxozoan cluster within a clade was composed of Kudoa thyrsites, Kudoa minithyrsites, and Kudoa lateolabracis, all having stellate spores with 1 polar capsule larger than the other 3. On the basis of these characteristics, we describe this parasite as Kudoa megacapsula n. sp. Morphological and molecular analyses of the myxozoan from splendid alfonso identified it as K. thyrsites, which has been described from many marine fishes. To our knowledge, this is the first record of K. thyrsites in splendid alfonso.

Animals↗
PubMed2005

ADAMTS-1 is involved in normal follicular development, ovulatory process and organization of the medullary vascular network in the ovary.

To clarify the role of disintegrin-like and metalloproteinase with thrombospondin type I motifs-1 (ADAMTS-1) in ovarian function, we examined abnormalities in ovulatory processes, folliculogenesis and the vascular system of ADAMTS-1 null ovaries. First, when immature female mice were treated with pregnant mare serum gonadotropin (PMSG)/human chorionic gonadotropin (hCG), the number of ovulated oocytes was markedly decreased in ADAMTS-1 null mice in comparison to ADAMTS-1 (+/-) controls. The proportion of anovulated follicles to total mature follicles was significantly higher in ADAMTS-1 null females when compared with controls. The numbers of growing follicles at each stage were counted. The number of follicles at type 5b (late preantral) and later stages was markedly reduced in ADAMTS-1 null mice, irrespective of gonadotropin treatment (no gonadotropins, PMSG alone or PMSG/hCG). These data demonstrate that impairment of ovarian function to ovulate oocytes in ADAMTS-1 null mice occurs at two different levels: in the development of growing follicles and ovulatory processes. Furthermore, ADAMTS-1 null ovaries included a number of unusual atretic follicles that showed no sign of oocyte degeneration but lost the surrounding granulosa cell layers and were considered to be derived from type 4 or 5a follicles. These results suggest that ADAMTS-1 is important for follicular development beyond the type 4 and/or 5a and for maintaining normal granulosa cell layers in follicles. Finally, the number of large blood vessels in the medullar zone was significantly decreased in ADAMTS-1 null mice ovaries, suggesting that ADAMTS-1 is also involved in the organization of the medullary vascular network.

ADAM Proteins↗
PubMed2004

Modes of transmission of Glugea plecoglossi (Microspora) via the skin and digestive tract in an experimental infection model using rainbow trout, Oncorhynchus mykiss (Walbaum).

Glugea plecoglossi (Microspora) is a significant cause of economic loss in cultured ayu, Plecoglossus altivelis, in Japan, due to the unsightly appearance of infected fish harbouring xenomas in the body cavity. Modes of transmission of G. plecoglossi via the skin and digestive tract were studied in an experimental infection model using rainbow trout, Oncorhynchus mykiss. Combined with Uvitex 2B and in situ hybridization (ISH) assays, the early development of G. plecoglossi was successfully traced. Following a bath exposure of fish Uvitex 2B-labelled G. plecoglossi spores were observed to attach to microscopic injuries (trypan blue-positive sites) of fish skin, after which ISH-positive sporoplasms were found to invade the epidermis as early as 5 min post-infection (PI), migrating rapidly to the subdermis. It was also shown that G. plecoglossi entering via the skin does not spread into the internal organs but develops into subdermal xenomas. After rainbow trout were exposed to G. plecoglossi spores by oral intubation, spores germinated in the intestinal lumen, followed by penetration of sporoplasms into the gut mucosal epithelium 5 min PI. In vitro trials determining stimulation factors (fish mucus, changes in pH, digestive enzymes) for the extrusion of the polar tube were inconclusive. The present study indicates that skin wounds and the gut epithelium can be portals of entry of G. plecoglossi and that natural infection in fish seems to occur perorally rather than via the skin.

Animals↗
PubMed2004

Release of endothelium-associated proteins into blood by injection of heparin in normal subjects and in patients with Type 1 diabetes.

AIMS: Disturbances in heparan sulphate proteoglycans in patients with diabetic nephropathy might contribute to the pathogenesis of vascular disease in these patients. To investigate this possible link, we measured the heparin-induced, immediate release of eight proteins with heparan sulphate binding properties in patients with nephropathy. METHODS: We studied three groups, Type 1 diabetic patients with (n = 10) or without (n = 15) albuminuria and matched controls (n = 12). Blood samples were obtained before and 5 min after the injection of 40 anti-Xa IU low molecular weight heparin/kg body weight. RESULTS: Lipoprotein lipase increased more in diabetic patients without albuminuria than in controls and patients with albuminuria [261 (170-293) vs. 177 (103-438), P < 0.05 and 203 (159-280) mU/ml, P < 0.05]. Total tissue factor pathway inhibitor increased more in the diabetic patients [284 (198-449) and 275 (243-399)] than in the controls [221 (169-289) ng/ml, P < 0.005]. Vitronectin increased significantly only in the diabetic patients with albuminuria. The remaining proteins did not increase significantly (antithrombin, von Willebrand factor, fibronectin) or increased equally in the three investigated groups (extracellular superoxid dismutase and platelet factor 4). CONCLUSIONS: The different release of lipoprotein lipase and vitronectin in diabetic subjects with and without albuminuria may reflect novel aspects of vascular derangement in patients with albuminuria.

Adult↗
PubMed2004

Phylogeny of the multivalvulidae (Myxozoa: Myxosporea) based on comparative ribosomal DNA sequence analysis.

Fish parasites of the Multivalvulida (Myxozoa, Myxosporea) are widespread and can be associated with mortality or poor flesh quality in their commercially important marine hosts. Traditional classifications divide members of this order into families based on spore valve and polar capsule numbers. Analyses of the small-subunit (SSU) ribosomal DNA (rDNA) sequences from all representative families in the order (Trilosporidae, Kudoidae, Pentacapsulidae, Hexacapsulidae, and Septemcapsulidae) indicate that a revision of the taxonomy and nomenclature is warranted. In our phylogenetic analysis of (SSU and large subunit) rDNA sequences, members of Pentacapsula, Hexacapsula, and Septemcapsula root within a clade of Kudoa species with Unicapsula (Trilosporidae) as an outlier to these genera. Therefore, we propose to synonymize Pentacapsulidae, Hexacapsulidae, and Septemcapsulidae with Kudoidae alter the diagnosis of Kudoidae and Kudoa to accommodate all marine myxozoan parasites having 4 or more shell valves and polar capsules.

Animals↗
PubMed2004

Tuberculous pseudoaneurysm of the celiac artery. A case report.

We report a case of tuberculous pseudoaneurysm in the neck of the celiac artery involving the aorta. Recurrence of the aneurysm occurred after attempted direct repair. Therefore redo-surgery was performed, which involved resection of aneurysm and removal of the infected tissue with bilateral axillofemoral bypass.

Aged↗
PubMed2003

Ultralow-jitter, 1550-nm mode-locked semiconductor laser synchronized to a visible optical frequency standard.

Using high-bandwidth feedback, we have synchronized the pulse train from a mode-locked semiconductor laser to an external optical atomic clock signal and achieved what is to our knowledge the lowest timing jitter to date (22 fs, integrated from 1 Hz to 100 MHz) for such devices. The performance is limited by the intrinsic noise of the phase detector used for timing-jitter measurement. We expect such a highly stable device to play an important role in fiber-network-based precise time/frequency distribution.

Journal Article↗